conduction, convection and radiation

1. Transfer of Heat
By
JAVED IQBAL ANJUM PDT, AKU-IED, PDCN
for EDIP Project for Gorikote Cluster

2. Flow of Presentation
• Session Learning Outcomes
• Transfer of Heat
• Condition
• Convection
• Radiation
• Expansion matter

3. Session Learning Outcomes
• By the end of this session C.Ps could be able to;
• Develop their understanding regarding
conduction, convection and radiation.
• Demonstrate some experiments regarding
conduction, convections, expansion in liquids and
solids.

4. Transfer of Heat
• Heat can be transferred from place to place
by conduction, convection and radiation. Dark matt
surfaces are better at absorbing heat energy than
light shiny surfaces.
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/energy/heatrev1.s
html
• In the simplest of terms, the discipline of heat transfer is
concerned with only two things: temperature, and
the flow of heat. Temperature represents the amount of
thermal energy available, whereas heat flow represents
the movement of thermal energy from place to place.
• http://www.efunda.com/formulae/heat_transfer/home/overview.cfm

5. Cont…

6. Conduction
• Conduction is heat transfer by means of molecular
agitation within a material without any motion of the
material as a whole. If one end of a metal rod is at a
higher temperature, then energy will be transferred down
the rod toward the colder end because the higher speed
particles will collide with the slower ones with a net
transfer of energy to the slower ones.

7. Convection
• Convection is heat transfer by mass motion of a fluid such as
air or water when the heated fluid is caused to move away
from the source of heat, carrying energy with it. Convection
above a hot surface occurs because hot air expands,
becomes less dense, and rises. Hot water is likewise less
dense than cold water and rises, causing convection currents
which transport energy
• Convection can also lead to circulation in a liquid, as in the heating of a pot
of water over a flame. Heated water expands and becomes more buoyant.
Cooler, more dense water near the surface descends and patterns of
circulation can be formed, though they will not be as regular as suggested
in the drawing http://hyperphysics.phy-
astr.gsu.edu/hbase/thermo/heatra.html
• .

8. Radiation
• Definition: Radiation is the emission and propagation of
energy in the form of waves, rays or particles.
• Examples:
• A burning candle emits radiation in the form of heat and
light.
Electrons dropping from one energy state to a lower
state emit radiation in the form of a photon.
• http://chemistry.about.com/od/chemistryglossary/g/Radiation-Definition.htm

9. Expansion in matters
• Solids, Liquids and gases expand when they are
heated. This is because the particles in liquids and
gases move faster when they are heated than they do
when they are cold. As a result, the particles take up
more volume. This is because the gap between particles
widens, while the particles themselves stay the same
size.
• The liquid or gas in hot areas is less dense than the
liquid or gas in cold areas, so it rises into the cold areas.
The denser cold liquid or gas falls into the warm areas.
In this way, convection currents that transfer heat from
place to place are set up.

10. Food for thought
• Science is a first-rate piece of furniture for a man's upper
chamber, if he has common sense on the ground floor.
• Oliver Wendell Holmes (1809-1894)
The Poet at the Breakfast-Table, 1872
Chapter 5

11. Questions Please