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Overunity from Heating and Cooling

  1. Jan 10, 2014 #1
    The kinetic energy of gas molecules or atoms is: (3/2)kTN/M where k is Boltzman constant, T is absolute temperature, N is avogadros number and M is molecular weight. The formula is derived from http://en.wikipedia.org/wiki/Kinetic_theory.
    Assume that the gas is steam with M = 18 kg/mol at 373K, it is equivalent to approximately 260 J/kg but suppose i cool the steam up to 40C based on Cdt + Lf (C is specific heat, dt is change in temperature and Lf is latent heat of vaporization), it becomes an overunity of 10420 more effective. From what assumption or derivation im wrong? or if i'm right where does the excess energy came from?
     
    Last edited: Jan 10, 2014
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  3. Jan 10, 2014 #2

    ZapperZ

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    That is the AVERAGE kinetic energy! It is a statistical ensemble derived via Maxwell-Boltzmann distribution!

    Zz.
     
  4. Jan 10, 2014 #3
    yes i compute the average kinetic energy of the molecules and then i multiply it with the total number of molecules using avogadros number and molecular weight so i computed the total kinetic energy1 kg steam of approximately 260 J, which is very small.
     
  5. Jan 10, 2014 #4
    I actually computed the total kinetic energy since the average kinetic energy is only equal to kT/2.
     
    Last edited: Jan 10, 2014
  6. Jan 10, 2014 #5
    What is overunity? I've never heard the term before.
     
  7. Jan 10, 2014 #6
    It means that efficiency is greater than 1 or 100%, there is a gain of energy which violates law of conservation of energy.
     
  8. Jan 10, 2014 #7

    sophiecentaur

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    It's when you get more out than you put in - so very near the fringe of what's acceptable on PF.

    Suffice to say that someone with the time and inclination could find the flaw in the OP but there are better things to do with your time than chase things like that.
     
  9. Jan 10, 2014 #8

    berkeman

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    Yes, overunity processes are on the banned topics list of the PF. Thread is closed.
     
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