This document discusses applications of heat transfer in three areas: a) Keeping homes insulated to reduce heating and cooling costs by inhibiting heat transfer through walls. Insulation materials have high R-values which reduce the rate of heat flow. b) Examples of heat transfer in technology include regulating temperatures in orbiting satellites, the physics of how thermos bottles keep liquids hot or cold through insulation, and how halogen cooktop stoves absorb radiant energy. c) The greenhouse effect is a natural process that warms the Earth through the atmosphere absorbing and re-radiating solar energy trapped by greenhouse gases like carbon dioxide and methane. This summary outlines key applications and concepts related to heat transfer.

1. Applications
of
Heat Transfer

2. Objectives:
At the end of the class discussion, the
student must be able to:
a. list applications on heat transfer.
b. perform the activity on increasing the
insulators of heat.
c. relate the heat transfer on daily life by
giving additional applications.

3. Definition of Terms
1. insulators- substance which conducts heat
slowly.
2. conductors- substance which conducts heat
quickly.
3. absorption- the process by radiant energy is
taken up internally, or assimilated, by a
substance.

4. 4. reflection- bouncing of radiant energy upon
striking a surface.
5.emission- release of energy. This means to give off
energy. The opposite of absorption of energy.
6. radiant energy- the energy which travels in the form
of electromagnetic waves.

5.  To keep heating and air conditioning
bills to a minimum, it pays to use good
thermal insulation in your home.
Insulation inhibits convection between
inner and outer walls and minimizes heat
transfer by conduction.

6. Equation 13.1

7. Construction engineers, however,
prefer to use Equation 13.1 in the slightly
different form.

8. *An R value expresses in a single number the
combined effects of thermal conductivity and
thickness.
*Larger R values reduce the heat per unit time
flowing through the material.

9. Physics of regulating the temperature
of an orbiting satellite

10. Physics of a thermos bottle

11. How thermos bottle
severely inhibited the
transfer of heat?

12. Physics of halogen cooktop stove

14. Absorption of
Radiant Energy

15. A good absorber of radiant energy
reflects very little radiant energy,
including visible light.
Hence, a surface that reflects very little
or no radiant energy looks dark.

16. The hole in the box that Helen holds
looks perfectly black and indicates a
black interior, when in fact the interior
has been painted a bright white.

17. Radiation that enters the cavity has little
chance of leaving because most of it is
absorbed. For this reason, the opening to any
cavity looks black to us.

18. Reflection of
Radiant Energy

19. Good reflectors, on the other hand, are
poor absorbers. Clean snow is a good
reflector and therefore does not melt rapidly
in sunlight. If the snow is dirty, it absorbs
radiant energy from the sun and melts faster.

20. When the containers are filled with hot
(or cold) water, the blackened one cools
(or warms) faster.

21. Emission of
Radiant Energy

22.  If the surface is hotter than the
surroundings, for example, it will be a net
emitter and will cool. If the surface is
colder than the surroundings, it will be a
net absorber and will cool.

23. Cooling at
Night by
Radiation

24. Bodies that radiate more energy than they
receive become cooler. This happens at night
when solar radiation is absent.
An object left out in the open at night radiates
energy into space and, because of the absence of
any warmer bodies in the vicinity, receives very
little energy in return

25. Which is likely to be
colder; a night when the
stars are out or a night with
no stars?

26. Newton’s Law
of Cooling

27. The rate of cooling of an object- whether by
conduction, convection, or radiation- is
approximately proportional to the temperature
difference between the object and its
surroundings.

28. Greenhouse
Effect

29. Greenhouse Effect- is the effect
of atmospheric gases on the balance
of terrestrial radiation and radiant
energy from the sun.

30.  The greenhouse effect is a natural
process that warms the Earth’s surface.
When the Sun’s energy reaches the Earth’s
atmosphere, some of it is reflected back to
space and the rest is absorbed and re-
radiated by greenhouse gases.

32. Greenhouse gases
water vapor
 carbon dioxide
 methane
nitrous oxide
ozone
artificial chemicals such as
chlorofluorocarbons (CFCs)

34. Real Greenhouses

35. Solar Power,
Energy, and
Resource
Conservation

36. Important Facts About the
Sun:
a. Diameter: 1,392,000 km
b. Temperature at Surface: 6000 degree
Celcius
c. Distance from the Earth: 150,000,000 km

37. Solar Constant- the amount of radiant
energy received each second over a
square meter that is at right angles to
the sun’s rays at the top of the
atmosphere.
Numerical Value= 1400 joules

38. Distribution System of Solar
Energy
a. active system- the distribution system
requires external energy to operate fans or
pumps.
b. passive system- the distribution is by
natural means ( conduction, convection, or
radiation)

39. Solar Cell- a photo-electric cell that
converts sunlight into electrical energy and
is used as a power source.

40. Central Receiver System- these systems consist
of a tall tower surrounded by thousands of
mirrors called heliostats.

41. Photovoltaic System-Producing
electricity directly from sunlight.

42. Solar Wind Power: Generating Power In
The Future
Scientists at Washington State University have now
combined solar power and wind power to produce
enormous energy called the solar wind power, which will
satisfy all energy requirements of human kind.

43. References:
1. Hewitt, Paul G. Conceptual Physics, 8th edition.
Beethoven Publishing. Philippines. 1998.
2. Jones, Mary. et al. Physics, 2nd edition. University
Press. United Kingdom. 2000.
3. Cutnell, John D., Kenneth W. Johnson. Introduction
to Physics, 8th edition. John Wiley & Sons Pte. Ltd.
Singapore. 2010.