An Introduction to Fire Dynamics

About this book

This is a new edition of the leading introduction to the science of fire phenomena, complete with the latest research, data and additional problems. This book is unique in that it identifies fire science and fire dynamics and provides the scientific background necessary to the development of fire safety engineering as a professional discipline. It is essential reading for all involved in the field from fire safety engineering students to fire prevention officers.

After 21 years as a bestseller, Dougal Drysdale's classic introduction has been brought up-to-date with the latest data and research in a third edition. It features numerical problems with answers illustrating the quantitative applications of the concepts presented. It includes quantitative experimental data regarding material properties. It is successfully course-tested at Massachusetts' Worcester Polytechnic Institute and the University of Edinburgh, and widely adopted throughout the world. It is of relevance to those working in building design, fire physics and chemistry.

Contents

About the Author xi Preface to the Second Edition xiii Preface to the Third Edition xv List of Symbols and Abbreviations xvii 1 Fire Science and Combustion 1 1.1 Fuels and the Combustion Process 2 1.1.1 The Nature of Fuels 2 1.1.2 Thermal Decomposition and Stability of Polymers 6 1.2 The Physical Chemistry of Combustion in Fires 12 1.2.1 The Ideal Gas Law 14 1.2.2 Vapour Pressure of Liquids 18 1.2.3 Combustion and Energy Release 19 1.2.4 The Mechanism of Gas Phase Combustion 26 1.2.5 Temperatures of Flames 30 Problems 34 2 Heat Transfer 35 2.1 Summary of the Heat Transfer Equations 36 2.2 Conduction 38 2.2.1 Steady State Conduction 38 2.2.2 Non-steady State Conduction 40 2.2.3 Numerical Methods of Solving Time-dependent Conduction Problems 48 2.3 Convection 52 2.4 Radiation 59 2.4.1 Configuration Factors 64 2.4.2 Radiation from Hot Gases and Non-luminous Flames 72 2.4.3 Radiation from Luminous Flames and Hot Smoky Gases 76 Problems 79 3 Limits of Flammability and Premixed Flames 83 3.1 Limits of Flammability 83 3.1.1 Measurement of Flammability Limits 83 3.1.2 Characterization of the Lower Flammability Limit 88 3.1.3 Dependence of Flammability Limits on Temperature and Pressure 91 3.1.4 Flammability Diagrams 94 3.2 The Structure of a Premixed Flame 97 3.3 Heat Losses from Premixed Flames 101 3.4 Measurement of Burning Velocities 106 3.5 Variation of Burning Velocity with Experimental Parameters 109 3.5.1 Variation of Mixture Composition 110 3.5.2 Variation of Temperature 111 3.5.3 Variation of Pressure 112 3.5.4 Addition of Suppressants 113 3.6 The Effect of Turbulence 116 Problems 118 4 Diffusion Flames and Fire Plumes 121 4.1 Laminar Jet Flames 123 4.2 Turbulent Jet Flames 128 4.3 Flames from Natural Fires 130 4.3.1 The Buoyant Plume 132 4.3.2 The Fire Plume 139 4.3.3 Interaction of the Fire Plume with Compartment Boundaries 151 4.3.4 The Effect of Wind on the Fire Plume 163 4.4 Some Practical Applications 165 4.4.1 Radiation from Flames 166 4.4.2 The Response of Ceiling-mounted Fire Detectors 169 4.4.3 Interaction between Sprinkler Sprays and the Fire Plume 171 4.4.4 The Removal of Smoke 172 4.4.5 Modelling 174 Problems 178 5 Steady Burning of Liquids and Solids 181 5.1 Burning of Liquids 182 5.1.1 Pool Fires 182 5.1.2 Spill Fires 193 5.1.3 Burning of Liquid Droplets 194 5.1.4 Pressurized and Cryogenic Liquids 197 5.2 Burning of Solids 199 5.2.1 Burning of Synthetic Polymers 199 5.2.2 Burning of Wood 209 5.2.3 Burning of Dusts and Powders 221 Problems 223 6 Ignition: The Initiation of Flaming Combustion 225 6.1 Ignition of Flammable Vapour/Air Mixtures 225 6.2 Ignition of Liquids 235 6.2.1 Ignition of Low Flashpoint Liquids 241 6.2.2 Ignition of High Flashpoint Liquids 242 6.2.3 Auto-ignition of Liquid Fuels 245 6.3 Piloted Ignition of Solids 247 6.3.1 Ignition during a Constant Heat Flux 250 6.3.2 Ignition Involving a 'Discontinuous' Heat Flux 263 6.4 Spontaneous Ignition of Solids 269 6.5 Surface Ignition by Flame Impingement 271 6.6 Extinction of Flame 272 6.6.1 Extinction of Premixed Flames 272 6.6.2 Extinction of Diffusion Flames 273 Problems 275 7 Spread of Flame 277 7.1 Flame Spread Over Liquids 277 7.2 Flame Spread Over Solids 284 7.2.1 Surface Orientation and Direction of Propagation 284 7.2.2 Thickness of the Fuel 292 7.2.3 Density, Thermal Capacity and Thermal Conductivity 294 7.2.4 Geometry of the Sample 296 7.2.5 Environmental Effects 297 7.3 Flame Spread Modelling 307 7.4 Spread of Flame through Open Fuel Beds 312 7.5 Applications 313 7.5.1 Radiation-enhanced Flame Spread 313 7.5.2 Rate of Vertical Spread 315 Problems 315 8 Spontaneous Ignition within Solids and Smouldering Combustion 317 8.1 Spontaneous Ignition in Bulk Solids 317 8.1.1 Application of the Frank-Kamenetskii Model 318 8.1.2 The Thomas Model 324 8.1.3 Ignition of Dust Layers 325 8.1.4 Ignition of Oil - Soaked Porous Substrates 329 8.1.5 Spontaneous Ignition in Haystacks 330 8.2 Smouldering Combustion 331 8.2.1 Factors Affecting the Propagation of Smouldering 333 8.2.2 Transition from Smouldering to Flaming Combustion 342 8.2.3 Initiation of Smouldering Combustion 344 8.2.4 The Chemical Requirements for Smouldering 346 8.3 Glowing Combustion 347 Problems 348 9 The Pre-flashover Compartment Fire 349 9.1 The Growth Period and the Definition of Flashover 351 9.2 Growth to Flashover 354 9.2.1 Conditions Necessary for Flashover 354 9.2.2 Fuel and Ventilation Conditions Necessary for Flashover 364 9.2.3 Factors Affecting Time to Flashover 378 9.2.4 Factors Affecting Fire Growth 382 Problems 385 10 The Post-flashover Compartment Fire 387 10.1 Regimes of Burning 387 10.2 Fully Developed Fire Behaviour 396 10.3 Temperatures Achieved in Fully Developed Fires 404 10.3.1 Experimental Study of Fully Developed Fires in Single Compartments 404 10.3.2 Mathematical Models for Compartment Fire Temperatures 406 10.3.3 Fires in Large Compartments 418 10.4 Fire Resistance and Fire Severity 420 10.5 Methods of Calculating Fire Resistance 427 10.6 Projection of Flames from Burning Compartments 435 10.7 Spread of Fire from a Compartment 437 Problems 439 11 Smoke: Its Formation, Composition and Movement 441 11.1 Formation and Measurement of Smoke 443 11.1.1 Production of Smoke Particles 443 11.1.2 Measurement of Particulate Smoke 447 11.1.3 Methods of Test for Smoke Production Potential 450 11.1.4 The Toxicity of Smoke 455 11.2 Smoke Movement 459 11.2.1 Forces Responsible for Smoke Movement 459 11.2.2 Rate of Smoke Production in Fires 465 11.3 Smoke Control Systems 469 11.3.1 Smoke Control in Large Spaces 470 11.3.2 Smoke Control in Shopping Centres 471 11.3.3 Smoke Control on Protected Escape Routes 473 References 475 Answers to Selected Problems 527 Author Index 531 Subject Index 545

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