This paper presents the results of an experimental study on the heat transfer characteristics of an inverse diffusion flame (IDF) impinging vertically upwards on a horizontal copper plate. The IDF burner used in the experiment has a central air jet surrounded circumferentially by 12 outer fuel jets. The heat flux at the stagnation point and the radial distribution of heat flux were measured with a heat flux sensor. The effects of Reynolds number, overall equivalence ratio, and nozzle-to-plate distance on the heat flux were investigated. The area-averaged heat flux and the heat transfer efficiency were calculated from the radial heat flux within a radial distance of 50 mm from the stagnation point of the flame, for air jet Reynolds number (Reair) of 2000, 2500 and 3000, for overall equivalence ratios (Φ) of 0.8-1.8, at normalized nozzle-to-plate distances (H/dIDF) between 4 and 10. Similar experiments were carried out on a circular premixed impinging flame for comparison. It was found that, for the impinging IDF, for Φ of 1.2 or higher, the area-averaged heat flux increased as the Reairor Φ was increased while the heat transfer efficiency decreased when these two parameters increased. Thus for the IDF, the maximum heat transfer efficiency occurred at Reair= 2000 and Φ = 1.2. At lower Φ, the heat transfer efficiency could increase when Φ was decreased. For the range of H/dIDFinvestigated, there was certain variation in the heat transfer efficiency with H/dIDF. The heat transfer efficiency of the premixed flame has a peak value at Φ = 1.0 at H/dP= 2 and decreases at higher Φ and higher H/dP. The IDF could have comparable or even higher heat transfer efficiency than a premixed flame.
|Number of pages||10|
|Journal||International Journal of Heat and Mass Transfer|
|Publication status||Published - 1 Aug 2007|
ASJC Scopus subject areas
- Condensed Matter Physics
- Mechanical Engineering
- Fluid Flow and Transfer Processes