| The goal of this project was to perform numerical simulations of the deposition of magnetite particles from suspension in sub-cooled boiling water onto Alloy-800 heat exchanger tubes.; The thermal-hydraulic properties inside the loop test section were first investigated. This involved two-phase turbulent flow, heat transfer and species transport. A two-fluid model associated with a dispersed turbulence model was used for predicting the sub-cooled boiling flow. The transport of magnetite particles was then treated with two different approaches. The first approach used a Lagrangian model which is based on a particle trajectory calculation. The other used an Eulerian model which treats the particles as chemical species and solves a convection diffusion equation.; Some experiments were conducted in order to have an estimation of the average bubble diameter, which was needed in the two-fluid model. The validity of the two-fluid model was then tested using experimental data from the literature. The simulation results were in agreement with the experiments. Finally, deposition fluxes were computed and the influence of some flow parameters on the deposition rate was investigated. The computed deposition flux was found to increase with increasing heat flux and to be influenced strongly by the presence of vapour---as observed experimentally. The overall deposition, however, is over-predicted, indicating that mechanisms other than convection and diffusion are acting. |
