1. Possible Swain journals for first Article Summary.
Scientific American (e.g. Sept. 2006)
Nature (e.g. Nov. 2001)
Science (access through Swain library web page, they no longer have paper copies)
Science News
Physics Today
The Physics Teacher
Bulletin of the Atomic Scientists
Summary will be graded on how well it covers the essential thrust of the article itself as well as on the quality of your writing.
Look at syllabus on ONCOURSE for the “article” link that describes in more detail what the assignment entails.

2. Swain Hall West- 2nd Floor
Swain Hall Library

3. Phase transitions in water

4. Passive Solar House

5. Specific Heats Temperature Scales:
Ice (near 0oC) J/kg.K=2090 J/kg.Co
Water (near 0oC) J/kg.K=1.00 cal/kg.Co
Aluminum J/kg.K
Copper J/kg.K
Temperature Scales:
0oC = K ice melts at this temp
100oC = K water boils at this temp
O K absolute zero, the coldest temperature possible.
Note that 1Co = 1 K. The Celsius degree and the Kelvin are the same size! The only difference in the scales is the position of the origin, hence the two scales are equivalent for talking about temperature DIFFERENCES, but not for talking about actual temperatures.

6. Power=(Q/Dt) = kA(TH – TC)/L
Thermal Conduction
Power=(Q/Dt) = kA(TH – TC)/L
k: thermal conductivity (depends on the material, not on the geometry). Units?

7. Some thermal conductivities
Diamond >1000 W/m.K
Aluminum ~225 W/m.K
Stainless steel W/m.K
Window glass W/m.K
Fiberglass insulation W/m.K
Polyurathane foam W/m.K
Air (still, dry) W/m.K

8. Some thermal conductivities
Diamond >1000 W/m.K
Aluminum ~225 W/m.K
Stainless steel W/m.K
Window glass W/m.K
Fiberglass insulation W/m.K
Polyurathane foam W/m.K
Air (still, dry) W/m.K
Question: Look at fiberglass vs. air (still dry). Why do you put fiberglass insulation
in your attic if still air is a better insulator than fiberglass?

9. Why replace a thin layer of air (k=0
Why replace a thin layer of air (k=0.026) near the floor of your attic with fiberglass (k=0.048)?
Toutside Tc

10. Heat Transfer through a window
Conduction is NOT the only
means of heat transfer!!!
There is also:
CONVECTION
When a fluid (gas or liquid)
flows, it transfers heat
much more effectively than
when it is still.

11. Convection in your attic It’s efficient at bringing the T of the attic floor to the T of the outside. Insulation allows the attic floor to be at a much lower (or higher) T than the house ceiling
Toutside Ta Tc

12. One way to use Solar Heat in a home
You can use of convection to your advantage, if you’re clever!

13. The Electromagnetic Spectrum

14. Radiative Heat Transfer
Wavelength
Power = esAT4
Effect of increasing temperature:
more power, shorter wavelengths
lpeak T= 2898 mm.K

15. Basic Heat Engine
Efficiency = h = W/QH = (QH-QC)/QH

16. OTEC
Tsurf = 25 C
Tdeep = 5 C

17. Second Law of Thermodynamics
The entropy (disorder) of the universe may never decrease.
If we let S denote entropy, then the change in the entropy of an object associated with an exchange of heat, Q, at ABSOLUTE temperature, T, is given by:
DS = Q/T

18. Carnot (reversible) Heat Engine
The entropy change of the universe in an operation of a heat engine is given by:
DS = QC/TC - QH/TH
Since this cannot be negative, the best you can do is have DS = 0, in which case:
QC/TC = QH/TH

19. Carnot Heat Engine (cont.)
For a Carnot cycle then we can rewrite the efficiency in terms of the ABSOLUTE temperatures of the two reservoirs (note the symbols := or =: denotes a definition for the quantity next to the colon):
h= 1 - QC/QH = 1 - TC/TH =: hCarnot

20. Chapter 5 Home Energy Cons.
Thermal Resistance:
Q/Dt = kADT/L =: ADT/R
R:= L/k
This is useful because it folds in both the material property (k) and the thickness of the insulating layer (L), AND if you combine layers, then the thermal resistances (R) simply add, as shown on the next slide.

21. R-value for a typical wall
See table 5.2 in H&K for typical values of building materials