Talk:Polytropic process

Gamma heading

When referring to an isentropic gas under this heading, is the isentropy a function of position or of the process? Perhaps it should read "a gas undergoing an isentropic process", and similarly for the phrase "isothermal gas". This may seem like obvious shorthand to the initiated, but for newbies it can leave niggling uncertainties about important concepts. Jeffzda (talk) 04:41, 19 February 2008 (UTC)

Thank you for correcting. The original word looks like: Πολύ --ZJ (talk) 10:17, 8 March 2010 (UTC)

I'm afraid I can't make much sense out of this section. The first two lines basically just repeat information in the first section. But the rest - about the two gammas - can someone explain what that is trying to convey? What are the "two gammas"? At first I thought it just meant that there was a notational variation, but the formula seems to imply otherwise... Thanks. David Hollman (Talk) 21:40, 4 September 2010 (UTC)

Range of gamma

In the end of section 1, it is stated that 1<=gamma<=2. Can the limit 2 be correct as it implies that for instance R<= C_V is a limit? April 2010

The adiabatic index come from the Gibbs phase rule (degrees of freedom). Its maximum is 2 and less if the number of atoms more and more in the molecule. Theoretically it is 1 for big molecules.ZJ (talk) 17:43, 29 June 2010 (UTC)

I think the discussion of the range of the adiabatic index does not belong in this article at all. David Hollman (Talk) 19:32, 6 September 2010 (UTC)

Derivations

Showing some of the derivations related to the polytropic process will help improve the article. Kindly show some derivations like the general expression for the work done in a polytropic process. — Preceding unsigned comment added by AdityaRaj16 (talk • contribs) 18:04, 30 November 2011 (UTC)

The derivation is a bit unclear, when stating: "$\ln P+n\ln v=C$ which can be differentiated and re-arranged to give..." What is differentiated here? To differentiate $P$ and $v$ have to be functions of a variable to differentiate by. Sorry if this is not correct English. What I mean is, if you want to differentiate i. e. $f$, then $f$ is a function of a variabel, say $f=f(x)$ an you can differentiate by $x$. But with $P$ and $v$, I don't see the function, or the variable they depend on. — Preceding unsigned comment added by 178.8.199.254 (talk) 14:22, 13 September 2014 (UTC)

n<0

In the table for the different ranges of n, the first line states that n<0 is equal to an explosion. This seems wrong. n simply isn't defined for values smaller than zero. An explosion (e.g. dynamite) would produce a lot of heat and therefore probably have an n of 2 or something like that. This should either be removed, since I don't know of any sources that cover n<0 or should state, that this case doesn't exist.--188.174.0.179 (talk) 19:47, 19 March 2012 (UTC)

This isn't saying that *all* explosions must have n<0, just that if n<0 an explosion occurs. for n<0, P *increases* with V, which is an unstable condition (hence the claim of an eplosion) perhaps "An unstable condition; leads to explosion" is clearer?

128.200.44.243 (talk) 20:49, 13 July 2012 (UTC)

It actually seems, that negative n can be meningfull in some cases not dominated by thermal interactions. I found references to its use in the processes of certain plasmas, mostly in astro-physics it seems.

English language reference: [1], Japanese reference which may or may not be relevant (I can't read Japanese, but the title looks promising): [2]

As it seems impossible for a "normal" thermodynamic system (dominated by pressure and temperature) to exhibit a negative index, and thus expand uncontrolably, I will go ahead and remove the unsourced "explosion" comment, and replace it with a note about the use in plasma processes in astro-physics. - Tøpholm (talk) 16:32, 25 July 2012 (UTC)

I don't understand most of these comments. n=0 is a constant-pressure process because the polytropic equation reduces to P = constant since v^0 = 1. I also don't understand the comments about negative polytropic exponent. Look at the derivation regarding the energy transfer ratio. For example, a process would have a polytropic exponent of -1 if it has an energy transfer ratio of 6. This is a perfectly normal process where we don't need to talk about explosions or plasmas or anything like that. Just my two cents.

Why does "pantropic" redirect here?

Not mentioned or explained in article. 109.157.79.50 (talk) 22:56, 3 February 2015 (UTC)

Exponentiation of volume

How can the dimensionful quantity of volume be raised to a non-integer exponent? 2A01:799:952:4500:115D:84C8:EEA5:B28C (talk) 18:52, 9 January 2024 (UTC)