Numerical simulation of slip flow heat transfer in a microtube

Abstract

The constant- wall temperature convective heat transfer characteristics of a model fluid flow in two-dimensional micro tube under hydro- dynamically fully developed conditions was investigated. In which it covers the slip flow regime 0.01 ¡Ü Kn ¡Ü 0.1, where Kn , the Knudsen number is defined as the ratio of molecular free mean path and the hydraulic diameter of the micro tube . So in case of slip flow regime solving the fluid flow and heat transfer governing equation can no longer be sufficient for simulating the flow. We will require incorporating slip velocity and temperature jump boundary conditions. Slip velocity and temperature boundary conditions were derived by Maxwell and Smoluchowski respectively. Investigation has been done in a commercial CFD package ¡°FLUENT ¡° velocity slip and temperature jump boundary condition is taken into account through program called udf (User Defined Function). The validity of UDF is done by forward backward approach in which outcome of the UDF is considered as the input for the FLUENT inbuilt shear stress slip model. The error calculated in slip velocity by forward-backward approach is 1.485 %. The main interest is to investigate the effect of Knudsen number on various flow variable. Also the heat transfer rate , skin friction coefficient ,axial wall shear stress , slip velocity , Nusselt number , heat transfer coefficient and wall fluxes with varying Knudsen Number and Reynold Number is also studied.