Measurement of the Transport Coefficients for Coupled Flow of Heat and Moisture in a Medium Sand

Abstract

A two‐column experiment was designed to measure the primary and cross‐coupling transport coefficients for the simultaneous flow of heat and moisture through a medium sand (Plainfield sand) in the liquid‐dominated regime of moisture flow. Values for the moisture diffusivity and thermal conductivity were obtained in the range from 20% to 90% of saturation. Thermal conductivity values fell within ± 7% of a curve calculated by the method of de Vries. In addition, the coefficient for transport of heat under gradients of moisture content was found to be zero within the accuracy of the experiment. The experiment was not sufficiently accurate to yield quantitative estimates of the coefficient for transport of moisture by temperature gradients, so a different experiment was performed to measure this coefficient indirectly. In this latter experiment the dependence of soil water potential upon temperature was found to be as much as five times larger than predicted by the surface tension model used by Philip and de Vries. These large values suggest that thermal effects should be considered for long‐term movement of soil moisture, and perhaps in certain circumstances for shorter term simulations in moist soil.

Formulation of electro-chemico-osmotic processes in soils

“…However, one must be careful not to mix these two approaches in an attempt to formulate a transport process in porous media. A comparison of these two techniques is given by Jury and Miller [21].…”

“…One must note that the symmetry of Onsager's phenomenological coefficients is valid only when a proper choice of fluxes and forces is made. However, in writing Equations (21) and (24), we simply added each component of the flux resulting from each driving force. A comparison of parameters resulting from these two different techniques is given by Luikov [22].…”

“…If we summarize the complete set of equations in terms of p, Cs, 4a, pf and #y in a one-dimensional field, we can list the following equations (1) The assumption of constant parameters and the substitution of Equation (21) into Equation (18) …”

“…(2) With an assumption of no reaction, i.e., R = 0, the substitution of Equation (21) into (17) Obviously, other simplifications and approximations are also possible, depending on an estimate of the order of magnitude for the various terms. In all these equations we have a clear coupling between pressure, voltage, mass fraction of a chemical, density of water phase, and viscosity.…”

Numerical investigation on the temperature effect on the transport of soil solute

“…The soil under investigation was the same as that in Jury and Miller's work [15]. The authors had measured its physical properties which were applied in the present paper.…”