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cooling with a vortex tube  RSS feed

 
paul wheaton
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I was out for a few days ...  and while I was out, I happened to strike up a conversation with an enginer who happens to have visited several ice caves.  His very logical mind was not buying into a lot of the justifications for how ice caves exist.  As a younger man, he had visited one particular ice cave several times and later learned about vortex tubes.  Then, he went back to that ice cave and found that the shape of the cave combined with and air inlet and and air exit ....  it is his theory that some ice caves may be ice caves because they are a naturally occurring vortex tube. 

http://en.wikipedia.org/wiki/Vortex_tube

So then I got to thinking:  I wonder if a person could make a root cellar in such a way that it might actually be a freezer - with temps hovering around zero (F). 

If nothing else, I wonder what would happen if you took any ole root cellar and hooked up something so that every time the wind was blowing a bit, you channeled that wind into one of these:  http://www.abbeon.com/store/item.cfm?code=2082 ; or one of these http://www.newmantools.com/vortex.htm

In the mean time, I'm trying to line up visits to local ice caves to see if I can figure out how they get icy.






 
Alex Ojeda
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After spending too much time on looking into this, I've gotten some notes and will plan on working on this at some point in the future. What an interesting thing!
 
Tyler Ludens
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Really looking forward to what you develop Alex!
 
Alex Ojeda
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Tyler Ludens wrote:Really looking forward to what you develop Alex!


Me too!

Actually, I live in Florida where it's already up to 95°F and it's humid, so finding a way to create cool air is amazing. I'm also thinking about the fact that even if it takes the same amount of energy as a regular A/C unit, it's something I can build myself and maintain and especially DOESN'T use freon or any other chemicals.

Compelling research. I'll see what I can do. Currently working on structures in my back yard and keeping the "food forest" project progressing. I live in an historical neighborhood, so hence the quotes around food forest.

I'd love to see if any other permies work on this too!
 
Abe Connally
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Location: Chihuahua Desert
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I studied these a few years back, and the conclusion was, for the amount of cooling, they are really inefficient compared to other means. So, if you have to create the moving air with energy (like with fans, blower, compressor, etc), then you'd be better off with a closed loop refrigeration system. So, it depends on the local conditions and the source of moving air. If you have wind blowing from the same direction at least 60% of the time (14 hours of the day), then it could probably work, but I'd start with a scale model first.

I have to admit, I'm somewhat skeptical of the ice cave theory, unless there is a fire cave nearby. The thing with vortex tubes is that they separate cold and hot, so that heat has to go somewhere. If you are extracted enough cold to freeze a cave, then you're also extracting enough heat to cook a cave.

Fridge systems don't have to use freon for their working fluid, you can even use air. It's just a matter of compressing the working fluid, cooling it down, then letting it expand again.

Here's a design that uses a simple windmill and helps to explain the concept a bit: http://mb-soft.com/public3/selfsuff.html Scroll down to "Providing Refrigeration and a Food Freezer"

The zeolite/water designs have promise as well. Google zeolite refrigerator.
 
Alex Ojeda
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Abe Connally wrote:I studied these a few years back, and the conclusion was, for the amount of cooling, they are really inefficient compared to other means. So, if you have to create the moving air with energy (like with fans, blower, compressor, etc), then you'd be better off with a closed loop refrigeration system. So, it depends on the local conditions and the source of moving air. If you have wind blowing from the same direction at least 60% of the time (14 hours of the day), then it could probably work, but I'd start with a scale model first.

I have to admit, I'm somewhat skeptical of the ice cave theory, unless there is a fire cave nearby. The thing with vortex tubes is that they separate cold and hot, so that heat has to go somewhere. If you are extracted enough cold to freeze a cave, then you're also extracting enough heat to cook a cave.

Fridge systems don't have to use freon for their working fluid, you can even use air. It's just a matter of compressing the working fluid, cooling it down, then letting it expand again.

Here's a design that uses a simple windmill and helps to explain the concept a bit: http://mb-soft.com/public3/selfsuff.html Scroll down to "Providing Refrigeration and a Food Freezer"

The zeolite/water designs have promise as well. Google zeolite refrigerator.


Abe, thanks for the sober look at this. The whole time I'm reading about it, it smacked of the Electrolysis Hydrogen on Demand stuff. Seeing it work in a YouTube video makes it a few steps better! I kept thinking that if the heat was going outside then it would work. Also, if I could get a solar panel to power the compressor (heat of the day) in a hyper insulated house, then this might be a good thing as well.

I'm looking for ways to cool a standard cracker jack box house (a utility company's wet dream) like we all live in currently. I'd like to build an earthship or an Oehler home, but until then I live where I live. Looking for cool, dry air when it's hot and humid outside. I'm toying with the idea of a geothermal system with air conditioning conduit running 5 feet below ground and then up into my off-grade house. It'll be a nice experiment. Loads of work, but if it works...
 
Abe Connally
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vortex coolers are really good for spot cooling, not cooling large spaces. They create a column of cold air, but also a column of hot air. That hot air must go somewhere, and in a small setting (like where they are most often employed, it is easy, you vent away from the spot you are cooling. But in a house, that means you are raising the temperature of the air around the house, and working against yourself.

Look into earth tubes and also this: http://www.sunnyjohn.com/indexpages/shcs_faq.htm

Your best bet would be to try and cool your hot humid air down to the dew point, which would give you a phase change as the water condensed, and release a lot of heat energy along with it. The air would end up being cooler and drier, which would help you considerably. There are a number of ways to do this.

Doing this below ground is a good idea, and you should try it on a small scale before investing too much into it.
 
C. Letellier
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Vortex tubes are dependent on tight spirals and high air velocity. I can't imagine finding those conditions in an ice cave.

Taking a guess based on physics. What would be the best conditions for the formation of an ice cave? First lets look at cold air sinks and warm air rises. That would say the coldest part of the cave should be lower than the mouth so the cold air is trapped when things are warm and so cold air falls in. To help the cold air fall in likely the cave mouth should be in some sort of valley to create a cold air feeder bowl. This would also probably help water and snow fall in. But this in and of itself is not enough because I know many caves that should be ice caves if this were true. Why no? Well caves do sort of breath as air pressure changes but there is very little flow in them creating a sort of trapped air pocket that acts as an insulator. So what else might be needed? What about lots of cold air through the whole of the cave to cool it off. How might that be achieved? Well warm air rises. So what if there is a tall chimney at the back of the cave. Cold air would fall in low, be warmed by the earth and rise being vented out the chimney. This would flow very little in reverse because all the coldest air would sort of be trapped at the bottom of the pocket. This might be improved both directions if the very top of the chimney was narrow while it was wider below. In the cold direction the air would have time to build energy and velocity so it flowed up the chimney giving it energy to overcome the restriction. In the reverse direction the restriction comes first so the air builds very little. Still know a few caves that meet these that are not ice caves although they are much cooler. But the ones I know that do have large caverns on back to add heat. So maybe a restricted structure. So would an ice cave basically look like a giant "J" with a mouth at the low end of the J and ice at the bottom of the J and a chimney out at the top of a cliff? The only ice cave I have ever visited meets this. It adds a couple of other things that go with this. The mouth faces rough northeast so very little sun to add heat. The cave is nearly up to the tree line meaning it sees cold weather a lot of the year so a short season to melt the ice. Finally the geology is such that the water that melts off the cliff runs down into the cave to be frozen. Melt off during the day and freeze in the bottom at night. Does this match other ice caves people have visited?

 
Tim Barker
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Hi All I too am fascinated by vortex tubes but as one poster has already said they require compressed air to work. Now the (usually correct ) supposition is compressed air is very wasteful to produce and as i intimated most of the time thats correct but there are instances where that is not the case. Consider when we say compressed air the method we use to do the actual work of compressing the air is typically done either by and electric or gas driven compressor. Also when you compress air you produce heat so if you have a use for the heat from the compression process(compressor and motor) then that process just became more efficient. Obviously if the compressed air is a by product of some other process then its also good fit. Also if you just happen to have a trompe https://en.wikipedia.org/wiki/Trompe in your back yard then you are blessed. Trouble is the physical conditions for the location of a Trompe are somewhat limited. One other thing to note is Vortex tubes will also work on vacume so if you have a vacume source just lying around then happy days!

The actual vortex tube itself is a mechanically simple device but be warned the question we should be asking ourselves whenever we think about appropriate technology is not can we make it but should we or is it worth making it. I'm very much of the opinion that you will be hard pushed to make a vortex tube at home that will approach the performance of the huge number of reasonably priced ones you can buy off the shelf. Its very easy to make something that works and demonstrates a principal but far harder to refine it to a point where it is worth doing it. A case in point was advising a student during one of my App tech internships on a treadle water pump they wanted to build. In the end the pump worked and pumped water but it was woefully innefficient because as i pointed out it was easy to get it to pump something but all the work on optomising was still to come and that was the hard part.

By implication if you are using vortex tubes you will have compressed air (or vacum) and so there is a lot you can do over and above "just " cooling. That is what i find exciting and so to me the problem is developing systems to produce compressed air cheaply not what can we do with it. Remember too that the greater our distribution network the greater our storage (think black poly pipe) and if that pipe is getting heated in the sun even better as we get more bang for our buck due to the increased pressure from the heated air not to mention that unlike water we dont need to pump it up hills or such as it effectively has little weight. I'm teaching an App Tech course at Paul's in the coming months and always cover Ranke Hilsch tubes and compressed air as i find the subject fascinating.
 
C. Letellier
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Tim Barker wrote:Hi All I too am fascinated by vortex tubes but as one poster has already said they require compressed air to work. Now the (usually correct ) supposition is compressed air is very wasteful to produce and as i intimated most of the time thats correct but there are instances where that is not the case. Consider when we say compressed air the method we use to do the actual work of compressing the air is typically done either by and electric or gas driven compressor. Also when you compress air you produce heat so if you have a use for the heat from the compression process(compressor and motor) then that process just became more efficient. Obviously if the compressed air is a by product of some other process then its also good fit. Also if you just happen to have a trompe https://en.wikipedia.org/wiki/Trompe in your back yard then you are blessed. Trouble is the physical conditions for the location of a Trompe are somewhat limited. One other thing to note is Vortex tubes will also work on vacume so if you have a vacume source just lying around then happy days!

... A case in point was advising a student during one of my App tech internships on a treadle water pump they wanted to build. In the end the pump worked and pumped water but it was woefully innefficient because as i pointed out it was easy to get it to pump something but all the work on optomising was still to come and that was the hard part.

... Remember too that the greater our distribution network the greater our storage (think black poly pipe) and if that pipe is getting heated in the sun even better as we get more bang for our buck due to the increased pressure from the heated air not to mention that unlike water we dont need to pump it up hills or such as it effectively has little weight. I'm teaching an App Tech course at Paul's in the coming months and always cover Ranke Hilsch tubes and compressed air as i find the subject fascinating.


I am also interested in air power. Primarily because many power jobs in my shop I have an air option for. I have been interested in vortex tubes since the mid 80's when I learned they existed so they have been part of nearly every air power pipe dream since. The thing is that for cooling while they can be part of the process that isn't where the real cooling capability of air comes in. To make really cold air the simplest is to go back to how the early cryogenic liquids were produce. The air is run through a compounder to produce a little extremely high pressure air. Dump that heat to cool to ambient temperature then run the high pressure air piping through the waste stream from the compounder to cool it even farther. Then vent the already cold extreme pressure air.(this is where an added vortex tube might get real gain in this system) Multiple stages of this was how the early cryogenic liquids were produced. But for a freezer a tiny inflow of super cold air is nearly ideal if done correctly. Put the vent high and the inlet low. There are also other ways systems that deliberately vented air might be used to make gains. For example zeolites allow for oxygen and nitrogen purification. Where might you want this. Apples store longer and better in a low oxygen environment. If you are already venting air these systems would have basically no real energy cost to run. Another place deliberately vented air might have value is a hydroponic or aquaponic system. One I already use, for the radiator shop is the vent air for the hoist runs through the water recycling system settling tank to helping improve setting plus keeping the water from getting stinky. It is a simple hose from the vent down into the water. I could improve it with a surge tank for the vent air and an airstone down in the water and that is on the long term goals list.

Now getting slightly out of order a comment on running air through black poly line. Be sure you allow for how black poly derates for safe pressure with heat. For example my 5 HP single stage compressor running all day steady the tank and outlet line temperature typically runs between 140 and 160 degrees depending on room air temperature and use rate. At 140 degrees depending on the type of black poly this can be solidly over 50% derating. At 160 it gets way worse. That means a pipe rated for 200 psi now will not handle 100 psi safely. This will apply whether sun heating air or if your air source is hot going into the pipe. Be aware the flying debris when a pipe ruptures can be dangerous.

Now a question on your comment on a treadle pump. Why should optimizing it be difficult? For low horsepower and widely varying power source obviously a positive displacement pump will be needed. Optimizing them the movable counter weight on the treadle or on the pump jack if speed reduced and friction/drag reduction through materials choices will probably get 90% or better of the this. The only real optimization left would be for a piston type pump adjusting the trade off between friction gains in a bigger piston vs friction losses in a mechanical speed reducer, in a gear pump it would be gear size vs friction and in an Archimedes or spiral pump it would be bigger is better till the friction of the pumping action equals the friction of the mechanical reduction to handle the bigger pump. Most of the optimization should have been done in the initial design.




 
Amit Enventres
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Very cool

So, I got excited and ran some calculations based on PV=nRT. To see if I could use the difference in (let's say) roof temperature to indoor temperature to create a noticeable temperature change. I got about 0.05 atm change from 110 degrees to 70 degrees. The research I saw on the tube was 1 or more atm difference, so the questions is: will this generate ANY sort of vortex. Now, if you actively put energy into the system, then perhaps you can build pressure and get cooling out of it, but all accounts say that this actually is inefficient compared to other methods. This design I think may still be useful in designing an air chimney. What if we pointed the hot exit up and the cold exit down, that follows natural airflow patterns. If we then make the top of the chimney heat absorptive, we then add more air draw. The inlet could be room temperature, whereas the cold outlet could be in a cooler basement, which I would think would cause the draw to pull from the room, not the cellar. It may not vortex, but perhaps it will enhance the effectiveness of an air chimney?

What do you think?
 
Creighton Samuiels
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paul wheaton wrote:

So then I got to thinking:  I wonder if a person could make a root cellar in such a way that it might actually be a freezer - with temps hovering around zero (F). 



Did you ever try to do anything along these lines?  My calculations imply that a walk-in freezer would require an unrealistic amount of energy, and harnessing a natural cross wind is out of the question, but dropping a few cubic feet of well insulated cooler is well within the possibilities of a solar array and DC air compressor; but enough energy storage to make it through the darkness is the issue.
 
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