Particle deposition at patterned bend regions as a supplementary air cleaning technique in ventilation ducting systems

Particle deposition can occur at several locations of ventilation ducts, including straight region and bend region, where could be a reservoir for microbes and affect the air quality of the built environment. Recently, an energy-efficient air cleaning technique was proposed by mounting washable patterned substrates on the ventilation ducting systems. The patterned surfaces act as a filter and enhance particle deposition, but the deposition has been mainly studied for the straight ducting with fully developed turbulent flow. In this work, the particle deposition study on patterned surface is extended to bend regions where the turbulent flow is not fully developed. The deposition rates of submicron- and micron-particles with seven particle sizes (0.1, 0.3, 0.5, 1.0, 2.0, 3.0, and 5.0 μm) on patterned bends were calculated. Bends of 45°, 60°, 90°, 150°, and 180° were numerically investigated. It was found that the non-dimensional deposition velocity for the patterned bend duct of obtuse angles is larger than that of acute angles. The deposition velocity of the patterned bends is not as large as a high-grade filter, but the enhanced pressure drop caused by the patterned bend regions is much lower than the filter, thus achieving the same magnitude of overall efficiency. Given the fact that the patterned surfaces can be easily cleaned and reused, they are suitable to be installed at both bend regions and straight duct as a technique of regular duct cleaning and a supplementary air cleaning technique in ventilation ducting systems.