Scale Modeling of the Transient Behavior of Wood Crib Fires in Enclosures

Abstract

Scale modeling affords engineers the ability to appreciate the dynamic enclosure fire environment of larger than life structures in the laboratory. Conventional approaches to scaling have expressed results in terms of time-averaged values. Transient scaling accuracy must be achieved in order to reasonably assess the interaction of the fire environment with the structural components of a prototype building. A wood crib is used to represent a typical fuel arrangement. The parameters of the wood crib and its surrounding enclosure are designed based on length scale relationships derived from the governing conservation equations. Experiments conducted at three model scales, in ventilation limited enclosures, demonstrate a high degree of both transient and spatial accuracy in the prediction of burning rates, temperatures and gas concentrations. Although it seems that a global energy balance is achieved, some inconsistencies in the scaling of local radiant heat fluxes are highlighted for future attention.