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Managed to find the humidity ratio

  1. Oct 18, 2004 #1
    Moist air has these values; 760mmHg, 80%, 30 degrees C. I have managed to find the humidity ratio (21,65 g/kg), but how can I determine the specific enthalpy? :grumpy:
  2. jcsd
  3. Oct 18, 2004 #2
    Can you assume the water vapor is at saturation, then look up the enthalpy in a steam table for that temp/press combination?
  4. Oct 18, 2004 #3
    No, the answer should be 85.25 kJ/kg, and this value is not in the table for this temp/pressure comb., so there must be some equation in use to figure it out...I guess.
  5. Oct 18, 2004 #4
    Use a psychometric chart for water in air (One is presented in " Basic Principles and Calculations in Chemical Engineering" -David Himmelblau ,Fourth Edition- Prentice Hall, Inc. ) and intercept temperature ( 30 C) and relative humidity ( 80 %). Then you read the corresponding specific enthalpy 85. 25 kJ/kg.
  6. Oct 19, 2004 #5


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    What about if you prove with:

    [tex]h=h_{air}+\omega h_{water}[/tex]

    where [tex]\omega[/tex] is the humidity ratio?
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