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### Transcript of Chapter 01

• MEC551

THERMAL ENGINEERING

PREPARED BY:

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

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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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• 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

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Heat can be transferred from place to another place by three PROCESSES or MODES.

i) CONDUCTION

ii) CONVECTION

• 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

28

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

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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

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

33

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

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

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

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

39

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

40

• 1.2 FUNDAMENTAL MECHANISM OF HEAT TRANSFER

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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

46

• APPLICATIONS

47

• 1.3 SUSTAINABLE ENERGY MANAGEMENT