Abstract:
New technology allows the production of thinner kiln sticks
manufactured of phenolic resin impregnated paper which are both
structurally and economically realistic. This project tested the effects
of kiln stick thicknesses on dry kiln air circulation and on
lumber drying degrade.
Three variables, stick thickness (3/4, 9/16, 7/16 and 1/4
inch), fan speed (250, 480, and 660 RPM), and plenum width (13 and
25 inches) were tested in a laboratory kiln in different combinations
to explore their effects on air velocity and power consumption of the
fan motors. The results indicated that the 1/4 inch kiln sticks produce
very ununiform drying with correspondingly, low velocities.
However, with 9/16 inch sticks, maximum velocities were obtained
followed by a slight drop in velocities with the 3/4 and 7/16 inch
sticks. Uniformity of air velocities was maximized when using the
wider 25 inch plenum width and any of the three thicker sticks.
Power consumption of the fan motors was not greatly influenced
by plenum width or stick thickness. However, fan speed directly
affected power consumption.
In a second experiment, evaporation rates were measured
using the four different stick thicknesses. The results indicated the
same pattern as the magnitude of the air velocities followed. Highest
evaporation was with the 9/16 inch stick, lowest with the 1/4 inch
stick.
In a commercial dry kiln, the amount of degrade was recorded
in lumber cried using both 3/4 inch wood sticks and 1/2 inch phenolic
sticks. No significant difference in drying degrade was found. Since
air velocities were slightly lower and there was ten percent more
lumber using the thinner kiln sticks, a higher moisture content distribution
resulted.
