EXPERIMENTAL INVESTI GATION OF HEAT TRANSFER ......8.73% at 0.02% concentration when compared to...

International Journal of Mechanical Engineering and Technology (IJMET)Volume 8, Issue 8, August 2017, pp.

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ISSN Print: 0976-6340 and ISSN Online: 0976

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EXPERIMENTAL INVESTI

TRANSFER COEFFI

FACTOR IN A DOUBLE P

EXCHANGER WITH AND W

TAPE INSERTS

GLYCOL

Dept. of Mechanical Engineering

Dept. of Mechanical Engineering

ABSTRACT

Heat transfer coefficient and friction factor of ZnO Nanofluid passing in the

double pipe heat exchanger with and without twisted tapes along with wire coil are

placed in the experimental investigation. The ratio of the base fluids are 60:40 water

and Propylene glycol are considered. The volume concentrations of ZnO Nanofluid

0.15, 0.25, and 0.4 % are taken. The double pipe heat exchanger has an inner tube in

which different twisted tape configurations are inserted, the twist ratios are 10, 5, and

3 are taken. The flow rates are taken for cold and hot water, the ranging of cold and

hot water are 0.083 to 0.3116 and 0.1466 Kg/Sec are taken in the experimental study.

The results shows that the Nusselt number for double pipe heat exchanger was

increased at 0.4% concentration of ZnO Nanofluid with twisted tape at the ratio of

H/D= 3 the heat transfer enhanced by 23.56% and the friction factor was increased

by 15.32% compared with the base fluid. The Reynolds number ranging from 3000 to

8000. The error ranging of �Keywords: Double pipe heat exchanger, Heat transfer, Friction

Twisted tape, Wire coil.

Cite this Article: T. Vijaya sagar,

heat transfer coefficient and friction factor in a double pipe heat exchanger with and

without twisted tape inserts using zno

Journal of Mechanical Engineering and Technology

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International Journal of Mechanical Engineering and Technology (IJMET) 2017, pp. 94–106, Article ID: IJMET_08_08_012

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=8

6340 and ISSN Online: 0976-6359

Scopus Indexed

EXPERIMENTAL INVESTIGATION OF HEAT

TRANSFER COEFFICIENT AND FRICTION

FACTOR IN A DOUBLE PIPE HEAT

EXCHANGER WITH AND WITHOUT TWISTED

INSERTS USING ZNO-PROPLYENE

GLYCOL NANO FLUID

T. Vijaya sagar

Dept. of Mechanical Engineering K L University Guntur,

Andhra Pradesh, India

Dr.Y.Appalanaidu

Dept. of Mechanical Engineering K L University Guntur,

Andhra Pradesh, India




ylene glycol are considered. The volume concentrations of ZnO Nanofluid



en. The flow rates are taken for cold and hot water, the ranging of cold and



concentration of ZnO Nanofluid with twisted tape at the ratio of


by 15.32% compared with the base fluid. The Reynolds number ranging from 3000 to � 5 of the experiment.

Double pipe heat exchanger, Heat transfer, Friction factor, Nanofluid,

T. Vijaya sagar, Dr.Y.Appalanaidu, Experimental investigation of


without twisted tape inserts using zno-proplyene glycol nanofluid, International

Journal of Mechanical Engineering and Technology 8(8), 2017, pp. 94–106.

T/issues.asp?JType=IJMET&VType=8&IType=8

T&VType=8&IType=8

GATION OF HEAT

CIENT AND FRICTION

IPE HEAT

TWISTED

PROPLYENE




ylene glycol are considered. The volume concentrations of ZnO Nanofluid



en. The flow rates are taken for cold and hot water, the ranging of cold and



concentration of ZnO Nanofluid with twisted tape at the ratio of


by 15.32% compared with the base fluid. The Reynolds number ranging from 3000 to

factor, Nanofluid,

Experimental investigation of


International

T. Vijaya Sagar,Dr.Y.Appalanaidu

http://www.iaeme.com/IJMET/index.asp 95 [email protected]

1. INTRODUCTION

Heat exchangers are the equipment that is commonly used to transfer heat between two

passing fluids at different temperatures without any mixing of fluids with each other. Transfer

of energy from one fluid to another fluid can be done modes of heat transfer. Heat exchangers

with the convective heat transfer of fluid inside the tubes are frequently used in the many

engineering applications like heavy industries, power plants, automotive, chemical industries,

metallurgical, electronics components, refrigeration’s, air conditions and duct systems.

Enhancement of heat transfer intensity in all types of thermo technical apparatus is of very

important for industries. For the savings of power generations, it also leads to a moderating in

size and weight. Up to the present work, several heat transfer enhancement techniques have

been developed. Twisted tapes is one of the most important element of enhancement

techniques. The combination of water and propylene glycol are being used as the coolant due

to advantages of new technologies there are a number of improvements in the field

engineering applications including the enhancement of heat transfer capabilities. Tubes with

rough surfaces have much higher heat transfer coefficients than tubes with smooth surfaces.

Therefore, tubes surfaces are often intentionally roughened, corrugated, or finned in order to

enhance the convection heat transfer coefficient and thus the convection heat transfer rate.

Turbulence flow in tube the heat transfer has been increased as much 40% by roughening the

surface. Among many techniques investigated for augmentation of heat transfer rates inside

circular tubes, a wide span of inserts has been utilized, specifically, when turbulence flow is

considered.

The inserts investigated that included coil wire inserts, brush inserts, mesh inserts, strips

inserts, twisted tapes inserts etc. Augmentation of convective heat transfer in internal flow

with tape placed in tubes is a well approved technique hire in industrial particles. The present

investigation is aimed at studying the frictional and heat transfer characteristics in turbulent

region using varying width twisted tape with coil spring placed under constant will heat flux.

The objective of using varying width twisted tapes is to minimize the pressure drops

associated with full width twisted tapes without seriously impairing the heat transfer

augmentation rates and to achieve material ranges .However, due to micron size of particles

there were several problems like sedimentation and erosion of tubes and pumps while in

transmit. In the resent past the availability of Nano material’s renewed the interest in the

application of Nanofluids. The suitability and performance of the conventional fluids can be

enhanced by introducing Nano particles like Al2O3, TiO2, ZnO and CuO, by converting them

in to Nanofluids.

[1] Chandra Sekhara teddy: The experimental carried out by heat transfer coefficient

and friction factor for Tio2 Nanofluid passing in a double pipe heat exchanger with and

without heical coil placed are experimentally studied. The volume concentrations are

0.0004% to 0.02% of Nanofluid are taken and the based fluid ratio are 60:40 for water and

ethylene glycol. The heat transfer coefficient and friction factor are enhanced by 10.83% and

8.73% at 0.02% concentration when compared to base fluid without helical coil. Heat transfer

coefficient and friction factor further get enhanced by 13.85% and 10.69% respectively for

0.02% concentration Nanofluid when compared to base fluid flowing in a tube with helical

coil placed P/d = 2.5.

[2] P.V.Durga Prasad and Gupta: The experimental carried out by investigation on heat

transfer enhancement on U-bend heat exchanger and twisted tape using water Al2O3

Nanofluid. The volume concentration of Nanofluid are 0.01% and 0.03% are taken. Twist

ratio for twisted tapes are ranging between 5 and 20. The results showed that the Nusselt

number of entire pipes for 0.03% concentration of Nanofluid with twisted tapes placed is

Experimental investigation of heat transfer coefficient and friction factor in a double pipe heat exchanger with and without twisted tape inserts using zno-proplyene glycol nanofluid


enhanced by 31.28% compared to the water. The friction factor increased by 1.23 times

compared with the water while placing the twisted tapes H/D = 5.

[3] Hasanpour, Farhadi and Sedighi: The experimental carried out by which has inner

tube filled with various categories of twisted tapes. From conventional to modified types

which includes perforated V-cut and U-cut types. The twist ratios are 3, 5 and 7 and the

Reynolds number range from 5000 to 15000. The results showed that the Nusselt number and

friction factor for all cases of twisted tapes corrugated tube are more than the empty

corrugated tube.

[4] V. Chandraprabu and Sankaranarayanan: The experimental carried out by heat

transfer performance of Nanofluid Al2O3 water and CuO water is expressed by using the

condensing unit of an air conditioner. The volume concentrations of Nanofluid are 1, 2, 3, and

4. Two nanofluids shows better heat transfer rate than does the base fluid. The Cuo water

Nanofluids better heat transfer rate than Al2O3 water Nanofluids.

[5] P.V.Durga Prasad and gupta: In this study the volume concentrations of Al2O3

Nanofluid are 0 to 0.03%, and longitudinal strip placed of aspect ratios are 1, 2, 4, and 12 are

taken. The results shows that the Nusselt number and friction factor of entire pipes for 0.03%

concentration of Nanofluid with longitudinal strip placed ratio of 1 enhances by 47.35% and

1.21 times compared with base fluid.

[6] Hamid and Mohammadiun: In this study of Al2O3/ethylene glycol (EG) are taken,

The three different volume concentrations of Al2O3 Nanofluid are 0.5, 1, and 1.5% and at

three different twist ratios of twist tapes y/w = 2, 3.6 and 5 are taken. The results shows that

utilization of twists together with Nanofluid tends to increase the heat transfer and friction

factor, the thermal performances factor 4.2 is found with the use of Al2O3/EG Nanofluid at

concentration at 0.5% by volume is corrugated tube together with twisted tape at twist ratio 2.

[7] Kushalkamboj and rohitsharma: In this study experimentally investigated the heat

transfer augmentation by means of divergent-convergent spring coil turbulent and tried to find

the optimum pitch which augmentation heat transfer is maximum. The pitch ratios are 5, 10

and 15cm. The Nusselt number enhanced by 26.76% and maximum friction factor is 66.87%

at pitch ratio=5cm, thermalperformance factor maximum is 1.0525 at pitch ratio=15.

[8] SarmadA.Abdal Hussein: Experimentally Investigation of heat transfer and friction

factor of double pipe heat exchanger, inserted semi circular disc baffles with spacing of 15cm

and 45cm carriedout for turbulent flow. The semi circular disc baffles 15 and 45cm the heat

transfer rate by 1.9 and 1.3 times of smooth tube are placed. The results shows that the

inserted tape with 15cm has maximum friction factor than that with 45cm and the

experimental data with average error of �7.8%for nusselt number and �6.5%for friction

factor.

[9] Anil Singh Yadav: Investigation on double pipe heat exchanger with and without

twisted tapes at different mass flow rate. As compared to conventional heat exchanger, the

augmented has heat exchanger has shown a significant improvement in heat transfer

coefficient by 40% for half-length twisted tape. At the equal mass flow rate heat transfer

performance of half-length twisted tape is maximum compared to smooth tube. The results

shows that on unit pressure drop basis the heat transfer performance of smooth tube is

maximum compared to twisted tape, thermal performance of smooth tube is better than half-

length twisted tape by 1.3-1.5 times.

[10] Madhav Mishra and Nayak: Experimentally investigation of effectiveness and

overall heat transfer coefficient of double pipe heat exchanger. Triangular baffles of 100mm

and 50mm pitches enhance the average effectiveness by 1.42 and 1.62 times in parallel flow



and in counter flow are 1.338 and 1.62. The average heat transfer rate are 1.6 and 1.9 times in

parallel flow and in counter flow are 1.48 and 1.67 that of smooth tube respectively.

[11] Swathi and Kishore: Experimentally investigation of effectiveness in double pipe

heat exchanger, setup-1 rectangular fins and twisted tapes insert inside pipe, setup-2 only

twisted tapes without fins insert outside pipe. Effectiveness is higher for setup-1 heat

exchanger then setup-2 heat exchanger. LMTD and Turbulence increased for setup-1 heat

exchanger than setup-2 heat exchanger. So by using fins in addition to twisted tapes

effectiveness can be enhanced.

[12] Amar Raj and Sing Suri: Multiple square perforated with square wing twisted tape,

the width ratio is wd/wt 0.042 to 0.167. The results showed that the maximum value

increases at 6.96 and 8.34 times nusselt number and friction factor at depth ratio of 0.167 with

compare to plain tube.

[13] BehroutRaei: fully developed turbulence slow heat transfer and the pressure drop

behavior of Al2O3/ water. The volume concentrations of nanofluids are 0.05 to 0,15 are taken.

The results shows enhancement of heat transfer and friction factor are 23 and 25% at 0.15

volume concentration compare with base fluid.

[14] K.M. Elshazly: Thermal performance of shell and coil heat exchanger with different

ferent coil torsions. Five helical coil tubes ranging between 0.0442< and > 0.1348 are taken.

The volume concentration of nanofluid are 0 to 2% are taken. The results shows that reduces

the coil torsion and enhance heat transfer rate of Nanofluid.

[15] Byung-Hee chen: Alumin Nanofluid and transformer oil of which flow through

double pipe heat exchanger system in the laminar flow enhances the heat transfer coefficient.

At highest concentration the heat transfer rate is increases.

The data on the mixture of propylene glycol and water based Nanofluid passing in a tube

with inserts twisted tapes with coil springs is not available in the literature. Therefore, the

focus of the present work is on the estimation heat transfer coefficient and friction factor of

propylene glycol and water mixture based on ZnO Nanofluid passing in double pipe heat

exchanger with twisted tapes with coil spring are placed in investigation. The experiments on

heat transfer are conducted by the Reynolds number range from 3000 to 8000. Based on the

experimental data generalized correlations are proposed for Nusselt number and friction

factor.

2. PREPARATION OF ZNO NANOFLUID

Preparation of Nanofluids is one of the key tasks for enhancing the heat transfer by using

nanofluids in many applications .particle agglomeration and particles dispersion in base fluid

are two key factors to look upon for preparing a stable nanofluid , particle agglomeration

leads to increase in particle size and particles should be well dispersed so that there will be no

settlement in the base fluid and generally there are two methods for preparation of one step

method and two step method. The Zno (Zinc oxide) nano particles used in this study were

purchased from Sigma-Aldrich having 50nm nearly spherical particles. The two step method

is used for preparing the nanofluid .the base fluid used in this experiment is water -propylene

glycol mixture (60:40). Firstly, the nano particles are dissolved in the base fluid and of

20litres and constantly stirred for 45 min and for eliminating the agglomeration and for the

proper dispersion of the nano particles the fluid is sonicated for 2h.the nano fluids are

prepared in three different concentrations (i.e. 0.15%, 0.25% and 0.4%) the amount of

particles required for each concentration is calculated by:

Experimental investigation of heat

exchanger with and without twisted tape inserts using zno

∅

ρ��C��

A) Thermal conductivity of Nanofluid:

Thermal conductivity is one of the important parameter which has a impact on the heat

transfer enhancement .the effective thermal conductivity of Nanofluid is measured by KD2

PRO thermal property meter .which is done by probe (Read time

for Nanofluid and base fluid are measured at different temperatures to predict the Thermal

conductivity of Nanofluids is calculated using the following equation given by Hamilton and

Crosser:

��In the above equations ∅ , p ,

and density subscripts basefluid and Nanofluid refer to the base fluid and Nanofluid

respectively. z is the empirical shape factor as the Nano particles used in this investigation

are nearly spherical z is taken as 3 cp is the specific heat.

Figure 1 represents the comparison between the ratio of thermal conductivity of Nanofluid

to the base fluid and the double pipe heat exchanger inlet temperatures from the literature

thermal conductivity of Nano fluid found to be increasing with increase in temperature and

Nano particle volume concentration. in the above graph the two trends depicts the measured k

value of 0.4% ∅ nanofluid and theoretical values of k obtained from hamilton

Experimental investigation of heat transfer coefficient and friction factor in a double pipe heat

exchanger with and without twisted tape inserts using zno-proplyene glycol nanofluid

∅ � � �� ! " 100 (1)

�� ∅ρ% & '1 ( ∅)ρ*� (2)

�� '1 ( ∅) +�,-�.-/C�*� & ∅+�0�.-/ C%� (3)

Thermal conductivity of Nanofluid:


ment .the effective thermal conductivity of Nanofluid is measured by KD2

PRO thermal property meter .which is done by probe (Read time- 60 Seconds).the values of k


onductivity of Nanofluids is calculated using the following equation given by Hamilton and

�� 1��'234)15�3∅'234)'15�31�)1��'234)15�3∅'15�31�) �6� (4)

, p ,7 ,8 refer to the volumetric concentration ,particle, viscosity



erical z is taken as 3 cp is the specific heat.

Figure 1

represents the comparison between the ratio of thermal conductivity of Nanofluid


ivity of Nano fluid found to be increasing with increase in temperature and


nanofluid and theoretical values of k obtained from hamilton-crosser

transfer coefficient and friction factor in a double pipe heat proplyene glycol nanofluid


ment .the effective thermal conductivity of Nanofluid is measured by KD2

60 Seconds).the values of k


onductivity of Nanofluids is calculated using the following equation given by Hamilton and

refer to the volumetric concentration ,particle, viscosity



represents the comparison between the ratio of thermal conductivity of Nanofluid


ivity of Nano fluid found to be increasing with increase in temperature and


crosser model


.the measured values are much higher than the prediction . probably because these classical

models do not account for the parameters like particle size, Brownian motion and Nano

layering .which are important to consider in Nanofluids.

B) Viscosity of Nanofluid :

The viscosity of the Nano fluid is measured by using the rotary viscometer

(BROOKFIELD) .the reading were taken at different concentrations an

Nano fluid. The viscosity of the Nano fluid increases with increase in the particl

concentration and decreases with the increase in temperature. is observed from the

measurements and the literature as well

Figure 2 represents the comparison between the viscosity and the fluid inlet temperatures

of the double pipe heat exchanger temperature is an important parameter to consider for

viscosity of Nanofluids. The viscosity of the Nanofluids decreased with increased in

temperature. The graph depicts that the Nanofluid of highest concentration i.e., 0.4% at lowest

temperature shows highest value of viscosity and vice versa.

3. EXPERIMENTAL SETUP

The experimental unit consists of flow meters, thermocouple, u tube manometer data logger,

receiving tanks(hot, cold) induction motor of 0.5 Hp capacity .The test section consists of

concentric pipes and u bend made of stainless steel inner diameter of inner tube is 0.019

length of test section is 2m,u bend radius of 0.32

small compared to surface of concentric pipes so heat transfer in bend region can be

neglected. Two motors of 0.5Hp capacity are used to pump the Nanofluid and

hot fluid is pumped through the annulus of the concentric tube and Nanofluid flows through

inner tube. Flow meter of maximum 0.3116 kg/sec are used to control the flow rates and

throughout the experiment mass flow rate of hot water is kept

flow rates of Nanofluid is varied from 0.0833 to 0.3116 Kg/sec. The surface area related to

bend region is relatively small compared to areas of inner and outer tubes. In order to measure

the temperature a total of four (4) therm

in the inlet and outlets of pipes.




layering .which are important to consider in Nanofluids.


(BROOKFIELD) .the reading were taken at different concentrations and temperatures of

he viscosity of the Nano fluid increases with increase in the particl


ents and the literature as well.

Figure 2

represents the comparison between the viscosity and the fluid inlet temperatures

of the double pipe heat exchanger temperature is an important parameter to consider for

he viscosity of the Nanofluids decreased with increased in


temperature shows highest value of viscosity and vice versa.

EXPERIMENTAL SETUP

unit consists of flow meters, thermocouple, u tube manometer data logger,


concentric pipes and u bend made of stainless steel inner diameter of inner tube is 0.019

m,u bend radius of 0.32m. As surface area related to bend is very


neglected. Two motors of 0.5Hp capacity are used to pump the Nanofluid and hot Fluid, The



throughout the experiment mass flow rate of hot water is kept constant 0.1416 kg/sec and



the temperature a total of four (4) thermocouple are used and thermocouple needles are placed




d temperatures of

he viscosity of the Nano fluid increases with increase in the particle


represents the comparison between the viscosity and the fluid inlet temperatures

of the double pipe heat exchanger temperature is an important parameter to consider for the

he viscosity of the Nanofluids decreased with increased in


unit consists of flow meters, thermocouple, u tube manometer data logger,


concentric pipes and u bend made of stainless steel inner diameter of inner tube is 0.019 cm

m. As surface area related to bend is very


hot Fluid, The



constant 0.1416 kg/sec and



ocouple are used and thermocouple needles are placed

Experimental investigation of heat

exchanger with and without twisted tape inserts using zno

① Hot water Tank③ Induction Motors 0.5Hp⑤ U-Tube manometer ⑦ Coil Heaters

ZnO Nano fluid flow

The thermocouple readings are recorded by using multi point digital temperature

indicator. In order to minimize the heat loss from the system to atmosphere it is insulated the

outer surface of annulus tube is wounded with asbestos rop

Nanofluid and hot water are of 20 ltrs capacity made of stainless steel. Pressure drop across

Experimental investigation of heat transfer coefficient and friction factor in a double pipe heat

exchanger with and without twisted tape inserts using zno-proplyene glycol nanofluid

Figure 3

Hot water Tank ② ZnO Nano fluid Tank

Induction Motors 0.5Hp ④ Flow control valves

Tube manometer ⑥ Flow meter

ZnO Nano fluid flow Hot water flow

Figure 3 (a) [H/D=3]

Figure 3 (b) [H/D=5]

Figure 3 (c) [H/D=10]



outer surface of annulus tube is wounded with asbestos rope. The tank capacities of both


transfer coefficient and friction factor in a double pipe heat proplyene glycol nanofluid

Tank



e. The tank capacities of both




the inner tube of test section is calculated by a u tube manometer with mercury as a

Manometric fluid. The tubes in the test section were cleaned with distilled water prior to using

Nanofluid. The Thermo physical properties of the Nanofluid are estimated at bulk mean

temperature. Primary purpose of the work is to place twisted tape with wire coils in the inner

tube of the test section and this passive augmentation technique is to generate a swirl /

turbulent flow and they obstruct the flow leading to more fluid mixing for high heat transfer

enhancement. Three variations of Twist Ratios are shown in figure 3 (a),3(b),3(c) and spring

pitch was kept constant for all twisted tape configurations.

4. THEORETICAL ANALYSIS

Data reduction

Measurement of Heat transfer coefficient:

The heat transfer coefficient for hot fluid as follows as:

@A � BA∁DA∆F � BA∁DA'FAG ( FAH) (5)

Where Qh is the heat transfer coefficient at hot fluid, mh is the mass flow rate at hot fluid,

Cph is the specific heat at hot fluid and Thi and Tho are the inlet and outlet temperatures at hot

fluid.

The heat coefficient for cold fluid follows as:

@I � BI∁DI'FIH ( FIG) (6)

Where Qc is the heat transfer coefficient at cold fluid, mc is the mass flow rate at cold

fluid, Cpc is the specific heat at cold fluid and Tci and Tco are the inlet and outlet temperatures

at cold fluid.

The average heat transfer coefficient follows as:

@JKL � MN�M�O (7)

Where Qavg is the average heat transfer coefficient, Qh is the heat transfer at hot fluid and

Qc is the heat transfer coefficient at cold fluid.

The temperature difference at LMTD follows as:

∆FPQRS � 'RN�3R��)3'RNT3R�T)U�VWN�XW�TWNTXW��Y (8)

Where ∆FPQRS is the temperature difference at LMTD, Thi is the hot inlet temperature, Tci

is the cold inlet temperature, Tho is the hot outlet temperature and Tco is the cold outlet

temperature.

The Nusselt number follows as:

Z[\]D^ A_`�"S1 (9)


Where NuExp is the Nusselt number at experimental, hexp is the heat transfer rate, D is the

diameter and k is the thermal conductivity.

4A� � 4a�3b�c�d�� (10)

eG � Mfghij"∆RklWm (11)

nG � opGL (12)

The heat transfer rate is given follow as:

q\]D � M�gh∆RklWm"ij (13)

Where hexpis the experimental heat transfer rate, Qavg is the average heat transfer

coefficient, ∆FPQRS is the difference in temperature and Ai is the area at inner side.

rs � tuvNw (14)

'Z[)S.x = 0.023 × rs{.|}~{.� (15)

Where Nu is the Nusselt number, Re is the Reynolds number and Pr is the Prandlt number.

Measurement of friction factor:

�s]D = ∆�+km/V

�� Y

(16)

�x�J�G�� = 0.3164 × r�3{.O� (17)

Where fexp is the experimental friction factor,∆P is the mean pressure, L is the length, D is

the diameter, 8 is the density, V is the volume and Re is the Reynolds number.

5. RESULTS AND DISCUSSIONS:

a) Base Fluid data:

The setup is validated before conducting experiment by using base fluid Distilled water and

propylene glycol (60:40) ratio. and the results were plotted for Nusselt number and friction

factor with equation number 15 of Dittus- Boelter and equation number 17 Blasius .the

difference between experimental and theoretical data were found to be 5% for Nusselt

number and 8% for friction factor as shown in figure 4 and figure 5.

Figure 4

050

100150

0 2000 4000 6000 8000

Nu

sse

lt N

um

be

r, N

u

Renolds Number Re

Nu D- B

Nu Exp


b) Base Fluid with twisted tape configuration:

Now the experiment is conducted with base

Compared to the plain tube the Nusselt number and friction factor is more for twist ratio

configuration H/D=3. The data obtained is shown in

0

0.01

0.02

0.03

0.04

0.05

0.06

0Fri

ctio

n f

act

or

f

0.00

0.02

0.04

0.06

0

Fri

ctio

n f

act

or

f


Figure 5

Base Fluid with twisted tape configuration:

t is conducted with base fluid on different twisted tape configurations.


configuration H/D=3. The data obtained is shown in figure 6 and figure 7.

Figure 6

Figure 7

2000 4000 6000 8000

Renolds Number Re

nu

nu exp

2000 4000 6000 8000

Renolds Number Re

f Exp

f 10 TT

f 5 TT

f 3 TT

fluid on different twisted tape configurations.



c) ZnONano Fluid data:

Figure 9

Now the experiment is conducted with ZnO Nanofluid of 0.15, 0.25, 0.40 % volume

concentrations in a tube and the Nu values are estimated from equation 9 and shown in figure.

From the graph it is known that for ZnO Nanofluid 0.4% volume concentration the Nusselt

number enhancement is 13.7% and 19.72% within Reynolds number of 3000 and 8000 as

shown in figure 8. another graphical plot of frictional factor for the same volume

concentrations is shown in figure 9 . There was a pressure drop across the test section and it

was compared to the base fluid for 0.4% volume concentration it is increased by 9.72% and

11.48% with Reynolds number ranging between 3000 and 8000. Figure 8

d) ZnONano Fluid with twisted tape configuration:

From figure 10 the experimental data for Zno Nanofluid 0.4% volume concentration the

Nusselt number enhancement obtained were 14.1% & 20.96% at twisted tape configuration

H/D=10 and for H/D=3 the Nusselt number enhancement obtained were 15.21% & 23.56%

with Reynolds number between 3000 and 8000. It is observed from data that Nusselt number

at twisted tape configuration H/D=3 exhibits higher values. By introducing the twisted tape

configuration it produces swirl / turbulent flow in the tube which gives higher fluid mixing, so

higher the convective heat transfer. Further friction factor analysis for the ZnO Nanofluid of

0.4% and 0.15% volume concentration with different twisted tape configurations are obtained

were more compared to base fluid as shown in figure 11. observations from figure 11 are for

0.4% volume concentration and twisted tape configuration H/D=3 friction factor enhancement

at Reynolds number 3000 is 12.16% and at Reynolds number 8000 is 15.32% that of base

fluid. It was found that friction factor decreases with increase in Reynolds number and

volume concentration, and decreases with Twist ratio.

Figure 10

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0 2000 4000 6000 8000

fric

tio

n f

act

or

f

Reynolds number Re

f base fluid

f 0.15%

f 0.25%

f 0.4%

0

20

40

60

80

100

120

140

160

0 1000 2000 3000 4000 5000 6000 7000 8000Nu

sse

lt N

um

be

r N

u

Renolds Number Re

Nu 0.15% H/D=15

Nu 0.15% H/D=10

Nu 0.15% H/D=5

Nu 0.25% H/D=15

Nu 0.25% H/D=10

Nu 0.25% H/D=5

Nu 0.4% H/D=15


Figure 11

6. CONCLUSION

The experimental results of the heat transfer enhancement by using ZnO nanofluid in a double

pipe heat exchanger fitted twisted tape with wire coil inserts leads to following conclusions.

• Compared to the base fluid in a tube and 0.4% volume concentration of nanofluid in a

tube with twisted tape configuration of H/D=3 the Nusselt number improvement is

15.21% and 23.56% with in the Reynolds number of 3000 and 8000.

• The friction factor of 0.4% Zno nanofluid flowing in a tube with twisted tape

configuration of H/D=3 increases 12.16% at a Reynolds number of 3000 and 15.32%

increase at a Reynolds number of 8000 compared to identical concentration fluid

without twisted tape inserts.

REFERENCES

[1] M. Chandra Sekhara Reddy, Veeredhi Vasudeva Rao, Experimental investigation of heat

transfer coefficient and friction factor of ethylene glycol water based TiO2 nanofluid in

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0

0.01

0.02

0.03

0.04

0.05

0.06

0 2000 4000 6000 8000

fric

tio

n f

act

or,

f

Renolds Number , Re

f 0.15% H/D=15

f 0.15% H/D=10

f 0.15% H/D=5

f 0.25% H/D=15

f 0.25% H/D=10

f 0.25% H/D=5

f 0.4% H/D=15

f 0.4% H/D=10



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EXPERIMENTAL INVESTI GATION OF HEAT TRANSFER ......8.73% at 0.02% concentration when compared to...

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