Heat transfer can occur through radiation, which involves the transfer of electromagnetic waves, mainly in the infrared region. An experiment showed that dark, matt surfaces are better emitters of infrared radiation than light, shiny surfaces. Heat transfer in buildings occurs through walls, roofs, and windows, and practical insulation methods can prevent heat from entering a house in summer through these areas.

1. 1
Heat transferHeat transfer
Level: Form 4.Level: Form 4.
Date: 06/05/16Date: 06/05/16

2. 2
Learning objectives
By the end of this session you should be able
to:
• Describe the process of heat transfer by
radiation.
• Describe how to distinguish between good
and bad emitters/absorbers of infra-red
radiation.
• Describe how heat is transferred to or
from buildings and to or from a room.
• State and explain the use of the important
practical methods of thermal insulation for
buildings (Project work).

3. 3
Recap
• Conduction-heat transmitted through
vibrating molecules without net
movement of the material itself.
• Convection-mass motion of heated
fluid carrying energy away from the
source.

4. 4

5. 5
Radiation
-Heat transfer through EM waves,
mainly in the infrared region.
-It does not require any matter.

6. 6

7. 7
Experiment to determine good
and bad emitters/absorbers
of infra-red radiation.

8. 8
Good absorbers of IR

9. 9
Good emitters of IR.

10. 10
Procedures
For each group:
• Two beakers are filled with hot
water.
• The temperature readings are
monitored.
• Record some observations and
discuss.
• Conclusions?

11. 11
Conclusion
For surfaces at the same
temperature, dark, matt
surfaces are better emitters
of thermal radiation than light,
shiny surfaces.

12. 12
Exercises.
Explain each of the following in terms of thermal
energy (heat) transfer :
• (a) People in very hot climates wear white clothing
in order to stay cool.
• (b) Clean snow does not melt quickly in bright
sunshine, whereas dirty snow does.
• (c) After finishing the London marathon, athletes
are wrapped in aluminium-coated plastic sheets.
• (d) Some casserole dishes which are used to cook
food in ovens are black, but the outside of an
electric kettle is shiny.

13. 13
Heat transfer in a building.

14. 14
Project work:
Practical methods of thermal
insulation.
Finding insulations for the house in summer
to prevent heat from entering the house
through:
• Walls
• Roof
• Windows

15. 15

16. 16
Summary
• Process of heat transfer through radiation
in the form of EM wave, mainly infrared.
• Black surfaces are good emitters /
absorbers of infrared radiation.
• Heat transfer in a house.