R236fa/R32大滑移温度混合工质的优选方法及实验验证

针对适用不同制冷工况下混合工质组成及组分的多样化选择问题，提出了对应用于双温制冷机组的大滑移温度混合工质R236fa/R32组分在冷凝温度范围为311～333K、蒸发温度范围为269～290K的优选方法。对R236fa/R32的温度随焓值非线性变化特性进行了理论研究；建立了混合制冷剂蒸发换热过程由于温度随焓值非线性变化特性产生的熵增模型，通过对混合工质不同组分高、低温蒸发器的熵增变化情况确定最佳组分。并搭建了试验台，通过实验研究得到了该混合工质不同组分下在换热器中的温度分布情况、制冷效率（COP）及压缩机功耗情况验证该优选方法的结果。研究结果表明：该熵增模型能够较好地反映该混合制冷剂不同组分的COP特性及压缩机功耗，随着R32质量分数的增加，蒸发器的熵增先增大、后减小，在R236fa/R32为4∶6时，低温蒸发段和高温蒸发段由于温度随焓值非线性变化特性产生的熵增都最小，因此为该机组的最佳组分，验证了理论分析的正确性。该方法可以为不同工况下混合工质的优选提供参考。

R236fa/R32 mixed refrigerant of large glide temperature selection and experimental verification

For the diversified selection of the composition and components of the mixed refrigerant under different refrigeration conditions, the optimal selection method of R236fa/R32 components with large glide temperature mixed refrigerant for two evaporation temperature refrigeration unit was proposed, which has the condensation temperature range of 311-333K and the evaporation temperature range of 269-290K. The nonlinear change of temperature with enthalpy of R236fa/R32 was studied theoretically. The entropy increase calculation model of mixed refrigerant evaporation heat transfer process was established based on the nonlinear change characteristics of temperature and enthalpy. The optimum composition of the mixed refrigerant was determined by the change of entropy of the high and low temperature evaporator with different components. The temperature distribution in the heat exchanger, the coefficient of performance (COP) value and the power consumption of the compressor were obtained by the experimental study. The results of the optimized method were verified. The results showed that the entropy increase model could better reflect the COP characteristics of the refrigerant and the power consumption of the compressor with different components. The entropy of the evaporator increased first then decreased with the increase of R32mass fraction. When the refrigerant mixture was R236fa/R32(4:6), both the entropy increase of low temperature evaporator and high temperature evaporator were the smallest due to the nonlinear variation of temperature with enthalpy value. Therefore, 4:6 was the best component of 236fa/R32 in the two evaporation temperature refrigeration system. The experimental results were highly consistent with the theoretical analysis. This method can provide reference for the selection of refrigerant mixtures under different refrigeration conditions.