Friday, February 19, 2016

Vortex Tubes – Cooling without moving parts

The focus of my current research is looking at the possibility of using a vortex tube for efficient cooling of low temperature hydrogen. Our first commercial vortex tubes [1] to be used in testing arrived the other day, so I wanted to post a little demo of how this tech works to separate hot and cold gasses from a pressurized input stream.

First, let me give a brief introduction to what happens inside a vortex tube. As you can see from the image above, [2] a vortex tube does not need any mechanical apparatus to create hot and cold streams from the input stream. High pressure gas is fed tangentially into the initial section of the tube, generating a vortex. In more efficient commercial applications, this section of the tube has engineered geometry to enhance the creation of a vortex, and in simpler designs there is just a tube. The high velocity vortex causes separation in the flow, with higher energy particles on the outside slowly transitioning to the lowest energy particles on the inside of the flow. At the end of the tube, a stopper allows the outside flow to exit the tube, while forcing the cooler center of the flow back out the other end of the tube. This stopper is usually adjustable to allow for optimization of flow rate and temperature of each exit of the vortex tube.
And now, some pictures of my tube [1] in action! As you can see below, the cold exit reached -28.3 °C and the hot exit reached 40.5 °C. This 68.8 °C temperature difference was driven by about a 90 psi pressure drop.
IMG_0671 IMG_0673
1. The Vortex tube we are testing is a 106-2-H vortex tube from ITW Vortec
2. This image is public domain, from Wikimedia Commons

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