The Effect of Vertical Air Gaps, Air Velocities and Fan Revolutions on the Drying Characteristics of Thick Pacific Coast Hemlock Lumber

Thick Pacific Coast Hemlock (Tsuga heterophylla and Abies amabilis) specimens, 105mm square in cross-section, were dried in a laboratory conventional kiln by using different vertical air gap sizes (0, 10 and 20mm), air velocities (2.25 to 5.08 m/s) and fan revolutions (62() to 1380 rpm). The research results showed that the introduction of vertical air gaps can reduce kiln drying time. High air velocities and fan revolutions were also found to reduce kiln drying times when lumber was stacked with vertical air gaps. Vertical air gaps, fan revolutions and air velocities did not affect the moisture content differences between core and shell. total shrinkage, level of drying stresses and final quality of the specimens. Lumber density can mask the effect of gaps and air velocity on drying rates unless lumber presorting based on basic density is introduced.