B212 HEAT TRANSFER CHARACTERISTIC OF COMPACT EVAPORATIVE HEAT EXCAHNGER

概要

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A new heat exchanger with latent heat transport for small and medium scale air conditioning system and industrial refrigerator was developed. This system consists of heated tube where coolant flows inside, wetted porous media layer and membrane which penetrates only vapor. Outside the membrane, forced convective air flow is applied. Most of heat from heated tube is transported by latent heat due to evaporation of water in wetted porous media and vapor penetrates membrane and is removed by air flow. In this way, very efficient heat transfer is realized. Moreover, in this system, water is kept by the thin layer of porous media and the membrane. Therefore, the quantity of water in this system is very small and no water circulation system needed. Then, very compact evaporative cooling system with latent heat transport becomes possible. Heat transfer coefficient of evaporative cooling system was measure at various flow conditions. The results showed that heat transfer coefficient augmented at least twice of that without evaporative cooling. The surface temperature of heated surface was maintained within the operational condition of practical heat exchanger. However, at some conditions, dryout phenomenon was observed due to the insufficient water flow in porous media.
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