The influence of natural convection on thermal performance of ground heat exchangers

摘要

Ground-source heat pump (GSHP) systems efficiently heat and cool buildings using sustainablerngeothermal energy accessed via ground heat exchangers (GHEs). Thermal performance of GSHP systems isrntypically investigated considering either pure conduction in the ground or also accounting for hydro-geologicalrnconditions (i.e., groundwater flow). However, in saturated soils, the temperature gradient in the ground inducedrnby the GSHP systems operation may result in natural movement of groundwater due to the changes in waterrndensity, which leads to an emerging natural convective heat transfer in the ground, potentially influencingrnthermal performance of GHEs. To capture and quantify this effect, a GHE-field installed in a fully saturatedrnsoil is modelled using a state-of-the-art 3D FE model. In these simulations, groundwater flow in the groundrnand the convective-conductive heat transfer and fluid flow in the fluid circulating in the pipes are coupled to thernconvective-conductive heat transfer in the ground and the GHEs.