Blackbody Heat Shields/Metal Sheets

  • #1

Main Question or Discussion Point

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.
 

Answers and Replies

  • #2
33,816
9,529
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
 
  • #3
ummmm I still don't get it xD

do I use the equation:

Q = mC deltaT?
 
  • #4
33,816
9,529
No, that looks like regular conduction.
##P_{emitted}=\sigma A T^4## (Stefan-Boltzmann)
 

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