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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Thermal Network

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Steady State Heat Conduction

We assumes that there is:
    • No internal heat generation
    • Steady state conditions 
    • Isotropic material 
    • 1-D heat transfer
Conductive Resistance

Convective Resistance
Radiative Resistance

Composite Wall

Chart for Thermal Resistance and Heat Transfer

Contact Resistance


Critical Radius of Insulation (Only for Cylindrical and Spherical Case)

Keep it mind the following things:
      • Sphere wall  ↠  Temperature profile is inverse of radius.
      • Rectangular Wall  ↠  Temperature profile is linear.
      • Cylindrical Wall  ↠  Temperature profile is Logarithmic.
      • If ractual < rcr  →  heat loss increases.
      • If ractual > rcr  →  heat loss decreases.
      • For Free Convection (air)  →  no fan (external source, h ≈ 5 W/m2.K, k ≈ 0.01 W/m.K).
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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