The use of energy pile foundation has been increased for economic utilization of geothermal energy. In particular, a coilshaped ground heat exchanger (GHE) is preferred than conventional U-shaped heat exchanger to ensure better efficiency of heat exchange rate. This paper presents experimental results by changing different pitch spaces of spiral coils. Joomunjin sand was filled in a steel box of which the size was 5m×1m×1m. Thermal response tests (TRTs) were conducted to measure the ground

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... al conductivity with temperatures of circulating water using line source model and ring coil model. Experimental results and analytical solutions were compared to validate the applicability of these models. Ring coil model showed more accurate similar results with experimental data rather than line source model and cylindrical source model.