Observation of thermally driven water flow in soils via micro-focus X-ray Computed Tomography

Abstract

It is well-known that moisture movement and heat transfer often happen simultaneously in unsaturated soils, therefore forming a coupled flow pattern. This process is relevant for ground source heat pump systems, nuclear waste disposal or other areas of energy geotechnology. However, studies on the analysis of water flow in response to thermal variations are still required, especially in terms of quantitative analysis in three-phase unsaturated soil systems. This paper presents a study conducted using advanced microfocus X-ray Computed Tomography (micro-XCT) techniques, which enables both the visualisation of moisture progression and quantification of water change within the soil system. Heat was applied to the soil specimen, inducing heat transfer accompanied with the water flow under the thermal gradient. A series of short scans were operated at different temporal stages during the heating process, enabling the acquisition of representative image data for quantitative analysis. The results in terms of moisture distribution during the heating process have been obtained and interpreted. The study shows that the micro-XCT is able to assess the imposed coupled thermal-moisture flow processes in soils, which will help understand fundamental soil processes and provide quantitative data for the relevant model validation.

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Identifiers

ORCID for Richard Boardman: orcid.org/0000-0002-4008-0098

ORCID for Fleur Loveridge: orcid.org/0000-0002-6688-6305

ORCID for William Powrie: orcid.org/0000-0002-2271-0826

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