Heat transfer in pool fires at a certain small lip height

Abstract

Under the assumptions of a gray-diffuse and homogeneous disk flame at the top plane of the vessel, a diffuse-gray fuel and vessel wall surfaces, and a transparent medium in the ullage space of the vessel, the longitudinal temperature and heat flux distributions at the vessel wall surface for ethanol and kerosene pool fires were calculated numerically. The calculations were performed using the data of Rasbash et al. The emissive power of the disk flame assumed at the top plane of the vessel, which is determined from the heat balance in the combustion system, is approximately equal to the mean values of the radiative flux measured near the top plane of the vessel in the similar fuel type and pool size at the relatively small lip height. The calculated emissive power of the assumed disk flame decreases with time and approaches the asymptote, depending on the depth of the vapor zone. The heat of evaporation and the rate of increase of the sensible heat of the liquid increases and decreases, respectively, with time and approach asymptotes. The time evolution of the sum of them is similar to that of the emissive power of the disk flame derived from the heat balance in the combustion system. Even in relatively small lip heights and low emissive power flames, as in non-hot-zone-forming pool fires, the rates of heat transfer between the wall and the ambient fluids are large, and cannot be neglected in comparison to the heat input from above to the fuel surface.