1 Geometry Parameters Analysis of CPU Heat Sinks GlacialTech, INC. 27th September 2002

2 To understand the effects of the geometry parameters for aluminum extrusion fins, we employed PHOENICS and experimentation to prove the results each other. The parameters are: the ratio of thickness and pitch between fins fin number length for heat sink height of fins Introduction

3 Phoenics simulation VR-EDITOR 1. Build physics module 2. B.C. setting 3. Phoenics setting EARTH Iteration Convergen ce Yes No VR-VIEWER Generate temperature velocity and pressure field Decide the geometry parameter of heat sinks Manufacturing extrusion fins Check thermocouple Keep environment temp. is 35 Stead y Yes No Measure CPU temp. 1.Calculate thermal resistance 2. Discussion of results Experimentation Flowchart for the research

4 Physics model environment temp. is 35 heat flux is 45 W Flow rate is 17 CFM

5 PHOENICS Setting steady state elliptic – staggered formulation cartesian coordinate system the fluid is incompressible k-ε turbulence model convergence criterion is 0.1 no heat flux in heat sink

6 Experimentation

7 Discussion : blue line: green line: The ratio of thickness and pitch between fins Fin number p: pitch of fins t: thickness of fins We have better performance in more fins in the same ratio of p/t.

8 Discussion : Length for heat sink The effect of increasing length of heat sinks is not apparent for decreasing thermal resistance. The good value of length of heat sink is about 75 mm.

9 Discussion : Height of fins When the height of fins is less than 20 mm, thermal resistance has large drop.

10 Conclusion and Development 1. Thermal resistance will decrease when thickness were increased, but increasing fin number has bigger effect than increasing thickness of fins. 2. Increasing height of fins will provide good solution but increasing length of heat sinks is not apparent for decreasing thermal resistance. 3. We will build a system which will help us to design extrusion fins quickly in the future. 4. General extrusion ratio is 20 now, but the ratio in GlacialTech is 28, so to promote extrusion ratio is our purpose in the future.

11 Power dissipation=70W Environment Temp. = 35 Flow rate = 13.3CFM Noise=25 dB Thermal Resistance=0.357 /W Application