COUPLED CONDUCTION-CONVECTION PROBLEM FOR AN UNDERGROUND RECTANGULAR DUCT CONTAINING 3 INSULATED CABLES

The coupled heat conduction-convection problem for three insulating ca bles resting in a rectangular duct filled with air, which is buried un derground, is solved by an operator-splitting pseudo-time-stepping fin ite element method. The method automatically satisfies the continuity of the interfacial temperature and heat flux. The temperature distribu tion in the metal cores, in the insulating layers, and in the surround ing air and soil, together with the convective flow pattern, are obtai ned simultaneously. From the profile of the local Nusselt number, whic h is strongly dependent on the thermal conductivity ratios and weakly dependent on the Rayleigh number, it is concluded that most of the hea t transfer takes place via the bottom of the enclosure through a condu ctive mode.