The refrigerator is an electric appliance that works intermittently! That is to say, it stops working after cooling for a period of time, and then starts cooling again at regular intervals. In this case, it is not difficult to understand. When it is not cooled, ice cubes will melt into water, water will vaporize into steam (the vaporization process is always there, not when the temperature is low), and ice will sublimate into steam. Reverse refrigeration is the opposite.