The Ignition of low-exothermicity solids by local heating
Shah, A., Brindley, J., McIntosh, A., Griffiths, J. and Pourkashanian, M. (2004) The Ignition of low-exothermicity solids by local heating. Process Safety and Environmental Protection; Official Journal of the European Federation of Chemical Engineering: Part B, 82, (B2 Special Issu), 156-169. (doi: 10.1205/095758204322972799).
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Description/Abstract
In this paper we bring together a number of recent studies associated with the burning of low-exothermicity porous materials that are inadvertently, or otherwise, exposed to a maintained heat source (hotspot). Additionally, we provide some new results in the form of dimensionless ignition criteria, which allow us to generalize previous results to a broader class of materials and to larger sample sizes. It is shown that systems of the type described can be represented by a hierarchy of mathematical models, depending on whether oxygen is in limited supply, is not required (as in the case of thermal decomposition), and/or a significant volume of gaseous products is present. We summarize the behaviour of systems in which gas motion through the solid pores has a negligible effect, including cases where the burning is dependent on a limited supply of oxygen. The effects of geometry and initial-boundary conditions are discussed. Finally, for reactions involving gaseous products, we present numerical solutions to a system of equations that incorporates the gas motion through the solid pores by employing Darcy's law. In comparison with the previous cases, it is demonstrated that ignition of low-exothermicity materials is more difficult to achieve (a larger hotspot heat-flux is required), essentially because of transportation of heat by advection towards the unburnt solid, and, consequently, increased reactant depletion. Furthermore, ignition will always take place away from the hot-spot surface; this is in complete contrast to highly exothermic materials, in which reactant depletion is negligible during the early stages of ignition, and in which ignition occurs at the hotspot boundary.
| Item Type: | Article |
|---|---|
| ISSNs: | 0957-5820 (print) |
| Subjects: | Q Science > Q Science (General) |
| Divisions: | University Structure - Pre August 2011 > School of Engineering Sciences > Thermofluids and Superconductivity |
| Item ID: | 44777 |
| Date Deposited: | 16 Mar 2007 |
| Last Modified: | 01 Jun 2011 09:17 |
| Contributors: | Shah, A. (Author) Brindley, J. (Author) McIntosh, A. (Author) Griffiths, J. (Author) Pourkashanian, M. (Author) |
| Date: | March 2004 |
| Status: | Published |
| Contact Email Address: | A.Shah@soton.ac.uk |
| URI: | http://eprints.soton.ac.uk/id/eprint/44777 |
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