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Cooling Helium at Bottom Dollar

Cooling Helium at Bottom Dollar

Cooling Helium at Bottom Dollar

(OP)
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?

    

RE: Cooling Helium at Bottom Dollar

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?

RE: Cooling Helium at Bottom Dollar

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?

RE: Cooling Helium at Bottom Dollar

(OP)
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)?

RE: Cooling Helium at Bottom Dollar

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.

RE: Cooling Helium at Bottom Dollar

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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