Simterm 2013-Book of Abstracts

BBOOOOKK OOFF AABBSSTTRRAACCTTSS 1166tthh SSyymmppoossiiuumm oonn TThheerrmmaall SScciieennccee aanndd EEnnggiinneeeerriinngg ooff SSeerrbbiiaa

SSookkoobbaannjjaa,, SSeerrbbiiaa,, OOccttoobbeerr 2222 –– 2255,, 22001133

UUnniivveerrssiittyy ooff NNiišš,, FFaaccuullttyy ooff MMeecchhaanniiccaall EEnnggiinneeeerriinngg iinn NNiišš SSoocciieettyy ooff TThheerrmmaall EEnnggiinneeeerrss ooff SSeerrbbiiaa

IISSBBNN 997788--8866--66005555--004444--88

PPuubblliisshheerr:: UUnniivveerrssiittyy ooff NNiišš,, FFaaccuullttyy ooff MMeecchhaanniiccaall EEnnggiinneeeerriinngg iinn NNiišš

22001133

16th Symposium on Thermal Science and Engineering of Serbia

under title:

“Energy – Ecology – Efficiency”

is organized by:

University of Niš, Faculty of Mechanical Engineering in Niš and

Society of Thermal Engineers of Serbia

Under patronage of the

GOVERNMENT OF THE REPUBLIC OF SERBIA MINISTRY OF EDUCATION, SCIENCE AND TECHNOLOGICAL DEVELOPMENT

and supported by:

General Sponsor

SERBIAN CHAMBER OF ENGINEERS, Belgrade

Grand Donor

ENERGOPROJEKT ENTEL, Belgrade

Sponsors and Donors

ŠUKOM, Knjaževac

JUGOTERM, Merošina

HERZ, Belgrade

KGH INŽENJERING, Zaječar

FENIKS BB, Niš

MIKOTERM, Niš

RADING, Kraljevo

TROX TECHNIK, Belgrade

VIA OCEL, Belgrade

RADIJATOR INŽENJERING, Kraljevo

WILO, Belgrade

HENCO, Belgium

YUTKL, Niš

ВладаРепубликеСрбије

Министарствопросвете,наукеитехнолошкогразвоја

Инжењерска комора Србије

ENERGOPROJEKT ENTEL

v

International Scientific Committee Dr. Gligor Kanevče [MK] Dr. Sophia Natalia Boemi [GR]

Dr. Slavtcho G. Slavtchev [BG] Dr. Dušan Golubović [BA]

Dr. Agis M. Papadopoulos [GR] Dr. Petar Gvero [BA]

Dr. Petar Novak [SI] Dr. Maria Ichim [RO]

Dr. Neven Duić [HR] Dr. Vesna Barišić [FI]

Dr. Ljubica Kanevče [MK] Dr. Dečan Ivanović [ME]

Dr. Sašo Medved [SI] Dr. Uroš Karadžić [ME]

Dr. Peter Stankov [BG] Dr. Gyula Gróf [HU]

Dr. Jordan Hristov [BG] Dr. Friedrich Dinkelacker [DE]

Program Committee Prof. Dr. Mladen Stojiljković University of Niš, Faculty of Mechanical Engineering in Niš Prof. Dr. Milan Radovanović University of Belgrade, Faculty of Mechanical Engineering in Belgrade

Prof. Dr. Simeon Oka Vinča Institute, Belgrade Prof. Dr. Miroljub Adžić University of Belgrade, Faculty of Mechanical Engineering in Belgrade Prof. Dr. Gradimir Ilić University of Niš, Faculty of Mechanical Engineering in Niš

Prof. Dr. Bratislav Blagojević University of Niš, Faculty of Mechanical Engineering in Niš Prof. Dr. Dragoljub Živković University of Niš, Faculty of Mechanical Engineering in Niš Prof. Dr. Velimir Stefanović University of Niš, Faculty of Mechanical Engineering in Niš

Prof. Dr. Dragoslava Stojiljković University of Belgrade, Faculty of Mechanical Engineering in Belgrade Dr. Predrag Stefanović Vinča Institute, Belgrade

Prof. Dr. Dragoslav Šumarac University of Belgrade, Faculty of Civil Engineering in Belgrade Dr. Miodrag Mesarović Energoprojekt ENTEL, Belgrade

Prof. Dr. Dušan Gvozdenac University of Novi Sad, Faculty of Technical Sciences Prof. Dr. Milun Babić University of Kragujevac, Faculty of Enginnering Sciences in Kragujevac

Prof. Dr. Vladan Karamarković University of Kragujevac, Faculty of Mechanical and Civil Eng. in Kraljevo Dr. Žarko Stevanović Vinča Institute, Belgrade Prof. Dr. Zoran Stajić University of Niš, Faculty of Electronic Engineering in Niš Prof. Dr. Miloš Banjac University of Belgrade, Faculty of Mechanical Engineering in Belgrade

Prof. Dr. Maja Todorović University of Belgrade, Faculty of Mechanical Engineering in Belgrade Prof. Dr. Goran Jankes University of Belgrade, Faculty of Mechanical Engineering in Belgrade

Honoured Committee Prof. Dr Vlastimir Nikolić, University of Niš, Faculty of Mechanical Engineering in Niš

Prof. Dr. Dragan Antić, University of Niš, Faculty of Electronic Engineering in Niš Prof. Dr. Jovan Stepanović, University of Niš, Faculty of Technology in Leskovac Prof. Dr. Ćemal Dolićanin, State University of Novi Pazar

Prof. Dr. Maja Đurović Petrović, European University, Faculty for International Engineering Management Jaroslav Urošević, Energoprojekt ENTEL

Organizing Committee Doc. Dr. Dejan Mitrović University of Niš, Faculty of Mechanical Engineering in Niš Doc. Dr. Mirjana Laković University of Niš, Faculty of Mechanical Engineering in Niš

Prof. Dr. Branislav Stojanović University of Niš, Faculty of Mechanical Engineering in Niš Prof. Dr. Mića Vukić University of Niš, Faculty of Mechanical Engineering in Niš

Doc. Dr. Jelena Janevski University of Niš, Faculty of Mechanical Engineering in Niš Prof. Dr. Gordana Stefanović University of Niš, Faculty of Mechanical Engineering in Niš

Dr. Goran Vučković University of Niš, Faculty of Mechanical Engineering in Niš Doc. Dr. Predrag Zivković University of Niš, Faculty of Mechanical Engineering in Niš Mr. Dragan Kuštrimović University of Niš, Faculty of Mechanical Engineering in Niš

Mirko Stojiljković University of Niš, Faculty of Mechanical Engineering in Niš Marko Ignjatović University of Niš, Faculty of Mechanical Engineering in Niš

vi

Disclaimer

The contents of the papers presented in this publication are the sole responsibility of their authors and can in no way be taken to reflect the views of the Organizer.

vii

Contents

1. Plenary Session 1

1.01. Upgrade by an Innovative Installation of Additional Economizer at the 620 MWe Lignite‐Fired Power Plant

Vladimir Stevanovic 2

1.02. The Main Strategic Objectives of the Romanian Energy Sector in National and International Context

Maria Ichim 3

1.03. Integral‐balance Method to Transient Heat, Mass and Momentum Transfer of Integer and Fractional Order

Jordan Hristov 4

1.04. Some Controversial Issues on Energy Sustainability Miodrag Mesarović 5

1.05. Ranking Literature Sources for Multidisciplinary Research Miodrag Mesarović 6

2. Technologies and Plants 7

2.01. Design of a bulb turbine stay vane and runner for the small hydro power plant “Grčki mlin’’ near Prokuplje

Božidar Bogdanović, Dragica Milenković, Jasmina Bogdanović‐Jovanović, Živan Spasić 8

2.02. The Use of Preheated Low‐Enriched Air in Downdraft Gasifiers: Energy and Exergy Analysis

Rade Karamarković, Vladan Karamarković, Anđela Lazarević, Miljan Marašević, Nenad Stojić 9

2.03. Energy and exergy analysis of Brayton cycle with working fluid of temperature dependent physical properties

Antun Galović, Marija Živić , Mario Holik, Ružica Končić 10

2.04. Alternative modeling approaches to sulfation reactions of calcium based sorbents injected in the pulverized coal furnace

Ivan D. Tomanović, Srđan V. Belošević, Andrijana D. Stojanović, Dragan R. Tucaković, Titoslav V. Živanović 11

2.05. Energy Consumption of Compressed Air Systems and Potential of Heat Recovery with example

Milovan Medojević, Jovan Petrović 12

viii

2.06. Analysis of dynamic behaviour of hot water boilers during start up Milena Todorović, Dragoljub Živković, Marko Mančić, Dragan Milčić 13

2.07. Technology for manufacturing of turbine parts for micro and mini hydroelectric power plants

Dragan Temeljkovski, Stojanče Nusev, Dragana Temeljkovski 14

2.08. Vertical Limited Fluid Bed for Burning Granulated Bio, Fossil and Waste Fuel in Power Plant Boilers and Conversion of Coal by Biomass

Radislav Vujadinović 15

2.09. Thermal Fatigue of Materials Dušan Petković, Goran Radenković 16

3. New and Renewable Energy Sources 17

3.01. Potential Fire Hazards of Renewable Energy ‐ Horizons of Tomorrow Miloš Banjac, Barbara Vidaković 18

3.02. Possibilities and Directions for Participation of Available RES in Macedonia with Scenarios for Achieving the 20/20/20 Goal of the EC

Mile Dimitrovski 19

3.03. Optical Design of a Solar Parabolic Concentrator Based on Square Flat Facets Saša R. Pavlović, Velimir P. Stefanović, Ivan Stojanović, Suad Suljković, Dragan Kuštrimović 20

3.04. Techno‐economic Analysis of Photovoltaic‐based Stand‐alone Power System for Supply of Metrological Masts’ Equipment

Saša Stojković, Vukman Bakić 21

3.05. Solar Drying of Fruits and Vegetables Filip Mojsovski 22

3.06. Comparative Analysis Between Two Methods for Temperature Measurement of PV panels Uglješa Jovanović, Igor Jovanović, Zoran Petrušić, Dragan Mančić 23

3.07. Technical and Economic Analysis of Hybrid Wind‐photovoltaic Power System for Supply of Meteorological Masts’ Measuring Equipment

Saša Stojković, Vukman Bakić 24

3.08. Technical Feasibility and Financial Analysis of Hybrid Wind‐photovoltaic System for Supply of One Educational Institution

Saša Stojković, Snežana Dragićević 25

3.09. Current State Wind Energy Utilisation in the Republic of Macedonia Monika Lutovska, Vladimir Mijakovski, Cvete Dimitrieska, Vangelče Mitrevski 26

3.10. Agricultural biomass utilization for energy purposes Dejan Đurović, Branislav Repić, Dragoljub Dakić, Aleksandar Erić, Stevan Nemoda 27

3.11. Biogas – Overview of the Possibilities for Implementation in the Macedonian Agricultural Sector

Dame Dimitrovski, Mile Dimitrovski, Gordana Popsimonova, Done Tashevski 28

3.12. Utilization of crude glycerol for the production of biofuels Bojana Danilović, Dragiša Savić, Vlada Veljković 29

ix

3.13. Renewable energy potential in the Rusanda rehabilitation center Milana Perić, Milovan Medojević 30

3.14. Guide Vane Position Control of the Mini Hydro Power Plant by Digital Sliding Mode with Additional Integral Action

Vladislav Blagojević, Miodrag Stojiljković, Živan Spasić 31

3.15. Recent Progress in Biomass Pyrolysis/Gasification Technologies Velimir Stefanović, Andrijana Stojanović, Saša Pavlović 32

4. Mathematical Modeling and Numerical Simulation 33

4.01. Dimensioning of Underground Vertical Heat Exchangers for Geothermal Heat Pump Miloš Banjac, Zara Komnenić 34

4.02. Heat exchangers comparation Kire Popovski, Igor Andeevski 35

4.03. Modeling Thermal Processes Using Bond Graphs Gordana Janevska 36

4.04. Referent Wind Speed and Turbulence Intensity Estimation and on‐Site Wind Turbines Classification

Žarko Stevanović, Nikola Mirkov, Žana Stevanović, Borislav Grubor, Maja Đurović‐Petrović 37

4.05. Wind Load Modeling and Structural Response of Guyed Mast Vukman Bakić, Milada Pezo, Gordana Kastratović, Nenad Vidanović 38

4.06. Numerical Investigation of Thermal Processes in Shell and Tube Heat Exchanger Mića Vukić, Predrag Živković, Mladen Tomić, Ivan Stojanović 39

4.07. CFD Analysis of Forced Convection Heat Transfer Cu‐Water Nanofluids in Circular Tube Kamil Arslan 40

4.08. Flow Simulation and Noise Prediction in Axial Fans Altin Dorri 41

4.09. Numerical Investigation of the Influence of Tip Clearance on Reversible Axial Fan Characteristics

Živan Spasić, Božidar Bogdanović, Vladislav Blagojević, Jasmina Bogdanović‐Jovanović 42

4.10. Review of Critical Heat Flux Predictions

Andrijana Stojanović, Vladimir Stevanović, Dragoljub Živković, Milada Pezo, Ivan Tomanović 43

4.11. Determination of centrifugal pump operating parameters in turbine operating regime Živojin Stamenković, Jasmina Bogdanović‐Jovanović, Jelena Manojlović 44

4.12. Euler‐Euler Granular Flow Model Applied on Numerical Simulation of Liquid Fuels Combustion in a Fluidized Bed

Stevan Đ. Nemoda, Milica R. Mladenović, Dragoljub V. Dakić, Mirko S. Komatina, Aleksandar M. Erić, Milijana J. Paprika 45

4.13. A Parametric Study on Correlations for Transport Parameters in Fixed Bed Regenerators Milan Đorđević, Šefik Bajmak, Marko Mančić 46

4.14. Numerical Prediction of Drag Coefficient for Lattice Structures Milada Pezo ,Vukman Bakić, Gordana Kastratović, Nenad Vidanović 47

x

4.15. Comparison between the energy integration of processes for 1G/2G ethanol production and bioelectricity

Cássia M. Oliveira, Antonio J. G. Cruz, Caliane B. B. Costa 48

4.16. Mathematical models for evaluating evaporation rates from free water surface of indoor swimming pools

Marko Mančić, Dragoljub Živković, Jelena Manojlović, Milena Todorović 49

4.17. Software for Testing the Heat Transfer and Pressure Drop in Vertical Thermosiphon Reboiler

Sonja Stefanov, Dragan Skobalj 50

4.18. Numerical Simulation of Friction Stir Welding Miroslav Mijajlović, Dragan Milčić, Miodrag Milčić 51

5. Experimental Investigation of Processes 53

5.01. Experimental Plant for Testing of Agricultural Biomass Combustion

Zoran Čepić, Biljana Miljković, Branka Nakomčić‐Smaragdakis, Nevena Šenk, Dušan Marković 54

5.02. Investigation of Wood Chips Combustion in Experimental Combustion Chamber Branislav Stojanović, Jelena Janevski 55

5.03. Experimental and Numerical Study of Biomass Combustion in 50 kW Cigar Furnace

Aleksandar M. Erić, Stevan Đ. Nemoda, Dragoljub V. Dakić, Mirko S. Komatina, Branislav S. Repić 56

5.04. Experimental and numerical research of thermal processes in the TST tanks with thermal oil and a phase change medium

Goran Živković, Nedžad Rudonja, Mirko Komatina, Branislav Repić 57

5.05. Determining the Theoretical Reliability Functions of the Thermal Power Systems in Power Plant "Nikola Tesla A"

Dragan Kalaba, Milan Đorđević, Dušan Adamović 58

5.06. An Experimental Research of Effects of Adding a Supplementary Component Generated by a Catalytic Reactor on the Combustion of the Primary Fuel at Internal Combustion Engines

Miloš Milošević, Jovica Pešić, Boban Nikolić, Miodrag Milenković 59

5.07. Experimental investigation of flow‐thermal and operating properties of adsorption filter prototype under climate

Miomir Raos, Ljiljana Živković, Nenad Živković, Jasmina Radosavljević, Milena Jovanović 60

6. Energy Efficiency in Industry, Civil Engineering, Communal Systems and Traffic 61

6.01. Survey of Potential Energy Savings in the Building Sector in Serbia and Needed Investments Maja N. Todorović, Dragoslav M. Šumarac, Radoslav D. Galić 62

6.02. Heat pump application for hot water production in a hotel Sofia‐Natalia Boemi, Elli Kyriaki, Thomas Aslanidis, Agis M. Papadopoulos 63

6.03. Possibilities of applying heta lower temperatures level for heating by using two‐stage heat pump

Šefik M. Bajmak, Milan Đorđević 64

xi

6.04. Analysis of the possibilities of using geothermal heat pumps in the heating and cooling systems with special emphasis spa Ilidža in Peć

Šefik M.Bajmak 65

6.05. Usage of Low‐temperature Energy from the Cooling Tower by applying Cascade Heat Pumps

Vladimir I. Mijakovski, Vangelče B. Mitrevski 66

6.06. Refurbishment of Residential Buildings According to Regulation and Policy Vladimir Jovanovic, Karin Stieldorf 67

6.07. Impact of Insulation on School Building Energy Consumption Snezana Dragićević, Sasa Stojkovic 68

6.08. Determining important factors for improving the energy efficiency, optimal economic and ecological characteristics of a building

Biserka Marković, Vlada Nikolić, Milica Stojanović, Olivera Nikolić, Vuk Milošević, Stevan Marković 69

6.09. Building Facade with Temperature Barrier in Context of Increasing Building Energy Efficiency

Branislav Stojanović, Jelena Janevski, Milica Stojanović, Marko Ignjatović 70

6.10. Energy efficiency of thermal power plant depending on the hydraulic load of cooling tower Mirjana Laković, Milica Jović, Slobodan Mitrović 71

6.11. Endogenous and Exogenous Exergy Destruction and Exergoeconomic Evaluation of Thermal Processes in a Complex Industrial Plant

Goran Vučković, Mirko M. Stojiljković, Gradimir Ilić, Mića Vukić, Miloš Simonović 72

6.12. Introducing curricula of energy efficiency and renewable energy sources by TEMPUS project ENERESE

Ćemal Dolićanin, Bojan Kovačić, Edin Dolićanin 73

6.13. Energy efficiency increasing of indoor swimming pools using solar technology

Dragoljub Živković, Marko Mančić, Peđa Milosavljević, Milena Todorović, Dobrica Pejović, Bojan Stanković 74

6.14. Energy Efficiency Measures Implemented through Projects in Serbia Dragan Pavlović, Pedja Milosavljević, Andjela Lazarević 75

6.15. Calibrating Building Energy Models – “FBB” Building Case Study Bratislav Blagojević, Marko Ignjatović 76

6.16. Energy Efficiency of an Elementary School “Prva Vojvođanska Brigada” Dušan Savić 77

6.17. Energy‐Efficient Technologies Applied in Zero Energy Buildings Suad Suljković, Velimir Stefanović, Saša Pavlović, Ivan Stojanović 78

6.18. Analysis of the Natural Lighting and Energy Demand in the Student Dormitory in Terms of Architectural Design

Petar Pejić, Dušan Petković, Marko Ignjatović, Sonja Krasić 79

6.19. Principles of design and construction of passive houses Sanja Spasić 80

xii

6.20. Application of passive solar systems in architecture Sanja Spasić 81

7. Expert Systems 83

7.01. Governance of energy transition of non‐residental buildings by policy intervention Miroslav Kljajić, Dušan Gvozdenac, Jovan Petrović, Aleksandar Andjelković 84

7.02. Energy systems and their use in public sector in Autonomus Province of Vojvodina Igor Mujan, Aleksandar Anđelković, Jovan Petrović , Miroslav Kljajić 85

7.03. Risk Analysis Methods for Small Hydro Power Plants in Creating Insurance Policy Andjela Lazarevic, Rade Karamarkovic, Vladan Karamarkovic, Dragoljub Lazarevic 86

7.04. Optimization of Trigeneration Systems: A Combinatorial Metaheuristic Approach Mirko M. Stojiljković, Mladen M. Stojiljković, Bratislav D. Blagojević 87

7.05. Cogeneration and Heat Storage in Optimized District Heating Plants. Impact on Heat Costs and Primary Energy Consumption

Mirko M. Stojiljković, Goran D. Vučković, Dejan M. Mitrović 88

7.06. Particle Swarm Optimization for the optimal tilt angle of solar collectors Emina Petrović, Milica Jović, Vlastimir Nikolić, Dejan Mitrović, Mirjana Laković 89

7.07. Intelligent contemporary heating control of an amphitheatre Žarko Ćojbašić, Milan Ristanović, Vlastimir Nikolić, Slavica Stojiljković, Nemanja Marković 90

7.08. Intelligent Control System for Thermal Vision‐Based Person‐Following Robot Platform Ivan Ćirić, Žarko Ćojbašić, Vlastimir Nikolić, Tomislav Igić 91

7.09. Classification of Mobile Objects According to Shape and Size by Applying the Technique of Digital Image Processing

Aca Micić, Biljana Đorđević, Boban Andjelković 92

7.10. Non‐linear contrast image enhancement Biljana Djordjević, Boban Andjelković 93

8. Fluid Flow, Heat and Mass Transfer, and Combustion 95

8.01. Protective Measures Against Water Hammer in a Long Pipeline Hydropower Plant with Pelton Turbine

Dragica Milenković, Dragan Svrkota, Milica Nikodijević 96

8.02. Flow and Heat Transfer of Three Immiscible Fluids in the Presence of Uniform Magnetic Field

Dragiša Nikodijević, Živojin Stamenković, Miloš Kocić, Milica Nikodijević 97

8.03. Influence of Water in Liquid Fuel on the Combustion Stability in Fluidized Bed

Milica R. Mladenović, Stevan Đ. Nemoda, Dragoljub V. Dakić, Milijana J. Paprika, Ana D. Marinković, Branislav S. Repić, Mirko S. Komatina 98

8.04. Influence of Burner Operating Parameters and Fuel Properties On Pulverized Fuel Combustion

Branislav Repić, Dejan Djurović, Ana Marinković, Aleksandar Erić, Goran Živković, Milica Mladenović 99

xiii

8.05. Combustion Experiments with Granular Biomass in a Fluidized Bed Facility

Milica R. Mladenović, Stevan Đ. Nemoda, Dragoljub V.Dakić, Milijana J. Paprika, Dejan M. Đurović, Branislav S. Repić, Srđan B. Uzelac 100

8.06. Determination of a heat transfer coefficient for the back surface of a perforated plate Mladen Tomić, Predrag Živković, Anica Milošević, Biljana Milutinović, Petar Đekić 101

8.07. Determination of a perforated plate convective heat transfer coefficient for wide range of Prandtl numbers

Mladen Tomić, Mića Vukić, Predrag Živković, Gradimir Ilić 102

8.08. Research of Effectiveness of HHO Production for Use in Internal Combustion Engines Miodrag Milenković, Miloš Milošević, Dušan Stamenković, Milan Pavlović 103

8.09. Long‐wavelength Marangoni instability in a binary mixture layer with nonlinear Soret effect

Slavtcho Slavtchev, Penka Kalitzova‐Kurteva, Alex Oron 104

8.10. Analysis of thermodynamic parameters in the injection mold with metal inserts Saša Ranđelović, Saša Nikolić, Mladomir Milutinović 105

9. Environmental Protection 107

9.01. Carbon Dioxide Emission from TPP Nikola Tesla A and B units

Zoran Marković, Milić Erić, Dejan Cvetinović, Predrag Stefanović, Vuk Spasojević , Predrag Skobalj 108

9.02. Reduction of Particulate Matter Emission of the Upgraded Electrostatic Precipitators at Unit B2 of the TPP “Nikola Tesla”

Milić Erić, Predrag Stefanović, Zoran Marković, Predrag Škobalj, Nikola Živković, Vuk Spasojević, Dejan Cvetinović 109

9.03. Indoor air parameters measurements in kindergartens located in different urban environments

Ivan Lazović, Sandra Stefanović, Žana Stevanović, Marija Živković, Maja Đurović‐Petrović, Žarko Stevanović 110

9.04. The Environmental Indicators Related to Indoor Air Quality in Schools Valentina Turanjanin, Biljana Vučićević, Marina Jovanović, Sandra Stefanović 111

9.05. Indoor Air Pollution Modeling of Belgrade Typical Dwelling

Sandra Stefanović, Marija Živković, Ivan Lazović, Žana Stevanović, Maja Đurović‐Petrović, Borislav Grubor, Žarko Stevanović 112

9.06. AHP method for waste treatments ranking in terms of impact on the environment Biljana Milutinović, Gordana Stefanović, Goran Vučković, Mladen Tomić, Petar Djekić 113

9.07. Effective and Environmental Parameters of Diesel Engines Using Biodiesel and Biodiesel – Petro Diesel Blends

Dame Dimitrovski 114

1. Plenary Session

16th Symposium on Thermal Science and Engineering of Serbia Sokobanja, Serbia, October 22–25, 2013

Society of Thermal Engineers of Serbia Faculty of Mechanical Engineering in Niš

2

Upgrade by an Innovative Installation of Additional Economizer

at the 620 MWe Lignite-Fired Power Plant

Vladimir Stevanovic

Abstract: Increase of energy efficiency and power upgrade was achieved at the Unit B1 of the 620 MWe

lignite‐fired Thermal Power Plant “Nikola Tesla B” by the installation of an additional economizer. A new

type of connection of the additional economizer with existing economizer sections was applied, which

enables the utilization of more than 30 MWth of the flue gas waste heat and the increase of the Unit gross

efficiency by 0.53 percentage points, which leads to 9.0 MWe of the electric power production. In

addition, the applied parallel connection of the additional economizer with the first section of the

originally existing economizer leads to the partial feedwater bypass of the high pressure heaters, which

enables an increase of the plant electric power up to 30 MWe. The accompanying effects are the

reduction of the pressure drop in the feedwater line and the economizers, which leads to the decrease of

the energy consumption for the main feedwater pump operation. Also, the change of the feedwater flow

through the additional economizer leads to the change of the turbine power; hence, this effect enables

the utilization of the thermal power plant for the primary control of the electric power system. The

applied technical solution is presented together with the measured and calculated energy effects.

Keywords: waste heat, flue gas, economizer, boiler.

Corresponding author: Vladimir Stevanovic, e‐mail: [email protected]



3

The Main Strategic Objectives of the Romanian Energy Sector in

National and International Context

Maria Ichim

Abstract: This paper shows that the main strategic objectives of Romania's energy. Our symposium theme

with reference to energy efficiency and ecological objectives fit very well in EU Directive on energy

efficiency nr.27/2012.

Energy efficiency is a central element of the EU strategy Europe 2020 is a very important strategy for

European countries for smart, sustainable and inclusive growth and the transition to an economy in which

resources are used efficiently and ecologically.

In all this energy objectives contained in the Commission's communication "Energy 2020" represents a key

step in achieving long‐term EU countries in energy and climate.

Keywords: energy efficiency, ecology, resources, renewable energy.

Corresponding author: Maria Ichim, e‐mail: [email protected]



4

Integral-balance Method to Transient Heat, Mass and Momentum Transfer

of Integer and Fractional Order

Jordan Hristov

Abstract: The communication collates results on approximate solutions of evolution equations involving

integer order derivatives (parabolic equations) and fractional‐time derivative of Riemann‐Liouville. The

example encompasses transient heat conduction, subdiffusion equations, and transient flows of

viscoelastic fluids and transient diffusion of mass with non‐local integral conditions. The approximate

solutions are in closed forms and allow seeing clearly the controlling parameter; in case of fractional

order the retarding effect of the fading memory. Additional example demonstrating the method with a

heat conduction equation with fading memory based on the Jeffrey’s kernel demonstrates that the final

approximate solution clearly distinguishes the long‐time and the rapidly decaying memory effects in the

heat diffusion.

Keywords: Integral‐balance method; heat conduction, Subdiffusion; Viscoelastic fluid; Memory kernel;

Approximate solution.

Corresponding author: Jordan Hristov, e‐mail: [email protected]



5

Some Controversial Issues on Energy Sustainability

Miodrag Mesarović

Abstract: Energy sustainability is a long exploited issue by many organizations and individuals worldwide.

The notions of sustainability, its real meaning, frameworks, goals and even philosophical background are

very often misunderstood, misused or neglected. To achieve sustainability goals in energy field proves to

be a very difficult task in many parts of the world, particularly as different indigenous energy sources are

to be addressed, so that a few countries only are close to achieve it. The World Energy Council (WEC), a

UN accredited international organization, celebrating 90th anniversary this year, keeps energy

sustainability in its logo in an effort to ensure “sustainable energy supply for the greatest benefit of all”.

Here the major messages of WEC on the energy sustainability are incorporated into a review of numerous

controversies present in today’s energy and climate policy, and elsewhere.

Keywords: Energy sustainability index, climate change, renewable energy, energy “trilemma”.

Corresponding author: Miodrag Mesarović, e‐mail: mmesarovic@ep‐entel.com



6

Ranking Literature Sources for Multidisciplinary Research

Miodrag Mesarović

Abstract: Multidisciplinary research often proves to be a very difficult task, particularly as different

literature sources are to be addressed. Researchers in thermal science and engineering have at their

disposal different methods which guide them towards the higher ranked academic journals. However,

there are quite noticeable differences in ranks of journals in different academic fields even when the same

ranking method is applied. There are different quantitative ranking indicators, ranging from simple and

easy to calculate (Journal Impact Factor ‐ JIF), to rather complex ones, that employ iterative calculation

procedure (Scimago Journal Ranking ‐ SJR). Here the major ranking indicators for a sample of 40 journals

are presented and compared, including their mutual statistical correlation tests.

Keywords: Citation index, journal impact factor, journal ranking indicator, correlation tests.

Corresponding author: Miodrag Mesarović, e‐mail: mmesarovic@ep‐entel.com

2. Technologies and Plants



8

Design of a bulb turbine stay vane and runner for the small hydro power plant

“Grčki mlin’’ near Prokuplje

Božidar Bogdanović, Dragica Milenković, Jasmina Bogdanović-Jovanović, Živan Spasić

Abstract: Turbine stay vane (SV) and runner blades (TR), of existed bulb turbine in a small hydro power

plant “Grcki mlin” near the town Prokuplje, are produced from the plane steel panels with the same

profile inclination angle for all flow surfaces. Such blade shape causes small turbine efficiency (=0.56). By designing new SV and TR, keeping the basic dimensions of the turbine (as owner’s requirement), the

power of the bulb turbine can be increased for approximately 34% (from the current 19.2 kW to 25.8 kW).

As is shown in the paper, to design a new SV and a new TR, it should be increased turbine number of

revolution, from the current 278 rpm to 400 rpm. It can be achieved only by replacing one belt pulley

(weather on the turbine shaft or on the generator shaft). The hydraulic calculation of profile cascades in

elementary stages of turbine is presented in the paper, and here is explained the basic principles of stay

vanes and runner blades modeling. Runner blades are modeled according to blade profiles obtained in 9

chosen flow surfaces. For modeling of turbine stay vanes, profiles obtained in 7 chosen flow surfaces are

used. The paper is illustrated with characteristic drawings, as a part of technical documentations in the

production of turbine stay vanes and runner blades.

Keywords: Small hydropower plant (SHP), bulb turbine, runner blade, stay vane.

Corresponding author: Božidar Bogdanović, e‐mail: [email protected]



9

The Use of Preheated Low-Enriched Air in Downdraft Gasifiers:

Energy and Exergy Analysis

Rade Karamarković, Vladan Karamarković, Anđela Lazarević, Miljan Marašević, Nenad Stojić

Abstract: In comparison with air, the use of oxygen as a gasifying agent is less exergetically efficient. For

small‐scale cogeneration plants, smaller than 1MW of thermal power, the use of oxygen is expensive and

inefficient. The improvement in the technology of membrane separation of gases gives rise to the possible

inclusion of oxygen‐enriched air as a gasifying medium. The article aims at presenting a numerical study

analyzing the gasification of treated wood in downdraft gasifiers with preheated low‐enriched air (from 21

vol% to 30 vol%). The analyzed system consists of three subsystems: (i) for air enrichment by polymeric

membrane, (ii) for preheating of enriched air by heat exchange with the product gas, and (iii) a downdraft

gasifier. The increase of oxygen level in enriched air increases the temperature at the carbon boundary

point (optimal gasification point), the amounts of combustible gases in the product gas, energy and exergy

efficiencies and decreases the amount of air (oxygen) required for complete gasification as well as the

amount of N2 in the product gas. The preheating of enriched air by heat exchange with the product gas is

more beneficial for the gasification with lower levels of enrichment.

Keywords: Biomass gasification, Exergy analysis, Medium preheating, Oxygen enrichment, Treated wood.

Corresponding author: Rade Karamarković, e‐mail: [email protected]



10

Energy and exergy analysis of Brayton cycle with working fluid

of temperature dependent physical properties

Antun Galović, Marija Živić, Mario Holik, Ružica Končić

Abstract: In this paper, energy and entropy analysis of Brayton cycle with ideal gas of constant physical

properties and with flue gases of temperature dependent physical properties is given. The cycles are

analyzed in dependence of the pressure ratio p2/p1 and the ratio (T3/T1) of turbine inlet temperature T3

and the compressor inlet temperature T1. Irreversibility of the adiabatic processes in the turbine and

compressor is taken into account using the values of the isentropic efficiencies comp = 0.88 and turb =

0.92. In the adiabatic combustion chamber, methane completely burns by a factor of excess air, which is

determined by the temperature of flue gases on the turbine inlet. All relevant expressions are given in an

analytical form, and results are shown in diagrams and interpreted for the values of pressure ratio1.0 p2/p1 22.0 and the values of the temperature ratio T3/T1 = 3.0; 4.0 and 5.0. We studied the lower and

higher the pressure ratios and the temperature ratios than those that occur in the real performances of

the device, with the aim of quantifying the influence of the variables on borderline values of an amount of

the net work per cycle, the thermal efficiency and the entropy change of the overall system.

Keywords: Brayton cycle, temperature dependent physical properties, net work per cycle, thermal

efficiency.

Corresponding author: Marija Živić, e‐mail: [email protected]



11

Alternative modeling approaches to sulfation reactions of

calcium based sorbents injected in the pulverized coal furnace

Ivan D. Tomanović, Srđan V. Belošević, Andrijana D. Stojanović,

Dragan R. Tucaković, Titoslav V. Živanović

Abstract: Past researches of desulfurisation by direct furnace sorbent injection of pulverized sorbent into

pulverized coal‐fired boiler furnaces resulted in development of a number of mathematical models.

Reaction mechanism of sulfur reduction by injection of calcium based sorbent can be simulated by use of

different models, varying in complexity, precision and use of computational resources. In this paper,

different approaches to modeling complex calcination‐sintering‐sulfation reactions are analyzed, like

shrinking unreacted core models, grain models and pore models. In addition, we compare Borgwardt’s

semi‐empirical approach (shrinking unreacted core model) with partially sintered spheres model

(belonging to the group of grain models). Borgwardt’s model uses simplified chemical kinetics, resulting in

need for alteration of reaction parameters for each change of sorbent parameters or particle size. The

partially sintered spheres model is more complex and it requires some physical and structural parameters

of sorbent to be known. Its capability to simulate reactions of wide range of different particles and

sorbents makes it more versatile, because it simulates processes in grain, and takes into account different

particle reactant distribution and kinetics. Possibility of application of both models is evaluated, with their

advantages and limitations emphasized.

Keywords: desulfurisation, calcium, sorbent, furnace injection, modeling.

Corresponding author: Ivan D. Tomanović, e‐mail: [email protected]



12

Energy Consumption of Compressed Air Systems and

Potential of Heat Recovery with example

Milovan Medojević, Jovan Petrović

Abstract: Compressed air is one of the most important utilities for industry. It is also one of the largest

consumers of energy. Therefore, any savings made in compressed air systems have a significant impact on

costs and on the environment. While compressed air systems in general account for about 10% of total

industrial electricity consumption, this can amount to as much as 40% of the electricity bill for certain

plants. In view of this, the aim of this paper is to point out the possibilities for smart compressed air

utilization and measures to increase energy efficiency, potential energy savings in compressed air systems

in Serbia will be shown, while the special emphasis is devoted to heat recovery from air compressors. In

addition to previously mentioned, a method for quick assessment of available heat will be shown, as well

as small techno‐economic analyses.

Keywords: Compressed Air, Energy Consumption, Heat recovery.

Corresponding author: Milovan Medojević, e‐mail: [email protected]



13

Analysis of dynamic behaviour of hot water boilers during start up

Milena Todorović, Dragoljub Živković, Marko Mančić, Dragan Milčić

Abstract: Hot water boilers, as the most commonly used central units in district heating system, require

further analysis of reliability, safety and efficiency. Considerable exploitation experience and former

development have indicated new demands and possibilities of using hot water boilers, both in the

municipal heating plants and in the process industry. Today, it is not only expected to have efficient

operation in terms of energy efficiency of primary fuel, but also there are many strict requirements when

it comes to cost‐effective, reliable and safe operation. This paper presents mathematical ‐ empirical model

of a hot water boiler manufactured by “Minel – Kotlogradnja”. The dynamic behaviour of the object will

be discusses in start up regime, as one of the most critical transient regimes.

Keywords: Dynamic Behaviour, Hot Water Boiler, Start up, Transitional Operating Modes.

Corresponding author: Milena Todorović, e‐mail: [email protected]



14

Technology for manufacturing of turbine parts for

micro and mini hydroelectric power plants

Dragan Temeljkovski, Stojanče Nusev, Dragana Temeljkovski

Abstract: Turbine parts of micro and mini hydroelectric power plants can be manufactured using:

conventional casting, structure‐directed casting, and single crystal casting. The paper presents the above

technologies with an insight into the welding specificities of corrosion‐resistant steels. The examples of

acquired parts of turbine blades produced by domestic manufacturers are also presented. The

evaporative‐pattern casting method provides for objects of very complex shapes with excess material for

surface finishing of 0.3 to 2 mm, high casting hardness, surface quality with average surface roughness

from 0.4 to 6.0 m Ra, with the achieved measurement tolerance of 0.1 mm to 0.5 mm. Apart from

these advantages, the basic characteristics of the process are: high productivity, high usage of materials,

successful application in both small and large‐scale serial production, low tool and equipment costs, and

low reworking.

Keywords: Manufacturing technology, Evaporative‐pattern casting, Control device blades, Mini and micro

hydroelectric power plants.

Corresponding author: Dragan Temeljkovski, e‐mail: [email protected]



15

Vertical Limited Fluid Bed for Burning Granulated Bio, Fossil and Waste Fuel

in Power Plant Boilers and Conversion of Coal by Biomass

Radislav Vujadinović

Abstract: In this work is presented invented Vertical Limited Fluid Bed (VLFB) combustion systems

intended for burning granulated 3‐40mm, bio , fossil and waste fuel. Furthermore, here are presented

some VLFB solutions in new and in existing industrial and power plant boilers and some solutions for

conversion of coal by biomass. The base of VLFB combustion system makes Gravity Grate (GG) with

characteristic zig‐zag form and moving and burning fuel provided due to gravity. Thanks to constant

moving fuel in GG, good mutual mixture of fuel was achieved, with the air simultaneously as the

presumption of good combustion. Through the zig‐zag pillar of fuel in GG, intensive blowing by primary air

is applied. On the right side by GG is located oblique plate with the arranged nozzles for secondary air, at

the same time providing burning flown fuel particles from GG and stimulating the final combustion of

unburnt gases produced in GG. GG is modular system, so by combining modular units is possible to

achieve combustion chamber needed capacities, ranging from 1 to 300 MWth, as shown in Fig.2, 3, 4, 6.

Corresponding author: Radislav Vujadinović, e‐mail: [email protected]



16

Thermal Fatigue of Materials

Dušan Petković, Goran Radenković

Abstract: This paper describes the basic mechanisms that lead to the thermal fatigue phenomenon.

Thermal fatigue is a process of damage origination and growth in machine parts and structural

components due to changes in internal energy caused by multiple cyclic or periodic changes of

temperature. This phenomenon is produced basically by cyclic or periodic temperature changes and

complete or partial restriction of thermal deformation. The restriction may be due to external or internal

factors. The results obtained so far suggest that thermal fatigue has much in common with creep and

mechanical fatigue. At this time it is not possible to present a complete general mechanism for damage

growth in thermal fatigue, so that further research is needed. This complex phenomenon requires further

research efforts. The aim of this paper is to highlight the thermal fatigue phenomenon, its importance and

consequences which these thermal stresses can cause. In this paper the main concepts which appear in

this field was mentioned and pointed out the importance of thermal stresses. Mechanisms of initiation

and propagation of the thermal fatigue cracks are also briefly mentioned.

Keywords: Thermal fatigue, Thermal stress, Crack propagation, Failure mechanism.

Corresponding author: Dušan Petković, e‐mail: [email protected]

3. New and Renewable Energy Sources



18

Potential Fire Hazards of Renewable Energy - Horizons of Tomorrow

Miloš Banjac, Barbara Vidaković

Abstract: Dramatic climate change, caused by over consumption of coal, oil and other traditional energy

sources, as well as exhaustion of their reserves, imposed technological need to look for their substitution

with new, renewable energy sources. The exploitation of these new forms of energy, solar, wind, earth

and bio‐fuels, initiated the development and application of new technologies, so far unused in practice.

Rapid development and wide application of installations for use of renewable energy in many households

and companies opened a whole new risk and danger in the fire protection field. With the purpose of

introducing this problem to engineers in the area of fire protection, health and safety at work, this paper

systematically presents various types of facilities for exploitation of renewable energy sources as well as

potential dangers, risks and issues related to their safe operation.

Keywords: fire hazard, renewable energy sources, risk assessment, protection.

Corresponding author: Miloš Banjac, e‐mail: [email protected]



19

Possibilities and Directions for Participation of Available RES in Macedonia with

Scenarios for Achieving the 20/20/20 Goal of the EC

Mile Dimitrovski

Abstract: Protection of the environment and in particular to reducing greenhouse gas emissions, energy

import dependency of Macedonia, as well as providing greater diversity and thus security of supply of

energy, impose the necessity of further increasing the share of renewable energy sources. Macedonia has

a certain amount of non‐renewable energy sources, which are limited and also has available large

amounts of renewable energy sources, which are used only to a certain extent and the country has

relatively high utilization of renewable energy sources in total final energy consumption. The 20/20/20

Goal of the EC could be partly achieved by the energy generated from renewable sources consisting of

electricity (generated from hydro, wind and solar plants, biomass and biogas plants) and with the heat

generated from renewable sources (biomass, solar energy and geothermal energy) and biofuels.

Keywords: Biofuels, Climatic – Energy scenario 20/20/20, Energy Balance, Renewable Energy Sources.

Corresponding author: Mile Dimitrovski, e‐mail: [email protected]



20

Optical Design of a Solar Parabolic Concentrator Based on Square Flat Facets

Saša R. Pavlović, Velimir P. Stefanović, Ivan Stojanović, Suad Suljković, Dragan Kuštrimović

Abstract: We present a procedure to a design a square facet concentrator for laboratory –scale research

on medium – temperature thermal processes. The facet concentrator approximates a parabolic surface

with a number of flat square facets supported by a parabolic frame and having two edges perpendicular to

the concentrator axis. The optimum size of facets and their position of each facet are found by employing

Monte Carlo ray tracing analysis to achieve desired flux characteristics in the focal plane. A square facet

parabolic solar concentrator with realistic specularly surface and facet positioning accuracy will deliver up

to 19.628 kW of radiative power over a 25cm radius disk located in the focal plane on the focal length of

150 cm with average concentrating ratio exceeding 1200. The parabolic concentrator approximates an

ideal truncated circular paraboloid with square flat facets supported on a parabolic frame and having two

edges perpendicular to the concentrator axis. Analytical geometry and the Monte Carlo ray tracing

method are used to analyze the optical performance of the concentrator and to identify the set of

geometric concentrator parameters that allow for flux characteristics suitable for medium and high ‐

temperature applications.

Keywords: Monte Carlo method, Parabolic concentrator, Focal flux, Ray tracing analysis, TracePro

software.

Corresponding author: Saša R. Pavlović, e‐mail: [email protected]



21

Techno-economic Analysis of Photovoltaic-based Stand-alone Power System for

Supply of Metrological Masts’ Equipment

Saša Stojković, Vukman Bakić

Abstract: The paper presents the results of techno‐economic analysis of photovoltaic‐based system for

power supply of meteorological masts for wind assessment. Electrical load consists of modern digital

technology measuring equipment (anemometers, wind vanes, temperature and pressure sensors,

hygrometers, and so on), characterized as practically constant load. The obstacle lights are switched on

during night due to air traffic security. Power system consists of a certain number of photovoltaic (PV)

panels, batteries for electric energy storage, as well as charge controllers. Technical constraint is that

power supply of met masts must not be interrupted due to huge importance of measuring data for wind

assessment, which are to be used for wind farm dimensioning. Economic analysis is carried out by “Life

Cycling Costs (LCC)” method, and optimization criterion is the lowest cost of the power system.

Optimization variables were components’ sizes (number of units for PV panels and batteries), and PV

slopes. Furthermore, sensitivity analysis was carried out, and influence of the elements’ prices, interest

rates and panels’ slopes was analyzed. The analysis was done using HOMER software tool. The results of

the analysis show that for stand‐alone PV/battery power system feeding 40 W during day, and 80 W

during night the number of panels and batteries is relatively high, thus making the system considerably

expensive.

Keywords: Stand‐alone system, Photovoltaic (PV) system, HOMER, Solar power system, Meteorological

mast.

Corresponding author: Saša Stojković, e‐mail: [email protected]



22

Solar Drying of Fruits and Vegetables

Filip Mojsovski

Abstract: For on‐farm drying of small quantities of agricultural products, convective dryer with shelves

was developed. A prototype solar farm dryer for fruits and vegetables was produced. Test runs with the

dryer were carried out over a long period of time, at many locations across the country, in effort to reach

the correct drying conditions.

Keywords: psychrometrics, food drying, solar dryer, thermal storage, tomato, raspberry.

Corresponding author: Filip Mojsovski, e‐mail: [email protected]



23

Comparative Analysis Between Two Methods for

Temperature Measurement of PV panels

Uglješa Jovanović, Igor Jovanović, Zoran Petrušić, Dragan Mančić

Abstract: In this paper a comparative analysis between two methods for temperature measurement of

photovoltaic (PV) panels is presented whereas these methods are contact and non‐contact. For contact

method a DS18S20 temperature sensor is selected and for non‐contact it is a MLX90614. Both sensors

were implemented in a single microcontroller based test system. A virtual instrument made in LabVIEW is

created to monitor the operation and data acquisition as well as data storage. The accuracy of sensors is

not in issue hence it has not been evaluated, but their sensitivity to thermal gradient and ability to

measure temperature of PV panels. The main purpose of this study is to properly evaluate the sensors

before implementing them in the system for temperature measurement of PV panels.

Keywords: Contact and non‐contact temperature sensors, microcontroller, temperature measurement,

virtual instrument.

Corresponding author: Uglješa Jovanović, e‐mail: [email protected]



24

Technical and Economic Analysis of Hybrid Wind-photovoltaic Power System for

Supply of Meteorological Masts’ Measuring Equipment

Saša Stojković, Vukman Bakić

Abstract: The paper presents the results of both technical and economic analysis of the hybrid power

system which supplies measuring equipment and obstacle lights of the meteorological masts for wind

assessment. The system consists of a certain number of photovoltaic (PV) panels, batteries for electrical

energy storage and one small power wind generator. The system is stand‐alone, with no possibility of

connection to distribution network. The second technical constraint is absence of diesel or gasoline

generator, while the third constraint relates to operation continuity. It is demanded that electrical energy

must be available during 100% of time due to huge importance of wind measuring data. The load consists

of meteorological equipment for measuring, acquiring, and sending data remotely by the modem, as well

as obstacle lights for air traffic. It is supposed that load is 40 W during the day and 80 W during night. The

basic goal of the analysis is to determine the advantage of hybrid wind‐photovoltaic power system over

PV system alone, regarding the time complementarity of power resources (wind and sun). Economic

analysis is carried out using “Life Cycling Costs (LCC)“ method, as optimization criterion is minimum

system cost. The analysis was done using HOMER software tool. Results of the analysis show that hybrid

wind/PV/battery power system is much more efficient than the system which would consist of PV panels

and batteries alone, since a lower number of storage batteries are needed.

Keywords: Hybrid power system, Wind‐photovoltaic (PV) system, HOMER, Meteorological mast,

Renewable energy.




25

Technical Feasibility and Financial Analysis of Hybrid Wind-photovoltaic System for

Supply of One Educational Institution

Saša Stojković, Snežana Dragićević

Abstract: The paper presents the results of analysis of technical feasibility of the grid‐connected hybrid

system for power supply of one educational institution. The system consists of a certain number of

photovoltaic (PV) arrays, as well as small wind generators with total power of 1 kW, 3 kW and 5 kW. The

system is connected to distribution network via appropriate inverter. The basic goal is to determine

reducing the bill for electric energy, as well as pollutant emission reduction in the case of predefined load

diagram. Detailed economic analysis is carried out using “Life Cycling Costs (LCC)” method. The money

saving is determined in the cases of “normal” conditions about wind and solar energy (Belgrade). Typical

meteorological year data (TMY2) were used by HOMER software tool. Results of the analysis show that

hybrid wind/PV power system is economically viable.

Keywords: Energy efficiency, Renewable energy source, Solar energy, Wind energy, System Advisor Model

software, HOMER software.




26

Current State Wind Energy Utilisation in the Republic of Macedonia

Monika Lutovska, Vladimir Mijakovski, Cvete Dimitrieska, Vangelče Mitrevski

Abstract: Wind energy as renewable energy source with the highest growth rate in the last two decades,

is considered as a very important source of electricity for the future. According to the study WIND FORCE

which is funded and conducted by the EU, the share of wind energy in the global world electricity

generation in 2020 is estimated at 12%. So far, several studies for determination of most suitable locations

for construction of wind farms have been made in Macedonia. According to a study prepared by AWS

Truewind, atlas of wind energy potential of Macedonia is made. 15 most suitable locations for building of

wind farms determined out of this study. According to the wind map and according to conducted

measurements at 4 locations, projected installed capacity by location varies from 20 MW to 30 MW. State

owned electricity producing company (JSC Macedonian Power Plant ‐ ELEM), earlier this year, on a

location near Bogdanci, started with construction of first wind farm in the country.

Keywords: Wind, Energy, Wind farm.

Corresponding author: Monika Lutovska, e‐mail: [email protected]



27

Agricultural biomass utilization for energy purposes

Dejan Đurović, Branislav Repić, Dragoljub Dakić, Aleksandar Erić, Stevan Nemoda

Abstract: Biomass is one of key renewable energy sources in the Republic of Serbia. This is the reason for

the development of cheap thermal devices burning biomass from agricultural production as quite

available and cheap energy source. Researches in this area are very complex and in order to obtain

reliable data it is necessary to carry out theoretical and experimental research of the process. Therefore,

efforts have been made in the Laboratory for Thermal Engineering and Energy of the "Vinča" Institute to

develop a technology for utilizing bales of various sizes and shapes for energy production. Satisfactory test

results with low CO emission levels and stable thermal output of the 1.5 MW hot water boiler with

cigarette type of biomass combustion, for the purposes of greenhouse heating –– led to the new project

for building up the first combined heat and power (electricity) production facility (CHP), which will use

agricultural biomass as a fuel, in Serbia. This project will be financed by Swiss government. CHP plant will

be used for heating primary school, hospital and one hectare of greenhouse.

Keywords: Biomass, CHP, cigarette combustion, CO emission, greenhouse.

Corresponding author: Dejan Đurović, e‐mail: [email protected]



28

Biogas – Overview of the Possibilities for Implementation

in the Macedonian Agricultural Sector

Dame Dimitrovski, Mile Dimitrovski, Gordana Popsimonova, Done Tashevski

Abstract: The subject of the investigation of the article is determining the possible production of biogas in

the rural areas of the Republic of Macedonia and determining specific biogas application having in mind

the state of the art in the field, and the state of development of the agricultural sector. In the past years

Macedonian agriculture had few failed projects for production and utilization of biogas. The paper is

observing the potentials of biogas production, pros and contras for production and utilization of the

biogas. Integrated approach for utilization of biogas in the rural area has specific value in the time of

degradation of agricultural land and nonfunctional energy communities in the country. Few suggested

applications are developed that can influence the bust of the agricultural production, lower the expenses

and contribute to positive environmental impact.

Keywords: Biogas, Energy Conversion, GHG.

Corresponding author: Dame Dimitrovski, e‐mail: [email protected]



29

Utilization of crude glycerol for the production of biofuels

Bojana Danilović, Dragiša Savić, Vlada Veljković

Abstract: The production of biodiesel provides few by‐products which can be further processed into

valuable products. Crude glycerol obtained from biodiesel production has great potential as the source of

carbon in different microbial processes. Besides for the production of chemicals it can be used for the

production of biofuels. This paper reviews the possibilities of the use of crude glycerol as sole or co‐

substrate in the production of biofuels. The addition of crude glycerol to the process of anaerobic

digestion can contribute to the increase of both biogas production rate and methane yield. In some

processes the fourfold increase of biogas yield can be achieved by the addition of 4% of glycerol. Also,

crude glycerol can be used in order to overcome the barriers of low production rates and yields during the

production of biohydrogen. Additionally, these processes offer advantage in the terms of municipal solid

waste and manure treatment.

Keywords: crude glycerol, biogas, biohydrogen.

Corresponding author: Dragiša Savić, e‐mail: [email protected]



30

Renewable energy potential in the Rusanda rehabilitation center

Milana Perić, Milovan Medojević

Abstract: Energy efficiency and the rational use of energy is one of development priorities of the Republic

of Serbia, while the reduction of energy consumption from conventional sources and exploitation of

renewable energy sources is an imperative for achieving this goal. The aim of this paper is to show the

possibilities and potential of applicable measures to increase energy efficiency as well as integration of

renewable energy sources the in current energy system of Rusanda rehabilitation center facility, located in

Melenci near Zrenjanin .This paper analyzes the existing energy systems of center and upon that analysis

the corresponding energy indicators were created. These indicators offer a quick insight into the manner

of overall system functioning. Center has recognized the potential of renewable energy sources utilization

and special attention was paid to solar and geothermal energy.

Keywords: renewable sources, potential, geothermal energy, solar energy, energy efficiency.

Corresponding author: Milana Perić, e‐mail: [email protected]



31

Guide Vane Position Control of the Mini Hydro Power Plant by

Digital Sliding Mode with Additional Integral Action

Vladislav Blagojević, Miodrag Stojiljković, Živan Spasić

Abstract: The paper deals with the task of achieving the desired position of the hydraulic cylinder's piston

that is connected to the guided vane ring of the mini hydro power plant no matter on disturbances. The

purposes of the guide vanes are to control the water flow through the turbine. By varying the position of

the guide vanes the water flow is altered and the speed of the machine can then be controlled. In order to

represent as best as possible a real physical model, the mathematical model of the servo hydraulic system

with a hydraulic cylinder and proportional valve is designed. The control system is designed by applying

the variable structure system theory. The applied control algorithm is based on the digital sliding mode

with additional integral action. The conducted simulations have demonstrated that this control algorithm

provides a satisfactory positioning and great robustness.

Keywords: Mini hydro power plant, Guide Vane, Hydraulic system, Digital sliding mode, Integral action.

Corresponding author: Vladislav Blagojević, e‐mail: [email protected]



32

Recent Progress in Biomass Pyrolysis/Gasification Technologies

Velimir Stefanović, Andrijana Stojanović, Saša Pavlović

Abstract: The conversion of biomass by gasification into a fuel suitable for use in a gas engine increases

greatly the potential usefulness of biomass as a renewable resource. Gasification is a robust proven

technology that can be operated either as a simple, low technology system based on a fixed‐bed gasifier,

or as a more sophisticated system using fluidized‐bed technology. The properties of the biomass feedstock

and its preparation are key design parameters when selecting the gasifier system. Electricity generation

using a gas engine operating on gas produced by the gasification of biomass is applicable equally to both

the developed world (as a means of reducing greenhouse gas emissions by replacing fossil fuel) and to the

developing world (by providing electricity in rural areas derived from traditional biomass). In this review

we will be discussing existing techniques and recent progress in gasification and pyrolysis techniques for

the conversion of cellulosic biomass into a viable source of energy. The focus is given to biomass pyrolysis

for production of bio‐oil, co‐firing of biomass and coal and the use of co‐gasification and co‐pyrolysis, the

combination of pyrolysis and gasification to process pyrolysis products to syngas through gasification and

liquifaction of syngas.

Keywords: biomass gasification, biomass pyrolysis, co‐firing, biofuels, syngas.

Corresponding author: Andrijana Stojanović, e‐mail: [email protected]

4. Mathematical Modeling and Numerical Simulation



34

Dimensioning of Underground Vertical Heat Exchangers for Geothermal Heat Pump

Miloš Banjac, Zara Komnenić

Abstract: Ground source heat pump or a geothermal heat pump is a central heating system that transfers

thermal energy from the ground ‐ as a heat source, to the heating object ‐ as a heat sink, against a

temperature gradient. Ground source heat pump employs a heat exchanger in contact with the ground or

groundwater to extract thermal energy from the soil. These underground heat exchangers (GHE) are

consisted of a system of tubes that form the so‐called closed outer loop in which a mixture of water and

antifreeze circulates. Closed loop tubing can be installed horizontally as a loop field in trenches or

vertically as a series of long U‐shapes in wells. The size is the one of the loop tubing, i.e. the dimensioning

of underground heat exchanger is the most demanding and the most sensitive part of the calculation.

Besides heating load of the building being heated, the dimension of underground heat exchanger also

depends on the soil type and moisture content, the ground temperature and the dynamics and duration

of extraction of thermal energy from soil. Three analytical methods for dimensioning vertical underground

heat exchanger are presented in this work. The results obtained through analysis and comparisons have

shown that different calculation methods lead to variations in dimensioning in accordance to the applied

method.

Keywords: geothermal energy, ground source heat pump, dimensioning methods, vertical underground

heat exchanger.

Corresponding author: Miloš Banjac, e‐mail: [email protected]



35

Heat exchangers comparation

Kire Popovski, Igor Andeevski

Abstract: Extended surface heat exchangers are used for water and air as operating mediums, and can be

differentiated by the ribs shape. The one has sinuous type ribs, while the other one has flat lamella ribs. In

this paper comparison between both types of heat exchangers is made with reference to air velocity in the

minimum flow cross ‐ section and Reynolds' number. Better heat transfer can be provide using exchanger

with higher values of coefficient r and factor ja. Computer program for mathematical model is made and

graphical representation or the results is given.

Keywords: heat exchanger, heat transfer.

Corresponding author: Kire Popovski, e‐mail: [email protected]



36

Modeling Thermal Processes Using Bond Graphs

Gordana Janevska

Abstract: Bond graphs represent a systematic method for the modeling of systems in physics and

engineering. It is an advantage that systems from different domains (electrical, mechanical, hydraulic,

thermodynamic) are described in the same way. Bond graphs are a domain‐independent graphical

description of dynamic behavior of physical systems. The paper introduces an approach of the bond graph

modeling applied to thermal processes. The fundamental theory of bond graph focused on thermal

process is explored by considering the example of bath heated by hot fluid. Furthermore, a method to

systematically build a bond graph starting from an ideal physical model is given. In addition, procedure to

generate mathematical equations and block diagram out of a causal bond graph is presented.

Keywords: Bond Graphs, Modeling dynamic systems, Thermal processes.

Corresponding author: Gordana Janevska, e‐mail: [email protected]



37

Referent Wind Speed and Turbulence Intensity Estimation and

on-Site Wind Turbines Classification

Žarko Stevanović, Nikola Mirkov, Žana Stevanović, Borislav Grubor, Maja Đurović-Petrović

Abstract: The correct prediction of the maximum wind speed as well as wind turbulence intensity that are

expected to occur on a large time interval and consecutively the definition of the wind turbine class that is

to be installed in a given wind farm site is of crucial importance to the wind farm development. The

maximum wind speed is defined as extreme wind or reference wind speed by the standard IEC 61400‐1. A

turbine designed for a wind turbine class with a reference wind speed and estimated turbulence intensity,

is designed to withstand climates for which the extreme ten minutes average wind speed with a

recurrence period of future 50 years at turbine hub height is lower than or equal to reference wind speed

for the specific site.

This paper is dealing with uncertainty analyses of different methodologies for estimating the extreme

wind as well as turbulence intensity from available experimental datasets and uses it to guide the wind

turbine class definition. Obtained results from datasets based on two and three years measurement

period respectively have been compared and perform cost‐benefit analysis related to uncertainty of

calculated extreme wind and turbulence intensity, crucial for definition of required period for efficient site

characteristics measurement campaign. Uncertainty assessment as well as methodology of extreme wind

calculation is based on statistical tools from General Extreme Value theory.

Furthermore, from the given climatology data at the mast location, and digital terrain data, it is presented

how wind turbine class can be estimated at different wind turbines locations inside the wind farm using

Computational Fluid Dynamics technique coupled with General Extreme Value theory.

Keywords: Wind Energy, Extreme Wind, Wind Turbulence Intensity.

Corresponding author: Žarko Stevanović, e‐mail: [email protected]



38

Wind Load Modeling and Structural Response of Guyed Mast

Vukman Bakić, Milada Pezo, Gordana Kastratović, Nenad Vidanović

Abstract: Guyed masts are used for wireless communication, meteorological measurements, and even for

power transmission. The behavior of the mast is non‐linear due to its slenderness and compliant ‘guy‐

support’ system. For a guyed mast, wind load is the main factor affecting the stability of the structure. This

paper presents the results of modeling wind characteristics and associated dynamic response of a 139 m

tall guyed mast in ambient wind conditions. Modeling were performed for four wind velocities, 10 m/s, 20

m/s, 30 m/s and 40 m/s. The commercial finite element software ANSYS was used for finite element

modeling and numerical simulation of a guyed mast exposed to wind action.

Keywords: Modeling, guyed mast, wind loading.

Corresponding author: Milada Pezo, e‐mail: [email protected]



39

Numerical Investigation of Thermal Processes in Shell and Tube Heat Exchanger

Mića Vukić, Predrag Živković, Mladen Tomić, Ivan Stojanović

Abstract: Shell and tube heat exchangers (STHE) are one of the most often used apparatuses in chemical

industry. One of STHE manufacturer’s main goals is to improve their exploitation reliability and efficiency.

Two approaches in STHE design improve are possible: experimental investigation, which is very expensive

and long‐lasting, because of shell side complex geometry, and numerical investigations. Numerical

simulations can be used to check the old and to develop new, more efficient STHE designs. In this paper,

the results of the numerical simulations of fluid flow and heat transfer in laboratory experimental STHE

are presented. Numerical simulation has been performed by using PHOENICS code. The tube bundle has

been modeled by using the concept of porous media. Standard k‐� turbulence model has been used.

Keywords: Heat exchanger, Local heat transfer, Numerical.

Corresponding author: Mića Vukić, e‐mail: [email protected]



40

CFD Analysis of Forced Convection Heat Transfer

Cu-Water Nanofluids in Circular Tube

Kamil Arslan

Abstract: A nanofluid is defined as a stable, uniform suspension of nanometer sized solid particles (<100

nm) in conventional liquids such as water. Solid particles have greater thermal conductivity than fluids.

Therefore, using nanofluids in engineering devices mostly enhance heat transfer. Nanofluids are expected

to be used mostly in numerous applications in industry such as heat exchanger and cooling devices in the

future. In this study, forced convection heat transfer flow of Cu‐water nanofluid for different volume

fractions in a circular tube is numerically investigated. Water with Cu nanoparticles with a spherical size of

100 nm diameter is used as the heat transfer medium. Circular tube is heated at uniform heat flux. The

study is performed under laminar and turbulent flow condition. The three‐dimensional flow with

negligible buoyancy effects and viscous dissipation is regarded as steady‐state. The results of numerical

study are validated with experimental data in literature. Flow fields and temperature profiles in the

circular tube are investigated detail. New engineering correlations are obtained for three‐dimensional

numerical studies.

Keywords: CFD, Circular Tube, Cu‐Water Nanofluid, Forced Convection, Heat Transfer Enhancement.

Corresponding author: Kamil Arslan, e‐mail: [email protected]



41

Flow Simulation and Noise Prediction in Axial Fans

Altin Dorri

Abstract: Flow field around an axial fan surrounded by a round canal and noise propagation from it were

numerically studied. The numerical simulation was carried out by a Large eddy simulation (LES) and the

noise propagation is predicted by a hybrid method where LES provided acoustic sources to a acoustic

analogy. Results of the LES showed that maximum surface pressures occurred at blade tips which can be

considered as the main source of the noise generation.

Keywords: Axial fans, Noise prediction, Simulations.

Corresponding author: Altin Dorri, e‐mail: [email protected]



42

Numerical Investigation of the Influence of Tip Clearance on

Reversible Axial Fan Characteristics

Živan Spasić, Božidar Bogdanović, Vladislav Blagojević, Jasmina Bogdanović-Jovanović

Abstract: Aerodynamic characteristics of reversible axial fans are mainly defined by the choice of basic

design parameters of the impeller and its blades. Aerodynamic characteristics of reversible axial fans are

significantly affected by tip clearance which is the minimum distance between the tip of the fan blades

and the shroud. The size of tip clearance affects the flow structure which is also reflected on the operating

characteristics. This paper numerically investigates the influence of tip clearance on the characteristics of

a low pressure reversible axial fan with the casing diameter D′e=635 mm, and flow parameters: volumetric

flow Q = 3.61 m3/s, total pressure rise Δptot=180 Pa and rotation speed n=1405 min‐1. Numerical

simulations were performed only for the reversible axial fan with an impeller, with blades that have

straight profiles, for three values of tip clearance: 1mm, 2mm, and 3 mm. Software package ANSYS CFX

was used for the numerical simulation of flow. The results of numerical simulations are presented in

graphs p(Q), (Q and P(Q, for different sizes of tip clearance. On the basis of simulation and analysis of

the obtained characteristics, it is concluded that the increase in radial clearance of 1 mm causes a drop in

total pressure increment in the fan for about 3%, a drop in the fan efficiency of about 0.8 % and power

reduction of about 2% for the whole range of simulated flow.

Keywords: Axial Fan, Tip Clearance, Characteristics, Numerical Simulations.

Corresponding author: Živan Spasić, e‐mail: [email protected]



43

Review of Critical Heat Flux Predictions

Andrijana Stojanović, Vladimir Stevanović, Dragoljub Živković, Milada Pezo, Ivan Tomanović

Abstract: Understanding the CHF phenomenon, and in particular, the accurate prediction of flow

conditions that can lead to CHF, are important for the safe and efficient operation of many heat transfer

units including nuclear fission power reactors, fossil fuel boilers, fusion reactors, electronic chips, etc. CHF

is expected to occur during transients than steady‐state conditions. Therefore, knowledge of transient

CHF is of great importance for the safety evaluation of heat transfer units under transient conditions. The

crucial and practical importance of the CHF and the extreme physical complexity of the critical

phenomenon justify the tremendous number of experimental CHF studies that have been carried out

during the last 50 years. More research came to pay attention to the numerical simulation of boiling and

tried to find more information, which may be difficult to be found by experiments. In this paper, the

existing CHF modeling studies are discussed in order to understand the phenomena leading to CHF.

Keywords: critical heat flux, burnout, boiling crisis.

Corresponding author: Andrijana Stojanović, e‐mail: [email protected]



44

Determination of centrifugal pump operating parameters in turbine operating regime

Živojin Stamenković, Jasmina Bogdanović-Jovanović, Jelena Manojlović

Abstract: In recent times pump‐as‐turbine (PAT) systems have become very popular. In such a system a

pump is operated in reverse so that it functions as a turbine. This is especially popular in areas where the

availability of turbines is limited as pumps are typically easier to get hold. An investigation showing the

possibility of incorporation PAT aggregate in water supply system of city of Nis has been done recently.

Since this topic has become very interesting in the world, in this paper presents a review of BUTU method

and also the usage of CFX software in order to determine operating parameters of a pump operating in

turbine regime. It is presented an example of centrifugal pump operating in turbine regime and

comparison of results obtained using BUTU method and numerical simulations of fluid flow.

Keywords: PAT system, BUTU method, numerical simulation.

Corresponding author: Živojin Stamenković, e‐mail: [email protected]



45

Euler-Euler Granular Flow Model Applied on

Numerical Simulation of Liquid Fuels Combustion in a Fluidized Bed

Stevan Đ. Nemoda, Milica R. Mladenović, Dragoljub V. Dakić, Mirko S. Komatina,

Aleksandar M. Erić, Milijana J. Paprika

Abstract: In the present study a two‐fluid Eulerian‐Eulerian formulation incorporating the kinetic theory of

granular flow (KTGF) was applied to gas and solid phase flow prediction in the fluidized bed reactor.

Despite rigorous mathematical modeling of the associated physics, the drag laws used in the model

continue to be semi‐empirical in nature. Primarily, the semi‐empirical procedure is proposed for

prediction the drag law coefficients that correspond to real minimum fluidization conditions. In adopted

CFD two phase model of bubbled fluidization the energy and chemical reactions (species transport)

equations have been included. A series of numerical experiments was performed with combustion of the

liquid fuels without, and with significant water content. These estimates are unsteady, and they modeled

the time period which corresponds to flow passing time throw reactor column. Obtained results are of

interest for start of fluidization reactors when CO emission is critical. Also, the calculations were compared

with the experiments on a fluidized bed pilot furnace with in‐bed feeding of liquid waste fuels.

Keywords: CFD model, combustion, fluidized bed, granular flow, liquid fuels.

Corresponding author: Stevan Đ. Nemoda, e‐mail: [email protected]



46

A Parametric Study on Correlations for Transport Parameters in

Fixed Bed Regenerators

Milan Đorđević, Šefik Bajmak, Marko Mančić

Abstract: Several types of mathematical models approximating complex physical processes taking place in

packed bed heat regenerators are considered. Complexity of these phenomena makes an exact

mathematical description virtually impossible and simplified mathematical models in terms of averaged

quantities have been developed for their description. A number of theoretical and experimental

correlations are presented for evaluation of the effective thermal properties of packed beds. Presented

comparisons between the predictions from these correlations over a range of physical parameters and

working conditions assumed that the bed geometry is cylindrical with spherical particles of random

arrangement, the fluid and the solid thermophysical properties are temperature independents, there is no

chemical reactions and heat generation within the bed and there are some heat losses to the ambient.

Results indicate that there is no universal packed bed regenerator model and each problem should be

carefully analyzed to identify allowed simplifying assumptions and correlations for transport parameters.

Keywords: Correlations for Transport Parameters, Mathematical Modeling, Packed Bed Heat

Regenerators.

Corresponding author: Milan Đorđević, e‐mail: [email protected]



47

Numerical Prediction of Drag Coefficient for Lattice Structures

Milada Pezo, Vukman Bakić, Gordana Kastratović, Nenad Vidanović

Abstract: Wind load is the main factor affecting the stability of the structure for guyed masts.

Determination of drag coefficient forlattice structure has not been sufficiently investigate in past. There

are numerous results concerning simplified structures such as sphere or cylinder, but lattice structures

have been neglected in previous research. Numerical simulations of a flow around one segment of the

mast are presented in this paper. Three‐dimensional numerical simulations of the segment of a mast

exposed to a wind action with three models of turbulence are performed. Modeling were performed for

four wind velocities, 10 m/s, 20 m/s, 30 m/s and 40 m/s. Reynolds number for those velocities

corresponds to turbulence flow. Three models of turbulence: standard k‐ε model, RNG k‐ε model and

Reynolds stress model were used and compared with available experimental results. Drag coefficient was

calculated based on the knowledgeof pressure field, flow fieldanda reference area. The angle of attack

was also taken into account for determine the drag coefficient.

Keywords: Drag coefficient, lattice structure, CFD.

Corresponding author: Milada Pezo, e‐mail: [email protected]



48

Comparison between the energy integration of processes

for 1G/2G ethanol production and bioelectricity

Cássia M. Oliveira, Antonio J. G. Cruz, Caliane B. B. Costa

Abstract: The increase in demand for biofuels has driven the development of new technologies such as

ethanol production from sugarcane bagasse hydrolysis. This work performed energy integration in

processes for 1G/2G ethanol and electric power production using Pinch analysis. Four different scenarios

were considered in these biorefineries, since two different types of pretreatment for bagasse

(hydrothermal and diluted acid ones) and inclusion or not of pentose fermentation step were considered.

The processes with hydrothermal and diluted acid pretreatments which include pentose fermentation

step have higher ethanol production when compared to processes that do not make use of pentose

fraction to produce ethanol, but steam consumption increases in the same order of magnitude of ethanol

production. For the four scenarios evaluated the application of energy integration demonstrated a

reduction in energy consumption of more than 50% compared to the corresponding cases without

integration and of more than 30% compared to partially integrated processes, as commonly found in

Brazilian industrial plants. Besides the economical advantage, due to the decrease in costs of hot and cold

utilities, energy integrated processes increase bagasse availability for production of second generation

ethanol.

Keywords: Biorefinery, Energy Integration, Ethanol, Pinch, Pretreatment.

Corresponding author: Caliane B. B. Costa, e‐mail: [email protected]



49

Mathematical models for evaluating evaporation rates from

free water surface of indoor swimming pools

Marko Mančić, Dragoljub Živković, Jelena Manojlović, Milena Todorović

Abstract: Indoor swimming pool buildings are significant energy consumers. Energy consumption of a

typical indoor swimming pool consists of: indoor swimming pool hall ventilation 45%, swimming pool

water heating 33%, heating and air‐conditioning for the rest of the building 10%, electric equipment and

lighting 9% and sanitary hot water 3%. The greatest energy consumer is the swimming pool hall where

free water surface evaporation takes place, increasing air humidity in the hall and causing a demand of

fresh water supply for the pool. This increases energy consumption for heating and ventilation of the hall,

and for maintaining pool water temperature with the fresh water supply. Mathematical modeling of water

evaporation from free water surface of the swimming pool has brought much attention in research over

the years. In this paper, an energy model of a swimming pool hall was made, with a special focus on

mathematical models for prediction of free water surface evaporation rates in swimming pools. A review

of mathematical models of water surface evaporation has been made, with special consideration to

determination of the evaporation coefficient. A general mathematical model of water evaporation from

the swimming pool water surface is presented in the paper. Mathematical model of the swimming pool

hall is designed to be used for simulation of the indoor swimming pool multi‐zone building model.

Keywords: evaporation rate, indoor swimming pool, mathematical model.

Corresponding author: Marko Mančić, e‐mail: [email protected]



50

Software for Testing the Heat Transfer and Pressure Drop

in Vertical Thermosiphon Reboiler

Sonja Stefanov, Dragan Skobalj

Abstract: Vertical thermo‐siphon re‐boilers are ofen used in the chemical industry, especially in

petrochemical facilities. Many authors have dealt with the estimations of the pressure drop and heat

transfer in these devices. This work will present a program and estimation of the vertical thermo‐siphon

re‐boiler, using the FORTRAN77 programming language that is based on the method of Sarm and al.

Unlike previously proposed approaches and the literature this method in the estimation of the pressure

drop in pipes apparatus, takes into account the mechanism of the two‐phase flow. The results of the

program are analyzed in detail and discussed in the exploitation of real examples.

Keywords: Software, Hear Transfer, Pressure Drop, Vertical Thermosiphon Reboiler.

Corresponding author: Sonja Stefanov, e‐mail: [email protected]



51

Numerical Simulation of Friction Stir Welding

Miroslav Mijajlović, Dragan Milčić, Miodrag Milčić

Abstract: Friction stir welding is a solid‐state welding technique that utilizes thermo‐mechanical influence

of the rotating welding tool on parent material resulting with monolith joint ‐ weld. On the contact of

welding tool and parent material, significant stirring and deformation of parent material appears, and

during this process mechanical energy is partially transformed into heat. Generated heat affects the

temperature of the welding tool and parent material so proposed analytical model for estimation of the

amount of generated heat can be verified by temperature: analytically determined heat is used for

numerical estimation of the parent material's temperature and this temperature is compared to the

experimentally determined temperature. Numerical solution for analytical estimation of welding plates

temperature is estimated using finite difference method ‐ explicit scheme with adaptive grid, considering

influence of temperature on material's conductivity, contact conditions between welding tool and parent

material, material flow around welding tool etc.

Keywords: Numerical Simulation, Friction Stir Welding.

Corresponding author: Miroslav Mijajlović, e‐mail: [email protected]

5. Experimental Investigation of Processes



54

Experimental Plant for Testing of Agricultural Biomass Combustion

Zoran Čepić, Biljana Miljković, Branka Nakomčić-Smaragdakis, Nevena Šenk, Dušan Marković

Abstract: Agricultural biomass has great potential, but in our country it is used in a very small percentage

for energy purposes. Considering the intense market fluctuations of fossil fuels, and the obligations that

our country has in accordance with the Kyoto Protocol, the use of agricultural biomass as a renewable

energy source becomes significant. There are a number of ways of using biomass for energy purposes, but

combustion is certainly the most dominant one. Devices for combustion of agricultural biomass are still in

the development stage, and today the world market doesn't have a satisfactory solution. In order to

optimize the combustion process, an experimental plant for agricultural biomass combustion was

designed and built. In this experimental plant, it is possible to vary the biomass density and quantity and

the temperature of air used for combustion, because the measured parameters during combustion are

mass and temperature change in combustion chamber. The paper presents the relevant results of

combustion of wheat straw.

Keywords: Agricultural biomass, combustion, experimental plant, wheat straw.

Corresponding author: Zoran Čepić, e‐mail: [email protected]



55

Investigation of Wood Chips Combustion in Experimental Combustion Chamber

Branislav Stojanović, Jelena Janevski

Abstract: Wood chips are produced from foresting residues and by mechanical treatment it is prepared as

fuel for fully automated boilers. Their main advantage over other fuel types is that they have the shape

and dimensions that are very suitable for transport, storage and dispensing. Also if an automation of the

plant is requested, pellets provide the opportunity to manage such plant operation. By analyzing a

number of pellet combustion boilers solutions, it has been shown that there are some specific

constructional solutions that are different from traditional boilers for combustion of solid fuels. Therefore,

for the experimental combustion chamber the fuel supply from below is adopted. This type of combustion

is characterized by a steady supply of fuel and air for combustion. This paper presents the investigation of

pellets combustion in an experimental combustion chamber. The focus of this research was on the

elimination of CO in the combustion products by lowering the temperature in the boiler combustion

chamber. This was achieved through the varying refractory surface of combustion chambers. The results

show that by increasing the refractory surface of combstion chamber, higher quality of fuel combustion is

achieved, which also allows for a uniform composition of the combustion products during the

discontinuous operation of the boiler. By increasing the combustion chamber wall lining, lower values of

carbon monoxide in combustion products were also obtained.

Keywords: wood chips, combustion, refractory surface.

Corresponding author: Branislav Stojanović, e‐mail: [email protected]



56

Experimental and Numerical Study of Biomass Combustion in 50 kW Cigar Furnace

Aleksandar M. Erić, Stevan Đ. Nemoda, Dragoljub V. Dakić, Mirko S. Komatina, Branislav S. Repić

Abstract: This paper presents experimental and numerical investigations of baled agricultural biomass

combustion in the furnace capacity of about 50 kW with cigarette combustion method. In experimental

tests measured the characteristic values needed to determine the material and energetic balance, and the

quality of combustion process. As a result of numerical work, 3D CFD model of the combustion process in

the combustion chamber of this type of combustion was developed. The model includes complex thermo

mechanical processes that occur during combustion within a porous layer of bales of biomass and in the

fluid space around it. Combustion processes are considered as stationary, and was taken into account and

the impact of the environment on the temperature field within the model domain. Comparison of the

results showed satisfactory agreement with numerical results, so that the developed mathematical model

could be used to analyze the effects of structural and parametric changes to the facility.

Keywords: Biomass, Combustion, Experimental, Numerical.

Corresponding author: Aleksandar M. Erić, e‐mail: [email protected]



57

Experimental and numerical research of thermal processes in the TST tanks with

thermal oil and a phase change medium

Goran Živković, Nedžad Rudonja, Mirko Komatina, Branislav Repić

Abstract: This paper surveys a part of the activities (performed during the realization of the third year of

project III 42011 financed by the Ministry of education and science of the Republic of Serbia) on the

development of TST whose storage medium melts at the atmospheric pressure, enabling on that way the

use of the energy of phase change for energy storage. The original experimental setup adapted for use of

paraffin as a phase change media (volume 77 dm3, heating power 2.4 kW) was modified by inserting four

vertically positioned tubes (inner diameter 120 mm) filled by paraffin into the tank. The rest of the tank

was filled with thermal oil. Storage media was cooled by the air which circulates around the tank. The

research was realized in two phases: a) with thermal oil as the only storage media; b) with the

combination of paraffin and thermal oil. Inside the main body of the tank the temperature measurements

were performed by 12 thermocouples, 4 along the tanks height and 3 along the tank radius, and inside the

cylinder filled with paraffin with 4 vertically positioned thermocouples. For the development of the

numerical model of heat transfer and fluid flow processes in TST a commercial numerical package Fluent

12.1 was used, since it possesses its own routine for computation a temperature and flow fields in TST

with the change of phases, but also it allows to user to implement the package with its own model by

using the user define functions. Measurements and the numerical computation were performed for non‐

stationary as well as for stationary working regimes. A good agreement between the numerical and

experimental results was achieved.

Keywords: TES, Measurements, Numerical model, Phase change, Thermal oil, Paraffin.

Corresponding author: Goran Živković, e‐mail: [email protected]



58

Determining the Theoretical Reliability Functions of the

Thermal Power Systems in Power Plant "Nikola Tesla A"

Dragan Kalaba, Milan Đorđević, Dušan Adamović

Abstract: The objective of this paper is representation of the probabilistic reliability assessment of thermal

power systems. Exploitation research of the reliability of six power units in the fossil fuel power plant

"Nikola Tesla A" during useful life period is based on extensive longtime failure database. By applying the

reliability theory, based on statistics and theory of possibility, and using complex two‐parameter Weibull

distribution, the theoretical reliability functions of specified systems have been determined. Obtained

probabilistic laws of failure occurrences, according to which the random variable behaves, establish a

comprehensive insight in the field of probabilistic power system reliability assessment technique.

Comparison of reliability functions and indices of power units of the same type make possible to acquire a

better knowledge of current system state as well as a more accurate estimation of its behavior during

future exploitation.

Keywords: Fossil Fuel Power Plant System, Reliability, Weibull Distribution.

Corresponding author: Milan Đorđević, e‐mail: [email protected]



59

An Experimental Research of Effects of Adding a Supplementary Component

Generated by a Catalytic Reactor on the Combustion of the Primary Fuel at

Internal Combustion Engines

Miloš Milošević, Jovica Pešić, Boban Nikolić, Miodrag Milenković

Abstract: Considering strict restrictions on vehicle exhaust emissions as a part of global environmental

protection policy, as well as the compulsion for having fuel‐efficient vehicles caused by the upcoming

energy crisis reflected through the lack of fossil fuels, in this paper, the effects of adding a supplementary

component on the combustion of the primary fuel at internal combustion engines were experimentally

researched. The experimental results of the research carried out under laboratory conditions on a petrol

engine have shown that the use of a catalytic reactor, an efficient generator of the supplementary

component in the form of a plasma gas working as the endothermic plasma water vapor converter,

improves the energy value of the combustion process which may reflect in the reduction in the primary

fuels consumption, the reduction of the emission of harmful and toxic substances in the exhaust gases,

and increasing engine performances. The proposed system is easy for the installation, it does not require

modification of the equipped engine, it does not extra load vehicle electronic systems, and it is completely

self‐regulating because the amount of the produced gas is directly proportional to the engine load. The

system can be installed on any type of internal combustion engines (diesel/petrol), all engine generations,

and it can be combined to be suitable for different engine capacities.

Keywords: Catalytic Reactor, water vapor, Bubbling Internal Combustion Engines.

Corresponding author: Miloš Milošević, e‐mail: [email protected]



60

Experimental investigation of flow-thermal and operating properties

of adsorption filter prototype under climate

Miomir Raos, Ljiljana Živković, Nenad Živković, Jasmina Radosavljević, Milena Jovanović

Abstract: The paper presents the results of experimental research conducted on the original apparatuses

in the laboratory for air quality management at the Faculty of Occupational Safety in Niš. The aim of the

paper is an examination of flow‐thermal parameters, velocities of gas mixture, flow, pressure drop,

temperature, humidity, chemical pollutants test, and performance of the adsorption filter prototype in

the filter‐ventilation system. Examination of flow‐thermal parameters of the observed filter‐ventilation

system was carried out on an experimental setup with a flow rate of gas mixture up to 2000m3/h.

Experimental data were registered with appropriate measuring equipment, which helped us obtain a

picture of the behavior of the adsorption filter prototype compared to simulated parameters of the gas

mixture. By measuring and data acquisition, we reached the assumptions for identifying the observed

process, and thus the possibility of modeling and controlling process parameters.

Keywords: experiment, ventilation, flow‐thermal parameters, air purification, data acquisition, adsorption

filter.

Corresponding author: Miomir Raos

6. Energy Efficiency in Industry, Civil Engineering,

Communal Systems and Traffic



62

Survey of Potential Energy Savings in the Building Sector in Serbia

and Needed Investments

Maja N. Todorović, Dragoslav M. Šumarac, Radoslav D. Galić

Abstract: Energy consumption in buildings in Serbia has been growing steadily over the past few years and

account for the largest share of the country’s Total Final Energy Consumption (TFEC). Energy consumption

in buildings is 38% while in industry and traffic is 34% and 28% respectively. In this context, the buildings

sector provides significant opportunities for energy savings. This paper has resulted from the research

done for the “National building energy efficiency Study for Serbia” financed by World Bank and for the

national research projects No. TR 33047 and III 42012, financed by Ministry of Education, Science and

technological Development of Republic of Serbia. The paper presents the results of current energy

consumption in building sector, together with analysis of potential energy savings and assessment of

needed investmens. Also, given is market assessment of the building sector in Serbia, covering public,

residential and commercial buildings, that includes a review of existing market situation, data collection,

identification of gaps and steps to overcome it, justification of assumptions and estimates by walk through

energy audits (WTA), utility data, and information from line ministries. Recommended are cost‐optimal

sets of energy retrofit measures (ERMs) for each subsector, calculated are energy savings and payback

period, and given is an investment assessment for the future period of eight years.

Keywords: building sector, annual energy consumption, energy retrofit measures, potential energy

savings, payback period, needed investments.

Corresponding author: Maja N. Todorović



63

Heat pump application for hot water production in a hotel

Sofia-Natalia Boemi, Elli Kyriaki, Thomas Aslanidis, Agis M. Papadopoulos

Abstract: Heat pump systems offer economic alternatives of recovering heat from different sources for

use in various industrial, commercial and residential applications. As the cost of energy continues to rise, it

becomes imperative to save energy and to improve overall energy efficiency. Ii is within this light, that

heat pumps have become a key component in for the heating and cooling and DHW production in

commercial buildings.

The present paper is divided in two main sections. Initially, a review of the methods used in the design and

installation of high efficiency heat pumps is presented, focusing on the combination of heat pumps and

heat distribution systems, with respect to the building envelope’s features and the operational

requirements of the building.

A case study is then discussed, for a five hotel located in Halkidiki, an area in Central Macedonia, Greece.

The hotel replaced the liquefied petroleum gas (lpg) and oil burner that were used for providing hot water

to the spa, the restaurant, the kitchen and half of the rooms (100 rooms of 214 rooms) for the production

of hot water with four heat pumps of 16 kW each. The energy conservation achieved will be discussed, as

well as the feasibility of the intervention.

Keywords: Heat pumps, hot water production, hotel.

Corresponding author: Sofia‐Natalia Boemi, e‐mail: [email protected]



64

Possibilities of applying heta lower temperatures level for heating

by using two-stage heat pump

Šefik M. Bajmak, Milan Đorđević

Abstract: The two‐degrees pump is sometimes used into the heating supplying system, when heating

capacity is chosen depending from charge of the heating system. Based of the analysis, of maximum

heating charge the first degree condenser is about 62% from the maximum valve of the heating charge.

Maximum heating charge of the second degree condenser is as equal as maximum value of the heating

charge, hes been established about 78% of total installed power of the first and second degree

compressors’. Also annually energy consumption for the second degree compressor work is about 85‐95%

of the total consumed energy for a season heating. On the conditions’ for the town of Prizren, it is defined

number of hours for used the second degree compressors’ power.

Keywords: heat pumps, heating systems, two‐step.

Corresponding author: Šefik M. Bajmak, e‐mail: [email protected]



65

Analysis of the possibilities of using geothermal heat pumps in

the heating and cooling systems with special emphasis spa Ilidža in Peć

Šefik M.Bajmak

Abstract: One of the basic preconditions for a longer stay human in a space is tolerable difference

between the temperature of his body and the environment, that is, it is the difference that natural

temperature controllers human body can compensate. Developing awareness of lower operating costs for

heating and cooling, environmental factors and attempt to take from nature as a greater amount of

heating, respectively, cooling, influenced the emergence of advanced technical solutions. One of the most

interesting are heat pumps that take heat from the ground, on the way to producing 100% of heating or

for heating domestic hot water, use only 25 30% additional energy (usually to the compressor heat pump)

until 70 ‐75% of the energy is taken from the environment (usually ground). Globally, underground

geothermal reservoirs represent a huge potential directly usable energy. The paper analyzes the particular

characteristic of dry rocks and layers of natural groundwater. Featured is the heat content of the soil at a

depth depending on soil properties and temperature dependence of the water layer at depth h . The

procedure for defining the soil temperature, depending on the depth and season (summer, winter).

Keywords: geothermal energy, heat pumps, central heating, central cooling.

Corresponding author: Šefik M. Bajmak, e‐mail: [email protected]



66

Usage of Low-temperature Energy from the Cooling Tower

by applying Cascade Heat Pumps

Vladimir I. Mijakovski, Vangelče B. Mitrevski

Abstract: Economic and ecologic justification for the usage of low‐temperature cooling water from the

condensers (cooling towers) of TPP Bitola for heating of greenhouse complex by application of heat

pumps, connected in cascade, is analyzed and presented in this article. The unit is composed out of three

sub‐systems, each having two one‐stage heat pumps working in cascade mode. Calculation of the first

heat pump cascade is made for cooling fluid R407c, while for the second heat pump, cooling fluid R600a

(isobutene) is used. Full techno‐economic analysis of investment and operational costs on the usage of

low‐temperature cooling water at a temperature of 33C, is made. Period of investment payback is also

determined.

Keywords: cascade, heat pump, low temperature

Corresponding author: Vladimir I. Mijakovski, e‐mail: [email protected]



67

Refurbishment of Residential Buildings According to Regulation and Policy

Vladimir Jovanovic, Karin Stieldorf

Abstract: According to the First National Energy Efficiency Action Plan of the Republic of Serbia residential

buildings built in 1970s and 1980s are identified as the biggest problem regarding energy consumption in

the country due to the poor thermal properties of their building envelopes. The aim of this paper is to

evaluate building envelope retrofits for a single family house regarding state‐of‐the‐art policy in Serbia.

The paper describes specific measures that can be applied to satisfy current Regulation on Energy

Efficiency in Buildings, First NEEAP and possible incoming energy policy. A case study research and a

simulation in relation to experimental research are combined methodologies. The representative model of

the detached house is positioned in Nis, Serbia. Three retrofit solutions are evaluated through Euro‐

WAEBED and GEBA dynamic simulations. The refurbishments are compared by a reduction of heating

demands, annual savings that vary from 31% to 51% and possibility of overheating in summer. The

findings could be used as a first step in designing a renovation for typical detached houses in Serbia. More

information on benefits of refurbished homes could contribute to the increase of retrofit rates in Serbia.

Keywords: Building envelope, Energy efficiency, Policy, Refurbishment, Regulation, Serbia.

Corresponding author: Vladimir Jovanovic, e‐mail: [email protected]



68

Impact of Insulation on School Building Energy Consumption

Snezana Dragićević, Sasa Stojkovic

Abstract: The purpose of this study is to quantify the impact of insulation of various parts of building

envelopes on building energy consumption. Using DesignBuilder, a series of parametric simulation was

conducted to acquire building energy consumption data for a range of U‐values of walls, roof, and

windows of a primary school "Vuk Karadzic" in Čačak, Serbia. Analysis is conducted for annual heat losses

and benefits of the insulation measures of walls, roof and windows respectively. In addition, analysis of

heat gain and loss components was conducted for the purpose of identifying strategies for effectively

installing insulation on different parts of the building envelope. Obtained results show a possibility

measure to improve the energy efficiency of the analyzed school building by decreasing of heating power

up to 34 %.

Keywords: Heat losses, Heating power, Insulation, School.

Corresponding author: Snezana Dragićević, e‐mail: [email protected]



69

Determining important factors for improving the energy efficiency,

optimal economic and ecological characteristics of a building

Biserka Marković, Vlada Nikolić, Milica Stojanović, Olivera Nikolić, Vuk Milošević, Stevan Marković

Abstract: This paper shows the analysis of aspects of selected influence parameters for the choice and

optimization of supporting elements and the envelope of the building. On the selected model of the

building the optimal carrying structure is done through the use of prefabricated building technology, and

thus saves the building material, work power, and time for production and erection up to 50%. The

process of architectural design is in this case better, since it offers more freedom in achieving higher

flexibility and adaptability of the building. For valorization of the energy efficiency annual consumption of

the energy for heating is used. The influence of infiltration losses, and the solar and internal gains are

taken into account. The energy saving by replacing the façade, and the loggias are 13%, or 64719 kWh. By

enclosing the loggias the energy saving is 22%, or 58351 kWh.

Keywords: optimization, building technology, supporting structure, building envelope, energy efficiency,

cost‐effectiveness.

Corresponding author: Biserka Marković, e‐mail: [email protected]



70

Building Facade with Temperature Barrier

in Context of Increasing Building Energy Efficiency

Branislav Stojanović, Jelena Janevski, Milica Stojanović, Marko Ignjatović

Abstract: One of the possible ways to provide heating to the building is using temperature barriers within

the building facades. This type of heating, besides providing significant increase in building energy

efficiency, allows using low‐temperature heating sources. In this paper, special attention is given to

opaque part of the building facade with integrated temperature barrier. Due to fact that this type of

system strongly depends on temperature of this thermal element (barrier) and type and thickness of other

materials of the facade, influence of this parameters on energy efficiency was analyzed in this paper. Since

the simplest and most promising way of using geothermal energy is to use it directly, for our analysis this

source of energy was selected. Building energy needs for heating were obtained for typical residential

multi‐family building in Serbia by using EnergyPlus software. The building with all necessary input for

simulation was modeled in Google SketchUp with aid of Open Studio Plug‐in. Obtained results show that

temperature barrier represent good way to increase building energy efficiency and that applying certain

temperatures within the barrier passive house standard can be achieved.

Keywords: temperature barrier, facade, energy efficiency.

Corresponding author: Branislav Stojanović, e‐mail: [email protected]



71

Energy efficiency of thermal power plant depending on the

hydraulic load of cooling tower

Mirjana Laković, Milica Jović, Slobodan Mitrović

Abstract: This paper describes the effects of changes in hydraulic load and parameters of the atmospheric

air in the power plant cooling system with wet cooling towers. Decreasing of the hydraulic load in the

cooling tower leads to increasing of the energy efficiency of the plant, due to lower temperature of the

condenser cooling water.

With the change of the parameters of the atmospheric air there is change in the operating conditions of

the cooling tower and thus, temperature of cooled water. Cooling water temperature change affects the

change of the operating conditions of the condenser. Condensing pressure, specific heat consumption and

energy efficiency of the power plant strongly depend on the cooling water temperature. Those

dependences for the actual power plant operating conditions are presented in the paper, in case of the

different hydraulic loads of the cooling towers.

Keywords: cooling tower, hydraulic load, plant energy efficiency.

Corresponding author: Milica Jović, e‐mail: [email protected]



72

Endogenous and Exogenous Exergy Destruction and Exergoeconomic Evaluation

of Thermal Processes in a Complex Industrial Plant

Goran Vučković, Mirko M. Stojiljković, Gradimir Ilić, Mića Vukić, Miloš Simonović

Abstract: One of the roles of the Exergoeconomy is to provide energy systems designers and operators

with the information, necessary for the improvement of energy systems. It employs both economic

principles and the exergy concept, particularly taking into account the values of individual components’

exergy destruction: the thermodynamic loss due to irreversibilities within a system’s component.

The total exergy destruction occurring in a component is not only due to the component (endogenous

exergy destruction) but is also caused by the inefficiencies of the remaining system components

(exogenous exergy destruction). Hence, the care must be taken when using the total exergy destruction of

a component decisions making to optimize the overall energy system.

In this paper, a complex industrial plant is analyzed using the exergy destruction splitting in a component

into its endogenous part or that part which is due totally to the irreversibilities of the component and its

exogenous part which is due to the irreversibilities of other components within the system. The results

will then be applied to the exergoeconomic analysis with the aim of providing relevant additional

information for energy system optimization.

It is observed that the dominant effect is the of the steam generator. From the total exergy destruction in

the steam generator, 1,097.63 kW or 96.95 % come from internal irreversibility in the component, while

the influence of other components on the loss of useful work in the steam generator is only 3.05 %. Data

from exergoeconomics evaluation indicate that the best effects of increasing the efficiency of the overall

system, can be achieved with interventions on the steam generator, given that the sum of

exergoeconomics and non‐exergoeconomics costs of this component is 46.37 €/h or 80.36 %.

Keywords: exergy, exergy destruction, endogenous, exogenous, exergoeconomics, industry.

Corresponding author: Goran Vučković, e‐mail: [email protected]



73

Introducing curricula of energy efficiency and renewable energy sources

by TEMPUS project ENERESE

Ćemal Dolićanin, Bojan Kovačić, Edin Dolićanin

Abstract: Bearing in mind the significance of energy efficiency, renewable energy sources and their

environmental impacts, the State University of Novi Pazar (SUNP) has, as a pioneer in Republic of Serbia,

accredited and realised one‐year master study programme Energy Efficiency in Buildings, with the support

of WUS‐Austria, and now, as a coordinator at TEMPUS regional project, in cooperation of six Western

Balkan and four EU universities, it is preparing accreditation and realisation of two‐year master study

programme Energy Efficiency, Renewable Energy Sources and Environmental Impacts (ENERESE). The

ENERESE project intends to educate, train and deliver such specialists within a interdisciplinary and

independent problem‐solving framework. This project will fulfil this need by developing curricula and the

training programmes for integral sustainable energy design. Project aims is to train qualified master

engineers in relatively new and broad interdisciplinary field of energy efficiency and renewable energy

sources in Western Balkan project partner countries.

Keywords: education, energy efficiency, project ENERESE.

Corresponding author: Ćemal Dolićanin, e‐mail: [email protected]



74

Energy efficiency increasing of indoor swimming pools using solar technology

Dragoljub Živković, Marko Mančić, Peđa Milosavljević,

Milena Todorović, Dobrica Pejović, Bojan Stanković

Abstract: In this paper, preliminary energy balance of indoor swimming pools in the Sport and Recreation

Center “Dubočica” in Leskovac is performed. Energy efficiency analysis is done according to the results of

the performed analysis of energy balance. The most significant result of the preliminary energy balance

and energy efficiency analysis of indoor swimming pools is the proposal of measures for energy savings.

According to complexity and size of the investments required for their realization, proposed measures for

energy efficiency improvement are classified as: low‐budget, medium‐budget and high‐budget measures

of good housekeeping. Proposed high‐budget measures for energy efficiency improvement are based on

utilization of modern solar technology. Design and sizing of the system for heating sanitary hot water and

pool water is calculated using T*SOL Pro 5.0. The results show that installation of a solar thermal system

with 168 collectors type Viessmann VITASOL 200‐F SVE enable annual energy saving of 466.56 MWh, and

CO2 emission reduction of 100.78t.

Keywords: energy efficiency, indoor swimming pool, energy balance, solar technology.

Corresponding author: Dragoljub Živković, e‐mail: [email protected]



75

Energy Efficiency Measures Implemented through Projects in Serbia

Dragan Pavlović, Pedja Milosavljević, Andjela Lazarević

Abstract: Energy efficiency is becoming a priority since it helps in reducing emission of greenhouse gas

and allows a reliable energy supply with significant energy savings. Energy consumption in Serbia is

relatively high, which is particularly evident in the public and residential sectors. In order to increase

energy efficiency in Serbia a set of systematic and well synchronized measures are necessary. There is

number of strategic documents and its action plans aimed to contribute to this target in Serbia. However,

a lack of systematic incentive measures, complex administrative procedures and bad economic situation

are the reasons that Serbia is still very energy intensive country. In recent years the number of energy

efficiency projects that have been implemented in Serbia increased, as a result of different public, private

and individual initiatives and increased awareness. Reducing energy consumption is a real long‐term goal.

This paper aims to summarize importance of energy efficiency, especially of the most demanding energy

sector which is the building stock sector, and also to present basic information about the projects that

have been realized in Serbia so far.

Keywords: Buildingstock, Energy efficiency, Energy balance, Energy consumption.

Corresponding author: Dragan Pavlović, e‐mail: [email protected]



76

Calibrating Building Energy Models – “FBB” Building Case Study

Bratislav Blagojević, Marko Ignjatović

Abstract: Reducing energy consumption in buildings represents one of the greatest challenges in XXI

century. Serbia has adopted initial regulation considering building energy performance certification.

Detailed knowledge of particular building, systems serving it and energy flows within building boundaries

is needed in order to properly evaluate potential measures for reducing energy consumption. Use of

building energy simulation tools for new buildings in the design phase, as well as calibrated simulation for

existing ones is needed. In this paper, measurements for calibration of building energy model are

presented through the description of selected case study building: Feniks BB (FBB) combined office and

production building.

Keywords: Building energy model, Simulation, Model calibration, FBB building.

Corresponding author: Marko Ignjatović, e‐mail: [email protected]



77

Energy Efficiency of an Elementary School “Prva Vojvođanska Brigada”

Dušan Savić

Abstract: Today, energy costs represent an increasingly important part of total costs. Cause on the one

hand, the increase in energy prices and energy prices due to objective reasons and speculators, on the

other hand more and more stringent environmental standards, which determine the use of more

sophisticated and more expensive power plants. The international community argues that irresponsible

human activities cause climate change (primarily greenhouse gas emissions) and to prepare for the future

radical programs to reduce energy consumption, reducing greenhouse gas emissions, increased use of

renewable energy and energy efficiency. For each factory and institution individually, it is necessary to

establish a system of cost management, measurement of relative energy efficiency of individual objects

and processes and permanent effect on the cost of energy. The rise in energy costs can have a significant

impact, and possibly increase the safety requirements, standards of living and more numerous and more

sophisticated computer equipment, and the introduction of energy management. In this paper a primary

school building, its construction characteristics, the structure of the envelope and its energy infrastructure

was shown. Also there were presented and analyzed current energy consumption, volume and energy

use, and proposed that all potentially valid measures and packages of measures to increase the energy

efficiency of the building as a whole.

Keywords: Energy, energy efficiency, energy audit, heat, infiltration.

Corresponding author: Dušan Savić, e‐mail: [email protected]



78

Energy-Efficient Technologies Applied in Zero Energy Buildings

Suad Suljković, Velimir Stefanović, Saša Pavlović, Ivan Stojanović

Abstract: Today in the world there are a number of initiatives and low‐energy standards that promote

development of zero energy buildings. The complex concept of zero can be achieved in hot, moderate and

cold climates and energy efficient technologies are an important step towards achieving this goal.

This paper describes an energy‐efficient measures combined with passive and active techniques used in

zero energy buildings through examples of successfully completed projects and objects in different

climates.

Keywords: Energy efficiency, Optimization, Passive solar design, Zero energy buildings.

Corresponding author: Suad Suljković, e‐mail: [email protected]



79

Analysis of the Natural Lighting and Energy Demand in the Student Dormitory

in Terms of Architectural Design

Petar Pejić, Dušan Petković, Marko Ignjatović, Sonja Krasić

Abstract: There are many reasons for the adequate use of natural light inside the dormitories. Studies

show that natural light has a great impact on people, their physical, physiological and psychological

health, and therefore the results achieved by each person. The intensity of light required for the student

activities and the temperature inside the room is one of the major factors for the occupant comfortable

work and life. They depend directly on natural lighting or otherwise electricity is used to achieve optimal

conditions. Design building facades in relation to the orientation has a significant impact on the use of

natural light. In this paper, a comparative analysis of student rooms with different orientations and

different façade’s designs was performed in order to investigate what type of refurbishment in the facade

only is necessary in order to maximize use of natural lighting.

Keywords: Architectural Design, Natural lighting, Eaves upgrading, Thermal Comfort.

Corresponding author: Petar Pejić, e‐mail: [email protected]



80

Principles of design and construction of passive houses

Sanja Spasić

Abstract: The growing energy consumption and serious ecological crisis have caused increased focus on

renewable energy. In recent years, building of houses that promote the use of passive solar systems

became very often. The construction of such houses is more than desirable and advisable because of the

use of solar systems have enormous positive effects in reducing environmental pollution and energy

saving. The goal of this paper is to initiate the idea of the wide use of solar potential, based on the already

existing buildings and architectural examples from Europe and the world. This paper explores the

principles of design and construction of passive houses and also gives the examples from the world

practice.

Keywords: Solar energy, passive house, solar systems, architecture, energy efficiency.

Corresponding author: Sanja Spasić, e‐mail: [email protected]



81

Application of passive solar systems in architecture

Sanja Spasić

Abstract: Because of the pollution of the environment on planet Earth, unreasonable attitude towards

resources and global warming, the need for using renewable energy sources grow higher and higher, with

a special emphasis on the global importance of solar energy. Passive use of solar energy is the basic and in

the same time the cheapest way of energy use.The main reason for that is the way how it works. It

doesn’t use any expensive technology but instead of that the design and construction of the structure has

to be adapted to maximum use of solar energy. The goal of this paper is to point out the importance of

using solar energy in architecture by showing the system which should be applied in the design of

buildings, as well as by analyzing each system individually.

Keywords: Solar energy, Passive solar systems, Architecture, Energy efficiency, Trombe‐misel wall, The

greenhouse.

Corresponding author: Sanja Spasić, e‐mail: [email protected]

7. Expert Systems



84

Governance of energy transition of non-residental buildings by policy intervention

Miroslav Kljajić, Dušan Gvozdenac, Jovan Petrović, Aleksandar Andjelković

Abstract: Starting on previous experiences, which are based on undertaken energy efficiency measures,

recorded unsatisfied indicators and trends in energy consumption, energy mix and the level of

environmental pollution, the necessity and priority of the new system changes is revealed, in the building

sector and the segment of existing non‐residential buildings. Despite many efforts, systematic and

organized care about energy efficiency in non‐residential buildings is missing and consequently the

improvements, which suggests the need for new approaches to governance the process of transition of

energy systems in buildings. The aim of this paper is to analyze and explore the most suitable energy

policy intervention for success in energy transition process in non‐residential building sector in Serbia.

Professional public, stakeholders, decision makers and creators of energy policies and strategies have

different and even opposite views on how to direct the process of transition of energy systems in

buildings, what type of instruments should to be used and how to evaluate the effects of changes. The

paper deals with tracing the pathway of energy transition process in existing non‐residential buildings as

an important segment of sectorial energy activities. The importance stems from the facts that the volume

of consumption of this category is significant (from 3.5 Mtoe of final consumption in Serbia, share of

building sector is 48% from which nonresidential buildings is up to 35%), that users are vulnerable social

groups, that worsening trends of energy efficiency are evidenced and consequently becoming excessive

financial burden on the local community and the state, that disturb the health of people and the

environment because they do not use clean energy technologies and a wrong attitude about energy in the

society is created because of inadequate valuation of energy as resource of the future. The paper is based

on energy indicators in Serbia, collected through energy audit techniques and analysis of official statistics.

Multiple Criteria Analysis (MCA) method is used for analysis of the intensity of key influences on the

success of energy transition process by implementation of the energy efficiency policy in Serbia and also

for results interpretation.

Keywords: Non‐residential Buildings, Energy Transition, Policy Intervention, Multiple Criteria Analysis.

Corresponding author: Miroslav Kljajić, e‐mail: [email protected]



85

Energy systems and their use in public sector in Autonomus Province of Vojvodina

Igor Mujan, Aleksandar Anđelković, Jovan Petrović , Miroslav Kljajić

Abstract: Building sector represents one of the biggest energy consumers in European countries. Thus, the

facilities in the public sector have been in the focus of attention since they play a huge role in the building

sector energy consumption with the annually increasing energy demand and the absence of proper

energy management. The poor state of energy systems in public buildings and their inadequate operation

by the end user have driven the cooperative project between Faculty of Technical Sciences and the

Ministry of Education, Science and Technological Development on the extent of energy consumption in

the public sector which is in running for well over two years. This paper aims to present the results of the

work and define the current state and future needs of energy systems in buildings in relation to its users.

Three major parts of public building sector were covered: 22.6% of Education facilities in APV, 67.1% of

Medical facilities in APV and 58% of the Administrative sector (municipalities) in APV. The paper will show

the vast disparity between the Ordinance on energy efficiency of buildings issued in 2011 and the real

energy consumption in public sector as well as the outdated energy systems and their improper use.

Keywords: Energy Systems, Public Sector, Building, User.

Corresponding author: Igor Mujan, e‐mail: [email protected]



86

Risk Analysis Methods for Small Hydro Power Plants in Creating Insurance Policy

Andjela Lazarevic, Rade Karamarkovic, Vladan Karamarkovic, Dragoljub Lazarevic

Abstract: Small Hydro Power Plants provide more diversity in terms of financing projects, location

selection, ownership, its applications as well as insurance methods, comparing to the Conventional Hydro

Power Plants. Electricity produced by small hydro power plants could be used to improve energy

efficiency of different production facilities, domestic and public lighting and other applications. However,

those energy objects are exposed to the variety of risks that should be taken into consideration in

different ph ases of objects’ construction, operation and maintenance. Understanding of those risks is

crucial for undertaking of different techno‐economic analysis, as well as establishing of the insurance

policy for those power plants. The approaches used to create insurance policy for Small Hydro Power

Plants in certain countries depend of the technology applied and development level of the country and

will be provided in this paper.

Keywords: Small Hydro Power Plants, Energy Efficiency, Insurance Policy.

Corresponding author: Andjela Lazarevic, e‐mail: [email protected]



87

Optimization of Trigeneration Systems: A Combinatorial Metaheuristic Approach

Mirko M. Stojiljković, Mladen M. Stojiljković, Bratislav D. Blagojević

Abstract: On‐site energy supply systems with cogeneration and trigeneration are acceptable, convenient

and widely used solutions for increasing the efficiency of energy conversion, reducing pollution and

securing energy supply. In order to make these systems financially more attractive, more efficient or more

environmentally friendly, optimization of their structure, design parameters and operation is required. In

this paper, an approach to synthesis, design and operation optimization applicable primarily to the

systems for buildings energy supply is presented. Synthesis and design optimization is defined and solved

as a combinatorial problem, using genetic algorithms and particle swarm optimization, while optimal

operation regimes are determined using mixed integer linear programming, i.e. the branch‐and‐cut

method. This approach is applied to optimize structure, design and operation related parameters of a

trigeneration plant that could be used to supply a real residential settlement in Niš, Serbia. In this

example, only a financial objective function, i.e. annual total costs, is taken into account, although the

methodology might be used for other objective functions, as well as for multiobjective optimization.

Keywords: Cogeneration, Combinatorial optimization, Energy supply, Genetic algorithms, Mixed integer

linear programming, Particle swarm optimization, Trigeneration

Corresponding author: Mirko M. Stojiljković, e‐mail: [email protected]



88

Cogeneration and Heat Storage in Optimized District Heating Plants.

Impact on Heat Costs and Primary Energy Consumption

Mirko M. Stojiljković, Goran D. Vučković, Dejan M. Mitrović

Abstract: Implementation of cogeneration and heat storage technologies in the district heating systems

might result with benefits related to efficiency, environmental impact, flexibility and security in heat

supply. Impact on finances, and consequently the cost of heat depends on many factors. In this paper,

potential for implementation of cogeneration together with heat storage in a typical small Serbian district

heating system is analyzed from the heat cost and primary energy consumption viewpoints. Several

models of cogeneration units are considered, in combination with various sizes of heat storage tanks. It is

assumed that the plant operates during heating seasons only and always in an optimal regime. In order to

determine the optimal operation regime, a mixed integer linear optimization problem is defined.

Keywords: Cogeneration, District heating, Heat cost, Heat storage, Mixed integer linear programming,

Optimization, Primary energy.

Corresponding author: Mirko M. Stojiljković, e‐mail: [email protected]



89

Particle Swarm Optimization for the optimal tilt angle of solar collectors

Emina Petrović, Milica Jović, Vlastimir Nikolić, Dejan Mitrović, Mirjana Laković

Abstract: Solar energy will play an increasing important role in a future where reducing the dependence

on fossil fuels and addressing environmental issues are a priority. The energy technology sector is

experiencing marked change from its traditional architecture of large‐scale, centralized supply systems

that take advantage of significant economies of scale.

This paper deals with an optimum tilt angle and surfacing of solar collector. The annual optimum tilt angle

is dependent on many factors such as the weather condition. To find out optimum title angle of solar

collector in this work is used particle swarm optimization (PSO). The proposed methodology is shown to

successfully solve the problem.

Keywords: tilt angle, solar collectors, particle swarm optimization (PSO).

Corresponding author: Emina Petrović



90

Intelligent contemporary heating control of an amphitheatre

Žarko Ćojbašić, Milan Ristanović, Vlastimir Nikolić, Slavica Stojiljković, Nemanja Marković

Abstract: It is widely recognized nowadays that contemporary systems of building heating should be

designed in such manner that advanced central and local control is provided, which provides for both high

comfort and rational heating energy consumption. By the European standard „EN 15232 ‐ Energy

performance of buildings – Impact of Building Automation, Controls and Building Management“ building

automation, controls and building management systems that provide appropriate energy efficiency class

are demanded. In this paper such concept of control of heating system is presented through solution of

automation of high education institution amphitheatre, which provides for the highest energy efficiency

class A with contemporary concepts that provide comfort during system usage. Furthermore, such

sophisticated control systems are further empowered with intelligent functions based on application of

fuzzy and neural approaches, which add autonomous behaviour to the system that additionally stress user

friendliness and comfort. Control functions are presented along with description of proposed solutions,

while techno‐economic analysis is also briefly considered.

Keywords: Control, building automation, energy efficiency, heating, amphitheatre, computational

intelligence.

Corresponding author: Žarko Ćojbašić, e‐mail: [email protected]



91

Intelligent Control System for Thermal Vision-Based Person-Following Robot Platform

Ivan Ćirić, Žarko Ćojbašić, Vlastimir Nikolić, Tomislav Igić

Abstract: In this paper the supervisory control of the Person‐Following Robot Platform is presented. The

main part of the high level control loop of mobile robot platform is a real‐time robust algorithm for human

detection and tracking. The main goal was to enable mobile robot platform to recognize the person in

indoor environment, and to localize it with accuracy high enough to allow adequate human‐robot

interaction. The developed computationally intelligent control algorithm enables robust and reliable

human tracking by mobile robot platform. The core of the recognition methods proposed is genetic

optimization of threshold segmentation and classification of detected regions of interests in every frame

acquired by thermal vision camera. The support vector machine classifier determines whether the

segmented object is human or not based on features extracted from the processed thermal image

independently from current light conditions and in situations where no skin colour is visible. Variation in

temperature across same objects, air flow with different temperature gradients, person overlap while

crossing each other and reflections, put challenges in thermal imaging and will have to be handled

intelligently in order to obtain the efficient performance from motion tracking system.

Keywords: Computational intelligence, Genetic optimization, Thermal Vision.

Corresponding author: Ivan Ćirić, e‐mail: [email protected]



92

Classification of Mobile Objects According to Shape and Size

by Applying the Technique of Digital Image Processing

Aca Micić, Biljana Đorđević, Boban Andjelković

Abstract: Recognizing and classification of products on the conveyor belt accordingly to shape and size is

very significant in industrial processes. Economical solution of this problem implies the application of

standard industrial CCD camera, white diffuse light source and standard personal computer. The light

source gives away white diffuse light which is registered by CCD camera after the reflection from the

object surface and is being transmitted to the personal computer. Forming conditions of digital records

aren't always optimal, so they need to be processed in the most adequate way in order to make larger

quantity of informations more usable. Benefits of this method are: simple application of standard

techniques and commercial equipment, great reaction speed, contact‐less action and the possibility

includes large working surfaces in one single image. By using comparative analysis of the results obtained

with this method and results, obtained by already known methods, it's applicability can be confirmed.

Results of that research are shown in this paper.

Keywords: Digital image processing, Mobile object dimensions estimation, Pattern recognition.

Corresponding author: Biljana Đorđević, e‐mail: [email protected]



93

Non-linear contrast image enhancement

Biljana Djordjević, Boban Andjelković

Abstract: Precise notation of objects, processes and phenomena significantly affects the functionality of

mechatronical systems. Conditions, under which records of digital cameras are being realized, still aren't

optimal, so their quality needs to be improved in order to get a number of usable informations. In this

paper are presented few image filtering techniques, which contribute solving of this problem. Special

attention has been given to a group of non‐linear filters, which usage influences image contrast

modification and which obtains results that are applicable in real‐life situations. Several methods of image

contrast enhancing were analyzed: histogram equalization, adaptive histogram equalization, and method

of homomorphic filtering. Image contrast improvement and control of dynamical range are realized by

processing. Obtained results have been analyzed, estimation of original image quality and processed

image has been executed and their comparative analysis is given.

Keywords: non‐linear contrast enhancement, histogram equalization, adaptive histogram equalization,

homomorphic filtering, image quality estimation.

Corresponding author: Biljana Đorđević, e‐mail: [email protected]

8. Fluid Flow, Heat and Mass Transfer, and Combustion



96

Protective Measures Against Water Hammer

in a Long Pipeline Hydropower Plant with Pelton Turbine

Dragica Milenković, Dragan Svrkota, Milica Nikodijević

Abstract: Water hammer is an unsteady hydraulic problem which is commonly found in the penstocks of

hydropower plants. Due to either a malfunction of the system or inadequate operation conditions,

pipeline may collapse or burst. In this paper protective measures against water hammer problems in

hydropower plant Resavica with Pelton turbine are investigated. Water hammer phenomena have been

investigated as part of design process of new hydropower plant Resavica in Serbia. The small hydropower

plant Resavica is characterized by gross head of 186 meters, pipeline diameter DN800 and length of 7300

meters. Closure of the pipeline for Pelton turbine in the case of emergency shut‐down and load rejection

is modelled with closing of turbine main inlet valve, closing of the turbine needles, and combined closing

of turbine inlet valve with by pass valve. The results obtained with software developed by authors are

presented graphically and discussed.

Keywords: Long pipeline, Pelton turbine, protection, software, water hammer.

Corresponding author: Dragica Milenković, e‐mail: [email protected]



97

Flow and Heat Transfer of Three Immiscible Fluids

in the Presence of Uniform Magnetic Field

Dragiša Nikodijević, Živojin Stamenković, Miloš Kocić, Milica Nikodijević

Abstract: The magnetohydrodynamic flow of three immiscible fluids in a horizontal channel with

isothermal walls in the presence of an applied magnetic field has been investigated in the paper. All three

fluids are electrically conducting, while the channel plates are electrically insulated. The general equations

that describe the discussed problem under the adopted assumptions are reduced to ordinary differential

equations and closed‐form solutions are obtained in three fluid regions of the channel. Separate solutions

with appropriate boundary conditions for each fluid have been obtained and these solutions have been

matched at the interface using suitable matching conditions. The analytical results for various values of

the Hartmann number, the ratio of fluid heights and thermal conductivities have been presented

graphically to show their effect on the flow and heat transfer characteristics.

Keywords: flow of immiscible fluids, heat transfer, Hartmann number, magnetic field.

Corresponding author: Dragiša Nikodijević, e‐mail: [email protected]



98

Influence of Water in Liquid Fuel on the Combustion Stability in Fluidized Bed

Milica R. Mladenović, Stevan Đ. Nemoda, Dragoljub V. Dakić, Milijana J. Paprika,

Ana D. Marinković, Branislav S. Repić, Mirko S. Komatina

Abstract: This paper presents results of the experimental and numerical investigation of fluidized bed

combustion of unconventional liquid fuels fed by the lateral jet. A special emphasis is given to influence of

water content in the fuel on the combustion parameters. During the combustion of the liquid fuels with

significant water content, a withdrawal of zone of the intense combustion below the bed surface was

registered. In the paper, it is explained by the assumption that the water in the fuel boosts mixing of the

fuel and the oxidizer. This assumption was confirmed by applying Euler two‐fluid model with kinetic

theory of granular flow. Numerical simulations have shown that the enhanced mixing of the fuel and the

oxidizer is caused by instantaneous transition of the water to steam and the expansion of the inlet jet, in

case of the fuels with high content of volatiles, or spraying of the liquid fuel to fine droplets, in case of the

fuels with low content of volatiles.

Keywords: Lateral jet, Fluidized bed, Unconventional liquid fuel, Water content.

Corresponding author: Milica R. Mladenović, e‐mail: [email protected]



99

Influence of Burner Operating Parameters and Fuel Properties

On Pulverized Fuel Combustion

Branislav Repić, Dejan Djurović, Ana Marinković,

Aleksandar Erić, Goran Živković, Milica Mladenović

Abstract: Pulverized fuel firing is one of the wide modes of fuel utilization. For successful combustion of

pulverized fuel it is necessary to ensure adequate conditions by the appropriate choice of burners and

furnace characteristics. Combustion of pulverized fuel with swirl burners utilizing the swirl effects is very

significant and widely used. Swirl flows are used extensively because of their favourable influence on

stabilization and intensification of the combustion process and reduction of NOx emission. Optimal

operating conditions of pulverized fuel combustion depend on burner characteristics and fuel properties.

In the paper are presented the results of investigation of influence that constructive and operating

parameters of burner’s characteristics and fuel properties (biomass and coal) exert on pulverized fuel

combustion. Investigation of combustion of several types of fuels (biomass and coal) in swirl burner

models and prototypes were performed. Influence of the following parameters was investigated:

constructive parameters of burners (type, quarl), burner's operating parameters (velocity, temperature

and quantity of air, swirl number, excess air, concentration of pulverized fuel), and fuel properties (type,

quality, moisture, ash, volatile and combustible matters contents, pulverized fuel grinding fineness etc.).

Keywords: Burners, Pulverized fuel, Combustion, Biomass, Coal.

Corresponding author: Branislav Repić, e‐mail: [email protected]



100

Combustion Experiments with Granular Biomass in a

Fluidized Bed Facility

Milica R. Mladenović, Stevan Đ. Nemoda, Dragoljub V.Dakić, Milijana J. Paprika,

Dejan M. Đurović, Branislav S. Repić, Srđan B. Uzelac

Abstract: Rational use of limited energy resources is an increasingly important topic, and biomass thereby

takes a special place. Subject of this paper is the combustion of granular biomass – corn kernels. A

detailed description of the demonstrational‐experimental boiler, power 300 kW, combusting

unconventional solid and liquid fuels in fluidized bed. The experimental results of the combustion of

granular biomass are presented, comprising temperature field along the furnace height, outlet flue gas

analysis, as well as the FB combustion parameters of the fuel. On the basis of the obtained results, an

assessment of the suitability of FB combustion of the granular biomass and its utilization for energy

purposes are given. This assessment especially important is having in mind the 2012 problem with the

aflatoxin contamination of the corn when just 32% of the harvests were safe for human food.

Keywords: Fluidized bed, Granular biomass, Corn, Combustion.

Corresponding author: Milica R. Mladenović, e‐mail: [email protected]



101

Determination of a heat transfer coefficient for the back surface of a perforated plate

Mladen Tomić, Predrag Živković, Anica Milošević, Biljana Milutinović, Petar Đekić

Abstract: Numerical simulations were performed to determine heat transfer coefficient for back surface

of a perforated plate with square arranged cylindrical perforations. Three parameters were varied in the

study: plate porosity, pitch‐based Reynolds number and the fluid, while perforation diamter and plate

thicknes were constants. Plate porosity was varied in the range from 0.1 to 0.3 and for working fluid were

used helium, air, and carbon‐dioxide respectively. The Reynolds number was varied in the range from 50

to 7000. The Nusselt number was correlated in the function of Reynolds number, Prandtl number and

pitch‐to‐diameter ratio. On the end of the paper a comparison was done with other authors correlations.

The difference was found to be acceptable.

Keywords: heat transfer, perforated plate, pitch, porosity.

Corresponding author: Mladen Tomić, e‐mail: [email protected]



102

Determination of a perforated plate convective heat transfer coefficient

for wide range of Prandtl numbers

Mladen Tomić, Mića Vukić, Predrag Živković, Gradimir Ilić

Abstract: Numerical simulations were performed to determine heat transfer coefficient of a perforated

plate with square arranged cylindrical perforations. Three parameters were varied in the study: plate

porosity, pitch‐based Reynolds number and the fluid, while perforation diamter and plate thicknes were

constants. Plate porosity was varied in the range from 0.1 to 0.4 and for working fluid were usedt helium,

air, carbon‐dioxide and water respectively, thus making the range of Prandtl number between 0.68 and 7.

The Reynolds number was varied in the range from 50 to 7000. The Nusselt number was correlated in the

function of Reynolds number, Prandtl number and pitch‐to‐diameter ratio. On the end of the paper a

comparison was done with other authors correlations. The difference was found to be acceptable.

Keywords: heat transfer, perforated plate, pitch, porosity.

Corresponding author: Mladen Tomić, e‐mail: [email protected]



103

Research of Effectiveness of HHO Production for Use in Internal Combustion Engines

Miodrag Milenković, Miloš Milošević, Dušan Stamenković, Milan Pavlović

Abstract: HHO systems are designed to produce hydrogen and oxygen from water. The question is

whether and how much the combustion of fossil fuels in internal combustion engines can be enhanced

and complemented with such systems. There are several ways for producing HHO gas. In this paper one of

HHO systems, which uses electrolysis for obtaining HHO gas, is proposed. For electrolysis, the plates of

316L stainless steel with 15%‐ing aqueous solution of NaOH as the electrolyte were used. This research

was done in the function of obtaining a certain amount of gas under certain conditions: temperature of

generator, current, voltage, different frequency values and pulse width. Also, the required time for

obtaining one liter of HHO gas mixture was measured. This generator of HHO gas is composed of 13

panels of stainless steel 316L. With this configuration generator stands 1 liter of HHO gas per minute with

using of about 3 Wh of energy. At a constant current of I = 12.9 A, voltage of U = 26.9 V, 100% PWM pulse

width and 0.5 kHz of frequency, for 1 liter of HHO gas per minute, it was necessary to consume 2.852 Wh

of energy, while at a constant current of I = 9.8 A, a voltage of U = 27.8 V, 50% PWM pulse width and 0.5

kHz of frequency, for 1 liter of HHO gas per minute, it was necessary to consume 3.011 Wh of energy.

Keywords: Electrolysis, Generators of HHO gas, HHO gas, PWM.

Corresponding author: Miodrag Milenković, e‐mail: [email protected]



104

Long-wavelength Marangoni instability

in a binary mixture layer with nonlinear Soret effect

Slavtcho Slavtchev, Penka Kalitzova-Kurteva, Alex Oron

Abstract: The thermodiffusion or Soret effect in binary systems is called nonlinear when the

thermodiffusive flux is proportional to the temperature gradient with a coefficient being linear function of

the solute concentration, instead of constant as for linear Soret effect. The nonlinear effect is mostly

pronounced in very dilute solutions and can be significant in some separation processes.

The report deals with the long‐wavelength Marangoni instability in a thin horizontal layer of a binary

mixture, subjected to a vertical constant temperature gradient. The layer is bounded by rigid plate from

below and free non‐deformable surface from above. It is heated from below and the free surface is

considered to be poorly conducting.

The nonlinear dynamic behavior of the liquid layer is studied in the case of monotonic instability. The

solution of the dimensionless equations of mass and momentum balances, heat transfer and mass

diffusion is presented near the linear stability threshold in the form of series in a small parameter that

measures the supercriticality above the threshold. A nonlinear equation for spatiotemporal evolution of

the system is derived. The bifurcation analysis of that equation for three kinds of patterns: rolls, squares,

and hexagonal patterns, reveals the conditions for their emergence and stability.

Keywords: bifurcation analysis, long‐wavelength instability, monotonic Marangoni convection, non‐linear

Soret effect.

Corresponding author: Slavtcho Slavtchev, e‐mail: [email protected]



105

Analysis of thermodynamic parameters in the injection mold with metal inserts

Saša Ranđelović, Saša Nikolić, Mladomir Milutinović

Abstract: The process of injection molding today is the widespread industrial technology market throws

an increasing number of finished products. Although the process depends on a lot of the large number of

technological parameters is necessary to continuously monitor key thermodynamic quantities, such as

temperature, pressure, speed, melt etc. that have a decisive influence to the quality of the finished part

and the productivity of the entire process. On the example of molding complex parts for wide use to

analyze the parameters of the process.

Keywords: Injection molding, Temperature filed, Pressure filed.

Corresponding author: Saša Ranđelović, e‐mail: [email protected]

9. Environmental Protection



108

Carbon Dioxide Emission from TPP Nikola Tesla A and B units

Zoran Marković, Milić Erić, Dejan Cvetinović, Predrag Stefanović, Vuk Spasojević , Predrag Skobalj

Abstract: Low‐calorific lignite from Kolubara open‐pit mines is mainly used for heat and power generation

in "Thermal Power Plants Nikola Tesla" ‐ TENT, Obrenovac. TENT is the largest electricity producer in

Serbia. TENT units are not equipped with adequate carbon dioxide emission monitoring systems for

continuous measurements. Since the CO2 emission by lignite combustion is the primary source of GHG in

Serbia (with a share of more than 40% in total GHG emission), the IPCC methodology suggests that the

calculation of CO2 emissions shall be based on the actual coal characteristics and not on the constant

value carbon emission factor CEF =27.6 [tC/TJ] as defined by the Tier 1 methodology. This paper presents

the results of measurement/calculation of carbon and carbon dioxide emission factors of Kolubara lignite

and specific emissions of carbon dioxide from four TENT A and two TENT B units, based on the results of

in‐situ measurements and detailed laboratory analysis of Kolubara lignite, flying and bottom ash samples,

collected during in‐situ measurements of carbon dioxide emissions from these units. Analysis of the

obtained experimental results have proved that carbon emission factor of the Kolubara raw lignite CEFr

with net (lower) calorific value Qdr in the range 6 ÷ 10 MJ/kg, can be represented by a linear correlation

CEFr [tC/TJ] = 34 407 ‐ 0.5891 Qdr [MJ/kg], giving the considerably higher values for CEFr than value

recommended by the IPCC Tier 1 methodology for lignite. The result of the measurements suggest higher

specific CO2 emissions values for small thermal power units with power of 200MW (units A1 and A2)

compared with specific CO2 emissions from units of 350MW (units A4 and A6) and 670MW (units B1 and

B2).

Keywords: Carbon dioxide emission, carbon emission factor estimation, Kolubara mine low‐calorific

lignite.

Corresponding author: Zoran Marković, e‐mail: [email protected]



109

Reduction of Particulate Matter Emission of the Upgraded Electrostatic Precipitators

at Unit B2 of the TPP “Nikola Tesla”

Milić Erić, Predrag Stefanović, Zoran Marković, Predrag Škobalj,

Nikola Živković, Vuk Spasojević, Dejan Cvetinović

Abstract: According to obligations, transposition of the Directive 2001/80/EC into state legislation have

been performed: Low on air protection (Sl. Glasnik RS br. 36/09) and the Directive on Limitation emission

values for the pollutants emitted in air (Sl. Glasnik RS br. 71/10) were adopted by the Parliament, while

Electric Power Industry of Serbia (JP EPS) as a socially responsible company have started with

reconstructions and modernization of the electrostatic precipitators on all their units since 2005. TPP

Nikola Tesla B performed reconstruction of the electrostatic precipitators at unit B2 with increased power

level, during 2011.

Paper presents results of the measurements of particulate matter concentration performed as a part of

guarantee investigations for the reconstructed electrostatic precipitators. Measurements were performed

in accordance with standards ISO 9096 and EN 13284‐1, by the Institute of Nuclear Sciences Vinča,

Laboratory for Thermal Engineering and Energy as an independent institution.

Keywords: electrostatic precipitator, emission, modernization, particulate matter, reconstruction.

Corresponding author: Milić Erić, e‐mail: [email protected]



110

Indoor air parameters measurements in kindergartens

located in different urban environments

Ivan Lazović, Sandra Stefanović, Žana Stevanović, Marija Živković,

Maja Đurović-Petrović, Žarko Stevanović

Abstract: Children require good indoor environment since indoor air quality is very important for their

growth and wellbeing. Since their educational process begins in kindergarten, they spend indoors

between 5 and 10 hours a day, wherefore the quality of air within the building is of crucial importance.

This study caries out indoor air quality measurements results, performed in two naturally ventilated

kindergartens. Buildings were chosen based on urban environment features. Environmental air quality

was the main reference for choosing these buildings. One of kindergartens is located in the industrial part

of Bor city. The second is situated within Belgrade worst traffic core. The measurements were obtained

during the winter heating period, and the results implied air temperature, relative humidity and carbon

dioxide concentration. The classroom average concentration of carbon dioxide often exceeded the value

of 1500 ppm during its full occupancy, which indicates inadequate ventilation. Analysis of measurements

also determined high correlation between humidity and carbon dioxide concentration. This fact may

constitute a solid basis for implementation of the fresh air supply strategy.

Keywords: indoor air quality (IAQ), environmental air quality (EAQ), carbon dioxide (CO2), relative

humidity (RH), temperature.

Corresponding author: Ivan Lazović, e‐mail: [email protected]



111

The Environmental Indicators Related to Indoor Air Quality in Schools

Valentina Turanjanin, Biljana Vučićević, Marina Jovanović, Sandra Stefanović

Abstract: This paper presents set of environmental indicators of indoor air quality as a very important

component of indoor environment. The indoor air quality indicators are divided in three groups: physical

(temperature, relative humidity and Air Exchange Rates), gaseous (carbon dioxide, nitrogen dioxide,

ozone, formaldehyde, volatile organic compounds) and particulate (PM2.5 and PM10) IAQ indicators. The

indicators, formed for an elementary school in the urban area, are shown.

Keywords: Indoor Air Quality, Environmental Indicators, Schools, Sustainability.

Corresponding author: Valentina Turanjanin, e‐mail: [email protected]



112

Indoor Air Pollution Modeling of Belgrade Typical Dwelling

Sandra Stefanović, Marija Živković, Ivan Lazović, Žana Stevanović,

Maja Đurović-Petrović, Borislav Grubor, Žarko Stevanović

Abstract: The central concern of indoor air quality (IAQ) analysis is the prediction of airborne contaminant

dispersal in buildings. Airborne contaminants disperse throughout buildings in a complex manner that

depends on many parameters: the nature of air movements (in‐to, out‐of and within the building system),

the influence of the heating and natural ventilation, the possibility of removal by filtration or contribution,

by generation of contaminants etc. For IAQ analysis we seek to comprehensively model all of these

phenomena. The aim of this paper is to present methodology used for determination of airflow and

contaminant related phenomena. Subsequently, the goal was to model and investigate possible indoor

contaminant behavior as a result of implementation of building energy efficiency measures and GHG

emission mitigation scenarios. As a reference example representation, modeling and simulation

performance of one typical Belgrade dwelling has been performed. It incorporates developing of dwelling

idealization, schematic representation, defining its components, performing simulation and at the end

review of results.

Keywords: Indoor Air Quality, Contaminant behavior, Contaminant dispersal, Multi‐zone modeling.

Corresponding author: Sandra Stefanović, e‐mail: [email protected]



113

AHP method for waste treatments ranking in terms of impact on the environment

Biljana Milutinović, Gordana Stefanović, Goran Vučković, Mladen Tomić, Petar Djekić

Abstract: When making the decision on the selection of appropriate waste treatment, one of the

important aspects is environmental protection. Different waste treatments have different effects on the

environment, which is expressed through a variety of environmental indicators. To assess the

environmental impact of a certain waste treatment, it is necessary to carry out an adequate analysis of all

influential environmental criteria. The main problem in the analysis is to determine the indicators that

clearly and fully sublimate the most important influential factors. The presented study was carried out on

the example of waste management in the city of Niš. Several scenarios of waste management have been

made. Three experiments were conducted in order to assess influence of environmental indicators: first

experiment was done using four indicators, second was done using seven indicators and third experiment

was done using ten indicators. The comparative results of scenario analysis are presented in this paper.

Ranking of each scenario was performed based on multi‐criteria analysis, the AHP method is used. With

the increasing number of environmental indicators it is shown that it is possible to make a clearer

difference between the waste treatments in terms of the impact on the environment.

Keywords: Multi‐criteria analysis, AHP method, Waste management, Environmental Indicators.

Corresponding author: Biljana Milutinović, e‐mail: [email protected]



114

Effective and Environmental Parameters of Diesel Engines

Using Biodiesel and Biodiesel – Petro Diesel Blends

Dame Dimitrovski

Abstract: This paper describes the basic mechanisms that lead to the thermal fatigue phenomenon.

Thermal fatigue is a process of damage origination and growth in machine parts and structural

components due to changes in internal energy caused by multiple cyclic or periodic changes of

temperature. This phenomenon is produced basically by cyclic or periodic temperature changes and

complete or partial restriction of thermal deformation. The restriction may be due to external or internal

factors. The results obtained so far suggest that thermal fatigue has much in common with creep and

mechanical fatigue. At this time it is not possible to present a complete general mechanism for damage

growth in thermal fatigue, so that further research is needed. This complex phenomenon requires further

research efforts. The aim of this paper is to highlight the thermal fatigue phenomenon, its importance and

consequences which these thermal stresses can cause. In this paper the main concepts which appear in

this field was mentioned and pointed out the importance of thermal stresses. Mechanisms of initiation

and propagation of the thermal fatigue cracks are also briefly mentioned.

Keywords: Thermal fatigue, Thermal stress, Crack propagation, Failure mechanism.

Corresponding author: Dame Dimitrovski, e‐mail: [email protected]

Mramor 18251, Mramorsko brdo bb

Tel 018‐694‐550; 018‐694‐054;

018‐694‐332; 018‐694‐551;

018‐694‐552; 018‐694‐328

Akcionarsko društvo HERZ Armaturen proizašlo je iz firme Gebauer & Lehrner, koja je osnovana davne 1896. godine . Tokom svog postojanja dugog 116 godina, kompanija se specijalizovala za proizvodnju i razvoj visokokvalitetnih armatura za grejanje, hlađenje i klimatizaciju. Na čelu kompanije u svojstvu vlasnika i Generalnog menadžera nalazi se g‐din Dr Gerhard Glinzerer. Danas je HERZ Armaturen GmbH, sa oko 1.500 zaposlenih, jedini austrijski i jedan od najvažnijih proizvodača termostatskih ventila, regulacione armature, sistema podnog grejanja, kotlova na pelet, solarnih sistema i toplotnih pumpi u Evropi.

Sedište kompanije HERZ Armaturen od 1986. godine je u novoj poslovnoj zgradi u Wien – Itzendorf, A‐1230, Richard‐Strauss Strasse 22. Ovde se nalaze proizvodnja armatura, centralni magacin i poslovno rukovodstvo. HERZ Armaturen u svom sastavu ima 8 fabrika i sve su u okviru Evropske unije: Austrija, Poljska, Rumunija i Slovenija.

Kompanija HERZ Armaturen ima predstavništva u skoro svim evropskim državama, na Bliskom Istoku, Severnoj i Južnoj Americi. Oko 60% proizvedene armatura se izvozi.

Trajni uspeh HERZ Armaturen zasnovan je na proizvodnom principu, da se samo tehnički zreli i visokokvalitetni proizvodi puštaju na tržište. Dugogodišnje iskustvo, kao i specijalizacija na polju grejne i regulacione tehnike, doprineli su razvoju brojnih inovativnih rešenja u sektoru uštede energije, kao i unapredjenju oblika i dizajna HERZ proizvoda.

HERZ ‐ termostatski ventili "DE LUXE" predstavljaju simbiozu visoke tehnike i luksuznog oblika i dizajna. Osim toga, HERZ Armaturen razvija zajedno sa poznatim evropskim sistemskim proizvođačima koncepte za uvođenje regulacione armature "krojene po meri" sa ciljem uštede energije i troškova grejanja.

HERZ Armaturen poseduje moderan sistem osiguranja kvaliteta u kome mnoge firme tesno sarađuju. HERZ proizvodi se stalno podvrgavaju ispitivanjima u internacionalnim i nacionalnim nezavisnim institutima. HERZ termostatski ventili odgovaraju Evropskoj Normi (EN215).

HERZ Armaturen u Srbiji, više od 20 godina, vrši prodaju preko svojih distributera.U 2003. godini otvoreno je predstavništvo za Srbiju, Crnu Goru i Makedoniju. Od maja 2009. godine, HERZ Armaturen ima svoj poslovno‐skladišni objekat na 1650 m², Industrijska zona bb, Nova Pazova.

U sklopu poslovnog objekta nalazi se magacin na 1200 m² i školski centar, gde inženjeri tehničke podrške permanentno vrše obuku za projektante i instalatere termotehničkih instalacija.

* Senzori* Termostati, presostati* Mikroprocesorski regulatori* Regulacioni ventili* Elektromotorni pokreta i* Izmenjiva

* Centralni sistemi

čči toplote

* Merila toplotne energije

AUTOMATIKAU FUNKCIJI

www.feniksbb.com

18000 Niš, Toponički put bb018 / 4575-556, 4575-557, 4575-33311000 Beograd, Ustanička 152/4

011 / 347-3978, 288-0926

www.feniksbb.comfeniksbb feniksbb.com@

.

PREDUZEĆE ZA PROIZVODNJU, INŽENJERING, UNUTRAŠNJU I SPOLJNU TRGOVINU

Tadeuša Košćuška 56 11000 Beograd Tel/fax: +381 11 6557 930; 6557 927

http:// www.viaocel.rs e-mail: [email protected] e-mail: [email protected]

Osnovna delatnost preduzeća VIA OCEL d.o.o. je inženjering termotehničkih i termoenergetskih postrojenja, što podrazumeva sve faze počev od izrade projektno tehničke dokumentacije, izvođenja radova pa do kasnijeg održavanja sistema, trgovina proizvodima crne i obojene metalurgije. U kratkom periodu VIA OCEL je zauzeo jednu od vodećih pozicija u ovim delatnostima i postao pouzdan partner zahvaljujući visokom kvalitetu svojih usluga.

NAJZNAČAJNIJE REFERENCE:

JKP BEOGRADSKE ELEKTRANE:

Modernizacija toplotnih podstanica za daljinsko grejanje, toplovodi i priključenja objekata,

rekonstrukcija toplane Konjarnik i Novi Beograd , izmenjivačka stanica TO Novi Beograd .

JP ELEKTROPRIVREDA SRBIJE ‐ TE NIKOLA TESLA, OBRENOVAC:

Proizvodnja grejnih površina, isporuka elemenata za pregrejače

i međupregrejače, izrada i isporuka ekonomajzera , izrada i

isporuka ulaznih i izlaznih komora pregrejača pare, izrada i

isporuka parovoda, izrada i isporuka radnih kola mlina za

ugalj ‐ N 400.42,kapaciteta 130t/h. TE KRAJOVA, RUMUNIJA Izrada i isporuka aksijalnih ventilatora dimnog gasa.

Preduzece Nova Yutkl doo Nis je generalni zastupnik Nova TKL doo Duga Resa Karlovac (nekadasnja" Jugoturbina") za prostore Srbije, BIH, i Crne Gore. Pretezna delatnost preduzeca je distribucija, nalevanje i izrada novih kliznih lezajeva koji se primenjuju u raznim oblastima industrije(na kompresorma, EM velike snage , reduktorima, pumpama), crnoj i obojenoj metalurgiji, rudarstvu(na mlinovima uglja, cementa i rude), energetici ( klizni lezajevi parnih i hidro turbina i generatora), brodogradnji (lezajevi na brodskim motorima) kao i remont reduktora raznih dimenzija i snaga.

Neki od vaznijih korisnika nasih usluga su HE Bistrica,HE Perucica, TE Kolubara, TE Gacko, TE Ugljevik, RTB Bor i mnogi drugi na ovim prostorima.

U saradnji sa firmom Inkla GmbH iz Austrije pored ove delatnosti Nova Yutkl je distributer zaptivnih materijala americke kompanijea GARLOCK (pletenice, ravne zaptivke, semeninzi za industriju i energetiku, EVSP setovi za zaptivanje na vretenima ventila i vratilima pumpi. PS zaptivke u prehrambenoj , farmaceutskoj i hemijskoj industriji. Takode smo isporucivali i mozemo da isporucujemo i opremu za Termo i Hidro elektrane Ruske proizvodnje kao i rezervne delove LMZ turbine i rezervne delove generatora ruske proizvodnje. Od nedavno smo poceli distribuciju i isporuku regulacionih ventila za paru i toplu vodu engleskog proizvodaca WEER.

S obzirom na siroku nasu delatnost koja je vezana pretezno za energetiku tj. Hidro i Termo centrale otvoreni smo smo za svaku vrstu saradnje i pozivamo sve zainteresovane da nam se obrate putem E‐maila na adresu: [email protected] .

Nova Yutkl doo Nis

Sasa Todorovic

Simterm 2013-Book of Abstracts

Documents

Transcript of Simterm 2013-Book of Abstracts