Analysis of enclosure fires using the Isis-3D CFD engineering analysis code

The Isis-3D computational fluid dynamics (CFD) code is currently under development for the Defense Threat Reduction Agency (DTRA) as a tool for risk assessment and engineering level analysis. It is designed to provide reasonably accurate estimates of the total heat transfer to objects from large fires under a variety of circumstances, predict the medium characteristics such as temperature and species concentration distributions, and use fairly short computer turnaround times. Isis-3D models liquid fuel evaporation, transport of fuel vapor, oxygen and other relevant species, reaction and heat release, and soot and other gaseous species formation, destruction, and transport. It models diffuse radiation within the fire and view factor radiation from the fire edge to nearby objects and the surroundings. The fire models are well suited to the analysis of large fires both in open pools and in enclosures. Benchmarking of the code for open pool fires has been presented elsewhere, whereas benchmarking of the code for enclosures fires has been presented herein. In particular, comparisons to several of the Steckler enclosure tests and 2 SNL Igloo fires were made. The results demonstrate reasonable agreement between experiment and predictions for a wide range of geometric scales, ventilation conditions, and fuel types. Finally an application was demonstrated for a nuclear power plant cable tray mezzanine with a CO2 fire suppression system. In this application, Isis-3D predicts the 3 dimensional, transient, CO2 fire suppressant concentration distribution as a function of several variables such as injection timing and duration, fire damper position, and leakage pathways