介電液FC-72在水平微小管道中次冷及飽和流動沸騰熱傳之實驗分析

Abstract

本論文以實驗方法探討介電液FC-72於水平微小管道內，次冷及飽和狀態下之沸騰曲線及熱傳特性，另外對臨界熱通量亦進行探討。實驗的操作條件設定在壓力為一大氣壓的狀態，測試範圍在質通量320、425、530及635㎏/㎡s，次冷度則是3℃、6℃和10℃。結果顯示在核沸騰區內質通量對本實驗的影響不如次冷度的大，尤其較高質通量的影響就會越小；但以次冷度為改變參數下比較，則次冷度較小的情況下會有較佳的熱傳效果。而飽和狀態下的熱傳特性則與次冷態不同，其熱傳係數會隨質通量增加而上升，只有在最小質通量G=320㎏/㎡s時其熱傳係數較G=425㎏/㎡s之值高。至於本實驗之臨界熱通量主要受次冷度影響，而質通量的影響的程度相較之下就小的許多。 本論文針對次冷狀態下之沸騰熱傳發展了一個修正的熱傳關係式，其誤差範圍15％之內，可正確預測本實驗之熱傳係數。

This thesis experimentally investigated the boiling curve, heat transfer characteristics and critical heat flux of dielectric liquid FC-72 in horizontal microchannels. The experiments were carried out for mass flux at 320､425､530 and 635㎏/㎡s, and subcooled temperature at 3℃､6℃and 10℃.The resuls showed that the fluid inlet subcooled temperature has much more effects than mass flux on heat transfer characteristics in the regime of nucleate boiling. The lower subcooled temperature had the better heat transfer performance. On the contrary, in the saturated state, the measured results were far different from those in the subcooled state. The heat transfer coefficients increased with mass flux, except only at low mass flux 320 ㎏/㎡s where higher heat transfer coefficients were found. In this experiment, the critical heat flux was mainly affected by subcooled temperature, not mass flux. A modified correlation of heat transfer coefficients of subcooled flow boiling was developed,which could predict the heat transfer coefficient for this experiment within 15% band of deviation.