US20080110180A1

US20080110180A1 - Thermoacoustic Device

Info

Publication number: US20080110180A1
Application number: US11/662,297
Authority: US
Inventors: Yoshiaki Watanabe; Shinichi Sakamoto
Original assignee: Doshisha Co Ltd
Current assignee: Doshisha Co Ltd
Priority date: 2005-01-07
Filing date: 2005-04-22
Publication date: 2008-05-15
Also published as: JP4652821B2; WO2006073006A1; JP2006189218A

Abstract

A thermoacoustic device 1 for reliably generating standing and traveling waves, which have a large sound pressure, in a loop tube, has a loop tube 2 in which a working fluid is sealed; first stacks 3 a, each of which has a plurality of communication paths 30 along a heat transportation direction and is provided between a first high-temperature side heat exchanger 4 and a first low-temperature side heat exchanger 5, which are provided in this loop tube 2; and a second stack 3 b which has a plurality of communication paths 30 along a heat transportation direction and which is provided between a second high-temperature side heat exchanger 6 and a second low-temperature side heat exchanger 7, which are provided in the loop tube 2, and in the thermoacoustic device 1, self-excited standing and traveling waves are generated by heating the first high-temperature side heat exchanger 4, so that the second low-temperature side heat exchanger 7 is cooled by the standing and traveling waves. The first stacks 3 a each provided between the first high-temperature side heat exchanger 4 and the first low-temperature side heat exchanger 5 are provided at a plurality of positions which are in the vicinities at which the phase of change in acoustic particle velocity is the same as the phase of change in sound pressure.

Description

TECHNICAL FIELD

The present invention relates to a thermoacoustic device capable of cooling an object to be cooled or of heating an object to be heated using a thermoacoustic effect, and more particularly, relates to a thermoacoustic device capable of amplifying acoustic energy generated in a tube and of efficiently converting the amplified acoustic energy to thermal energy.

BACKGROUND ART

Heat exchange devices using an acoustic effect have been disclosed, for example, in the following Patent Document 1.
The device disclosed in Patent document 1 includes a resonance tube in the form of a loop having a circumference of an integral multiple of an acoustic wavelength, a plurality of speakers disposed at intervals of an odd multiple of one fourth of an acoustic wavelength, an acoustic wave generation control means which changes the phases of acoustic waves generated from the speakers by an odd multiple of one-fourth cycle, and a regenerative member disposed at a predetermined position in the loop-shaped resonance tube, and in this device, an acoustic wave traveling only in one direction is allowed to remain in the resonance tube, so that the amplitude of the acoustic wave is amplified as is the resonance. According to this thermoacoustic device, when the acoustic waves emitted from the speakers travel in two directions in the loop-shaped resonance tube, acoustic waves traveling in one direction are overlapped with each other by the intervals at which the speakers are disposed and are amplified, and acoustic waves traveling in the other direction are counteracted by waves having an opposite phase; hence, an acoustic wave amplified only in one direction can be generated.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 10-325625

DISCLOSURE OF INVENTION

Problems to be Solved by the Invention

Since the device disclosed in Patent Document 1 is a device to input acoustic waves using speakers, an object to be cooled cannot be cooled using waste heat or the like. In addition, as the case of the above Patent Document 1, when speakers are mounted to the outside of a tube, acoustic waves emitted from the speakers are reflected by an outer peripheral portion of the tube, and hence stable acoustic waves cannot be input in the tube. In addition, when speakers are mounted in the vicinity of the tube, the whole tube also vibrates as the speakers vibrate, and hence acoustic waves in the tube cannot be well counteracted with each other.
Accordingly, the present invention has been conceived in consideration of the above problems, and an object of the present invention is to provide a thermoacoustic device capable of reliably generating large standing and traveling waves in a tube.

Means for Solving the Problems

In order to achieve the above object, in accordance with one aspect of the present invention, there is provided a thermoacoustic device including: a tube in which a working fluid is sealed; first stacks which each have a plurality of communication paths along a heat transportation direction and which are each provided between a first high-temperature side heat exchanger and a first low-temperature side heat exchanger, which are provided in the tube; and a second stack which has a plurality of communication paths along a heat transportation direction and which is provided between a second high-temperature side heat exchanger and a second low-temperature side heat exchanger, which are provided in the tube, in which self-excited standing and traveling waves are generated by heating the first high-temperature side heat exchanger, and the second low-temperature side heat exchanger is cooled by the standing and traveling waves, or self-excited standing and traveling waves are generated by cooling the first low-temperature side heat exchanger, and the second high-temperature side heat exchanger is heated by the standing and traveling waves. In the above thermoacoustic device, the first stacks each provided between the first high-temperature side heat exchanger and the first low-temperature side heat exchanger are provided at a plurality of positions in the tube.
According to the structure described above, since an acoustic wave is generated in the tube instead of inputting an acoustic wave from the outside of the tube, the acoustic wave is not reflected by the outside wall surface of the tube. In addition, since the first stacks are provided at a plurality of positions, the acoustic wave can be amplified, and at this stage, a self-excited acoustic wave can be generated using heat; hence, for example, an object to be cooled can be cooled by using waste heat.
In addition, according to the present invention, the first stacks each provided between the first high-temperature side heat exchanger and the first low-temperature side heat exchanger are preferably provided in the vicinities of positions at which the phase of change in acoustic particle velocity is the same as the phase of change in sound pressure.
According to the above structure, the acoustic wave generated in each first stack can be reliably amplified.
In addition, in accordance with another aspect of the present invention, there is provided a thermoacoustic device including: a tube in which a working fluid is sealed; an acoustic wave generator generating an acoustic wave provided in the tube; and second stacks which each have a plurality of communication paths along a heat transportation direction and which are each provided between a second high-temperature side heat exchanger and a second low-temperature side heat exchanger, which are provided in the tube, in which standing and traveling waves are generated in the tube by the acoustic wave generator so that the second low-temperature side heat exchanger is cooled or the second high-temperature side heat exchanger is heated by the standing and traveling waves, and heat obtained by the cooling or the heating is output outside. In the above thermoacoustic device, the second stacks each provided between the second high-temperature side heat exchanger and the second low-temperature side heat exchanger are provided at a plurality of positions in the tube.
According to the structure described above, by the second stacks provided at a plurality of positions in the tube, the conversion efficiency from acoustic energy to thermal energy can be improved.
In addition, as is the case described above, the second stacks each provided between the first high-temperature side heat exchanger and the first low-temperature side heat exchanger are provided in the vicinities of positions at which the phase of change in acoustic particle velocity is the same as the phase of change in sound pressure.
According to the structure described above, the acoustic energy generated in the tube can be efficiently converted to the thermal energy, and an object to be cooled can be further cooled.
Furthermore, the first high-temperature side heat exchanger, the first low-temperature side heat exchanger, and the first stack are formed to have the same structures as those of the second high-temperature side heat exchanger, the second low-temperature side heat exchanger, and the second stack, respectively.
Accordingly, when stacks each provided between a high-temperature side heat exchanger and a low-temperature side heat exchanger are provided beforehand at appropriate positions in the tube, that is, are provided in the vicinities at which the phase of change in acoustic particle velocity is the same as the phase of change in sound pressure, the number of stacks at the acoustic wave generation side and the number of stacks at the heat output side can be increased or decreased only by selecting heat input positions and heat output positions.

Advantages

According to one aspect of the present invention, the thermoacoustic device has a tube in which a working fluid is sealed; first stacks which each have a plurality of communication paths along a heat transportation direction and which are each provided between a first high-temperature side heat exchanger and a first low-temperature side heat exchanger, which are provided in the tube; and a second stack which has a plurality of communication paths along a heat transportation direction and which is provided between a second high-temperature side heat exchanger and a second low-temperature side heat exchanger, which are provided in the tube, in which self-excited standing and traveling waves are generated by heating the first high-temperature side heat exchanger, and the second low-temperature side heat exchanger is cooled by the standing and traveling waves, or self-excited standing and traveling waves are generated by cooling the first low-temperature side heat exchanger, and the second high-temperature side heat exchanger is heated by the standing and traveling waves. In the above thermoacoustic device, since the first stacks each provided between the first high-temperature side heat exchanger and the first low-temperature side heat exchanger are provided at a plurality of positions in the tube, compared to the case in which an acoustic wave is input from the outside of the tube using a speaker, the acoustic wave is not reflected by the outside wall surface of the tube, and hence the acoustic wave can be reliably amplified in the tube. In addition, at this stage, since a self-excited acoustic wave is generated using heat, for example, waste heat can be used.
According to another aspect of the present invention, the thermoacoustic device has: a tube in which a working fluid is sealed; an acoustic wave generator generating an acoustic wave provided in the tube; and second stacks which each have a plurality of communication paths along a heat transportation direction and which are each provided between a second high-temperature side heat exchanger and a second low-temperature side heat exchanger, which are provided in the tube, in which standing and traveling waves are generated in the tube by the acoustic wave generator so that the second low-temperature side heat exchanger is cooled or the second high-temperature side heat exchanger is heated by the standing and traveling waves, and heat obtained by the cooling or the heating is output outside. In the thermoacoustic device described above, since the second stacks each provided between the second high-temperature side heat exchanger and the second low-temperature side heat exchanger are provided at a plurality of positions in the tube, the conversion efficiency from acoustic energy to thermal energy can be improved.

Best Mode for Carrying Out the Invention

Hereinafter, a first embodiment of a thermoacoustic device 1 according to the present invention will be described with reference to figures.
As shown in FIG. 1, the thermoacoustic device 1 of this embodiment includes a loop tube 2 having an approximately rectangular shape as a whole, and in this loop tube 2, there are provided first heat exchangers 300, each of which is composed of a first high-temperature side heat exchanger 4, a first low-temperature side heat exchanger 5, and a first stack 3 a, and second heat exchangers 310, each of which is composed of a second high-temperature side heat exchanger 6, a second low-temperature side heat exchanger 7, and a second stack 3 b. By heating the first high-temperature side heat exchangers 4 at the first heat exchanger 300 side, self-excited standing and traveling waves are generated, and when acoustic energy by the standing and traveling waves is transported to the second heat exchanger 310 side, it is converted to thermal energy at the second heat exchanger 310 side so as to cool the second low-temperature side heat exchangers 7.
In this embodiment, in order to generate standing and traveling waves having a high sound pressure in the loop tube 2, the first heat exchangers 300 are provided in the vicinities of positions at which the phase of change in acoustic particle velocity is the same as the phase of change in sound pressure, and in order to improve conversion efficiency of acoustic energy of the standing and traveling waves generated in the loop 2 to thermal energy, the second heat exchangers 310 are disposed in the vicinities of positions at which the phase of change in acoustic particle velocity is the same as the phase of change in sound pressure. Hereinafter, a particular structure of this thermoacoustic device 1 will be described in detail.
The loop tube 2 forming the thermoacoustic device 1 is formed of a pair of straight tube portions 2 a and connection tube portions 2 b connecting therebetween so as to form a closed curved line. Those straight tube portions 2 a and the connection tube portions 2 b are formed of metal pipes; however, a material is not limited to a metal, and for example, a transparent glass or resin may also be used. When a transparent glass or resin is used, in an experiment or the like, the positions of the first stack 3 a and the second stack 3 b can be easily confirmed, and the state in the tube can be easily observed.
In addition, in the loop tube 2 thus formed, there are provided the first heat exchangers 300, each of which is composed of the first high-temperature side heat exchanger 4, the first low-temperature side heat exchanger 5, and the first stack 3 a, and the second heat exchangers 310, each of which is composed of the second high-temperature side heat exchanger 6, the second low-temperature side heat exchanger 7, and the second stack 3 b. All the first heat exchangers 300 have the same structure, and all the second heat exchangers 310 also have the same structure.
The first high-temperature side heat exchanger 4 and the first low-temperature side heat exchanger 5 are both formed, for example, of a metal having a large heat capacity, and as shown in FIG. 3, communication paths 30 having a small diameter are provided inside each of the heat exchangers along the axial direction of the loop tube 2. Of the heat exchangers 4 and 5, the first high-temperature side heat exchanger 4 is mounted so as to be in contact with an upper surface of the stack 3 a and is heated to a temperature relatively higher than that of the first low-temperature side heat exchanger 5 by waste heat or the like supplied from the outside. Alternatively, besides the waste heat, this first high-temperature side heat exchanger 4 may be heated by electric power or the like supplied from the outside.
In addition, as is the case described above, the first low-temperature side heat exchanger 5 is mounted so as to be in contact with a lower surface of the first stack 3 a and is set to a temperature, such as 15 to 16° C., which is relatively lower than that of the first high-temperature side heat exchanger 4, by circulating water or the like in an outer peripheral portion of the first low-temperature side heat exchanger 5.
The first stack 3 a provided between the first high-temperature side heat exchanger 4 and the first low-temperature side heat exchanger 5 has a cylindrical shape in contact with the inside wall surface of the loop tube 2 and, as shown in FIG. 3, is formed of stack constituent elements 3 eL and 3 eH which are laminated together and which have different thermal conductivities. Those stack constituent elements 3 eL and 3 eH are formed using a material, such as a ceramic, a sintered metal, a metal mesh, or a metal nonwoven cloth, and the stack constituent element 3 eL having a low thermal conductivity, the stack constituent element 3 eH having a high thermal conductivity, and the stack constituent element 3 eL having a low thermal conductivity are disposed in that order from the first high-temperature side heat exchanger 4 side. Of the stack constituent elements 3 eL and 3 eH, the stack constituent element 3 eH having a high thermal conductivity is formed thicker than the stack constituent element 3 eL having a relatively low thermal conductivity, and by the structure described above, an area in which heat exchange can be performed with a working fluid is increased. Inside those stack constituent elements 3 eL and 3 eH, communication paths 30, which penetrate therethrough and which have a small diameter, are provided along the axial direction of the loop tube 2, as shown in FIG. 2. Those stack constituent elements 3 eL and 3 eH are laminated together in the top and down direction so as to be closely in contact with each other. When those stack constituent elements 3 eL and 3 eH are laminated together, and lamination is performed using an adhesive, an adhesive which overflows may block the communication paths 30 having a small diameter, provided in the stack constituent elements 3 eL and 3 eH. Accordingly, without using an adhesive, for example, the widths of the first high-temperature side heat exchanger 4 and the first low-temperature side heat exchanger 5 are set to be equal to a thickness width of the first stack 3 a, and the stack constituent elements 3 eL and 3 eH are provided between the first high-temperature side heat exchanger 4 and the first low-temperature side heat exchanger 5 by a holding force generated therebetween. Alternatively, when the first stack 3 a is provided in the erected straight tube portion 2 a of the loop tube 2, the stack constituent elements 3 eL and 3 eH are disposed so as to be closely in contact with each other by their own weights.
In addition, the stack constituent elements 3 eL and 3 eH are each formed, for example, from a single material so as to obtain a constant thermal conductivity in a plane surface direction. When the thermal conductivity is nonuniform in a plane surface direction, the difference in temperature between the inside and the outside of the first stack 3 a is generated, and thereby a nonuniform acoustic wave is generated; hence, the time for generating standing and traveling waves is delayed, and as a result, the heat exchange efficiency is degraded. Hence, the stack constituent elements 3 eL and 3 eH are each formed of a single material so as to obtain a constant thermal conductivity in a plane surface direction.
In addition, while the first high-temperature side heat exchangers 4 are disposed so as to face in the same direction, the first heat exchangers 300 formed as described above, that is, the first high-temperature side heat exchanger 4, the first low-temperature side heat exchanger 5, and the first stack 3 a, are provided in the vicinities of positions in the tube 2 at which the phase of change in acoustic particle velocity is the same as the phase of change in sound pressure. FIG. 4 is a view showing the tube 2 in an open state and shows the relationship of positions of the first heat exchanger 300 and the second heat exchanger 310 with positions at which the phase of change in acoustic particle velocity is the same as the phase of change in sound pressure. In general, properties of an acoustic wave are change, for example, by the difference in temperature between the first high-temperature side heat exchanger 4 and the first low-temperature side heat exchanger 5 and the pressure in the loop tube 2. Hence, an alterable mechanism for altering the position of the first heat exchanger 300 or a pressure adjustment mechanism for adjusting the wavelength of an acoustic wave by the pressure may be provided. As the alterable mechanism, for example as shown in FIG. 5, a mechanism may be conceived in which a part 20 of the loop tube, to which the first heat exchanger 300 is fitted, is formed to be slidably separated from a main frame of the loop tube 2, and the part 20 thus separated is allowed to slide therealong to adjust the position of the first heat exchanger 300. In addition, as the pressure adjustment mechanism, gas injection devices 9 a and 9 b, which will be described below, may also be conceived.
Next, operation of the first heat exchanger 300 thus formed will be described. First, when the first high-temperature side heat exchanger 4 of the first heat exchanger 300 is heated while the first low-temperature side heat exchanger 5 is cooled, heat is transported in the directions (axial direction) form the first high-temperature side heat exchanger 4 to the first low-temperature side heat exchanger 5. At this stage, heat at a temperature of approximately 600° C. obtained by heating in the first high-temperature side heat exchanger 4 is transported to the first low-temperature side heat exchanger 5 via the first stack 3 a; however, the heat transportation described above is inhibited by the stack constituent elements 3 eL having a low thermal conductivity, which are provided at end portions of the first stack 3 a. Hence, the heat is not transported to the first low-temperature side heat exchanger 5, and as a result, the difference in temperature between the first high-temperature side heat exchanger 4 and the first low-temperature side heat exchanger 5 can be increased. In addition, the heat at a temperature of approximately 600° C. obtained by heating in the first high-temperature side heat exchanger 4 is transported to the first low-temperature side heat exchanger 5 side via a working fluid present in the communication paths 30 of the first stack 3 a. As a result, the temperature gradient between the first high-temperature side heat exchanger 4 and the first low-temperature side heat exchanger 5 is formed, and by this temperature gradient generated in this working fluid, wobbling thereof is generated, so that an acoustic wave is generated while heat exchange is performed with the first stack 3 a. At this stage, since large heat exchange is performed with the stack constituent element 3 eH having a relatively high thermal conductivity, an acoustic wave is rapidly generated, and as a result, the heat exchange efficiency can be improved.
The acoustic wave thus generated is turned into the standing and traveling waves in the loop tube 2, is amplified by the first heat exchangers 300 located at a plurality of positions, and is then transported to the second heat exchanger 310 side as acoustic energy having a high sound pressure.
This second heat exchanger 310 is formed of the second high-temperature side heat exchanger 6, the second low-temperature side heat exchanger 7, and the second stack 3 b. The second high-temperature side heat exchanger 6 and the second low-temperature side heat exchanger 7 are both formed, for example, of a metal having a large heat capacity and are provided at two ends of the second stack 3 b, as is the case of the first stack 3 a, and in addition, inside the heat exchangers 6 and 7, there are provided communication paths 30 having a small diameter through which the standing and traveling waves are allowed to pass. This second high-temperature side heat exchanger 6 is set to a temperature, such as 15 to 16° C., by circulating water in an outer peripheral portion of the second high-temperature side heat exchanger 6. On the other hand, the second low-temperature side heat exchanger 7 has a heat output portion and is designed to cool an exterior object to be cooled. As the object to be cooled, for example, ambient air, a home electric appliance which generates heat, and a CPU of a personal computer may be mentioned. In addition, the second stack 3 b has the structure similar to that of the first stack 3 a. That is, three layers, a stack constituent element 3 eL having a low thermal conductivity, a stack constituent element 3 eH having a high thermal conductivity, and a stack constituent element 3 eL having a low thermal conductivity, are provided in that order from the second high-temperature side heat exchanger 6 side. In addition, the stack constituent element 3 eH having a high thermal conductivity is formed thicker than the stack constituent element 3 eL having a relatively low thermal conductivity. The second heat exchanger 310 formed as described above is provided in the vicinity of a position in the loop tube 2 at which the phase of change in acoustic particle velocity is the same as the phase of change in sound pressure, as shown in FIG. 4. In addition, as shown in FIG. 5, the second heat exchanger 310 is mounted in a mechanism in which a part 20 of the loop tube, to which the second heat exchanger 310 is fixed, is formed to be slidably separated from a main frame of the loop tube 2, and the part 20 thus separated is allowed to slide therealong to adjust the position of the second heat exchanger 310.
Inside this loop tube 2, an inert gas, such as helium or argon, is sealed. Besides the inert gases as mentioned above, a working fluid, such as nitrogen or air, may also be sealed. The pressure of the working fluid is set in the range of 0.01 to 5 MPa.
In the case in which the working fluid as described above is sealed, when helium or the like, having a small Prandtl number and also having a small specific gravity, is used, the time for generating an acoustic wave can be decreased. However, when the working fluid as described above is used, the acoustic velocity is increased, and as a result, heat exchange with stack inside walls cannot be well performed. On the other hand, when argon or the like, having a large Prandtl number and also having a large specific gravity, is used, since the viscosity is increased this time, and as a result, an acoustic wave cannot be rapidly generated. Hence, a mixed gas of helium and argon is preferably used. The mixed gas mentioned above is sealed as described below.
First, helium having a small Prandtl number and also having a small specific gravity is sealed in the loop tube 2, so that an acoustic wave is rapidly generated. Subsequently, in order to decrease the acoustic velocity of the generated acoustic wave, a gas, such as argon, having a large Prandtl number and also having a large specific gravity is injected. When this argon is mixed, as shown in FIG. 1, the helium gas injection device 9 a and the argon gas injection device 9 b are provided at a central portion of the connection tube portion 2 b formed at an upper side, and argon is injected therefrom. Accordingly, argon equally flows into the right-side and the left-side straight tube portions 2 a and are then mixed with helium present inside. The pressure of the mixed gas described above is set in the range of 0.01 to 5 MPa.
Next, an operation state of the thermoacoustic device 1 thus configured will be described.
First, helium is sealed in the loop tube 2 using the helium gas injection device 9 a, and in this state, water is circulated in an outer peripheral portion of the first low-temperature side heat exchanger 5 of the first heat exchanger 300 and that of the second high-temperature side heat exchanger 6 of the second heat exchanger 310. In the above state, the first high-temperature side heat exchanger 4 of the first heat exchanger 300 is heated to approximately 600° C., and in addition, the first low-temperature side heat exchanger 5 is set to approximately 15 to 16° C. As a result, heat is transported from the first high-temperature side heat exchanger 4 to the first low-temperature side heat exchanger 5. At this stage, the heat from the first high-temperature side heat exchanger 4 is transported to the first low-temperature side heat exchanger 5 via a member of the first stack 3 a; however, this heat transportation is inhibited by the presence of the stack constituent elements 3 eL having a low thermal conductivity. Hence, the difference in temperature between the first high-temperature side heat exchanger 4 and the first low-temperature side heat exchanger 5 can be increased. On the other hand, the heat (600° C.) of this first high-temperature side heat exchanger 4 is transported to the first low-temperature side heat exchanger 5 side by the working fluid present in the communication paths 30 of the first stack 3 a. Accordingly, the temperature gradient is formed between the first high-temperature side heat exchanger 4 and the first low-temperature side heat exchanger 5, and by this temperature gradient generated in this working fluid, wobbling thereof is generated, so that an acoustic wave is generated while heat exchange is performed with the first stack 3 a. At this stage, large heat exchange is performed with the stack constituent element 3 eH which is relatively thick and which has a high thermal conductivity, and the acoustic wave is rapidly generated, so that the heat exchange efficiency is improved. In addition, an acoustic wave can also be generated in the other first heat exchanger 300 as described above, and the acoustic wave can be amplified by the first heat exchangers 300. The acoustic wave thus generated is transported as acoustic energy by the standing and traveling waves to the second heat exchanger 310 side. This acoustic energy is transported based on the energy conservation law in a direction opposite to that of transportation of the thermal energy in the first heat exchanger 300 (from the first high-temperature side heat exchanger 4 to the first low-temperature side heat exchanger 5), that is, in a direction from the first low-temperature side heat exchanger 5 to the first high-temperature side heat exchanger 4.
Subsequently, immediately after the standing and traveling waves are generated, argon is injected from the argon gas injection device 9 b provided at the upper side of the connection tube portion 2 b so that the pressure is set at a predetermined value, thereby improving the heat exchange efficiency.
Next, at the second heat exchanger 310 side, based on the standing and traveling waves, the working fluid in the communication paths 30 of the second stack 3 b is expanded and contracted. Thermal energy which is heat-exchanged at this stage is transported in a direction opposite to the transportation direction of the acoustic energy, that is, in a direction from the second low-temperature side heat exchanger 7 to the second high-temperature side heat exchanger 6 side. At this stage, high heat is accumulated at the second high-temperature side heat exchanger 6 side, and low heat is accumulated at the second low-temperature side heat exchanger 7 side. Subsequently, by the difference in temperature described above, the high heat is transported to the second low-temperature side heat exchanger 7 side via the second stack 3 b; however, since the stack constituent elements 3 eL having a low thermal conductivity are provided at the second high-temperature side heat exchanger 6 and the second low-temperature side heat exchanger 7 sides, the heat transportation is inhibited. Accordingly, the temperature of the second low-temperature side heat exchanger 7 can be further decreased, and hence an object to be cooled can be further cooled.
In addition, acoustic energy which is not converted to thermal energy in this second heat exchanger 310 passes through the communication paths 30 thereof and is transported to the other second heat exchanger 310 located next thereto. Subsequently, the acoustic energy is converted to thermal energy in the manner as described above, and the second low-temperature side heat exchanger 7 of the other second heat exchanger 310 is cooled.
According to the embodiment described above, in the thermoacoustic device 1 including: the loop tube 2 in which a working fluid is sealed; the first stacks 3 a, each of which is provided in this loop tube 2 and between the first high-temperature side heat exchanger 4 and the first low-temperature side heat exchanger 5 and has the communication paths 30 along the heat transportation direction; and the second stacks 3 b, each of which is provided in this loop tube 2 and between the second high-temperature side heat exchanger 6 and the second low-temperature side heat exchanger 7 and has the communication paths 30 along the heat transportation direction, self-excited standing and traveling waves are generated by heating the first high-temperature side heat exchanger 4, and by the standing and traveling waves, the second low-temperature side heat exchanger 7 is cooled. In the thermoacoustic device 1 described above, since the first stacks 3 a each provided between the first high-temperature side heat exchanger 4 and the first low-temperature side heat exchanger 5 are provided at a plurality of positions, compared to the case in which an acoustic wave is input from the outside of the tube by a speaker, an acoustic wave is not reflected by the outside wall surface of the loop tube 2, and as a result, the acoustic wave can be reliably amplified in the tube. In addition, at this stage, since the self-excited acoustic wave is generated using heat, waste heat or the like can be used.
In addition, since the first stack 3 a provided between the first high-temperature side heat exchanger 4 and the first low-temperature side heat exchanger 5 is provided in the vicinity of a position in the loop tube 2 at which the phase of change in acoustic particle velocity is the same as the phase of change in sound pressure, standing and traveling waves having a larger sound pressure can be generated.
In addition, as is the case described above, at the second heat exchanger 310 side at which acoustic energy is converted to thermal energy, since the second stacks 3 b each provided between the second high-temperature side heat exchanger 6 and the second low-temperature side heat exchanger 7 are provided at a plurality of positions, the acoustic energy can be efficiently converted to the thermal energy by the second stacks 3 b.
In addition, as is the case described above, since the second stack 3 b provided between the second high-temperature side heat exchanger 6 and the second low-temperature side heat exchanger 7 is provided in the vicinity of a position at which the phase of change in acoustic particle velocity is the same as the phase of change in sound pressure, the conversion efficiency from acoustic energy to thermal energy can be improved, and an object to be cooled can be further cooled.
The present invention is not limited to the above embodiment, and various embodiments may be performed without departing from the spirit and the scope of the present invention.
For example, in the above embodiment, the thermoacoustic device 1 in which the second stack 3 b side is cooled by heating the first stack 3 a side is described by way of example; however, in a manner opposite thereto, by cooling the first stack 3 a side, the second stack 3 b side may be heated. An example of this thermoacoustic device 1 is shown in FIG. 6.
In FIG. 6, the same reference numerals as in the above embodiment indicate elements having the same structures as described above. A thermoacoustic device 1 b of this embodiment has a plurality of the first heat exchangers 300 and a plurality of the second heat exchangers 310 as is the first embodiment. In addition, in this embodiment, the first low-temperature side heat exchanger 5 is cooled to minus several tens of degrees or less, and at the same time, a nonfreezing solution is circulated in the first high-temperature side heat exchanger 4 and the second low-temperature side heat exchanger 7. As a result, by the law of the thermoacoustic effect, a self-excited acoustic wave is generated by the temperature gradient formed in the first stack 3 a. The traveling direction of acoustic energy of the standing and traveling waves is opposite to the transportation direction (direction from the first high-temperature side heat exchanger 4 to the first low-temperature side heat exchanger 5) of thermal energy in the first stack 3 a, and the acoustic energy is amplified in the other first heat exchanger 300. The acoustic energy by the standing and traveling waves is transported to the second stack 3 b side, and at the second stack 3 b side, a working fluid is repeatedly expanded and contracted by the pressure change and the volume change of the working fluid based on the standing and traveling waves. Subsequently, thermal energy generated at this stage is transported from the second low-temperature side heat exchanger 7 to the second high-temperature side heat exchanger 6 side, that is, in a direction opposite to the transportation direction of the acoustic energy. As described above, the second high-temperature side heat exchanger 6 is heated.
In addition, in another embodiment, when the first heat exchanger 300 and the second heat exchanger 310 are formed to have the same structure, the first heat exchanger 300 may also be used as the second heat exchanger 310, and vice versa. In this case, the first high-temperature side heat exchanger 4 and the first low-temperature side heat exchanger 5 provided in the first heat exchanger 300, and the second high-temperature side heat exchanger 6 and the second low-temperature side heat exchanger 7 provided in the second heat exchanger 310 are not necessarily set beforehand to be the high temperature side and the low temperature side, and when metal plates of the heat exchangers 4, 5, 6, and 7 are selected to be heated or cooled, the first high-temperature side heat exchanger 4, the first low-temperature side heat exchanger 5, the second high-temperature side heat exchanger 6, and the second low-temperature side heat exchanger 7 are set. Accordingly, when it is desired to increase the sound pressure, a thermoacoustic device 1 b having an increased number of the first heat exchangers 300, that is, a thermoacoustic device 1 b having three heat input portions, may be formed, as shown in FIG. 7, and when the sound pressure is sufficient, and a cooling temperature is not sufficient, a thermoacoustic device 1 c having an increased number of the second heat exchangers 310, that is, a thermoacoustic device 1 c having three cold-heat output portions, may be formed, as shown in FIG. 8.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a thermoacoustic device of one embodiment according to the present invention.

FIG. 2 is a view of a stack according to the above embodiment, when viewed along an axial direction.

FIG. 3 is a cross-sectional view of the stack according to the above embodiment.

FIG. 4 is a view showing the positional relationship of a standing wave with the first and the second heat exchangers according to the above embodiment.

FIG. 5 is a view showing an alterable mechanism for a first heat exchanger and a second heat exchanger according to the above embodiment.

FIG. 6 is a schematic view of a thermoacoustic device according to another embodiment.

FIG. 7 is a schematic view of a thermoacoustic device according to another embodiment.

FIG. 8 is a schematic view of a thermoacoustic device according to another embodiment.

REFERENCE NUMERALS

Accordingly,

1 . . . thermoacoustic device
2 . . . loop tube
2 a . . . straight tube portion
2 b . . . connection tube portion
3 a . . . first stack
3 b . . . second stack
30 . . . communication path
3 eL, 3 eH . . . stack constituent element
4 . . . first high-temperature side heat exchanger
5 . . . first low-temperature side heat exchanger
6 . . . second high-temperature side heat exchanger
7 . . . second low-temperature side heat exchanger
300 . . . first heat exchanger
310 . . . second heat exchanger

Claims

1. A thermoacoustic device comprising: a tube in which a working fluid is sealed; first stacks which each have a plurality of communication paths along a heat transportation direction and which are each provided between a first high-temperature side heat exchanger and a first low-temperature side heat exchanger, which are provided in the tube; and a second stack which has a plurality of communication paths along a heat transportation direction and which is provided between a second high-temperature side heat exchanger and a second low-temperature side heat exchanger, which are provided in the tube, in which self-excited standing and traveling waves are generated by heating the first high-temperature side heat exchanger, and the second low-temperature side heat exchanger is cooled by the standing and traveling waves, or in which self-excited standing and traveling waves are generated by cooling the first low-temperature side heat exchanger, and the second high-temperature side heat exchanger is heated by the standing and traveling waves, wherein the first stacks each provided between the first high-temperature side heat exchanger and the first low-temperature side heat exchanger are provided at a plurality of positions in the tube.

2. The thermoacoustic device according to claim 1, wherein the first stacks each provided between the first high-temperature side heat exchanger and the first low-temperature side heat exchanger are provided in the vicinities of positions at which the phase of change in acoustic particle velocity is the same as the phase of change in sound pressure.

3. A thermoacoustic device comprising: a tube in which a working fluid is sealed; an acoustic wave generator generating an acoustic wave provided in the tube; and second stacks which each have a plurality of communication paths along a heat transportation direction and which are each provided between a second high-temperature side heat exchanger and a second low-temperature side heat exchanger, which are provided in the tube, in which standing and traveling waves are generated in the tube by the acoustic wave generator so that the second low-temperature side heat exchanger is cooled or the second high-temperature side heat exchanger is heated by the standing and traveling waves, and heat obtained by the cooling or the heating is output outside, wherein the second stacks each provided between the second high-temperature side heat exchanger and the second low-temperature side heat exchanger are provided at a plurality of positions in the tube.

4. The thermoacoustic device according to claim 3, wherein the second stacks each provided between the second high-temperature side heat exchanger and the second low-temperature side heat exchanger are provided in the vicinities of positions at which the phase of change in acoustic particle velocity is the same as the phase of change in sound pressure.

5. A thermoacoustic device comprising: a tube in which a working fluid is sealed; first stacks which each have a plurality of communication paths along a heat transportation direction and which are each provided between a first high-temperature side heat exchanger and a first low-temperature side heat exchanger, which are provided in the tube; and second stacks which each have a plurality of communication paths along a heat transportation direction and which are each provided between a second high-temperature side heat exchanger and a second low-temperature side heat exchanger, which are provided in the tube, in which self-excited standing and traveling waves are generated by heating the first high-temperature side heat exchanger, and the second low-temperature side heat exchanger is cooled by the standing and traveling waves, or in which self-excited standing and traveling waves are generated by cooling the first low-temperature side heat exchanger, and the second high-temperature side heat exchanger is heated by the standing and traveling waves, wherein the first stacks each provided between the first high-temperature side heat exchanger and the first low-temperature side heat exchanger have the same structure as the structure of the second stacks each provided between the second high-temperature side heat exchanger and the second low-temperature side heat exchanger, and the first stacks and the second stacks, which have the same structure, are provided at a plurality of positions in the tube.