I was at the end of the nomographic era of engineering. My professors were
moving to computer generated tables over diagrams and nomographs. A good
friend of mine, using nomographs, designed an air to air missile for the
same dollar cost spent on the computational time using a Cray computer. Laws
are good, but application of the Law is better.
I built my own gas chromatograph from junk parts. It could resolve H2/N2
and contaminate gas mixtures down to 5000 PPM. A smaller capillary column
would have improved the resolution.
The "lingering" effect of the fog is the result of a very cold gas bubble
of CO2 being surrounded by the high specific heat, polar solvent water. The
high heat capacity of the water delays the thermal transfer to the CO2 gas
sink, keeping the condensed water visible.
Krell
In a message dated 8/22/2015 3:02:02 A.M. Pacific Daylight Time,
johndom@xxxxxxxxx writes:
To understand T-s diagrams and J-T expansion is another task to study. I
have been browsing for the subject but as yet found no T-s graphs including
decent explanations. Those practical diagrams were not part of our
thermodynamics courses which were mainly about laws and cycles.
There was that large helium tank (used for gas chromatography) standing
outside the lab. Outside near the cold exhaust tube on it were indeed large
chunks of (water) ice de-sublimated on it from the environment air.
Related: throwing chunks of solid carbon dioxide in water makes it bubble
with sublimated cold CO2 vapor. But why does that gas produce a *lingering*
fog on rock&roll stages?
jd
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx]
On Behalf Of Timothy J Massey
Sent: vrijdag 21 augustus 2015 22:15
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: scuba or astronaut gas temperature question
The water that freezes is, I'm sure, not from the air in the tank. You are
right: that is very, very dry air. It's the water in the natural outdoor
air that is cooled by a super cool jet of recently and quite quickly freed
scuba air.
This isn't speculation: I've seen it and done.
Maybe snow is overstating it: it's not exactly large snowflakes. But there
is definitely condensation coming out of the air in a visible white cloud.
Timothy J. Massey
Sent from my iPad
On Aug 21, 2015, at 1:08 PM, (Redacted sender "_JMKrell@aol.com_
(mailto:JMKrell@xxxxxxx) " for DMARC) <_dmarc-noreply@freelists.org_
(mailto:dmarc-noreply@xxxxxxxxxxxxx) > wrote:
John,
The compressed air temperature drop will be approx 30 C from 200 to 1 bar.
Reference T-s diagrams for N2. The largest T drop occurs at the first
stage of the regulator, 200 to 10 bar. In water >10 C the 10 bar air is
reheated to near water temperature. Diving in water at temperatures <5 C does
present a regulator freeze issue. Special regulators and procedures are
required.
Dumping a full dive tank will not produce snow in the summer. Done that.
SCUBA air dew point of -53 C (<24 PPM H2O).
Krell
In a message dated 8/21/2015 7:05:51 A.M. Pacific Daylight Time,
_johndom@skynet.be_ (mailto:johndom@xxxxxxxxx) writes:
Is there an expansion due air (gas) temperature drop, say from a 200 bar
cylinder to a diver’s mouthpiece after the pressure regulator? Like a JP
expansion effect? Of course with scuba diving, the regulated pressure is depth
dependent, but still. Any values in °C?
jd