Jump to content
Science Forums

TomBooth

Members
  • Content Count

    51
  • Joined

  • Last visited

  • Days Won

    3

Reputation Activity

  1. Like
    TomBooth got a reaction from OceanBreeze in Nikola Tesla Vs. The Second Law Of Thermodynamics   
    Yes, though I don't have the thermometer yet. Mail order is agonizingly slow these days. I really appreciate your input. It is very encouraging.
     
    "If the sink gets as hot as the source, the machine will not work", That is absolutely true, as far as anyone who has ever worked with these engines, model builders and such, has ever known. The idea that insulating the heat outlet or "sink" was so "Out there" and completely contrary to what "everybody knows" I didn't bother with the time and expense to test it, for Ten Years. Why bother? Obviously insulating the sink would cause the heat to build up and the engine to slow down and stop, but I kept noticing strange things about these engines that told me something was wrong with the prevailing view.
     
    Like this video, which I've posted, probably a dozen times:
     
    https://youtu.be/DyPxNNJQo9M
     
    Now compare that with what "everybody knows": "The engine will not run without a flywheel period. The flywheel gives the engine the inertia to rotate the crankshaft when there is no combustion in any of the cylinders."...   https://www.3geez.com/forum/3geez-accords/39958-rear-main-oil-seal.html#post473847
     
    That is something I was taught in trade school engine repair class back in high school. You can't get 100% combustion, there is always some left over heat in the cylinder, so the flywheel is absolutely necessary to carry the engine through a complete cycle.
     
    But this guy discovers BY ACCIDENT, that his model Stirling engine can run without a flywheel. So what brings the piston back?
     
    My conclusion is that, in SOME Stirling engines, at least, the gas in the engine is cooling enough that the piston is able to completely return without any assistance from a flywheel, presumably due to adiabatic expansion (converting heat into work).
     
     
     
     
     
     
    On another forum, I offered to have the kits mailed to them if someone would repeat the experiments. (Instead I was banned). The offer generally holds though.   
    Again, your thoughts on the subject are very much appreciated. More than you know. I've seen some odd things as well.
     
     
    Yes, almost all Stirling engines need an initial manual boost to get them "kick started". But that is true of internal combustion engines as well.
     
    Very rarely, if the piston is positioned just right, and heat is applied, the initial expansion might be enough to get the engine going.
     
    I've seen a few posts of people who said they had an engine that was reliably "self starting", but that is not common.
  2. Like
    TomBooth got a reaction from OceanBreeze in Nikola Tesla Vs. The Second Law Of Thermodynamics   
    This is probably nothing, and not really worth reporting, but It seems rather strange to me.
     
    Over the years, several times in various forums on this topic, I posted this video, because it looks like, when the engine is picked up, that it is frozen to the ice.
     
    https://youtu.be/L6Jmdve1JK8
     
    I speculated, that, because that engine comes as a kit, there are a lot of ways to put it together. I had one or these engines (before I destroyed it, experimenting with it) and the piston pushes onto the connecting rod and is retained by a retaining clip by pressure.
     
    There is a lot of leeway in terms of how far the piston is pushed on. How far it is pushed on changes the throw of the engine, which I theorized, could easily alter the amount of or degree of adiabatic expansion. i.e. cooling.
     
    So, maybe this guy got lucky and happened to push the piston on, just the right amount, to turn his engine into a refrigerator of sorts, or a Stirling cooler/engine purely by accident.
     
    Very unlikely, but it really looked to me like that engine was frozen on, not just hanging on by adhesion from moisture, though that was a possibility, it just didn't look that way to me. The heavy block of ice probably would have slid to the side and fallen off.
     
    Anyway, I shaped and drilled and tapped the epoxy piston this evening.
     
    It did have a lot of drag, friction. It isn't graphite, so I tried adding some 3 in 1 oil. That worked well enough to get it running.
     
    First I ran it on hot water for a while, but the engine was laboring pretty hard, due to the extra drag.
     
    I decided to try running it on ice for a while. I had a couple of vacuum flasks with ice in the freezer, so took one out, figuring I'd just leave the engine running for a few hours to break in the piston. The last time I ran one of these engines on ice it ran for 33 hours. That should be enough to break in the new piston, and I won't have to babysit the thing.
     
    I had dinner, while the engine was running. Just a bit of lasagna.
     
    After that I went to check on the engine, but it wouldn't lift off the ice.
     
    When I first put the warm engine on the ice, it was still warm from running on hot water and was sliding all over the place on the wet ice, which partly melted from the heat. (This can be seen in the other video in the begining also, he keeps repositioning the engine and it keeps sliding to the side).
     
    Well, as the engine was running during dinner, the ice had refrozen to the bottom of the engine. It was really frozen solid, not adhering due to suction from the moisture or anything like that. It was definitely frozen.
     
    I was finally able to break the engine loose, but it was not easy, and I could see that the bottom was frosty looking, not wet at all, and the ice was still solid. Not melted on top, like it had been before.
     
    I put the engine back on the ice.
     
    About five minutes later, I checked again and it was frozen to the ice again.
     
    The third time I went to check a few minutes later, I wanted to have a recording of what I found. So I let the engine run a few more minutes to give it time to refreeze again, then made a video.
     
    After uploading the video and writing a discription and everything, Before posting the video, I checked the engine again. It was frozen to the ice again.
     
    I left it to run, to see what happens. As I write this it is still running, but very very slowly. About 25 RPM.
     
    Probably the ice was just very very thoroughly cold from being in the freezer for a long time, but This did not happen before. At least I didn't notice it, and I've already done several experiments running engines on ice.
     
    I'm still surprised the ice could refreeze that many times, in particular, if the engine is supposed to be pushing heat through into it, as the "sink".
     
    I'm wondering, because the engine is laboring harder than normal with the drag from the new piston, and the epoxy transmits so much less heat than the graphite, maybe it's converting more heat into work??
     
    I hope that thermometer arrives soon.
     
    It is about midnight, so I'm turning in. I'll be curious to see what develops by morning, if the engine is still running.
     
    I counted 26 RPM on the kitchen timmer (digital on the microwave) this time.
     
    It is hard to believe the engine can run so slow. Less than one revolution every two seconds.
     
    Anyway, looks like the epoxy piston is a success.
     
    The engine is running anyway.
     

     
    One thing I can say is that I don't think I have ever in my entire lifetime seen any ice refreeze by itself once it had started to melt.
     
    Of course, I don't normally keep ice in a vacuum insulated cup in the freezer either.
     
    BTW, is there some way to embed videos? I can't figure out how to do that here, but I see videos embedded on other threads, so I guess it is possible, or is it one or those things you have to be a forum member for X amount of time or something?
     
    PS. I woke up to a knock on the door early this morning. That was really fast.
     
    It was FedEx with my new thermometer! But I have to go out and get a 9v battery.

  3. Like
    TomBooth got a reaction from OceanBreeze in Nikola Tesla Vs. The Second Law Of Thermodynamics   
    I said "If", hypothetically.
     
    Just supposing that the engine could utilize that additional 7 joules otherwise rejected to the sink. That would only bring the temperature back down to equilibrium with the environment, not absolute zero.
     
     
    In common sense plain words, how do you define "100% efficiency"? or "applied heat"? and what does either of those terms, in common sense every day language have to do with "absolute zero" or 0 Kelvin?
     
    Heat is transfer of energy. If the engine is at thermal equilibrium with the environment, then there is no transfer of energy. Applied "heat" then, is whatever energy is used to bring the temperature of the engine some degree above the ambient baseline. If that added heat is, for the sake of argument, entirely converted to work, or the mechanical motion of the engine, then there is a return in temperature back down to the ambient baseline, whatever it may have been.
     
    In theory, any "heat" or kinetic energy that exists, or existed below that ambient baseline is "unavailable to do work", but that "heat" was never added, never "applied". As it exists in equilibrium, it cannot even be defined as "HEAT" at all. At equilibrium it cannot be transferred.
     
    I agree that that equation determines the percentage of kinetic energy "available to do work". It is just the difference between the ambient baseline and the added energy above that baseline. The energy added between Tc (ambient) and Th. (on an absolute temperature scale). But availability is not efficiency.
     
     
    Before adding the insulation, just feeling the top of the running engine, it felt relatively cool. Considering the engine was running on top of scalding hot water straight out of the tea kettle, poured into a vacuum flask, the top of the engine felt as if it were room temperature, possibly it felt slightly cooler than room temperature. If that was true, then either no heat transfer was taking place or heat was flowing from the ambient into the engine.
     
    Call that whatever you want, but it did not seem to correspond to the mathematical "Carnot efficiency" which says that more than 80% of the applied heat should be passing through to the sink. If that were the case the engine certainly should have felt hot to the touch. VERY HOT to the touch, don't you think????
     
    If 80% of the applied heat was passing THROUGH to the sink, then insulating the sink, should trap that heat inside the engine, raising the temperature of the sink and destroying the temperature difference.
     
    Insulating the sink should cause the engine to slow down and stop or not operate at all. It cannot operate without a temperature difference.
     
    But on the contrary, insulating the sink INCREASED the RPM considerably. This would seem to indicate that the engine is actually refrigerating the cold side or "sink" heat exchanger rather than dumping waste heat into it.
  4. Like
    TomBooth got a reaction from OceanBreeze in Nikola Tesla Vs. The Second Law Of Thermodynamics   
    I ordered this digital thermometer a few days ago. It comes with four probes for taking simultaneous readings. It doesn't record data to the cloud or have software to build charts and plug into the computer like the $300 units, but appears to be a quality tool.
     
    "The K-type Thermocouple Thermometer - TC41 displays three different measuring units ˚C,˚F and K (Kelvin) with a temperature range of - 200°C ~ 1372°C (-328°F ~ 2501°F), perfect for measuring home appliance temperatures whilst maintaining high accuracy measurements for lab or industrial uses."
     
    https://perfectprime.com/products/tc9815?_pos=1&_sid=f155af95c&_ss=r
  5. Like
    TomBooth got a reaction from OceanBreeze in Nikola Tesla Vs. The Second Law Of Thermodynamics   
    Carnot efficiency is the maximum theoretical efficiency of a heat engine operating between ANY two temperatures. 
    That would be for a "perfect" engine without any loses to friction, heat leakage,bad seals, etc.
     
    Given my previous example, a model Stirling operating between ambient at 300k and boiling water, at whatever that was, 375 or something. The Carnot efficiency limitation at those temperatures is 9% if I remember right
     
    Edit: sorry, boiling water is 373 K (about).
     
    https://www.omnicalculator.com/physics/carnot-efficiency
     
    So, I'm talking, boosting efficiency from 9% to perhaps 9.5% or maybe 10%.
     
    The main point being that at anything above the Carnot limit, in this case 9%, heat will no longer be rejected to the sink. Above 9% at those two temperatures, heat is no longer passing through the engine to the sink All of the heat, above the equilibrium baseline, or ambient, is being utilized by the engine for "work". Discounting losses to friction etc.
     
    Unless someone has a better explanation.
×
×
  • Create New...