Effect of Thermophoresis on Mass Transfer from a Mixed Convection Flow along a Vertical Permeable Surface with a Variable Surface Heat Flux

熱泳效應在混合對流流經變熱通量垂直孔隙壁中質量傳遞之影響

蔡瑞益(Ruey-Yih Tsai) ； 黃建勝(Jian-Sheng Huang) ； 黃俊豪(Kuei-Hsun Huang) ； 黃桂勳(Chun-Hao Huang)

《中國機械工程學刊》 30卷4期 (2009/08) Pp. 279-288

https://doi.org/10.29979/JCSME.200908.0002

摘要

本文以理論模式探討混合對流流經一垂直的孔隙壁面時，熱泳效應對質量傳遞之影響。流場的建立是二維不可壓縮、穩態層流，其流體之流動包括強制和自然之混合對流。當對流流體流經一非達西多孔性介質時，考慮壁面條件為存在著吸附或吹離效應和可變熱通量，q(下標 w)(x)=Ax(上標 n)。其傳輸機制耦合慣性、混合對流、非達西、吸附或吹離及熱泳效應。研究方法是以相似分析法配合阮奇庫塔法及射擊法來求解速度、溫度與濃度場。此外，我們以有限差分法與阮奇庫塔法所求得之解做數值驗證。研究結果顯示在熱壁條件下，熱泳、吸附或吹離值、質量擴散係數及浮力將對質量傳遞率有顯著的影響，特別是在不同的史密數時，由溫度梯度所形成的熱泳效應將降低傳向熱壁之質量。

並列摘要

A theoretical study of thermophoretic effect on mass transfer from a mixed convection flow along a vertical permeable surface is proposed. The flow was modeled as a two-dimensional, incompressible and steady-state laminar flow driven by a combination of forced convection and natural convection. The mixed convection flow is considered through a porous medium over a vertically permeable surface with suction/injection and a variable heat flux, q(subscript w)(x)=Ax(superscript n) embedded in a non-Darcian porous medium. The transport mechanisms were coupled using inertia, mixed and non-Darcian convections, suction/injection flow and thermophoresis. Similarity analysis and Runge-Kutta integration with shooting scheme were used to determine the velocity, temperature and concentration fields. In addition, a finite-difference scheme solution was obtained to do a comparison with the results from the Runge-Kutta integration. The results showed that the effects of thermophoresis, suction/injection, mass diffusivity and buoyancy force on the mass transfer rates are strong, particularly for different Schmidt number at hot wall surface conditions. The thermophoretic effect is from the temperature gradient that decreases the mass transfer to the hot wall surface.

並列關鍵字

Thermophoresis ； Suction/injection ； Mixed convection ； Non-Darcian porous medium