JP7484566B2 - Thermoacoustic Device - Google Patents

Description

This disclosure relates to a thermoacoustic device.

Thermoacoustic devices are known that include a stack that exchanges energy based on the thermoacoustic effect. Patent Document 1 describes a technique for manufacturing a stack made of ceramic by extrusion molding. This manufacturing method makes it possible to manufacture a stack with multiple flow paths.

JP 2008-249223 A JP 2020-12601 A

In general, the amount of energy that can be converted can be increased by increasing the diameter of the stack. However, when manufacturing a stack made of ceramics by extrusion molding, increasing the diameter of the stack may cause distortion in the stack due to deformation caused by its own weight before firing or uneven temperature during firing. In this case, the inner diameter of each flow path in the stack may not be uniform, and the amount of energy that can be converted and the efficiency of the conversion may decrease. Similar problems may also occur when manufacturing stacks made of materials other than ceramics.

Furthermore, if the stack is simply made larger, the temperature difference between the peripheral and central parts of the stack will become larger when the thermoacoustic device is in use, which may reduce the amount of energy that can be converted.

This disclosure can be realized in the following forms:

(1) According to one aspect of the present disclosure, there is provided a thermoacoustic device. The thermoacoustic device includes a first heat exchanger disposed at one end of a stack unit and configured to heat the one end of the stack unit or be cooled by the one end, a second heat exchanger disposed at the other end of the stack unit and configured to keep the other end of the stack unit at a constant temperature, and the stack unit disposed between the first heat exchanger and the second heat exchanger and configured to convert thermal energy and vibration energy. The stack unit includes a holder having a plurality of holding holes communicating with the first heat exchanger and the second heat exchanger, and a plurality of stack members having a plurality of flow paths communicating with the first heat exchanger and the second heat exchanger and at least a portion of which is accommodated in each of the holding holes.
In this embodiment, the number of stack members can be increased to improve the functionality of the stack unit without increasing the size of the stack members, and therefore, compared to an embodiment in which the stack is increased by simply increasing the size of the stack members, a decrease in the energy that the stack unit can convert can be suppressed.
(2) In the thermoacoustic device of the above aspect, the stack member may be made of ceramic, and the holder may be made of a material having a higher thermal conductivity than ceramic.
In this embodiment, since the holder is made of a material having a higher thermal conductivity than ceramics, the holder can suppress the occurrence of a temperature difference in a cross-sectional direction perpendicular to the axial direction of the stack of stack members, and therefore the occurrence of a temperature difference between the peripheral portion and the central portion within the stack unit can be suppressed, and therefore the reduction in the energy that the stack unit can convert can be suppressed.
(3) In the thermoacoustic device of the above form, the holder may be arranged at different positions in a direction communicating with the first heat exchanger and the second heat exchanger, and may include a plurality of metal plate-shaped members spaced apart by a predetermined gap, each of the metal plate-shaped members having a hole that constitutes part of the plurality of retaining holes.
In this embodiment, the effect of the holder on the temperature gradient in the direction of communication between the first heat exchanger and the second heat exchanger of the stack member can be reduced, thereby preventing a decrease in the energy that can be converted by the stack unit.
(4) In the thermoacoustic device of the above aspect, the holder may be configured to receive thermal energy from outside the stack unit and to supply the thermal energy to the stack member.
In this configuration, the temperature gradient of the stack members can be easily controlled compared to a configuration in which thermal energy is not supplied from outside the stack unit.

The present disclosure can also be realized in various forms other than a thermoacoustic device. For example, it can be realized in the form of a stack unit for a thermoacoustic device, a prime mover equipped with a stack unit for a thermoacoustic device, a manufacturing method thereof, etc.

1 is an explanatory diagram showing a schematic configuration of a thermoacoustic device according to a first embodiment; FIG. 2 is an explanatory diagram showing a schematic configuration of a prime mover. FIG. 2 is an explanatory diagram showing a schematic configuration of a stack unit. FIG. 2 is a cross-sectional view showing a schematic configuration of a prime mover. FIG. 11 is a perspective view showing a schematic configuration of a stack unit in another embodiment. FIG. 11 is a plan view showing a schematic configuration of a stack unit in another embodiment. A plan view showing a schematic configuration of a stack unit in yet another embodiment.

A. First embodiment:
Fig. 1 is an explanatory diagram showing a schematic configuration of a thermoacoustic device TA according to a first embodiment. Note that Fig. 1 does not accurately show the shapes of each component of the thermoacoustic device TA. The thermoacoustic device TA is a loop-tube type thermoacoustic device. The thermoacoustic device TA is connected to a heat source HS and a cooling target CO. The thermoacoustic device TA is supplied with thermal energy from the heat source HS and can cool the cooling target CO.

The thermoacoustic device TA includes a prime mover PM, a heat pump HP, and loop pipes LT1 and LT2. One end of the prime mover PM and one end of the heat pump HP are connected by the loop pipe LT1. The other end of the prime mover PM and the other end of the heat pump HP are connected by the loop pipe LT2. As a result, the prime mover PM, the heat pump HP, and the loop pipes LT1 and LT2 form a ring-shaped piping structure PA. This ring-shaped piping structure PA is filled with a fluid FL1. In this embodiment, the fluid FL1 is air. The ring-shaped piping structure PA is configured so that the internal fluid FL1 can flow within the ring-shaped piping structure PA.

The prime mover PM receives thermal energy from the heat source HS and generates sound waves (see the lower left part of Figure 1). The prime mover PM includes a first heat exchanger 40, a second heat exchanger 20, and a stack unit 30.

2 is an explanatory diagram showing a schematic configuration of the prime mover PM. Note that FIG. 2 does not accurately show the shape of each component of the prime mover PM. In this embodiment, the stack unit 30 has piping, but this is omitted for convenience of illustration. The stack unit 30 is installed in a portion between the first heat exchanger 40 and the second heat exchanger 20 (see the lower left part of FIG. 1 and FIG. 2). The stack unit 30 has a large number of through holes. These through holes form a flow path 32 through which the fluid FL1 flows. The stack unit 30 is connected to the first heat exchanger 40 and the second heat exchanger 20 so that the fluid FL1 can flow through them. The stack unit 30 forms a temperature gradient and converts thermal energy and vibration energy. More specifically, the stack unit 30 generates sound waves in the loop tube LT1.

Figure 3 is an explanatory diagram showing the schematic configuration of the stack unit 30. Note that Figure 3 does not accurately show the shape of each component of the stack unit 30. The stack unit 30 comprises a holder 31 and seven stack members 33. In this embodiment, the stack unit 30, holder 31, and stack members 33 have a substantially circular cross section in a direction perpendicular to the flow path 32. The diameter of the stack unit 30 is approximately three times the diameter of the stack members 33.

The holder 31 has seven holding holes 31h that communicate with the first heat exchanger 40 and the second heat exchanger 20. Six holding holes 31h are arranged around one holding hole 31h arranged at the center of the holder 31 so as to be equally spaced from each other. In this embodiment, the holder 31 is made of a metal material having a higher thermal conductivity than ceramics. The holder 31 is also provided with two metal plate-shaped members 31m arranged at different positions in the direction communicating with the first heat exchanger 40 and the second heat exchanger 20, each having a hole that constitutes a part of the multiple holding holes 31h, with a predetermined gap between them. The dimension of each plate-shaped member 31m in the direction communicating with the first heat exchanger 40 and the second heat exchanger 20 is smaller than 1/2 the dimension of the stack member 33 in the direction communicating with the first heat exchanger 40 and the second heat exchanger 20.

The stack member 33 has a plurality of flow paths 33P that communicate with the first heat exchanger 40 and the second heat exchanger 20. The flow paths 33P of each stack member 33 are collectively referred to as the flow paths 32. Each stack member 33 is arranged so that at least a portion of it is accommodated in each of the retaining holes 31h of the two plate-like members 31m (see FIG. 2). For convenience of illustration, in FIG. 3, the stack member 33 is shown in a state where it is not accommodated in the holder 31. In this embodiment, the stack member 33 is made of ceramic.

The inner diameter of the holding hole 31h of the holder 31 and the outer diameter of the stack member 33 are approximately the same. Therefore, when the stack member 33 is housed in the holding hole 31h, the gap between the holding hole 31h and the stack member 33 is almost zero. In addition, when the stack member 33 is housed in the holding hole 31h, the stack members 33 are formed so that they do not come into contact with each other.

Figure 4 is a cross-sectional view showing the general configuration of the prime mover PM. Note that Figure 4 does not accurately show the shape of each component of the prime mover PM.

The first heat exchanger 40 is connected to the loop pipe LT1 at one end of the prime mover PM so that the fluid FL1 can flow through it, and is also disposed at one end 38 of the stack unit 30 (see the lower part of Figure 4). The first heat exchanger 40 is further connected to a heat source HS. The heat source HS is, for example, a rod-shaped heater that uses a resistance heating method. The first heat exchanger 40 receives heat from the heat source HS and imparts heat to the fluid FL1 in the piping structure PA, which is in contact with the first heat exchanger 40.

The first heat exchanger 40 includes a heat transfer ring 43 and a fin module 44 (see the lower part of FIG. 4). The heat transfer ring 43 is connected to the heat source HS and receives heat from the heat source HS. The fin module 44 is disposed in a central hole of the heat transfer ring 43. The fin module 44 includes a large number of fins. The gaps between adjacent fins in the fin module 44 form a flow path 42 through which the fluid FL1 flows. The fin module 44 receives heat from the heat transfer ring 43 and provides the heat to the fluid FL1 flowing through the flow path 42. In this way, the first heat exchanger 40 heats one end 38 of the stack unit 30.

The second heat exchanger 20 is connected to the loop pipe LT2 at the other end of the motor PM so that the fluid FL1 can flow through it, and is disposed at the other end 39 of the stack unit 30 (see the upper part of FIG. 4). The second heat exchanger 20 is equipped with a chiller (not shown). The temperature of the second heat exchanger 20 is kept constant by the chiller. The second heat exchanger 20 controls the temperature of the fluid FL1 in the piping structure PA that is in contact with the second heat exchanger 20 to a predetermined range. As a result, the second heat exchanger 20 makes the other end 39 of the stack unit 30 lower in temperature than the one end 38. In other words, the second heat exchanger 20 is kept at a temperature that can make the other end 39 of the stack unit 30 lower in temperature than the one end 38.

The stack unit 30 is disposed between the second heat exchanger 20 and the first heat exchanger 40. In this embodiment, the stack unit 30 includes a pipe T1 having the same diameter as the loop pipes LT1 and LT2, and a holder 31 and a stack member 33 are housed in the pipe T1.

The second heat exchanger 20 includes a jacket 23 and a fin module 24 (see the upper part of FIG. 4). The jacket 23 is an annular structure that constitutes a flow path 26 through which the fluid FL2 flows. The jacket 23 is connected to a chiller, and the chiller causes the fluid FL2 to flow through it. The fin module 24 is disposed in a hole in the center of the jacket 23. The fin module 24 includes a large number of fins. The gaps between adjacent fins in the fin module 24 constitute a flow path 22 through which the fluid FL1 flows. The fin module 24 exchanges heat with the jacket 23. The flow of the fluid FL2 by the chiller controls the temperature of the jacket 23 and the fin module 24 to a predetermined range. As a result, the fluid FL1 flowing through the flow path 22 is controlled to a predetermined range.

The prime mover PM operates as follows. The fluid FL1 heated by the first heat exchanger 40 gives heat to one end 38 of the stack unit 30 and its surrounding parts, causing the temperature to rise near the one end 38 of the stack unit 30. The fluid FL1, which is kept at a constant temperature by the second heat exchanger 20, takes heat from the other end 39 of the stack unit 30 and its surrounding parts, causing the temperature to fall near the other end 39 of the stack unit 30 lower than the temperature near the one end 38. As a result, a temperature gradient is formed in the stack unit 30. Then, the stack unit 30 undergoes thermoacoustic self-excited vibration, generating standing waves in the flow path 32. The sound waves of the standing waves generated by the stack unit 30 are transmitted from one end of the prime mover PM to one end of the heat pump HP via the fluid FL1 in the loop tube LT1 (see arrow K1 in FIG. 1).

The temperature gradient formed in the stack unit 30 is, more specifically, a temperature gradient formed in each stack member 33. The fluid FL1 heated by the first heat exchanger 40 causes the vicinity of one end 38 of each stack member 33 to become high temperature. The fluid FL1 maintained at a constant temperature by the second heat exchanger 20 causes the vicinity of the other end 39 of the stack member 33 to become low temperature. As a result, a temperature gradient is formed in the stack member 33. Then, each stack member 33 causes thermoacoustic self-excited vibration and generates a standing wave in the flow path 33P. Of the multiple stack members 33, the stack members 33 arranged in the peripheral portion of the stack unit 30 tend to have a lower temperature than the stack members 33 arranged in the central portion of the stack unit 30 because heat is easily transferred from the peripheral portion to the outside of the stack unit 30. In this embodiment, the holder 31 is made of a material with a higher thermal conductivity than the stack members 33, so the holder 31 can suppress the temperature difference between each stack member 33.

The heat pump HP is supplied with sound waves from the prime mover PM and cools the cooling target CO (see the upper right part of Figure 1). The heat pump HP has a configuration substantially similar to that of the prime mover PM. The heat pump HP includes a third heat exchanger 90, a fourth heat exchanger 70, and a stack unit 80. The fourth heat exchanger 70 corresponds to the first heat exchanger 40. The third heat exchanger 90 corresponds to the second heat exchanger 20. The stack unit 80 corresponds to the stack unit 30.

The third heat exchanger 90 is connected to a loop pipe LT1 at one end of the heat pump HP so that fluid FL1 can flow through it (see the upper right part of FIG. 1). The third heat exchanger 90 is equipped with a chiller (not shown). The third heat exchanger 90 is maintained at a constant temperature by circulating fluid through the chiller. The third heat exchanger 90 controls the temperature of the fluid FL1 in the piping structure PA that is in contact with the third heat exchanger 90 to a predetermined range. The third heat exchanger 90 may be connected to a chiller provided in the second heat exchanger 20.

The fourth heat exchanger 70 is connected to a loop pipe LT2 at the other end of the heat pump HP so that fluid FL1 can flow through it (see the upper right part of Figure 1). The fourth heat exchanger 70 is further connected to the object to be cooled CO. The fourth heat exchanger 70 absorbs heat from the fluid FL1 in the piping structure PA that is in contact with the fourth heat exchanger 70, and absorbs heat from the object to be cooled CO. As a result, the object to be cooled CO is cooled.

The stack unit 80 is installed between the fourth heat exchanger 70 and the third heat exchanger 90 (see the upper right part of FIG. 1). The stack unit 80 has a large number of through holes. These through holes form a flow path 82 through which the fluid FL1 flows. The stack unit 80 is connected to the fourth heat exchanger 70 and the third heat exchanger 90 so that the fluid FL1 can flow through the stack unit 80. The stack unit 80 forms a temperature gradient by the sound waves of the standing waves transmitted by the fluid FL1 in the loop tube LT1.

The heat pump HP operates as follows. In the flow path 82 of the stack unit 80, the fluid FL1 oscillates with a standing wave. When a minute portion of the fluid FL1 moves in a direction from one end 88 of the stack unit 80 toward the other end 89, the fluid FL1 expands adiabatically. The temperature of the minute portion of the fluid FL1 decreases. The minute portion of the fluid FL1 takes heat from the structure of the stack unit 80. On the other hand, when a minute portion of the fluid FL1 moves in a direction from the other end 89 of the stack unit 80 toward the one end 88, the fluid FL1 is adiabatically compressed. The temperature of the minute portion of the fluid FL1 increases. The minute portion of the fluid FL1 gives heat to the structure of the stack unit 80. As a result, due to the vibration of the fluid FL1, heat transfer occurs in the flow path 82 of the stack unit 80 in a direction from the other end 89 of the stack unit 80 toward the one end 88. Thus, a temperature gradient is formed in the stack unit 80. In addition, the temperature near one end 88 of the stack unit 80 is kept constant by the third heat exchanger 90. As a result, the area near the other end 89 of the stack unit 80 is cooled by the transfer of heat caused by the vibration of the fluid FL1. Then, the object to be cooled, CO, is cooled through the fourth heat exchanger 70.

When the fluid FL1 moves from near the other end 89 of the stack unit 80 to near one end 88, the fluid FL1 is adiabatically compressed. As a result, the temperature of the fluid FL1 rises. The fluid FL1 provides heat to the third heat exchanger 90 near one end 88 of the stack unit 80. The heat provided to the third heat exchanger 90 is released to the outside via the chiller of the third heat exchanger 90.

The stack unit 30 in this embodiment has a holder 31 having a plurality of holding holes 31h communicating with the first heat exchanger 40 and the second heat exchanger 20, and a stack member 33 having a plurality of flow paths 32 communicating with the first heat exchanger 40 and the second heat exchanger 20, at least a portion of which is accommodated in each of the holding holes. In this manner, the number of stack members 33 can be increased to improve the function of the stack unit 30 without increasing the size of the stack members 33. Therefore, compared to an embodiment in which the stack is increased by simply increasing the size of the stack members 33, the occurrence of distortion in the stack members 33 can be suppressed, and the inner diameter of each flow path 33P of the stack members 33 can be suppressed from becoming uneven. Therefore, the energy that the stack unit 30 can convert can be suppressed from decreasing.

In addition, in this embodiment, the stack member is made of ceramic. Therefore, the efficiency of energy conversion is higher than in an embodiment in which the stack member 33 is made of a metal with a higher thermal conductivity than ceramic. On the other hand, since the holder 31 is made of a material with a higher thermal conductivity than ceramic, the holder 31 can suppress the occurrence of a temperature difference in the cross-sectional direction perpendicular to the flow path 33P direction of the stack member 33. Therefore, the occurrence of a temperature difference between the peripheral portion and the central portion within the stack unit 30 can be suppressed, and a decrease in the energy that the stack unit 30 can convert can be suppressed.

The holder 31 is configured such that multiple metal plate members 31m are arranged with a predetermined gap in the direction communicating with the first heat exchanger 40 and the second heat exchanger 20. This reduces the effect of the holder 31 on the temperature gradient in the direction communicating with the first heat exchanger 40 and the second heat exchanger 20 of the stack member 33. This prevents a decrease in the energy that the stack unit 30 can convert.

B. Other embodiments:
(B1) Fig. 5 is a perspective view showing a schematic configuration of a stack unit 30 in another embodiment. In the above embodiment, the holder 31 includes two plate-like members 31m. However, the holder 31 may include three or more plate-like members 31m, such as four, as shown in Fig. 5. The holder 31 may also include only one plate-like member 31m.

(B2) Figures 6 and 7 are plan views showing the schematic configuration of a stack unit 30 in another embodiment. Figures 6 and 7 are plan views of the stack unit 30 as viewed in the flow path 33P direction. In the above embodiment, the stack unit 30 has stack members 33 whose cross sections in a direction perpendicular to the flow path 33P direction are circular and whose radii are the same. Alternatively, the stack unit 30 may have stack members 33 whose cross sections in a direction perpendicular to the flow path 33P direction are different in radius, as shown in Figure 6. The stack unit 30 may also have stack members 33 whose cross sections in a direction perpendicular to the flow path 33P direction are hexagonal, as shown in Figure 7.

(B3) In the above embodiment, the holder 31 may be supplied with thermal energy from outside the stack unit 30 and supply the thermal energy to the stack member 33. For example, the holder 31 is connected to a heat source HS and is supplied with thermal energy from the heat source HS. The holder 31 supplies the thermal energy supplied from the heat source HS to the stack member 33 and controls the temperature gradient of the stack member 33. In this configuration, the temperature gradient of the stack member 33 can be more easily controlled than in a configuration in which thermal energy is not obtained from outside the stack unit 30.

(B4) In the above embodiment, the stack unit 80 in the heat pump HP has the same configuration as the stack unit 30. Alternatively, the stack unit 80 may be configured by simply enlarging the stack member 33. In other words, only the stack unit 30 in the prime mover PM may be configured to include the holder 31 and multiple stack members 33.

The present disclosure is not limited to the above-described embodiments, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features of the embodiments corresponding to the technical features in each form described in the Summary of the Invention column can be replaced or combined as appropriate to solve some or all of the above-described problems or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

20...second heat exchanger, 22...flow path, 23...jacket, 24...fin module, 26...flow path, 30...stack unit, 31...holder, 31h...retaining hole, 31m...plate-shaped member, 32...flow path, 33...stack member, 33P...flow path, 38...one end, 39...other end, 40...first heat exchanger, 42...flow path, 43...heat transfer ring, 44...fin module, 70...fourth heat exchanger, 80...stack unit, 82...flow path, 88...one end, 89...other end, 90...third heat exchanger, CO...cooling target, FL1...fluid, FL2...fluid, HP...heat pump, HS...heat source, K1...arrow indicating the direction of sound wave, LT1...loop tube, LT2...loop tube, PA...piping structure, PM...motor, T1...piping, TA...thermoacoustic device

Claims (4)

1. A thermoacoustic device comprising:
a first heat exchanger disposed at one end of the stack unit and configured to heat the one end of the stack unit or to be cooled by the one end;
a second heat exchanger disposed at the other end of the stack unit and configured to maintain the other end of the stack unit at a constant temperature;
The stack unit is disposed between the first heat exchanger and the second heat exchanger and converts thermal energy and vibration energy,
The stack unit includes:
a holder having a plurality of holding holes communicating with the first heat exchanger and the second heat exchanger;
A thermoacoustic device comprising: a plurality of stack members each having a plurality of flow paths communicating with the first heat exchanger and the second heat exchanger, and at least a portion of the stack members being accommodated in each of the retaining holes. 2. The thermoacoustic device of claim 1,
The stack member is made of ceramic,
The thermoacoustic device, wherein the holder is made of a material having a higher thermal conductivity than ceramic. 3. A thermoacoustic device according to claim 1 or 2,
The holder is a thermoacoustic device that is provided with a plurality of metal plate-shaped members arranged at different positions in a direction communicating with the first heat exchanger and the second heat exchanger, and each of the metal plate-shaped members has a hole that constitutes a part of the plurality of retaining holes, and is spaced apart with a predetermined gap. A thermoacoustic device according to any one of claims 1 to 3,
The holder is a thermoacoustic device that receives thermal energy from outside the stack unit and supplies the thermal energy to the stack member.

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