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.
In France, the design of smoke control systems for buildings open to the public commonly depends on regulatory requirements on minimal values of smoke vent areas for each building space, in natural ventilation.These regulations proved unsatisfactory for atrium buildings, and in some cases building designers as well as safety authorities must be provided with specific means for designing a smoke control system and evaluating its efficiency. This paper gives an illustration of what computer analysis can bring for this purpose, through the example of an atrium building in a new business centre near Paris (CNIT / La Defense) .Simulations of smoke movement throughout this 5-storey building containing an 18-metre high atrium were carried out with the CSTB multiroom computer code CIFI.The roughness of zonal description in the model is balanced by the capability of treating the physical system as a whole for the computer simulations. Consequently, the analysis allowed us to draw relevant information from simulation results, and then contributed to the elaboration of a reasonable agreement resulting in the acceptance of the project (the business centre has been recently inaugurated) .
This paper aims at illustrating the potential flexibility of the use of smoke movement modelling for the purpose of elaborating tables or diagrams specifying in a straightforward way minimal values of ventilation parameters such as vent areas or fan-powered flow rates, for the control of smoke flows in the case of building fires.This is particularly relevant to the case of atrium buildings since the regulatory codes in force in France have so far proved unsatisfactory for smoke control. Despite the number of parameters intervening in smoke movement processes that cannot all be controlled at design level, such an approach has the advantage of clearly highlighting theoretical assumptions, especially with regard to safety criteria. The effectiveness of a smoke control system based upon such assunlptions can thus be more easily assessed. However, this may sometimes result in very high levels of ventilation rates, leading to a potential increase in implementation costs.
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