EME - Module - 1.pptx

Prepared by:
Dr. Anand A
Assistant Professor,
Department of Mechanical Engineering,
Rajarajeswari College of Engineering,
Bengaluru – 74.
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Module 1:
Introduction to Mechanical Engineering (Overview only): Role of Mechanical
Engineering in Industries and Society- Emerging Trends and Technologies in different sectors
such as Energy, Manufacturing, Automotive, Aerospace, and Marine sectors and contribute to
the GDP.
Steam Formation and Application: Formation of steam and thermodynamic properties of
steam (Simple Problems using Steam Tables), Applications of steam in industries namely, Sugar
industry, Dairy industry, Paper industry, Food processing industry for Heating/Sterilization,
Propulsion/Drive, Motive, Atomization, Cleaning, Moisturization, Humidification.
Energy Sources and Power Plants: Review of energy sources; Construction and working of
Hydel power plant, Thermal power plant, Nuclear power plant, Solar power plant, Tidal power
plant, Wind power plant.
Introduction to basics of Hydraulic turbines and pumps: Principle and Operation of
Hydraulic turbines, namely, Pelton Wheel, Francis Turbine and Kaplan Turbine. Introduction to
working of Centrifugal Pump.

Energy Sources and Power Plants:
Preamble:
The term “Energy “ is defined as “the ability or capacity of a system to do
work”. Energy exists in everybody whether they are human beings or animals or
non living things.
Energy can have many forms: kinetic, potential, chemical, light, sound, wind,
gravitational, elastic, electromagnetic or nuclear.
According to the law of conservation of energy, any form of energy can be
converted into another form and the total energy will remain the same.
Energy sources are available either on the earth surface or below the earth
surface which are classified as Renewable Energy source ( Non – Conventional)
and Non - Renewable Energy source (Conventional).
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Renewable Energy& Non-renewable Energy
 They are in-exhaustible (in-
finite).
 Freely available in nature and
eco-friendly.
 They are continuously restored
by nature after utilization.
 Initial cost for utilizing these
resources is high, but cost of
maintenance is low.
 Eg: Solar, Wind, Bio-mass, tidal,
ocean thermal, geo thermal etc.
 They are exhaustible (finite).
 Not freely available nor eco
friendly (emit higher carbon).
 These sources once used cannot be
recovered any more.
 Both initial cost and maintenance
costs are high.
 Eg: fossil fuels, natural gas, oil and
coal, nuclear fuels etc.
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Hydro Electric Power Plant
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Hydro Electric Power Plant

PRINCIPLE :Hydropower plants capture the energy of falling water to generate
electricity. A turbine converts the kinetic energy of falling water into
mechanical energy. Then a generator converts the mechanical energy from
the turbine into electrical energy.
Parts of a Hydroelectric Plant:
Most conventional hydroelectric plants include four major components.
Dam:
 The dam is made on a river to collect water. Whenever it rains, the water
is collected into the dam so it serves as a water reservoir. The potential
energy for further work is generated by the water level difference
between the dams and the turbines because the water level in the dams is
very high. Dams also control the water flow through penstocks.
Intake:
 Gates on the dam open and gravity pulls the water through the penstock,
a pipeline that leads to the turbine. Water builds up pressure as it flows
through this pipe.
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Dam:
Intake:
through this pipe.
Dam:
Intake:
through this pipe.
Dam:
Intake:
through this pipe.

Turbines:
 The next step is to convert this kinetic energy of water into mechanical energy.
The water flows from a height throw the penstocks which are the channeled
vessels to the turbines which have blades. The falling water has enough kinetic
energy that when they strike hard with the blades of the turbines, they start
spinning which means that the kinetic energy is converted into mechanical
energy. The turbines resemble a lot with the windmills in which wind energy is
used instead of water.
Generators:
 The shafts of the turbines convert the mechanical energy into electric energy.
Basically, the generators work on the principle of magnets which is that when
you pass a magnet near a conductor, electric current flows through it.
Transformer :
 The transformer inside the powerhouse takes the AC and converts it to higher-
voltage current. The electricity via power lines is transferred to substation which
provides it to the consumers.
Outflow:
 Used water is carried through pipelines, called tailraces, and re-enters the river
downstream.
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Thermal power plant
Thermal Power Plants also called Thermal Power Generation Plant or Thermal Power.
Station.
Working Principle of Thermal Power Plants
Thermal power station’s working principle is “Heat released by burning fuel which produces
(working fluid) (steam) from water. Generated steam runs the turbine coupled to
a generator which produces electrical energy in Thermal Power Plants.

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Typical Layout of a Thermal Power Plant

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Major parts of a Thermal Power Plant
1. Coal hopper with Pulverizer
2. Boiler [Heat Exchanger]
 Superheater [The superheated high-pressure steam 540 °C is fed to the steam turbine]
 Economizer [Pre-heat the water fed to boiler]
 Air pre-heater [Pre-heat the air fed to combustion chamber]
3. Steam turbine
4. Condenser and Cooling tower [Heat Exchanger]
5. Feed water pump
6. Alternator/Generator

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General Layout of a Thermal power plant

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Arrangement of Furnace, Boiler, Turbine , Generator, Condenser
and Feed pump.

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Dry superheated steam used in driving the steam
Turbines

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Turbine is coupled to Generator (usually three-phase alternator), which
generates electrical energy.

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Exhaust steam from the turbine is allowed to condense into the water in steam
condenser.

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In the condenser, the steam is condensed by cooling water. Cooling water recycles
through the cooling tower.

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Working Principle of a Thermal Plant:
In a steam boiler, the water is heated up by burning the fuel with the air in the furnace, and
the function of the boiler is to give dry superheated steam at the required temperature.
The steam so produced is used in driving the steam Turbines. This turbine is coupled to
synchronous generator (usually three-phase synchronous alternator), which converts
mechanical energy and generates electrical energy.
The exhaust steam from the turbine is allowed to condense into water in steam condenser. The
principal advantages of the condensing operation are the increased amount of energy extracted
per kg of steam and thereby increasing efficiency, and the condensate which is fed into the
boiler again reduces the amount of fresh feed water.
The condensate along with some fresh makeup feed water is again fed into the boiler by a
pump (called the boiler feed pump). In the condenser, the steam is condensed by cooling
water. Cooling water recycles through the cooling tower.
The ambient air is allowed to enter the boiler after dust filtration. Also, the flue gas comes out
of the boiler and gets exhausted into the atmosphere through stacks.

Nuclear Power Plant
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Figure: Principle of Fission Chain Reaction
 Nuclear fission is a nuclear reaction or a decay process (called spontaneous fission) in which the heavy
nucleus splits into smaller parts (lighter nuclei). The fission process often produces free neutrons, photons (in the
form of gamma rays) and releases a large amount of energy.
 1 gram of any fissile material yields about one megawatt (MW) of heat energy.
 The amount of reactions must be changed (using the control rods) to raise or lower the power so that the number
of neutrons present (hence the power generation rate) is either reduced or increased.

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Nuclear Power Plant

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Figure: Fuel rod assembly
Figure: The Nuclear reactor core shown
in a) contains the fuel rods, b) control
rods into the nuclear core between the
fuel rods.

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Figure: The containment structure of a Nuclear Power
Plant. [A steel shell that is 3–20-centimeters thick,
main shield of 1–3 meters of high-density concrete].

Working Principle of Nuclear Power Plant
• In a nuclear power plant, nuclear fuel is used such as Uranium U235. The difference
between a thermal power plant and nuclear power plant is fuel. Both use their
fuel to convert water into steam in Boilers (Steam Generator). This steam is used to run
the steam turbine to produce electricity. The thermal power plant uses oil, coal, or
gas while nuclear plant uses nuclear fuel.
• When the nucleus of an atom of Uranium is split, the two or three neutrons released in
this reaction these neutrons hit other atoms and split them in turn. More energy is
released each time another atom splits. This phenomenon is called a chain reaction.
 One kg of uranium is equivalent to 4500 metric tons of high grade coal.
A nuclear power station has mainly four components.
 Nuclear reactor [Reactor vessel, Fuel Rods, Control Rods, Moderator, steam
generator]
 Steam turbine – Heat energy to Mechanical energy
 Generator/Alternator – Mechanical energy to Electrical energy
 Heat exchangers - Condenser & Cooling tower
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 The power plant that is used to warm the water to generate steam, then this steam can be
used for rotating huge turbines for generating electricity. These plants use the heat to
warm the water which is generated by nuclear fission. So the atoms in the nuclear fission
will split into different smaller atoms for generating energy.
Nuclear Reactor:
 A nuclear reactor is a cylindrical shaped stunt pressure vessel. The fuel rods are made of nuclear
fuel i.e. Uranium moderates, which is generally made of graphite cover the fuel rods. The
moderates slow down the neutrons before collision with uranium nuclei. The controls rods are
made of cadmium because cadmium is a strong absorber of neutrons.
 In nuclear reactor, Uranium 235 is subjected to nuclear fission. In nuclear fission, the nuclei of
nuclear fuel, such as U235 are bombarded by slow flow of neutrons. Due to this bombarding, the
nuclei of Uranium is broken, which causes release of huge heat energy and during breaking of
nuclei, number of neutrons are also emitted. The heat released during nuclear reaction, are
carried to the heat exchanger by means of coolant consist of sodium metal.
Steam Boiler/generator [Heat Exchanger]:
 In heat exchanger, the heat carried by coolant [sodium metal], is dissipated in water and water is
converted to high pressure steam here. After releasing heat in water the sodium metal coolant
[it has excellent thermal conductivity/heat transfer property] comes back to the reactor
by means of coolant circulating pump.
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Generator & Turbine:
Once the steam is generated, then it travels with high pressures to speed up the turbine. The
rotating of the turbines can be used to rotate an electric generator for generating electricity
that is transmitted to the electrical grid.
Condenser & Cooling Towers:
After that the steam is exhausted to the condenser. This condensed steam is fed to the heat
exchanger through feed water pump.
Cooling towers are specialized heat exchanging towers which aid in reducing
the temperature of circulating hot water, which gets heated up during the industrial process. In
this process, the water stream from an industrial process is pumped into a cooling tower
through a water inlet valve and meets air in a cooling tower. As soon as the heat is extracted,
the water begins to evaporate in small volumes thus plummeting the water’s temperature,
sending out the cooled water to continue with the industrial process.
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Introduction to Solar Energy
 Solar energy is the heat energy(radiant energy) radiated to the earth, is emitted from
the Sun as a result of fusion reaction.
 Solar energy received in the form of radiation(electro magnetic waves) can be
converted directly or indirectly into other forms of energy, such as heat and
electricity.
 Solar energy has the greatest potential of all the sources of renewable energy available
today.
Applications of Solar Energy:
 Water heating
 Heating of buildings
 Thermal electric conversion (Solar Pond)
 Photo voltaic electric conversion
 Cooking
 Desalination of salt water
 Used in vehicles
 For irrigation to run pumps
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Solar Energy harvesting:
Solar energy can be utilized directly in two ways,
 By collecting the radiant heat and using it in a “thermal
system.”
 By collecting and converting it directly to “electrical energy
using a photovoltaic system.”
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Liquid flat plate collector (Solar thermal system)
Figure : Flat-plate collector.
PRINCIPLE: The purpose of a solar thermal
collector is to absorb the radiant energy of the
sun and to transfer the resultant heat to a fluid
of application.
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Major Components of a flat plate collector system
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Absorber Plate & Channels or Tubes:
 Is a metal surface, mostly black in color. It absorbs and converts radiation into thermal energy and then,
by convection and conduction it is transferred to the circulating cold fluid.
The Transparent Cover:
 Is the upper part of the collector covering the absorber plate. It is made from transparent glass to permit
penetration of solar beams. It therefore protects the absorber from environmental damages and
decreases thermal loss.
Thermal Insulation:
 Consists of a material with very low thermal conductivity. It is installed in the bottom and around the
sides of the collector, in order to minimize heat loss. Insulation materials usually used are polyurethane,
glasswool and rockwool.
The Heat Transfer Medium:
 Flowing through the collector to transfer the heat from the absorber to the utilization system. Can be
either air or a liquid, usually water.
The Casing of the Collector:
 The frame or shell is the most important part because it houses all other collector components. It is
constructed usually from aluminum or plastic material having high resistivity to all weather conditions,
and to solar radiation intensity.
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Evacuated vacuum tube solar water heater

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Components of Evacuated vacuum tube solar water heater

Solar Pond(Thermal system)
A pool of very salty water in which convection is inhibited, allowing accumulation of energy
from solar radiation in the lower layers.
WORKING PRINCIPLE:
• The solar pond works on a very simple principle. It is well-known that water or air is heated they
become lighter and rise upward. Similarly, in an ordinary pond, the sun’s rays heat the water and the
heated water from within the pond rises and reaches the top but loses the heat into the
atmosphere. The net result is that the pond water remains at the atmospheric temperature. The
solar pond restricts this tendency by dissolving salt in the bottom layer of the pond making it
too heavy to rise.
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Fig: Schematic of a Photovoltaic Cell
PRINCIPLE: Solar cells convert light energy into electrical energy through a
direct process known as the photovoltaic effect.
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Fig: Schematic of a Photovoltaic Cell - Contd..
It is interesting to see what happens to the electrons and holes once these two pieces of silicon are joined.
Because of the random thermal motion of the free electrons, electrons from the n-type side start to diffuse into
the p-type side. Similarly, Holes in the p-type side, therefore, start to diffuse across into the n-type side.
As the electrons in the n-type material diffuse across towards the p-type side, they leave behind positively
charged ions, near the interface between the n and p regions. Similarly, the positive holes in the p-type region
diffuse towards the n-type side and leave behind negatively charged ions.

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Depletion Region:
Within the depletion region, there are very few mobile electrons and holes. It is "depleted" of mobile
charges, leaving only the fixed charges associated with the dopant atoms. As a result, the depletion region
is highly resistive and now behaves as if it were pure crystalline silicon: as a nearly perfect insulator.
These fixed ions set up an electric field right at the junction between the n-type and p-type material. This
"built-in" electric field results from the positively charged ions in the n-type material to the negatively
charged ions in the p-type material. Thus, the “built-in” electric field causes some of the electrons and holes
to flow in the opposite direction to the flow caused by diffusion as shown in the Figure below.

Working Principle of a Solar Cell (photovoltaic cells)
 Solar cells convert light energy into electrical energy through a direct process known as the
photovoltaic effect.
 which occurs when light falling on a two-layer semiconductor material produces a potential difference,
or voltage, between the two layers. The voltage produced in the cell is capable of driving a current
through an external electrical circuit that can be utilized to power electrical devices.
 In a typical photovoltaic cell, two layers of doped silicon semiconductor are tightly bonded together.
 One layer is modified to have excess free electrons (termed an n-layer), while the other layer is
treated to have an excess of electron holes (a p-layer).
 When the two dissimilar semiconductor layers are joined at a common boundary, the free electrons in
the n-layer cross into the p-layer in an attempt to fill the electron holes.
 The combining of electrons and holes at the p-n junction creates a barrier that makes it increasingly
difficult for additional electrons to cross.
 As the electrical imbalance reaches an equilibrium condition, a fixed electric field results across the
boundary separating the two sides.
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 When light of an appropriate wavelength (and energy) strikes the layered cell and is absorbed,
electrons are freed to travel randomly.
 Electrons close to the boundary (the p-n junction) can be swept across the junction by the fixed field.
Because the electrons can easily cross the boundary, but cannot return in the other direction (against
the field gradient), a charge imbalance results between the two semiconductor regions.
 Electrons being swept into the n-layer by the localized effects of the fixed field have a natural tendency
to leave the layer in order to correct the charge imbalance.
 By providing an external circuit by which the electrons can return to the other layer, a current flow is
produced that will continue as long as light strikes the solar cell.
 In the construction of a photovoltaic cell, metal contact layers are applied to the outer faces of the two
semiconductor layers, and provide a path to the external circuit that connects the two layers.
 The final result is production of electrical power derived directly from the energy of light.
 The amount of energy produced by the cell is wavelength-dependent with longer wavelengths
generating less electricity than shorter wavelengths.
Working Principle of a Solar Cell (photovoltaic cells) Contd…
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PRINCIPLE : Kinetic energy present in
wind is converted into electrical
energy by a wind turbine.
NOTE: Wind Turbine’s working
principle is exactly opposite to
the working of a ceiling/table
fan.
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Fig: Arrangement inside the Nacelle of a wind
Turbine
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Major Parts of Wind Turbine:
Tower of Wind Turbine:
 Tower is very crucial part of wind turbine that supports all the other parts. It is not only
support the parts but raise the wind turbine so that its blades safely clear the ground
and so it can reach the stronger winds at higher elevations. The height of tower
depends upon the power capacity of wind turbines. Larger turbines usually mounted on
tower ranging from 40 meter to 100 meter.
Nacelle of Wind Turbine:
 Nacelle is big box that sits on the tower and house all the components in a wind
turbine. It houses Power Converter, Shaft, Gearbox, Generator, Turbine controller,
Cables, Yaw drive.
Rotor Blades of Wind turbine:
 Blades are the mechanical part of wind turbine that converts wind kinetic energy into
mechanical energy. When the wind forces the blades to move, it transfers some of its
energy to the shaft. Blades are shaped like airplane wings blades can be as long as 150
feet.
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Shaft of Wind Turbine:
 The shaft is connected to the rotor. When the rotor spins, the shaft spins as well. In
this way, the rotor transfers its mechanical, rotational energy to shaft which enters to
an electrical generator on the other end.
Gearbox:
 The rotor turns the shaft at low speed ex. 20 rpm but for generator to generate
electricity it needs higher speed. Gearbox increases the speed to much higher value
required by most generator to produce electricity.
 For example, if Gearbox ratio is 1:80 and if rotor speed is 15 rpm then
gearbox will increase the speed to 15 × 80 = 1200 rpm that is given to
generator shaft.
Generator:
 Generator is electrical device that converts mechanical energy received from shaft into
electrical energy. It works on electromagnetic induction to produce electrical voltage
or electrical current. A simple generator consists of magnets and a conductor. The
conductor is typically a coiled wire. Inside the generator shaft connects to an
assembly of permanent magnets that surrounded by magnets and one of those parts
is rotating relative to the other, it induce the voltage in the conductor.When the rotor
spins to the shaft, the shaft spins the assembly of magnets and generate voltage in
the coil of wire.
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Anemometer:
 It measures the wind speed and passes the speed information to PLC to control the
turbine power.
Wind Vane:
 It senses the direction of wind and passes the direction to PLC then PLC faces the
blades in such a way that it cuts the maximum wind.
Pitch Drive:
 Pitch drive motors control the angle of blades whenever wind changes it rotates the
angle of blades to cut the maximum wind, which is called pitching of blades.
Yaw Drive:
 Blades and other components in wind turbine is housed in Nacelle , whenever any
change in wind direction is there Nacelle has to move in the direction of wind to extract
the maximum energy from wind. For this purpose yaw drive motor are used to rotate
the nacelle .It is controlled by PLC that uses the wind vane information to sense the
wind direction.
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Why Turbine Structures Are So Big?
 Wind is more prevalent at higher elevations [due to drag and obstructions, wind gets slower
the closer it gets to the ground].
 Larger rotor diameters allow wind turbines to sweep more area, capture more wind, and
produce more electricity.
 Longer blades capture more wind power even with less wind.

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Figure : Used wind turbine blades are filling the land.

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Figure : Used wind turbine blades are filling the land.

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Tidal power plant
Principle: Tidal energy is a form of
hydropower that works by
harnessing the kinetic energy
created from the rise and fall of
ocean tides and currents, also
called tidal flows, and turns it into
usable electricity.
The main advantage of tide over
wind: it is that because water is more
than 800 times denser than air, tidal
turbines do not need enormous rotor
diameters to yield a lot of power.

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Figure: Tidal Power Plant

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Working Principle of Tidal Power Plant
Principle of Tidal power generation:
Tide or wave is periodic rise and fall of water level of the sea. Tides
occur due to the attraction of sea water by the Sun & Moon. It is a form of
hydropower that converts the energy of tides into useful form of
power – mainly electricity. Tidal power plants are renewable
energy sources.
Working of Tidal power generation:
The arrangement of this system is shown in image. The ocean tides rise and
fall and water can be stored during the rise period and it can be discharged
during fall. A dam is constructed separating the tidal basin from the sea and
a difference in water level is obtained between the basin and sea.

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High Tide Power Generation
During high tide period, water flows from the sea into the tidal basin through the
water turbine. The height of tide is above the tidal basin. Hence the turbine unit
operates and generates power, as it is directly coupled to a generator.
Low tide Power Generation
The generation of power stops only when sea level and the tidal basin level are
equal. For the generation of power economically using this source of energy requires
some minimum tide height and suitable site. During low tide period, water flows from
tidal basin to sea, as the water level in the basin is more than that of the tide in the
sea. During this period also, the flowing water rotates the turbine and generates
power.

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Introduction to basics of Hydraulic turbines and pumps:
What is a Turbine?
 A turbine is a “prime mover or a fluid
machine or a rotary engine”, for producing
continuous power in which a wheel or rotor,
typically fitted with vanes, is made to revolve
by a fast-moving flow of water, steam, gas, air,
or other fluid to produce “mechanical
energy.”
 The moving fluid “acts on the
blade(Impulse force) or the blade reacts
to the fluid flow(Reaction force)” causing
the blades to turn mounted on a shaft, which
in turn rotate the shaft. The energy produced
from the shaft rotation is collected by a
generator which converts the motion to
“electrical energy using a magnetic field.”
 “Claude Burdin” invented this device.
Fig 1: moving fluid “acts on the
blade(Impulse force).
Fig 2: the blade reacts to the fluid
flow(Reaction force)”

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Principle of Impulse and Reaction

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Introduction to Water Turbine
 It is an hydraulic prime mover, which converts the energy of an elevated water supply
(hydraulic energy) into mechanical energy. This mechanical energy is used in running
an electric generator which is directly coupled to the shaft of the turbine. Thus the mechanical
energy is converted to electrical energy. The electric power which is obtained from the
hydraulic energy is known as Hydro-electric power.
Classification of water turbine:
Type of energy available at the inlet of the turbine:
 Impulse turbine
 Reaction turbine
Head at the inlet of the turbine:
 High head (head upto 1000m)
 Medium head (head upto 500m)
 Low head (head less than 50m)
Based on the direction of flow of water through the runner:
 Tangential flow
 Axial flow
 Radial flow
 Mixed flow

Fig : Flow of water on the bucket
Fig: Pelton Turbine

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Fig: Hemispherical buckets
fitted to the runner
Fig: Pelton wheel with buckets

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 The Pelton wheel is an impulse turbine, it was invented by Lester Allan Pelton in the
1870s. Pelton wheel is a high head turbine.
Major components:
 Nozzle with a spear head
 Runner and Buckets
 Casing and Brake nozzle
Working Principle:
 A Pelton turbine consists of a set of specially shaped buckets mounted on a periphery of a
circular disc. It is turned by jets of water which are discharged from one or more nozzles
and strike the buckets. The buckets are split into two halves so that the central area
does not act as a dead spot incapable of deflecting water away from the oncoming
jet. The cutaway on the lower lip allows a smoother entrance of the jet into the bucket.
 High speed water jets emerging from the nozzles (obtained by expanding high pressure
water to the atmospheric pressure in the nozzle) strike a series of spoon-shaped buckets
mounted around the edge of the Pelton wheel.

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 As water flows into the bucket, the direction of the water velocity
changes to follow the contour of the bucket. These jets flow along
the inner curve of the bucket and leave it in the direction opposite to
that of incoming jet. When the water-jet contacts the bucket, the
water exerts pressure on the bucket and the water is decelerated as
it does a "U-turn" and flows out the other side of the bucket at low
velocity.
 The change in momentum (direction as well as speed) of water jet
produces an impulse on the blades of the wheel of Pelton Turbine.
This "impulse" does work on the turbine and generates the torque
and rotation in the shaft of Pelton Turbine.

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• The Kaplan turbine is a propeller-
type water turbine which has
adjustable blades to admit
comparatively a large quantity of
water at lower head.
• It was developed in 1913 by
Austrian professor Viktor Kaplan
• Its invention allowed efficient power
production in low-head applications
that was not possible with Francis
turbines.
• The head ranges from 10–70 meters.
Fig: Kaplan turbine(Propeller Turbine)

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A Kaplan turbine comprises mainly the four
components:
 Spiral Casing,
 Guide Vanes,
 Runner and Moving Blades,
 Draft-tube

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Fig: Kaplan Turbine

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Fig : Francis Turbine

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A Francis turbine comprises mainly the four components:
 Spiral Casing,
 Guide Vanes,
 Runner and Moving Blades,
 Draft-tube
• Spiral Casing : The fluid enters from the penstock (pipeline leading to the turbine from the reservoir
at high altitude) to a spiral casing which completely surrounds the runner. This casing is known as scroll
casing or volute. The cross-sectional area of this casing decreases uniformly along the
circumference to keep the fluid velocity constant in magnitude along its path towards the
guide vane. This is so because the rate of flow along the fluid path in the volute decreases
due to continuous entry of the fluid to the runner through the openings of the guide vanes.
• Guide or Stay vane: The basic purpose of the guide vanes is to convert a part of pressure energy of
the fluid at its entrance to the kinetic energy and then to direct the fluid on to the runner blades at the
angle appropriate to the design. Moreover, the guide vanes are pivoted and can be turned by a suitable
governing mechanism to regulate the flow while the load changes.

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• Runner and Moving blades: The flow in the runner of a Francis turbine is not
purely radial but a combination of radial and tangential. The flow is inward, i.e.
from the periphery towards the centre. The main direction of flow change as
water passes through the runner and is finally turned into the axial direction
while entering the draft tube.
• Draft tube: The draft tube is a conduit (Channel) which connects the runner
exit to the tail race where the water is being finally discharged from the turbine.
The primary function of the draft tube is to reduce the velocity of the discharged
water to minimize the loss of kinetic energy at the outlet.
• Tailrace: A fast-flowing stretch of a river or stream below a dam or water mill.
The path through which water is pumped out of the hydro power plant after
power generation.

ME Dept. RRCE 83
Centrifugal pumps
 Centrifugal pumps (or dynamic pumps) is a hydraulic machine which
converts mechanical energy into hydraulic energy by the use of
centrifugal force acting on the fluid.
 When a certain mass of liquid is made to rotate by an external source, it is
thrown away from the centrifugal axis of rotation(kinetic energy is
added to the fluid by increasing the flow velocity. This increase in
energy is converted to a gain in potential energy (pressure))
 These are the most popular and commonly used type of pumps for the
transfer of fluids from low level to high level.
 It is used in places like agriculture, municipal (water and wastewater
plants), industrial, power generation plants, petroleum, mining,
chemical, pharmaceutical and many others.

ME Dept. RRCE 87
Main Parts of Centrifugal Pump
1. Impeller
• It is a wheel or rotor which is provided with a series of backward curved blades or vanes. It is
mounded on the shaft which is coupled to an external source of energy which imparts the liquid
energy to the impeller there by making it to rotate.
2. Casing (Volute Casing)
• The centrifugal pump casing is the component of the pump that converts all of the velocity created by
the rotating impeller into a controlled and stable flow and directs it out of the pump through the
discharge point.. The lower end dips into liquid in to lift. The lower end is fitted in to foot valve and
strainer.
3. Delivery Pipe
• It is a pipe which is connected at its lower end to the out let of the pump and it delivers the liquid to
the required height. Near the outlet of the pump on the delivery pipe, a valve is provided which
controls the flow from the pump into delivery pipe.
4. Suction Pipe with Foot Valve and Strainer
• suction pipe is connected with the inlet of the impeller and the other end is dipped into the sump of
water. At the water end, it consists of foot value and strainer. The foot valve is a one way valve that
opens in the upward direction. The strainer is used to filter the unwanted particle present in the water
to prevent the centrifugal pump from blockage.

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Working of Centrifugal Pump
 The first step in the operation of a centrifugal pump is priming. Priming is the
operation in which suction pipe casing of the pump and the position of fluid with
the liquid which is to be pumped so that all the air from the position of pump is
driven out and no air is left. The necessity of priming of a centrifugal pump is due
to the fact that the pressure generated at the centrifugal pump impeller is directly
proportional to density of fluid that is in contact with it.
 As the electric motor starts rotating, it also rotates the impeller. The rotation of the
impeller creates suction at the suction pipe. Due to suction created the water from
the sump starts coming to the casing through the eye of the impeller.
 From the eye of the impeller, due to the centrifugal force acting on the water, the
water starts moving radially outward and towards the outer of casing.
 Since the impeller is rotating at high velocity it also rotates the water around it in
the casing. The area of the casing increasing gradually in the direction of rotation,
so the velocity of the water keeps on decreasing and the pressure increases, at the
outlet of the pump, the pressure is maximum.
 Now form the outlet of the pump, the water goes to its desired location through
delivery pipe.

Steam Formation and Application:

Definition and Introduction to Steam
 Steam is the gaseous phase of water. When water molecules are provided with continuous heat
then at 100oC temperature and at 1 atm pressure, it boils and changes its phase from liquid to
vapour as a result of some molecules break free. These 'free' molecules form the transparent gas
know as steam.
 Steam produced from water forms one of the most important working fluids in engineering
energy conversion systems.
 Steam is generated in boilers at constant pressure. Generally, steam may be obtained starting from ice
or straight away from the water by adding heat to it.
 Hence, it could be used as a working substance for heat engines , steam turbines etc.
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Formation of Steam at constant pressure
Figure : Shows the various stages of formation of steam starting from water at 0oC at
constant pressure.
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ME Dept. RRCE 93
Figure :The graphical representation of transformation of 1 kg of ice into 1 kg of superheated
steam at constant pressure (temperature vs. enthalpy) is known as t-h diagram.

Formation of Steam (temperature-Enthalpy Diagram t-h diagram)
 (a) Consider 1 kg of ice in a piston -cylinder arrangement as shown. it is under an Absolute
Pressure say P bar and at temperature –t 0 C ( below the freezing point). Keeping the
pressure constant, the gradual heating of the ice leads to note the following changes in it,
These are represented on a t-h diagram on heating, the temperature of the ice will
gradually rises from p to Q i.e. from – t C till reaches the freezing temperature 0.
 (b) Adding more heat, the ice starts melting without changing in the temperature till the
entire ice is converted into water from Q to R. The amount of heat during this period from
Q to R is called Latent heat of fusion of ice or simply Latent heat of ice.
 (c) Continuous heating raises the temperature to its boiling point t C known as Saturation
Temperature. The corresponding pressure is called saturation pressure. it is the stage of
vaporization at 1.01325 bar atmospheric pressure (760mm of hg at 100'C). As pressure
increases, the value of saturation temperature also increases. The amount of heat added
during R to S is called Sensible Heat or Enthalpy of Saturated Water or Total Heat of Water
(h, or h "' ). During the process, a slight increase in volume of water (saturated water) may
be noted. The resulting volume is known as Specific volume of Saturated Water (Vf or vW).
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 (d) On further heating beyond S, the water will gradually starts evaporate and starts
convert it to steam, but the temperature remains constant. As long as the steam is in
contact with water, it is called Wet Steam or Saturated Steam.
 (e) On further heating the temperature remains constant, but the entire water converts to
steam. But still it will be wet steam. The total heat supplied from OOC is called Enthalpy of
Wet Steam (h wet). The resulting volume is known as Specific Volume of Wet Steam (v
wet).
 (f) On further heating the wet steam, the water particles, which are in suspension, will
start evaporating gradually and at a particular moment the final particles just evaporates.
The steam at that moment corresponding to point T is called Dry Steam or Dry Saturated
Steam. The resulting volume is known as Specific Volume of Dry Steam (vg). The amount
of heat added during S to T is called Latent Heat of Vaporization of Steam or Latent Heat
of Steam (hfg). During the process, the saturation temperature remains constant. The
total heat supplied from O'C is called Enthalpy of Dry Steam (hg).
 (g) On further heating beyond point T to U the temperature starts from ts to tu, the point
of interest. This process is called Super heating. The steam so obtained is called Super
Heated Steam.
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Types of Steam
If water is heated beyond the boiling point, it vaporizes into steam, or water in the gaseous state. However,
not all steam is the same. The properties of steam vary greatly depending on the pressure and temperature
to which it is subject.
Unsaturated Steam (Wet):
 When steam is generated using a boiler, it usually contains wetness from non-vaporized water molecules
that are carried over into the distributed steam. As the water approaches the saturation state and begins
to vaporize, some water, usually in the form of mist or droplets, is entrained in the rising steam and
distributed. When steam includes these tiny droplets, it is called wet steam.
Saturated Steam (Dry):
 A steam at the saturation temperature corresponding to a given pressure and having no water molecules
entrained in it is known as dry and saturated steam or dry steam. Since the dry saturated stream does
not contain any water molecules in it, its dryness fraction will be unity.
Superheated Steam:
 Superheated steam is created by further heating dry saturated steam beyond the saturated steam
point. This yields steam that has a higher temperature and lower density than saturated steam at the
same pressure. Superheated steam is mainly used in propulsion/drive applications such as turbines, and
is not typically used for heat transfer applications.

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Unsaturated Water Saturated Steam &
Wet Steam
Superheated Steam
Various States of Water

ME Dept. RRCE 98
The work done on the piston during the change of volume of the steam from vw
to vs
The steam in the steam space of a boiler generally contains water mixed with it in the form of a mist (fine
water particles). Such a steam is termed as wet steam. The quality of steam as regards its dryness
is termed as dryness fraction.
Dryness fraction in simple words denotes the mass of dry steam in given steam. Or how much steam is
dry or in other words how much water vapour is present in steam. It is denoted by ‘x’. If ms = mass of
dry steam contained in the steam considered, and m = mass of water in suspension in the steam
considered. Thus, if drynes -fraction of wet steam, x = 0.8, then one kg of wet steam contains
0.2 kg of moisture (water) in suspension and 0.8 kg of dry steam.

ME Dept. RRCE 99
Applications of steam in Industries
 Steam is used in a wide range of industries. Common applications for steam are, for example, steam
heated processes in plants and factories and steam driven turbines in electric power plants, but the
uses of steam in industry extend far beyond this. Here are some typical applications for steam in
industry:
1. Applications of steam in industries namely, Sugar industry, Dairy industry, Paper industry, textile, tire
etc.
2. Steam for Heating
a. Positive Pressure Steam
b. Vacuum Steam
3. Steam for Propulsion/Drive
4. Steam as Motive Fluid
5. Steam for Atomization
6. Steam for Cleaning
7. Steam for Moisturization
8. Steam for Humidification

ME Dept. RRCE 100
Applications of steam in Sugar industries
Introduction to Sugar industry : India is the second largest producer of sugar in the
world. Sugar Industry is the largest agro industry located in rural India. Sugarcane is the cash crop and its
cultivation plays a vital role towards socio-economic development of farmer’s fraternity
through income and employment generation. Latest technology available is used to minimize cost
of production thereby improving efficiency.
Process Description of Sugar Industry:
The various steps involved for the production of Sugar are as follows:
1. Procurement of Sugarcane.
2. Milling of Sugarcane.
3. Juice Preparation.
4. Juice Concentration.
5. Syrup Processing and Crystallization.
6. Sugar Crystal Separation, Drying, Packaging and Molasses Handling.
7. Bagasse Utilization.

ME Dept. RRCE 101
Figure : Simplified process flow diagram for cane sugar production.

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Applications of steam in Sugar - Industries contd..
The steam requirements in the sugar industry for various applications such as:
 With the concept of Integrated Industrial Complexes (centralized control system used
for industrial process), Sugar Plants are involved in, Cogeneration (the generation
of electricity and useful heat jointly, especially the utilization of the steam left
over from electricity generation for heating.) of electric power for [in-house
consumption and the surplus power is sold to national grid] and Fuel-Ethanol
Distilleries.
 Bagasse Drier units are used to reduce moisture of Bagasse to maximum possible
extent before being fed to the boilers.
 The system uses flue gases as the heating media for drying of Bagasse i.e. waste
heat recovery concept.
 Generally, Moisture of Bagasse coming out of the last Milling tandem remains about 49
– 50 %. After installation of Bagasse Drier, it has been reported that factories have
achieved a drop of about 8- 10% of Bagasse moisture i.e. final bagasse moisture
after drying comes to the tune of 40- 42%.
 Boiler Efficiency increase by about 4% thereby resulting in significant
improvement in Steam/Fuel ratio.

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Bagasse dryers for Bagasse Utilization:
 Bagasse is a by-product of sugar milling. Bagasse is a fibrous, low density
material and high moisture content. The moisture level is up to 50% after the
milling process because of the moisture content, its calorific value is affected.
 Based on the mode of heat transfer, Bagasse dryers can be classified into two
types.
1. Indirect or non contact dryers. [vertical steam pipes - moisture
removal rate up to 5%]
2. Direct or contact dryers. [waste flue gases at boiler outlet - moisture
removal rate 8-10%]
Applications of steam in Sugar - Industries, contd..

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INDIRECT DRYERS:
 A typical indirect dryer for bagasse application can be a bin dryer. The large bin is kept
vertical with large diameter (100 or150mm) pipes passing along the vertical axis and
bin circumference is also lined with vertical steam pipes.
 The pipes are fed at the top with low pressure steam with radial outlets from a common
feed header, reaching to individual pipes.
 The pipes are again connected together at the bottom end and the condensate
removed out of the system.
 The bagasse is charged to the dryer at the top from belt conveyors. The bagasse
descends vertically down to the bottom where it is extracted by bagasse extractor.
 During its travel down the container bin, the bagasse gets dried by physical contact
with the steam pipes and the liberated water vapour travels up and out of the container
bin.

ME Dept. RRCE 105
Figure: Bagasse after
extracting sugarcane
juice, with more than
50% moisture.
Figure: Bagasse after
extracting moisture,
which enhances the
calorific value as fuel to
boiler.

ME Dept. RRCE 106
Applications of steam in Sugar - Industries, contd..
Evaporation is performed in two stages:
Initially in an evaporator station to concentrate
the juice and then in vacuum pans to crystallize
the sugar.
Steam to generate Concentrated Juice :
How Falling Film Evaporators Work:
 In falling film evaporators, the liquid product
usually enters the evaporator at the head of
the evaporator.
 In the head, the product is evenly
distributed into the heating tubes. The liquid
enters the heating tube and forms a thin
film on the tube wall where it flows
downwards at boiling temperature and is
partially evaporated.
 In most cases, steam is used for heating the
evaporator. The product and the vapor both
flows downwards in a parallel flow.
 The separation of the concentrated product
from its vapor takes place in the lower part
of the heat exchanger and the vapor/liquid
separator.

ME Dept. RRCE 107
Evaporation in evaporator station to concentrate the juice :
 The clarified juice is passed through heat exchangers to preheat the juice and then to the
evaporator stations.
 Evaporator stations consist of a series of evaporators [five evaporators]. Steam from large
boilers is used to heat the evaporators. This heat transfer process continues through the
five evaporators and as the temperature decreases (due to heat loss) from evaporator to
evaporator, the pressure inside each evaporator also decreases which allows the juice to boil
at the lower temperatures in the subsequent evaporator.
 The evaporator station in sugarcane manufacture typically produces a syrup with about
65 percent solids and 35 percent water.
 Following evaporation, the syrup is clarified by adding lime, phosphoric acid, and a polymer
flocculent, aerated, and filtered in the clarifier.
 From the clarifier, the syrup goes to the vacuum pans for crystallization.

ME Dept. RRCE 108
Figure: Vacuum pans to crystallize the sugar

Vacuum pans to crystallize the sugar [Sugar Formation through Vacuum
Pan Processes]:
 After being evaporated in a multiple-effect evaporator to a syrupy consistency, clarified juice must be
evaporated further for the sugar to crystalize. This is accomplished in a vacuum pan, a vessel in which
syrup is boiled under vacuum to form a heavy mixture of crystals and mother liquor, called
massecuite.
 Initially, a sub saturated standard liquor is pumped in the vacuum pan. To heat the juice & evaporate
the water, vacuum pans are equipped with CALANDRIA.
 Here, steam flows at a pressure greater than the atmospheric pressure and as the steam condenses, it
releases heat to the syrup. Evaporation of water leads to an increase in the concentration of the juice
to super saturation level.
 Seeds of sucrose crystals dissolved in alcoholic solution are added to the vacuum pan. The sucrose
mass generally added is around 10gm and the size of the crystals is about 5μm. Super saturation
conditions are maintained till the crystals attain their final size 0.5μm.
 The centrifuge is filled with the massecuite and centrifuged at 150rpm. This presses the massecuite
against the wall. Centrifuge is accelerated to a max. speed of 1100rpm. Sugar crystals and the syrup
[molasses] is separated. Sugar is washed with water. Remains of the syrup are eliminated by injecting
hot water. Sugar is then discharged and dried.
 BAROMETRIC CONDENSER helps in maintaining the partial vacuum and 65-70°C temperature, as it
absorbs the steam and condenses it by means of cooling.

ME Dept. RRCE 110
Paper industry:
 Paper plays a key role in our daily life and papers have been used for many years from
now. Papers are made with the pulp of the woods, which is an Eco-friendly
product.
 The steam requirement of paper mills is high. It is pivotal (crucial importance) in the paper
industry for various process applications such as
 Energy requirement [power generation to run the industry]
 Heating and cooking the wood chips in the digester to make wood pulp
 Drying the paper with Dryer drums
 Heating of chemicals etc.
 Hence, Boilers in the paper industry are used to generate steam for power and
process system mentioned above.
 The high-pressure steam is used in steam turbines to produce electricity for the
paper mill. While, requires medium and low-pressure steam for process
applications.
Medium and low-
pressure steam for
process applications.

Paper is made through the following processes:
1) Pulping procedure will be done to separate and clean the fibers
2) Refining procedure will be followed after pulping processes
3) Dilution process to form a thin fiber mixture
4) Formation of fibers on a thin screened
5) Pressurization to enhance the materials density
6) Drying to eliminate the density of materials
7) Finishing procedure to provide a suitable surface for usage

ME Dept. RRCE 112
Heating and cooking the wood chips in the
digester:
 The pulping process is aimed at removing lignin without loosing
fiber strength, thereby freeing the fibers and removing impurities that
cause discoloration and possible future disintegration of the paper.
 Chips are freed from the lignin binder by heating in alkaline
solutions [cooking liquor] under pressure in large cylindrical
tanks called digesters. At the end of the "cooking" period, a small
port in one end of the digester is opened, and the slurry of softened
wood chips is allowed to blow to complete the breakup of the chips
and the separation of the fibers.
Figure: Digester with a steam jacket
Figure : Paper pulp
Figure : Lignin and cellulose
fiber in Paper pulp

ME Dept. RRCE 113
Figure: Digester - Heating and cooking the wood chips

ME Dept. RRCE 114
Figure: Liquid
paper pulp onto a
moving wire
screen.

ME Dept. RRCE 115
The dryer as heat exchanger
 Dryers of paper machines are only tube heat
exchangers.
 As the pulp is carried along by the screen, the water in
it is removed, and the cellulose fibers become
bonded together, forming paper.
 While the paper is still damp, it is fed through a
series of heated rollers which press it and dry it.
 Steam flows into the dryer, the dryer is cooled by the
paper and steam condensates. The condensate is
collected at the bottom of the dryer.
 It is essential to maintain an even temperature
across the surface of the rolls for uniformity and
high-quality products. Steam is an ideal choice as
it condenses and distributes heat evenly.
 The paper is then spooled into huge rolls, cut into
various sizes, and converted into paper products.

ME Dept. RRCE 116
Figure : The dryer as heat exchanger to evaporate the
moisture by heat from steam at 250oC

Figure : Dryer cylinder showing steam and condensate elements

ME Dept. RRCE 118
Figure: Paper spooled into huge rolls

ME Dept. RRCE 119
Recovery of pulping liquors - Heating of chemicals in evaporators
 Chemicals those are used in the pulp and paper
making process are called pulping liquor.
 white liquor is used to cook wood chips and
yields pulp and weak black liquor (separated by
washing in multiple steps).
 This weak black liquor is concentrated in
evaporators (another large steam user) to
produce a fuel the recovery boiler(s) can use to
produce power and process steam.
 The inorganic portions fall into the smelt tank
and are dissolved to produce green liquor.
 This green liquor is then converted to produce
white liquor (hence the term liquor loop).
 This recovery loop aids in saving money by
reducing waste of cooking chemicals,
producing steam, and producing power. Thus,
makes paper mill operations economical.

ME Dept. RRCE 120
Note: From paper to more paper
 Recycling paper helps make sure we get the most out of every tree we use. This it
helps keep paper from clogging up our landfills. Each time paper is recycled, the
cellulose fibers get shorter, until eventually the paper won’t hold together. That’s why
most “recycled” papers contain some new paper fibers mixed in with the old.

ME Dept. RRCE 121
Applications of steam in Dairy industry:
 Use of high-quality steam is a major factor in the efficient production of high-grade dairy
products. What is steam used for?
 Raw milk is processed into a wide variety of dairy products which include: pasteurised
milk, cheese, butter and yoghurt. In the modern dairy, steam is used in a variety of
processes to promote chemical reactions and physical changes in raw milk and to
help maintain clean, sterile conditions.
 Steam is used because it is an efficient carrier of heat. It is produced in the boiler and
carried to the dairy processing plant by a pipework distribution system. At each process
steam transfers its heat and condenses back to condensate.
 A very important property of saturated steam is that its temperature is directly related to its
pressure. Therefore, the temperature of many processes can be accurately controlled by
controlling the pressure of the steam.
 To enable accurate control of temperatures, it is essential to deliver high quality, dry
saturated steam to the process at the correct pressure. Any entrained moisture or
incondensable gases in the steam can lower its heat content and impair the heat transfer
rate.

123
PASTEURIZATION OF MILK:
Pasteurization is the process of heating the product to a predetermined temperature and
holding it until all or nearly all objectionable microorganisms, which may be present, are killed.
Which Improves preservation quality and helps to retain good flavor over a longer period of
time.
Methods of Pasteurization:
 Low Temperature Long Time [LTLT] – temperature range 63oC for 30 min.
 High Temperature Short Time [HTST] - temperature range 72oC for 15 sec.
 Ultra High Temperature [UHT] - temperature range 135oC to 150oC for 2 sec.

ME Dept. RRCE 125
Figure: High Temperature Short Time pasteurization – Plate type
(HTST PASTEURIZATION)

ME Dept. RRCE 126
Figure: High Temperature Short Time
pasteurization – Plate type (HTST
PASTEURIZATION)
Figure: Schematic
of a Plate.

ME Dept. RRCE 127
Figure : Homogenizer incorporated in HTST pasteurization system

ME Dept. RRCE 128
Basic working principle of HTST pasteurization system:
 The HTST pasteurization process and its basic components are shown in Figure. First from
a constant level tank, milk is pumped by a booster pump into a heat exchanger to heat it
with the help of pasteurized milk to about 60°C.
 As the pasteurized milk is used for heating the raw milk and there is no external heating
source, we call that a regenerative heater. The regenerator reduces the actual heat
requirement for pasteurization and hence is very important for the overall cost
effectiveness of the system.
 Then the milk enters into the heater where the temperature of milk is raised to the actual
pasteurization temperature. The milk then passes through the holder, where the milk
temperature is maintained for the specific time so that pasteurization is completed.
 Then the pasteurized milk goes to the regenerator so that it gives away some heat to the
raw milk. It is also simultaneously cooled so that the refrigeration requirement is reduced.
 After the regenerator, the pasteurized milk goes to a chiller, where the milk temperature is
reduced to about 4-5°C.

ME Dept. RRCE 129
Application of Steam to manufacture Milk Powder
Method 1 - Application of Steam to
manufacture milk powder
 The product is pumped through a
pipe with a narrow end (nozzle, 1
to 3 mm). The wall of this pipe
contains several small openings
through which high pressure
steam is injected, enabling very
fast heating of the product.
 The resulting concentrated milk
is then sprayed into a fine mist to
remove further moisture and get
transformed into powder.

ME Dept. RRCE 130
Method 2 – Use of
thin sheets in
Filtration, steam in
Evaporation and
hot air in Drying.

ME Dept. RRCE 132
Steam is used to generate
Condensed milk also.

ME Dept. RRCE 133
Steam to generate milk powder :
 Milk powder is the process of removing water content by boiling the milk under vacuum
conditions or at low pressure and temperature. The resulting concentrated milk is then
sprayed into a fine mist of hot air to remove further moisture and get transformed into
powder.
 Atomizer is a unit which distributes milk in form of very small droplets. Atomization is
aimed at forming droplets fine enough to dry quickly, but not so fine as to escape with the
outlet air after having been dried.
 Thus, the objective of atomizing is to reduce the milk to a particle size so small that due to
the tremendously increased surface area, the resulting mist of milk projected into the
current of heated fluid, surrenders its moisture nearly instantly.
 The minute particles of milk are dried before they reach the side walls or floor of the drying
chamber. The average particle size of the milk fog provided by efficient atomization has a
diameter of ~ 50µ.

ME Dept. RRCE 134
The food industry needs heat at every stage of the process. Direct heat or heat
from the hot water is an essential factor of food processing industry.
Use of Steam Boilers in Food Processing industry:
 Hot Water Generation for Sanitation [Food and water can be contaminated
easily. Steam cleaning is perfect for both homes and restaurants. It uses steam
that is produced by boiling water, and this will make the kitchen smell and look
nice.]
 Hot Water and Heating Requirement for Facilities
 Steam for Cooking
 Reducing Microbiological Risks in Food
 Steam for Drying Food
 Steam & Heat for Packaging
Steam Boiler in Food Industry:

ME Dept. RRCE 135
Application of Steam in Food processing industry :
Steam is now mostly known for its heating
applications, as both a source of direct and
indirect heat.
Direct Steam Heating:[Positive Pressure]
 The direct steam heating method refers to
processes where steam is in direct contact
with the product being heated.
 The example below shows Chinese
dumplings being steamed. A steaming
basket is placed over a pot of boiling water.
As the water boils, steam rises into the
basket and cooks the food. In this setup,
the boiler (pot) and steaming vessel
(basket) are combined together.
 The principle behind steaming food is that
by allowing steam to come in direct
contact with the product being heated, the
latent heat of steam can be directly
transferred to the food.

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Steam Oven:
Superheated steam heated to 200 – 800°C (392 - 1472°F) at atmospheric
pressure is particularly easy to handle, and is used in the household steam ovens
seen on the market today.

ME Dept. RRCE 137
Indirect Steam Heating:[Vacuum Steam]
 The indirect steam heating method refers to processes where steam is not in direct contact with the
product being heated. It is widely used in industry because it provides rapid, even heating. This method
often uses a heat exchanger to heat the product.
 In a heat exchanger, steam raises the temperature of the product by heat transfer, after which it turns
into condensate and is discharged through a steam trap.
 The advantage of this method over direct steam heating is that the water droplets formed during
heating will not affect the product. Steam can therefore be used in a variety of applications such as for
melting, drying, boiling etc. However, a vacuum pump must be used in conjunction with the equipment.
 Indirect steam heating is used in a wide range of processes such as those for the production of foods
and beverages, sugar, paper, cardboard, fuels such as gasoline and medicine to name a few.

ME Dept. RRCE 138
Steam for Propulsion/Drive
 Steam is regularly used for propulsion (as a driving force) in applications such as steam turbines. The
steam turbine is an equipment that is essential for the generation of electricity in thermal electric power
plants.
 Superheated steam is often used in steam turbines to prevent damage to equipment caused by the
inflow of condensate. In certain types of nuclear power plants, however, the use of high temperature
steam must be avoided, as it would cause problems with the material used in the turbine equipment.
 Instead, high pressure saturated steam is typically used. When saturated steam is used, separators are
often installed in the supply piping to remove entrained condensate from the steam flow.
Generator Turbine:
The driving force from the steam causes the
fins to turn, which then causes the rotor on
the attached power generator to rotate, and
this rotation generates electricity as shown in
the figure.

ME Dept. RRCE 139
Steam as Motive Fluid: As Ejector for Surface Condenser
 Steam can also be used as a direct “motive” force to move liquid and gas streams in piping. They are
also used for continuous removal of air from surface condensers, in order to maintain desired vacuum
pressure on condensing (vacuum) turbines.
 For most water-cooled surface condensers, the shell is under [partial] vacuum during normal
operating conditions. For water-cooled surface condensers, the shell's internal vacuum is most
commonly supplied by and maintained by an external steam jet ejector system. Such an ejector system
uses steam as the motive fluid to remove any non-condensable gases that may be present in the surface
condenser.
 High pressure motive steam enters the jet ejector through the inlet nozzle and is then diffused. This
creates a low-pressure zone which entrains air from the surface condenser.

ME Dept. RRCE 140
Steam for Atomization:
 Steam atomization is a process where steam is used to mechanically separate a fluid. In some burners,
for example, steam is injected into the fuel in order to maximize combustion efficiency and minimize the
production of hydrocarbons (soot).
 Steam boilers and generators that use fuel oil will use this method to break up the viscous oil into
smaller droplets to allow for more efficient combustion. Flares also commonly use steam atomization to
reduce pollutants in the exhaust.
Figure : Steam Assisted Flare
In flares, steam is often mixed in
with the waste gas before
combustion. [pilot – high
temperature ignition rod]

ME Dept. RRCE 141
Steam for Cleaning:
 Steam is used to clean a wide range of surfaces. One such example from industry is the use of steam in
soot blowers. Boilers that use oil or coal as the fuel source must be equipped with soot blowers for cyclic
cleaning of the furnace walls and removing combusted deposits from convection surfaces to maintain
boiler capacity, efficiency, and reliability.
 Steam released out of the soot blower nozzle dislodges the dry or sintered ash and slag, which then fall
into hoppers or are carried out with the combusted gasses.
Figure : Boiler Tube Cleaning with Soot Blower

ME Dept. RRCE 142
Steam for Moisturization:
 Steam is sometimes used to add moisture to a process while at the same time supplying heat. For
example, steam is used for moisturization in the production of paper, so that paper moving over rolls at
high speed does not suffer microscopic breaks or tears. Another example is pellet mills. Often mills that
produce animal feed in pellet form use direct-injected steam to both heat and provide additional water
content to the feed material in the conditioner section of the mill.
 The moisturizing of the feed softens the feed and partially gelatinizes (viscous) the starch content of the
ingredients, resulting in firmer pellets.
Figure : Pellet Mill Conditioner
Figure : Pellet

ME Dept. RRCE 143
Steam for Humidification:
 Many large commercial and industrial facilities, especially in colder climates, use low pressure saturated
steam as the predominant heat source for indoor seasonal heating.
 HVAC coils, often combined with steam humidifiers, are the equipment used for conditioning the air for
indoor comfort and infection control. When the cold air is heated by the steam coils, the relative humidity
of the air drops, and it must then be adjusted to normal levels with addition of a controlled injection of
dry saturated steam into the downstream air flow.
 Steam is used to humidify air within an air duct before the air is distributed to other regions of a building.
Figure : Steam
Humidifier in Air
Duct
[The process of addin
g moisture to a volum
e of air].

ME Dept. RRCE 144
Introduction to Mechanical Engineering (Overview only):
Role of Mechanical Engineering in Industries and Society:
Roles & Responsibilities:
 Mechanical engineers should be creative, inquisitive (interest to learn), analytical, and detail
oriented.
 They should be able to work as part of a team and communicate well in both writing and
orally since mechanical engineers must interact with a broad array of specialists in a wide
range of fields like manufacturing, automobile, agriculture, aerospace, marine, energy etc.
 Mechanical engineers must provide engineering designing and guidance along side other
team members to develop better and more advanced ways of production of an object or
tool.
 Also, they must be able to solve complex problems where analysis of a situation and data
in-depth evaluation are required in order to meet the requirement of the customer.
 Also, this type of engineer as well as any other kind of engineer must be able to prepare
and present technical status reviews to show its customers overall improvement of a give
task or project.

ME Dept. RRCE 145
Emerging Trends and Technologies in different sectors: Manufacturing
Need for new Manufacturing Trends:
 Reduce operating costs, while maximizing long-term profitability and increasing product quality
 Improve ability to quickly respond to market changes and customer demand
 Improve supply chain efficiency
 Improve demand planning scope and accuracy
 Improve availability and visibility of key information needs
 Close functional gaps and increase integration between back-office and shop floor systems.
Many commonly known practices used today that facilitate cost reduction, quality improvement and flexibility
in the manufacturing environment. Some examples of these are:
(a) Lean Manufacturing (focuses on minimizing the waste within the firm – defects, excess processing,
inventory, waiting, transportation, non-utilized talent & increase value of products delivered to customers.)
(b) Agile Manufacturing (respond quickly to customer needs and market changes while still controlling the
cost & quality.)
(c) Just-in-Time (inventory mgmt. system – right material at right time to right place, for this inventory
forecast demand should be accurate.)

ME Dept. RRCE 146
(d) Flexible Manufacturing System (ability to quickly adapt to variations/deviations in
product variety & production schedules.)
(e) Rapid Manufacturing (control the manufacturing process by computer using a
mathematical tool created with the aid of a computer.)
(f) Demand Flow Manufacturing (linked to daily changes in demand, a closed loop b/w
customer orders, production scheduling and manufacturing execution is established along with
flow of material across the supply chain)
(e) Advanced Planning and Scheduling (MPS, MRP & CP - it is a mfg. mgmt. process by
which raw materials and production capacity are optimally allocated to meet demand.)
(f) Smart Manufacturing & Industry 4.0 (“centralized” to “decentralized”, industry relies
on cyber-physical based automation where sensors send data directly to the cloud and
services such as monitoring, control and optimization automatically to necessary data in real
time).

ME Dept. RRCE 147
Emerging Trends and Technologies in different sectors such as Energy:

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