Deposition of aerosol in a laminar pipe flow

In a laminar pipe flow, thermophoretic deposition occurs when the temperature of the pipe wall is less than the temperature of the fluid. For a horizontal pipe, gravity has a significant effect on the deposition of aerosol. Due to the laminar flow of gas fluid, a lift force is imposed on the particle and could affect the deposition of aerosol. In the present work, we considered the influences of various factors on the deposition of aerosol, including diffusion and convection, thermophoresis, gravitational settling and the lift force effect. The revised semi-implicit method for pressure-linked (SIMPLER) was employed to solve the aerosol transport equation. The deposition efficiency of aerosol in a pipe was obtained and the concentration distribution of aerosol at an arbitrary cross-section of pipe was given. The results reveal that when gravitational settling was considered the deposition efficiency had a minimum, corresponding to the penetration efficiency having a maximum. For large particles, the deposition of aerosol was dominated by external forces, and the critical particle trajectory method (CPTM) was used to analyze the deposition of aerosol with the action of thermophoretic force and gravity. The result from CPTM coincided very well with the result from SIMPLER. Supported by the National Natural Science Fundation of China (Grant No. 50476010) and the Tsinghua University Key Personnel Support Plan (Grant No. 05321400)