Patent Grant
10808968
The disclosure of Japanese Patent Application No. 2016-156725 filed on Aug. 9, 2016 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
The disclosure relates to a thermoacoustic cooling device that uses conversion between thermal energy and sound energy.
Recently, there has been proposed a thermoacoustic cooling device using a thermoacoustic effect, which is a conversion phenomenon between thermal energy and sound energy. For example, Japanese Patent Application Publication No. 2008-101910 (JP 2008-101910 A) describes a thermoacoustic device in which a first stack and a second stack are disposed inside a looped tube. The first stack is sandwiched between a first high-temperature heat exchanger and a first low-temperature heat exchanger. The second stack is sandwiched between a second high-temperature heat exchanger and a second low-temperature heat exchanger. In the thermoacoustic device, self-excited acoustic waves are generated by generating a temperature gradient in the first stack. The second low-temperature heat exchanger can be cooled by the acoustic waves.
JP 2008-101910 A describes that a length of the looped tube, a state of a working fluid enclosed in the looped tube, and diameters of conduction paths in the first stack and the second stack are set appropriately, so as to improve efficiency of heat exchange in the stacks.
In the thermoacoustic device in the related art, when the temperature gradient of the first stack exceeds a critical point, acoustic waves are generated. In order to cool the low-temperature heat exchanger of the second stack to a desired temperature, a temperature of the high-temperature heat exchanger of the first stack may be required to be further increased so that the temperature gradient is made larger than the critical point. That is, in the thermoacoustic cooling device, a temperature required to operate the thermoacoustic cooling device tends to be high.
The present application discloses a thermoacoustic cooling device that can decrease a temperature required to operate the thermoacoustic cooling device.
A thermoacoustic cooling device according to an aspect of the disclosure includes a tube which includes at least one looped tube, and in which a working fluid is enclosed; a first stack that is provided inside the tube and generates acoustic waves in the working fluid in the tube with use of a temperature gradient in the first stack; a first high-temperature heat exchanger provided at a first side of the first stack and configured to heat the first side of the first stack with use of heat from an outside of the tube; a first low-temperature heat exchanger provided at a second side of the first stack and configured to make a temperature of the second side of the first stack lower than a temperature of the first side of the first stack; a second stack which is provided inside the tube, and in which a temperature gradient is generated in the second stack by the acoustic waves of the working fluid in the tube; a second high-temperature heat exchanger provided at a first side of the second stack, the first side of the second stack having a high temperature at a time when the temperature gradient is generated in the second stack; a second low-temperature heat exchanger provided at a second side of the second stack, the second side of the second stack having a low temperature at the time when the temperature gradient is generated in the second stack; and a heat transfer portion configured to connect the second low-temperature heat exchanger to the first low-temperature heat exchanger so as to transfer heat between the second low-temperature heat exchanger and the first low-temperature heat exchanger.
According to the disclosure of the present application, an operating temperature of the thermoacoustic cooling device can be decreased.
Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:
A thermoacoustic cooling device according to an embodiment of the disclosure includes a tube which includes at least one looped tube, and in which a working fluid is enclosed; a first stack that is provided inside the tube and generates acoustic waves in the working fluid in the tube with use of a temperature gradient in the first stack; a first high-temperature heat exchanger provided at a first side of the first stack and configured to heat the first side of the first stack with use of heat from an outside of the tube; a first low-temperature heat exchanger provided at a second side of the first stack and configured to make a temperature of the second side of the first stack lower than a temperature of the first side of the first stack; a second stack which is provided inside the tube, and in which a temperature gradient is generated in the second stack by the acoustic waves of the working fluid in the tube; a second high-temperature heat exchanger provided at a first side of the second stack, the first side of the second stack having a high temperature at a time when the temperature gradient is generated in the second stack; a second low-temperature heat exchanger provided at a second side of the second stack, the second side of the second stack having a low temperature when the temperature gradient is generated in the second stack; and a heat transfer portion configured to connect the second low-temperature heat exchanger to the first low-temperature heat exchanger so as to transfer heat between the second low-temperature heat exchanger and the first low-temperature heat exchanger (a first configuration).
In the first configuration, the temperature of the first high-temperature heat exchanger of the first stack is increased by heat of the outside of the tube, and the temperature of the first low-temperature heat exchanger is kept lower than the temperature of the first high-temperature heat exchanger, and thus, the temperature gradient is generated in the first stack. Acoustic waves are generated in the working fluid inside the tube by the temperature gradient in the first stack. The acoustic waves generate, in the second stack, a temperature gradient corresponding to the temperature gradient of the first stack. The second high-temperature heat exchanger can control the temperature of the high-temperature side of the second stack (i.e., the first side having a high temperature) at the time when the temperature gradient is generated in the second stack. The temperature at the low-temperature side (i.e., the second side) of the second stack can he made lower than the controlled temperature at the high-temperature side of the second stack. When heat exchange is performed between the low-temperature side of the second stack and the outside of the tube via the second low-temperature heat exchanger, the outside of the tube is cooled. Further, the second low-temperature heat exchanger is connected to the first low-temperature heat exchanger by the heat transfer portion such that heat can be transferred between the second low-temperature heat exchanger and the first low-temperature heat exchanger. Accordingly, due to a decrease in the temperature of the second low-temperature heat exchanger, the temperature of the first low-temperature heat exchanger also decreases. Thus, the temperature gradient in the first stack becomes larger. That is, the temperature gradient in the first stack can be made larger without increasing the temperature of the first high-temperature heat exchanger. This accordingly makes it possible to decrease a required temperature at the high-temperature side (i.e., the first side) of the first stack, that is, a temperature required to obtain a desired cooling function. That is, it is possible to decrease a temperature required to operate the thermoacoustic cooling device.
In the first configuration, the heat transfer portion may include a heat transfer tube through which a fluid flows between the second low-temperature heat exchanger and the first low-temperature heat exchanger (a second configuration). The heat can be transferred efficiently between the second low-temperature heat exchanger and the first low-temperature heat exchanger by the fluid flowing through the heat transfer tube.
In the second configuration, the heat transfer tube may be configured to cause the fluid to flow from the second low-temperature heat exchanger to the first low-temperature heat exchanger (a third configuration). In the third configuration, the fluid cooled by the second low-temperature heat exchanger can be moved to the first low-temperature heat exchanger. Therefore, the first low-temperature heat exchanger can be cooled efficiently.
In the first configuration, the heat transfer portion may include a metal heat transfer body that connects the second low-temperature heat exchanger to the first low-temperature heat exchanger (a fourth configuration). This makes it possible to simplify the configuration of the heat transfer portion.
In any of the first to the fourth configurations, the thermoacoustic cooling device may further include a cooler configured to cool the second high-temperature heat exchanger (a fifth configuration). By cooling the second high-temperature heat exchanger with the use of the cooler, the temperature of the second low-temperature heat exchanger can be further decreased when the thermoacoustic cooling device operates. Thus, the temperature gradient in the first stack can be made larger.
The embodiment will be described with reference to the drawings. The same reference numeral is assigned to the same and equivalent constituents in the figures, and the same description is not repeated. For the convenience of description, in each of the figures, a configuration may be illustrated simply or schematically, or the configuration may be partially omitted.
The first stack 13 includes a plurality of conduction paths 13k extending through the first stack 13 in a lengthwise direction (also referred to as an axial direction) of the tube 3. The second stack 23 includes a plurality of conduction paths 23k extending through the second stack 23 in the lengthwise direction of the tube 1 The conduction paths 13k, 23k are passages for the working fluid. That is, in the first stack 13 and the second stack 23, the working fluid can move inside the conduction paths 13k, 23k. The working fluid can pass through the first stack 13 and the second stack 23 in the lengthwise direction of the tube 3. Note that the stack can be also referred to as a heat accumulator.
When a temperature gradient inside the first stack 13 exceeds a critical point, the working fluid inside the stack 13 vibrates. When a temperature gradient inside the second stack 23 exceeds a critical point, the working fluid inside the stack 23 vibrates. The vibration of the working fluid generates acoustic waves. As a result, acoustic waves are generated in the working fluid inside the tube 3. Further, when the working fluid inside the first stack 13 or the second stack 23 vibrates due to the acoustic waves inside the tube 3, a temperature gradient is generated inside the first stack 13 or the second stack 23. The temperature gradient is generated between a first side (one end) 13A and a second side (the other end) 13B of the first stack 13 in a tube lengthwise direction. Similarly, a temperature gradient is generated between a first side (one end) 23A and a second side (the other end) 23B of the second stack 23 in the tube lengthwise direction. Thus, the first stack 13 and the second stack 23 can convert thermal energy to sound energy and vice versa. Note that, in the present specification, the first side (one end) of the stack indicates one end surface of the stack and a part inward of the one end surface, and the second side (the other end) of the stack indicates the other end surface of the stack and a part inward of the other end surface.
In the first stack 13 and the second stack 23, the conduction paths 13k, 23k may be formed by a plurality of walls extending in the lengthwise direction of the tube 3, for example. In this case, the plurality of walls may have, for example, a grid-shape in a section perpendicular to the lengthwise direction of the tube 3. In another example, each of the first stack 13 and the second stack 23 may be a columnar body extending in the lengthwise direction of the tube 3 and having a plurality of holes extending in the lengthwise direction. In yet another example, in each of the first stack 13 and the second stack 23, a plurality of hollow columns extending in the lengthwise direction of the tube 3 may be arranged. In this case, each of the columns has a hexagonal sectional shape perpendicular to the axial direction, and thus, the columns can be arranged without any gap. That is, each of the first stack 13 and the second stack 23 may have a honeycomb structure.
Each of the first stack 13 and the second stack 23 may be made of metal or ceramic, for example. The first stack 13 and the second stack 23 may have many conduction paths 13k, 23k, respectively. A sectional area of each of the conduction paths 13k, 23k may be sufficiently smaller than a sectional area of an inside of the tube 3, the sectional area of each of the conduction paths 13k, 23k and the sectional area of the inside of the tube 3 being perpendicular to the lengthwise direction of the tube 3. Note that the first stack 13 and the second stack 23 do not necessarily need to have the same configuration.
In the present embodiment, a temperature gradient is generated such that a temperature of the first side 13A of the first stack 13 is higher than a temperature of the second side 13B. Acoustic waves are generated in the tube 3 by the temperature gradient in the first stack 13. Due to the acoustic waves thus generated by the temperature gradient in the first stack 13, a temperature gradient is generated in the second stack 23.
A heat exchanger 14 is provided at the first side 13A of the first stack 13. and a heat exchanger 12 is provided at the second side 13B of the first stack 13. A heat exchanger 24 is provided at the first side 23A of the second stack 23, and a heat exchanger 22 is provided at the second side 23B of the second stack 23. Each of the heat exchangers 12, 22, 14, 24 performs heat exchange between an outside of the tube 3 and the first stack 13 or the second stack 23. When the thermoacoustic cooling device 10 operates, acoustic waves are generated in the tube 3, and a temperature gradient is generated between the first side 13A and the second side 13B of the first stack 13 and between the first side 23A and the second side 23B of the second stack 23. The heat exchanger 14 provided at the first side 13A of the first stack 13 is referred to as the “first high-temperature heat exchanger 14”, the first side 13A having a high temperature due to the temperature gradient when the thermoacoustic cooling device 10 operates. The heat exchanger 12 provided at the second side 13B of the first stack 13 is referred to as the “first low-temperature heat exchanger 12”, the second side 13B having a low temperature due to the temperature gradient when the thermoacoustic cooling device 10 operates. The heat exchanger 24 provided at the first side 23A of the second stack 23 is referred to as the “second high-temperature heat exchanger 24”, the first side 23A having a high temperature due to the temperature gradient when the thermoacoustic cooling device 10 operates. The heat exchanger 22 provided at the second side 23B of the second stack 23 is referred to as the “second low-temperature heat exchanger 22”, the second side 23B having a low temperature due to the temperature gradient when the thermoacoustic cooling device 10 operates. Note that the heat exchangers 14, 24, 12, 22 do not necessarily need to make contact with the first sides 13A, 23A and the second sides 13B, 23B of the stacks 13, 23.
The first high-temperature heat exchanger 14 is disposed on an outer peripheral surface of the tube 3 at a position corresponding to the first side 13A of the first stack 13. The first low-temperature heat exchanger 12 is disposed on the outer peripheral surface of the tube 3 at a position corresponding to the second side 13B of the first stack 13. The second high-temperature heat exchanger 24 is disposed on the outer peripheral surface of the tube 3 at a position corresponding to the first side 23A of the second stack 23. The second low-temperature heat exchanger 22 is disposed on the outer peripheral surface of the tube 3 at a position corresponding to the second side 23B of the second stack 23.
The first high-temperature heat exchanger 14 heats the first side 13A of the first stack 13 with the use of heat from the outside of the tube 3. The first high-temperature heat exchanger 14 is connected to an external heat source 30 such that heat can be transferred from the external heat source 30 to the first high-temperature heat exchanger 14. The heat of the heat source 30 reaches the first side 13A of the first stack 13 via the first high-temperature heat exchanger 14.
The first low-temperature heat exchanger 12 transfers heat between the outside of the tube 3 and the second side 13B of the first stack 13, so as to adjust the temperature of the second side 13B of the first stack 13. For example, the first low-temperature heat exchanger 12 can prevent the temperature of the second side 13B of the first stack 13 from becoming higher than a prescribed reference temperature. That is, with the use of the first high-temperature heat exchanger 14 and the first low-temperature heat exchanger 12, the temperature gradient (temperature difference) between the first side 13A and the second side 13B of the first stack 13 can be controlled.
The first low-temperature heat exchanger 12, the first stack 13 and the first high-temperature heat exchanger 14 constitute a thermoacoustic prime mover (a thermoacoustic engine) that generates acoustic waves by converting input heat into vibrations of the working fluid.
In the present embodiment, when the temperature gradient is generated in the second stack 23 by the acoustic waves thus generated by the temperature gradient in the first stack 13, the temperature of the second side 23B of the second stack 23 becomes lower than the temperature of the first side 23A. The second high-temperature heat exchanger 24 is provided at the first side 23A that has a high temperature at the time when the temperature gradient is generated inside the second stack 23 due to the temperature gradient in the first stack 13. The second low-temperature heat exchanger 22 is provided at the second side 23B that has a low temperature at the time when the temperature gradient is generated inside the second stack 23 due to the temperature gradient in the first stack 13.
The second high-temperature heat exchanger 24 transfers heat between the outside of the tube 3 and the first side 23A of the second stack 23, so as to adjust the temperature of the first side 23A of the second stack 23. For example, the second high-temperature heat exchanger 24 can maintain the temperature of the first side 23A of the second stack 23 at a prescribed temperature.
The second low-temperature heat exchanger 22 absorbs heat of the outside of the tube 3 and introduces the heat into the second side 23B of the second stack 23. Thus, the outside of the tube 3 is cooled. In other words, the second low-temperature heat exchanger 22 takes out cold energy of the second side 23B of the second stack 23 in which the temperature decreases due to the temperature gradient generated in the second stack 23, and transfers the cold energy to the outside of the tube 3. The second low-temperature heat exchanger 22 is connected to, for example, a cooling target 40 provided outside the tube 3 such that heat can be transferred between the second low-temperature heat exchanger 22 and the cooling target 40.
The second low-temperature heat exchanger 22, the second stack 23, and the second high-temperature heat exchanger 24 constitute a thermoacoustic heat pump that generates a temperature gradient from acoustic waves (vibrations of the working fluid).
The thermoacoustic cooling device 10 includes a heat transfer portion 4 that connects the second low-temperature heat exchanger 22 to the first low-temperature heat exchanger 12 such that heat can be transferred therebetween. That is, the heat transfer portion 4 transfers heat between the second low-temperature heat exchanger 22 and the first low-temperature heat exchanger 12. With the use of the heat transfer portion 4, the cold energy of the second low-temperature heat exchanger 22 is transferred to the first low-temperature heat exchanger 12.
Next, an example operation of the thermoacoustic cooling device 10 will be described. In the configuration illustrated in
When the temperature gradient in the first stack 13 exceeds a critical point, the working fluid inside the first stack 13 vibrates to generate acoustic waves. The vibration of the working fluid inside first stack 13 is transmitted to the working fluid inside the tube 3. That is, the acoustic waves generated in the first stack 13 reach the second stack 23 via the tube 3. Thus, the working fluid in the second stack 23 vibrates. When the working fluid inside the second stack 23 vibrates, a temperature gradient is generated inside the second stack 23. That is, the temperature of the first side 23A of the second stack 23 becomes higher than the temperature of the second side 23B.
The second high-temperature heat exchanger 24 transfers heat between the outside of the tube 3 and the first side 23A of the second stack 23, so as to maintain the temperature of the first side 23A of the second stack 23 at a prescribed second reference temperature (e.g., ambient temperature). Accordingly, when the temperature gradient is generated in the second stack 23, the temperature of the second side 23B of the second stack 23 becomes lower than the second reference temperature. That is, the second side 23B of the second stack 23 is cooled. The second low-temperature heat exchanger 22 transfers cold energy of the second side 23B of the second stack 23 to the cooling target 40 outside the tube 3. Thus, the cooling target 40 is cooled.
Further, the cold energy of the second low-temperature heat exchanger 22 is partially transferred to the first low-temperature heat exchanger 12 via the heat transfer portion 4, and then further transferred to the second side 13B of the first stack 13 from the first low-temperature heat exchanger 12. Accordingly, the temperature of the second side 13B of the first stack 13 decreases. Thus, due to the temperature decrease of the second side 23B of the second stack, both the cooling target 40 and the second side 13B of the first stack 13 are cooled. When the second side 13B of the first stack 13 is cooled via the heat transfer portion 4, the temperature gradient between the first side 13A and the second side 13B of the first stack 13 is increased. Thus, the temperature gradient in the first stack 13 can be made larger without increasing the temperature of the first side 13A of the first stack 13. As a result, it is possible to decrease a required temperature of the heat source 30, that is, a temperature required to operate the thermoacoustic cooling device 10. Further, by increasing the temperature gradient in the first stack 13, it is possible to improve cooling efficiency of the thermoacoustic cooling device 10.
The first low-temperature heat exchanger 12 surrounds the outer peripheral surface of the tube 3 disposed radially outward of the second side 13B of the first stack 13. The first low-temperature heat exchanger 12 has a passage 12a surrounding the outer peripheral surface of the tube 3. A fluid 5 flows through the passage 12a. The fluid 5 flows in a circumferential direction of the tube 3. The passage 12a has an inlet 12b into which the fluid flows, and an outlet 12c from which the fluid 5 flows out. The inlet 12b is connected to the heat transfer portion 4, for example. The outlet 12c is connected to a drain (discharge tube) 6, for example.
In the example illustrated in
The fluid 5 is cooled while passing through the passage 22a of the second low-temperature heat exchanger 22. Then, the fluid 5 flows into the passage 12a of the first low-temperature heat exchanger 12 through the heat transfer tube 4a. The fluid 5 in the passage 12a absorbs heat from the first low-temperature heat exchanger 12. The first low-temperature heat exchanger 12 is cooled by the fluid 5 flowing into the passage 12a, and thus, the temperature of the second side 13B of the first stack 13 decreases. The fluid 5 that absorbs the heat from the first low-temperature heat exchanger 12 in the passage 12a is discharged from the outlet 12c.
In an example, the heat transfer tube 4a may be configured to cause the fluid 5 to flow from the second low-temperature heat exchanger 22 to the first low-temperature heat exchanger 12. For example, by disposing the second low-temperature heat exchanger 22 at a position higher than the first low-temperature heat exchanger 12, the fluid 5 can flow from the second low-temperature heat exchanger 22 to the first low-temperature heat exchanger 12. Alternatively a pump that causes the fluid 5 to flow from the second low-temperature heat exchanger 22 to the first low-temperature heat exchanger 12 may be provided. Note that the fluid 5 may flow so as to circulate through the second low-temperature heat exchanger 22 and the first low-temperature heat exchanger 12. In this case, the heat transfer portion 4 may include a heat transfer tube through which the fluid 5 flows in a direction from the second low-temperature heat exchanger 22 to the first low-temperature heat exchanger 12, and a heat transfer tube through which the fluid 5 flows in a direction opposite to the above-described direction. That is, the heat transfer portion 4 may include two heat transfer tubes.
Further, although not illustrated in
The second low-temperature heat exchanger 22 surrounds the outer peripheral surface of the tube 3 disposed radially outward of the second side 23B of the second stack 23. The second low-temperature heat exchanger 22 has a passage 22a surrounding the outer peripheral surface of the tube 3. The fluid 5 flows through the passage 22a. The fluid 5 flows in the circumferential direction of the tube 3. The passage 22a has an inlet 22b into which the fluid 5 flows and an outlet 22c from which the fluid 5 flows out. The inlet 22b is connected to a source of the fluid, such as a faucet. The outlet 22c is connected to the heat transfer tube 4a of the heat transfer portion 4, for example. Thus, the fluid 5 can flow from the second low-temperature heat exchanger 22 to the first low-temperature heat exchanger 12. In the case where the fluid 5 circulates between the second low-temperature heat exchanger 22 and the first low-temperature heat exchanger 12, the inlet 22b may be connected to the outlet 12c of the first low-temperature heat exchanger 12 via the heat transfer portion 4.
Each of the fluids 5, 5a may be a liquid such as oil, water, or ethylene glycol aqueous solution, or gas, for example.
In one example, in a case where the second high-temperature heat exchanger 24 is configured as illustrated in
In the example illustrated in
The second low-temperature heat exchanger 22 at the second side 23B of the second stack 23 and first low-temperature heat exchangers 12 at the second sides 13B of the first stacks 13 are connected to each other such that heat can be transferred between the second low-temperature heat exchanger 22 and the first low-temperature heat exchangers 12 by heat transfer portions 41, 42. Since the heat transfer portions 41, 42 are provided, temperatures of the first low-temperature heat exchangers 12 decrease due to a decrease in the temperature of the second low-temperature heat exchanger 22. Thus, when the thermoacoustic cooling device 10b operates, temperatures of the second sides 13B of the first stacks 13 are decreased due to a decrease in the temperature of the second side 23B of the second stack 23. This makes it possible to increase temperature gradients in the first stacks 13.
The embodiments of the disclosure have been described, but the disclosure is not limited to the above embodiments. For example, although each of the heat transfer portions 4, 41, 42 preferably has a linear shape such that a length of a heat transfer path is shortened, the heat transfer portions 4, 41, 42 may be curved. Further, outer peripheral surfaces of the heat transfer portions 4, 41, 42 may be covered with a heat insulation material.
The configurations of the heat exchangers 12, 14, 22, 24 are not limited to the configurations in the above examples. In an example, at least one of the heat exchangers 12, 14, 22, 24 may further include a heat conduction portion including, for example, fins disposed inside the tube 3. In another example, each of the heat exchangers 12, 14, 22, 24 may further include a heat conduction portion having a plurality of conduction paths extending in the lengthwise direction of the tube 3, and the beat conduction portions may be disposed on the sides of the stacks 13, 23 in the tube 3. In this case, the first stack 13 is sandwiched between the heat conduction portions of the first high-temperature heat exchanger 14 and the first low-temperature heat exchanger 12 inside the tube 3. The second stack 23 is sandwiched between the heat conduction portions of the second high-temperature heat exchanger 24 and the second low-temperature heat exchanger 22 inside the tube 3. When each of the heat exchangers 12, 14, 22, 24 further includes the heat conduction portion thus disposed inside the tube 3, temperatures of the both ends of the stacks 13, 23 can be adjusted to desired temperatures more efficiently. That is, it is possible to further improve the efficiency of heat exchange in the stacks 13, 23.
The configurations of the stacks 13, 23 are not limited to the configurations in the above examples. For example, in the first stack 13 and the second stack 23, the conduction paths 13k, 23k extending in the lengthwise direction of the tube 3 may be curved.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-156725 | Aug 2016 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20060185370 | Watanabe | Aug 2006 | A1 |
| Number | Date | Country |
|---|---|---|
| 1761846 | Apr 2006 | CN |
| 2007-147192 | Jun 2007 | JP |
| 2008-101910 | May 2008 | JP |
| Entry |
|---|
| U.S. Pub. No. 2006/0185370 cited in Jan. 10, 2020 Office Action. |
| Apr. 14, 2020 Office Action issued in Chinese Patent Application No. 201710674641.9. |
| Number | Date | Country | |
|---|---|---|---|
| 20180045435 A1 | Feb 2018 | US |
