in the Atmosphere

©2008 Norm Ivey

Heat Transfer

What is Heat Transfer?

• Heat transfer is the movement of heat energy from one substance to another.

• Heat (energy) always moves from a warmer substance to a cooler substance.

HotCold

What is Heat Transfer?

• Heat will continue to move until both substances are the same temperature.

HotCold WarmWarm

What is Heat Transfer?

• The greater the difference in temperature between the substances, the faster the heat will transfer.

What is Heat Transfer?

• There are three types of heat transfer:– Conduction– Convection– Radiation

What is Heat Transfer?

Examples

• You touch a black car in the summer and the heat from the car transfers into your hand.

• A breeze makes you feel cooler because the wind transfers heat away from your body.

• You feel the cold of a winter day because the cold air transfers into you.

• Your Coke in a cooler gets cold because the cold from the ice moves into the Coke.

Anti-Examples

Conduction

• Heat transfer by conduction is the transfer of heat through direct contact.

Conduction

• Molecules transfer energy to the molecules next to them.

Conduction

• The molecules do not have to be the same substance.

http://www.theelusivefish.com/articles/wp-content/uploads/2007/09/hot-stove.jpg

Example 1

http://www.vernier.com/caliper/fall07/images/heat_transfer_large.jpg

The metal conducts heat from the cup of warm water to the cup of cool water.

Your Coke becomes cold because the heat from the soda transfers into the ice, not the other way around.

http://www.photoanswers.co.uk/ImgGalleryTn/91/10191/2417_16333.jpg

Example 2

No matter what it feels like, cold does not

transfer into your body.

What is really happening here?

Why do you wear heavy clothes when it’s cold

outside?http://www.alaska-in-pictures.com/data/media/9/man-in-extreme-cold_355.jpg

Radiation

• Heat transfer by radiation is the transfer of heat through electromagnetic waves.

http://www.nmsu.edu/~safety/images/fire_meaney.gif

Radiation

• There is no direct contact between the substances.

http://www.blog.thesietch.org/wp-content/uploads/2007/04/earth.jpghttp://stardate.org/images/gallery/sun5.jpg

Heat from the sun radiates throughempty space to earth.

Example 1

http://www.lifefam

ilytraining.com/img/roasting-m

arshmallow

s.jpg

Example 2

The heat from the campfire transfersinto your marshmallow, giving you a yummy, gooey treat!

(Direct contact between the fire and your marshmallow will ruin it!)

Convection

• Heat transfer by convection is the transfer of heat through the fluid (liquids and gases) movement of currents.

Convection

• Warm fluids rise, cool down, sink, and then are warmed again.

http://www.eeb.ucla.edu/test/faculty/nezlin/Lecture1/Fig0803.jpg

The radiator warms the room by warming theair around it. Then the warm air transfers heat

to the rest of the room through convection.

http://physics.uoregon.edu/~jimbrau/BrauImNew/Chap07/FG07_03.jpg

As air above the road warms up, it rises and is replaced bycooler air, forming a convection current.

http://www.aos.wisc.edu/~aalopez/aos101/wk5/heatrans.jpg

This picture illustrates all three type of heat transfer.Can you identify them all?

Conduction

Radiation

Convection