STUDY ON FROSTING CHARACTERISTICS OF AN EVAPORATOR USING R407C AS REFRIGERANT

摘要

The frosting characteristics of the evaporator are critical to the running of an air source heat pump. As the phase-out of HCFCs is in process, some non-azeotropic refrigerant mixtures are introduced into use. Compared with pure refrigerants, these mixtures have temperature glides that make the temperature distribution of the refrigerant uneven along the heat exchanger. In this paper, the distributed parameter model of a finned evaporator is established to simulate the frosting process. R407C is selected as the refrigerant. Quasi-steady heat transfer and refrigerant flow are assumed. Numerical algorithm is discussed and the simulation is carried out with a sample evaporator. It is found that the change in the flow rate of the air is the most influencing factor. There is a turning point from which the evaporating temperature goes down quickly. The temperature glide of R407C during evaporation also has an obvious impact on the frosting process.