# PD ISO TR 16730-2-2013

BSI Standards Publication PD ISO/TR 16730-2:2013 Fire safety engineering — Assessment, verification and validation of calculation methods Part 2: Example of a fire zone modelPD ISO/TR 16730-2:2013 PUBLISHED DOCUMENT National foreword This Published Document is the UK implementation of ISO/TR 16730-2:2013. The UK participation in its preparation was entrusted to Technical Committee FSH/24, Fire safety engineering. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. © The British Standards Institution 2013. Published by BSI Standards Limited 2013 ISBN 978 0 580 82090 8 ICS 13.220.01 Compliance with a British Standard cannot confer immunity from legal obligations. This Published Document was published under the authority of the Standards Policy and Strategy Committee on 31 August 2013. Amendments issued since publication Date Text affectedPD ISO/TR 16730-2:2013 © ISO 2013 Fire safety engineering — Assessment, verification and validation of calculation methods — Part 2: Example of a fire zone model Ingénierie de la sécurité incendie — Évaluation, vérification et validation des méthodes de calcul — Partie 2: Exemple d’un modèle de zone TECHNICAL REPORT ISO/TR 16730-2 First edition 2013-07-01 Reference number ISO/TR 16730-2:2013(E)PD ISO/TR 16730-2:2013ISO/TR 16730-2:2013(E)ii © ISO 2013 – All rights reserved COPYRIGHT PROTECTED DOCUMENT © ISO 2013 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of the requester. ISO copyright office Case postale 56 • CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyright@iso.org Web www.iso.org Published in SwitzerlandPD ISO/TR 16730-2:2013ISO/TR 16730-2:2013(E)© ISO 2013 – All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 General information on the zone model considered 1 3 Methodology used in this Technical Report . 2 Annex A (informative) Description of the calculation method . 3 Annex B (informative) Complete description of the assessment (verification and validation) of the calculation method 9 Annex C (informative) Worked example 11 Annex D (informative) User’s manual 21 Bibliography .22PD ISO/TR 16730-2:2013ISO/TR 16730-2:2013(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2. www.iso.org/directives Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received. www.iso.org/patents Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement. The committee responsible for this document is ISO/TC 92, Fire safety, Subcommittee SC 4, Fire safety engineering. ISO 16730 consists of the following parts, under the general title Fire safety engineering — Assessment, verification and validation of calculation methods: — Part 2: Example of a fire zone model (Technical report) — Part 3: Example of a CFD model (Technical report) — Part 4: Example of a structural model (Technical report) — Part 5: Example of an Egress model (Technical report) The following parts are under preparation: — Part 1: General (revision of ISO 16730:2008)iv © ISO 2013 – All rights reservedPD ISO/TR 16730-2:2013ISO/TR 16730-2:2013(E) Introduction Certain commercial entities, equipment, products, or materials are identified in this document in order to describe a procedure or concept adequately or to trace the history of the procedures and practices used. Such identification is not intended to imply recommendation, endorsement, or implication that the entities, products, materials, or equipment are necessarily the best available for the purpose. Nor does such identification imply a finding of fault or negligence by the International Standards Organization. For the particular case of the example application of ISO 16730-1 described in this document, ISO takes no responsibility for the correctness of the code used or the validity of the verification or the validation statements for this example. By publishing the example, ISO does not endorse the use of the software or the model assumptions described therein and states that there are other calculation methods available.© ISO 2013 – All rights reserved vPD ISO/TR 16730-2:2013PD ISO/TR 16730-2:2013Fire safety engineering — Assessment, verification and validation of calculation methods — Part 2: Example of a fire zone model 1 Scope This part of ISO 16730 shows how ISO 16730-1 is applied to a calculation method for a specific example. It demonstrates how technical and users’ aspects of the method are properly described in order to enable the assessment of the method in view of verification and validation. The example in this part of ISO 16730 describes the application of procedures given in ISO 16730-1 for a fire zone model (CFAST). The main objective of the specific model treated here is the simulation of a fire in confined compartments with a natural or forced ventilation system. 2 General information on the zone model considered The name given to the zone model considered in this Technical Report is “CFAST”. CFAST is a two-zone fire model capable of predicting the environment in a multi-compartment structure subjected to a fire. It calculates the time-evolving distribution of smoke and fire gases and the temperature throughout a building during a user-prescribed fire. This Technical Report describes the equations which constitute the model, the physical basis for these equations, and an evaluation of the sensitivity and predictive capability of the model. The modelling equations take the mathematical form of an initial value problem for a system of ordinary differential equations (ODEs). These equations are derived using the conservation of mass, the conservation of energy (equivalently, the first law of thermodynamics), the ideal gas law, and relations for density and internal energy. These equations predict as functions of time quantities such as pressure, layer height, and temperature given the accumulation of mass and enthalpy in the two layers. The 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. TECHNICAL REPORT ISO/TR 16730-2:2013(E) © ISO 2013 – All rights reserved 1PD ISO/TR 16730-2:2013ISO/TR 16730-2:2013(E) 3 Methodology used in this Technical Report For the calculation method considered, checks based on ISO 16730-1 and as outlined in this Technical Report are applied. This Technical Report lists in Annexes A and B the important issues to be checked in the left-hand column of a two-column table. The issues addressed are then described in detail, and it is shown how these were dealt with during the development of the calculation method in the right- hand column of the Annexes A and B cited above, where Annex A covers the description of the calculation method and Annex B covers the complete description of the assessment (verification and validation) of the particular calculation method. Annex C describes a worked example and Annex D adds a user’s manual.2 © ISO 2013 – All rights reservedPD ISO/TR 16730-2:2013ISO/TR 16730-2:2013(E) Annex A (informative) Description of the calculation method A.1 Purpose Definition of problem solved or function performed The model has been developed for solving practical fire problems in fire protection engineering while at the same time providing a tool to study fundamental fire dynamics and smoke spread. It is intended for system modelling of building and building components. It is not intended for detailed study of flow within a compartment such as is needed for smoke detector siting. Space scales from ~1 m 3to 1 000 m 3and time scales from ~1 s to approx- imately a few hours. (Qualitative) description of results of the calculation method The outputs of the model are the sensible variables that are needed for assessing the environment in a building subjected to a fire. These include temperatures of the upper and lower gas layers within each compart- ment, the ceiling/wall/floor temperatures within each compartment, the visible smoke and gas species concentrations within each layer, target temperatures, and sprinkler activation time. Justification statements and feasi- bility studies The model predicts the environment within compartmented structures resulting from a fire prescribed by the user. It is an example of the class of models called finite element. This particular implementation is called a zone model and, essentially, the space to be modelled is broken down to a few elements. The physics of the compartment fire phenomena is driven by fluid flow, primarily buoyancy. The usual set of elements or zones are the upper and lower gas layers, partitioning of the wall/ceiling/floor to an element each, one or more plumes, and objects such as fires, targets, and detectors. One feature of this implementation of a finite element model is that the interface between the elements (in this case, the upper and lower gas layers) can move, with its position defined by the govern- ing equations. The attached bibliography [1-4]has a compendium of all validation testing which has been done.© ISO 2013 – All rights reserved 3PD ISO/TR 16730-2:2013ISO/TR 16730-2:2013(E) A.2 Theory Underlying conceptual model (governing phenomena) The modelling equations take the mathematical form of an initial value problem for a system of ordinary differential equations (ODEs). These equations are derived using the conservation of mass, the con- servation of energy (equivalently, the first law of thermodynamics), and the ideal gas law. These equations predict as functions of time quantities such as pressure, layer height, and temperature given the accumulation of mass and enthalpy in the two layers. The assump- tion of a zone model is that properties such as temperature can be approximated throughout a control volume by an average value. Theoretical basis of the phenomena and physical laws on which the calculation method is based The equations used take the mathematical form of an initial value problem for a system of ordinary differential equations (ODEs). These equations are derived using the conservation of mass, the conserva- tion of energy (equivalently, the first law of thermodynamics), the ideal gas law, and relations for density and internal energy. These equations predict as functions of time quantities such as pressure, layer height, and temperature given the accumulation of mass and enthalpy in the two layers. A.3 Implementation of theory Governing equations The modelling equations used take the mathematical form of an initial value problem for a system of ordinary differential equations. These equations are derived using the conservation of mass, the conserva- tion of energy (equivalently, the first law of thermodynamics), and the ideal gas law. These equations predict as functions of time quantities such as pressure, layer height, and temperature given the accumula- tion of mass and enthalpy in the two layers. The assumption of a zone model is that properties such as temperature can be approximated throughout a control volume by an average value. The formulation uses the definitions of density, internal energy, and the ideal gas law. These rates represent the exchange of mass and enthalpy between zones due to physical phenomena such as plumes, natural and forced ventilation, convective and radiative heat transfer, and so on. For example, a vent exchanges mass and enthalpy between zones in connected rooms, a fire plume typically adds heat to the upper layer and transfers entrained mass and enthalpy from the lower to the upper layer, and convection transfers enthalpy from the gas layers to the surrounding walls.4 © ISO 2013 – All rights reservedPD ISO/TR 16730-2:2013ISO/TR 16730-2:2013(E) Mathematical techniques, proce- dures, and computational algorithms employed, with references to them The equations used in zone fire modelling are ordinary differential equations (ODEs), which are stiff. The term “stiff” means that large variations in time scales are present in the ODE solution. In our prob- lem, pressures adjust to changing conditions more quickly than other quantities such as layer temperatures or interface heights. Special solvers are required in general to solve zone fire modelling ODEs because of this stiffness, which are used here. There are two assumptions which reduce the computation time. The first is that relatively few zones or elements per compartment are sufficient to model the physical situation. The second assumption is to close the set of equations without using the momentum equation in the compartment interiors. This simplification eliminates acoustic waves. Though this prevents one from calculating gravity waves in compartments (or between compartments), coupled with only a few elements per compartment allows for a prediction in a large and com- plex space very quickly. Identification of each assumption embedded in the logic; limitations on the input parameters that are caused by the range of applicability of the calcula- tion method The model has been developed for solving practical fire problems in fire protection engineering while at the same time providing a tool to study fundamental fire dynamics and smoke spread. It is intended for system modelling of buil