Experimental research and numerical simulation of the periodic frost melting process

In order to study the frosting characteristics of the circular pipe below -60?, a test rig for frosting visualization on a double-pipe heat exchanger has been built based on a cascade refrigeration system. In a series of experimental studies, the periodic melting phenomenon was observed during the frost development and maturity period, in which the thickness of the frost layer increases and decreases in a periodic way. The periodic frosting process in experiments is systematically summarized. For further investigation on the frosting characteristics, a frost melting criterion is added to the transient mathematical model of unsteady frosting on the circular pipe. The simulated results have the same trend as the experimental results, which show, that the model can accurately predict the melting process. The results show that the higher the humid air temperature or wall temperature is, the earlier the melting node appears. When the first melting phenomenon occurs, the interval of the periodic melting phenomenon becomes longer.