natural refrigerant, novel cycle, refrigerator, heat pump, performance
Natural refrigerants are eco-friendly substitutes for HCFCs and HFCs in vapor compression cycles, such as refrigeration or heat pump cycles. In this paper, three appliance systems are analyzed based on refrigerants characteristics for performance improvement, and novel and practical cycles are proposed and briefly analyzed. Dual-evaporator (DE) cycle for refrigerator can reduce the irreversible thermodynamic loss in one-stage cycle. Rotary compressors which have advantages in efficiency and dynamic balance capability are highly suitable to DE cycles. The improvement of theoretical refrigeration coefficient for DE cycle is up to 24.4% comparing with conventional one-stage cycle under refrigerator condition. Vapor injection heat pump (VIHP) cycle can efficiently improve the cycle performance especially under low ambient temperature. In the VIHP using R290 as refrigerant, the discharge temperature of compressor is usually not high enough for proper solubility of refrigerant in lubricant oil. Two techniques are applied to raise the discharge temperature, which brings higher performance and lubricating property to the compressor, and also brings the promotion to the cycle. The maximum improvements of theoretical heating coefficient and volumetric heating capacity are up to 17.8% and 40.7% respectively when evaporation temperature is -30℃. Heat pump cycle is suitable for electric vehicles because of its high coefficient of performance (COP) and heating capacity. In the heat pump cycle using CO2, combining with the fresh air heating progress in vehicle and wet compression, a particular cycle is proposed with much higher cycle performances. The COP and volumetric heating capacity can be at least 39.5% higher than that of conventional heat pump cycle when evaporation temperature is -30℃. And wet compression makes further improvements.