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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Water & It's Treatment

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Why do we need to treat water?

We need to treat water due to following reasons:
  • The consumable water has its pH between 6.6-7.5.
  • Water contain hardness, more TDS (total dissolved solids) than in consumable water.
  • Presence of gases in water make it acidic like oxygen, Sulphur dioxide, nitric oxide, carbon dioxide, chlorine and many more. 

Acidity of Water:

It is the ability of water to neutralize a base is called Acidity of water. 
It occurred in water due to the following reasons:

1. Dissolved Gases:

Most of the gases when dissolved in water, it produce acid which turns water into acidic.

2. Biological Oxidation of Hydrocarbons :

Biological decomposition of Hydrocarbon also produce acid which causes acidity of water. 

3. Metallurgical Waste :

When industries waste are drawn into rivers and sea, it causes acidity because it contains some metals like (As, Pb, Cd, Hg) which are dangerous for life.
FeS +O2 +H2O → FeSO4 + H2SO4

Alkalinity of Gases:

It is the ability of water to neutralize an Acid.
  • Phenolphthalein can indicate 8-14 pH substances.
  • Methyl orange can indicate 2-5 pH substances.
These alkalinity causing anions show single or double step dissociation which are as follows:

Hardness of Water:

Soap consuming capacity of water is called Hardness of Water. 

Causes of Hardness of Water:

There are two causes of hardness of water. 
  1. Monovalent cations of group I-A produce soft water.
  2. Divalent cations of group II-A and some of the transition. Metals (ferrous and manganese ions) produce hard water.

Types of Hardness of Water:

Hardness is further divided into 2 types:

1. Temporary Hardness:

It is due the presence of bicarbonate of calcium or magnesium. It maybe removed by boiling. 

2. Permanent Hardness:

It is due the presence of sulphate, nitrate and chloride of calcium and magnesium. It cannot be removed from boiling. 

Determination of Hardness of Water:

There are two methods for the determination of Hardness. 

1. Soap Titration Method:

When soap is added to hard water, it does not give lather because hardness producing metal ions (calcium and magnesium) get precipitated. After complete precipitation of calcium and magnesium ions, further addition of soap gives lather.
The total hardness can be determined by titrating the water sample against standard soap solution. 

2. EDTA Method:

The total hardness in water is determined by titrating the water sample against standard EDTA solution in ammonical buffer solution having pH=10 using eriochrome balck-T as an indicator. The calcium and magnesium ion present in hard water forms stable compound with EDTA and less stable compound with eriochrome balck-T.

The calcium and magnesium ion combine with indicator at pH 9-10 to form less stable wine red complex.


Scale & Sludge Formation:

When precipitation of dissolved salts take place inside the boiler in the form of soft, slimy and non-adherent layer is called Sludge. If the precipitation takes place in the form of hard adherent layer inside the boiler is called Scale.

Priming & Foaming :

When water is boiled in a boiler, the formation of bubbles in the surface of water take place, is called Foaming. 
When water is boiled rapidly the bubbles and drops of liquid water entered into engines or pipes, is called Priming. 

Portable Water Treatment:


Steps for the treatment of portable water are given below:
  • Screening
  • Sedimentation
  • Coagulation
  • Filtration
  • Sterilization or disinfection

Ion Exchange Process or Demineralization:

Following steps are important to taken for obtaining deionized water.
  • Choose of ion-exchange resin. Due to their functional group resins are divided into 2: cation and anion exchange resins. 
  • Cation exchange resions are acidic groups like carboxylic, sulphonate groups. 
  • Anion exchange resins are basic groups like amine, substituted amine, quaternary ammonium groups. 
  • Now acidic and basic resins are allowed to react with cations and anions.
  • The released H+  ion from cation exchanger and OH- ion from anion exchanger combined to form water. 
                 

  • Regeneration of resins take place by passing cation exchanger from (2% HCl or sulphuric acid) and anion exchanger from an alkali (dil. NaOH). 


Note: I have numericals as well, if someone want those, contact me. 

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