Method for Maintaining One-Dimensional Temperature Gradients in Unsaturated, Closed Soil Cells
Heitman, J. L.
Ochsner, T. E.
Ewing, R. P.
Sauer, T. J.
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.
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: 10.2136/sssaj2005.0336N. Posted with permission.