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Homework Help: Non flow process

  1. Dec 10, 2012 #1
    A piston-cylinder assembly contains 20kg of air with a specific internal energy of 28K J/kg. It is compressed to a high pressure and the final specific internal energy is 65K J/kg. During the process there is a heat loss of 3.2K J. Determine the work energy input needed for the compressor.


    Just wanna ask how come I need to use the mass times the internal energy? What's the concept behind?



    Thanks.
     
  2. jcsd
  3. Dec 10, 2012 #2

    BruceW

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    You have been given the "specific internal energy". This is different to the "internal energy". And the question asks for a calculation of energy. So you need to calculate the internal energy by using the specific internal energy. I think you have already guessed how to do that.
     
  4. Dec 10, 2012 #3
    oops... why didn't i see that haha... anyway thank you Mr Brucew :)
     
  5. Dec 10, 2012 #4

    BruceW

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    ha, no worries. It is easy to miss.
     
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