Numerical study on settlement characteristics of inhalable particles in under-floor air distribution system

Abstract Particles deposited on the surface and floor will again enter the air in a suspended state due to airflow disturbance, which will threaten people's health. Thus, the purpose of this study is to explore the effects of different particle sizes on the settlement and trajectory of floor particles in the under-floor air distribution (UFAD) system. In this paper, the indoor temperature distribution and particle concentration of office room in Shanghai are simulated by numerical simulation, and verified by experiments. On the basis of ensuring that the numerical simulation results are consistent with the experimental results, the numerical model is used to further analyze the trajectory and settlement characteristics of particles with different sizes in the UFAD system. The results show that the particles less than 1 μm are easy to be suspended in the air under the influence of floor air supply, and the particles larger than 2.5 μm are less affected and mainly settle on the floor. Moreover, the particles close to the air inlet are easier to suspend, so the personnel stay area should keep a certain distance from the air inlet area. Finally, the mosquito coil smoke diffusion simulation is carried out to simulate the unsteady diffusion process of particles when there is particle pollution source on the floor. It is found that most mosquito coil particles could be discharged from the air outlet in 10 min.