Ch_1_Basic_concept_and_definitions.ppt .

Department of Mechanical & Manufacturing Engineering, MIT, Manipal 1 of 3
THERMODYNAMICS – I
(MME 2155) [2 1 0 3]
THERMODYNAMICS - I

Introduction to Mechanical Engineering
 Mechanical Engineering is one of the oldest, largest
and broadest engineering discipline.
 Mechanical engineers apply principles of mechanics
and energy to the design of machines and devices.
 Energy and Motion

What we are studying in Mechanical Engineering
 Forces, motion, structures: Statics, Dynamics, Kinematics,
Mechanics of solids and fluids
 Energy: Thermodynamics, heat transfer
 Materials: Materials engineering & processing, Manufacturing.
 Machines: Graphics, design, machine elements, controls.
 Economics: Engineering economic analysis, cost engineering

MME 2155: THERMODYNAMICS - I [2 1 0 3] No. of Lecture hours: 36
Basic concept and definitions: Macroscopic and Microscopic points of view, system
and surroundings, property and state, thermodynamic equilibrium, change of state,
process and cycle, Zeroth law of thermodynamics, concept of temperature,
temperature scales. Work and Heat-Thermodynamics definition of work, displacement
work for different thermodynamic processes, definition of heat, comparison between
heat and work. [06]
First law of thermodynamics: First law for a closed system undergoing a cyclic
process, non-cyclic process, Energy is a property of a system, First law for an open
system, steady flow energy equation and its applications. [05].
Second law of thermodynamics: Limitations of first law, definition of heat engine
and reversible heat engines and their performance, two statements of second law,
corollaries of second law, reversible and irreversible processes, Carnot cycle,
statement of third law, thermodynamic temperature scale. [07]

Entropy: Clausius inequality, entropy - property, principle of increase of entropy,
Temperature-entropy diagram, entropy relations to other thermodynamic
properties. [04]
Pure substance: Definition, two property rule, specific heats of pure substances,
phases, equilibrium between phases, PvT surface, P-T diagram, triple point and
critical point, dryness fraction and its measurement, Tabulated properties, State
change of a system involving pure substance, different constant property
processes. [07]
Ideal and real gases: Definition, universal gas constant, Thermodynamic
processes, Evaluation of properties of mixture of ideal gases, adiabatic mixing of
ideal gases, Vander Waal’s equation of state, law of corresponding states,
compressibility factor, generalized compressibility chart. [07]

References:
1. Nag P. K., Engineering Thermodynamics, McGraw - Hill Education
India Pvt. Ltd, 2013.
2. Yunus A. Cengel and Michael A. Boles, Thermodynamics: An
Engineering Approach, Tata McGraw - Hill Education, 2011.
3. Gordon J. Van Wylen and Richard E. Sonntag, Fundamentals of
Classical Thermodynamics, Wiley, 1986.
4. Rogers G. F. C., and Yon Mayhew “Engineering Thermodynamics:
Work and Heat Transfer”, Prentice Hall, 1996.
5. Gupta S. C., Thermodynamics, Pearson Education, 2009.
6. B.T. Nijaguna and B S Samaga ‘Thermodynamics Data hand book’
Sudha publications, Bangalore

THERMODYNAMICS - I
The design of many engineering systems, such as
solar hot water system, involves thermodynamics.

Performance Analysis of IC engines
THERMODYNAMICS - I

Performance Analysis of Jet engines
THERMODYNAMICS - I

Thermal Analysis of space systems
THERMODYNAMICS - I

CHAPTER 1
BASIC CONCEPTS AND DEFINITIONS
THERMODYNAMICS - I

THERMODYNAMICS - I
Introduction to Thermodynamics:
 It is the science that deals with heat and work
and those properties of substances that bear a
relation to heat and work.
 It is the science of energy transfer and its effect
on the physical properties of substances.
 It deals with three E’s, namely Energy,
Equilibrium and Entropy.

THERMODYNAMICS - I
• Thermodynamics pertains to the study of:
 Interaction of system and surroundings
 Energy and its transformation.
 Relationship between heat, work and physical
properties of substance employed to obtain
energy conversion.
 Feasibility of a process and the concept of
equilibrium

THERMODYNAMICS - I
• The study of thermodynamics is the basis for
 Steam power plants,
 IC Engines,
 Gas dynamics and aerodynamics,
 Refrigeration and Air conditioning
 Heat transfer
 Fluid mechanics

THERMODYNAMICS - I
Laws of thermodynamics
• Systematic observation of nature, study of the
properties of fluid and repeated experimentations
has resulted in four laws of thermodynamics
named as
 Zeroth law
 First law,
 Second law
 Third law
• There is no mathematical proof for any of these
laws of thermodynamics but they are deduced
from experimental observations.

THERMODYNAMICS - I
Macroscopic & Microscopic approaches:
 Macroscopic & Microscopic approaches are the
two approaches in the study of thermodynamics
 In macroscopic approach, certain quantity of
matter is considered, without a concern on the
events occurring at the molecular level.
 These effects can be perceived by human
senses or measured by instruments.
eg: Pressure, Temperature

THERMODYNAMICS - I
Characteristics of macroscopic point of view are:
 No attention is focused on the behavior of
individual particles constituting the matter.
 The system is regarded as continuum devoid of
any voids and cavities.
 Study is made of overall effect of several
molecules; the behavior and activities of the
molecules are averaged

THERMODYNAMICS - I
 In microscopic approach, the effect of molecular
motion is considered.
 At microscopic level the pressure of a gas is
not constant,
 The temperature of a gas is a function of the
velocity of molecules.
 Most microscopic properties cannot be
measured with common instruments nor can be
perceived by human senses.

THERMODYNAMICS - I
Characteristics of microscopic point of view are:
 Necessity of complete knowledge of the
structure of the matter
 Requirement of a large number of variables for
complete specification of the state of matter
 Easy and precise measurement of variables is
not possible
 It is complex, cumbersome and time consuming.

THERMODYNAMICS - I
System and surroundings
 In our study of thermodynamics, we will choose a
small part of the universe and apply the laws of
thermodynamics. We call this subset a System.
 It is analogous to the free body diagram to which
we apply the laws of mechanics.
 The system is a macroscopically identifiable
collection of matter on which we focus our
attention.

THERMODYNAMICS - I
 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.

THERMODYNAMICS - I
Types of thermodynamic Systems
1. Closed system: In a closed system there is no mass transfer across
the system boundary and there will be energy transfer into/out of the system.

THERMODYNAMICS - I
Open system: - Open system is one in which matter crosses the
boundary of the system and there may be energy transfer also.
(i) Air compressor
(ii) Open cycle gas turbine
(iii) Fan, blower, pump
In the analysis of open systems that involves flow of
mass into and out of the system, an imaginary
boundary considered around the system is called as
control volume or control surface.

THERMODYNAMICS - I
Isolated System: An isolated system is one that is not influenced
in any way by its surroundings. This means that no mass transfer and no
energy transfer between the system and surroundings.
(A system disconnected from everything else) Ex: Thermos flask, Universe

THERMODYNAMICS - I
Property: -
 A property is any characteristic that can be used to
describe the state of the system.
 It is some characteristic of the system to which
some physically meaningful numbers can be
assigned without knowing the history behind it.
 Properties are some measurable characteristics of
a system when it is in equilibrium with its
surroundings.
 The properties of a system is a state function and
not a path function and it is an exact differential so
that can be written as dT, dP, dV, ds, dh etc.,

THERMODYNAMICS - I
Types of Properties:
 Extensive property
Varies with the mass
mass, energy, enthalpy
 Intensive property
independent of mass
Temperature,
Pressure
density

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Specific property:
 It is the value of an extensive property per unit mass of a
system. (lower case letters as symbols)
eg: specific volume, density (v, , ρ)
 It is a special case of an intensive property.
 Specific properties are most widely used in thermodynamics.
 Specific entropy, specific enthalpy; specific internal energy are
intensive properties.
 Relevant property- temperature, pressure etc., and irrelevant
properties in thermodynamics are color, shape.

THERMODYNAMICS - I
State:
 It is the condition of a system as defined by the
values of all its properties.
 The condition of the system as defined by the
properties of a system is known as the state of the
system.
 It gives a complete description of the system. Any
operation in which one or more properties of a system
change is called a change of state.
The state is described by some observable
macroscopic properties like pressure temperature etc.

THERMODYNAMICS - I
Phase:
 It is a quantity of matter that is homogeneous
throughout in chemical composition and physical
structure.
 When the system is in more than one phase then
they are separated by phase boundaries.
 Phase consisting of more than one phase is
known as heterogenous system
eg. solid, liquid, vapour, gas.

THERMODYNAMICS - I
Equilibrium State (Thermodynamic equilibrium)
 A system is said to be in an state of equilibrium
when there is no change in any property is
observed if the system is isolated from its
surroundings.

 Between the system and surroundings, if there is no
difference in
 Pressure Mechanical equilibrium.
 Temperature Thermal equilibrium
 Concentration of species Chemical equilibrium
If the system satisfies all the above condition, then it is
said to be under thermodynamic equilibrium.
 The properties for a system are defined only under
equilibrium conditions.
THERMODYNAMICS - I

THERMODYNAMICS - I
 Nature has a preferred way of directing changes in
the system as:
 Water flows from a higher to a lower level.
 Electricity flows from a higher to lower potential.
 Heat flows from a higher temperature body to
the a lower temperature body.
 Momentum transfer occurs from a point of
higher pressure to a lower one.
 Mass transfer occurs from higher concentration
to a lower one.

THERMODYNAMICS - I
Quasi-static Processes
A quasi-static process is one in which
the deviation from thermodynamic
equilibrium is infinitesimal and all states
of the system passes during the change
of state are considered as equilibrium
states.

THERMODYNAMICS - I
 Eg -1. Consider a gas, piston cylinder arrangement as shown.
 If we remove the weights slowly one by one the pressure of
the gas will displace the piston gradually upwards, then the
system is said to be undergoing quasi-static process.
 On the other hand if we remove all the weights at once the
piston will be kicked up by the gas pressure at once.

THERMODYNAMICS - I
 When the weights are removed at once it leads to unrestrained
expansion of gas but we don’t consider that the work is done because
it is not in a sustained manner.
 In both cases the systems have undergone a change of state.
 When the weights are removed one by one in small increments, each
state of the system passes through equilibrium state, it means each
state is almost in equilibrium with respect to its earlier state.
 When all such quasi-equilibrium states are joined together we can
trace the path and the process is called as quasi-equilibrium process

THERMODYNAMICS - I
Path and Process
 The succession of states passed through during a
change of state is called the path of the system.
 Series of the state of the system through which
process occurs is known as path of the system.
 A system is said to undergone a process whenever
its properties changes from one equilibrium state to
another equilibrium state.
 The path of succession of states
through which system passes is
called the process.

THERMODYNAMICS - I
 A system may undergo changes in some or all of its
properties.
 Processes in thermodynamics are like streets in a city.
 Due to some specific reasons we allow one of the
properties (pressure, temperature, enthalpy, entropy)
to remain a constant during a particular process.
 If one property remains constant prefix ‘iso’ is used
for that process.
 We can consider as many processes as we can with
different property kept constant one by one.

THERMODYNAMICS - I
Types of process
 Isothermal process - Temperature held constant
 Isobaric process - Pressure held constant
 Isochoric process - Volume held constant
 Isentropic process - Entropy held constant
 Isenthalpic process - Enthalpy held constant
 Isosteric process - Concentration held constant
 Reversible adiabatic process - No heat
addition/removal during the process

 Thermodynamic cycle
 When a system with a given initial state
undergoes number of different changes of state
or processes and finally returns to initial state
is said to undergone a cycle.
 For a cycle all the final properties should have
the same value as that of initial properties.
 Mechanical cycle
 Final and initial properties need not be same
but only processes repeat according to some
sequence.
THERMODYNAMICS - I

THERMODYNAMICS - I
Temperature
It is a property of a system which
determines the degree of hotness or
coldness.
 It is a relative term.
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.

THERMODYNAMICS - I
 Two systems are said to be equal in
temperature, when there is no change in any
properties is observed during their thermal
communication.
 In other words, “when two systems are at the
same temperature they are said to be in thermal
equilibrium with each other.

THERMODYNAMICS - I
 Zeroth law of Thermodynamics:
 It states that when two bodies have equality of
temperature separately with the third body, they
in turn have equality of temperature with each
other.
 When a body A is in thermal equilibrium with
body B and also separately with body C then B
and C will be in thermal equilibrium with each
other.

THERMODYNAMICS - I
 Temperature scales
 In order to measure the relative hotness or
coldness quantitatively temperature scales are
constructed.
 Two scales commonly used for measurement of
temperature are Fahrenheit scale and Celsius
scale.
 The Celsius scale was formerly called the
centigrade scale but is now designated the
Celsius scale.

THERMODYNAMICS - I
 In order to construct the temperature scale- a
reference body is used, and a certain physical
characteristic of this body which changes with
temperature is selected
 The changes in the selected characteristic may
be taken as an indication of change in
temperature.
 The selected characteristic is called the
thermometric property and the reference body
which is used in the determination of
temperature is called the thermometer.

THERMODYNAMICS - I
Standard reference points
 Ice point- Equilibrium temperature of ice with air
saturated with water at a pressure of
101.325kPa which is assigned a value of 00C in
Celsius scale
 Steam Point: Equilibrium temperature of pure
water with its own vapor at a pressure of
101.325kPa which is assigned a value of 1000C
in Celsius scale.
Thermometric materials: Hg, ethyl alcohol for
normal range

THERMODYNAMICS - I
Temperature measurement using different
thermometric properties:
 Mercury in Glass- Length – L
 Thermocouple - Thermal -emf – voltage
 Electrical resistance thermometer-resistance
change
 Constant pressure thermometer- Volume change
 Constant volume thermometer – pressure change

Ch_1_Basic_concept_and_definitions.ppt .

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