Gas thermodynamic conditions of cold air entrainment by natural smoke exhaust system in case of compartment fire

Conditions of occurrence of abnormal operation of natural smoke exhaust system are analyzed when cold air is entrained into smoke exhaust windows preventing extraction of smoked heated gas layer beneath a ceiling (also known as plugholing). Analytical equation is derived for prediction of critical average volumetric temperature of gas layer beneath a ceiling when plugholing starts with consideration for the height of smoke exhaust window. This equation was compared with published experimental data and with numerical experiments using 3D field model of fire gas thermodynamics. It was found that the height of smoke exhaust window exerts significant influence on occurrence of plugholing and on maximum bulk flow rate of combustion products extracted from compartment via the window. © 2020, Institute of Advanced Scientific Research, Inc.. All rights reserved.