飽和多孔性介質內暫態自然對流熱傳遞分析

• Main Author: 洪漢青
• Other Authors: 陳朝光
• Format: Others
• Language: zh-TW
• Published: 1986
• Online Access: http://ndltd.ncl.edu.tw/handle/65534668473283689501

碩士 === 國立成功大學 === 機械工程研究所 === 74 === The purpose of this work is to investigate the non-Darcian effects on the transient natural convection about two kinds of bodies, the vertical plate and the horizontal cylinder, which are embedded in a high-porosity medium and abruptly subjected to two kinds of heating condition, constant wall temperature and constant wall heat flux separately. By taking into account of the boundary effect, inertia effect and convective effect, the non-dimension-alization of the governing coupled boundary layer equation results in the following parameter: Pr, the Prandtl number; K, the non-dimensional permeability and □, the non-dimensional inertia number. When using the cubic spline integration method to solve the equations, the results for a fixed Pr＝5.4 (corre-sponding to water) show that: (1) For short time, heat transfer is by one-dimensional conduction only, following this initial period, the body force generates motion in the fluid and the convective heat transfer becomes important gradually, but being the presence of porous media, convection is not so obvious as when no porous medium exists. The smaller the permeability, the harder to reach steady state. (2) The boundary and convective effects have a significant influence on the velocity profile and reduce the surface heat transfer. When the inertia effect is considered, the heat transfer is further reduced. For porous media with high porosity, all the effects considered in this study should be included in the analysis.