Experimental study and analysis of radiation heat fluxes received by a floor beneath an inclined ceiling

This study experimentally investigates the radiation heat flux distribution received on the floor due to fire plume impinging upon an inclined ceiling, which has not been quantified previously. The radiation heat fluxes were measured on the floor for 160 experimental conditions, involving various fire source heat release rates, source-ceiling heights, angles of ceiling inclination and dimensions (aspect ratios) of the rectangular sources. The main findings include that the declining rate of the radiation heat flux along with distance received by the downstream floor decreases, while that received by the upstream floor increases, with the increasing of ceiling inclination angle. The radiation heat flux received by the floor is higher as the ceiling inclination angle is smaller for the downstream side, while it is lower as the ceiling inclination angle is smaller for the upstream side. Both of these variations can be explained by change of the flow distribution as well as flame length due to combustion and heat released in the two directions beneath the inclined ceiling. Further, a model with various fire source heat release rates, source-ceiling height, and ceiling inclination angles is proposed, to globally describe the radiation heat flux received by both the upstream and downstream floors.