Experimental analysis of unsteady heat and moisture transfer around a heated cylinder buried into a porous medium

An experimental analysis of heat and moisture transfer around a heated cylinder surrounded by an unsaturated soil is performed. The main motivation for the work is its application for high-voltage electrical power distribution in urban areas which, in general, makes use of underground cables. In the presence of electrical current, those cables generate heat that has to be dissipated through the surrounding soil in order to keep the cable temperature at safety levels; the cable operating temperature depends upon the soil ability to dissipate this heat. This is a complex phenomenon that involves several mechanisms of heat and moisture transfer. Experiments were performed for both constant and cyclic heating ranging from 8 to 80 W m(-1). Spatial as well as temporal temperature, heat flux and moisture content results are reported. Computations using a two-dimensional continuum model were also performed and a good agreement prevailed between numerical and experimental results. It was found that well-graded soils such as the one used in the present work have a great capacity for retaining moisture which is an important feature if high thermal conductivities around the heat source are desired. (C) 1999 Elsevier Science Ltd. All rights reserved.