Research On The Performance Of CO₂ Air-source Heat Pump For Heating

Taking the CO₂ air-source heat pump for heating as the research object,the composition,working principle and thermodynamic cycle analysis method of the CO ₂air-source heat pump system for heating are summarized.Considering the influence of internal and external factors of the system on the performance of the system,on the basis of the existing CO₂ air-source heat pump equipment,the technical scheme of adding the regenerator in the heat pump unit and combining with the frequency conversion of the compressor is put forward.At the same time,the whole heating system adopts low t emperature heating mode.The technical principle involved in the scheme is expounded,the feasibility of the technical scheme is analyzed qualitatively,and the theoretical basis for the experimental implementation of the optimized scheme is established.A CO₂ air-source heat pump system for heating is designed by means of compressor frequency conversion,heat exchanger and gas separator with electric heating.On this basis,through establish response surface models of the compressor operating frequency of CO₂ air-source heat pump,which is suited to heating,to improve the low temperature performance of the heat pump.The results show that,reasonably increasing the frequency of the compressor can effectively improve the heat capacity of CO₂ air-source heat pump for heating in low temperature environment,although the compression ratio increases,but the compressor stable operation still can be guaranteed.In order to improve coefficient of performance?COP?of CO ₂ air-source heat pump for heating,compresso r in low temperature environment can be segmented frequency operation.When the ambient temperature is-5?,-10?and-15?,the maximum value of COP corresponds to the frequency is 55 Hz,58 Hz and 60 Hz respectively.The supercritical CO₂ air-source heat pump heating system in cold region was built.According to outdoor ambient temperature and heating load,the heating period is divided into five different stages,and the heating operation parameters of CO ₂ air-source heat pump are adjusted in different stages.The test results show that the CO₂air-source heat pump can meet th e heating demand in cold area,and the average performance coefficient of the heating system in the heating periods can reach 2.236,in the same time the heating room has good comfo rt.Taking coal-fired boiler and gas-fired boiler as reference,t he energy utilization efficiency and CO ₂ emission amount of three kinds of heat source heating are compared and analyzed by using equivalent electricity method.The results show that the ener gy utilization efficiency of CO ₂ air source heat pump heating is higher than that of gas boiler heating and is slightly lower than that of coal-fired boiler heating after considering the energy grade.The CO ₂emission amount of CO₂ air-source heat pump heating is higher than that o f gas-fired boiler heating,but less 20.89%than that of coal-fired boiler heating.