An experimental study of airflow in lumber kilns

Abstract Stacked lumber in a box-shaped kiln is prone to non-uniform flows due to the appearance of re-circulation zones before and after the stack. Flow visualisations in a hydraulic model of a kiln were conducted to test the effectiveness of different kiln configurations for eliminating the larger re-circulation zone at the inlet to the stack. When the sharp right-angled bends are streamlined with sufficient curvature and the geometry of the kiln is such that the flow converges through these transitions, then the re-circulation zones vanish and the flow distribution over the height of the stack becomes less peaky and more even. The experiments show that progressively narrowing plenum chambers in a symmetrical kiln cause more severe flow non-uniformity over the height of the lumber stack than plenum chambers with constant width.