Spectral framework for geothermal borehole heat exchangers

Abstract

Purpose

This paper aims to present a framework for deriving analytical and semi‐numerical models for coupled conductive‐convective heat transfer processes in a borehole heat exchanger subjected to general initial and boundary conditions.

Design/methodology/approach

The discrete Fourier transform and the spectral element method have been utilized for deriving two spectral models for a single U‐tube borehole heat exchanger in contact with a soil mass.

Findings

Verification and numerical examples have shown that the developed models are accurate and computationally very efficient. It is illustrated that one spectral element is capable of producing results which are more accurate than those produced by 200 finite elements.

Practical implications

The gained computational efficiency and accuracy will boost considerably the possibilities for more insight into geothermal analysis, which will improve the procedure for designing competitive energy extraction systems.

Originality/value

The models are capable of calculating exactly the temperature distribution in all involved borehole heat exchanger components and their thermal interactions.

Citation

Al‐Khoury, R. (2010), "Spectral framework for geothermal borehole heat exchangers", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 20 No. 7, pp. 773-793. https://doi.org/10.1108/09615531011065566