Modeling dynamic variation of drag force acting on single hot particle
2019
Duan, Mengjie | Wang, Yi | Wang, Dengchao | Da, Guillaume | Liu, Li | Yang, Yang
Hot particles produced at much higher temperatures than ambient are very common in industrial production. The presence and movement of such contaminants in buildings may cause great harm both to the indoor air quality and human health. The movement characteristics and residence times of such hot particles could help us evaluate their potential to cause harm, thereby assisting the development of a precision control design. The present study focuses on investigating the movement of a single hot particle in two typical (free-falling and rising) industrial processes. A numerical model based on a function compilation and dynamic mesh is developed to perform the dynamic variation analysis. The airflow distribution around the hot particle is discussed, and the velocity and drag force for a hot particle and room-temperature particle are compared. The movement characteristics and residence time of the particle will thus become available eventually. Results show that the air flowing around the hot particle will get heated due to the temperature difference between the hot particle and its surroundings. The heated air hinders the free-falling process but plays a promoting role during the rising movement. In comparison with a particle with room temperature, the hot particle, therefore, has a larger drag force and smaller velocity during the free-falling process whereas the reverse condition is observed in the rising process. The slower velocity attenuation allows the hot particle to move further during the rising process, while the small value of acceleration leads to the particle falling slowly. The residence time for the hot particle thus gets prolonged, causing greater harm to human health.
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