Pipe–pipe thermal interaction in a geothermal energy pile

Abstract

The use of energy loop(s), fitted into the structural foundation piles, also known as geothermal energy piles (GEPs) is on the rise. This dualizes the role of the piles in meeting the structural performance and the thermal comfort demand of the overlying structure. Heat carrier fluid (HCF) is circulated through the loops, to extract or reject heat energy into the ground, during the space heating or cooling operation. However, this results in thermal interaction between the inlet and outlet leg of the loop. This paper presents a numerical study to investigate the pipe–pipe thermal interaction between the inlet and outlet loop–legs. It was found that factors such as the number of loops, pipe location, soil and concrete thermal conductivity have a significant influence on the magnitude of thermal interaction between inlet and outlet pipes. Similarly, it was found that the central steel bar, used in contiguous flight auger (CFA) piles, contributes towards higher thermal interaction.