Water and heat transport in hilly red soil of southern China: II. Modeling and simulation

摘要

Simulation models of heat and water transport have not been rigorously tested for the red sods of southern China Based on the theory of nonisothermal water-heat coupled transfer, a simulation model, programmed in Visual Basic 6 0, was developed to predict the coupled transfer of water and heat in hilly red soil. A series of soil column experiments for so. water and heat transfer, including soil columns with closed and evaporating top ends, were used to test the simulation mode . Results showed that in the closed columns, the temporal and spatial distribution of moisture and heat could be very well predicted by he model while in the evaporating columns, the simulated soil water contents were somewhat different from the observed ones. In the heat flow equation by Taylor and Lary (1964), the effect of soil water evaporation on the heat flow is not involved, which may be the main reason for the differences between simulated and observed results. The predicted temperatures were not in agreement with the observed one with thermal conductivities calculated by de Vries and Wierenga equations, so that it is suggested that K_h, soil heat conductivity, be multiplied by 8.0 for the first 6.5 h and by 1.2 later on. Sensitivity analysis of soil water and heat coefficients showed that the saturated hydraulic conductivity, K_s, and the water diffusivity, D(theta), had great effects on soil water transport, the variation of soil porosity led to the difference of soil thermal properties, and accordingly changed temperature redistribution, which would affect water redistribution.