Software System for Analysing the Ventilation of a fire
The SYLVIA software system, developped by IRSN, simulates the consequences of a fire in an industrial facility featuring a ventilation network. It calculates the development of the fire, the transportation of hot gases and soot, the resuspension and the transportation of aerosols, whether radioactive or not, the clogging of filters and the damage of isolating equipment such as firebreak doors and fire dampers.
The SYLVIA software system simultaneously processes all of the different phenomena brought into play (fire, ventilation, airborne contamination).
The SYLVIA software system is the reference fire calculation tool used at the IRSN for evaluating the safety of nuclear facilities; it more particularly allows the hundreds of simulations associated with probabilistic safety studies to be performed.
Modelling of the fire is a zone-based approach: the volume of each room is divided into two zones of variable height in which the thermodynamic properties (pressure, temperature and concentration of the gaseous and particulate species) are uniform, the upper zone containing the hot gases and soots.
The ventilation network is modelled using a set of elements, conduits, filters, valves, fans, etc. Mass and heat exchange correlations (between zones, flames and walls) supplement the mass and energy balance equations for the zones. The rates of putting into suspension and deposition of the aerosols on the walls of the rooms and in the ventilation network are also estimated.
Constant attention is paid to system validation, particularly on the basis of the numerous full-scale tests performed by the IRSN.
A flexible and user-friendly system
A HMI (human machine interface) facilitates data entry by the user, checks data consistency and relevance and allows graphic post-processing of the calculation results.
When coupled with the Sunset software, the IRSN's uncertainties propagation tool, the SYLVIA system enables parametric and sensitivity studies to be carried out thanks to the usually very short calculation time of applications.
Implementation et portability
The Sylvia system is portable under Linux, Solaris and Windows 2000/XP.
One of the key steps in the medium term is the coupling of the tridimensionnal fire simulation software Isis to the SYLVIA system. The ISIS software
is developed by the IRSN and available under an open-source license. This will provide both the precision of a 3-D simulation by the ISIS software of the development of the fire in premises, and SYLVIA system's ability to describe a complete ventilation network linked to these premises.
Constant efforts are made to improve the combustion models of complex solid fire sources (glove boxes, electrical cabinets, cables trays, waste packages, etc.).
The SYLVIA system covers all the different phenomena involved (fire, ventilation, aerocontamination) whether interlinked or not, and with different modelling levels. An Gui (Graphic User Interface) facilitates data entry by the user, checks data consistency and relevance and allows the graphic processing of the calculation results.
When coupled with the SUNSET software, the IRSN's uncertainties propagation tool, the SYLVIA system enables parametric and sensitivity studies to be carried out thanks to the usually very short calculation time of applications.