Predictive assessment of heat exchange performance of geothermal piles

Heat exchange performance of geothermal piles with single U-shaped circulation tube is quantified as a function of design, operational and site-specific variables. A finite difference model is developed to simulate heat transport by circulation fluid and heat conduction in pile and surrounding soil. Finite difference analyses (FDAs) are performed to quantify the effects of several input parameters on heat transfer performance of a geothermal pile. Based on FDA results, closed-form equations are proposed that can be used in calculation of power output from a single geothermal pile with U-shaped circulation tube embedded in it. Parameter sensitivity study and advanced first order second moment (AFOSM) reliability analysis are performed to determine the hierarchy of different input variables in order of their relative impacts on heat transfer performance. Thermal conductivity of soil, initial temperature difference between circulation fluid and ground, and radius of the circulation tube are identified as the three most important parameters that control heat transfer through geothermal piles.

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