S. Chander, National Institute of Technology Jalandhar, Jalandhar, India; A. Ray, Indian Institute of Technology Delhi, New Delhi, India
An experimental study has been conducted to determine the heat transfer characteristics for methane/air laminar flame impinging on a flat surface. Variations of average heat flux (impingement region was divided into two parts, i.e., stagnation region and wall jet region) were examined for different values of Reynolds number (Re), dimensional separation distance (H/d) and equivalence ratio (f).The average heat flux in both regions increased with increase in Re. Average heat flux was maximum corresponding to separation distance when the cool central core region was small (case when inner reaction zone was intercepted by the impingement surface) or the flame was just touching the surface. Dimensionless correlations for heat flux distribution in radial direction were developed in terms of burner intensity (defined as the firing rate divided by the cross-sectional area of the burner exit). Correlations were also developed in terms of Nusselt number in radial direction as a function of Re, H/d and f. Influence of Re was less significant on heat transfer compared to turbulent isothermal jet impinging on a flat surface. This was because of the fact that in case of flame it was the proximity of inner reaction zone with impingement surface that significantly affected the heat transfer.
Summary: Flame impingement heating of solids has been used for many years. Melting of scrap metal, shaping glass and heating metal billets in a reheat furnace prior to rolling or shaping are some of its industrial applications. This heating technique is frequently used in other metal fabrication and assembly applications including soldering, brazing, cutting and welding. Significantly enhanced convective heat transfer rates can be achieved by impinging the flame directly to the load.
An experimental study has been conducted to determine the heat transfer characteristics for methane/air laminar flame impinging on a flat surface. Variations of average heat flux (impingement region was divided into two parts, i.e., stagnation region and wall jet region) were examined for different values of Reynolds number (Re), dimensional separation distance (H/d) and equivalence ratio (ƒÖ).The average heat flux in both regions increased with increase in Re. Average heat flux was maximum corresponding to separation distance when the cool central core region was small (case when inner reaction zone was intercepted by the impingement surface) or the flame was just touching the surface. Dimensionless correlations for heat flux distribution in radial direction were developed in terms of burner intensity (defined as the firing rate divided by the cross-sectional area of the burner exit). Correlations were also developed in terms of Nusselt number in radial direction as a function of Re, H/d and ƒÖ. Influence of Re was less significant on heat transfer compared to turbulent isothermal jet impinging on a flat surface. This was because of the fact that in case of flame it was the proximity of inner reaction zone with impingement surface that significantly affected the heat transfer.
