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Homework Help: Boiler efficiency and fuel consumption

  1. May 1, 2012 #1
    1. The problem statement, all variables and given/known data
    A boiler is to produce 6250 kg/h of steam superheated by 40 oC at a pressure of 2.1 MN/m2. The temperature of the feedwater is 50 oC. If the thermal efficiency of the boiler is 70%, how much fuel oil will be consumed in one hour? The calorific value of the fuel oil used is 45000 kJ/kg, cp of superheated steam is 2.093 kJ/kg K.

    for pressure 2.1 Mn/m2
    Hfg = 1880 kJ/kg
    Hf = 920 kj/KG
    sat temp - 214.9

    2. Relevant equations
    I want to know how to calculate the enthalpy of the feed water to put back into the boiler efficiency question.
    why am i given cp?

    3. The attempt at a solution
    using the formula : boiler efficiency = m x (H2-H1) / fuel consumption x calorific value

    H1 is the feed water enthalpy and i am told not to use thermodynamic tables

    I got some help from a university lecturer and solved it.
    Last edited: May 1, 2012
  2. jcsd
  3. Nov 29, 2015 #2
    how did you solve this?
  4. Nov 29, 2015 #3


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    Staff Emeritus
    Science Advisor
    Homework Helper

    The OP posted this problem 3 and a half years ago and never was seen again. I don't think you're going to get a response. :frown:
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