High Temperature Vortex Tube for Sensor Cooling

Last year I worked with a power company that was having issues with Position Feedback Sensors overheating causing erroneous readings and early failures.  The sensors were located above a steam turbine, and the ambient temperatures reached 128°F with spikes to 140-150°F.  The customer had called in looking for a way to keep the sensors cool, using minimal compressed air, and in a robust package.  After reviewing the details, we recommended the High Temperature Vortex Tube, model HT3210.  While using just 10 SCFM of 100 PSIG compressed air, the HT3210 provides 8 SCFM of cold air at a temperature drop of 54°F from the supply air temperature.  Bathing the sensor with this cool air keeps prevents it from heating up and has eliminated the bad readings and prevented the early failures.

The customer recently implemented the same fix for another set of sensors.

Plant Photo
Power Generation Process, with (3) Position Feedback Sensors
Sensor
Position Feedback Sensor

The High Temperature Vortex Tube is a special Vortex Tube offering from EXAIR that utilizes a brass generator and hi-temp seal for use in ambient temperatures up to 200°F.  Simply supply clean, dry compressed air, and get cold air starting at 50-54°F lower than the supply air temperature.  With sizes ranging from 2 to 150 SCFM, there is a Vortex Tube that will meet most applications.

Vortex tube
High Temperature Vortex Tube

If you have questions about the Vortex Tubes, or would like to talk about any of the EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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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.