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Colt International and the Building Research Establishment (BRE) have carried out a series of tests
in a simulated car park that successfully demonstrated the effectiveness of smoke control using
impulse fans. They also found that the conditions during the tests were very similar to those
predicted by the computational fluid dynamics (CFD) modelling approach as used by Colt for system
design.
A team of engineers from Colt and BRE carried out the tests with the aim of demonstrating how an
impulse ventilation system can be used to control the flow of smoke within a car park, keeping large
areas effectively smoke free. This allows the fire service to see and approach close to the fire in
good conditions, allowing effective fire fighting. Systems of this type can be offered as an
alternative to a sprinkler system, when sprinklers are required. A further objective of the tests
was to prove the effectiveness of CFD in predicting the spread of smoke in a car park fitted with
impulse fans.
The test rig, set up in a simulated car park at a Middlesborough test facility, was 35m x 30m x 3m.
The two opposing ends of the rig were open, but protected as far as possible from wind effects,
nd ventilation was provided by two Colt Cyclone 100 fans running at 80% full speed (64% thrust).
These were located to limit the smoke to one side of the test rig, keeping the other side
substantially free of smoke. A car shell containing a tray of diesel fuel was ignited to create a
1MW fire size.
Prior to the test, a CFD model was constructed and run to predict the heat and smoke flows through
the rig. The modelling followed normal Colt practice using the FDS (Fire Dynamics Simulator) CFD
model from NIST (the National Institute of Science and Technology, in America).
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The results of the tests clearly indicated that impulse systems are capable of controlling the
spread of smoke from a car fire and keeping significant areas of a car park effectively smoke free.
BRE confirmed that: 'The smoke movement during the fire with the impulse fans running was as
predicted by the CFD modelling Colt had carried out before the tests.'
Paul Compton, smoke control executive at Colt International, was pleased with the outcome: 'Impulse
fans have been shown to provide a system capable of limiting smoke flows to a predefined area,
allowing their use to assist fire fighting or to protect means of escape. The similarity of the
test and CFD results means that approving authorities can now confidently accept validated CFD
analysis as proof of performance for an impulse system, without the need for hot smoke tests on
the completed system.'
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