Numerical Simulation Of Suspended Particulate Matter Penetration Through Building Envelopes

A good understanding of ambient air pollutant transport from source to receptor requires knowledge about pollutant penetration across building envelopes. Therefore, it is essential to gain insight into particle penetration in infiltrating air and the factors that affect it in order to assess human exposure more accurately, and to further prevent adverse human health effects from ambient particulate pollution.Researchers most familiar with these studies have speculated that two types of sources may be particularly important: primary emissions from combustion sources, and secondary particles formed in the atmosphere. At present, in order to reduce the concentration of indoor particle, there are three methods which use extensively: using cleaning device, diluting indoor air and controlling the sources.The factors that affect particle infiltration across leaks in the building envelope are introduced, e.g. crack dimension and crack geometry, physical characteristics and shape characteristics of particles, the pressure between indoor and outdoor air, air parameters, diffusion coefficient, sedimentation velocity of suspended particles and Stockes number. According to FLUENT software, the trajectories of particles penetration across leaks are simulated and penetration factor of different diameter particles is predicted according to different effect factors (e.g. crack dimension, crack geometry and the pressure between indoor and outdoor air). The simulation results show that: particles of 0.1~10μm are predicted to have the highest penetration efficiency, nearly unity for crack heights of 1mm or higher. All particles can't penetrate the crack for crack heights of 0.1mm or less and a pressure difference of 4Pa or less. Penetration factor is higher with bigger crack height and bigger pressure difference; Penetration factor is less with bigger crack length. It also is affected by crack configurations. The maximum penetration factors of L-shaped crack and double-bend crack are less than that of straight-through crack, but penetration factors of supermicron and ultrafine particles are higher than that of straight-through crack as the same conditions. This paper emphasizes on this aspect, and it is also an innovation of this paper. The simulation result is compared with other's experiment result, and it is certified that it agrees well with the experiment result.The penetration factor of particles is predicted rapidly and lower cost by simulation, and we can control it according to the simulation results for reducing the concentration of indoor pollutants and decreasing health risk in indoor environments.