Energy and Power Engineering, 2010, 2, 298-305
doi:10.4236/epe.2010.24042 Published Online November 2010 (
Copyright © 2010 SciRes. EPE
Thermodynamic and Experimental Analysis of an
Ammonia-Water Absorption Chiller
Dingfeng Kong, Jianhua Liu, Liang Zhang, Hang He, Zhiyun Fang
School of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai, China
Received August 4, 2010; revised September 15, 2010; accepted October 16, 2010
A single stage ammonia-water absorption chiller with complete condensation is designed, built and tested.
The apparatus is designed for a cooling capacity of 2814 W, which is obtained using electric heater as heat-
ing source. The thermodynamic models have been derived using the First and Second Laws. Calculated re-
sults are compared with experimental data. The results show that the cooling capacity of experimental appa-
ratus is found between 1900 and 2200 W with the actual coefficient of performance (COP) between 0.32 and
0.36. The contribution of the components to internal entropy production is analyzed. It shows that the larger
irreversibility is caused by spanning the largest temperature and dissipated thermal energy by heat transfer
losses at the generator and evaporator. In the experimentation, the low pressure is lower than the designed
value. This is a consequence of a large capacity in the falling film absorber which performs as expected. This
decreases the evaporation pressure, and the evaporating temperature could be reduced to the designed value.
Keywords: Absorption Chiller, Ammonia-Water, Thermodynamic Modeling, Experimental, Performance
1. Introduction
Widespread efforts are currently underway to utilize
available energy resources efficiently by minimizing
waste energy and develop replacements for the tradition-
ally refrigerants (CFCs and HCFCs), which contribute to
ozone depletion and greenhouse warming. Absorption
chillers which are heat-powered refrigeration systems
have got more and more attention, due to the recognition
of rational utilization of energy and the concerns about
ecological problem.
The ammonia-water mixture is environmental friendly,
which is the only working pair currently used for refrig-
eration purposes in absorption systems, and despite of
the new mixtures under investigation, the ammonia-water
mixture is the only one with a clear future [1]. The prin-
ciple of the absorption is providing the necessary pres-
sure difference between the vaporizing and condensing
processes, which alternately condenses under high pres-
sure in the condenser by rejecting heat to the environ-
ment and vaporizes under low pressure in the evaporator
by absorbing heat from the medium being cooled. Am-
monia-water absorption chillers have been widely used
in many occasions [2].
Amount of work associated with theoretical and ex-
perimental analysis of the commercial absorption chillers,
using ammonia-water as the working fluid, is available in
the literature [3,4]. There are three classical kinds of en-
doreversible modeling in previous approach [5-9]. K. C.
Ng et al. presented an explicit irreversible thermody-
namic model, which considered external and internal
losses, to permit easy determination of optimal operating
conditions of chiller, as well as a predictive and diagnos-
tic capability [10-14]. Via comparison with actual data of
an absorption chiller, firstly, it clearly demonstrated that
all endoreversible models fail to capture part of the key
losses which contribute to the chiller COP. By account-
ing for only the external irreversibilities, they over pre-
dict the chiller COP by as much as 160-180%. Secondly,
endoreversible models portray an incorrect trend for
COP in the upper region of the characteristic plot, which
also predicts no maximum for the COP at the practical
cooling range of absorption chillers. The reasons for this
is all endoreversible models ignore the presence of in-
ternal losses stemming from heat and mass transfer in the
generator and absorber, internal regeneration and throt-
tling. A key element of accounting for internal entropy
production is the use of a process average temperature to
The research is funded by The Innovation Fund Project for Graduate
Student of Shanghai (JWCXSL0901)
Copyright © 2010 SciRes. EPE
analyze energy and entropy flows. An accurate process
average temperature is essential to perform chiller diag-
nostics, or predict chiller performance under different
operating conditions, or evaluate efficiency improve-
ments that would derive from diminishing a given source
of irreversibility. H. T. Chua et al. developed a general
definition of the process average temperature. It is based
on the method of computing for the process average
temperature for the evaporator, condenser, generator and
absorber [15].
However, most of the research is carried out with
commercially fashioned chillers that have been specifi-
cally designed as an air-cooled system. To investigate the
system characteristics being consistent with the reality,
an experimental apparatus is designed and fabricated,
using the irreversible thermodynamic model. All air-
cooled components are replaced by water-cooled com-
ponents, and variation of some operating parameters
should be carried out. The model considers both the ex-
ternal and internal losses in ammonia-water absorption
chiller to accurately predict the chiller COP at its nomi-
nal range of cooling capacity.
2. Experimental Testing of the Apparatus
2.1. Description of the Apparatus
An experimental apparatus has been designed and built
to study the performance of a single stage ammonia–
water system with complete condensation. A schematic
diagram and a photograph of the experimental apparatus
are shown in Figure 1. The major components are the
generator, vertical sieve tray tower with complete con-
densation (VST), absorber, condenser, evaporator, solu-
tion heat exchanger (SHE), subcooler, ammonia fluid
reservoir (AFR), solution fluid reservoir (SFR), pump
and refrigerant expansion device (RED) and weak solu-
tion expansion device (SED).
The ammonia-water mixture is heated in the generator
Pump 1
Cooling water
valve 1
Pump 2
valve 2
Figure 1. A schematic diagram of the apparatus. State points are same in figures and tables below.
Copyright © 2010 SciRes. EPE
by electric heater, which is equipped with three sets of
electric resistances, 3000 W each. The heater power can
be adjusted and controlled. The heat power reaches val-
ues of up to 9000 W. An electro connecting pressure
gauge is installed in the generator. For normal operating
conditions, the system high pressure side is approxi-
mately 14 bar. The electric heater is turned off under the
conditions of more than 23 bar. Then ammonia vapour is
separated, but it is mixed up with fractions of water va-
pour. The purification process is carried out by a VST,
where a counter-current contact is established between
an upward vapour flow and a downward liquid flow.
The VST is built with the seamless tube in Steel
ASTM 1020 of 68 mm inner diameter and a total length
of 1800 mm, divided into 6 sections, in order to disas-
semble conveniently, 300 mm each. Two pairs of 10 mm
thick Pyrex glasses are installed in each section mounted
on 102 mm from bottom, which allow checking if flood-
ing inside the VST occurs. To reduce heat losses to the
environment, the stripping section of VST and generator
are insulated with a mineral wool preformed pipe of
thickness 15 mm.
The vapour enriched in ammonia content leaving the
VST is condensed in a plate type condenser, cooled by
water, which removes heat from the gas mixture and the
vapour is condensed to a liquid. After the vapour is com-
pletely condensed, the liquid leaves the condenser and
passes to the subcooler. The subcooler is a shell and tube
heat exchanger, which reduces the temperature of the
liquid. When the liquid mixture leaves the subcooler, the
pressure drops as it passes through a RED into the
evaporator. After leaving the evaporator, the vapour is
further heated as passing through the subcooler to the
absorber. The high pressure weak solution leaving the
generator enters a SHE. Finally, the weak solution passes
through a SED and enters into the absorber with the re-
frigerant vapour coming from the subcooler. Then the
vapour is absorbed into the weak solution from the gen-
erator in the water-cooled absorber, which is a falling
film type. The strong solution is now at the lower cycle
pressure, and it must be sent to the stripping section. This
is achieved by a diaphragm pump. Then the cycle is
2.2. Data acquisition System
The experimental apparatus has been equipped with an
acquisition data system based on a PC and an acquisition
data card. Refrigerant, absorbent temperatures are col-
lected from PT-100 probe with accuracy of ±0.15 K.
Pressures are obtained from piezoelectric transducers
with an accuracy of ±0.2 bar. The cooling water flow
rate in the condenser and absorber is measured by means
of a rotary flowmeter with an accuracy of ±0.2%. The
rest of flow rate in the apparatus is measured by means
of a Coriolis sensor with accuracy of ±0.1% and elec-
tromagnetic turbine sensors with an accuracy of ±0.3%.
Concentrations of the binary mixture are determined by
titration with an uncertainty of ±4%. Before experimen-
tation, the entire instruments have been calibrated.
Evaporation and condensation temperatures, high and
low pressures, and concentration are recorded.
2.3. Experimental Procedure
After the system is evacuated with a vacuum pump, the
SFR and generator are filled with 120 l of aqueous solu-
tion of ammonia with mass concentration of 0.40. All
valves on the apparatus are closed. The required experi-
mental generation heat value is of 6000 W. In order to
generate the needed temperature, it is needed to adjust
the power of electric heater. The rate of heating is con-
trolled below 363 K/h. When the generation pressure is
raised in the scope of 6-7 bar, the SED and pump 1 are
opened to start the cycle of ammonia-water solution. The
cooling water valve of condenser is opened, when gen-
eration pressure gradually equals to condensing pressure.
Then the valve through the vapour on the top of VST is
opened. The cooling water flow is adjusted to control
pressure of VST whenever necessary. The quantity of
reflux is controlled to avoid for weeping or flooding. The
RED is opened as the liquid mixture passes into the
evaporator. The suction valve of saturated vapour leav-
ing from evaporator on the absorber is opened, while the
cooling water valve of absorber is opened. The absorbent
pressure and absorbent temperature are controlled to de-
signed values by adjusting cooling water flow on ab-
sorber. The cooling capacity is determined using a calo-
rimetric measuring procedure based on the regulations of
the thermal balance. In each test, a 120 kg of fresh water
in a thermal balance water box is kept at 293 K. An
aquarium pump is used to circulate the water. Once the
apparatus has reached the steady state, all test data are
recorded by the data acquisition system.
3. Mathematical Model
A mathematical model is developed to analyze the per-
formance of the experimental system. Temperatures and
pressures of working fluid are based on designed values.
Water and ammonia properties are obtained from stan-
dard properties of pure substances table in the ASHRAE
[16]. Specifically, ammonia-water properties are based
on procedures developed by Tillner-Roth and Friend
Copyright © 2010 SciRes. EPE
3.1. First and Second Law Analysis
The thermodynamic models of components ensure en-
ergy balance, mass balance and entropy production ap-
plying the Second Law of Thermodynamics. With the
expression for heat transfer rate i
Q, the thermal con-
ductance of component is calculated from
[()() ]
 
S represents the summations of the entropy genera-
tion due to heat and mass transfer in the certain compo-
int /
out in
 (2)
From Equation (2), an accurate process average tem-
perature i
T is essential as defining and deriving int
which translates into accurate evaluation of heat ex-
changer effective thermal conductance. i
T is intent
upon performing chiller diagnostics, or predicting chiller
performance under different operating conditions, or
evaluating efficiency improvements that would derive
from diminishing a given source of irreversibility.
From Equation (3), i
T is computed from the properly
weighted piecewise compilation of measured tempera-
tures along nonisothermal paths. In practical situations,
the thermodynamic system is expected to relate to as an
effective blackbox which can be probed from the outside
only, i.e., for which only nonintrusive measurements at
the inlets and outlets are realistic. These claims were
demonstrated in Ref. 18. So the correct process average
temperature should be calculated using experimental
measurements and basic thermodynamic analysis for
ammonia-water absorption chiller. All the terms on the
right hand side of Equation (3) can be computed from the
thermodynamic properties of the refrigerant if the local
pressures and temperatures at the inlets and outlets are
3.2. Assumptions
It is saturated state, when the weak solution leaves
the generator at the generation temperature.
The refrigerant leaves the condenser at the con-
densing temperature as saturated liquid.
The refrigerant leaving the evaporator is evapo-
rated completely as saturated vapour.
The strong solution leaves the absorber at the ab-
sorbent temperature as saturated liquid.
The energy balances do not contain the heat losses
in the VST, so the effect of VST is neglected.
Applying Equations (1) and (2) for each component,
the heat transfer rates and entropy generation are sum-
marized in Table 1 below.
3.3. System Thermal Balance
The internal energy and the entropy of the working fluids
in the absorption cycle are written as follows:
intint int int int intint
totgcaeSHE sc
int intint
 
  (4)
3.4. Coefficient of Performance
The general refrigeration system can be considered as a
perfectly reversible system, the net refrigerating effect is
the heat absorbed by the refrigerant in the evaporator.
The theoretical COP is given by
In the absorption refrigeration system, the total energy
supplied to the system is the total of the heat supplied in
the generator and work done by the pump. The actual
COP of the ammonia-water absorption chiller is calcu-
lated from
4. Discussion
4.1. Comparison between Actual and Calculated
Table 2 tabulates the summary of heat transfer rates and
performance parameters of the apparatus. The actual
COP decreases reaching values of 90% at the theoretical
COP of 0.469. Therefore the work of the pump can not
be neglected when considering the performance of ab-
sorption chiller.
Referring to the Figure 2, the actual results are found
to lie between 75% and 85% of the calculated values.
The difference may result from heat loss from the gen-
erator, low concentration and large resistance of refrig-
erant and supercooling degree does not meet the re-
quirements, etc. When deciding which one is main factor,
multiply the surface area of the generator with the dif-
ference between the temperature of the surrounding and
that of the generator. Then divide the result with the ad-
Copyright © 2010 SciRes. EPE
Table 1. Summary of first and second law relations for each component of the apparatus.
Component Mass balance Energy balance Entropy generation
Generator 47 8
44 7788
mx mxmx g447788
Condenser 910
Qmh-h int
Absorber 612a 1
mm m
66 12a12a11
mxm xmx
a661212 11aa
Qmhmh mh 
Evaporator 11 12
Qmh-h int
SHE 23
SHE3 3 24 4 5
SHE2 2435
Subcooler 10 10a
sc101010a12 12a 12
Qmhh mhh-= -
sc10 10a12a1012
Pump 1 12
mm P2211
Wmhmh int
SED 56
RED5 56 6
Qmhmh= int
RED 10a 11
mm RED10a10a11 11
Qmhmh= int
RED10a 11 10a
Table 2. Properties of the various state points for the chiller.
State h (kJ/kg) m (kg/s) P (bar) T (K) x
(kg/kg) s(kJ/kg·K)
1 65 0.01756 2.06 309 0.40 0.7647
2 65 0.01756 14.37 309 0.40 0.6493
3 326 0.01756 14.37 363 0.40 1.854
4 430 0.01481 14.37 393 0.29 1.858
5 100 0.01481 14.37 319 0.29 0.649
6 100 0.01481 2.06 319 0.29 0.6497
7 1830 0.00274 14.37 368 0.95 5.6577
8 350 0.01781 14.37 368 0.40 1.4752
9 1680 0.00274 14.32 318 0.998 5.9196
10 500 0.00274 14.32 318 0.998 1.7853
10a 414 0.00274 14.32 313 0.998 1.6321
11 414 0.00274 2.36 258 0.998 1.6415
12 1440 0.00274 2.36 258 0.998 6.3315
12a 1526 0.00274 2.36 293 0.998 6.5272
Summary of heat transfer rates and performance parameters of the apparatusCOP0.424 th
COP 0.467 P636WW sc 236WQ SHE 4300WQ
g6000WQ e2814WQ a4526WQ c4100WQ.
dition of the ratio of the thickness of the generator and
thermal conductivity of the generator and that of the
thickness of the insulation material and thermal conduc-
tivity of the insulation material. It can be seen that, the
heat loss from the generator is the main reason of the
In the experimentation, adjust the flow of refrigerant
by changing the opening of RED to ensure the constant
temperature level of the generator along with increasing
the heat load. The calculated cooling capacity increases
almost linearly with the generator heat input. It is dis-
covered that to operate the experimental apparatus there
is a minimum generator input (around 4800 W). When
the heat input is lower than the minimum value, the sys-
tem is not able to produce any cooling capacity. To ob-
tain a rectifying effect, a minimum vapour generated is
required. Then the vapour rises through the VST and
flows counter-currently with a liquid introduced at the
Copyright © 2010 SciRes. EPE
Figure 2. Comparison between actual and calculated cool-
ing capacity.
top of the VST. When the heat input increases beyond
the minimum value, it can produce cooling capacity
since there is enough liquid ammonia throttled and en-
tered the evaporator. Further increase in heat input pro-
duces a higher cooling capacity as more pure refrigerant
vapour is generated. This also causes COP to increase.
Then the liquid refrigerant completely evaporates in the
evaporator and maximum cooling capacity is obtained.
From the curve, it can be seen that when the heat input
continues to increase around 6000 W, the cooling capac-
ity increases with a lower rate. This implies that the lev-
elling off cooling capacity is limited due to the fixed
condensing pressure, temperature limitations, or rising
need for rectification.
4.2. Discussion of the Results and Structure
The measured pressures, temperatures, mass flow rate
and mass concentration of the component for steady state
operation are listed in Table 3, along with the computed
states at each point.
In the experimentation, the low pressure is lower than
the designed value. This is a consequence of a large ca-
pacity in the falling film absorber which performs as
expected. This decreases the evaporation pressure, and
the evaporating temperature could be reduced to the de-
signed value. Considering the actual results are found to
lie between 75% and 85% of the calculated values, the
contribution of the components to internal entropy pro-
duction based on a general macroscopic equation is ana-
lyzed. Table 4 presents the contribution of the compo-
nents depicted in Figure 1 to internal entropy production
based on the above mentioned entropy production equa-
When calculated results are compared with actual val-
ues, this should show how losses for different devices
occur and how the system could be modified. The analy-
Table 3. Measured and computed properties of the chiller.
Parameters (Point) Computed Measured
Weak solution (4)0.29 0.2919 ± 0.0061
Strong solution (1)0.40 0.4138 ± 0.0070
x (kg/kg)
Refrigerant (9) 0.998 0.9689 ± 0.0012
Inlet Generator 14.37 14.035 ± 0.281
Condenser 14.32 14.00 ± 0.455
P (bar)
Inlet Evaporator 2.36 1.95 ± 0.09
Weak solution (4)0.01481 0.015 ± 0.0002
Strong solution (1)0.01756 0.01756 ± 0.0009
m (kg/s)
Refrigerant (9) 0.00274 0.00199 ± 0.0001
Outlet VST 318 321 ± 0.31
Outlet RED 258 259 ± 0.03
T (K)
Evaporator 293 298 ± 0.15
Table 4. Contribution of the components to internal entropy
Components int
S int int
Generator 1.4786 0.2377
Condenser 1.8978 0.3051
Absorber 0.1543 0.0248
Evaporator 1.9436 0.3125
SHE 0.0755 0.0121
Subcooler 0.1164 0.0187
SED 0.0104 0.0017
RED 0.0258 0.0042
Pump 1 0.5176 0.0832
S 6.2199 1
sis shows that the generator contributes to the entropy
generation, approximately 24% of the total internal en-
tropy production. Thermal energy is dissipated by heat
transfer losses at the generator. The irreversibility in the
generator results from spanning the largest temperature
and low utilization of electric heater. The utilization fac-
tor of the electric heating is low and the degree of the
irreversibility is high, which leads to the increase of in-
ternal entropy. Other heating methods in the generator
should be developed to deduce irreversibility, such as
exhaust gas, solar energy and solar energy. The entropy
generation of the evaporator contributes 31% to the total
entropy generation. Insulation condition for evaporator
Copyright © 2010 SciRes. EPE
may be improved to diminish irreversibility, to promote
COP and cooling capacity.
The entropy generation of the condenser contributes
30% to the total entropy generation. Counter-current
condenser causes a larger temperature differences lead-
ing to a bigger entropy generation, in spite of high heat
transfer efficiency.
When the thermodynamic state point remains in 10a
instead of 10 with the subcooler before throttling, the
cooling capacity is 9% more than the values without a
subcooler. The entropy generation of the subcooler con-
tributes 1.9% to the total entropy generation. It is con-
cluded that, if the apparatus with a subcooler, the bene-
fits outweigh its drawbacks.
Simultaneous heat and mass transfer in the absorber
contributes only about 2.5% to the internal entropy pro-
duction of the chiller. The result also presents the con-
tribution of the RED and SED on the chiller’s perform-
ance, and it is only a significant, though not a dominating
5. Conclusions
A mathematical model is developed to analyze the per-
formance of a single stage ammonia-water absorption
refrigeration chiller with complete condensation. The
apparatus is tested with heat input values between 4800
and 6400 W for a high pressure of 14 bar. The cooling
capacity is found to be between 1900 and 2200 W with
COP between 0.32 and 0.36. The actual results are found
to lie between 75% and 85% of the calculated values.
Comparisons between actual and calculated values
show that heat loss from the generator have a remarkable
effect on the system performance, and the cooling capac-
ity is also limited due to fixed condensing pressure, tem-
perature limitations, or rising efficiency for rectification.
A more efficient thermal system should have a higher
COP and a lower total entropy generation. The entropy
generation is used to identify and quantify performance
degradation and the components responsible for it. The
results show that the larger irreversibility is caused by
spanning the largest temperature and dissipated thermal
energy by heat transfer losses at the generator and evapo-
6. Acknowledgements
An earlier version of this paper was presented at 2010
Asia-Pacific Power and Energy Engineering Conference.
7. References
[1] F. Ziegler, “Recent Developments and Future Prospects
of Sorption Heat Pump Systems,” International Journal
of Thermal Sciences, Paris, Vol. 38, 1999, pp. 191-208.
[2] A. Apte, “Ammonia Absorption Refrigeration Plants the
Ideal Refrigeration System for New Millennium,” Trans-
parent Energy Systems Private Limited, Pune, 2006.
[3] K. C. Ng, T. Y. Bong, H. T. Chua and H. L. Bao, “Theo-
retical and Experimental Analysis of an Absorption
Chiller,” International Journal of Refrigeration, London,
Vol. 17, 1994, pp. 351-358.
[4] A. Kececiler, H. I. Acar and A. Dogan, “Thermodynam-
ics Analysis of Absorption Refrigeration System with
Geothermal Energy: An Experimental Study,” Energy
Conversion and Management, London, Vol. 41, 2000, pp.
[5] J. Chen and B. Andresen, “Optimal Analysis of Primary
Performance Parameters for an Endoreversible Absorp-
tion Heat Pumps,” Heat Recovery Systems and CHP,
London, Vol. 15, 1995, pp. 723-731.
[6] A. Bejan, J. V. C. Vargas and M. Solokov, “Optimal
Allocation of a Heat Exchanger Inventory in Heat-Driven
Refrigerators,” International Journal of Heat Mass
Transfer, Vol. 38, No. 5, 1995, pp. 2997-3004.
[7] N. E. Wijeysundera, “Analysis of the Ideal Absorption
Cycle with External Heat-Transfer Irreversibilities,” En-
ergy, London, Vol. 20, 1995, pp. 123-130.
[8] C. Wu, “Cooling Capacity Optimization of a Waste Heat
Absorption Refrigeration Cycle,” Heat Recovery Systems
and CHP, Vol. 13, No. 4, 1993, pp. 161-166.
[9] C. Wu, “Specific Heating Load of an Endoreversible
Carnot Heat Pump,” International Journal of Ambient
Energy, Vol. 14, 1993, pp. 25-28.
[10] K. C. Ng, H. T. Chua and Q. Han, “On the Modeling of
Absorption Chillers with External and Internal Irreversi-
bilities,” Applied Thermal Engineering, Vol. 17, No. 5,
1997, pp. 413-425.
[11] H. T. Chua, J. M. Gordon, K. C. Ng and Q. Han, “En-
tropy Production Analysis and Experimental Confirma-
tion of Absorption Systems,” International Journal of
Refrigeration, Vol. 20, No. 3, 1997, pp. 179-190.
[12] K. C. Ng, K. Tu and H. T. Chua et al., “Thermodynamic
Analysis of Absorption Chillers: Internal Dissipation and
Process Average Temperature,” Applied Thermal Engi-
neering, Vol. 18, No. 8, 1998, pp. 671-682.
[13] H. T. Chua, “Universal Thermodynamic Modeling of
Chillers: Special Application to Adsorption Chillers,”
Ph.D. Dissertation, National University of Singapore,
Singapore, 1998.
[14] H. T. Chua, H. K. Toh, A. Malek and K. C. Ng, K. Srini-
vasan, “A General Thermodynamic Framework for Un-
derstanding the Behavior of Absorption Chillers,” Inter-
national Journal of Refrigeration, Vol. 23, No. 7, 2000,
pp. 491-507.
[15] H. T. Chua, H. K. Toh and K. C. Ng, “Thermodynamic
Modeling of an Ammonia-Water Absorption Chiller,”
International Journal of Refrigeration, Vol. 25, No. 7,
2002, pp. 896-906.
Copyright © 2010 SciRes. EPE
[16] “Thermo Physical Properties of Refrigerants,” ASHRAE
Handbook, 2005.
[17] R. Tillner-Roth and D. G. Friend, “A Helmholtz Free
Energy Formulation of the Thermodynamic Properties of
the Mixture {Water + Ammonia},” Journal of Physical
and Chemical Reference Data, Vol. 27, No. 1, 1998, pp.
[18] K. C. Ng, H. T. Chua and K. Tu, “The Role of Internal
Dissipation and Process Average Temperature in Chiller
Performance and Diagnostics,” Journal of Applied Phys-
ics, Vol. 83, No. 4, 1998, pp. 1831-1836.
AFR Ammonia fluid reservoir
COP Coefficient of performance
h Specific enthalpy (kJ/kg)
m Mass flow rate (kg/s)
P Presser (bar)
Q Heat transfer rate (W)
RED Refrigerant expansion device
Specific entropy (kJ/kg•K)
S Entropy production rate (W/K)
SED Weak solution expansion device
SFR Solution fluid reservoir
SHE Solution heat exchanger
T Temperature (K)
VST Vertical sieve tray tower with complete con-
W Work (kJ)
Ammonia mass concentration
a Absorber
c Condenser
e Evaporator
g Generator
i Component numbering index
in Inlet conditions
int Internal
out Outlet conditions
P Pump
RED Refrigerant expansion device
sc Subcooler
SED Weak solution expansion device
SHE Solution heat exchanger
th Theoretical value
Phase numbering index
tot Total value