Under the given conditions, the system performances of R744/R600 and R744/R600a to substitute for conventional refrigerant R22 in a subcritical heating cycle were theoretically analyzed respectively with consideration of heat transfer pinch point in heat exchangers. Results show that R744/R600 and R744/R600a have different optimum mass fraction of which the system works with the maximum heating coefficient of performance (COPh). Compared to R22 system, the optimum COPh of R744/R600 and R744/R600a are increased by 11.98% and 8.24%; and increased by 36.43%, 36.24% compared to pure R600 and R600a; increased by 7.07%, 4.71% compared to pure R744 system in a transcritical cycle respectively. With the optimum mass fraction, condensation pressures of R744/R600 and R744/R600 are 0.84MPa and 1.18MPa lower than that of R22. Discharge temperatures are below 90V which are also lower than that of R22.%基于换热器中的传热窄点温差的限制,对R744/R600及R744/R600a在所研究的工况范围内分别替代传统制冷剂R22的亚临界热泵循环特性分别进行了计算分析.结果表明:R744/R600和R744/R600a具有不同的最优配比,可以使得制热性能系数(COPh)最大；R744/R600及R744/R600a在最优配比下的COPh分别比R22系统增大11.98％和8.24％,分别比纯质R600和R600a大36.43％和36.24％,比跨临界循环R744系统增加7.07％和4.71％.在最优配比下,R744/R600和R744/R600a的冷凝压力低于R22,分别为0.84MPa和1.18MPa;压缩机排气温度也低于R22,在90℃以下.
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