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Heat exchange, emissivity and reflectance

  1. Mar 14, 2017 #1
    Hi Guys
    I´m studying the heat exchange problem in furnaces and, to begin with, i started with Incropera´s book.
    One thing is actually driving me crazy
    On the last part of this exercise´s solution (part 3), the physical principle involved is not very clear to me. To calculate the absorptivity of the wall, it´s assumed that emissivity = absorptivity. But, as far as i know, this is the famous Kirchhoff Law and it´s only valid when the system reaches thermal equilibrium, which is clearly not the case here. Can someone explain me what is going on?
    exc incropera 1.png
    exc incropera.png
     
  2. jcsd
  3. Mar 19, 2017 #2
    Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.
     
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