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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Introduction To Conduction

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Conduction Rate Equation (or Fourier Law of Heat Conduction)

According to the Fourier Law of Heat Conduction, steady state heat transfer is directly proportional to change in temperature and inversely proportional to the thickness.

    • Proportionality is valid for all materials.
    • Heat Flux  →  heat per unit perpendicular area (isothermal surface).

Thermal Properties of Matter

1. Thermal Conductivity

It is defined as, "the ability of a material to conduct heat".
    • For anisotropic material (different k in different directions)
    • For isotropic material (k is same in all direction)

2. Thermal Diffusivity

It is defined as, "material ability to conduct heat relative to its ability to store thermal energy".

Heat Diffusion Equation

There cases for Heat diffusion equation, which are:
      • For isotropic material  →  k become constant.
      • Steady state condition  →  No change with time (energy storage = 0).
      • For 1D and no internal heat generation  →  equation reduced to qx'' (heat flux) is constant. 
In cylindrical coordinates: 
In spherical coordinates:
Note:

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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