介電液FC-72在次毫米矩形流道內的冷凝熱流分析

Abstract

本論文主要以實驗的方法分析介電液FC-72在水力直徑為1mm及0.67mm的矩形渠道內之冷凝熱傳係數及壓降。熱通量、質通量及蒸汽乾度對於冷凝熱傳係數及壓降的影響有詳細的討論。實驗結果顯示冷凝熱傳係數隨著平均乾度、質通量及熱通量增加而增加，壓降也是隨著平均乾度及質通量增加而增加，但熱通量對於壓降並無明顯的影響。目前通用的Akers及Shah冷凝熱傳關係式對本實驗的實驗結果不能作出準確的預測，都低估本實驗結果，因此修正了Akers的熱傳關係式，以應用在小管徑冷凝器的設計。

This thesis experimentally investigated the characteristics of condensation heat transfer and pressure drop for dielectric fluid FC-72 flowing in horizontal rectangular channels. The rectangular channels have two hydraulic diameters of 1mm and 0.67mm. The effects of the heat flux, mass flux and vapor quality of FC-72 on measured condensation heat transfer and pressure drop were examined in detail. The heat transfer coefficient was shown to be higher at a higher vapor quality, at a higher mass flux and at a higher heat flux. The pressure drop was shown to be higher at a higher vapor quality and a higher mass flux, but the heat flux has no effect on pressure drop. The Akers and Shah correlations did not predict well in this study. For practical design of micro heat exchangers, the empirical correlation was proposed to correlate the present data for the heat transfer coefficient.