Direct flame impingement heating for rapid thermal materials processing

Combined experimental and theoretical investigations have been carried out to study heat/mass transfer and combustion in the direct flame impingement (DFI) furnace for rapid heating of metals in materials processing. A large- size industrial DFI furnace, equipped with a multiflame combustion system, has been instrumented for performing detailed fluid dynamics and heat trans fer measurements. The mean and local pressure, fuel mass fractions, tempera tures and convective/radiative heat fluxes have been measured and are repor ted for high jet velocities (up to 230 m/s) and firing rates. In the case o f natural gas-air firing, the convective heat fluxes as high as 500 kW/m(2) were recorded with relatively 'cold' refractory wall temperatures (<1400 K ). The combustion gas temperature varied between 1500 and 1800 K. A simplif ied two-dimensional theoretical model was developed to analyze gas flow, fl ame jet combustion and heat/mass transfer in the DFI furnace. The model dev eloped has been Validated against the experimental data and was used to obt ain a fundamental understanding of the physical processes taking place in t he furnace. In addition, the model has been used as a tool to optimize desi gn and operation of the DFI furnace. <(c)> 2001 Elsevier Science Ltd. All r ights reserved.