Diffusion Absorption Refrigeration Cycle Research Articles

Exergy and energy analysis of a hybrid natural Gas/Hydrogen liquefaction cycle combined with methanol production plant

This paper presents an innovative renewable multi-generation system designed to simultaneously produce various fuels, including biomass-based methanol, liquid hydrogen, and liquid natural gas. This system is part of a broader strategy aimed at streamlining different processes within a comprehensive plant, enabling the simultaneous production of multiple biomass-based fuels at a single location. The implementation of this system in regions where natural gas liquefaction plants coexist with abundant forest resources allows for the efficient production of all required fuels. In this process, a new configuration leverages to regenerate the waste heat of methanol synthesis process in the diffusion absorption refrigeration cycle integrated to the natural gas liquefaction process to maximize energy and exergy efficiencies. Additionally, three hydrogen liquefaction processes are evaluated to identify the most suitable option based on performance, efficiency, and power consumption. The investigations reveal that the combined mixed refrigerant cycle (CMRC) emerges as the ideal choice for hydrogen liquefaction process, characterized by lower power consumption and a higher coefficient of performance. The energy and exergy efficiencies of biomass gasification and methanol synthesis processes are 87.54% and 80.41%. The energetic coefficient of performance of the natural gas liquefaction process and CMRC is 0.9 and 0.2209. The specific power consumption of natural gas liquefaction process is 0.225 kWh/kgLNG, and the specific power consumption of CMRC is 5.462 kWh/kgLH2. The natural gas liquefaction process is responsible for the highest portion of the total exergy destruction, with 32%.

Analytical and experimental evaluation of a household refrigerator operating under a diffusion-absorption refrigeration cycle

The diffusion-absorption refrigeration (DAR) cycle has characteristics as the use of three working fluids and a low COP. In this work, an analytical and experimental investigation of a household refrigerator operating under a H20-NH3-H2DAR cycle is performed. A thermodynamic model of the DAR cycle was developed and adjusted based on models available in the literature. An experimental investigation was performed aiming to validate the developed DAR model using operating data collected in a real refrigerator. Subsequently the role of refrigerant rectification in the cycle was investigated and it was found that the temperature at the outlet of the rectifier should not exceed 70 °C. In addition, the importance of the production of liquid refrigerant in the condenser was investigated. It was observed that the COP decreases with the increase in the temperature of the inert gas entering the liquid heat exchanger (LHE). Finally, it was demonstrated that by increasing the amount of inert gas in the evaporator, there is a drop in evaporation temperature and consequently in the system COP.The model proved to be robust in the operational conditions tested experimentally.

A Parametric Examination of the Factors Affecting the Performance of a Diffusion Absorption Refrigeration System

Abstract Despite being identified nearly a century ago, the diffusion absorption refrigeration (DAR) cycle has received relatively little attention. One of the strongest attractions of the DAR cycle lies in the fact that it is thermally driven and does not require high value work. This makes it a prime candidate for harnessing low-grade heat from solar collectors, or the waste heat from stationary generators, to produce cooling. However, to realize the benefits of the DAR cycle, there is a need to develop an improved understanding of how design parameters influence its performance. In this vein, this work developed a new, validated, parametric model that can be used by designers and practitioners to examine the performance of the DAR cycle for a range of operating conditions. The results showed that the cycle’s performance was particularly sensitive to several factors: the rate of heat added and the temperature of the generator, the effectiveness of the gas and solution heat exchangers, the mass flowrate of the refrigerant and the type of the working fluid. It was shown that it can deliver good performance at low generator temperatures if the refrigerant mass fraction in the strong solution is made as high as possible. Moreover, it was shown that a H2O–LiBr working pair could be useful for achieving cooling at low generator temperatures.

Steady state numerical simulation and studying performance of a modified diffusion absorption refrigeration cycle

In this paper, numerical simulations of Diffusion Absorption Refrigeration – DAR cycle were conducted in order to study the performance of two configurations in steady state mode and use ammonia, water, hydrogen as working fluids. The two configurations were numerically simulated using models developed with the commercial flow sheet Aspen HYSYS V10 software. The first configuration where the main simple DAR cycle components were simulated and validated the experimental results. The second configuration where the modified DAR cycle was simulated which has an auxiliary heat exchanger added to the main simple DAR cycle as a modification. It was found that for the same input assumptions and heat applied, the modified DAR cycle shows higher cooling load. Therefore, higher COP than the simple DAR cycle. The optimal operation of the modified cycle is 36 W applied to the generator to achieve a COP of 0.235 instead of 0.209 for simple DAR cycle. The Simulation results show that by using the modified cycle, the COP improves by 12.4%.

Conceptual design and evaluation of an innovative hydrogen purification process applying diffusion-absorption refrigeration cycle (Exergoeconomic and exergy analyses)

A novel process for hydrogen purification by a diffusion-absorption refrigeration cycle and auxiliary nitrogen refrigeration stream is proposed and exergoeconomically analyzed. The diffusion-absorption refrigeration cycle provides a refrigeration load of 7.125 kW at a refrigeration temperature of −32.61 °C. The coefficient of performance of this refrigeration cycle is calculated to be 0.424. The thermal energy of 16.81 kW is supplied to drive the refrigeration unit. This refrigeration system utilizes ammonia as the refrigerant, water as the absorbent, and helium as the inert gas. The feed gas stream is divided into high-hydrogen and low-hydrogen streams by passing through cryogenic heat exchangers, expansion valves, and flash drums. The inlet unprocessed stream consists of H2, CH4, C2H6, C3H8, N2, and C6H6. Power of 63.42 kW is consumed by the compressors and air coolers to increase the pressure of the feed stream to 4482 kPa. The Aspen HYSYS V11 simulator and MATLAB software are utilized to develop the integrated process and perform the exergy-economic analysis. It was found that the purity of the separated hydrogen stream is about 88%. Two novel criteria for the overall exergy efficiency are introduced to evaluate the overall exergy efficiency of the process. The first and the second-mentioned criteria are computed as 93.825% and 35.053%, respectively. Also, the overall exergy destruction rate is found to be 45.764 kW that 32% of the irreversibility occurred in the air cooler as the main component of exergy wasting. Exergy-economic analysis of the system shows that air coolers are the most important equipment of the plant and should be precisely designed, manufactured, and arranged. Besides, the highest amount of relative cost difference and exergoeconomic factor are related to HX-104 and HX-107 heat exchangers with values of 750.34% and 60.53%, respectively. Finally, sensitivity analyses are conducted to determine the effective parameters on the system performance.

Experimental analysis on diffusion absorption refrigeration cycle with the magnetic field

ABSTRACT The main objective of this paper is to understand the impact of Diffusion Absorption Refrigeration (DAR) system coupled with a magnetic field through experimental investigation. DAR is an emerging technology which converts waste heat into useful work. The addition of the magnetic field increases the coefficient of performance of the DAR system. The waste heat from automobile exhaust was introduced as heat input and the performance and feasibility were studied for a different arrangement of the magnets. The absorption enhancement was compared with and without magnetic effect. The influence of magnetic field reduces the viscosity of the working fluid which causes the free flow and impacts the heat transfer rate due to its higher mass flow rate. The result indicates that the performance of the system increased with the application of magnets.

Performance analysis on a novel micro-scale combined cooling, heating and power (CCHP) system for domestic utilization driven by biomass energy

The CCHP system driven by biomass energy is essential for mitigating the fossil energy crisis and reducing CO2 emission. But few research work focuses on the micro-scale system due to the limited efficiency. In this paper an efficient household CCHP system is designed, which is driven by the water steam (100 °C-120 °C) from the biomass boiler and is consisted of an R245fa power cycle with a gravity assisted thermal driven “pump”, a single-pressure R134a/DMF/He diffusion absorption refrigeration cycle, and several heat exchangers for heating supply. The models of the system are constructed, and the energy, economic and environmental indexes are evaluated. The results reveal that the higher temperature of heat source and the lower temperature of ambient could improve the thermal efficiency of the CCHP system, and realize the lower cost and CO2 emission. The highest thermal efficiency of the CCHP system can reach to 55.26%. The quarterly energy saving for summer of a 100 m2 isolated house of a rural family can reach to 5059 kW⋅h (497 kW⋅h for cooling, 3154 kW⋅h for heating and 1408 kW⋅h for power generation), which can save about 3121.40 RMB electricity bill and reduce 0.15 t CO2 emissions.

Experimental study on diffusion absorption refrigeration systems with low GWP refrigerants

The diffusion absorption refrigeration (DAR) cycle is driven by heat input. The DAR systems do not employ pumps or compressors; they use refrigerants, absorbents, and auxiliary gases as working fluids. In this study, experiments were conducted on refrigerants with low GWP. The refrigerants R1234ze(E) and R600a (a natural refrigerant) were used in the DAR cycles with dimethylacetamide (DMAC) and isooctane as the absorbents, respectively. To investigate the operating characteristics of refrigerants with low GWP in the DAR cycle, the evaporation temperature and generator outlet temperature of the cycle were analyzed against the concentration of the working fluid and its charge pressure. In addition, the performance of the cycle was evaluated by the bubble pump shape. Using the results, the relationship between the shape of the bubble pump and the performance of the DAR cycle was analyzed. The maximum coefficient of performance of DAR achieved using R600a/isooctane was estimated as 0.157with the tube diameter of 3.17 mm and that of R1234ze(E)/DMAC DAR was estimated as 0.134 with the tube diameter of 4.76 mm.

Experimental study of a diffusion absorption refrigeration cycle supplied by the exhaust waste heat of a sedan car at low engine speeds

The wasted energy from a car exhaust can be considered as the heat supply for an absorption refrigeration cycle. In practice however, application of such cooling systems in automobiles has been facing a number of technical restrictions one of which is once the car engine runs idle or at low speed. To tackle this matter, the present experimental study has been carried out. A commercial diffusion absorption refrigerator with internal volume of 0.04 cubic meters (Electrolux 27A1) and the exhaust flow from a compact car engine (X100 KIA) are applied. Various engine speeds (1000–2500 rpm) have been tested. First, it was confirmed that the amount of heat transferred to the generator at low engine speeds was not adequate to obtain the low temperature required for the refrigerator compartment. A new generator was therefore designed and built. The experimental results show that by using the modified generator, the heat transfer to the generator improves by more than 19%. The evaporator and refrigerator compartment reached the desirable temperatures of −5.7 °C and 4.2 °C respectively at the engine speed of 2000 rpm. Further improvement of the results was observed at the engine speed of 1000 rpm where the temperatures at the evaporator and the refrigerator compartment were reduced by about 4 °C once the modified generator was applied.

Experimental investigation of an ammonia-water-hydrogen diffusion absorption refrigerator

Diffusion absorption refrigeration (DAR) is a small-scale cooling technology that can be driven purely by thermal energy without the need for electrical or mechanical inputs. In this work, a detailed experimental evaluation was undertaken of a newly-proposed DAR unit with a nominal cooling capacity of 100 W, aimed at solar-driven cooling applications in warm climates. Electrical cartridge heaters were used to provide the thermal input which was varied in the range 150–700 W, resulting in heat source temperatures of 175–215 °C measured at the generator. The cooling output during steady-state operation was determined from the power consumed by an electric heater used to maintain constant air temperature in an insulated box constructed around the evaporator. Tests were performed with the DAR system configured with the default manufacturer’s settings (22 bar charge pressure and 30% ammonia concentration). The measured cooling output (to air) across the range of generator heat inputs was 24–108 W, while the coefficient of performance (COP) range was 0.11–0.26. The maximum COP was obtained at a generator heat input of 300 W. Results were compared to performance predictions from a steady-state thermodynamic model of the DAR cycle, showing a reasonable level of agreement at the nominal design point of the system, but noteworthy deviations at part-load/off-design conditions. Temperature measurements from the experimental apparatus were used to evaluate assumptions used in the estimation of the model state point parameters and examine their influence on the predicted system performance.

Diffusion-absorption refrigeration cycle simulations in gPROMS using SAFT-γ Mie

Diffusion-absorption refrigeration (DAR) is a clean thermally-powered refrigeration technology that can readily be activated by low- to medium-grade renewable heat. There is an ongoing interest in identifying or designing new working fluids for performance improvement, particularly in solar applications with non-concentrating solar collectors providing heat at temperatures < 150 °C. In this work, the state-of-the-art statistical associating fluid theory (SAFT) is adopted for predicting the thermodynamic properties of suitable DAR working fluids. A first-law thermodynamic analysis is performed in the software environment gPROMS for a DAR cycle using ammonia as the refrigerant, water as the absorbent and hydrogen as the auxiliary gas. The simulation results show good agreement with experimental data generated in a prototype DAR system with a nominal cooling capacity of 100 W. In particular, at a charge pressure of 17 bar and when delivering cooling at 5 °C, the model results agree with experimental COP data to within ± 7 % over a range of heat inputs from 150 to 500 W. The maximum coefficient of performance (COP) is estimated to be 0.24 at a heat input of 250 W. The group-contribution SAFT-γ Mie equation of state is of particular interest as it offers good agreement with experimental data and provides flexibility in extending the model to test different working fluids with a high degree of fidelity. A methodology is also presented that allows the DAR thermodynamic analysis and working-fluid modelling to be integrated into a more general technology optimisation framework.

Performance Evaluation of Solar Energy Driven Diffusion Absorption Refrigeration Cycle Using Inorganic Fluid Pair

In the present era, the refrigeration and air conditioning have become essential requirements, and consume significant portion of energy available. The refrigeration requirements are severe in the hot and humid countries and, the refrigeration systems based upon solar energy are desirable. This study focuses on the thermodynamic modelling of ammonia water diffusion absorption refrigeration cycle with helium as pressure equalizing gas. The performance of the cycle is investigated parametrically by computer simulation based on thermodynamic modeling. It is found that the performance shows a loss of 37.36% at 110[Formula: see text]C while only 23.52% at 140[Formula: see text]C a generator temperature in the range of 120 to 150[Formula: see text]C is best suited for ammonia concentration range of 0.25–0.45 to get optimum performance.

شبیهسازی سیکل جذبی پخشی با منبع حرارتی اگزوز خودرو و بهبود عملکرد در دورهای پایین موتور

A diffusion absorption refrigeration cycle as a car refrigerator, which uses the car exhaust waste heat as a heat source of the cycle has been simulated in this study. An internal combustion engine with a volume of 1.3 liters at different engine speeds and throttle openings was examined experimentally and exhaust conditions such as flow rate and temperature were used as the input of the cycle. For engine speeds above 2000 rpm, there was no trouble and the evaporator temperature ranged from -0.4oC to -7.1oC. For 1500 rpm and 1000 rpm, the evaporator temperature did not reach the desired range of variations, which is the case in other reported researches. There is no available solution for the situations where the engine is running at low speed such as in traffic jam or idle condition. Therefore, a new generator was designed and simulated to solve this problem. The simulation results show that by using the modified generator, the heat transfer to the generator improves by 16.8% on average. Consequently, the cooling capacity increases by 4.7%. Therefore, the current diffusion absorption cycle is capable of performing well at the low engine speeds.

Numerical Investigation of Solar Energy Driven Diffusion Absorption Refrigeration Cycle

The refrigeration requirements are stringent in the countries which have ample sunshine and, the technological solutions based upon solar radiations for meeting the refrigeration requirements could a boon. The present work deals with the development of a diffusion absorption refrigeration cycle based refrigeration system operated by solar energy. This study focuses on the thermodynamic modelling of NH 3 – H 2 O diffusion absorption refrigeration cycle with helium as pressure equalizing gas. Results obtained from the parametric analysis show that 1.3% profit in refrigerating effect is observed when 3 °C sub-cooling occurs in condenser. The coefficient of performance gain gets up to 23% for ammonia mass fraction ranges from 0.28 to 0.58 as compared to the DAR cycle using saturated condensed liquid. A loss of 3.02% in coefficient of performance is seen for 10°C decrease in evaporator temperature. A range of the generator temperature lies between 140°C≤ T g ≥ 160°C is best suited for optimum coefficient of performance.

Modeling of a Von Platen-Munters diffusion absorption refrigeration cycle

This article presents a thermodynamical model of a Von-Platen diffusion absorption refrigeration cycle for power electronics applications. It is first validated by comparison with data available in the literature for the classical water-ammonia-helium cycle for commercial absorption fridges. Then new operating conditions corresponding to specific ABB applications, namely high ambient temperature and new organic fluids combinations compatible with aluminium are simulated and discussed. The target application is to cool power electronics converters in harsh environments with high ambient temperature by providing refrigeration without compressor, for passive components losses of about 500 W, with a compact and low cost solution.

The influence of the evaporator inlet conditions on the performance of a diffusion absorption refrigeration cycle

The purity of the condensate at the evaporator inlet on the performance of a diffusion absorption refrigeration cycle is examined under three configurations of sub-cooling. Three sub-cooling configurations were studied numerically: the no sub-cooling (nSC) configuration where the condensate flows directly to the evaporator inlet without sub-cooling, the partial sub-cooling (pSC) configuration where the condensate is sub-cooled by the refrigerant heat exchanger before the evaporator inlet and the full sub-cooling (fSC) configuration where the condensate is sub-cooled both by the refrigerant heat exchanger and the evaporator. It was found that for the same heat input the pSC configuration shows the highest cooling effect at the evaporator and therefore the highest COP. The influence of the evaporator inlet condition on the triple tube gas heat exchanger was also studied. It was found that the temperature at the evaporator inlet has to be as low as possible. Finally, the influence of the purity of the vapor phase at the rectifier outlet on the cycle performance was also studied. It was found that less effort has to be invested in the purification of the hot refrigerant vapor in the rectifier.

Low-source-temperature diffusion absorption refrigeration. Part II: Experiments and model assessment

The diffusion absorption refrigeration cycle can enable passive fully thermally activated refrigeration for off-grid applications. In the accompanying paper, a new system configuration was proposed that employs alternate working fluids (NH3–NaSCN–He), a coupling-fluid heated bubble-pump generator, and an enhanced absorber. Detailed component and system level models were formulated for this design. In Part II of this work, the subject of this paper, these results are applied to implement a complete low-source-temperature (110–130 °C) passively cooled diffusion absorption refrigeration (DAR) system. Cooling was achieved at temperature ranges suitable for refrigeration (Tevap = 6 → 3 °C, COP ~ 0.06) and air-conditioning (12 → 8 °C, COP ~ 0.14). Device performance was also assessed at elevated ambient temperatures, reduced ambient air velocities, and varying system pressures. Results from this investigation agreed well with the predictions of the models developed in Part I.

Energy and exergy analyses of the diffusion absorption refrigeration system

This paper describes the thermodynamic analyses of a DAR (diffusion absorption refrigeration) cycle. The experimental apparatus is set up to an ammonia–water DAR cycle with helium as the auxiliary inert gas. A thermodynamic model including mass, energy and exergy balance equations are presented for each component of the DAR cycle and this model is then validated by comparison with experimental data. In the thermodynamic analyses, energy and exergy losses for each component of the system are quantified and illustrated. The systems' energy and exergy losses and efficiencies are investigated. The highest energy and exergy losses occur in the solution heat exchanger. The highest energy losses in the experimental and theoretical analyses are found 25.7090 W and 25.4788 W respectively, whereas those losses as to exergy are calculated 13.7933 W and 13.9976 W. Although the values of energy efficiencies obtained from both the model and experimental studies are calculated as 0.1858, those values, in terms of exergy efficiencies are found 0.0260 and 0.0356.

Performance analysis of a diffusion absorption refrigeration cycle working with TFE–TEGDME mixture

The binary mixture of TFE–TEGDME has good thermo-physical properties and been investigated by many absorption chiller and heat pump researchers. However, few studies have been reported on the diffusion absorption refrigeration (DAR) system using TFE–TEGDME as the working fluid. The present article numerically investigates the potential of TFE–TEGDME used in the DAR system with two cooling mediums, viz. water (32°C) and air (35°C). It is found that with the absorber effectiveness of 0.8, the optimum generation temperature for the air-cooled TFE–TEGDME DAR system is around 170°C, and the corresponding coefficient of performance (COP) is up to 0.45. In comparison, the performance of the water-cooled system is better with a lower optimum generation temperature around 130°C and a higher COP reaching 0.56. Parametric studies are also conducted to analyze the effects of the cooling medium, generation temperature, evaporation temperature and absorber effectiveness on the system performance. Finally, the performance of the TFE–TEGDME and NH3–H2O DAR cycles is compared in terms of the COP and circulation ratio. Overall, it can be concluded that the TFE–TEGDME mixture is a good working fluid for the DAR cycle.

Research Progress of Diffusion Absorption Refrigeration Technology

Compared with the gas-compressed refrigeration system, the diffusion absorption refrigeration cycle has no moving part and the associated noise and vibration. It can be operated without any electric input and driven by various energy sources, has no the problem of the substitute of CFC, furthermore it has positive significance in energy conservation, off peak, environmental protection, and promoting the use of gas. So it has broad application prospects as a kind of absorption refrigeration mode. In the development of diffusion absorption refrigeration technology, the performance of diffusion absorption refrigeration system has been improved and enhanced continuously. The paper presents and discusses the recent research progress of diffusion absorption refrigeration which contains design of bubble pump, adjustment and optimization of operation parameters, utilization of low-grade thermal energy and selection of working medium. The research direction of diffusion absorption refrigeration in the future is suggested.