Method for Maintaining One-Dimensional Temperature Gradients in Unsaturated, Closed Soil Cells

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2006-01-01
Authors
Zhou, J.
Heitman, J. L.
Horton, Robert
Horton, R.
Ren, T.
Ochsner, T. E.
Prunty, L.
Ewing, R. P.
Sauer, T. J.
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Agronomy
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Abstract

One-dimensional temperature gradients are difficult to achieve in nonisothermal laboratory studies because, in addition to desired axial temperature gradients, ambient temperature interference (ATI) creates a radial temperature distribution. Our objective was to develop a closed soil cell with limited ATI. The cell consists of a smaller soil column, the control volume, surrounded by a larger soil column, which provides radial insulation. End boundary temperatures are controlled by a new spiral-circulation heat exchanger. Four cell size configurations were tested for ATI under varying ambient temperatures. Results indicate that cells with a 9-cm inner column diameter, 5-cm concentric soil buffer, and either 10- or 20-cm length effectively achieved one-dimensional temperature conditions. At 30°C ambient temperature, and with axial temperature gradients as large as 1°C cm−1, average steady-state radial temperature gradients in the inner soil columns were−1 Thus, these cell configurations meet the goal of maintaining a one-dimensional temperature distribution. These cells provide new opportunities for improving the study of coupled heat and water movement in soil.

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<p>This article is published as Zhou, Jian, J. L. Heitman, Robert Horton, Tusheng Ren, T. E. Ochsner, Lyle Prunty, R. P. Ewing, and T. J. Sauer. "Method for maintaining one-dimensional temperature gradients in unsaturated, closed soil cells." Soil Science Society of America Journal 70, no. 4 (2006): 1303-1309. doi: <a href="http://dx.doi.org/10.2136" target="_blank">10.2136/sssaj2005.0336N</a>. Posted with permission.</p>
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