RSICC CODE PACKAGE PSR-389

1. NAME AND TITLE

COMPBRN3: Modeling Compartment Fires Behavior.

2. CONTRIBUTOR

Oak Ridge National Laboratory, Oak Ridge, Tennessee through the Energy Science and Technology Software Center, Oak Ridge, Tennessee.

3. CODING LANGUAGE AND COMPUTER

FORTRAN 77; PC 386; (P00389PC38600).

4. NATURE OF PROBLEM SOLVED

COMPBRN3 is a deterministic fire hazards program designed for use in probabilistic analysis of fire growth in a particular room. This analysis is required when assessing the risk associated with fires in nuclear power plants. An air entrainment model is included which consists of a plume entrainment model, a wall jet entrainment model, and a model for the doorway mixing effect. Output available includes the total heat release rate of the fire, the temperature and thickness of the hot gas layer formed near the compartment ceiling, the mass burning rate for individual fuel elements, the surface temperature of the elements, and the thermal heat flux at user-specified locations.

5. METHOD OF SOLUTION

A quasi-static approach is followed to simulate the process of fire growth during the pre-flashover period in an enclosure. The compartment is modeled as two zones (or control volumes) which divide it into two distinct, homogeneous, stably-stratified regions. The hot gases accumulating under the ceiling due to fire plume entrainment and negative buoyancy are defined as the upper layer (the ceiling hot gas layer). The lower region is assumed to be thermally inert and contains relatively quiescent cool air, which remains at ambient conditions at all times. These regions are separated by a thermal interface with uniform height inside the room and a higher elevation at the doorway. At each time-step, the hot gas layer model computes the thermal interface heights, the hot gas layer temperature, and the heat fluxes to fuel elements by solving several coupled mass and heat steady-state balance equations by a Newton-Raphson iteration scheme. Correlations are used to determine the convective heat transfer in the buoyant plume of hot gases above the flames. The COMPBRN3 steady-state models and submodels are taken from the fire research literature.

6. RESTRICTIONS OR LIMITATIONS

Maxima of 30 super modules, 10 fuel cells initially on fire, and 5 fuel types.

7. TYPICAL RUNNING TIME

RSICC executed the sample problem in 1 second on an Pentium II/266 Mhz.

8. COMPUTER HARDWARE REQUIREMENTS

PC 386 or better with 1 Mbytes of free hard disk space.

9. COMPUTER SOFTWARE REQUIREMENTS

DOS 3.1 or later. The Lahey F77L-EM/32 V5.01 compiler was used to build the executable included in the package. This executable can be run in a DOS window of Windows95.

10. REFERENCE

V. Ho, N. Siu, G. Apostolakis, and G. F. Flanagan, "COMPBRN III - A Computer Code for Modeling Compartment Fires," NUREG/CR-4566, ORNL/TM-10005 (July 1986).

11. CONTENTS OF CODE PACKAGE

Included are the reference documents and one diskette, which includes source code, sample problem input and output and executable written in a self-extracting DOS file.

12. DATE OF ABSTRACT

April 1999.

KEYWORDS: FIRES; HEAT TRANSFER; REACTOR SAFETY