Theoretical Study of Affecting Parameters on Drying Process of Organic Materials. (Dept. M.)

Drying is considered one of the most complex processes encountered in engineering, the drying of porous materials has a vital role in many applications and industrial fields. Drying is process accompanied with a simultaneous heat and moisture transport within material and from its surface to the surroundings caused by a number of mechanisms. The moisture can be either transported to the surface of the material and then evaporated or evaporated internally at a liquid vapor interface and then transported as vapor to the surface. The transfer of heat depends on the air temperature, relative humidity, air flow rate, exposed area of material and pressure. The physical nature of material, including temperature, pore structure, and moisture content, governs the rate of moisture transfer. A numerical model is developed for simulating a convection drying process. The model incorporates mass and heat transfer relationships within the porous material, as well as the heat and mass transfer at the air solid interface of the material and drying medium. A computer program in FORTAN is developed to solve the two-dimensional coupled heat and mass transfer equations inside a porous material during the drying process. The model initially validated by comparing the numerical results with published results. This validated numerical model is used to investigate the effect of external conditions of the drying medium and internal conditions of the porous material. The numerical results if drying curves, heat and mass transfer coefficients in terms of Nusselt and Sherwood numbers are presented. In addition, the numerical predictions for average moisture content are in good and acceptable agreement with experiments.