Modeling of particle deposition phenomena in heat exchangers

This project will be a Norwegian contribution to the European MATERA FOULSURFACE program, dealing the the physics of fine particle deposition in heat exchengers. The work in the proposed Norwegain activity will be on the modeling of the particle flow in t urbulent thermal boundary layers. The main challenge is to develop a model that is capable of dealing with the combined turbulence and thermophoretic transport in liquids. Models for the thermal force itself will be taken from literature and from results obtained in MATERA FOULSURFACE. Existing flow boundary layer models have to be improved in order to deal with the particle hydrodynamics in liquid systems. In addition the effects of particle-wall interactions will be included. In a turbulent flow the wall shear stresses imposed by the flow have an intermittent nature. This again affects the probability that a depositing particle will adhere to a wall or not. In addition already deposited particles may be re-entrained. A fundamental issue that is assum ed known is the strength of the adhesion forces. Then the main challenge in this project will be to represent the particle-wall-flow interactions in the best possible way, such that the model can have the necessary predictive power. The basic concept is that an Eulerian-Eulerian multiphase ensemble averaged approach can be taken. The effects of particle wall adhesion and near wall hydrodynamics will be included in a statistical approach, which will be an improvement over the approach described in our ear lier work. The model will represent the particle and fluid flow in the entire boundary layer, assuming developed flow. Finally, using a multi-scale strategy, the model will be developed into a module that will take care of the particle field boundary con ditions in large scale Computational Fluid Dynamics simulations of complex heat exchanger systems.