| At present,the analysis and research of mixed refrigerant blends is an alternative research direction,among them,if the new refrigerant HFO1234 ze is directly used in the heat pump system,its thermodynamic performance is not very ideal,the COP of system performance coefficient and the volume refrigerating capacity are both low,but it has a certain degree of flame suppression;the new refrigerant HFO1234 yf has a small latent heat,which will seriously degrade the performance of the system when used alone,however,but it has good physical and chemical properties;natural working medium HCs has good thermodynamic performance,but has the disadvantage of inflammable and explosive.In this paper,HFO and HC with substitution prospect were mixed,take HFO1234ze/HCs and HFO1234yf/HCs as research objects,according to the principle of complementary advantages,in order to improve the use of a single working medium for the lack of research objectives,the cycle characteristics of the mixed refrigerant blends with the optimal mass ratio interval are analyzed,its main research work is as follows:(1)Based on environmental protection and thermodynamic performance,HFO1234 ze and HFO1234 yf are selected as basic components,HC290,HC600,HC600 a and HC170 are compared and analyzed in terms of density,dynamic viscosity,thermal conductivity,specific volume at constant pressure and specific enthalpy of the working medium and the critical parameters of the corresponding mixed refrigerant blends,finally,HC290,HC600 and HC600 a were screened out and mixed with basic components HFO1234 ze and HFO1234 yf.Based on non-azeotropic mixed refrigerant blends of the heat pump cycle thermodynamic model,to simplify the analysis,and set the temperature at the inlet and outlet of the heat source is 15 ℃,10 ℃,the inlet and outlet of the heat sink temperature of 15 and 55 ℃ ℃.(2)For the mixed refrigerant blends HFO1234ze/HCs and HFO1234yf/HCs screened in the previous section,the analysis of the specific optimal combination,the results show that HFO1234ze/HC600 and HFO1234yf/HC600 have the best cycle performance and the optimal mass ratio,which are 20/80 and 10/90,respectively,and make the COP maximum value of heating performance 3.414 and 3.413.(3)The two mixed refrigerant blends with the best cyclic performance HFO1234 ze/HC600 and HFO1234yf/HC600,under the condition of optimal mass ratio,the theoretical analysis of heat pump cycle performance is carried out.COP is the most important index to evaluate the cyclic performance of mixed refrigerant blends,among them,the heating COP of HFO1234ze/HC600(20/80)is 3.414 higher than that of HFO1234ze/HC600a(40/60),HC290,HC600 and HC600 a systems,which are 2.7%,0.09%,16.3% and 17.8% higher,respectively;the heating COP of HFO1234yf/HC60 0(10/90)is 3.413 higher than that of HFO1234yf/HC600a(10/90)and HFO1234yf/HC290(10/90),HC290,HC600 and HC600 a systems,which are 3.16%,3.19%,0.06%,16.2% and 17.78% higher,respectively.(4)HFO1234ze/HC600(20/80)of the exhaust temperature t2 is 76.9 ℃,the condensing pressure PC is 0.711 MPa,compression ratio r is 6.32;HFO1234yf / HC600(10/90)of exhaust temperature t2 is 76.26 ℃,the condensing pressure PC is 0.681 MPa,compression ratio r is 6.284.Exhaust temperature is mainly affected by compressor power consumption,specific heat capacity at constant pressure of refrigerant gas and compressor lubrication,under the same condition,the lubrication condition has little change,so the exhaust temperature is mainly affected by the former two,pressure ratio is directly related to the efficiency and safety of compressor,low boiling point refrigerant blends has higher vapor pressure,the ground pressure is relatively low,and the pressure ratio is positively correlated with the outlet temperature of heat sink.HFO1234ze/HC600(20/80)of the exergy efficiency η is 0.212,the heating qh is 204.5 kJ/kg,the power consumption w is 59.91 kJ/kg;HFO1234yf/HC600(10/90)of the exergy efficiency η is 0.212,the heating qh is 193.6 kJ/kg,the power consumption w is 56.7 kJ/kg.Under given conditions,compressor exergy loss rate are dominant,the change of heat production of mixed refrigerant blends with the ratio of working medium is,it is related to the enthalpy and density of mixed medium,at certain proportions,the lower system power consumption is mainly related to the lower system condensation pressure under the component.Studies have shown that the mixing of refrigerant blends can achieve complementary advantages to improve the shortage of pure refrigerants,therefore,the combination of new HFO refrigerant and natural refrigerant HCs is of great significance,HFO1234ze/HC600 and HFO1234yf/HC600 are expected to be alternative refrigerant blends. |
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