Talk:Thermodynamic equilibrium

1.What the formula for specific heat capacity????

see Heat capacity, Specific heat capacity

2.What the formula for specific latent heat of vaporization and specific latent heat of fusion?

see Latent heat, Heat of fusion, Heat of vaporization.

Please show some examples that can prove the formula are correct.

Please help us improve articles. If this article Thermodynamic equilibrium would be improved by the above links, please add those links to the article. --DavidCary 13:11, 23 September 2005 (UTC)

---

'Local t. e.' Anybody got a reference for that? It's not what my understanding is.GangofOne 06:28, 15 August 2005 (UTC)

---

The first paragraph is general but good. I have a problem with LTE, namely the field to which these considerations apply need be mentioned (heat transfer?). Local thermodynamic equilibrium can mean many other tings, for instance it is an hypothesis on which calculations of collective diffusive processes are often based (not only radiation heat), and the basis for the Onsager approachuser:ThorinMuglindir

---

The definition of TE should include the word "isolated" somewhere - otherwise we could be talking about a non-equilibrium stationary state, for example a material with a constant flow of heat through it. The zeroth law then needs to say that the systems in equilibrium need to be in contact with each other, but otherwise isolated. The LTE is too specific - it should say that parts of the system are approximately equilibrium states, but not in equilibrium with each other, for example if the temperature varies with position. Carl Dettmann, Bristol 24 October 2005.

Global thermodynamic equilibrium means that the values of intensive parameters are homogeneous throughout the whole system Temperature certainly and pressure maybe, but density by no means (e.g. water at the triple point). --Art Carlson 17:23, 25 October 2005 (UTC)

Art, you are certainly right, that statement is too far-encompassing. Density doesn't work because it is not a quantity linked to the exchange of some extensive quantity (like pressure is linked to the exchange of volume, and temperature is linked to the exchange of heat). Otherwise on another notice sometimes the intensive parameter that controls equilibrium is not always something simple as (just) P. For example, in the presence of a gravity field, equilibrium is reached not when P is constant, but rather when $P-\rho gz$ is constant over the system. It seems the text needs to be more careful, though I need a bit of thinking in order to explain these subtleties as simply as possible. The rewriting from what I left is great.ThorinMuglindir 21:17, 25 October 2005 (UTC)

OK I made a more careful rewriting of that part.ThorinMuglindir 22:57, 29 October 2005 (UTC)

On a similar notice I reworded slightly the part about the glass of water at the end. An out-of-equilibrium state can be maintained in a system, not only "artificially maintained" as I had written. For example, the sun maintains a certain amount of non-equilibrieum on the surface of earth, but this is not "artifical."ThorinMuglindir 21:28, 30 October 2005 (UTC)

Two points:

• Density gradients are linked to the exchange of mass, through the process of diffusion

• diffusion of molecules will sometimes happen according to the gradient of density (like within a gas, if gravity is negligible), but not always (like at a liquid vapor interface). I believe that most generally, diffusion of a certain species will happen according to the gradient of chemical potential of that species: that's $\mu$ in thermodynamics equations and $\mu _{j}$ in statistical mechanics (grand-canonical ensemble).

• What is the equilibrium nature of water at the triple point, in the absence of gravity and boundaries? Would there be a tendency as time goes by to form large scale density variations, like water/ice planets, or would it be a big cloud of small ice crystals and water droplets? If so, how small? PAR 22:05, 30 October 2005 (UTC)

• If the system is not submitted to external gravity, but gravity between components of the system would remain, there would be a tendancy to form ice and water planets (or planets made of both more probably), though that would be only for very large systems. If gravity is totally suppressed, or for a smaller system, capillarity would prevent water drops from divinding when they are below a certain size. Sometimes two water drop would collide each other and merge. Big droplets would have a tendancy to divide, but would this process eventually eliminate all water masses above a certain size before they have time to form by random merging? I can't answer to this last question.ThorinMuglindir 23:58, 30 October 2005 (UTC)

That makes sense, except the part about large droplets having a tendency to divide. What's the force causing the division, just the random accumulation of angular momentum? PAR 02:47, 31 October 2005 (UTC)

---

Shouldn't the relation of thermodynamic equilibrium to entropy (specifically, the fact that entropy is maximized at equilibrium) be mentioned in here somewhere? I'm not knowledgeable enough about the technical details to add it myself, but I thought it was pretty important. Hypnosifl 21:50, 19 October 2006 (UTC)

Steady state versus uniform conditions

It would seem the article needs to make a clearer distinction between the concepts of a "uniform" medium versus a system in steady state, the latter allowing spatial but not temporal dis-uniformity. I can take a stab at some of this in the thermal context. Rnestle 18:31, 22 February 2007 (UTC)

There's another state - equilibrium, which may not be uniform but will be steady state. This article should confine itself to the equilibrium state, with mention of other possibilities which should be developed in their own article. PAR 20:25, 22 February 2007 (UTC)

As far as other articles, shouldn't we have an article called Thermal equilibrium? presently that link just takes one to the present article. Rnestle 21:40, 22 February 2007 (UTC)

Definition?

I'm a little confused about the wording and inferences implied in the definition. Can ANY system EVER be said to actually be in 100% equilibrium or 100% isolated from its environment or surroundings. i.e. will ΔS ever actually equal 0 or does it just 'approach' it?

---

—Preceding unsigned comment added by Nomdelapaix (talk • contribs) 12:15, 9 April 2010 (UTC)

You are right. No physically real system can be in strictly exact thermodynamic equilibrium. One studies approximations to it, and they are useful for theoretical studies, and for practical measurements. Practically all real physical systems involve transport of matter or energy or both, and are thus not strictly exactly in thermodynamic equilibrium.Chjoaygame (talk) 21:53, 28 November 2011 (UTC)

Thermal dispersion?

What the heck is thermal dispersion? I am removing it from the article as it means nothing to me. --Drozdyuk (talk) 14:44, 14 July 2010 (UTC)

Furthermore I removed the reference to C.Michael Hogan et al., 1973, as I was not able to find it immediately, and there is not journal, publisher or any other indication as to the origin of the reference. --Drozdyuk (talk) 14:47, 14 July 2010 (UTC)

Agreed, the reference was too ambiguous for any one to find it. I believe the term that the previous author was looking for was "thermal diffusion", but perhaps by the term "dispersion" he was trying to to be inclusive of advective effects. However, there is still a serious problem with this section in that the river example contradicts the previous statement "in an equilibrium state, there are no unbalanced potentials (or driving forces) with the system." The river, while not time variant, has temperature gradients (i.e. potentials) driving heat flows via Fourier's Law and is encountering thermodynamic irreversablity. I think this section is confusing "equilibrium" with "steady". Even so, the river analogy has complications in that the flow is only valid in the Eulerian frame of reference and that real rivers are turbulent and hence stationary (invariant statistics with respect to time) rather than steady (invariant spacial distribution of state variables). Not sure what your background is Drozdyuk, so I apologize if I lost you with any of the aforementioned terminology. In any case, I wish to look at some text books for reference next week for a solid reference on the meaning of the term "thermal equilibrium". I think the truth is that it is often causally used in situations that really don't stand up to rigorous scrutiny because they depend on the frame of reference and a good article needs to discuss the distinction in a manner that people can understand. —Preceding unsigned comment added by Bdentremont (talk • contribs) 04:29, 15 July 2010 (UTC)

Definition of Thermal equilibrium

TThe current article (08/10/10) states:

"Thermal equilibrium is achieved when two systems in thermal contact with each other cease to exchange energy by heat"

I believe is more proper to state that

"Thermal equilibrium is achieved when there is no longer a net change of heat exchange between two systems in thermal contact with each other"

in the same sense as when a chemical reaction reaches equilibrium. My point is that heat exchange never "ceases," but that the rate of heat exchange between AB and BA are the same. I don't think my version expresses this idea fully, Can someone paraphrase properly?

I think an even better definition would be "when the net energy exchange rate by heat between two system is zero". But I'd like to dig what textbooks say, before. --Cyclopia^talk 00:44, 11 August 2010 (UTC)

Global stationarity

I feel that the phrase "global stationarity" is too technical for this article. I "think" I understand what it means, but I am very sure that the average reader won't. Q Science (talk) 16:36, 14 November 2010 (UTC)

Equilibrium Temperature? (of planets. Copied from Kepler 11.)

This chart is copied straight out of the article for Gliese 581 g.
Does anyone else think it would be a good idea to make it a standard chart for all extra-solar planets that are compared to Earth?
With the relevent values swapped in of course.
24.79.40.48 (talk) 17:05, 26 November 2011 (UTC)

Temperature comparisons	Venus	Earth	Gliese 581 g	Mars
Global equilibrium temperature	307 K 34 °C 93 °F	255 K −18 °C −0.4 °F	209 K to 228 K −64 °C to −45 °C −83 °F to −49 °F	206 K −67 °C −88.6 °F
+ Venus' GHG effect	737 K 464 °C 867 °F
+ Earth's GHG effect		288 K 15 °C 59 °F	236 K to 261 K −37 °C to −12 °C −35 °F to 10 °F
+ Mars' GHG effect				210 K −63 °C −81 °F
Tidally locked	Almost	No	Probably	No
Global Bond Albedo	0.9	0.29	0.5 to 0.3	0.25
Refs.

break

Possibly. I'd definitely find it useful in visualizing the planets more accurately. I'll request more input by notifying WikiProject Astronomy, see if this can get any extra opinions. --Starstriker7^(Talk) 19:11, 26 November 2011 (UTC)

No, many exo-planets are Super-Jupiter or Neptune sized, comparing those to Jupiter or Neptune would be better. Large Super-Jupiters should be compared to the smallest theoretical brown dwarf and Jupiter, smaller ones ( <5M_J ) can drop the brown dwarf comparison. 70.24.248.23 (talk) 23:11, 26 November 2011 (UTC)

That's why I mentioned, with relevent values swapped in. I know for example Jupiter has a suface temperature, core temperature, and equilibrium temperature. I don't see the problem with swapping the gas giant values in. I think the main point would be the comparison of equilibrium temperatures, which is mainly influenced by distance. The irradiance of each planet would be good also but no one does a comparison of those, the equilibrium temperature is the closest thing. 24.79.40.48 (talk) 15:35, 28 November 2011 (UTC)

Remember that thermodynamic equilibrium is a laboratory and theoretical thing, not found in general in nature, useful for basic theoretical studies, but not directly in practical applications. Thermodynamic equilibrium is a special kind of equilibrium, in which there is zero transport of everything. The kinds of equilibrium that pertain to planets involve massive transport of energy and matter, and are thus quite far from thermodynamic equilibrium.Chjoaygame (talk) 21:48, 28 November 2011 (UTC)

♦ What I will remember is your suggestion that a great many Astrophysicists, using Equlibrium Temperature, are out to lunch. 24.79.40.48 (talk) 03:25, 15 December 2011 (UTC)

That chart is nonsense. For instance, the Earth's "Global equilibrium temperature" is close to 5°C, not -18°C (which includes the albedo of clouds, ice, and the like). If the albedo is included for Venus (in order to make a fair comparison), the surface temperature should be 184.2K (-89°C), not 34°C. The greenhouse stuff is also nonsense, as is the claim that Venus is almost tidally locked (? - not really). Note: that chart was created by user:GabrielVelasquez the day before he was permanently blocked. I suggest that everything written by that person needs a real close look. Q Science (talk) 04:35, 29 November 2011 (UTC)

Apart from the above criticism of the content of the chart, I would add that the chart would not be appropriate for this article on thermodynamic equilibrium even if it were not nonsense.Chjoaygame (talk) 22:43, 29 November 2011 (UTC)

I find these comments silly since the chart is already in several articles for extrasolar planets, there is no need to dismiss it based on a hatred of a particular user. In fact I would go as far as to say the criticism is very irrational since almost every popular article on an extrasolar planet refers to its Equilibrium Temperature.
If scientist keep referring to this ( and it is -18°C for Earth) in many articles for extrasolar planets, then where is the article for this idea??? 24.79.40.48 (talk) 02:39, 15 December 2011 (UTC)
Maybe this thing that scientist keep refering to needs its own article! instead of being directed back here. 24.79.40.48 (talk) 03:30, 15 December 2011 (UTC)

I agree with Chjoaygame: this chart is completely inappropriate to this article, and even this talk page is not the place to discuss the usefulness of producing a standard chart. For a proper discussion, move it to someplace where editors with a suitable knowledge of the area will be involved. Quondum^talk_contr 08:11, 15 December 2011 (UTC)

It seems that my above remarks are not making sense to some editors. Please let me try again. Equilibrium is a widely used word, with many meanings. Thermodynamic equilibrium is a term of art in thermodynamics, a specifically defined kind of equilibrium, indeed a kind that practically never occurs exactly as defined; it can be approximated in laboratory experiments. Thermodynamic equilibrium explicitly forbids flow of any kind, while the energy budgets of planets are all about significantly large flows of energy, the very denial of thermodynamic equilibrium. The question here is not as to the content of the table but as to the content of an article on thermodynamic equilibrium. I have not studied the table in question here, but it does not need study to say that the present Wikipedia article on thermodynamic equilibrium is not its natural home. Without prejudice as to the value of the table for elsewhere in the Wikipedia, the table has no place here.Chjoaygame (talk) 18:38, 15 December 2011 (UTC)

Note, it would be courteous to state the actual question when starting an RFC. I infer it's whether to include the above chart? No, it refers to a different kind of equilibrium. Nobody Ent (Gerardw) 22:03, 16 December 2011 (UTC)

I have removed the text-wrap code and displayed the references. Notice that 2 of the references don't go anywhere. Also, that most of the data in the table is not referenced. Q Science (talk) 07:57, 17 December 2011 (UTC)

♦ How convenient for your argument that they don't work here, but they work fine where the chart was copied from: Original Chart
24.79.40.48 (talk) 07:11, 19 December 2011 (UTC)
♦ Again, Maybe this thing that scientist keep refering to needs its own article! instead of being redirected back here. 24.79.40.48 (talk) 07:14, 19 December 2011 (UTC)
♦ Regardless of anyone understanding your comments about Thermodynamic Equilibrium or not, by default the relevant and important point you are both missing is that mentions of Equilibrium Temperature in articles about extrasolar planets do link to this Thermodynamic Equilibrium Article. All mentions in all articles. Any mention in any article of Equilibrium Temperature, here, Hello? If you are correct then correct all the redirects of Equilibrium Temperature. 24.79.40.48 (talk) 07:23, 19 December 2011 (UTC)