SIMULATION OF THE EFFECT OF AIR VELOCITY IN THE DRYING OF HARDWOOD TIMBER

The effects of different air velocities on the drying of Australian hardwood timber have been investigated using a drying model based on Fickian diffusion. The air velocities studied were 0.05, 0.5, and 2 m.s^-1, corresponding to typical velocities covering the range used from pre-drying to normal kiln conditions. Decreasing tbe air velocity from 2 m.s^-1 to 0.05 m.s^-1 reduces the maximum strain experienced with an optimised drying schedule by 34%, although if the lower velocity is used throughout the drying period, the drying time is predicted to be 40% longer. Explorations with a program to optimise drying schedules suggest that there may Dot be any significant advantage in moving from a low air velocity of 0.05 m.s^-1 to a higher one (2 m.s^-1) in terms of reducing drying time, for the same maximum strain during drying, compared with using a constant air velocity of 0.5 m.s^-1.