Cooling Helium at Bottom Dollar

[dfly9891]

Calling all Cryo-guru's,

I'm designing a rig to test a circulation fan. The system is closed loop with Helium as the fluid at temp 50K and pressure 100-300 psi. The piping is 5/8" od (wall thickness is up to me). How does one cool the Helium without spending more than a few hundred dollars on hardware?

My initial thoughts: Buy 100' of 5/8" od (wall thickness .035) from McMaster for $200 (PN: 5174K37). Drop the whole coil into an Igloo marine cooler. Drill two undersized 5/8" holes in the side near the top and pop the two end of the copper piping though. Drill a small hole in the lid for a pressure relief valve. Open the lid, dump a bunch of LN2 in there and call it a day.

Thoughts Please?

 

[Compositepro]

What are you trying to test? LN2 boils at 77K. Under vacuum it will boil lower. The fan load depends mainly on gas density. Can you use a different gas at a different temperature and pressure?

 

[iainuts]

The problem is the temperature. LIN freezes solid around 63 K so you won't get to 50 K with LIN, even pulling a vacuum.

I'd suggest getting liquid helium for use as the cooling media.

How big is this fan? How much power and what flow is it producing?

 

[dfly9891]

I would be happy if I could get it down to 77K. That would suffice for test purposes. But 50K would be better.

If I go with liquid Helium as the cooling media, can I use the same setup as I described in my first post? Or am I getting myself into a $500 cryo thermos.

The purpose is to test the circulating fan performance, overall efficiency, clearances at cryo, vibration and displacement checks, and heat leak. I am circulating Helium gas at the following conditions:

Inlet Pressure 7 [bar]absolute
Pressure Ratio 1.034
Inlet Temperature 50 K (or as close I can get)
Mass Flow Rate about 8 [g/s] , 11 [g/s] corrected

Fan Electrical: 110 VAC 100W, .5 amp (small unit, impeller od is about 1 inch. overall length is about 12 in)


Anyone know if the Helium in this case would react with copper (piping)?

 

[iainuts]

The flow could be cooled first with LIN to 77 K then cooled the rest of the way to 50 K using a second heat exchanger using LHe. You won't be able to use a styrofoam cooler for the helium. Instead, you'd need to get a dewar and run a VJ line (such as are used by the MRI industry) into an insulated heat exchanger to cool the rest of the way.

Problem would be cost. You'll use a lot of liquid helium which is very expensive, materials would cost even more, and just engineering the test is going to be a significant undertaking. If $500 seems like a lot of money, you can forget trying to cool it like this however. It will be tens of thousands of $ to set up a test like that.

I'd suggest that using LIN should be sufficient. Most of your thermal shrinkage will have already occured. How the fan behaves at 77 K should be very representative of how it behaves at 50 K.

 

[EdStainless]

If you can set it up as a sealed system then cool/purge with LIN and then use liquid Hydrogen. A lot less money than helium. Just be careful on you venting.

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