A simplified approach to predicting the Heat Extraction Rate of Borehole Heat Exchangers from parametric analysis

Abstract

Predicting Borehole Heat Exchanger (BHE) performance is crucial in shallow geothermal applications, and efforts have been made to develop more efficient and accurate Heat Extraction Rate (HER) prediction approaches. In this investigation, a simple analytical approach to estimating the HER of a BHE has been proposed through the parametric analysis from the results of a validated numerical simulation framework. At first, 12 factors considering geotechnical condition, carrying fluid material, U-pipe configuration, etc. and their connection with HER were studied, the results showed that a linear function was able to express the tendency of HER with each factor, and the R2 ranges between 0.56 and 1.0. Next, the coefficients and the intercept of the linear function was obtained. Subsequently, the obtained analytical approach was compared with the conventional Infinite Line Source (ILS) model by randomly generated numerical simulations and in-situ measurement. The results showed that the proposed linear function model based on parametric analysis matches the numerical simulation results with a R2 of 0.72, while the ILS method is with a R2 of 0.45. Further, the proposed approach has a smaller error than the ILS method, compared with the in-situ measurement. The investigation provides a simple approach to estimating the heat exchange potential of BHEs, which is especially prospective for projects without the information of equivalent thermal conductivity.