-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
1/35
Understanding Heat Transfer,
Conduction, Convection and
Radiation
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
2/35
Heat Transfer
Heat always moves from a warmer place to a
cooler place.
Hot objects in a cooler room will cool to room
temperature.
Cold objects in a warmer room will heat up to
room temperature.
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
3/35
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
4/35
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
5/35
Conduction
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.
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
6/35
Why does metal feel colder than wood, if they
are both at the same temperature?
Metal is a conductor, wood is an insulator. Metalconducts 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.
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
7/35
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
8/35
What is an insulator???
A thermal insulatoris a material that conducts heatpoorly.
Heat flows very slowly through the plastic so that thetemperature of your hand does not rise very much.
Liquids and gases are also extremely poor conductors.
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
9/35
Convection
What happens to the particles in a liquid or a
gas when you heat them?
The particles spread out andbecome less dense.
This affects fluid movement.
Remember, fluid = liquid OR gas
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
10/35
Fluid movementCooler, more dense, fluidssink through warmer, lessdense fluids.
In effect, warmer liquids and gases riseupwards.
Cooler liquids and gases sink downwards.
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
11/35
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
12/35
Why is it windy at the seaside?
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
13/35
Much of the Earths climate is regulated by giant convection
currents in the ocean.
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
14/35
Cold air sinks
Where is thefreezercompartment
put in a fridge?
Freezercompartment
It is put at the top,because cool air
sinks, so it cools thefood on the way
down.
It is warmer at
the bottom, sothis warmer air
rises and aconvection
current is set up.
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
15/35
The third method of heat transfer
How does heat energy get
from the Sun to the Earth?There are no particles betweenthe Sun and the Earth so it
CANNOT travel by conduction or
by convection.
?RADIATION
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
16/35
Radiationis heat transfer
by electromagnetic waves.
Thermal radiationis
electromagnetic waves
(including light) producedby objects because of their
temperature.
The higher the
temperature of an object,
the more thermal radiation
it gives off.
Radiation
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
17/35
We do not see thethermal radiation
because it occurs atinfrared wavelengthsinvisible to the humaneye.
Objects glow differentcolors at differenttemperatures.
ALL objects emit SOME
form of radiant energy. ALL objects also
ABSORB some amountof radiant energy.
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
18/35
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
19/35
The Greenhouse Effect
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
20/35
Earths Atmospheric Gases
Nitrogen (N2)
Oxygen (O2)
Water (H2O)
Carbon Dioxide (CO2)
Methane (CH4)
Non-Greenhouse
Gases
99%
Greenhouse
Gases
1%
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
21/35
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
22/35
Sun
Earths Temperature
Solar
Energy
RadiationCooling
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
23/35
Sun
Earths Temperature
Solar
EnergyRadiationCooling
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
24/35
Sun
Earths Temperature
Solar
Energy
Radiation
Cooling
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
25/35
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
26/35
To change phases of matter,
you either gain or lose
thermal energy (you
transfer some heat)!
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
27/35
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
28/35
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
29/35
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
30/35
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
31/35
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
32/35
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
33/35
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
34/35
-
8/12/2019 Understanding Heat Transfer, Conduction, Convection And
35/35
Enthalpy of Fusion
Enthalpy of Vaporization