Theoretic Study On Performance Of Transcritical CO2-[emim][Tf2N] Absorption Refrigeration Cycle Driven By Low-grade Energy

The technology of absorption refrigeration was invented when the sulfuric acid wasused as absorbents and ether used as refrigerant. With ammonia and water used inabsorption refrigeration and the using of NH3-H2O and H2O-LiBr absorption refrigerationmachine unit promoted the developing of the technology of absorption refrigeration. After1818s, the absorption refrigeration was gradually replaced by the vapor compressionrefrigeration which could perduce more cold, but the shortcoming of the vaporcompression refrigeration which took a large amount of energy appeared, the developing ofthe absorption refrigeration was attracting more and more attention. On the other hand,with the growing of greenhouse effect and the improvement of people’s awareness ofprotecting environment, the bad influence of synthetic refrigerant such as CFCs，HFCs etc.showed up, and the natural refrigerant had been taken seriously. In1989, G.Lorentzen,fomer president of International Institute of Refrigeration, came up with transcritical cyclerefrigeration system with carbon dioxide. Unfortunately, the disparity in coolingperformance limited the developing of carbon dioxide using in absorption refrigeration.In this study, aiming at the problem of the low efficiency of traditional absorptionrefrigeration, according to the principle of energy cascade utilization, the new system oflow-grade heat-driven transcritical CO2-[emim][Tf2N] absorption refrigeration cycle wasproposed. The system used CO2-[emim][Tf2N] as absorption refrigerant pair and had twolow-grade heats in different temperature, because of using the principle of energy cascadeutilization, the efficiency of the absorption refrigeration would be improved effectively,simultaneously had advantages such as friendly to environment，no noise, waste heatusable etc.. This absorption refrigeration system had done some improvement based on thetraditional absorption refrigeration system, the energy transformation was achieved by thecirculation of refrigerant through the components in the system and the thermodynamicchange of refrigerant itself. The high thermal transformation efficiency was the important symbolic of low-grade energy using effectively, the energy cascade utilization improvedthe utilization of energy further, and the use of low-grade energy agreed the study directionof refrigeration today which is energy-saving and protecting the environment.By building the mathematical model of components in the system and usingnumerical calculation to analysis the influence of important parameter to the cyclingperformance of the system. Under the condition of keeping the circulating volumeunchanged, the influence of the cooling water temperature, the containing refrigeranttemperature, the heat temperature and the working ratio of the two generators, theoperational pressure to the system was obtained; then the influence of circulating volumeto the system performance was also obtained with the other parameters unchanged. Afterthat, optimized design had been done to the system and the influence of all parameters wasconsidered so that the best cooling efficiency of the system in specific condition had beendetermined, compared with the traditional absorption refrigeration system which using thesame refrigerant pair, it showed that the COP of the system in this study could reach as0.69, which was over50%improved than the traditional one, it proved that this study hascertain research value, and the energy cascade utilization could do good to theimprovement of the cooling performance of the absorption refrigeration system.