Research On Thermodynamic Properties And Cycle Performance For Low GWP Refrigerant Mixtures

The promulgation of European directive on Mobile Air-Conditioning systems（MACs） in2006marked compulsory measures had been made by the European Unionto dealing with climate change, which means that the transition from high GWP tolow GWP had become the inevitable trend of international refrigeration industry. Withthe favorable thermal physical properties and good environmental performance,HFO1234yf and HFO1234ze have become a research hotspot on low GWPrefrigerants; therefore, the theoretical researches of thermodynamic properties,thermalphysical properties and cycle performance corresponding to the mixtures ofHFC32/HFO1234yf and HFC32/HFO1234ze were presented in this article.Based on the experimental data regarding to the thermalphysical properties ofHFO and HFC32/HFO in the literatures, the PR, PRSV, Helmholtz equations of stateare chosen as the main state equation model of mixtures for optimization, and theinteraction coefficient of HFC32/HFO suitable for different equations of state and thecharacteristics parameters of HFO are obtained. With the comparisons among theaccuracy of physical properties calculated by the three optimized equations of stateand software REFPROP, the PRSV equation of state has the highest calculationaccuracy and better stability, and meanwhile its calculation accuracy increases to±2%relative to±8%by REFPROP.Combined the PRSV equation with auxiliary equation and thermodynamicrelation, the calculation program of the thermodynamic properties for mixedrefrigerant by making use of residual function method is developed, and furthermorethe thermodynamic properties, such as enthalpy, entropy, vaporization latent heat, thetemperature glide and heat capacity, with the variation of HFC32/HFO mixing ratioare analyzed. After determining the calculation formula of transport properties forHFC32and HFO, calculation program of viscosity and thermal conductivity forHFC32/HFO by using the theoretical relationship of transport properties for mixtureis obtained, and the influence of proportion for HFC32on the transport properties ofHFC32/HFO is discussed.Lastly, the influence of basic cycle parameters and mixing ratio of HFC32/HFOon the cycle performance at the specific working condition are theoretically investigated. According to the aforementioned transport properties models of HFO,the effects of pressure drop in the evaporator and condenser on cycle performance thatthe relative cycle performance coefficient (COP/COP_R410A) of HFC32/HFO mixtureare respectively studied, which has guiding significance for the refrigerant substitutionand system performance optimization.