Impact of Solid Body Emissivity on Radiative Heat Transfer Efficiency in Furnaces - a Numerical Study

In this paper a theoretical approach is proposed and applied for quantifying the relevant radiation heat fluxes between the furnace walls, the internal surfaces and the flue gas. Numerical fluid dynamics calculations (CFD) are performed using a commercial code in which different wall emissivities are applied. To consider the spectral properties of the gas phase, the exponential wide band model (EWBM) was implemented into the CFD solver. Simulations results with a simplified gray radiation model and the EWBM clearly show that the simplified model leads to a considerable overestimation of the radiative heat transfer. Furthermore it can be shown, that for certain gas atmospheres the widely used gray radiation model is not suitable to identify the effect of high emissivity coatings on radiative heat transfer.