Physicists help needed!!! Current technology limitations.

Discussion in 'General Science & Technology' started by Tirstan, Nov 15, 2005.

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  1. MetaKron Registered Senior Member

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    Well, I'm always guilty of responding to it, but I'm not the one who started flame-baiting.
     
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  3. Flunch Registered Senior Member

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    From an impartial 3rd party standpoint your refusal to believe well established laws of thermodynamics is kind of maddening but Light could definitely tone down the rhetoric and personal attacks. If, in fact he is (was) a teacher I hope he didn't teach by ridiculing people.
     
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  5. Light Registered Senior Member

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    I retired from teaching, Flunch. And no, I didn't ridicule anyone. However, this particular kid is NOT one of my students and deserves no slack. Why? Because he continuously claims to know all the answers. I've led him through this whole process and he HAS learned from it. But every single time he picks up a new fact he then proceeds to try and make it appear that he knew it all along. That is not the way a true student behaves. And that's why I say he's no student of mine - I'd chase him from the classroom in a heartbeat! Again, why? Because he's smug, denies what he said earlier (many times!), and acts far too superior. In essence, he's just a jerk.

    As to my personal style, check out some other threads - like the one on hurricanes - and see how I deal with ordinary reasonable people like Valich. You will find that I did ridicule URI and that's simply because he is another nut case - but not as bad as Buddah1 and Duendy.

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    I'm also very patient with people like The Empty Force of Chi and several others who are actually trying to learn.

    But back to this particular individual for a moment. He hasn't even the good sense to ask questions - he simply makes statements. Over and over again that have to be constantly cleared up. And yes, it's rather maddening when you have to teach by something that approaches brute force.

    Incidentally, I never once treated any of my students like that during eleven years of teaching - but I did force a few out of the class because they acted just like this jerk we're discussing.
     
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  7. MetaKron Registered Senior Member

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    Yeah, I'll bet you were a real prince.
     
  8. Light Registered Senior Member

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    It would seem close to being true. All of my students that made it through the whole session expressed appreciation for having been in my class. I just eliminated all the jerks first - it made it better for the other students.

    And no, you probably wouldn't have made it past the first day.
     
  9. MetaKron Registered Senior Member

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    Whatever.
     
  10. leopold Valued Senior Member

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    i read the first post and the last page and it seems you have gotten off the track.
    why not bioengineer a giant butt muscle to power our cars? or a giant electric eel to power electric cars?
    or a giant squid to power our submarines? (silent drive?)
    think outside the box.
     
  11. Light Registered Senior Member

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    If I had any of those I'd certainly want to keep them INside the box!

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  12. leopold Valued Senior Member

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    i read somewhere that the most efficient internal combustion engine can achieve is 50% the other half(or more) is expended as heat, so the only way to increase an engines efficiency is to utilize the waste heat somehow.
     
  13. CANGAS Registered Senior Member

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    The thread starter described a BOMB CALORIMETER. Now, the trick would be, how to turn the heat into work before it escapes as waste heat.

    We are already half way there! It's so easy when we break the problem down into parts!

    OK, I did MY half. Now its your turn(s).
     
  14. Light Registered Senior Member

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    Pretty much true. But another way is use more efficent prime-movers. One is a turbine and it's already been suggested to develop smaller ones. Even current ones will outperform both standard gasoline and diesel engines. They also deliver more useful power per pound of engine. But they need to be made smaller and used in a hybrid vehicle in order to be practical.

    From an engineering standpoint, there's little that can be done to use any more of the waste heat from standard engines. The additional weight is the main problem.
     
  15. leopold Valued Senior Member

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    what is a bomb calorimeter?
     
  16. Light Registered Senior Member

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    It's a device for determining the amount of heat (Calories) in a substance. It's immersed in a water bath, an electrical current (carefully measured) is applied to the substance until it's completely oxidized (burned up). The temperature increase in the water indicates precisely how much energy was released (after subtracting was was supplied electrically).
     
  17. leopold Valued Senior Member

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    light:
    are you familiar with the sterling engine? uses heat to produce rotary motion, maybe you could use them both somehow. (i'm not an engineer)
     
  18. Light Registered Senior Member

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    Hello Leopold,

    Yes, and it's a fine device! Excellent for producing power from low-level heat sources.

    It would also be nice to include one, two or three in ordinary vehicles for additional heat recovery. But the problem is that adding even one increases the weight to the point that you'll actually have a net overall loss of energy by carrying it around.

    You could also use it as the only engine in a car and get a very good improvement in energy efficiency. However, it's response time to changing loads - like taking off from a traffic light or attempting to pass - is so slow that it would drive people nuts. You would never be able to pass any regular vehicle with it.

    They are very good for stationary applications, though, provided the load doesn't change or changes very little or very slowly. And it's due to those limitations that you don't see them in industrial settings. Unchanging loads are very, very rare.
     
  19. leopold Valued Senior Member

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    light
    isn't that also true of turbines? isn't it true that a turbine has to "idle" at 75% of it's total rpm? they wouldn't be very responsive either.
     
  20. Light Registered Senior Member

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    No, not exactly. Please forgive me but it's been a long time since I saw turbine response curves but they operate at maximum efficiency at max load somewhere around 85 - 90% of top RPM.

    The reason I said "not exactly" is because it would have to be incorporated into a hybrid vehicle that used battery power for quick responsiveness and the turbine would have to be small so that it could be run all the time at that steady-state RPM and loading. The whole assembly would be about a third the size of a normal 4-cylinder engine and weigh less than 1/3 as much. I honesty can't say why is isn't being done so I feel pretty sure that I'm missing something. Itook some mechanical courses in college and have worked on many different engines including gasoline, diesel, and gas-fired turbines BUT I'm no design engineer.

    Some of the more recent (in the past year or so) numbers I've seen for efficiency are pretty doggone good - numbers like 85% efficient. Very impressive!
     
  21. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    If I try hard, I can believe that for the conversion of the kinetic energy of the gas flow into shaft energy, but the Carnot engine limits still apply to turbines so the thermal efficiency is much lower.

    BTW, your earlier comments about the Sterling engine are no doubt correct, but Its main claim to fame is that in can, unlike the IC, actually approach the Carnot limit, in principle, but not in actual economic-viable practice.
     
  22. MetaKron Registered Senior Member

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    Even plain old IC piston engines do tremendously better when used in electric hybrid setups. Around 1980 a guy was able to get 75 mpg from an old Suburu pickup that was set up that way. The top speed was something like 45, though, which is something that could have been improved on because he was using a 35 hp diesel engine as his primary source of power. Looking at it this way, a Stirling engine is not so unviable. I find it hard to believe, actually, that people think they can afford not to save at today's gas prices. Maybe convenience is worth more than we like to think it is.
     
  23. MetaKron Registered Senior Member

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    Have you read this discussion? I'm the one who has recited doctrine on these "well established laws." I realize that in the eyes of many physical laws are variable depending on the authority who spake them.
     
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