Performance Research Of A Combined Dual Different Temperature Heat Sources Cascade High Temperature Heat Pump

In view of the situation that the relatively low temperature heat energy output of the traditionalheat pumps, the usual high temperature heat source required for the single stage high temperatureheat pumps and the inability to composite use of dual different temperature heat sources for mosttypes of heat pumps, a new type of combined dual different temperature heat sources cascade hightemperature heat pump system has been proposed. This system, characterized by a key and specialcomposite heat exchanger of heat-source-condenser-evaporator, was able to effectively utilize dualdifferent temperature heat sources and product high temperature hot water to meet the heating andcertain industrial processes. In this paper, we studied the cycle performance of this systemtheoretically and experimentally. Firstly, we analyzed the effectiveness on the improvement ofcycle performance of this new type system comparison with the single low temperature heat sourcetypes. Additionally, chose R124and R22as the high and low stage working fluid respectively anddid theoretical calculation at the specified condition that the condenser temperature was85℃,evaporator temperature was5℃a nd heating capacity was10kW. Finally, designed and set up theperformance test platform and investigated its operating characteristics.The experimental results were as follows: In the dual heat sources mode, the performance ofthis system was significantly affected by inlet temperature of the moderate-temperature heat sourceand the compressor frequency of low stage, while relatively less affected by flow rate of themoderate-temperature heat source. When the flow rate remained0.8m3/h, with the inlettemperature rose from42℃to53℃, the cascade heat pump heating capacity(QC) increased by18.6%and the cascade heat pump coefficient of performance(COPC) increased by8.9%; When theinlet temperature remained48℃，with the flow rate rose from0.4m3/h to1.165m3/h, the QCincreased by4.3%and the COPCincreased merely by1%; When the inlet temperature and flowrate of the low-temperature heat source remained respectively15℃and0.7m3/h, and the inlet temperature and flow rate of the moderate-temperature heat source remained respectively48℃a nd0.8m3/h, with the compressor frequency of low stage decreased from38Hz to30Hz, theQCdecreased by4.2%and the COPCincreased by7.2%.The new system proposed was suitablefor composite use of dual different temperature heat sources, especially for recovery ofmoderate-temperature waste heat, and could product high temperature hot water of80℃, whichwas significant for energy saving. The proposition of this new system and the study on it werehelpful for efficiently lifting the output temperature for heat pump technology.