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MEC551
THERMAL ENGINEERING
PREPARED BY:
PN. ROSNADIAH BAHSAN
FACULTY OF MECHANICAL ENGINEERING
UiTM SHAH ALAM
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CHAPTER 01
THERMODYNAMIC & HEAT TRASNFER
ENERGY & SUSTAINABILITY
http://www.childrensbiblestudy.com
OBJECTIVES:
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The objectives of Chapter 1 are to: Understand how thermodynamics & heat transfer related to each other, Understand the basic mechanisms of heat transfer, Develop an awareness on global warming issues, ozone depleting substances, renewable energy and sustainable energy issues.
1.1 THERMODYNAMICS
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What is Thermodynamics?
Energy Heat
Conservation of Energy principle
Law of Thermodynamics
1.1 THERMODYNAMICS
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From the Greek words:
therme (heat) & dynamis (power) – the efforts
to convert heat into power
The science of energy transfer
The study of the effects of work, heat and energy on a system
1.1 THERMODYNAMICS
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concerned with the amount of total
heat transfer as a system undergoes a
process from one equilibrium state to
another
gives no indication of how long the
process will take
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1.1 CONSERVATION OF ENERGY PRINCIPLE
1.1 CONSERVATION OF ENERGY PRINCIPLE
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Energy cannot be created or destroyed. It
only can be transform from one form to another
form
Conservation of energy principle: During an interaction,
energy can change from one form to another but the total amount of energy remains constant.
1.1 ZEROTH LAW OF THERMODYNAMICS
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Zeroth Law of Thermodynamics:
Thermodynamic equilibrium & Temperature
If two bodies are in thermal equilibrium with a
third body, they are also in thermal equilibrium
with each other.
By replacing the third body with a thermometer, the Zeroth law can be
restated as two bodies are in thermal equilibrium
if both have the same temperature reading
even if they are not in contact.
1.1 ZEROTH LAW OF THERMODYNAMICS
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Zeroth Law of Thermodynamics:
Thermodynamic equilibrium & Temperature
Two bodies reaching thermal equilibrium after being brought
into contact in an isolated enclosure.
1.1 FIRST LAW OF THERMODYNAMICS
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The first law of thermodynamics: An expression of
the conservation of energy principle.
Mathematical model
Ein – Eout = Δesystem
The first law asserts that energy is a thermodynamic property.
1.1 SECOND LAW OF THERMODYNAMICS
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It asserts that energy has quality as well as
quantity, and actual processes occur in the
direction of decreasing quality of energy.
Example; “a cup of hot coffee left on a table eventually cools,
but a cup of cool coffee in the same room never get hot by
itself”
The high temperature energy of the coffee is degraded
(transform into less useful form at a lower temperature) once
it is transferred to the surrounding air
1.1 APPLICATION AREAS
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1.1 APPLICATION AREAS
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1.1 APPLICATION AREAS
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1.1 APPLICATION AREAS
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1.1 APPLICATION AREAS
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What is Heat?
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the form of energy
can be transferred from one system to
another
as a result of a temperature difference
Heat
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What is Heat Transfer ?
the physical process by which heat energy moves from one area to another
the determination of rates of energy
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What is Heat Transfer ?
It occurs when the difference temperature exists in a medium or between media
The transfer of heat is normally from high temperature to a lower temperature object.
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Heat can be transferred from place to another place by three PROCESSES or MODES.
i) CONDUCTION
ii) CONVECTION
iii) RADIATION
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Conduction Process
The transfer of energy from the more energetic particle of substance to the adjacent less energetic ones as a result of interactions between the particles.
http://sheryltan789.blogspot.com
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Conduction in solids
it is due to the combination of vibrations of the molecules in a lattice and energy transport by free electron
www.bbc.co.uk/scotland/learning
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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www.bbc.co.uk/scotland/learning
Conduction in solids
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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www.bbc.co.uk/scotland/learning
Conduction in solids
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Conduction in liquids and gases
it is due to the collision and diffusion of the molecules during their random motion
http://www.spaceflight.esa.int/
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Conduction Process
Heat flows from the warmer to the cooler
object until the temperature for both objects are the same
The transfer of heat between two bodies or two parts of the same body through molecules
The heat transfer that will occur across the
medium in solids, liquids and gases and from
one to another
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Convection Process
occur between a solid surface and moving fluid at different temperatures
the combined effects of conduction and fluid motion
change of phase of a fluid also considered to
be convection
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Convection Process
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Convection Process
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Natural/Free Convection
if the fluid motion is caused by buoyancy forces that are induced by density differences due to the variation of temperature in the fluid.
The cooling of boiled egg by convection
Convection Process
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Forced convection
if the fluid is forced to flow over the surface by external means such as a fan,
pump, or the wind.
The cooling of boiled egg by convection
Convection Process
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Convection Process
water.me.vccs.edu/
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Convection Process
npg2.com/krdo/weatherblog/
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Convection Process
http://sheryltan789.blogsp
ot.com In Boiling Water
www.grammarpolice.net/ www.sltechgroup.com/blog
CONDENSATION
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Convection Process
http://sheryltan789.blogspot.com
http://sheryltan789.blogspot.com
A radiator in the room heats up the room by convection
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Radiation Process
Interacts with matter via either:
Emission: Light is released
Absorption: Light is captured
Transmission: Light is allowed to pass through
Reflection: Light is bounced away
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Radiation Process
The energy emitted by matter in the form of
electromagnetic waves (or photons)
Does not require any intermediate
medium for energy transfer
Take place in a vacuum Heat from the sun reaches us by infrared radiation Absorption of infrared radiation causes temperature rise
the transmission of heat energy by
rays passing from a heat source to an absorbing material.
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Thermal Radiation Process
the form of radiation emitted by bodies because
of their temperature
It is volumetric phenomenon and all solids, liquid and
gases emit, absorb, or transmit radiation to varying
degrees.
It differs from other forms of electromagnetic radiation such as X-rays, gamma rays, microwaves, radio waves, and
television waves that are not related to temperature.
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Thermal Radiation Process
1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER
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Thermal Radiation Process
Emission of infrared radiation causes the
temperature of the objects themselves to fall
The rate of heat transfer by radiation is affected by the
following factors:
i) Color and texture of the surface
ii) Surface Temperature
iii) Surface Area
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ACTIVITY 1
MODE 1?
MODE 2????
MODE 3?
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ACTIVITY 2
MODE 1?
MODE 2????
MODE 3?
APPLICATIONS
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http://www.sfu.ca/~mbahrami/research.html
APPLICATIONS
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APPLICATIONS
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APPLICATIONS
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1.3 SUSTAINABLE ENERGY MANAGEMENT
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energy sources that will allow the Earth to sustain balanced,
healthy ecosystems and human life
WHAT IS SUSTAINABLE ENERGY
energy that can potentially be kept up well into the future without causing harmful repercussions for future generations
1.3 SUSTAINABLE ENERGY MANAGEMENT
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TYPES OF ENERGY RESOURCES
Renewable Nonrenewable
can be replenished in a human lifetime
take longer than a human lifetime to replace
Source: www.ncpre.iitb.ac.in
1.3 SUSTAINABLE ENERGY MANAGEMENT
50 World Energy Consumption
1 Quadrillion BTU = 1015 BTU = 1015 x 1054 Joules
World Energy Scenario
Source: www.ncpre.iitb.ac.in
1.3 SUSTAINABLE ENERGY MANAGEMENT
51 Electricity Consumption Bar Graph
Source: www.ncpre.iitb.ac.in
World Electricity Scenario
OZONE-DEPLETING SUBSTANCES
a chemical substance
consisting of some combination of chlorine, fluorine,
or bromine plus carbon, such as chlorofluorocarbons
and hydro chlorofluorocarbons that has been shown to
destroy stratospheric ozone
commonly found in aerosol products, foams, and fire
extinguishers, and are used as refrigerants and in air-
conditioning and cooling equipment
1.3 Ozone Depleting Substances and Global Warming
Issues
1.3 Ozone Depleting Substances and Global Warming
Issues
1.3 Ozone Depleting Substances and Global Warming
Issues
www.epa.gov/ozone/science/process.html
1.3 Ozone Depleting Substances and Global Warming
Issues
1.3 Ozone Depleting Substances and Global Warming
Issues
1.3 Ozone Depleting Substances and Global Warming
Issues
1.3 Ozone Depleting Substances and Global Warming
Issues
1.3 Ozone Depleting Substances and Global Warming
Issues
1.3 Ozone Depleting Substances and Global Warming
Issues
1.3 Ozone Depleting Substances and Global Warming
Issues
1.3 Ozone Depleting Substances and Global Warming
Issues
1.3 Ozone Depleting Substances and Global Warming
Issues
1.3 Ozone Depleting Substances and Global Warming
Issues
1.3 Ozone Depleting Substances and Global Warming
Issues
1.3 Ozone Depleting Substances and Global Warming
Issues
1.3 Ozone Depleting Substances and Global Warming
Issues
1.3 Ozone Depleting Substances and Global Warming
Issues
1.4 Renewable Energy Resources and Technologies.
Sustainable Energy Management
1.4 Renewable Energy Resources and Technologies.
Sustainable Energy Management
1.4 Renewable Energy Resources and Technologies.
Sustainable Energy Management
1.4 Renewable Energy Resources and Technologies.
Sustainable Energy Management
1.4 Renewable Energy Resources and Technologies.
Sustainable Energy Management
REFERENCES
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1. Yunus A. Cengel, MEC551 Thermal Engineering, McGraw Hill, 1st
Edition, 2011.
2. Yunus A. Cengel, Introduction to Thermodynamics and Heat
Transfer, McGraw-Hill, 2008.
3. Incropera et.al., Heat and Mass Transfer, John Wiley, 6th Edition,
2007.
4. J.P.Holman, Heat Transfer, McGraw-Hill, 10th Edition,2010.
5. P.K.Nag, Heat Transfer, Tata McGraw-Hill, 2003.
THANK YOU
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SOLID
LIQUID GAS
MELTING/FUSION
FREEZING
BOILING/EVAPORATION
CONDENSATION
DEPOSITION
SUBLIMATION