U.S. patent application number 11/205665 was filed with the patent office on 2006-03-23 for apparatus and method for enhanced heat transfer.
Invention is credited to Ari Glezer, Samuel Neil Heffington, Marc K. Smith.
Application Number | 20060060331 11/205665 |
Document ID | / |
Family ID | 35968208 |
Filed Date | 2006-03-23 |
United States Patent
Application |
20060060331 |
Kind Code |
A1 |
Glezer; Ari ; et
al. |
March 23, 2006 |
Apparatus and method for enhanced heat transfer
Abstract
One embodiment of the system is implemented as a device for
two-phase heat transfer. This device comprises a chamber containing
a fluid, where a heated wall makes up a portion of the chamber. The
device also comprises an actuator that emits pressure vibrations.
The pressure vibrations dislodge vapor bubbles that form at the
heated wall due to the heat in the wall.
Inventors: |
Glezer; Ari; (Atlanta,
GA) ; Heffington; Samuel Neil; (Kennesaw, GA)
; Smith; Marc K.; (Marietta, GA) |
Correspondence
Address: |
THOMAS, KAYDEN, HORSTEMEYER & RISLEY, LLP
100 GALLERIA PARKWAY, NW
STE 1750
ATLANTA
GA
30339-5948
US
|
Family ID: |
35968208 |
Appl. No.: |
11/205665 |
Filed: |
August 17, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60603436 |
Aug 20, 2004 |
|
|
|
Current U.S.
Class: |
165/104.29 ;
165/104.31; 257/E23.088; 257/E23.098 |
Current CPC
Class: |
H01L 23/427 20130101;
F28D 15/0266 20130101; H01L 2924/0002 20130101; H01L 23/473
20130101; H05K 7/20272 20130101; F28F 13/10 20130101; H01L 2924/00
20130101; H01L 2924/0002 20130101 |
Class at
Publication: |
165/104.29 ;
165/104.31 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Claims
1. A device for cooling a heated object, comprising: a chamber
containing a fluid; a heated wall comprising a portion of said
chamber; and an actuator, said actuator emitting pressure
vibrations for dislodging vapor bubbles from a surface of said
heated wall.
2. The device of claim 1, wherein said fluid comprises water.
3. The device of claim 2, wherein said fluid further comprises
methanol in addition to water.
4. The device of claim 1, wherein said actuator comprises an
ultrasonic actuator and said pressure vibrations comprise
ultrasonic pressure waves.
5. The device of claim 1, wherein said actuator comprises: a
diaphragm; a piezoelectric element attached to said diaphragm; and
a circuit for driving said piezoelectric element, said driving
circuit comprising a sinusoidal function generator and an
amplification chip.
6. The device of claim 5, wherein said diaphragm comprises a
ceramic disk.
7. The device of claim 1, wherein said chamber further comprises:
an inflow pipe at a first wall of said chamber, said inflow pipe in
fluid communication with an interior of said chamber; an outflow
pipe at a second wall of said chamber, said outflow pipe in fluid
communication with an interior of said chamber; and wherein said
fluid in said chamber moves out from said chamber through said
outflow pipe and into said chamber through said inflow pipe.
8. The device of claim 7, further comprising: a reservoir in fluid
communication with said chamber via said inflow pipe and said
outflow pipe, said reservoir containing said fluid.
9. The device of claim 1, wherein said heated wall comprises a heat
sink material.
10. The device of claim 9, further comprising a heat-producing
object adjacent to said heat sink material.
11. The device of claim 10, wherein said heat-producing object
comprises a microelectronic circuit.
12. The device of claim 1, wherein said heated wall comprises a
portion of a microelectronic circuit.
13. The device of claim 1, further comprising a synthetic jet
actuator in said chamber.
14. A method for cooling, comprising the steps of: providing a
chamber with a fluid; generating heat in a wall of said chamber;
causing the formation of vapor bubbles at said wall of said
chamber; emitting pressure vibrations into said fluid; and said
vapor bubbles dislodging from said wall of said chamber due to the
pressure vibrations.
15. The method of claim 14, further comprising the step of
circulating said fluid through said chamber.
16. The method of claim 15, wherein said emitting step comprises
the steps of: providing an actuator, said actuator having a
diaphragm; vibrating said diaphragm at a resonant frequency of said
diaphragm; and causing pressure waves to move through said fluid
from said diaphragm, said pressure waves impinging upon said
wall.
17. The method of claim 14, further comprising the steps of:
providing a fluid reservoir, said fluid reservoir in fluidic
communication with said chamber; moving said fluid from said
chamber to said reservoir and back to said chamber; and cooling
said fluid in said reservoir.
18. The method of claim 17, wherein said moving step comprises:
providing a fluidic pump; and pumping said fluid from said fluid
reservoir to said chamber, and from said chamber back to said fluid
reservoir.
19. A cooling device, comprising: a chamber containing a fluid a
heat source supplying heat into said fluid of said chamber; and an
actuator for emitting pressure vibrations into said fluid.
20. The device of claim 19, wherein said heat source comprises a
wall of said chamber.
21. The method of claim 20, wherein said actuator comprises a
diaphragm vibrating at a resonant frequency of said diaphragm.
Description
CLAIM TO PRIORITY
[0001] The present application claims the benefit of the filing
date of U.S. Provisional Patent Application Ser. No. 60/603,436,
filed on Aug. 20, 2004, which is hereby incorporated by reference
herein.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention is generally related to thermal
management technology and, more particularly, is related to an
apparatus and method for cooling heat-producing bodies or
components using a two-phase cooling heat transfer device based on
a vibration-induced bubble ejection process.
[0004] 2. Description of the Related Art
[0005] Cooling of heat-producing bodies is a concern in many
different technologies. Particularly in microprocessors, the rise
in heat dissipation levels accompanied by a shrinking thermal
budget has resulted in the need for new cooling solutions beyond
conventional thermal management techniques. In the microelectronics
industry, for example, advances in technology have brought about an
increase in transistor density and faster electronic chips. As
electronic packages increase in speed and capability, the heat flux
that must be dissipated to maintain reasonable chip temperatures
has also risen. Thermal management is recognized as a major
challenge in the design and packaging of state-of-the-art
integrated circuits in single-chip and multi-chip modules.
[0006] One method for effective heat transfer is so-called
"two-phase" heat transfer. Two-phase heat transfer involves,
generally, the evaporation of a liquid in a hot region and the
condensation of the resulting vapor in a cooler region. This type
of cooling is a highly effective cooling strategy for at least
three reasons. First, the liquid to vapor phase change greatly
increases the heat flux from the heated surface. Second, the high
thermal conductivity of the liquid medium, as opposed to that of
air, enhances the accompanying natural or forced convection. A
third reason for the efficient heat transfer that occurs during
two-phase heat transfer is that buoyancy forces remove the vapor
bubbles generated at the heated surface away from the heated
surface.
[0007] Two-phase, or "boiling," heat transfer is known and has been
studied for a number of years. Heat pipes and thermosyphons are
examples of efficient heat transfer devices that have been
developed to exploit the benefits of two-phase heat transfer.
Immersion cooling, which involves the pool boiling of a working
fluid on a heated surface, is another example of a two-phase
cooling technology.
[0008] There are limitations to the current state of the art in
two-phase cooling. First, two-phase heat transfer systems have
traditionally been viewed as incompatible with microelectronic
packages. This is largely due to the fact that liquid is involved
in the process.
[0009] Second, two-phase heat transfer systems are constrained by a
phenomena that manifests itself most noticeably in microgravity
environments. When the heat flux from the surface is increased past
a critical level, a large, potentially catastrophic increase in
temperature occurs. This critical heat flux marks the transition
from nucleate boiling to what is known as film boiling. In film
boiling, a thin insulating layer of vapor completely covers the
heated surface, which then produces a large temperature increase.
This transition occurs at much lower heat fluxes in a microgravity
environment because buoyancy forces are almost negligible. Thus,
the performance of immersion cooling in this environment is
drastically reduced.
[0010] A heretofore unaddressed need exists in the industry to
address the aforementioned deficiencies and inadequacies.
SUMMARY
[0011] Embodiments of the present invention provide a system and
method for cooling heated bodies and environments by using a
vibration-induced bubble injection system, method, and device.
[0012] A cooling cell based on the submerged vibration-induced
bubble ejection (VIBE) process in which small vapor bubbles
attached to a solid surface are dislodged and propelled into the
cooler bulk liquid capitalizes on the benefits of two-phase cooling
while improving on traditional methods of implementing two-phase
heat transfer. The VIBE device described below exceeds the
performance of conventional immersion cooling devices because it
delays the onset of the critical heat flux. By forcibly removing
the attached vapor bubbles with pressure instabilities, the VIBE
device and method dissipate more energy for a given surface
temperature than previous immersion coolers.
[0013] Briefly described, in architecture, one embodiment of the
VIBE device described herein, among others, can be implemented as a
device for two-phase heat transfer. This one embodiment comprises a
chamber containing a fluid. This embodiment also comprises a heated
wall making up a portion of the chamber. Finally, the embodiment
comprises an actuator that emits pressure vibrations. The pressure
vibrations dislodge vapor bubbles forming at the heated wall due to
the heat in the wall.
[0014] Embodiments of the present invention can also be viewed as
providing methods for cooling. In this regard, one embodiment of
such a method, among others, can be broadly summarized by the
following steps: (i) providing a chamber with a fluid; (ii)
generating heat in a wall of the chamber; (iii) causing the
formation of vapor bubbles at the heated wall; and (iv) emitting
pressure vibrations into the fluid, wherein the vapor bubbles
dislodge from the heated wall due to the pressure vibrations.
[0015] Other devices, systems, methods, features, and advantages of
the present invention will be or become apparent to one with skill
in the art upon examination of the following drawings and detailed
description. It is intended that all such additional devices,
systems, methods, features, and advantages be included within this
description, be within the scope of the present invention, and be
protected by the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] 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.
[0017] FIG. 1 is a cut-away side view of a first embodiment of a
two-phase heat transfer device.
[0018] FIG. 2 is a cut-away side view of an alternative embodiment
of an actuator used in a two-phase heat transfer device.
[0019] FIG. 3 is a cut-away side view of a second embodiment of a
two-phase heat transfer device.
[0020] FIG. 4 is a cut-away side view of a third embodiment of a
two-phase heat transfer device.
[0021] FIG. 5 is a cut-away side view of a fourth embodiment of a
two-phase heat transfer device.
[0022] FIG. 6 is a cut-away side view of a fifth embodiment of a
two-phase heat transfer device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0023] The present disclosure is directed to a method and apparatus
for heat transfer. The cooling method and apparatus described
herein generally use a two-phase cooling heat transfer device based
on a vibration-induced bubble ejection ("VIBE") process.
Construction of the Vibe Device
[0024] FIG. 1 depicts a first embodiment 10 of an apparatus for
accomplishing the disclosed method through the use of a VIBE
cooling apparatus. The VIBE apparatus 10 of the first embodiment
generally comprises a chamber 11 for holding a fluid 12.
[0025] The chamber 11 could be constructed of any suitable
material. Generally, the material used for the chamber 11 will
depend to some degree on the particular fluid 12 in the chamber 11
and on the particular heat transfer characteristics desired. The
preferred material from which the chamber 11 is to be constructed
is a light-weight metallic material from which the chamber 11 can
be easily and inexpensively manufactured. For example, the material
for the chamber 11 of the present embodiment 10 is aluminum.
[0026] In the present embodiment 10, the entire chamber 11 is
constructed from an aluminum material. However, in an alternative
embodiment, the chamber 11 is manufactured from more than one
material. In other words, different parts of the chamber 11 are
manufactured from different materials. Such a configuration
minimizes heat transfer to certain parts of the chamber 11, while
maximizing heat transfer to other parts of the chamber 11.
[0027] More specifically, in this alternative embodiment, some
parts of the chamber 11 are constructed from a highly thermally
conductive material. Other parts of the chamber 11 are constructed
from a thermally insulating material. This possibility will be
discussed more specifically below.
[0028] Generally, the chamber 11 may be manufactured in any shape
desired or dictated by the use to which the VIBE apparatus 10 will
be put. One of ordinary skill in the art will easily be able to
size and shape an appropriate chamber 11 for a given application.
In the present embodiment 10 the chamber 11 is cubic. The cubic
chamber 11 has a lower wall 13, an upper wall 14, and two side
walls 15, 16. Of course, the chamber 11 also comprises a front wall
and a back wall. As FIG. 1 is a cut-away side view of the present
embodiment 10, the front wall is not depicted in FIG. 1.
[0029] As will be explained in more detail below, the fluid 12 in
the chamber 11 of the VIBE device 10 will be involved in a heat
transfer process. For this reason, the selection of the fluid 12 to
be used with the VIBE device 10 may change depending on the
particular application of the device 10. As will be readily
understood by one of ordinary skill in the art after reading this
description, different fluids will exhibit different heat transfer,
safety, availability, and other characteristics. After reading the
present description, one of ordinary skill in the art would easily
be able to make an appropriate fluid selection.
[0030] The fluid 12 in the present embodiment 10 is a mixture of
methanol and water. The preferred mixture of the present fluid 12
is 70% distilled water and 30% methanol. However, the fluid 12 of
the present embodiment 10 does not have to comprise such a
mixture.
[0031] For example, if more viscosity in the fluid 12 is desired,
ethylene glycol, or an ethylene glycol/water mixture, is used as
the working fluid 12 of the device 10. Alternatively, 100%
distilled water could be used of the working fluid 12 of the
present embodiment 10. Almost any fluid could be used in the VIBE
device 10, depending on the particular application of the device 10
and the particular performance characteristics desired. Generally,
it has been found that lower viscosity fluids are preferred for
most applications. Lower viscosity fluids in the VIBE device 10
generally permit greater heat transfer and, thereby, a greater
cooling effect. In most applications, greater cooling is
desired.
[0032] In the present embodiment 10, the chamber 11 is preferably
hermetically sealed except for an inlet pipe 17 and an outlet pipe
18. These two pipes 17, 18 permit the fluid 12 to flow into and out
of the chamber 11, respectively. Preferably, a fluid flow is
established in the chamber 11 by moving fluid into the chamber 11
through the inlet pipe 17, thereby forcing fluid 12 out of the
chamber 11 through the outlet pipe 18. Of course, the fluid flow
could also be established in the chamber 11 by withdrawing fluid 12
through the outlet pipe 18, thereby creating a pressure gradient
that draws fluid 12 into the chamber 11 through the inlet pipe 17.
Although described in the present embodiment, a fluid flow in the
chamber 11 is not required for the VIBE device 10 to function
properly. Alternative embodiments of a VIBE device without a fluid
flow will be discussed in more detail below.
[0033] The fluid flow described above is created in the present
embodiment 10 because the inlet pipe 17 and outlet pipe 18 are both
part of a connected fluidic system, as depicted in FIG. 1. In the
present embodiment, the pipes 17, 18 are fluidically connected to a
fluid reservoir 19 and/or a remote heat exchanger. The fluid 12 is
caused to flow into the chamber 11 though the inlet pipe 17, and
out of the chamber 11 through the outlet pipe 18. The outlet pipe
18 carries the fluid 12 to the fluid reservoir 19, where the fluid
12 is circulated back into the inlet pipe 17 and carried back to
the chamber 11. Of course, the fluid reservoir 19 of the present
embodiment 10 is not required for the VIBE device to function. In
some embodiments, the fluid reservoir 19 can be omitted.
[0034] In an alternative embodiment of the present VIBE apparatus
10, the device includes a process for cooling the fluid 12 while
the fluid 12 is in, or passing through, the reservoir 19. This is
preferably accomplished by the fluid reservoir 19 taking the form
of a container in a refrigerated cabinet. Alternatively, the
reservoir 19 is equipped with other means of refrigeration. In
either configuration, heat is directly extracted from the fluid 12
in the reservoir 19 by an external cooling mechanism.
[0035] In an alternative embodiment, the fluid reservoir 19 takes
the form of a heat exchanger remote to the chamber 11. In this
alternative embodiment, the fluid 12 is cooled as it moves through
the fins of the remote heat exchanger.
[0036] Preferably, a pump 21 is affixed at the fluid reservoir 19
in order to move the fluid 12 from the fluid reservoir 19 through
the inlet pipe 17 back to the chamber 11. Basically, the pump 21 is
the apparatus of the fluid system that actually creates the desired
fluid flow in the chamber 11.
[0037] The VIBE device 10 of the present description does not
require that a pump 21 be used to circulate the fluid 12 through
the fluid system. Indeed, if a fluid flow is desired, the fluid 12
may be moved through the pipes 17, 18 and chamber 11 in a variety
of ways consistent with the present embodiment 10. For example, fan
blades, louvers, or other fluid movement apparatus may be used to
move the fluid 12 through the system. In addition, the type and
size of pump 21 of the present embodiment 10 may be altered in
order to increase or decrease the fluid flow rate as desired for a
particular application. One of ordinary skill in the art, upon
reading the present description, can readily select and implement a
pump 21 of the appropriate size and configuration.
[0038] The present embodiment 10 also includes an actuator 22
situated in the chamber 11. The actuator 22 is mounted to the upper
wall 14 of the chamber 11. Alternatively, the actuator 22 could be
manufactured into the structure of a wall of the chamber 11. This
alternative design will be discussed in more detail below.
[0039] The actuator 22 of the present embodiment 10 can be of many
possible designs. However, the depicted actuator 22 comprises a
diaphragm 23 secured to a mounting body 24 (or simply a
"mount").
[0040] The diaphragm 23 is preferably constructed of a ceramic
material with a copper or brass layer; however, this particular
construction is not required. The diaphragm 23 is preferably
securely attached to the mount 24. The diaphragm 23 may be attached
to the mount 24 by any appropriate means, and the particular method
of attachment is not critical to the present embodiment 10.
[0041] In the depicted embodiment of the actuator 22, the mount 24
is preferably cubic in shape. The diaphragm 23, therefore, is
formed into a square shape such as to form one wall of the mount's
cube shape.
[0042] Attached to an inner side of the diaphragm 23 is a
piezoelectric element 26. The piezoelectric element 26 is
preferably attached to the diaphragm 23 by an adhesive, or other
means. The piezoelectric element 26 is actuated by a discrete
electronic driving circuit 27 of this embodiment that is preferably
positioned exterior to the chamber 11. The driving circuit 27
comprises a sinusoidal function generator and an amplification chip
(not separately depicted in FIG. 1). The driving circuit 27 is
electronically connected to the piezoelectric element 26 by
appropriate wiring 30 that passes through the upper wall 14 of the
chamber 11.
[0043] The mount 24 is preferably constructed of a lightweight
metal, such as aluminum. The cubic shape of the mount 24 of the
present embodiment is not required. Indeed, the mount 24 could be
formed into, for example, a cylindrical shape. In this situation,
the diaphragm 23 is manufactured into a circular shape in order to
correspond to the cross-section of the mount 24. The shape of the
mount 24 and the diaphragm 23 are not critical to the functioning
of the VIBE apparatus 10.
[0044] An alternative configuration of the actuator 22 positions
the driving circuit 27 inside the mount 24. FIG. 2 is a cut-away
side view of this alternative actuator 22 configuration. In such a
configuration, the driving circuit 27 is placed inside the mount 24
such that the actuator 22 is completely self-contained.
[0045] As briefly mentioned above, the actuator 22 of a second
embodiment 35 is built into a wall of the chamber 11. See FIG. 3.
For example, the diaphragm 23 of the actuator 22 could be
positioned flush with, or at least closer to, the upper wall 14 of
the chamber 11. This embodiment for a VIBE device 35 is depicted in
FIG. 3. In this configuration, the mount 24 is entirely exterior to
the chamber 11.
[0046] In another alternative embodiment 40, the mount 24 is
completely eliminated and the diaphragm 23 forms one of the chamber
walls 14. This configuration 40 is depicted in FIG. 4, which is a
cut-away side view of this third embodiment 40. In such a
configuration 40, the upper wall 14 of the chamber 11 is comprised
of a diaphragm 23. The driving circuit 27 is positioned on a side
wall 16 of the chamber 11. The diaphragm 23 is still equipped with
a piezoelectric element 26 that is driven by the driving circuit
27.
[0047] Returning to FIG. 1, the bottom wall 13 of the chamber 11 is
adjacent to a heated body or heat-producing body 28. For example, a
microelectronic circuit or chip may be situated adjacent to the
bottom wall 13 of the chamber 11. Thus, the heat from the
heat-producing body 28 travels into the bottom wall 13 of the
chamber 11. As will be apparent to one of ordinary skill in the
art, the material that forms the bottom wall 13 of the chamber 11
affects the rate of heat transfer into this wall 13. As noted
above, the preferred material for all the walls of the chamber 11
is aluminum. Since the preferred bottom wall 13 is constructed of
aluminum, the heat transfer into the wall 13 will be at a
relatively high rate.
[0048] In an alternative embodiment, the bottom wall 13 of the
chamber 11 is constructed of a different material from the
remainder of the chamber 11 in order to increase heat transfer into
the bottom wall 13, but reduce heat transfer into the other walls
of the chamber 11. The bottom wall 13 of the chamber 11 in this
alternative configuration is constructed of copper, but the other
walls of the chamber 11 are constructed of a less thermally
conductive material, such as aluminum, brass, or most preferably
plastic.
[0049] Regardless of the material making up the walls of the
chamber 11, the configuration of the VIBE device 10 is modified in
other alternative embodiments. For example, in one other
alternative embodiment, the bottom wall 13 of the chamber 11 is
positioned next to a larger heat sink structure. With such an
embodiment, the heat sink absorbs heat from one or more
heat-producing bodies. Then, the VIBE device would remove heat
from, and consequently cool, the heat sink.
[0050] In another alternative embodiment, a heat-producing body
actually forms the bottom wall 13 of the chamber 11 itself.
Basically, a housing of a microelectronic circuit makes up at least
a portion of the bottom wall 13 of the chamber 11. In this
alternative embodiment, the VIBE device 10 directly cools the
heat-producing device itself.
Operation of the Vibe Device
[0051] In operation, the VIBE apparatus 10 functions to cool the
heated body 28. As the heated body 28 produces heat, the heat flows
into the bottom wall 13 of the chamber 11. The heat is further
transferred into the cooler fluid 12. As the fluid 12 absorbs heat,
the temperature of the fluid 12 adjacent to the bottom wall 13
rises. At some point in time, the temperature of the fluid 12
adjacent to the bottom wall 13 will reach the boiling temperature
of the fluid 12. Upon the fluid 12 reaching its boiling
temperature, vapor bubbles 29 will begin to form at the bottom wall
13 of the chamber 11. In essence, the fluid 12 begins boiling.
[0052] Initially, the vapor bubbles 29 tend to cling to the bottom
wall 13 of the chamber 11. If the VIBE device 10 was is not
operating, the vapor bubbles 29 continue to cling to the bottom
wall 13 as the temperature of the wall 13 and the adjacent fluid 12
continues to rise. As the temperature of the fluid 12 adjacent to
the bottom wall 13 continues to rise, a critical temperature is
reached where nucleate boiling of the fluid 12 generally ceases and
film boiling begins. This critical point varies depending on the
fluid 12 used. In this situation, the vapor bubbles 29 begin to
form a thin insulating layer of vapor along the bottom wall 13 of
the chamber 11. If this were allowed to continue, there would be a
dramatic reduction in cooling of the bottom wall 13, and
consequently, the heated body 28.
[0053] The present VIBE device 10, however, remedies this potential
limitation by causing the actuator 22 to vibrate the diaphragm 23.
The vibration of the diaphragm 23 creates a series of pressure
waves 31 that emit from the diaphragm 23. The waves 31 strike the
bottom wall 13 and cause the vapor bubbles 29 to become dislodged.
Once dislodged, the buoyancy of the vapor bubbles 29 carry them up
and away from the bottom wall 13 of the chamber 11. At this point,
the fluid flow discussed above sweeps the vapor bubbles 29 away
from the bottom wall 13 and out of the chamber 11. Once away from
the bottom wall 13 of the chamber 11, the vapor bubbles 29 begin to
cool. As the bubbles 29 cool, they condense, release their stored
heat into the surrounding fluid 12, and are thus reincorporated
into the fluid 12. In this manner, the heated bottom wall 13 of the
chamber 11 is cooled. In turn, this process cools the heated body
28. Basically, the action of the VIBE device 10 in dislodging the
vapor bubbles 29 prevents the formation of the thin insulating
layer of vapor discussed above, and prevents reaching the critical
heat flux in which the surface is coated with vapor.
[0054] Preferably, the diaphragm 23 of the present embodiment 10 is
caused to vibrate at its resonant frequency of its first
axisymmetric mode of vibration. Nominally, this frequency in the
first embodiment is about 1.65 MHz. Vibration of the diaphragm 23
at this frequency produces ultrasonic pressure waves in the fluid
12. It is not necessary to vibrate the diaphragm 23 at its resonant
frequency, but this is preferred. This is because ultrasonic
pressure waves 31 are also preferred, though not required.
[0055] An alternative embodiment of a VIBE apparatus 50 is depicted
in FIG. 5. As will be seen in the figure, this embodiment 50
comprises no inflow pipe and no outflow pipe. The chamber 11 is
completely sealed. In this embodiment 50 the bubbles 29 that are
released from the bottom wall 13 of the chamber 11 move away from
the bottom wall 13 and into cooler fluid 12, which causes the
bubbles 29 to condense. This embodiment 50 of a VIBE apparatus has
the advantage of being self-contained and smaller. This embodiment
50 can be used as a portable device to be attached wherever heat
removal and/or cooling is needed. However, the heat removal
capacity and rate may not be as efficient as that of the first
embodiment 10.
[0056] An alternative embodiment of a VIBE apparatus 60 is depicted
in FIG. 6. This embodiment 60 is very similar to the previous
embodiment 50. However, small synthetic jet actuators 61, 62 have
been placed within the chamber 11. Synthetic jet actuators,
generally, are described in detail in U.S. Pat. No. 5,758,853 to
Glezer et al., entitled "Synthetic Jet Actuators and Applications
Thereof," which is incorporated herein by reference. Basically, the
synthetic jet actuators 61, 62 create jets 63, 64 of fluid without
net mass injection into the chamber 11. The fluidic jets 63, 64
agitate the fluid 12 in the chamber 11 resulting in more effective
heat transfer.
[0057] Other alternative embodiments of the VIBE device involve
modifications of the actuator 22. One of these alternative
embodiments involves using more than one actuator 22 in the chamber
1. An array of actuators is positioned along the upper wall 14 of
the chamber 11. In another alternative embodiment, the actuator 22
comprises a mount and a piston system in order to create the
pressure waves 31.
[0058] It should be emphasized that the above-described embodiments
of the present invention, particularly, any "preferred"
embodiments, are merely possible examples of implementations,
merely set forth for a clear understanding of the principles of the
invention. Many variations and modifications may be made to the
above-described embodiment(s) of the invention without departing
substantially 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.
* * * * *