Prediction Of Entrained Mass Flows Through Vertical Openings In A Multiroom Fire Model

Abstract

CIFI (Circulation dans un Immeuble des Fumees de l'incendie) is a computer program based on a multiroom zone model. It has been developed at CSTB for the purpose of predicting air and smoke movement in a multistorey building. In the previons versions of CIFI, the mass flows circulating from room to room through vertical openings were calculated from the differences in vertical pressure fields across these openings, but no estimate of entrainments was made. We introduced recently in CIFI a simple set of criteria in order to decide on the possibility of distributing each flow through a vertical opening between the two gaseous layers located downstream. This results in plumes and entrained flows into these plumes, which were approximately estimated. A description of our approach in given and applied to the interpretation of experiments at NBS.

Iteration Of Smoke Movement Simulation Processes For An Optimized Specification Of Ventilation Parameters, With A View To Control Fire-induced Smoke Flows In Atrium Buildings

“…calculation of air entrainment into the flame plume: Thomas' formulae [12] fan-powered exhaust ventilation, if any, starts 30 sec. after fire outbreak A first automation procedure aimed at determining the minimal value of smoke exhaust area in natural ventilation, and 1.08 m2 was found for a series of cases where the same value was considered for the smoke exhaust area and air inlet area (from and to walkway).…”

“…Restricting our ambitions, we shall now present several procedures which iterate smoke movement simulation with a view to optimizing ventilation parameters such as vent area or fan-powered flow rate, in cases where atrium buildings are concerned. The CIFI computer model was used for the various simulations involved: CIFI is a multiroom model (already presented in [2] and [12]), the main features of which are: a finite volume model incorporating gas stratification in rooms; heat and mass transfer for each of the zones (gases/walls); fire plumes and doorjet entrainments calculated by means of appropriate formulae found in the literature (eg. [13,14] for further information).…”