Solidification by Convective Drying of Particle Layer Wetted with Dilute Agar Gel

Abstract:

Solidified porous slab is formed through convective drying of glass particle layer wetted with aqueous dilute agar gel. Measured critical mean moisture content increases with increasing initial moisture or agar content. The agar gel moves in viscous flow caused by capillary pressure during drying. A new drying model based on the receding evaporation plane model is proposed. Drying period is divided into surface and internal evaporation periods. Wet slab consists of dried and wet zones during the internal evaporation period, while the wet slab consists of wet zone only during the surface evaporation period. In the new model, the evaporation rate from the wet zone in the internal drying period is estimated with the linear driving force (LDF) approximation in the field of adsorption engineering. Critical moisture content, that is, mean moisture content between the surface and internal periods, is estimated with a mass balance on the surface. Simulated results by the new drying model with reasonable fitting parameters agree very well with measured drying data.

Keywords:

• Receding evaporation plane
• Critical moisture content
• Convective drying
• Agar gel
• Glass particle layer

Notes

T _a  = 333 K, H _a  = 0.0053 kg moisture/kg-dry air, h = 31.6 W/(m² · K), k _H  = 0.031 kg water/(m² · s [kg moisture/kg dry air]).