Numerical study and sensitivity analysis on convective heat transfer enhancement in a heat pipe partially filled with porous material using LTE and LTNE methods

Abstract

An improved design for convective heat transfer in a heat pipe partially filled with porous medium is presented. In the present study, porous media is used to increase heat transfer in laminar flow inside the tube with a constant heat flux boundary condition. The porous segments are set in different positions in the tube, while the ratio of porous volume to total volume of tube is considered to be constant. A performance evaluation criteria (PEC), which takes account of both heat transfer and pumping power, is defined to find the enhanced mode of porous media arrangement. According to the current results, PEC increases with the number of porous segments. Moreover, the sequence of unequal segments arrangement within the tube is from the largest to the smallest part for a higher PEC. Effects of parameters including porosity, Darcy number, and ratio of effective coefficient of thermal conductivity to coefficient of thermal conductivity of fluid (TKR) are investigated for sensitivity analysis. Simulations are conducted using the local thermal equilibrium method. In addition, the local thermal nonequilibrium is also used for comparison. For TKR numbers less than 10, these models show the same results with negligible differences except for TKR more than 10. K E Y W O R D Sheat pipe, heat transfer enhancement, local thermal nonequilibrium and equilibrium model, microchannels, performance evaluation criteria, porous media