TRANSIENT NATURAL CONVECTION OF WATER NEAR ITS DENSITY EXTREMUM IN A RECTANGULAR CAVITY FILLED WITH POROUS MEDIUM

摘要

A numerical study is performed to analyze the transient flow field and heal transfer behavior of cold water in a rectangular enclosure filled with a porous medium. The numerical method was employed by the SIMPLE-C algorithm, The accurate nonlinear relation between density and temperature developed by Gebhart and Mollendorf was used. The numerical results show that, for R < 0.5, the size of the clockwise vortex beside the high-temperature surface increases as time increases. The clockwise vortex occupies almost the whole space when the steady state is reached. For R = 0.5 the size of the clockwise vortex adjacent to the high-temperature surface increases as time increases. However, two counterrotation vortices having the same strength and size exist in the space when steady state is reached. For R > 1, only one counterclockwise vortex exists in the space the entire lime. For tau > 10(-3), the heat transfer rate increases with increase in Darcy number for the entire time. However, as time increases, the heat transfer rate on the high-temperature surface decreases and that on the low-temperature surface increases. [References: 19]