Mathematical Modeling of Isothermal Drying and its Potential Application in the Design of the Industrial Drying Regimes of Clay Products

Abstract

The processes of simultaneous moisture and heat transfer, which are often nonstationary, and the distinct nature and properties of the material to be dried complicate the description of the drying process. The theory of moisture migration and modeling of drying process has been the subject of many studies. Three theories, the difusion, the capillary low, and the evaporation-condensation, have won general recognition for the explanation of moisture transfer in porous media. This study has several objectives. The irst one was to present a new method for calculation of the variable efective difusivity as well as to identify diferent drying mechanisms and its exact transitions during isothermal drying of clay tiles. The second and main objectives were to analyze all obtained isothermal data, to create a link with the comprehensive theory of moisture migration during drying, and to set up the non-isothermal drying process. The procedure was based on the principle of controlling the mass transport during the drying process. Proposed regimes were consisted from several isothermal segments. Isothermal segments were selected and speciicated in accordance with the clay raw material nature and the moisture migration theory.

Non-isothermal drying kinetics of human feces

“…[23,24] It also implies that there is a thin boundary layer for drying that favors evaporation from within the material rather than from the surface. [25] Here, the migration of water to the surface is typically achieved by capillary action and by progressive evaporation-condensation, processes that are accompanied by a temperature gradient within the material. The multiple falling rates with no intermittent constant rate characterize the drying of HF as a partially wet and dry process.…”