Conductive and steam-diffuse constituents of thermotransfer in different soil moisture contents: case study of the Altai Region’s soils

Abstract

The goal of this study was to determine the conductive and steam-diffusive heattransfer constituents in the soil. Based on the solution of differential equation system ofheat and mass transfer, the method to determine the conductive and steam-diffusiveheat transfer constituents in wet soils was developed. To measure the thermophysicalproperties in laboratory setting, a pulse method of a two-dimensional heat source wasused. The method takes into account the patterns of temperature field equalization inan unbounded medium after the heat source termination. A feature of this process isthe occurrence of peak temperature at the investigated point of the medium at a giveninstant. In this experiment, the temperature was controlled not only at the investigatedpoint of the medium, but also at the soil-heater interface. The proposed method wasused to study the thermophysical indices of the chernozems of the Altai Region’sPriobye area (the Ob River area). The chernozem under study is of light-loamy particlesize composition; the illuvial horizon В is enriched by a sand fraction. It has been foundthat the soil conductive thermal diffusivity is reduced with increasing moisture content.The steam-diffusive thermal diffusivity has the extremum at the moisture close to thediscontinuous capillary moisture. In humus horizons it plays a smaller role than in themineral horizons. The thermal diffusivity determined by the steam molecule motion inthe pore space of the soil exceeds the conductive thermal diffusivity two or three times.At the same time thermal steam diffusivity is more than ten time lower than theconductive constituent. Eventually, the stem molecules though dramaticallyaccelerating the processes of heat transfer in the soil profile conduct a small amount ofheat and make a weak contribution to soil thermal accumulation.