Study on coupled heat and moisture transport and induced stresses in rapid drying process

摘要

In this paper the mechanism of moisture propagation by pressure gradient in porous structure during rapid drying was proposed. Based on a relationship between forces and fluxes from the linear non-equilibrium thermodynamics theory, a mathematical model that describes the coupled heat and mass transfer process was developed. A set of governing equations was obtained. The resulting stresses in porous material caused by dehydration water removal were analyzed. A numerical simulation for a piece of biological material under microwave heating was conducted to obtain temperature, moisture and stress distribution in the material during the drying process. The results show that there exist two different regions, that is, dried region and wet region, the temperature drops is very fast in dried region, especially near the wet front and it is obvious that the fast release of water during drying might induce a large inner stress locally.