The Exergy Analisis On CO₂Two-stage Compression Refrigeration And Heat Pump System Of Tandem Style

With the improvement ofpeople's living standards, more and more people need theheating and cooling demand simultaneously, and a series of air conditioning equipmentswhich can cooling and recover condensation heat are used widely. But most of thisequipments have these disadvantages such as heating and refrigerating limited by eachother and lower operating efficiency. In order to solve these problems, this paperpresents a sort of tandem style of CO2two-stage compression refrigeration and heatpump cycle system, which can not only cooling and heating, but also supply coolingcapacity and heating capacity at the same time according to the needs of users. The frontstudies which based on the first law of thermodynamics showed that: in some workingconditions, the performance of the system is even higher than the refrigeration and totalheat recovery cycle, This article is a more in-depth study of the system, it is desirable toidentify weaknesses parts of the system and find ways to improve system performancethrough exergy analysis.According to the basic theory of exergy analysis method, this paper establishedthe exergy analysis model of each component of the system at first; then used the exergyanalysis model to calculate and analyze in the total heat recovery working conditions,part heat recovery working conditions, cooling and heating simultaneously workingconditions; analyzed the influence to the exergy efficiency of the system focuses on thehigh-pressure, intermediate pressure, chilled water temperature, cooling watertemperature, inlet and outlet hot water temperature, subcooling, superheat, flowcoefficient,etc,find the weak links of the system.The results show that: under the working condition of total heat recovery, the main parts of the system exergy losses are the second throttle value, high pressure compressor,and hot-water heater. Under the working condition of part heat recovery, with increasingof high pressure, hot water inlet temperature determines if there is a peak of the exergyefficiency of the system; the main parts of the system exergy losses are the secondthrottle value, outdoor heat exchanger, high pressure compressor, and hot-water heater.Under the working condition of cooling and heating simultaneously, the exergyefficiency of the system will decline when the cooling capacity reduced or heatingcapacity increased; the main parts of the system exergy losses are the first throttle value,high pressure compressor and hot-water heater.