Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Steam Power Plant

  1. May 3, 2007 #1
    Hi guys been given the following as some home work, haven't got a clue really its a bit confusing!

    Steam ar 40 bar and 400C enters the high pressure turbine of a steam power plant at a rate of 20kg/s and explands to a pressure of 3 bar at which point it is just dry saturated. at this point part of the steam is re heated to 400C and then expands in the low pressure turbine to a condenser pressure of 0.05 bar with an isentropic efficiency of 88%. the remainder passes directly to asingle 'open' feed heater. the water leaving the condenser is raised to the feed heater pressure which it enters at a temp of 50C

    1) Draw a schematic diagram of the plant and a corredponding cycle diagram on a temperature-entropy axes

    2) neglecting feed pump work inputs, find:
    a) the mass flow rates of steam and water entering the feed heater
    b) the plnats power output and heat input
    c) the plants thermal efficiency

    Thank you in advance
  2. jcsd
  3. May 4, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    Use steam tables.

    "Steam at 40 bar and 400C" is a thermodynamic statepoint with which is associated a specific enthalpy. One must know if it is superheated or otherwise.

    "3 bar, dry saturated" is another statepoint - key here is 'dry saturated'. What is the saturation temperature of water at 3 bar?

    The inlet conditions of the LP turbine (assuming negligible pressure drop across the reheater) is 400 C at 3 bar.

    Then one must determine the liquid vs steam proportions based on "condenser pressure of 0.05 bar with an isentropic efficiency of 88%".
  4. May 8, 2007 #3
    i'm not sure if it is super heated or not, all i have is the information i posted.

    From my basic knowledge of steam tables i think the saturation temp of water at 3bar is about 133.5C

    and to be honest from then on im lost with where to look and what to do...


    Pain in the bum Thermodynamics!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook