Leaks and Why They Matter

Leaks can be discussed quite frequently around industrial environments. These can be refrigerant leaks, water leaks, gas leaks, even information leaks. All of these leaks have one thing in common, they all cost the company money in the end. I often think about several classic cartoons when I hear about leaks being fixed as they are found. They can become a little overwhelming like the “Squirrel” from the movie Ice Age 2.

1 – Ice Age 2 – Scrat – Mission Impossible

When it comes down to it, not many leaks create good results, that is why I want to take a second and educate on the costs your facility may be seeing from compressed air leaks. The leaks within an industrial environment can often account for up to 30% of the total compressed air generated.

So let’s take a look at that, the cost of compressed air is derived from the kWh cost the facility pays to the utility company. Here in the Midwest the average cost is around $0.08 / kWh. The equation to convert this to cost per cubic foot of compressed air is shown below. This formula assumes that the compressor generates four standard cubic feet of compressed air per horsepower of compressor. Again this is an industry acceptable assumption.

The size of a leak will determine how much compressed air is wasted, most of these leaks are not even to the audible range for the human ear which leads them to be undetected for long periods of time. A leak that is equivalent to a 1/16″ diameter orifice can result in an annual loss of more than $836.50 USD. While the scale of this number when compared to the annual revenue of a company may be small, the fact remains that this single leak would more than likely not be the only one. This isn’t the only way leaks will cost money though.

Leaks can also generate false demand which can result in pressure drops on a system. When the pressure on a production line drops this could result in unscheduled shutdowns. Often, when a pressure drop is observed the quick answer is to increase the header pressure which causes even more energy to be utilized and even more compressed air will be pushed out of these leaks. That increase in system pressure comes at a price as well. When increasing a system pressure by 2 psi the compressor will consume an additional percent of total input power. This again will hit the bottom line and result in lower efficiency of operation for the facility.

If you hear that distinct hiss of compressed air leaks when you are walking through your facility, or even if you don’t hear the his and you know that a leak detection action plan is not being practiced and want to find out the best ways to get one in place, contact us. We are always willing to help you determine how to lower the leaks in your facility as well as reduce the system pressure required to keep your lines up and running by implementing engineered solutions at the point of use.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

1 – Ice Age 2 – Mission Impossible Scrat – retrieve from YouTube – https://www.youtube.com/watch?v=S-HniegbnFs

 

The Theory of the Vortex Tube

There are many theories regarding the dynamics of a vortex tube and how it works. Many a graduate student has studied them as part of their research requirements.

VT_air2

The Vortex Tube was invented by accident in 1928, by George Ranque, a French physics student. He was performing experiments on on a vortex-type pump that he had developed and noticed that warm air exhausted from one end and cold air from the other! Ranque quickly stopped work on the pump, and started a company to take advantage of the commercial possibilities for this odd little device that produced both hot and cold air, using only compressed air, with no moving parts. The company was not successful, and the vortex tube was forgotten until 1945 when Rudolph Hilsch, a German physicist, published a widely read paper on the device.

A vortex tube uses compressed air as a power source, has no moving parts, and produces hot air from one end and cold air from the other. The volume and temperature of the two air streams is adjustable with a valve built into the hot air exhaust.  Temperatures as low as -50°F (-46°C) and as high as 260°F (127°C) are possible.

Here is one widely accepted explanation of the physics and the phenomenon of the vortex tube.VT

Compressed air is supplied to vortex tube and passes through nozzles that are tangent to to an internal counterbore (1). As the air passes through it is set into a spiraling vortex motion (2) at up to 1,000,000 rpm. The spinning stream of air flows down the hot tube in the form of a spinning shell, like a tornado (in red). The control valve (4) at the end allows some of the warmed air to escape (6) and what does not escape reverses direction and heads back down the tube as a second vortex (in blue) inside of the low pressure area of the larger warm air vortex. The inner vortex loses heat and exits the through the other end of as cold air (5).

It is thought that that both the hot and cold air streams rotate in the same direction at the same angular velocity, even though they are travelling in opposite directions. A particle of air in the inner stream completes one rotation in the same amount of time that an air particle in the outer stream. The principle of conservation of angular momentum would say that the rotational speed of the inner inner vortex should increase because the angular momentum of a rotating particle (L) is equal to the radius of rotation (r) times its mass (m) times its velocity (v).  L = r•m•v.  When an air particle moves from the outer stream to the inner stream, both its radius (r) and velocity (v) decrease, resulting in a lower angular momentum. To maintain an energy balance for the system, the energy that is lost from the inner stream is taken in by the outer stream as heat. Therefore, the outer vortex becomes warm and the inner vortex is cooled.

At EXAIR, we have harnessed the cooling power of the vortex tube, and it can be found and utilized in such products as Spot Coolers, Cabinet Coolers, and the Vortex Tube themselves.

Harnessing the cooling power of the vortex tube 

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

Brian Bergmann
Application Engineer
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