Biological Kinetics - Biosystems Engineering

1. Roof Radiation
Kira Bartlett, Ashleigh Hough, Jeannie Ossorio
BE 4120

2. Purpose
Investigate the heat
transfer due to solar
radiation through
commonly used roofing
materials

3. Why this Project Topic?
There is plenty of
research and
advertising for the
“green” vegetative
roofing and “cool”
light painted roofing
because of their
effects on energy
efficiency. We wanted
to see the effects of
regular roofing
materials have
efficiency.
http://ngm.nationalgeographic.com/2009/05/gre
en-roofs/klinkenborg-text
http://www.jagarchitect.com/leed.html

4. The Set Up
● Hobo Data Loggers
o Temperature
o Ambient Air
o Solar Radiation
● Types of Roofing
o Cedar
o Clay
o Asphalt
o White Tin
o Tan Tin

5. Environment
● Mix of Sun and Clouds
● 73 ⁰F (22.78 ⁰C)
● Time: 1:40 pm - 5:45 pm

6. MATERIAL ANALYSIS
Determining the surface absorptivity (αs) of
each material
HOBOs: Surface Temperatures
Radiation Flux
Dimensions
Using assumed values for thermal conductivity (k)
Fourier’s Law:
Solar Irradiation:

7. ANALYTICAL ANALYSIS PROCESS (Asphalt)
Fourier’s Law:
Solar Irradiation:

8. ANALYSIS OF ASPHALT SHINGLES
Assumed K Value:
0.11 W/mK
Thickness:
0.002 m
q” = 729.85 W/m2K
αS = 0.912

9. ANALYSIS OF CEDAR SHINGLES
Assumed K Value:
0.12 W/mK
Thickness:
0.0045 m
q” = 9.687 W/m2K
αS = 0.012

10. ANALYSIS OF CLAY ROOFING TILES
Assumed K Value:
0.163 W/mK
Thickness:
0.01 m
q” = 356.7 W/m2K
αS = 0.45

11. OVERALL TEMPERATURE COMPARISON

12. COMSOL ANALYSIS PROCESS
Modeled as flat plates using assumed thermal
conductivity (k) values
Modeled using steady state conditions (3-4:30 PM)
Boundary Conditions
BS1: Calculated Heat Flux
BS2: Constant Temperature
right side → temperature of bottom surface
Compared temperature of the exposed side (left) to
temperature from HOBO

13. COMSOL ANALYSIS
ASHALT SHINGLES CLAY TILES CEDAR SHINGLES
TS1 = 304.952 K
TS2 = 318.211 K
TS1 = 304.944 K
TS2 = 310.606 K
TS1 = 304.947 K
TS2 = 305.31 K

14. Real Time vs. COMSOL

15. Conclusion
● Tin shingles reflect heat from the sun and they utilize
the dead-air space between the metal ridge and roof
deck to minimize some of the heat generated through
conduction.

16. References
Vandervort, Don. "Pros & Cons of Metal Roofing." HomeTips.com. HomeTips,
2015. Web. 25 Apr. 2015.
"Thermo-Physical Properties of Construction Materials | CBERD." CBERD.
2011. Web. 25 Apr. 2015.
Drapcho, Caye. “Appendix A” Handout. Heat and Mass Transport in BE. (Dr.
Caye Drapcho). Clemson University. Spring 2015. Print (unpublished).