Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Max efficiency (thermodynamics)

  1. Mar 11, 2010 #1
    I'm observing the circular process of a heat engine. It's p-v diagram is

    heaengcyc.gif

    So between points 3 and 4 the heat is extracted. That causes losses since the efficiency if given by
    [tex] \eta =1- \frac {Q_c} {Q_h} [/tex]

    Where Qh is the heat the heat source has given and Q_c the amount of heat that the "cold" container took.
    If we don't cool down the engine in during the process between 3 and 4, the efficiency would grow to 100% (if friction is not consigered).
    The process would then look like the picture below, and 3 and 1 we would do an isobaric contraction.

    attachment.php?attachmentid=24297&stc=1&d=1268325038.gif

    I've encountered isobaric processes through my studies, but only as a theoretical concept. What are the reasons why it couldn't be used here?
     

    Attached Files:

  2. jcsd
  3. Mar 11, 2010 #2

    QuantumPion

    User Avatar
    Science Advisor
    Gold Member

    How can you do compress the working fluid without changing its pressure or temperature?
     
  4. Mar 11, 2010 #3
    I don't know, how do you get an isobaric process ever? :)
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook