Simulation of Convective Heat-Transfer Coefficient in a Buried Exchanger

Maher Raddaoui,Rached Ben Younes,Salem Elouragini,Taoufik Mnasri

doi:10.3844/ajassp.2008.927.933

Abstract

This study presents analytical models allowing to study a forced convection laminar flow in non-established dynamic and thermic regimes. We treated a flow in a bitubular exchanger in permanent thermal contact with a semi-infinite medium, such as the ground. The wall temperature as well as the wall heat flux evolve in the course of time until a quasi-steady mode. The theoretical method is original because it uses Green's functions method to determine the analytical solutions of the heat propagation equation on the wall during the heating phase. These analytical solutions allow to identify the temperature distribution versus time. The complexity of the system geometry as well as the infinity of the medium surrounding the exchanger make the traditional methods of numerical resolution unable to solve the problem. We used, to solve it, the finite volume method coupled with the finite element method at the boundary. We studied the effect of Reynolds number, the fluid entry temperature and the transfer duration on the axial evolution of the heat transfer coefficient. We illustrated also the profile of the temperature field in the fluid medium.

Highlights

The problem of the thermal flow, once the conduct wall is subjected to an imposed temperature or heat flux, interested much the researchers
In order to compare with the results presented in the literature, we impose on the entry annular space uniform velocity and temperature fields
A precise sight of the results enables us to note that: The profile of the temperature, uniform at the section of entry, deforms progressively and tends asymptotically towards a profile corresponding to the established thermal regime

Summary

Introduction

The problem of the thermal flow, once the conduct wall is subjected to an imposed temperature or heat flux, interested much the researchers. This present work relates primarily to determinate the heat transfer coefficient of an exchanger in permanent contact with a semi-infinite medium such as the ground.

Results

Conclusion