CFAST - Consolidated Model of Fire Growth and Smoke Transport (Version 6) Technical Reference Guide - NIST Special Publication 1026

The modeling equations used in CFAST take the mathematical form of an initial value problem for a system of ordinary differential equations (ODEs). These equations predict as functions of time quantities such as pressure, layer height and temperatures given the accumulation of mass and enthalpy in the two layers. The CFAST model then consists of a set of ODEs to compute the environment in each compartment and a collection of algorithms to compute the mass and enthalpy source terms required by the ODEs. This 2009 document provides the technical documentation for CFAST along with significant information on validation of the model. The algorithms, procedures, and computer programs described in this report constitute a methodology for predicting some of the consequences resulting from a prescribed fire. They have been compiled from the best knowledge and understanding currently available, but have important limitations that must be understood and considered by the user. The program is intended for use by persons competent in the field of fire safety and with some familiarity with personal computers. It is intended as an aid in the fire safety decision-making process. Disclaimer......Page 5 Intent and Use......Page 7 Preface......Page 9 Nomenclature......Page 11 Acknowledgments......Page 15 History......Page 25 Model Evaluation......Page 26 Type of Model......Page 29 Governing Equations and Assumptions......Page 30 Property Data......Page 31 Uses and Limitations of the Model......Page 32 Description of Scenarios of Interest......Page 34 Degree of Accuracy Required for Each Output Quantity......Page 35 Theoretical Basis for CFAST......Page 37 Derivation of Equations for a Two-Layer Model......Page 38 Equation Set Used in CFAST......Page 40 Source Terms for the Model......Page 41 The Fire......Page 42 Plumes......Page 46 Vent Flow......Page 52 Corridor Flow......Page 59 Heat Transfer......Page 63 Ceiling Jet......Page 74 Heat Detection......Page 76 Sprinkler Activation and Fire Attenuation......Page 77 Species Transport......Page 78 HCl Deposition......Page 79 Single Zone Approximation......Page 80 Review of the Theoretical Development of the Model......Page 81 Assessment of Justification of Approaches and Assumptions......Page 82 Assessment of Constants and Default Values......Page 83 Structure of the Numerical Routines......Page 85 Numerical Tests......Page 87 Comparison with Analytic Solutions......Page 88 Factorial Design Studies......Page 89 Model Inputs and Outputs......Page 90 Sensitivity to Larger Changes in Model Inputs......Page 93 Response Surface Studies......Page 95 Latin Hypercube Sampling Studies......Page 98 Summary......Page 99 Comparisons with Full-Scale Tests Conducted Specifically for the Chosen Evaluation......Page 101 Comparisons with Previously Published Test Data......Page 103 Multiple Compartments......Page 104 Prediction of Flashover......Page 105 Comparison with Documented Fire Experience......Page 107 Nuclear Facilities......Page 108 Unusual Geometry and Specific Algorithms......Page 109 Summary......Page 111 Conclusion......Page 113 References......Page 115