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The thermal behaviour of three different auger pressure grouted piles used as heat exchangers

The thermal behaviour of three different auger pressure grouted piles used as heat exchangers
The thermal behaviour of three different auger pressure grouted piles used as heat exchangers
Three auger pressure grouted (APG) test piles were constructed at a site in Richmond, Texas. The piles were each equipped with two U-loops of heat transfer pipes so that they could function as pile heat exchangers. The piles were of two different diameters and used two different grouts, a standard APG grout and a thermally enhanced grout. Thermal response tests, where fluid heated at a constant rate is circulated through the pipe loops, were carried out on the three piles, utilising either single or double loops. The resulting test data can be used to determine the surrounding soil thermal conductivity and the pile thermal resistance, both essential design parameters for ground source heat pump schemes using pile heat exchangers. This paper uses parameter estimation techniques to fit empirical temperature response curves to the thermal response test data and compares the results with standard line source interpretation techniques. As expected, the thermal response tests with double loops result in smaller thermal resistances than the same pile when the test was run with a single loop. Back analysis of the pile thermal resistance also allows calculation of the grout thermal properties. The thermally enhanced grout is shown to have inferior thermal properties than the standard APG grout. Together these analyses demonstrate the importance of pile size, grout thermal properties and pipe positions in controlling the thermal behaviour of heat exchanger piles.
ground source heat pumps, piling, pile heat exchangers, thermal properties, thermal response tests
0960-3182
273-289
Loveridge, F.
fb5b7ad9-d1b8-40d3-894b-bccedf0e8a77
Olgun, C.G.
e1ad2ef2-7e65-4c04-8b89-d57826ebcf51
Brettmann, T.
6b6b4465-13af-44e1-a237-6f305390995b
Powrie, W.
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c
Loveridge, F.
fb5b7ad9-d1b8-40d3-894b-bccedf0e8a77
Olgun, C.G.
e1ad2ef2-7e65-4c04-8b89-d57826ebcf51
Brettmann, T.
6b6b4465-13af-44e1-a237-6f305390995b
Powrie, W.
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c

Loveridge, F., Olgun, C.G., Brettmann, T. and Powrie, W. (2014) The thermal behaviour of three different auger pressure grouted piles used as heat exchangers. Geotechnical and Geological Engineering, 33 (2), 273-289. (doi:10.1007/s10706-014-9757-4).

Record type: Article

Abstract

Three auger pressure grouted (APG) test piles were constructed at a site in Richmond, Texas. The piles were each equipped with two U-loops of heat transfer pipes so that they could function as pile heat exchangers. The piles were of two different diameters and used two different grouts, a standard APG grout and a thermally enhanced grout. Thermal response tests, where fluid heated at a constant rate is circulated through the pipe loops, were carried out on the three piles, utilising either single or double loops. The resulting test data can be used to determine the surrounding soil thermal conductivity and the pile thermal resistance, both essential design parameters for ground source heat pump schemes using pile heat exchangers. This paper uses parameter estimation techniques to fit empirical temperature response curves to the thermal response test data and compares the results with standard line source interpretation techniques. As expected, the thermal response tests with double loops result in smaller thermal resistances than the same pile when the test was run with a single loop. Back analysis of the pile thermal resistance also allows calculation of the grout thermal properties. The thermally enhanced grout is shown to have inferior thermal properties than the standard APG grout. Together these analyses demonstrate the importance of pile size, grout thermal properties and pipe positions in controlling the thermal behaviour of heat exchanger piles.

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More information

Accepted/In Press date: 16 April 2014
e-pub ahead of print date: 20 May 2014
Published date: 20 May 2014
Keywords: ground source heat pumps, piling, pile heat exchangers, thermal properties, thermal response tests
Organisations: Faculty of Engineering and the Environment

Identifiers

Local EPrints ID: 364339
URI: http://eprints.soton.ac.uk/id/eprint/364339
ISSN: 0960-3182
PURE UUID: 20156a41-837e-42f0-b46b-24eb108fde29
ORCID for F. Loveridge: ORCID iD orcid.org/0000-0002-6688-6305
ORCID for W. Powrie: ORCID iD orcid.org/0000-0002-2271-0826

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Date deposited: 24 Apr 2014 10:58
Last modified: 01 Oct 2019 01:00

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Contributors

Author: F. Loveridge ORCID iD
Author: C.G. Olgun
Author: T. Brettmann
Author: W. Powrie ORCID iD

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