Thermodynamic work vs. real work

[Fool]

Tom, depends on how much moisture is in the balloon. And whether the balloon absorbs microwaves or not and gets hot and pops. Try Saran Wrap. Or a Ziploc bag and soup.

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[Tom Booth]

Tom, depends on how much moisture is in the balloon. And whether the balloon absorbs microwaves or not and gets hot and pops. Try Saran Wrap. Or a Ziploc bag and soup.

Soup?

Can you use soup as a working fluid in a hot air engine?

Your such a moron it hurts just to think about the depths of your idiocy.

[VincentG]

Please keep the nonsense out of this thread.

[Fool]

Yes.

[Fool]

VincentG, thank you for this thread. I just realized that you just got me to demonstrate that for the Stirling Cycle given :

A compression ratio of 2 to 1, is needed for a temperature cycle of 300 to 600 K, giving an efficiency of 50%.

A temperature range from 300 to 1K requires a compression ratio of about 28 to one, for an efficiency of about 99.7%.

Thanks, everyone knows that IC Engines with higher compression ratios have highers efficiencies. The same apparently is true of Stirling Engines, and directly related to Temperature. Thanks, another proof of the Carnot Theorem.

Kudos.

P.S., If you want, send me, for piston and displacer, the bore and stroke data for an LTD Stirling Engine. And I'll calculate the compression ratio, and potential effective temperature ranges, and efficiencies. Please.

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[VincentG]

A compression ratio of 2 to 1, is needed for a temperature cycle of 300 to 600 K, giving an efficiency of 50%.

A temperature range from 300 to 1K requires a compression ratio of about 28 to one, for an efficiency of about 99.7%.

Negative, those above are only pressure ratios. For a perfectly ideal 300-600k cycle the pp to dp ratio is 1:1.

Are those overall numbers efficiencies or percentages of Carnot efficiency?

[VincentG]

Edit to above post. You are correct for most intents and purposes, essentially 2 to 1 compression ratio, or 1:1 volume ratio. I'm stuck here trying to idealize a balanced atmospheric Stirling cycle, which has different values.

[Fool]

A temperature range from 300 to 1K requires a compression ratio of about 28 to one, for an efficiency of about 99.7

Actually, A temperature range from 300 to 1K requires a compression ratio of about 300 to one. (Not 28) 28 was for the 15 K engine. Slight drop in efficiency for a more practical engine, a compromise.

Going from 2 m^3 to 0.0066666 is 300 to one, volume ratio equals pressure ratio. Look at the PV diagram. The pressure have from volume change or temperature change is 300 to one. The example equates all three ratios.

The PP volume to DP volume isn't on a PV diagram.

The percentages are straight Carnot :

n=(Th-Tc)/Th x 100 = %

I just find it interesting that people accept that IC Engines increase efficiency with increased compression, which comes from temperature ratios, but won't accept the same theory for a Stirling Engine just because it uses T ratio instead of compression ratio. It's the same theory.

Of course someone could measure indicator diagrams, and or power output and calculate efficiency for different temperatures and see. Oh, I guess Phillips did that back in the 1940's. We got many good engines out of Phillips using classical thermodynamic theory. But people here overlook and disbelieve that, instead charging out into their own theories. Sorry, I digress.

What would be interesting is a study of predicted and measured, PP to DP ratios compared to power to size ratios.

I think about the difference between a displacer cylinder the size of a house versus one the size of a roll of coins, paired with the same piston of 1/3 feet (4", 10 cm), diameter, and stroke.

One PP would have full stroke P∆V work, the pressure would change very little. And the other would mostly have adiabatic bounce, with a slight input, maybe, of heat and cooling. Neither would have good power to size ratios. An obvious compromise is important.


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[VincentG]

I just find it interesting that people accept that IC Engines increase efficiency with increased compression, which comes from temperature ratios, but won't accept the same theory for a Stirling Engine just because it uses T ratio instead of compression ratio. It's the same theory.

Of course someone could measure indicator diagrams, and or power output and calculate efficiency for different temperatures and see. Oh, I guess Phillips did that back in the 1940's. We got many good engines out of Phillips using classical thermodynamic theory. But people here overlook and disbelieve that, instead charging out into their own theories. Sorry, I digress.

Don't misunderstand my stance. I don't discount thermo, or the work of Philips. Their work was extremely valuable. For me that is the right answer for the wrong path. If anything, I'm advocating and extreme adherence to pv=nrt and the 2nd law, with a focus on making the mechanical aspect of these engines fall in line. Also increasing the size of PP to DP is paramount.

[VincentG]

I should say what I mean is increasing pp to dp size far beyond “normal” is paramount. I’m just trying to get a solid grasp on how work and efficiency integrate. Like Tom, I don’t see how taking Tmin all the way to 0k is relevant for practical efficiency.

Once we called Tom crazy for advocating self cooling, and now we all(fool included) openly talk about Tmin going below ambient. I still don’t think that’s happening on an ltd model, but it now seems plausible with a better design.

[Fool]

Naw, I was brainstorming how the cold plate might become colder than Tc, by putting heat of compression out through the piston by atmospheric work, but Matt correctly nixed the idea. It may still be happening, but not the way I suggested.

So I'm back to wondering why Tom is measuring a temperature anomaly, including possible instrument error. The truth has to be more interesting than the second law bashing and Tesla worshipping he's doing out of spite. He just isn't willing to get to the bottom of it, and I don't care. So it begins and ends with he.

I think the little LTD pancake Stirling Engines, or any, running with zero load, zero useable output power, are able to reject their small amount of heat with minimal temperature rise which goes unnoticed.

I agree, I've heard compromise numbers, but I've never heard why or where those numbers come from. Theory, experiment?

I also think it is important to have higher internal pressures, and greater temperature differences. No calculating of those parameters along with displacer, to power, cylinder volumes, and size to power output. The Essex thread got into power and size a little bit.

Matt goes on and on about beating Carnot, but I haven't seen anything that could do it. Beating Carnot would require an indicator, or ideal PV, diagram outside the Carnot or Stirling Cycles, and have paths above Th or below Tc or both. Hence my desire to see them in a real engine, or theory.

Theory prevents it. Real indicator diagrams confirm it. Matt and Tom need to provide them or no one will take them seriously. Matt could supply them for each unit of mass for his model's positional drawings.

You began this tread with one, so it was easy to supply numbers. I learned something because of it. Kudos. I'm glad you clarified your stance on classical thermodynamics, thanks. I wasn't sure. Kudos again.

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[VincentG]

https://images.app.goo.gl/zq3Eyy2fqzTHWRTu5

This is the only image I could find that overlays a Carnot and Stirling cycle. Is this wrong?

[Tom Booth]

...
So I'm back to wondering why Tom is measuring a temperature anomaly, including possible instrument error. The truth has to be more interesting than the second law bashing and Tesla worshipping he's doing out of spite. He just isn't willing to get to the bottom of it, and I don't care. So it begins and ends with he.
...

Maybe you should clarify what you mean by keeping foolishness, or "nonsense" off your thread.

This piece of shit "fool" posts nothing but idiocy and nonsense and his slimy insinuations, misrepresentations and lies about me, my motives and character etc which you appear to tolerate or pass over without comment.

I think it is foolish to suggest we can discover if radio waves can power a Stirling engine by putting soup in the microwave, so since what constitutes "nonsense" is largely subjective and subject to opinion your request could use some clarification.

Here, quoted about me is an example of "fool" freely spewing lies about me and getting away with it, but I'm not allowed to respond to such attacks or comment on his other nonsense posts but the "fool" has unfettered run of the place.

Lucky for him the owner/moderator is MIA or this "fool" would no doubt have been banned (again) long ago.

[VincentG]

My comment was directed at both of you. But it takes two to tango.

[VincentG]

And to be perfectly honest Tom, after being baselessly accused of forming an alter ego, Jack, my tolerance for your "nonsense" is less than others.