"T o d d P a t t i s t" wrote in message
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I can recall being labeled a troll. I was trying to figure
out why my glider's oxy tank got hot when it was filled.
Every pilot I spoke to said it was because the oxy was being
"compressed" That just makes no sense. You start with a
high pressure fill tank and my empty oxy tank, connect the
two together and let the oxy that was at high pressure in
the fill tank, expand to fill the increased volume defined
by the fill tank volume plus the empty tank volume. That
seems like it should cause cooling due to expansion, not
heating due to compression.

Well, that hardly seems fair. You post a perfectly interesting question,
without sharing the answer?

I'm not entirely swayed by your reasoning that it can't be due to
compression because the gas is expanding. It seems to me that tack ignores
the fact that the tank being filled *does* have gas inside it that is being
compressed. The gas coming in should get cooler while the gas already in
should get hotter. The net could go either way as far as I can tell.

Your hint implies that energy not used in the transfer (to run a windmill,
for example) must be expended some other way (as heat, for example). But to
me that ignores the fact that the energy IS actually being used in the form
of the velocity of the transfer (the windmill would extract energy and
reduce the velocity).

Of course, the gas moving at a high velocity has to slow down eventually,
once in the other tank. Was your conclusion that it was this reduction in
velocity that resulted in the increase in temperature?

I'm not saying your conclusion is incorrect, but you haven't posted enough
information to explain it (that is, we don't even know what the conclusion
was, never mind the method used to arrive at it). Unfortunately, you also
have already posted too much information for the curious among us to just
let it go.

Pete