Radiation From Luminous and Non-Luminous Natural-Gas Flames

Abstract From the data presented in the paper, these conclusions in regard to the transfer of heat from luminous and non-luminous gas flames are made: Luminous gas flames are now being obtained principally with slow-moving, stratified streams of air and gas, which, from the viewpoint only of efficient combustion, are much inferior to non-luminous flames. Combustion is extremely rapid in premised, non-luminous flames, which results in a high-temperature zone near the burners. Although natural-gas flames can be produced that have an emissivity approaching that of a black body and consequently a higher rate of heat transfer than a non-luminous flame, the total radiant-heat transfer from the flame and the wall, in those furnaces having walls hotter than the work being heated, will not be much greater for the same flame temperature than with a non-luminous flame. The advantage of a luminous flame in many heating processes lies not in a higher rate of heat transfer, but in a more uniform transfer over the entire furnace as a result of the slow combustion and slow heat liberation. The presence of free carbon probably has a beneficial effect in the reduction of oxidation and the scaling of steel.