Response of a Thermoacoustic Flashover Detector to Thermal Radiation

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The thermoacoustic flashover detector is a device designed to be mounted on the helmet of a firefighter which creates a loud whistle when exposed to conditions that are consistent with flashover in order to provide firefighters with a warning and time to escape. The detector is based off a previous device designed at the University of Maryland which was operated using an electric band heater. This device was optimized by slightly altering the stack design and by the addition of approximately 0.3 mL of water to the stack, yielding an activation temperature of 125°C. Once the activation temperature was sufficiently lowered, the device was outfitted with copper fins which were designed to collect radiant heat from a propane-burning radiant panel and transfer it to the detector. When using four of these copper fins and exposed to a radiant heat flux of approximately 25 kW/m2, the detector activated around 125°C after 7 minutes. This was the first known activation of a thermoacoustic device to unconcentrated thermal radiation. The response time of the device was lowered after two more fins were added to the design. Once the detector was shown to work using radiant heat, it was tested at the Maryland Fire and Rescue Institute (MFRI) at the University of Maryland using full scale fires in order to replicate the conditions in which it would be expected to operate. While the detector did not activate during the full scale tests, the radiant panel tests proved that the design is feasible and that some slight design changes are needed in order for the detector to operate in a real fire environment.