Theoretical and experimental study on several refrigerants of moderately high temperature heat pump

The aim of the study is to select working fluids which have excellent performance and are environment friendly for moderately high temperature heat pump. Theoretical study is executed on several HCFCs and HFCs, with ODP of zero or small value firstly. And then research is carried out on a water-to-water vapor compression heat pump system applying the experimental assessment method of specifying working fluid parameters. Based on theoretical analysis, HFC245fa, HC600, HC600a, and a zeotropic refrigerant mixture HC600/HFC245fa (mass fraction: 2.83%/97.17%) are used as refrigerant for the experiment, with the evaporating temperature range of 30–55 °C, and condensing temperature range of 60–100 °C. Theoretical analysis shows that HCFC141b, HCFC123, HFC245ca, HC600 and HFC245fa have large COPh. However, pressure ratio of HFC245ca, HCFC141b and HCFC123 is too large. The experimental results indicate that both the natural working fluids have excellent cycle performances in moderately high temperature heat pump cycle. Their heating coefficients of performance (COPh) have little difference in the conditions of lower temperature cycle, but the cycle performance of HC600 is better than HC600a in higher temperature conditions. When the evaporating temperature and the condensing temperature are 44 °C and 90 °C, COPh of HC600 and HC600a are 3.84 and 3.33 respectively. In higher temperature conditions, the performance of the zeotropic refrigerant mixture HC600/HFC245fa is much better than HFC245fa. When the evaporating temperature is 50 °C, and the cycle temperature lift is 45 °C, COPhs of HC600/HFC245fa are 3.74 and 3.83 respectively.