Numerical study of gas injected heat pump using zeotropic R32/R1234ze(E) mixture: Comparison of two type economizers

Rare pure refrigerants can meet the environmental, thermodynamic, and safety requirements to new-generation refrigerants completely. R32/R1234ze(E) zeotropic mixture is a potential replacement in the field of air conditioning and heat pumps. At the same time, gas injection technology is considered as a good solution to increase the seasonal energy performance of heat pump system. Accordingly, a comprehensive model of gas-injected water-water heat pump with R32/R1234ze(E) is built in this paper. Based on it, the performance of the gas injected heat pump with flash tank economizer and intermediate heat exchanger economizer are researched. Finally, the effect of type of the economizer type on the performance is identified. Three potential key parameters affecting the performance of the gas injection system, including molar fraction of refrigerant, inlet temperature of heat transfer fluid in evaporator, mass flowrate of heat transfer fluid in evaporator, are investigated. As a result, both flash tank gas injection and intermediate heat exchanger injection can largely enhance the heating capacity and COP of water-water heat pump using R32/R1234ze(E) mixture. Intermediate heat exchanger injection promotes the heat pump with zeotropic mixture more effectively than flash tank injection.