Radiation energy devaluation in diffusion combusting flows of natural gas

CFD (Computational fluid dynamics) is used to evaluate the thermodynamic second-law effects of thermal radiation in turbulent diffusion natural gas flames. Radiative heat transfer processes in gas and at solid walls are identified as important causes of energy devaluation in the combusting flows. The thermodynamic role of thermal radiation cannot be neglected when compared to that of heat conduction and convection, mass diffusion, chemical reactions, and viscous dissipation. An energy devaluation number is also defined, with which the optimum fuel-air equivalence for combusting flows can be determined. The optimum fuel-air equivalence ratio for a natural gas flame is determined to be 0.7. The CFD model is validated against experimental measurements.