Q.1 60 Kg of spherical wet silica particles (dp = 8 mm) in a tray is to be dried by through- circulation of hot air with superficial velocity of 2 m/s. The initial and critical moisture contents (wet basis) of the solid are 37.5 % and 16.67 % respectively. The density of wet silica particles is 1900 kg/m. Calculate the drying time for the constant-rate period. Temperature of hot air is 80C, Relative humidity of air is 9 % and viscosity of air is 2 X 10-5 kg/(m-s)