Accordion style heat input plates

[Tom Booth]

I seem to always be coming up with radical, or unorthodox theories, but IMO they are simply logical deductions based on observation.

I put the question into the search engine:

"does radiant heat heat the air?"


And got a supposedly "AI generated" response, which personally I don't really believe. These AI's are mostly just auto-responders programmed by humans to spit out whatever they are programmed to spit out, but anyway...

Generative AI is experimental. Learn more

No, radiant heat does not heat the air. Radiant heat works by transmitting infrared waves, which warm objects and surfaces directly without heating the air. Radiant heat is similar to the way the sun works, transmitting electromagnetic waves that are invisible to the human eye.

OK, let's say that is observably true. There is no direct measurable with a thermometer temperature rise in the atmosphere when sunlight travels through it. But perhaps the air does absorb energy directly from radiant heat causing it to expand rather than heat up, which would not be detectable by a thermometer and since the atmosphere is unbounded changes in volume would be difficult if not impossible to measure and quantify.

If the air were enclosed so it could not expand, perhaps then it WOULD heat up as sunlight passed through as the energy passing through would not be able to effect expansion.

Does ALL the warming of the atmosphere on a sunny day result exclusively from heating the ground, which then heats the air above it by conduction and convection? That seems unlikely.

[VincentG]

I had the same issue of the displacer rod binding with my new zero clearance displacer. This aluminum misalignment joint was machined to allow some side to side movement and keep everything free. With your flat displacer design, you could make something similar pretty easily by hand with some thin plastic.

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[Tom Booth]

The assertion by the AI above seems to be largely untrue.

For example:

"most infrared wavelengths are completely absorbed by the atmosphere and never make it to the ground"

https://www.icc.dur.ac.uk/~tt/Lectures/ ... ndows.html

Apparently a great deal of solar radiation is absorbed by the upper atmosphere resulting in temperatures of thousands of degrees.

Different gases absorb different wavelengths.

Infrared it seems is absorbed largely by "greenhouse gas" i.e. carbon dioxide and methane as well as water vapor, which perhaps has implications for the "wet thermoacoustic" engine.

Would there be an advantage then in charging a Stirling engine with CO2 ?

[MikeB]

Apparently a great deal of solar radiation is absorbed by the upper atmosphere resulting in temperatures of thousands of degrees.

Thousands? My understanding is that temps in the upper atmosphere were rather low.

[Tom Booth]

Apparently a great deal of solar radiation is absorbed by the upper atmosphere resulting in temperatures of thousands of degrees.

Thousands? My understanding is that temps in the upper atmosphere were rather low.

https://youtu.be/crGkP4AYOfs?si=XQzMhkmxnWkHRERd


The "Thermosphere" in particular. It also greatly expands and contracts with the amount of sunlight it receives.

Strange it is "thousands of degrees" but you would still freeze because the air is so thin.

Apparently the thermosphere doesn't absorb infrared though.

[Tom Booth]

I don't know, but it seems the thermosphere is largely composed of lighter gases like helium and hydrogen that absorb high energy waves in the x-ray and ultra violet range rather than infrared (heat), so why are these good choices as working fluid in a heat engine if they tend to NOT absorb infrared?

CO2 or a saturated vapor of H2O seem like potentially better options since these absorb infrared.

[Tom Booth]

BTW, the formatting in the forum seems messed up. Is anyone else experiencing this?

[matt brown]

Yep, everything has changed, and I'm assuming an upgrade to thwart spam (note contiguous underscore when attempting inline reply). A definite bummer as previous interface was sweet...

[VincentG]

New format and I can't start a new thread or use full editor.

[Tom Booth]

OK, well at least I know it's not just me, so I can stop fooling around with my browser settings.

So I finally got compression, though now from all the grinding down of the power piston and cylinder as well as the displacer rod, to try and alleviate binding and misalignment, there is a lot of "blow by".

I put some soap on the displacer rod sleeve after making the video and there was a steady stream of rather large bubbles.

With all that, pressure in general was still, or still seemed to me, way too high. The piston is not stock for this engine. It is a much smaller diameter so cannot utilize all the pressure generated on the power stroke so A LOT of pressure is lost to "blow by" then the engine is left with little working fluid or a partial vacuum.

Perhaps a check valve to let air in but not out might help.

Matt, (or somebody) I think, theorized at one point that the leaks might be what allows the engine to run (without a cold side), by allowing air exchange. Hot air gets blown out and fresh cold air gets sucked in and heated, kind of like a Manson engine (or is it Mason?)

Anyway, I had to reduce the displacer lift to a bare minimum to get the engine to run relatively constantly.

The timing is also unusual. The displacer lifts at TDC. Not sure that is best, but it got it going.

I'd like to try a Ringbom displacer and also a diaphragm piston.

The engine speed tends to fluctuate randomly.

Strangely, the RPM increased momentarily when I switched off the steam generator power.


https://youtu.be/V4pT0QWaJfM?si=CqNUMrL3qcVC_MPJ

[Tom Booth]

Because the piston kind of hangs up at times and also leaks, to demonstrate that phenomenon of the working fluid expansion and contraction paralleling the displacer position, I used a balloon instead of the piston as it is a lot less ambiguous.


https://youtu.be/4VjzmkREgbw?si=smLpSfuBbuWpjdLO


I took the balloon off at the end to show inside that it is still the spiral displacer.

Maybe it is obvious why the working fluid expands and contracts the balloon - due to heating and cooling, but I still find it strange, or not what I'd expect.

Yes, the top of the chamber is still much cooler than the bottom, but I would think that with six long spiral slits in the displacer for air to pass through there would be more rapid mixing between the lower hot and upper cold air volumes.

At this point I'm not trying to forward any theory or refute any theory, I'm just rather puzzled

All I can surmise is that the air below the displacer is subject to radiant heat that keeps it in an expanded state, while above the air is "shaded", as previously theorized above.

Any other ideas?

[Tom Booth]

The main problem with this design concept so far is the displacer material. What to make it out of that is flexible like a spring yet not subject to thermal deformation when heated.

Resistance to moisture or humidity is also a problem.

When the engine starts out cold and is then heated, any water vapor inside the engine tends to condense on the interior, if only temporarily. Several times I've had to peel off a soggy outer layer of paper from the foam board.

I've also had to sand between the spirals to provide extra clearance to compensate for when the foam heats up and swells. Over time the springy spiral foam board has come to resemble a soggy noodle.

On the other hand, the coatings of the hollow glass microspheres in muffler paste and aluminum foil added weight and rigidity

The foam board has limited experiments to mostly low temperatures, steam, being only slightly hotter than a fresh cup of coffee.

I'm also experimenting with "spare parts" of old worn out engines, which parts don't always fit together perfectly.

These are in part "excuses" for the observable poor performance but any trial or experiment that results in a running engine seems open to further development and improvement, IMO.

I do recall the initial prototype running impressively well on the hot wood stove, before the plastic parts started to melt.

I may try building another engine using different more heat resistant materials. The question is what?

Maybe this stuff:


https://youtu.be/SQCxZ8XEMns?si=V-3oEU5658L1SL4J


That is the material used in toasters and heat guns or hair dryers and the like to hold the tungsten heating elements in position made of mineral mica pressed together under pressure with a silicone binder.

[Tom Booth]

It occurs to me that if radiant heat has a significant role, or even a dominant impact then any conventional displacer is acting to block radiant heat, confining that heat to the underside as it is raised greatly limiting the rate of heat input.

Perhaps some kind of louvres that flip open and shut very quickly would be more effective letting the radiant heat flood the entire engine interior all at once, then close shutting off the heat input just as quickly.

Charging the engine with CO2 might be of additional benefit as far as effective absorption of the heat as it is switched on and off.

[Tom Booth]

I got to thinking about those auto darkening welding helmets, and also sun glasses, and began wondering if there might be some way to control the light blocking properties of the liquid crystals by applying an electric current, or some such thing.

Turns out, it is possible.

There are websites and videos and manufacturers with various types of "smart glass" or "switchable mirrors" and so forth that basically use liquid crystal like microscopic louvers.

There is mention here and there of the possibility of blocking thermal or infrared and/or heat control type applications, but this does not seem to be a common application.

The glass or film can be customized for different wavelengths of light, different degrees of opacity, clarity, refrectivity.

There is also mention of the fact that heat is used to fuse the layers of liquid crystal laminate between layers of glass, so maybe it could be made relatively heat resistant?

Anyway here's one explanatory video, there are dozens more to be found.


https://youtu.be/WCzeuL7hNhk?si=sdNwrVdtTiKNTIOI

[matt brown]

Hey Tom, can you start a new topic ? I can't and heard same from another member...