WO2022268320A1

WO2022268320A1 - Thermo-acoustic generated air flow device for electronics cooling

Info

Publication number: WO2022268320A1
Application number: PCT/EP2021/067329
Authority: WO
Inventors: Yasir ABDUL QUADIR; Vadim Tsoi
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2021-06-24
Filing date: 2021-06-24
Publication date: 2022-12-29
Also published as: CN117581012A

Abstract

A thermo-acoustic device comprising a thermo-acoustic engine (15) arranged to take heat from a heat source (2) and to generate acoustic waves (16) due to a thermal gradient in its resonator tube (12), with a membrane (10) being arranged in a connected branch pipe (9) so that the generated acoustic waves (16) can vibrate the membrane (10) at a certain frequency, thereby generating a jet-like air flow through openings (11) in the branch pipe (9). This jet-like air flow is then used to cool the heat source (2) or a heat sink (1) on which the heat source (2) is mounted, thereby providing a self-powered cooling device with a forced convection cooling effect without any moving parts.

Description

THERMO-ACOUSTIC GENERATED AIR FLOW DEVICE FOR ELECTRONICS COOLING

TECHNICAL FIELD

The disclosure relates to thermo-acoustic cooling, in particular a self-powered thermo-acoustic cooling device providing a forced convection cooling effect for electronic devices, as well as a method of thermo-acoustic cooling for electronic devices.

BACKGROUND

It is important to remove heat from electronic devices, which act as heat sources, either on their own or within a system with multiple heat sources, such as personal computers, servers, cameras, electrical appliances, telecom equipment and the like. If the heat is not removed, the electronic device overheats, resulting in damage to the device and/or a reduction in overall system performance. In order to remove heat, cooling devices such as heat sinks are used in conjunction with heat sources. The heat sink is usually formed of a material, like Aluminum, which conducts heat easily. The heat sink usually consists of multiple fins to increase the surface area of the heat sink and thus maximize the transfer of heat from the heat sink into the surrounding air. In most of the telecom solutions the cooling is done through Natural Convection Cooling (NCC).

Over the years, the power of electronic devices has increased and the size of the electronic devices has been reduced. Thus, the power density of the electronic devices has increased as well as the amount of heat generated by these devices. In order to adequately cool these higher powered electronic devices, cooling devices with greater cooling capacities have been required and the reliability of the cooling devices has become increasingly important. Accordingly, with increasing heat dissipation, NCC becomes less and less adequate solution. Heat sinks alone are often not sufficient to cool modern electronic devices and therefore other and/or additional cooling mechanisms, such as electrically powered fans, water cooling systems, heat pipes, and the like are required for removing excess heat. These cooling mechanisms, in addition to the heat sinks, have become critical components to the reliability of various electronic devices. Fans in particular are subject to failure since they have mechanical and electrical components that can fail. Also, fans require external electrical power which can fail, or which can be depleted when drawn from limited power sources such as batteries. While much work has been done to produce highly reliable, cost competitive fans specifically for the microelectronics industry, many cases exist where the overall system reliability, or system availability is paramount. In these cases, fans are often fitted with feedback mechanisms and are monitored by the operating system of the machine. The electrically powered fans consume additional electricity and have moving parts that are susceptible to wear and malfunction. Another problem with fan assisted heat sink cooling devices is the noise generated by the fans, particularly in situations where larger and/or multiple fans are used to achieve increased cooling capacity. This is particularly a problem in personal computers and mobile devices where users are commonly situated in close proximity to the heat source.

For these reasons, natural convection cooling (NCC) remains the preferred cooling solution of many wireless devices, such as remote radio units (RRU), mainly due to less maintenance, cost and reliability issues compared to other solutions. However, with increasing heat load, the capacity of NCC is reaching its limit and there is a strong need to introduce a force convection cooling (FCC) technology which is reliable and has no moving parts exposed to external harsher environment.

SUMMARY

The prior art is thus characterized by several disadvantages that are addressed by the present disclosure. The present disclosure minimizes, and in some aspects eliminates, the above- mentioned failures, and other problems, by utilizing the methods and structural features described herein.

The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

According to a first aspect, there is provided a thermo-acoustic device comprising a thermo acoustic engine with a hot heat exchanger, a stack of low thermal conductivity material, and a cold heat exchanger arranged within a resonator tube. The thermo-acoustic engine is configured to generate an acoustic wave in the resonator tube according to a temperature gradient between the hot heat exchanger and the cold heat exchanger due to the thermoacoustic effect. The device comprises at least one branch pipe arranged with a volume of gas filled therein in a way to receive the generated acoustic wave, with at least one opening and a membrane arranged within the branch pipe. When the membrane is excited by the acoustic wave it moves the volume of gas in the branch pipe which in turn generates pulsating gas flow through the at least one opening.

The resulting device has no rotating parts exposed to external environment and hence can provide a more robust and reliable cooling solution than fan cooling or other force convection cooling technologies with rotating parts. The device enables to utilize the heat from a heat source, such as an electronic unit, to generate acoustic waves in a tube, which can provide enough acoustic power to be able to vibrate a membrane in an oscillating manner at a certain frequency. This oscillation of the membrane helps in generation of jet-like air flow through the openings in the branch pipe(s). This airflow can then be used to cool the same electronics unit that is used to power the thermo-acoustic device, thereby resulting in a self-powered cooling system. The device also reduces the noise issues present as described in prior art solutions.

In a possible implementation form of the first aspect the stack comprises at least one of a stainless steel mesh, a ceramic element having an array of parallel channels, or a low thermal conductivity material with a porous structure, which allows gas flow between two sides of the stack.

In a possible implementation form of the first aspect at least one of the hot heat exchanger and the cold heat exchanger is made of metal, such as copper or aluminium, for enhanced heat conductivity.

In a further possible implementation form of the first aspect the cold heat exchanger comprises at least one first cooling fin to increase the temperature gradient between hot heat exchanger and cold heat exchanger.

In a further possible implementation form of the first aspect the thermo-acoustic engine is configured to generate a traveling wave, and the length of each of the at least one branch pipe is determined to produce a predefined target frequency for the traveling wave, further based on the power of the acoustic wave generated in the resonator tube, which enables the device to provide specific oscillations in the membrane, thereby adjusting the generated jet flow through the openings in the branch pipe.

In a further possible implementation form of the first aspect the membrane is arranged to oscillate with a simple harmonic motion when being excited by the traveling wave, the excitation and the oscillation of the membrane thereby generating a pulsating jet gas flow through the at least one opening.

In a further possible implementation form of the first aspect the volume of gas in the at least one branch pipe comprises at least one of air or an inert gas. This allows designing a device for specific purposes and to achieve different cooling effect according to the devices to be cooled.

In a further possible implementation form of the first aspect the thermo-acoustic device further comprises a heat source and a two-phase device arranged to transfer heat from the heat source to the hot heat exchanger; with the branch pipe(s) being arranged so that at least a portion of the gas flow through the at least one opening is directed towards the heat source to provide a cooling effect. This enables a self-powered cooling system.

In a further possible implementation form of the first aspect the thermo-acoustic device further comprises a heat sink arranged to transfer heat away from the heat source, the heat sink comprising at least one groove for channeling gas flow; the branch pipe(s) being arranged so that at least a portion of the gas flow through the at least one opening is directed towards the at least one groove, thereby providing additional gas/air movement along the grooves for a more effective forced convection cooling effect for the heat sink.

In a further possible implementation form of the first aspect the heat sink comprises a plurality of second cooling fins arranged in parallel to provide the grooves for channeling gas flow directed from the at least one opening in the at least one branch pipe, thereby enhancing the forced convection cooling effect.

In a further possible implementation form of the first aspect the heat source is an electronic device; and the thermo-acoustic device is arranged as a self-powered cooling device providing a forced convection cooling effect for at least one heat sink arranged in thermally conductive connection with the electronic device.

In one embodiment the electronic device is a wireless communication device, such as a remote radio unit, RRU, in a radio base station system, which results in a wireless self-powered forced convection cooling device.

In a further possible implementation form of the first aspect the thermo-acoustic device comprises a plurality of thermo-acoustic engines, at least two of the plurality of thermo-acoustic engines being arranged in series for amplifying the acoustic wave generated in the respective the resonator tubes.

In a further possible implementation form of the first aspect a number N of thermo-acoustic engines are arranged to be connected in a loop using the same number N of feedback loop pipes, each feedback loop pipe being arranged to connect one side of a resonator tube of a thermo-acoustic engine with an opposite side of a respective resonator tube of another thermo-acoustic engine. This arrangement enables to further amplify the acoustic wave(s) generated in the resonator tubes.

In one embodiment the number N of thermo-acoustic engines and feedback loop pipes is N=2. This arrangement provides an efficient amplification of the acoustic wave(s) while still keeping the number of parts low in the device.

In another embodiment the number N of thermo-acoustic engines and feedback loop pipes is N=4. This arrangement provides a more effective heat dissipation and amplification of the acoustic wave(s) while still keeping the number of parts relatively low in the device.

In a further possible implementation form of the first aspect each of the branch pipes branch out from a feedback loop pipe. This arrangement provides efficient cooling in terms of use of space and amplification of acoustic wave(s).

In a further possible implementation form of the first aspect a branch pipe branches out from each feedback loop pipe. This arrangement provides efficient cooling in terms of use of space and amplification of acoustic wave(s).

In a further possible implementation form of the first aspect the thermo-acoustic device comprises at least two branch pipes connected by a common pipe section, wherein at least one of the at least one opening is arranged in the common pipe section. This arrangement provides an efficient use of space.

In one embodiment all of the at least one opening is arranged in the common pipe section. This arrangement provides efficient use of space as well as a targetable pulsating gas flow through the openings through adjusting the layout and direction of the common pipe section.

In a further possible implementation form of the first aspect the common pipe section comprises a connecting section and an orifice section, with the orifice section branching out from a branch opening in the connecting section and housing all of the openings, and a shared membrane arranged in the branch opening for the (at least) two branch pipes. This arrangement provides efficient use of space and an enhanced pulsating gas flow through the openings towards the heat sink and/or the heat source.

In a further possible implementation form of the first aspect the resonator tube and/or the feedback loop pipe is sealed and filled with at least one gas, such as He or C02 gas, which enables to pressurize the inside of the resonator tube and/or the feedback loop pipe to further amplify the acoustic wave(s) generated, and further enables to adjust wavelength of the acoustic wave(s) due to different speed of sound in the different gases. In a further possible implementation form of the first aspect the at least one gas in the resonator tube or the feedback loop pipe is pressurized to a higher than atmospheric pressure, which enables to reduce the diameter of the resonator tube and/or the feedback loop pipes.

According to a second aspect, there is provided a method for generating a pulsating gas flow, the method comprising providing a thermo-acoustic device according to any one of the possible implementation forms of the first aspect, comprising a resonator tube and arranged within the resonator tube a hot heat exchanger, a stack of low thermal conductivity material, and a cold heat exchanger; generating an acoustic wave in the resonator tube by creating a temperature gradient between the hot heat exchanger and the cold heat exchanger; arranging at least one branch pipe comprising a volume of gas to receive at least a portion of the generated acoustic wave, each of the at least one branch pipe comprising at least one opening and a membrane arranged within the branch pipe to be excitable by the acoustic wave; and moving the volume of gas in the branch pipe by exciting the membrane by the acoustic wave to generate pulsating gas flow through the at least one opening.

The resulting method enables a forced convection cooling solution with no rotating parts exposed to external environment and hence can provide a more robust and reliable cooling solution than fan cooling or other force convection cooling technologies with rotating parts. The method enables to utilize the heat from a heat source, such as an electronic unit, to generate acoustic waves in a tube, which can provide enough acoustic power to be able to vibrate a membrane in an oscillating manner at a certain frequency. This oscillation of the membrane helps in generation of jet-like air flow through the openings in the branch pipe(s). This air flow can then be used to cool the same electronics unit that is used to power the thermo-acoustic device.

In a possible implementation form of the second aspect the method further comprises providing a heat source and a two-phase device arranged to transfer heat from the heat source to the hot heat exchanger; and cooling the heat source by directing at least a portion of the gas flow through the at least one opening towards the heat source to provide a cooling effect, thereby enabling a self-powered cooling system.

In a further possible implementation form of the second aspect the method further comprises providing a heat sink arranged to transfer heat away from the heat source, the heat sink comprising at least one groove for channeling gas flow; and directing at least a portion of the gas flow through the at least one opening towards the at least one groove to provide a forced convection cooling effect for the heat sink, thereby further enhancing the heat dissipation. In a further possible implementation form of the second aspect the heat source is an electronic device and at least one heat sink is arranged in thermally conductive connection with the electronic device; and the method comprises providing a forced convection cooling effect for the at least one heat sink, thereby providing a self-powered cooling device.

These and other aspects will be apparent from the embodiment(s) described below.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present disclosure, the aspects, embodiments and implementations will be explained in more detail with reference to the example embodiments shown in the drawings, in which:

Fig. 1 shows a schematic cross-sectional view of a thermo-acoustic device according to an example of the embodiments of the disclosure;

Fig. 2 shows a schematic cross-sectional view of a thermo-acoustic engine according to an example of the embodiments of the disclosure;

Fig. 3 shows a top view of a thermo-acoustic device according to an example of the embodiments of the disclosure;

Fig. 4 shows a top view of a thermo-acoustic device according to another example of the embodiments of the disclosure;

Fig. 5 shows a cross-sectional view of a heat sink according to an example of the embodiments of the disclosure;

Fig. 6 shows a cross-sectional view of a thermo-acoustic device comprising multiple thermo acoustic engines, according to an example of the embodiments of the disclosure;

Fig. 7 shows a top view of a thermo-acoustic device comprising multiple thermo-acoustic engines, according to an example of the embodiments of the disclosure;

Fig. 8 shows a schematic top view of a thermo-acoustic device according to an exemplary arrangement of the embodiments of the disclosure;

Fig. 9 shows a schematic diagram of components of a thermo-acoustic device according to an exemplary arrangement of the embodiments of the disclosure;

Figs. 10-11 show schematic top views of a thermo-acoustic device comprising multiple thermo acoustic engines arranged in a loop, according to exemplary arrangements of the embodiments of the disclosure; and

Figs. 12-13 show schematic top views of a thermo-acoustic device comprising multiple thermo acoustic engines connected by a common pipe section, according to exemplary arrangements of the embodiments of the disclosure. DETAILED DESCRIPTION

In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant disclosure. However, it should be apparent to those skilled in the art that the present disclosure may be practiced without such details. In other instances, well known methods, procedures, systems, components, and/or circuitry have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present disclosure.

Fig. 1 illustrates a thermo-acoustic device comprising a thermo-acoustic engine 15.

Thermo-acoustic engines use a temperature difference to produce work in form of sound waves or vice-versa in a tube called as resonator. A simple thermoacoustic engine contains a hot heat exchanger (HHX), a cold heat exchanger (CHX), a stack or regenerator and the accompanying tubes.

Accordingly, the disclosed thermo-acoustic engine 15 comprises a resonator tube 12 and arranged within the resonator tube 12 a hot heat exchanger 4, a stack 5 of low thermal conductivity material, and a cold heat exchanger 6, the thermo-acoustic engine 15 being configured to generate an acoustic wave 16 in the resonator tube 12 according to a temperature gradient between the hot heat exchanger 4 and the cold heat exchanger 6 due to the thermoacoustic effect.

The stack 5 may comprisee a stainless-steel mesh, a ceramic element having an array of parallel channels, or a low thermal conductivity material with a porous structure allowing gas flow between two sides of the stack 5. The hot heat exchanger 4 and/or the cold heat exchanger 6 may be made of metal, such as copper or aluminium. The resonator tube 12 may have a diameter of a few mm to a few cm. The diameter of the resonator tube 12 may be between 0,1-10 cm. In certain exemplary embodiments the diameter of the resonator tube 12 is between 2-5 cm, in particular around 3 cm.

The thermo-acoustic device also comprises a branch pipe 9 filled with a volume of gas and arranged to receive at least a portion of the generated acoustic wave 16. The branch pipe 9 may be acoustically sealed, and sealingly connected to the thermo-acoustic engine 15. The branch pipe 9 comprises at least one opening 11, and a membrane 10 arranged within the branch pipe 9. This membrane 10 is excitable by the acoustic wave 16 and moves the volume of gas in the branch pipe 9 to thereby generate pulsating gas flow through the at least one opening 11. In the illustrated examples the branch pipe(s) are arranged with a plurality of openings 11. The generated pulsating gas flow may be a jet-like air flow, wherein jet-like refers to a stream of fluid that is projected into a surrounding medium, and can travel long distances without dissipating, while maintaining a higher momentum compared to the surrounding fluid medium. The gas arranged in the branch pipe 9 may be air, an inert gas such as He or C02, or any suitable gas that can be moved by a moving membrane and can be pushed through orifices of small dimensions.

As illustrated in Fig. 2, the thermo-acoustic device usually comprises a heat source 2 which produces heat, and a two-phase device 3 arranged to transfer heat from the heat source 2 to the hot heat exchanger 4 of the thermo-acoustic engine 15. The two-phase device 3 can be a copper block, a heat pipe (HP), or vapour chamber (VC).

The heat source 2 can be an electronic device, for example a wireless communication device, such as a remote radio unit (RRU) in a radio base station system.

The thermo-acoustic device can thus be arranged as a self-powered cooling device providing a forced convection cooling effect for the heat source 2 or at least one heat sink 1 arranged in thermally conductive connection with the electronic device, as illustrated below in Fig. 4.

The cold heat exchanger 6 may further comprise first cooling fins 7 to increase the temperature gradient between hot heat exchanger 4 and cold heat exchanger 6 by enhancing heat dissipation of the cold heat exchanger 6 to the surrounding environment.

As illustrated in Fig. 3, the branch pipe 9 can be arranged so that at least a portion of the gas flow through the openings 11 is directed towards the heat source 2 to provide a cooling effect, thereby resulting in a self-powered cooling system for the heat source 2.

As illustrated in Fig. 4, the thermo-acoustic device may comprise a heat sink 1 as shown separately in Fig. 5, arranged to transfer heat away from the heat source 2. The heat sink 1 may be any suitable Natural Convection Cooling (NCC) based heat sink, and may be made from of any suitable material which conducts heat easily, such as aluminium. The heat sink 1 may comprise grooves 14, as illustrated in Fig. 4 and 5, for channeling air/gas flow within. In particular, as illustrated in the figures, the heat sink 1 may comprise a plurality of second cooling fins 13 arranged in parallel to provide the grooves 14 in between, for channeling air/gas flow directed from the openings 11 in the branch pipe(s) 9.

In other words, the branch pipe or pipes 9 are arranged so that at least a portion of the pulsating air/gas flow through the openings 11 is directed towards the grooves 14 to provide a forced convection cooling effect for the heat sink 1 , thereby resulting in a self-powered cooling system for the heat source 2. Fig. 5 shows an exemplary heat sink 1 to be arranged in connection with and, in particular, arranged to transfer heat away the heat source 2. The size of the heat sink 1 may depend on the heat source 2. According to exemplary embodiments, the heat sink 1 may be rectangular in shape, made of Aluminum, and arranged to have a Thermal Conductivity (TC) value of 140 W/mK. The heat sink 1 may have a base plate of a thickness of approx. 5-6 mm, with a second cooling fin 13 height of approx. 60-70 mm.

Figs. 6 through 13 show further exemplary embodiments of the thermo-acoustic device comprising a plurality of thermo-acoustic engines 15. In these exemplary embodiments at least two of the thermo-acoustic engines 15 are arranged in series for amplifying the acoustic wave 16 generated in the respective the resonator tubes 12. Such embodiments are especially useful where the temperature difference between two sides of the stack in the resonator tube 12 is not large enough to generate sufficient acoustic energy for moving the membrane 10. In these cases, the temperature difference between different sides of respective resonator tubes 12 in the system adds up, thereby multiplying the available temperature difference and thus the available acoustic energy for moving the membrane 10. For example, in some electronic devices the temperature difference between different sides of the resonator tube 12 would only amount to approx. 60 degree Celsius, which would not be sufficient to generate an acoustic wave powerful enough to oscillate the membrane 10, however when multiplied by using two thermo-acoustic engines 15 connected in a series, the resulting temperature difference of approx. 120 degree Celsius would be sufficient to oscillate the membrane 10 and thereby to provide pulsating jet air flow for cooling the electronic device itself.

Figs. 6 and 7 illustrate such a thermo-acoustic device with two connected thermo-acoustic engines 15 arranged at different locations on the heat sink 1. The thermo-acoustic engines 15 may be arranged at opposite sides (as shown in Figs. 6-7) or on the same side of the heat sink 1 (as shown in Fig. 8). The heat sink 1 may be provided as a common heat sink 1 for multiple heat sources 2, each heat source being thermally connected with a respective thermo-acoustic engine 15, or there may be one heat source 2 thermally connected with multiple thermo acoustic engines 15 at different locations, the heat source 2 being thermally connected with one or multiple heat sinks 1.

As illustrated in Fig. 7 which shows a schematic top view of the thermo-acoustic device, the thermo-acoustic engines 15 may be arranged to be connected in a loop using feedback loop pipes 8 connecting the resonator tubes 12 of the respective engines, and to amplify the acoustic waves 16 generated in the respective the resonator tubes 12. The feedback loop pipes 8 may be filled with air, or an inert gas such as He or C02. Using C02 gas instead of He enables to reduce length of the feedback loop pipes 8 and/or the branch pipes 9. The gas in the feedback loop pipe 8 and/or the branch pipes 9 may further be pressurized, if a suitable gas is used as filler, to a higher than atmospheric pressure, which enables to further reduce the respective tube diameters.

As shown in the figure, a branch pipe 9 may be connected to each thermo-acoustic engine 15, with a membrane 10 arranged in each branch pipe 9. The branch pipes 9 may be further connected by a common pipe section 17, with at least a portion or all of the openings 11 arranged in the common pipe section 17 and directed towards the respective grooves 14 of the heat sink 1 for providing a forced convection cooling effect.

Fig. 8 shows another arrangement for the thermo-acoustic device wherein the thermo-acoustic engines 15 are arranged on the same side of the heat sink 1 and are connected by a common branch pipe 9 that provides the forced convection cooling effect through pulsating jet air/gas flow through openings arranged according to respective grooves 14 of the heat sink 1. In such embodiments the generated acoustic wave 16 may be a standing wave. As the figure shows the branch pipe 9 may comprise a separate section for arranging the openings 11 and providing the pulsating jet air/gas flow, in a similar fashion as will also be explained below with respect to Figs. 12-13.

Figs. 9-11 illustrate further possible arrangements for the thermo-acoustic device wherein a number N of thermo-acoustic engines 15 are arranged to be connected in a loop using the same number N of feedback loop pipes 8, each feedback loop pipe 8 being arranged to connect one side of a resonator tube 12 of a thermo-acoustic engine 15 with an opposite side of a respective resonator tube 12 of another thermo-acoustic engine 15. Each of the branch pipes 9 in these arrangements may be arranged to branch out from a feedback loop pipe 8.

In particular, as shown in Fig. 9, the number N of thermo-acoustic engines 15 and feedback loop pipes 8 may be N=2, and two branch pipes 9 may be arranged in total, each one arranged to branch out from a respective distinct feedback loop pipe 8.

As further shown in Fig. 10, in an alternative exemplary embodiment the number N of thermo acoustic engines 15 and feedback loop pipes 8 may be N=2, and one branch pipe 9 may be arranged to branch out from one of the feedback loop pipes 8 and comprise the openings 11 for providing the pulsating jet air/gas flow to the heat sink 1.

As further shown in Fig. 11 , in a further alternative exemplary embodiment the number N of thermo-acoustic engines 15 and feedback loop pipes 8 may be N=4, and one branch pipe 9 may be arranged to branch out from one of the feedback loop pipes 8 and comprise the openings 11 for providing the pulsating jet air/gas flow to the heat sink 1. The thermo-acoustic engine according to these exemplary embodiments can generate a traveling wave, wherein the length of each branch pipe 9 is carefully chosen to produce a certain target frequency for the traveling wave, further based on the power of the acoustic wave 16 generated in the resonator tube 12. In particular, the frequency of the traveling wave may be determined by the speed of the sound in the medium, the power of acoustic wave 16 generated by the temperature gradient in the resonator tube 12, and other properties. The determination of the length of each branch pipe 9 may be done using readily available simulation software, such as the open source software DeltaEC (Design Environment for Low- amplitude ThermoAcoustic Energy Conversion) which is often used for such thermo-acoustic simulations.

Accordingly, the membrane 10 is oscillated at a given frequency with a simple harmonic motion when being excited by the traveling wave, the excitation and the oscillation of the membrane 10 thereby generating a pulsating jet gas flow through the at least one opening 11. This oscillation frequency may be between 500-1000 Hz, and in particular examples approx. 600 Hz or 800 Hz, resulting in a jet gas flow through the openings 11 of a speed of approx. 5-10 m/s.

Figs. 9-11 illustrate further possible arrangements for the thermo-acoustic device with at least two branch pipes 9 connected by a common pipe section 17, wherein at least one or all of the openings 11 are arranged in the common pipe section 17, as also shown in the arrangement of Fig. 8. The common pipe section 17 in these exemplary arrangements comprises a connecting section 18 and an orifice section 19, wherein the orifice section 19 comprises all of the openings 11 and is arranged branching out from a branch opening 20 in the connecting section. The branch pipes 9 comprise one shared membrane 10 arranged in the/each common pipe section 17, the shared membrane 10 being arranged in the branch opening 20 to be oscillated by the acoustic waves 16 generated by the thermo-acoustic engines 15 and to provide the air/gas movement in the orifice section 19 and to generate the pulsating jet air/gas flow through the openings 11.

In particular, as shown in Fig. 12, the thermo-acoustic engines 15 may be arranged on the opposite sides of the heat sink 1 , each connected to its own branch pipe 9, with the branch pipes 9 connected by the common pipe section 17, as described above.

Alternatively, as shown in Fig. 13, thermo-acoustic engines 15 or groups of thermo-acoustic engines 15 may also be arranged on the same side of the heat sink 1 and be connected by a common branch pipe 9 provided for each group, in which case the common branch pipes 9 are connected by the common pipe section 17, as described above. The various aspects and implementations have been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed subject-matter, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

It will further be understood that when a unit, module or engine is referred to as being “on”, “connected to” or “coupled to” another unit, module, or engine, it may be directly on, connected or coupled to, or communicate with the other unit, module, or engine, or an intervening unit, module, or engine may be present, unless the context clearly indicates otherwise. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. The reference signs used in the claims shall not be construed as limiting the scope.

Claims

1. A thermo-acoustic device comprising: a thermo-acoustic engine (15) comprising a resonator tube (12) and arranged within the resonator tube (12) a hot heat exchanger (4), a stack (5) of low thermal conductivity material, and a cold heat exchanger (6), the thermo-acoustic engine (15) being configured to generate an acoustic wave (16) in the resonator tube (12) according to a temperature gradient between the hot heat exchanger (4) and the cold heat exchanger (6) due to the thermoacoustic effect; and at least one branch pipe (9) comprising a volume of gas and arranged to receive at least a portion of the generated acoustic wave (16); wherein each of the at least one branch pipe (9) comprises at least one opening (11) and a membrane (10) arranged within the branch pipe (9) to be excitable by the acoustic wave (16) and move the volume of gas in the branch pipe (9) to generate pulsating gas flow through the at least one opening (11).

2. The thermo-acoustic device according to claim 1 , wherein the stack (5) comprises at least one of a stainless steel mesh, a ceramic element having an array of parallel channels, or a low thermal conductivity material with a porous structure allowing gas flow between two sides of the stack (5).

3. The thermo-acoustic device according to any one of claims 1 or 2, wherein the cold heat exchanger (6) comprises at least one first cooling fin (7) to increase the temperature gradient between hot heat exchanger (4) and cold heat exchanger (6).

4. The thermo-acoustic device according to any one of claims 1 to 3, wherein the thermo acoustic engine is configured to generate a traveling wave, and wherein the length of each of the at least one branch pipe (9) is determined to produce a predefined target frequency for the traveling wave, further based on the power of the acoustic wave (16) generated in the resonator tube (12).

5. The thermo-acoustic device according to any one of claims 1 to 4, wherein the membrane (10) is arranged to oscillate with a simple harmonic motion when being excited by the traveling wave, the excitation and the oscillation of the membrane (10) thereby generating a pulsating jet gas flow through the at least one opening (11).

6. The thermo-acoustic device according to any one of claims 1 to 5, wherein the volume of gas in the at least one branch pipe (9) comprises at least one of air or an inert gas.

7. The thermo-acoustic device according to any one of claims 1 to 6, further comprising: a heat source (2), and a two-phase device (3) arranged to transfer heat from the heat source (2) to the hot heat exchanger (4); wherein the at least one branch pipe (9) is arranged so that at least a portion of the gas flow through the at least one opening (11) is directed towards the heat source (2) to provide a cooling effect.

8. The thermo-acoustic device according to claim 7, further comprising: a heat sink (1) arranged to transfer heat away from the heat source (2), the heat sink (1) comprising at least one groove (14) for channeling gas flow; wherein the at least one branch pipe (9) is arranged so that at least a portion of the gas flow through the at least one opening (11) is directed towards said at least one groove (14) to provide a forced convection cooling effect for the heat sink (1).

9. The thermo-acoustic device according to claims 8, wherein the heat sink (1) comprises a plurality of second cooling fins (13) arranged in parallel to provide the at least one groove (14) in between the plurality of second cooling fins (13) for channeling gas flow directed from the at least one opening (11) in the at least one branch pipe (9).

10. The thermo-acoustic device according to any one of claims 7 to 9, wherein the heat source (2) is an electronic device; and wherein the thermo-acoustic device is arranged as a self- powered cooling device providing a forced convection cooling effect for at least one heat sink (1) arranged in thermally conductive connection with the electronic device.

11. The thermo-acoustic device according to any one of claims 1 to 10, wherein the thermo acoustic device comprises a plurality of thermo-acoustic engines (15), at least two of the plurality of thermo-acoustic engines (15) being arranged in series for amplifying the acoustic wave (16) generated in the respective resonator tubes (12).

12. The thermo-acoustic device according to claim 11 , wherein a number N of thermo acoustic engines (15) are arranged to be connected in a loop using the same number N of feedback loop pipes (8), each feedback loop pipe (8) being arranged to connect one side of a resonator tube (12) of a thermo-acoustic engine (15) with an opposite side of a respective resonator tube (12) of another thermo-acoustic engine (15).

13. The thermo-acoustic device according to any one of claims 11 or 12, wherein each of the at least one branch pipe (9) branches out from a feedback loop pipe (8).

14. The thermo-acoustic device according to claim 13, wherein a branch pipe (9) branches out from each feedback loop pipe (8).

15. The thermo-acoustic device according to any one of claims 1 to 14, wherein the thermo acoustic device comprises at least two branch pipes (9) connected by a common pipe section (17), wherein at least one of the at least one opening (11) is arranged in the common pipe section (17).

16. The thermo-acoustic device according to claim 15, wherein the common pipe section (17) comprises a connecting section (18) and an orifice section (19), wherein the orifice section (19) comprises all of the at least one opening (11) and is arranged branching out from a branch opening (20) in the connecting section and, and wherein the at least two branch pipes (9) comprise one shared membrane (10) arranged in the branch opening (20).

17. The thermo-acoustic device according to any one of claims 11 to 16, wherein at least one of the resonator tube (12) or the feedback loop pipe (8) is sealed and filled with at least one gas, such as He or C02 gas.

18. The thermo-acoustic device according to claim 17, wherein the at least one gas is pressurized to a higher than atmospheric pressure.

19. A method for generating a pulsating gas flow, the method comprising: providing a thermo-acoustic device according to any one of claims 1 to 18, comprising a resonator tube (12) and arranged within the resonator tube (12) a hot heat exchanger (4), a stack (5) of low thermal conductivity material, and a cold heat exchanger (6); generating an acoustic wave (16) in the resonator tube (12) by creating a temperature gradient between the hot heat exchanger (4) and the cold heat exchanger (6); arranging at least one branch pipe (9) comprising a volume of gas to receive at least a portion of the generated acoustic wave (16), each of the at least one branch pipe (9) comprising at least one opening (11) and a membrane (10) arranged within the branch pipe (9) to be excitable by the acoustic wave; and moving the volume of gas in the branch pipe (9) by exciting the membrane (10) by the acoustic wave (16) to generate pulsating gas flow through the at least one opening (11).

20. The method according to claim 19, further comprising: providing a heat source (2) and a two-phase device (3) arranged to transfer heat from the heat source (2) to the hot heat exchanger (4); and cooling the heat source (2) by directing at least a portion of the gas flow through the at least one opening (11) towards the heat source (2) to provide a cooling effect.

21. The method according to claim 20, further comprising: providing a heat sink (1) arranged to transfer heat away from the heat source (2), the heat sink (1) comprising at least one groove (14) for channeling gas flow; and directing at least a portion of the gas flow through the at least one opening (11) towards said at least one groove (14) to provide a forced convection cooling effect for the heat sink (1).

22. The method according to any one of claims 20 or 21, wherein the heat source (2) is an electronic device and at least one heat sink (1) is arranged in thermally conductive connection with the electronic device; and wherein the method comprises providing a forced convection cooling effect for the at least one heat sink (1), thereby providing a self-powered cooling device.