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Homework Help: Steam Problems

  1. Feb 25, 2013 #1
    1.I am currently working through some steam questions and I am struggling with this problem. I am using "Thermodynamic and Transport Properties of Fluids byG.F.C Rogers and Y.R Mayhew

    Here are my questions as it is written:

    "(A) Steam at 30 bar, 375 degrees C flows through a cooling coil with a negligible change in velocity and pressure, such that the exit dryness fraction is 0.5.

    Calculate the heat transfer per kg of water substance."

    I have worked this out by using the steady flow equation, linear interpolation and the unknown which was the "h2" value using h=(1-x)hf+xhg. (Obviously not in that order)

    Here is my issue below...

    One kg of steam at 30 bar, 375 degrees C, is contained in a rigid container and is cooled until the pressure is 13 bar.

    Calculate the final dryness fraction and the heat transfer

    Now I have been given a data sheet with the equation for x (dryness fraction) which is x= mass of saturated steam/total mass but I am still unsure how to calculate the dryness fraction from the information from the Steam Tables as I can not get the value of -966kJ

    So I am asking for your help with this please.

    I also have many more problems as well I need help with.

    Many thanks

    Scott


    2. x (dryness fraction) which is x= mass of saturated steam/total mass

    I believe once I have calculated the dryness fraction I need to use the steady flow equation of Q=m(h2-h1) to calculate the work done [I have disregarded the other values as they state that they are negligible]




    3. I can not continue this until I know how to work out the dryness fraction correctly. As I have obviously not worked out the dryness fraction correctly I can not seem to get the correct answer.

    PLEASE HELP

    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
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