Answer to Question #344647 in Engineering for eloise

Question

The falling-rate portion of the drying time for a particle of skim milk begins at a critical moisture content of 25%, and the final moisture content is 4%. The air used for drying is 120 °C was heated from ambient air of 20 °C and 40% RH. The particle size at the critical moisture content is 20 micron, and the specific heat of the product solids is 2.0 kJ/kg °C. The mass diffusivity for water vapor within the product is 3.7´10^-12 m²/s, and the density of the product particle is 1150 kg/m³.

a.   If the equilibrium moisture content for the product is 3.5%, estimate the time for the falling-rate portion of the drying

b.   If 5000 m³/min of heated air are needed for product drying, determine the thermal energy needed to heat the air to 120 °C.