Importance of Wall Flows at the Early Stages of Fire Growth in the Mathematical Modeling of Enclosure Fires

Abstract

This paper considers the negatively buoyant, two-dimensional wall flows that arise during the growth of a compartment fire. Such flows affect the distribution of mass, momentum and energy in the enclosure. The enclosed environment is generally assumed to be comprised of two stably stratified zones in the mathematical modeling of enclosure fires and the transport between these zones is affected by these wall flows. An experimental study is carried out to determine the important thermal characteristics of such negatively buoyant wall flows, particularly the entrainment into the flow, the penetration distance and the heat transfer to the walls of the enclosure. Employing analytical experimental results of buoyancy driven wall and plume flows, the resulting effects in compartment fires are determined. It is shown that the wall flows are very important at the early stages of fire growth,particularly during the establishment of the two zones in the enclosure. Also, the additional transport generated by buoyancy induced wall flows, following the establishment of these zones,is found to be important for a satisfactory modeling of the changing environment in the enclosure.