EXERGETIC ANALYSIS OF TWO STAGE Li-Br/H2O VAPOUR ABSORPTION REFRIGERATION SYSTEM

1. EXERGETIC ANALYSIS OF TWO STAGE Li-
Br/H2O VAPOUR ABSORPTION
REFRIGERATION SYSTEM
Dissertation (Phase-I)
In
Mechanical Engineering
(Thermal Engineering)
By
Md Khurshid Alam
MTTE-15-07
Department of Mechanical Engineering
Al-Falah University,
Dhauj, Faridabad, Haryana, (India)
Dec-Jan 2015-16

2. EXERGETIC ANALYSIS OF TWO STAGE Li-
Br/H2O VAPOUR ABSORPTION
REFRIGERATION SYSTEM
Dissertation (Phase-I)
Submitted In partial fulfillment of the
Requirement for the award of the degree
Of
Master of Technology
In
Mechanical Engineering
(Thermal Engineering)
By
Md Khurshid Alam
MTTE-15-07
Under the supervision of
Mr .Subodh Kumar (asst-professor)
Department of Mechanical Engineering
Al-Falah University,
Dhauj, Faridabad, Haryana, (India)
Dec-Jan 2015-16

3. CERTIFICATE
I hereby certify that the work which is being presented in the M.Tech. minor project “Exergetic
Analysis Of Two Stage Li-Br/H2o Vapour Absorption Refrigeration System”in partial fulfillment
of the requirement for the award ofthe Master of Technology in Thermal Engineering and
submitted to the Department ofMechanical Engineering is an authentic record of the work
carried out from various research papers under the supervision of Mr.Subodh Kumar Asst-
professor, Departmentof Mechanical Engineering.
The matter presented in this project has not been submitted by me for the award of any other
degree elsewhere.
Md Khurshid Alam
MTTE-15-07
This is to certify that the above statement made by the candidate is correct to the best of my
knowledge.
Dr.Mohd.ParvezGUIDE
HODMr. Subodh Kumar
Department of Mechanical EngineeringAsst-Professor
Al-Falah University,Dhauj, Haryana. Al-Falah University,Dhauj, Haryana.

4. ACKNOWLEDGEMENT
First of all, I am thankful to “Allah” for compilation my project and to the entire crew of
thisproject, I would like to extend a giant thank to my supervisorMr. Subodh KumarAsst-
Professor,
Mechanical Engineering Department, for their intuitive and meticulousguidance in completion of
this minor project report. I want to express my profound gratitude for hisgenial and kindly co-
operation in scrupulously scrutinizing the manuscript and his valuablesuggestions throughout the
work. I will like to thank the Prof. (Dr.) Mohd. Parvez, HOD, Deptt. Of Mechanical Engineering
and all other professors for his valuable support in carrying out my work with sincere efforts.
I am especially indebted to my parents especially my father Nasruddin Ansari for their love and
support. They are my firstteachers after I came to this world and have set great examples for me
about how to live, study and work.
Md Khurshid Alam

5. ABSTRACT
Absorption refrigeration is increasingly becoming more applicable in process industries for
generating refrigeration. Waste heat available in the industries can be utilized for producing
useful refrigeration by heat operated absorption refrigeration cycles. Restricted use of
chlorofluorocarbons (CFCs) owing to the deplection of ozone layer will make absorption
refrigeration more prominent. However, thermodynamic efficiency of absorption refrigeration
cycle must be improved if it is to compete with vapour compression refrigeration cycles in most
application.
All current residential absorption chillers are used on the single effect cycles. Many studies have
been performed to analyze the performance under different operating conditions and employing
advanced cycles. Single-effect absorption are severely limited in their ability to utilize high-
temperature between 70 C and 100 Cs. Expectations of reducing energy supply, as well as an
interest in diversification of the motive power employed by HVAC technologies, have led to the
development of advanced absorption machines. Many unexplored advanced cycles exist, which
may be used to increase the coefficient of performance (COP) or the temperature lift provided by
such a device.
Double-effect absorption refrigeration cycles usually, two single-effect cycles are often
combined to increase the thermal efficiency or large operating ranges of generator temperatures.
In order to improve utilization of the high temperature heat source available from natural gas or
cogeneration systems, many advanced multi-effect cycles have been proposed that are capable of
substantial performance improvement over the single and double-effect cycles.
Energy and exergy analysis has been applied to double-effect vapour absorption refrigeration
sytem using a LiBr-H2O solution as the working fluid with the expectation of reduced energy
supply as well as an interest in diversification of the motive power employed by HVAC
technology.
This communication presents the energy and exergy analysis of an actual double effect steam
powered LiBr–H2O vapor absorption refrigeration system. Exergy loss, COP, exergy efficiency
and heat rate for each component of the system are calculated. The effect of generator as well as

6. evaporator temperature on the COP and exergy efficiency is evaluated and it is found that the
irreversibility rate is highest in the generator while it is found to be the lowest in the case
ofabsorber and condenser. It is also found that the COP of the system increases with the increase
in the evaporator temperature while it is found to be reverse in case of exergy efficiency. Results
revealed that average exergy loss is highest in the generator as compared to other components.
The results obtained are helpful for designers to bring changes in the actual system for
performance optimization and less wastage of energy.

7. NOMENCLATURE
Notations
COP ……………………………………Coefficient of Performance
VCR …………………………………… VapourCompression System
TR ……………………………………. Tonn of Refrigeration
HCFCs …………………………………. Hydro-Chlorofluorocarbons
HFC ……………………………………. Hydro-Flouro Carbon
CFC …………………………………… Chloro –Flouro Carbon
RAC …………………………………. Refrigeration and Air-Conditioning
m ……………………………………Mass flow rate
t …………………………………… Temperature
W …………………………………… Work Input
Q …………………………………... Heat
H …………………………………… Enthalpy
C …………………………………… Specific Heat
te....................................................... Evaporator Temperature
tc……………………………………. Condenser Temperature
LI-BR...........................................................Lithium Bromide
H2O..............................................................Water
…………………………………………. exergy efficiency

8. Table Of ContentsContent Page no.
 Certificate ……………………………………………………………………… 3
 Acknowledgement ………………………………………………………………. 4
 Abstract …………………………………………………………………………. 5-6
 List of Figures …………………………………………………………………… 11
 Nomenclature ……………………………………………………………………. 7
1. INTRODUCTION……….…………………………………………………….. 9-15
2. LITERATURE OVERVIEW………………………………………………… 16-23
3. METHODOLOGY...................................................................................................24
4. REFERENCES …………………………………………………………………25

9. 1. INTRODUCTION
Energy is considered to be major driving factor foreconomic development of any nation.
Recentdevelopments in cooling and heating systems show agrowing interest in the application of
vapor absorptionrefrigeration (VAR) systems. Absorptioncooling systems provide opportunities
for energysaving by utilizing waste heat, low grade energy, etc.to produce cooling. With increase
in the worldpopulation, thermal comfort requirements and lifestandards, the demand for energy
and its use for cooling is ever increasing. In order to optimize energyuse for cooling and heating
applications, research is being carried out to develop technologieswith reduced energy
consumption, peak electricaldemand and cost of energy without compromisingon the desired
level of comfort. Furthermore, renewablesources of energy such as, solar, geothermalbesides
waste heat can be used as their primaryenergy input.
In recent years, there has been growing interest touse principles of second law of
thermodynamics foranalyzing and evaluating the thermodynamic performance of thermal energy
systems. Second lawanalysis is based on the concept of exergy, which canbe defined as a
measure of work potential or qualityof energy relative to environmental conditions. Thishas been
used for understanding the irreversiblenature of real thermal processes and defining themaximum
available energy. In other words, exergycan be defined as the maximum theoretical
work,derivable by the interaction of an energy resourcewith the environment. Exergy analysis
applied toa system describes all losses both in the variouscomponents of the system and in the
whole system.With the help of this analysis, the magnitude of theselosses or irreversibilities and
their order of importancecan be understood. With the use of irreversibility,which is a measure of
process imperfection,the optimum operating conditions can be easily determined.The advantage
of exergy analysis based onthermo-economic optimization is that the differentelements of the
system could be optimized independently.It is possible to say that exergy analysis canindicate the
possibilities of thermodynamic improvementof the process under consideration.A large number
of researchers have used secondlaw analysis for thermodynamic optimization ofrefrigeration
plants based on the theoretical analysis given by authors. Ideal absorption cycle

10. wasdemonstrated as the combination of a Carnot drivingcycle with a Reverse Carnot cooling
cycle. Performanceand temperature relations of double, tripleand multistage cycles were derived
and the validationof fundamental thermodynamics for absorptioncycles was presented by
applying exergy analysis.The energy and exergy balance of an NH3–H2Oabsorption refrigerator
was also presented. Thebehavior of two-stage compound compression cyclewith °ash inter-
cooling, using refrigerant R-22, byexergy method was also investigated and the effectsof
temperature changes in condenser and evaporatoron the plant's irreversibility were determined.
Theexergy analysis of LiBr–H2O VAR cycle was carriedout and results reported that
thermodynamic processin the absorption refrigeration system releases alarge amount of heat to
the environment at temperaturesconsiderably above the ambient temperature,which results in a
major irreversible loss in thesystem components.An experimental investigation of a 10 kW
commerciallyavailable aqua-ammonia vapor absorption system was carried out and the response
of thesystem to variations in chilled water inlet temperature,chilled water level in evaporator
drum, chilledwater °ow rate and variable heat input were presented.An experimental evaluation
of a plant aimedat stimulating and verifying performances of singlestage H2O–LiBr absorption
machine was performed.The present communication carries the exergyand energy analysis of
496 TR absorption coolingsystem using LiBr–H2O as working fuids.
2. System Description (Double-Effect Two-Stage Unit) The system to be analyzed is a 496 TR
vapor absorption system as shown in Fig. 1 and uses saturated steam as heat source, H2O as
refrigerant andLiBr as an absorbent. It produces the chilled water under vacuum conditions for
the purpose of air conditioning applications. The chiller consists of a high pressure generator, a
low pressure generator, acondenser, an evaporator, an absorber, a high temperature heat
exchanger, a low temperature heat exchanger, a condensate heat exchanger and an auxiliary
generator for high pressure generator, having purging unit, de-crystallization piping and two
hermetically sealed pumps each for fluid and refrigerant. A double-effect chiller is very similar
to the single-effect chiller, except that it contains an additional generator unlike single effect
absorption refrigeration system. In a single-effect absorption chiller, the heat released during the
chemical process of absorbing refrigerant vapor into the liquid is rejected to the cooling water.
The main objective of a higher effect cycle is to increase system performance when high
temperature heat source is available. As shown in Fig. 1, high temperature heat from an external

11. source (steam) is supplied to the first effect generator. The chiller is purged from the
noncondensable gases and kept under the vacuum conditions. Weak solution from the absorber is
pumped into the high pressure generator through low temperature heat exchanger and high
temperature heat exchangers. It is heated by external heat source concentrating into intermediate
solution, and high temperature refrigerant vapor is produced.
Fig. 1. Block diagram of the vapor absorption system.
Refrigeration is a thermodynamic process in which external work is provided in order to move
heat from one location at lower temperature to other maintained at a higher temperature. It has
wide applications industrial and domestic areas including a major impact on agriculture and food
production as it allows large scale storage and processing of food and agricultural products.
Industrial applications include large scale air conditioning, refrigeration, cooling in
manufacturing, liquefaction of gases in chemical and petroleum industry, etc. Continuous

12. refrigeration consists of a refrigeration cycle, where heat is removed from a low-temperature
space or source and rejected to a high-temperature sink with the help of external work. Presently
most of the cooling produced is by vapour compression or vapour absorption refrigeration
system. The compressor of these vapor-compression systems use a huge amount of electrical
energy generated by burning fossil fuel. However the scarcity of energy around the world creates
the need for the development of a refrigeration system that may run on an alternative source of
energy. The traditional absorption refrigeration system has a number of shortcomings that
includes the complexity and the high manufacturing cost of the system including the solution
pump and the compressor and so on, the strict demand on the heat supply in both quality and
quantity.
Vapor absorption systems using water as the refrigerant and the lithium-bromide as the absorbent
represent the simplest idea in absorption refrigeration technology and are assuming greater
importance due to their environmentally friendly operation. The cost of these systems is
dependent on whether they are single effect or double effect. This in turns depends on the
application and the source of heat available.
Absorption refrigeration systems differ from compression systems by the use of a heat source as
the energy input in order to operate; conversely, compression based systems require mechanical
energy to operate. Thus the main advantage of the absorption systems is that they can run
burning a fuel or using waste heat recovered from other thermal systems. Moreover, these
systems present other advantages, such as high reliability, low maintainability and a silent and
vibration-free operation (New Buildings Institute, 1998). Another important aspect is the
elimination of CFC and HCFC refrigerants.
Single-effect absorption refrigeration systems have only one heating level of the working fluid
(dilute solution). The coefficient of performance (COP) of these systems, working with a
LiBr/H2O solution, is in the range of 0.6 to 0.7.
Double-effect absorption refrigeration systems have two stages of vapor generation to separate
the refrigerant from the absorbent. The heat transfer occurs at a higher temperature compared to
the single-effect cycle.

13. In recent years, interest in absorption systems has been growing because they use friendly
refrigerants and absorbents which don’t deplete the ozone layer. They use cheap alternative
energy sources, such solar energy or a waste byproduct heat source helping in control of global
warming. Therefore, in recent years, research has been increased to improve the performance of
the absorption refrigeration systems. The main way of improving efficiency is through
thermodynamic analysis and optimization.
Recent developments in cooling and heating systems show a growing interest in the application
of absorption systems. Absorption cooling and heat pump systems provide opportunities for
energy saving because they can use heat energy to produce cooling, instead of electricity which
is used by conventional compression chillers. Furthermore, non-conventional sources of energy
such as solar, waste heat, and geothermal sources can be used as their primary energy input. In
addition, due to the fact that absorption units use environmentally friendly working fluid pairs,
they do not deplete the ozone layer of the atmosphere.
Consequently the ban of certain CFCs and HCFCs has encouraged engineers and researchers to
give more consideration to absorption systems. Apart from these advantages, due to not having
compressor, absorption chillers have less moving and spinning parts, and therefore lower noise
and vibration, and consequently higher useful lifetime. However, these systems have some
disadvantages such as low coefficient of performances, crystallization, and corrosion etc. which
have attracted some investigations.
A single-effect absorption refrigeration cycle using aqueous lithium-bromide was first invented
in 1950s.Nowadays it is the most common and widely used absorption machine.Due to the
relatively low COP associated with single- effect technology, it is difficult for single-effect
machines to compete economically with conventional vapor compression systems except in low
temperature waste heat applications where the input energy is free.
Double-effect technology, with COP in the range of 1.0 to 1.2, is much more competitive. Gas-
fired double-effect water/lithium bromide technology is a mature technology that competes for
the gas cooling market segment. Competing gas-fired technology include gas engine-driven
vapor compression system and desiccant systems. Double-effect machines, using water/lithium
bromide as working fluid, are produced by a large number of manufactures world-wide. Each
manufacture uses a different design depending on its view of the market economics. The heat
input occurs at a much higher temperature in the double effect cycle than in the single effect one.

14. The COP of the double-effect technology is greater than of the single effect one because it is able
to utilize the increased availability of the higher temperature input heat. When compared to a
single-effect machine, the double-effect machine takes heat in at a higher temperature but it
rejects heat at approximately the same temperature and it provides the refrigeration at
approximately the same temperature.
The single effect water-lithium bromide cycle has been analyzed based on the first law of
thermodynamics, second law of thermodynamics and exergy. Kilic and Kaynakliused the first
and second law of thermodynamics to analyze the performance of a single-stage water-lithium
bromide absorption refrigeration system. They found that the highest exergy losses occur in the
generator regardless of the oper operating conditions. Sencan et al. studied a single effect water-
lithium bromide absorption system for cooling and heating applications. Talbi and Agnew
optimized a single-stage refrigeration system operating with the water-lithium bromide mixture
making enthalpy and entropy balances in each one of the components of the system. Misraetal,
used the exergetic cost theory to the water-lithium bromide vapour absorption system. Lee and
Sherif utilized the second law analysis to analyze the performance of multi stage water–lithium
bromide absorption heat transformers. The results provided theoretical basis for the optimal
operation and design of absorption systems. Liao and Radermacher are focused on combined
heat and power generation applications. Similar analysis has also been investigated for double
effect water-lithium bromide cycle. Furthermore, only few works are available on triple effect
absorption refrigeration system.
Recent analyses of ARS (absorptionrefrigeration systems)have included the second law of
thermodynamics to provide better understanding of the thermal performance characteristics of
each system components. This facilitated the detection of a component with high energy
dissipation or irreversible losses. Attention can then be focused on such a component to
minimize its irreversibile losses. Lee and Sherif applied both the first and the second law
ofthermodynamics to analyze multi-stage lithium bromide–water ARSs. The second law
efficiency of the chillers was calculated from the thermal properties, as well as the entropy
generation and exergy of the working fluids. Furthermore, Lee and Sherif used the second law
efficiency to quantify the irreversible losses compared to the total entropy generation, which
represents the energy dissipation of the system. Adewusi and Zubairused the second law of
thermodynamics to study the performance of single-stage and two-stage ammonia-water ARSs.

15. The entropy generation of each component and the total entropy generation of all the system
components as well as the coefficient of performance (COP) of the ARSs were calculated. The
results show that the two stage system has higher total entropy generation and COP, while the
single-stage system has a lower total entropy generation and COP. Apart from the other studies,
in this paper a thermodynamic analysis, including First and Second Law analyses, to LiBr-H2O
single-stage ARS powered by solar energy has been carried out. The entropy generation of each
component, the total entropy generation of all the components and the COP of the ARS are
calculated from the thermodynamic properties of the working fluid at different operating
conditions using manually.

16. Literature Review
1, SANJEEV ANAND* and ANKUSH GUPTA [2014] [1]: To carry out the comparative study
of the LiBr–H2O vapor absorption system the real-time data was measured and the calculations
were made using simple excel sheet. The temperature, pressure and mass flow rate were measured
using sensor-based thermocouple, pressure meter and flow meter, respectively, at different state
points. The basic properties such as entropy and enthalpy were calculated assuming the steady
state operation. The exergy loss (irreversibility) and other performance parameters were calculated
using a simple excel sheet.Imperfect heat and mass transfer in the system components, frictional
losses, mixing and circulating losses are the main factors responsible for the reduction in COP and
exergy efficiency. The losses due to mixing are because of evaporation of refrigerant in the
generator from a strong solution and this required large amount of heat as compared to refrigerant
in pure state. Due to this there is large exergy loss in the generator. In the present system, the
exergy loss for the condenser and absorber are same but usually the exergy losses in the absorber
are more as compared to condenser and this may be due to the fouling of the condenser heat
exchanger which has led to the increase in the exergy loss of condenser.
2, R. Palacios Bereche et.al [2009] [2]: The results show that, as expected, the exergetic cost of
the main product of the system is higher in the direct-fired case. On the other hand, the unit
exergetic costs of hot water and electricity in the second case are higher than unity because the
exergy to produce them in the cogeneration plant is being considered here. Concerning the
single-effect system the results of this work can be compared with those of Gonzales and Nebra
(2005), who applied functional analysis for a single-effect LiBr/H2O absorption refrigeration
system in a cogeneration plant. However the unit exergetic cost of the cooling effect was lower
for these authors (Gonzales and Nebra, 2005) due to several differences in the calculation.The
work of Accadia and Rossi (1998) also presented lower exergetic costs than the present work. It
is possibly due to better efficiency of the compression system and that those authors considered
the unit exergetic cost of the electricity equal to unity. Regarding the double-effect system, it can
be observed that the unit exergetic cost of the negentropy flow produced in the cooling tower in
the direct-fired system is lower than the cost for the steam-driven system. In the literature there
are a few works about thermo economic analysis for double-effect LiBr/H2O absorption
refrigeration systems. One of these works was done by Misra et al. (2005). Their exergetic costs

17. were lower, However, they assumed the unit exergetic cost equal to 1 for both steam and
electricity (fuels of the system).
3, B.Babu, G. Maruthi Prasad Yadav [2015] [3]: A considerable decrease of 52 in the
circulation ratio is observed due to the increase in the concentration of solution leaving the
generator with the increase generator temperature of 35o
C. This causes a rise in the C.O.P by
0.34 due to the fact that C.O.P increases with the decrease in circulation ratio. The generator
temperature rise by 25o
C causes a decrease of 3374kJ/kg in absorber and 3336.03kJ/kg in
generator heat load. Whereas the evaporator heat load and condenser heat load remains constant
since evaporator and condenser temperatures are constant.
4, Saeed Sedigh and Hamid Saffari [2011] [4]:The basic function provided by EES (Engineering
Equation Solver) is the numerical solution of non-linear algebraic and differential equations. In
addition, EES provides built-in thermodynamic and transport property functions for many fluids,
including water, dry and moist air, most CFC and HCFC refrigerants, and others. Included in the
property data base are thermodynamic properties for lithium bromide/water and ammonia/water
mixtures. The combination of a robust non-linear equation solver and absorption fluid properties
makes EES a very powerful tool for analysis and design of absorption systems. A computer
program has been developed using EES for carrying out the energy and energy analyses of the
double-effect absorption refrigeration systems. COP, overall heat transfer coefficient times area
and heat transfer rates of each component and amount of energy consumption by pumps. The
high mass fraction in the machine must be maintained below the point at which crystallization
occurs. This requirement was imposed as an assumption in modeling for convenience. In real
machine, the mass fraction change across a given component will be a complex function of the
operation characteristics and conditions. Thus, in general, it is not possible to design in a way
that the mass fraction difference is the same. In practice, some additional mixing irreversibility is
encountered when the solution returning from the high temperature generator is mixed with the
solution returning from the low temperature generator before it is sent to the absorber.Another
observation concerning mass fraction is that the change across the solution circuits displayed
here isabsorber. The variations of coefficient of performance in the two cycles with the output
flow rate in absorber. It can be seen that the coefficient of performance of the parallel cycle is
higher than that of the series cycle but the coefficient of performance increases in both the cycles
with the increases of output flow rate in absorber. The COP of the series flow configuration is

18. lower than that of the parallel flow configuration but the capacity of the series flow configuration
is higher. A number of parameters change between the two cycle solutions causing the COP
difference. Careful study of the solutions reveals, however, that the key difference is the
increased heat transfer load on the high solution heat exchanger. The relatively larger solution
flow rate in the upper solution circuit causes a small mass can be seen that the heat exchanged is
higher in series cycle than the parallel cycle. The increased capacity of the series flow
configuration is apparently the result of a better temperature match in the high temperature
generator and the internal heat transfer between the high temperature condenser and low
temperature generator. A better temperature match in the high temperature generator would be
relatively simple to achieve in the parallel flow case by simple decreasing the heat transfer fluid
to decrease, it actually decrease the capacity of the parallel flow machine. The point of this is
that the comparisons between the two design choices are not very straightforward. It is somewhat
simplistic to compare the configurations on the basis of an arbitrary set of design parameters.
The variations of the heat exchanged in absorber against the output flow rate in absorber. It can
be seen that the heat exchanged is higher in series cycle than the parallel cycle. The variations of
the heat exchanged in high temperature generator and condenser in terms of the output flow rate
in both the series and parallel cycles respectively. It can be seen that the heat exchanged is higher
in series cycle than the parallel cycle.
5, A.I.Shahata, et.al [2012] [5]: The results are presented by plotting the coefficient of
performance and the exergetic efficiency versus the temperature for the different components of
the vapor absorption system. The effect of the generator temperature on the COP and the
exergetic efficiency for both single and double-effect absorption systems. The following
parameters are used: [Qe=425.56 kW, Te=1.3oC, Tc= 350
C, ε=0.7and Ta=350
C] for single effect
system while [Qe=425.56 kW, Te=1.30
C Tlc=35 0
C, ε=0.7and Ta=350
C] for double effect
system. It is shown that there is an increase in both COP and exergetic efficiency initially for
both single and double effect systems and then both COP and exergetic efficiency decrease as
the generator temperature increases. The maximum COP and exergetic efficiency for single
effect is 0.76 and 12.3 while the maximum COP and exergetic efficiency for double effect
system is 1.31 and 11.48 respectively. The parallel flow-double effect system has a higher COP
compared with the single effect system. On the other hand, the parallel flow-double effect system
has a lower exergetic efficiency compared with the single effect system.

19. 6, A. Pongtornkulpanich et.al [6]:A theoretical comparative study of thermodynamic between a
lithium-bromide ejection absorption heat transformer and a conventional cycle is investigated and
presented in this paper. Based on the thermodynamic equation (P,T,X) and (h,T,X), the required
enthalpies for each component are obtained for calculations of heat applied at evaporator, heat
supplied at generator, heat delivered to condenser and to absorber on both two cycles. With the only
different analysis at the ejector-absorber unit, the exit diffuser pressure of solution, which is the most
significant parameter and equals the absorber pressure, is lifted. This pressure causes the solution
temperature of inlet solution to the absorber to increase which leads to increased enthalpy of solution
entering to the absorber. The energy balance (first law analysis) at the absorber shows that the
upgraded heat load is obtained to be increased. Then, the COP of a modified cycle is improved with
the value of 0.654 from that of 0.486 for a conventional cycle as compared to the same energy input
supplied to the system. Based on energy flow analysis, the sum of the heat input at the evaporator
and at the generator is found to be slightly different to that of the heat rejected at the condenser and
at the absorber with the energy loss of 0.0669 kW for a conventional cycle. For a modified cycle
obtained by a Carnot engine operating between Tab and To, increases due to increasing heat rejected
at the absorber. This exergy increased causes the exergy efficiency based on the second law to
increase with the value of 44.66% from the value of 33.17% for a conventional cycle when the two
cycles is considered at the same energy input introduced to the system. The next largest exergy loss
is occurred in the generator due to the temperature difference between the heat source and the
temperature of the working fluid.
7, Saeed Sedigh, et.al [2012] [7]:The analysis of the first law of thermodynamics has been
investigated for each of the system components, and then having obtained the properties of all
the points of the system, the second law analysis has been carried out on different system
components. The thermodynamic states for different points of the system. As it can be seen,
when the LPG temperature increases, the total coefficient of performance of the system increases
while with the increase of the HPG temperature, the total coefficient of performance of the
system decreases. The exergy efficiency of the system in terms of HPG and LPG temperatures.
As it can be seen, the exergy efficiency increases with the increase the LPG temperature, and the
exergy efficiency decreases with the increase of the HPG temperature. The heat exchanged in

20. four components of the system including absorber, condenser, HPG and LPG in terms of the
HPG and LPG temperatures. the heat exchanged in four components of the system including
absorber, condenser, HPG and LPG in terms of the HPG and LPG temperatures. The heat
exchanged in absorber does not vary with HPG temperature, but when the LPG temperature
increases, the heat exchanged inabsorber decreases.
8, J. M. ABDULATEEF, et.al [8]: A computational routine was written in MatLab for the
thermodynamic analysis. The initial conditions were given to the routine as initial inputs/data
including solar collector conditions, component temperatures, pump efficiency and effectiveness
of heat exchanger. With the given parameters, the thermodynamic properties of the fluid at all
reference points in the cycle were calculated. In this work, the thermodynamic properties of the
LiBr- H2O mixture are taken from the correlations provided by Patek and Klomfar. The property
data of the liquid water and vapor were determined by the Talbi and Agnew. Simulations are
carried out for pump efficiency=80%, while the effectiveness of the SHX is 70%. Condensation
temperature is equal to the absorber temperature. Condensation temperature is varied in the
following range: Tcond= 25-45 0
C. Evaporation temperature is varied in the following range:
Tevp=3-150
C. Generation temperature is varied in the following range: Tgen=60-100 0
C. The
mass flow rate of solution through the pump is 1 kg/min and the environment temperature, To=
25 0
C was taken. The thermodynamic properties of the solar single-stage ARS at all state points
for theaverage of three selected days.The effect of the generator temperature on COP and total
entropy generation of the ARS. An increase in the generator temperature results in an increase in
COPand then decreases while the total entropy generation of the system increases. There is an
optimal value of generator temperature which gives maximum COP. It is important to
emphasize, that the COP is sensitive to the output and input energies alone. The effect of the
evaporator temperature on COP and total entropy generation of the ARS. This figure shows that
an increase in the evaporator temperature results in an increase in both COP and total entropy
generation of the system. The COP is more sensitive to changes in the operating conditions of
the generator and the evaporator or any other component that affects them, while the total
entropy generation considers the effect of all the system components. The effect of absorber
outlet temperature on COP and total entropy generation of the ARS. The effect of condenser
outlet temperature on COP and total entropy generation of the ARS. Both figures show that an

21. increase in temperature results in a decrease in both COP and the total entropy generation of the
systems. The effect of the solution heat exchanger effectiveness on COP andtotal entropy
generation rate (kW/K). As expected, the COP of solar single-stage ARS increased with an
increase in the effectiveness, but the effect of changes in the effectivenesses is negligible on the
total entropy generation.
9, Dillip Kumar Mohanti [2015] [9]: The properties at various locations of the cycle were
determined taking into account the state of the refrigerant. The pressure was limited by the
saturation temperature that was obtained by cooling in condenser and the evaporator
temperature. The design in this work is based on evaporator which can cool up to 5oC. Thus the
lower pressureand higher pressure in the system was designed to be 0.087 kPa and 4.5 kPa. The
absorber temperature and generator temperature were varied to their effect on Coefficient of
Performance (COP). The major outcome of this work is the investigation of the variation of COP
of the system corresponding to variation in absorber and generator temperature. The variation of
COP with respect to absorber temperature within a range of 350
C to 550
C for three different
values of generator temperature. Similarly the variation of COP with respect to generator
temperature for four different values of absorber temperature. The general trend from these
figures indicates that the COP decreases as absorber temperature decreases. This can be
attributed to the fact that the concentration of most of the solution, falls as temperature increases
which satisfies the Raoult’s law. The more is the concentration of weak solution the more is the
refrigerant evaporated giving more cooling thus more COP. But the nature of curve also tells
another story. The COP attains a maximum. Going by these curves one can predict that after
certain temperature of absorber the COP won’t show considerable increase. In this work the
absorber temperature is focused within a range of 350
Cto 400
C which is determined by hit and
trial method. The optimum point lies close to 40 0
C. The COP attains a maximum after the
optimum point, after which there is no considerable increase in COP. The point lies close to
900
C. Clearly the absorber temperature being close to 40 0
C and simultaneously generator
temperature being close to 90 0
C may give a maximum value of COP. A further increase in
generator temperature and decrease in absorber temperature won’t increase the COP
considerably. The variation between the difference in concentration of weak and strong solutions
and their effect on COP. Unlike the traditional view it was found that after a particular difference

22. in the concentrations of weak and strong solutions, the COP remained fairly constant giving the
impression that there is not much improvement in COP even though we increase the
concentration difference between the weak and strong solutions. Higher generator temperature
requires high concentration difference between the concentrations to attain higher COP. The
optimum difference lies within a range between 0.07 to 0.09. When the concentration ratio was
plotted with respect to the generator and absorber temperature it was found to vary almost
linearly. This can be correlated to Raoult’s law.
10, M.* and Saraei et.al [2014] [10]:The effects of various important design parameters on
system COP and exergy efficiency have been studied here. COP variations with generator inlet
hot water temperature and evaporator chilling water temperature. It can be seen increasing and
cause sensible increase in system COP. These can be interpreted as follows: Increasing generator
inlet hot water temperature, causes more refrigerant to vaporize and separates from absorbent
which leads to high quality refrigerant vapor and, subsequently improved COP. Likewise,
improvement in system COP is achieved by increasing evaporator chilling water temperature.
This ismainlydue to increased refrigerant potential, to extract heat from the refrigerated space
(i.e. refrigeration effect) with higher chilling water temperature. This can be also
understoodincreasing QE leads to a higher COP. The effect of generator inlet hot water
temperature on exergy efficiency ( ). A heat source with higher temperature, provide hotter
supply water for generator; however, the input exergy and subsequent exergy dissipation would
be greater through the heat transfer process in the generator. This leads to a significant drop in
exergy efficiency. Furthermore, variation of exergyefficiencywith evaporator chilling water
temperature. Results show that, an absorption system with lower chilling water temperature has
higher second-law efficiency. In fact, less input power is required to provide specified
refrigeration effect, when chilling water enters to the evaporator with cooler temperature. As a
result, exergy efficiency improves with decreasing. The main reason to cause irreversibility in
absorption system is undesirable heat transfer in system heat exchangers (Sencanet al., 2005).
Changes in system total irreversibility, with generator inlet hot water temperature, absorber inlet
cooling water temperature, condenser cooling water temperature and evaporator chilling water
temperature, respectively. In fact, rising temperature thermodynamicmodel of a systemwas
presented. Then, optimization process was carried out in energy, exergyand cost approaches by

23. using concepts of COP and second-law efficiency. Genetic algorithm method was applied to
achieve optimum design. Also, the effects of various design parameters on system optimum
performance were investigated.
11, *Manoj Dixit et.al [2015] [11]:The results of the present analysis have been compared
with theresults of Ma and Deng (1996). It is observed that the COP inthe present work is about
5% higher than the value obtained in their work. The difference in values is due to the fact that
the properties of water lithium bromide have been taken fromMcNeely (1985) whereas in the
present study the water lithium bromide properties are referred from Pa´tek and Klomfar(2006).
Moreover, the values of heat exchanger effectivenesshave not been reported by them whereas in
the present work the same have been considered as 0.7. The effect of variation in LP and HP
generator temperatures on COP and exergetic efficiency of the Half Effect Generation VAR
system. A small increase in the generator temperatures above 60.5°C causes the COP and
exergeticefficiency values to increase abruptly. With further increase in HP and LP generator
temperatures, the COP becomes constant whereasexergetic efficiency shows a decreasing trend.
The of COP and exergetic efficiency are nearly zero since the solution circulation ratio in HP
stage is very high and consequently heat duty rate in HP generator is high. The maximum values
of COP and exergetic efficiency obtained are about 0.41 and 9.5% respectively.
intermediatepressure for different absorber temperatures. For a constant absorber temperature, it
isobserved that with increase in generator temperature the optimum intermediate pressure
increases. When generator temperature is increased beyond the value corresponding to maximum
COP and maximumexergetic efficiency, then the requirement of heat in the generator increases
resulting in fall of both COP and exergetic efficiency. Thus, in order to obtain the point of
maximum COP and maximum exergetic efficiency corresponding to the increased generator
temperature (at constant absorber temperature) the intermediate pressure has to be increased.

24. REFRENCES:
1) ANAND, S., GUPTA, A. and TYAGI, S.K., 2014. EXERGY ANALYSIS OF A LiBr–H
2 O VAPOR ABSORPTION REFRIGERATION PLANT: A CASE
STUDY. International Journal of Air-Conditioning and Refrigeration, 22(02), p.1450010.
2) Bereche, R.P., Palomino, R.G. and Nebra, S.A., 2009. Thermoeconomic analysis of a
single and double-effect LiBr/H2O absorption refrigeration system. Int J
Thermodynamics, 12, pp.89-96.
3) Babu, B. and Yadav, G.M.P., Performance Analysis of Lithium-Bromide Water
Absorption Refrigeration System Using Waste Heat of Boiler Flue Gases.
4) Sedigh, S. and Saffari, H., 2011. Thermodynamic analysis of series and parallel flow
water/lithium bromide double effect absorption system with two condensers. system, 14,
p.16.
5) Shahata, A.I., Aboelazm, M.M. and Elsafty, A.F., 2012. Energy and exergy analysis for
single and parallel flow double effect water-lithium bromide vapor absorption
systems. International Journal of Science and Technology, 2(2).
6) Pongtornkulpanich, A., Thepa, S. and Amornkitbamrung, M., 2004. Exergy Analysis:
Absorption heat transformer cycle with a combining ejector using Lithium bromide/water
as working fluid. heat transfer, 10, p.5.
7) Sedigh, S., Saffari, H. and Taleshbahrami, H., 2012. Thermodynamic Analysis of Double
Effect Absorption System along with Boiler and Cooling Tower. Journal of
Environmental Science and Engineering A, 1(2), pp.261-270.
8) Abdulateef, J.M., Alghoul, M.A., Sirwan, R.A.N.J., Zahrim, A. and Sopian, K., 2012.
Second law thermodynamic analysis of a solar single-stage absorption refrigeration
system. Models and Methods in Applied Sciences, pp.163-168.
9) Mohanty, D.K. and Padhiary, A., Thermodynamic Performance Analysis of a Solar
Vapour Absorption Refrigeration System.
10) Abbaspour, M. and Saraei, A.R., 2015. Thermoeconomic Analysis and Multi-Objective
Optimization of a LiBr-Water Absorption Refrigeration System. International Journal of
Environmental Research, 9(1), pp.61-68.
11) Arora, A. and Kaushik, S.C., COMPUTATION OF OPTIMUM PARAMETERS OF A
HALF EFFECT WATER-LITHIUM BROMIDE VAPOUR ABSORPTION
REFRIGERATION SYSTEM.