CFD comparison of immersed heater and open fire burner designs for casting furnaces

In essence, only a small fraction of the heat supplied to the conventional aluminum casting (holding) furnaces is used up for its main purpose - alloying and maintaining the metal set point temperature. As the metal introduced to furnace is most often already in the molten phase, most of the energy supplied via open fire burners is usually lost through the furnace walls, door openings and the flue gas. In this theoretical study, fire-tubes are immersed in the metal as an alternative for the conventional open fire burners. Using the Finite Volume Method (FVM), Computational Fluid Dynamics (CFD) models, with heat transfer and combustion incorporated, are developed for both design options, using the commercial code StarCCM+. Thermodynamic analyses are adapted in making a comparison between both designs. In both options, the non-premixed flame (heat source) is simulated using the Eddy Break Up (EBU), 3-step reaction models. The participating media radiation models are adapted for a comprehensive estimation of the radiation heat transfer within the furnace. Turbulence within the flame is modeled using the standard K-epsilon model. Results show that the immersed fire tube improved the furnace's thermal efficiency.