管道熱傳增益之動態分析研究

Abstract

隨著工程上發展的需要，高溫壁面熱傳效應對機械的影響越益受到重視，而元件其性能及可靠度的提升將取決於其散熱技術，為了要達到最佳的熱傳增益，瞭解並分析高溫壁面其對流熱傳的問題，勢必為必要的研究課題。因此本計畫首先研究關於一具有高溫壁面的三維管道可壓縮流，在其高溫壁面上加裝一移動薄板，探討薄板往復運動於強制對流及混合對流下的現象，造成高溫壁面上溫度與速度邊界層不斷的被移除與重新生成，因此可大幅的提升熱傳效率。此外，並研究關於三維垂直管道自然對流的問題，探討在高雷利數時從層流轉變成不穩定之現象，以及對於高溫壁面熱傳效率的影響，之後藉此基礎分析研究三維管道純自然對流誘導衍生成紊流之問題，以期能提升熱傳效率，提高對實際工業應用之範圍。

With the improvement of the technology, the effect of heat transfer of a heat surface is getting more seriously concern in industry. The promotion of reliability and performance is dependent on the technology of heat transfer enhancement. So the problem of heat transfer of a heat surface in a convection flow is a very important issue. First, this study investigates the problem of three-dimensional compressible convection flow with insertion of a moving block numerically. The phenomena of interaction between the moving block and channel flow are observed. The enhancement of heat transfer is remarkable due to destroying the boundary layers by the moving block. Besides, the varied processes of natural convection in three-dimensional vertical channels of single heated wall with different aspect ratios and Rayleigh numbers from stable to unstable situation are investigated numerically. The phenomena from laminar to unstable transition and the relationship between Rayleigh number and heat transfer rate are observed. The results are expected to be useful for the future study about turbulence flow induced by pure natural convection. Therefore, this study is a foundation potentially for the heat transfer enhancement of practical industry.