The document covers the properties of steam and the introduction of internal combustion engines, detailing the characteristics of pure substances and mixtures. It explains the phase transformation processes of steam through various diagrams, including T-V, P-V, T-S, and H-S diagrams, while distinguishing between homogeneous and heterogeneous mixtures. Key features of steam as a thermodynamic medium are highlighted, emphasizing its heat-carrying capacity and industrial applications.

1. Basic Mechanical Engineering
UNIT-3
Steam & I.C. Engine
Part-One (Properties of steam)
By
Mr. Varun Pratap Singh

2. SYLLABUS
UNIT-3:
Properties of steam: Properties of steam, Phase transformation process and its graphical representation on P-V,
T-V& T-s diagram, Mollier diagram and Steam Tables, Processes involving steam in closed and open systems.
Introduction to I.C. Engines: Two & four stoke S.I. and C.I. engines. Otto cycle, Diesel cycle, Dual cycle.

3. Pure Substance
Everything that exists in the earth is a form of a matter which is further defined as any substance that
occupies space and has mass. The matter is further divided into various forms such as solid, liquid and gas.
Apart from these, it is also classified as pure substances and mixtures.
What is Pure Substance?
Pure substances are substances that are made up of only one kind of particles and has a fixed or constant
structure.
Characteristics and Properties Of Pure Substances
•Pure substances are mostly homogeneous in nature containing only one type of atoms or molecules.
•These substances mainly have a constant or uniform composition throughout.
•The substances have fixed boiling and melting points.
•A pure substance usually participates in a chemical reaction to form predictable products.
Examples of Pure Substances
All elements are mostly pure substances. A few of them include gold, copper, oxygen, chlorine, diamond, etc.
Compounds such as water, salt or crystals, baking soda amongst others are also grouped as pure substances.
PURE SUBSTANCE

6. What is a Mixture?
A substance, on the other hand, is impure if it consists of different kinds of elements combined physically and not chemically. Impure
substances are also called mixtures. Mixtures are further divided into a homogenous or heterogeneous mixture.
•A homogeneous mixture occasionally called a solution, is comparatively unvarying in configuration or constant. Every unit of the
mixture is like every other unit. For instance, if you liquefy sugar in water and blend it really well, your concoction is essentially the
same, no matter where you sample it. This mixture contains two or more chemical substances.
•A heterogeneous mixture is a concoction whose configuration varies from spot to spot within the sample. For example, if you put a
little amount of sugar in a vessel, add some sand, and then shake the jar a couple of times, your concoction doesn’t have the same
configuration all throughout the jar. As the sand is heftier, there’s possibly more amount of sand at the bottom of the jar and more sugar
at the top part. These mixtures can be identified visually and separated easily by physical means.
Characteristics And Properties Of Mixtures Or Impure Substance
•It does not have any specific properties, the properties of the mixture are a result of the average properties of all the constituents.
•It is formed as a result of a physical change.
•They have a variable composition.
•Their melting and boiling points differ.
Example Of Mixtures
Some common examples of mixtures include;
•Gas and gas like nitrogen and oxygen in the atmosphere.
•A solution like water and oil.
•Gas and liquid such as water.
•Solid and liquid such as sand and water

7. Pure Substances Mixtures
It cannot be broken down or
separated into new products.
It can be separated using different
separation methods.
Constant physical and chemical
properties.
Mixtures have varying physical
and chemical properties.
Pure substances are made up of a
single element.
A mixture is a combination of two
substances or elements.
Differences Between Pure Substances and Mixtures
The differences between pure substances and mixture are given below.

8. Introduction
Steam, which is gaseous form of pure water, is an excellent working medium in various thermodynamic systems
because of its following properties:
1) It can carry large quantities of heat
2) It is produced from water which is cheap and readily available
3) It can be used for heating purposes after its duty as working agent is completed.
4) It can be used purely as a heating medium in food processing Industries because of a fast, easily controllable
and hygienic method of heating.
FORMATION OF STEAM AND ITS PROPERTIES

12. T-v Diagram of Steam
The phase-change process of water under 1atm described
in the previous section can be repeated for different
pressures. Put all the processes in the T-v diagram. A line
connected by all the saturated liquid states is called
saturated liquid line. All the saturated vapor states are
connected to create the saturated vapor line. When
pressure becomes as high as Pcr (critical pressure), the
saturated liquid state and the saturated vapor state
become a single point in T-v diagram. This point is
called the critical point. For water, Pcr=22.09 MPa,
Tcr (critical temperature) =374.147 oC. At pressure above
the critical pressure, there will not be a distinct phase.
The saturated liquid line and saturated vapor line divide
the region on the T-v diagram into three regions:
subcooled liquid region, saturated liquid-vapor region
and superheated vapor region.

13. P-v Diagram for Steam
The water vaporization process can also be
described in P-v diagram. The method of creation
the P-v Diagram is much like the method for the T-
v diagram. By considering the piston-cylinder
device again, the temperature keeps constant by
heat transfer. The pressure is changed by removing
the weight. Like the process in previous section,
the water will become saturated liquid, saturated
mixture, saturated vapor and superheated vapor if
enough heat added. The process is repeated under
several different temperatures and plot them in a P-
v diagram. By connecting all the saturated liquid
states under different temperatures, one can create
the saturated liquid line and connecting all the
saturated vapor states, one can create the saturated
vapor line on the P-v diagram. There are three
regions on the P-v diagram: subcooled liquid
region, saturated liquid-vapor region, and
superheated vapor region.

14. The T-S Diagram for Steam
A T-s diagram can be constructed for any
pure substance. It exhibits the same features
as P-u diagrams. In the liquid-vapor region
in Figure 13, water and steam exist together.
For example, at point A, water with an
entropy (sf) given by point B, exists together
with steam with an entropy (sg) given by
point C.

15. The P-H Diagram for Steam

17. The h-S Diagram (Mollier diagram) for Steam
Another type of entropy diagram which is used by engineers is
the Mollier diagram or Enthalpy – Entropy (h-s) diagram. This
diagram represents the entropy and total heat or enthalpy of
steam.
It is a plot of enthalpy on ordinate and entropy on abscissa scale.
Constant pressure, constant volume and constant temperature
lines are also drawn on it.

20. P-T Diagram
The P-T diagram is called the phase
diagram because three phases are
separated from each other by three
lines (sublimation, melting, and
vaporization). The three lines meet
at the triple point where three
phases coexist in equilibrium.

24. Wetness fraction
It is the ratio of the weight of water/ moisture
in suspension in a wet steam sample to the total
weight of wet steam. It is calculated by
subtracting x from 1

29. STEAM TABLE