Modelling pyrolysis of charring materials: determining flame heat flux using bench-scale experiments of medium density fibreboard (MDF)

Published Date
17 February 2015, Vol.123:39–48, doi:10.1016/j.ces.2014.10.043

Author 

• Kaiyuan Li ^a,,1,
• Dennis S.W. Pau ^b
• Jinhui Wang ^c
• Jie Ji ^a,,1,

• aState Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230027, China
• bCosgroves Limited, PO Box 842, Christchurch 8140, New Zealand
• cCollege of Ocean Science and Engineering, Shanghai Maritime University, Shanghai 201306, China

Received 3 June 2014. Revised 15 October 2014. Accepted 27 October 2014. Available online 4 November 2014. 

Highlights

• Mass loss rate and total incident heat flux has linear correlation.
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  We measured the total incident heat flux caused by flame and cone.
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  The extra heat flux led by flame is found to be increasing with heat release rate.

Abstract 

Medium density fibreboard is a homogenous wood product which is a suitable candidate for validating the pyrolysis model of charring materials. For comparison between model and experiment, this article presents the burning behaviour of MDF under cone calorimeter with different experimental conditions. The total incident heat flux, as a significant boundary condition for pyrolysis modelling, is specifically studied both experimentally and theoretically. The experimental conditions were found to have no significant impact on the ignition phase however the sample thickness would lead to different burning behaviours. The total incident heat flux led by cone and flame at sample surface was experimentally measured and the experimental results were evaluated using non-flaming experiments with inert gas. An analytical model based on classical ignition theory is developed to address the mechanism of mass loss caused by incident heat flux, involving the effects of char layer and back boundary. The model shows that the mass loss rate correlates linearly with the total incident heat flux for a specific char layer thickness and back boundary condition. The model was validated for the non-flaming and flaming experiments to further justify the reliability of heat flux measurements. An empirical equation describing the flame heat flux is proposed.

Keywords

Charring material

Wood

Pyrolysis

Cone calorimeter

Flame

Incident heat flux

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  Corresponding authors. Tel./fax: +86 551 63606431.

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