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Homework Help: Thermodynamics-Finding Internal energy

  1. Mar 16, 2008 #1
    I am going over this example

    0.5 kg of air undergoes a Carnot cycle with η = 0.5.
    Given the initial pressure p1 = 700 kPa, initial
    volume V1 = 0.12 m3 and heat transfer during the
    isothermal expansion process Q12 = 40 kJ, Find
    the highest and the lowest temperatures in the
    (b) the amount of heat rejection.
    (c) work in each process.

    They have Th to be 585.4k and Tl to be 292.7k
    and so
    W23 = m(u2 – u3)= 0.5(423.7 – 208.8) = 107.5 kJ

    I do not know how to findu2 and u3. Looking at the tables at he back of the book doesn't help because they don't list the temperatures in this problem. So what equation is used to find u2 and u3 with the given information.
  2. jcsd
  3. Mar 17, 2008 #2
    What is the work done during an isothermal process?

    What is the efficiency of a carnot cycle?
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