Fully Coupled 3-D Conjugate Heat Transfer Algorithm for Borehole Heat Exchanger Performance Prediction

Abstract

Quantitative three-dimensional prediction of the thermal performance of a vertical borehole heat exchanger (BHE) in a ground-source heat pump installation is sought. As BHE installation exhibits exceptionally disparate characteristic length scales, an alternative formation-fluid-thermal fully coupled algorithm is derived to quickly predict the 3-D temperature distributions. The time scale of the steady prediction is of order minutes. This simulation capability can be readily coupled to long-time (order months) unsteady simulation of an entire wellbore field. Algorithm prediction is validated by comparison with data from an instrumented commercial installation for a unique BHE conduit design, followed by illustrative design optimization or variation assessments.