Low charge ammonia vapour compression refrigeration system for residential air-conditioning

Guided by
Dr. D. Mohan lal
Professor, R&AC
Presented by
Rajesh kumar N
2017251036
M.E Thermal (RAC)
5/24/2019
Low charge Ammonia Vapour compression refrigeration system
for residential air conditioning
1

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.
5/24/2019
LOW CHARGE AMMONIA VAPOUR COMPRESSION REFRIGERATION SYSTEM FOR
RESIDENTIAL AIR CONDITIONING
2

OBJECTIVE
 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
 To develop a prototype ammonia chiller with a microchannel
condenser and a plate evaporator with minimum charge
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Barriers for the use of Ammonia in Small scale
systems
• Reduction of refrigerant charge to reduce safety hazards because of
toxicity of ammonia
• Ammonia’s incompatibility with copper
• Lack of components
• Safety regulations
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Schematic Of Ammonia Chiller
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Ammonia chiller circuit
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1- Open type reciprocating compressor
2- Evaporator-PHE
3- Microchannel aluminium condenser
4- Manual expansion device
5- Suction line accumulator
6- Oil separator
7- Receiver
8- Filter drier
9- Suction line
10- Discharge line
11- Vapour line
12- Liquid line
13- Chilled water pump

Ammonia chiller – components specification
• Compressor
Compressor model: WAK-2N Open type reciprocating compressor
Volumetric displacement: 15.13 m3/hr (range 14-25 m3/hr )
Speed: 810 rpm (range 750-1450 rpm)
Necessary driving motor: 5 hp (3.7 kW) - belt driven
Compressor oil – mineral oil
Connecting pipelines
(suction, discharge, liquid lines) – stainless steel
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• Evaporator
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Model: Alpha Laval 52-20 H
Type: single pass fusion bonded 100% SS
plate liquid to liquid heat exchanger
Number of Plates = 20
Overall Dimensions = 85*111*526 mm
Net Weight = 6.42 kg
Max Working Temperature = 225 °C
Max Working Pressure = 25 bar
Evaporator Geometry
HPCD = 0.05 m
VPCD = 0.466 m
Port diameter (PD) = 23 mm
Plate pitch (PP) = 2.35 mm
Plate thickness = 0.35 mm
Channel type = H 8

• Condenser
Model : Micro-channel Aluminium Heat Exchanger
Exchanger width = 520 mm
Tube depth = 18.771 mm
Wall thickness = 1.905 mm
Tube material = Aluminium
Fin thickness = 0.127 mm
Fin pitch = 1.537 mm
Fin material = Aluminium
• Expansion device
Model – Danfoss manual expansion valve REG 10-A Straight
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Experimental procedure
• Ammonia chiller refrigeration system is tested for leakage under high pressure and low
pressure.
• High pressure leakage test - nitrogen under 300 psi pressure for 24 hours.
• Low pressure leakage test - 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 this, compressor is switched ON.
• 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.
• The chiller system is tested under no load and loaded condition.
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10

Experimental set up
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11

INPUT VALUES FOR THE SIMULATION MODULE
• EVAPORATOR SIDE INPUT:
Model Alpha Laval 52-20 H
Flow arrangement counter current
Secondary fluid water
Return water temperature** 12 °C
Inlet pressure 200 kPa
Flow rate of water 2.267 m3/hr
Suction super heat 5 °C
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• CONDENSER SIDE INPUT
Model
Microchannel – parallel flow
heat exchanger
Secondary fluid Air
Inlet air temperature** 35 °C
Inlet air pressure 100 kPa
Face velocity 3 m/s
Receiver capacity 3 dm3
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SIMULATION RESULTS
5/24/2019 14LOW CHARGE AMMONIA VAPOUR COMPRESSION REFRIGERATION SYSTEM FOR

Effect of condenser inlet air temperature
Fig.1 Variation of condenser inlet air temperature with respect to condensing temperature and
evaporator cooling capacity
1. The condensing temperature
increases as the inlet air
temperature increases
2. the cooling capacity decreases
with the increase of condenser
temperature. This reduction in
cooling capacity is due to the
increase of evaporation
temperature which is
accompanied with the condenser
temperature
3. The reduction of cooling
capacity is about 10.8% as the
condensing temperature
increased by 48%.
5/24/2019 15

0
1
2
3
4
5
6
7
8
9
10
0
500
1000
1500
2000
2500
3000
3500
4000
COP
POWERCONSUMPTION(W)
INLET CONDENSER AIR TEMPERATURE (°C)
30 to 50 °C
power consumption
COP
Fig.2 Effect of condenser inlet air temperature on compressor power
consumption and cycle COP
1. As condenser inlet air T
increases, condensing
temperature also
increases
2. Thus the increase in
condenser pressure and
the pressure ratio, leads to
an increase in power
consumption and a
decrease in the cycle
COP.
3. The power consumption
is increased by 36% and
the reduction in COP is
about 34% as shown in
the figure.
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16

Effect of condenser inlet air temperature for variable air flow rates
Fig.3 Effect of condenser inlet air temperature on compressor
power consumption for varying air flow rates
1. As condenser air flow rate
increases with same inlet
condenser air temperature,
compressor power
consumption decreases with
increased air flow rates by
increasing the face velocity
of the condenser.
2. As inlet air temperature of
condenser increases, power
consumption also increases
due to increase in condenser
pressure and pressure ratio.
2.2
2.5
2.8
3.1
3.4
3.7
30 32 34 36 38 40 42 44 46 48 50
POWERCONSUMPTION(KW)
CONDENSER INLET AIR TEMPERATURE (°C)
V=2 m/s
V = 2.5 m/s
V = 3 m/s
V = 3.5 m/s
V = 4 m/s
5/24/2019 17

Effect of condenser airflow
CONSTANT AIR TEMPERATURE = 36 °C
Fig.4 Variation of condenser airflow with respect to condensing
temperature and compressor power consumption
1. The temperature of air, which cools
the condenser, is kept constant at
36ºC and the airflow through the
condenser was varied by
controlling the speed of fan.
2. The decreased condensing
temperature results in a
considerable reduction in
compressor electric demand. This
is shown in Fig.
3. As the rate of air flow increases
from 2 to 5 m/s the condensing
temperature decreased by about
17.54 % and the corresponding
reduction in compressor power
consumption is about 14.2 %.
2200
2400
2600
2800
3000
3200
3400
3600
3800
4000
0
10
20
30
40
50
60
70
2 2.5 3 3.5 4 5
POWERCONSUMPTION(W)
CONDENSINGTEMPERATURE(°C)
CONDENSER AIR FLOW (m/s)
condensation temperature
power consumption
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Effect of Return water temperature
Fig.5 Effect of return water temperature on evaporating temperature and
cooling capacity
1. The evaporating temperature
increases as the return water
temperature increases
2. the cooling capacity increases
with the increase of evaporator
temperature. This increase in
cooling capacity is due to the
increase of mass flow rate of
refrigerant with the slight
variation in the enthalpy
(refrigerating effect).
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6
7
8
9
10
11
12
13
14
-3
-1
1
3
5
7
9
11
13
15
5 7 9 11 13 15
COOLINGCAPACITY(kW)
EVAPORATINGTEMP(°C)
RETURN WATER TEMPERATURE (°C)
Evaporating temp
cooling capacity
FLOW RATE OF WATER = 2.267 m3/hr
19

Fig.6 Effect of Return water temperature on compressor power
consumption and cycle COP
1. As return water T
increases, condensing
temperature also
increases
2. Thus the increase in
condensing pressure and
the pressure ratio, leads
to an increase in power
consumption and a
increase in the cycle
COP.
3. The power consumption
is increased by 25% and
the increase in COP is
about 12% as shown in
the figure.
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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)
power consumption
COP
FLOW RATE OF WATER = 2.267 m3/hr
20

Effect of Return water temperature on mass flow rate of
refrigerant
1. Mass flow rate of refrigerant
increases from 33 kg/hr to 45
kg/hr, when the inlet water
temperature increases from 5 to
15 °C.
2. This is the reason for the
increase in cooling capacity.
3. Mass flow rate outweighs the
enthalpy difference.
5/24/2019
25
30
35
40
45
50
4 6 8 10 12 14 16
MASSFLOWRATE(kg/hr)
FLOW RATE OF WATER = 3 m3/hr
21

Variation of evaporator outlet water temperature for constant
flow rate of water
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0
2
4
6
8
10
12
5 7 9 11 13 15
OUTLETTEMPERATUREOFWATER
(°C)
FLOW RATE OF WATER = 3 m3/hr
22

Effect of Return water temperature for variable flow rate of water
1. As evaporator inlet water flow
rate increases with same inlet
temperature, compressor
power consumption increases
due to increase in mass flow
of refrigerant.
2. When the inlet water
temperature increases, the
power consumption also
increases with respect to
variable flow rates.
Fig.7 Effect of return water temperature on compressor power consumption
for varying flow rates of water
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2.43
2.53
2.63
2.73
2.83
2.93
3.03
3.13
4 6 8 10 12 14 16
Q = 2.267 m3/hr
Q = 2.5 m3/hr
Q = 3 m3/hr
Q = 4 m3/hr
Q = 5 m3/hr

9.5
10
10.5
11
11.5
12
12.5
13
13.5
14
4 6 8 10 12 14 16
COOLINGCAPACITY(kW)
FLOW RATE = 2.267 m3/hr
FLOW RATE = 2.5 m3/hr
FLOW RATE = 3 m3/hr
FLOW RATE = 4 m3/hr
FLOW RATE = 5 m3/hr
Fig.8 Effect of return water temperature on cooling capacity
5/24/2019 24

Charge optimization
 By varying the refrigerant
charge from 250 to 750 grams
for different flow rates of
water, condenser pressure is
increased with the increase of
pressure ratio as well
 At an optimum charge(certain
limit), the condenser vapour
volume decreases with
increase in liquid volume. so
discharge pressure is
increased drastically.
5/24/2019 25
1500
1700
1900
2100
2300
2500
2700
2900
0.2 0.3 0.4 0.5 0.6 0.7 0.8
CONDENSERPRESSURE(kPa)
REFRIGREANT 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
Fig.9 Effect of refrigerant charge on condenser pressure for different flow
rates of water

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2
2.3
2.6
2.9
3.2
3.5
3.8
0.2 0.3 0.4 0.5 0.6 0.7 0.8
REFRIGREANT 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
26
Fig.10 Effect of refrigerant charge on power consumption for different
flow rates of water

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3.3
3.4
3.5
3.6
3.7
3.8
3.9
4
4.1
4.2
4.3
0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65
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
27
Fig.11 Effect of refrigerant charge on COP for different flow rates of water

5/24/2019 28
EXPERIMENTAL RESULTS

Pull Down Characteristics
Initial test condition at no load:
 Suction pressure = 55 psi
 Discharge pressure = 230 psi
 Charge quantity = 600 grams
 Water tank temperature = 22 °C
 Flow rate of water = 0.61 kg/s
 Mass of water in the tank = 82 kg
 Specific heat of water = 4.187 kJ/kgK
5/24/2019 29
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)
Fig.12 Pull down characteristic curve – Temperature vs
Time graph
Capacity = m*cp*dT/dt
Q = 82*4.187*(22-8)/492
Q = 9.77 kW.

Performance Analysis of Ammonia Chiller at Loaded Condition
Initial test condition with load
• Evaporating pressure = 65 psi
• Condensing pressure = 240 psi
• Refrigerant Charge = 600 grams
• Flow rate of water = 0.61 kg/s
• Initial Tank temperature = 8 °C
Final condition after 3 hours
• Final Tank temperature reached = 14 °C
• Final chilled water inlet temperature = 11 °C
• Supply air temperature = 17 °C
• Return air temperature = 31 °C
5/24/2019 30
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
Fig.13 Variation of compressor power with respect to time

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34
36
38
40
42
44
46
48
50
0 15 30 45 60 75 90 105 120 135 150 165 180
Massflowrate(kg/hr)
8
8.5
9
9.5
10
10.5
11
11.5
0 15 30 45 60 75 90 105 120 135 150 165 180
Coolingcapacity(kW)
Fig.14 Variation of mass flow rate of refrigerant with respect
to time
Fig.15 Variation of cooling capacity with respect
to time

5/24/2019 32
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
8
9
10
11
12
13
14
15
0 15 30 45 60 75 90 105 120 135 150 165 180
WaterTanktemperature(°C)
Fig.16 Variation of coefficient of performance with respect
to time
Fig.17 Variation of water tank temperature with respect
to time

CONCLUSION
Simulation study
 When the condenser inlet air temperature is increased from 30 to 50 °C, the
cooling capacity decreases by 10.8%, condensing temperature increases by 48%,
power consumption increases by 36% and the COP decreases by 34%.
As the rate of air flow increases from 2 to 5 m/s, the condensing temperature
decreases by 17.54 % and the compressor power decreases by 14.2 %.
When the return water temperature increases from 5 to 15 °C, the power
consumption is increased by 25% and the increase in COP is about 12%.
The optimum charge for the 3 TR ammonia chiller was found to be 550 grams.
The lowest possible charge was 250 grams for which the COP was 3.6.
5/24/2019 33

Experimental study
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.
5/24/2019 34

Comparison
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.
5/24/2019 35
Parameter Simulation
Results
Experimental
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

REFERENCES
Andy Pearson (2018), Star Refrigeration, “Refrigeration with ammonia”,
International Journal of Refrigeration, Vol. 31, les 44, pp. 545-551.
Bjorn Palm (2007), “Ammonia in low capacity refrigeration and heat pump
systems”, 2008 International Journal of Refrigeration, Vol. 31, pp. 709-715.
Bontemps A (2007), “Refrigerant charge in refrigerating systems and strategies of
charge reduction”, 2008 International Journal of Refrigeration, Vol. 31, pp. 353-
370.
Caleb Nelson P.E (2018), “Analysis of the long-term suitability of ammonia
chillers”, 2008 International Journal of Refrigeration, Vol. 31, pp. 459-473.
Corberan J.M (2015), “Optimal design of a light commercial freezer through the
analysis of the combined effects of capillary tube diameter and refrigerant charge
on the performance”, 2015 International Journal of Refrigeration, Vol. 52, pp. 1-
10.
5/24/2019 36LOW CHARGE AMMONIA VAPOUR COMPRESSION REFRIGERATION SYSTEM FOR

Fuji taka A (2010), “Application of Low Global Warming Potential Refrigerants for
Room Air Conditioners”, 2010 International Symposium on Next Generation Air
Conditioning and Refrigerant Technology, 17-19 February, Tokyo, Japan
Hoehne M.R, Hrnjak P.S (2004), "Charge minimization in systems and components
using hydrocarbons as a refrigerant", ACRCTR224.
Kamlesh chhajed, Nilesh patil (2015)," Adsorption of N2, CH4, CO and CO2 gases in
single walled carbon nanotubes", IJARSMT.
Pega Hrnjak (2008), “Microchannel heat exchangers for charge minimization in air-
cooled condensers and chillers”, International Journal of Refrigeration, Vol. 31, pp. 658-
668.
Perk C. V, Hrnjak P. S (2004), "R-410A air conditioning system with micro-channel
condenser", International refrigeration and air conditioning conference p.no-556.
Santiago Martinez Ballester (2011), “Influence of the source and sink temperatures on
the optimal refrigerant charge of a water-to-water heat pump” International Journal of
Refrigeration, Vol. 34, pp. 881-892.
5/24/2019 37

5/24/2019 38
THANK YOU

Low charge ammonia vapour compression refrigeration system for residential air-conditioning

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