A porous media model for sprinkler wetting: Ceramic fiberboard validation

摘要

A one-dimensional porous media model has been developed to investigate water based fire suppression. The model is for heat and mass transfer in porous materials subjected to external water sprays and radiant heating. In the model, heat transfer inside the material occurs by conduction, convection, and phase change. Mass transfer occurs by gas phase diffusion and convection in the liquid and gas phases. Convective mass fluxes are driven by pressure gradients according to Dairy's Law. Boundary conditions that are appropriate for a range of cases are presented. Experiments were conducted to validate the model and investigate two scenarios relevant to water based suppression: spray wetting and radiant heating. Both of these scenarios represent a novel application of a porous media model. Ceramic fiberboard samples were used as a test material. For the wetting tests, the model is shown to be able to reasonably predict the rate of water absorption into the samples. Radiant heating tests were conducted in the cone calorimeter with pre-wetted samples. For the heating tests, the model is shown to reasonably predict the drying behavior that would directly precede an ignition event.