The ppt covers about the concept of formation of steam and Introduction to Boilers.

1. SITCOE,Yadrav-Ichalkaranji. Mr.S.S.Sajane
Thermodynamics & Heat
Transfer
Chapter 2:
Steam Generators and
Steam Turbines

2. Sharad Institute of Technology Polytechnic,Yadrav-Ichalkaranji. Mr.S.S.Sajane
What Is Steam?
Steam is vapor of water and is invisible when pure and dry.
It is used as the working substance in steam engines, boilers and turbines.

3. Types of heat
Sensible Heat:
When an object is heated, its temperature rises as heat is added. The increase in heat is called
sensible heat. Similarly, when heat is removed from an object and its temperature falls, the heat
removed is also called sensible heat. Heat that causes a change in temperature in an object is
called sensible heat.
Latent Heat:
The heat that causes does not affect the temperature of a substance - for example, water remains
at 100°C while boiling. The heat added to keep the water boiling is latent heat. Heat that causes
a change of state with no change in temperature is called latent heat.

4. Formation/ Generation of Steam at Constant
Pressure

5. A-B :
Consider 1 kg of ice at
temperature -100C which
is below the freezing
point. Let it be heated at
constant pressure P. The
temperature of ice starts
increasing until it reaches
the melting temperature
of ice i.e., 00C and during
this course ice absorbs its
sensible heat.
A-B : Heat of Ice from -100C to melting temp. of Ice.

6. B-C:
On further addition of
heat, ice starts melting,
its temperature remains
constant at 00C and it
absorbs latent heat of
fusion and converts
completely into water at
00C
B - C : Latent heat of fusion of Ice.

7. C-D:
On further addition of
heat, the temperature of
water starts rising until it
reaches the boiling
temperature or saturation
temperature
corresponding to
pressure P. This heat
absorbed by water is
sensible heat.
C - D : Sensible heating of water from 00C to saturation.

8. D-E:
After the boiling
temperature is reached, it
remains constant with
further addition of heat
and vaporization take
place. The water absorbs
its latent heat and
converts into dry
saturated steam
remaining at same
saturation temperature.
D - E : Latent heat of vaporization of water.

9. If further the heat is
added, the temperature
of this dry saturated
steam starts rising from
saturation temperature
and it converts into
superheated steam.
E - F : Superheating of steam.

10. This heat absorbed is
again the sensible heat.
The total rise in
temperature of
superheated steam above
the saturation
temperature is called
degree of superheat.

11. Temperature – Entropy (T-S) Diagram.

13. Various Conditions of Steam.
Dry Saturated Steam:
If steam does not contain any moisture, it is known as Dry Saturated Steam. It contains just sufficient
heat energy to maintain all of the water in a gaseous state.
Wet Steam:
If saturated steam contains liquid particles, it is known as Wet Steam. These liquid particles are called
as Moisture.
Superheated Steam:
If the temperature of the steam is greater than that of the boiling point corresponding to the pressure of
steam generation, the steam is known as Superheated Steam.
Degree of Superheat:
It is defined as the difference between superheated temperature of steam and its saturation temperature.
Degree of Superheat = Tsup – Tsat.

14. Rankine Cycle:
The power plant consists of four elements:
1. Boiler : In boiler, the working fluid receives
heat by combustion of fuel and it is converted
into steam.
2. Steam Turbine: In steam turbine, steam from
the boiler pressure expands to deliver work of
expansion.
3. Condenser: In condenser, the exhaust steam
from the turbine gives heat to cooling water
and completely condenses to water.
4. Feed Pump: Feed pump feeds the condensate
from hot well to boiler at boiler pressure.

15. Fig: PV & TS Diagram

16. • Process 1-2: It is isentropic expansion of steam in the turbine from pressure P1 to
pressure P2.
• Process 2-3: At constant pressure P2 and temperature T2 the exhaust steam is condensed in condenser
giving latent heat to cooling water.
• Process 3-4: The water from hot well which is at low pressure P2 is pumped isentropically into the
boiler at high pressure P1.
• Process 4-5: As the water enters the boiler, it is first heated upto the saturation temperature or
evaporation temperature T1 and during this process the state point moves along the curve 4-5 called as
sensible heating. The heat supplied during this process is hf5 –hf4 and is represented by area L-3-4-5-M
i.e sensible heat of water.
• Process 5-1: At constant pressure P1 and temp. T1 water is completely converted into steam. The heat
added in this process is h1-hf5 and is represented by M-5-1-N i.e Latent heat of vaporization. The state
point 1 shows the dry and saturated condition of steam.
•Efficiency = Wnet/QA = (h1 – h2) – (hf4 – hf3)
(h1 – hf4)

17. Steam generators/
Boilers.

18. Steam Boiler:
The equipment used for producing and transferring steam is called Steam
generators.
Principle of Steam Generators/ Boilers:
The fluid (water) contained in the boiler and the thermal energy released
during combustion of fuel, which may be solid, liquid or gaseous, is
transferred to water and this converts water into steam at the desired
temperature and pressure.

19. Classification of boilers:
Boilers may be classified according to the
following-
1. Relative position of Hot gases and Water
a) Fire tube boiler:
The hot gases passes through the tubes that are
surrounded by water.
b) Water tube Boiler
The water passes through the tubes and the hot
gases
produced by combustion of fuel, flow outside.

20. 2. Method of firing
a) Internally fired Boilers:
The furnace is provided inside the
boiler shell and is completely
surrounded by water cooled
surfaces.
b) Externally fired Boilers:
The furnace is provided outside/
under the boiler. It has an
advantage that its furnace is
simple to construct and can
easily be enlarged, as and when
required.

21. 3. Pressure of Steam:
a) High pressure Boilers:
Boilers producing steam 80 bar and above are called High pressure boilers.
b) Low pressure Boilers:
Boilers producing steam Lower than 80 bar are called Low pressure boilers.
4. Method of circulation of water:
a) Natural circulation method
Circulation set up by convection current or by gravity.
b) Forced circulation method
Circulation set up for high pressure steam through pumps.

22. 5. Nature of service to be performed:
a) Land Boilers:
Boilers which are used with stationary plants
b) Portable Boilers:
Boilers which can be readily dismantled and easily carried out
from one site to another.
c) Mobile Boilers:
Boilers which are fitted on mobile carriages are called Mobile
Boilers. E.g. marine and locomotive boilers.
6. Once through Boilers:
The boilers in which no circulation of water takes place i.e. the
feed water leaves the tube as steam

23. 7. Nature of Draught:
a) Natural Draught:
When the fuel burns in the furnace of the Boiler, with the circulation of air,
the draught is named as Natural Draught.
b) Artificial Draught:
When the air is forced by means of forced fan, the draught is named as
Artificial Draught.