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Second law of thermodynamic question

  1. Apr 30, 2008 #1
    A steam turbine in a power plant accepts 4500 kg/hr of steam at 60 bar and 500°C and exhausts steam at 10 bar. Heat transfer to the surroundings (Tsurr = 300K) at a rate of 70 kW.

    (a) What condition needs to be satisfied for the turbine to generate the maximum possible power? (2 marks)

    (b) Calculate the specific entropy of the steam leaving the turbine when the latter is generating the maximum possible power. (8 marks)

    (c) Show that at this condition, the exiting steam temperature is 199.9°C. (3 marks)

    (d) Calculate the maximum possible power generated by the turbine. (5 marks)

    (e) Calculate the actual power of the turbine when the isentropic efficiency is 66.5%. (3 marks)

    (f) Without doing any calculation, do you expect the actual temperature of the exiting steam be higher or lower than 199.9°C? Briefly explain your decision. (4 marks)

    I think once i know (b) i can complete the rest

    For (a) i think the system process has to be reversible??

    For (b) i thought the steady state equation is 0=m(s2-s1)-Qrev/T
    but where is work in this equation??

    any help is appreciated
  2. jcsd
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