Heat transfer measurements and predictions for a heated cylinder in gas-solid flows

摘要

The rate of heat transfer between an electrically-heated cylinder and the gas-solid suspension in the riser of a cold circulating fluidized bed was studied for different conditions. Measurements of the averaged heat transfer coefficient were carried out for different values of solids mass flux, superficial air velocity, and particle size diameter. The contribution of the solids to the heat transfer coefficient seems to be significant even under dilute conditions. This particular assertion is investigated using an Eulerian-Lagrangian numerical model, where the gas-phase is modelled using 3-D RANS equations with a two-equation model for the turbulence closure, and the effect of the particles introduced through the source terms of the momentum equations. The particles motion is formulated using a simplified BBO equation along with a stochastic model for the particle-eddy interaction. A submodel is developed to take into account the heat transfer between particle and cylinder. The work clearly shows that even under dilute conditions the heat transfer between particles and cylinder cannot be neglected, and the proposed submodel yields realistic results.