Physical model for heat transfer in porous media.

摘要

A new geometric model is used to model the flow and heat transfer in a porous medium. The model is based on the physical phenomena that occurs in a porous medium. The solutions to the governing equations of the model show that this type of simple physical model is successful in predicting the flow characteristics of porous media at a large range of Reynolds numbers and heat transfer characteristics of porous media at lower Reynolds numbers.; A momentum equation retains the full viscous terms and is solved analytically by linearizing the inertial term. The solution to the momentum equation results in a developing velocity profile that is valid over a large Re number range, from Re {dollar}to{dollar} 0 to Re {dollar}to{dollar} {dollar}infty{dollar}, and represents the flow development in a circular tube. Analytically calculated friction coefficient for a porous bed displays good agreement with experimental results.; Experiments have been performed to study the flow characteristics in porous media and the values of parameter d/{dollar}ell{dollar} for selected porous metals are determined by these experimental results.; The energy equations for both the fluid phase and solid phase of the modeling tube are solved numerically. The numerical scheme used is a finite difference SOR iteration procedure. The predicting internal heat transfer coefficients are in good agreement with experimental results for both the Darcy and the inertial flow regimes.; Also presented in this thesis are solutions to the laminar combined hydrodynamic and thermal entry region problem for the case of a circular tube with the boundary conditions of both the constant wall temperature and constant wall heat flux. The numerical results show that the fluid axial conduction has significant effect on heat transfer. Specifically the inclusion of axial conduction results in a much longer thermal development length.