Question

A batch of wet solid was dried on a tray dryer using constant drying conditions and a thickness of material on the tray of 25.4 mm. Only the top surface was exposed. The drying rate during the constant-rate period was R=2.05 kg H2O/h.m? (0.42 Ibm H2O/h.ft?). The ratio L/A used was 24.4 kg dry solid/m² exposed surface (5.0 Ibm dry solid/ft). The initial free moisture was Xi = 0.55 and the critical moisture content xc 0.22 kg free moisture/kg dry solid. Calculate the time to dry a batch of this material from XI = 0.45 to x2 = 0.30 using the same drying conditions but a thickness of 50.8 mm, with drying from the top and bottom surfaces. (Hint: First calculate Ls/A for these new cases.)

Answer 1