Investigation of Heat Transfer in Mini Heat Sink with Dispersal Micro Droplets
|關鍵字:||熱傳;迷你流道;薄霧流;Heat transfer;Mini channel;Mist flow|
The mist flow, produced by adding micro droplets in the air stream, can achieve higher forced heat convection than the traditional single phase flow. The heat transfer mechanism was very complicated since the mist flow was influenced by the interaction of air and droplets. Three mini channel heat sinks (width of 0.5mm, 1.0mm, and 3mm) with the same height of 0.5mm were investigated. The corresponding number of flow channels was 14, 11 and 5, and the temperature of the wall was 40℃、50℃、60℃. Reynolds number ranged from 1000 to 6000. The flow phenomenon of the mist flow and the effect on the mini-size channels can be observed using high speed camera. The result showed that the effect of the mist flow is better than that of the air cooling. With the rise of wall temperature, the evaporation rate increased, and produced the dry regions, reducing the heat transfer. Owing to the different sizes of channels, Reynolds number and the temperature of the wall can cause different trends of the heat transfer enhancement. The heat transfer from the mist cooling was 1.5 to 4 times as high as the air cooling. The friction coefficient of the mist flow was higher than that of the air flow and it was about 2 to 3 times higher than air flow. The tiny droplets attached to the wall, causing the increased friction coefficient. However, the droplets on the wall started to evaporate and caused lower friction coefficient as the wall temperature increased.