Working Fluids And System Optimization Of Moderate/High Temperature Heat Pump

One important aspect of the researches on the moderate/high temperature heat pump technology is to find out new alternative working fluids with zero Ozone Depletion Potential and low Global Warming Potential. In this paper, some new working fluids were proposed, and the researches of their theoretical and experimental cycle performances were carried out at condensing temperature from 60 to 140 oC. Further more, optimal designing methods of heat pumps have been investigated.In each range of the working temperature theoretical cycle performances of many, some working fluids with zero Ozone Depletion Potential have been assessed, some good ones of them have been recommended to the different temperature parts.Some improvements have been carried out on the existing system before the experiment, for example, flow meters have been changed and checked up, several thermal couples for heat transfer fluid have been added along the heat exchangers, heat preservation has been enhanced, and certain heat transfer fluid used in high temperature conditions has been selected.The experimental cycle performances of R245fa, M3 and M4 were observed at different working temperature levels. The near-fair assessment of cycle performances of the working fluids were carried out based on the improved approach, at each specified working temperature level, R245fa showed the best cycle performances. A 115.3oC delivery temperature was achieved in the heat pump test system, which had broken through the highest delivery temperature level in existing papers.Optimal design has been done for water to water moderate/high temperature heat pump system from the viewpoint of saving energy and material in this paper. An economic parameter F is defined as the objective function to make economic evaluation for the system. The calculations have revealed that the rationality of superheat, subcooling, water flux of the heat exchangers and the distribution of the heat-transfer areas of the heat exchangers will influence the economic performance of heat pumps.