U.S. patent application number 12/566841 was filed with the patent office on 2011-03-31 for thermal wick cooling for vibroacoustic transducers.
Invention is credited to Stephen C. Butler, Benoit G. Gauthier, Stephen J. Plunkett.
Application Number | 20110073293 12/566841 |
Document ID | / |
Family ID | 43778999 |
Filed Date | 2011-03-31 |
United States Patent
Application |
20110073293 |
Kind Code |
A1 |
Gauthier; Benoit G. ; et
al. |
March 31, 2011 |
Thermal Wick Cooling For Vibroacoustic Transducers
Abstract
A soft thermally-conductive wick is provided to be connected
between the metallic components on a transducer and onto a thermal
sink. Beryllia ceramic is provided to improve heat flux within the
transducer while maintaining electrical insulation. The wick
provides adequate heat flux and such that the mass and stiffness of
the wick do not adversely affect the vibroacoustic properties of
the transducer in the frequency band of interest. The mass of the
wick attachment is considered in the transducer design with the
location and direction of the wick attachment designed so as to not
introduce rocking modes or other adverse affects in the frequency
band of interest. The wick may be strung, coiled, folded or
configured in many ways between the transducer and the thermal sink
to ensure that no acoustic or vibrational energy is transmitted
down the length of the wick.
Inventors: |
Gauthier; Benoit G.; (Little
Compton, RI) ; Butler; Stephen C.; (Newport, RI)
; Plunkett; Stephen J.; (Middletown, RI) |
Family ID: |
43778999 |
Appl. No.: |
12/566841 |
Filed: |
September 25, 2009 |
Current U.S.
Class: |
165/185 |
Current CPC
Class: |
B06B 1/0618 20130101;
G10K 11/004 20130101 |
Class at
Publication: |
165/185 |
International
Class: |
F28F 7/00 20060101
F28F007/00 |
Goverment Interests
STATEMENT OF GOVERNMENT INTEREST
[0001] The invention described herein may be manufactured and used
by or for the Government of the United States of America for
governmental purposes without the payment of any royalties thereon
or therefore.
Claims
1. A device for cooling a vibroacoustic transducer, said device
comprising: a thermally-conductive and pliable wick connectable at
a first end to a metal component of a transducer with a second end
of said wick connectable to a thermal sink; wherein said wick is
capable of sufficient heat flux.
2. The device in accordance with claim 1, said device further
comprising a beryllia washer interposed between the first end of
said wick and the metal component of the transducer.
3. The device in accordance with claim 2 wherein the material of
said wick is copper.
4. The device in accordance with claim 2 wherein the material of
said wick is silver.
5. The device in accordance with claim 1 wherein the material of
said wick is copper.
6. The device in accordance with claim 1 wherein the material of
said wick is silver.
7. A system for cooling a vibroacoustic transducer, said device
comprising: a pliable and thermally-conductive wick connectable at
a first end to a metal component of a transducer with a second end
of said wick connectable to a thermal sink wherein said wick is
capable of sufficient heat flux; and a component for thermal
conduction interposed within the transducer.
8. The system in accordance with claim 7 wherein the material of
said thermal conduction component is beryllia.
9. The system in accordance with claim 7 wherein said thermal
conduction component is in the shape of a wafer.
10. The system in accordance with claim 9 wherein the material of
said thermal conduction component is beryllia.
11. The system in accordance with claim 7 said system further
comprising a beryllia washer interposed between the first end of
said wick and the metal component of the transducer.
12. The system in accordance with claim 11 wherein the material of
said thermal conduction component is beryllia.
13. The system in accordance with claim 12 wherein the material of
said wick is copper.
14. The system in accordance with claim 12 wherein the material of
said wick is silver.
15. The system in accordance with claim 11 wherein said thermal
conduction component is in the shape of a wafer.
16. The system in accordance with claim 15 wherein the material of
said thermal conduction component is beryllia.
17. The system in accordance with claim 16 wherein the material of
said wick is copper.
18. The system in accordance with claim 16 wherein the material of
said wick is silver.
19. The system in accordance with claim 16 wherein the material of
said wick is gold.
20. The system in accordance with claim 16 wherein the material of
said wick is lead.
Description
CROSS REFERENCE TO OTHER PATENT APPLICATIONS
[0002] None.
BACKGROUND OF THE INVENTION
[0003] (1) Field of the Invention
[0004] The present invention provides a device for cooling a
vibroacoustic transducer without adversely affecting vibrational
characteristics of the transducer.
[0005] (2) Description of the Prior Art
[0006] Vibroacoustic transducers, such as piezoceramic tonpilz
sonar array elements, generate heat as a byproduct of operation.
These transducers are mounted in such a manner (gas-backed,
syntactic foam mounted) as to have limited heat flux to their
foundations or array plates. Therefore, as the drive levels and
duty cycles increase, output power becomes heat-limited.
Furthermore, as the frequency bandwidth of operation increases,
these devices are driven further from their efficient resonant
points, again increasing heat generation. During some operations,
failure modes such as syntactic foam mount melting and acoustic
window debond and melting have been observed.
[0007] Consider the section view of a typical prior art
vibroacoustic transducer 10--shown in FIG. 1. In operation,
acoustic energy is radiated from a headmass 12 as the headmass
oscillates out of phase with a tailmass 14 when driven by a stack
of piezoceramic wafers 16. The piezoceramic wafers 16 exhibit a
mechanical strain proportional and parallel to an alternating
electrical voltage provided by oppositely-charged electrode discs
18, 20. The piezoceramic wafers 16 generate heat in this excitation
process. Heat is conducted to the tailmass 14 and headmass 12. The
headmass 12 and tailmass 14 may be electrically insulated from the
electrodes by insulating wafers 22.
[0008] The piezoceramic wafers 16 may also be insulated
electrically by core insulating collars 24 or more typically by air
gaps around a central stress rod 26. With a pre-defined load, the
stress rod 26 clamps the stack of piezoceramic wafers 16,
electrodes and insulators between the headmass 12 and the tailmass
14. The clamping operation is typically tuned by tightening a
binding nut 28 or by using a screw thread 30 in the tailmass 14 if
a nut is not used. This assembly is typically mounted to a
foundation or to an array plate 100 by a syntactic foam mounting
ring 110 as shown in FIG. 2.
[0009] The mounting ring 110 may have resonant characteristics to
provide mechanical isolation. Generally, the mounting ring 110 is a
poor thermal conductor. An acoustically-transparent elastomeric
window is often cast over the headmass 12, thereby providing a
hydrodynamic surface. Heat is also generated in the window material
as the window is vibrated by the headmass 12.
[0010] Generally, the elastomer properties of the window are a poor
heat conductor. This heat may be conducted or convected from the
outer surface by presence or flow of a surrounding fluid, such as
seawater in the case of an underwater application. Excessive heat
generated in the window may also be conducted back to the headmass
12; thereby, increasing element heating.
[0011] As such a need still exists for alternative transducer
cooling and the prior art includes numerous references that attempt
to provide such cooling. In Krempl (U.S. Pat. No. 4,169,387), a
transducer is disclosed for mechanical measured variables having a
heat pipe system that is connected on one side to the thermally
high stressed parts of the transducer and on the other side to
parts that not exposed to heat or cold. The sensor element of the
transducer is cooled through heat transport by means of an
alternatively vaporizing and condensing working fluid within the
heat pipe system.
[0012] In Boeglin et al. (U.S. Pat. No. 5,291,461), an elastomer
support for a sonar transducer includes a ceramic stack
electromechanical driver, a pair of rigid support members and a
pair of elastomer layers disposed between the ceramic stack
electromechanical driver and the support members. The elastomer
support provides effective mechanical stress reduction in the
ceramic stack driver, as well as, a simple reliable heat
dissipation means for the transducer.
[0013] In Sliwa, Jr et al. (U.S. Pat. No. 5,560,362), an ultrasound
transducer is provided as an assembly having a housing, a
transducer array mounted in the housing, and an active cooling
mechanism positioned adjacent to the transducer array for actively
removing heat generated by the array by transport of energy from
the affected site. The active cooling mechanism may comprise a heat
exchanger including a closed loop circulating coolant system
circulating coolant or a single-pass flowed coolant, passing
through the heat exchanger, a heat pipe, a thermoelectric cooler,
an evaporative/condenser system and/or a phase change material. One
or more heat exchangers may be used having gas or liquid coolants
flowing there through. The heat exchangers and coolant pumps may be
located in various components of the transducer assembly, including
the array housing, the connector assemblies or the ultrasound
console.
[0014] In Drumheller (U.S. Pat. No. 5,703,836), an acoustic
transducer is disclosed that has a one-piece hollow mandrel into
the outer surface of which is formed a recess with sides
perpendicular to the central axis of the mandrel and separated by a
first distance and with a bottom parallel to the central axis and
within which recess are a plurality of washer-shaped discs of
piezoelectric material and at least one disc of a
temperature-compensating material with the discs being captured
between the sides of the recess in a pre-stressed interface
fit.
[0015] In Nilsson et al (U.S. Pat. No. 5,955,823), a method is
provided to improve the output characteristics of an ultrasonic
transducer by urging a cooling gas to flow through the transducer,
thereby passing a cooling member between each adjacent pair of
piezoelectric elements.
[0016] In Wildes et al. (U.S. Pat. No. 7,105,986), a composite
structure of a backing material with enhanced conductivity for use
in a transducer is presented. The composite material includes a
plurality of layers of backing material alternatively arranged with
a plurality of thermal conductive elements, wherein the plurality
of thermal conductive elements are configured to transfer heat from
a center of the transducer to a plurality of points on the
composite structure of backing material.
SUMMARY OF THE INVENTION
[0017] Accordingly, it is a primary object and general purpose of
the present invention to provide a device for cooling a
vibroacoustic transducer without adversely affecting vibrational
characteristics of the transducer.
[0018] It is a further object of the present invention to provide a
device for cooling a vibroacoustic transducer which allows higher
drive levels to be achieved for longer duty cycles and broader
frequency bandwidths.
[0019] It is a still further object of the present invention to
provide an inexpensive method of conducting waste heat from the
transducer to any location--such as a heat sink.
[0020] In order to attain the objects described, the present
invention provides a soft thermally-conductive wick connected
between the metallic components on a transducer and onto a thermal
sink. The wick provides adequate heat flux and such that the mass
and stiffness of the wick do not adversely affect the vibroacoustic
properties of the transducer in the frequency band of interest. The
mass of the wick attachment is considered in the transducer design
with the location and direction of the wick attachment designed so
as to not introduce rocking modes or other adverse affects in the
frequency band of interest. In operation, heat is conducted from
the transducer via the wick to the thermal sink.
[0021] Improved heat transfer by beryllia insulators is also
claimed for transducers requiring electrical isolation of metallic
components. The wick may be strung, coiled, folded or configured in
many ways between the transducer and the thermal sink to ensure
that no acoustic or vibrational energy is transmitted down the
length of the wick.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] A more complete understanding of the invention and many of
the attendant advantages thereto will be readily appreciated as the
same becomes better understood by reference to the following
detailed description when considered in conjunction with the
accompanying drawings wherein like reference numerals and symbols
designate identical or corresponding parts throughout the several
views and wherein:
[0023] FIG. 1 depicts an exploded view of a prior art
transducer;
[0024] FIG. 2 depicts a prior art transducer mounted on an array
plate;
[0025] FIG. 3 depicts a prior art transducer connected with thermal
wick assembly of the present invention; and
[0026] FIG. 4 depicts a prior art transducer with thermal wick
assembly of the present invention mounted on an array plate.
DETAILED DESCRIPTION OF THE INVENTION
[0027] As shown in FIG. 3, a soft, tactile and pliable
thermally-conductive wick 200 is connected between the metallic
components on the transducer 10 and onto a thermal sink (not
shown). This wick 200 may be a loosely-braided length of thermally
conductive material such as copper or silver. An example of a
suitable conductor for the role of the wick 200 is the copper
de-soldering wick used in printed circuit board manufacturing. The
assembly of the wick 200, a lug 210 and tailmass 14 is designed and
configured such that the wick 200 is of sufficient total material
cross-section and of appropriate metal alloy to conduct the
required thermal energy from the hot transducer to the cooler
surrounding masses which serve as heat sinks 300. For harsh duty
cycles, the conduction equation is solved conservatively to
determine this required wick cross section, using the allowable
maximum temperature for the transducer element and the maximum
expected temperature for the heat sink 300, in order to minimize
the available temperature differential. The contact area of the lug
210 on the tailmass 14 and stress rod 26 also allows thermal
conduction at a rate not less than the heat flux required in the
wick 200.
[0028] The total cross-sectional area of the wick is determined by
the cross-section of the strands of the wick, the tightness of the
weave and the constitutive properties of the alloy from which the
wick is made. These strand parameters are selected by consideration
of the thermal conduction requirements as derived above and the
mechanical requirement that the resulting stiffness of the wick
does not adversely affect the vibroacoustic properties of the
transducer in the frequency band of interest.
[0029] The wick 200 is connected to the metallic components of the
transducer 10 via means known to those ordinarily skilled in the
art (such as the lug 210 or stud) or by directly soldering or
brazing the wick to the appropriate metallic component (such as the
tailmass 14, headmass 16 or the stress rod 26. The mass of the
attachment is considered in the transducer design as follows. The
vibroacoustic requirement of the transducer of prior art sets the
total allowable mass of the tailmass 14 (and the nut 28 if the tail
mass itself is not threaded and solder/brazing material.
[0030] The location and direction of the wick attachment are
designed so as to not introduce rocking modes or other adverse
affects in the frequency band of interest. Generally, the lug 210
is designed to be azisymmetric on the centerline of the stress rod
26. Furthermore, the assembly can be designed using modal analysis
such that the stiffness, aspect ratio, orientation of the wick and
resonant modes of the tail assembly do not introduce unwanted
response modes in the complete transducer assembly within the
frequency range of operation.
[0031] Thermal conduction to the metallic components may be
enhanced by the introduction of thermally conductive dielectric
wafers in place of the end insulating wafers 22. Another feature of
the invention is the use of beryllia for these dielectric wafers
22, which has the rare properties of high thermal conduction, high
stiffness and is an electrical insulator. The use of this unique
ceramic has not been demonstrated in the prior art in vibroacoustic
transducers. As such, this embodiment is a novel and beneficial
feature enhancing heat transfer in vibroacoustic
transducers--independent of the incorporation of the wick 200.
[0032] In operation, heat is conducted from the transducer 10 via
the wick 200 to a thermal sink 300. The thermal sink 300 may be the
array foundation, or may be a remote structure such as a heat
exchanger. The wick 200 may be connected to the thermal sink 300 in
a variety of attachments known to those ordinarily skilled in the
art (such as the lugs or studs previously discussed).
[0033] If electrical isolation of the transducer wick 200 is
required, a washer made of thermally conductive dielectric such as
beryllia may be introduced. The wick 200 may be strung, coiled,
folded or configured in many ways between the transducer 10 and
thermal sink 300 to ensure that no acoustic or vibrational energy
is transmitted down the length of the wick.
[0034] The wick 200 is preferably composed of fine (thin) filaments
in a loose cord or weave such that no appreciable mass is added to
the transducer 10 and no appreciable acoustic energy or vibrational
energy is transmitted down the length of the wick. Lossy materials
or masses may be added at discrete points along the length of the
wick to mitigate acoustic energy transfer.
[0035] The foregoing description of the preferred embodiments of
the invention has been presented for purposes of illustration and
description only. It is not intended to be exhaustive nor to limit
the invention to the precise form disclosed; and obviously many
modifications and variations are possible in light of the above
teaching. Such modifications and variations that may be apparent to
a person skilled in the art are intended to be included within the
scope of this invention as defined by the accompanying claims.
* * * * *