着霜時 蒸發器 熱傳達 特性에 관한 基礎 硏究

Abstract

Frost deposition is an important phenomenon in the cryogenic industries in connection with gas cooler, refrigerator, air-condition, etc. When humid air is exposed to a cold surface, whose temperature is below 0℃, frost deposition occurs and continues to accumulate on the surface. Frost deposition is an important phenomenon. In general, this kind of problem should be treated as a moving boundary problem to predict heat and mass flux from a gas stream to deposit surface, but cannot be solved simply because of lack of information about frost thermal properties. In spite of many researches, the frost properties have not been clarified in detail up to now. In the case of heat exchangers operating under frosting condition, the growth of a frost layer causes to increase the thermal resistance and pressure loss of the air flow. In this experiment, study on fundamental analysis of evaporator heat transfer characteristics during frost depositions was performed. The results obtained were as follows: 1. On velocity, a growth height of frost was different but structure of frost was similar. 2. At velocity 0.1, 0.5, 1.0 m/s, the initial superficial heat transfer coefficient of evaporator diminished about 90% than final it by being full of frost at evaporator front. 3. Frost deposition was accomplished much at evaporator front but frosting wasn’t almost at its rear.