振動渠道之熱傳分析

Abstract

本研究利用數值方法與實驗量測，研究ㄇ字型管道高溫面在強制對流與混合對流下的熱傳效率，並利用管道的振動來幫助增強高溫面的平均紐塞數。受到管道的振動影響，本研究可以歸屬於移動邊界問題，因此特別採用了適於分析移動邊界的ALE座標描述以及有限元素法來做數值模擬的分析；而對於實驗方面，則是設計了一振動系統，使ㄇ字型管道可以往復運動，並量測流體從高溫面帶走的熱量，以了解高溫面的熱傳效率。而研究結果顯示，增加入口流體的雷諾數是增強熱傳效率最有效方法；且管道開始振動後，在強制對流情況下，振動可以幫助熱傳效率，但在混合對流的情況下，則必須視管道的擺設位置而定，在管道擺成ㄩ字型的情況下，振動對於增強熱傳效率的幫助有限。

Heat transfer rates of a high temperature surface in a ㄇ shape channel under forced and mixed convection situation are studied numerically and experimentally. In order to simulate behaviors of a piston, a ㄇ shape channel possessing reciprocating motions is designed for experimental study. Due to the reciprocating motion of the channel, the problem becomes a moving boundary problem and arbitrary Lagrangian-Eulerian Kinematics method is used for numerical study. Parameters of Reynolds number and frequency are used, and different relationships between the directions of the inlet fluid flow and gravity are considered. The results show that in the most of the situations the effect of reciprocating motion on the enhancement of the heat transfer rate of the channel is remarkable. However, as the heat surface is installed on the bottom surface of the channel, the heat transfer rate of channel can not guarantee to be improved by the reciprocating motion of channel.