what is steam boiler & working principle??

Boilers::-

Introduction:-
According to the Indian boiler act 1923, a boiler is a steam generating closed vessel whose minimum capacity is 22.75 liters.
In order to generate steam, boiler water is subjected to heat-produced combustion of fuel in the boiler furnace.

Use of stem:-
Steam produced in a boiler can be used for the following purpose, …

i) for operating steam engines.
ii) for operating steam turbines.
iii) operating reciprocating pump.
iv) for industrial process work in chemical engineering.
v) for producing hot water required to be supplied to rooms in very cold areas.

Definition of some useful drum:-
Boiler shell:- the boiler shell hollow cylindrical body made of a steel plate riveted or welded together.

Furnace:-  hardness is that the boiler in which the fuel is conveniently burnt to produce heat. This heat is utilized in generating steam in the boiler.

Grate:-  The grate is a space on which the fuel is banned. It consists of a combination of several cast iron bars so arrange that the fuel may be placed on it. Some space is always provided in between two consecutive Bars so that air may flow to the fuel from below the grate. The grate may be circular or rectangular in shape.

Grate Area:-  the area of the grate upon which the fuel burns is called the grate area. The grate area is always measured in square meters.

Heating surface:- the heating surface is the surface of a boiler that is exposed to hot gases on one side and water on the other.

water peace and steam face:-. The water place is the dead volume of the boiler which is occupied by the water. The remaining space is called steam space because it is needed for the storage of steam in the boiler until it is drawn off through the steam pipe.

Flue gases:-. Flue gases are hot gases produced due to the combustion of fuel in the boiler furnace. Flue gas usually contains water vapour(H2o), carbon dioxide(Co2), carbon monoxide(Co) and nitrogen(N2). Flue gas includes complete and incomplete products of combustion of fuels.

Free circulation and forced circulation of water in the boiler:-

Free circulation:-  in any water heating Basil heat is transmitted from one place to another not by conduction by Convection. Because water is a bad conductor of heat. A vessel containing water be heated at its bottom. As the water in the bottom portion is heated it is TV comes reduced in compression to the density of water in the upper portion of the vessel. As a result, the least dense water at the bottom portion of the basal rise of and comparatively more dense and cold water at the upper portion of the Basil comes down to take its place and does a convection current is set off in the water until temperature of all water becomes the same.

the method of circulation of what is described above is known as free circulation or natural circulation. In boilers like Lancashire, Babcock, and Wilcox, etc. Fees circulation of water takes place,…

Advantages of free circulation:-
A) circulation of water helps to maintain a uniform temperature everywhere within the boiler so that an equal expression of various parts of the boiler is prevented.

B) free circulation of what are facilities the escape of steam from the heating surface as soon as it is formed. Its team does not escape quickly after its formation the boiler takes place does not remain constantly in touch with water and as a result, this place may be overheated.
the arrangement as shown in the above figure is devices for increasing heating surface and for retaining at the same time the advantage of free circulation.


forced circulation:-  in forced circulation pumps are used to maintain the continuous flow of water in the boiler. In such cases, the circulation of water takes place due to the pressure created by the pump. The forced circulation system is adopted in modern high-pressure high capacity boiler all of which are water tube type boiler.

Advantages of forced circulation:-
a) heat transfer from the flue gases to the water is higher.
b)  having comparatively smaller diameter can be used. This reduces the overall weight of the boilers.
c). The number of boiler drums required may be reduced.
d)  Les scales formation in the boilers is ensured.
e)  steam can be quickly generated.
f). Fluctuation of load can be easily meet without taking the help of any complicated controlled device.
g)  change of overheating of the boilerplates is minimum.
h) weight per unit mass of steam generated is less.

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