Blackbody Heat Shields/Metal Sheets

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Discussion Overview

The discussion revolves around the concept of a "blackbody heat shield" designed to minimize radiant heat loss in scenarios where conventional insulation is ineffective. Participants are exploring the theoretical underpinnings of how such a shield operates, particularly focusing on the use of parallel metal sheets with high emissivity. The scope includes theoretical reasoning and mathematical modeling related to heat transfer and radiation.

Discussion Character

  • Exploratory, Technical explanation, Homework-related, Mathematical reasoning

Main Points Raised

  • One participant describes the function of a blackbody heat shield and its construction using parallel metal sheets with emissivity of 1.0.
  • Another participant suggests simplifying the problem to a one-dimensional model and proposes starting with a single heat shield to analyze where it receives and emits radiation.
  • A third participant expresses confusion about the problem and inquires whether to use the equation for heat transfer involving mass and specific heat.
  • A later reply corrects the previous suggestion, indicating that the equation mentioned pertains to conduction rather than radiation, and introduces the Stefan-Boltzmann law for calculating emitted power.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the approach to solving the problem, with some expressing confusion and others providing differing suggestions for analysis.

Contextual Notes

There are unresolved assumptions regarding the environment's temperature and the specific conditions under which the heat shield operates. The discussion also lacks clarity on how to quantitatively determine the number of sheets required to achieve the desired reduction in heat loss.

sweetdreams12
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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.
 
Science news on Phys.org
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
 
ummmm I still don't get it xD

do I use the equation:

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

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