investigation of air mover for small volume spot cooling applications

Investigation of Air Mover for Small Volume Spot Cooling

ApplicationsDesign Group Members:

Thomas StaleyAndrey Tsinovkin

Tuan LeDan Somlea

Faculty Advisor:James E. Morris

Industry Advisor:Christopher Coleman

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.

Background

Design Requirements

Design Constraints• Limited Space• Must survive high acceleration

events• Easily manufactured• Low cost performance ratio

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

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.

Designing for Reliability• Eliminate wear parts• Use solid state solutions wherever

possible• Durable structure and packaging!

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.

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

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

Piezoelectric Advantages• Simple • Cheap• Reliable

Courtesy of CUI Inc. 2007

www.cui.com

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!

Diffuser Concept

Valve Assembly• A diaphragm pump

needs two valves to operate, a suction and discharge.

• Therefore the valve arrangement requires two inline diffusers

Valve Assembly

Putting It All TogetherExploded View

Putting It All TogetherPump Cross Section

Prototype Parts

Assembled Product

ResultsHot Film Anemometer

- JLC Industries EE57-1 Miniature Air Velocity Transmitter

- Peak velocity occurs at:First Prototype - 500-600 HzSecond Prototype – 5,000 – 6,000 Hz

- Peak velocityFirst Prototype - 120 lfmSecond 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

Results

Pump On/Off

47

48

49

50

51

52

53

54

55

40 45 50 55 60 65 70 75 80

Time (s)

Tem

p (

deg

C)

Pump On/Off

62

64

66

68

70

72

74

76

20 30 40 50 60 70 80

Time (s)T

emp

(d

eg C

)

Pump Off

Pump On

Pump On

Pump Off

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

PIV Setup

Physical Setup

Flow VisualizationParticle Trace Image

More Flow Visualization

More Flow Visualization

Visualized Operation