CFD simulation of the BS 8414 test for cladding applications

A numerical BS 8414 model has been developed using surface ignition temperature, cone calorimeter data and a heat release rate curve from a wood crib, for simulating cladding fires. The model predicts burning rates of combustible materials, temperature profiles, burn-through of materials, burning locations and activation states of functional intumescent cavity barriers. The model is validated using seven DCLG BS 8414 tests, by correctly reproducing pass/fail results and failure mechanisms; producing comparable fire flames and reasonable agreement of temperature profiles, which are essential to the pass/fail criteria; and producing reasonable burning/burnt locations for the cladding system. The model has also been used to investigate factors affecting fire spread including cavity size, state of fire barriers, reduction of core material mass by for example dripping and the consistency of the HRR behaviour of the wood crib fire source. The limitations of the BS 8414 model are discussed including the uncertainty of surface ignition temperature; the approach to the activation of intumescent cavity barriers; the uncertainties in HRRs of the wood crib fire and the material properties. To improve the repeatability of the BS 8414 test, it is suggested that a gas burner is used rather than a wood crib fire.