Tag: spot cooling

Which Vortex Tube Do I Need?

Published on by Dave WoernerLeave a comment

Last week, I wrote a brief introduction to vortex tubes, titled “One Item Generates ¼ Ton of Refrigeration and Fits in the Palm of your Hand.” In it I introduced the Vortex Tube and the other products made from Vortex Tubes: Cabinet Coolers, Cold Guns, Adjustable Spot Cooler and Mini Coolers. I also introduced the idea of a cold fraction.  Today, I want to talk about specific Vortex Tube models.

The flow from the cold side of the Vortex Tubeis characterized in two different ways. First, we characterize the air by ΔT (temperature drop) from the starting compressed air temperature. With a supply pressure of 100 PSIG, the drop in temperature can range from 54° to 123° Fahrenheit. Second, we characterize the flow of air in Standard Cubic Feet per Minute. The different models of vortex tube are design to provide a range of flows and temperature.

Vortex Tube Specification
Vortex Tube Specification Chart

When facing this list you have numerous choices that can be daunting. My priorities for selecting a Vortex Tube for a customer are twofold. First, you need the Vortex Tube that will work in your application. Second, I want to choose the model with the least amount of compressed air in order to solve their problem with the least amount of air possible. The smallest Vortex Tube is a model 3202. It also utilizes the least amount of compressed air, 2 SCFM. At 100 PSIG and an 80 percent cold fraction, it will produce a cold flow of 1.6 SCFM at 54° F  below your compressed air temperature. If your compressed air temperature is starting at 70° F, your cold temperature will 16° F. All of the Vortex Tubes will be able produce this same temperature drop, but depending on which Vortex Tube you use will determine the volume of flow produced at that temperature.

1.6 SCFM of flow 54° F below compressed air temperature will take 135 BTU/HR away from a small 100°F box, which is enough energy to cool a needle, a small sensor, or a tiny camera, but what if you have a bigger area you need to cool. Then you need to use a Vortex Tube that will produce more flow. The 3202, 3204, and 3208 will all produce air at the same temperature, but the 3204 and 3208 will produce more volume of cold air.  With the same parameters as above (100 PSIG of inlet pressure and 80 percent cold fraction) the 3204 will produce 3.2 SCFM of cold air and cool 275 BTU/Hr. out of a 100° F environment. The 3208 will produce 6.4 SCFM of cold air and cool 550 BTU/Hr. These larger Vortex Tubes could be used to cool a closed circuit camera in a hot environment or a small drill bit where coolant is prohibited or undesired. From here our product continue to produce more volume of flow and we can go up to our largest Vortex Tube, 3299 which will use 150 SCFM of compressed and cool up to 10,200 BTU/HR.

What if you have an application where you don’t need more air but 16°F  isn’t cold enough? Then you can adjust your cold fraction. Adjusting the cold fraction will allow you to increase the temperature drop. Opening the brass hot valve, will lower the cold fraction. As more air is allowed to escape out of the hot end of the Vortex Tube, the temperature and the flow rate of the cold flow decrease.  If you need to cool below a 50% cold fraction we recommend the 3400 series Vortex Tubes. At 100 PSIG this would occur when you need more than 100° F temperature drop.

Vortex Tubes can be used in a variety of cooling application. If you have any question about the topic discussed above please contact me or another application engineer.

Dave Woerner
Application Engineer
DaveWoerner@EXAIR.com
@EXAIR_DW

Cooling Efficiently

Published on by Dave WoernerLeave a comment

Last week, I had the opportunity to work with a customer who was trying to cool a thermoformed film from 85° C (185° F)  down to room temperature, 21° C (69.8° F) or low enough for the package to be handled by an operator. This container was 270 mm X 170 mm X 100 mm (10.63″ x 6.69″ x 3.94″)

 

In applications like this, the customer often calls in with the idea of using a Vortex Tube to produce the cold air.  There are two reasons to use a different product than a vortex tube in this application. First, a vortex tube is only going to cool a small area, so to cool anything this size would take several vortex tubes.  Second, the cold air is going to mix with the ambient air very quickly. When the ambient air mixes with the cold air from the vortex tube, the air will lose the cold temperature generated by the vortex tube. To counter act this mixing, we have had customers create an insulated container to hold cold air from a vortex tube close to a product, similar to a cooling tunnel. This works in some applications, but my customer had a continuously moving line. He did not have time to stop the line and install insulation around each product.  He also didn’t have the length of conveyor needed to put a cooling tunnel over the line.

Super Air Knife Promo

Instead of using the vortex tube, I suggested that he use a 12” (305 mm) Super Air Knife to cool the thermoformed container. The 12” Super Air Knife moves significantly more air than a vortex tube over the surface of the part. Thanks to the 40:1 amplification ration of the Super Air Knife, it creates more cooling to the product and use less compressed air than a series of Vortex Tubes.  By mixing a large volume of free ambient air, that is the same temperature he needs to cool the part to, and a small amount of compressed air over the product they can easily cool their part to close to ambient so the operator can handle the part. The best benefit for this customer was they would not need change their manufacturing line.  The air knife is the best choice when cooling a very hot, fairly flat, large surface part to a temperature close to ambient. If you need to cool a product to a temperature lower than room temperature, then a vortex tube would be a great product to do the job.

Dave Woerner
Application Engineer
DaveWoerner@EXAIR.com
@EXAIR_DW

Vortex Tube Cooling: One Vortex Tube, Multiple Targets, Will This Work?

Published on by Neal RakerLeave a comment

VortexTubes

I had this question posed to me the other day. The customer asks, “I have three, small, enclosed spaces that are all within about five feet of each other. I’d like to put vortex tube cooling into each space. Can I do it with one vortex tube or will I have to use three of them?”

Imagine if you will, the cold air output of a single vortex tube being split three ways and ducted into each of these small chambers. While it is definitely technically possible to do, it isn’t always a feasible idea from the point of view of lost cooling power. Also, anytime that you can split up the effect you are trying to create whether that be cooling with a Vortex Tube or blowing off a large target that has many features to it, generally it is better practice to divide the application solution up to be applied over multiple, smaller units rather than one large one.

In this customer’s case, he wanted to save money on the purchase of multiple vortex tubes by purchasing one model 3230 vortex tube and plumbing the cold air output to his three cooling chambers. The problem is that the ambient temperature outside the boxes is rather hot and also contains high humidity. How exactly is this a problem?  You might ask. The problem is in all of the heat lost in cooling down the cold air distribution pipe (the pipe, hose or tube delivering the cold air into the chambers) that lies outside each box. That results in a net temperature gain (higher temperature) of the cold air you are trying to use for cooling the chambers or enclosures. With that lost cooling power, the customer runs a risk of not having sufficient cooling power to offset the heat load in each chamber. There is also the issue of back-pressure being presented to the Vortex Tube itself from the cold air distribution piping. When subjected to back-pressure, vortex tubes will lose their cooling capacity. Finally, there is the problem of getting equal cooling power delivered to each chamber. In this case, the solution of piping cold air to each chamber would cause an un-even distribution of the cold air with the closest chamber receiving the lion’s share of the cooling, leaving the other two under-cooled.

So, what is a better way to do this?  The method I suggested to the client was to use three of our model 3208 (8 SCFM) vortex tubes, allowing for direct connection of the vortex tube cold air output to each chamber. The cold air no longer has to cool down the cold air piping thus leaving more cooling power for each chamber, there is no back-pressure issue, and finally and probably most importantly would be the total air consumed would only be 24 SCFM in this case (3 x 8 SCFM) vs. 30 SCFM with a single larger vortex tube. That is a 20% savings on compressed air use in a straight up comparison. Depending on how many hours a day the system would be used, the difference in purchase price could be made up by lower operating cost in less than a year.

Neal Raker
Application Engineer
nealraker@exair.com

A Straight Forward Vortex Tube Cooling Application

Published on by Neal RakerLeave a comment

As the title suggests, I wish to quickly visit a simple and effective cooling application with you. The customer builds custom test fixtures to test any electronic circuit board and components prior to final assembly of the board into whatever it will be used in. Their requirement is to cool an IC processor chip that would normally have a heat sink and a fan to cool them once fully assembled. During board level test the heat sink and fan are not there, so to keep it cool they want to use a Vortex Tube cooler. Physically, the test parts will range in size from 2.25″ square to 1.125″ square with a height of around .156″.

How a Vortex Tube Works

I recommended the customer incorporate our Model 5215 Cold Gun System into their test fixture to provide the necessary cooling. The reason for recommending this model over a plain vortex tube is that it is supplied with all the necessary heat shielding and sound muffling accessories anyone using a vortex cooler would want for ease of use. Besides these features, the Cold Gun comes with a magnetic base to mount the unit and also flexible tubing to allow for aiming of the cold air flow precisely where it is needed.

The customer incorporated the Cold Gun into their test rig and found it to be quite useful and fast at cooling the target.

That, my friends, is a straight forward Vortex Tube cooling application.

Neal Raker
Application Engineer
nealraker@exair.com