U.S. patent application number 12/518296 was filed with the patent office on 2010-01-21 for pulsating fluid cooling with frequency control.
This patent application is currently assigned to Koninklijke Philips Electronics N.V.. Invention is credited to Ronaldus Maria Aarts.
Application Number | 20100012301 12/518296 |
Document ID | / |
Family ID | 39321485 |
Filed Date | 2010-01-21 |
United States Patent
Application |
20100012301 |
Kind Code |
A1 |
Aarts; Ronaldus Maria |
January 21, 2010 |
PULSATING FLUID COOLING WITH FREQUENCY CONTROL
Abstract
A pulsating fluid cooling device comprising a transducer (1) for
generating a pulsating fluid flow and a fluid guiding structure (3)
for directing the pulsating flow towards an object (4) to be
cooled. The device further comprises a sensor (7) for detecting at
least one variable external to the transducer, a feedback path (6)
for providing a feedback signal 5 indicative of this variable, and
control circuitry (5) arranged to receive the feedback signal and
generate a frequency control signal based on said feedback, for
controlling a working frequency of the transducer. By providing the
control circuitry with information about the conditions at the
object, the frequency can be controlled based on actual
performance. The performance can be 10 optimized in terms of the
measured variable. For example, if the feedback signal includes
information about the temperature change of the object, the control
circuitry can be arranged to select a working frequency that
results in optimal cooling.
Inventors: |
Aarts; Ronaldus Maria;
(Eindhoven, NL) |
Correspondence
Address: |
PHILIPS INTELLECTUAL PROPERTY & STANDARDS
P.O. BOX 3001
BRIARCLIFF MANOR
NY
10510
US
|
Assignee: |
Koninklijke Philips Electronics
N.V.
Eindhoven
NL
|
Family ID: |
39321485 |
Appl. No.: |
12/518296 |
Filed: |
December 10, 2007 |
PCT Filed: |
December 10, 2007 |
PCT NO: |
PCT/IB2007/054981 |
371 Date: |
June 9, 2009 |
Current U.S.
Class: |
165/120 |
Current CPC
Class: |
H01L 23/467 20130101;
H01L 2924/0002 20130101; H01L 2924/0002 20130101; F04F 7/00
20130101; H01L 2924/00 20130101 |
Class at
Publication: |
165/120 |
International
Class: |
F28C 3/00 20060101
F28C003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 15, 2006 |
EP |
06126250.7 |
Claims
1. A pulsating fluid cooling device comprising a transducer for
generating a pulsating fluid flow and a fluid guiding structure for
directing the pulsating flow towards an object (4) to be cooled,
the cooling device comprising: a sensor for detecting at least one
variable external to the transducer, a feedback path for providing
a feedback signal indicative of the variable, and control circuitry
arranged to receive the feedback signal and generate a frequency
control signal based on said feedback, for controlling a working
frequency of the transducer.
2. The cooling device according to claim 1, wherein said variable
relates to conditions at the object (4) to be cooled.
3. The cooling device according to claim 2, wherein said variable
relates to one of a temperature change of the object, a fluid flux
in a vicinity of the object and a fluid velocity in a vicinity of
the object.
4. The cooling device according to claim 1, wherein the control
circuitry includes a voltage controlled oscillator.
5. The cooling device according to claim 1, wherein the control
circuitry includes: a combination unit for combining a first signal
indicative of the phase of the voltage across the transducer and a
second signal indicative of the phase of the current through the
transducer, so as to generate a phase difference signal, and a
control unit for generating said frequency control signal based on
this phase difference signal.
6. The cooling device according to claim 1, wherein the working
frequency is the resonance frequency or the anti-resonance
frequency of the device.
7. A method for cooling an object (4) by generating said pulsating
fluid flow and directing said fluid flow towards said object (4),
said method characterized by: detecting at least one variable
external to the transducer, providing a feedback signal indicative
of this variable, and generating a frequency control signal based
on said feedback, and using said control signal to control a
working frequency of the transducer.
8. The method according to claim 7, wherein said variable relates
to conditions at the object to be cooled.
9. The method according to claim 8, wherein said variable relates
to one of a temperature change of the object, a fluid flux in a
vicinity of the object and a fluid velocity in a vicinity of the
object.
10. The method according to claim 7, wherein the working frequency
is the resonance frequency or the anti-resonance frequency of the
device.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to pulsating fluid cooling,
i.e. cooling where a transducer induces an oscillation creating a
pulsating fluid stream that can be directed towards an object that
is to be cooled. It may be advantageous to drive the system at, or
at least close to, its resonance frequency, in order to obtain a
high fluid velocity.
BACKGROUND OF THE INVENTION
[0002] The need for cooling has increased in various applications
due to higher heat flux densities resulting from newly developed
electronic devices, being, for example, more compact and/or higher
power than traditional devices. Examples of such improved devices
include, for example, higher power semiconductor light-sources,
such as lasers or light-emitting diodes, RF power devices and
higher performance micro-processors, hard disk drives, optical
drives like CDR, DVD and Blue ray drives, and large-area devices
such as flat TVs and luminaires.
[0003] As an alternative to cooling by fans, document WO
2005/008348 discloses a synthetic jet actuator and a tube for
cooling purposes. The tube is connected to a resonating cavity, and
a pulsating jet stream is created at the distal end of the tube,
and can be used to cool an object. The cavity and the tube form a
Helmholtz resonator, i.e. a second order system where the air in
the cavity acts as a spring, while the air in the tube acts as the
mass.
[0004] Another example is given by N. Beratlis et al, Optimization
of synthetic jet cooling for microelectronics applications,
19.sup.th SEMITHERM San Jose, 2003. Here a synthetic jet is
disclosed having two diaphragms each communicating with the same
orifice.
[0005] A pulsating fluid stream (typically air stream) of this kind
has been found to be more efficient for cooling than laminar flow,
as typically used in conventional cooling systems (e.g. cooling
fans). The resonance cooling systems further require less space,
and generates less noise.
[0006] In order to obtain maximum efficiency, such pulsating
cooling systems are preferably driven at a specific working
frequency, e.g. the resonance frequency or anti-resonance frequency
of the system. Prior art cooling devices lack satisfactory means to
ensure such efficient driving.
[0007] More generally stated, conventional pulsating cooling
devices lack the ability to adapt and control the working frequency
of the transducer based on the conditions and performance of the
cooling device.
SUMMARY OF THE INVENTION
[0008] It is therefore an object of the present invention to enable
adaptation of the working frequency of a pulsating cooling device
to the conditions and performance of the cooling system.
[0009] According to a first inventive concept, this and other
objects are achieved by a pulsating fluid cooling device comprising
a transducer for generating a pulsating fluid flow, a fluid guiding
structure for directing the pulsating flow towards an object to be
cooled, a sensor for detecting at least one variable representing a
condition of the object, a feedback path for providing a feedback
signal indicative of this variable, and control circuitry arranged
to receive the feedback signal and to generate a frequency control
signal based on said feedback, for controlling a working frequency
of the transducer. Control of the working frequency is thus
performed based on an external feedback path, which may provide
information from the object to be cooled. Such information may
include, but is not limited to: a temperature change of the object,
a fluid flux in a vicinity of the object, a fluid velocity in a
vicinity of the object, etc.
[0010] The frequency control will thus enable adaptation of the
working frequency to the performance of the cooling device. For
example, such frequency control can be utilized to ensure
satisfactory cooling efficiency.
[0011] By providing the control circuitry with information about
the conditions at the object, the frequency can be controlled based
on actual performance. The performance can be optimized in terms of
the measured variable. For example, if the feedback signal includes
information about the temperature change of the object, the control
circuitry can be arranged to select a working frequency that
results in optimal cooling.
[0012] According to a second inventive concept, a pulsating fluid
cooling device comprises a transducer for generating a pulsating
fluid flow, a fluid guiding structure for directing the pulsating
flow towards an object to be cooled, a combination unit for
combining a first signal indicative of the phase of the voltage
across the transducer and a second signal indicative of the phase
of the current through the transducer, so as to generate a phase
difference signal, and control circuitry for controlling the
frequency of the transducer in accordance with this phase
difference signal.
[0013] In this case, the working frequency is the resonance
frequency or the anti-resonance frequency of the device (i.e.
transducer and guiding structure), and the control unit is arranged
to ensure this working frequency.
[0014] Such circuitry, for ensuring resonance frequency driving, is
disclosed in the document WO 2005/027569, but has not been
suggested for use in a pulsating fluid cooling device. This
combination is therefore novel per se.
[0015] In the context of the first inventive concept, a control
system according to WO 2005/027569 is complemented by the external
feedback from the sensor, thereby enabling adjustments of the
control strategy based on resonance frequency control in
combination with external feedback (such as temperature).
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] This and other aspects of the present invention will now be
described in more detail, with reference to the appended drawings
showing a currently preferred embodiment of the invention.
[0017] FIG. 1 is a schematic view of a pulsating fluid cooling
device according to an embodiment of the invention.
[0018] FIG. 2 is a block diagram of a first alternative of the
controller in FIG. 1.
[0019] FIG. 3 is a schematic view of a pulsating fluid cooling
device according to the invention.
[0020] FIG. 4 is a block diagram of a second alternative of the
controller in FIG. 1.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0021] FIG. 1 shows an embodiment of a pulsating fluid cooling
system according to an embodiment of the present invention. The
system comprises a transducer 1, arranged in an enclosure 2, and a
fluid directing structure 3, here in the form of a tube extending
from the cavity. In operation, the transducer creates a pulsating
fluid flow, that is directed by the fluid directing structure
towards an object 4 to be cooled, such as an integrated
circuit.
[0022] The system further comprises a control unit 5, adapted to
control the frequency of the transducer, in order to optimize the
cooling process. A feedback path 6 is adapted to provide a feedback
signal to the control unit. The feedback signal represents a
variable external to the cooling device, and may advantageously be
related to a physical quantity the object 4. The feedback signal
can be generated by a sensor 7.
[0023] In the illustrated example, the feedback signal relates to
the temperature of the object, and the sensor 7 is designed to
generate a signal indicative of the temperature.
[0024] According to one embodiment, the sensor is arranged to
detect a current flowing through an object 4 in the form of an IC.
By performing the measurement at a position exposed to a constant
voltage difference, the detected current will be indicative of the
temperature of the IC.
[0025] According to another embodiment, the sensor is a more
conventional temperature transmitter, providing a voltage
proportional to the temperature that the sensor is subjected
to.
[0026] An example of a control unit 5 is illustrated in FIG. 2. The
unit 5 comprises a processing unit 11, a voltage controlled
oscillator (VCO) 12, and an operational amplifier 13. The
processing unit 11 is connected to the feedback path 6, and
receives the feedback signal, e.g. a temperature indication from a
sensor 7. Based on this feedback, the processing unit 11 determines
a frequency suitable for achieving a desired cooling performance,
and provides a voltage corresponding to this frequency to the VCO
12. The VCO 12 oscillates at the requested frequency, and its
output is supplied to the operational amplifier 13, which in turn
is connected to the transducer 1.
[0027] The processing in the processing unit 11 depends on the
feedback provided, and also of the desired performance. According
to one example, the processing unit 11 is adapted to monitor a
temperature change of the object 4 in relation to the applied
frequency. Form this relationship, an absolute or local minimum can
be selected, i.e. a frequency for which the temperature of the
object 4 is minimal. This corresponds to the currently most
efficient cooling frequency. Note that such feedback ensures that
an optimal frequency is maintained also in a dynamic process, i.e.
in case the optimal cooling frequency should vary over time.
Another to another example, the feedback signal relates to a net
fluid flux in close vicinity of the object 4. The processing unit
can then adjust the frequency so as to ensure a maximum net flux,
which typically will ensure satisfactory cooling.
[0028] A different embodiment of the invention is illustrated in
FIG. 3. Here, the transducer 1 is arranged to be controlled at a
working frequency equal to the resonance frequency or
anti-resonance frequency of the device. Characteristic for these
working frequencies is that they will result in a voltage across
the transducer in phase with the current flowing through the
transducer. The frequency control can therefore be based on this
relationship.
[0029] The control circuitry in FIG. 3 comprises a voltage
controlled oscillator (VCO) 12, connected to the transducer via an
operational amplifier 13. It further comprises a resistor 23
connected between the transducer coil and ground. The voltage
across the resistor V.sub.R will thus be in phase with the current
through the coil. This voltage V.sub.R is connected to a
combination unit 24, e.g. a multiplier, also provided with the
drive voltage from the VCO 12, V.sub.VCO. The output of the
combination unit 24 is connected to a control unit 25, which in
turn controls the VCO 12.
[0030] The output from the combination unit 24 is representative of
a phase difference between the voltages V.sub.R and V.sub.VCO. The
control unit 25 provides a control signal to the VCO 12 based on
the phase difference, so as to control the VCO 12 to generate a
resonance (or anti-resonance) frequency. The details of such
control are described in WO 2005/027569, herewith incorporated by
reference.
[0031] As illustrated in FIG. 4, the control schemes of FIGS. 2 and
3 may be combined. The resulting control will thus combine external
feedback control, as shown in FIG. 2, with a phase difference
control, as described in FIG. 4. Most elements in FIG. 4 correspond
to the elements in FIGS. 2 and 3, and have therefore been given
identical reference numerals and will only be described in terms of
their function.
[0032] The control unit 31 is here adapted to receive two feedback
signals; one external, from the sensor 7, and one internal, from
the combination unit 24. Just as in FIG. 3, the control unit 31 is
adapted to perform frequency control based on the phase difference
signal from the combination unit 24. However, the target phase
difference does not need to be zero, as in FIG. 3. Instead, a
target phase difference is determined by the control unit based on
the external feedback, thus allowing an optimization of the cooling
process, as outlined above with reference to FIG. 2.
[0033] The person skilled in the art realizes that the present
invention by no means is limited to the preferred embodiments
described above. On the contrary, many modifications and variations
are possible within the scope of the appended claims. For example,
various other types of sensors may be employed to provide suitable
feedback. Further, a variety of control schemes may be developed in
order to optimize and improve the cooling performance based on
available feedback.
* * * * *