23-200-0105A

Basic Mechanical Engineering

Dr. Harikrishnan S
Assistant Professor
Division of Mechanical Engineering
Syllabus
Syllabus…
Mechanical Engineering

• Thermal Engineering
• Manufacturing
• Machine Design
• Industrial Engineering
 Mechanical Engineering
1. Thermodynamics
1. Computational Fluid Dynamics 2. Fluid mechanics and machinery
2. Finite Element Methods 3. Heat power engineering
Thermal
3. Computer Aided Design and
Manufacturing

1. Metallurgy and material

science
Mechanical 1. Mechanics of solids
2. Manufacturing process 2. Design of machine
3. Operations research elements
4. Instrumentation and control Manufacturing Design 3. Kinematics of machines
systems 4. Dynamics of machines
5. Metrology 5. Machine drawing
6. Industrial engineering
Text Books for Thermodynamics

Note: Always refer standard textbooks mentioned in the syllabus for detailed reading
Thermodynamics

• Science of energy transfer and its effect on the physical properties of

substances
• It is based upon observations of common experience which have been
formulated into thermodynamic laws
• Thermodynamics:- Science of energy
• Therme:- Heat
• Dynamics:- Force
• One of them is ‘Law of conservation of energy’
Thermodynamics:- Applications
Thermodynamics:- Applications

Engines Boiling

Radiator in cars Condensation

Electronic cooling Heat Pipe in Realme phone Cooling tower in power plant
Classification of Systems

• System:-Quantity of matter/ a region of space chosen for study

• Surrounding:- Mass or region outside the system

• Boundary:- Real/imaginary surface that separate system from its

surrounding, can be fixed or movable
Moving/Flexible boundary?
Energy interactions

• Heat:- Form of energy that is transferred between two systems (system

with surrounding) by virtue of temperature difference

• Heat is energy in transition, it is recognized only as it crosses the

boundary of a system

• Adiabatic system:- No heat transfer

• Either system is well insulated
• Or System and Surrounding are at same temperature
Energy interactions
• If energy crossing the boundary of a closed system is not heat, then it
must be work

• Work:- Energy transfer associated with a force acting through a

distance

• Eg: Rising piston, rotating shaft etc.

Energy interaction

+ve

-ve

-ve

+ve
Type of system?
Dimensions and Units

• Any physical quantity can be characterized by dimensions.

• The magnitudes assigned to the dimensions are called units.

• Primary/Fundamental dimensions

• Derived dimensions
Derived Quantities
• Velocity

• Acceleration

• Force

• Work

• Pressure
Few Properties
• Density

• Specific volume

• Specific gravity

• Specific weight
Problem

For a SG = 13.6; Calculate

• Density

• Specific volume

• Specific weight
Properties of a system

• Characteristics of a system is known as Properties

• Ex: P, T, V etc.

• Extensive properties:- Value depends on size/extent of size

• Intensive properties:- Independent of size

• How to identify extensive and intensive?

Properties of system
State and Equilibrium
• When a system not undergoing any change, all properties can be
measured and it gives us a set of properties that describes condition or
state of the system

• State:- Property values are fixed

• If one of them change; state will change

• Equilibrium:- state of balance, no unbalanced potential with in the system

• Thermodynamics deals with Equilibrium states

• A system in Equilibrium experience no changes when it is isolated from its

surroundings
Equilibrium

• Equilibrium
• Thermal:- Temperature does not change

• Mechanical:- No unbalanced force

• Chemical:- Chemical composition does not change

• Phase:- Mass of each phase does not change

Thermodynamic Process
• If any one or more properties of the system undergo a change due to
energy or mass transfer we say that the system has undergone a change
of state
• The successive change of state of the system due to energy or mass
transfer defined by definite path is called a process.
• The curve joining the successive state represents the process path
• If a system undergoes two or more processes and returns to its original
state after conclusion of processes, the system is said to have undergone
a cycle
• Process – change from one equilibrium state to another
Temperature and Zeroth Law of TD

• Temperature: – is associated with ability to distinguish hot from cold

• Thermal Equilibrium:- Same temperature

• “If two bodies are in thermal equilibrium with a third body, they are also in
thermal equilibrium with each other”
Temperature and Zeroth Law of TD
• Serves as basis for validity of temperature measurement

• Temperature scales

• All of them based on Ice point and Steam point

• Ice point:- temperature at which liquid and solid water are in equilibrium under
atmospheric pressure

• Steam point:- mixture of liquid water and water vapor (with no air) in equilibrium
at 1 atm pressure
Temperature Scales

• Kelvin

• Degree Celsius

• Fahrenheit
Problem

Calculate temperature values in other scales

• Body Temperature = 98.6oF
• oC=
• K=

• Body Temperature (during fever) = 100.4°F

• oC=
• K=
Energy Interactions

• Thermodynamics:- Mainly studies energy interactions and the associated

property changes of the system

• In TD:- No information about absolute value of energy, only deals with

change in total energy

• Ex: Falling rock example, only height difference not absolute height
Energy Interactions
• Total Energy = Microscopic + Macroscopic

• Macroscopic:- Form of energy system possesses as a whole w.r.t. some

outside reference frame
Ex: KE, PE etc.

• Microscopic:- Related to molecular structure of a system and degree of

molecular activity, independent of outside reference frames

• Sum of all microscopic forms of energy is called internal energy (U)

Energy Interactions

Macroscopic Energy

• Kinetic Energy:- Energy that a system possesses as a result of its motion

relative to some reference frame, when all parts of a system move with
same velocity, KE is expressed as,

• Potential Energy:- Energy of a system possesses as a result of its

elevation in a gravitational field
Energy Interactions
• Other forms of Energy
• Magnetic
• Electric
• Surface tension etc.

• Total Energy:

• Open systems (Control Volume):- Energy transfer due to fluid flow also
exist
First Law of Thermodynamics
• Conservation of energy principle

• i.e. every bit of energy should be accounted during a process

• Based on experimental observations of Joules

• Basis for studying the relationship among the various forms of energy and energy
interactions

• Consequence of First law:- definition of a new property internal energy

First Law of Thermodynamics

• Change in the energy of a system during a process is simply equal to the

net energy transfer to/from the system

• Energy Balance
First Law of Thermodynamics

• Energy change of a system

First Law of Thermodynamics

• Mechanism of energy transfer

▪ Heat Transfer
▪ Work Transfer
▪ Mass Transfer
First Law of Thermodynamics:- For a cycle
Need of 2nd Law of Thermodynamics
2nd Law of Thermodynamics
• Process must satisfy 1st law, but satisfying 1st law alone does not ensure
that the process will actually takes place

• Eg: Hot coffee in cold room

• Process occurs in certain directions, 1st law places no restrictions on the

direction of a process, but satisfying the first law does not ensure that the
process can actually occurs

• 2nd Law of TD:- can help us to know whether process can occur or not

• A process cannot occur unless it satisfies both 1st and 2nd Law of TD
2nd Law of Thermodynamics
• Process should follow 2nd Law, violation of 2nd Law can easily detected
with the help of a property called ‘Entropy’

• 2nd Law also asserts that Energy has quality as well as quantity

• 1st Law:- Quantity of Energy

• 2nd Law:- Quality of Energy

• 2nd Law of TD is also used in determining the theoretical limit for the
performance of commonly used engineering systems such as heat
engines, refrigerators etc.
2nd Law of Thermodynamics

• 1st Law is concerned with quantity of energy and transformation of energy

from one form to another with no regard to its quality

• Preserving quality of energy is major concern for engineers, and second

law provides necessary means to determine the quality as well as degree
of degradation of energy

• In other words, more of high temperature energy can be converted to

work, and thus it has higher quality than the same amount of energy at
lower temperature
Thermal Energy Reservoirs
• A hypothetical body with a relatively large thermal energy capacity (mass x
specific heat) that can supply/absorb finite amounts of heat without
undergoing any change in temperature

• Eg: Ocean, lakes, river, atmospheric air etc.

• Source:- A reservoir that supplies energy in the form of heat

• Sink:- A reservoir that absorbs energy in the form of heat

Heat Engines
• Work can be easily converted to other forms of energy, but converting
other forms of energy to work is not that easy

• Heat Engines:- Device which convert heat to work

• Characteristics:
• They receive heat from higher temperature source
• They convert part of this heat to work
• They reject the remaining waste heat to low-temperature sink
• They operate in a cycle

• Eg: Steam engines

Thermal Efficiency
• Fraction of heat input that is converted to net work output is a measure of the
performance of a heat engine

• How efficiently a heat engine converts the heat that it receives to work

• Petrol Engine = 25 %
• Diesel engine = 40 %
• Gas Turbine = 40 %
• Steam power plant = 60 %

• Even with most efficient heat engines available today, almost one half of the
energy supplied ends up in the rivers, lakes, or atmosphere
Thermal Efficiency
Problem
2nd Law of Thermodynamics:- Kelvin-Planck
Statement

• No heat engine can have a thermal efficiency of

100 percent, or as for a power plant to operate,
the working fluid must exchange heat with the
environment as well as the furnace

• Note that the impossibility of having a 100

percent efficient heat engine is not due to friction
or other dissipative effects.
Refrigerator and Heat Pump

• Heat:- high temperature to low temperature

• Transfer of heat from low temperature to high

temperature:- device is known as Refrigerator

• Device that transfers heat from a low-temperature medium

to a high-temperature one is the heat pump:- Heat pump

• Refrigerators and heat pumps operate on the same cycle

but differ in their objectives.
Heat Pump
Coefficient of Performance

• The objective of a refrigerator is to maintain the

refrigerated space at a low temperature by removing
heat from it. Discharging this heat to a higher-
temperature medium is merely a necessary part of the
operation, not the purpose.

• The efficiency of a refrigerator/heat pump is

expressed in terms of the coefficient of performance
(COP)
2nd Law of Thermodynamics:- Clausius Statement

• It simply states that a refrigerator cannot operate

unless its compressor is driven by an external power
source, such as an electric motor

• Both the Kelvin–Planck and the Clausius statements of

the second law are negative statements, and a
negative statement cannot be proved
2nd Law of Thermodynamics
Kelvin-Planck Statement Clausius Statement
Internal Combustion Engines
Gas Power Cycle
• Working fluid:- Gas/Air

• Examples:- Otto cycle, Diesel cycle, Gas Turbine cycle etc.

• Energy is provided by burning fuel within the boundary

• Air + Fuel => Combustion products

• But air is predominantly Nitrogen, it hardly undergoes any chemical reaction

during combustion, working fluid closely resembles air
Air-Standard Cycle
• Approximations used for analysis of Gas Power Cycle (Air-standard cycle)

• Working fluid is Air, which continuously circulates in a closed loop and

always behaves like an ideal gas

• All processes are internally reversible

• Combustion process is replaced by heat addition process from an external

source

• Exhaust process is replaced by heat rejection process

Overview of Reciprocating Engine

• Top Dead Center (TDC):- Smallest volume

• Bottom Dead Center (BDC):- Largest volume
• Bore
• Stroke
• Inlet and outlet valves
• Clearance volume:- Min vol
Overview of Reciprocating Engine
• Displacement volume:- volume displaced by piston as it
moves from TDC to BDC

• Compression Ratio = Ratio of max. volume to min

volume

• Reciprocating Engines (based on the way combustion

initiated)
• Spark Ignition Engine
• Compression Ignition Engine
IC Engine components
Otto Cycle:- Ideal cycle for Spark Ignition
Engines
Diesel Cycle
• Working very similar to SI Engine, only
difference is: method of initiating combustion

• SI Engine:- Air-Fuel mixture is compressed

below autoignition temperature, and
combustion is initiated with the help of spark
plug

• CI Engine:- Air is compressed to temp above

auto ignition temp, and fuel is injected into
compressed air

• Diesel Engine compression ratio:- 14-24

4 Stroke Vs 2 Stroke Engine

4 Stroke SI Engine 2 Stroke SI Engine

2 Stroke Vs 4 Stroke
2Stroke 4Stroke
• One revolution of the crankshaft • Two revolutions of the
during one power stroke. crankshaft during one power
• Uses a port for fuel’s outlet and stroke
inlet • Uses valves for fuel’s outlet and
• Lesser thermal efficiency inlet
• Large ratio in terms of power to • Higher thermal efficiency
weights • Lesser ratio in terms of power to
• Requires more lubricating oil as weight
some oil burns with the fuel • Requires less lubricating oil
• More wear and tear due to poor • Less wear and tear
lubrication • Engines are heavier because
• Engines are lighter and noisy their flywheel is heavy and less
noisy
 Two stroke Petrol Engine

How 2 Stroke Engine Works - YouTube

 Two stroke Diesel Engine

2 Stroke Diesel Engine Animation - YouTube

Multi Cylinder Engines
Applications of IC Engines
• Single cylinder • 2 Cylinder
Examples
• 3 Cylinders • 4 Cylinders
Examples
• ≥ 6 Cylinder
Other applications
 Boilers and Turbines

Steam Turbine
Boiler
Power Plants

• A power plant is an industrial facility used to generate electric

power with the help of one or more generators which converts
different energy sources into electric power.
• Electricity is a secondary energy source - obtained from the
conversion of other primary sources of energy :-
coal, natural gas, nuclear, solar, hydraulic or wind energy.
• The power plant is the location in which the energy conversions
take place.
Conventional Power Plants

• Fossil fuel power plants: Generates electric power by burning fossil

fuels like coal, natural gas or diesel.
• Nuclear power plants: Controlled nuclear reaction is maintained to
generate electricity.
• Hydroelectric power plants: Electricity is produced by building dams
on suitable rivers.
Non-Conventional Power Plants

• Wind power plants: The kinetic energy of wind is used to create

power.
• Solar power plants: Generates power by collecting solar radiation.
• Geothermal power plants: Uses the natural heat found in the deep
levels of the earth to generate electricity.
• Biomass power plants: Natural organic matter is burnt to
produce electricity.
Boilers / Steam generators

• Boiler/Steam generators:- The equipment used for producing steam

• Thermal energy released during combustion of fuel is transferred to water
and this converts water into steam at the desired temperature and
pressure
• Applications:
• Power Generation
• Process industries (chemical plant, food processing etc.)
• Heating the residential and commercial buildings in cold weather
countries
Classification of boilers
Relative position of Hot gases and Water
Water Tube Boilers Fire Tube Boilers
• The water passes through the tubes and • The hot gases pass through the tubes that
the hot gases produced by combustion of are surrounded by water.
fuel, flow outside
Classification of boilers
Method of firing
Internally fired Externally fired
• The furnace is provided inside the boiler • The furnace is provided outside/ under the
shell and is completely surrounded by boiler
water cooled surfaces
Examples: Chochran Boiler

COCHRAN BOILER
Example: Locomotive Boiler
 Turbines
Machines to extract fluid power from flowing fluids

Steam Water Wind Gas

Turbine Turbines Turbines Turbines
Gas Turbines
Steam Water Wind Gas
Turbine Turbines Turbines Turbines

•High Pressure, High Temperature gas

Aircraft Engines
•Generated inside the engine
Power Generation
•Expands through a specially designed TURBINE

Applications:
• Locomotion eg; ships,
aircrafts etc.
• Power generation
Working of Gas Turbine

• Intake:- Slow down incoming air

• Compressor:- Dynamically Compress air
• Combustor:- Heat addition through chemical reaction
• Turbine:- Run the compressor, Generation of thrust power/shaft power
Advantages and Disadvantages

Advantages: Disadvantages
• Great power-to-weight ratio compared to • Expensive:
reciprocating engines. • high speeds and high operating
• Smaller than their reciprocating temperatures
counterparts of the same power. • designing and manufacturing gas
turbines is a tough problem from both
• Lower emission levels
the engineering and materials
standpoint
• Tend to use more fuel when they are idling
• They prefer a constant rather than a
fluctuating load

That makes gas turbines great for things like transcontinental jet aircraft and power plants, but
explains why we don't have one under the hood of our car.
Steam Turbines

High Pressure
High KE Steam System

Shaft power to generator

Dead must be properly recycled Dead Steam

Steam Turbines

Components
1. Energy converter: Nozzle/stationary vanes

2. Energy exchanger: Rotor or moving blades

Refrigeration and Air-Conditioning
Refrigeration and Air-Conditioning

• Refrigeration:- Transfer of heat from lower temp region to higher

temperature region
• Heat always flow from higher temp to lower temp
• Working fluid Refrigerant
• Refrigerator:- Maintain refrigerated space at a low temperature by
removing heat from it. Discharging this heat to a higher temp medium
is merely a necessary part of the operation, not purpose
• Heat Pump:- To maintain space at a high temp. This is accomplished
by absorbing heat from a low temperature source, and supplying this
heat to a warmer medium
Refrigeration and Air-Conditioning

• Air-conditioning:- Defined as the treatment of indoor air in order to

control certain conditions required for human comfort.
• The desirable conditions may be
• Temperature
• Humidity
• Dust particle level
• Odor level, and air motion
• Heat always flow from higher temp to lower temp
Applications
Vapor Compression Refrigeration System (VCRS)

Capillary tube/Throttle
valve

Condenser
Compressor
Vapor Compression Refrigeration System (VCRS)
Unit of Refrigeration Capacity

• Ton of Refrigeration
• Rate of heat removal from refrigerated space is often expressed in
terms of ‘Ton of refrigeration’
• “Capacity of refrigeration system that can freeze 1 ton (2000 lb) of
liquid water at 0oC into ice at 0oC in 24 Hours’
• Calculations
• 1Ton = 907kg, Latent heat of water/ice = 333.5 kJ/kg
• Heat extracted?
• In kW
• In kJ/Hr
1 TR = 211kJ/Hr = 3.5kW
Refrigerant

Examples:
• Chlorofluorocarbons (CFCs)
• Ammonia
• Hydrocarbons (propane, ethane, ethylene,
etc.)
• carbon dioxide
• Air (in the air-conditioning of aircraft)
• Water (in applications above the freezing
point)
Properties of refrigerant

• Critical temperature and pressure

• Specific heat
• High latent heat of vaporization
• Low freezing point
• Chemical stability and inertness
• Less toxic
• Flammability
Air-Conditioning
Psychrometry

• Psychrometry is an engineering science that deals with the behaviour

of moist air(dry air + water vapour mixture)
• The amount of water vapour in air plays important role in both
comfort and industrial air conditioning
Terms in Psychrometry
• Dry air: Air contains no water vapour
• Moist air: Mixture Of dry air and water vapour
• Saturated air: Air Which contains maximum amount of water vapour
which air can hold at a given temperature and pressure
• Dry bulb temperature: Temperature of air measured by ordinary
thermometer
• Wet bulb temperature: Temperature Recorded by a thermometer,
when its bulb is covered by a wet cloth
• Specific humidity: Ratio of the mass of water vapour to the mass of
dry air
Terms in Psychrometry

• Specific humidity: Ratio of the mass of water vapour to the mass of

dry air
• Relative humidity: Ratio of mass of water vapour in a given volume of
moist air at a given temperature to the mass of water vapour
contained in the same volume of moist air at the same temperature,
when the air is saturated
Psychrometric Processes
Human Comfort Conditions

• Temperature: 22oC - 27oC

• Relative Humidity: 55-65%
• Air Velocity: 0.2-0.5 m/s
Window AC vs Split AC

Window AC Split AC
Window AC vs Split AC

Window AC Split AC
• Single unit:- includes all • Two units:- indoor unit (air
components handling unit) and outdoor unit
• Usually mounted on window • Mounted on walls
frames • Less noise as compared to
• Easy to install window AC
• More noise compared to split
AC
Thank You