Experimental study on the validation of thermal equilibrium assumption between solid and liquid phases in convective heat flow in porous media

Abstract:

The thermal equilibrium between the solid and the liquid phases is generally assumed for numerical simulations in heat transport through soils. However, the validation of this assumption is not well investigated, especially in heat transport through coarse materials under high pore water velocity. It is important to understand heat transport mechanism in such a condition when the ground-source heat pump systems that exploit the soil as thermal source or sink are applied to permeable sand and gravel aquifers. Therefore, to investigate heat transfer between the solid and liquid phases, we conducted one-dimensional heat transport experiments using different size fractions of glass beads. In the experiments, hot water was injected to the 50-cm column packed with glass beads under different water fluxes. The temperatures of the solid and liquid phases were independently measured. In addition to glass beads, materials with different thermal properties (e.g. stainless balls) were tested. The convection-dispersion equations with the assumption of the thermal equilibrium and non-equilibrium between solid and liquid phases were applied to the measured breakthrough curves.