Thermal performance of heat storage-enhanced PCM energy pipe pile with heat conduction fin

Abstract

Improving heat transfer efficiency while maintaining operational safety is crucial for energy piles. This study proposes a novel energy pipe pile (EPP) enhanced with phase change material (PCM), integrating metal fins and spiral heat exchange pipes to optimize the PCM performance further. Laboratory-scale experiments were systematically conducted to evaluate the proposed EPP’s heat transfer performance and thermal response. Additionally, numerical simulations were conducted for three pipe configurations to investigate their effects on heat transfer efficiency, temperature distribution along the pile shaft, and PCM utilization under continuous and intermittent operational conditions. Comparative analyses considering thermal storage enhancement, inlet temperature variations, and soil saturation demonstrated a 7.84% improvement in heat exchange capacity compared with the ordinary designs. The integration of PCM and metal fins altered internal thermal pathways, significantly reducing temperature fluctuations and thermal stress variations within the pile. Numerical results indicated PCM utilization efficiencies of 49.06%, 22.2%, and 56.33% for the 5U in series (5US), 5U in parallel (5UP), and spiral configurations, respectively. In terms of temperature uniformity, the 5US configuration exhibited the largest deviation (86%) between the local minimum and average cross-sectional temperatures. In contrast, the spiral and 5UP configurations exhibited substantially lower deviations of 26.64% and 22.51%, respectively. The spiral-type configuration demonstrated superior heat transfer performance, optimal PCM utilization, and superior temperature uniformity. Therefore, integrating PCM with metal fins offers a promising approach for enhancing energy piles’ thermal performance and operational reliability.