Numerical investigation of thermal comfort and transport of expiratory contaminants in a ventilated office with an air curtain system

Air distribution systems generally focus on diluting contaminants and distributing conditioned air. However, this strategy has a potential for spreading particulate matter or bioaerosols. Thus, it is considered to be useful to create a non-uniform indoor environment to prevent such dispersion of particulate matter or bioaerosols, and an air curtain could serve for this purpose. This study investigates the effects of an air curtain system in a ventilated office to prevent the dispersion of expiratory droplets that are generated locally, while also considering thermal comfort. Droplets dispersion was modelled with computational fluid dynamics (CFD) with the Lagrangian method. In the CFD simulations, an air curtain system was installed in the middle of an office with varied factors of design, orientation and jet velocity of the air curtain system. Numerical results showed that unless there was an independent inlet and outlet for each region, the air curtain system alone could not create a non-uniform thermal environment; however, it was effective in removing and preventing dispersion of the expiratory droplets. The droplet removal performance of an air curtain system was not proportional to its jet velocity, but a velocity of 3 m/s was found to be feasible for this office. The air curtain system showed better performance than an air cleaner used to exhaust and filter the expiratory droplets.