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This paper studies the estimation of unsaturated soil parameters based on thermal, moisture, and solute characteristics, which are important factors that affect productivity and the environment. The objective of this investigation was to determine optimal hydraulic parameters in unsaturated soil. The soil thermal, moisture, and solute transport processes are approached using one-dimensional isothermal models characterized with nonlinear permeability effects, sorption, and reaction that generally cause considerable experimental and numerical difficulties. The spectral element method is presented for space discretization while the time scheme is constructed along the fully implicit approach with the modified Picard iterative procedure. The iterative Levenberg-Marquardt optimization algorithm is adopted for the inverse process. The reliability and performance of the studied model is conducted using refinement indicators based on error, residual, and variance analyses, which allow drawing more representative uncertainty of model parameters estimation. Good agreement with the nonlinear optimization of soil hydraulic parameters estimated and true values is obtained. The estimated responses from respective shape curves show relatively small variability. A consideration of ionic diffusional and average temperature effects was revealed, indicating that the change of one of these factors might not necessarily improve parameter identification responses. For soil moisture content ranges between 0.04 and 0.5 cm 3 cm −3 , average temperature input from 20 to 40°C as well as when the ionic molecular diffusion coefficient is greater than 10 cm 2 hr −1 , a rough representation of moisture, thermal, and hydrochemical characteristics might be sufficient to estimate soil hydraulic parameters.

This paper studies the effects of the absorber plate geometry on the thermal performance of an indirect solar dryer considering temperature dependent thermal conductivity and heat transfer coefficients. The main goal was to explore the effects of the absorbers confined air as well as the absorber plate thicknesses and to provide more realistic characterizations of the thermal dynamic of an indirect solar dryer. The heat transfer process is described using highly nonlinear partial differential equations. The mathematical model accounts the contribution of the upper soil surface temperature calculated using the boundary layer similarity theory. The established mathematical equations describing heat transfer in the solar drying system are solved numerically using a developed MATLAB program. The investigations of heat transfer of the proposed model reveal excellent agreement of prediction responses with the experimental results from the literature. Mathematical model of indirect solar drying prototype developed with double absorber plates separated with a confined air layer operates more effectively with a thermal efficiency greater than 6% compared to the model without confined air configuration. The numerical experiments also show the non-negligible effects of the absorber plate thickness on the thermal dynamic of an indirect solar dryer.

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