Jump to content

Tom Booth

Senior Members
  • Content Count

  • Joined

  • Last visited

Posts posted by Tom Booth

  1. 29 minutes ago, studiot said:

    You are welcome to demonstrate this in practice, which is why I invited you to do just that (theatrically large flywheels are unneccessary).

    What would be refrigerated?

    I believe I already have.

    By simply insulating the cold plate, which is where the engine's refrigeration winds up, to prevent ambient heat infiltration, the same way an ice box is insulated, the "sink" or cold plate getting colder, demonstrably causes the engine to run better and faster.

    8 minutes ago, Strange said:

    Moderator Note

    Gosh, yes. How on earth did anyone communicate science and technology before the invention of video!?

    Just try writing. You know, words. With some diagrams, if necessary.

    If you want to reference other peoples work, then find published "words" and "pictures". It really isn't that hard. (If you can only find videos, then that means that there is no good, reliable information available.)

    If you don't want to follow the rules of the forum, we can close the thread.


    Why not just carve it out on some stone tablets?

    Sorry, but I don't need this, there ia a multitude of forums I could be posting to that don't have such nonsensical restrictions.

    Close the thread if you want boo hoo. Your loss.

  2. "demonstrate"?



    Please stop using videos as support for your ideas...

    I was recording experiments so the results could be known to everyone, with as little interpretation on my part as possible, but apparently posting video is frowned upon here, if not outright grounds for expulsion, so, who can possibly demonstrate anything with such restrictions?


  3. 15 minutes ago, studiot said:

    What do you mean by direction ?.

    Direction of rotation.

    In other words, if a Stirling engine were operated, turning clockwise, putting energy into a big giant external flywheel, then the heat source was removed, and the flywheel continued to drive the engine, in the same clockwise direction, the engine would then be functioning as a refrigerator.

    This is not any different than what takes place, or can, take place, as a result of a Stirling engine storing energy in its own flywheel, then proceeding through the remainder of the cycle on that stored momentum.

  4. 1 hour ago, swansont said:

    We were discussing Stirling engines. One example at a time, remember?

    It has been my observation that the Stirling engine cycle is functionally equivalent to the expansion refrigerating engine described above. The comparison is appropriate.

    4 minutes ago, studiot said:

    exotic machinery.

    What exotic machinery?

    A Stirling cryo-cooler is essentially the same machine as a Stirling engine 

    An expansion engine is similarly not at all "exotic" or complicated. It is simply any piston in a cylinder driven by the expansion of a gas.


  5. 23 minutes ago, swansont said:

    Heat converted to work to drive a piston is not how a refrigeration cycle works


    "Driving the engine mechanically" is not a conversion of heat into work.

    Hot things cooling off/cool things warming up requires no engine; it happens spontaneously. A refrigerator takes the cold bit and makes it colder. This requires and engine, as it will not happen spontaneously.

    Expansion engines are used in cryogenic refrigeration. It IS a variety or type of refrigeration, just not one many people are familiar with.





    This is from a public domain document: https://operations.fnal.gov/rookie_books/Cryo_Primer.pdf

  6. .


    Moderator Note

    Please stop using videos as support for your ideas. The membership is not required to watch them, and you're basing too much of this discussion on their content. Please adhere to the rules you agreed to when you joined

    How does that post violate any rule? The video is highly relevant to the discussion, the relevant points are written out and quoted in the text of my post. The relevant content is at the very beginning of the video, nobody is required to watch the entire video, or any of it for that matter to participate in the discussion, the video and the point being made are certainly open to discussion, it is the point of the discussion. It is not MY video, is not in my YouTube lineup at all, so it's not to boost my YouTube ranking which is not even monetized  I've read the rules pertaining to videos and have complied in every possible way  Videos as supporting material are useful and add to the discussion. This used to be, years ago, quite a friendly forum, but if simple links and videos are so intolerable here now, it has become less useful IMO. What rule specifically does my previous post violate? None that I'm aware of.


    5 hours ago, swansont said:

    If it runs in the same direction, how does it cool?

    The same way it normally does. 1. By converting heat into work. Heat converted to work is heat that is absent, otherwise known as cold. 2. Momentum in the piston is utilized for expansion. When a gas is mechanically expanded it cools. The engine is doing the same thing, the same processes are taking place, but by eliminating the heat input and driving the engine mechanically, everything takes place at a "lower octave" so to speak. The same cycle at a lower temperature. In reality, a Stirling engine, as part of its normal functioning, is a kind of refrigeration machine.

  7. I've been looking for some kind of "authoritative" confirmation of my statement, that a Stirling cryo-cooler is THE SAME as a Stirling engine running in The SAME direction as a Stirling engine, as very often, there is quite a bit of misinformation on the internet that a Stirling cooler runs in the opposite direction from a Stirling engine.

    There is, at least, this old video:

    This does not seem to be a very well documented point of fact. "The machine running in the same forward direction in both cases".

  8. 12 minutes ago, studiot said:

    You should be able to measure the temperatures of the hot and cold plates with and without insulation.

    That would be useful information, as well as the speed and timing of the running ( since you now have an idea of the timings, there is no need to babysit it like your earlier experiments)

    Also please let us deal with the simple machine first, before moving on to the more complicated one you have mentioned.

    Yes, I do plan on getting some sort of temperature probes. I don't know of anywhere locally that would carry that sort of thing. Anyone have any recommendations? Something thin preferably, that maybe could be taped to the hot & cold plates.

    The first engine is still intact, except for having stripped off the insulation for that video.

    I'm building another engine.

    This time my plan is to add Regenerator matrix. I'm not sure what you mean by, let us deal with the simple machine first.

    My time for working on this stuff is very limited, so when I have time, I'm not just going to twiddle my thumbs.


  9. 1 hour ago, Ghideon said:

    I watched the movie clip where the engine is removed from the insulation. I notice that it looks like the whole engine is insulated, not only the cold plate but also the hot side of the engine.

    Is there any chance that the observed effect is caused by the insulation on the hot side? I mean if the insulation makes the cold side lets say 5 degrees warmer for a while but the hot side 10 degrees warmer that means the temperature difference is increased. What effect would that have? 


    Good point.

    The hot bottom plate was insulated everywhere except between that and the Dewar flask mouth, so indeed that certainly cut down on heat loses from the hot plate, which would have made it hotter.

    However, thinking about it, the bottom periphery had been insulated the whole time as well s the whole Dewar and all.

    The increase in RPM took place after the cold plate was covered.

    The sides of the engine are mostly a short section of plexiglass tubing, so is not very conductive, but the air spaces between the nylon bolts could transfer heat between the plates by convection. So that was insulated.

    Also, I had run the engine with the same setup, insulation everywhere, except on top. If I'm not mistaken, it ran faster and longer only after the top was insulated, everything else being the same, but I was not being as careful as I should have been, and times of day, ambient temperature, and probably other variables were not well controlled.

    That is why I ordered so many kits, to run engines side by side at the same time, but I only have one built so far.

    What I do know for sure is after I covered the sink, the RPM increased, which was what my theory told me might happen but was the opposite of what everyone else thought would happen.

    Really if the engine did not continue running and instead speeded up as it did, I would have discarded the whole theory and nobody would be seeing this.

  10. In regard to these experiments, this article is also significant:


    The section on Stirling cryo-coolers. There is also additional information on Stirling coolers in the FAQ on this website.


    What is important to understand, I think, is that a Stirling cryo-cooler is not a Stirling heat engine "running backwards".

    As a cooler, the engine runs in the same direction as for power output. It functions in almost exactly the same way, mechanically, as a cooler as it does as an engine.

    A Stirling engine is really a refrigeration device that works by converting heat into work to effect cooling. Running the engine with a motor, the same way, in the same direction, simply amplifies the cooling effect, so that the engine can produce much colder temperatures, all the way down to the cryogenic range.

    The effect in a small toy engine is so minute, though, it requires very careful insulating to produce any measurable effect.


  11. 19 hours ago, studiot said:


    19 hours ago, studiot said:

    So can we all analyse the system in my picture in relation to the laws of Thermodynamics ?

    Like other members I have already said that this machine in in perfect accord with these laws, including the second law.

    We have also asked why you think the second law is appropriate, when this is really a First Law matter.

    The picture/animation originated here:


    There is a ton of information on that site, as well as the American Stirling Engine site.

    Originally I had wanted to, and intended to order engines from the ASE company, but their website was inaccessible at the time.

    The animation is overly simplistic and does not really begin to delve into the thermodynamics of the engine.

    For example, the illustration shows water cooling of the top plate, which is common. But imagine that instead of cooling the top plate with water, it were insulated, as in my experiment, which would, presumably, retain most of the heat from the burners.

    Without the active cooling, one might expect the engine to overheat and quit working. But in my experiment, that is not what happened.

    Insulating the top, instead of cooling it, did not cause the engine to quit. Instead it ran measurably better. Something else was keeping the top plate cold. Something not shown or discussed on that page.

  12. In talking about Stirling engines there are some technical terms that can't be avoided. "Displacer" is one. It is, as far as I know, unique to Stirling heat engines.

    I've explained the function of the displacer in as many ways as possible and from as many different angles as possible. Displacement is not a common word, but the dictionary definition for displacement describes what the displacer does in a Stirling engine.

    It makes no difference what I say or how I say it, if you don't know the technical terminology and what it means in the context of Stirling engines, it will have no meaning 

    There is nothing wrong with my sentence structure.

    18 hours ago, studiot said:

    So can we all analyse the system in my picture in relation to the laws of Thermodynamics ?

    Like other members I have already said that this machine in in perfect accord with these laws, including the second law.

    We have also asked why you think the second law is appropriate, when this is really a First Law matter.

    Sorry, I think your post slipped in and I did not see it until now. Sounds great.


    17 hours ago, swansont said:


    And it’s not fair to people who might not have visited in a day or two to try and tell them they can’t participate because you posted something a couple of days ago. One thread = one conversation

    And it IS fair to drop in on the middle of a conversation you haven't been following and start criticising because you don't know what's being discussed?

    It helps to go back and read and find out what you may have missed. Discussions progress. Usually.

    The topic is "Heat engine experiments and 2nd law of thermodynamics."

    Notice the plural in "experiments"? The "s" at the end of the word means more than one.

  13. 7 minutes ago, swansont said:

    You’ve posted lots of stuff. Everyone else is responding to it. If you wanted to focus on one example, we could have done that. But you’re the one who has presented multiple examples.


    That’s what new threads are for. To keep things separate. And also why mods admonish responders for thread hijacking. But that all goes out the window when the thread starter keeps bringing up more examples.


    I copy-pasted, so there is no doubt you said it.

    A common theme here has been people explaining that heat is converted to mechanical work. (but not all of it can be converted)


    In case you missed my edit above:

    Here it is again:

    Edit: as a matter of fact, this was my statement:


    I was just trying to clarify that "work" is not done to expand the gas, or to work against atmospheric pressure BY THE DISPLACER

    You left off the bolded and underlined part I had emphasised. Why?

    You copy pasted completely out of context.

  14. 1 hour ago, swansont said:

    I was previously admonished and directed to focus on one example, so much like the second law, I can’t win.


    Did you, or did you not say “I was just trying to clarify that "work" is not done to expand the gas”?

    We can discuss whatever you like, but let's just try to be clear what is being discussed. I'm talking about an engine running on hot water, and you interject, so why does the ice melt.

    It's like I'm talking about a submarine and someone asks about the airplane wings I mentioned in another conversation two days ago. One thing has nothing to do with the other.


    Did you, or did you not say “I was just trying to clarify that "work" is not done to expand the gas”?

    I may have said something like that, or possibly those words exactly, but that is out of context.

    It is true though that no mechanical element, not the displacer, not the piston, is doing work to expand the gas.

    HEAT expands the gas and the GAS does work as it expands. So that is probably a perfectly valid statement in context, as Studiot was talking about the piston and displacer at the time if I'm not mistaken.

    Would it be a valid statement to say that the heat does work? I don't think so, but it might be a way of looking at it.

    Edit: as a matter of fact, this was my statement:


    I was just trying to clarify that "work" is not done to expand the gas, or to work against atmospheric pressure BY THE DISPLACER

    You left off the bolded and underlined part I had emphasised. Why?

  15. 7 minutes ago, swansont said:

    That’s obvious.

    Vacuum and atmosphere

    You claim work is not being done against atmosphere. it’s the only other option.

    That’s not what I said, or what’s going on.

    But you keep saying work is not being done against atmosphere, and that’s not right. (“I was just trying to clarify that "work" is not done to expand the gas”) 

    The fact that you are focused on the marbles suggests you aren’t getting what other people are talking about. 


    You aren't or haven't been following the conversation.

    Much earlier Studiot said the displacer: "drives the crank via what I would call a push rod".

    I'm just trying to clarify the function of the displacer. It does not drive the crankshaft, it is in no way in direct contact with atmosphere.

    I'm not trying to say no work is being done by the piston, I'm trying to clarify the function of a displacer. The marbles are the displacer! You are the one who is not focused on what the topic of the conversation is and not getting what is being talked about.

    Nobody says no part of a Stirling engine does work against the atmosphere.

    9 minutes ago, studiot said:

    Is this the type of engine you are referring to  ?


    American Stirling Company

    Displacer Type Stirling Engine

    Displacer Type Stirling Engine Animation

    Gas expands when heated, and contracts when cooled. Stirling engines move the gas from the hot side of the engine, where it expands, to the cold side, where it contracts.


    When there is a temperature difference between upper displacer space and
    lower displacer space, the engine pressure is changed by the movement of
    the displacer. The pressure increases when the displacer is located in the
    upper part of the cylinder (and most of the air is on the hot lower side).
    The pressure decreases when the displacer is moved to the lower part of
    the cylinder. The displacer only moves the air back and forth from the hot
    side to the cold side. It does not operate the crankshaft and the engine.
    In other words, the connecting rod to the displacer could be a string in
    this engine and it would still work.


    When the engine pressure reaches its maximum because of the motion of the
    displacer, a power piston is pushed by the expanding gas adding energy to
    the crankshaft. The power piston should ideally be 90 degrees out of phase
    with the displacer piston. The displacer type Stirling engine is operated
    by the power of the power piston.

    Exactly, thank you.

    "The displacer only moves the air back and forth from the hot
    side to the cold side. It does not operate the crankshaft and the engine.
    In other words, the connecting rod to the displacer could be a string in
    this engine and it would still work."

  16. 2 minutes ago, swansont said:

    It’s not a vacuum, right? So work is being done against atmospheric pressure, i.e. there is a pressure on the plunger. There is a difference between expansion in those two conditions


    I have no idea what you're driving at.

    What plunger? What "two conditions?"

    What does a vacuum have to do with anything?

    How is work being done against outside atmospheric pressure by those marbles rolling back and forth.

    Yes their rolling away from the heat source causes the displacement of the air which results in increased pressure in the test tube, but the pressure has no effect on the marbles, they are isolated from the atmosphere. 

    The DISPLACER has ample clearance around it and air moves freely around it, it does not form any seal or work against any pressure.

  17. 11 hours ago, studiot said:

    I don't know how to converse with someone who seems to believe that things can expand without work being done, within our atmousphere.

    I was just trying to clarify that "work" is not done to expand the gas, or to work against atmospheric pressure BY THE DISPLACER.

    The displacer is not any kind of power piston.

    Imagine an empty soup can. Completely sealed, containing a gas. Inside the can is another smaller loose fitting soup can.

    If you tip the can on one end, gravity will cause the inside can to fall to the bottom so the air in the can will be DISPLACED to the top.

    Tip the can around the other way, again the can inside falls and DISPLACES the air back to the opposite end.

    Now heat one end of the can.

    Do the same flip flop and the inside can, or "displacer", still DISPLACES the air in the can but now, when the air is displaced to the hot side the air gets hot and the pressure in the can increases.

    Tip the can the other way and the air is displaced to the cold side, cools down and the pressure in the can drops.

    Hopefully, it can be seen that the small can inside is not performing any appreciable work to turn a crankshaft or to work against the pressure of the outside atmosphere.

    It is just a means of periodically delivering heat to the inside of the can to heat the air and create pressure. It does this by moving away from the heated end of the can, displacing the air to the hot end, or put another way, simply uncovering the hot heat exchanger.

    Often, in a Stirling engine the displacer is not attached to the crank at all. It may be moved back and forth by other means, such as a magnet., Or in some cases by actually tilting the engine.

    Here the displacer is some marbles in a test tube. They full back and forth by gravity, have no connection to any crank and do not work against atmospheric pressure. They just displace air to the heated side of the engine periodically.



  18. BTW, I do have a question.

    My original engine design works similar to and/or incorporates heat pump/refrigeration.

    In thermodynamics, is a vapor compression system, (refrigerators, heat pumps, freezers etc ) considered an "open system" or a "closed system", so does the second law apply or not?

    The "working fluid" is contained in a closed loop, but part of the "system" is the heat exchangers and the air being blown through them.

    Some say the second law applies to everything because the whole universe is a closed system, so... How exactly do we determine if a system is open or closed so we know if the second law is supposed to apply or not.

    It all seems vaguely philosophical to me with no clear cut answer.

  19. 6 hours ago, Markus Hanke said:

    I’m not an expert on the engineering applications of thermodynamics, so others here are more qualified to address this. I’m more of a theory guy - so in what way do you think this is related to the second law? I don’t see a direct connection, and most certainly not anything that would put the law into question.

    Years ago I designed a heat engine. As a lifelong engine mechanic and repair person I thought it was a great design.

    I was told it would not work because it violated the second law.

    Now I'm doing experiments with model heat engines. I posted results on another forum. The discussion was locked and I was banned, because the moderators determined it was "a perpetual motion machine of the second kind" and that it violated the second law. (Or would if it was real).

    How does it violate the second law? is actually MY question!

    I'm not saying it does, that is what OTHER PEOPLE have been throwing in my face for the past 25 years.

    If there is no such violation that's wonderful news to me!

  20. On 7/31/2020 at 1:37 AM, Markus Hanke said:

    No, the second law follows directly from fundamental considerations of statistical mechanics and some basic maths, and as such is not in contention. It also follows more or less directly from Z2 symmetry and unitarity, so it is fundamentally motivated by manifest symmetry considerations. Essentially, in a world where unitarity holds for quantum systems (as is evidently the case in our universe) you can't not have the second law of thermodynamics, if that makes sense.

    I am not sure what the point of all this really is, since the setup you have there is not an isolated system in the thermodynamics sense - so what does it have to do with the second law at all? Note also that the second law is a global statistical statement, and as such it does not contradict temporary (even long-lasting) local decreases in entropy. 

    What exactly are you attempting to show here?

    I think in general what I'm examining or testing is the nature of heat, and how it really interacts with a heat engine, or how it is utilized by a heat engine.

    Popular ideas or statements regarding how these engines work and what their potential may be does not square well with my own experience.

    For example, above, the statement:

    " This system is ~20% efficient because ~80% of the energy goes into heating the cold plate and the reservoir it’s coupled to. "

    (Not to pick on Swansont or anyone in particular)

    Generally this 80% pass through of heat into the sink is not what happens.

    Here is a link to another experiment conducted by someone else years ago using a thermal imaging camera.

    As can be seen in this thermal image of a running Stirling engine on a hot cup of water compared with a non operational  dummy engine.

    In the same environment the real heat engine is clearly maintaining a cold temperature. The heat is not passing through to the top plate.

    In my own experiments I found the same situation. The bottom plate above boiling hot water was too hot to touch. I'm sure hot enough to raise a blister. At the same time the top plate remained cool to the touch.

    This does not seem to support the common assumption that the majority of heat passes right through the engine.

    In my experience virtually no heat makes it through these engines to the sink. Also, nearly all the incidental and parasitic heat loses are preventable to a great degree with proper insulation.

    The implications are far reaching, IMO.


    stirling2 (1)_crop_46_resize_24.jpg

    Source: https://concord.org/blog/an-infrared-investigation-on-a-stirling-engine/


  21. 4 hours ago, studiot said:

    This is exactly why I asked for a proper description of your machine.

    In the absence of one I chose perhaps the wrong type, but I was nearly right.

    I hope you understand that there are diaphragm type Stirling engines ?

    The difference between a displacer (not a very good engineering term) and a diaphragm is that the diaphragm seals the working fluid, and you did say there was such a seal.
    Further the displacer is a rigid plate which creates the expansion space by bodily movement, whereas the diaphragm creates the expansion space by deflection.
    Either way work must be done against the atmouspheric pressure.
    And either way each drives the crank via what I would call a push rod.


    So if you change diaphragm to displacer, this is exactly what I said.


    So what do you think does the isothermal expansion work shown in the Stirling cycle diagram ?



    The isothermal work is given by the formula


    You did not offer a derivation of your efficiency formula I asked for, but you may like to know that the work formula I just quoted is used to derive it.



    With an attitude like that I am not suprised with your lack of headway interesting others in your topic.

    I recommend the following reading


    I'm finding it a nearly hopeless task to try to sort out what your thinking may be in regard to how a Stirling engine operates. I don't mean that to be insulting or anything.

    It took me literally years of dedicated study and research to arrive at an understanding of how these engines work. It is not intuitive, yet, it really is not complicated, it just doesn't make sense, in some ways.

    For example, a Stirling engine actually, it could be said; "destroys heat".

    Heat goes into the engine and goes out of existence. It no longer exists in the form of energy we recognize as sensible heat.

    In that sense a Stirling engine is a cryo-cooler. In converting heat into work the engine creates an absence of heat, which we sense as "cold".

    Heat being conducted, we understand, convection, radiation, are understandable intuitively. Heat simply disappearing and leaving cold is not a phenomenon we are familiar with in life.

    Heat converted into Work is no longer heat but cold, the absence of heat.

    So efforts to trace the heat as it passes through the engine are liable to result in confusion.



    displacer is a rigid plate which creates the expansion space by bodily movement, whereas the diaphragm creates the expansion space by deflection.

    Either way work must be done against the atmouspheric pressure.
    And either way each drives the crank via what I would call a push rod.


    I don't know what you mean exactly by "expansion space". I have no idea what you mean by "the diaphragm creates the expansion space by deflection."

    As far as this statement: "Either way work must be done against the atmouspheric pressure.
    And either way each drives the crank via what I would call a push rod." It is entirely wrong.

    The displacer does not drive the crank.

    The displacer is not a power piston or diaphragm.

    I did not intend this thread to be a course on how a Stirling engine works, I assume if people are interested they would research the subject. But I'll try to clarify things if I can.

    But it seems you are thinking of a power piston or diaphragm that drives a crankshaft. The function of a displacer is not to drive the crankshaft. It does not drive the crankshaft. It does not do work against atmospheric pressure.

    Basically the displacer is a kind of valve that allows heat into the engine in metered bursts. Heat enters the engine through the hot plate or hot heat exchanger, but not while the displacer is blocking the heat from entering.

    The displacer is, rather than a valve, it is more like an umbrella used for shade, to block the heat of the sun.

    When the displacer moves out of the way temporarily, some radiant heat is allowed into the engine, expanding the gas to do work.

    When the gas has used up it's energy performing work, the displacer moves out of the way again, allowing in another burst of heat for another cycle. In that sense the displacer serves the same function as the spark plugs which ignites that fuel mixture in an internal combustion engine to deliver heat.

  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.