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The Joule-Thomson Effect and Models We Know

mattferraro.dev

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Re: The Joule-Thomson Effect and Models We Know

#21

Post by wizzwizz4 »

avmich wrote: post #5

Good article. Certain tempting things left unexplained though :) . Like, why properties of H, He and Ne are such that they are at this part of their diagram at normal conditions? Or where dispersion bonding stores the kinetic energy - when two atoms bond this way, both momentum and energy should be preserved, so some places to put excess of energy should be present, otherwise the pair should be unstable. Like, requir…

> Like, why properties of H, He and Ne are such that they are at this part of their diagram at normal conditions?

This is the wrong question. You should, rather, ask: “under what conditions are things at various parts of the diagram?” “Normal conditions” are really just happenstance, if you're considering physics; stars and the immense void of space are both much more common than room temperature, room pressure.

Re: The Joule-Thomson Effect and Models We Know

#22

Post by chermi »

mattb314 wrote: post #20
Pulcinella wrote: post #2

One of my favorite things about the JT effect is how gases not being “perfect” is actually “better” than if they were. What I mean is, if gases all behaved as some kind of perfect, platonic* ideal of a gas and followed the ideal game law exactly, there would be no temperature change. But because they don’t, the Joules-Thomson effect is what allows for refrigeration. *Helium is probably the closest to some platonic id…

> Joules-Thomson effect is what allows for refrigeration I don't think this is true. The "simple" model of refrigeration taught in highschool is just a carnot cycle running backwards, and this can be modeled with an ideal gas. The author of the post covers this the section on "the Thermodynamics 101 Answer"[1], where all you need to drop the temperature of a gas is to let it do work on the piston. That's not to say t…

Yes, you can explain refrigeration with ideal gas. But...

You need non-ideal gas (attraction) to get temperature inversion. Then you just need compressor and voila, look at PT charts to find what temperature range you need. With ideal gas reverse carnot refrigerator your refrigeration effect is bounded on low temperature side by the available low temperature source.

So yes, you can refrigerate with ideal gas, but it's not very helpful in warm areas or if you need to get something super cold.

Re: The Joule-Thomson Effect and Models We Know

#24

Post by pdonis »

onos wrote: post #23

The physics answer may be right but it sounds like nonsense. Any clearer discussions?

What sounds like nonsense? The fact that atoms are not actually infinitely solid billiard balls that just bounce off each other instantaneously should not be controversial. I think what's given is actually a pretty good layman's explanation of why a certain amount of the total internal energy of a gas is stored as potential rather than kinetic energy.

Re: The Joule-Thomson Effect and Models We Know

#25

Post by onos »

pdonis wrote: post #24
onos wrote: post #23

The physics answer may be right but it sounds like nonsense. Any clearer discussions?

What sounds like nonsense? The fact that atoms are not actually infinitely solid billiard balls that just bounce off each other instantaneously should not be controversial. I think what's given is actually a pretty good layman's explanation of why a certain amount of the total internal energy of a gas is stored as potential rather than kinetic energy.

I misunderstood and humbly retract my mean criticism. You’re right it does make sense.
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