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Homework Help: Heat transfer

  1. Dec 19, 2009 #1
    1. The problem statement, all variables and given/known data
    The absolute value of the heat flow rate through a slab of area 0.83 m2 is 240 W. The
    thickness of the slab is 1.4 cm and its thermal conductivity is 0.6 W/(m·K). If the hot surface of the slab is at 40°C find the temperature of the cold surface.


    2. Relevant equations

    H = -kA([tex]\Delta[/tex]T/[tex]\Delta[/tex]x)

    H = Q/t?

    3. The attempt at a solution

    A = 0.83 m^2; [tex]\Delta[/tex]x = 1.4; k = 0.6 W/(m·K); Thot = 40°C;

    Missing H?
     
  2. jcsd
  3. Dec 19, 2009 #2

    rock.freak667

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    Homework Helper

    this should be

    [tex]\frac{dQ}{dt}=-kA \frac{d\theta}{dx}[/tex]

    or

    ΔQ/Δt=-kA(Δθ/Δt)

    you were given ΔQ/Δt as 240 W
     
  4. Dec 19, 2009 #3
    ok so

    [tex]\Delta[/tex]T = ([tex]\Delta[/tex]x*H)/(kA)

    [tex]\Delta[/tex]T = 1.2*240/0.6*0.83


    [tex]\Delta[/tex]T = 578 K = 305 C ?? That's way above any answer options
     
  5. Dec 19, 2009 #4

    rock.freak667

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    Homework Helper

    this should be 0.014m
     
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