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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Distance Measurement

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METHODS OF DISTANCE MEASUREMENT

There are many methods for the measurement of distance. 

1. Pacing :

Pacing is a very useful but imprecise technique of distance measurement. First of all, the one who wants to measure distance should measure distance between his feet and then make a walk up to which distance is to be measured. 
Total distance = distance between 2 feet × No. Of pacing

2. Odometer :

Odometer is an instrument used to measure distance in wheel based vehicles. The most important for distance measurement is to find out the radius of wheel and the number of rotation. Then using the following formula for distance measurement. 
Total distance = Radius of wheel × No. of rotation
                        H = R × θ

3. Electronic Distance Measurement (EDM) :

EDM is used for measuring distance electronically between two points through electromagnetic waves. 

EDM have following parts, namely 
  • Frequency generator
  • Transmitter & receiver
  • Beam splitter
  • Phase meter
  • Display screen 
  • Retro reflector 
  • Amplifier
  • Filter ( Variable & Interference )
  • Modulator 
EDM is further classified into long wavelength, visible instruments depending upon the distance to be measured. 

4. Substense Bar :

A Substense bar is a tripod-mounted bar having targets precisely 2-m apart. First we need to find the angle from the point we target objects then make it half then use the following formula

5. Gunter's Chain :

A chain which is 66 ft long and is used to measure distance is called Gunter's Chain. The length of 66-ft was apparently chosen because of its relationships to other units in the imperial system.
           80 chains = 1 mile = 1.6 km
10 Sq. Chains = 1 acre (10×66×66 = 43,560-sq.ft)


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