List of top Mass Transfer Questions on Drying

Alumina particles with an initial moisture content of 5 kg per kg dry solid are dried in a batch dryer. For the first two hours, the measured drying rate is constant at 2 kg m\(^{-2}\) h\(^{-1}\). Thereafter, in the falling-rate period, the rate decreases linearly with the moisture content. The equilibrium moisture content is 0.05 kg per kg dry solid, and the drying area of the particles is 0.5 m\(^2\) per kg dry solid. The total drying time, in hours, to reduce the moisture content to half its initial value is:
A wet solid containing 20% (w/w) moisture (based on mass of bone-dry solid) is dried in a tray-dryer. The critical moisture content of the solid is 10% (w/w). The drying rate (kg m$^{-2}$ s$^{-1}$) is constant for the first 4 hours, and then decreases linearly to half the initial value in the next 1 hour. At the end of 5 hours of drying, the percentage moisture content of the solid is \(\underline{\hspace{2cm}}\) % (w/w) (rounded off to one decimal place).
In a batch drying experiment, a solid with a critical moisture content of 0.2 kg H\(_2\)O/kg dry solid is dried from an initial moisture content of 0.35 kg H\(_2\)O/kg dry solid to a final moisture content of 0.1 kg H\(_2\)O/kg dry solid in 5 hours. In the constant rate regime, the rate of drying is 2 kg H\(_2\)O/(m\(^2\)·h). The entire falling rate regime is assumed to be uniformly linear. The equilibrium moisture content is assumed to be zero. The mass of the dry solid per unit area is \(\underline{\hspace{1cm}}\) kg/m\(^2\) (round off to nearest integer).