通道內置散熱片之混合對流熱傳分析

ANALYSIS OF MIXED CONVECTION HEAT TRANSFER IN A CHANNEL WITH FINS

本論文主要探討在具有散熱片之兩平行板通道內，針對在相同截面積但不同散熱片的高寬比熱傳變化情形。以有限差分數值方法求解，在給定不同Re, Gr等參數下進行數值計算，以獲得不同之速度場與溫度場分布圖。理論分析係假設散熱片形狀為矩形結構，在二維平板間流體為穩態層流，探討混合對流熱傳問題。首先，導入無因次參數，將統御方程式與邊界條件給予無因次化，進而分析不同高寬比之散熱片在流場中對速度與溫度場影響。由研究結果知，具散熱片之通道內，在相同截面積但不同高寬比時，可求得速度及溫度之分佈；當Gr／Re2＝1時，可以得知Re愈大，得到的Nu愈大；另外，固定雷諾數時，2 Gr／Re參數由0.1變為1時，此參數大，所求得之Nu愈大；而當2 Gr／Re為0.1和1時，傾斜角對於Nu值影響不大；最後，由不同型式散熱片之Nu比較後，可得到Type-1型式散熱片有最佳的熱傳效果。

This study mainly investigates the channel flow with transverse inline fins which has different height-width ratios but of same cross-sectional area. Numerical technique of finite difference method is employed to solve the mixed convection problem. A two-dimensional steady laminar flow is assumed in the channel with rectangular fins. Introducing the dimensionless parameters, the governing equations as well as boundary conditions are first non-dimensionalized. Then, giving various parameters of Re and Gr, the discrete equations are solved simultaneously to obtain the velocity and temperature distributions in the channel. The results reveal that Nusselt numbers increase with Reynolds number in the channel with rectangular fins when . In addition, while Gr / Re2 increases from 0.1 to 1, Nusselt number gets higher for a larger Gr / Re2 at a fixed Reynolds number. Differing from Gr / Re2 = 10. The effects of inclination on Nu is insignificant for Gr / Re2 = 0.1 and 1. Finally, after comparing different height-width ratios of the fins, the Type-1 is shown superior in heat transfer performance to all other types.