Struggling With Internal Energy..

[Tom Booth]

That was all in response to you asking Jack "how do you expand gas adiabatically?".
(...)
Maybe the problem is that I understood what he was asking early on and saw your responses as nothing short of demeaning.
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That wasn't my question and I wasn't asking "Jack".

viewtopic.php?p=23677#p23677

You seem to confuse yourself with Jack quite often, which is what led me to think you two(?) might be one and the same.

So far you haven't actually denied it.

[Tom Booth]

This is rich, coming from someone who admittedly has only just now figured out what "free expansion" means:

viewtopic.php?p=23680#p23680

Jack I would recommend you do some research on Wikipedia, don't let Tom confuse you over these basic issues. Having alternative views and theories is great but you should first (try to) understand the established theories of thermo.

[VincentG]

That wasn't my question and I wasn't asking "Jack".

Good catch, I meant me. I am not Jack and its hilarious that you think I am.

Do I have alot to learn? Do I say stupid stuff that makes me look dumb? Yes!

Do I believe I can build an engine that keeps to within 75% of isothermal or adiabatic ideals? Also yes.

It seemed he had no problem understanding the situation....

Jack if you heat 1 liter of 300k air to 600k and expand it adiabatically, it will reach 1 bar well before it lowers to 300k.

I'll try to find the real values fir you but maybe Matt will beat me to it.

Just curious, but how do you heat air and have it expand adiabatically?

First do one, then the other.
This is just to get an understanding of what air or a fluid goes under these conditions.

Just like when you had your beef with Stephenz, things could go alot smoother here if you had more respect for people.

[Tom Booth]

That wasn't my question and I wasn't asking "Jack".

Good catch, I meant me. I am not Jack and its hilarious that you think I am.

Well, I never said you were. you did. You've made this "slip of the tongue" so many times, answering for "Jack".

This is another example of Jack answering for you.

Based on the objective evidence, the theory is not unreasonable IMO.

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It seemed he had no problem understanding the situation....

Jack if you heat 1 liter of 300k air to 600k and expand it adiabatically, it will reach 1 bar well before it lowers to 300k.

I'll try to find the real values fir you but maybe Matt will beat me to it.

Just curious, but how do you heat air and have it expand adiabatically?

First do one, then the other.
This is just to get an understanding of what air or a fluid goes under these conditions.

Just like when you had your beef with Stephenz, things could go alot smoother here if you had more respect for people.

Likewise.

I have respect for those who earn respect.

Sorry but you've lost mine.

[VincentG]

I am Jack.

Matt is a secret agent.

Matt, IMO, seems to be our resident agent saboteur. I suppose he considers it his patriotic duty to protect US oil interests or something.

Matt and Fool are the same.

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And I don't resurrect old threads. Someone else does. I then join in....

You have a short memory.

Between you and Matt If your not actually one and the same.

You just started posting to a thread that has been dead for six months:

viewtopic.php?p=20525#p20525

There is 1658 topics in this forum going back to 2006 and your always free to start your own but you choose to resurrect some old thread of mine then complain I have too many threads. Just part of your ongoing smear campaign. Liar

Matt and Fool are clowns.

The capillary tube is the "orifice". It's diameter and length must be sized to the pressure difference, and flow rate. Longer and narrower for lower flows and higher pressure drops. Shorter and wider for higher flows an lower pressure drops. Higher pressure drops are needed for higher temperature differences. Those fake ones were claiming a large temperature drop, so a high pressure differential is needed. It appears to have a very small pump so very low flow are possible at the pressure needed. So a small diameter and long length is needed. Neither were installed.

xlnt catch
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Butane systems are very LOW pressure, The vacuum side is a literal vacuum (about 1/2 atmospheric pressure).

Anyone can verify that such a low pressure Butane refrigerator requires a LESS restrictive rather than a more restrictive metering device because the pressure is so low, that what the two of you glibly suggest, "a small diameter and long length" cap tube is the opposite of what would be needed in reality and this can be verified by any and all available data pertaining to the subject.

Such a restriction would cause such a small low pressure system to cease operating or fail entirely.

You two are clowns passing completely bogus opinion you cannot possibly substantiate.

[VincentG]

Tom please stop the personal attacks. Any issues I have here are purely based on trying to understand other members.

Words alone are hard enough to convey thoughts, let alone debating theory of operation for Stirling engines.

[Tom Booth]

Aside from that, the forum owner who of course, has (or had) access to the server data, IP addresses etc. informed me in PM a while back that there has been someone, possibly more than one, using "made up names". Hacking the forum, circumventing the security and even using legal threats.

What exactly is going on, I don't know.

I would not normally post any portion of a PM, especially from the forum owner, but he has not deleted spam in a very long time, Is no longer responding to emails or PM's. I don't know what's going on and he hasn't mentioned you VincentG or Jack specifically, but alerted me that there is at least one person using "made up names" in "trying to get to" me.

Compress_20240704_125536_6317.jpg (84.05 KiB) Viewed 2805 times

The whole "Build Your Own Stirling Engine from Free Plans" section has disappeared. For all I know this forum seems to be in free fall and may not be here tomorrow.

[VincentG]

Well I'm not one for drama. I will leave the forum if anyone would like me to.

I'll reach more people on YouTube anyway, but the comment section sucks so quality feedback is a problem.

[Tom Booth]

Well I'm not one for drama. I will leave the forum if anyone would like me to.

I'll reach more people on YouTube anyway, but the comment section sucks so quality feedback is a problem.

Nobody is asking you to leave the forum, but apparently the owner has been getting some kind of hacker attacks on the forum and direct legal threats from some entity that specifically wants to shut up Tom Booth.

[Jack]

I am Jack.

What a coincidence, I am as well.

[Fool]

I'm sorry to hear about the hacker and threats. Tom leaving this site, would be a bad thing. Being careful about what we say is a good thing. I'm only here to improve the description of classical thermodynamics, because there is a lot of misleading writing out there. I'm glad Daryl tolerates all of us.

[Fool]

If I get this right, you're saying that a hot gas doing expansion work on a piston will cool down more than a (same temperature) gas that is allowed to expand the same amount freely?

I think we are all agreed that this is true.

The issue with a real Stirling (and other engines) is that the reverse is also true - when the piston returns, it does work 'in reverse' thus warming up the working fluid by a certain amount. There will only be a difference if the _engine_ does some work - if we are looking at a 'perfect' engine on paper, with no friction and no load, then the energy lost to the piston on expansion will be cancelled out by the energy gained on compression. (As I understand it.)

Good one. You've gotten to the crux of the misconception being used around here. Thanks.

I think it started years ago when someone posted a solar Stirling Engineers comment something along the line of "When these engines lose their load they tend to overheat."

This on the surface looks as if the work from and to the gas somehow changes. I contend that the compression and expansion per cycle remains the same. Therefore the temperature difference, ∆T, of the gas is the same for adiabatics. Delta pressure remains the same, gas pushes piston out, piston pushes the gas back for the same exact volume change, ∆V, hence the gas does the same work load or no load.

The following numbers are invented to help explain what to look for. Real numbers should be obtained to verify the thoughts here.

What changes is that the RPM increases. The power in and out went from 3000 Watts in 1000 W work out 2000 W to the cold side. 30% efficiency, which is excellent for solar. The extra RPMs has to generate work in the form of friction and windage/pumping loss internal to the engine. This increases the energy getting dumped to the cold side and atmospheric air.

They will tend to get hotter because that's what increased Wattage does. That in turn resists the dumping of heat. That increases the gas temperature. Less heat can get in. Causing the hot side to get hotter. Which causes the gas to get hotter, etc...

Solar temperature 2000 K. Cooking effect on hot side while under load, brings hot side down to 900 K cold 300 K. Cold side absorbing 2000 W. ∆T gas 600 K.

After loss of load. Cold side attempting to absorb 1000 W 30% more, from friction and windage, from higher RPM. Temperature of cold side responds by increasing. Cold side rises to 600 K, hot side rises to 1200 K. Perhaps higher. ∆T of the gas remains the same at 600 K. Same work out of gas. Same adiabatic temperature drop 'cooling' from work. Tending to overheat, not massive overheat.

When a gas expands inside a cylinder it does work to the piston, gas getting colder. When the piston makes the volume smaller, compressing the gas it does work to the gas making it hotter. Work out colder. Work in hotter. With or without an external load.

More work out if kept hotter, less work in if kept colder. The actual cycle is a compromise. That basic necessity is seen in indicator diagrams of real engines.

[Tom Booth]

If I get this right, you're saying that a hot gas doing expansion work on a piston will cool down more than a (same temperature) gas that is allowed to expand the same amount freely?

I think we are all agreed that this is true.
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That would be a great milestone if true, that "we are all agreed that this is true".

Given Matt's recent "Tom" bashing rant, however, I don't think we're there yet, unfortunately.

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[Jack]

If the quote above is true. Is that the internal energy losing energy? Losing it because the molecules are hitting their surroundings?

Extrapolating that, some is probably lost in heat transfer to its surroundings, but the part that's turned into work does that by hitting a moving target? (I've seen that mentioned before, not sure but who, seems plausible to me)

[Tom Booth]

If the quote above is true. Is that the internal energy losing energy? Losing it because the molecules are hitting their surroundings?

Extrapolating that, some is probably lost in heat transfer to its surroundings, but the part that's turned into work does that by hitting a moving target? (I've seen that mentioned before, not sure but who, seems plausible to me)

If we assume the working fluid and it's immediate surroundings (interior of the engine)are at the same temperature, then heat transfer would not be possible, or would, put another way, be in balance.

That would leave "mechanical" transfer of energy to the only thing that can move, the piston.

When talking about "internal energy" I think we need to make a distinction between the internal energy of "the system" and the internal energy of the "working fluid".

Generally speaking a gas is such a simple structure it does not have any "hidden" internal energy, such as crystal structures or chemical bonds, so the internal energy of a gas is reflected by its "temperature only".