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 Heat and Mass Transfer

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Firstly I am gonna tell you what is the basic difference between heat and thermodynamics.
    • Heat  ⇒  Energy moves due to the temperature difference untill thermal equilibrium.
    • Thermodynamics  ⇒  heat along a cycle (without rate).
    • Heat Transfer  ⇒  rate of energy transfer (at any time).
        • Non-equilibrium phenomena 
        • Help you in Cost reduction.

Different Modes of Heat Transfer

There are three modes of heat transfer which are discussed ahead:
    1. Conduction  ⇒  By molecular vibration (if fixed pattern solids → conduction rate high called conductors).
    2. Convection  ⇒  Conduction + Advection (bulk fluid motion).
    3. Radiation  ⇒  Heat transfer in vacuum.
Ques: Why Diamond (non-metal, 2300 W/m.K) has high thermal conductivity than metals (copper = 430 W/m.K)?
Ans: Diamond's arrangement of atoms is more perfect than copper, that's why diamond has higher thermal conductivity.

1. Conduction

It is defined as, "a mode of heat transfer due to the molecular vibration". For heat conduction, the rate equation is known as Fourier Law of Heat Conduction.

2. Convection

Convection is defined as, "a mode of heat transfer which includes conduction and bulk fluid motion". Convective heat transfer is governed by Newton's Law of Cooling".
    • Convective coefficient depends on fluid, type of convection (natural or forced) and fluid speed.

3. Radiation 

It is defined as, "a mode of heat transfer due to the movement of electromagnetic wave in vacuum (all real bodies above 0 Kelvin emit radiations)". Radiative heat transfer is governed by Stefan's Law.
    • Black or Ideal Body  ⇒  Absorb all radiations.
    • Real or Gray Body  ⇒  not perfect absorber or emitter.
    • At same temperature, εof black body > εof gray body.
    • At lower temperature  ⇒  conduction/convection significant.
    • At higher temperature  ⇒  radiation significant.

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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