Effects of burner aspect ratio on heat flux distributions beneath unconfined ceilings with different inclination angles

Abstract

The present study experimentally investigated the heat flux distributions produced by rectangular fire sources under unconfined inclined ceilings, which have not been quantified in previous studies. The source–ceiling heights, heat release rates, inclination angles of the ceilings (from 0∘ to 20∘ ), and aspect ratios of the rectangular burners (from 1 to 10) were considered comprehensively for a total of 160 sets of test conditions. The results showed that the ceiling heat fluxes in the upstream and downstream areas decreased with an increase in the radial distance. However, with an increase in the ceiling's inclination angle, the attenuation rate of the upstream ceiling heat flux decreased, while the attenuation rate of the downstream ceiling heat flux increased. The upstream and downstream heat flux distributions beneath the ceiling under all the experimental conditions could be well described by a modified model. This study provided quantitative data and a basic understanding of the heat flux distributions under an inclined ceiling induced by different rectangular-source fire impingements, which were essentially different from other previously reported ceiling jets.