申論題

(b) (8%) A granular insoluble solid material wet with water is being dried in the cons stant-rate period in a pan 0.61 0.61 x 0.6I m²and the depth of material is 25.4 mm. The sides and bottoms are insulated. Air flows parallel to mi's and has a dry bulb temperature of 60℃ and wet bulb tempe rallel to the top drying surface at a velocity of 3.05 erature of 29.4℃. The pan contains 11.34 kg of dry solid having a free moisture content of 0.35 kg H₂O/kg dry solid, and the material is to be dried in the constant-rate period to 0.22 kg H₂O/kg dry solid. Please predict the drying time (unit: hours) needed.