Fire dynamics in open compartments
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abstract
Fire events in car parks have been a major problem for buildings,vehicles and humans.The main cause for fire propagation are the combustible materials of the vehicles. Ceiling jet flow occurs when the fire plume impinges the ceiling and develops in the radial direction.
Both temperature and velocity prediction sare decisive for sprinklers positioning,fire alarms positions,detectors (heat,smoke) positions and activation times and back-layering predictions.
With the aim to increase fire safety in open compartments, such as open car parks, some correlative models were used to test the ability to recover both dynamics and thermal characteristics of a ceiling-jet flow. The heat flow, coming from a burning vehicle, occurs when the fire plume impinges the ceiling and develops in the radial direction of the fire axis. Both temperature and velocity predictions are decisive for sprinklers positioning, fire alarms positions, detectors (heat, smoke) position and activation times and back-layering predictions. This investigation deals with a parametric analysis using different fire events (class of the vehicle) and two fire scenarios. Some correlative formulations were used: Alpert, Cooper, Heskestad & Delichatsios and Motevalli & Marks. An advance calculation method (CFAST) based on a two-zone model formulation was used to compare the results, as well as the CFD software ANSYS Fluent, based on the finite volume method. A total of 16 simulation results were obtained taking into consideration 2 different heights for the compartment (H=3m and H=5m), 4 different car classes (fire events), 6 radial positions (R) and two software (CFAST and ANSYS Fluent). The correlative model from Motevalli & Marks overestimates the dynamic characteristics in small compartments. The two zone model overestimates the maximum temperature in the biggest compartment and the CFD results for temperature and velocity are always higher than the other calculation methods.
With the aim to increase fíre safety in open compartments, such as open car parks, some correlative models were used to test the ability to recover both dynamics and thermal characteristics ofa ceiling-jet flow. The flow occurs when the fire plume impinges the ceiling and develops in the radial direction ofthe fire axis. Both temperature and velocíty predictions decisive for sprinklers positioning, fire alarms positions, detectors (heat, smoke) position and activation times and back-layering predictions. This investigation deals with a parametric
analysis using different fire events, fíre scenarios and correlative formulations (Alpert, Cooper, Heskestad and Delichatsios, Motevalli and Marks). An advance calculation method (CFAST) based on a two zone model fonnulation was used to compare the results.
