Radiation Intro ME 114 Powerpoint

Radiation Intro ME 114 Powerpoint - Introduction to Thermal...

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Unformatted text preview: Introduction to Thermal Radiation Figures except for the McDonnell Douglas figures come from Incorpera & DeWitt, Introduction to Heat and Mass Transfer or Cengel, Heat Transfer: A Practical Approach Thermal Radiation Occurs in solids, liquids, and gases Occurs at the speed of light Has no attenuation in a vacuum Can occur between two bodies with a colder medium in between Applications: satellite temperature management, taking accurate temperature measurements, designing heaters for manufacturing, estimating heat gains through windows, infrared cameras, metal cooling during manufacturing, Greenhouse effect, lasers, insulating cryogenic tanks, Background Electromagnetic radiation – energy emitted due to changes in electronic configurations of atoms or molecules where λ =wavelength (usually in μ m), ν =frequency In a vacuum c=c o =2.998x10 8 m/s Other media: c=c o /n where n=index of refraction ν = λ c Background, cont. Radiation – photons or waves? Max Planck (1900): each photon has an energy of h=Planck’s constant=6.625 x 10-34 Js Shorter wavelengths have higher energy λ = ν = hc h e Radiation Spectrum Types of Radiation Two categories – Volumetric phenomenon – radiation emitted or absorbed throughout gases, transparent solids, some fluids – Surface phenomenon – radiation to/from solid or liquid surface Thermal radiation – emitted by all substances above absolute zero Includes visible & infrared radiation & some UV radiation. Radiation Properties Magnitude of radiation varies with wavelength – it’s spectral ....
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This note was uploaded on 04/15/2008 for the course ME 114 taught by Professor Okamoto during the Spring '08 term at San Jose State University .

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Radiation Intro ME 114 Powerpoint - Introduction to Thermal...

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