Heat transfer of energy pipe piles with spiral heat exchanger

Abstract

This paper presents a study on heat transfer for energy pipe piles with a spiral heat exchanger (i.e., spiral-tube energy pipe pile). Physical model testing and a heat transfer analytical model were used to analyze the thermal performance of spiral-tube energy pipe piles filled with different backfill materials. The analytical model was developed using the law of energy conservation and Laplace transforms, and its reliability was validated against both experimental data and numerical simulation results. Furthermore, the model was utilized to conduct full-scale pile simulations and analyze the factors influencing heat transfer. Compared to the classical models for heat transfer, the proposed model was found to be more suitable. This study shows that the choice of backfill materials influences the heat exchange efficiency of spiral-tube energy pipe piles due to variations in their thermal properties. Furthermore, lowering the pile's thermal conductivity increases the amount of heat transferred into the surrounding soil. Additionally, variations in the soil's thermal properties significantly affect the heat transfer in energy pipe piles.