The deposition characteristics of micron particles in heat exchange pipelines

Comprehensive understanding of particles deposition in heat exchange pipelines is significant for environment and energy engineering applications. In this study, a numerical simulation method was used to investigate the deposition characteristics of micron particles in heat exchange pipelines based on Reynolds stress model and discrete particle model. Based on previous research, an improved particle deposition model combined with particle rebound was presented. Moreover, the improved model was used to study the effect of thermophoretic force (hot wall and cold wall), flow velocity, and particle diameter on the non-dimensional deposition rate of particles. The results showed that the non-dimensional deposition rate increased with the increase of non-dimensional relaxation time and then approached a certain value. After introducing the particle rebound, the non dimensional deposition rate exhibited different trend, i.e., first increasing and then decreasing. When the gas had significant temperature gradient in the boundary layer, the effect of thermophoretic force on small particles was found to be significantly stronger than that of large particles. Moreover, the higher the temperature gradient, the more obvious the thermophoretic force of the particles. The results indicated that the thermophoretic forces prevented the deposition of particles on the hot wall, and promoted this process on the cold wall. Furthermore, the flow velocity also significantly affected the particle deposition rate. At the same flow velocity, the particles non-dimensional deposition rate first increased and then decreased with the increase in the particle diameter, and it showed a different maximum at different flow velocities.