Heat Transfer from Flame Impingement Normal to a Plane Surface: Importance of radiation, convection, and thermochemical heat release in impinging flames

Impinging flame jets have been widely studiedbecause of their importance in a range ofapplications such as materials processing and firesafety. The purpose here was to determine theimportance of radiation, convection, andthermochemical heat release (TCHR) under a range ofconditions. Natural gas was premixed with oxidantsranging from air to pure oxygen in a round burnerthat produced uniform exit conditions. Flamesimpinged perpendicular to a water-cooled flat disksegmented into 6 concentric calorimeteric sectionsto measure radial heat flux distribution.Many parameters were varied such as firing rate,burner-to-disk spacing, oxidant composition anddisk surface treatment. Untreated, polished,blackened, alumina-coated and platinum-coated disksurfaces made of stainless steel, copper or brasswere tested. High (blackened) vs. low (polished)emissivity surfaces showed nonluminous gaseousradiation was less than 10% of the total heat flux.Noncatalytic (alumina) vs. catalytic (platimum)surfaces showed that TCHR was only important forhigh O2 oxidants. The radial location of the highestheat flux depended on oxidant composition.

Charles E. Baukal, Jr. has a PhD from the Univ. of Penna. and nearly 30 years experience in industrial combustion. He has authored or edited 6 books on industrial combustion, authored over 100 technical papers, and has 11 US patents. He is a licensed PE, a Qualified Environmental Professional, and a Board Certified Environmental Engineer.