Carnot was being too generous

[Tom Booth]

It's funny how an "offer that can't be refused", leaves all those inventors, poor, discredited, often I'll, and followed by ever becoming more stubborn fools.

Only those that can't be bought.

Only the well educated seems capable of seeing through their veil of lies, and self delusion.

By "well educated" you mean thoroughly indoctrinated and no longer capable of performing simple objective observation and using common sense reasoning.

[Fool]

Why would anyone pay for something that doesn't work?

No. Indoctrinated does not equal educated. Education teaches to be skeptical, inquisitive, and comprehensive. Only the well educated would realize that.

[Tom Booth]

Why would anyone pay for something that doesn't work?

No. Indoctrinated does not equal educated. Education teaches to be skeptical, inquisitive, and comprehensive. Only the well educated would realize that.

When (science) "education" has no basis in the real world. No empirical evidence to back it up, just rote repetition of obsolete theory, when it takes on the moniker of infallible, unquestionable "LAW" that just has to be accepted without demonstration or proof, it is nothing but indoctrination.

The "Carnot Limit" as peddled today as an unbreakable "law of the universe" fits into that category IMO.

It's absolute nonsense.

[Stroller]

https://ntrs.nasa.gov/api/citations/200 ... 025987.pdf

The Component Test Power Convertor The CTPC is a 12.5-kWe free-piston Stirling convertor designed, built, and tested in the late 1980s and early 1990s by Mechanical Technology Inc. (MTI) (ref. 5). The convertor took heat from radiant electric heaters or from heat pipes and converted it to about 70-Hz AC electric power. With an input temperature of 800 K and a temperature ratio of 2.0, overall conversion efficiency was about 22 percent.

In this paper, this real world engine's test results were modeled using mainstream thermodynamical theory both linearly and non-linearly and a comparison between the real world engine and the simulations is summarized below.



XDamplitude: Displacer position amplitude (m)
Tc Compression space gas temperature (K)
Te Expansion space gas temperature (K)
Th Hot heat exchanger gas temperature (K)
Tk Cold heat exchanger gas temperature (K)

Note the close agreement between the real world test results and the simulations, mostly within a few percent or so.

The SDM model shows good correlation between the test data for most parameters, with the larger differences attributable to the isothermal (schmidt) model assumption used in SDM. This assumption results in a reduced pressure amplitude but higher pressure phase angle.

The Isothermal assumption of the Schmidt model clearly leaves something to be desired, but doesn't lead to catastrophically incorrect conclusions. We could try to improve on it with the use of gradients and use the power of modern computing to handle the resulting complexity.

When (science) "education" has no basis in the real world. No empirical evidence to back it up, just rote repetition of obsolete theory, when it takes on the moniker of infallible, unquestionable "LAW" that just has to be accepted without demonstration or proof, it is nothing but indoctrination.

I posted this thread for a discussion of mainstream thermodynamic theory. Kindly take your alternative ideas and opinions to one of the many threads you already dominate with them and continue your arguments there.

Thank you.

[matt brown]

So, eff was ~25% before alternator. A table like this tells one story, but a PV would tell another. Considering how much time and moola went into this, I doubt we can expect a stand alone CHP anytime soon. I'm all too familiar will this NASA type of stuff, and currently sitting less than 2 miles from where the original Mac-Dac solar SE was left to rot in the corner of a parking lot for many years. Hmmm MEP=150 bar, but that pressure swing has me guessing at the volume ratio which is always rather fuzzy due to out-of-phase dynamics. I expect the low eff is mostly due to regen load which is likely 5-6x ideal input. Even when regen=.95 per blow, that .05 loss per blow will cascade thru calcs like a wildfire. I think most regen and/or heatX processes are poorly integrated into engine cycles which often ends in the tail wagging the dog.

[Stroller]

Matt, yes, and the Chambadal-Novikov efficiency I started this thread with comes out at
η = 1 – √(418.5/800) = 27.7%
It should be noted that calc is using the Th and Tc internal gas temperatures not the external heater and cooler temperatures.

A pretty accurate result from an elegantly simple equation: η = 1 – √(Tc / Th)

I haven't read the paper in detail yet, but the regenerator does seem to be included in the model (equation 11). Let's explore that a bit as we find time.

[Tom Booth]

This is a diagram of the 12.5-kW Stirling convertor built by Mechanical Technology Inc. (MTI)

Resize_20240520_054933_3508.jpg (117.05 KiB) Viewed 3106 times

As can be seen it incorporates a heater and cooler virtually sandwiched together on either side of a regenerator of modest extent.

In other words, it is not only possible, but inevitable that heat supplied by the heater will transfer directly into the cooler through the engine body.

This is a flaw in the design of all NASA type engines I've studied. Including the 3kw model I've been testing recently in my workshop

https://youtu.be/upO-S9hylCo

Such engines make very effective water heaters and/or room heaters if all the waste heat from the cooling water can be utilized in that way.

Even Carnot pointed out that this is a "useless transport of caloric" where the heat is conducted through the engine but does not enter into and expand the actual working fluid.

https://ntrs.nasa.gov/api/citations/200 ... 025987.pdf

The Component Test Power Convertor The CTPC is a 12.5-kWe free-piston Stirling convertor designed, built, and tested in the late 1980s and early 1990s by Mechanical Technology Inc. (MTI) (ref. 5). The convertor took heat from radiant electric heaters or from heat pipes and converted it to about 70-Hz AC electric power. With an input temperature of 800 K and a temperature ratio of 2.0, overall conversion efficiency was about 22 percent.

In this paper, this real world engine's test results were modeled using mainstream thermodynamical theory both linearly and non-linearly and a comparison between the real world engine and the simulations is summarized below.



XDamplitude: Displacer position amplitude (m)
Tc Compression space gas temperature (K)
Te Expansion space gas temperature (K)
Th Hot heat exchanger gas temperature (K)
Tk Cold heat exchanger gas temperature (K)

Note the close agreement between the real world test results and the simulations, mostly within a few percent or so.

The SDM model shows good correlation between the test data for most parameters, with the larger differences attributable to the isothermal (schmidt) model assumption used in SDM. This assumption results in a reduced pressure amplitude but higher pressure phase angle.

The Isothermal assumption of the Schmidt model clearly leaves something to be desired, but doesn't lead to catastrophically incorrect conclusions. We could try to improve on it with the use of gradients and use the power of modern computing to handle the resulting complexity.

When (science) "education" has no basis in the real world. No empirical evidence to back it up, just rote repetition of obsolete theory, when it takes on the moniker of infallible, unquestionable "LAW" that just has to be accepted without demonstration or proof, it is nothing but indoctrination.

I posted this thread for a discussion of mainstream thermodynamic theory. Kindly take your alternative ideas and opinions to one of the many threads you already dominate with them and continue your arguments there.

Thank you.

Your thread, in reality, is nothing more than Stirling engine efficiency bashing.

It is well known that Stirling engines are able to, or theoretically should be able to match Carnot efficiency, which for an engine such as the 12.5-kW Mechanical Technology engine under discussion, at the ∆T described, SHOULD BE more like 62.5%

Your thread is not "mainstream thermodynamic theory" it's cherry picking data with the intent of making Stirling engine efficiency look bad and is therefore IMO inimical to the purposes for which this forum was created as well as the goals and intentions of the majority of its members and visitors.

Your recommendation to visitors is to forget Stirling engines and buy a gasoline powered internal combustion generator.

viewtopic.php?p=22600#p22600

[Stroller]

At 150 bar of pressure I wouldn't want to be anywhere near MTI's engine when Tom disconnected the coolant flow to show the design engineers how much better it'd work without it.

Highly pressurised Stirling engine efficiency isn't much different than nuclear reactors or coal fired plant, though it's true NASA haven't improved on MTI's effort much since. Still a lot better than the TEGs they've used previously for space missions though.

Currently available RPS options use the radioisotope fuel’s energy at an efficiency of approximately 6%. A Stirling-based RPS could boost this efficiency to 20% or higher, significantly increasing the power NASA science and exploration missions can obtain from the finite U.S. supply of plutionium-238. A Stirling-based RPS also has the potential to significantly increase the specific power of a generator, which could enable a new class of science missions by coupling RPS with electric propulsion.
https://rps.nasa.gov/news/39/high-effic ... rformance/

I'd love to see NASA use this technology in space. It's a niche where Stirling engines could excel.

For charging car batteries properly down here on Earth, Small gasoline powered generators are still a lot more practical for everyman than any Stirling engine commercially available at the moment.

That won't deter me from building a Stirling engine for other more modest purposes though.