Lecture 17 RAC HVAC Systems in IITK V1.ppthome.iitk.ac.in/~samkhan/ME340A/Lecture_18_RAC_HVAC... ·...

ME340A

Prof. Sameer KhandekarDepartment of Mechanical Engineering

Room: SL-109, Indian Institute of Technology Kanpur, Kanpur (UP) 208016, INDIATel: +91-512-259-7038 (O) Fax: +91-512-259-7408 (O), E-mail: [email protected]

http://home.iitk.ac.in/~samkhan

Installed RAC Systems at IIT Kanpur: An Overview

Sameer Khandekar Professor-in-charge (Institute HVAC: 2012-2015)

Sir M. Visvesvaraya Chair

Department of Mechanical Engineering

Vinay Kumar Tiwari Executive Engineer - RAC

Institute Works Department

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IIT Kanpur: Important Data 1200 acres campus

6800 students

430 faculty members

Nearly 10000 campus residents

12 Boys hostels; 2 Girls hostels

Lecture Hall complex: 20 lecture halls (90 to 660 sitting capacity)

Library, Computer Center, Core Labs, HITEM Microscopy, Animal House

High performance computing

Summer Tmax: 45°C - 47°C; Winter Tmin: 2°C to 5°C;

Monsoon: 800 to 840 mm rain; RH variation: 20% to 100%

Nearly 7000 tons of refrigeration (not including private ACs)

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Overview of Systems

1. Central Air-conditioning system

i) High Side Equipments/System

ii) Low Side Equipments/System

2. Domestic Air-conditioning System

i) Window AC’s

ii) Split AC’s

iii) Packaged Ductable AC’s

The Institute has complete set up of HVAC (Heating, Ventilation & Air-conditioning) covering the academic area and the hostels

3. Refrigeration System

i) Cold Rooms

ii) Deep Freezers

iii) Refrigerators

4. Ventilation System

i) Kitchen Fume Exhaust System with DIDW backward curve Fans .

ii) Labs and large area ventilation through Evaporative Cooling System.

5. Heating

i) Solar Water Heating System

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Central Air-Conditioning System

Chilled Water AC plants Central AC Plant (ACMS) 4 x 400 TR = 1600 TR (Screw) Central AC Plant (IWD office) 4 x 400 TR = 1600 TR(Screw) Computer Centre PAC Plant 3 x 90 TR = 270 TR (Magnetic Core) IME Building AC Plants 2 x 75 TR = 150 TR (Screw) Environmental Science Bldg. 1 x 75 TR = 75 TR (Screw) Nano Science Engg. Bldg. 3 x 25 TR = 75 TR (Scroll) Microscope Building 2 x 25 TR = 50 TR (Scroll)

Total Chilled water Central AC Capacity = 3820 TRVariable Flow Refrigerant AC Plants New Core Lab (VRF type) = 190 T Noida VRF AC Plant = 140 TR DOFA office (VRF Type) = 16 T Central Store & Purchase section (VRF Type) = 16 T Core Lab (VRF Type) = 16 T Total VRF AC Plant Capacity = 378 TR

i) High Side Equipments/System ( This comprises of Chilled Water AC plants and Variable Flow Refrigerant AC Plants )

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Chilled Water based Central AC Plant Layout

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System Design for Central AC plantsi) Heat load Estimation

Heat loads are estimated for the highest peak load that may occur during extreme ambient weather conditions. (Climatic Zone, Psychrometrics, Associated equipment, Green building norms)

The System actually runs on load varying from 50 % to 90 % most of the times.

ii) Equipment Selection, capacity/suitable design choice.

Chillers (Centrifugal, Reciprocating, Screw, Scroll, Rotary, Magnetic core bearing etc.,) COP, IKW/Ton,

Water circulation pumps (High Efficiency pumps)

Cooling Towers

Water softening plants

Heating Equipment (Boiler)

Controls/SCADA/Automation System (Bacnet, BMS protocols)

iii) Green Buildings

IGBC & TERI are promoting and made some standards for equipment selection to promote Green Buildings (GRIHA ratings)

iv) Choice between chilled water ac plant (air cooled/water cooled) or VRF AC plant 6

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Central AC Plant: At a Glance

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Condenser and Evaporator Unit

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Condenser and Evaporator Units

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Condenser and Evaporator Unit

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Water Pumps

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Cooling Towers

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Computer Center Plant

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Cooling Towers

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Spray Pond

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IWD AC PLANT (3x400 TR)

CC PAC Plant (3x90 TR)

This ac plant only caters to

Data centre of CC

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VRF AC Plant: General Layout

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VRF System VRF AC system has facility of connecting several Indoor Units in

series to single outdoor unit.

The refrigerant piping can go up to 250-300 meters.

This system does not involve any separate pumping.

It is suitable for spaces or dedicated buildings with AC load variation from 10 to 100 %.

The compressor are inverter driven, leading to energy saving opportunity of up to 40 %.

In chilled water based system Variable Frequency Drives are being now a days used to minimise the electricity consumption.

VRF has limited life 8- 10 years.

Capital cost is higher in this system.

Maintenance cost are high.

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VRF Air Cooled Units

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Air Handling Unit

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Operation & Maintenance Strategies

All the central AC plants are under Operation & maintenance contracts.

All VRF type ac plants are under comprehensive AMCs.

The chillers of large ac plants are under non-comprehensive maintenance as few faults occurs other wise CAMC will cost more.

Predictive maintenance, measurement, verification & management

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Effective System Operation

Breakdown Maintenance

Maintaining minimum inventory of spares, oil, filter, valves etc.

Upkeep of all associated tools & plants like manifolds, charging kit, vacuum pump, etc.

Preventive Maintenance

Regular checking of Chillers by OEM

Replacement of defective or worn out parts sensors, oil, filter , controls etc.

Descaling of the coils of evaporators & condensers

Protection of all control of chillers, pumps, cooling tower

Parameters checking of motors, servicing of motors and pumps

Servicing of valves, strainers, cooling tower fills, softening water plant system.

Measurement of temperature, pressure and flow rate of chilled water.

To avoid the breakdown maintenance performance analysis of equipment at regular interval is required to be done.

Predictive maintenance, measurement, verification & management

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Low Side Equipment

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Low Side Equipment/System

AHU, FCU, Valves, Piping, Ducting, Dampers, Actuator, sensor, thermostats and other associated controls:

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Air Handling UnitThe unit which utilises chilled water or hot water and blowers assembly for air-conditioning or heating by blowing air in the conditioned space.

The basic functions of AHU are:i. Filter the airii. Cool and Dehumidify the airiii.Heat the airiv.Deliver the conditioned air in the

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Fan Coil Unit (300 -1600 CFM)

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Functions & Different Components of AHU’s & FCUFunctions: (Horizontal, Vertical & Ceiling type AHU unit, High Static)

1. Humidifying dry air for winter heating or for maintaining high inside RH

2. Cleaning the air to much higher degree than average for several types of applications

3. Evaporative cooling of dry air for comfort, industrial cooling or dust proofing of space.

4.Dehumidifying air and maintaining air changes per hour for conditioning the space.

Terminal unit or device

Such as fan coil units, VAV boxes

Air handling unit (AHU)

Primary equipment of the air system

Handle & condition the air, control it to a required state, and transport it

Basic components:

Supply fan, water cooling coil, filters, mixing box, dampers, controls & outer casing.

Heating element , humidifier tank is optional

For energy saving the motor are installed with VFD (Variable Frequency Drive) for speed control

Return air temperature sensors or pressure differential sensors are installed for feed back to VFD

Fresh air mixing in return is easily possible 27

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Piping, Valves, Strainers and other Low Side systemsCondenser Water Piping Selection Criteria's: Pressure drop

Water velocity Height of the cooling tower above water level

Fixed pumping

Variable pumping

Condenser Pump Selection Criteria: 1. Pump Head

2. Flow Rate in GPM, lpm or m3/hr.

3. Allowable Friction rate

Chilled Water Piping Selection Criteria's:1. Piping Design

2. Types of Pumping System

3. Functions of various Pumps

4. Options in multiple pumping system

5. Pressure Drop 28

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Chilled Water Piping Size Selection Chart

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Condenser Pump Selection

1. Pump Head

2. Flow Rate in GPM, lpm or m3/hr.

3. Allowable frictional rate

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Air DistributionGrilles, Registers

Many optionsGU Russell Theatre Return Grille

Return PlenumExtra cost for plenum rated cable is less than cost of return ductworkNo Combustibles

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. Square Ductwork

Most common

Low height

Round Ductwork Less Expensive

Easy to Install

Lower static pressure

Taller than Rectangular

Higher pressure

Less Sound

Oval Ductwork Same advantages of round

Height similar to rectangular

More expensive than rectangular

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HEPA Filters High Efficiency Particulate Air (HEPA)

High Efficiency Particulate Absorber

High Efficiency Particulate Arresting

High-efficiency particulate Arrestance

Type of air filter - It must satisfy certain standards of efficiency such as those set by the United States Department of Energy (DOE).

A HEPA filter must remove (from the air that passes through) 99.97% of particles that have a size greater-than-or-equal-to 0.3 µm.

HEPA was commercialized in the 1950s, and the original term became a registered trademark and later a generic term for highly efficient filters

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HEPA Filters: Photographs

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HEPA Filters Characteristics

HEPA filters are composed of a mat of randomly arranged fibres.[5]

The fibres are typically composed of fiberglass and possess diameters between 0.5 and 2.0 micrometers.

Key factors affecting its functions are fibre diameter, filter thickness, and face velocity.

The air space between HEPA filter fibres is typically much greater than 0.3 μm.

The common assumption that a HEPA filter acts like a sieve where particles smaller than the largest opening can pass through is incorrect and impractical.

Unlike membrane filters at this pore size, where particles as wide as the largest opening or distance between fibres can not pass in between them at all, HEPA filters are designed to target much smaller pollutants and particles.

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HEPA Filter Mechanisms

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Interception

Where particles following a line of flow in the air stream come within one radius of a fibre and adhere to it.

Impaction

Where larger particles are unable to avoid fibres by following the curving contours of the air stream and are forced to embed in one of them directly; this effect increases with diminishing fibre separation and higher air flow velocity.

Diffusion

An enhancing mechanism that is a result of the collision with gas molecules by the smallest particles, especially those below 0.1 µm in diameter, which are thereby impeded and delayed in their path through the filter; this behaviour is similar to Brownian motion and raises the probability that a particle will be stopped by either of the two mechanisms above; this mechanism becomes dominant at lower air flow velocities.

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Domestic UnitsWindow/Split/Tower/DX

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Domestic Air-conditioning/DX based AC Systems

DORD (Packaged Ductable type) = 22 T

Media Lab (Packaged Ductable) = 20 T

Computer Centre (Packaged Ductable Type) = 27 T

Samtel Centre (DX type AHU Ductable based) = 54 T

Window ACs (1.5TX800 & 2.0 Tx133) 933 Nos. = 1466 T

Split ac/Tower/cassette type (550 units) approx. = 1000 T

Water coolers (250 nos.) & Cold rooms (25 nos.) = 300 T

Total DX type AC Systems Capacity = 2889 TR

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Selection of DX based System1. DX (Direct Expansion) Type Air-Conditioning System

a. Window AC Unit

The easiest mode of providing ac in any space

Suitable for individual rooms of sizes up to 15 sq.mtr., 25 sq.mtr., & 30 sq.mtr.

Consumes higher power in comparison to other systems

Provision of mixing fresh air in the air-conditioned space

The noise level is more (65 dB)

b. Split AC Unit

The condensing unit is located outside the air-conditioned space

Consumes less power than window ac unit of same size

No provision of fresh air mixing in the air-conditioned space

Very low noise level

Drain pipe layout is challenging

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Selection of DX based System

c. Package Air conditioning Units:

Suitable for spaces from 100 to 500 sq. m.

Their is single /multi outdoor unit connected with no. of split/cassette/ductable indoor units

Packaged units may be water cooled/air cooled.

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Working of Window & Split AC

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Cold Room (+ve and –ve) Positive Cold Room: Maintains Temperature from +2°C to +6°C

They are used for storing vegetables, fruits and other kitchen eatables.

Negative Cold Rooms: -4 to -15 Deg C. They are used for meats, ice cream and other contaminable items.

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Ventilation Systems (Kitchen Fume Exhaust System)

Kitchen ventilation is designed for 15-20 ACH. This provides better hygiene inside dining area.

Kitchen exhaust systems are designed for grease exhaust applications, for heat and steam removal and other non-grease applications.

High static DIDW backward curve fans are utilized for exhaust of gases through ducting of heavy gauze.

Scrubbers (Dry or Wet Type) are being used for removal of smell and oil particles, thus discharging pollution free air.

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Kitchen Ventilation

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Ventilation System

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Solar Water Heaters

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Details of Solar Water Heater Installations (60000 LPD)

All the Solar Water Heater systems installed in the campus is of Flat Plate Collector Technology.

There is continuous requirement of Hot Water for the mess and canteen areas of the Hostels for dish washing.

Accordingly all the Hostels Mess has been facilitated with Solar Water Heater System.

All the Bathrooms of Hostels have been provided hot water facility through solar water heater system and electric geysers.

Approximately 350 Geysers of capacity 50 Litres and of 2 KW heating elements of each.

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Rooftop Solar Water Heaters

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Ways to Reduce Energy Consumption in HVAC Use of High COP, EER rated equipment i.e. Chillers, AC’s

Use of controls to optimise the energy consumption i.e., actuators valves, dampers, sensors, VFD (Variable Frequency Drive),BMS (Building Management System)

Use of star rated equipment

Use of environmental friendly gases and materials.

Evaporative type cooling for big spaces.

Minimising the chilled air leakages from the ac spaces.

Use of double glazed glasses in windows

Over Deck insulation of the terraces

Underdeck insulation /False ceiling inside the rooms

Insulated walls construction

Temperature be kept at 25±1°C., will reduce compressor running time.

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Thank you

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Lecture 17 RAC HVAC Systems in IITK V1.ppthome.iitk.ac.in/~samkhan/ME340A/Lecture_18_RAC_HVAC... ·...

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