Analysis on performance of borehole heat exchanger in a layered subsurface

In the current design of borehole heat exchangers (BHEs), the ground is commonly considered to be homogenous. However, in a layered subsurface, thermal performance of BHE can deviate drastically with different strata. Thereby, analysis of the heat transfer of a BHE with different geological layers is important for optimal sizing of BHE. s paper, we examine thermal performance of BHEs settled in a ground with five bedded sedimentary layers. Thermal and hydraulic properties of the borehole field are firstly investigated. Based on the experimental data, a numerical model is developed to examine thermal exchange of the BHEs in this layered subsurface. Two modeling approaches, where the ground properties considered to be homogenous or stratified, are implemented. Numerical results from both approaches are validated and they give similar thermal output of the BHEs. The model with a stratified subsurface further indicates that there is only 74.1% amount of heat transferred in the basal layer with negligible groundwater flow as compared to that of aquifer layers.