On 24 Apr 2006 14:55:29 -0700, "Bob" wrote:


Hi Dave:
Okay........... I agree, most likely wrong. Im not sure about the dead
part, although I felt like sunday morning. Thats what I was wondering.
Let try this: How is BTU related to Degrees Fahrenheit?

If air is compressed doesn't it get hot? If so, how measure it? But I
guess what caught my eye was when a previous post said that compressing
air does not create heat. But I may be pretty ignorant about the term
HEAT.

Confused Bob

If I remember correcty from chem class 35 years ago:

PV=NRT

pressure * volume = moles * R * Temperature

I don't really remember the units, but I think moles is a measure of
mass, R is a constant (.082?), temperature = degrees kelvin.
Google "ideal gas law" for better info. But solve for T and you get

T=PV/NR

The rest is left as an exercise for the student :-)

__________________________________________________ __________
Glen "Wiley" Wilson usenet1 SPAMNIX at world wide wiley dot com
To reply, lose the capitals and do the obvious.

Take a look at cpRepeater, my NMEA data integrator, repeater, and
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Glen "Wiley" Wilson wrote:
On 24 Apr 2006 14:55:29 -0700, "Bob" wrote:

If I remember correcty from chem class 35 years ago:
PV=NRT
pressure * volume = moles * R * Temperature
I don't really remember the units, but I think moles is a measure of
mass, R is a constant (.082?), temperature = degrees kelvin.
Google "ideal gas law" for better info. But solve for T and you get
T=PV/NR
The rest is left as an exercise for the student :-)


Oh no.... not moles !!!

That is almost as helpful to me as Avogadro's Number.

I think I will stick with the brick analogy......................... I
can understand bricks.

I new a Wiley Wilson in Ballard, WA in the early 1980s. Same person?
Bob

On 25 Apr 2006 09:00:21 -0700, "Bob" wrote:


Glen "Wiley" Wilson wrote:
On 24 Apr 2006 14:55:29 -0700, "Bob" wrote:

If I remember correcty from chem class 35 years ago:
PV=NRT
pressure * volume = moles * R * Temperature
I don't really remember the units, but I think moles is a measure of
mass, R is a constant (.082?), temperature = degrees kelvin.
Google "ideal gas law" for better info. But solve for T and you get
T=PV/NR
The rest is left as an exercise for the student :-)


Oh no.... not moles !!!

That is almost as helpful to me as Avogadro's Number.

I think I will stick with the brick analogy......................... I
can understand bricks.

I new a Wiley Wilson in Ballard, WA in the early 1980s. Same person?
Bob

I remember studying Avogadro's Number. It goes like this: If Jane has
8 avogadros and she makes guacamole from 1/2 of them, what is the
number of avogadros she has left?

Must have been a different guy in Ballard. I didn't get to that part
of the country till about 2002.


__________________________________________________ __________
Glen "Wiley" Wilson usenet1 SPAMNIX at world wide wiley dot com
To reply, lose the capitals and do the obvious.

Take a look at cpRepeater, my NMEA data integrator, repeater, and
logger at http://www.worldwidewiley.com/

Glen "Wiley" Wilson writes:

If I remember correcty from chem class 35 years ago:

PV=NRT

T is for temperature. Temperature is not heat. Chemistry is not
thermodynamics.

Dave writes:

And the significance of this distinction between Chemistry and
thermodynamics is ...

The study of physics involving temperature, pressure, heat, work, etc., is
called "thermodynamics". Chemistry as such does not answer such questions,
although chemists use thermodynamics.

It is kind of like the old quarrel over whether chemistry is a branch of
physics, or physics of chemistry.

In any case, PV = nRT presumes zero heat transfer (denoted Q in
thermodynamics).

On Tue, 25 Apr 2006 19:50:59 -0500, in message

Richard J Kinch wrote:

Dave writes:

And the significance of this distinction between Chemistry and
thermodynamics is ...

The study of physics involving temperature, pressure, heat, work, etc., is
called "thermodynamics". Chemistry as such does not answer such questions,
although chemists use thermodynamics.

It is kind of like the old quarrel over whether chemistry is a branch of
physics, or physics of chemistry.

In any case, PV = nRT presumes zero heat transfer (denoted Q in
thermodynamics).

Actually PV = nRT is just an equation of state for an ideal gas that
would be equally at home in either a thermo or a chem text book. It
doesn't presume a lack of heat transfer, it simply tells you that if
you increase the temperature by adding heat, then either the volume or
the pressure will increase.

One equation in three variables is not enough to fully describe a
problem.

Ryk


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Ryk writes:

it simply tells you that if
you increase the temperature by adding heat, then either the volume or
the pressure will increase.

No variable in the equation expresses heat. It does not tell you
*anything* about heat or its relationship to the variables it does express.
It does *presume* that Q = 0. If Q happens to be non-zero, then the
equation still holds while the values change, but the equation tells you
*nothing* about an unexpressed Q relating to T, any more than it tells you
there are unexpressed forces changing V, or a leak in the container
changing n, or radioactive decay changing n, or any other physical
principle you can imagine.

An equation must express a quantity to "say" (predict) anything about it.

An equation may be affected by unexpressed quantities, but the equation
literally does not say anything about unexpressed quantities.

Ryk writes:

Actually PV = nRT is just an equation of state for an ideal gas that
would be equally at home in either a thermo or a chem text book.

If there are any meaningful definitions of "chemistry", "thermodynamics",
and "physics" anymore, then PV = nRT belongs in the second, which is a
branch of the third. But this is a philosophical quarrel that we'll not
solve here.

All I know is, there ain't no oil in my raw shop air, hot as it may be.
And certainly not compared to proximity to my 2-stroke outboard, 2-stroke
chain saw, 2-stroke string trimmer, or 2-stroke Weber charcoal grill.

Salty Bob,
Man, that is an old set up! I remember pictures like that from the period
before those wiley divers hooked a new fangled gasoline engine to a
compressor!
The Navy used various models, without much change in design, of the Mk 5 hat
from the 1840s to the 1980s.
As I remember (got an old dive manual around here somewhere, hell if I know
where) the handle was like on the old manual rail cars, you know the ones 2
guys would stand on and pump the handle from the ends, up and down for
moving down a rail to perform maintanence?
Didn't John Wayne have a rig like that in "Wake of the Red Witch"?
As I remember a Mk 5 diver would be conscious for something like 6 minutes
if he lost his air supply, so if the supply flow replaced the air in the
suit every 2-3 minutes he'd be fine. Running a compressor like that directly
to a hat or mask, would only require a 2-3 cfrm and about 15 psi over bottom
pressure? Add depth and add cfm.
MMC
"Bob" wrote in message
oups.com...

MMC wrote:
Good post Robb.
The toxins are minute until the compressor pistons rings get worn (or do
not
fit right from the beginning) and allow oil to enter the cylinders.
Absolutely right about the oil free compressor!

Thanks for adding your ideas here. Finally some advice based on
training, experince, and still here to give it. Unlike the other past
posts that simply said, "Ive been doing it this way for years and never
had any porblems."

Here is my question for you MMC:

A few comments earlier in this discssion I described a hand pump that
supplied diver air to about 20'. Did you ever run into anything like
that in the service? They were a little (maybe 25 lbs.) two cylinder
thing with a five foot handle that a person push-pulled too operated
the pump. The guy who made the new prototype said he got the idea from
one he saw in an old USN Dive Manual.

Thanks,
Bob

Hey, if we adapt this train of thought we can do away with diving related
illnesses like nitrogen narcosis and embolism! Oh, happy day!
Could it be that the rings in your compressor aren't shot? Breathe the
exhaust of any of the other items you list at depth and under pressure and
let me know what you find out.
MMC
"Richard J Kinch" wrote in message
. ..
Ryk writes:

Actually PV = nRT is just an equation of state for an ideal gas that
would be equally at home in either a thermo or a chem text book.

If there are any meaningful definitions of "chemistry", "thermodynamics",
and "physics" anymore, then PV = nRT belongs in the second, which is a
branch of the third. But this is a philosophical quarrel that we'll not
solve here.

All I know is, there ain't no oil in my raw shop air, hot as it may be.
And certainly not compared to proximity to my 2-stroke outboard, 2-stroke
chain saw, 2-stroke string trimmer, or 2-stroke Weber charcoal grill.