AIRFLOW DISTRIBUTIONS IN THE FILLET SPACES OF A TIMBER STACK

摘要

An important requirement for producing evenly dried timber (lumber) in a kiln is thatrnthe airflow is uniformly distributed throughout the timber stack. The airflow distributionrnwithin the timber stack of a semi-scale kiln, which has multiple fans, was investigatedrnto determine the possible causes of any airflow non-uniformity. Airflow measurementsrnalong the length of the timber stack illustrated the importance of ensuring that each fanrngenerates the same flowrate, and that end-baffles are placed on either side of the timberrnstack to reduce bypass around these edges. Airflow measurements down the height ofrnthe timber stack demonstrated the effects of a separation zone near the air-inlet face ofrnthe stack, which partially reduced the airflow through the upper portion of the stack, andrnof non-aligned boards, which generated a saw-toothed velocity profile. Once the datarnhad been smoothed to account for these effects, the down-stack velocity profile took onrnthe expected form, with the maximum and minimum velocities at the top and bottom ofrnthe stack, respectively. Comparison of the velocity profiles at the air-inlet and outletrnfaces of the stack indicated a significant redistribution of the flow through the stack.rnThe prediction of a one-dimensional model of airflow in a kiln was shown to be in goodrnagreement with the smoothed experimental data at the air outlet of the stack.