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A multiscale model of wood pyrolysis in fire to study the roles of chemistry and heat transfer at the mesoscale
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1-s2.0-S0010218020300924-main.pdf | Published version | 1.87 MB | Adobe PDF | View/Open |
Title: | A multiscale model of wood pyrolysis in fire to study the roles of chemistry and heat transfer at the mesoscale |
Authors: | Richter, F Rein, G |
Item Type: | Journal Article |
Abstract: | Pyrolysis is a key process in all stages of wood burning from ignition to extinction. Understanding each stage is crucial to tackle wildfires and assess the fire safety of timber buildings. A model of appropriate complexity of wood pyrolysis and oxidation is missing, which limits the understanding of fires fuelled by wood. Progress towards this aim has been slow in recent years, as the role of chemical kinetics is still debated. Three predominant theories hypothesis that chemistry is either infinitely fast (de Ris), a function of char depth (Atreya), or a function of heat flux (Suuberg). This paper proposes a novel multi-scale model of wood pyrolysis and oxidation for predicting the charring of timber. The chemical kinetics sub-model was previously validated at the microscale (mg-samples). We favourably compare the complete model against a large range of mesoscale experiments (g-samples) found in the literature of different moisture contents (0–30%), heat fluxes (0–60 kW/m2), oxygen concentrations (0–21%), grain directions (parallel/perpendicular), and combinations thereof. The model was then used to calculate the transient Damköhler number of wood at different depths and heat fluxes. This analysis showed that chemistry and heat transfer are both important at all heat fluxes and stages of burning relevant to fire, which unifies the three theories by Suuberg, Atreya, and de Ris. We argue that the model is of currently appropriate complexity to predict the charring of timber. These findings improve our understanding of wood pyrolysis and the modelling of timber burning across scales. |
Issue Date: | 1-Jun-2020 |
Date of Acceptance: | 26-Feb-2020 |
URI: | http://hdl.handle.net/10044/1/81736 |
DOI: | 10.1016/j.combustflame.2020.02.029 |
ISSN: | 0010-2180 |
Publisher: | Elsevier |
Start Page: | 316 |
End Page: | 325 |
Journal / Book Title: | Combustion and Flame |
Volume: | 216 |
Copyright Statement: | ©2020 The Authors. Published by Elsevier Inc. on behalf of The Combustion Institute. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). |
Sponsor/Funder: | EPSRC Engineering & Physical Science Research Council (EPSRC) |
Funder's Grant Number: | EP/M506345/1 EPSRC Doctoral prize 2019/20 |
Keywords: | Science & Technology Physical Sciences Technology Thermodynamics Energy & Fuels Engineering, Multidisciplinary Engineering, Chemical Engineering, Mechanical Engineering Pyrolysis Wood Multiscale Modelling Smouldering Timber SMOLDERING COMBUSTION MASS-TRANSFER BIOMASS IGNITION GASIFICATION KINETICS OXYGEN SCALES Science & Technology Physical Sciences Technology Thermodynamics Energy & Fuels Engineering, Multidisciplinary Engineering, Chemical Engineering, Mechanical Engineering Pyrolysis Wood Multiscale Modelling Smouldering Timber SMOLDERING COMBUSTION MASS-TRANSFER BIOMASS IGNITION GASIFICATION KINETICS OXYGEN SCALES Energy 0902 Automotive Engineering 0904 Chemical Engineering 0913 Mechanical Engineering |
Publication Status: | Published |
Open Access location: | https://doi.org/10.1016/j.combustflame.2020.02.029 |
Online Publication Date: | 2020-04-08 |
Appears in Collections: | Mechanical Engineering Grantham Institute for Climate Change |
This item is licensed under a Creative Commons License