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Transcript of Chapter 01

  • MEC551

    THERMAL ENGINEERING

    PREPARED BY:

    PN. ROSNADIAH BAHSAN

    FACULTY OF MECHANICAL ENGINEERING

    UiTM SHAH ALAM

    1

    CHAPTER 01

    THERMODYNAMIC & HEAT TRASNFER

    ENERGY & SUSTAINABILITY

    http://www.childrensbiblestudy.com

  • OBJECTIVES:

    2

    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

    3

    What is Thermodynamics?

    Energy Heat

    Conservation of Energy principle

    Law of Thermodynamics

  • 1.1 THERMODYNAMICS

    4

    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

    5

    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

  • 6

    1.1 CONSERVATION OF ENERGY PRINCIPLE

  • 1.1 CONSERVATION OF ENERGY PRINCIPLE

    7

    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

    8

    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

    9

    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

    10

    The first law of thermodynamics: An expression of

    the conservation of energy principle.

    Mathematical model

    Ein Eout = esystem

    The first law asserts that energy is a thermodynamic property.

  • 1.1 SECOND LAW OF THERMODYNAMICS

    11

    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

    12

  • 1.1 APPLICATION AREAS

    13

  • 1.1 APPLICATION AREAS

    14

  • 1.1 APPLICATION AREAS

    15

  • 1.1 APPLICATION AREAS

    16

  • 17

    What is Heat?

  • 18

    the form of energy

    can be transferred from one system to

    another

    as a result of a temperature difference

    Heat

  • 19

    What is Heat Transfer ?

    the physical process by which heat energy moves from one area to another

    the determination of rates of energy

  • 20

    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

    21

    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

    22

    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

    23

    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

    24

    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

    27

    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

    30 The cooling of boiled egg by convection

    Convection Process

  • 1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER

    31

    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

    32

    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

    34

    Convection Process

    npg2.com/krdo/weatherblog/

  • 1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER

    35

    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

    36

    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

    37

    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

    38

    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

  • 42

    ACTIVITY 1

    MODE 1?

    MODE 2????

    MODE 3?

  • 43

    ACTIVITY 2

    MODE 1?

    MODE 2????

    MODE 3?

  • APPLICATIONS

    44

    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