Experimental and numerical investigation of submicron particle deposition enhancement by patterned surface

Exposure to inhaling airborne particles in indoor and outdoor environments is a threat to public health. Indoor air passes through ventilation ducts and continuously circulates with the air outdoors, resulting in a higher concentration of suspended particles in indoor environments when compared to outdoor environments. Thus removing airborne particles in ventilation ducts becomes essential, especially in large buildings. Repeated surface ribs have been reported to greatly enhance the particle collection efficiency while it also causes a significant pressure drop, leading to higher energy consumption. In this study, an overall efficiency ratio is defined, taking into consideration the particle removal rate and the associated pressure drop, to evaluate the overall performance of different surface patterns in a ventilation duct. After the design and optimization processes, the semi-circular patterns are shown to have the best overall efficiency, i.e. a 1137 times increase when compared with having no patterned surface. The deposition velocity on the semi-circular surface found in simulation results were validated with a fully-developed wind tunnel experiment. This study shows that semi-circular surface patterns with a pitch-to-height ratio of 4 are recommended for the overall enhancement in the ventilation duct, especially for capturing submicron particles. (paper)