Performance Of Adsorption Refrigeration System Research Articles

Numerical study on the performance of adsorption refrigeration system with finned bed structure paired with MOF-water as working fluid

A single-bed finned tube adsorption refrigeration system model was established to compare the adsorption characteristics of three metal organic framework materials, MIL-101(Cr), MIL-101(Cr)/CaCl2-10%, MIL-101(Cr)/ CaCl2-20%. The change of material properties under different thickness/length/number of fins was characterized, and the most suitable adsorption bed structure for different materials was obtained. The results show that the number of fins has little effect on the COP and specific cooling power of the material in the system. Choosing thinner fins can improve the COP of the system. With the increase of fin height, the COP showed a trend of increasing first and then decreasing. The three materials, MIL-101(Cr), MIL-101(Cr)/CaCl2-10%, MIL-101(Cr)/CaCl2-20%, obtained the highest COP when the fin heights were 50 mm, 60 mm, and 70 mm, respectively. The maximum specific cooling power was obtained when the fin heights were 20 mm, 60 mm, and 70 mm, which were 21.7 W/kg, 90.1 W/kg, and 174.5 W/kg, respectively. The height of the fin has a great influence on the performance of the system. When designing the adsorption bed, the appropriate fin height should be selected for the specific adsorbent.

Performance prediction of adsorbent in an adsorption refrigeration system based on variable temperature and constant pressure experiment and dynamic model

• A method was designed to predict the performance of MOFs in adsorption refrigeration system using a small amount of MOFs. • The addition of calcium chloride increases the range of suitable cooling conditions for MIL-101(Cr). • The screening time of MOFs in adsorption refrigeration system is shortened. In order to study the performance of metal organic framework materials (MOFs) in adsorption refrigeration systems, the current research method is to test the equilibrium adsorption characteristics of the materials, estimate the adsorption refrigeration conditions of the materials, and then prepare a large amount of them and fill them into the adsorption bed for testing. However, the above methods affect the authenticity evaluation of materials due to the adsorption refrigeration experimental device. In addition, the preparation time of MOFs materials is generally long, and the time cost of verifying materials is high. Therefore, the purpose of this paper is to shorten the prediction time of material performance of adsorption refrigeration system. The large temperature jump method is used to carry out the dynamic adsorption and desorption experiments of three kinds of adsorbents at variable temperature and constant pressure. The dynamic adsorption and desorption model is established and combined with the experimental results to calibrate and verify the combination of heat and mass transfer coefficients of adsorbents. Finally, the performance coefficient of the adsorbent under different conditions is predicted, and the suitable refrigeration operating range is determined. The results show that the addition of calcium chloride increases the range of suitable cooling conditions for MIL-101(Cr). When the desorption temperature is 90°C, the minimum evaporation temperatures of MIL-101 (Cr) and MIL-101 (Cr)/CaCl 2 -20% are 12 °C and 5°C, and the maximum adsorption temperatures are 31 °C and 38°C, respectively.

Review on improvement of adsorption refrigeration systems performance using composite adsorbent: current state of art

ABSTRACT As adsorption refrigeration systems are powered by waste heat from automobile/industries and run by environment-friendly refrigerants, they have very promising cooling technology compared to vapor compression and absorption cooling systems. But due to large size, less performance and high installation cost, adsorption cooling systems have not yet been commercially popular. Literature review shows the physical adsorbent has poor adsorption capacity as compared to the chemical adsorbent. However, the salt swelling and agglomeration are the phenomenal challenges associated with chemical adsorption systems leading to reduction in the heat and mass transfer performances. To overcome the demerits of the physical and the chemical adsorbents, composite adsorbent systems have been developed to harness the potentiality of the adsorption capacity and increase the heat and mass transfer performances of adsorbent. In the present work the performance of different adsorption refrigeration system working on physical and chemical adsorbent has been discussed and compared on the basis of COP (Coefficient of Performance) and SCP (Specific cooling Power). A detailed comparative analysis has been provided between different composite adsorbents developed by using Silica-gel, Activated Carbon, Expanded Natural Graphite and Zeolite as a parent material. The performance of different composite adsorbents has been compared on the basis of thermal conductivity and adsorption capacity (of water, methanol, ethanol and CO2). Also, a novel composite adsorbent using polymeric binder (silica-gel and expanded natural graphite bound with polyvinyl alcohol) has been proposed and their physical properties are also discussed. In addition to this, three different methods of composite adsorbent materials preparation using silica-gel, activated carbon, zeolite with expanded natural graphite have been discussed. It is observed from the present study that the composite adsorbent of Metal Organic Frameworks shows better heat and mass transfer properties as compared to the conventional adsorbent. It is also observed that the performance of the adsorption refrigeration system can be improved significantly by developing high-performance composite adsorbents.

INFLUENCE OF VARIABLE THERMAL CONDUCTIVITY AND PERMEABILITY OF ADSORBENTS ON SIMULATION: A CASE STUDY OF A TWO-STAGE FREEZING SYSTEM

In the conventional simulation of the adsorption refrigeration performance, the constant thermal conductivity and permeability were always chosen for the construction of a mathematical model. Recent research works showed that the thermal conductivity and permeability change significantly in the adsorption and desorption processes, which means that the consequent adsorption refrigeration performance will also be influenced. In order to evaluate the influence of the variable thermal conductivity and permeability of adsorbents on the performance of adsorption refrigeration system, the variable thermal conductivity and permeability in the adsorption processes were tested for CaCl2 and BaCl2, and the two-stage adsorption refrigeration system was simulated using CaCl2 -BaCl2 -NH3 as a working pair. The simulation results for the variable thermal conductivity and permeability were compared with those for the constant thermal conductivity and permeability, as well as with experimental results. The research showed that the maximum relative error between the simulation result with variable properties and the experimental result was 9.1% for SCP, 8.3% for cooling capacity, and 12% for COP, respectively, while the maximum relative error between the simulation results with constant properties and experimental results was as high as 42.8% for SCP, 41.4% for cooling capacity, and 36% for COP, respectively. The foregoing demonstrates that the variable properties influence significantly the simulation results, and should be investigated in the first place before constructing mathematical models for chemical adsorption refrigeration systems.

Thermodynamic analysis and performance simulation of different kinds of mass recovery processes applied in adsorption refrigeration system

Mass recovery process is an efficient way to improve the performance of adsorption refrigeration system. By researching two kinds of conventional mass recovery cycle (i.e., mass recovery between two beds [TBMRC] and between evaporators [TEMRC]), double mass recovery cycle (DMRC) is proposed to reduce heat loss. Thermodynamic analysis shows that the heat loss of DMRC is less than the other two kinds. Consequently, DMRC system performance should be the best, followed by TEMRC and TBMRC as the worst. A mathematical model of heat and mass transfer was then built and simulation was performed to analyze the system performance. The simulation results show that the optimal cycle time and mass recovery time are 30 mins and 10 s, respectively. Compared with the basic cycle, both coefficient of performance and specific cooling power of mass recovery cycle are much better. The system performance of different kinds of mass recovery cycle is almost the same in most cases, caused by a small reduction of heat loss in DMRC or TEMRC, when compared with the cooling capacity and heating power. However, under some conditions (i.e., large cycle time or high evaporation temperature), performance of DMRC is better than the other two kinds, which is consistent with the thermodynamic analysis results.

Performance study of a high efficient multifunction heat pipe type adsorption ice making system with novel mass and heat recovery processes

The purpose of this paper is to present the performance analysis of a multifunction heat pipe type adsorption ice maker with activated carbon–CaCl 2 as compound adsorbent and ammonia as refrigerant. For this test unit, the heating, cooling and heat recovery processes between two adsorbent beds are performed by multifunction heat pipes. A novel mass and heat recovery adsorption refrigeration cycle is developed. When mass recovery process is implemented before heat recovery process, the performance of the cycle with novel mass and heat recovery processes is much better than that for the cycle with the conventional mass and heat recovery processes. The experimental results show that the former cycle can increase the coefficient of performance (COP) and specific cooling power (SCP) by more than 17% compared with the latter cycle. In comparison with the basic adsorption cycle, the mass and heat recovery cycle can enlarge the cycled refrigerant mass and reduce the power consumption of boiler; the COP and SCP were improved by more than 11% when the mass recovery time was 20 s, while at the optimal mass recovery time of 40 s, the COP improvements for conventional and novel mass and heat recovery cycles are 43.8% and 68.7%, respectively. It was concluded that the novel mass and heat recovery processes are more beneficial to improve the performance of adsorption refrigeration system in comparison with the conventional mass and heat recovery processes.

Experimental investigation and mathematical modelling of a solid adsorption refrigeration system

The objective of this work is to study the thermodynamic mechanism and performance of an engine exhaust-powered adsorption refrigeration system using CaCl 2 as adsorbent and NH 3 as refrigerant. A 6 kW nominal refrigerating capacity adsorption refrigerator was developed. The working performance of the refrigerator is presented. It is concluded that the refrigerating capacity at constant evaporating temperatures varies with the input heat into the generator, and the heat transfer affects strongly the mass transfer in the adsorbent, making it work in different mean generation and adsorption temperatures. A conventional test bed was developed for investigating the properties of CaCl 2–NH 3 adsorption/desorption unit tube. A mathematical model based on non-equilibrium thermodynamics was developed to describe the performances of the adsorption refrigerating system.