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 the 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 not 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).