The Heat Sink
Heat Transfer Class Project
Tim Bishop Nathan Packard
Fall 2006
Introduction
Project was derived from summer
internship at Moxtek in Orem, UT
Involves basic conduction/convection
through fins
Wanted to mathematically SHOW what
had previously been OBSERVED
The Original Setup
Assumed temperature of lights and base- 150 deg. F (72 deg. C )
Introduction
Luxeons-
-Popular type of LED- very bright
- Run on about 350 mA and 12 volts
- Will produce 35-40 lumens per watt- this is 5 to
20 time brighter then standard LEDs.
These LEDs get VERY HOT! As mentioned in the online advertisement-
“You must order a Heatsink, otherwise you must fix the LUXEON® to
something that will draw the heat from the part.”
**We decided on the latter!!**
The Solution
Assumed temperature of lights and base- 75 deg. F (24 deg. C )
Assuming h=5, 14.8 W are emitted!
Analysis
Solution was a simple analysis of heat
transfer from extended surfaces:
2 large fins (9 x 5 x ½ inches) pure aluminum
4 smaller fins (5 x 3 x ¼ inches) of alum. alloy
Small fan to increase h (assuming 25)
Methodology
Used Figure 3.18 on page 138 of text to
determine efficiency of fins
Knowing lengths, widths, k (237 for pure aluminum,
177 for alloy) and h (50) we found efficiencies of 0.83
(large) and 0.84 (small)
Plugging efficiencies into heat transfer
equation, found the temperature difference
to be about 19 deg. C.
Iteration lead to a temperature change of
about 8 deg. C, which seems accurate!
Resources
Moxtek Inc.- Special thanks to Michael Yost- Research and
Development Engineer
http://www.fiberopticproducts.com/Luxeon.htm
ME 340 textbook