Questions

Soldato
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7 Jul 2009
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Well you know a while back compressed air was used to get some crazy temperatures?

  • What sort of CFM would this have been putting out?
  • What BAR (or PSI) would be in an aerosol of compressed air?

Because i have a sort of plan. I assume you're familiar with digital tyre inflater's?
 
Cans of compressed air get cold as a result of the pressure of the air decreasing significantly when sprayed. The same thermal energy is spread over a larger area so the temperature falls. I'm not familiar with tyre inflators, but I'd be surprised if they ran from a can of compressed gas rather than from a compressor. Consequently the air coming out of one isn't going to be freezing.

Does this make the plan more difficult, or do you have something more subtle in mind?
 
So you would have to have an air piston of some sort constantly compressing air into a container, while the container has a constant outlet on the object you want to cool? The piston would have to be able to fill it at a speed the same as it's being released, and it would have to fill the canister before it started to release the air...

Complicated, but i think it can be done. Would be a lot cheaper than the other forms of extreme cooling too. Another problem would be the noise... hmm.
 
You would have to drive the air into the container, wait for it to reach the same temperature as the air outside of it, then allow it to release. Otherwise when you ram the air into the container it'll get hot, and when it escapes it'll come down to around room temperature.

As a result of the time required for it to cool down, I suspect it would need to be large. It would cost a fortune to make, how were you planning on machining this for less than a few grand?

Peltiers are the way to go, I'm sure of it :)
 
Meh, pelts don't really solve the problem of heat output. They just move the problem. I prefer Phase Change.

Wait... you can get a 170W pelt for less than £10? :o
 
Fridge is where we all want to be really...

Not that my plan has made any progress yet. I'm still at the point of learning the thermofluids required to allow me to start the design process.

Phase change doesn't get rid of heat either. That's why there's a damned great radiator thing with fans attached involved. No cooling solution ever gets rid of it, it just moves it to a more convenient place.

There's more to peltiers than the wattage. Most critical is how much heat it moves across for a given wattage of electricity. Say you could move 80W, but it'll cost you 60W to do so. One side goes down by 80, the other goes up by 140. When undervolted the efficiency can be pretty good, at 12V it's shocking. Say, 5 or 6V, both being conveniently available from a (good) atx psu. Say one of them can move 50W fairly efficiently, and you have to drag 300W out of the loop. Fairly clearly you'd need six of them. This is why you can't just mount them between processor and waterblock anymore, processors are too powerful for a reasonably sized pelt.

So, if you run one loop through processor, chipset, graphics. And another through some radiators. You can then join them together via a heat exchanger, which is where the pelts sit. So one loop gets somewhat colder, while the other gets a lot hotter. As radiator efficiency improves with temperature, having one loop at 60/70 degrees while the other is at 10 isn't so bad. As long as the pump and tubing can cope.

Next up, condensation. The solution I like is controlling the peltiers to keep the cold loop temperature at ambient/above dew point. Two thermometers, one at ambient, one at loop temperature, and run the pelts at variable voltage to keep the two equal. Fairly simple electronics, I think.

I think it's possible to build the exchanger into the 5.25" form factor. This depends a bit on available pelts and required wattage. However if possible, a (very heavy, and internally insulated) 5.25" box, with four G1/4" threaded holes on the back, and power connectors in the shape of 8 pin pci-e leads, would find great application in powerful matx systems.

I think it'll be about £200 in materials. Probably going to take me a few years to get the design down though. So, I'm rambling. Going back to Rogers & Mayhew I think. Cheers Super, you've got me thinking again :D
 
Yeah. Could think of it as having an ek supreme on each loop, clamped together base to base with a peltier inbetween. 'Cept with more peltiers, and not made by ek. Two pumps needed obviously, and the electricity bill would not thank you for it.
 
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