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A study on the effects of air gaps, air velocities and fan revolutions on the drying characteristics of western hemlock baby squares

University of British Columbia

The purpose of this study was to explore whether or not vertical air gaps, air velocities, and fan revolutions had any effect on drying characteristics of 105 by 105 mm in cross-section western hemlock baby squares. Western hemlock squares at different lengths are widely used in Japan for housing construction. Today, about 95% of the baby squares are shipped to Japan in green condition. However, the demand for dried baby squares has been recently increased. Baby squares need about eight days to dry with a conventional drying schedule. Not only is the drying cycle long, but honeycomb, checking, splitting and uneven final moisture content distribution are often found among the dried lumber pieces. Therefore, finding an optimum method to dry baby squares, which will result in less degrade and more uniform final moisture content distribution is imperative. In this research project, stacking lumber with 10 mm and 20 mm vertical air gaps and two fan revolutions levels, namely, 620 rpm and 1220 rpm, was carried out on 105 by 105 by 890 mm long western hemlock lumber using a conventional drying schedule. The research results showed that vertical air gaps can increase lumber drying rate of baby squares especially when the average moisture content is above the fibre saturation point. Higher fan revolutions or air velocities can reduce drying times when lumber is stacked with vertical air gaps. The vertical air gaps, fan revolutions and air velocities do not affect moisture content differences between core and shell, shrinkage percentages, quality and drying stresses of baby squares

Thesis/Dissertation

application/pdf

2009-02-10

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http://hdl.handle.net/2429/4380

Forestry

University of British Columbia

UBCV

DSpace