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Homework Help: Thermal energy power station problem

  1. Feb 19, 2010 #1
    1. The problem statement, all variables and given/known data:
    A power station with an efficiency of 0.3 generates 10^8 W of electric power and dissipates 2.33 multiplied by 10^8 W of thermal energy to the cooling water that flows through it. Knowing the specific heat of water in SI units is 4184 J/kg°C, calculate how many kilograms of water flow through the plant each second if the water is heated through 3 degrees Celsius.



    2. Relevant equation:
    Q=cm* change in temperature



    3. The attempt at a solution:
    2.33*10^8=4184*m*3
    m=(2.33*10^8)/(4.184*3)
     
  2. jcsd
  3. Feb 19, 2010 #2

    Andrew Mason

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    Why are you using 4.184 and not 4184 in the denominator?

    AM
     
  4. Feb 19, 2010 #3

    Q = mcΔt

    Q = Energy in Joules
    m = Mass in kilograms
    c = Specific heat capacity Jkg-1K-1
    Δt = Temperature in degrees

    4184Jkg-1K-1 is how much energy that's needed to heat 1kg of water from 0degrees to 1degrees (quite alot of energy). You putting 4.148Jkg-1K-1 says that it only requires 4.148joules of energy to change in 1 degree.
     
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