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A fast approximate method for simulating thermal pile heat exchangers

A fast approximate method for simulating thermal pile heat exchangers
A fast approximate method for simulating thermal pile heat exchangers

Ground source heat pump systems, operating in conjunction with vertical ground heat exchangers, will play a key role in decarbonising heating and cooling of buildings. Design of traditional borehole heat exchangers relies on tools which implement routine analytical relationships between heat transferred and the temperature change in the ground and circulating thermal fluid. However, for novel piled foundations used as ground heat exchangers, there are few such analytical solutions available that are practical for routine implementation. This paper examines the use of a radial approximation to simulate the dynamic thermal behaviour of pile heat-exchangers. Originally developed for small diameter and high aspect ratio borehole heat exchangers, the approach is more challenging for piles since unsteady heat transfer within the pile material is more significant over typical timescales. Nonetheless, we demonstrate that for pile diameters between 300 mm and 1200 mm, generally the error is <1 °C with centrally placed heat transfer pipes or four or more pipes placed near the edge with circumferential spacing less than 550 mm. The radial model is therefore practical for most pile configurations. The strong performance of the model is demonstrated for a year of hypothetical heating and cooling cycles, and also against a field-scale thermal response test.

Energy piles, Ground source energy, Heat transfer, Pile foundations, Renewable energy, Thermal piles
2352-3808
Loveridge, Fleur
fb5b7ad9-d1b8-40d3-894b-bccedf0e8a77
Woodman, Nicholas
9870f75a-6d12-4815-84b8-6610e657a6ad
Javed, Saqib
cf0a5b6e-8389-4288-bb5f-2e75487eb918
Claesson, Johan
a69ef5ff-921e-4f70-96fb-3a3eee30bd0a
Loveridge, Fleur
fb5b7ad9-d1b8-40d3-894b-bccedf0e8a77
Woodman, Nicholas
9870f75a-6d12-4815-84b8-6610e657a6ad
Javed, Saqib
cf0a5b6e-8389-4288-bb5f-2e75487eb918
Claesson, Johan
a69ef5ff-921e-4f70-96fb-3a3eee30bd0a

Loveridge, Fleur, Woodman, Nicholas, Javed, Saqib and Claesson, Johan (2022) A fast approximate method for simulating thermal pile heat exchangers. Geomechanics for Energy and the Environment, 32, [100368]. (doi:10.1016/j.gete.2022.100368).

Record type: Article

Abstract

Ground source heat pump systems, operating in conjunction with vertical ground heat exchangers, will play a key role in decarbonising heating and cooling of buildings. Design of traditional borehole heat exchangers relies on tools which implement routine analytical relationships between heat transferred and the temperature change in the ground and circulating thermal fluid. However, for novel piled foundations used as ground heat exchangers, there are few such analytical solutions available that are practical for routine implementation. This paper examines the use of a radial approximation to simulate the dynamic thermal behaviour of pile heat-exchangers. Originally developed for small diameter and high aspect ratio borehole heat exchangers, the approach is more challenging for piles since unsteady heat transfer within the pile material is more significant over typical timescales. Nonetheless, we demonstrate that for pile diameters between 300 mm and 1200 mm, generally the error is <1 °C with centrally placed heat transfer pipes or four or more pipes placed near the edge with circumferential spacing less than 550 mm. The radial model is therefore practical for most pile configurations. The strong performance of the model is demonstrated for a year of hypothetical heating and cooling cycles, and also against a field-scale thermal response test.

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Accepted/In Press date: 1 June 2022
e-pub ahead of print date: 8 June 2022
Published date: 23 November 2022
Additional Information: Funding Information: This work was supported under the EPSRC, UK grant EP/P001351/1 , ‘Non Steady Analytical Models for Energy Pile Testing and Design’. The authors acknowledge the use of the IRIDIS High Performance Computing Facility, and associated support services at the University of Southampton, in the completion of this work. In particular, we thank David Hempston for his indefatigable support. Funding Information: This work was supported under the EPSRC, UK grant EP/P001351/1, ‘Non Steady Analytical Models for Energy Pile Testing and Design’. The authors acknowledge the use of the IRIDIS High Performance Computing Facility, and associated support services at the University of Southampton, in the completion of this work. In particular, we thank David Hempston for his indefatigable support. All authors have read and agreed to the published version of the manuscript. The main G-functions presented in this paper and the Matlab code used to calculate temperature changes according to the CJRM analytical model are freely available from the University of Leeds research data repository at https://doi.org/10.5518/1167. Publisher Copyright: © 2022 The Author(s)
Keywords: Energy piles, Ground source energy, Heat transfer, Pile foundations, Renewable energy, Thermal piles

Identifiers

Local EPrints ID: 472935
URI: http://eprints.soton.ac.uk/id/eprint/472935
ISSN: 2352-3808
PURE UUID: c68bef14-84c8-4564-8d33-04c9a6e6cc26
ORCID for Fleur Loveridge: ORCID iD orcid.org/0000-0002-6688-6305
ORCID for Nicholas Woodman: ORCID iD orcid.org/0000-0002-5571-0451

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Date deposited: 06 Jan 2023 12:48
Last modified: 07 Jan 2023 02:42

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Contributors

Author: Fleur Loveridge ORCID iD
Author: Saqib Javed
Author: Johan Claesson

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