JP2007527618A - System and method for thermal management using distributed synthetic jet actuators - Google Patents

Abstract

One embodiment of the device comprises a device for thermal management. More specifically, one embodiment comprises a synthetic jet actuator (60) and a tube (61). The synthetic jet actuator (60) is typically but not necessarily provided with a housing (47), which defines an internal chamber (45) and an orifice (in the wall (44) of the housing (47) ( 46). The synthetic jet actuator (60) also typically includes a flexible diaphragm (42) that forms part of the housing (47). The tube (61) of this exemplary embodiment typically comprises a proximal end (64) and a distal end (65) that is adjacent to the synthetic jet actuator (60). Is positioned. In this embodiment, actuation of the synthetic jet actuator (60) causes a synthetic jet stream (52) to form at the distal end (65) of the tube (61).

Description

(Technical field)
The present invention relates generally to thermal management techniques, and more specifically to a system and method for cooling an object or component that generates heat using a distributed synthetic jet actuator.

(Background of the Invention)
Cooling objects that purify heat is a concern in many different technologies. In particular, in microprocessors, the increased heat dissipation level associated with a reduced thermal budget has created a need for new cooling solutions that are superior to conventional thermal management techniques. Furthermore, it is increasingly demanding that effective thermal management strategies be used in small portable devices such as portable digital assistants (PDAs), cell phones, portable CD players, and similar consumer products. ing. Indeed, thermal management is a major challenge in the design and packaging of prior art integrated circuits in single-chip and multi-chip modules.

  Traditionally, the need to cool large microelectronic devices has been met by using forced convection air cooling techniques. Forced convection can be performed either with or without a heat sink, and conventionally, fans are used to provide either global or local cooling.

  Although fans can provide a sufficient volume of flow, there are some inherent disadvantages to using fans. Fans are relatively inefficient in terms of the heat removed for a given volume flow. Furthermore, the use of fans to cool the unheated environment globally or locally often results in electromagnetic interference and noise generated by magnetic-based fan motors. The use of a fan also requires a relatively large number of moving parts to obtain any success in cooling a heated object or microelectronic component. For this reason or other reasons, fans can be disturbed by long-term reliability.

  The application of movement introduces the additional complexity of space limitations, which can be difficult to achieve with fans, while at the same time, increased thermal management requirements result in larger fans having higher flow rates. It is essential to drive. As the power dissipation requirement, in some cases, requires that the fan be placed directly in the heat sink, the accompanying noise level due to flow and structure interaction becomes a further problem. ing.

  In some instances, in portable devices such as portable digital assistants (“PDAs”), cell phones, etc., the need for thermal management is the result of the use of heat spreaders, resulting in the use of heat spreaders. It is satisfied by using a strategy that spreads to the outer cell of the device. As a result, the generated heat is dissipated through the outer cell (ie, the shell) of the device via natural convection.

  While these approaches are normal, they present certain drawbacks that are exacerbated as new products that produce more heat are developed. The difficulty of the heat spreading strategy is simply that this is often not effective in removing a sufficient amount of heat. Furthermore, the heat dissipated can cause an increase in the temperature of the casing of the portable device, which is undesirable from an ergonomic point of view for consumer use.

  In an effort to remedy some of the limitations of previous cooling technologies, the use of synthetic jet actuators or “zero net mass flux” jet actuators in thermal management has been used. For example, US Pat. No. 6,123,145 discusses the use of synthetic jet actuators for use in cooling. US Pat. No. 6,123,145 is hereby incorporated by reference as if fully set forth herein. Unlike conventional jets, synthetic jet actuators do not require that mass be added to the system, thus providing a compact manner that efficiently directs airflow across a heated surface. Since the jet streams are generated entirely from the surrounding fluid, these streams can be conveniently integrated without the need for complex piping.

  As a further example of the development of thermal management technology using synthetic jet actuators, Glezer and Mahalingam have developed apparatus and devices for channel cooling. This apparatus and method is described in US Pat. No. 6,588,497, which is hereby incorporated by reference herein as if fully set forth herein. Incorporated as a reference.

  While the technology described in the above US patents solves some of the limitations in the industry, there is still a growing need for improving even the technology described above. For example, a need exists for a synthetic jet actuator that is more effective, efficient, or compact. It would be desirable to have a smaller cooling device. On the other hand, it is also necessary to distribute the cooling flow to parts that extend far into the heated environment.

  Thus, there is an unmet need in the industry to address the shortcomings and deficiencies noted above.

(Summary of the Invention)
Embodiments of the present invention provide devices for thermal management in various environments. More specifically, embodiments of the present invention include a device for cooling a region or device by use of a synthetic jet actuator in a distributed cooling apparatus.

  Briefly described, in configuration, one embodiment of this device can be implemented as a device for thermal management comprising, inter alia, a synthetic jet actuator and channel. The channel of this exemplary embodiment typically includes a proximal end and a distal end, which is positioned adjacent to the synthetic jet actuator. Actuation of the synthetic jet actuator preferably forms a synthetic jet stream at the distal end of the channel. Of course, the synthetic jet stream can also be formed at the proximal end of the channel.

  The synthetic jet actuator of this exemplary embodiment, or other exemplary embodiments, is not required, but may comprise a housing, which defines an internal channel and at least one orifice in the wall of the housing Have The synthetic jet actuator of this embodiment also preferably comprises a device for changing the volume in the internal chamber, wherein the volume changing device is preferably positioned adjacent to the housing. In some embodiments, the device for varying the volume may actually constitute a portion of the composite jet actuator housing. For example, the volume change device of some exemplary embodiments comprises a flexible diaphragm that forms part of the housing of the synthetic jet actuator.

  In some exemplary embodiments, the channel is comprised of one or more tubes connected to the outer surface of the synthetic jet actuator housing wall. In these exemplary embodiments, the tube typically surrounds at least a portion of the orifice of the synthetic jet actuator.

  Other systems, methods, features, and advantages of the present invention will be apparent to those skilled in the art or upon examination of the following drawings and detailed description. All such additional systems, methods, features, and advantages are intended to be included within the scope of this disclosure, within the scope of the present invention, and protected by the accompanying claims. .

  Many aspects of the invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

Detailed Description of Preferred Embodiments
(I. Synthetic jet actuator)
(A. Basic design of typical synthetic jet actuator)
FIG. 1A illustrates an example of a synthetic jet actuator 10 that includes a housing 11 that defines and surrounds an internal chamber 14. Although the housing 11 and the chamber 14 can take virtually any geometric configuration, for purposes of discussion and understanding, the housing 11 has a rigid side wall 12, a rigid front wall 13, and a rear side in the cross-section of FIG. 1A. Shown as having a diaphragm 18, this rear diaphragm is flexible to the extent that allows inward and outward movement of the diaphragm 18 relative to the chamber 14. The front wall 13 has an orifice 16 of any geometric shape. This orifice is directly opposite the rear diaphragm 18 and connects the internal chamber 14 to an external environment having an ambient fluid 39.

  The flexible diaphragm 18 can be controlled to move by any suitable control system 24. For example, the diaphragm 18 can comprise a metal layer and a metal electrode can be disposed adjacent to but spaced from the metal layer such that the diaphragm 18 is between the electrode and the metal layer. It can be moved by the applied electrical bias. Further, the generation of electrical energization can be controlled by any suitable device (eg, but not limited to a computer, logic processor, or signal generator). The control system 24 can periodically move the diaphragm 18 or adjust it in a time-harmonic manner and can force fluid into and out of the orifice 16.

  The operation of the exemplary synthetic jet actuator 10 will now be described with reference to FIGS. 1B and 1C. FIG. 1B illustrates the synthetic jet actuator 10 when the diaphragm 18 is controlled to move inwardly into the chamber 14 as illustrated by arrow 26. The chamber 14 is reduced in volume and fluid is exhausted through the orifice 16. As the fluid exits the chamber 14 through the orifice 16, the flow separates at the sharp orifice edge 30 and creates a vortex sheet 32, which vortexes into a vortex 34, and It begins to move away from the orifice edge 30 as illustrated by arrow 36.

  FIG. 1C illustrates the synthetic jet actuator 10 when the diaphragm 18 is controlled to move outward relative to the chamber 14 as illustrated by arrow 38. Chamber 14 is increasing in volume and ambient fluid 39 is expelled into chamber 14 as illustrated by arrow 40. Diaphragm 18 is affected by control system 24 when vortex 34 has already been removed from orifice edge 30 when diaphragm 18 moves away from chamber 14 and is therefore affected by ambient fluid 39 drawn into chamber 14. It is controlled not to receive it. In the meantime, a jet 39 of ambient fluid is synthesized by the vortex 34, causing a strong entrainment of the ambient fluid and being drawn from a distance far away from the orifice 16.

(B. Synthetic jet actuator with hybrid piezoelectric actuator)
As explained above, the diaphragm 18 of the synthetic jet actuator 10 of the first exemplary embodiment comprises an electrical actuation consisting of a metal layer and a metal electrode driven at a specific excitation frequency. This electrical stimulation causes diaphragm 18 of synthetic jet actuator 10 to vibrate, thereby altering the internal volume of chamber 14 of synthetic jet actuator 10.

  Alternatively, as illustrated in FIG. 2, the synthetic jet actuator 40 may include a housing 47 that defines a chamber 45. The volume of this chamber can be changed by moving the flexible diaphragm 42 in a time-harmonic motion due to the excitation of the diaphragm 42 by the piezoelectric actuator 41. FIG. 2 is a cutaway side view of a synthetic jet actuator 40 having a housing 47 that forms a relatively rigid circular top wall 43, a relatively rigid cylindrical side wall 44, and a bottom wall of the actuator 40. Defined by a flexible diaphragm 42. As illustrated in this figure, this side wall connects the top wall 43 to the diaphragm 42. Preferably, the sidewall 44 and the top wall 43 are manufactured from a single piece of rigid material (eg, plastic). Of course, it is also possible to construct the walls 43, 44 from a metallic material or other suitably rigid material. Furthermore, the material forming the composite jet actuator 40 need not necessarily be rigid. The material can have some flexibility. Those skilled in the art will readily understand suitable materials for the synthetic jet actuator 40 based on the particular implementation.

  As described above, the top wall 43, the flexible diaphragm 42, and the side wall 44 define the housing 47 of the synthetic jet actuator 40 and define a chamber 45 having a volume. The housing 47 of this embodiment 40 comprises the shape of a cylindrical element. This configuration is not essential and a specific configuration has been selected for the purpose of fully understanding that the synthetic jet actuator 40 can take almost any overall shape.

  In this embodiment of the synthetic jet actuator 40, the orifice 46 is formed in a portion of the side wall 44. Orifice 46 fluidly connects chamber 45 to ambient fluid 48. The particular size and shape of the orifice 46 is not critical to the exemplary embodiment 40 of the present invention. By way of example, the orifice 46 can be in the form of a circular opening or can be a horizontal or vertical slot in the sidewall 44.

  FIG. 3 is a plan view of a second exemplary embodiment of the synthetic jet actuator 40, more specifically illustrating a piezoelectric actuator 41 and a flexible diaphragm 42. In other words, FIG. 3 can be thought of as a view of the synthetic jet actuator 40 from the underside, or “bottom”, of the actuator 40. As can be seen from this figure, the diaphragm 42 is attached to the side wall 44. Preferably, the attachment of diaphragm 42 to side wall 44 is accomplished by an adhesive suitable for the material used to construct diaphragm 42 and side wall 44. Alternatively, the diaphragm 42 can be attached to the sidewall 44 by another attachment mechanism or attachment device. The method of attachment is not critical to the exemplary embodiment 40 of the present invention. However, the selected bonding method preferably results in a seal between the sidewall 44 and the diaphragm 42.

  Diaphragm 42 is preferably constructed from an elastomeric or polymeric material. The elastomeric or polymeric diaphragm 42 is not essential in embodiment 40 of the present invention; however, diaphragms constructed from these materials are preferred. Conventionally, a piezoelectric actuator is composed of a metal diaphragm coupled to a piezoelectric disk. However, in certain implementations, it may be advantageous to use a polymer (such as plastic) or elastomer (such as rubber) material for the diaphragm of the piezoelectric actuator. Alternatively, a polymer or elastomeric diaphragm can be used in combination with a metal diaphragm to create a hybrid diaphragm.

  Elastomers or polymers can be constructed from a number of special materials such as polyisoprene, polyisobutylene, polybutadiene, and / or polyurethane. For embodiment 40 of the present invention, a diaphragm 42 constructed from an elastomeric or polymeric material is selected due to its ability to stretch and rebound to its original shape without being permanently deformed. .

  There are at least two advantages of building such a modified actuator. First, the use of an elastomer or polymer diaphragm generally reduces the natural resonant frequency of the actuator, allowing preferred use at low frequencies (eg, less than 200 Hz). This makes the operation of this actuator relatively quiet. Second, such construction generally has excellent reliability when compared to metal diaphragms. Metal diaphragms tend to produce greater stress in the piezoelectric material and the adhesive that typically attaches the piezoelectric material to the metal.

  As described above, the piezoelectric actuator 41 is attached to an elastomer or polymer diaphragm 42. The piezoelectric actuator 41 is preferably placed on the diaphragm 42 by a suitable adhesive. The piezoelectric actuator 41 is supplied with electric power through an electric wiring 49. The electrical wiring 49 not only supplies power to the piezoelectric actuator 41 but also controls the operation of the actuator 41. Specifically, the wiring 49 connects the piezoelectric actuator to the power supply and control system 50. This system is separate from the housing 47 of the synthetic jet actuator 40. Of course, in certain embodiments, the power and control system 50 can be installed in the housing 47 of the synthetic jet actuator 40, or even inside this housing.

  The power supply and control method stem vibrates the piezoelectric actuator 41. The vibration of the piezoelectric actuator 41 causes the diaphragm 42 to vibrate with time-harmonic motion. The piezoelectric actuator 41 is preferably vibrated at the resonance frequency of the diaphragm 42. Of course, the magnitude and frequency of diaphragm vibration can be controlled by operating the piezoelectric elements at different frequencies. A person skilled in the art can easily adjust the vibration of the piezoelectric actuator 41 in order to obtain a desired frequency and amplitude of vibration of the diaphragm 42.

  As described above with respect to the first exemplary embodiment 10, the vibration of the diaphragm 42 in the second exemplary embodiment 40 causes a fluid composite jet stream 51 to form at the orifice 46 of the actuator 40. . As the diaphragm 42 moves inward relative to the chamber 45, the chamber 45 decreases its volume and fluid is expelled through the orifice 46. As the fluid exits the chamber 45 through the orifice 46, the flow separates at the orifice edge and creates a vortex sheet that vortexes, vortexes, and leaves the orifice 46. To move. These vortexes entrain the surrounding fluid 48 and use this fluid to form the synthetic jet stream 52.

  Similar to the operation of the first exemplary synthetic jet actuator 10, when the diaphragm 42 is moved outward relative to the chamber 45, the chamber 45 increases its volume. This increase in volume creates a pressure gradient at the orifice 46 and the ambient fluid 48 is expelled into the chamber 45. Then, as the diaphragm 42 vibrates back into the chamber 45, the fluid in the chamber 45 is evacuated to form the synthetic jet stream 52 as described above.

(III. Distributed cooling device)
(A. First embodiment: single actuator device)
The synthetic jet actuator 10, 40 can be used in many different embodiments. However, one particular adaptation of the synthetic jet actuator 10, 40 is to what may be referred to as a distributed cooling application. A distributed cooling application is a situation where a single synthetic jet actuator may be required to provide a synthetic jet stream for cooling to multiple locations. Alternatively, the distributed cooling application may require a synthetic jet actuator to provide cooling fluid flow to a single location somewhat away from the actuator location. Without limiting the examples, these two examples are common distributed cooling applications.

  FIG. 4A illustrates one embodiment of a distributed cooled synthetic jet actuator 60. For ease of explanation, the exemplary embodiment of the distributed cooling synthetic jet actuator 60 is designed as a modification of the second exemplary embodiment 40. Accordingly, the dispensed cooled composite jet actuator 60 includes a housing 47 that defines an internal chamber 45. Although the housing 47 and the chamber 45 can take virtually any geometric configuration, for purposes of discussion and understanding, the housing 47 is shown in FIG. 4A in cross section with a rigid sidewall 44, a rigid top wall 43, and a diaphragm. This diaphragm is flexible to the extent that it allows inward and outward movement of the diaphragm 42 relative to the chamber 45. A portion of the side wall 44 forms an orifice 46. As described above, the orifice 46 may have any geometric shape.

  As in the exemplary embodiment 40 above, the distributed cooled composite jet actuator 60 also includes a power supply and control system 50 connected to the piezoelectric actuator 41 on the diaphragm 42 by electrical wiring 49. As described above, the power supply and control system 50 can be remote from the actuator 60 or can be attached to, for example, the housing 47 or the interior of the housing 47.

  The exemplary distributed cooling device 60 further comprises a channel (or tube) 61. The tube 61 may have a cross-sectional shape similar to the cross-sectional shape of the orifice 46. However, it may also be desirable to have a cross-sectional shape of the tube 61 that is quite different from the shape of the orifice 46. For example, the use of different cross-sectional shapes may allow for more effective orientation of any flow exiting the tube 61. The tube 61 is formed from a preferably rigid shell 62 that surrounds the interior region 63. Tube 61 further comprises a proximal or attached end 64 and a distal or open end 65. The tube 61 is preferably composed of a plastic material so that the tube 61 is relatively rigid but still lightweight. Alternatively, the pipe 61 is formed of a flexible material that is formed in a certain shape and has the ability to hold the shape. In FIG. 4A, the tube 61 is formed in a substantially meandering shape. The shape of tube 61 is not critical to the principles of the present invention, and the particular shape described has been selected only to illustrate the principles of exemplary embodiment 60 of the present invention.

  As shown in this figure, the tube 61 is preferably attached to the side wall 44 of the synthetic jet actuator 60 such that the actuator orifice is fluidly connected to the interior region 63 of the tubing 61. In a preferred embodiment, the piping 61 has an inner diameter that is equal to or greater than the diameter of the orifice 46. Accordingly, the orifice 46 does not communicate directly with the surrounding environment 48, in other words, the tube 61 completely covers the orifice 46. Although tube 61 is said to be “attached” to sink wall 44, it should be understood that housing 47 and tube 61 may be made from a single piece of material.

  As will be explained in more detail below, during operation, a vortex is formed at the edge of the outlet end 65 of the tubing. These vortexes swirl and move away from the outlet of the tube 61. These vortexes entrain the surrounding fluid 48 that forms the fluid jet 52 at the outlet 65 of the tube 61. In essence, the use of piping 61 allows the fluid jet 52 to exit the piping 61 and leave the actuator itself. Basically, the composite jet of fluid exiting the orifice 46 of the composite jet actuator is discharged from the outlet end 65 of the tube 61 instead of the tube 61 when the tube 61 is not present. This feature of this embodiment 60 allows the cooling system designer to position the synthetic jet actuator 40 in any convenient position, but still allows the fluid flow 52 to move the tube 61 to the desired position. It is possible to direct to a relatively distant position by simply directing to.

  For example, the actuator 40 can be positioned far away from an area to be cooled (eg, a central position). The pipe 61 may be shaped to direct the flow through the heat sink fins. The fact that the synthetic jet actuator is not near the heat sink generally increases the flow through the heat sink fins. Indeed, if the actuator is positioned at the inlet of the fin channel, the flow through the fin channel is hindered by the presence of the actuator housing. This is not a problem for distributed cooling.

  As described above, the piping 61 can be either preformed or flexible. If flexible, the designer can place the device 40 and then form the tube 61 as desired. This can be very advantageous for applications of additional introduction of new parts. However, in most common embodiments, the tube 61 is relatively rigid so that the overall design of the cooling system can be fine-tuned prior to implementation.

  As noted above, the shape or size of the tube 61 is not critical to the exemplary embodiment 60 of the present invention. However, the length and / or shape of the tube 61 can affect the performance of the distributed cooled composite jet actuator 60. In order to better illustrate this point, a reclassification to the operation of the distributed cooling device 60 should be made.

  The operation of the synthetic jet actuator 40 in the distributed cooling device 60 is similar to the operation of the synthetic jet actuator in the second exemplary embodiment. Specifically, the piezoelectric actuator 41 is vibrated at an appropriate frequency (preferably, the resonance frequency of the diaphragm 42). This vibration causes the diaphragm 42 to vibrate in a time-harmonic motion. As the diaphragm 42 moves inwardly relative to the inner chamber 45, the volume of the chamber 45 decreases, the pressure in the chamber 45 increases, creating a pressure gradient at the orifice 46, and the fluid flows into the synthetic jet actuator 40. It is discharged from the orifice 46. Since the surrounding fluid is not entrained at the orifice 46, the flow exiting the orifice 46 is essentially pulsed and generally reflects the frequency of the diaphragm 42 driven by the piezoelectric actuator 41. This fluid pulse travels into the interior region 63 of the tube 61 attached to the orifice 46. As the diaphragm 42 moves outward relative to the chamber 45, fluid is drawn from the interior 63 of the tube into the synthetic jet actuator 45. If the diaphragm 42 then continues its harmonic vibration for that time and moves back into the chamber 45, fluid is also discharged from the chamber 45 into the interior 63 of the tube.

  FIGS. 5A and 5B illustrate the fluid interaction within the interior 63 of the tube 61 during operation of the synthetic jet actuator 40 of the dispensed chiller 60. When fluid from the chamber 45 of the synthetic jet actuator enters the interior 63 of the tube 61, this entering fluid acts like a “virtual piston” 66. The pulse of fluid 66 entering the interior 63 of the tube 61 compresses the fluid in the interior 63 of the tube, which in turn discharges the fluid 67 from the outlet end 65 of the tube 61. When the diaphragm 42 moves outward from the synthetic jet actuator chamber 45, the “virtual piston” 66 moves out of the interior 63 of the tube 61 and draws fluid from the interior 63 of the tube into the chamber 45. To reduce the pressure in the pipe 61. This lower pressure in the tube 61 creates a pressure gradient at the outlet end 65 of the tube, thereby drawing fluid from the periphery 48 into the tube 61. Again, the fluid at the attachment end 64 of the tube acts as a “virtual piston” 66 and acts in time-harmonic vibration.

  The central portion 68 of the tube 61 acts like another synthetic jet actuator “chamber” 69 that borders the wall 62 of the tube 61. The fluid at the orifice 46 of the synthetic jet actuator 40 borders this “chamber” 69 and acts as a virtual piston 66 for this virtual synthetic jet actuator “chamber” 69. The fluid entering and exiting the orifice 46 acts as a piston 66 resulting in a flow of fluid 67 exiting the outlet end 65 of the tube 61. The fluid 67 exiting the tube 61 vortexes at the outlet 65 of the tube 61. These vortexes swirl and move away from the tube outlet 65. As this vortex is formed and how it leaves, these vortexes entrain the ambient fluid 48 to form a synthetic jet stream 67 at the outlet 65 of the tube 61.

  Depending on the length of the tube 61, the operation of the diaphragm 42 of the synthetic jet actuator 40 can be specially adjusted to produce a virtual synthetic jet actuator in the tube 61. As will be clear from the above discussion and as will be appreciated by those skilled in the art, the operation of diaphragm 42 is preferably such that the frequency of air pulse 66 exiting orifice 46 of synthetic jet actuator 40 is at the resonant frequency of tube 61. It should be prepared to be released. Tube 61 essentially acts as a kind of Helmholtz resonator and can operate in a similar manner. The attachment end 64 of the tube 61 serves as the closed end of a typical Helmholtz resonator and also serves as the excitation force for this resonator.

  One skilled in the art can calculate the resonant frequency of the tube 61 if the diameter of the tube 61 is known. The frequency and amplitude of diaphragm 42 vibration is then calculated so that the pulse 66 emitted from the orifice 46 of the synthetic jet actuator 40 excites the tube 61 at the resonant frequency. Of course, all this can be controlled automatically by a suitable control system 50.

  In another exemplary configuration of distributed cooled synthetic jet actuator 70, synthetic jet actuator 40 is configured to drive multiple tubes. Such a configuration is illustrated in FIG. 4B. FIG. 4B is a cut away top view of a dispensed cooled synthetic jet actuator. As shown, the composite jet actuator housing 47 of the actuator 70 preferably has a plurality of orifices 46a, 46b, 46c, 46d, 46e, 46f. A large number of tubes 61a, 61b, 61c, 61d, 61e, 61f are provided outside the housing 47, and these tubes 61a, 61b, 61c, 61d, 61e, 61f are orifices 46a, 46b, 46c, 46d, 46e, 46f. It is attached so as to correspond to each of the above. Tubes 61a, 61b, 61c, 61d, 61e, 61f can all be configured to direct fluid flow in the same region, or in preferred applications, synthetic jet streams 52a, 52b, 52c, 52d, 52e, 52f. Are directed to separate heated regions or objects 71a, 71b, 71c, 71d, 71e.

  In another embodiment of a distributed cooling device, it may be desirable to have a means ready to attach the synthetic jet actuator module to another surface. For example, if a distributed cooling device is used in an application for additional introduction of deep parts, there may not be a method ready to install. In such situations, it may be desirable to configure the top wall 43 of the synthetic jet actuator 40 to be already adhered to the surface. Synthetic jet actuator 40 may be manufactured to “stick” to the surface. This can be achieved by applying double-sided tape, foam material with adhesive on both sides, and the like.

(B. Second Example: Multiple Actuator Device)
In some implementations of distributed cooling devices, it may be desirable to generate multiple composite jet streams. As described above, a single synthetic jet actuator 40 may drive multiple tubes and thereby generate multiple distributed synthetic jet streams of fluid. This is of course not the only possible implementation of a cooling device in which multiple synthetic jets are distributed. Another exemplary embodiment may comprise a plurality of synthetic jet actuators that drive a plurality of tubes and thereby emit a plurality of synthetic jet streams. The tubes of such embodiments may be directed to different regions, different heat sink channels, or all may be directed to the same location.

  An exemplary embodiment of a cooling device 80 with multiple actuators distributed is illustrated in FIG. The device 80 generally comprises a plurality of tubes 81 exiting from a generally cubic housing 82. The housing 82 has two “plenums” 83 formed in the housing 82, which cause the two plenums 83 to descend from the top surface 84 of the housing 82. These two plenums 83 are spaced from the side walls 85, 86 of the housing 82 and preferably do not reach the full length of the bottom surface 87 of the housing 82.

  A cross-sectional immediate view of the cooling device 80 in which a plurality of actuators are distributed is shown in FIG. One of the plenums 83 of the housing 82 is shown to interface with the bottom surface 87, the front wall 88, and the rear wall 89 of the device 82. The front wall 88 and the rear wall 89 each form a pair of upper platforms 91, 92 and a pair of lower platforms 93, 94, preferably these platforms 91, 92, 93, 94 are walls 88, 89. And is not simply glued to the walls 88, 89. Of course, this is not an essential feature of the cooling device 80 in which a plurality of actuators are distributed. Further, a top wall 95 (shown in FIG. 8) can be installed on the device 80 for the purpose of sealing the plenum 83.

  FIG. 8 shows the device of FIG. 7 after two actuators 96, 97 are positioned within the plenum 83 and the top wall 95 is installed over the plenum 83. As illustrated in this figure, the first actuator 96 rests on the upper platforms 91, 92 and the second actuator 97 rests on the lower platforms 93, 94. These two actuators 96, 97 preferably comprise a flexible diaphragm 98, 99 having piezoelectric actuators 101, 102, which are placed on the flexible diaphragm 98, 99. The preferred actuators 96, 97 are elastomeric or polymeric actuators described above with respect to exemplary embodiment 40. See FIG. Other actuators may be used with the device 80 described herein. However, elastomer / polymer actuators are preferred due to their low profile design, rugged operation, and low cost.

  Power and control are supplied to actuators 96, 97 by electrical wiring (not shown). These wires typically pass through four small channels 103a, 103b, 103c (only three are shown in FIG. 6) cut into both the upper and lower side walls 86, 86 of the housing 82. Enters the housing 82. Indeed, it is anticipated that the entire control electronics (not shown) can be positioned in these channels 103a, 103b, 103c. Only power is then preferably supplied to these channels 103a, 103b, 103c and the control hardware that contains them.

  Actuators 96, 97 are preferably secured to platforms 91, 92, 93, 94 in the housing 82 of the device. This is achieved by using some kind of adhesive. Since the material of the diaphragms 98, 99 is preferably an elastomer or polymer, and the preferred material of the housing 82 is plastic, one skilled in the art can easily select an appropriate adhesive, or other attachment mechanism. obtain.

  Once the actuators 96, 97 are secured to the interior portion of the device housing 82, the device plenum 83 is essentially divided into three parts. The positioning of the actuators 96, 97 forms three separate chambers that result in three separate but related synthetic jet actuators. The first (ie bottom) chamber 105 abuts the housing bottom wall 87, the housing front wall 88, the housing rear wall 89, and the second actuator 97. The second chamber 106 is bounded by the first actuator 96, the front wall 88, the rear wall 89, and the second actuator 97. The third actuator 107 is in contact with the first actuator 96, the front wall 88, the rear wall 89, and the top wall 95.

  Recall that the above implementation of distributed cooling device 60 (FIG. 4A) has a single orifice 46 leading from chamber 45 to a single tube 61. However, in the exemplary embodiment 80, each chamber 105, 106, 107 has one or more orifices 108. In the exemplary embodiment 80, each chamber 105, 106, 107 has two orifices formed in the front wall 88 of the device housing 82. Each orifice is further fluidly connected to one of the tubes 81 exiting the front wall 88 of the housing 82. Of course, it is not essential that each chamber 105, 106, 107 has two orifices 108 and a tube 81. This exemplary embodiment 80 also operates when there are more or less than two orifices 108 and tubes 81, or when there are different numbers for each chamber 105, 106, 107. To do.

  The tube 81 is preferably attached to the housing 82 in approximately the same horizontal plane, as illustrated in FIG. For this reason, FIGS. 7 and 8 only appear to have one tube 81 (and one orifice 108) attached to the housing 82 at approximately the midpoint of the front wall 88 of the housing. The tube 81 includes a mounting end 109 (attached to the front wall 88 of the housing) and a fluid outlet end 110 (which fluidly connects the interior 111 of the tube to the surrounding fluid 112).

  The tube 81 is preferably attached to the housing 82, all in the same horizontal plane, and the chambers 105, 106, 107 are not in the same horizontal plane, so that the contoured passage 113 is preferably in each chamber 105. , 106, 107 are each used to fluidly connect to an orifice 108 and a tube 81 provided by a particular synthetic jet actuator.

  These ported passages 113 are illustrated in the cut-away sectional view of FIG. In addition, FIG. 10 illustrates a cutaway view of the three chambers 105, 106, 107 and the orifices 108a-f provided by each chamber 105, 106, 107. By way of example, in FIG. 10, the first chamber 105 has two orifices 108e, 108f; the second chamber 106 has two orifices 108c, 108d; and the third chamber 107 has two There are two orifices 108a, 108b. As can also be seen from FIGS. 9 and 10, the three chambers 105, 106, 107 in the housing 82 do not necessarily have a rectangular cross-section, but rather a fluid is passed through each chamber 105, 106, 107. Is a strange shape that directs to the various tubes 81 provided by

  Of course, in alternative embodiments, the tube 81 need not necessarily be attached to the housing 82 in the same horizontal plane. For example, the tube 81 provided by each chamber 105, 106, 107 can be directly connected to the chamber 105, 106, 107. In this case, the chambers 1015, 106, 107 can be formed such that they have a substantially rectangular cross section.

  The operation of the exemplary multiple actuator distributed cooling device 80 will now be described by a specific discussion of one of the “plenums” 83. It should be understood that the operation of the other “plenums” 83 is similar. In operation, the two diaphragms 96, 97 are vibrated in time-harmonic motion by a control system (not shown) that controls each piezoelectric actuator 101, 102 on each diaphragm 98, 99. The diaphragms 98, 99 are preferably actuated so that the two diaphragms 98, 99 are oscillated out of phase with each other.

  As the two actuators 96, 97 move toward each other, the volume of the second chamber 106 decreases and the volumes of the top chamber 107 and the bottom chamber 105 increase. Accordingly, the second chamber 106 pushes fluid from the chamber 106 into the interior 111 of the tube 81 connected to the chamber 106. Recall from the discussion regarding the exemplary embodiment 60 of the single actuator above that pushing this fluid into the interior 111 of the tube acts like a “virtual piston” of fluid. For a description of this process, see the description regarding FIGS. 5A and 5B above. This virtual piston moves into the interior 111 of the tube 81 and compresses the fluid in the interior 111 of the tube, thereby allowing the composite jet stream of fluid 115 to flow in the tube 81 connected to this second chamber 106. Formed at the outlet end 110.

  The top chamber 107 and the bottom chamber 105 have the opposite effect. Specifically, as the two diaphragms 98, 99 move toward each other, both the top chamber 107 and the bottom chamber 105 are removed from the interior 111 of the tube 81 connected to these chambers 107, 105, Draw fluid. This causes a “virtual piston” of fluid to move into the top chamber 107 and the bottom chamber 105, thereby delivering fluid from the periphery 112 to the outlet end 110 of the tube 81 connected to these chambers 107, 105. Let them pull in.

  As the diaphragms 98, 99 oscillate away from each other, the volume of the second chamber increases and fluid is drawn from the periphery 112 into the tube 81 connected to the chamber 106. Of course, the volume of the top chamber 107 and the bottom chamber 105 decreases as well. A fluid composite jet stream 115 is thereby formed at the outlet end 110 of the tube 81 connected to these two chambers 107, 105.

  As will be appreciated by those skilled in the art, the operation of the cooling device 80 with a plurality of actuators distributed is very similar to the basic operating principle of the distributed cooling device 60 described above. For example, the tube 81 of this embodiment 80 acts as a Helmholtz resonator in the manner discussed above with respect to the cooling device 60 with a single actuator dispensed.

  One common implementation 120 of cooling device 80 with multiple actuators distributed is illustrated in FIGS. 11A and 11B. Of course, many other implementations are possible for device 80, depending on the thermal management requirements of the system and configuration of device 80. This exemplary implementation 120 does not limit the scope of implementation of the device 80. An exemplary implementation is provided merely to better illustrate the features of this embodiment 80.

  The exemplary implementation 120 includes the use of an external sump 121 to transfer heat away from the heated object 122. The cooling device 80 in which a plurality of actuators are distributed is such that each of the tubes 81 in the device 80 is aligned with a series of channels 123 formed with a series of fins 124 in a heat sink 121 so that the jet flow 125 is Positioned to pass through channel 123 between fins 124. This jet flow 125 then entrains the secondary cooling air flow 126 formed in the channel 123 of the heat sink 121.

  In another use 132 of this cooling module 80, an array of synthetic jets of tubes 81 is used to reduce the flow bypass 130 in the heat sump 121 cooled by the fan-driven flow 127. FIG. 12A illustrates the situation without the synthetic jet actuator 80. In this embodiment, fan 128 draws fluid flow 127 through channel 123 between fins 124 of heat sink 121. However, most of the airflow 130 bypasses the heat reservoir 121 due to the pressure drop generated by the channel 123 of the heat reservoir 121. This is for some applications (such as blade servers, telecommunications racks, etc., where the spacing between the component plates is narrow, and a large amount of airflow is stored in the heat reservoir installed in the hot component. A common problem encountered in which there is a large row of fans trying to drive through.

  In this implementation, as illustrated in FIG. 12B, the synthetic jet actuator is positioned so that the tube 81 of the actuator 80 is oriented to clear the flow 115 into the channel 123 of the heat sink 121. Is done. Note that due to the distributed nature of the device 80, the actuator can be positioned below the surface of the heat sink 121, thereby preventing any obstruction of the flow. When the actuator 80 is activated, the tangential composite jet 115 is directed near the left edge of the sump 121. The fan 128 continues to operate. The low pressure, high moment synthetic jet allows for significant entrainment 131 of the airflow 130 that previously bypassed the heat sink 121.

  It is emphasized that the above-described embodiments of the present invention, and in particular any "preferred" embodiments, are merely possible descriptions of implementations and are merely set forth for a clear understanding of the principles of the invention. Should. Many modifications and variations can be made to the above embodiments of the invention without substantially departing from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.

  Accordingly, since the invention has been described as such, it is claimed that at least what is described in the appended claims.

FIG. 1A is a schematic cross-sectional side view of a first embodiment of a synthetic jet actuator having a net mass flux of zero with a control system. 1B is a schematic cross-sectional side view of the synthetic jet actuator of FIG. 1A illustrating the jet as the control system moves the diaphragm inward and toward the orifice. 1C is a schematic cross-sectional side view of the synthetic jet actuator of FIG. 1A illustrating the jet as the control system moves the diaphragm outward and away from the orifice. FIG. 2 is a cross-sectional side view of a second exemplary embodiment of a synthetic jet actuator. 3 is a bottom view of a second exemplary embodiment of the synthetic jet actuator of FIG. FIG. 4A is a cross-sectional side view of a distributed cooling device. FIG. 4B is a cross-sectional top view of a distributed cooling device for directing fluid flow to different regions of the heated environment. FIG. 5A is a cross-sectional side view of a tube used in the distributed cooling device of FIG. 4A when the tube is drawing fluid from the surroundings. FIG. 5B is a cross-sectional side view of a tube used in the distributed cooling device of FIG. 4A when the tube is generating a synthetic jet stream of fluid at the outlet of the tube. FIG. 6 is a three-dimensional view of a cooling device in which a plurality of actuators are distributed. FIG. 7 is a cross-sectional side view of a cooling device with multiple actuators of FIG. 6 focusing on one of the “plenums” of the cooling device with multiple actuators distributed. FIG. 8 is a cross-sectional side view of this device of FIG. 6 focusing on one of the “plenums” of the cooling device to which a plurality of actuators are distributed, where these actuators are the “ It is installed in the “Plenum”. FIG. 9 is a three-dimensional cutaway view of the cooling device in which the plurality of actuators of FIG. 6 are distributed. FIG. 10 is a schematic rear view of the cooling device in which the plurality of actuators of FIG. 6 are distributed. FIG. 11A is a side view of a cooling device with a plurality of actuators of FIG. 6 distributed in the cooling system. FIG. 11B is a front view of the cooling device with the plurality of actuators of FIG. 6 distributed in the cooling system. FIG. 12A is a side view of a prior art cooling system. 12B is a side view of the cooling system of FIG. 12A in which the cooling device to which the plurality of actuators of FIG. 6 are distributed is implemented in the cooling system.

Claims (40)

A device for thermal management, including:
A housing defining an internal chamber and having an orifice in a wall of the housing;
A volume change device adjacent to the housing, wherein the volume change device is for changing the volume of the internal chamber; and a tube connected to the outer surface of the wall of the housing The tube surrounds at least a portion of the orifice;
A device comprising:   A control system for controlling operation of the volume change device, wherein the operation of the volume change device draws gas from the interior of the tube to the chamber and forces gas from the chamber; The device of claim 1, wherein the device exits and enters the interior of the tube.   The device of claim 1, wherein the volume change device comprises a flexible diaphragm forming a portion of the housing.   The device of claim 3, wherein the volume change device further comprises a piezoelectric actuator adhered to the flexible diaphragm.   The device of claim 4, wherein the flexible diaphragm comprises an elastomeric material.   The device of claim 4, wherein the flexible diaphragm comprises a polymeric material.   The tube includes an attachment end and an open end, the attachment end is connected to the housing, and actuation of the volume change device causes a synthetic jet stream at the open end of the tube. The device of claim 1, wherein the device is generated.   The device of claim 7, wherein the tube generates the synthetic jet stream at a location remote from the housing.   8. The device of claim 7, wherein the tube is sized such that due to operation of the volume change device, Helmholtz resonance occurs within the tube.   The heat sink further comprising fins, wherein the open end of the tube is positioned adjacent the heat sink so that the synthetic jet stream passes between the adjacent fins. Device described in.   Further comprising a fan, wherein the fan is positioned at one end of the heat sink so that the synthetic jet stream assists the fan by reducing flow diversion due to pressure drop in the fins. The device according to claim 10. The internal chamber is:
A first subchamber;
A second subchamber adjacent to the first subchamber; and a third subchamber adjacent to the second subchamber;
The device of claim 1, comprising:   The first sub-chamber and the second sub-chamber are formed from a first common wall, the first common wall is received within the internal chamber of the housing, and the first sub-chamber The device of claim 12, wherein the common wall comprises a first flexible diaphragm.   The second sub-chamber and the third sub-chamber are formed from a second common wall, the second common wall is received within the inner chamber of the housing, and the second sub-chamber The device of claim 13, wherein the common wall comprises a second flexible diaphragm.   The device of claim 14, wherein the orifice comprises at least one opening in each of the sub-chambers.   The device of claim 15, wherein the tube comprises a pipe adjacent to each of the at least one opening, each pipe surrounding at least a portion of the opening. In addition:
A first piezoelectric element attached to the first flexible diaphragm; and a second piezoelectric element attached to the second flexible diaphragm;
The device of claim 16, comprising:   The device of claim 17, wherein the first flexible diaphragm and the second flexible diaphragm comprise an elastomeric material.   The device of claim 17, wherein the first flexible diaphragm and the second flexible diaphragm comprise a polymeric material. A device for cooling, the following:
A synthetic jet actuator; and a channel having a proximal end and a distal end, wherein the proximal end is adjacent to the synthetic jet actuator, the synthetic jet actuator forming a synthetic jet stream;
A device comprising:   21. The device of claim 20, wherein the synthetic jet stream is formed at the distal end of the channel.   21. The device of claim 20, wherein the synthetic jet stream is formed at a proximal end of the channel.   21. The device of claim 20, further comprising a control system for controlling operation of the synthetic jet actuator. The synthetic jet actuator is:
A housing defining an internal chamber and having an orifice in a wall of the housing;
A volume changing means adjacent to the housing;
21. The device of claim 20, comprising:   25. The device of claim 24, wherein the volume changing means comprises a flexible diaphragm that forms a portion of the housing.   26. The device of claim 25, wherein the volume changing means further comprises a piezoelectric actuator adhered to the flexible diaphragm.   27. The device of claim 26, wherein the flexible diaphragm comprises an elastomeric material.   27. The device of claim 26, wherein the flexible diaphragm comprises a polymeric material.   27. The device of claim 26, wherein the channel is sized such that due to the operation of the volume changing means, Helmholtz-type resonance occurs within the channel.   30. The device of claim 29, wherein the channel comprises a tube.   The heat sink further comprising fins, wherein the distal end of the channel is positioned adjacent the heat sink so that the synthetic jet stream passes between the adjacent fins. 30. The device according to 29.   Further comprising a fan, wherein the fan is positioned at one end of the heat sink so that the synthetic jet stream assists the fan by reducing flow diversion due to pressure drop in the fins; 32. The device of claim 31.   21. The device of claim 20, wherein the channel constitutes a portion of a heat sink. The synthetic jet actuator comprises a first synthetic jet actuator, the device further comprising:
A second synthetic jet actuator adjacent to the first synthetic jet actuator;
A third synthetic jet actuator adjacent to the second synthetic jet actuator;
21. The device of claim 20, comprising:   The synthetic jet actuator is formed by a common housing, and the first synthetic jet actuator and the second synthetic jet actuator are formed from a first common wall, and the second 35. The device of claim 34, wherein the synthetic jet actuator and the production synthetic jet actuator are formed from a second common wall. The channel comprises a first tube and the device comprises:
A second tube having a proximal end and a distal end, the proximal end adjacent to the second synthetic jet actuator; and a proximal end and a distal end A third tube having a proximal end adjacent to the third synthetic jet actuator;
36. The device of claim 35, further comprising:   37. The device of claim 36, wherein the first common wall comprises a first flexible diaphragm and the second common wall comprises a second flexible diaphragm. In addition:
A first piezoelectric element attached to the first flexible diaphragm; and a second piezoelectric element attached to the second flexible diaphragm;
38. The device of claim 37, comprising:   40. The device of claim 38, wherein the first flexible diaphragm and the second flexible diaphragm comprise an elastomeric material.   40. The device of claim 38, wherein the first flexible diaphragm and the second flexible diaphragm comprise a polymeric material.

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