Thermophoretic Deposition in Tube Flow

Abstract

Thermophoretic deposition in laminar and turbulent circular-pipe flows is investigated. One-dimensional (1D) Eulerian and two-dimensional (2D) Eulerian and Lagrangian models are developed. In 1D models the importance of correct reference scales is demonstrated. A 1D universal expression for the thermophoretic deposition efficiency in a long tube is derived that is valid for laminar and turbulent flows and that gives excellent agreement with previous empirical correlations and theoretical results. Two-dimensional models incorporating radial-profile effects are developed to assess the effectiveness of the 1D approach. The 2D modelling is based on a nonstochastic Lagrangian methodology that allows the calculation of thermophoretic deposition with computationally inexpensive means. The developed models are extensively validated by comparing their predictions to experimental results, previous numerical calculations, and theoretical results in laminar and turbulent flows. The models are also used to calculate thermophoretic deposition in large-scale experiments simulating fission-product behavior during a postulated severe accident at a nuclear power plant. It is found that in laminar flow a properly constructed 1D description provides accurate predictions. In turbulent flow 1D and 2D predictions provide the same degree of accuracy, unless large bulk gas-to-wall temperature differences prevail where the more detailed 2D approach offers significant improvement.