Cold Air Gun Coolant Systems?

Have any of you used the various cold air gun coolant
systems and if you have, what are your opinions on the
products?
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Reply to
Hari Seldon
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I've used the Exair brand. Works great on plastics.
Put hot water pipe insulation wrap on the outlet nozzle and run the intake air line into a bucket of ice water. Use a long length (10-20 feet) of air line coiled up in the bucket. That will really help drop the temp of the output air.
Reply to
skuke
Drained ice is more efficient than floating ice at flash cooling. Try putting a hole in the bucket so you don't have liquid water in it. It is insulating the hose from phase change of the ice and thus the flash cooling efficiency (like a wet suit keeps you warm). And put a refrigerated air drier ahead, so you're not wasting time removing latent heat and sputtering liquid condensate.
Reply to
Richard J Kinch
We had a drier so condensation was not a problem.
I am confused though why you say drained iced would be more efficient than a water bath of ice water.
Water is a much better conductor of heat than air, so wouldn't more heat tranfer from the hose into the bucket of ice water rather than a bucket of ice air? I know that if I stuck my hand into ice water, it would be much colder than sticking into a bucket with ice cubes.
Please un-confuse me.
Reply to
skuke
It depends on what you're going to use it for. I see a fellow said it works great for plastics. Sounds right. I tried one for grinding endmills, almost useless. There's just too much heat being generated compared to the ability of the gun to carry it away. On occasion I use an air blast for cooling and chip evacuation when milling deep pockets. Again, a cold air gun wouldn't help much here.
Karl
Reply to
Karl Townsend
You have to appreciate thermodynamics. Conduction is not the issue. The phase change of the ice is the heat sink, not the liquid water. The ice should be in direct contact against the hose, pressing against it by force of gravity. Melted ice has spent its cooling ability, so you must drain it away. Unlike ice, liquid water temperature rises as it gains heat, and the efficiency drops.
An example is how a cold plate works for flash cooling beverages in a soda fountain. Drained ice is piled on top. Look at just about any restaurant, like Wendy's where the fountain is right at the sales counter.
No, you're confusing temperature and heat, two different things. Liquid water has no heat sinking capacity compared to ice. If you put your hand into a pound of chilled water, the result will be a much higher temperature than if you put your hand into a pound of slush.
Reply to
Richard J Kinch
Seems like this is where a cold air gun would really come in handy.
According to one of the web sites above, if the incoming air is at 75* the cold air gun will drop this to 0* and you have the benefit of the chips being blown out of the pocket/slot, in addition to not having to deal with the mess from liquid coolant.
Reply to
Hari Seldon
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Those are all baased on the Hilsch Vortex Tube idea which is a really cool device (no pun intended). The technology has been around since before WWII (see
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).
Depending on whether you have the time for such a project... a simple one that "works" can be built in minutes out of scrap bin and bits of threaded pipe. I certainly wouldn't pay $200 for one.
I built my first one based on an article from an old copy of Scientific American. A copy is here:
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Lots of good info on the web about these devices. There are no particular patents on the basic device... its original patent has long since expired. There might be some on significant improvements to the device but I am not aware of them.
As far as boosting the cooling effect is concerned you would be MUCH better off if you pre-cool the incoming air to the device rather than trying to cool the outgoing air. All of mine cool the incoming, nominally room temperature, air to _below_ freezing already. In fact to pass the output through an "ice bath" or whatever may actually heat it up!
In essence the way it works is that it separates the cool molecules from the warm molecules... send the cool ones out one end and the warm out the other.
Unless you have plenty of compressed air on hand the device is not very efficient as far as cooling effect/KWh.
For much more info see the links at the bottom of the Wikipedia page. Especially check out:
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Reply to
David Utidjian
In use, aren't these guns quite loud? - GWE
David Utidjian wrote:
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Reply to
Grant Erwin
Yes, they can be. The device can make a full range of audible sounds (and does) it just depends on which one(s) are dominant. On most of the commercial units have some sort of muffler on one of both ends. The higher frequencies are a particular problem. One of my units was made by MAC tools for testing chokes and thermal switches on cars. It has a foam lined "cold side" and a wire mesh in the "hot side". To my ears it puts out a very dull roar. It was made about 20 years ago.
In some of the literature they mention attempts to use the devices for cooling/heating where compressed air would be plentiful (in jet aircraft?)... I seem to remember they tried using lead plates to damp out some of the higher frequency harmonics. If the particular noise the device makes is irritating enough it wouldn't be very useful in such an environment.
Another use where noise may be a problem is in environmental suits for sand blasters. Since compressed air is plentiful it can be used to cool and ventilate the hood (or the whole suit). I have never used such a suit so I don't know how they deal with the noise levels.
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Reply to
David Utidjian

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