Phase Equilibrium And Heat Pump Cycle Performance Of Ternary Refrigerant Mixture Based On R134a System

R134a is the most widely used low temperature refrigerant.To solve the problems in R134a heat pump such as high condensing pressure,low system efficiency,not environment-friendly,etc.,this paper aimed at finding out new refrigerant mixture used under heat pump working condition of condensing temperature at 70-90 ~oC.The equation of state(EoS)and mixing rule of the ternary refrigerant mixture based on R134a heat pump were analyzed by comparing the calculation accuracy and the application range of various EoS and mixing rules.Interaction parameters of vdW mixing rule and Peng-Robinson(PR)EoS were studied.Base on PR EoS and vdW mixng rule,the vapor liquid equilibrium(VLE)and thermodynamics model of ternary refrigerant mixture was established.VLE and thermodynamics data were calculated in 0-90 ~oC by relative error analysis method.Three ternary refrigerant mixtures M1,M2 and M3 were proposed according to the principle of complementary advantages.The cycle performance was compared with R134a,C1 and C2 under variable working conditions.The method of calculating refrigerant mixture interaction parameters of vdW mixing rule and the compressibility factor of PR EoS were proposed.The relative error is below6%.The VLE and thermodynamics model of ternary refrigerant mixture was validated.The average error of vapor and liquid mole component is 3.13%and 1.61%,respectively.The average error of enthalpy and entropy is 3.27%and 3.49%respectively.The model has high accuracy.Under the working condition of variable condensing temperature,the COP of M1 is the highest and varies steady,about 4.0.The discharge temperature of M2 is lowest,among 78~98 ~oC.The compression rate of M3 is lowest,among 2.6~2.9.M1,M2and M3 have the high COP,low discharge temperature and low compression rate,respectively.Under the working condition of variable temperature rise,the compression rate of M3 is lowest.When temperature rise is 75 ~oC,compression rate is 6.6.M1 and M2are fit under heat pump working condition of cycle temperature rise below 65 ~oC,while M3 is fit under heat pump working condition of cycle temperature rise below 75 ~oC.The proposed mixture has a better cycle performance compared to the contrast mixtures.According to the study of variable working condition,M1,M2 and M3 are environment-friendly,thermal performance are close to R134a,and can be directly replace in R134a heat pump system.M1,M2 and M3 are fit for practical application of the low heat resource temperature and high heating temperature condition.