Abstract
The article explores a fire plume mitigation strategy within a horizontally vented enclosure, potentially applicable in nuclear plants, ship cabins, and building ventilation systems. The investigation consists of a compartment with dual horizontal ceiling vents operating under both forced and natural ventilation conditions, featuring a centrally located fire source. The study models the turbulent three-dimensional flow and heat transfer characteristics using a Large Eddy Simulation model. Parametric investigations vary the fire size, location, and forced ventilation velocity through the horizontal vent. The findings reveal various flow regimes, from pure natural convection to a mixed convection regime of bidirectional flow phenomena. Results show that temperature reduction of 83% in the overall ceiling gas temperature for the case of 3 m/s ventilation velocity. It is also observed that with rise in the ventilation velocity, the Froude number increases and for higher heat release rates, the plume temperature increases and hence the Froude number is decreased by 42%. The fire sources mounted adjacent to the wall and beneath the naturally vented horizontal vent demonstrate the maximum fire plume velocity of 2 m/s. The heat transfer analysis suggests that the average temperature ratio for the fire source of 0.1 m diameter case is dropped by 30% in the case of maximum ventilation velocity of 3 m/s and whereas for the case of 0.141 m diameter fire source, the 40% drop in the average temperature ratio is observed in this study. The proposed correlation, which links the dimensionless mass flow rate through the vent with the Froude number, provides insights into hybrid ventilation phenomena. This study enhances the understanding of airflow and safety design in buildings, particularly concerning smoke control.