An experimental and numerical approach to derive ground thermal conductivity in spiral coil type ground heat exchanger

This paper presents an experimental and numerical study on the evaluation of thermal response test (TRT) results observed in a precast high-strength concrete (PHC) pile and a general conventional vertical type borehole with spiral coil type ground heat exchangers (GHEs). Field TRTs were carried out on a PHC energy pile and a general vertical type borehole, and an equivalent ground thermal conductivity was estimated using the spiral coil source model. The PHC energy pile and conventional vertical type borehole were numerically modeled using a three dimensional finite element method for the estimation of borehole thermal resistance and the comparison with the TRT results. Based on the results, this paper suggested a method to evaluate the ground thermal conductivity using the infinite line source model and the results were compared with those of the spiral coil source model.