Law of gearing

In order to have a constant angular velocity ratio  for all position of the wheels, the pitch point must be fixed point for gears.

Or

The common normal at point of contact must be pass through pitch point.

Pitch point

It is in a common point of contact between two pitch circles is called as a Pitch point. 

Pitch circle diameter

The distance between the axis of rotation of the shaft and Pitch Circle surface is called as a pitch diameter or it is called as a pitch circle diameter

Pitch circle

It is an imaginary circle by which pure rolling action would give the same motion as the actual gear

Gear OR toothed wheels

a gear is a cylindrical surface Wheel on which number of projection  are projected which can, fit the corresponding projection on another wheel is called as a gear..

Kinematics friction wheel without slip is equivalent to the gear

Preparation of Low density polyethylene (LDPE) :

It is formed by heating ethene at 200°C to 300°C and at 1000 atm pressure using small amount of oxygen as acatalyst. Oxygen form peroxide and reaction is initiated. This is a branched chain polymer, as growing chain abstracts hydrogen atom from the middle of the chain and the branch grows.

i) Growing chain unit takes proton from another to form secondary free radical.

ii) Secondary free radical combine with another molecule ethylene to form branched polymer and thus branch grow.


LDPE have low m.p. It is used as insulation for cables, as packing bags, making toys.

This LDPE is chemically inert and tough but mechanically weak.

b) Preparation High density polymer (HDPE) :

b) Preparation High density polymer (HDPE) : 

It is linear addition polymer. The catalyst used is Zeiglar-Natta (TiCl4 + (C2H5)3Al). The polymerisation takes place at 373 K, 6-7 atm pressure. Ethylene first forms titanium complex with TiCl4, hence it is also called co-ordination polymer.

HDPE has high density and high mp. used to make bottle, jar, buckets, drums, pipes etc.

Free radical polymerisation :

Free radical polymerisation :

In tree radical polymerization, dilferent initiators used are benzoyl peroxide, ter.butyl peroxide or acetyl peroxide which generate free radicals. Following steps are involved.

Consider the polymerisation of ethene

Chain growth polymerisation/Addition polymerisation :

Chain growth polymerisation/Addition polymerisation :

On treatment with small quantity of initiators. alkenes undergo chain gowth polymerisation. The chain grows by adding, the reactive end of growing chain to double bond of monomer. The intermediates formed are reactive and which may be free radicals, carbocation or carbanions.

CO-POLYMERIZATON

Co-polymerization : 

l) Homopolymer :

Apolymer made from identical repeating unit of One monomer is called homopolymer.

e.g. polythene, nylon-6, polystyrene, PVC

2) Heteropolymer :

A polymer made from more than one kind of repeating unit of monomers is called heteropolymers. Heteropolymers are also called co-polymers.

e. g. terylene, nylon-66, Buna-N, Buna-S

CLASSIFICATION OF POLYMERS

POLYMERS CLASSIFICATION  :

Polymers are classifed by different ways

I) Based on source :

By this way polymers are classified into three types

    1) Natural polymers :
       
           These polymers are obtained from natural sources.They are of two types 
           
                     a) Vegetable polymers (plant polymers) These polymers are obtained from plants e.g.                                cotton, jute, hemp, sisal, flex, linen, rubber 
             
                    b) Animal polymers (protein polymers.) These are obtained from animals. These are                                 polyamide polymers. e.g. wool, silk
     
     2) Semisynthetic polymers :

            These are chemically treated natural polymers. Generally these are modified cellulose fibres. Due to chemical treatment its properties like tensile strength, lustre and appearence are modified. 6. g. acetate rayon, viscose rayon, cupra-ammonium silk.

     3) Synthetic polymers:

           These polymers are obtained from chemical substances by polymerisation process. e g. nylon, terylene, polythene, PVC, teflon etc.


I) Based on the structure of polymers:

           By this way paymers are classitied into three types

 i) Linear polymers: These polymers are made up of long continuous chains without branching. e.g. polytlrene,PVC, tetlon, nylon, terylene.

2) Branched polymers : These polymers consist of long chain with small chain as a branch. e.g. poly propylene, glycogen, starch .


3) Network or cross linked polymers : These polymers consist linking of chain polymers by strong covalent bonds leads to network structure e.g. melamine, bakelite, vulcanized rubber etc.


III) Based on polymerisation process :

 By this way polymers are classified into two types

1) Addition Polymers : These polymers are formed by addition of repeated one type monomer units without elimination 01 Dy product. In this type monomers are unsaturated compounds. e.g. orlon, teflon, polythene, PVC, buna-S.

 2) Condensation polymers : These polymers are formed by condensation reaction between two different monomers. e.g. nylons, polysters, polyurethanes. Here small molecules like water, alcohol, HX are eliminated.

IV) Based on molecular forces : 

The properties of polymers depend upon molecular forces. Molecular forces bind polymer chains either by hydrogen bonds or by vander Waal ’s forces. These forces are called intermolecular forces. By this way polymers are classified into four types

1) Elastomers : These polymers have elastic character like rubber. In these polymers, chains are held together by weak

intermolecular forces. e.g. neoprene, vulcanized rubber.

2) Fibres : In these polymers, the intermolecular forces of attraction between the polymer chains are strongest. Here chains are closely packed having high tensile strength and less elasticity. Here the forces are hydrogen

bonding.

e.g. nylon, terylene, silk. 3) Thermoplastic polymers :

These are linear or slightly branched chain polymers. Their properties are in between elastomers and fibres. On heating they becomes soft and on cooling becomes hard. e.g. polythene, polystyrene, PVC, teflon.

4) Thermosetting polymers :

Thesetare cross linked or heavily branched polymers and undergoes permanent change on heating. They cannot be remoulded or recycled. e.g. bakelite, urea -formaldehyde resin, melamine-fonnaldehyde resin.

V) Based on growth polymerisation :

By this method polymers are classified into two types.

1) Chain growth polymers (addition polymers) :

It involves the addition of monomer unit at the reactive end of growing chain across the double bond. e.g. polythene. Aikenes undergo growth chain polymerization when treated with small quantity of suitable initiator. Other examples PVC, orlon.

2) Step growth polymers (condensation polymers) :

Any pair of monomer molecules having functional group, they undergo series of condensation with elimination of water or alcohol or H-X molecule in step wise manner. e.g. Nylon-66, dacron, bakelite.

DEFINITION OF POLYMERS

POLYMERS :

Polymers are macromolecules with high molecular weight and composed of smaller repeating units by covalent bond.

The repeating unit is called monomer and final product is polymer.

The process of converting monomer into polymer is called polymerization.

ln polymers, monomers arejoined by covalent bond.

https://mshete001.wooplr.com/s/QFes3LGWC?ref=cp.c.i.c.a

TYPES OF UNIT CELL / PRIMITIVE AND NON PRIMITIVE UNIT CELL

Types of unit cells :

Basically unit cglls are of two types

1) Primitive unit cells : (simple unit cells) 

ln these unit cells constituent particles like atoms, ions or molecules are present only at the comers of the unit cell.

2) Non-primitive unit cells (central unit cells)

In these unit cells constituent particles are present at the corners as well as at some other positions. They are further classilied into three types.

i) Face centred unit cell
ii) Body centred unit cell
iii) End centred unit cell

i) Face centred unit cell: In these unit cell the constituent particles are present at the corners as well as at the centre of each face.

ii) Body centred unit cell : In these unit cells the constituent particles are present at the corners as well as at the centre of the unit.

iii) End centred unit cell : In these unit cells constituent particles are present at the corners as well as at the centre of two opposite faces.

WHAT IS CRYSTAL LATTICE OR SPACE LATTICE

Crystal Lattice (space lattice) : 

Three dimensional arrangement of the constituent pam'cles of crystalline solid having simillar environment in three dimensional spaceis called crystal lattice or space lattice.

Lattice point : A position occupied by constitueth particles like atom, ion or molecule in the crytal lattice is called lattice point. Unit cell is characterised by following parameter:


a) Edges or edge lengths : The intersection oftwo faces of crystal lattice is called b edge. The three edges are denoted by ab and c which represents the dimensions of a -_7 the unit cell along the three axes. These edges may or may not be mutually perpendicular.


b) Angles between the edges (or planes) : There are three angles between the l5 a edges of the unit cell represented as a, B and 1. These angles are called interfacal angle.

DEFINITION OF UNIT CELL

Unit Cell : 

The smallest repeating structural unit of a crystalline solid (or crystal lattice) is unit cell.

Number of unit cells come together and form crystal. Characteristics of unit cell and crystalline solid are same.

CLASSIFICATION OF CRYSTALLINE SOLIED

Crystalline solids are classified into four main types 

1) Molecular solids 

 2) Ionic solids

 3) Metallic solids  

4) Covalent solids 




1) Molecular solids :

The crystalline solids in which constituent particles are molecules of the same compound are called molecular solids.

Molecular solids are again classified into three types depending on types of molecules and the nature of intermolecular forces of attraction between the neighbouring molecules.

a) Polar molecular solids
b) Non-polar molecular solids.
c) Hydrogen bonded molecular solids,

a) Polar molecular solids :

i) In these crystalline solidsfhie constituent particles are polar molecules like HCL SOZ, NH3 etc. ii) Polar molecules have dipoles and posseses dipole moment.

iii) These molecfes in solid state are held together by strong dipole-dipole interaction.

iv) They arrange in such a way that opposite end of the neighbouring molecules are brought closer. v) These solids are soft, bad conductor of electricity.

vi) Meltingpoints of these solids are relatively low

b) Non-polar molecular solids :

i) In these solids, the constituent particles are non-polar molecules like H2, C12, CH‘, (:02 or wwkly polar molecules like C0.

ii) In these solids the atoms of non-polar molecules are held by weak dispersion forces or London fom, iii) These solids are soft and do not conduct electricity.

iv) They have very low m.p. which are lower than polar molecular solids

c) Hydrogen bonded molecular solids: 

i) In these crystalline solids. the constituent particles are the molecul to highly electronegative atom like F, O and N.

ii) In these. molecules are held by hydrogen bonds in which H atom of one molec electronegative atom like 0, N and F of another molecule.

iii) As hydrogen bonding ts weaker these solids have very low m p and generally at room temperature they exist in liquid or gaseous state.

iv) Hydrogen bonded solids are non-conductors of electricity.
                                                                                                                                                                   


Hydrogen bonding in Ice and Water:

i) Ice has hemgonal three dimensinal cry stal structure formed due to hydrogen bonding.

ii) In  H20 two hydrogen atoms are covalently bonded to oxygen H atom.

iii) The structure of ice and water are almost identical. iv) H20 molecule is polar molecule.

v) Number of H20 molecules are linked to each other by dipole-dipole interation called hydrogen bonding.

vi) in ice, H2o molecules are linked forming tetrahedral arrangement .

vii) In this arrangement, two covalently bonded H-atoms and two N H-atoms bonded by hydrogen bonds are at four corners of the tetrahedral.

Tetrahedral geometry of water molecules formed by  covalent and hydrogen bond -

                  The volume of single water molecule is 15 x 102‘ cm’, hence total volume of 1 mole of water i.e. 18g of water may be 15 x 102‘ x 6.022 x 1023 = 9 cm}. However volume of 1 mole of water is found to be 18 cm’. Hence in water 9 cm3 space is empty. Due to more vacant space, water can accomodate more solute molecules Hence water is very good solvent.

Ice is lighter than water : 

i) Due to inter molecular‘hydrogen bonding, ice has hexagonal three dimensional crystal structure.

it) Structure of water arid ice are almost same.

iii) on melting of 10;, some hydrogen bonds are broken and vacant space is occupied by water
molecules aria they comes closely.

iv) In ice vacant space is more than tn water. Hence density of ice is less than water.

v) Due to which ice is lighter than water and ice floats on the surface of water.
                                                                                                                                                                   




 Ionic solids : 

i) In these crystalline solids constituent particles are cation or anion.
ii) All salts are crystalline ionic solids.
iii) In ionic solids ions are held together by strong elestrostatic force of attraction.
iv) The arrangment of ions depends on
              a) Size of mtion and anion
              b) The charge on the ions
              c) The polarisability of anions

v) lonic solids are hard and brittle and have high mp. and b.p.

vi) in solid state they are non conductor but in molten state or in aqueous solution they conduct electricity due to free ions.

vii) They undergo distorion and fracture in crystal structure on applying shearing force.

                                                                                                                                                                    
i) In these solids, the constituent particles are positively charged metal ions.

ii) The bonding electrons are delocalised in a metal.

iii) In metallic solids metal cation and free ele3) Metallic solids :

ctrons are held together by electrostatic force of attraction called metallic bond.

iv) Metallic bonds are stronger than ionic and covalent bonds. Metallic solids have high m.p. and b.p.

v) In metallic solid several layers are . arranged one over the other.

vi) By applying shearing force to metals, the layers can slide and hence show the properties like malleability and ductility.
                                                                                                                                                                   

4) Covalent solids :

i) These are crystalline solids in which the constituent particles are non-metal atoms linked to neighbouring atoms by covalent bonds through out the crystal.

ii) Covalent solids are called giant solids.

iii) They are hard or brittle depending upon type of covalent bonding.

iv) They have high metling points.

v) They are good conductors of electricity or insulators depending upon the availability of free electrons. e.g. diamond, graphite, carborundum, fullerence.

Diamond :

i) It is covalent crystalline solid

ii) It has giant network structure containing very large number of carbon atoms bonded to each other by covalent bond.

iii) Each carbon tom sp3-hybridised and bonding continues in all directions of four corners of regular tetrahedron .

 iv) It is hardest substance with m. p. 3550°C  .

Graphite :

i) Graphite is a covalent crystalline solid, which is an allotrope of carbon.

ii) all the carbon atoms in graphite are sp2-hybridised.

iii) Each carbon atom is covalently bonded to other three sp2-hybridised carbon atoms forming beta - bonds and fourth electron in 2Pz orbital of each carbon atom is used in the formation of piy-bond.

iv) In graphite layers consisting of hexagonal carbon network and held together by weak vander Waal’s forces.

v) Distance between layers is 340 pm while C-C bond length is 141 .5 pm

vi) n-bond electrons in the ring are delocalised and responsible for electrical conductivity.

vi) As layers of carbon atoms in graphite can slide over another layer, hence it is used as a lubricant

Fullerence : 

i) Fullerence is a new allotrope of carbon discoyered in 1985.

ii) Fullerences are carbon cluster componds of formula C32. C 50‘ C 60, C70 and C84

iii) Fullerences are obtained by irradiating carbon to high power lasers.

iv) C60 fullerence is called buckminster fullerence it looks like soccer ball.

v) On sphere  60 sp2-hybridised carbon atoms are placed at equidistant and joined by covalent bonds.

vi) Fulletence consists of fused system of live and six membered ring.

vii) Fullerence react with potassium to form compound Ksscoo which act as a super conductor at l8K.

viii) Tubes made from fullerence and graphite are called nanombes. They are used as electric conductor, molecular sensors and semiconductors.

xi) Fullerences are observed in carbon soot.

POLYMORPHOUS

Polymorphous: 

a single substance whitch crystalline in two or more forms under different cinditions of solidification is called polymorphous and phenomenon is polymorphism. These polymorphic forms are also called allotropic forms or allotropes. ‘

e.g. Carbon exists as diamond and graphite

           Sulphur exists as rhombic and monoclinic.

Glass is a homogeneous mixture ofSiOz, NaIO, boron oxide (B203) and transition metaloxide to impart colour.

                       It is optically transparent material.
                      About 800 ditlerent types of glasses are manufactured by changing the composition. Quartz glass is obtained only from SIO2
Pyrex glass is obtained by fusing together 60-80% SiO2, 10-25% B2O3 and remaining amount of AL2O3. Glass is amorphous solid is considered as a super cooled liquid.

Sodalime glass : 75% SiOz, 15% N320 and 10% C30

Red glass : SiO2 and trace amount of gold & copper.

Yellow glass : SiO2 + U02

Blue glass : SiOz + CaO or CuO

Green glass : SiO2 + FeZO3 or CuO

DISTINCTION BETWEEN CRYSTALLINE AND AMORPHOUS SOLIDS

Distinction between crystalline and Amorphous solids

            Crystalline solid                                               Amorphous solid
l) Constituent particles are arranged               1) Constituent Particles are not in a
    in a orderly regular pattern .                            orderly regular pattern .
2) They have definite geometrical shape        2) They do not have definite geometrical shape .
3) These are true solids ‘                                 3) These are pseudo solids or super cooled liquid.

4) They may or may not be isotropic              4) they are isotropic like liquids.

5) Heat of fusion is delinite                             5) Heat of fusion is not definite. 

CHARACTERISTICS OF AMORPHOUS SOLIDS

Characteristics of amorphous solids : 

 

1) They do not have regular arrangement of the atoms, ions or molecules.

2) They do not posses any definite geometrical shape.

3) The arrangement of constuent particles is to short range.

4) They do not have sharp melting point.

5) Physical properties do not change in directions hence they are isotropic.

6) They resemble the super cooled liquids.

7) When cut, they split into pieces with irregular and rough surface.

CHARACTERISTICS OF CRYSTALLINE SOLID

Characteristics of crystalline solid :

 

 

 

 

1) They have a definite and ordering arrangement of the atoms, ions or molecules.

2) They have definite geometrical shape.

3) They consists of large number of tiny crystals called unit cells.

4) Unit cell is repeating structural unit and have definite shape and properties of the crystalline solid.

5) The forces in the crystalline solid may be ionic bonds, covalent bonds, hydrogen bonds or vander

Wall's force .

 6) It has long range order of regular pattern of arrangement which repeats in entire crystal.

7) they have  sharp melting point.

8) Crystalline solids show different physical properties in different directions, hence they are aniso tropic.

classification of solid statas

Classification of solids :

Solids are of two types

                   1) Crystalline solid                   2) Amorphous solid

1) Crystalline solid : A homogeneous solid in which the constituent particles like atoms, ions or mol

ecules are arranged in adefrnite repeating pattern through out the solid is called crystalline solid. e.g. NaCl, KN03, urea, sugar etc.

 2) Amorphous solid : A substance in which Igoo 'tuent particles are not arranged in a regular pattern

is called amorphous solid. Amorphous solids appear like solidsb tdo 0t have perfectly ordered crystalline structure.

e. g. glass, rubber, plastic etc.

 

solid state characteristics

Characteristics of solid state :

 

 

 

 

 

 l) The solid of fixed composition has defined mass, volume, shape and density.

2) Solids have more density than liquid and gasesous state of the same matter (except ice )

3) Most of the solids are hard, incompressible and rigid. ‘

4) Intermolecular forces of attraction in solid state is strong.

S) In solid state molecules have no freedom.

6) All pure solids have characteristic melting point.

METALLIC SOLIDS

i) In these solids, the constituent particles are positively charged metal ions.

ii) The bonding electrons are delocalised in a metal.

iii) In metallic solids metal cation and free

ctrons are held together by electrostatic force of attraction called metallic bond.

iv) Metallic bonds are stronger than ionic and covalent bonds. Metallic solids have high m.p. and b.p.

v) In metallic solid several layers are . arranged one over the other.

vi) By applying shearing force to metals, the layers can slide and hence show the properties like malleability and ductility.
                                                                                                                                                                 

IONIC SOLIDS

 Ionic solids : 

i) In these crystalline solids constituent particles are cation or anion.
ii) All salts are crystalline ionic solids.
iii) In ionic solids ions are held together by strong elestrostatic force of attraction.
iv) The arrangment of ions depends on
              a) Size of mtion and anion
              b) The charge on the ions
              c) The polarisability of anions

v) lonic solids are hard and brittle and have high mp. and b.p.

vi) in solid state they are non conductor but in molten state or in aqueous solution they conduct electricity due to free ions.

vii) They undergo distorion and fracture in crystal structure on applying shearing force.

MOLECULAR SOLIDS

                       Molecular solids 

The crystalline solids in which constituent particles are molecules of the same compound are called molecular solids.

Molecular solids are again classified into three types depending on types of molecules and the nature of intermolecular forces of attraction between the neighbouring molecules.

a) Polar molecular solids
b) Non-polar molecular solids.
c) Hydrogen bonded molecular solids,

a) Polar molecular solids :

i) In these crystalline solidsfhie constituent particles are polar molecules like HCL SOZ, NH3 etc. ii) Polar molecules have dipoles and posseses dipole moment.

iii) These molecfes in solid state are held together by strong dipole-dipole interaction.

iv) They arrange in such a way that opposite end of the neighbouring molecules are brought closer. v) These solids are soft, bad conductor of electricity.

vi) Meltingpoints of these solids are relatively low

b) Non-polar molecular solids :

i) In these solids, the constituent particles are non-polar molecules like H2, C12, CH‘, (:02 or wwkly polar molecules like C0.

ii) In these solids the atoms of non-polar molecules are held by weak dispersion forces or London fom, iii) These solids are soft and do not conduct electricity.

iv) They have very low m.p. which are lower than polar molecular solids

c) Hydrogen bonded molecular solids: 

i) In these crystalline solids. the constituent particles are the molecul to highly electronegative atom like F, O and N.

ii) In these. molecules are held by hydrogen bonds in which H atom of one molec electronegative atom like 0, N and F of another molecule.

iii) As hydrogen bonding ts weaker these solids have very low m p and generally at room temperature they exist in liquid or gaseous state.

iv) Hydrogen bonded solids are non-conductors of electricity.
                                                                                                                                                                   


Hydrogen bonding in Ice and Water:

i) Ice has hemgonal three dimensinal cry stal structure formed due to hydrogen bonding.

ii) In  H20 two hydrogen atoms are covalently bonded to oxygen H atom.

iii) The structure of ice and water are almost identical. iv) H20 molecule is polar molecule.

v) Number of H20 molecules are linked to each other by dipole-dipole interation called hydrogen bonding.

vi) in ice, H2o molecules are linked forming tetrahedral arrangement .

vii) In this arrangement, two covalently bonded H-atoms and two N H-atoms bonded by hydrogen bonds are at four corners of the tetrahedral.

Tetrahedral geometry of water molecules formed by  covalent and hydrogen bond -

                  The volume of single water molecule is 15 x 102‘ cm’, hence total volume of 1 mole of water i.e. 18g of water may be 15 x 102‘ x 6.022 x 1023 = 9 cm}. However volume of 1 mole of water is found to be 18 cm’. Hence in water 9 cm3 space is empty. Due to more vacant space, water can accomodate more solute molecules Hence water is very good solvent.

Ice is lighter than water : 

i) Due to inter molecular‘hydrogen bonding, ice has hexagonal three dimensional crystal structure.

it) Structure of water arid ice are almost same.

iii) on melting of 10;, some hydrogen bonds are broken and vacant space is occupied by water
molecules aria they comes closely.

iv) In ice vacant space is more than tn water. Hence density of ice is less than water.

v) Due to which ice is lighter than water and ice floats on the surface of water.
                                                                                                                                                                   

ANISOTROPY , ISOTROPY , ISOMORPHOUS ,POLYMORPHOUS

                 

Anisotropy :

 It is the ability of crystalline solids to change their physrcal properties when measured In drfferen

directions. The property is due to different arrangment of constituents in different directions. Different types 0f

particles fall on the way of measurements in different directions. Hence composition of crystalline solid

changes with directions, changing physical propertie

Different arrangement of constituent particles about different directions AB, CD and EF.
Isotropy : The ability  amorphous solids to exhibit identical physical properties even through measured in different direction .
                   in amorphous solid order of regular pattern of arrangement is to short range. Hence arrangement is irregular along  all directions. Due to which magnitude of physical property is identical along all directions.

Isomorphous :
When two or more crystalline substances have the same crystalline structure, they are said to be isomorphous and phenomenon is isomorphism. '

e.g. NaCl & KCl; KZSO‘ & KZSeO‘, NaN03 & CaCOJ, NaF & MgO, Cr203 & Fe 0

Polymorphous: 
a single substance whitch crystalline in two or more forms under different cinditions of solidification is called polymorphous and phenomenon is polymorphism. These polymorphic forms are also called allotropic forms or allotropes. ‘

e.g. Carbon exists as diamond and graphite

           Sulphur exists as rhombic and monoclinic.

Glass is a homogeneous mixture ofSiOz, NaIO, boron oxide (B203) and transition metaloxide to impart colour.

                       It is optically transparent material.
                      About 800 ditlerent types of glasses are manufactured by changing the composition. Quartz glass is obtained only from SIO2
Pyrex glass is obtained by fusing together 60-80% SiO2, 10-25% B2O3 and remaining amount of AL2O3. Glass is amorphous solid is considered as a super cooled liquid.

Sodalime glass : 75% SiOz, 15% N320 and 10% C30

Red glass : SiO2 and trace amount of gold & copper.

Yellow glass : SiO2 + U02

Blue glass : SiOz + CaO or CuO

Green glass : SiO2 + FeZO3 or CuO

distribution between crystalline and amorphous solids

Distinction between crystalline and Amorphous solids

            Crystalline solid                                               Amorphous solid
l) Constituent particles are arranged               1) Constituent Particles are not in a
    in a orderly regular pattern .                            orderly regular pattern .
2) They have definite geometrical shape        2) They do not have definite geometrical shape .
3) These are true solids ‘                                 3) These are pseudo solids or super cooled liquid.

4) They may or may not be isotropic              4) they are isotropic like liquids.

5) Heat of fusion is delinite                             5) Heat of fusion is not definite. 

                                                                                                                              

stats of matter

Solid, liquid and gas are three physical states of matter: They are inter converteable

Character istics of solid state :

 l) The solid of fixed composition has defined mass, volume, shape and density.

2) Solids have more density than liquid and gasesous state of the same matter (except ice )

3) Most of the solids are hard, incompressible and rigid. ‘

4) Intermolecular forces of attraction in solid state is strong.

S) In solid state molecules have no freedom.

6) All pure solids have characteristic melting point.

Classification of solids :

Solids are of two types

                   1) Crystalline solid                   2) Amorphous solid

1) Crystalline solid : A homogeneous solid in which the constituent particles like atoms, ions or mol

ecules are arranged in adefrnite repeating pattern through out the solid is called crystalline solid. e.g. NaCl, KN03, urea, sugar etc.

 2) Amorphous solid : A substance in which Igoo 'tuent particles are not arranged in a regular pattern

is called amorphous solid. Amorphous solids appear like solidsb tdo 0t have perfectly ordered crystalline structure.

e. g. glass, rubber, plastic etc.

Characteristics of crystalline solid :

1) They have a definite and ordering arrangement of the atoms, ions or molecules. 2) They have definite geometrical shape.

3) They consists of large number of tiny crystals called unit cells.

4) Unit cell is repeating structural unit and have definite shape and properties of the crystalline solid.

5) The forces in the crystalline solid may be ionic bonds, covalent bonds, hydrogen bonds or vander

Wall's force .

 6) It has long range order of regular pattern of arrangement which repeats in entire crystal.

7) they have  sharp melting point.

8) Crystalline solids show different physical properties in different directions, hence they are aniso tropic.

Characteristics of amorphous solids : 
1) They do not have regular arrangement of the atoms, ions or molecules.
2) They do not posses any definite geometrical shape.
3) The arrangement of constuent particles is to short range.
4) They do not have sharp melting point.
5) Physical properties do not change in directions hence they are isotropic.
6) They resemble the super cooled liquids.
7) When cut, they split into pieces with irregular and rough surface.

all about drugs ,sops,detergent,narcotics,antibiotics,and anti-septic.

DRUGS , SOPS,DETERGENTS,NARCOTICS AND ANTI-SEPTIC ALL DETAIL -  

Drug :

  A chemical substance which is used for the purpose of diagnosis, prevention, cure or relief of disease is called drug or medicine.

 Ideal drug :

 Ideal drug is one which
i) destroys hamrfull organisms but not harmless organisms
ii) does not disturb physiological processes.
iii) has minimum side effects
iv) should attack on affected site
v) it should not be habit forming

Chemotherapy : 

It is a technique by which diseases are cured by suitable chemical compounds(i.e. drugs) .

Classification of drugs : 

Drugs are classified by different ways :
 I) Classification based on pharmacological effects of the drug : 

           These drugs affect normal processes of the body like digestion, blood circulation, breathing etc. e.g. Analgesic used as pain killer. ' Antibiotic and antiseptics stop the growth or kill the bacteria

II) Classification based on action of drugs :

           These drugs are disease oriented. They have different mode of action. e. g. pain killer, antiarthritis, local anaesthetic agents etc.

III) Classification based on chemical structure : 

            Drugs are classified into different categaries like alcohols, ketones, hydrocarbons, esters, amides etc. Drugs having simillar chemical structure are expected to have simillar chemical properties. e.g. all sulphomides having simillar type chemical structure show antibacterial activity.

VI) Classification based on molecular target :

i) The drugs which interact‘target biomolecules are called target oriented drugs.
ii) The biomolecules like carbohydrates, proteins, nucleic acids etc, are target molecules with which drug interact
iii) This classificationis very important

V) Classification of drugs by lay public :

This classification depends upon the action of the drugs like analgesics, cough syrup, laxatives and purgatives,ointments, injections etc. |

Chemicals in medicines :

Depending on purpose for which they are used, medicines are classified as -

                                                           ANALGESICS

The drugs which relieve the pain by acting on central nervous system without loss of consciousness or wrthout much disturbing the nervous systemarecalled analgesises.

There are two types of analgesics

           1)Norcotic                                         2) Non-norcotic

I) Narcotic analgesics :

They Produces sleep and unconsciousness. They are derivatives of opium. e.g. morphine, codeine, heroin

These drugs are habit fonning i.e. person gets addicted. They have some adverse effects.

2) Non-norcotic analgesics :

These drugs when consumed do not produce any significant depression of CNS. These are antiinflammatory and antipyretic. They do not form addiction e.g aspirin.

Aspirin: 

It is common analgesic. It 15 acetyl derivative ofsaiicylic acid or 2-acetoxy benzoic acid. It IS obtained by acetylation of salicylic acid .

Medicinal properties of aspirin : 

 i) Common analgesic
ii) Antipyretic

iii)Anti-inflammatory drug
iv) Antiblood clotting agent
v) Antirheumatic drug

Side effects of aspirin:
 i) Toxic to liver
ii) Gastric irritant 
iii) When taken in empty stomach, aspirin gets hydrolysed to salicylic acid which causes bleeding in stomach.

other non-norcotic  drugs are paracetamol, ibuprofen, diclophenac sodium, diclophenac potassium.

                                                       ANTIPYRETICS

The chemical substances with reduces body fever are called antipyretics

           aspirin, phenacetin,
           analgin, novalgin etc.





                                                     TRANQUILIZERS
     The chemical substances used to relieve or reduce the stress and anxiety leading to calmness are called tranquilizers .
      These are used to relieve stress, mental tension mania (disorder of mood), insomnia (sleeping sickness), feeling of discomfort etc.

The mild tranquilizers used are equanil, valium, chlordiazepoxide, veronal, meprobarnate, serotonin.

Derivatives of barbituric acids called barbiturates are also used to control hypertension and depression. Barbiturates are hypnotic drug and produce sleep.

valium

                                                            chlodiazepoxide

                                                             merporbanmate

Side effects: 

Headache, weight gain, discomfort ,blurring of Vision .

Working of tranquilizers in body:

Noradrenaline isone of the nemoti‘ansrrutters that play role 1n mood changes. If the level of noradrenaline is low for some reason, the signals sending become low and person suffers from depression In such situation antidepressant drugs are required which balance the level of noradrenaline

Iproniazid and phenefzine are used as mood elevators.

                                                 ANTIMICROBIALS

The drugs used to kill or stop the growth of micro organisms like fungi, bacteria, viruses are called antimicrobial .

The atimicrobial drugs are antibiotics, antiseptics and disinfectants.

1) Antibiotics:

Antiboitics are derived from micro-organisms and used to kill or prevent the growth of other microorganisms.

e.g. penicillin, streptomycin


 a) Broad spectrum antibiotics : 
      These antibiotics are effective against all hannfull micro-organisms.

e.g. chlorompheniool, tetracycline, cephalosporin, chloromycetin, aminoglycosiders.
.
  b) Narrow spectrum antibiotics : 
These antibiotic kill or prevent the growth of specific microorganisms e. g. penicillin, Penicillin was discovered by Alexander Fleming in 1 929

types of antibiotics :
 i) Bactericidal : They kill the micro-organism

ii) Bacteriostatic : They strop the growth of micro-organism.

Bactericidal                                                                      Bacteriostatic 
 l) Penicillin                                                                      i) Erythromycin
 ii) orlaxaein                                                                     ii) Tetracycline
iii)Amino glycosiders                                                      iii) Chloramphenicol .
iv) Cephalosporin

                       Streptomycin is bacteriostatic in low concentration and bactericidal in high concentration.






ampicillin and anoxycillin are semisynthentic modifications of penicillin . these are broad spectrum .









2) Antiseptics: 
The drugs which are applied to the living tissues to kill the bacteria and to stop their growth in wound,thus preventing Its infection are called antiseptics. They are used in talcum powder, deodorants, soaps,breath purifiers, shampoos.

e ..g
i) Dettol , it is a mixture of terpeneol and chloroxylenol.

ii) Tincture of iodine 2-3% solution of iodine in ethyl alcohol and water. It is powerfull antiseptic.

iii) Bithional is used as antiseptic in soaps.


iv) H3BO3 (boric acid) is mild antiseptic used for eyes.
v) dil. Phenol
vi) H2o2 under the name perhydrol
vii) CHI3.(lodoform)


3) Disinfectants : 
The chemical substances that are applied to non-living objects to kill the micro-organisms are called disinfectants. .
         They are used in public health sanitation, floors, steralise instruments.

e.g. Cl2 , SO2 phenol

Dil. solution of phenol is used as an antiseptic where as concentrated phenol is used as disinfectant.

                                           ANTIFERTILITYDRUGS 

Antifertility drugs are used to control population:

The chemical substances which control the pregnancy are called antifertility drugs. These drugs are a mixture of synthetic estrogen and progesterone hormones.

e. g. Novestrol (estrogen derivative) Norethindrone (progesterone derivative)

                                                       

                                                                ANTACIDS

The Chemical substances which neutrallses the excess of acid.in stomach and raise the pH of stomach to appropriate level are called antacids.

Acidity is due to the secretion of HCl in gastric Juices.
The commonly used antacids are
ii)Baking soda (NaHCO3).
ii) MgO, Mg(OH)2, MgCO3 and magnesium trisilicate . '
iii) CaCO3 _
iv)Al(OH)3,AlPO4

Omeprazole and lanSOprazole prevent the formation of acid in stomach. Ranitidine (zantac) and cirnitidine (Tegamet) are also used as antacids. Some other examples are digene,gelusil, aciguard etc.

                                                    Ranitidine(Zantac)


                                        ANTIHISTAMINES (ANTIALLERGIC DRUGS)

The drugs which inhibit or reduce the action ofhistamine 1n the body there by preventing allergy are called antihistamines. '

Number of different sensitising substances (called antigens) derived from food or environment may cause allergic reaction in human. This is due to release of chemical substance called histamine inthe body.

Histamine in stomach stimulate the secretion of HCl and pepsin. Antihistamines compete with histamines for the binding sites of receptors and prevent allergy.

                                                   CHEMICALS IN FOOD 

Preservatives : The substances which when added to food is capable of inhibiting, retarding or arresting

the process of fermentation, acidification or other decomposition of food by growth of microbes are called presevatives.

Food preservatives retain colour, texture, flavour, nutritive value of food. The latest methods used for food preservation are vacuum packing, freeze drying, U.V. or ionizing radiation to control micro-organism growth, irradiation by y-rays.

I) Physical methods for preservation of food : 

i) By removal of heat (By cooling) :
      i It involves refrigeration, freezing preservation, dehydrofreezing preservation or carbonation. Due to cooling, growth of micro-organism is lowered. Fish, meat, vegetables, fruits are stored by this method.
2) By addition of heat : 
      Strong heating kill the micro-organism :
      It includes stationary and agitating pastereurisation or sterilization.
     Solid and liquid foods are preserved by this method.
     e. g. milk is pasteurised for preservation.
3) By removal of water (Dehydration) : 
   Water is removed by sun drying, low temperature evaporation, freeze drying or puff drying. As gamer is removed, the growth of micro-organism is prohibited. Food graims, fruits, vegetables are preserved by this method.
4) By irradiation : 
  UV or ionizing radiations or y-rays or electron beam are used to preserve food. The irradiation kill the micro-organisms.
  Milk and fruits are preserved by this method, sprouting of potatoes and onion is prevented by y-rays.

II) Chemical methods: 

1) Addition of sugar : 
Here food is heated with sugar to the point of crystallisation and then dried. High concentration of sugar remove water by osmosis and growth of micro-organism is retarded. This is cheap and easy method. . Fruit j ams,jellies are preserved by this method.
2) Addition of salt : 
Salt has water retaintion property. It remove the water causing dryness and death of microbes.pickles, fishes are preserved by salting, lemon, chillies, raw mango are preserved by this method.
3) Addition of vinegar : 
Vinegar is 6 to 10% acetic acid. It preserve pickles, salad dressings, mustard, fish etc.
4) Addition of chemicals : 
Chemicals like sodium benzoate, salts like sorbic acid and propionic acid are used as preservatives.

Artificial Sweetning Agents : 
The chemical susstances which do not occur in nature but are synthesised in laboratory, have sweet
taste, no food value are called artificial sweetning agents or artificial sweeteners. They do not increase any calorie, are non digestable. It is excreted as such in urine.

e.g.

                                                                          Saccharin,

                                                     Sodium salt of saccharin


Saccharin is 550 times more sweet than sucrose. Saccharin is insoluble in water but its sodium salt is soluble in water.

Some other artificial sweeteners 

Sucaralos : It is trichloro derivative of sucrose. It is 600 times sweeter than sucrose,. It is unstable at high temperature hence not used in cooking.

Alitame :It is 2000 times sweeter than sucrose and stable at high temperature.

Aspartame : It is about 100 times sweeter than sucrose. It is unstable at higher temperature. Hence only used in cold foods.

Artificial sweeteners are used in

i) Soft drinks, cold drinks,
ii) Baked goods,
iii) Medicines,
iv) Toothe paste
v) Chewing gums,
vi) Canned foods

                                                           ANTIOXIDANTS

The substances which when added to food, retards or prevents oxidative deterioration of food are called antioxidants.

Antioxidant prevent the rancidity of oils and fats. During oxidation of food, free radicals are generated. The antioxidants react with these free radicals and stops further oxidation of food.

1)BHT : Butylated hydroxy toluene 

  2,6-di(2-methyl-2-propyl) 4-methy1 phenol









Fat react with oxygen to from free radical, which react further with BHT to form stable BHT free radical. This freé radical does not react with fat, thus stop the chain reaction. This prevent rancidity of fats

2) BHA: Butylated hydroxy anisole:

                                       2-(2-methy1-2-propyl) 4-methoxy phenol

It is used to preserve fats from becoming rancid. It is used in cosmetics, pharmaceutical, animal feed and in butter, chewing gum, baked food, beer and dehydrated potatoes.

3) SO2 and Sulphites :

    S02, sodium metabisulphite (Na2S205) potassmm metabisulphite (K2S2O5) are used to prevent growth 1 of microbials.
    SO2 act as preservative and also antioxidant for dried fruits, vegetables, soft drinks and alcoholic beverages.
    Sulphite are used as antioxidants and reduce discolouration of fruits, vegetables, preservative for wine, dairy products, sauce, jams, jellies etc.

                                                       CLEANSING AGENTS

Soaps and detergents are used as cleansing agents.
Soaps : Soaps are sodium or potassium salts of higher fatty acids containing more than 4,2 an atoms
Soaps are represented by R-COONa or R-COOK. Potassium soaps are soft soaps and are used in shampoo, shaving cream and bathing soaps. Sodium soaps are hard soaps and are used in toilet soap and used for washing purpose.

Preparation of soaps : 

Soaps are prepared by two ways
1) By hydrolysis of fats (Triglycerides):
When oil or fat is hydrolysed by dil. NaOH or KOH, soap is obtained . This reaction is called
saponitication.

Formed soap and glycerol are separated by adding salt Soap is insoluble 1n salt solution, precipitates out due to common ion effect and glycerol remain in a solution as it is soluble.

2) By neutralization of fatty acids :

When fatty acids are neutralised by dil. NaOH or NazCO3, soaps are obtained.
                   
                          R-COOH + dil .NaOH  ------   (R-COO- )(Na+) + H20
                      higher fatty acid                            soap

Soaps are not used in hard water: 
Soaps are insoluble in hard water. Hard water contain metal 1ons like Ca2 and Mg2+ . These ions react with soap and form white curdy ppt. of calcium and magnesium salt.

                        soap                                                                  insoluble salt

This ppt stick to the cloth and blocks cleansing action of soap. This wastes the soap.

Detergents :

      Synthetic detergents are formulated products containing either sodium salts of alkyl hydrogen sulphate or sodium salts of long chain alkyl benzene sulphonic acids. 

      Detergents are superior to soaps. Detergents can be used in soft and also in hard water. 

Types of detergents :

There are three types :
l) Anionic detergents :

These detergents are sodium salts of sulphonated long chain alcohols or hydrocarbons.

Long chain alcohols or hydrocarbons are reacted with concentrated H2S04 to form alkyl hydrogen sulphate, which is neutralised with alkali to form salt.

2) Cationic detergents:

Cationic detergents are quaternary  ammonium salts of amines with acetate, chloride or bromide

n-hexadw tnmethyl amm. chloride (or cetyl tnmethyl amm. chloride)

In cationic detergents , the cationic part (+ve part) of molecule is hydrophilic and involved in cleasing action.
      They have germicidal property and used in hair conditioners.

3) Non-ionic detergents: 

    They non-ionic like esters of high molecular mass. They contain polar group which can form hydrogen bond with water.
    These detergents are either monoesters of polyhydnc alcohols or polyethers derived from ethylene
oxide

Mechanism of cleansing action of soap and detergent: 
Soap and detergents have two parts. A long chain of hydrocarbon (tail) soluble in oil and other part (head) soluble in water. It form emulsified oil droplets in watér and are removed from cloth .The anions of emulsion repel to each other and cannot reprecipitate.
Detergents are superior to soaps : 
i) Detergents are soluble in hard water but soaps are insoluble in hard water, hence soaps are not used as cleansing agent in haed water .
 ii) Synthetic detergents can be used in acidic solution while soaps precipitates in acidic solution.
iii) Synthetic detergents are easily soluble in water and produce more leather than soaps. Hence detergents are superior to Soaps.

How are detergents and soaps used check hardness of water?

i) Hard water contains Ca2+ and Mg2+
ii) Soaps get precipitated to from insoluble salts of calcium and magnesium in hard water but detergents do not form any precipitate.
iii) Hence soaps are used to check hardness of water.

How detergents cause water pollution?
i) Detergénts  contain 20% active ingredients and remaining are sodium sulphate, inorganic phosphates, perborgy foaming agents.
ii) phosphates from detergents assists algae and weeds to grow in water, which deplete the oxygen for sea animals .
iii) Hence detergents cause water pollution.

‘

click to know: BOILER - boiler is a closed vessel havin...

click to know: BOILER -          boiler is a closed vessel havin...: BOILER -          boiler is a closed vessel having minimum capacity of 14.5 and working pressure of 3.5 kgF/cm^2  or above th...

STEAM BOILER AND WORKING OF BOILER-

         boiler is a closed vessel having minimum capacity of 14.5 and working pressure of 3.5 kgF/cm^2
 or above they are used to produce steam from water by combustion of fuel . According to IBR
the closed vessel having minimum capacity of 20. 75 letter comes under boiler act such a boiler
are to be registered at boiler Inspector office.  every year various types of inspections will be
carried out by boiler inspector .

classification of boilers-

according to relative position of water and  flue gases

•  fire tube -  flue gases flow through tubes and water surrounds  the tubes is called fire tube Ex  Cochran boiler , lancashire boiler , locomotive boiler .

• Water tube- water flows through pipes and flue gases flow over the tube is called water tube boiler

backup , wilcox

Strirling , La-mont ,Laeffler

According to method of circulation of water

• Natural circulation type
• forced circulation type

According to major axis of shell

• Horizontal
• Vertical
•  Inclined

According to applications

• Stationery
• Mobile
• Marie

according to working pressure of boiler

• low pressure boiler( 3.5 to 10 KGF/  CM^2)
• medium pressure boiler( 11 to 25 KGF/ CM^2)
• high pressure boiler( more than 25 KGF/  CM^2)

                                                          

characteristics of high pressure boilers -

              

     the high pressure boilers differ in construction  and working from low or medium pressure boilers
following are some characteristics and features of high pressure boilers .

Method of water circulation -

the water circulation in boiler maybe natural circulation due to density difference  air force circulation
by using water pump.  in all high pressure boilers, the water is always forced circulation ,  by using
the separate circulation pump .  natural circulation cannot be used for high pressure boiler due to
following -

figure shows the steam- water drum connected to unheated Unheated riser

the cold water flows down words in town come tubes and it Rises up due to heat supplied by flue
gases in Riser to .  the circulation of water is accuring due to density difference .  called natural
circulation .  the pressure difference causing the natural circulation of water is -

          

Δৎ = (ৎc )(g)( h1) - ৎh (g)(h2)                                 ৎc = Density of cold water.

       = ((ৎc h1)-(ৎh h2))g

But  h1=h2=h

         Δৎ  = (ৎc - ৎh  )g

at critical pressure of 221.2 bar, density of water and steam becomes equal so pressure difference
causing natural circulation becomes zero.

                        the use of natural circulation is limited only upto subcritical boiler with working pressure
release then 25 KGF/ centimetre^2 and above pressure Boiler  forced circulation becomes essential

type of tubing -

in all high pressure boilers the water is circulated through  tube .  hence they are water tube boilers .  
however the single tube  having very large length is  not used because a pressure drop me a cure
which is directly proportional to the length  of tube .  hence large number of tubes arranged in parallel
with shortage length are always preferred .

improved methods of heating -

in order to increase rate of heat transfer following improved methods are used in high pressure boilers.

• Deceiving of latent heat of evaporation by keeping boiler pressure higher than critical pressure

          of water example Benson boiler .

• the heating of feed water can be carried by using superheated steam.  the maximum of

superheated steam in highest heat transfer rate( to reduce the sensible heat)

• the heat transfer rate are also increased by keepingvel.  of water inside the tube higher and the

and by maintaining volume of flue gases outside the Hue blower

these improved methods of heating are used in different high pressure boilers .

Comparison between low and high pressure boiler .-

Low pressure boiler

High pressure boiler

These are fire took shell boilers and are suitabl with pressure of 30kgf/cm^2 and capacity of            30 tonnes /h       2.Finance are not water cooled .       3. this Still waters are factory build and are            cheaper than water tube boilers .       4. these are natural circulation type       5.these boilers include water drum .       6. these are heavy and large space is required .       7. Example -  cochran boiler ,  simple vertical ,  lancashire  locomotive .

1. These ar  water tube and are suitable for pressure above 30kgf/ cm^2  capacity 50 tonnes /hr . 2. Furnace walls are water cooled and cold wate walls .  3. these are usually  builder in parts which are easily  transport. 4. These are forced circulation type . 5. Water drume may or may not present . 6. Low weight and compact . 7. Example - hartmannet , velcox , benson etc .

                                                                                                                                                                   

La Mont  boiler -

this is the first high pressure boiler introduced by

the feed water from hot well is pumped into the boiler by feed pump .  most of sensible heat required
is supplied to feed water in Equaliser itself .  this hot water from drum is force the circulated through
Radiant section of   evaporating tube with the help of pump .  the water from inlet header is distributed
to different tubes in proportion of heat absorption capacity of each  tube .

Usually ,  the quantity of water circulated in each cube is 3 times the quantity of steam generated
in the tube .  so that no  overheating results .

the mixture of water and steam  formed into then comes back to drum where dry skin is separate Taken
from top of drug and faster too conviction superhit placed in the path of two gases and finally steam is
supplied to the turbine .

wireless of this design have been mail in capacity up 6,58,000 kg/hr . or 658 tonn/hr and pressure
and temperature upto 180 kgf/cm^2 and 600^o C resp.

evaluating performance of boiler -

1.  evaporation rate or evaporation capacity

evaporation rate is the amount of steam generator by boiler in kg/hr .  this evaporation rate is defined
as various basic such as-

                  area grate , furnace  value or quantity of fuel burn .

Evaporation rate = mass of steam generated / area of grate

                          = kg/m^2.hr

                          = Ms / Af

Evaporation rate = Mass of steam / vol. Of furnace = Kg/m^3.hr

Evaporation rate = mass of steam generated / amt. Of fuel burnt = Ms/Mf = Kg / Kg of fule .

Evaporation rate is not a good factor for comparing performance of boiler because the parameters
like temperature of feedwater,  quality of steam generated ,  type of fuel used ,  working pressure are
also affect evaporation rate .  so when boilers are generating scheme under different working conditions
(  temperature, pressure , quality of steam etc.)  the capacity comparison can be best done by
comparing amount of heat error in each boiler for steam generation under standard conditions .
         the standard conditions are -  atmospheric pressure of 1.013 bar and temperature of feedwater at
100°C ,  temperature of dry saturated steam at 100°C ,  this is typically called as -

                              form  100°C   to   100°C

the latent heat only required to add that is  hfg =  2256.9 kj/kg .

2. equivalent evaporation -

          for comparing the your operating rate of various boilers working under different conditions and
temperature and pressure term used is equivalent evaporation .  late MS kg of steam is actually
generator in the boiler and certain amount of heat ( say Q kg . ) Is required to produce this MS kg of
Steam .  the same quantity of heat is supplied to the feed water under standard conditions of temperature
and pressure it will be produced Me  kg of Steam .

              this quantity of steam Me  it said to be equivalent to the quantity of steam Ms  the specific
enthalpy of evaporation and 1.01 32 bore corresponding to saturation temperature of 100°C is 225 6.9 kj/kg .  
or 2257 kj/kg .

factor of evaporation -

it is defined as the ratio of heat absorbed by 1 kg of feed water to convert it into steam under actual
working condition to heat absorbed by 1 kg of water from and at hundred degree Celsius at 1.0132 bar .

FACTOR OF EVAPORATION =  (h - hf1) / 2257

Where -

h  - enthalpy of Steam produces an actual working and temperature .

hf1  -  enthalpy of water at given Temperature .

     thus  , ratio of equivalent evaporation to actually operation is also called factor of operation and it is
always Greater than 1 .

3. Boiler Efficiency -

it is defined as the ratio of actual heat utilised to produce steam to the total heat supplied by fuel .

              = ms(h-hf1) / mf*calorific value of fuel .

Ms - mass of steam produced per hour .

Mf - mass of fuel burnt per hour .

---

PROBLEMS -

1)  Boiler produce which team having x= 0.9 ,  the working pressure of boiler is 12 bar .  it generate
steam at rate of 640 kg/HR  and consume the code and rate of 80 kg/hr .  if calorific value of coal is
31400 kJ/kg .  and water is filled at 20 degree Celsius.

             equivalent evaporation from and at 100 degree Celsius .

             factor of evaporation

             efficiency of boiler

Answer -                       

                                  

Ms = 640 kg/hr .

Me = Ms(h-hf1) / 2257

     = 640 ( (hf+xhfg)-hf1)/ 2257

     = 640 ((798.4+0.9*1984.3)-83.74) / 2257

     = 709.01 Kg/hr

Per kg of fuel burnt = equivalent evaporation / Kg of fuel burns

                               =  Ms(h-hf1) / 2257*Mf

                               = 709.01 / 80

                               = 8.86 Kg/Kg of fuel .

Factor of evaporation = Me / Ms = 1.108 (always > 1)

Effysiancy ()=Ms(h-hf1) / Mf*calorific value = 63.7 %

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2 ) 6000 Kg of steam is produced per hour at presser of 8 bar . in a boiler feed with water at 36.5^0 C .
dryness fraction of steam generated is 0.98 . the amount of coal burnt is 750 Kg/hr . cal.
Value = 28000Kj/kg .

Calculate -

1. Equivalent evaporation per kg of coal .
2. Boiler Efficiency
3. Boiler HP .

Answer-  

        Ms = 6000 Kg/hr

Me=Ms(h-hf) / 2257

    = Ms(( hf+xhfg)-hf1 ) / 2257

    = 6841.83 kg/hr .

Eq. evaporation/Kg = Me/Mf

                               = 9.122Kg/kg of fuel .

= Ms(h-hf1)/Mf*cal.value

   = 73.53%

Boiler HP -   the amount of water which a boiler can  repo rate per hour from and at hundred degrees
known as power of  boiler .

 Unit = called  boiler HP

one boiler HP =  evaporation of 15. 3 kg of per hour from and at 100 degree Celsius into dry          
saturated steam .

boiler HP =  ( equivalent  evaporation / hr )/15.65 = Ms(h-hf1)/15.65*2257=Me/15.65

Boiler HP = 437.17 HP

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Evaporation :

the quantity of steam generated Buy a boiler per hour in KG at full load is known as the operative
capacity of boiler .

Evaporative rate evaporative rate =  total steam generator /  area of grate  = Ms/A   = kg/m^2/hr .
= Total steam generated/  volume of furnance = Ms/Vf =kg/m3
                                                     =Total steam generator/ total fuel burnt=Ms/Mf=kg/kg Of fuel .                                                    

          evaporation capacity is the main specification required for the design of grate ., furnace ,
heating surface and other components .

Equivalent evaporation-

          if the generating capacity of to boilers is same but if steam is generated at different pressure
and temperature using the same grade of fuel,  then some common base is required to compare
the performance of this to boiler.

          on the basis of equivalent evaporation the boiler performance can be compared. the quantity of
dry saturated steam that Could be generated by the boiler per unit time from water of hundred
degree Celsius( at a pressure corresponding 200 degree Celsius saturated temperature )  is
known as equivalent evaporation. the quality of heat supplied in this saturation by the boiler to
1 kg of steam is 2257 kg .

              Me = Ms(h-hf1) / 2257   Kg/hr

Me = Equalent mass of  steam per unit time

Ms =  total mass of steam  Per unit time

h  =  enthalpy of steam per kg under given condition .

hf1 = Specific enthalpy of water at  Given feed water condition .

Always,   Me > Ms .

Boiler thermal efficiency -

it is the ratio of heat absorbed by the steam from the boiler permit time so the heat liberated by the
combustion of fuel during the same time . -

     

             =( Ms(h-hf1) / Mf*CV of fuel  ) * 100%

Ms = Mass of  steam generated per hour

Mf =  mass of fuel burnt per hour .

                                                                                                                                                                                                    

HEAT LOSS IN BOILER PLAINT -

the total heat produced in the boiler due to combustion of fuel is not utilised for  reducing Steel. only
certain amount is used and remaining heat may be lost in following ways -

heat loss to few flue gases -

this can be divided into categories as flue gases contain dry products of combustion as well as steam
generated due to combustion of hydrogen present in the fuel-

     

heat created away by drive flue gases -

       Q1 = Mg*Cpg(Tg-Ta)

Mg   =  mass of flue gases per kg of fuel .

Cpg = Specific heat of flue gases .

Tg   = Temperature of flue gases .

Ta =  temperature of air entry in boiler furnace .

          (Boiler house /  room temperature .)

     

Heat carried away by steam ( water vapour)  from due to combustion of H2 in fuel -

Q2 = Ms1(hs1-hf1)

Where -

            Ms1 =Mass of water vapour per kg of fuel due to combustion of H2 in fuel .

            hf1=  enthalpy of water at boiler house temperature

            hs1 = Enthalpy of moisture of flue gases .

    Heat loss due to incomplete combustion -

 if 1 kg of carbon burns to CO Instead of CO2  It releases 10200 kg of heat where as it can release
35000 kg of heat is it burn to CO2 .

Incomplete combustion of 1 kg of c results in heat losses = 35000-10200=24800Kg (  loss )

the percent of CO in the  flue gases indicates incomplete combustion of fuel. if the percentage of CO  
and CO2  in the flue gases by  volume  are known ,  then carbon burn to CO    instead of CO2  per kg
of fuel is given by -

                mass of C 12 CO= CO/CO+CO2 .

Heat loss due to unburnt fuel -  

Small particles of fuel fall through fire great ones and are created away with Ash and clinker.  this heat
loss due to unburned fuel is ,

convention and radiation  losses-

hot surfaces of boiler are always exposed to atmosphere so some amount of heat is always lost by
convention and radiation to surrounding.  this loss usually measured and calculated by difference .

Boiler trial and heat balance -

the boiler performance is to be check the periodically .  hence trial/ tests on the boilers are conducted
who's objective are -

1. To determine and check specified generative capacity of boiler when working on full load condition.
2. to determine Boiler Efficiency.
3. to drop heat balance sheet so that suitable corrective action may be taken to improve efficiency .

Following reactions are taken during boiler trials -

1. the quantity of fuel supply and its quality
2. the pressure and temperature of steam generator as well as quality of steam generated
3. feed water temperature
4. flue gases volumetric analysis
5.  the inlet temperature of air and exhaust temperature of gases
6. the mass of fuel left unburnt in ash

the observation should be recorded at running boiler under study conditions at an interval of 15 minute
for 6 hour in case of coal fired boiler and for 4 hours in case of oil fired boilers .

                                                                                                                                                                   

HEAT BALANCE SHEET -

                  It is the systematic representation of total heat supplied and heat distributed on per minute
 or hour or per kg of fuel burnt basis .

   

Heat supplied	KJ	%	heat utilised	KJ	%
Heat supplied by combustion of fuel toatl	Qs=Mf *CV Qs	100% 100%	Heat used to produce steam Heat carried away buy dry flu gases heat carried away by water vapour in flue gases heat loss due to incomplete combustion get lost due to unburned fuel heat loss due to conversion	Q1=Ms(h-hf1) Q2=MgCpg(Tg-Ta) Q3=Ms1(hs1-hf1) Q4=(Co*(C/100)*24800)          / (Co+Co2) Q5=Mf*CV Q =	(Q1/Qs)*100 Similar to all 100%

                                                         

                                                                                                       

boiler  thermal efficiency -

it is the ratio of heat absorbed by steam from the boiler per unit time to the heat  liberated by
the combustion of fuel during the same time .

THANKS FOR VISIT