带回热器的R404a/CO_2复叠式制冷系统的理论分析

Theoretical analysis of R404a /CO_2 cascad refrigeration system with heat regenerator

建立低温环境下带回热器的R404a/CO_2复叠式制冷系统的模型,为提高系统COP,对其进行热力学分析。应用控制变量法,通过理论计算对比分析系统的蒸发温度、低温循环冷凝温度、过冷度以及冷凝蒸发器传热温差等因素对该系统COP的影响。结果显示,在其他参数一定时,过冷度的增加对于提高系统COP具有显著作用;存在低温循环冷凝温度的最优值,使得系统COP最大;过冷度不变时,系统COP随着蒸发温度、冷凝蒸发器传热温差的增大而增大,随冷凝温度的增大而减小。

This paper establishes a model of R404a/CO2 cascade refrigeration system with heat regen- erator under the low - temperature environment. In order to improve coefficient of performance, a thermodynamic analysis are carried out. Through theoretical calculation, the influences of evaporation temperature, condensation temperature of low temperature cycle, the degree of supercooling as well as the temperature difference in the condenser evaporator on COP are contrasted and analyzed by control variable. The result showed that the degree of supercooling has obvious effect in improving COP when the other parameters are constant ; there exists a optimal value of condensation temperature of low temperature cycle makes COP to be maximum; COP increases with the increase of evaporation temperature and the temperature difference in the condenser evaporator while decreases with the increase of condensation temperature when the degree of supercooling is constant.