# Pumping Liquid Nitrogen - Page 3

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## Re: Pumping Liquid Nitrogen

Tim Williams wrote:

I think if the rotor and stator shrink, the gap gets larger.

--
Paul Hovnanian     mailto:Paul@Hovnanian.com
------------------------------------------------------------------
The Three Laws of Thermodynamics:
1) You can't win.
2) You can't break even.
3) You can't quit the game.

## Re: Pumping Liquid Nitrogen

Everything shrinks proportionally in all dimension.  "Everything"
includes the gap.

## Re: Pumping Liquid Nitrogen

Somewhere on teh intarweb "Richard Henry" typed:

Assuming similar materials for rotor and stator (housing).
--
TTFN,

Shaun.

'blanking', nz.comp,  20 Dec 2007.

'blanking', nz.comp, 21 Dec 2007.

## Re: Pumping Liquid Nitrogen

True, but the difference in shrinkage betwen the rotor and stator
would have to be greater that the shrinkage of the stator in order for
the gap to become larger.

## Re: Pumping Liquid Nitrogen

Richard Henry wrote:

Lets see: The rotor gets smaller. The stator gets thinner and its
circumference decreases. Unlike a solid ring, the interior of a rotor is
(usually) slotted, so its circumferential shrinkage doesn't reduce the
ID in the same manner as with a solid ring. The pole pieces do shrink in
length, increasing the stator ID.

I've seen the results of the reverse problem, heating a motor with a
very small air gap to the point that the rotor hit the poles.

--
Paul Hovnanian    paul@hovnanian.com
-----------------------------------------------------------------------

## Re: Pumping Liquid Nitrogen

The circumference, inside and out, decreases.  It gets thinner, but the
inside diameter does not increase; that would be absurd.

If the rotor and stator are made of the same material (they are in an
induction motor, made of laminated steel) and are the same temperature,
then the gap will get smaller as the temperature decreases.

If the materials are not equal (e.g., aluminum housing or rotor, permanent
magnets, etc.), behavior may differ.

Most likely, in a DC motor, the rotor heats up more than the
stator/housing, so the gap will tend to shrink, regardless of the outside
air temperature.  Different types of induction motors (wound, fixed and
permanent rotors, etc.) may behave differently.

Tim

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms

## Re: Pumping Liquid Nitrogen

Tim Williams wrote:

Absurd? That's how one gets a press fit bearing race on a shaft (by
heating it).

That may be the case. I've seen generators fail at high temps by rubbing
the rotor/stator due to decreased clearance. At first, it seemed to be
counter intuitive.

That's possible as well. Behavior of a stator and rotor in contact with
LN2 may have different effects than a machine cooled mainly from the
outside.

--
Paul Hovnanian    paul@hovnanian.com
-----------------------------------------------------------------------

## Re: Pumping Liquid Nitrogen

Not simultaneously.  The bearing (or other socket) is kept at room
temperature or heated, while the shaft (or peg, or...) is cooled or kept at
room temperature, respectively.  Heat makes the inner diameter expand, not
cold.

Tim

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms

## Re: Pumping Liquid Nitrogen

On Sun, 23 Dec 2007 18:08:25 -0600, the renowned "Tim Williams"

And you have exactly one chance to get them into the correct position
before the temperature equalizes...

Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

## Re: Pumping Liquid Nitrogen

Tim Williams wrote:

That's how you get a press fit bearing race _off_ a shaft as well. Not
much chance of maintaining a temp difference between them in this case.

--
Paul Hovnanian    paul@hovnanian.com
-----------------------------------------------------------------------

## Re: Pumping Liquid Nitrogen

Except for certain circumstances: I've heard of CNC heads which have
ferrite transformers in the cutting head to inductively heat the spindle,
expanding it away from the cutter's shank quickly.  Sweet!

Tim

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms

## Re: Pumping Liquid Nitrogen

Richard Henry wrote:

Pretty much, but it still depends on the materials TCE.

--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.
--Schiller

## Re: Pumping Liquid Nitrogen

"Guy Macon" <http://www.guymacon.com/ skrev i en meddelelse

Lucky bastard! That what I want for chrismas.

How about a "bubble pump" or "vapour lift pump"?

Basically the principle used by aquariums. That way you "only" need to pump
very cold nitrogen gas - which could be the gas boiled off from the CPU
cooler

## Re: Pumping Liquid Nitrogen

On Dec 19, 4:27 pm, Guy Macon <http://www.guymacon.com/ wrote:

Imagine an insulated chamber, half-filled with liquid nitrogen, having
a lid with two holes.  One hole is for the nitrogen output tube, which
goes all the way from the lid down to within say 1/8 inch from the
bottom of the chamber.  The other hole is for the input tube, which is
just a short tube.  This is where you blow.

Now you just need a way to blow measured amounts of gas into the short
tube, pushing the liquid nitrogen up the output tube.

Compressed air tank with a needle valve... aquarium pump... CO2 gun
cylinders... ?

Have fun

Michael

## Re: Pumping Liquid Nitrogen

On Wed, 26 Dec 2007 22:58:12 -0800 (PST), mrdarrett@gmail.com wrote:

With that idea, I think the LN2 could pump itself..
How about using gas pressure regulator.
Feed the 'exhaust' N2 gas back to pressurize the tank.
Excess pressure is vented.

D from BC

## Re: Pumping Liquid Nitrogen

So where does the pressure come from?

If I could pull my emitter follower up entirely by its boostraps, I
wouldn't need a battery anymore.  :-)

Maybe with a seperate expansion chamber and keen connections, but offhand,
it doesn't work: internal pressure is internal pressure.

Tim

--
Deep Fryer: A very philosophical monk.
Website @ http://webpages.charter.net/dawill/tmoranwms

## Re: Pumping Liquid Nitrogen

On Thu, 27 Dec 2007 01:41:09 -0600, "Tim Williams"

A nice demo of pressure from nitrogen.
Bottle blowing up from liquid nitrogen

I was thinking this..

Release              +-----------------------+
Valve ||<----+A    |+---------------------+|
+---------||-----||----||-+                   ||
|   N2 pressure           |                   ||
|~~~~~~~~~~~~~~~~~~~~~~~~ |  B                ||
|   LN2                   +->-----------------||
+--------------------------->------------------+
~CPU~

'A' is a pressure sensor which operates an electrically controlled
valve.
'B' is a one way valve.

After awhile, the LN2 eventually disappears and the system blows up.
:)

D from BC

## Re: Pumping Liquid Nitrogen

D from BC wrote:

The above system has equal pressure at all points and thus
will not do any pumping.  You would have to do this instead:

Release
Valve
||<----+A
+--------||-----||--------+                Vent To
|   N2 pressure           |                Room Air
|~~~~~~~~~~~~~~~~~~~~~~~~ |                  | |
|   LN2                   +------------------+ |
+----------------------------------------------+
~CPU~

Alas, you left out the part that caused me to ask
this question:

+------------+
|  Liquid    |
|  Nitrogen  |
|  Generator |
+----+ +-----+
| |
C--->| | Release
| |  Valve
| |   ||<----+A
+--+ +---||-----||--------+                 Vent To
|   N2 pressure           |                 Room Air
|~~~~~~~~~~~~~~~~~~~~~~~~ |                   | |
|   LN2                   +-------------------+ |
+-----------------------------------------------+
~CPU~

"C" is whatever pressure the liquid Nitrogen generator
puts out.  If C has enough pressure to fill the tank,
I can replace the avove system with:

+------------+
|  Liquid    |
|  Nitrogen  |
|  Generator |      Vent To
+----+ +-----+      Room Air
| |
| |              | |
| +--------------+ |
+------------------+
~CPU~

If C does not have enough pressure to fill
the tank, the tank will run out of liquid
and my liquid Nitrogen generator might as well
be something inert and useless, like an
engineering manager.

--
Guy Macon
<http://www.guymacon.com/

## Re: Pumping Liquid Nitrogen

On Thu, 27 Dec 2007 10:21:46 +0000, Guy Macon
<http://www.guymacon.com/ wrote:

k.. gonna go back to the electronics..cause my gas/liquid physics
sucks.. :)

D from BC

## Re: Pumping Liquid Nitrogen

On Thu, 27 Dec 2007 10:21:46 +0000, Guy Macon wrote:

You've just drawn the diagram I was too lazy to draw. ;-) Just insulate
the bejabbers out of the CPU, and use that container as your dewar,
with room for extra as needed. :-)

Would using the exhaust N2 enhance the operation of the genny?
It's sure to be quite cold, you know. :-)

Have Fun!
Rich