Particle transport and deposition from non-isothermal gas-particle flows

Abstract

The transport and deposition of particles suspended in a nonisothermal particulate gas flows was studied ecperimentally and numerically for a wide range of particle sizes(having diameters from about 0.1 to 30 micrions). First, for two-dimensional stagnation point flows around flat ribbon, relative thermophoretic particle deposition rates were measured by SEM(scanning electron microscopy) techniques. Using an LDA (laser-Doppler anemometry) system, the velocities of the two-phase and the particle size were masured simultaneously. Particle sizes were measured using the maximum pedestal amplitude of Doppler signal and the visibility. Also, particle motion that considered the effects of thermophoresis and inertial impaction was computed by numerically solving Eulerian partial differential equations of momentum, energy and mass for the gas and particle phases (two-fluid model). the experimental data were compared to the numerical results for variation of Stokes numbers. Good agreement between experimental and numerical results was obtained for velocity, temperature and particle deposition rates. Also the importance of combined thermophoresis and inertial impaction was examined. Next, for the cross flows around a circular cylinder, the local particle deposition rates for two Reynolds numbers (Re=36, 54) and three wall-to-gas temperature ratio parameters($T_w/T^\infty$=0.731, 0.853, 0.897) were obtained by using SEM techniques. Mainstream particle number density and velocity fields were measured also by LDA system. Calibration for particle concentration was accomplished by the particle size and number density data obtained from inertial impaction and filtration method. The effects of particle size, target temperature ratio parameter, and flow Reynolds number on the particle deposition rates at each local angular position were estimated. The experimental particle deposition rates for small particles is compared to the theoretical thermophoresis correlation. Also, paricl...