E. K. Sackey, S. Avramidis, L.C. Oliveira
Exploratory evaluation of oscillation drying for thick hemlock timbers
The study explores the effect of dry-bulb (Tdb) and wet-bulb
(Twb) temperature oscillation in a conventional kiln
on the drying characteristics of 105-mm-square Pacific
coast hemlock. Five kiln-charges were dried using four
oscillating drying schedules and a control. The base drying
temperatures for the control were Twb=53°C,
Tdb=60°C for the first drying phase and increased to
Twb=65°C, Tdb=80°C in the second phase. These temperatures
were oscillated at two amplitude and frequency
combinations, namely, 3°C for 4 h (low) and 6°C for 8 h
(high). The results indicated that the total impact of oscillating
schedules on the drying rate was more pronounced
at the early stages of the drying process.
Oscillating Tdb at higher amplitudes increased drying rate
by 12%, whereas the low amplitude counterpart reduced
kiln residence time by 10–14%. The final moisture content
variability decreased in both Twb oscillated schedules.
Core and shell moisture content variation also
slightly decreased in the low amplitude Twb oscillated
schedules. High amplitude oscillated Tdb also showed
5% less casehardening than the control, whilst its low
amplitude counterpart increased. The low amplitude Twb
oscillated schedule had the least surface checks and
splits.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 58, 07/2004
Pages: 428 - 433
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