Numerical investigation on transport characteristics of high-temperature fine particles generated in a transiently welding process

摘要

The motion feature of particulate pollutants in industrial buildings, has a significant impact on the indoor environment and workers' health. In this study, the numerical simulations are performed to investigate the transport characteristics of high-temperature fine particles generated during the welding processes, influenced by four different factors (i.e, release temperature (T_0), release velocity (v_0), operation time (t_0), and particle diameter (dp)). Specifically, the movement mechanism of particles is clarified through the conservation of energy and Newton's second law. The maximum horizontal diffusion distance of particles (△R_(max)) has been proposed to assess the exposure risk of particles. Results show that the transformation between heat energy and kinetic energy drives the two-phase flow to move up. The temperature of particles drops sharply and reaches the environmental temperature at 3.0 s approximately, while their velocity increases first before decreasing slowly. The gravity acting on particles and vortex interaction of airflow result in different motion behaviors of particles in both vertical and horizontal directions. Moreover, △R_(max) is positively correlated with T_o, v_0. and t_0, but negatively correlated with d_p, and has a maximum value of 6.4 m. Generally, the motion and exposure risk of particles are dependent on the heat exchange amount and particle size. The results can contribute to health risk assessment and ventilation system design in the industrial plants.