SIMULTANEOUS TRANSFER OF HEAT, WATER, AND SOLUTE IN POROUS-MEDIA .1. THEORETICAL DEVELOPMENT

Soil heat and mass transport occurs simultaneously under field conditions. The processes are complicated and difficult to study experimentally. Therefore, three governing equations were developed to theoretically describe the simultaneous transient transfer of heat, water, and solute in soil. Heat, water, and solute flux equations were developed and combined with conservation of mass and beat equations to yield the three partial differential equations. Each of the equations includes three diffusivity coefficients. The diffusivity coefficients are dependent on soil water content, temperature, and solute concentrations. Water transfer includes expressions for the vapor phase and for the liquid phase. Heat transfer is based on conduction and convection (with both latent and sensible beat considered). Sensible beat transfer occurs in both vapor and liquid phases. The solute transfer equation describes the movement of noninteracting solutes. The theory considers solute transport associated with the movement of liquid water, with ionic diffusion and hydrodynamic dispersion, and in response to temperature gradients and salt sieving.