Investigation of Air Mover for Small Volume Spot Cooling Applications

1. Investigation of Air Mover for Small Volume Spot Cooling Applications Design Group Members: Thomas Staley Andrey Tsinovkin Tuan Le Dan Somlea Faculty Advisor: James E. Morris Industry Advisor: Christopher Coleman

2. Background • A chip on the Differential Probes produced by Tektronix overheats and is damaged in the process. • Investigate and develop a practical component and a realizable method to move air in a small volume for the purposes of spot cooling.

3. Background

4. Design Requirements

5. Design Constraints • Limited Space • Must survive high acceleration events • Easily manufactured • Low cost performance ratio

6. Possible Solutions • Axial Flow fan • Radial flow fan • Gear Pumps • Piston Pumps • Diaphragm Pumps • Corona Discharge

7. Design Selection • Rotating equipment is undesirable • The target application may experience acceleration loads in excess of 20g difficult to stabilize rotating equipment under these conditions • 10,000 hour lifetime creates incentive to eliminate wear parts. • Rotating equipment is difficult to scale down to the desired level.

8. Designing for Reliability • Eliminate wear parts • Use solid state solutions wherever possible • Durable structure and packaging!

9. Designing for Manufacturability • Engineering materials based on manufacturing processes rather than design requirements when possible. • Eliminate 3D part features by means of a 2D layering strategy. • Think of a soccer ball, it is a three dimensional structure, but it is manufactured as a composition of 2D pieces.

10. Final Selection • A diaphragm pump concept was chosen • A piezoelectric bending element was used as the diaphragm • Solid state diffusers used as intake and discharge valves • Manufactured from stainless steel in three steps, assembled with silicone RVT

11. Piezoelectric Bender • Actuated electrically • Behaves like a diaphragm • Commonly used as speakers in portable devices such as cellular phones, laptops, etc. Piezoelectric Bender Modes of Vibration

12. Piezoelectric Advantages • Simple • Cheap • Reliable Courtesy of CUI Inc. 2007 www.cui.com

13. Valves • The valves were constructed using inline diffusers • Diffusers in this application operate based on the principle of vena contracta • The geometric arrangement acts as a high loss valve with no moving parts!

14. Diffuser Concept

15. Valve Assembly • A diaphragm pump needs two valves to operate, a suction and discharge. • Therefore the valve arrangement requires two inline diffusers Valve Assembly

16. Putting It All TogetherExploded View

17. Putting It All TogetherPump Cross Section

18. Prototype Parts

19. Assembled Product

20. Results Hot Film Anemometer • JLC Industries EE57-1 Miniature Air Velocity Transmitter • Peak velocity occurs at: First Prototype - 500-600 Hz Second Prototype – 5,000 – 6,000 Hz • Peak velocity First Prototype - 120 lfm Second Prototype -600 lfm at 5V @ 20mA Heat Transfer Analysis - First Prototype • 8.6% Difference in heat transfer coefficient - Second Prototype • 42.8% Difference in heat transfer coefficient • Resistor – 0.25 watt Carbon Film Resistor • 30% Reduction in thermal resistance

21. Results Pump On Pump On Pump Off Pump Off

22. Particle Image Velocimetry (PIV) • Utilizes a sheet of light in a dark room to visualize particles moving in one plane • The concept relies on CCD cameras to track the particles as a function of distance traveled over time • Results provide speed and direction of the flow field

23. PIV Setup

24. Physical Setup

25. Flow VisualizationParticle Trace Image

26. More Flow Visualization

27. More Flow Visualization

28. Visualized Operation