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Thermodynamics: Calculating total resistance of window

  1. Mar 1, 2016 #1
    1. The problem statement, all variables and given/known data
    A triple glazed window consists of 3 clear glass panes of 3 mm thickness each, separated by air cavities of 12 mm each. The window area is 1.0 m2 . If the thermal conductivity of the glass panes is 0.8 W•m-1•K-1 and of the air cavities is 0.028 W•m-1•K-1 what is the total thermal resistance of the window?

    2. Relevant equations


    3. The attempt at a solution
    83c151065d.jpg

    The correct answer is meant to be 1 KW. I was initially going to do something with the internal air and external air but the question says the total thermal resistance of the window. So it should be conduction1 through the first pane of glass, then convection1 through first air gap then conduction2 through second glass pane then convection2 through second air gap then finally conduction3 thorugh third glass pane.
     
  2. jcsd
  3. Mar 1, 2016 #2

    CWatters

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    I think the air gaps are small enough for convection to be ignored?

    In your working, where you calculate the resistance of the air gaps... You appear to have the thickness as 1m rather than 12mm?
     
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