Theoretical And Experimental Cycle Performance Of Working Fluids For Moderate/High Temperature Heat Pumps

The moderate/high temperature heat pump technology has wide prospects in enlarging heat pump applications to achieve the higher delivery temperature and make use of waste heat. One important aspect of the researches on the moderate/high temperature heat pump technology is to find out new alternative working fluids with excellent environmental and cycle performances, based on conventional heat pump systems. In this thesis, some working fluids at condensing temperature from 60 to 100°C were proposed and evaluated for the moderate/high temperature heat pump in theoretical and experimental investigations.In the existed methods of theoretical calculations of heat pump cycle performances, in general, the condensing/evaporating temperature of the zeotropic mixtures is designated to be the arithmetical mean value of the phase change tempreature. But the arithmetical and actual mean temperatures are different beacause of the non-linear enthalpy-temperature relationship, bringing an unfair factor to comparison and evaluation. In this thesis, the factors which lead to the difference between above two mean temperatures and influences on cycle performances caused by the difference were analyzed. And the actual mean temperature was adopted to improve existed methods, making improved results more practical.Theoretical cycle performances of many HFCs(Hydrofluorocarbons) and HCFCs (Hydrochlorofluorocarbons) have been assessed. Some good pure ones and seven zeotropic mixtures(M1-M7) have been recommended to different temperature ranges. According to glide matching analysis, M2-M5 are prone to have the perfect glide matching.Some experimental investigations on pure components were firstly carried out in the condensing temperature range of 60 to 90°C, with fixed temperature lift of 45°C. Then zeotropic mixtures M3 and M4 which have excellent theoretical cycle performances were investigated experimentally, also the R245fa as a comparison, at the condensing temperature of 90 and 95°C, with various temperature lifts. It is shown that, compared with R245fa, M3 and M4 offered higher heating capacity and COP except for 10°C higher discharge temperature. And M3 has a more excellent environmental and cycle performance than M4.