1. CHILLER SYSTEM

2. CONTENTS CHILLER BASICS WORKING PRINCIPLE OF CHILLER
REFRIGERATION CYCLE
CHILLER COMPONENTS
COMPONENTS FUNCTIONS & COMPARISON
LOAD TERMINAL CONTROL OPTIONS
CHILLER SYSTEM CONFIGURATION
TECHNICAL TERMINOLOGY
CHILLLER PERFORMANCE MEASUREMENT

3. CHILLER BASICS What is a Chiller?
The refrigeration machine that produces chilled water is referred to as a “Chiller”. A chiller is a water-cooled air conditioning system that cools inside air, creating a more comfortable and productive environment.
Basically, there are two types of chillers based upon the refrigeration cycle:
Vapour Compression Chiller
Absorption Refrigeration Chiller
Based upon the condensation process of working fluid , there are two types of chiller:
Air-Cooled Chiller
Water Cooled Chiller

4. WORKING OF CHILLER SYSTEM
Chillers circulate chilled water to air-handlers(AHU’s) in order to transfer heat from air to water.
This water then returns to the evaporator side of the chiller where the heat is passed from the water to a liquid (LP) refrigerant .
The refrigerant leaves the evaporator as a cold vapor (LP) and enters the compressor where it is compressed into a hot vapor (HP).
Upon leaving the compressor, the vapor enters the condenser side of the chiller where heat is transferred from the refrigerant to the air/water side of the condenser where it is circulated to an ACC/open cooling tower for the final removal of heat from the refrigerant as a liquid (HP).
(Water Cycle) (Air/Water Cycle)
AHU Evaporator Compressor Condenser C.Tower
(Refrigerant Cycle)

5. AIR-COOLED CHILLER

6. WATER-COOLED CHILLER

7. HEAT TRANSFER LOOP

8. HEAT TRANSFER LOOP
Heat Transfer Loops In Refrigeration System Thermal energy moves from left to right as it is extracted from the space and expelled into the outdoors through five loops of heat transfer: – Air loop. Air is driven by the supply air fan through a cooling coil, where it transfers its heat to chilled water. The cool air then cools the building space. – Chilled water loop. Driven by the chilled water pump, water returns from the cooling coil to the chiller’s evaporator to be re-cooled. – Refrigerant loop. Using a phase-change refrigerant, the chiller’s compressor pumps heat from the chilled water to the condenser water. – Condenser water loop. Water absorbs heat from the chiller’s condenser, and the condenser water pump sends it to the cooling tower. – Cooling tower loop. The cooling tower’s fan drives air across an open flow of the hot condenser water, transferring the heat to the outdoors.

9. VAPOUR COMPRESSION CYCLE

10. VAPOUR COMPRESSION CYCLE

11. Vapour Compression Cycle

12. ABSORPTION REFRIGERATION CYCLE

13. Vapour Compression Chiller Absorption Water Chiller
Use a Compressor to move refrigerant around the system. Energy source for the compressor is an electric motor.
Use heat to drive the refrigeration cycle. Energy sorce are steam, hot water or burning of oil or natural gas
Vary by type of compressor such as reciprocating, scroll, screw, centrifugal.
Use of absorption refrigeration cycle.
Lower initial cost
Higher initial cost due to additional cost of heat transfer tubes & absorbent.
In emergency situation, continous electricity required for electricity-driven chillers.
Minimal electricaity needed for generator during emergemcy situations
Not applicble
Waste heat recovery - Wasted energy can be used to fuel an absorption chiller
Application in Cogeneration system

14. CHILLER SYSTEM COMPONENTS

15. CHILLED WATER SYTEM COMPONENETS
Chiller (Evaporator)
Compressors
Chilled Water Pumps
ACC in Air Cooled Chiller
Cooling Tower in Water-cooled Chiller
Condensate water pumps in water-cooled chiller
Load Terminals (chilled water cooling coils)
Chilled and condenser-water distribution systems include piping, expansion valve, control valve, check valves, strainers etc.

16. COMPRESSORS Reciprocating Compressor Used in small chiller
Available in capacity up to 100 tons (350kw)
Multiple Compressor used in a single chiller for capacities up to 200 tons(700kW)
Scroll Compressor
Used in small water chiller less than 200 tons (700kw)
10 to 15% more efficienct than reciprocating because of 60% fewer moving parts
Available in hermetic configurations in capacity up to 15 tons (53kW) for use in water chiller
Multiple are used in single chiller to meet larger capacities
Helical Rotary (Or Screw)
Used in medium sized water chiller 50 to 500 tons (175 to 1750kw)
More reliable & better efficiency due to fewer moving parts
Centrifugal Compressor
Used in large water chiller
Available in prefabricated chiller from 100 to 3000 tons (350 to 10500kW) & up to 8500 tons (30000kW) as built-up machines
High efficiency, superior reliability, reduced sound levels, relatively low cost as compared to others

17. CONDENSER

18. Water Cooled Condensor
Air Cooled Condensor
Water Cooled Condensor
Available from 7.5 to 500tons (25 to 1580kW)
Available from 10 to 3000tons (35 to 10500kW)
Packaged System - Reduced design time , simplified installation, higher reliability & single source responsibility.
Additional requirement of condenser-water piping, pump, CT & associated controls.
Better low-ambient operation (i.e. below frezing weather conditions)
Cooling tower require special control sequences, basin heaters or even an indoor sump for safe operatin in freezing weather
Elimination of cooling tower
Cooling tower in the system
Lower Maintenace - Eliminates concers & maintenance requirements related to cooling tower
Mainteance requirements associated with water treatment, chiller condensor-tube cleaning, tower mechanical maintenance , freeze protection & availability of make up water with its quality
Reduce Operating Costs of cooling tower
Additional Costs of cooling tower & condensor pump

19. Water Cooled Condensor
Air Cooled Condensor
Water Cooled Condensor
Refrigerant Condensing temperature is higher due to dependent on DBT
Refrigerant Condensing temperature is lower due to dependent on condensor-water temperature, which is dependent on WBT.
Higher condensing temperature & therefore higher condensing pressure means compressor to do more work & consume more enrgy.
Greater Energy Efiiciency due to lower condensing temperature & pressure
More preferable at Part load conditions because DBT tends to drop faster than WBT in a day (from day to night).
Less preferable to work at part load conditions
Efficency advatage lessen at part load condition
Efficiency advantage much less due to additional cost of CT & pump.
Life approx. 15 to 20 yrs. (Outdoor installation)
Longer equipment life 20 to 30 yrs. (Indoor Installation & water as condensing fluid operate at lower pressures)

20. AIR COOLED v/s WATER COOLED CONDENSER

21. AIR COOLED V/S WATER COOLED CONDENSER

22. AIR COOLED V/S WATER COOLED CONDENSER

23. LOAD TERMINAL CONTROL OPTIONS

24. LOAD TERMINAL CONTROL OPTIONS

25. LOAD TERMINAL CONTROL OPTIONS

26. LOAD TERMINAL CONTROL OPTIONS

27. LOAD TERMINAL CONTROL OPTIONS

28. SINGLE CHILLER SYSTEM

29. PARALLEL CHILLER SYSTEM

30. TERMINOLOGY Tons of refrigeration (TR):
One ton of refrigeration is the amount of cooling obtained by one ton of ice melting in one day i.e kcal/h or thermal kW.
2. Net Refrigerating Capacity:
A quantity defined as the mass flow rate of the evaporator water multiplied by the difference in enthalpy of water entering and leaving the cooler, expressed in kcal/h, tons of Refrigeration.
3. kW/ton rating:
Commonly referred to as efficiency, but actually power input to compressor motor divided by tons of cooling produced, or kilowatts per ton (kW/ton). Lower kW/ton indicates higher efficiency.

31. TERMINOLOGY 4. Coefficient of Performance (COP):
Chiller efficiency measured in cooling output (kcal/hr) divided by electric power input.
5. Energy Efficiency Ratio (EER):
Performance of smaller chillers and rooftop units is frequently measured in EER rather than kW/ton. EER is calculated by dividing a chiller's cooling capacity (in kcal/h) by its power input (in watts) at full-load conditions. The higher the EER, the more efficient the unit.

32. PERFORMANCE ASSESSMENT OF CHILLER SYSTEM
● The refrigeration TR is assessed as
TR = Q x Cp x (Ti – To) / 3024
Where Q is mass flow rate of coolant in kg/hr
Cp is coolant specific heat in kCal /kg deg C
Ti is inlet, temperature of coolant to evaporator (chiller) in °C
To is outlet temperature of coolant from evaporator (chiller) in °C.
The above TR is also called as chiller tonnage.
● The specific power consumption kW/TR is a useful indicator of the performance of refrigeration system. By measuring refrigeration duty performed in TR and the kiloWatt inputs, kW/TR is used as a reference energy performance indicator.

33. PERFORMANCE ASSESSMENT OF CHILLER SYSTEM
● In a centralized chilled water system, apart from the compressor unit, power is also consumed by the chilled water (secondary) coolant pump as well condenser water (for heat rejection to cooling tower) pump and cooling tower fan in the cooling tower.
Effectively, the overall energy consumption would be towards:
– Compressor kW
– Chilled water pump kW
– Condenser water pump kW
– Cooling tower fan kW, for induced / forced draft towers

34. PERFORMANCE ASSESSMENT OF CHILLER SYSTEM
● An indicative TR load profile for air conditioning is presented as follows:
Small office cabins = 0.1 TR /m2
Medium size office i.e., = 0.06 TR/ m2
10 – 30 people occupancy with central A/C
Large multi-storeyed office = 0.04 TR/ m2 complexes with central A/C

35. PERFORMANCE ASSESSMENT OF CHILLER SYSTEM
S.No.
Parameters
UOM
TG Chillers - 3nos.(2W+1SB)
Design
Chiller No.1
Chiller No.3
Actual 1
Chilled water Outlet Set Temp.
deg.C
5 to 25 10
10.1 2
Power Consumption of Compressor kW
210
94.86
93.3 3
Power Consumption of Fan 11
8.28
8.41 4
Power Consumption of Chiller Pump 22
18.2
18.69 5
Total Power Consumption
194
121.34
120.40 6
Total Pump Flow
m3/hr
105
81.5 7
Inlet Chilled water temp. (entering into Evaporator) 12
12.1
11.9 8
Outlet Chilled water temp. (leaving Evaporator)
9.2
8.9 9
Chilled water temp difference across chiller
5.0
2.9
Refrigeration Effect of Chiller Plant
kcal/hr
529200
236350
244500 TR
175
78.16
80.85
Specific Power Consumption
kW/TR
1.11
1.55
1.49

36. PERFORMANCE ASSESSMENT OF CHILLER SYSTEM
S.No.
Parameters
UOM
ESP Chillers - 2nos.(1W+1SB)
Chiller No.1
Design
Actual 1
Chilled water Outlet Set Temp.
deg.C
5 to 25 10 2
Power Consumption of Compressor kW
310
92.00 3
Power Consumption of Fan
35.2
12.47 4
Power Consumption of Chiller Pump 15
12.49 5
Total Power Consumption
288
116.96 6
Total Pump Flow
m3/hr
125 85 7
Inlet Chilled water temp. (entering into Evaporator) 12
12.8 8
Outlet Chilled water temp. (leaving Evaporator)
9.9 9
Chilled water temp difference across chillar
5.6
2.9
Refrigeration Effect of Chiller Plant
kcal/hr
695520
246500 11 TR
230
81.51
Specific Power Consumption
kW/TR
1.25
1.43

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