Operation Predry: Variables in Drying Southern Pine

Southern pine lumber was predried at various temperatures using air velocities ranging from 200 to 1000 fpm. The amount of degrade, drying time, moisture content, and power consumption were evaluated. Air velocity and temperature had a significant effect on drying time. During the winter when temperatures averaged 42?F., the drying time from 85 percent MC to an average of 25 percent was 12, 10, and 7.5 days, respectively, for the air velocities of 300, 500, and 800 fpm. In the spring when temperatures averaged 72?F, the drying time from 91 percent MC to an average of 25 percent was 7.3, 5.6, and 4.0 days, respectively, for air velocities of 300, 500, and 800 fpm. The power consumption increased significantly at higher air velocities. With 200 fpm air velocity as the base, the power consumption increased 71 percent at 600 fpm and 185 percent at 1000 fpm. In view of this and the above drying time, an air velocity of approximately 600 fpm is optimum. When predrying was conducted at a temperature of approximately 80?F., seasoning degrade did not exceed 5 percent.

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