Thermodynamics Lectures Notes 1

Thermodynamics
V
TOPICS INCLUDE:
Introduction To Thermodynamics.
Basics concepts Thermodynamics.
Types Of Systems.
Properties Of System .
Zeroth Law of Thermodynamics.
 Concept Of Heat and work.
 Properties Of steam .
 Properties of ideal gas .

1
MODULE
© mech4u.weebly.com Notes Prepared BY Mohd Shoaib
1

Introduction To Thermodynamics
It is the science of Relation between HEAT ,WORK,& properties of
Systems.
Thermodynamics is the science of regularities governing process of
energy conversations.
Thermodynamics is the science that deals with the interaction
between energy and material.
 The Fundamental law is the conservation of energy principle: energy
cannot be created or destroyed, but can only be transformed from one
form to another.
2

Basics Concepts Of Thermodynamics
System ,Surroundings , Boundary
 System: it is the finite quantity of matter or prescribed region of space.
 Boundary: The surface which separates the system from the surroundings are called boundary
 Surroundings: The real or imaginary surface that separates the system from its surroundings.
3

Types Of Systems
• Closed System
• Open System
• Isolated System
• Adiabatic System
• Homogenous System
• Heterogeneous system
4

Types Of System ( closed system)
boundary
Heat work out
Heat work IN
• If the boundary of the system is impervious to the flow of matter it is called
closed system
• No mass is permitted to cross the system boundary . We should always consider a
system of constant mass.
• We do permit heat and work to enter or leave but not mass.
• It is based on law of conservation of energy.
SYSTEM
5

Types Of system(Open system)
Boundary mass out
Mass IN Heat work IN
• An open system is one which matter flows into or out of the system
• both mass and energy can cross the selected boundary
 Example: an open cup of coffee
SYSTEM
6

Types Of System ( Isolated System)
• An isolated system is that system which exchange neither energy nor
matter with any other system or with Environment.
No mass Transfer
No energy transfer
ISOLATED
SYSTEM
7

Types of System(Homogenous, Heterogeneous &
Adiabatic)
Homogenous: A System which consist of single phase is termed as homogenous system. EG
mixture of air and water , nitric acid etc.
Heterogeneous: A System which consist of two or more phase called heterogeneous system. EG
water+steam,ice+water,water+oil.
Adiabatic : The system is one which is thermally insulated from it surroundings , it can exchange
work with surroundings ,if it does not it becomes an isolated system.
8

Properties Of System
Properties of a system is a measurable characteristic of a system that is in
equilibrium.
Properties may be intensive or extensive.
Intensive Property: These properties do not depend on the mass of the system.
Eg : Temperature ,Pressure, Density.
Extensive Property : These Properties depend on the mass of the system.
Eg : volume , Energy, Mass.
 Specific Property : The ratio of any extensive property of a system to that of the
mass of the system is called an average specific value of that property (also known
as intensives property)
9

State, Equilibrium and Process
• A set of properties that describes the conditions of a system. Eg. Mass m,
Temperature T, volume V
10

State, Equilibrium and Process
• Process :
11

State, Equilibrium ,Process & Path
PATH
12

PATH & PROCESS EXPLANATION
• The succession of states passed through during a change of state is called the
path of the system.A system is said to go through a process if it goes through a
series of changes in state. Consequently:
• 􀂾A system may undergo changes in some or all of its properties.
• 􀂾A process can be construed to be the locus of changes of state
• Processes in thermodynamics are like streets in a city
• eg: we have north to south; east to west; roundabouts; crescents
13

Isothermal (T), Isobaric (p), Isochoric (v), Isentropic (s)
• Isothermal process: A process during which the temperature T remains
constant.
• Isobaric process: A process during which the pressure P remains
constant.
• Isochoric (or isometric) process: A process during which the specific
volume v remains constant
14

Types Of Thermodynamics Process
• Adiabatic process - a process that has no heat transfer into or out of the system. It
can be considered to be perfectly insulated.
• Isentropic process - a process where the entropy of the fluid remains constant.
• Polytrophic process - when a gas undergoes a reversible process in which there is
heat transfer, it is represented with a straight line, PVn = constant.
• Throttling process - a process in which there is no change in enthalpy, no work is
done and the process is adiabatic
15

Types Of Thermodynamics Process
• Cyclic process - when a system in a given initial state goes through various
processes and finally return to its initial state, the system has undergone a cyclic
process or cycle.
• Reversible process - it is defined as a process that, once having take place it can
be reversed. In doing so, it leaves no change in the system or boundary.
• Irreversible process - a process that cannot return both the system and
surrounding to their original conditions
16

Quasi-statics Process
 The deviation from thermodynamic equilibrium is infinitesimal
 All states of the system passes through are equilibrium states
17

Thermodynamics Equilibrium
18

Zeroth Law Of Thermodynamics
• “ If two bodies are in thermal equilibrium with a third body, there are also in
thermal equilibrium with each other.”
• If two system are each equal in temperature to a third , they are equal in
temperature to each other.
• eg: A hot cup of coffee is at a higher temperature than a block of ice. On the
other hand, ice is hotter than liquid hydrogen.
19

Concept Of Heat and work
• Thermodynamics Definition of Work:
In Thermodynamics work transfer is considered as occurring between the
system and surroundings.
Work is said to be done by system if the sole effect on things external to the
system can be reduced to the raising of weight .
When work is done by a system it is arbitrarily taken to the positive and when
work is done on a system. It is taken to be negative
W(-ve)
w(+ve)
Surroundings
Surroundings
SYSTEM
SYSTEM
20

Sign Conventions
• Work done BY the system is +ve
• work done ON the system is –ve
• Heat given TO the system is +ve
• Heat rejected by the system is -ve
21

Concept Of Heat and Work
Thermodynamics Definition of Heat :
• It is the energy in transition between the system and the surroundings by virtue
of the difference in temperature.
•Closed system can also interact with the surroundings, when it is not possible to
transfer the energy in form of work. This non-work type of heat interaction is called
Heat.
•Heat (Q) is a form of energy. Heat always flows from higher temperature region to
lower temperature region. Unit of heat is Joule (J) or Calorie.
•Whenever there is a heat exchange between system and surroundings, state
(represented by thermodynamic properties like pressure, temperature, volume
etc.) changes due to this heat exchange. 22

Sign Convention (HEAT)
•When heat flows to the system (heat absorption by system), heat is taken as positive quantity
When heat flow from the system (heat rejection by system), heat is taken as negative quantity
23

Different Types of Heat..
• Sensible Heat: Heat which just raises the temperature of body or substance is
called sensible heat. E.g. heating of water.
• •Latent Heat: Heat required to change the phase of the substance is called latent
heat. E.g. Steam generation from water.
• •Heat capacity: Heat required to raises the temperature of substance or body
through unit degree centigrade/Kelvin is called heat capacity and per mass heat
capacity is called specific heat (C). Unit of specific heat is J/kg K or J/kg C
24

Work Transfer and Heat Transfer
•Heat and work transfer are nothing but purely energy interactions to system and
surroundings. A closed system can interact with surrounding by work as well heat.
•Both heat and work transfer are energy interactions which are boundary phenomena
means work and heat transfer can be observed at boundary of the system.
•Heat transfer interaction is only depend on temperature difference. All other type of
energy interaction is work only.
•Both heat and work are path function. They depends on the how the work and heat are
supplied, not on the basis of point function. You cannot say dw=w2-w1. where 1 & 2
refers to change of state from 1 to 2. and also heat and work are inexact differential not
exact. Exact differential of any variable is called property
25

Properties of Steams
• Steam is a vapour . It is used as the working substances in the operations of the
steam engine and steam turbines.
• a vapour is a partially evaporated liquid carrying in it particles of liquid and it can
be liquefied by minor changes in temperature or pressure. Steam as a vapour
would not obey the laws of perfect gases unless it is in a highly dried condition.
Steam in such a dried state is known as superheated steam and it is assumed to
behave like a perfect gas when highly superheated.
• Although steam is considered as a perfect gas on account of It being a mixture of
dry steam (gas) and moisture (water), it possesses properties like those of gases :
namely, pressure, volume, temperature, internal energy, enthalpy and entropy.
But the pressure, volume and temperature of steam as a vapour are not
connected by any simple relationship such as is expressed by the characteristic
equation for a perfect gas.
26

Properties Of Steams
• Properties of steam were first investigated experimentally by Regnault and
subsequently investigated by Prof. Callender by carrying out extensive
thermodynamic experiments by means of electrical calorimeters. Tables giving
the properties of steam in each condition were compiled from study of the
equations derived experimentally. These properties are also represented on
charts. The quantities tabulated in steam tables are : -
• Pressure, - Temperature, - Specific Volume, - Enthalpy, and – Entropy.
27

• Pressure, temperature and volume can be given their actual absolute
values; whereas, enthalpy and entropy are purely relative quantities.
They are measured relatively from convenient datum condition and
calculated per 1 kg of steam. For steam, datum point is arbitrarily
fixed as the condition of the water at O'C. Thus, the enthalpy, the
internal energy and the entropy of water at O'C are assumed to be
zero. All their values measured above this temperature are
considered positive and those measured below are taken as negative.
The general conservation of energy equation is applicable to steam in
the same manner as it is applicable to gases. The properties of steam
and the changes in the properties can be determined by using
standard steam tables or steam charts
28

Properties of steams contd….
29

Properties of steam contd..
30

Properties of steam contd….
31

Properties Of Ideal Gas
32

Thermodynamics Lectures Notes 1

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