Numerical Simulations of Airborne Particle Removal Rates for Air-Ventilated Spaces of Different Obstacle Setups Available to Purchase

As a result of industrialization, human activities and consequently the time spent in indoor spaces has significantly increased. As airborne particles, especially those of relatively small sizes (less than 2 μm), can easily enter human respiratory tract and cross the thin air-blood barrier inside the lungs, necessary measures need to be taken to minimize exposure to these particles. In this study numerical simulations were done by coupling the “Laminar” and “Turbulent Flow” and the “Particle Tracing for Fluid Flow” interfaces in COMSOL Multiphysics to investigate the effects of obstacle setup on air flow profile and particle removal rate in a confined space of an air-ventilated office using 3D models. Particle tracing for fluid flow was used with a Newtonian formulation to simulate and trace particles with diameter of 0.5 μm and density of 1086 kg/m³. A total of 100,000 particles were simulated to reduce the uncertainty in particle concentration calculations and also to yield statistically more accurate results. Simulations were done for a control model with no obstacles, and 3 other models of different obstacle setups in a cubic room of 2.5 m * 4 m * 1 m with the same inlet and outlet configurations and a maximum interval of 180 minutes (3 hours). All cases had a monodisperse particle distribution, where particles were released transiently and evenly distributed through the entire space at the initial time step (t = 0 min). All models reached a steady-state stage after 180 minutes, with the remaining particles circulating and trapped. Analyzing the results revealed that a positive correlation exists between path-length and particle removal rate. Thus, it was concluded that an obstacle orientation and setup leading to increased flow path-length would greatly enhance the particle removal rate and pollutant dilution. Also, regions of recirculation and stagnation proved to have a negative impact on particle removal by trapping the particles and hence should be avoided in obstacle configuration.