Low-pressure Generator Research Articles

Experimental investigation of two-stage NH3–H2O resorption heat storage system with solution concentration difference

Widespread application of solar energy is severely restricted to its instability in time and space. Heat storage system is considered to be one of the most effective pathways to achieve long-term heat supply. Among all the heat storage technologies, solution concentration difference storage technologies stand out for low heat loss and high energy density. By substituting condenser and evaporator in conventional absorption cycle with a high-pressure absorber and low-pressure generator, a resorption cycle could be established. Compared with absorption heat storage cycle, working pressure of resorption heat cycle is lower, making it possible to utilize low-pressure heat source. Two-stage heat source cycle is further proposed to lower working pressure and upgrading supply water temperature. Resorption energy storage cycle with solution concentration difference is established and studied. A prototype based on two-stage ammonia-water resorption heat storage cycle was set up and tested. The result shows that the constraint relation between ambient temperature and heat source temperature of the proposed system. In single-stage mode, the lowest working ambient temperature is 5 °C when heat source temperature is 90 °C. The lowest working ambient temperature could be declined to 0 °C when heat source temperature rises to 120 °C. In two-stage mode, the lowest working ambient temperature is 0 °C when heat source temperature is only 110 °C, which proves the adaptability of two-stage cycle. The highest ESCOP appears in the 15 °C–120 °C single-stage mode, which is 0.742. The highest COP is 1.324 under the same condition. The highest energy density occurs in two-stage mode, which is 467.07 kJ/kg when ambient and heat source is set as 15 °C, 120 °C. The advantage that two-stage mode could enlarge solution concentration difference is verified.

Performance Evaluation of LiBr-H2O and LiCl-H2O Working Pairs in Compression-Assisted Double-Effect Absorption Refrigeration Systems for Utilization of Low-Temperature Heat Sources

To improve the performance of conventional double-effect absorption refrigeration systems (DEARS), new series parallel (SP) and reverse parallel (RP) configurations using LiCl-H2O and LiBr-H2O as working fluids, combined with two vapor compressors (VC), are proposed and thermodynamically evaluated. The effects of the distribution ratio (D) and compression ratio (CR) on the system performance are discussed. The results reveal that both configurations can extend the operation ranges of DEARS effectively at a higher distribution ratio, and the performance for low-grade heat source utilization is improved substantially by the use of VC. The compressor positioned between the evaporator and absorber is superior to that between the high-pressure generator and low-pressure generator because of the better performance improvement and larger operating ranges. In all the examined cases, LiCl-H2O systems perform better than LiBr-H2O systems in terms of the coefficient of performance (COP) and exergetic efficiency. At the higher CR of approximately 2, the compression-assisted DEARS can be driven by heat sources below 100 °C with high levels of COPs above 1.16 for the LiBr-H2O working pair and 1.29 for the LiCl-H2O working pair. The system can operate at the optimum condition by adjusting the CR values according to the characteristics of the heat sources.

Performance investigation and collaborative optimization of power, economy and NOx removal for waste heat cascade utilization system in ocean-going vessels

Waste heat recovery technology of ships is meaningful for the enhancement of system efficiency and protection of environment. Compared with conventional diesel engines, the natural gas engines have the advantage of low emission, and its exhaust gas with quite high temperature is very suitable for utilization as the heat source of cascade waste heat system. This study integrates an over-expansion transcritical CO2 cycle with a double effect absorption refrigeration cycle to recover the heat energy from a natural gas engine. At the same time, a post-processing unit is proposed to remove the nitrogen oxide of flue gas. The research results indicate that the higher engine load contributes to improving the equivalent output work and economy of the combined cycle while the post-processing unit can further reduce the payback time under the given conditions. In terms of the parameters analyses, the turbine outlet pressure of transcritical cycle has an optimal value of 2.25 MPa, which can make the output work to reach the maximum value of 305.0 kW, and the performance improvement of refrigeration cycle can be achieved by decreasing the temperature of high pressure generator or increasing the temperature of low pressure generator. After multi-objective optimization, the residual equivalent output work, payback period and amount of NOx reduction of the total system are 150.77 kW, 4.20 years and 8.16 g/kWh, respectively. In addition, the Energy Efficiency Existing Ship Index is further reduced to 8.21 gCO2/ton·nm with the aid of the proposed system.

Parametric optimization of blowdown operated double-effect vapour absorption refrigeration system

The present work investigates the thermodynamic optimality of a double-effect vapor absorption refrigeration system (VARS) driven by blowdown heat of a 210 MW thermal power plant at Badarpur using response surface methodology (RSM). RSM helps to develop a relation amongst the decision variables and the second law efficiency vi a se cond-order nonlinear polynomial regression equation. In addition, the analysis of variance technique (ANOVA) is applied to identify the decision variables having a significant effect on th e system’s thermal performance. Moreover, coefficient of structural bond (CSB) analysis of the evaporator is carried out. The decision variables are the temperatures of the high-pressure generator, low-pressure generator, condenser, absorber, and evaporator. Results conclude that the second law efficiency is affected significantly by absorber temperature (F value = 2049.4), followed by condenser temperature (F value = 1596.4), and is least affected by high-pressure generator temperature (F value = 495). CSB value of the Evaporator is 0.5851.

Performance analysis of a novel double stage multifunctional open absorption heat pump system: An industrial moist flue gas heat recovery application

Rising industrial energy consumption and waste heat in moist flue gas exhausts are the key scientific issues. A potential hybrid system with efficient heat recovery technology can fulfill the industrial energy demand for dehumidification, heating and cooling applications by utilizing the waste latent heat. The main objective of this study is to present a multifunctional hybrid system for double stage open absorption cycle to recover the latent heat from the exhaust moist flue gas for heating and to dehumidify the ambient humid air for cooling applications by operating at low-grade heat source. The validated thermodynamic models for energy and exergy analysis are developed for its performance optimization and to conduct a comparison with single stage system. The operating inlet parameters are varied to analyze the performance of both systems. The parametric study results showed that the double stage system can operate for a wider moist gas humidity range such as 0.054–0.2 kg/kg at lower regeneration heat source of 96.3℃ with varying thermal performance of 1.24–2.39 as compared to the single stage system which operates for 0.118–0.2 kg/kg and at 112.3–153.8℃. Furthermore, this hybrid system is capable to provide heating effect of 280.1 kW at thermal performance of 1.73 and 9.85 kW cooling capacity while operating at 113.7℃ heat source temperature. The thermal performance of system is related to the operating pressure in low pressure generator and can be increased 8–11% when pressure is increased from 25 kPa to 35 kPa. However, the cooling capacity is found to be sensitive only to the absorbers and the dew point cooler. The exergy performance results indicate that the exergy efficiency of double stage system is 3–16% higher as compared to single stage with effect of regeneration temperature and varies from 46.2 to 58.63%. Moreover, the highest exergy destruction is found to be in regenerators which accounts for about 49–51% of overall destructed exergy.

Performance analysis of no-insulation long distance thermal transportation system based on single-stage absorption-resorption cycle

High source temperature demand (>100 °C) and inflexible working pressure restrict the widespread application of solution transportation systems. Absorption-resorption heat pump cycles stand out in significantly lowering the demand of heat source temperature (to 80 °C), as well as multiplying working pressure choices (lower to 500 kPa) attributed by solution concentration adjustment and simplifying system structure (no rectifier). In this paper, a novel solution transportation resorption system is proposed based on the single-stage absorption-resorption heat pump cycle by assigning high-pressure generator and high-pressure absorber on the source site while placing low-pressure generator and low-pressure absorber on the user site. Feasible working pressure combinations and outlet temperature of high pressure-absorber to effect the system are investigated, illustrating the pressure range difference between resorption cycle and cycle -based heat transportation system. Thermodynamic parameters such as thermal coefficient of performance, electrical coefficient of performance, heat supply temperature range of the system are revealed in this paper. Under the condition that transporting distance is 20 km, the maximum COP value of the proposed system could reach 0.53 when high/low pressure pair is 700 kPa/405 kPa. The highest supply water temperature could reach 53.84 °C with COP of 0.477, which is suitable for floor heating. Besides, hydrodynamic and economic analysis of the proposed system are conducted, indicating that when the transportation distance exceeds 4 km, the proposed system is more economical than conventional sensible heat transportation systems. According to restriction to pump power, the longest distance is supposed to be no more than 113 km when loading power is 20 MW.

Multi-dimensional assessment and multi-objective optimization of electricity-cooling cogeneration system driven by marine diesel engine waste heat

Although the prosperous shipping industry promotes economic globalization, it causes the environmental issues like air pollution and ecological destruction, due to the emission of harmful substances. Accordingly, many waste heat recovery technologies of ships have been developed and improved, among which the supercritical Brayton cycle has attracted wide attention due to its high energy conversion efficiency. Taking an actual diesel engine as the research object, this study presents four waste heat utilization schemes by combining different supercritical carbon dioxide cycles with a double effect absorption refrigeration system. The indicators of each scheme are calculated from three perspectives of thermodynamics, economy and environment, and the overall evaluation of all schemes is carried out through the analytical hierarchy process. The addition of the refrigeration system to the recuperation supercritical carbon dioxide cycle is considered to be the optimal combination. Parameter study indicates that output power, thermal and exergy efficiency increase with the turbine inlet pressure and temperature. The maximum of these thermodynamic indexes are 5987 kW, 27.35% and 56%, respectively. Furthermore, to lower temperature of high pressure generator is conducive to improving the refrigeration performance and to raise the temperature of low pressure generator also has a similar effect. Before optimization, the capital payback period and product exergoenvironmental impact of the combined system are 6.845 years and 63.023 mPts/s. After operating the optimization program, both of them become 5.81 years and 54.94 mPts/s, which are reduced by 15.12% and 12.83%, respectively.

Experimental Investigation on an Absorption Heat Transformer for Production of Hot Water or Steam Generation

The absorption heat transformer is widely used to utilize low-temperature waste heat in the field of distributed energy, industrial processing, and long-distance indoor heating, because it can upgrade energy level and deliver heat to heated medium. In this work, an experimental system of a vertical single-stage LiBr/H2O absorption heat transformer was established to study its performance in the case of producing high-temperature water or low-pressure steam generation under different heating water flow rates. The useful output heat, coefficient of performance, exergy coefficient of performance, and gross temperature lift of the single-stage heat transformer have all been tested. The results show that the absorber cannot directly generate low-pressure steam under the condition of counter-flow heat exchange but can obtain more useful output heat. The largest useful output heat is 20.3 kW, which is higher than that in the case of parallel-flow heat exchange. The generation of low-pressure steam has certain requirements on the mode of heat transfer. The largest internal gross temperature lift of 28.1°C corresponds to the smallest coefficient of performance of 0.22 when the heating water flow rate is 2.1 m3/h. The performance of the single-stage absorption heat transformer can be improved to some extent by increasing the heating water flow rate.

Защита персонала от аэрозольных выбросов при проведении дезактивационных работ при выводе из эксплуатации радиационно опасных объектов

This article discusses the experience of using low-pressure fog generation systems to ensure the safety of work in contaminated and emergency rooms for fixing suspended particles of dust fractions containing alpha-emitting nuclides mobilized by convective air flows, and provides data on the required size of droplets and the method of their further deposition.

A novel absorption–compression combined refrigeration cycle activated by engine waste heat

Absorption refrigeration is an admirable means of refrigeration to use waste heat and decrease electricity and power consumption in air conditioning and refrigeration. A novel absorption–compression combined refrigeration cycle, which is driven by waste heat from the internal combustion engine of overload vehicles, vessels, or diesel generating sets, is proposed and investigated in this study. The high-pressure generator and the low-pressure generator are activated by exhaust gases and coolant liquids from the engine, respectively. Correspondingly, the high- and low-pressure compressors and solution pump are driven by the output power from the engine. The proposed refrigeration cycle can use the waste heat of the engine to the greatest extent and decrease engine power consumption. First, the thermodynamic circle model of the combined system was constructed. Then, the model was solved under different control strategies and operating modes. Theoretical calculation results show that the proposed combined cycle had a higher performance coefficient compared with compression refrigeration. The calculation results can be used as a reliable design, control strategy, and optimization tool for the combined refrigeration cycle future utilization in overload vehicles, vessels, or diesel generating sets.

Thermodynamic Analysis of Cogeneration Cycle by Utilizing Waste Heat of Blow Down Water

In the present work, the potential usage of blow down water from National Thermal Power Corporation Limited, Badarpur is investigated in the running of double effect H2O-Li-Br vapor absorption refrigeration system. So mass of blow down water available is computed. The blow down water is at 342.45°C which can be used for process heating.So that after process heating water enters high pressure generator at 155°C and transfer heat in such a way that at exit of high pressure generator water temperature is 140°C. The heat recovered is used as a source of energy in high pressure generator of vapor absorption refrigeration system. Results of parametric analysis show that coefficient of performance increases with increase in evaporator temperature and low pressure generator temperature; whereas, coefficient of performance decreases with increase in absorber temperature, condenser temperature and high pressure generator temperature. Parametric analysis also shows that low pressure generator temperature is most significant factor on which coefficient of performance depends. Exergy analysis of individual components of vapor absorption refrigeration system shows exergy destruction is maximum in absorber (26.17 kW) and least in high pressure generator (2.377 kW).The given model is validated with the research work carried out by Kaushik and Arora.

Energy and Exergy Analysis of a Triple Effect Absorption Refrigeration System

Absorbsiyonlu soğutma sistemleri atık ısı kullanarak soğutma yapmanın en etkili yolunu sunmaktadırlar. Bu çalışmada üç etkili bir absorpsiyonlu soğutma sisteminin enerji ve ekserji analizi yapılmıştır. İncelenen sistem seri akışlı ve su – lityum bromür çözeltisiyle çalışmaktadır. Ek olarak üç farklı eşanjör yardımıyla sistem içinde ısı kazanımı sağlanmıştır. Üç etkili absorpsiyonlu soğutma sistemleri çift ve tek etkili absorpsiyonlu soğutma sistemlerinden daha verimlidirler. Ayrıca bu sistemler daha fazla sistem elemanına sahip ve termodinamik açıdan daha karmaşıktırlar. Yapılan analizde düşük basınçlı kaynatıcı sıcaklığına bağlı olarak sistem elemanlarının ekserji yıkımları ve sistemin toplam ekserji yıkımındaki değişim gösterilmektedir. Ayrıca birinci ve ikinci kanun verimliliğinde meydana gelen değişimde analiz sonuçlarına eklenmiştir. Sonuç olarak düşük basınçlı kaynatıcı sıcaklığının artmasıyla sistemin toplam ekserji yıkımında azalma olmuştur. Sistemin toplam ekserji yıkımdaki azalma birinci ve ikinci kanun verimliliklerine artış olarak yansımıştır. Sistem elemanları içerisinde yüksek ve düşük basınçlı kaynatıcıya ait ekserji yıkımında azalma olurken absorbere ait ekserji yıkımında artma olmuştur. Isı geri kazanımı sağlayan eşanjörlere ait ekserji yıkımlarında ise azalma gözlenmiştir.

Experimental investigation on a novel triple heat sources-driven absorption heat pump system

This paper presents a novel triple heat sources-driven absorption heat pump system. The exhaust gas is used as the heat source for a high-pressure generator. The superheated refrigerant vapor generated by the high-pressure generator is used for heating the solution in the low-pressure generator 1 by releasing the latent and sensible heat. The low-temperature solar thermal energy serves as the heat source of the low-pressure generator 2. The geothermal energy supplies heat to the evaporator. Heat discharged from the condenser and the absorber is supplied to the air conditioner heat medium water. The high- and low-pressure generators are coupled to each other through an ejector. The introduction of the ejector reduces the pressure of the low pressure generator 2 below the condensing pressure so that the lower temperature solar thermal energy can be utilized. An experimental setup for this heat pump cycle is built, and an experimental investigation is carried out. The influences of the independent variables on the key internal operating parameters and heating performance have been investigated. Experimental studies show that when the hot air temperature is 213 °C and the temperature of the hot water is 43.5 °C, a heating capacity of 26.6 kW can be achieved with a heating performance coefficient greater than 1.7. In this way, an efficient and full use of waste heat is realized, and the results can provide an important basis for the design and wide application of low-temperature solar thermal and geothermal energy.

Experimental evaluation of a 1.x-effect ejector-absorption refrigeration system

In this paper, a 1.x-effect (hybrid ejector-absorption refrigeration working between single-effect and double-effect) cycle is evaluated experimentally. Through the use of the ejector, the external heat sources’ grade is reduced. Part of the refrigerant vapor at the outlet of the low-pressure generator is directly entrained by the refrigerant vapor from the outlet of the high-pressure generator to the condenser. The system with 10 kW cooling load is experimentally studied. The COP of the system is 30.0% higher than a single-effect absorption refrigeration system, and generation temperature is at least 20 °C lower than a double-effect absorption refrigeration system.

Thermodynamic analysis and optimization of double effect absorption refrigeration system using genetic algorithm

Abstract World energy demand is continuously increasing due to population growth, extensive urbanization and rapid industrialization as growth in global energy demand will rise by 30% in 2040. This demand can be met by utilizing traditional and alternative energy resources and by enhancing energy efficiency. The energy efficiency of an energy intensive process may be improved by utilization of waste or low grade energy, design and operation optimization, and running the plant in flexible mode with improved control strategies. Waste heat of an industrial plant can be utilized by employing the so called absorption refrigeration systems (ARS). ARS is capable of utilizing the low quality energy or waste heat which otherwise may have been lost as compared to conventional compression refrigeration system (CRS) where huge quantity of electricity is required for compression of the refrigerant. One of the major concerns associated with ARS is its low efficiency. Efficiency improvement of ARS can be achieved by analyzing and optimizing the various configurations of ARS using any mathematical technique. In the present work, the aim is to analyze and maximize the performance of ARS using exergy efficiency instead of conventional coefficient of performance (COP) approach. Both the series and parallel flow configurations have been considered for the analysis and optimization. Thermodynamic model has been implemented in MATLAB® using the best available correlations for phase equilibria and thermodynamic properties. Operating conditions including temperatures of all the units of both configurations of ARS and distribution ratio for parallel configuration have been optimized. Genetic Algorithm (GA) was used to optimize the operating conditions. The effect of distribution ratio and effectiveness of heat exchanger on the maximum allowable temperature of low pressure generator (LPG) and high pressure generator (HPG) to avoid crystallization has also been evaluated. Exergy efficiency of parallel flow configuration came out to be 6.45% more than that of series flow configuration at nominal operating conditions. At optimal operating conditions, exergy efficiency improved by 11.6% and 20.81% for series and parallel flow configurations, respectively. Furthermore, exergy efficiency for parallel flow configuration is 15.1% higher than series flow configuration at optimal operating conditions. The effect of variation of effectiveness of solution heat exchangers on the optimization results has also been evaluated. Effect of weather conditions, type of energy source, application for solvent cooling and variable cooling load also needs to be considered in future.

Performance Assessment and Solution Procedure for Series Flow Double-Effect Absorption Refrigeration Systems Under Critical Operating Constraints

In this study, the effects of critical operational constraints on the operational domain of a double-effect lithium bromide/water absorption refrigeration system and its performance were investigated. These constraints were determined as the equivalence state of concentrations, the thermal unbalance between the system components of high-pressure condenser and low-pressure generator, freezing and crystallization risk of lithium bromide/water solution. For the system analysis, a simulation program was developed, and its detailed solution procedure was presented. The program outputs were initially validated with the literature. Subsequently, parametric studies were conducted for broad ranges of the component temperatures. The results demonstrate that the considered constraints were essential for acceptable design and the operational control of double-effect absorption refrigeration systems. The simulations will help to figure out under which operating conditions a double-effect absorption refrigeration system functions effectively and what kind of control strategies are essentially required to increase the coefficient of performance. Based on the operation scenario of fixed high-pressure generator temperature, the proposed system can enhance the coefficient of performance up to 31% and 84% as compared to its counterparts which function under the variable high-pressure generator temperature and the pinch point temperature difference (5 K between the high-pressure condenser and the low-pressure generator), respectively.

Performance analysis of a variable-stage open absorption heat pump combined with a membrane absorber

Compared to conventional closed absorption cycles, the open absorption cycle has a greater potential in latent heat recovery from exhausted moist gas since it recovers latent heat by mass transfer instead of heat transfer. Existing open absorption cycles including single-effect and multi-stage cycles have limitations on the waste heat utilization. This paper suggests a novel variable-stage open absorption heat pump cycle which can work on a wide range of temperature and humidity of exhaust gas. A membrane contactor is also suggested to replace traditional direct-contact absorbers to integrate with the new cycle. The membrane contactor has a higher mass and heat transfer efficiency and a greater potential to avoid solution carryover. Thermodynamic model of the new cycle combined with the membrane absorber model is developed. Parametric analysis is carried out to evaluate the performance of the new cycle. Simulation results show that, under the analyzed conditions, the equivalent stage number of the new cycle varies from 4 to 1 while coefficient of performance increases approximately from 1.2 to 2 with the increase of generation temperature and air humidity ratio. It indicates that the new cycle can cover the working temperature or humidity ranges of at least four conventional absorption cycles, including single-stage, 1.5-stage, double-stage, triple-stage absorption cycles. The new cycle works on a much wider temperature and humidity ranges than conventional multi-stage cycles because the pressures of the low-pressure generator and absorber will adjust themselves to adapt to the variations of generation temperature and air humidity ratio. The self-adaption of the pressures of the low-pressure generator and absorber is realized by the control of the solution mass flow rate. During the evaluated working ranges, coefficient of performance of the new cycle increases by 5.9–28.2% compared to conventional multi-stage absorption cycles. Influences of the operating conditions on the absorption rate of the membrane absorber is also conducted and discussed.

Multi-objective optimization of double effect series and parallel flow water–lithium chloride and water–lithium bromide absorption refrigeration systems

In this study, multi-objective optimization of the series and parallel flow type double effect absorption refrigeration systems is presented. Genetic algorithm is used to find the optimal solutions and the Pareto-optimal fronts. First, a thermodynamic model is developed to simulate the double effect series and parallel flow configurations with water–lithium chloride and water–lithium bromide solution pairs. Energy and exergy balances are applied to evaluate coefficient of performance, exergy efficiency and irreversible losses in the system components separately for the two working fluid pairs. Next, optimization is done considering coefficient of performance, exergy efficiency and the total system irreversibility rate as objective functions. The low and high pressure generator temperatures are taken as decision variables in the series configuration while for the parallel system; additionally the distribution ratio is also taken as a decision parameter. The optimization is done for four different cases of fixed evaporator, absorber and condenser temperatures. For each case, the optimal decision parameter values are determined for both the water–lithium chloride and water–lithium bromide operated double effect series and parallel configurations. The optimized coefficients of performance were found slightly lower for water–lithium chloride. Contrary to this, the optimal exergy efficiencies were more and the total system irreversibility were less for water–lithium chloride. Further, the optimal performances of the double effect water–lithium chloride systems were obtained comparatively at lower generator temperatures than those of the water–lithium bromide systems.

A new AMTEC/TAR hybrid system for power and cooling cogeneration

In this paper, a new AMTEC/TAR hybrid system was proposed to utilize condensation heat of the alkali metal thermal to electric converter (AMTEC) as heat source for the triple-effect absorption refrigeration (TAR). Based on the first and second laws of thermodynamics, a theoretical analysis has been undertaken to evaluate the performance of the hybrid system. Meanwhile, the effects of the electrode current density, the condenser temperature in AMTEC, the pressure of medium pressure generator, and the temperatures of absorber, medium pressure generator and low pressure generator on the performance of the hybrid system were investigated and discussed. The results show that the AMTEC condensation heat can be effectively utilized by the TAR. When the evaporation temperature of AMTEC is 1200 K, the maximum value of exergetic efficiency of hybrid system is 42.7%, the input heat flow rate is 166.4 kW, and the output electric power and cooling load are 48.8 kW and 110.2 kW, respectively. The maximum exergy destruction rate is generally from the heat loss of AMTEC, but when the electrode current density is relatively high or the temperature of AMTEC evaporator is relatively low, the maximum exergy destruction rate comes out of the BASE.

Performance of double effect H2O–LiCl absorption refrigeration systems and comparison with H2O–LiBr systems, Part 1: Energy analysis

In this study, the series, parallel and reverse parallel configurations of double effect H2O–LiCl vapour absorption refrigeration system (VARS) are thermodynamically modeled to provide performance comparison among the three systems under identical operating conditions. Parametric analysis is performed to investigate the effect of component temperatures and distribution ratio on coefficient of performance (COP) of the double effect VARS configurations. Results show that the maximum solution concentration, which is limited to 0.5 in H2O–LiCl VARS, is mainly controlled by the system operating temperatures. In case of the parallel and reverse parallel systems, maximum solution concentration also depends upon the distribution ratio. It was found that there exists an optimal combination of HPG and low pressure generator (LPG) temperature at which the COP of a particular double effect H2O-LiCl system is maximized. This optimal combination however varies with temperatures in the other components (absorber, condenser and evaporator). A performance comparison between double effect H2O–LiCl and H2O–LiBr systems under identical conditions showed better performance in case of the double effect H2O–LiCl VARS configurations. Due to its low maximum concentration limit (0.5 against 0.65 of H2O–LiBr VARS), double effect H2O–LiCl VARS configurations would be more appropriate and efficient compared to the H2O–LiBr systems, particularly at low LPG and HPG temperature applications.