Steam is the vapor form of water and is used in steam engines and turbines. It forms when water is heated under constant pressure. As water is heated from 0°C, its temperature increases until it reaches the boiling point. At this point, further heating causes water to evaporate into steam while the temperature remains constant. This uses heat energy called the latent heat of vaporization. If heating continues, any remaining water particles evaporate, forming dry saturated steam. Dry steam can be further superheated by adding more heat at constant pressure. The temperature and pressure affect the boiling/saturation point, with higher pressure requiring more heat to reach the same temperature. Superheated steam provides benefits like more power and increased thermal efficiency.

1. Formation and Properties Of
Steam
Submitted to – Prashant sir
Submitted by – Anuharsh Gaur

2. Introduction: What is Steam?
• Steam is vapour of water and is invisible when
pure and dry
• It is used as the working substance in the
operation of steam engines and steam
turbines
• Steam does not obey laws of perfect gases
until it is perfect dry

3. Formation of steam at a
constant pressure from water

5. Theoretical description of above figure
• Consider 1 kg of water at 0 degree Celsius
contained in piston cylinder arrangement as
shown in above figure(i) the piston and
weights maintains a constant pressure in
cylinder
*if we heat water contained in cylinder it will
converted to steam as follows

6. Contd…..
• The volume of water will increase slightly as increase in
temperature hence it will cause the piston to move
upwards and work is obtained .
• On further heating temperature reaches boiling point ,
the boiling point of water is 100 degree Celsius at
1.103 bar but increases with increase in pressure .
When boiling point is reached, temperature remains
constant and water evaporates thus pushing the piston
up at constant pressure . The specific volume of steam
increases as shown in (iii). At this stage steam will have
some particles of water in suspension and is termed as
wet steam . Process will continue till whole water is
converted to steam

7. Cont..
• On further heating the suspended water
particles will get converted into steam. The
entire steam in such a state is called dry steam
(iv). It acts as a perfect gas
• On further heating the temperature of steam
starts rising and is termed as superheated
steam(v)

8. Temperature vs Total Heat Graph
during Steam Formation

9. Theoretical explanation of above
graph
• The process of steam formation above can
also be explained in graphical form.
• The point A represents the initial condition of
water at 0 degree Celsius and pressure ‘p’.
• The graph is depicted in following three stages

10. Cont..
1. The heating of water up to boiling temperature
or saturation temperature ‘Ts’is shown by AB
the heat absorbed by water is AF known as
sensible heat
2. The change of state from liquid to steam is
shown by BC heat absorbed during this stage is
FG known as latent heat of vaporization
3. The superheating process is shown by CD heat
absorbed during stage is GH , known as heat of
superheat

11. Cont..
• If the pressure is increased the boiling
temperature also increase. The point B1
represent the boiling temperature or
saturation temperature at pressure p1 and
point F is point of dry saturated steam
• Line C1D1 shows the constant pressure
process in which steam is super heated

12. Cont..
• Line passing through points A,B,B1,B2 are
known as saturated liquid line
• Line passing through A1,C,C1,C2 are known
as dry saturated steam line .

13. Important terms for steam

14. Basic definitions
• Wet steam – when the steam contains the
moisture or particles of water in suspension .
it is said to be wet steam ,evaporation of
water is not complete and whole of latent
heat is not absorbed
• Dry saturated steam when the wet steam is
further heated and it does not contain any
suspended water particles it is called dry
steam

15. Cont..
• Superheated steam- when dry steam is further
heated at constant pressure thus raising its
temperature i.e. it is said to be super heated
steam
• Sensible heat – it is the amount of heat
absorbed by 1 kg of water to raise the
temperature from 0 degree to temperature of
saturation point

16. cont
• Latent heat of vaporization- it is the amount of
heat required to evaporate 1 kg of water at its
boiling point without changing its
temperature
• Specific volume – it is defined as volume
occupied per unit mass at a given temperature
and pressure.

17. Advantages of Superheated Steam
• We already know that when dry steam is
further heated then the steam is superheated
steam . The process of superheating follows
Charles law
1 . It contain more heat content and has more
power to do a specific work
2. Increased thermal efficiency

18. Internal energy of the system
• It is the actual heat energy stored in the
system above the freezing point of water
• It is calculated by subtracting external work
done during evaporation from enthalpy or
total heat of steam .

19. Dryness Fraction
• It is defined as ratio of mass of actual dry
steam to the mass of same quantity of wet
steam
• Generally denoted by ‘x’
• Formulae – Mg/Mg+Mf = Mg/M
Mg = mass of dry steam
Mf = mass of suspended water particles
M = Mg+Mf

20. References
• Slideshare.net
• Google.com
• Wikipedia.org

21. Thank you