Heat flux profile upon building facade with side walls due to window ejected fire plume: An experimental investigation and global correlation

This paper investigates the heat flux profile upon building facade with side wall constraints due to ejected fire plumes from a window of an under-ventilated compartment fire. A reduced-scale model (1:8), consisting of a cubic fire compartment with a facade wall attached and two side walls located symmetrically at both sides of the window is developed. The window dimensions and the side wall distances are changed in experiments, representing different ventilations and constraints on fire plume entrainment. Five heat flux gauges are employed in measurement of vertical heat flux profile upon the facade wall. Results show that with the decrease in separation distance of side walls, the heat flux increases for small windows where dimensionless excess heat release rate Q̇ex⁎≥1.3 (“(half) axisymmetric fire” regime), meanwhile shows weak dependency on side wall separation distance for large windows where Q̇ex⁎<1.3 (“wall fire” regime). A new global formula is proposed to characterize the vertical profile of heat flux based on Lee's model without side walls as further modified by a parameter K in relation to the separation distance of side walls and characteristic length scales of the window. Experimental data for different windows and side wall separation distances are well collapsed by the proposed formula.