Application of a simple enthalpy-based pyrolysis model in numerical simulations of pyrolysis of charring materials

• Published in: Fire and materials 2010-01, Vol.34 (1), p.39-54
• Main Authors: Wasan, S. R., Rauwoens, P., Vierendeels, J., Merci, B.
• Format: Article
• Language: English
• Subjects: Applied sciences; Building technical equipments; Buildings; Buildings. Public works; charring materials; Computation methods. Tables. Charts; enthalpy model; Exact sciences and technology; Fire behavior of materials and structures; Fire protection; pyrolysis; Structural analysis. Stresses
• ISSN: 0308-0501; 1099-1018
• DOI: 10.1002/fam.1010

A new, simple pyrolysis model for charring materials is applied to several numerical and experimental test cases with variable externally imposed heat fluxes. The model is based on enthalpy. A piecewise linear temperature field representation is adopted, in combination with an estimate for the pyrolysis front position. Chemical kinetics are not accounted for: the pyrolysis process takes place in an infinitely thin front, at the ‘pyrolysis temperature’. The evolution in time of pyrolysis gases mass flow rates and surface temperatures is discussed. The presented model is able to reproduce numerical reference results, which were obtained with the more complex moving mesh model. It performs better than the integral model. We illustrate good agreement with numerical reference results for variable thickness and boundary conditions. This reveals that the model provides good results for the entire range of thermally thin and thermally thick materials. It also shows that possible interruption of the pyrolysis process, due to excessive heat losses, is automatically predicted with the present approach. Finally, an experimental test case is considered. Copyright © 2009 John Wiley & Sons, Ltd.