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Free convection heat transfer

  1. May 11, 2012 #1
    Dear all

    I got a value of 37 for h ( convection heat transfer )

    Does it consider as free or natural convection heat transfer coefficient?

    Thanks in advance !

    And Sorry its not a Homework problem :)
  2. jcsd
  3. May 11, 2012 #2
    What is the application. English or SI units. More information would be helpful.
  4. May 14, 2012 #3


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    Your question is difficult to answer without more informtation, but as a general rule free convection is driven by differential density due temperature difference in a fluid and forced convection is driven by some external means (for example a fan).
  5. May 14, 2012 #4
    For nature convection heat transfer coefficient h =10w/m^2-k(including radiation)
    For force convection, h range is more large, however you can take 25w/m^2-k for coarse estimate.
  6. May 14, 2012 #5


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    Where exactly do these estimates come from? Without citing a source they're gibbereish and can't be used; especially since they don't take into account anything regarding fluid properties, geometry, etc.
  7. May 15, 2012 #6
    Thanks for Mech's remind. The listed value is for air cooling.
    Acctually the precise h value needs detailed information such as shape, fluid, ambient condition. Normally i use CFD software to calculate.
    However, the listed value can be used for draft esimated and may answer the raised question.
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