Determining the Terminal Velocity of Wood and Bark Chips

Abstract

Designing an efficient air flotation segregator to segregate bark chips from wood chips requires that the terminal velocities be determined for various pulpwood species. The technique described here uses forced air in a vertical wind tunnel with the chip initially at rest on a stationary screen; when the terminal air velocity in reached, the chip begins to float. A unique air velocity distribution in the center portion of the vertical tube and a higher velocity near the tube wall, thus preventing the chip from moving up on its edge against the wall. A calibration curve correlating the air veloctiy to the voltage applied to the blower motor eliminated the need of the pitot tube and manometer in each velocity measurement, thus making the test procedure much simpler and more efficient. Preliminary results show a significant difference between terminal velocities of aspen wood and bark chips, thus air flotation is a promising segregation method.

Citation

Sturos, John A. 1972. Determining the Terminal Velocity of Wood and Bark Chips. Research Note NC-131. St. Paul, MN: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station