Thermal interaction of slender geothermal boreholes with strong groundwater flows

J. Rico, M. Hermanns

International Journal of Heat and Mass Transfer Vol. 253, pp. 127418

Summary:

Geothermal boreholes benefit from the presence of aquifers, as they promote heat exchange with the ground. Adequate modeling of this interaction is essential for the optimal design of geothermal heat exchangers, ensuring both the required thermal efficiency and economic viability of the installation. The state of the art provides an appropriate theoretical framework for creeping groundwater flows, when the Peclet number of the flow remains much smaller than unity. Although this situation is common in many installations, real-world scenarios involving high-permeability soils or energy piles can result in Peclet numbers of order unity or higher. In these cases, current models fail to correctly capture the velocity field near the borehole, leading to unsatisfactory results or the need of empirical tuning parameters. The present work aims to fill this gap in the literature by employing asymptotic expansion techniques to develop a mathematically rigorous and physically consistent model that captures the effects of strong groundwater flows. Apart from demonstrating excellent accuracy compared to high-fidelity numerical simulations, the proposed model provides a critical evaluation of the strengths and limitations of the state of the art.

Spanish layman's summary:

Las bombas de calor geotérmicas aprovechan las aguas subterráneas para mejorar la transferencia de calor. Este trabajo presenta un modelo matemático riguroso y coherente para casos con números de Peclet de orden de unidad o mayores, donde los modelos previos resultan insuficientes.

English layman's summary:

Geothermal heat pumps take advantage of groundwater to enhance heat transfer. This work presents a rigorous and physically consistent mathematical model for cases with Peclet numbers of order unity  or higher, where previous models prove insufficient.

Keywords: Geothermal heat exchangers; AquifersThermal interaction; Matched asymptotic expansions; Moderate Peclet numbers

JCR-JIF Impact Factor and WoS quartile: 6,600 - Q1 (2025)

DOI reference: https://doi.org/10.1016/j.ijheatmasstransfer.2025.127418

Published on paper: December 2025.

Published on-line: July 2025.

Citation:
J. Rico, M. Hermanns, "Thermal interaction of slender geothermal boreholes with strong groundwater flows", International Journal of Heat and Mass Transfer, Vol. 253, pp. 127418, December 2025. [Online: July 2025] doi: 10.1016/j.ijheatmasstransfer.2025.127418