Wheel speed sensors are part of the feedback loop for a vehicle’s computer system to monitor the condition of the various systems and react accordingly. The wheel speed sensors monitor wheel speed at all four wheels and compares them to one another to activate traction control or the anti-locking braking system depending on the conditions of the road and traffic situation.
One of our customers recently called in and was looking for a way to keep these sensors cool prior to the manufacturing assembly process. Cooled sensors made for much easier installation into the wheel hub assembly.
The customer has a small cooling chamber of about 2 cubic feet and they wanted to keep it at 0°C. The external environment has a maximum, summer-time temperature of about 40°C. There is not any heat being produced by the sensors themselves, so we only have to worry about the external environment temperature.
The customer did not want to go the route of making a major purchase of a pre-made cooling chamber. Their preference was to make their own cooling chamber, using what they already had in place and using a Vortex Tube to provide the cooling. Running the necessary calculation, the application required approximately 280 Btu/hr. to maintain the target temperature.
In order to generate 280 Btu/hr. with 0°C as the target temperature, the net output flow of the Vortex Tube needs to be at approximately -10 to -15 degrees C. It is then just a matter of determining how much volume of cold air flow that is necessary to accomplish the goal. For this application, a 30 SCFM vortex tube set at 50% cold fraction and operating at 100PSIG would get the application to where it needs to be in terms of providing sufficient cooling power.
I did throw one curve to the customer though. Instead of suggesting a plain Vortex Tube, I suggested our model 3730 (Adjustable Spot Cooler). The reasons for suggesting the Adjustable Spot Cooler are that is it much more user friendly as it has heat shielding and sound muffling already built into its design. Also, it has complete flexibility to change the temperature of the output flow to be in the range that we needed for the application.
They took the advice and went with my suggestion. They now have a refrigerated chamber at the assembly area in order to chill down the sensors and problem is solved.
If you have a similar application where you need to create a small, chilled space on the manufacturing floor, consider building your own unit with a Vortex Tube or even Adjustable Spot Cooler as your cooling source.
Neal Raker, Application Engineer
nealraker@exair.com
