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Concentric Tube Heat Exchanger - Clarification on Energy Balance

  1. Oct 29, 2013 #1
    I'm trying to model a Transfer function for the response of the deviation in temperature of water coming out of the concentric tube heat exchanger in response to an input velocity of water function.


    I start the derivation with a couple equations in Seborg's Process Dynamics and Controls and then go off on deriving on my own since my application of the equations are different then what they were using them to show.

    A short snippet before I started my derivation:



    Now I understand what A_s and A_L are (the area available for heat transfer for those two... the length times 2(pi)R for the outside and inside radii, respectively).

    What the heck is Aw? Is that an average of the two areas or the total amount of area available for heat transfer?

    I got my model into standard form for what I want, but I'm having trouble putting in actual numbers.

    Any help is much appreciated!
  2. jcsd
  3. Oct 29, 2013 #2


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    It's not clear from the OP where Aw is used.
  4. Oct 30, 2013 #3
    Feel dumb now, I was up awake for an extremely long stretch of time and read the equation wrong... in my mind somehow the variable subscripts were flipped.

    I am not confused after a good night's rest :D
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