Design and Analytical Analysis of Foundation Pile Ground Heat Exchanger with Spiral Coils
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Recently, utilization of building foundation piles as the ground heat exchanger (GHE) received more and more attention since it can reduce the initial cost and land area requirement compared with the borehole GHE. This study designs a foundation pile GHE with spiral coil (FPGHE) by intertwing the circulating coil pipe tightly in spiral shape against the reinforcing steel of a pile. The distinct advantage of this proposed FPGHE is that it can offer higher heat transfer efficiency, reduce pipe connection complexity, prevent air blocking and decrease the thermal �short-circuit� between the feed and return pipes compared with other existing configurations. In order to analyze its heat transfer characteristic, analytical models are established for the proposed FPGHE. Analytical thermal analysis is carried out to simulate temperature responses of the coil pipe wall and the circulating water entering/effusing the FPGHE to the short time step heat transfer loads based on the established analytical model. Furthermore, the operation performance and heat exchange capacity of the FPGHE is investigated.