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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Fuel

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FUEL


Fuel is defined as,
Any combustible substance which during combustion gives a large amount of heat for industrial and domestic use.  

Classification of Fuels:

 (A) Types on the basis of Occurrence:

There are two types of fuel on the basis of occurrence:

I- Natural Fuels (Primary Fuel) :

Fuels which occurs in nature. For example: wood, coal, peat, lignite, anthracite, natural gas, etc.

II- Artificial Fuels (Secondary Fuel) :

Fuels which are derived from primary fuel. For example: liquefied petroleum gas(LPG), coke, gasoline, etc.

(B) Types on the basis of Physical State:

I- Solid Fuel : wood, sand, coal, anthracite, etc.
II- Liquid Fuel : gasoline, coal tar, alcohol, etc.
III- Gaseous Fuel : LPG, coal gas, coke, oven gas, etc.

Characteristic of a Good Fuel:


Characteristics of a good fuel are as follows:
  • High Calorific Value : Direct measure of its efficiency.
  • Moderate Ignition Temperature : It is the minimum temperature to which the fuel is to be heated to start combustion.
  • Low-moisture Content : Presece of high percentage of moisture reduces the efficiency of fuel.
  • Low-ash Content : Formation of ash during combustion is due to the presence of inorganic matter in the fuel.
  • Combustion Control : large wastage of fuel can be avoided by regulating the combustion rate properly and stopping the process immediately.

Coal :

Coal is a solid fuel which formed due to the bacterial decomposition of plants and animals which were burried in the surface of Earth. It contains carbon, hydrogen, Sulphur, oxygen, nitrogen, etc. 

Types of Coal :

There are four types of coal on the basis of carbon content and Calorific value.
The conversion of wood into coal is called coalification.

1. Peat :

It is considered to be the first stage of coalification. It contain 57% of carbon content and its Calorific value is 5400 Kcal/kg.

2. Lignite :

It is a brown colored and low quality coal. It contain 60-70% of carbon content and its Calorific value is 6500-7500 Kcal/kg. 

3. Bituminous Coal :

It is a soft coal and contains 75-95% of carbon content and its Calorific value is 7000-8600 Kcal/kg. 

4. Anthracite :

It is black colored and highest grade coal. It contains 92-98% carbon content and its Calorific value is in between 8650-8700 Kcal/kg. 

Calorific Value :

It is defined as:
Amount of heat liberated when a unit mass of fuel burnt completely in excess of oxygen. 

  • It is used for the calculation of efficiency of fuel.
  • Calorific Value of fuels can be determined by Steel Bomb Calorimeter. 
  • Calorific value is determined by using following formula:

Types of Calorific Value :

There are two types of Calorific value:

1. Gross Calorific Value (GCV) :

It is also called Higher Calorific Value (HCV) or Higher heat value (HHV). It is defined as :
Quantity of heat produced by combustion when water vapour produced by combustion is returned to the liquid state. 
 Dulong's formula for the GCV of fuel is given by:

2. Net Calorific Value (NCV) :

It is also called Lower Calorific Value (LCV) or Lower Heat Value (LHV). It is defined as :
Quantity of heat produced by combustion when water produced during combustion remains in gaseous form. 
Dulong's formula for the LCV of fuel is given by:

Analysis of Coal :


The composition of coal varies widely so it is necessary to analyze its content. The quality of coal can be determined by two types of analysis:

1. Proximate Analysis :

This analysis includes the percentage determination of:
  • Moisture Content
  • Volatile Matter
  • Fixed Carbon Content
  • Ash Content

(a) Moisture Content in Coal:


(b) Volatile Matter in Coal:


(c) Ash Content in Coal:


(d) Fixed Crbon Content in Coal:


2. Ultimate Analysis:

 In this analysis, we determine the percentage composition of:

  • Hydrogen and Carbon Determination
  • Nitrogen Determination 
  • Sulphur Determination 
  • Ash Content Determination 
  • Oxygen Determination 

(a) Determination of Hydrogen & Carbon:


(b) Determination of Nitrogen:


(c) Determination of Sulphur:


(d) Determination of Ash Content:


(e) Determination of Oxygen:

% Oxygen = %100 - %( C+H+N+S+Ash content)
Note: If anyone wants numericals related to the topics discussed above can contact me by filling contact form. 

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