[AR] Re: Pressurizing gasses
- From: Norman Yarvin <yarvin@xxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Wed, 3 Aug 2016 19:03:30 -0400
On Wed, Aug 03, 2016 at 06:09:02PM -0400, Henry Spencer wrote:
On Wed, 3 Aug 2016, Norman Yarvin wrote:
Of course the helium would start mixing in, on its way up, rather than
all reaching the top, but it'd be trying to reach the top, and what is
important is not that it gets to the top but that it doesn't stay at the
bottom.
However, "the bottom" here isn't fixed -- it effectively moves upward (!)
because GOX diffusing down through the helium condenses into the liquid.
What's important is not whether the helium diffuses toward the top, but
whether it diffuses upward *faster* than the cold liquid removes GOX
diffusing down. If the removal is effective enough, there's no way the
helium can get away from the liquid surface against the downward GOX flow.
Ah, so that's the trick. It presumes you're going to encounter a fair
bit of the problem -- GOX flowing downwards into the LOX -- and uses
that to force the helium down. And that in a tank that was initially
pressurized with helium, meaning that there's quite a bit of helium
there; helium might, say, be responsible for 10% of the pressure, so
random GOX that flows downwards has 10% of its molecules being helium,
which then gets concentrated considerably above the surface of the
liquid. Even with "bubbles" of helium accumulating on the surface,
then breaking loose and rising up toward the top of the tank, the
surface helium still will constantly be replenished -- at the cost of
being nowhere near a complete barrier, just something that ameliorates
the situation.
--
Norman Yarvin
http://yarchive.net/blog
Other related posts:
