A mathematical model on drag effect of sprinkler spray to adjacent horizontal smoke venting

A mathematical model has been developed to investigate the effect of sprinkler spray on adjacent horizontal smoke venting and in particular the drag component from water droplets. The pressure difference at a roof vent and the volumetric flow of smoke venting are determined by considering the interaction between the drag force of the sprinkler spray and the buoyancy of the smoke layer in the spray region. Smoke venting may become progressively more inefficient as the sprinkler operating pressure increases due to the cooling and drag effect of the sprinkler spray. Full scale experiments were carried out to validate the model. The results show that the prediction of decrease in volumetric flow with the increase in sprinkler operating pressure determined by the mathematical model agrees well with the measured values. Experimental results with different smoke venting areas show that the area has little influence on smoke flow once the sprinkler pressure causes a loss in smoke flow efficiency since the vents have already begun to lose their function