Ammonia is widely used as a refrigerant in industrial systems for food refrigeration, distribution warehousing and process cooling. It has more recently been proposed for use in applications such as water chilling for air-conditioning systems but has not yet received widespread acceptance for this application. This project was envisaged to develop an ammonia vapour compression refrigeration system of 3 TR capacity for residential air conditioning and to analyze the minimum possible charge in order to reduce leakage hazards associated with the system. This would increase the use of ammonia in a more efficient way. It has Zero ODP and GWP which makes it to be environment friendly. Even though Ammonia is a cost effective and energy efficient alternative to conventional refrigerants like HCFCs and HFCs, etc., it is toxic. So, toxicity of ammonia needs to be addressed. This calls for low inventory of refrigerant in individual system. The present work aims at reducing the specific charge of ammonia for residential air conditioning system with air cooled condenser.

1. LOW CHARGE AMMONIA VAPOUR COMPRESSION REFRIGERATION SYSTEM FOR
RESIDENTIAL AIR CONDITIONING
N. RAJESH KUMAR, Dr. D. MOHAN LAL (Guide)
Department of Mechanical Engineering, College of Engineering Guindy, Anna University, Chennai-25.
Introduction
Ammonia is widely used as a
refrigerant in industrial systems for food
refrigeration, distribution warehousing and
process cooling. It has more recently been
proposed for use in applications such as
water chilling for air-conditioning systems
but has not yet received widespread
acceptance for this application. This project
was envisaged to develop an ammonia
vapour compression refrigeration system of
3 TR capacity for residential air
conditioning and to analyze the minimum
possible charge in order to reduce leakage
hazards associated with the system. This
would increase the use of ammonia in a
more efficient way. It has Zero ODP and
GWP which makes it to be environment
friendly. Even though Ammonia is a cost
effective and energy efficient alternative to
conventional refrigerants like HCFCs and
HFCs, etc., it is toxic. So, toxicity of
ammonia needs to be addressed. This calls
for low inventory of refrigerant in
individual system. The present work aims at
reducing the specific charge of ammonia for
residential air conditioning system with air
cooled condenser
Objective
The aim of this project is to develop a
vapour compression refrigeration system
using ammonia as a refrigerant for household
air conditioning and to analyze the
possibility to reduce the charge quantity in
the system.
• Simulate the ammonia chiller system using
IMST-ART software
• Optimize the 3 TR cooling capacity chiller
system with minimum charge
• To design and fabricate the ammonia
chiller system
Experimental Facility
The experimental facility consists of
three sections: an ammonia vapor
compression test bed, a pumped water circuit
and a fan coil unit. A schematic of the entire
setup is shown in Figure.
Experimental Procedure
Ammonia chiller refrigeration system
is tested for leakage under high pressure and
low pressure. High pressure leakage test is
done by filling nitrogen under 300 psi
pressure in the entire refrigeration circuit for
24 hours. Low pressure test is done by using
vacuum pump under -25 psi pressure for 24
hours. After the leakage test is completed,
pump is switched ON to circulate the water
through the fan coil unit and evaporator.
After the evaporator is flooded with water,
compressor is switched ON to start the
refrigeration system. Now the system is
loaded with ammonia refrigerant through the
ammonia cylinder using refrigerant hose.
The ammonia gas is loaded to the system
until the suction and discharge pressure
reaches 65 psi and 240 psi respectively. The
total refrigerant charge required for the
system is found to be 600 grams. It is
measured using the weighing balance. The
chiller system is tested with fan coil unit and
without fan coil unit operation.
Experimental Setup
Results and Discussion
Conclusion
Ammonia chiller experimental set up is
loaded with 600 grams’ refrigerant charge
and it is able to achieve 3 TR cooling
capacity. The specific charge quantity of the
low charge ammonia chiller system is found
to be 50 g/kW. The space to be conditioned
is maintained by the fan coil unit with the
supply air temperature of 17 °C in the hot
ambient conditions itself. By maintaining the
chilled water inlet temperature at the fan coil
unit less than 10 °C, we can able to achieve
even lesser supply air temperature. It is
possible by increasing the refrigerant charge.
Comparing the experimental results with
the simulation, it is found that the various
parameters are tabulated for 600 grams’
refrigerant charge at 0.61 kg/s of water.
Parameter Simulation
Results
Experiment
al Results
%
Deviation
Power
Consumption (kW)
2.75 2.84 3.17
Mass Flow Rate
(kg/hr)
40 37 8.1
Cooling Capacity
(kW)
11.1 9.684 14.6
COP 4.04 3.41 18.47
Simulation results (IMST- ART Software)
5
7
9
11
13
15
17
19
0
10
20
30
40
50
60
70
30 32 34 36 38 40 42 44 46 48 50
COOLINGCAPACITY(kW)
CONDENSINGTEMPERATURRE(°C)
CONDENSER INLET AIR TEMPERATURE (°C)
Condensing temperature
Cooling capacity
3.5
3.8
4.1
4.4
4.7
5
1.5
1.9
2.3
2.7
3.1
3.5
5 7 9 11 13 15
COP
POWERCONSUMPTION(kW)
RETURN WATER TEMPERATURE (°C)
power consumption
COP
FLOW RATE OF WATER = 2.267 m3/hr
3.3
3.6
3.9
4.2
4.5
0 . 2 5 0 . 3 0 . 3 5 0 . 4 0 . 4 5 0 . 5 0 . 5 5 0 . 6 0 . 6 5
COP
REFRIGERANT CHARGE (KG)
Q=2.5 m3/hr
Q= 3 m3/hr
Q=3.5 m3/hr
Q= 4 m3/hr
Q= 4.5 m3/hr
Q= 5 m3/hr
Experimental results
492
0
80
160
240
320
400
480
560
8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
Timetaken(seconds)
Water tank temperature (°C)
Effect of refrigerant charge on COP for different flow rates of water
Variation of condenser inlet air temperature with respect to
condensing temperature and evaporator cooling capacity
Effect of return water temperature on power consumption
and COP
Pull down characteristic curve – Temperature vs Time
Pull down characteristics
The figure shows the pull down characteristic
curve – Temperature vs Time graph. Initially, water is
at 22°C in the tank. At no load condition, the water
tank temperature is dropped down to 8°C from 22°C
(i.e. Without fan coil unit operation). It takes 492
seconds to reach 8 °C. The capacity of the system at
no load condition is measured using the below
mentioned equation. After this condition is reached,
fan coil unit is switched on for conditioning the space.
Capacity = m*cp*dT/dt
Q = 82*4.187*(22-8)/492
Q = 9.77 kW.
Performance Analysis of Ammonia Chiller at Loaded Condition
1.7
1.8
1.9
2
2.1
2.2
2.3
2.4
0 15 30 45 60 75 90 105 120 135 150 165 180
CompressorPower(kW)
Time taken (minutes)
Flow rate of water = 0.61 kg/s
2.8
2.89
2.98
3.07
3.16
3.25
3.34
3.43
3.52
0 15 30 45 60 75 90 105 120 135 150 165 180
COP
Time taken (minutes)