Thermophoretic Deposition in a Cylindrical Tube: Computations and Comparison with Experiments

Thermophoresis causes particle deposition on nuclear reactor components from gas/vapor streams, both during normal and accident conditions, and it is of interest to develop good computational tools for estimation of such deposition. This paper describes a numerical technique to solve the coupled equations of energy and particle continuity. The numerical technique was verified by comparing the solution of the Graetz energy transport problem obtained by using the present numerical technique with the series solution. Thermophoretic deposition efficiency obtained from the present numerical technique agrees with the analytical solution for short tubes. Deposition efficiencies for the case RePr = 1 and Pr K = 1 are in good agreement with the published theoretical expressions for thermophoretic deposition efficiency. Also, the results from the numerical solution for thermophoretic deposition efficiency compare well with some experimental data published in the literature. Dependence of deposition efficiency on thermophoretic coefficient K was studied, and it was observed that the dependence is more linear for smaller thermal gradients than for the larger gradients. Further, the computational fluid dynamics program FLUENT® 6.3 was also used to explore calculations of the thermophoretic deposition efficiencies for some cases, and it was noted that results are sensitive to mesh size and that very fine mesh near the surface was needed for accurate results. The results computed are in good agreement with our numerical calculations and experimental data.