A computer model for fluid dynamic aspects of a transient fire in a two room structure

Abstract

A computer model which treats the fluid dynamic aspects of a transient fire in a two-room structure is described. In the model, the gas in each room is divided into two regions of uniform density: A ceiling layer which contains hot products of combustion, and a layer next to the floor which contains uncontaminated air. The fire plume entrains this fresh air, mixes it with hot combustion products and transports it to the ceiling layer. Flow through openings is described by a calculation similar to that used for orifice flows. Fire growth, heat transfer to the walls, and other important features of a fire are described by ad hoc selection of parameters. The thickness and temperature of the ceiling layers and the rate of flow of hot and cold air through opening are calculated as a function of the time by numerical integration of ordinary differential equations derived from the conservation laws of mass and energy. A number of examples are presented to illustrate the use of the program and some general scaling rules for the initial stages of a room fire.