1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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: Designing of a steam power plant

  1. May 10, 2012 #1
    1. The problem statement, all variables and given/known data

    electric power = one million kW
    working fluid = steam
    maximum steam temperature = 550°C
    river mean speed = 10m/min
    river,8m deep,60 meter wide

    2. Relevant equations

    It is proposed to build a one million kW electric power plant with steam as the working fluid. The condensers are to be cooled with river water (see figure below). The maximum steam temperature will be 550°C. As an engineering consultant, you are to convince the authorities that the discharge to the river will not be harmful to the environment.

    3. The attempt at a solution
    this question may have several answer

    Attached Files:

  2. jcsd
  3. May 10, 2012 #2


    User Avatar
    Homework Helper

    Well what is the range of temperatures can the heated water enter the river again at? (35C? Also what the exit condition of the steam turbine? Vacuum/Back pressure? If so you will need that pressure condition.
  4. May 11, 2012 #3

    rude man

    User Avatar
    Homework Helper
    Gold Member

    Initial assumptions:
    1. Carnot efficiency
    2. River entering temperature Tin

    1st equation: 1st law expressed in time-derivative form
    2nd equation: 2nd law expressed in time-derivative form
    Third equation: temperature buildup of river water as function of dm/dt, c and dQ2/dt where dQ2/dt is rate of expelled heat into river, dm/dt = rate of water mass flow, c = water specific heat, J/C-kg.

    So: 3 knowns: dW/dt = 1 MW, T1 = 550C, Tin
    3 unknowns: dQ1/dt, dQ2/dt, ΔT
    where dQ1/dt = heat rate into system and ΔT = Tout - Tin = temperature rise of river water.

    Assume T2, the effective lower temperature in the Carnot cycle, is halfway between Tin and Tout, i.e. T2 = (Tin + Tout)/2.

    Finally, you must do some research to find what the typical steam-generated electric plant mechanical efficiency is beyond the Carnot efficiency.
  5. May 11, 2012 #4
    the the range of temperatures is 6c that is between 32-38c
    thanks guys...i will try to finish it up.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook