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Blackbody Heat Shields/Metal Sheets

  1. Sep 21, 2012 #1
    A “blackbody heat shield” is used to reduce radiant heat loss in situations where standard low conductivity insulation (i.e. normal insulation) cannot be used. The shield is constructed using a set of parallel metal sheets, each with emissivity 1.0.

    Explain how/why this “heat shield” works and determine how many sheets of metal are
    required to reduce the heat loss to less than 20% of the unshielded value. (Hint: think
    about the radiation absorbed by each sheet and how this energy will be re-radiated.)

    Diagram:
    gbZNa.jpg

    I really need help with this xD I don't even know where to begin.
     
  2. jcsd
  3. Sep 21, 2012 #2

    mfb

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    Staff: Mentor

    Here are some ideas:
    - assume that the whole problem is 1-dimensional
    - begin with 1 heat shield: Where does it receive/emit radiation?
    - assuming that the environment has a temperature of ~0, calculate the temperature of that heat shield in equilibrium
     
  4. Sep 21, 2012 #3
    ummmm I still don't get it xD

    do I use the equation:

    Q = mC deltaT?
     
  5. Sep 21, 2012 #4

    mfb

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    Staff: Mentor

    No, that looks like regular conduction.
    ##P_{emitted}=\sigma A T^4## (Stefan-Boltzmann)
     
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