Study of short-term evaporation in sand specimens via micro-focus Xray computed tomography

Abstract

Water flow and heat transfer often occur simultaneously in soils, in coupled flow, for example in applications such as ground heat thermal storage and disposal of nuclear waste. It is proposed that micro-focus X-ray computed tomography (micro-XCT) can be used to investigate this phenomenon. A natural thermally-driven water flow, evaporation from an exposed soil specimen, is studied to assess the applicability of micro-XCT techniques to other problems in soil heat / moisture transfer. This paper presents studies of short-term evaporation from a sand. A series of scans were conducted on a specimen of sand during evaporation, to provide data for comparison with simultaneous gravimetric measurements made using a sensitive balance in the scanner. Both qualitative and quantitative data from the micro-XCT are presented. Drying of the specimen during each stage can be clearly seen in the image data. However, quantification of the change in water content by image analysis is more challenging, owing to the compromise between the image quality and the scanning time. To overcome this, an alternative approach to segmentation of the image data using Gaussian curve fitting is proposed and validated against global gravimetric measurements. It is concluded that this approach to the analysis of the rapid movement of moisture within the soil is promising, and it will be applied in future experiments.

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Identifiers

ORCID for Kui Liu: orcid.org/0000-0002-7533-1272

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

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

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

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