The Exergy Analisis On Two-stage Compression Heat Pump With The Function Of Heating And Cooling Simultaneously

There are cooling and heating demand in the same time in many areas of daily life.In order to meet various requirements, the industry researchers designed a series ofmore energy saving system.the currently widely used system is using the refrigeratingunit or air conditioning unit with the function of the condenser heat recovery which canmeet the requirements of heat load relying on the heat recovery in the refrigeration work.But, in practice this scheme exists some defects: the heating capacity is restrainted bythe refrigerating capacity. To solve the problem, in recent years, our research groupcome up with the two-stage compression heat pump with the function of heating andcooling simultaneously. And the comprehensive analysis has been carried on theperformance of the system with the first law of thermodynamics,the result shows that ithas the more economical and more energy efficient advantages,but also a good solutionto the problems of heat recovery refrigeration system.This article is a more in-depthstudy of the system,execting exergy analysis to identify the weak links and point out theway and direction of further improvement.On this, this paper set up the exergy analysis model of the high and low pressurecompressor, hot water heater, heat source side heat exchanger, the user side heatexchanger, throttle valve G and throttle valve H, and then calculated it based on themain evaluation index of the exergy analysis method, analyzed the outdoor airtemperature ta, the refrigerant flow ratio α, condensing temperature tc, evaporationtemperature te, degree of super-cooling and heat transfer temperature difference teffecting on the exergy efficiency of the system, and by comparing the exergy losscoefficient and exergy loss rate of the system components, find out the weak link of thesystem, the results showed that: under low refrigerant flow ratio, the main parts of the system exergy losses are heat source side of heat exchanger D, condenser C, throttlevalve G, and high pressure compressor B; Under high refrigerant flow ratio, the mainparts of the system exergy loss are the throttle valve H, high pressure compressor B,condenser C and low-pressure compressor A;On this basis, the system has been optimized to give the exergy analysis model,and has carried on the comprehensive analysis and calculation, and then to contrastsystem before the optimization, the result showed that economy implement can improvethe system’s exergy efficiency, and make up for weak links existing in the system.