Analysis of Heat Pump Cycle Using CO2/DME Mixture Refrigerant

In this study, the performance analysis of heat pump cycle using carbon dioxide (CO2) and dimethyl ether (DME) zeotropic mixture has been carried out by cycle calculation in order to clarify the characteristics and coefficient of performance (COP) of CO2/DME heat pump cycle. The calculation conditions were established as a hot-water supply system and the calculations were conducted by considering the heat transfer between the refrigerant and heat source/sink water. The heat pump cycle is formed around the critical point for high CO2 concentration mixtures and it is formed under the critical point for low CO2 concentration mixtures. The COP has the maximum at a certain pressure for each mixture and the COPs of the mixture and pure DME are higher than that of pure CO2. Operating pressure and refrigerant mass flow rate decreases with increase of DME concentration. The effects of concentration on characteristics of the cycle have also been discussed.