Miniature Air Moving Device: Progress Report

Table of Contents: Page

Introduction/Background Information 2

Document Purpose 2

Mission Statement 2

Project Plan/Timeline 3

Product Design Specifications 3

External Search 4

Internal Search 5

Concept Evaluation 11

Detailed Design 12

Current Project Status 12

Conclusions 12

Appendix A: Gantt Chart 13

Appendix B: Product Design Specifications 14

Appendix C: External Search Results 15

2 Miniature Air Moving Device: Progress Report

Introduction Intel Corporation is the world’s largest semiconductor manufacturer and the inventor of the x86 microprocessor, which is found in most of the world’s personal computers. Within Intel, the Mobile Platforms Group is responsible for investigating and developing promising new technologies specifically for implementation in mobile electronic devices such as laptop computers. These smaller devices encompass an ever increasing percentage in world-wide computer sales.

As manufacturers seek to decrease the size of electronic devices without decreasing their performance, the need for smaller components grows. Especially important is any technology that facilitates the cooling of these components within the device. Desktop PC’s and many larger electronic devices use relatively large axial fans that can sit vertically due to few size constraints. As computers decrease in size, and specifically thickness, radial fans or blowers that have been flattened are used to move air and cool components through convection. Currently, some of these miniature blowers have a footprint of less than a dime and operate in a space 6mm high. Blowers can be made increasingly smaller, but the technology is primitive and the efficiency is static.

Intel is actively exploring new methods of air movement on an even smaller scale. The goal of this project is to produce an air moving device that that fits into a space 3mm high, with limited decrease in air volume transport, air speed, and pressure with respect to current technology.

Mission Statement Our mission is to design and prototype a non-traditional miniature air-moving device that operates in a space 3mm high and satisfies air-flow and design specifications requirements set forth by Intel. Project Plan

The air moving device is well on its way to design and prototype. A detailed project plan is provided in Appendix A. The major milestones that need to be tackled include final concept selection, detail design, prototyping, and final documentation. The final concept selection will be accomplished by March 17, allowing the team to wrap-up all of the detailed design by April 10. The team will then assemble and test the prototype from April 27 through May 5. Final drawings, cost analysis, and detailed report will be available and presented on or before June 12. Product Design Specifications

The main customers for this project are Intel and the Mobile Platforms Group, Intel sponsor Jered Wikander, the capstone project team, the project’s PSU advisor, Dr. Chien Wern, and mobile electronic device manufactures that will use this application in the future.

Highest priority specifications mandate that the device operate in a space 3mm high, have an air transport of 0.01-0.1 cubic feet per minute, a pressure range of 0.01-0.05 inches of water, and an air velocity between 0.1-1 meters per second. Intel has also requested that the device explore new or non-traditional methods of moving air. Detailed design specifications according to priority and metrics, as discussed in the Product Design Specification Report (Feb 6th, 2009) are provided in Appendix B.

External Search

Current technology for moving air on the scale required with today’s mobile electronic devices involves mostly radial and axial fans. Radial fans have the advantage of a slimmer profile than axial fans. There are at least two radial fans on the market which have a height of 3 mm or less. However, the minimum height required for their operation is 6mm which includes a 3mm space for air inlet. The smallest axial fan that was researched was the Sunon 8mm fan which could operate in the 8mm space with no additional height requirements. All of these devices move air within or near the required range for this project.

Other fans or devices that have been miniaturized include cross-flow fans and diaphragm pumps. Cross flow fans move air in a direction perpendicular to blade axis of rotation. Cross-flow fans have not been miniaturized to the extent of radial and axial fans. Cross-flow fans are louder than radial and axial fans and move less air. Diaphragm pumps are best suited for incompressible fluids. The smallest diaphragm pump found was 21mm in height.

Another technology researched was electrostatic fluid motion (EFM) otherwise known as “ionic wind”. EFM uses Corona ionization to charge oxygen and nitrogen air molecules. These ions are subjected to an electric field which pulls them to the oppositely charge terminal. The motion of the charged ions causes non-charged molecules to move which results in bulk air movement. These devices exist on the scale of the project, and larger versions have shown to have comparable or increased air flow over similarly sized fans. However, power requirements for even the smallest EFM device are beyond the limitations imposed by Intel, and the EFM technology is still in the development stage.

Images of the search results and summarized pros and cons of the devices can be found in Appendix c.

Internal search

The following designs are a result of project brainstorming for non-traditional air movement devices.

Screw Pump

The screw pump is a modified axial or mixed-flow type fan. Air enters the opening in a direction perpendicular to the blade axis of rotation where forward curved blades or vanes act to “grab” the air. The direction of the air is then forced into a flow parallel to the axis of rotation. The large pitch of the “screw” acts to accelerate the air in this direction. The profile of the vanes switches from curved forward to neutral and finally to curved backwards as the pitch of the “screw” increases. The effect of these changes acts to increase velocity and build pressure as the air moves to the end of the screw. At the end of the screw the air is forced into a funnel which changes the direction of flow back to its original direction. The funnel also increases the velocity as the cross sectional area decreases at the exit.

The screw pump’s potentially small size is an advantage for this application. The devices’ foot-print could be kept under 5 x 30 mm. The design also allows for one motor to run two pumps set end to end. Many pumps could be used to achieve the desired flow rate. Driving the pumps could be accomplished with a small stepper motor which would have minimal power requirements, also an advantage due to the limited power. There is only one moving part which reduces the potential failure of the device. Finally, all parts could be injection molded which is inexpensive, and assembly and installation would be quick and easy keeping costs low.

Disadvantages of the design include the small diameter of the vanes and the size of the inlet which would effectively move less air than a radial fan with larger blades and inlet. The smaller diameter of the vanes would require an increase in rpm in order to achieve the same flow as a radial design, another disadvantage. Sealing the pump chamber to ensure air movement with the rotation of the blades relies on a boundary layer of air at the chamber wall which would lower the efficiency of the design and possibly decrease the pressure the pump was able to create. Finally, it is doubtful that the device could achieve the desired velocity even if the flow rate could be achieved by using many devices at once.

Parachute Pump

The Parachute pump is a modified diaphragm pump. The diaphragm consists of a flexible membrane with a magnet adhered in the center. The membrane is stretched over short “walls” which contain one-way valves on opposite walls. The pump is actuated by alternating current to electromagnets above and below the membrane magnet. The alternating current causes the membrane to rise on the first half of the cycle, which pulls air into the chamber through the one-way valves. When the bottom electromagnet is “turned on” in the second half of the cycle, the membrane is forced downward expelling the air from the chamber through the second set of valves.

Advantages of the design include relatively low power requirements, and ease of manufacturing. Air movement could be significant if the chamber is sized large enough, but is limited by the efficiency of the one-way valves and area of the inlets. However, difficulty sourcing out the tiny one-way valves and durable flexible material is a short fall. The design also has the potential of vibration and noise, and a short life span if proper material for the diaphragm is not selected.

Milking Machine

(View from top)

The “milking machine” is a 3mm high box with miniature valves situated on the shorter sides. A movable, magnetic partition or piston exists between the valves inside the box. Electromagnets on either side of the partition are used to pull the piston back and forth. Springs could be fixed to the piston for centering purposes when the magnets are not activated. By alternating current through the electromagnets, the piston is cycled back and forth, simultaneously pushing air out of one chamber and drawing air into the other. In this manner air output is continuous (two pulses of air per magnetic cycles), as opposed to the parachute design which only produces one pulse of air per magnetic cycle.

The benefits of this device are the compact size, simplistic movement of air, ease of installation and concept validity. The pump takes up 3 square inches of space. Electromagnets are activated and deactivated by routing electricity from one magnet to the next. The installation is simple because it is a box that is packaged and wired directly to the circuit board similar to fans currently in service. The air volume transport is also adjustable according to the speed of the electromagnet cycle.

Disadvantages of this design include creating the air-tight seal between the partition and the inside of the box while limiting friction. This will be crucial to the efficiency of the fan. Another disadvantage is finding an electro magnet that is less than 3mm in diameter. Lastly, finding readily available valves that are 3mm in diameter will be a challenge.

Worm Device

The “Worm Device” pushes pockets of air horizontally through the plates due to a membrane which moves in a wave-like fashion. There are three iterations of the worm device, the mechanical worm, the membrane worm, and the magnet worm. All of these designs have the advantage of large potential inlet areas for maximum air movement.

Membrane Worm

This Device was partially conceptualized from the workings of the human esophagus. The design moves air by semi-sinusoidal motion of a malleable material which captures air and pushes the air through the two parallel plates from one end to the other. The flexible material would be attached to the side, guide posts via mounting bars that span the width of the design, or by the insertion of ringlets into the sides of the material which would connect the material directly to the posts. Several methods of controlling the motion of the material have been proposed. The first is a system of electromagnets which could be turned on and off to drive either the metal mounting bars or ringlets up and down. Another method of controlling the wave motion would be a lever system utilizing piezocrystals to raise and lower the material.

The strongest aspect of this design is that, when sealed, it pushes the entire volume of air exposed at the inlet through the device as opposed to most fans which, between the stator and blades, can effeciently move 50% of the air in the space that the device is installed in. The effect of the wave motion is that when one cycle begins to move through the device, the inlet is again opened (the materials opposite side) as an inlet for the next cycle. The result is a continuous supply of air moving through the device at all times. Difficulties in the design include procuring the flexible material, and finding, or manufacturing, thin electromagnets or the lever systems to control the motion. Sealing the edges of the material, to ensure all air is moving forward, is another obstacle to be overcome with this particular iteration. Finally, the device will last only as long as the membrane, so material selection is crucial in the longevity of the design.

Mechanical Worm

The mechanical worm substitutes the flexible membrane with a series of plates that expand and contract, while moving vertically in tracks, to simulate the sinusoidal motion. This design has an advantage over the membrane worm because it eliminates the difficulties of controlling a flexible material with the inflexible plates. Mechanics of operating the plates would be controlled in a similar manner to the membrane worm, and it has the same large air volume movement qualities. The design of the device is simple in that it requires only one plate part (flipped and interlinked) and one side rail (same part both sides) be manufactured.

However, because of the spaces between the expanding plates, some sort of flexible, air-tight material would still have to be found and adhered to the surface of the plates. The design also suffers from air leakage around the outside of the plates. Manufacturing of the plates may prove difficult because of their small size, and the life of the device is dependent upon the durability of the plates. Finally, the plates themselves are .5 mm thick, which takes up more space than the thin flexible material of the membrane worm, slightly decreasing the total volume of air moved with each cycle.

Magnet worm

The magnet worm uses a series of metal plates inserted into slots along the length of a flexible membrane with a cross section in the shape of the number eight. The “tube-like” nature of the membrane functions to seal the design, ensuring all air is moved in the desired direction by preventing escape of air around the outside of the plates. Electromagnets on the upper and lower plates alternate along the length of the design moving the plates first to the top and then back down in series. The results are pockets of air in the membrane forced in the

10 Miniature Air Moving Device: Progress Report desired direction. Once again, material procurement and the thickness of the electromagnets are weaknesses in the design.

Concept Evaluation

The design team used an evaluation method that consisted of initial screening, averaged team concept scoring matrix, and final team evaluation.

Initial Screening

Upon initial screening the ionic device was removed from consideration for further concept evaluation. The ionic device was deemed too costly and unproven to pursue. Four viable concepts remained after screening. These included the milk machine, parachute device, screw device, and the worm device. The worm device concept consisted of three different iterations.

Evaluation Criteria

The concepts were evaluated based on power draw, installation, cost, manufacturability, material procurement, and air volume transport. These criteria were weighted based on Intel’s specifications as can be seen on the product design specifications in Appendix B. For example, Air volume transport was of utmost concern and carried a weighting of forty percent. Power draw was a low priority for Intel, and our team, and carried a rating of ten percent. Each member of the design team rated the six concepts with an integer value of one thru five, with five being the best and one being the worst. The members’ evaluations were averaged to yield an unbiased concept selection. Table 1 represents the members’ averaged values for each concept along with the selection results. The concept selected using this method was the screw compressor.

Table 1: Averaged concept selection

Final Team Evaluation

Final evaluation is the process of evaluating the averaged weighted values and examining the concept which the team would most like to pursue. This will be a simple vote among the team with input from our Intel sponsor. Detailed Design

Detailed design will begin as soon as all manufacturing and material research is concluded. Current Status

At this point in time the group is in the process of sourcing manufacturers for the plates in the mechanical worm, and materials for the membrane worm and magnet worm. As soon as material and manufacturing possibilities are ascertained, the group will proceed with concept selection and detailed design of the device. Currently, the favored device is the worm machine due to its adjustability and large volume of air movement. Conclusions

Thus far the group has defined the needs and priorities of Intel, and completed a comprehensive external and internal search. As a result of these searches concepts were presented and evaluated for concept strength. At this stage the group is finalizing the concept selection and gearing up for design analysis and material selection. The team is confident that we can meet the high-priority needs of Intel.

As for the timeline, the team has amended the project plan for concept evaluation, allowing for more time for final concept selection. Although amended, the team feels comfortable that once concept selection is complete the project will proceed quickly. Material selection and procurement will take time, but we feel confident that the two months allotted will be amenable.