Slabs of filter cake with a bone-dry density of 1600 kg/m3 are to be dried from an initial free moisture content of 90% (dry basis) to a final free moisture content of 5% (dry basis) batchwise in trays that are 1 m long by 0.5 m wide with a depth of 3 cm. Drying will take place only from the top surface. The drying air conditions are 1 atm, 60oC and a 39oC wet bulb temperature. Air flows perpendicular to the top surface at velocity of 3.5 m/s. Experiments under these drying conditions show a critical free moisture content of 45% (dry basis) with assuming that the drying rate is a linear with free moisture content through origin.
Determine:
a) The drying time for the constant rate period in hours.
b) The drying time for the falling rate period in hours.