Cooling a Thermal Manikin After a Fire

Not to be persnickety, but there is a difference between mannequins, life size model for displaying or tailoring clothes, and manikins, an anatomical model used for testing and teaching, usually with movable joints. (The enunciation is exactly the same though).  A lab designed a test for thermal protective clothing.  They had a manikin that was 6 feet in height and had 120 copper slug sensors located all over its body. The sensors would record the temperature gradients on the surface of the manikin, representing skin exposure to heat.  They would dress their manikin with thermal protective clothing from head to toe and expose it to intense fires at various temperatures and exposure times.  After each test was completed, they would record the results and cool the manikin to 26 deg. C before they started the next fire test.  These results were used for safety limits to protect wearers from second and third degree burns, very important in keeping firefighters safe.

Fire Suit under test
Fire Suit under test

In their application, they were looking to cool the sensors on the manikin as quickly as they can to increase test cycle rates. Initially they used a “cool down” area fitted with fans to blow air across the manikin.  The problem was that it took too long to cool to the 26 deg. C mark required in their testing protocol.  They decided to manually use an air gun to blow compressed air across the sensors to increase cooling.  This did reduce the cycle time, but because of the force created by the air gun, some sensors would shift and be out of calibration.  This was a huge concern for the test lab.

The design of the copper slug sensor has a small piece of copper set inside a silicone holder. To isolate the copper metal, there are small ruby spheres between the holder and copper slug.  This creates an air gap around the copper slug to help increase sensitivity to temperature changes.  A thermocouple is attached to the back side of the copper slug for analytical measurements.

Adjustable Spot Cooler
Adjustable Spot Cooler

After they discussed their application with me, I suggested the model 3725 Adjustable Spot Cooler. This base unit comes without a magnetic base and hose kit, which makes it lighter in weight. The customer could easily attach it directly to their compressed air line, replacing the air gun that was damaging the sensors.  The Adjustable Spot Cooler incorporates the Vortex Tube which makes standard compressed air into cold air.  With a turn of a knob, they could control the temperature and the velocity of the cold air.  This feature was key in determining just the right amount of force to not affect the calibration of the sensors.  An added benefit of the Adjustable Spot Cooler is if you reduce the amount of outlet cold air, the temperature will decrease even more.  This feature allowed the customer to reach their target much more quickly and without damaging the sensors.

If you need to cool things down in your application, you can contact an Application Engineer at EXAIR. We have many different styles and combinations of Vortex Tubes and Spot Coolers to give you the right form of cooling, whether it is a mannequin or a manikin.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

 

DDI-2007-Burning Man by Interpretive Arson.  Common License.

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