Experimental Study of Fire Suppression with Water Mist 1. Small Gaseous Diffusion Flame

Abstract

Abstract : This report presents a study of the relative contributions of latent heat, heat capacity effects and oxygen dilution in the water mist suppression of a gaseous diffusion flame. The work is motivated by the urgent need to find an alternative to the banned halogen based fire suppressing agents. Water mist is a contending alternative agent especially in total flooding applications. A modified Wolfhard- Parker burner was used to establish a 2D methane air diffusion flame. Drops in flame temperature were measured when various quantities of nitrogen, steam and water mist were added independently in a co-flow arrangement. Thermal images of the flames were also obtained using the Agema Thennovision (trade name) Instrument. Both temperature and IR measurements show that water mist suppresses both the flame temperature and flame height. A simple model of the flame was used to estimate the heat generation and loss processes taking place in the flame when small amounts of various suppressants were added. The results of both experiments and the analysis show that in a co-flow arrangement, where small quantities of water mist are added to the diffusion flame, the effects of latent heat, heat capacity and oxygen dilution are all important. The report also shows that overall, the contributions of thermal cooling are slightly bigger than those of oxygen dilution.