Talk:Stirling cycle

message: This is a great addition to Wiki's Stirling engine content (I particularly love the clear illustration that the adiabatic component of compression and expansion can actually produce a gas temperatures swing higher than the temperature difference between the heater and cooler - so watch those volume ratios all you would-be builders of low and medium temperature difference engines!) but the link to it from the main engine article is somewhat buried - would it be better to merge it into that article? Also, citing Alan Organ's work might be polite.
213.123.247.91 (talk) 12:15, 18 January 2008 (UTC)
thread_title: Untitled

message: It would be nice to have a common T-s and P-v diagrams for all thermodynamic cycles in both their ideal and realistic forms.
bmunden   —Preceding unsigned comment added by 128.211.166.182 (talk) 08:46, 8 January 2010 (UTC)
thread_title: Untitled

message: Heater, Annular-Gap Heat-exchanger
Dimension                                       	Inches	cm  	mm    	m
Inner diameter of pipe                          	4.920 	12.5	125.0 	0.125
Perimeter                                       	15.450	39.2	392.4 	0.392
Length of gap (same as length of tubular heater)		11.191	28.4	284   	0.284
Gap Depth (thickness) (=Aff/perimeter)          	0.050 	0.13	1.3   	0.001
Hydraulic Radius                                	0.025 	0.06	0.6   	0.001
Total outer HX-area (linear units^2)            		192  	1238	123811	0.124
				
				
				
Cooler, Slot Heat-exchanger
Dimension                             	Inches	cm  	mm   	m
Inner diameter of pipe                	5.174 	13.1	131.4	0.131
Minimum Required pipe diameter        	5.17  	    	     	
Minimum Required Pipe wall thickness  	0.303 		0.769	7.69 		0.007689
Length of heat exchanger              	3.392 		8.616		86.2		0.086157
Hydraulic Radius of slots             	0.013 		0.033		0.326		0.000326
Width of slots (min = kerf)           	0.030 		0.1		0.76		0.000762
Slot Depth (or fin height)            	0.178 		0.5		4.5 		0.005
# of slots   (# of slot & fin pairs)  	361   		361		361 		361
Width of fins (material between slots)	0.015 		0.04		0.38		0.000381
Total wetted-area (linear units^2)    	490   		3163		316317		0.316
this information is not relevant, to the heat exchange involved in heat engine.  — Preceding unsigned comment added by 2601:1C1:8B00:3B10:5479:1F9C:76EA:212F (talk) 16:27, 31 December 2019 (UTC)
thread_title: Example heat exchanger Data

message: Some of this is helpful, but I have to say, "constructive criticism" goes a lot further than negative criticism.  This article is barely 3 months old, and there haven't been a lot of contributers.  So consider these too: WP:WIKIFY, WP:STUBS, WP:CINA.  I guarantee this topic belongs in Wikipedia.  Ask any contributor to the Stirling engines article.  While you're there, ask them to verify the references.  They know these authors.   (also see previous discussion).  We absolutely need some sort of article for this topic, and what's there now is better than nothing.  Until 2008, there was nothing at all!  Don't threaten to delete it, because that is not helpful, and it's personally offensive.  As I said, there are a million other articles that are worse than this one, so I think you're being awfully harsh in your judgment.  If you judged them all this harshly, you would end up deleting a significant portion of the articles.  Try to understand that this is not an easy subject to cover.  Be patient, because it takes time to edit and revise and make a good article.  I have a feeling that part of what you dislike is the formatting.  It might help to right-justify the images, but I'm not exactly an expert in formatting.  It is engineering oriented.  It may go to wikibooks, it's not entirely clear yet.  But don't jump to conclusions so fast.  First of all, below are some comparable topics to compare and contrast:
*Rankine cycle - Some people start out with the engine, which might seem to help with the intuitive explanation, but this is technically incorrect, because the engine could be a turbine or a reciprocating piston.  The "cycle" is short for "thermodynamic cycle".  I'm telling you the category is thermodynamic cycles.  So all of the engine context should really be subtext.  
*Ericsson cycle - Is mostly about the Ericsson engine.  The only material about the actual cycle is what I added.  BTW, there also was no image, I had to make that too.  So you can see, it's a stub!
*Brayton cycle - Needs organization.  Needs to separate "cycle" from "engine".  It uses center-justified graphs that show the cycle performance, but actually don't tell the reader much about the cycle itself.  So in some ways, the Stirling cycle article is more pertinent to its topic.  Note that what one reader considers excessively-technical another reader may consider informative.  We go to the encyclopedia to get information and knowledge, so if someone does not want that anymore they will stop reading.  So the process is self-regulating.  You can't have too much information, only a lack of organization of information.  
*Carnot cycle - Here's a good one.  You'd probably like it.  Keep in mind however that this is the most famous, and probably the most popular cycle.  The formatting is nice.  The pictures are pretty and colorful, ooohhh, ahhh.   It's also much easier to explain, because it is an ideal cycle.  The 4 processes are discrete, which also makes it easier to walk the reader through it.  This gives me an idea though.  I can divide the PV curve into 4 pseudo-processes and describe them.  Actually this would be easy since the graph is already marked.  Anywho, the Carnot cycle article makes for a good template and/or guideline.
*Carnot heat engine - I just touched it up a bit, and now the formatting looks better.  The previous version was funky.
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This article may need more background, context, clean up and formatting, but that's one thing.  Saying that the content is bunk, is quite another.  You may not like the technical style, but you didn't list a WP opposing it, and believe it or not, it is a sound explanation, and may be one of the best that's available on the web for what it is.  In terms of content, the article is about a thermodynamic cycle, and this is what the images pertain to, so I don't really see why you think that's a problem.  Maybe it is more of a book style, I may need to read more WP, and think about it more before I decide what it is and/or how to change it or how to deal with it.  I don't doubt that the transitions and flow can be improved to make it more "cohesive", but this is a 3 month old stub, alright?   Do you really want to understand the Stirling cycle?  because if you didn't, then you wouldn't read it, so you wouldn't really care right?  Take it from me, as someone who really does want to understand this cycle, that these images are gold, and they speak 1000 words.  It's hard to get this level of truth in a more concise and accurate way.  --Mikiemike (talk) 06:37, 27 April 2008 (UTC)
replies: text: I found this article interesting.  Maybe it can be improved but I think it would be a great loss for mankind if it was deleted.  A cycle seems a little different than an engine, and also layering articles so that there is a nontechnical main article ie the sterling engine, with more technical articles as branch articles seems to me to be very helpful for the general welfare as it meets the needs of both those who want a non-technical explanation as well as those who want more indepth coverage.
Hobojaks (talk) 07:35, 30 December 2008 (UTC)
thread_title: This topic is welcomed and is here to stay

message: The idealized Stirling cycle consists of four thermodynamic processes acting on the working fluid:
*Points 1 to 2, Isothermal Expansion.  The expansion-space is heated externally, and the gas undergoes near-isothermal expansion.
*Points 2 to 3, Constant-Volume (known as isometric or isochoric) heat-removal.  The gas is passed through the regenerator, thus cooling the gas, and transferring heat to the regenerator for use in the next cycle.
*Points 3 to 4, Isothermal Compression.  The compression space is intercooled, so the gas undergoes near-isothermal compression.
*Points 4 to 1, Constant-Volume (known as isometric or isochoric) heat-addition.  The compressed air flows back through the regenerator and picks-up heat on the way to the heated expansion space.
This idealized Stirling cycle is commonly known as a "squared-cycle" , because when graphed on a Pressure-Volume plot, the rapid transitions between the processes produce a shape with corners.  In a real Stirling engine, physical design constraints limit the net force on each engine component, and thus limit the maximum acceleration (or rate-of-change of velocity).  Thus a real Stirling cycle in a Stirling engine requires relatively smooth motion, which is commonly sinusoidal or quasi-sinusoidal.  In this case the shape of the PV-plot is quasi-elliptical.  Also in a real engine cycle, the heat transfer performance of the heat exchangers ranges from 100% effectiveness in an isothermal process, to 0% effectiveness in an adiabatic process (no heat transfer).  The compression and expansion processes can be modeled as a polytropic processesDavid Haywood: An introduction to Stirling-cycle machines (pdf) 
:: P V^n = k \,\! 
where  k is constant, and n is bounded by:
::1 \le n \le \frac{c_p} {c_V} \le 2 .  
where {c_V} is the  specific heat capacity at constant volume (J/kgK)
and  {c_p} is the  specific heat capacity at constant pressure (J/kgK)
Compared to the idealized cycle, the efficiency of a real engine is reduced by irreversibilities, friction, and the loss of short-circuit conducted heat, so that the overall efficiency is often only about half of the ideal (Carnot) efficiency.Israel Urieli (Dr. Iz), Associate Professor Mechanical Engineering: Stirling Cycle Machine Analysis
		
		
--Wtshymanski (talk) 18:03, 25 August 2008 (UTC)
thread_title: Stirling cycle thermodynamics

message: THis is a great article and was useful to me as a physics teacher.
I suggest cutting the whole section about the topic's complexity. eg
"The Stirling cycle is a highly advanced subject that has defied analysis by many experts for over 190 years. Highly 
advanced thermodynamics are required to describe the cycle." This is silly. To describe the cycle you just need 2 concepts (1) isothermal expansion/compression; (2) heat exchanger.  Yes, there have been people who did not understand this, but it is not highly advanced
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I reply:
Maybe this is the place to say that the above passage is emphatically correct!
Yes, isothermal compression at the lowest-possible temperature; and isothermal expansion at the highest-possible temperature will obviously give optimal efficiency.
...with storage and re-use of heat, to reduce need for the use of heat-source & heat-sink. 
That's all that's needed to tell the purpose, principle & intent of the Stirling. That's what the introduction to the Stirling-Cycle should say, at the outset, at the very top of the Stirling-Cycle article.
Do real Stirlings achieve the ideal cycle? Of course not. That's why it's called "ideal".  But if Robert Stirling had an approach or approximation to the  ideal Stirling-Cycle as his goal or model, let's not forget that it resulted in the most efficient heat-engine.
And no, the above is all that's necessary to explain the optimality of the Stirling-Cycle. No need to bring up entropy or reversability. (...though such matters are of course relevant for engineers, and may have a valid place farther down in the article, in a special section for engineering-topics for those interested.)
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, and does not defy analysis.  86.22.79.205 (talk) 10:49, 3 February 2009 (UTC)
replies: text: I agree that saying this cycle "defies analysis" is patently silly. Its not a highly advanced, and the analysis is pretty straightfoward once you get down to it.Headbomb {ταλκκοντριβς – WP Physics} 18:47, 3 February 2009 (UTC)
replies: text:  Ha ha ha ha ha, no way!!!   "Isothermal expansion/compression" is actually a terrible model of a real Stirling cycle.  At the very least you need an adiabatic model.  See the Stirling cycle Course notes by Prof. Urieli, PhD. Read any book by A.J. Organ PhD, who has essentially devoted his career to this subject. Mikiemike (talk) 23:59, 11 February 2009 (UTC)
replies: text: That may be true, but it is still pretty straightforward to perform the analysis of the cycle. Headbomb {ταλκκοντριβς – WP Physics} 05:00, 17 February 2009 (UTC)
thread_title:  Suggestion to cut a small section 

message: What are these?
86.3.108.41 (talk) 13:03, 1 October 2011 (UTC)
thread_title:  Alpha, beta and gamma engines 

message: This article states that there is a difference between the idealized and adiabatic stirling cycles. It even outlines each of the four general steps in the cycle, for each of the idealized and adiabatic. However, there is nothing different about their descriptions whatsoever: 
Idealized:
Isothermal expansion. The expansion space is heated externally, and the gas undergoes near-isothermal expansion.
Constant-volume (known as isovolumetric or isochoric) heat removal. The gas is passed through the regenerator, thus cooling the gas, and transferring heat to the regenerator for use in the next cycle.
Isothermal compression. The compression space is intercooled, so the gas undergoes near-isothermal compression.
Constant-volume heat addition. The compressed air flows back through the regenerator and picks up heat on the way to the heated expansion space.
Adiabatic: 
180° to 270°, pseudo-isothermal expansion. The expansion space is heated externally, and the gas undergoes near-isothermal expansion.
270° to 0°, near-constant-volume (or near-isometric or isochoric) heat removal. The gas is passed through the regenerator, thus cooling the gas, and transferring heat to the regenerator for use in the next cycle.
0° to 90°, pseudo-isothermal compression. The compression space is intercooled, so the gas undergoes near-isothermal compression.
90° to 180°, near-constant-volume (near-isometric or isochoric) heat addition. The compressed air flows back through the regenerator and picks up heat on the way to the heated expansion space.
I recognize that the qualifiers before each description have changed; nonetheless, the descriptions of each phase of the cycle themselves are literally copied from one cycle to the other. 
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I reply:
Yes, the description of the ideal-cycle is obviously incorrect. In the genuine ideal-cycle, the compression and expansion aren't "nearly isothermal".  They're isothermal.
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How is this useful in any way? This article would have one believe that exactly the same physical process happens during each phase of either type of cycle, but for some reason the two cycles are different. Could this be addressed somehow?  — Preceding unsigned comment added by Phruizler (talk • contribs) 03:16, 15 February 2013 (UTC)
thread_title:  Adiabatic vs. Idealized cycles