熱泳效應對混合對流下拉伸孔隙壁質量傳遞之影響

Effects of Thermophoresis on Mass Transfer in a Linearly Stretching Permeable Surface with Mixed Convection

魏家鴻(Chia-Hung Wei)

指導教授 ： 蔡瑞益

中原大學/工學院/機械工程學系/碩士(2007年)

https://doi.org/10.6840/cycu200700708

摘要

本文探討當受到熱泳效應影響時，混合對流中拉伸孔隙壁的熱質傳遞現象。流體以二維混合對流邊界層流，流經一向上拉伸並包含吸附或吹離效應之垂直壁。統御方程式包括連續方程式、動量方程式、能量方程式及濃度場方程式，將統御方程式經過無因次化相似轉換過程後，數值計算方面以Runge-Kutta積分法求解。本文將針對溫度差的存在造成熱泳效應產生的影響做一詳細分析。
當混合對流參數 增加，流場速度梯度增加，而溫度場以及濃度場的邊界層相對減小，吸附作用的產生也將使得邊界層減小。壁温小於外在溫度時，微粒因熱泳效應影響，壁面濃度增加。而當壁温大於外在溫度時，粒徑越大者將隨溫度梯度增大而被吹離平板，熱泳現象所產生的效應越大，濃度邊界層厚度會變的越厚。再加上吹離效應，因此而產生無塵層。而當溫差越大，無塵層厚度也隨之增加。¬而當微粒粒徑小時，相對於熱泳效應微粒受擴散影響較大。但當微粒粒徑增大時，擴散效應減少，熱泳效應則增大。

關鍵字

混合對流 ； 熱泳效應 ； 質量傳遞 ； 拉伸孔隙壁

並列摘要

A theoretical study of the effect of thermophoresis on heat and mass transfer by mixed convection from a linearly stretching permeable surface is reported. Considering the two-dimensional mixed convection boundary layer flow over a vertically moving upward surface with suction or blowing at the surface. The governing equations include the continuity, momentum, energy and concentration equations. The solution methods are used similar transformation and dimensionless technique for the governing equations. In numerical analysis, the equations are solved by the Runge-Kutta integration method.
When the mixed convection parameter increases, the velocity gradient increases. Thermal and concentration boundary layer thickness decrease as increase. Boundary layer thickness also decrease with suction effect. The effects of thermophoresis were predicted to be particularity important for particle moving toward a cold surface or blowing away a hot surface at a given temperature gradient.

並列關鍵字

stretching ； mass transfer ； mixed convection ； thermophoresis

參考文獻

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