RADIATIVE AND TOTAL HEAT FEEDBACK FROM FLAMES TO SURFACE IN VERTICAL WALL FIRES

Measurements of radiative and total heat transfer from turbulent flames to a wall are presented for combustion of propane, methane, and natural gas. Flames were generated by a linear burner placed at the bottom of an instrumented, cooled copper wall. The radiative heat feedback from the flames to the wall was determined from measurements using a narrow-angle radiometer and by employing mean-beam-length analysis. The radiative fraction of the total heat feedback was found to be almost independent of the burner power output when plotted against scaled height (vertical distance normalized with flame length). Among the three fuels tested, radiative fraction in flame-to-wall heat transfer was the maximum, for propane and minimum for methane, which can be explained based on sooting characteristics of flames. The total radiative energy transfer as a fraction of the burner output power is also presented for the three fuels.