Experimental investigation on drag effect of sprinkler spray to adjacent horizontal natural smoke venting

Discharge rate of a horizontal adjacent smoke vent under sprinkler spray is experimentally investigated. Temperature of smoke layer and velocity of smoke venting were measured, under different sprinkler operating pressures and smoke venting areas. CO concentration at the smoke vent center and velocity of vent flow with fresh air outside were recorded in tests under different smoke venting conditions. Experimental results have shown that efficiency of smoke venting is controlled by a combination of smoke buoyancy and drag force of sprinkler spray. Only when buoyancy is greater than drag force the smoke could be extracted by venting. Velocity of smoke venting has shown to decrease as the operating pressure increases. Smoke venting logging, which represents the failure of smoke venting, was experimentally found from certain operating pressure called initial logging pressure. The CO concentration was found to increase after sprinkler was operated as the smoke is constrained in the spray region with horizontal momentum decreased. Negative pressure difference is caused at the vent when there is smoke venting logging, which might practically bring the exterior fresh air into the fire building. Additionally, experiments results have shown that the venting area has little influence on smoke flow under smoke venting logging.