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Exhaust Heat Question

  1. Jul 21, 2010 #1
    Hey everyone, a recent argument came up between two people which had to do with the temperature of a car hood.

    Basically, the argument was what kind of heat would an exhaust manifold mainly use to get the hood of a car hot, convectional or radiated heat.

    The exhaust manifold is made of stainless steel but is ceramic coated, id say it gets around 800 Fahrenheit. I do not believe it emits any light at that temp.

    Thanks in advance!
  2. jcsd
  3. Jul 21, 2010 #2


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    Anything at any temperature emits radiation. At 800F, not enough of it is in visible range to be visible. In IR, however, 800F positively glows.

    Whether that's enough to be dominant mode of heat transfer, however, I'm not sure. There are ways to estimate how much heat is actually radiated, but I'm not sure how to estimate convective transfer under car's hood.
  4. Jul 21, 2010 #3
    Thanks for the 1st reply, I understand that at almost every temp things emit radiation, even if if the value is extremely small.

    The argument was mainly if a clear heat-shield could be used to prevent the hood from getting as hot.
  5. Jul 21, 2010 #4


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    Oh, whatever you end up using is most likely not transparent in wavelengths that are being radiated. Clear plastics tend to be opaque in IR.
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