Deposition of fine particles from a turbulent liquid flow: Experiments and numerical predictions

Abstract

A theoretical model is developed to predict the deposition rate of fine particles from turbulent, non-isothermal liquid flow. The model accounts for the relevant transport mechanisms, describing particle adhesion by the interaction forces calculated from the DLVO-theory. Predictions reasonably agree with the experimental data obtained in a simple plate heat exchanger. The influence of chemical and thermal conditions on adhesion is adequately described by the equilibrium and reaction enthalpy data of the surface ionisation reactions. Transport is found to be dominated by hydrodynamic lift which is often referred to as a secondary effect. The hydrodynamic lift suppresses deposition of 1.2 μm-particles even under laminar flow conditions. The experimental results show that thermophoretic transport is important, but overpredicted by theories developed for stagnant fluids. Apparently particle rotation induced by flow shear diminishes temperature gradients within the particle and in the surrounding fluid and leads to a considerable decrease of the thermophoretic migration velocity.