Talk:Thermodynamic cycle

Manson and Manson-Guise cycle in table of processes
Can whomever placed the reference to Manson-Guise cycle in the table create a good article on the Manson cycle? Without this, the line appears as a buried advertisement to your cute engine. The Manson-Guise article has no diagrams to explain how it works; shows evidence of advertisement based article. — Preceding unsigned comment added by 73.34.109.242 (talk) 13:32, 11 November 2018 (UTC)

Gravity chimney based cycle
Does anyone know the name of the gravity based cycle used in things like solar chimneys, thunderstorms and very large airconditioning systems? The cycle heats a gas at a constant pressure, expands the gas in a tall chimney (i.e. hundreds of meters tall), cools at a constant pressure and compresses down another tall chimney. I read a paper on it years ago and I can't find any references to it now. njh 00:37, 28 January 2006 (UTC)

Removed some spam. 76.184.116.146 08:10, 28 April 2007 (UTC)

Entropy equation untrue!!
There is a severe failure in this article

The integral (integral( dQ/T))over a hole cycle is only zero if it is an ideal cycle but for any other cycle the so called Clausius inequality is true!! where the Integral is smaller or equal zero! —Preceding unsigned comment added by 83.27.25.158 (talk) 11:05, 8 January 2008 (UTC)

Absorption
"The absorption refrigeration cycle is an alternative that absorbs the refrigerant in a liquid solution rather than evaporating it."

The main difference between the absorption and vapor-compression cycles is the method by which the cycle is driven: vapor-compression cycles are work-driven and absorption cycles are heat-driven. The COMPRESSOR of the vapor-compression cycle is replaced by the absorption components, NOT the evaporator. Both cycles evaporate the refrigerant to provide a cooling heat sink. The article statement quoted above is simply untrue.

Removed material
I removed the 'Demonstration' section which was a highly confusing 'demonstration' that the delta S over a cycle is zero. Looked like it was copied from a textbook or course notes.Cerireid (talk) 20:04, 14 August 2008 (UTC)

FrauEngineer (talk) 19:04, 19 June 2008 (UTC)

Help! I'm confused about the Stoddard cycle!
This page says that the Stoddard cycle has 4 stages: adiabatic, isometric, adiabatic, isometric. But the Stoddard engine page says this cycle is adiabatic, *isobaric*, adiabatic, *isobaric*. Can some expert fix the page that's wrong?

Stoddard's 1933 patent --- you can see it on the Stoddard engine page --- says: "It is to be noted that the increase in pressure at the end of the up stroke of the piston is due to the rise in temperature and not to mechanical work". That sounds like an isometric stage, not an isobaric one. John Baez (talk) 17:42, 13 February 2010 (UTC)

Use of the term "isometric" in the "table of thermodynamic cycles"
Wouldn't it be better to substitute the word "isometric" by "isochoric", since the only occurence of this term is in the said table, while the rest of the article uses the term "isochoric" for processes with constant volume? I couldn't access the table myself, since I'm not used to edit pages on wikipedia, but would somebody mind to change it?

Rankine cycle in the "Some example thermodynamic cycles"
The table of thermodynamic cycles (Some example thermodynamic cycles) in this page, as error the Rankine cycle isn't cycle with internal combustion. This cycle has an external source of heat (external combustion). I would correct the mistake but I don´t how. Apologies for my mistakes.Gonçalo Quintal (talk) 11:51, 3 May 2011 (UTC)

--79.208.112.246 (talk) 08:59, 22 September 2010 (UTC)


 * Agreed, the article should be internally consistent. FYI this table is in Template:Table of thermodynamic cycles; the change was not a problem for any of the other articles it is used in.
 * ✅ David Hollman (Talk) 10:36, 22 September 2010 (UTC)

Ideal cycle
Why is it this cycle that is chosen to be ideal: that is, what about it is 'ideal'?

(There is no 'ideal cycle' article, which suggests that it is not all that notable).

86.3.108.41 (talk) 15:30, 28 September 2011 (UTC)

I believe that the author of the article sees this cycle as an ideal because it represent the maximum amount of work for a piston steam engine given a boiler pressure and fixed stroke. Steam locomotives use this cycle when starting from a standstill in the station giving the greatest accelerating force to get the train rolling. However it is horribly inefficient as the expansion is done at constant volume which means that at the end of the stroke the high pressure steam is throttled to the atmosphere. As the locomotive approaches its design speed, the full pressure is only applied for part of the stroke and the steam is left to expand to atmospheric pressure within the cylinder in an (ideally) adiabatic process. When the exhaust valve open atmospheric pressure steam is evacuated from the cylinder during the exhaust stroke. This greatly increases the efficiency of the locomotive. The inefficient cycle is only used for a small fraction of the whole journey to quickly get the train up to speed. — Preceding unsigned comment added by 67.193.115.51 (talk) 03:52, 15 December 2011 (UTC)

Ideal cycle
This cycle is great for first year physics classes, and among physics teachers is possibly second only to the Carnot cycle in importance. The problem lies in the parallel nature of two articles Heat engine and Thermodynamic_cycle. I found the former article but not the latter and for that reason failed to find the figure to the left. That forced me to make the figure to the right. The proposed page would carefully explain why the area equals the work done, how to interpret the isotherms, and how heat engines establish that work and heat are not state variables. If the Ideal Cycle had its own page we could enter it in this list of heat engines: https://en.wikipedia.org/wiki/Heat_engine#Gas-only_cycles. --guyvan52 (talk) 23:33, 15 December 2013 (UTC)

P-V Diagrams look odd
I noticed the curved lines on the P-V diagram are not labeled and appear to not lie as I would expect. If the curved lines are constant temperature they should appear to run asymptotic to the P and V axis'. I'm not sure how the lines of constant entropy should lie but should probably appear nearly asymptotic to those axis' also. They are only sketches but the lines of constant this or that might be labeled as such. I need to pick up the skill to create such diagrams and other sketches.Zedshort (talk) 19:20, 18 January 2014 (UTC)

On the figure to the right, isotherms are by definition curves of constant temperature. With an ideal gas, the isotherms are hyperbolas (of the form xy=constant). I tried to deliberately make them not hyperbolic curves for the generic substance. On some of the cycles we need to plot both adiabats (constant entropy) and isotherms (I think either the Otto or Sterling cycle needs this). I hesitate to make the diagrams because cris-crossing sets of curves seems a bit fussy. Need to think about this for a while.--guyvan52 (talk) 20:20, 18 January 2014 (UTC)

Problems with accurately describing heat iin the listed thermodynamic processes (1.3 A list of thermo...._
Under item 1.3	"A list of thermodynamic processes", under Isothermal, the last sentence "Energy transfer is considered as heat removed from or work done by the system." does not relate the heat transferred and the work associated with the process - the net energy (the sum) of heat and work is zero - the linked article on Isothermal says it much better. under Isochroic, "Energy transfer is considered as heat removed from or work done by the system." - there is no change in volume so no work involved - again, the linked Isochroic article gets it right. under Isentropic, "no physical work is done by/to the system." Again, the linked isentropic article gets it right. An isentropic process is an adiabatic process with the additional requirement that the process is isentropic (no increase in entropy thus an isentropic process is reversible)  108.51.46.68 (talk) 04:29, 17 November 2020 (UTC) 108.51.46.68 (talk) 04:29, 17 November 2020 (UTC)

Atkinson Cycle
The ideal Atkinson cycle is actually a combination of isochoric heat addition with isobaric heat rejection. Atkinson-cycle exhaust volume is greater than intake volume, so describing heat rejection as "isochoric" is clearly inaccurate. In actual Atkinson engines, expansion is truncated before reaching actual isobaric conditions due to engine friction. Since the Atkinson cycle is actually the isentropic-isochoric-isentropic-isobaric thermodynamic cycle, there is no distinct "Humphrey Cycle". So, unless Humphrey predated Atkinson (1882), that listing is out of place in this article. — Preceding unsigned comment added by 198.208.46.93 (talk) 13:02, 6 June 2022 (UTC)