understanding heat transfer: conduction, convection and radiation

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Understanding Heat Transfer: Conduction, Convection and Radiation. What is Heat?. This is the movement of thermal energy from a substance at a higher temperature to another at a lower temperature. Heat vs. Temperature. Heat is the actual energy… - PowerPoint PPT Presentation

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Page 1: Understanding Heat Transfer: Conduction, Convection and Radiation
Page 2: Understanding Heat Transfer: Conduction, Convection and Radiation

What is Heat?This is the movement of

thermal energy from a substance at a higher

temperature to another at a lower temperature.

Page 3: Understanding Heat Transfer: Conduction, Convection and Radiation

Heat vs. Temperature

Heat is the actual energy…

Temperature is the measure of average kinetic energy of particles in a

substance.

Page 4: Understanding Heat Transfer: Conduction, Convection and Radiation

Heat is NOT Temperature

Page 5: Understanding Heat Transfer: Conduction, Convection and Radiation

Heat TransferHeat TransferHeat always moves from a warmer place to a Heat always moves from a warmer place to a

cooler place.cooler place.

Hot objects in a cooler room will cool to room Hot objects in a cooler room will cool to room temperature.temperature.

Cold objects in a warmer room will heat up to Cold objects in a warmer room will heat up to room temperature.room temperature.

Page 6: Understanding Heat Transfer: Conduction, Convection and Radiation

Heat Transfer MethodsHeat transfers in three ways:

ConductionConvectionRadiation

Page 7: Understanding Heat Transfer: Conduction, Convection and Radiation

Conduction Conduction heat transfer is the flowing of heat

energy from a high-temperature object to a lower-temperature object.

Page 8: Understanding Heat Transfer: Conduction, Convection and Radiation

When you heat a metal strip at one end, the heat travels to the other end.

As you heat the metal, the particles vibrate, these vibrations make the adjacent particles vibrate, and so on and so on, the vibrations are passed along the metal and so is the heat. We call this? Conduction

Page 9: Understanding Heat Transfer: Conduction, Convection and Radiation

The outer e______ of metal atoms drift, and are free to move.

When the metal is heated, this ‘sea of electrons’ gain k_____ energy and transfer it throughout the metal.

Insulators, such as w___ and p____, do not have this ‘sea of electrons’ which is why they do not conduct heat as well as metals.

lectrons

inetic

ood lastic

Page 10: Understanding Heat Transfer: Conduction, Convection and Radiation

Metal is a conductor, wood is an insulator. Metal conducts the heat away from your hands. Wood does not conduct the heat away from your hands as well as the metal, so the wood feels warmer than the metal.

Page 11: Understanding Heat Transfer: Conduction, Convection and Radiation

ConvectionConvection takes place when heated molecules move from one place to another, taking the heat

with them. Convection is common in both the atmosphere, as well as in the oceans.

Convection is the primary way that heat moves through gases and liquids.

Page 12: Understanding Heat Transfer: Conduction, Convection and Radiation

Convection

Page 13: Understanding Heat Transfer: Conduction, Convection and Radiation

What happens to the particles in a liquid or a gas when you heat them?

The particles spread out and become less dense.

Page 14: Understanding Heat Transfer: Conduction, Convection and Radiation

Hot water rises

Cooler water sinks

Convection current

Cools at the surface

Page 15: Understanding Heat Transfer: Conduction, Convection and Radiation

Where is the freezer

compartment put in a fridge?

Freezer compartmen

t

It is put at the top, because cool air sinks, so it cools the food on the way down.

It is warmer at the

bottom, so this warmer

air rises and a

convection current is

set up.

Page 16: Understanding Heat Transfer: Conduction, Convection and Radiation
Page 17: Understanding Heat Transfer: Conduction, Convection and Radiation

How does heat energy get from the Sun to the Earth? There are no particles

between the Sun and the Earth so it CANNOT travel by conduction or by convection.

?RADIATION

Page 18: Understanding Heat Transfer: Conduction, Convection and Radiation

Radiation travels in straight lines

True/False

Radiation requires particles to travel

True/False

Radiation travels at the speed of light

True/False

Page 19: Understanding Heat Transfer: Conduction, Convection and Radiation

Radiation The transfer of energy by electromagnetic waves.

Examples:

SunFireLight bulb

Page 20: Understanding Heat Transfer: Conduction, Convection and Radiation

Why are houses painted white in hot countries?

White reflects heat radiation and keeps the house cooler.

Page 21: Understanding Heat Transfer: Conduction, Convection and Radiation
Page 22: Understanding Heat Transfer: Conduction, Convection and Radiation

1. Which of the following is not a method of heat transfer?

A. Radiation

B. Insulation

C. Conduction

D. Convection

Page 23: Understanding Heat Transfer: Conduction, Convection and Radiation

2. In which of the following are the particles closest together?

A. Solid

B. Liquid

C. Gas

D. Fluid

Page 24: Understanding Heat Transfer: Conduction, Convection and Radiation

3. How does heat energy reach the Earth from the Sun?

A. Radiation

B. Conduction

C. Convection

D. Insulation

Page 25: Understanding Heat Transfer: Conduction, Convection and Radiation

4. Which is the best surface for reflecting heat radiation?

A. Shiny white

B. Dull white

C. Shiny black

D. Dull black

Page 26: Understanding Heat Transfer: Conduction, Convection and Radiation

5. Which is the best surface for absorbing heat radiation?

A. Shiny white

B. Dull white

C. Shiny black

D. Dull black

Page 27: Understanding Heat Transfer: Conduction, Convection and Radiation

http://www1.teachertube.com/viewVideo.php?video_id=159713