Numerical Investigation of the Influence of the Particle/Pipe Diameter Ratio in a Non-Isothermal Gas-Solid Flow

Heat transfer in a gas-solid suspension flowing upwards in a heated pipe has been addressed numerically using an Eulerian-Lagrangian approach. Following the basic idea of available experimental studies, several configurations have been simulated and compared, varying the relative size of the particles, i.e. the ratio d_p/D. Numerical results show that this ratio has a significant influence upon the fluid and particle velocities and temperatures. However, the resulting suspension Nusselt number is found to be only weakly modified by the parameter d_p/D at moderate loading ratio m. This is in accordance with available measurements (e.g. Farbar and Depew, 1963) which do not show a clear dependence of the Nusselt number upon d_p/D in the range 0 < m < 3. Associating the influence of this relative size parameter with effects related to inter-phase exchange area, other dimensionless parameters like the flow and particle Reynolds numbers, some Froude number, as well as the heat capacity ratio, density- and loading ratios, would of course be required in order to achieve full similarity of the suspension flow.