The Interaction of the Simultaneous Diffusions of Heat and Water Vapor

Abstract

Abstract The theory of thermodynamics of irreversible processes and the Onsager reciprocal relation were tested for the case of thermally induced water vapor diffusion through air and through moist soil in the temperature range of 15° to 45°C. The general rate equations for heat and mass flow were transformed into simple relations giving the flux as a function of temperature. The simultaneous steady state rates of heat and vapor flow through air and moist soil were measured. A portion of these data was used to solve for the specific phenomenological coefficients, and the remainder was used to test the rate equations. It appeared that the rate equations so derived, were applicable over the range of soil conditions tested. Furthermore, the interaction coefficients between heat and vapor flow and between vapor and heat flow were found to be nearly identical, which was in agreement with Onsager's theory.