Can Joule-Thomson effect freeze air?

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In summary, the question is whether air escaping through a narrow opening into a vacuum can cause frozen N2/O2 to accumulate and clog the opening due to cooling from Joule-Thomson expansion. The answer is that it depends on the conditions, but in steady flow, the frictional heating of the air will prevent it from cooling to cryogenic temperatures and clogging the opening. However, if the flow reaches sonic conditions and the orifice becomes choked, some cooling may occur, but it would not be considered a Joule-Thomson effect. It is also worth noting that in the non-JT regime, cooling would occur in the approach to the orifice but could not cool more than the point where sonic velocity is reached.
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Malapine
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TL;DR Summary
Would air escaping thru a narrow opening into vacuum eventually clog it shut with frozen N2/O2, due to cooling from J-T effect?
Could air escaping through a narrow opening into a vacuum freeze due to cooling from Joule-Thomson expansion, and cause frozen N2/O2 to accumulate around the edges of the opening until it clogged shut ?
 
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Malapine said:
Summary:: Would air escaping thru a narrow opening into vacuum eventually clog it shut with frozen N2/O2, due to cooling from J-T effect?

Could air escaping through a narrow opening into a vacuum freeze due to cooling from Joule-Thomson expansion, and cause frozen N2/O2 to accumulate around the edges of the opening until it clogged shut ?
Are you talking about the case of steady flow through an orifice, or the case where you have two closed chambers and you let the pressures equalize?
 
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Steady flow through an orifice, from an unlimited reservoir of STP air (for example an extremely large space habitat) into an unlimited vaccum.
 
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Malapine said:
Steady flow through an orifice, from an unlimited reservoir of STP air (for example an extremely large space habitat) into an unlimited vaccum.
Are you sure you want to do it with STP air? That won't produce much of a JT effect. The JT effect is based on the deviation from ideal gas behavior, and, at STP, air behaves very close to an ideal gas.

Did you think that expansion cooling would take place? It wouldn't, because, for an ideal gas, it is offset by the viscous frictional heating in the orifice. In JT flow, the change in specific enthalpy between inlet and outlet from the orifice is zero.
 
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So: frictional heating of normal air flowing through the orifice will prevent it from cooling to crygenic temperatures as it expands into the vacuum, and the hull breach won't seal itself with a block of frozen air.
 
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Malapine said:
So: frictional heating of normal air flowing through the orifice will prevent it from cooling to crygenic temperatures as it expands into the vacuum, and the hull breach won't seal itself with a block of frozen air.
No. Not if there is steady flow.

Of course, the JT effect assumes no change in kinetic energy. If the flow reaches sonic conditions and the orifice become choked, some cooling will occur by conversion of enthalpy to kinetic energy. But this would not be considered a JT effect.
 
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Would there be any decrease in temperature or pressure upstream from the orifice? I am assuming some sort of tornado-like vortex forms in the area above the breach, but if there is no pressure or temperature drop, then there won't be a visible condensation funnel (or no funnel at all, just inflow jets?)
 
  • #8
Well, if we are now talking about the non-JT regime, then cooling would be occurring in the approach to the orifice. But it could not cool more than where you get sonic velocity at the orifice.
 

1. What is the Joule-Thomson effect?

The Joule-Thomson effect is a phenomenon in thermodynamics where a gas experiences a temperature change when it is forced through a valve or porous plug. This effect occurs due to the conversion of kinetic energy to potential energy as the gas expands.

2. Can the Joule-Thomson effect freeze air?

Yes, the Joule-Thomson effect can cause air to freeze if the conditions are right. When air is forced through a valve or porous plug, it experiences a decrease in temperature, which can lead to the formation of frost or ice.

3. What are the conditions for air to freeze due to the Joule-Thomson effect?

The conditions for air to freeze due to the Joule-Thomson effect include a high pressure and low temperature. This can be achieved by compressing the air and then allowing it to expand rapidly through a valve or porous plug.

4. Is the Joule-Thomson effect used in any practical applications?

Yes, the Joule-Thomson effect is used in various industrial processes, such as liquefying natural gas and refrigeration. It is also used in air conditioning systems to cool air.

5. Can the Joule-Thomson effect be reversed?

Yes, the Joule-Thomson effect can be reversed by changing the pressure and temperature conditions. This is known as the Joule-Thomson inversion and is used in some industrial processes to heat gases.

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