Numerical investigation of the heat transfer characteristics of propane/air flames impinging on a cylindrical surface

Abstract

To better understand the complex phenomena occurring inside furnaces with direct flame impingement and extend the existent studies to situations with multiple enclosed jets, numerical simulations of a radial array of four turbulent confined flame jets impinging on a cylinder are presented. The three-dimensional, incompressible, steady, averaged equations for the transport of mass, momentum, energy and species were solved. Turbulence was modeled with the realizable k-ε model, combustion with the finite-rate/eddy-dissipation model and radiation with the finite-volume scheme. The reference condition simulated is based on the operation of an existent industrial furnace, but the Reynolds number, excess air ratio, impinging distance, cylindrical target diameter and reactant temperature were varied in order to analyze their influence on the fluid flow and heat transfer and to determine a correlation for the area-averaged Nusselt number. The curvature of the target and the interaction of adjacent opposed wall jets lead to the increase of the heat transfer to the target. For the parameter values considered, the excess air ratio, Reynolds number and reactant temperature are of primary importance to enhance heat transfer and reduce the power required, while the target curvature is of secondary importance and the least influential parameter is the impinging distance.