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The experimental assessment of a new absorption cooling system cooled exclusively by air operating with the ammonia-lithium nitrate mixture is presented. The generator, the economizer and the evaporator are flat plate heat exchangers, while the condenser and absorber consist of serpentine of finned tubes. A pump is used to circulate the solution into the system, and a fan is used to circulate the air through the condenser and absorber. The effect of the generation and condensation temperatures, on the cooling power, evaporation temperatures and the coefficient of performance was analyzed. The system operated at generation temperatures between 80 °C and 100 °C, while condensation temperatures varied between 20 °C and 32 °C. External cooling powers of up to 3.4 kW were achieved with external coefficients of performance of up to 0.33. The cooling temperatures were as low as 2.6 °C. Due to the developed system is air-cooled; a cooling tower is not required.

A packaged ammonia-water absorption chiller using a waste-heat stream and operating at severe ambient conditions is developed and experimentally evaluated. The chiller is designed to provide 2.6 kW of cooling at an ambient temperature of 51.7 °C. The system is directly coupled to exhaust gas from a diesel generator to drive the absorption cycle. The absorber and condenser reject heat directly to ambient air. Direct coupling to the heat source and the ambient heat sink leads to reduced system size and minimization of parasitic electrical power required for coupling fluid pumps. The dimensions of the unit are: 0.66 m × 0.61 m × 0.48 m (L × W × H). An autonomous control system is also developed and demonstrated experimentally. System performance is measured at ambient temperatures of 40–52 °C, delivering cooling duties of 2.5–1.8 kW, with overall coefficients of performance (COPs) of 0.38–0.3. Performance limitations and areas for future development are discussed.

In this paper, a parallel flow double-effect water-lithium bromide absorption refrigeration cycle is investigated using comprehensive exergy-based analyses. The exergy destruction of each device is calculated and used for further analysis. The performance of the system is optimized for maximum coefficient of performance and exergy efficiency, considering the distribution ratio as a variable using the Golden Section method. The maximum coefficient of performance, i.e. 1.295, is obtained at a high pressure generator temperature of 169.6 °C, and the maximum exergy efficiency, i.e. 0.225, is obtained at a high pressure generator temperature of 142.7 °C. Advanced exergy analysis, a state of the art thermodynamic method, is employed for diagnosing equipment and cycle malfunctions. Not only can the aforementioned analysis pinpoint the source of irreversibility, it also provides the avoidable irreversibility as well. The results show that the endogenous part of the exergy destruction is much larger than the exogenous part, implying it is better to focus on component efficiencies to improve system performance. Moreover, the unavoidable part of the total exergy destruction is much larger than the avoidable portion, indicating that exergy destruction cannot be decreased owing to technical limitations of equipment.

A generator is a heart of an absorption refrigeration system. It plays a significant role in the operation cycle by desorbing the water vapor from a lithium bromide (LiBr) solution. The wettability of the solution over the heating tubes has been considered for heat transfer enhancement in a water-LiBr falling film generator. This paper proposes seven types of heating tube bundles modified by surface treatments to improve the wettability. Each heating tube bundle was installed in the falling film generator for each experimental set, and the heat transfer characteristics were observed to evaluate the shell side heat transfer coefficients. Experiments were carried out with the following operating conditions: feed solution temperature (63.5 °C), solution flow rate (4–9 kg/min), feed solution concentration (55–58%), and pressure at the shell side (4.7–6.7 kPa). Hot water was used as a heat source, and the operating parameters were the feed temperature (85–97 °C) and the flow rate (10–28 L per minute). Each heating tube bundle had entirely different heat transfer characteristics, which were distinctly illuminated. The experimental correlations for a shell side heat transfer were developed to estimate the real benefits of using the proposed heating tube bundles. All the obtained empirical correlations were validated within an error limit of around ±20%.

This work describes the exergy analysis applied to a single effect LiBr - H 2 O refrigeration system working together with a flat-plate-collector array. The main objective was to properly match the refrigeration cycle and the heat source. I used the experimental data collected from a solar-assisted air-conditioning system operating in the Solar Energy Research Center (Ciesol). The system employs a flat-plate-collector array, a hot-water single-effect LiBr - H 2 O absorption chiller, a cooling tower, two hot storage tanks, an auxiliary heater, as well as two chilled water storage tanks. The findings demonstrate that, from the exergetic point of view, I can achieve best results by supplying the absorption chiller with water within a temperature range of 70 – 80 ° C supporting it with the action of the chilled water storage tanks. As a result of this analysis, I recognized that there is great optimization potential for the control system of the studied system. At the same time I have ensured a proper balance between the refrigeration cycle and the heat source, making the solar-assisted air-conditioning system less energy intensive and safeguarding environmental protection.

In this paper, thermodynamic analysis of novel ionic liquid 1 Ethyl-3-methylimidazolium ethyl sulphate (EMISE) as absorbent and water as green refrigerant for absorption refrigeration system (ARS) is performed. Thermodynamics excess properties like excess Gibbs free energy (GE), excess enthalpy (hE) and equilibrium Duhring’s plot (P-T-x1) of EMISE-H2O binary mixture are assessed using non-random two liquid (NRTL) activity coefficient model for composition x 1 of 0.45–1. The performance of single effect ARS with SHE are mathematically modeled and simulated by applying first and second laws (exergy analysis) of thermodynamics. Simulated results of ARS are compared with other widely used working fluids and revealed higher COP of 0.66 for EMISE-H2O in comparison to NH3-H2O but lower than LiBr-H2O. In addition, the deviation in the COP and ECOP with the generator temperatures are compared for the evaporation temperature of 5, 10, 15 °C. Result showed noticeable difference between the optimum generator temperature based on COP and ECOP. This indicates the exergy analysis is used for evaluation of ARS and selection of heat source supply temperature obtained from waste heat and renewable solar energy.

This investigation presents the results of the development and experimental assessment of a single-stage absorption cooling system built with plate heat exchangers as the main components and operated with the ammonia-water mixture thus resulting in a very compact design. The system utilized water as the auxiliary heating and cooling fluid. For the experimental assessment, the heating water was supplied to the generator at temperatures between 85 °C and 105 °C, for condensation/absorption temperatures between 20 °C and 32 °C. Several experimental curves describing parameters such as the internal cooling power, evaporation temperature and internal coefficient of performance as a function of generation and condensation temperatures are presented. The maximum values achieved for these parameters were close to 2.6 kW, −19 °C and 0.61, respectively. In addition, the effects of the expansion valve aperture on parameters such as the mass flow rate and stability of the produced refrigerant, evaporation temperature and internal coefficient of performance are presented. Due to the cooling temperatures achieved, the absorption system proposed can be operated either for food conservation or air-conditioning applications.

The thermal-driven refrigeration system (TRS) has emerged as a green solution in the chilled water system due to its ability to recover waste heat. However, the implementation of TRS in multiperiod thermal operations is not as straightforward as in continuous process because the heat source does not always match with the cooling sink at a particular time period. This imposed difficulties in achieving an optimal solution for simultaneous waste heat recovery and the chilled water supply. Previous literature focused on the continuous process waste heat recovery in chilled water generation. In this paper, a multiperiod mathematical optimization model with variable cooling demand and waste heat supply is developed to achieve maximum waste heat recovery through the integration of thermal energy storage (TES). From the optimization results, the TES-TRS scheme decreased the capital cost by 15% through the reduction of chiller capacity and quantity; promoted the energy efficiency by storing the excess waste heat for subsequent periods with waste heat deficit. Finally, 39% improvement in waste heat recovery and 30% reduction in total annualized cost are accrued from the implementation of TES-TRS scheme as compared to the base case without TES.

An ammonia–water absorption refrigeration system with a novel generator structure driven by temperature-distributed heat sources to increase the utilization rate of waste heat is presented. The stripping section of the distillation column and generator were replaced by a generator with temperature-distributed heat sources. The heat sources were distributed throughout the entire process in the generator, so the mass and heat transfer were coupled at different temperatures, which increased the waste heat utilization at low temperatures. Compared with a traditional system, temperature–distributed heat sources increased the utilization temperature range. In the simulation of the system, the condition at cold end kept unchanged while the heating distributions and quantity inside the generator were changed. The performance of the new generator driven by temperature-distributed heat sources was analyzed while compared with a traditional system through the coefficient of performance, separation efficiency and waste heat utilization.

This paper describes and analyzes an integrated trigeneration system for the production of air conditioning, fresh water and refrigeration at different temperatures. A single effect steam driven H2O-LiBr absorption cooling (ABC) cycle is integrated with a multi effect distillation (MED) unit and a CO2 based parallel compression economization-vapor compression refrigeration (PCE-VCR) cycle. The thermo-economic analysis is performed to identify how the integration can improve the energy utilization and annual costs. A detailed parametric study of several key design and operating parameters and an economic optimization are also conducted. The analysis shows that the MED plant can produce a significant amount of fresh water using the free steam supplied by the ABC cycle. Changes in the number of effects, top and last effect brine temperatures, size of the VCR cycle and number of operating hours significantly impact the MED plant productivity and unit production cost of water (UPCW). The integrated ABC-MED-VCR system, in a base case analysis, reduces the unit production cost of cooling (UPCC) for combined cooling and refrigeration and the UPCW by 25% and 27%, respectively compared to separate use of the three systems. Due to integration, substantial improvements in the fuel energy utilization and reductions in the annual capital cost (ACC) and annual operating cost (AOC) are achieved. Also, the AOC and ACC decrease 38% and 13%, respectively. At the optimized conditions, utilization of exhaust waste gas to drive the integrated ABC-MED-VCR system leads to additional 52%, 41% and 0.13% reductions in the AOC, UPCC and UPCW, respectively.

This study proposed a novel micro-scale falling film absorber with its experimental data on a complete absorption refrigeration system. Micro-scale liquid-distributor has been carefully designed and manufactured by special techniques. An experimental system for absorption refrigeration has been established to test the novel absorber. This unique absorber applies ammonia/lithium nitrate as working pair which is considered to own application potential for small-scale absorption refrigeration units. Experimental analysis has been done under various of working conditions for making contrasts. Relationships between significant working parameters and absorption parameters have been discussed. Under series of working conditions, absorption rates ranging from 1.2 to 2.6×10-3 kg/(m2·s) have been obtained. Approach to equilibrium factor which characterize the perfection of absorption process ranges from 0.5 to 0.98 while absorption ratio ranges from 0.02 to 0.12. With the increase of Reynolds number from 3 to 52, the mass transfer coefficient rises from 12 to 98×10-6m/s and Sherwood number ranges from about 30 to 60 respectively. According to the analysis, absorption pressure potential and cooling water temperature are two major factors which enhance the absorption intensity. Absorption pressure potential and inlet solution subcooling degree owns nearly linear relationship with parameters such as absorption rate, absorption ratio and approach to equilibrium factor. However, normalized absorption rate and approach to equilibrium factor gain negative correlations with absorption pressure potential and Reynolds number respectively. Effects of inlet solution flowing features on absorption performance are distinguished under different working condition series. In general, solution flowing intensity inside absorber is a positive factor for absorption process. All the experimental results reveal that, this micro-scale falling film absorber has its priority on absorption perfection and absorption rate for per unit of mass transfer area. Compact structure makes it more valuable for further research and application on small-scale absorption refrigeration unit with the working pair of ammonia/lithium nitrate.

The existing combined absorption refrigeration and liquid desiccant dehumidification systems have the disadvantages of small temperature difference in waste heat utilization and high cost of working pair. For effective and deep utilization of low-grade heat below 80 °C, a novel air conditioning system cascade driven by waste heat is established. In this system, the low-grade heat is used to drive an absorption chiller to produce chilled water for air cooling and then drive a liquid desiccant system for air dehumidification. The cheaper and non-corrosive KCOOH solution is selected as the comparative working pair of LiBr solution to conduct the experimental study in the system. Operation parameters such as inlet temperature, flow rates of both hot water and cooling water that directly affect the application of the system are studied. The results show that the system can be driven by 80 °C hot water, which is much lower than that of the conventional single absorption refrigeration system. Besides, both working pairs can be used for the system. As the inlet parameters of supply air are fixed, the cooling capacity of KCOOH solution is 10% lower than that of LiBr solution. The KCOOH solution has comparable COP compared to LiBr solution only when the dilute solution flow rate is low. The conclusion is summarized that considering the much lower cost, the KCOOH solution is a promising working pair for this novel air conditioning system, nevertheless, the structure of this system needs to be redesigned to match this working pair.

The commercial model of diffusion absorption refrigeration operated purely via thermal energy utilizes ammonia as a refrigerant. Ammonia is not only a toxic substance but also reacts with copper; thus, most commercialized diffusion absorption refrigerator is fabricated using carbon steel instead of copper. In the previous research, copper cannot be used in the diffusion absorption refrigerator because of the ammonia. However, in this study, via the newly proposed low global warming potential refrigerant R600a, copper absorber can be employed to improve the coefficient of performance of diffusion absorption refrigerator. R600a, n-octane and helium are used as the refrigerant, absorbent, and auxiliary gas, respectively. Simultaneously, the bubble pump and absorber are fabricated from copper to improve the heat transfer rate. As a result, a high coefficient of performance is achieved despite the use of a low global warming potential refrigerant. In particular, the experimental analysis is conducted with a focus on how the effectiveness and performance of the absorber vary by comparing carbon steel and copper as the absorber material. The configuration of the two diffusion absorption refrigerators is exactly the same but the absorber material is changed. When employing copper, the effectiveness of the absorber is improved by 9.09–35.71% compared to that of carbon steel absorber under the same heat input. In addition, an experimental investigation is conducted by changing the pressure to 400 kPa, 465 kPa, 530 kPa, and 600 kPa for heat input in the range of 30–100 W to analyze the effect of heat input and operating pressure. By utilizing copper for diffusion absorption refrigerator with R600a, a coefficient of performance of 0.20 is achieved at a low generator temperature of 71.07 °C, which is the highest coefficient of performance and the lowest generator temperature with low global warming potential, so that solar energy can be utilized as the heat source in the present diffusion absorption refrigerator system.

Absorption refrigeration systems (ARS) are thermally-driven technologies used to generate cold utilities. When the working pair H2O/LiBr is used in ARS, severe crystallization and corrosion problems may arise. Aiming to avoid these issues, investigations concerning ionic liquids (ILs) to replace LiBr has been conducted. This paper presents a thermodynamic performance analysis for a single-effect ARS using water and two 1-ethyl-3-methylimidazolium-based ionic liquids as absorbents: 1-ethyl-3-methyl-imidazolium ethylsulfate ([EMIM][EtSO4]) and 1-ethyl-3-methyl-imidazolium tetrafluoroborate ([EMIM][BF4]), both not yet widely explored for this purpose. Simulations were performed using Engineering Equation Solver (EES) software. Results have shown that H2O/[EMIM][BF4] mixture is clearly unattractive. Particularly at lower temperatures in the absorber and condenser and higher temperatures in the evaporator, H2O/[EMIM][EtSO4] mixture presented COP and exergetic efficiency (ηex) profiles relatively close to those of the conventional H2O/LiBr. For an optimized case, COP and ηex were 8.2% and 19.2% greater for H2O/LiBr than for H2O/[EMIM][EtSO4] which has presented values of 0.764 and 0.114 respectively. For ηex this difference tended to decrease at higher temperatures in the generator, turning H2O/[EMIM][EtSO4] mixture competitive with H2O/LiBr at certain conditions, mainly in view of LiBr crystallization risk. The main contributions of this work regarding ARS studies is performing all the following studies simultaneously: sensitivity analysis, thermodynamic optimization and crystallization risk analysis also considering working pairs that still present some gaps in the literature.

The small CCHP system is adopted by majority of office buildings and markets. The heat supplementation under partial load is a problem for CCHP systems. In this research, a partial load model of a combined cooling, heating and power (CCHP) system was established. The CCHP system’s partial load analysis showed that the micro gas turbine (MGT) and the bottom absorption chiller were coupled by flue gas energy. Based on the coupling effects analysis, four different supplementary strategies (load adjustment method (LAM), mass flow first method (MFM), temperature first method (TFM) and maximum coefficient of performance (COP) method (MCOPM)) had been proposed and analyzed when flue gas heat was insufficient. The results showed that the CCHP system’s supplemental fuels under MFM, TFM and MCOPM were all less than that under LAM. And the additional fuel under the TFM was the least among the four different strategies. The CCHP system’s heating capacity under TFM was smaller than that under MFM and MCOPM, while the CCHP system’s primary energy and exergy efficiencies under the TFM were larger than that under MFM and MCOPM, at the same cooling load, when supplement heat was needed. The CCHP system’s total exergy destruction under TFM (106.236 kW) was smaller than that under the LAM (110.309 kW). So when the flue gas heat was insufficient, the TFM supplementation strategy was recommended.

Combined cooling, heating and power (CCHP) which is also called trigeneration can be designed and manufactured in diverse scales and applications. In the present paper a single person portable micro CCHP system based on a micro-gas turbine and micro-absorption chiller is proposed and its performance is analyzed under different operational conditions. People under attack of war or natural disasters such as earthquake can use this system. A thermodynamic model is introduced to evaluate the personal energy demands at different ambient conditions. Then a micro-gas turbine is designed to produce 20 W electricity at speed of 200000 rpm and ambient temperature of 50 °C. In the next step the 500 W-class ultra-micro gas turbine (UMGT), is simulated as prime mover to estimate the cycle performance. LPG is the main fuel and the CCHP performance under extremely cold /hot weather is evaluated thermodynamically for three load management strategies. The maximum efficiency and minimum fuel consumption were related to the following hybrid electrical and thermal load strategy. In this case the maximum single-person CCHP efficiency was about 29% and fuel consumption was about 0.0645 g r · s - 1 of LPG at ambient temperature of 50 °C. The number of people who their energy demand was provided became maximum when following electrical load. The weight of the CCHP system is estimated to be less than 15 kg that is easily portable by a single grown person.

A complete renewable energy source based on a solar and a geothermal system is proposed to produce desired electricity and cooling. The proposed system consists of a concentrated PVT, a double-effect LiBr-H2O absorption chiller and a geothermal unit. To better understand the system performance, energy, exergy and exergoeconomic analyses are investigated. The results show that recovering the waste heat of the geothermal unit increases the coefficient operation factor by about 15%. Second law analysis exhibits that one of the main parts of irreversibility occurs in the PVT with 29.6 kW. Results of exergoeconomic analysis show that in the second condenser and the cooling set, the exergy destruction cost has major effect on the component cost rate. In addition, the parametric study of major parameters (i.e., geothermal temperature, high pressure and low pressure turbine inlet pressure, PVT module’s temperature and area) is performed thermodynamically and thermoeconomically. In addition, by considering the overall exergy efficiency and the total product unit cost as objective functions, a multi-objective optimization is implemented based on genetic algorithm. From the Pareto frontier diagram, the value of an optimal point for single and multi-objective optimization are determined. Obtained results show that at the optimal point where the overall exergy efficiency and total product unit cost are optimized, the corresponding values are 12.31% and 35 $/GJ, respectively. Scattered distribution of the major parameters reveals that the geothermal temperature is a very sensitive parameter which should be kept at its highest value (i.e., 245 °C).

Distributed energy systems have advantages in mitigating environmental problems and improving energy utilization efficiency. However, the modelling and simulation of such kind system tend to apply the separate modelling method for various sub-systems. Based on the graph and matrix theory, this paper proposed a weak decoupling method to decompose the coupled output energy and thus match the decoupled demands. Then a matrix optimization model integrated with energy input, conversion, storage and output is introduced as well. Finally, a case study of a combined cooling, heating and power (CCHP) system consisting of a power generation unit (PGU), an absorption chiller, a storage tank and a ground source heat pump (GSHP) is proposed, and three strategies including following electric load, following thermal load and optimized operation strategy are employed to design the optimal nominal capacity configuration. Results show that under the mode so called “electricity feed in tariff” of optimized operation strategy, the optimal nominal capacity of PGU is the largest, and the optimal nominal capacity of GSHP is lower. Meanwhile the system has the optimal integrated performance. Compared with separate system, the integrated performance, annual total cost reduction ratio, carbon dioxide emissions reduction ratio and primary energy saving ratio are 49.99%, 36.33%, 73.54% and 60.11%, respectively.

A novel closed Brayton cycle using supercritical CO2–Kr mixture as working fluid integrated with an absorption chiller (CBC/AC) is proposed. The waste heat of the CO2–Kr in the cold end of the top closed Brayton cycle (CBC) is utilized to drive the absorption chiller, which further chills the CO2–Kr fluid exiting the precooler before it enters the main compressor. Compared with the stand-alone supercritical CO2 (S-CO2) CBC, the CBC/AC exploits the performance improvement potentials under low ambient temperature (T0) condition and alleviates the performance penalty under high T0 condition. The energy and exergy analyses of the CBC/AC in three typical T0 conditions (10 °C, 25 °C and 40 °C) show that the thermal efficiencies are improved by 3.12%, 0.40% and 6.86%, respectively, the exergy efficiencies are improved by 3.53%, 0.54% and 7.53%, respectively. The exergy loss from the precooler is significantly reduced in the CBC/AC relative to that in the stand-alone S-CO2 CBC. The comparisons between different working conditions for the CBC/AC indicate that the improvements of the thermal and exergy efficiencies are more apparent under water-cooling and high turbine inlet temperature conditions. The effects of the component performance on the CBC/AC are also evaluated.

In this study, the effect of different combinations of the ammonia-water Rankine power cycle and the ammonia-water absorption refrigeration cycle are investigated on the exergoeconomic performance of the cogeneration cycle. For this purpose, three different configurations from combining these cycles for simultaneous production of power and cooling are considered. After the calculation of the unit cost and cost rate of each stream as well as the exergoeconomic parameters of each component, the critical components of the cogeneration cycles are identified and some corrections for better performance of these components in the cogeneration cycles are suggested. Then, a parametric study is done and the effects of simultaneous variations of operating parameters on the exergoeconomic performance of the cogeneration cycles are examined. Also, the considered configurations are optimized using five objective functions including minimum unit cost of products, minimum unit cost of produced exergy, minimum overall amount of C D + Z and maximum the first and second law efficiencies. The optimization results indicate that the different combinations of the ammonia-water Rankine and absorption refrigeration cycles are very effective on the thermodynamic and exergoeconomic performance of the cogeneration cycle. Finally, the payback period is calculated for each considered configuration in all optimum conditions.

A Transcritical Carbon dioxide Compression (TCC) refrigeration system is a suitable tool to provide low-temperature refrigeration, but with a low COP. To improve the performance of a TCC, different combinations of Liquid Suction Heat Exchanger (LSHE), after-cooler and two-stage compression are embedded into the system configuration. The cooling load of the after-cooler is provided by an Absorption Chiller (ABSC) and the required heating energy to run the ABSC is recovered from the hot refrigerant leaving the compressors of the TCC. Eleven modified configurations are proposed and modeled in detail by EES software and energy and exergy analyzes are performed for each configuration. The results showed that the two-stage compression is a suitable method to upgrade the TCC system performance from both first and second laws of thermodynamics view point. The COP of a typical two-stage TCC is calculated to be 207% higher than its single-stage counterpart, in an evaporator temperature of −50 °C. It is also concluded that the combination of a two-stage compression TCC and a single-effect LiBr ABSC, performs with the highest performance. This combination increases the TCC system performances for about 4 and 2 times compared to single-stage and two-stage TCCs, respectively. A parametric study also revealed that well-calculated operating conditions are fundamental in design of TCCs to gain the highest performance.

This paper presents a comparison of the performance for three configurations of double effect absorption refrigeration systems with single effect one using ammonia lithium nitrate (NH3/LiNO3) and ammonia sodium thiocyanate (NH3/NaSCN) as working solutions. The effect of operating parameters on COP and exergetic efficiency of the cycles is investigated. In order to avoid error in estimation of solutions enthalpy and entropy at high temperatures, linear equations for specific heat of solutions are obtained from correlating the experimental data. Furthermore, the effects of operating parameters on crystallization possibility are studied. The COP of double effect systems are maximum 60% more, but exergetic efficiency is maximum 16% less than those for single effect cycles. The NH3/LiNO3 systems compared to the NH3/NaSCN systems can perform at lower generator temperatures with higher COP and exergetic efficiency. Operating range of NH3/LiNO3 system is wider, since it is limited for NH3/NaSCN cycle because of crystallization occurrence.

The present work analyses an intermittent absorption cooling system using a hydrophobic porous membrane unit as desorber/condenser and powered by thermal solar energy. Experimental test runs were carried out in a membrane unit to experimentally determine the amount of refrigerant produced at different operating temperatures. With the obtained information, an intermittent absorption cooling system was modelled at a larger scale using information from real solar collectors and considering a 1 m2 membrane area. According to the experimental performance of the desorber/condenser unit, after 4 h of operation, the total amount of refrigerant produced was 14.50, 11.59 and 7.20 kg for desorber temperatures of 95.1, 85.2 and 75.1 °C, respectively. The designed solar system was composed of a 0.3 m3 storage thermal tank, and 30.2, 25.6 and 20.9 m2 of solar collector area for each desorber thermal level. According to the simulation of the absorption cooling system, evaporator temperatures of 18 and 14 °C were achieved for desorber temperatures of 75.1 and 85.2 °C, while evaporator temperatures of 17 and 12 °C were obtained at 95.1 °C. The COPs were 0.15, 0.21 and 0.26, which increased according to the increase in the desorber temperatures. Based on the clear desorber/condenser tendencies obtained from the refrigerant production, additional absorption conditions were calculated and may be useful for future designs. The lowest evaporator temperature was 6 °C when the initial LiBr concentration was 54.83% w/w, instead of 50.30% w/w at a temperature of 95.1 °C; however, the COP decreased 33%.

Absorption chillers can use waste heat, solar heat, or excess heat by cogeneration facilities to supply chilled water. Therefore, absorption chillers are important components for poly-generation, which can improve plant utilization and efficiency of the overall energy supply system. Currently, 27 new small and medium-scale (30–160 kW cooling capacity) absorption chillers with high efficiency in full- and part-load as well as low specific size and weight are the focus of two research projects sponsored by German Federal Ministries. The chillers are located in 20 different sites, four of them in Jordan and the rest in Germany. The main objective of these projects is to enhance trigeneration and solar cooling system efficiency. The Jordan projects and more than 70% of the German installations use dry cooling towers. Combined heat and power (CHP) plants or district heating grids provide the driving heat for regeneration at the German installations. Solar thermal collectors drive one German and all Jordan installations. Within the projects, the chillers are provided with an intelligent control algorithm that allows achieving several objectives at the same time. One of the objectives, of course, is to match the desired chilled water temperature as well as the cooling capacity. Another objective is, for instance, to fit the hot water outlet temperature. This is commonly essential in cogeneration to avoid emergency shutdowns of the CHP engine. The field operation shows that the deviation of said temperatures from the set point is usually less than ±0.5 K in operation. In those operational hours in which the temperatures of the heat source or heat sink do not allow to reach all objectives, a set of hierarchical aims can be established within the algorithm so that the chiller can be controlled to match its prioritized objectives. Furthermore, the designed absorption chiller performs dynamically and autonomously in a very large range of temperatures and flow rates. These can vary from 20% up to 150% of nominal conditions. This flexibility can be used to achieve up to 80% savings of electrical power consumption using speed-controlled pumps in part load conditions. In contrast to the common opinion that small and medium-scale absorption chillers are not competitive as compared to compression chillers, this paper shows applications in which absorption chillers are advantageous because of synergies with and multiple benefits within the rest of the energy supply system.

This paper proposes a new ejector-absorption refrigeration cycle driven by two heat sources at different temperature levels to realize the economic optimization in low-grade heat recovery application. The cycle uses the exergy of steam from a high-pressure generator and entrains the steam out of a low-pressure generator. The quantity of the steam that comes out of the low-pressure generator for the new cycle is greater than that of a conventional double-effect cycle, which means that more low-temperature-level heat, such as non-focused solar thermal heat, can be used. Therefore, the heat required to input into the system and the temperature level required to drive the cycle declines. In this study, water-lithium bromide as the working pair and a hot air temperature level ranging from 185 °C to 215 °C is used as the high level driving heat source, while the hot water heated by a solar energy collector is the low level driving heat source. In some conditions of the new cycle’s COP, 0.95 can be achieved for refrigeration, which is about 20% higher than that of the single-effect cycle. Besides this, the proposed chiller requires lower driven temperature than that of a conventional double-effect cycle.

Overall energy efficiency remains a large and unexploited resource in combined cooling, heating, and power systems driven by solar energy. This study aims to explore the configuration effects on such systems using parabolic trough collector and organic Rankine cycle (ORC) technologies. The configurations are concisely clarified into sequential and parallel connections, in which a single-effect absorption chiller and a heat exchanger are considered for cooling and heating, respectively. A comprehensive assessment framework is proposed by establishing the thermodynamic performance, system size, and economic models. Under reasonable thermodynamic boundary conditions, the optimal operational parameters are obtained via a Pareto frontier solution for such a system, with an ORC of 200 kW. Promising technical solutions and enhancement potential are justified and quantified by means of system simulations and comparison on the annual time scale.

A novel combined cooling, heating and power system (CCHP) driven by solar energy is proposed. The system applies an organic Rankine cycle, a double effect lithium bromide-water absorption refrigeration system, and heat exchangers to generate electricity, cooling and heating, respectively. Energy and exergy analyses are conducted to determine system efficiencies and losses. The cycle is compared with similar combined cycle that differs by using a cooling subsystem having a single effect absorption chiller. The effects of some key thermodynamic parameters on the performance of the cycle are examined. The results reveal that, for the same amount of input heat, the usage of a double effect absorption refrigeration system instead of a single effect absorption chiller can raise the amount of cooling power up to 48.5% and consequently can improve the performance of the system. At the same time, heating power rises by 20.5%, resulting in an increase in the cogeneration heat and power efficiency to 96.0%, while net electrical power production declines by 27%. In addition, it is determined that a high exergy destruction rate occurs in the solar collectors.

In this study, an energy-exergy methodology was applied to achieve more precise conditions for hot water, cooling, power and hydrogen production via a proposed multi-generation system comprised of a geothermal based organic Rankine cycle, domestic water heater, absorption refrigeration cycle and proton exchange membrane electrolyzer. Furthermore, for evaluation of the proposed system performance, the effects of such key variables as brine temperature, turbine inlet temperature, generator temperature, brine mass flow rate and electrolyzer current density on the related efficiencies of energy and exergy for the whole system were investigated. For specified conditions, the results show that energy and exergy efficiencies of the entire system are calculated around 33.92% and 43.59%, respectively. Moreover, estimation of the exergy destruction rate in each system component indicated that the highest rate of exergy destruction occurred in the heat recovery steam generator (HRSG) with 16.65% of the total amount of exergy input to the system. And finally, net electrical power output, mass flow rate of hot water, cooling capacity and mass flow rate of hydrogen production are as follows: 816.7 kW, 7.06 kg/s, 1896 kW and 0.05g/s.

Experimental investigations and numerical simulations of a low capacity commercial diffusion-absorption refrigerator (DAR) in stationary mode are carried out. The tests are performed under different heat input conditions. Optimal operation of the DAR refrigerator is reached with a power supply of 46 W at a generator temperature of 167 °C, corresponding to a coefficient of performance ( COP ) of 0.159. Numerical simulations of the refrigerator using a model developed with the commercial flow-sheeting Aspen-Plus software are also perfomed. The computer model is validated by comparing its predictions with experimental data for three generator heat supply rates: 46 W, 56 W and 67 W. Deviations between model predictions and experimental measurements in terms of cooling capacity and coefficient of performance are less than 1%. The proposed model could be very useful to predict the functioning of the commercial diffusion-absorption refrigerator under steady state regime.

The authors proposed “Solution Transportation Absorption Chiller” which is driven by wasted heat and transfers absorbent solution instead of chilled water. It consists of generator-condenser pair on the heat source side, absorber-evaporator pair on the demand side and pipelines between them. In this study, the authors investigated the heat transportation performance of the system experimentally with the distance of 100 m, 200 m and 1000 m. The results suggest that the proposed system can work for transporting cooling with ammonia-water mixture as the working fluid. It was obtained that the COP of the system was the same as that of conventional absorption chiller without transportation. In other words, the performance does not suffer from the new function of long distance transportation. It can be concluded that the solution transportation is technologically feasible and also effective to replace conventional fossil fuels with remote wasted heat sources.

This paper presents experimental results of a 5 kW Diffusion-Absorption Chiller (DAC). The chiller has been tested at varying inlet generator temperatures, inlet cooling water temperatures and inlet chilled water temperatures. The lowest driving temperature to keep the bubble pump running was about 90 °C with 3.6 kW cooling capacity and chilled water inlet temperature being set at 18 °C. The maximum cooling capacity and COP reached for the DAC was about 4.52 kW and 0.45, respectively. The prototype has demonstrated a good potential for air-conditioning applications, while not requiring electricity internally for its operation and allowing coupling with waste heat or solar thermal collector systems.

The membrane-based desorber is considered a promising alternative to miniaturize the present generator in the absorption refrigeration system, owing to its large specific interfacial area, which is expected to reduce the required volume for the unit of cooling capacity of the system. The heat and mass transfer characteristics of a desorber consisting of a porous polytetrafluoroethylene hollow fiber membrane were evaluated by both experiment and simulation under practical working conditions. The Knudsen diffusion was verified by a gas permeability test prior to the water vapor desorption test. According to the desorption experiment results of the LiBr-H2O solution, a concentration difference of approximately 0.4% was achieved under the investigated conditions. The results also indicated that an increase in the solution flowrates leads to an increase in the water vapor desorption rate owing to the increase of sensible heat. The compared simulation and experimental results were consistent with an acceptable accuracy. This study provides a fundamental understanding of the heat and mass transfer of the membrane-based desorber, which benefits the design of the compact membrane-based absorption refrigeration systems.

This article presents a new effective utilization way of low-grade solar energy to produce cooling power with a novel integrated adsorption - absorption cooling system under climate conditions in Australia. In the integrated cooling system, the solution generation happens in the intermediate pressure, which is associated with the heat source temperature and can be adjusted according to the solution concentration and generation temperature. Two different solar system layouts with and without hot water storage tank are investigated. In the system without storage tank no cooling energy is generated at the beginning and ending cycle time and it reaches the maximum value of 16 kW around noon. While the maximum cooling capacity, 15 kW, is produced in the late afternoon between 14 h and 16 h along with higher cooling capacity at the beginning and ending cycle time in the system with storage tank. It is found that the average daily cooling capacity improve by 15% with better coefficient of performance by installing storage tank for a wide range of collecting area. Furthermore, the average daily coefficient of performance remains slightly stable at around 0.37 with expanding the solar collecting area. Results obtained from the economic analysis disclose that the lifecycle cost is minimised for the financially viable collector area of 34 m2. Moreover, the payback period of 10.46 years for the optimum collecting area indicates the high profitability of the solar energy application in the proposed cooling system in a 25-year project investment lifetime. The performance comparison among various solar systems indicates that the average daily specific cooling powers are as high as 106 and 121 Wkg−1 in the 1st and 2nd layouts respectively, which are achieved considerably greater than other systems operating at low driving hot water temperature of 60 °C. The low heat temperature required to run the proposed cooling system and the advantage of high solar radiation availability in Australia proves the high potentiality for operating the proposed system in most warm months.

In this paper we report on new experimental results of an absorption heat transformer. In order to have a concise view on the whole performance field the characteristic equation model, a novel version of ideas from the 80ies of the last century is developed. In the model insight from recent research on absorption chillers is used. The 40 kW prototype implements a single effect absorption cycle working with water as refrigerant and an aqueous LiBr solution as the solvent. As a novelty, the parameter set of the characteristic equation model has been obtained from the cycle analysis of the device based on the measurements of one single operating point. The resulting model predicts the prototype performance for driving heat temperature levels of low temperature industrial waste heat sources (60–100 °C), with variations of the temperature of the useful upgraded between 90 and 138 °C that result in gross temperature lifts (GTL) between 20 and 55 K. The measured COP values are between 0.30 and 0.48. An additional regression developed after evaluating the deviations from the model assumptions reduces the uncertainty of the model. The uncertainties for COP and upgraded heat flow rate predictions are below 11% (R2 = 0.812) and 4% (R2 = 0.918) respectively.

Optimum utilisation of the available energy is vital to eliminate waste heat and address other environmental issues. This study is concerned with the design of a heat exchanger for the optimum use of loss heat from flue gases. The heat content in exhaust gases can be applied in the absorption chiller to preheat a dilute solution (lithium bromide) before entering the high-temperature generator. The exploitation of the energy from a glass furnace outlet flue gas temperature of 400 °C will reduce the rate consumption of natural gas. The thermodynamic properties of flue gases were determined based on chemical composition analysis measured by the gas analyser. Moreover, the solution at the inlets and outlets of the Li-Br absorption chiller unit components was estimated using heat and mass balance equations. The heat recovery unit was designed to extract heat from flue gases to preheat, directly or indirectly, the Li-Br solution before entering the high-pressure generator using water as an intermediate solution. The heat exchanger design specification was determined for both cold fluids (Li-Br and H2O) at different tube diameters using copper and steel materials. Furthermore, the theoretical design analysis was executed using a FORTRAN program. It was found that the compact direct heat exchanger showed the best performance with respect to the overall heat transfer area, while the shell-and-tube heat exchanger was favourable because of its simple design and manufacturing. The results showed that the minimum outlet flue gas temperature was 200 °C to keep the glass furnace operating as a natural draught system. The feasibility study was carried out by the CONSUKORRA Company (Hitachi agent in Egypt) based on the current study data. The proposed feasibility study showed that the annual fuel savings was about 23%, while the annual cost saving was 18%. Moreover, the coefficient of performance of absorption unit will be enhanced by 34% after installing the heat recovery unit.

In the present work, an innovative configuration is proposed based on solar pre-heating concept and biomass direct-combustion for combined production of electricity, hot water and cooling load. The studied system consists of an externally fired gas turbine, a trans-critical organic Rankine cycle, and a Li-Br/H2O absorption refrigeration cycle. The proposed system is thoroughly analyzed from the energy, exergy, and exergo-economic viewpoint. The results of the exergo-economic analysis demonstrate that the energy and exergy efficiencies of the reference case are 55.56% and 20.38% and the product cost rate is 26.4 $/h. Comparing the thermodynamic results to the literature, it is proved that the proposed system generates a considerably higher amount of power, heating, and cooling load which results in an improvement of energy efficiency by about 10%. In further, the main design parameters of each cycle are parametrically assessed to gain a comprehensive understanding of the system behavior. Finally, a new multi-objective optimization algorithm called multi-objective multi-verse optimizer (MOMVO) is employed to maximize exergy efficiency and minimize the product cost rate of the system. Compared to the base case, TOPSIS implementation revealed that the optimal final solution of the Pareto-frontier found by the MOMVO has about 9% higher second law efficiency while the product cost rate is decreased by around 6%. This result proved the better performance of the MOMVO compared to other conventional evolutionary-based multi-objective optimzation algorithms.

The objective of this work is to investigate the solar cooling viability in various locations worldwide. A single stage absorption chiller operating with the LiBr-H2O working pair is coupled with evacuated tube collectors and this system produces the demanded cooling load for a typical building of 100 m2 floor area. Ten cities are examined and the analysis is performed with the commercial software TRNSYS. For every city, different combinations of collecting areas and storage tank volumes are investigated in order to determine the optimum combination which leads to the minimum levelized cost of cooling (LCOC). According to the final results, Abu Dhabi and Phoenix are the most suitable locations with LCOC equal to 0.0575 €/kWh and 0.0590 €/kWh respectively, while Rome, Madrid and Thessaloniki are the less suitable locations with 0.2125 €/kWh and 0.1792 €/kWh and 0.1771 €/kWh respectively. Moreover, it is found that the locations with high cooling loads and high solar potential are the most suitable locations for installing solar cooling. Furthermore, it is proved that higher collecting is associated with a greater optimum storage tank. Finally, the conclusions of this work can be used as guidelines for designing solar cooling system and determining the suitable locations and climate conditions for installing solar cooling systems.

Combined cooling, heating and power (CCHP) systems have widely theoretical researched and practical applied to solve the energy and environment problems. The schemes of CCHP systems are important to select, which can best satisfy users demand with high thermal economy and low pollutant emission. In this paper, a novel scheme of CCHP system with dehumidification and hybrid refrigeration is proposed, where an internal combustion engine (ICE) is utilized as a prime mover. The absorption dehumidifier is driven by jacket water of ICE to provide dehumidification, and hybrid refrigeration system is consisted of absorption chiller and electric compression refrigerator. A thermo-economic model of the CCHP system is established, and a comprehensive evaluation criteria is proposed as objective function. The analytic hierarchy process and the constrained nonlinear programming solution are employed to optimize design and operation strategy of the ICE-CCHP system. This research discuss its application in a case: the CCHP system apply to following the electric load (FEL), and the optimum equipment capacity of the CCHP system is obtained. Furthermore, the sensitivity analysis is carried out to assess effects on performance of the CCHP system.

In this paper a comparative study was performed between five classes of LiBr/water absorption refrigeration systems to investigate the influence of various operating parameters on the coefficient of performance, the thermal loads of the components, the exergetic efficiency and the total change in the exergy of systems. The exergetic analysis of all system’s components was done after their energy analysis. The half effect, single effect, series class of double effect, parallel class of double effect and triple effect absorption refrigeration cycles were compared together in this study. The exergetic evaluation of the thermodynamic flows, which go through this cycle, was performed for a refrigerating capacity 300 kW. According to energetic and exergetic analysis, the results showed that the coefficient of performance and exergy efficiency increases from the half effect, to the single, double and triple effect refrigeration system while total exergy change approximately decreases. Furthermore, it was found that there is an optimum generator temperature where the COP and exergy efficiency of the five configurations of absorption refrigeration systems is maximum and the total exergy change becomes minimum.

Recent technological developments have made it possible to generate power and cooling using the Kalina cycle (KC) through low grade heat sources utilization. The Kalina cooling-power cycle (KPCC) and Kalina LiBr-H2O absorption chiller cycle (KLACC) are two novel cases that have been proposed and analyzed with regard to their energetic and economic aspects. These systems combine the KC with NH3-H2O and LiBr-H2O absorption chillers, respectively. Having obtained the energy analysis results, exergy analysis is performed to analyze and compare the systems. A comparative exergoeconomic assessment is performed to obtain the unit cost of power-cooling generation. The exergetic analysis demonstrated total exergy destruction of KLACC is 40% higher than KPCC where major exergy destruction occurs in both condenser and second flash tank preheater. The KLACC exergetic efficiency is almost same as the KC although it is higher for KPCC system by 6.8%. According to the exergoeconomic analysis, the unit cost of power-cooling generation for KPCC is 20.5% lower than KLACC; therefore, KPCC performance is better than KLACC. The significant exergy destruction locations to optimize the system performance are the absorber in KPCC and second condenser in KLACC.

The volume of hot storage tank in sensible thermal energy storage (STES), integrated with solar-powered air conditioning to mitigate the misalignment between supply and demand, is too big which results in great thermal inertia. In this paper, a novel multi-tank thermal energy storage (TES) system for solar-power air conditioning, with the advantages of quick temperature rising and outstanding ability to fit variable weather, was proposed to mitigate the contradictions between demand and supply. In order to investigate effect of the number of tanks (NT) on system response time (SRT), total energy grade of water in tanks and temperature variations in charging and discharging periods, a series of experiments of TESs with different number of tanks (total volume of tanks is constant) were conducted under the same solar radiation conditions. Results show that the energy grade of water in tanks is improved through dividing thermal energy storage system into several tanks with different priorities of charging and discharging, and SRT decreases by 6.95 h in four-tank TES, compared with one-tank TES. Furthermore, the duration time of ideal heating inlet water temperature (IHIWT) in entire operational period increases slowly with the number of tanks, because NT has opposite effects on duration time of IHIWT in charging and discharging periods. An optimized control strategy that tanks stored heat successively in charging period and released heat simultaneously in discharging period was proposed. It is notable that the duration time of IHIWT in four-tank TES increases 2.59 h, about 26.67%, after the optimized control strategy is adopted. Therefore, the optimized TES makes the single-effect absorption chiller run at a high COP over a long time without strong variations of COP, compared with other TESs.

This paper presents an extensive review of heat and mass transfer correlations in the framework of sorption machines operating based on the falling film technology, in which ammonia-water and lithium bromide-water are used as the working fluid pairs. Heat and mass transfer correlations are summarized as well as the application range and geometrical configuration. In order to compare the correlations found in the recent and classical literature, typical operation conditions for absorption refrigeration cycles have been adopted. Heat and mass transfer correlations have been evaluated for both working fluid pairs, mapping the possible heat and mass transfer values for refrigeration and air-conditioning applications. The study allowed comparing the two technologies using the same operational conditions. The ascertainment that the transfer correlations may behave differently has been showed. Finally, this work suggests that future researches about heat and mass transfer behavior should be to carry out for realistic operational condition of the absorption refrigeration cycles.

This paper focuses a method to enhance an organic Rankine cycle (ORC) efficiency by using the sorption systems (absorption and adsorption) for reducing the ORC condenser temperature. Energy efficiency, exergy efficiency and levelized electricity cost (LEC) are used to evaluate the optimal combined unit. Testing data from a 25 kWe R-245fa ORC prototype, a 1 TR water-LiBr absorption chiller and a 1 TR water-silica gel adsorption refrigeration are tested and analyzed performance curve of each technology to predict thermal performance of the ORC-sorption units at various operating conditions. Projection of the integrating unit of the ORC and sorption systems represent the better energy and exergy efficiencies, when the ORC condenser temperature is decreased. The ORC-absorption efficiencies in terms of energy and exergy increase 7.22%, while the ORC-adsorption system improve 12.46% compared with the normal ORC efficiencies. In economic impact, the LEC of the normal ORC unit is 0.1145 USD/kW h, which is higher than the ORC-absorption unit and the ORC-adsorption unit of 0.1088 USD/kW h and 0.1043 USD/kW h, respectively, at chilled water temperature output the absorption system at 7 °C. Thus, it could be concluded that the ORC-adsorption system is the optimal technique to enhance the ORC electricity generation process in terms of energy efficiency, exergy efficiency and electricity cost.

A novel two refrigeration cycle process configuration for production of the liquefied natural gas is introduced and analyzed. In this process a single effect absorption refrigeration cycle which provides the refrigeration at −30 °C is used as the precooling cycle. Coefficient of performance for this cycle is 0.49. The second cycle is a mixed refrigerant vapor compression refrigeration system. The results show that liquefaction efficiency is 0.20 kW h kg LNG . This process is analyzed and compared with the conventional propane precooled mixed refrigerant (C3MR) process. Next conventional and advanced exergoeconomic analysis methods are used to evaluate the modified process. Based on the exergoeconomic factor values, compressors and air coolers investment costs should be considered for improvement of the process. Endogenous exergy destruction in all of the process components is higher than the exogenous. Results of the splitting of exergy destruction costs indicate that avoidable exogenous destruction portion is very small.

The addition of LiBr can significantly improve the performance of NH3-H2O absorption refrigeration system. It can also increase the ammonia concentration of the vapor stream, thus reducing energy consumption of rectification. However, the existence of LiBr has a negative effect on the absorber, especially at high LiBr mass fractions because it reduces the absorption capacity of the mixed ternary solution. This paper proposes a new NH3-H2O-LiBr absorption cycle that uses an electrodialysis device to separate the LiBr from the solution stream entering the absorber so that the LiBr is retained in the generator as much as possible. The model implemented in the ASPEN PLUS process simulator has been used to calculate the performance of the NH3-H2O-LiBr absorption refrigeration cycle. Simulation results indicate that, due to the integration of electrodialysis process, the operating temperature in the generator is significantly reduced and the COP of the proposed system is improved compared to the normal NH3-H2O-LiBr absorption refrigeration cycle when LiBr mass fraction varies from 0% to 50%.

A bubble pump is proposed to replace the traditional mechanical solution pump in lithium bromide absorption chillers, for its advantageous feature that can be driven by industrial waste heat or solar energy or other low-grade energy. In two-stage bubble pump driven lithium bromide absorption refrigeration system, flow patterns in lifting pipe have significant effects on the performance of bubble pump. In this paper, the single bubble motion and the double bubbles coalescence in vertical ascending pipe are simulated by an improved free energy model of lattice Boltzmann method, in which the two-phase liquid to gas density ratio is 2778. The details of bubbles coalescence process are studied. Density and velocity of bubbles have been obtained. The computational results show that the initial radius of each bubble has a great influence on the coalescence time. The larger the initial bubble radius, the shorter the coalescence time. The pipe diameter has a little effect on the two bubbles coalescence time while it has a significant effect on the bubble velocity. As the pipe diameter increases, the bubble velocity increases. The obtained results are helpful for studying the transition mechanisms of two-phase flow patterns and useful for improving the bubble pump performance by controlling the flow patterns in lifting pipe.

A combined cooling, heating, and power (CCHP) system based on biomass-derived gas has great potential in reducing fossil fuels consumption and CO2 emission. However, heating value of various biomass-derived gases is relatively low, which might restrict performance of the system. Hence, effect of LPG addition on a CCHP system based on different biomass-derived gases (including gasification gas, pyrolysis gas and anaerobic digestion gas) is evaluated in this article. Cooling and power mode of the system is focused on. The power generation unit and the mixed effect absorption chiller are modeled to anticipate electricity and cooling output. Furtherly, performance of the system on energy, exergy and CO2 emission aspects when LPG volume fraction varies from 0% to 100% is evaluated. For biomass-derived gas from gasification, pyrolysis and anaerobic digestion, due to the addition of LPG: (1) energy and exergy efficiency can be improved by up to 7.4% and 5.1%, 0.6% and 0.1%, 2.0% and 0.6%, respectively; (2) energy saving ratio can be increased by up to 17.8%, 0.3% and 1.9%, respectively; (3) the maximum difference of CO2 emission reduction ratio is 49.2%, 30.7%, and −10.1%, respectively.

The vapor compression system driven liquid desiccant dehumidification to realize temperature and humidity independence control (THIC) is a very good idea for the utilization of condensation heat. Absorption refrigeration system (ABS) is widely applied all over the world, due to its energy saving and environment protection; meanwhile, large amount of condensation heat is discharged to the environment. In this study, a hybrid compression-absorption refrigeration air-conditioning (AC) system combined with liquid desiccant dehumidification is proposed. All of the condensation heat from the condenser of the ABS can be recovered to regenerate the diluted liquid desiccant solution. Meanwhile the evaporation temperature in the ABS rises since the latent load is handled by liquid desiccant, which improves the performance of the ABS. The PEE of the proposed system is 34.97% higher than that of traditional absorption refrigeration AC system at the same operation condition. And compared with the traditional absorption refrigeration AC system, the generation temperature of the proposed system can decrease from 100 °C to 60 °C due to the existence of the compressor.

In this paper a two stage hybrid absorption compression refrigeration system utilizing LiBr-H2O as working fluid is proposed. The hybrid system is compared thermodynamically with the conventional two stage absorption refrigeration system and it is found that the former can be operated at lower generator temperature and performs better than the latter. The effects of various operating parameters on thermodynamic and thermoeconomic performance indices like exergetic efficiency, area of heat exchangers and cost of the system are also studied. The heat exchangers are designed to estimate the size and cost of the system. The objective of thermoeconomic optimization is the minimization of annual cost of system, which includes investment costs and exergy fuel costs. The optimized hybrid system has COP of 0.43 and exergetic efficiency of 11.68%. The optimization results in the reduction of heat exchangers area from 79.61 m2 to 71.96 m2 and annual cost of operation of hybrid system by 5.2%.