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Pre-flashover compartment fire temperature: a new calculation model validated with experiments
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. (Steel Structure)ORCID iD: 0000-0002-3112-0270
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. (Steel structure)
(English)In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226Article in journal (Refereed) Submitted
Abstract [en]

A new two-zone model for computing temperature of pre-flashover compartment fires is introduced. This model predicts upper layer fire temperatures in compartments with semi-infinitely thick boundaries as well as with boundaries of insulated or non-insulated steel sheets. The mass flows of air and fire gases are assumed controlled by the plume entrainment depending on a prescribed heat release rate and plume height. The combustion is limited by the rate at which gaseous fuel (pyrolysis gases) is released. The model is based on the assumption that the heat release rate is equal to the heat lost by convection of air and radiation out through the opening(s) and by losses to the surrounding structures.

For a constant heat release rate, this model yields the maximum upper layer temperature a fire would reach when lasting for a very long time as well as the fire temperature as a function of time depending on the inertia, on the design of the surrounding structure and on the ventilation conditions of the compartment.

This model is validated by comparisons with very accurately defined and controlled experiments.

Keyword [en]
two-zone fire model, flashover, compartment fire temperature, model validation
National Category
Other Engineering and Technologies
Identifiers
URN: urn:nbn:se:ltu:diva-62019OAI: oai:DiVA.org:ltu-62019DiVA: diva2:1074460
Available from: 2017-02-15 Created: 2017-02-15 Last updated: 2017-12-01
In thesis
1. Compartment Fire Temperature Calculations and Measurements
Open this publication in new window or tab >>Compartment Fire Temperature Calculations and Measurements
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Mätning och beräkning av temperatur i brandceller
Abstract [en]

This thesis is devoted to heat transfer and fire dynamics in enclosures. It consists of a main part which summarizes and discusses the theory of heat transfer, conservation of energy, fire dynamics and specific fire scenarios that have been studied. In the second part of this thesis, the reader will find an Appendix containing seven scientific publications in this field.

In particular, one- and two-zone compartment fire models have been studied. A new way of calculating fire temperatures of pre- and post-flashover compartment fires is presented. Three levels of solution techniques are presented including closed form analytical expressions, spread-sheet calculations and solutions involving general finite element temperature calculations. Validations with experiments have shown good accuracy of the calculation models and that the thermal properties of the surrounding structures have a great impact on the fire temperature development. In addition, the importance of the choice of measurement techniques in fire engineering has been studied. Based on the conclusions from these studies, the best techniques have been used in further experimental studies of different fire scenarios.

Abstract [sv]

Denna avhandling behandlar problem kopplade till värmeöverföring och branddynamik i slutna utrymmen med tonvikt på värmeöverföring mellan gaser och utsatta konstruktioner. Avhandlingen består av en huvuddel och ett appendix innehållande sju vetenskapliga artiklar. I huvuddelen sammanfattas och diskuteras grundläggande teorier och principer inom värmeöverföring och branddynamik samt studier av ett antal specialfall av brandscenarion som baseras på dessa teorier. I de avslutande bilagorna (Artiklar A1-A3 och Artiklar B1-B2) finns sju vetenskapliga artiklar som grundligare beskriver de ovan nämnda specialfallen.

Huvudfokus i avhandlingen ligger på temperaturutveckling vid brand i slutna utrymmen. I avhandlingen studeras i synnerhet en- och två-zonsmodeller för brand i slutna utrymmen, och en ny metod för att beräkna brandgastemperaturer före och efter övertändning i rumsbränder är framtagen. Validering av dessa modeller med experiment visar att deras noggrannhet är bra. Modellerna visar också att de termiska egenskaperna hos de omgivande ytorna har stor inverkan på brandtemperatursutvecklingen. I tillägg studeras i denna avhandling betydelsen av val av mätmetoder i brandtekniska tillämpningar. På grundval av slutsatserna från dessa studier har de främsta mätteknikerna använts i ytterligare experimentella studier av olika brandscenarier.

Place, publisher, year, edition, pages
Luleå University of Technology, 2017
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keyword
compartment fire temperature, heat transfer, FEM, calculation of temperature, temperature measurement, fire scenario, validation, flashover
National Category
Other Engineering and Technologies
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-59927 (URN)978-91-7583-812-0 (ISBN)978-91-7583-813-7 (ISBN)
Public defence
2017-03-20, F1031, Luleå tekniska universitet, Luleå, 13:00 (English)
Opponent
Supervisors
Available from: 2017-02-09 Created: 2016-10-24 Last updated: 2017-12-01Bibliographically approved

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Byström, Alexandra

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