Analyzing transient heat and moisture transport surrounding a heat source in unsaturated porous media using the Green's function

Abstract

Generally, in most areas, groundwater level is deep and heat sources (e.g., energy piles) are embedded in unsaturated soil media. Therefore, in order to accurately analyze the soil response close to heat sources, both heat and moisture transport in unsaturated soil domain should be considered. Thermal loading changes the moisture content in the porous media. In this study, the energy conservation and mass fluid continuity equations derived from hydrothermal analysis of a partially saturated soil medium are considered in cylindrical coordinate system. To make the analytical solution possible, partial differential equations (PDEs) are turned into ordinary differential equations (ODEs), through linearization of the governing equations, and separation of variables. An analytical solution for the non-homogeneous system surrounding a heat source in unsaturated porous media is developed using Green's function. Energy piles are considered to be the heat source in this study. Results show the moisture transport in the soil medium depends on the duration of the thermal loading and relaxation time. Analytical results determine different influence zones for temperature and moisture content variations surrounding a heat source.