Using transcritical CO2 air source heat pump for space heating is a clean and environmentally friendly solution. Based on the concept of the Lorenz cycle and CO2 heat pump system with traditional dedicated mechanical subcooling (DMS), CO2 system with DMS employing zeotropic mixture as working fluid for subcooling is proposed. Its life cycle economic performance is assessed. The results indicate that the energy performance of zeotropic working fluid with high-temperature glide is higher than that of the pure working fluid. The capital cost and fuel cost are obviously reduced by using high-temperature glide zeotropic mixtures for subcooling. The levelized total annual cost is saved by 5.70, and 19.12% compared with that using pure refrigerant, and baseline CO2 system. The mixture with high-temperature glide is recommended.
Keywords transcritical CO2 heat pump, dedicated mechanical subcooling, zeotropic mixture, space heating, life cycle economic performance, energetic performance