S. Chander, National Institute of Technology Jalandhar, Jalandhar, India; A. Ray, Indian Institute of Technology Delhi, New Delhi, India
The situation of flame impingement heating over curved surfaces is frequently encountered in metal and glass industries. Optimization of heating process for such applications is becoming necessary as industry demands increased efficiency and reduced emission of pollutants. An experimental study has been conducted to find the heat transfer characteristics of laminar methane/air flame impinging normal to cylindrical surface. Effects of variation in the values of Reynolds number (Re = 600-1300), equivalence ratio (f = 0.8-1.3), dimensionless separation distance (H/d = 1-5), and burner diameter to cylinder diameter ratio (d/D = 0.0536-0.1073) have been investigated. Three important configurations, viz., flame inner reaction zone far away, just touching and intercepted by the impingement surface were discussed in detail. It has been observed that the heat transfer characteristics were intimately related to the proximity of the flame inner reaction zone to the target surface. At moderate separation distances the stagnation point heat flux becomes lower and peak heat flux lies at certain distance in axial and angular direction. Very high heat fluxes were observed at the stagnation point when tip of the inner reaction zone was just touching the impingement surface. Negative stagnation point heat fluxes were observed when the inner reaction zone was intercepted by the impingement surface. High heat fluxes, at the stagnation region, were observed for smaller burner diameters for fixed Reynolds number and reverse trends were found in the wall-jet region. At large separation distances a second peak in heat flux was observed due to buoyancy effect.
Summary: Heat transfer characteristics of methane/air flame jet impinging normal to a cylindrical surface
Subhash Chander
Department of Mechanical Engineering
National Institute of Technology
Jalandhar-144011, Punjab (India)
Anjan Ray
Department of Mechanical Engineering
Indian Institute of Technology, Delhi
New Delhi -110016 (India)
Abstract
The situation of flame impingement heating over curved surfaces is frequently encountered in metal and glass industries. An experimental study has been conducted to find the heat transfer characteristics of methane/air flame impinging normal to cylindrical surface. Effects of variation in the values of Reynolds number (600-1300), equivalence ratio (0.8-1.3), dimensionless separation distance (1-5), and burner diameter to cylinder diameter ratio (0.0536-0.1073) have been investigated. Very high heat fluxes were observed at the stagnation point when tip of the inner reaction zone was just touching the impingement surface. Negative stagnation point heat fluxes were observed when the inner reaction zone was intercepted by the impingement surface. High heat fluxes, at the stagnation region, were observed for smaller burner diameters for fixed Reynolds number and reverse trends were found in the wall-jet region. At large separation distances a second peak in heat flux was observed due to buoyancy effect.
Keywords: Methane/air flame, impingement, heat transfer, cylindrical surface, curvature effect
second peak in heat flux was observed due to buoyancy effect.
