Basics Of Thermodynamics Part 1.pdf

Thermodynamics & Heat Transfer
Mr. S.S.Sajane
BE(Mech), ME (Heat & Power Engineering)
Department of Mechatronics Engineering,
Sharad Institute of Technology College of Engineering,
Yadrav-Ichalkaranji.

Suggested Books:
Basic
Thermodynamics
by P.K.Nag.
A Textbook of Thermal
Engineering by
R.S.Khurmi and
J.K.Gupta.
Thermal
Engineering by
R.K.Rajput.

Pure Substance:
Pure Substance is one with uniform and invariant chemical composition.
Eg: Elements and chemical compounds are pure substances. (water, stainless steel)
Mixtures are not pure substances. (eg: Humid air)
Exception!! Air is treated as a pure substance though it is a mixture of gases.

Fundamental Concepts and Definitions
Thermodynamics: It is the science of the relations
between heat, Work and the properties of the systems.
System : It is a small part of universe which is under
thermodynamic consideration.
• Ex: Engine

Definitions:
Surrounding: The rest of the universe outside the system
close enough to the system to have some perceptible
effect on the system is called the surroundings.
Boundary: The surfaces which separates the system from
the surroundings are called the boundaries.

Universe: The system, Surrounding and
boundary altogether is called as Universe.

Types of System:
1. Closed System
2. Open System
3. Isolated System

Types of System:
• Closed system-in which no mass is permitted to cross the
system boundary i.e. we would always consider a system of
constant mass. We do permit heat and work to enter or leave but
not mass.

• Open system- in which we permit mass to cross the
system boundary in either direction (from the
system to surroundings or vice versa).

• Isolated System- in which there is no interaction
between system and the surroundings. It is of
fixed mass and energy, and hence there is no
mass and energy transfer across the system
boundary.

Basics Of Thermodynamics Part 1.pdf

Properties of System:
• It is defined as any measurable or observable characteristics of the system
when it is in equilibrium.
• Properties may be Intensive or Extensive.
• Ex: Anand age is 62 years and height is 1m. He is graduated from IIT Delhi
and has excellent academics.
Case 1: If Anand is Missing then his age and height are the important
characteristics for the police to find him.
Case 2: If Anand is searching for a job then his qualification and academics
are the important characteristics to get him a job.

Intensive & Extensive Property:
• Intensive Property is a physical property that is not dependent
on the size or mass of the system.
Ex: pressure, temperature (p, T)
• Extensive property is a physical property that is dependent on
the size or mass of the system.
Ex: Volume, Mass (V, M)

Flow and Non-Flow Process:
• Flow process:
It is one in which fluid enters the system and leaves it after work interaction,
which means that such processes occur in the systems having open boundary
permitting mass interaction across the system boundary.

• Non flow process:
It is the one in which there is no mass interaction across the system
boundaries during the occurrence of process.
Ex. 1) A Cup of tea with a lid cover on top, which continuously loses heat to
the surrounding.
Ex. 2) Compression and Expansion stroke of IC Engine.

Important Terms:
1. Specific volume of a substance is the ratio of the substance's
volume to its mass. It is the reciprocal of density. The standard
unit is the cubic meter per kilogram (m3/kg)
v = V/m = 1/ρ
2. Density: The density denoted by ρ, is defined as mass per unit
volume.
The SI unit for density, kg/m3
ρ = m/V

Important Terms:
3. Temperature:
Temperature is a physical property of matter that quantitatively expresses
hot and cold. Temperature is measured with a thermometer. The most
common scales are the Celsius Scale (formerly called centigrade, (denoted
°C), the Fahrenheit Scale (denoted °F), and the Kelvin Scale (denoted K)
4. Pressure:
Pressure is defined as force per unit area. Formula for pressure is F/A
(Force per unit area). Unit of pressure is Pascals (Pa).
1 Pa = 1N/m2

Thermodynamic Process and Cycle:
Thermodynamic State of a system is the condition at
a specific time, that is fully identified by values of a
suitable set of parameters like pressure, Volume and
temperature.
Process is a change of state of
system from one state point to
another in a determined path.

Cycle is a series of two or more processes to form a
closed loop(reaching initial state point again)

Quasi-static Process :
A quasi-static process is one in which the system
deviates from one equilibrium state by only
infinitesimal amounts throughout the entire process.

• If we remove the weights slowly one by
one the pressure of the gas will displace
the piston gradually. It is quasi-static. On
the other hand if we remove all the
weights at once the piston will be kicked
up by the gas pressure.
• Another eg: if a person climbs down a
ladder from roof to ground, it is a quasi-
static process. On the other hand if he
jumps then it is not a quasi-static
process.

Path function:
• A Path function is a function whose value depends on
the path followed by the thermodynamic process
irrespective of the initial and final states of the process.
• Heat(Q) is path function.
• Work done in a thermodynamic process is dependent on
the path followed by the process.

For Example:
Process A: WA = 10 kJ
Process B: WB = 7 kJ

Point function :
• A Point function (also known as state function) is a function whose
value depends on the final and initial states of the thermodynamic
process, irrespective of the path followed by the process.
• Example of point functions are density, enthalpy, internal energy,
entropy etc.
• Since a point function is only dependent on the initial or final state
of the system, hence in a cyclic process value of a thermodynamic
function is zero, or change in thermodynamic property is zero.

For Example:
Process A: V2 - V1 = 3 m3
Process B: V2 - V1 = 3 m3

Difference between Point and Path Function:

Thermodynamic Equilibrium:
1) Mechanical Equilibrium.
A system is said to be in mechanical
equilibrium if the resultant force acting
on the system is zero. I.e. No unbalance
force is acting on any part of the system.

2) Thermal Equilibrium.
A system is said to be in thermal equilibrium
if the temperature of the system does not change with time and has
same value at all points throughout the system.

Thermodynamic Equilibrium:
3) Chemical Equilibrium.
A system is said to be in chemical equilibrium if there exist
no any chemical reaction or transfer of matter from one part
of system to another.
Summary:
1. Mechanical equilibrium: No unbalance force.
2. Thermal equilibrium: No change in temperature.
3. Chemical equilibrium: No chemical reaction.

Previous Lecture:
• Thermodynamic State, Process and Cycle.
• Quasi-Static Process.
• Path and Point Function.
• Thermodynamic Equilibrium
– Mechanical, Thermal, Chemical Equilibrium.

Work and Heat:
Thermodynamic definition of Work:
In thermodynamics, work performed by a system is the
energy transferred by the system to its surroundings.
W = F . d
where:
W = work (J), F = force (N), d = displacement (m)

Basics Of Thermodynamics Part 1.pdf

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