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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. Copyright © 2022 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Head orientations directly determine movement directions of exhaled pathogen‐laden droplets, while there is a lack of research about the effect of the infected person's head orientations on respiratory disease transmission during close contact. This work experimentally investigated the effect of different head orientations of an infected person (IP) on the bioaerosol deposition on a healthy person (HP) during close contact. Also, the effectiveness of PV flow in reducing bioaerosol deposition on the HP under the IP's different head orientations was investigated. Bacteriophage T3 was employed to represent viruses inside the cough‐generated aerosols. The bioaerosol depositions on different locations of the HP's upper body (chest, shoulder, and neck) and face (chin, mucous membranes, cheek, and forehead) were characterized by a cultivation method. Results showed that the IP's different head orientations resulted in significantly different deposition density on the HP. PV flow could reduce the bioaerosol deposition remarkably for most cases investigated. The effectiveness of PV flow in reducing deposition on the HP was significantly affected by the IP's head orientations. Findings suggest that changing head orientations can be a control measure to reduce the bioaerosol deposition. Personalized ventilation can be a potential method to reduce the bioaerosol deposition on the HP. [ABSTRACT FROM AUTHOR]

Building ventilation ducting systems play a core role in controlling indoor air quality by recirculating the indoor air and mixing with ambient air. The ventilation system can serve as an air cleaning system itself either through the filtration system or integrating other means, while at the same time, attention to energy consumption is needed. The high-efficiency fibrous filters in a conventional filtration system not only cause high-pressure drops that consume fan energy but also add to the high operation cost. This article proposes an air cleaning technique, aimed at submicron particles, by means of installing patterned surfaces on the walls of ventilation ducts, which can be easily cleaned by water and reused. The effect of patterned surfaces on particle deposition was studied numerically. In the numerical simulation, the Reynolds stress turbulent model was correlated at the near-wall regions by turbulent velocity fluctuation at the normal direction. Particle trajectory was solved by using Lagrangian particle tracking. The numerical model was then validated with a particle deposition experiment. A wind tunnel experiment was carried out to quantify the particle deposition on the semicircular micropatterns for a wide range of heights. Based on our numerical results, the semicircular pattern height of 500 µm with a pitch-to-height ratio (p/e) of 10 has 8.58 times enhancement of the energy efficiency compared with a high-efficiency particulate air filter. Our results indicated that adding surface micropatterns to ventilation ducting for submicron particle deposition is a possible energy-efficient air cleaning technique for practical usage. Copyright © 2020 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]