CFD STUDY OF THE HEAT TRANSFER BETWEEN A DILUTE GAS PARTICLE SUSPENSION FLOW AND AN OBSTRUCTION

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The heat transfer process between a dilute gas-particle suspension flow and an obstruction has been numerically investigated employing our novel Eulerian formulation for dilute gas particle suspension flows [1], which allows interaction of the key mechanisms to be quantified for the first time. As the particle reflection occurs around the obstruction, the heat transfer process has been modeled taking into account the incident and reflected particles explicitly. In the energy equations these particle families are treated separately. Only the effect on the gas convective heat transfer is expected to be of primary significance and investigated. The numerical computation is performed using the commercial computational fluid dynamics code, FLUENT, with our User Defined Subroutines. We study the heat transfer process between a dilute gas particle flow and an obstruction with simple geometries such as a 45 ramp and a cylindrical tube. The theoretical results for the latter case are compared with the available experimental data. Our numerical simulation shows that both the particle size and the particle concentration (in the thermal boundary layer) affect the heat transfer process. Since both the particle incidence and reflection depend on the particle size and strongly influence the particle concentration distribution, they have to be physically correctly treated in the modeling of the heat transfer, as is demonstrated in our novel formulation. There is an optimum particle size for a maximum enhancement of the heat transfer. The particle concentration increases the efficiency of the heat transfer process expressed in terms of the local Nusselt numbers.