Talk:Joule-Thomson effect/Draft

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Wikipedia has a similar article

I extensively contributed to the Wikipedia article of the same name. I would estimate that about 75 percent of the wording in that article was mine.

I reworked it somewhat in my CZ sandbox and conformed it to a CZ article format. - Milton Beychok 19:49, 17 February 2008 (CST)

comments

1) the equation for $\mu _{JT}$ is written as if it is a constant. Should this be written as $\mu _{JT}$(T,P) to reflect its dependence on the initial temperature and pressure?

2) Is there any theoretical explanation for this phenomenon, or is it typically thought of as a phenominological effect that is just measured? In other words, does it relate to electrostatic interactions between atoms/molecules, polarizability, etc? I haven't thought about the JT effect for quite some time (decades!), but I'll look around for a textbook or two and look for answers also. David E. Volk 15:49, 11 July 2009 (UTC)

3) The original reference, should you want to incorporate it is: J. P. Joule and W. Thompson, Proc. Roy. Soc. (London), 143, 357, (1853). Another fine experiment conducted in a Brewery!

4) The JT effect is valid for liquids also, not just gasses, at least according to the thermo classic text by G. N. Lewis and M. Randall, Thermodynamics, 2nd Edition, revised by Pitzer and Brewer, McGraw-Hill Series in Advanced Chemistry (1961).

David, in response to (1), I have always seen the J-T effect written simply as $\mu _{JT}$. I just made another Google search and all of the information I found used simply $\mu _{JT}$. The article does state that J-T effect "depends on the specific gas, as well as the temperature and pressure of the gas before expansion", so your point is made, don't you think?

As for (2), there probably is a theoretical mechanism that can explain the phenomenon in terms of the attractive and repulsive forces between molecules. My main focus in writing the article was to explain what the J-T effect is and how it is used in industry ... rather than trying to explain the theoretical mechanism. I know ... that is the typical engineering attitude. If you would like to add another section to the article that explains the theoretical mechanism, please do so.

In regard to (3) and 4, I will incorporate that original reference and I will include liquids in the lede.

Thanks for your comments, I really appreciate them. Milton Beychok 18:04, 11 July 2009 (UTC)

Milton, I checked my texts too and they also use $\mu _{JT}$ as you have done, so clearly that is the standard nomenclature. As for theory, no time to work on it currently, but one day perhaps. David E. Volk 12:48, 14 July 2009 (UTC)

Milt, I may have missed it here (astigmatism sometimes does that to me) but I didn't see the elements of the equation defined. Those with the appropriate background will know what they are but not everyone will recognized the "del P" and "del T" and the "sub H". Is there a standard we use for defining the terms in an equation below the equation? Karl D. Schubert 17:57, 30 September 2009 (UTC)

Good point, Karl. I have revised the first sentence in this section to make clear what the terms in the equation mean. There are a myriad of ways used in CZ (and in Wikipedia) for defining the terms in an equation, depending on the author. I usually list and define them below the equation. However, in this case I defined them in words (rather than math) in the first sentence preceding the equation because I don't want to get involved in explaining what "partial of T" and "partial of P" are ... or explaining thermodynamics notation.

By the way, Karl, please read the blue banner at the top of this page explaining how to use indentation on Talk pages. Milton Beychok 19:00, 30 September 2009 (UTC)