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Analyzing a partially reversible cycle

  1. Mar 18, 2012 #1
    Thermodynamic: Analyzing a partially reversible cycle

    1. The problem statement, all variables and given/known data

    A cycle (which at first appears to be a Carnot cycle) consists of a reversible isothermal
    process (with reversible heat exchange with a reservoir at 500 C), followed by an adiabatic
    process, which is followed by another reversible isothermal process (with reversible heat
    exchange with a reservoir at 200 C), and the cycle is closed with another adiabatic process.
    The magnitude of heat exchanged with the hot reservoir is 784 kJ per cycle, while the
    magnitude of heat exchange with the colder reservoir is 460 kJ per cycle.
    a. Is this a fully-reversible cycle? You must justify your answer.
    b. If it is not fully-reversible, is it an engine or a heat pump?
    c. What is the change in entropy of the device over one cycle of operation?
    d. Wwhat is the entropy change of the universe over one cycle of operation of the device?
    e. Sketch the cycle on T,s coordinates.


    2. Relevant equations

    dS≥dQ/T

    S2-S1=Q/T

    3. The attempt at a solution

    I got part a. of this Problem I just need some hints to get to Part b, c and d....

    For part b. I know that for an Engine: Qhigh goes from high temperature reservoir to engine, the engine creates work and releases Qlow to low temperature reservoir. A heat pump takes in work and Qlow and then release Qhigh.
    I have no idea how to determine whether we have an engine or a heat pump...

    I don't know where to start for part c and d
     
    Last edited: Mar 18, 2012
  2. jcsd
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