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Homework Help: Thermodynamcics quesstion (Diagrams)

  1. Jan 22, 2010 #1
    In a question He gives that :

    0.1 kg of water contained in cylinder-piston device .
    Water is initially at 1.5 bar and 403 k (Kelvin).
    More 0.1 kg of water at 2 bar and 403 kelvin is admitted to the cylinder.
    Through out this filling process, pressure and temperature of cylinder are maintained constant.

    Represent this filling process on p-v and T-s diagrams

    The confusion is how to represent a process at which both pressure and temperature are constant

    Please I need the answer urgently ​
  2. jcsd
  3. Jan 22, 2010 #2


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    Gold Member

    Hi and welcome to PF!
    Use the relation PV=nRT. If you keep P and T constant while increasing n, V must increase in the same proportion than n.
    Also, what is a T-s diagram? Temperature - seconds?
  4. Jan 22, 2010 #3
    First : Thank you for your speedy response

    Second : I mean that in p-v diagram
    horizontal line represents constant pressure
    but constant temperature process is represented by a curve
    So how to represent a process combining the two conditions ( P and T are constants ) !!!!
    Would it be a curve or horizontal line or neither of therm ??

    Third : T-S is Temperature -Entropy Diagram .
  5. Jan 22, 2010 #4


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    Gold Member

    Here is what I would do (I could be wrong though).
    Use PV=nRT. P, T and R are constants. n increases until it reaches its double value. What can you say about V?
    Plotting this in a P-V diagram should not be a problem once you've figured out the previous question.
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