[AR] Re: Keeping moisture out of cryogenic valves
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Mon, 29 Aug 2016 23:01:16 -0400 (EDT)
On Mon, 29 Aug 2016, Robert Watzlavick wrote:
The sides of the tank were covered in frost but the drops were coming
off of the bottom... I put a clean 5 gallon plastic bucket (SS or
aluminum would be better!) under the tank to catch the drops and they
evaporated as soon as they hit.
If they're evaporating as soon as they hit, that's pretty much got to be
liquid air (assuming that your tank isn't leaking!). Yeah, stainless or
aluminum would be a better choice of drip catcher.
haven't observed the phenomenon every LN2 test but maybe around 30% of
the time. I'll make a note of the humidity next time.
Hmm. The reason why liquid-hydrogen tanks don't normally form a frost
layer (and therefore need deliberately-provided insulation) is that the
dripping liquid air usually washes the frost off before it can get
established. Apparently you *can* get a frost layer on them if the
initial conditions are just right. Maybe you're running into a milder
version of the same thing, with the tank bottom sometimes getting too cold
too fast and the frost layer not getting well started before the liquid
air starts to show up.
Henry
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