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A comparison of laboratory and in situ methods to determine soil thermal conductivity for energy foundations and other ground heat exchanger applications

A comparison of laboratory and in situ methods to determine soil thermal conductivity for energy foundations and other ground heat exchanger applications
A comparison of laboratory and in situ methods to determine soil thermal conductivity for energy foundations and other ground heat exchanger applications
Soil thermal conductivity is an important factor in the design of energy foundations and other ground heat exchanger systems. It can be determined by a field thermal response test, which is both costly and time consuming, but tests a large volume of soil. Alternatively, cheaper and quicker laboratory test methods may be applied to smaller soil samples. This paper investigates two different laboratory methods: the steady state thermal cell and the transient needle probe. U100 soil samples were taken during the site investigation for a small diameter test pile, for which a thermal response test was later conducted. The thermal conductivities of the samples were measured using the two laboratory methods. The results from the thermal cell and needle probe were significantly different, with the thermal cell consistently giving higher values for thermal conductivity. The main difficulty with the thermal cell was determining the rate of heat flow, as the apparatus experiences significant heat losses. The needle probe was found to have fewer significant sources of error, but tests a smaller soil sample than the thermal cell. However, both laboratory methods gave much lower values of thermal conductivity compared to the in situ thermal response test. Possible reasons for these discrepancies are discussed, including sample size, orientation and disturbance
energy foundations, ground source heat pumps, needle probe, thermal cell, thermal conductivity
1861-1125
209-218
Low, J.
b43962ad-3717-4981-a2a6-e33118a33f85
Loveridge, F.
fb5b7ad9-d1b8-40d3-894b-bccedf0e8a77
Powrie, W.
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c
Low, J.
b43962ad-3717-4981-a2a6-e33118a33f85
Loveridge, F.
fb5b7ad9-d1b8-40d3-894b-bccedf0e8a77
Powrie, W.
600c3f02-00f8-4486-ae4b-b4fc8ec77c3c

Low, J., Loveridge, F. and Powrie, W. (2014) A comparison of laboratory and in situ methods to determine soil thermal conductivity for energy foundations and other ground heat exchanger applications. Acta Geotechnica, 10 (2), 209-218. (doi:10.1007/s11440-014-0333-0).

Record type: Article

Abstract

Soil thermal conductivity is an important factor in the design of energy foundations and other ground heat exchanger systems. It can be determined by a field thermal response test, which is both costly and time consuming, but tests a large volume of soil. Alternatively, cheaper and quicker laboratory test methods may be applied to smaller soil samples. This paper investigates two different laboratory methods: the steady state thermal cell and the transient needle probe. U100 soil samples were taken during the site investigation for a small diameter test pile, for which a thermal response test was later conducted. The thermal conductivities of the samples were measured using the two laboratory methods. The results from the thermal cell and needle probe were significantly different, with the thermal cell consistently giving higher values for thermal conductivity. The main difficulty with the thermal cell was determining the rate of heat flow, as the apparatus experiences significant heat losses. The needle probe was found to have fewer significant sources of error, but tests a smaller soil sample than the thermal cell. However, both laboratory methods gave much lower values of thermal conductivity compared to the in situ thermal response test. Possible reasons for these discrepancies are discussed, including sample size, orientation and disturbance

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e-pub ahead of print date: 16 October 2014
Published date: 16 October 2014
Keywords: energy foundations, ground source heat pumps, needle probe, thermal cell, thermal conductivity
Organisations: Infrastructure Group

Identifiers

Local EPrints ID: 364501
URI: http://eprints.soton.ac.uk/id/eprint/364501
ISSN: 1861-1125
PURE UUID: 72a32341-e180-4621-ac3a-8b7b48021767
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: 02 May 2014 09:07
Last modified: 15 Mar 2024 02:48

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Contributors

Author: J. Low
Author: F. Loveridge ORCID iD
Author: W. Powrie ORCID iD

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