Thermo-mechanical modeling of turbulent heat transfer in gas-solid flows including particle collisions

Abstract

A thermo-mechanical turbulence model is developed and used for predicting heat transfer in a gas-solid flow through a vertical pipe with constant wall heat flux. The new four-way interaction model makes use of the thermal kθ-τθ equations, in addition to the hydrodynamic k-τ transport, and accounts for the particle-particle and particle-wall collisions through a Eulerian/Lagrangian formulation. The simulation results indicate that the level of thermal turbulence intensity and the heat transfer are strongly affected by the particle collisions. Inter-particle collisions attenuate the thermal turbulence intensity near the wall but somewhat amplify the temperature fluctuations in the pipe core region. The hydrodynamic-to-thermal times-scale ratio and the turbulent Prandtl number in the region near the wall increase due to the inter-particle collisions. The results also show that the use of a constant or the single-phase gas turbulent Prandtl number produces error in the thermal eddy diffusivity and thermal turbulent intensity fields. Simulation results also indicate that the inter-particle contact heat conduction during collision has no significant effect in the range of Reynolds number and particle diameter studied. © 2002 Elsevier Science Inc. All rights reserved.