LAUSR

Abstract This paper presents a model that takes moisture migration (in unsaturated soil), the presence of groundwater seepage (in saturated soil), and soil stratification into consideration simultaneously. The thermal behavior of a ground heat exchanger field located in stratified soils across unsaturated and saturated layers is also investigated, experimentally and numerically. Simulated temperature data at three monitoring points based on a 3-dimensional finite volume numerical model were compared with the experimental data. The agreement between the simulated data and experimental data proves that the numerical model considering soil stratification and ground seepage has good accuracy. Based on the proposed model, the influencing factors of soil thermal conductivity, soil porosity, seepage velocity, daily operation time, inlet water temperature, and velocity on the heat transfer rate of a 3 × 3 bore field were investigated. In general, the heat transfer rate of the bore field located in the stratified subsurface increases as the soil thermal conductivity, seepage velocity, inlet fluid temperature, and velocity increase. Conversely, it decreases as soil porosity and daily operation time increase. This study achieves elaborate ground heat exchanger design and simulation, and consequently help promote a regulatory framework for design method formulation with soil stratification and groundwater flow.