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Railways NTPC (Technical Ability) Power Plant Engineering Question Bank Power Plant Engineering

  • question_answer
    The enthalpy of steam entering a, turbine in a Rankine cycle is 3200 kJ/kg. The enthalpy after isentropic expansion is 2400 kJ/kg and the enthalpy at the end of actual expansion is 2560 kJ/kg. What is the turbine efficiency?

    A) 75%                             

    B) 80%

    C) 85%                             

    D) 90%

    Correct Answer: B

    Solution :

    \[{{h}_{1}}=3200\,\text{kJ/kg,}\] \[{{h}_{2}}=2300\,\text{kJ/kg,}\] \[{{h}_{2}}=2560\,\text{kJ/kg}\] \[{{\eta }_{1}}=\frac{{{h}_{1}}-{{h}_{2}}}{{{h}_{1}}-{{h}_{2}}}=\frac{3200-2560}{3200-2400}\] \[\frac{640}{800}=0.8\,\,\,or\,\,\,80%\]


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