Investigating of heat conductivity equation with consideration of phase change and effect of soil moisture on heat diffusivity

Phase change in soil temperature should be taken into account in application of heat conductivity equation to different soil layers. In this study, applicability of the solution in daily soil temperature change was provided with consideration of phase change in the heat conductivity equation. Root mean square error, absolute error, maximum relative error, mean bias error, and conformity index between measured and estimated temperature values of the solution of heat conductivity equation, and efficiency of the model were calculated at 10, 20 and 50 cm depths of soil. Results of statistical evaluations showed that solution of heat conductivity equation within the given boundary condition, including phase change, can be used for the prediction of daily temperature change along with soil depth. Soil heat diffusivity showed declining increase with increasing in soil moisture content, and the relationship between heat diffusivity and moisture can be expressed by the parabolic function