An analysis of heat feedback effects of different height embedded plates on promotion of pool fire burning using a variable B number

Abstract

In this study, heat feedback effects of embedded plates with various heights on the enhancement of the pool fire burning were investigated through a variable Spalding B number. The study showed that the embedded plate had a significant effect on the increase in flame height and pool fire burning rate, but longer plate inhibited the effect, where a critical point arose. Besides, by increasing plate height, the solid temperature increased with a high growth rate before the critical point, while the growth rate decreased after the critical point. Below the liquid surface, the plate temperature of ethanol was generally lower as compared with n-heptane due to the lower boiling point of ethanol. While above the liquid surface, it was the opposite due to its less soot production with higher flame temperature. Secondly, the flame height had a significant positive effect on the heat feedback energy from solid radiation and solid-liquid nucleate boiling. For n-heptane fire, as its latent heat of gasification (hfg) was about 1/2.6 of ethanol, the nucleate boiling dominated total solid heat feedback. Finally, the solid heat feedback led the modified heat of gasification (Lm) to change oppositely, which first decreased then increased with the increasing plate height. Thus the B number decreased after a rise that made the same change in burning rate for both fires. Ethanol pool fire had a lower burning rate as compared with n-heptane fire because of its smaller values of B number affected by larger original heat of gasification.