Particle transport and deposition in high temperature gas-particle two-phase tube flow with thermal radiation

Abstract

The thermophoretic transport and deposition of chemically nonreacting particles have been investigated in thermally developing tube flow with thermal radiation. A particle trajectory model has been adopted to predict the particle transport. The P-1 approximation has been used to evaluate the radiative heat transfer. Numerical solutions to the governing equations have been acquired to capture the qualitative essentials of radiation and thermophoresis interaction. Radiation and thermophoresis interactions are described in detail. In the first, cases for thermophoretic transport and deposition of absorbing, emitting and isotropically scattering particles are considered in thermally developing laminar tube flow with high particle mass fraction. The radiative scattering due to suspended particles is assumed to be isotropic, because the effect of anisotropic scattering is not critical besides large values of scattering albedo. High particle mass fraction is always accompained by the change of gas flow field, the increase in thermal loading ratio and radiative absorption coefficient. Thus, the momentum equations for the two phases are treated as two-way coupling, and PSI-Cell model is applied to evaluate the apparent density of dispersed particles. The interactions between particle mass fraction and thermal radiation are investigated on the thermophoresis without Brownian coagulation. In the second, thermophoresis is strongly dependent upon the temperature profile, and thus the effect of radiation and mixed convection on the thermophoresis may be significant in high temperature particulate systems such as Modified Chemical Vapor Deposition process. Thermophoretic transport and deposition are investigated in a vertical tube with variable wall temperature and thermal radiation. The interest in this model problem is derived from its relation to the thermophoretic deposition in the fabrication of optical fiber preforms. Various results are presented to illustrate the ef...