Effects of Psychrometrics Conditions on the Drying of a Porous Soil

Abstract

Coupled heat and water movement investigation in porous media is becoming increasingly relevant in sciences and engineering such as geophysics, where geothermal flux is a key issue, and in building technology where mathematical models are developed to provide better energy efficiency. In the top layers of the earth for instance, the great annual and diurnal air temperature and humidity amplitudes under the influence of radiation and rain result in significant fluctuation in soil temperature and volumetric water contents. Column evaporation experiments have been carried out with sandy silt soil in a constant-temperature-relative humidity chamber, and also by the window side exposed to varying psychrometric conditions. Atmospheric temperature and relative humidity data have been measured and logged with the help of a dataloger while soil temperatures and moisture contents have been measured and logged using a data acquisition system. Soil column has been mounted on a digital weighing balance and programmed into a computer with the aid of an evaluation software for continuous weight data acquisition of the column. Comparing the observed experimental data with predicted numerical values shows substantial agreement suggesting that the developed model can be used to generate reliable moisture evolution and temperature data base, given the weather condition and necessary physical properties of the soil. Average overall moisture transport coefficient ranged from 1.25 E—06 to 2.01 E—06 and was largely representative of the pattern of evaporation from the soil. The evaporation rate was also strongly influenced by the initial moisture content at the surface and the ambient relative humidity.

Keywords

evaporation sandy silt moisture content temperature convective mass transfer.

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