Condensation-enhanced ignition of damp combustible material
The effect of dampness on the ignition characteristics of combustible material is considered by using a three-equation system in temperature, water liquid and water vapour. We adopt a well-stirred approach to both the energy equation and the species equations. Earlier work has already established that there is a fast time-scale natural to the problem (characterised by heat transfer). On this fast time-scale there is the possibility of a quasi-stationary unsteady state due to latent heat effects, even though in the long term, loss of vapour will lead (eventually) to a final decay to a single stationary state. This paper shows that analytically one can derive an approximate form for the critical ambient vapour content required to make the damp combustible material undergo large temperature excursions, and for all practical purposes undergo thermal runaway.
ignition dampness latent heat thermal runaway condensation