Theoretical And Experimental Study On The Heat Pump System Using R744/R600a Mixtures As Refrigerant

In recent years,energy crisis and environmental issues have increasingly become an important factor that restricts the economic development and social stability of all countries in the world.Heat pump technology is favored by people because of its dual advantages in energy saving and environmental protection.At present,the commonly used refrigerants of heat pump is R22,and alternative refrigerants such as R134 a,R410A,and R407 C that have no ozone layer destructive effect,but these synthetic refrigerants all have high GWP value,in the future development will eventually be incorporated into the ranks of elimination.Therefore,the search for new environmentally friendly refrigerants has become an important research subject.Based on the analysis of the environmental characteristics and thermophysical properties of the natural refrigerants R744 and R600 a,this paper proposes that use of the mixture in heat pump system,the cycle characteristics of heat pump system using mixed refrigerants are analyzed theoretically and experimentally,the main research includes the following aspects:(1)Under the conditions specified by the national standard of heat pump water heaters,the theoretical cycle characteristics of R744/R600 a mixed refrigerant used in heat pump system under different cyclic mass concentration were calculated and analyzed.The results show that the cyclic mass concentration of R744 in the mixed refrigerant is 7%,and the coefficient of the heating cycle performance of the corresponding system reaches a maximum value of 4.12,the condensing pressure of the mixed refrigerant system is 0.861 MPa,the pressure ratio is 4.12,and thecompressor discharge temperature is 65.53°C.(2)The experimental research was carried out by using the existing experimental device.The experimental results show that when the filling mass concentration of R744 is 7%,and the corresponding heating cycle performance coefficient of the system has a maximum value of 4.01,at this time,the heating capacity and power consumption of the system are 2.25 kW and 0.56 kW respectively,and the condensing pressure is 0.891 MPa,the pressure ratio is 2.95,and the exhaust temperature of the compressor is 69.42°C.Under the filling mass concentration,with the increase filling capacity of the mixture refrigerant,the heating performance coefficient and heating capacity of the system increase first and then decrease,the power consumption 、pressure ratio and compressor exhaust temperature first decreased and then increased,and the condensing pressure gradually increased.(3)Set the heat sink outlet temperature to 45°C,50°C and 60°C respectively was tested.The results show that when the filling mass concentration of R744 is 7% and the filling quantity is 0.7kg,with the increase of water temperature at the outlet of heat sink,the heating performance coefficient of the mixed refrigerant R744/R600 a system decreases gradually,condensation pressure,pressure ratio,power consumption increased gradually,heating capacity and compressor exhaust temperature increased first and then decreased.