WO2010136898A1

WO2010136898A1 - Cooling device

Info

Publication number: WO2010136898A1
Application number: PCT/IB2010/001459
Authority: WO
Inventors: Edmond Walsh; Patrick Walsh; Ronan Grimes; Jeff Punch
Original assignee: University Of Limerick
Priority date: 2009-05-28
Filing date: 2010-05-28
Publication date: 2010-12-02
Also published as: WO2010136898A4; US20120125572A1

Abstract

This disclosure relates to a low-profile cooling device (100) for applications such as spot cooling. The low-profile cooling device can include a first rotor (102), a second rotor (104), a motor (106) including a drive shaft (108) for driving and rotating each rotor, an upper plate (110), a middle plate (112), and a lower plate (114).

Description

COOLING DEVICE

CROSS-REFERENCE TO RELATED APPLICATIONS

This claims priority to and the benefit of Irish Patent Application No. 2009/0417, filed on May 28, 2009, the entire contents of which is incorporated herein by reference.

Also incorporated herein by reference is the entire contents of U.S. Patent Application Publication No. US 2009/0145584 Al, published on June 11, 2009. The entirety of International Patent Application Publication No. WO 2010/016046 Al, published on February 11, 2010, also is incorporated herein by reference.

TECHNICAL FIELD

The invention relates to cooling devices and, more particularly, to low-profile cooling devices for applications such as spot cooling. The types of things that can be cooled with one or more low-profile cooling devices according to the invention include one or more semiconductor chips, circuits, circuit boards, and generally various components of portable and non-portable devices and systems such as mobile phones, laptop computers, desktop computers, server computers, and telecommunications devices.

BACKGROUND INFORMATION

In the semiconductor industry, high temperatures of components threaten reliability and compromise user comfort. In large scale electronic systems, Moore's law causes the heat flux of many electronic devices to double every 18 months, thus threatening component reliability. Thus, at the micro scale, electronic devices incorporate cooling devices which include a number of heat transfer surfaces known as fins. However, in such micro scale systems, the problem of pressure losses becomes greater as an unfavorable relationship exists between channel size, flow rate and pressure drop. Other problems include space constraints, partial blockage of flow path, weight, difficulty of manufacture and integration, reduced effectiveness of fins as heat transfer surfaces, and ultimately, non-optimal thermal performance. In addition, as flow remains laminar and typically parallel with a heated surface within such systems, a thermal boundary layer grows along the surface and effectively acts as an insulator to heat flow.

It is known to use nozzles to generate jets which impinge upon a heated surface for impingement cooling. However, this provides significant difficulties which include nozzle back pressure, acoustic emissions, and practical limits due to enclosure size and design.

Therefore, various techniques have been employed to enhance fin heat transfer efficiency, such as staggering fins, and modifying manufacturing techniques to improve heat transfer through increased fin density. The presence of the fins results in an increase in heat transfer surface area and hence higher levels of heat transfer for a given mass flow. However, the fins also induce shear losses leading to higher pressure losses, which ultimately reduce the mass flow rate through and the hence the potential for heat transfer for a given pressure drop within the heat transfer surfaces.

One technique to enhance fin heat transfer efficiency is to use small ribs in an inverted V-shape to generate impingement zones. The ribs intersect the flow of fluid through the heat sink. Another technique is the use of corrugations in a heat exchanger for blending air passing between adjacent fins.

Such methods consist of physically modifying the heat sink structure to generate vortex fluidic structures, which is difficult and costly in a manufacturing process at small to micro scale applications. In addition, small diameter fans are very limited in the flow rate they can achieve, as above aspect ratios of greater than 0.2, little or no gain is achieved in flow rate.

SUMMARY OF THE INVENTION

The invention relates to low-profile cooling devices for applications such as spot cooling. One or more of the low-profile devices can be used to cool one or more chips, circuits, and other components in portable electronic devices as well as non-portable systems such as desktops, servers, and telecommunications devices. Cooling devices according to the invention have lower thermal resistance relative to existing cooling devices. One cooling device according to the invention is a dual-inlet low-profile cooling device. Its performance is better than that of a single-inlet cooling device such as disclosed in U.S. Patent Application Publication No. US 2009/0145584 Al . The inventive dual-inlet low-profile cooling device is configured for receiving air axially through two separate air inlets, each of which is disposed on an opposite face of the device. This axial inlet air is circulated within interior volumes defined between upper, middle, and lower plates. Two separate rotors (typically driven simultaneously by a common drive shaft coupled to a single motor, although a separate motor and drive shaft for each rotor is possible) force air from the axial air inlets radially into two separate interior volumes. This creates one or more vortices in each of the volumes, and this results in cooling of the plates as well as anything in direct or indirect thermal contact with one or more of the plates. The heated air is then expelled from the volumes through one or more radial air outlets associated with each interior volume.

Another cooling device according to the invention is a low-profile cooling device that includes one or more fin plates. This cooling device may be a single-inlet low- profile cooling device or a dual-inlet low-profile cooling device. At least one fin plate is disposed within each interior volume of the device. The single-inlet device has just one interior volume in which the one or more fin plates would be disposed, but the dual-inlet device has two separate interior volumes and thus typically uses one or more fin plates which each of those two volumes. A specific embodiment uses a single fin plate in each interior volume. These single-inlet and dual-inlet devices operate similarly to the operation described in the preceding paragraph.

In one aspect, the invention relates to a dual-inlet low-profile cooling device that includes a first rotor, a second rotor, a motor, an upper plate, a middle plate, and a lower plate. Each of the first and second rotors includes a plurality of blades. The motor includes a drive shaft for driving and rotating each of the first and second rotors. The upper, middle, and lower plates are substantially parallel to each other and substantially perpendicular to the drive shaft of the motor. The upper plate defines a first axial air inlet and the lower plate defines a second axial air inlet. The upper and middle plates are spaced apart to define a first interior volume and at least two first radial air outlets. The lower and middle plates are spaced apart to define a second interior volume and at least two second radial air outlets. Air from the first axial air inlet is forced radially into the first interior volume by the first rotor when it is driven and rotated by the shaft of the motor. This forced air ultimately exits from at least one of the at least two first radial air outlets. Air from the second axial air inlet is also forced radially into the second interior volume by the second rotor when it is driven and rotated by the shaft of the motor. This forced air ultimately exits from at least one of the at least two second radial air outlets.

In one embodiment according to this aspect of the invention, one or more vortices can be created within each of the first and second interior volumes without the need for physical structures within each of the first and second interior volumes. In addition, the cooling device can be comprised of support pillars for interconnecting the upper, middle, and lower plates. The cooling device can also be comprised of at least one heat pipe. The cooling device can be one in a stack of a plurality of cooling devices.

In another embodiment according to this aspect of the invention, the cooling device can be integrated within a portable device. The portable device can be a mobile phone or a laptop computer. The cooling device can also be integrated within a nonportable device or system such as a desktop computer or a server computer. The cooling device is useful for spot cooling generally, whether in a portable or a non-portable device or system. One or more of the cooling devices can be used to cool one or more graphics processing units, central processing units, and field programmable gateway arrays. At least one of the upper and lower plates of the cooling device can be formed by a wall of a housing of a device or system being cooled.

In a second aspect, the invention relates to a dual-inlet low-profile cooling device with fin plates. The cooling device includes a first rotor, a second rotor, a motor, an upper plate, a middle plate, a lower plate, a first fin plate, and a second fin plate. Each of the first and second rotors includes a plurality of blades. The motor includes a drive shaft for driving and rotating each of the first and second rotors. The upper plate defines a first axial air inlet and the lower plate defines a second axial air inlet. The first fin plate is disposed between the upper plate and the middle plate. The second fin plate is disposed between the middle plate and the lower plate. AU five of the plates are substantially parallel to each other and substantially perpendicular to the drive shaft of the motor. Each of the first and second fin plates defines openings at least as large as the first and second axial air inlets. The upper and first fin plates are spaced apart to define a first part of a first interior volume. The first fin and middle plates are spaced apart to define a second part of the first interior volume. The lower and second fin plates are spaced apart to define a first part of a second interior volume. The second fin and middle plates are spaced apart to define a second part of the second interior volume. Air from the first axial air inlet is forced radially into the first and second parts of the first interior volume by the first rotor when it is driven and rotated by the shaft of the motor. Air from the second axial air inlet is forced radially into the first and second parts of the second interior volume by the second rotor when driven and rotated by the shaft of the motor.

In one embodiment according to this aspect of the invention, the cooling device can be comprised of support pillars for interconnecting the upper, middle, lower, first fin, and second fin plates. The upper, middle, lower, first fin, and second fin plates can be substantially rectangular-shaped. The cooling device can also be comprised of at least one heat pipe. In addition, the cooling device can be integrated within a portable device. The portable device can be a mobile phone or a laptop computer. The cooling device can also be integrated within a non-portable device or system such as a desktop computer or a server computer. The cooling device is useful for spot cooling generally, whether in a portable or a non-portable device or system. One or more of the cooling devices can be used to cool one or more graphics processing units, central processing units, and field programmable gateway arrays. At least one of the upper and lower plates of the cooling device can be formed by a wall of a housing of a device or system being cooled.

In a third aspect, the invention relates to a single-inlet low-profile cooling device with a fin plate. The cooling device includes a rotor, a motor, an upper plate, a middle fin plate, and a lower plate. The rotor includes a plurality of blades. The motor includes a drive shaft for driving and rotating the rotor. The upper, middle fin, and lower plates are substantially parallel to each other and substantially perpendicular to the drive shaft of the motor. The upper plate defines an axial air inlet. The middle fin plate defines an opening at least as large as the axial air inlet. The upper and middle fin plates are spaced apart to define a first part of an interior volume. The middle fin and lower plates are spaced apart to define a second part of the interior volume. Air from the axial air inlet is forced radially into the first and second parts of the interior volume by the rotor when driven and rotated by the shaft of the motor.

In one embodiment according to this aspect of the invention, the cooling device can be comprised of support pillars for interconnecting the upper, middle fin, and lower plates. The upper, middle, lower, first fin, and second fin plates can be substantially rectangular-shaped. The cooling device can also be comprised of at least one heat pipe. The cooling device can be integrated within any one or more of a portable device, a desktop computer, a server, a graphics processing unit, a central processing unit, and field programmable gateway arrays, for example.

These and other objects, along with advantages and features of the invention herein disclosed, will become apparent through reference to the following description, the accompanying drawings, and the claims. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the same or similar parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

FIG. IA is an exploded broken view of an embodiment of a dual-inlet low-profile cooling device without any fin plates.

FIG. IB is a perspective view of the cooling device.

FIG. 1C is a top plan view of the cooling device.

FIG. ID is a cross-sectional view of the cooling device.

FIG. IE is a side view of the cooling device similar to FIG. IA but includes a motor on an external portion of the device.

FIG. 2 is a plan view of the cooling device of FIG. IA in a portable device. FIG. 3 is an exploded broken view of another embodiment of a dual-inlet low- profile cooling device with fin plates.

FIG. 4 is an exploded broken view of an embodiment of a single inlet low-profile cooling device with a fin plate.

FIG. 5 is a chart comparing thermal resistance relative to revolutions per minute of the rotor of a single-inlet cooling device without a fin plate.

FIG. 6 is a chart comparing thermal resistance relative to revolutions per minute of the rotor of the cooling device of FIG. 4.

FIG. 7 is a chart comparing thermal resistance relative to revolutions per minute of the rotor of the cooling device of FIG. IA.

FIG. 8 is a chart comparing thermal resistance relative to revolutions per minute of the rotor of the cooling device of FIG. 3.

FIG. 9A is a perspective view of heat pipes used with the cooling device of FIG. IA.

FIG. 9B is a top perspective view of heat pipes used with a single-inlet cooling device.

FIG. 9C is a bottom perspective view of heat pipes used with a single-inlet cooling device.

FIG. 9D is a perspective view of heat pipes used with two dual-inlet cooling devices.

FIG. 1OA is a perspective view of a stacked configuration of multiple dual-inlet cooling devices.

FIG. 1OB is a side view of the stacked configuration of FIG. 1OA. FIG. 1OC is a plan view of the stacked configuration of FIG. 1OA. DESCRIPTION

In general, the invention relates to low-profile cooling devices which lower thermal resistance. In the following description, embodiments of various types of low- profile cooling devices which receive air in an axial direction and expel air in a radial direction are disclosed. For example, low-profile cooling devices include a single-inlet low-profile cooling device including a fin plate, a dual-inlet low-profile cooling device, and a dual-inlet low-profile cooling device including fin plates.

FIGS. IA through IE illustrate the various elements of a dual-inlet low-profile cooling device. The dual-inlet low-profile cooling device according to the invention is configured for receiving air in an axial direction and expelling such air in a radial direction from the device. The device is comprised of a first and second rotor with a plurality of blades, a motor, and upper, middle, and lower plates. The upper, middle, and lower plates act as heat transfer surfaces. Air received axially is circulated within a first interior volume and a second interior volume.

FIG. 2 illustrates the dual-inlet low-profile cooling device incorporated into a portable device. The cooling device is disposed between various electrical components of the portable device. FIG. 3 illustrates another embodiment of the dual-inlet low- profile cooling device. In contrast to the cooling device set forth in FIGS. 1 A-IE and 2, this embodiment includes two fin plates. FIG. 4 illustrates an embodiment of a single- inlet low-profile cooling device with a fin plate.

FIGS. 5 through 8 are charts depicting measures of thermal resistance of various low-profile cooling devices. FIGS. 9 A through 9D illustrate the additional incorporation of heat pipes within the cooling devices. FIGS. 1OA through 1OC illustrate the cooling devices in a stacked configuration.

Referring to FIG. IA, in one embodiment according to the invention, a dual-inlet low-profile cooling device 100 includes a first rotor 102, a second rotor 104, a motor 106, a drive shaft 108, an upper plate 110, a middle plate 112, and a lower plate 114.

The first rotor 102 includes a first inner hub 103 and a plurality of blades 116. Like the first rotor 102, the second rotor 104 includes a second inner hub 105 and a plurality of blades 116. The drive shaft 108 is coupled to the motor 106 such that the drive shaft 108 drives and rotates each of the first rotor 102 and the second rotor 104. The drive shaft 108 extends from the motor 106 into the first inner hub 103 of the first rotor 102. The drive shaft 108 continues through the first rotor 102 and into the second inner hub 105 of the second rotor 104. The drive shaft 108 terminates at the second rotor 104. The drive shaft 108 may be configured such that it is longer or shorter in length. In addition, a second motor can be provided such that motor 106 can be configured to independently control the first rotor 102 and the second motor can be configured to independently control the second rotor 104.

The upper plate 110, middle plate 112, and lower plate 114 are substantially parallel to each other and substantially perpendicular to the drive shaft 108. Each of the plates can act as heat transfer surfaces and the upper plate 110, middle plate 112, and lower plate 114 can have a substantially rectangular shape. Each of the plates can also be interconnected via support pillars. Each of the upper plate 110 and the lower plate 114 includes air inlets. The upper plate 110 includes a first axial air inlet 118, which is defined as an opening on the surface of the upper plate 110. The lower plate 114 includes a second axial air inlet 120, which is defined as an opening on the surface of the lower plate 114. The first rotor 102 is disposed between the top plate 110 and the middle plate 112. The second rotor 104 is disposed between the lower plate 114 and the middle plate 112. The top plate 110 and the middle plate 112 are spaced apart to define a first interior volume 122. The top plate 110 and the middle plate 112 also define at least two first radial air outlets 126 when coupled together. The lower plate 114 and the middle plate are also spaced apart to define a second interior volume 124. The lower plate 114 and the middle plate 112 also define at least two second radial air outlets 128 when coupled together. The middle plate 112 includes an opening 119 which is sufficient in diameter to allow passage of the drive shaft 108. The opening 119 has a significantly smaller diameter in comparison to the diameters of each of the first axial air inlet 118 and the second axial air inlet 120.

Referring to FIGS. IA and IB, in operation, each of the first rotor 102 and the second rotor 104 draws air into the device 100. Air can be drawn into the device in an axial direction 130 and expelled from the device in a radial direction 132. Air received axially through the first axial air inlet 118 is forced radially into the first interior volume 122 by the first rotor 102 when the first rotor 102 is driven and rotated by the drive shaft 108. This air ultimately exits the first interior volume 122 through at least one of the first radial air outlets 126. In addition, air received axially through the second axial air inlet 120 is forced radially into the second interior volume 124 by the second rotor 104 when the second rotor 104 is driven and rotated by the drive shaft 108. This air also ultimately exits the second interior volume 124 through at least one of the second radial air outlets 128. Air entering the device 100 through the first axial air inlet 118 and the second axial air inlet 120 does not pass through the opening 119 of the middle plate 112. This configuration prevents the flow from either inlet to interact until it exits the device 100 through either radial air outlets. In addition, outside of the first radial air outlets 126 and the second radial air outlets 128, where the flow of air interacts, a reduced pressure loss occurs due to reduction in wake loss.

Depending on the configuration of the device 100, steady or unsteady fluid flow vortices may be created within each of the first interior volume 122 and the second interior volume 124 without need for physical structures such as a fin. For example, the devices disclosed in U.S. Patent Application Publication No. US 2009/0145584 Al are configured to create steady or unsteady fluid vortices.

By "unsteady", the vortices at a particular location within each of the first interior volume 122 and the second interior volume 124 change with time. The resulting flow field enhances heat transfer rates locally through impingement cooling and thermal transport by the vortices, whether generated to be steady or unsteady in nature. Also, the vortices drive a secondary flow within the device 100, which entrains fluid at each outlet, and draws it into each of the first interior volume 122 and the second interior volume 124, effectively creating a secondary pumping mechanism which further enhances heat transfer. Air is entrained into the vortices and expelled, thereby adding to the net heat transfer rate.

The cooling device 100 enhances heat flux in a given volume and is particularly appropriate for portable devices, such as mobile phones, and also for spot cooling in low- profile applications generally (whether in a portable device or a non-portable device or system) such as to cool a graphics processing unit, a central processing unit, field programmable gateway arrays, and/or one or more components in non-portable and portable devices and systems. The avoidance of fins from the first interior volume 122 and the second interior volume 124 makes the device 100 easier and cheaper to manufacture. The avoidance of fins also results in reduced aerodynamics noise. The pressure drop across each of the first interior volume 122 and the second interior volume 124 is less as there is less surface area to add to the viscous drag. Further, the vortices may be generated in small volumes.

In one embodiment according to the invention, cooling device 100 may have the following dimensions. These dimensions are merely exemplary and other dimensions may be contemplated. For example, the height of the device 100 is about 8 millimeters. Each of the first rotor 102 and the second rotor 104 has a diameter of about 15, 24, 30, 60, and 80 millimeters. In addition, each of the upper plate 110, the middle plate 112, and the lower plate 114 has a thickness of about 1 millimeter.

In other embodiments of the invention, the cooling device 100 may be presented in various configurations. For example, the height and diameter of the blades 116 of each of the first rotor 102 and the second rotor 104 may be adjusted to identify optimal acoustic noise levels and flow rate levels. For example, the optimal height of the blades 116 could be 8 to 12 millimeters when the first rotor 102 has a diameter of 80 millimeters. Such configuration could yield a low acoustic noise level for the cooling device 100. Additionally, each of the first axial air inlet 118 and the second axial air inlet 120 of cooling device 100 could be designed to incorporate a cover in order to improve acoustics.

Referring to FIG. 1C, the motor 106 can disposed within the first axial air inlet 118 such that it creates a flat surface on the upper plate 110. In this configuration, the motor 106 does not extend out of the upper plate 110. In this manner, the device 110 can be easy to handle and installed within a portable electronic device. Referring to FIG. ID, a cross-sectional view of the cooling device 100 of FIG IA is shown. At least one of the upper plate 110 and the lower plate 114 may be replaced with the wall of a housing of a portable device, such as a circuit board.

Referring to FIG. IE, another embodiment according to the invention is depicted as a cooling device 100 that includes a motor 106 that extends outward from the upper plate 110. In this configuration, the profile of the cooling device 100 is reduced. For example, the motor 106 may be disposed at any location external to the cooling device 100 in order to facilitate the placement of the cooling device 100 into a compact location within a portable device. The motor 106 can also be configured such that it extends outward from the lower plate 114. In operation, the cooling device 100 functions as does the cooling device 100 of FIGS. 1A-1D.

Referring to FIG. 2, the cooling device 100 may be configured to be disposed within a portable device 200, such as a mobile phone or a laptop computer. The cooling device 100 may also be disposed within a non-portable device or system such as a desktop computer or a server. The cooling device is useful for spot cooling applications generally such as to cool a graphics processing unit, a central processing unit, or field programmable gateway arrays. The cooling device 100 can be disposed adjacent to and on top of various heat generating electrical components 202. In operation, the electrical components 202 generate significant levels of heat when the device 200 is in use. The upper and lower plates of the cooling device 100 can be configured to act as heat transfer plates and thus draw heat axially from the components 202 into its interior volumes and expunges the heat radially. The inclusion of the cooling device 100 into the portable device 200 yields a significant increase in heat dissipation to maintain a lower temperature within the device 200. In addition, the cooling device 100 maintains a low- profile such that a cover 204 may be placed on top of the cooling device 100 and the electrical components 202 to allow a user to utilize the device 200 without discomfort or disruption.

Referring to FIG. 3, another embodiment according to the invention is depicted as cooling device 300. In contrast to all other embodiments described with respect to FIGS. 1 A-IE and 2, cooling device 300 includes fin plates.

Like the cooling device 100 depicted in FIG. IA, cooling device 300 includes a first rotor 302, a second rotor 304, an upper plate 306, a middle plate 308, and a lower plate 310. Cooling device 300 also includes a motor 106 and a drive shaft 108, as depicted in FIG. IA. In operation, the first rotor 302, the second rotor 304, the motor 106 (not shown in Figure), and the drive shaft 108 (not shown in Figure) functions as does the first rotor 102, the second rotor 104, the motor 106, and the drive shaft 108 of FIGS. IA- ID. In addition to these components, cooling device 300 includes a first fin plate 312 and a second fin plate 314. The upper, middle, lower, and fin plates can act as heat transfer surfaces.

The upper plate 306 defines a first axial air inlet 316 and the lower plate defines a second axial air inlet 318. The first fin plate 312 is disposed between the upper plate 306 and the middle plate 308. The second fin plate 314 is disposed between the middle plate 308 and the lower plate 310. All five of the plates are substantially parallel to each other and substantially perpendicular to the drive shaft of the motor. The first fin plate 312 includes a first opening 320. The second fin plate 314 includes a second opening 322. Each of the first opening 320 and the second opening 322 is at least as large as the first axial air inlet 316 and the second axial air inlet 318, respectively.

The first rotor 302 is partially disposed within the first opening 320. The second rotor 304 is partially disposed within the second opening 322. Each of a portion of the first rotor 302 and the second rotor 304 may partially extend above and below the first opening 320 and the second opening 322 respectively.

The upper plate 306 and the first fin plate 312 are spaced apart to define a first part 324a of a first interior volume 324. The first fin plate 312 and the middle plate 308 are spaced apart to define a second part 324b of the first interior volume 324. The lower plate 310 and the second fin plate 314 are spaced apart to define a first part 326a of a second interior volume 326. The second fin plate 314 and the middle plate 308 are spaced apart to define a second part 326b of the second interior volume 326.

Air received axially from the first axial air inlet 316 is forced radially into the first part 324a and second part 324b of the first interior volume by the first rotor 302 when it is driven and rotated by the shaft of the motor. In addition, air received axially from the second axial air inlet 318 is forced radially into the first part 326a and the second part 326b of the second interior volume by the second rotor 304 when it is driven and rotated by the shaft of the motor. Air entering the device 300 through the first axial air inlet 316 and the second axial air inlet 318 does not pass through an opening 328 of the middle plate 308. The opening 328 is sufficient in diameter to allow passage of the drive shaft. This configuration prevents the flow from either inlet to interact until it exits the device 300. Referring to FIG. 4, another embodiment according to the invention is depicted as cooling device 400. In contrast to the embodiment described with respect to FIG. 3, which describes a dual-inlet cooling device with fin plates, cooling device 400 includes a single inlet and a single fin plate.

Like the cooling device 300 depicted in FIG. 3, cooling device 400 includes a rotor 402, an upper plate 404, a middle fin plate 406, and a lower plate 408. Cooling device 400 also includes a motor 106 and a drive shaft 108, as depicted in FIG. IA. In operation, the rotor 402, the motor 106 (not shown in Figure), and the drive shaft 108 (not shown in Figure) functions as does the first rotor 102, the second rotor 104, the motor 106, and the drive shaft 108 of FIGS. 1A-3.

The upper plate 404 defines an axial air inlet 410. The middle fin plate 406 is disposed between the upper plate 404 and the lower plate 408. All three of the plates are substantially parallel to each other and substantially perpendicular to the drive shaft of the motor. The middle fin plate 406 has a generally rectangular-shaped configuration. The middle fin plate 406 may also have other configurations, such as, but not limited to, flat, and square. The middle fin plate 406 includes an opening 412. The opening 412 is at least as large as the axial air inlet 410. In addition, the rotor 402 is partially disposed within the opening 412. A portion of the rotor 402 may partially extend above and below the opening 412.

The upper plate 404 and the middle fin plate 406 are spaced apart to define a first part 414a of an interior volume 414. The middle fin plate 406 and the lower plate 408 are spaced apart to define a second part 414b of the interior volume 414. Air received axially from the axial air inlet 410 is forced radially into the first part 414a and second part 414b of the interior volume 414 by the rotor 402 when it is driven and rotated by the shaft of the motor.

Referring to FIG. 5, a chart 500 illustrates the comparison of the thermal resistance 502 of a single-inlet low-profile cooling device with no fins, such as the cooling device disclosed in U.S. Patent Application Publication No. US 2009/0145584 Al, relative to the revolutions per minute 504 (RPM) of a rotor of the cooling device. The chart 500 calculates thermal resistance 502 for a 12 and 24 millimeter chip. The thermal resistance is calculated over a range of 0.0 to 1.4 C/W. In addition, the revolutions per minute 504 are calculated over a range of 1000 to 3000 RPMs. For each 12 and 24 millimeter chip, the thermal resistance 502 decreases as the RPMs 504 increase over time. It may be necessary to generate a high level of RPMs 504 in order to reduce the thermal resistance 502. For example, a thermal resistance of approximately 0.8 C/W is achieved at approximately 1600 RPMs.

Referring to FIG. 6, a chart 600 illustrates the comparison of the thermal resistance 602 of a single-inlet low-profile cooling device 400 with a fin plate, as shown in FIG. 4, relative to the revolutions per minute 604 (RPM) of a rotor of the cooling device 600. The thermal resistance 602 is calculated for a 12 and 24 millimeter chip over a range of 0.0 to 1.0 CAV. In addition, the revolutions per minute 604 are calculated over a range of 1000 to 2000 RPMs. For each 12 and 24 millimeter chip, the thermal resistance 602 decreases as the RPMs 604 increase over time. For example, a thermal resistance of approximately 0.7 C/W is achieved at approximately 1600 RPMs.

Referring to FIG. 7, a chart 700 illustrates the comparison of the thermal resistance 702 of the dual-inlet low-profile cooling device 100, as described in FIG. IA, relative to the revolutions per minute 704 (RPM) of a rotor of the cooling device 100. The thermal resistance 702 is calculated for a 12 and 24 millimeter chip over a range of 0.0 to 1.2 C/W. In addition, the revolutions per minute 704 are calculated over a range of 800 to 1800 RPMs. For each 12 and 24 millimeter chip, the thermal resistance 702 decreases as the RPMs 704 increase over time. For example, a thermal resistance of approximately 0.9 C/W is achieved at approximately 850 RPMs, whereas a thermal resistance of approximately 0.6 C/W is achieved at approximately 1600 RPMs.

Referring to FIG. 8, a chart 800 illustrates the comparison of the thermal resistance 802 of a dual-inlet low-profile cooling device 300 with fin plates, as shown in FIG. 3, relative to the revolutions per minute 804 (RPM) of a rotor of the cooling device 300. The thermal resistance 802 is calculated for a 12 and 32 millimeter chip. The thermal resistance is calculated over a range of 0.0 to 0.7 C/W. In addition, the revolutions per minute 804 are calculated over a range of 600 to 2000 RPMs. For each 12 and 32 millimeter chip, the thermal resistance 802 decreases as the RPMs 804 increase over time. For example, a thermal resistance of approximately 0.4 C/W is achieved at approximately 1600 RPMs.

Referring to FIG. 9A, at least one heat pipe 900, such as the heat pipe disclosed in U.S. Patent Application Publication No. US 2009/0145584 Al, can be utilized in conjunction with the cooling device 100 of FIG. IA. Heat pipe 900 can be coupled to the housing of the cooling device 100. Heat pipe 900 is configured to draw heat from a surrounding environment, such as a chip or central processing unit, into the heat pipe 900. Such heat is then circulated into the interior volume of the cooling device 100 to facilitate heat dissipation. In operation, heat is drawn into the heat pipe 900 and dispersed into the first interior volume 122 and the second interior volume 124 of FIG IA. That heat is then circulated by each of the first rotor 102 and the second rotor 104 and ultimately expunged from the device through the radial air outlets 132. The heat pipe 900 may be soldered to an upper or lower plate of the device 100 in order to provide a secondary function to the cooling device 100.

Referring to FIGS. 9B and 9C, a heat pipe 902 can also be utilized in conjunction with the single-inlet low-profile cooling device 400 of FIG. 4 or, as shown, with a single- inlet low-profile cooling device without a fin plate. The heat pipe 902 is coupled to a component 904, such as a chip, which requires cooling. The component 904 is disposed to the lower plate of the single-inlet low-profile cooling device. In operation, heat pipe 902 functions as does the heat pipe 900 of FIG. 9 A. Referring to FIG. 9D, a plurality of heat pipes 906 can be utilized in conjunction with a plurality of low-profile cooling devices 100 in a series configuration. The plurality of heat pipes 906 are connected to a component 908, such as a chip, which requires cooling. In operation, heat pipes 906 function as does the heat pipe 900 of FIG. 9 A.

Referring to FIGS. 1OA, 1OB, and 1OC, the dual-inlet low-profile cooling device 100, as depicted in FIG. IA, may configured to be provided as one cooling device in a stack of a plurality of cooling devices 1000. The stacked configuration 1000 provides inlet and exit flows at different planes, such that the inlet and outlet flow streams are kept separate in order to prevent viscous loss. Air is received in the axial direction 130 and dispelled in the radial direction 132 through various first radial air outlets 126 and second radial air outlets 128. In addition, air 1001 circulating at each outlet may also be drawn into each of the first interior volume 122 and the second interior volume 124 to further enhances heat transfer. Thus air is entrained into the vortices created within the first interior volume 122 and the second interior volume 124 and expelled, thereby adding to the net heat transfer rate. The stacked configuration 1000 can be configured to also include heat pipes, such as the heat pipe depicted in FIG. 9D. In operation, the heat pipes could transport heat vertically within the cooling devices 1000.

In this configuration, the distance between the fan inlets can be varied for optimum thermal performance. For example, a distance of 10 millimeters between each inlet can provide for enhanced performance. This configuration may continue to be stacked indefinitely based upon both height and heat spreading constraints.

It will be understood that various modifications may be made to the embodiments disclosed herein. Those modifications are considered part of the disclosure. The above description should not be construed as limiting, but merely as illustrative of some embodiments according to the invention.

Claims

WHAT IS CLAIMED IS:

1. A dual-inlet low-profile cooling device, comprising: a first rotor and a second rotor, each of the first and second rotors including a plurality of blades; a motor including a drive shaft for driving and rotating each of the first and second rotors; and an upper plate, a middle plate, and a lower plate, the upper, middle, and lower plates being substantially parallel to each other and substantially perpendicular to the drive shaft of the motor, the upper plate defining a first axial air inlet and the lower plate defining a second axial air inlet, the upper and middle plates spaced apart to define a first interior volume and at least two first radial air outlets, the lower and middle plates spaced apart to define a second interior volume and at least two second radial air outlets, air from the first axial air inlet being forced radially into the first interior volume by the first rotor when driven and rotated by the shaft of the motor and this forced air ultimately exiting from at least one of the at least two first radial air outlets, air from the second axial air inlet being forced radially into the second interior volume by the second rotor when driven and rotated by the shaft of the motor and this forced air ultimately exiting from at least one of the at least two second radial air outlets.

2. The device of claim 1 wherein one or more vortices is created within each of the first and second interior volumes without need for physical structures within each of the first and second interior volumes.

3. The device of claim 1 further comprising support pillars interconnecting the upper, middle, and lower plates.

4. The device of claim 1 wherein the upper, middle, and lower plates are substantially rectangular-shaped.

5. The device of claim 1 further comprising at least one heat pipe.

6. The device of claim 1 wherein the device is one in a stack of a plurality of cooling devices.

7. The device of claim 1 wherein the cooling device is integrated within a portable device.

8. The device of claim 7 wherein the portable device is a mobile phone or a laptop computer.

9. The device of claim 1 wherein the cooling device is integrated within any one or more of a desktop computer, a server, a graphics processing unit, a central processing unit, and field programmable gateway arrays.

10. The device of claim 1 wherein at least one of the upper and lower plates is a wall of a housing of a portable device.

11. A dual-inlet low-profile cooling device with fin plates, comprising: a first rotor and a second rotor, each of the first and second rotors including a plurality of blades; a motor including a drive shaft for driving and rotating each of the first and second rotors; an upper plate, a middle plate, and a lower plate, the upper plate defining a first axial air inlet and the lower plate defining a second axial air inlet; and a first fin plate and a second fin plate, the first fin plate disposed between the upper plate and the middle plate, the second fin plate disposed between the middle plate and the lower plate, all five of the plates being substantially parallel to each other and substantially perpendicular to the drive shaft of the motor, each of the first and second fin plates defining openings at least as large as the first and second axial air inlets respectively, the upper and first fin plates spaced apart to define a first part of a first interior volume, the first fin and middle plates spaced apart to define a second part of the first interior volume, the lower and second fin plates spaced apart to define a first part of a second interior volume, the second fin and middle plates spaced apart to define a second part of the second interior volume, air from the first axial air inlet being forced radially into the first and second parts of the first interior volume by the first rotor when driven and rotated by the shaft of the motor, air from the second axial air inlet being forced radially into the first and second parts of the second interior volume by the second rotor when driven and rotated by the shaft of the motor.

12. The device of claim 11 further comprising heat-conducting support pillars interconnecting the upper, middle, lower, first fin, and second fin plates.

13. The device of claim 11 wherein the upper, middle, lower, first fin, and second fin plates are substantially rectangular-shaped.

14. The device of claim 11 further comprising at least one heat pipe.

15. The device of claim 11 wherein the cooling device is integrated within any one or more of a portable device, a desktop computer, a server, a graphics processing unit, a central processing unit, and field programmable gateway arrays.

16. A single-inlet low-profile cooling device with a fin plate, comprising: a rotor including a plurality of blades; a motor including a drive shaft for driving and rotating the rotor; and an upper plate, a middle fin plate, and a lower plate, the upper, middle fin, and lower plates being substantially parallel to each other and substantially perpendicular to the drive shaft of the motor, the upper plate defining an axial air inlet, the middle fin plate defining an opening at least as large as the axial air inlet, the upper and middle fin plates spaced apart to define a first part of an interior volume, the middle fin and lower plates spaced apart to define a second part of the interior volume, air from the axial air inlet being forced radially into the first and second parts of the interior volume by the rotor when driven and rotated by the shaft of the motor.

17. The device of claim 16 further comprising heat-conducting support pillars interconnecting the upper, middle fin, and lower plates.

18. The device of claim 16 wherein the upper, middle, lower, first fin, and second fin plates are substantially rectangular-shaped.

19. The device of claim 16 further comprising at least one heat pipe.

20. The device of claim 16 wherein the cooling device is integrated within any one or more of a portable device, a desktop computer, a server, a graphics processing unit, a central processing unit, and field programmable gateway arrays.