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 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     ME 340 textbook