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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Heat Transfer from Extended Surface

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Extended Surface Heat Transfer

Heat transfer of any body can be enhanced by:
        • Increase in h (convective coefficient, increase by forced convection e.g.: fan).
        • Increase temperature difference (Ts-T∞)
        • Increase in area (A)
However by changing the above parameters, you counter certain conditions:
        • If h is increase  ↠  cost increased.
        • T∞  ↠  cannot be controlled.
        • Only area (A) is feasible.

Fin Equation

Case A: Uniform Cross-sectional Area

Case B: Fin of Uniform Cross-sectional Area & Insulated Fin Tip

Case B: Fin of Uniform Cross-sectional Area & of Infinite Length

Fin Performance Factors

Following are the fin performance factors:

1. Fin Effectiveness 

Fin is used to enhance heat transfer (Cost added and complexity associated with fins). It is the ratio between heat transfer with fin and heat transfer without fin. 
        • If εfin > 1  ↠  fin enhancing heat transfer increase.
        • If εfin < 1  ↠  material lost, heat transfer decrease.
        • If εfin = 1  ↠  material lost.

2. Fin Efficiency

It is the ratio between actual heat transfer and the ideal heat transfer when it is at Tb. 

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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