Thermodynamic Analysis Of Heat Pump Water Heater Using R32/R290 Mixtures As Refrigerant

Currently, the refrigerant R22(HCFC22) as the working fluid circulation system is widely used in air conditioning heat pump industry, but in the course of the ozone layer caused damage and produce large amounts of greenhouse gases, a transitional refrigerants. R32(HFC32) refrigerant has good thermal performance, zero ODP, etc.,natural hydrocarbon refrigerants R290(HC290) with good environmental performance(ODP=0, GWP100yr≈20) and thermal properties, and freon refrigeration system compatibility, and both have been used in air conditioning systems. In this paper, the research object of R32/R290 mixed refrigerant and heat pump applications,the thermodynamic performance of the system using different mass fraction of R32/R290 mixture as refrigerant is theoretically analyzed and compared, and using the mixed refrigerant formed by different mass ratios of R32/R290 to instead of the R22 in perfusion method, which can be taken as references for large-scale applications of the refrigerant blends and system design in future. Main conclusions are summarized as follows:( 1) Dtermination of the optimal compositon of the refrigerant mixtures.According to the selection criteria of mixed refrigerant, the R32/R290 mixed refrigerants of environmental performance, thermal performance and safety performance parameters were analysed. Initially identified alternative refrigerants R22 mass ratio in the range of 0-30%.(2)Under the normal working condition of heat pump water heater system,the thermodynamic performance of the system using different mass fraction of R32/R290 mixture as refrigerant is theoretically analyzed and compared based on heat transfer pinch point in heat exchangers. Under the same operating conditions, the maximum value of the system COPh should attained to 4.64 at which the mass fraction of R32/R290 is 16/84, and that is increased by 6.7%, 3.2%, 16.8% compared to that of R22, R32 and R290 system respectively. For the system of the mixture at the mass fraction of 16/84, the system condensation pressure is 2.31 MPa, the pressureratio is 2.79, and the discharge temperature is 71.88℃.(3)Based on laboratory test conditions, taking a air-source heat pump water heater(ASHPWH) as the prototype with R22 as refrigerant, using the mixed refrigerant formed by different mass ratios of R32/R290 to instead of the R22 in perfusion method. Under the normal working condition of GB/T 23137-2008,The test results show that the compressor load increses and the heating system coefficient of performance decline with increasing mass ratio of R32; The heating water capacity of R32/R290 increases with the increase of R32 mass fraction, which greater than R22 system of 131.34L/h within the R32 range of 25% to 30% under the optimum charging quantity of mixture. The maximum value of the system heating water capacity should attained to 139.69L/h, and that is increased by 6.2% compared to that of R22 system, which shows a good thermodynamic properties.