Radiation Heat Transfer

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View Factor Orientation (or View factor or shape factor) plays an important role in radiation heat transfer. View factor is defined as, "fraction of radiation leaving surface 'i' and strike 'j' ". Summation Rule (View Factor) If there is are similar surfaces 'i' and 'j' , then: Blackbody Radiation Exchange Radiation Exchange between Opaque, Diffuse, Gray surfaces in an Enclosure 1. Opaque 2. Surfaces 3. Two surface enclosure Radiation Shield It is used to protect surfaces from radiation act like a reflective surface. References: Material from Class Lectures + Book named Fundamentals of Heat and Mass Transfer by Theodore L. Bergman + My knowledge.  Photoshoped pics  are developed.  Some pics and GIF from Google.   Videos from YouTube ( Engineering Sights ).
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Processes and Properties of Radiation

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Radiation

    • Radiation effects are significant at high temperature.
    • No material medium required.
    • Every body above 0 kelvin emit electromagnetic waves (disturbance of photons).
Radiation heat fluxes:
    • Emissive Power (E)  ⇔  rate of emitted radiations. It is a function of temperature.
    • Irradiation (G)  ⇔  rate of incident radiation on a body.
    • Radiosity (J)  ⇔  total radiation that leaves the surface.
    • Net Radiative Flux  ⇔  it is difference between radiation outgoing to radiation incoming.
Solid Angle:

Radiation Intensity:
It is defined as, "rate of emitted radiation per unit area per spectral intensity (wavelength) per solid angle".

Blackbody Radiations

It is a hypothetical body with:
    • No reflection and transmission.
    • Radiation intensity is governed by Planck distribution

1. Wien's Displacement Law

To find maximum emissive power, differentiate function with respect to wavelength and put it equals to zero.

2. Stefan - Boltzmann Law

For finding total emissive power, integrate whole function with respect to wavelength. 

Band Emission:

It is the portion of emission of band between 0 to specified value of wavelength (λ).
    • To find percentage of blue radiation in the given light.

Kirchhoff's Law

References:

  • Material from Class Lectures + Book named Fundamentals of Heat and Mass Transfer by Theodore L. Bergman + My knowledge. 
  • Photoshoped pics are developed. 
  • Some pics and GIF from Google.  
  • Videos from YouTube (Engineering Sights).

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