Randomly fractal approach to calculate the thermal conductivity of moist soil

Abstract

Ground coupled heat pump (GCHP) is an energy saving technology that uses the shallow geothermal energy for the building heating and refrigeration systems. An optimized design of ground heat exchangers (GHEs) is the key to minimize the installation fee of GCHP systems. The effective thermal conductivity of soil is an important input parameter in the design of GHEs. This paper proposed a randomly fractal approach to predict the effective thermal conductivity of soil-like materials (quartz sand). The fractal Monte-Carlo method combined with the Quartet Structure Generation Set (QSGS) method was used to reconstruct the random structure of the soil-like materials. Lattice Boltzmann method (LBM) was further applied to the complicated porous structure and compute the effective thermal conductivity. The simulation results were compared to the findings from experiments and other similar models. The impacts of porosity, fractal dimension, size ratio and accumulation structure on the effective thermal conductivity were also analyzed in detail.