Seasonal changes in thermal process based on thermal response test of borehole heat exchanger

•Seasonal changes in apparent thermal conductivity of BHEs were investigated.•Thermal response test was conducted for the same BHE in January, May, and October.•Rate of increase of apparent thermal conductivity was determined via simulations.•The effect of a partial aquifer on the apparent thermal conductivity was examined.•The study guides the thermal conductivity estimation considering seasonal changes.