Simulation of heat transfer to kaolin slurry which exhibits enhanced damping of turbulence

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.

The paper deals with simulation of mass and heat transfer of Kaolin slurry with a yield stress. The yield stress is caused mainly by very fine solid particles which are of non-settling type. Slurries with the yield stress appear frequently in chemical engineering, biotechnology, medicine, power and paper plants, food and mining industries and are often strongly influenced by heat exchange between the transported materials and the surroundings. The paper is focused on heat transfer in hydro-dynamically and thermally developed turbulent pipe flow of Kaolin slurry. The slurry contains solid particles with averaged diameter about 5 m, and concentration of solid phase which varies from 0% to 40% by volume. Experiments proved that such slurries exhibit enhanced damping of turbulence, so they require especially designed wall damping function. Simulation of slurry assumes that it is a single-phase flow with increased viscosity and density, and rheological properties can be described by Bingham model. The wall temperature and heat flux applied into the pipe wall are steady. The objective of the paper is to examine the influence of solids volume fraction on heat transfer by taking into account momentum and energy equations, and turbulence model with modified turbulence damping function. The effect of influential factors on the heat transfer between the pipe and the slurry were analyzed. The paper demonstrates substantial influence of solids volume fraction on velocity profile and as a consequence the temperature profile too. The results of numerical simulation demonstrate the importance of turbulence damping near a pipe wall. A possible cause of turbulence damping in the near-wall region is discussed.