WO2015115005A1 - 熱・音波変換部品及び熱・音波変換器 - Google Patents
熱・音波変換部品及び熱・音波変換器 Download PDFInfo
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- WO2015115005A1 WO2015115005A1 PCT/JP2014/084209 JP2014084209W WO2015115005A1 WO 2015115005 A1 WO2015115005 A1 WO 2015115005A1 JP 2014084209 W JP2014084209 W JP 2014084209W WO 2015115005 A1 WO2015115005 A1 WO 2015115005A1
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- heat
- conversion component
- sonic
- fluid
- sonic wave
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
- F25B9/14—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the cycle used, e.g. Stirling cycle
- F25B9/145—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the cycle used, e.g. Stirling cycle pulse-tube cycle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/14—Compression machines, plants or systems characterised by the cycle used
- F25B2309/1402—Pulse-tube cycles with acoustic driver
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/14—Compression machines, plants or systems characterised by the cycle used
- F25B2309/1404—Pulse-tube cycles with loudspeaker driven acoustic driver
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/14—Compression machines, plants or systems characterised by the cycle used
- F25B2309/1405—Pulse-tube cycles with travelling waves
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/14—Compression machines, plants or systems characterised by the cycle used
- F25B2309/1407—Pulse-tube cycles with pulse tube having in-line geometrical arrangements
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/14—Compression machines, plants or systems characterised by the cycle used
- F25B2309/1415—Pulse-tube cycles characterised by regenerator details
Definitions
- the present invention relates to a heat / sonic wave conversion component and heat which convert sound wave energy into heat energy or heat energy into sound energy between a fluid in which sound waves propagate and a wall in contact with the fluid.
- -It relates to a sonic transducer.
- a thermal / acoustic system is a system that uses thermal / sound conversion technology that converts energy between sound wave energy (sound pressure energy) and heat energy. Use the expansion process. Specifically, in the technique, the position where the fluid element performs the compression process (position in the propagation direction of the sound wave) and the position where the fluid element performs the expansion process (position in the propagation direction of the sound wave) Use different things by sound waves).
- a thermal / acoustic system using thermal / sound conversion technology in a device with sufficient contact frequency between a solid and a gas, while heating one end of the solid, part of the heat is converted into acoustic energy, A system that supplies this sound wave to a power generation device can be mentioned.
- the temperature gradient formed in the solid in the apparatus is a key, but the efficiency of energy conversion into sound waves is not sufficient in this apparatus. This is due to the fact that the heat / sonic wave conversion component having the role of converting heat energy into sound pressure energy did not have a preferable structure and physical properties.
- thermoacoustic device capable of self-excited vibration with a low temperature difference even at a higher frequency
- the stack for thermoacoustic devices has a plurality of through holes and is made of a material having a thermal conductivity of less than 10 [W / m ⁇ K]. This allows the temperature gradient to be scaled (proportionally reduced) even if the stack length is shortened, so that the temperature of the high-temperature side heat exchanger required to achieve the critical temperature gradient can be lowered. it can.
- the temperature of the high-temperature side heat exchanger required to achieve the critical temperature gradient can be efficiently lowered.
- the efficiency of energy exchange between sound waves and heat is low.
- the present invention provides a heat / sonic wave conversion component and a heat / sonic wave converter capable of efficiently performing energy conversion between sound waves and heat between a fluid in which sound waves propagate and a wall in contact with the fluid. For the purpose.
- This technology includes the following forms.
- Form 1 It is a heat / sonic wave conversion component that converts sound wave energy into heat energy or heat energy into sound wave energy between a fluid in which sound waves propagate and a wall in contact with the fluid.
- the heat / sonic wave conversion component is formed around each of a plurality of through holes configured to extend in one direction and pass through the heat / sonic wave conversion component to form a propagation path of sound waves.
- a wall configured to transfer heat to and from the fluid.
- the through hole includes a through hole having a hydraulic diameter of 0.4 mm or less, and an opening ratio of the plurality of through holes in the thermal / sonic wave conversion component is 60% or more.
- the thermal conductivity of the heat / sonic conversion component in the fluid atmosphere is 0.4 [W / m / K] or less, and the heat capacity at 400 ° C. of the heat / sonic conversion component in the fluid atmosphere is 0.5. Greater than [J / cc / K].
- Form 2 The thermal / sonic conversion component according to the first aspect, wherein the thermal / sonic conversion component has a thermal expansion coefficient of 6 [ppm / K] or less along the extending direction of the through hole between 20 ° C. and 800 ° C.
- Form 4 In Form 1 or Form 2, ribs protruding toward the inside of the cross-section of each through hole are provided on the inner wall surface of the wall in contact with each through hole, along the extending direction of the through hole.
- Forms 1 to 5 are formed of a long structure in which a partition wall that defines a through-hole serving as a fluid flow path extending from one end surface to the other end surface is formed of the same material as an integral structure. 5.
- the heat / sonic wave conversion component according to any one of 5 above.
- the heat / sonic wave conversion component is made of a material containing 80% by mass or more of a component selected from cordierite, mullite, aluminum titanate, alumina, zirconia, silicon nitride, silicon carbide, and synthetic resin.
- the heat / sonic wave conversion component according to any one of forms 1 to 7.
- a heat / sonic transducer comprising a heat / sonic conversion component that amplifies the sonic energy of a fluid using heat of a wall in contact with the fluid, The heat / sonic wave conversion component; A conduit configured to guide the sound wave to the through hole so as to form a propagation path of the sound wave of the fluid and to propagate the sound wave along the extending direction of the through hole of the thermal / sonic wave conversion component
- a pair of heat exchanging parts provided at both ends of the heat / sonic wave conversion component and configured to form a temperature gradient between the both ends of the heat / sonic wave conversion component along the extending direction.
- the conduit is configured to output a sound wave obtained by amplifying sound wave energy using the temperature gradient, and a transducer configured to convert the amplified sound wave energy into another energy using the output sound wave.
- a heat-sonic transducer having an output end connected to the heat-sound converter.
- a thermal / sonic transducer comprising a thermal / sonic transducer component that creates a temperature gradient on the wall in contact with the fluid using the acoustic energy of the fluid, The heat / sonic wave conversion component; A conduit configured to guide the sound wave to the through hole so as to form a propagation path of the sound wave of the fluid and to propagate the sound wave along the extending direction of the through hole of the thermal / sonic wave conversion component
- a heat exchanging section configured to have a constant temperature provided at a first end of both ends of the heat / sonic wave conversion component;
- a heat output unit provided at a second end different from the first end of the heat / sonic wave conversion component, and on the heat / sonic wave conversion component with the heat exchange unit by the propagation of the sound wave
- a heat / sonic converter comprising: a heat output unit configured to extract a temperature having a temperature difference from the temperature of the heat exchange unit from a formed temperature gradient.
- heat / sonic wave conversion component and the heat / sonic wave converter of the above-described aspect energy conversion of sound waves and heat can be efficiently performed between a fluid in which sound waves propagate and a wall in contact with the fluid.
- FIG. 1 It is a figure which shows an example of a structure of the heat / sonic wave converter of this embodiment to which the heat / sonic wave conversion component of this embodiment is applied. It is a figure which shows an example of a structure of the heat / sonic wave converter which is embodiment different from the heat / sonic wave converter shown in FIG. It is an external appearance perspective view of an example of the heat / sonic wave conversion component of this embodiment.
- (A), (b) is a figure explaining the conversion between the sound pressure energy and heat energy in a heat / sonic wave conversion component. It is a figure which shows an example of the cross-sectional shape of the through-hole with which the thermal / sonic wave conversion component in this embodiment is equipped.
- FIG. 1 is a diagram illustrating an example of a configuration of a heat / sonic transducer 10 of the present embodiment to which the heat / sonic wave conversion component of the present embodiment is applied.
- a heat / sonic converter 10 shown in FIG. 1 is an apparatus that increases sound pressure energy of sound waves propagating in a conduit and supplies the increased sound pressure energy to a converter 40 that converts the sound energy into other energy.
- Examples of the conversion device 40 include a generator that converts sonic energy into electrical energy and a device that converts sonic energy into thermal energy.
- an electromotive force is generated by generating electromagnetic induction by vibrating a coil, a magnet, or the like, which is a power generation element, with sound waves.
- a conversion device that converts sonic energy into thermal energy for example, a cooling medium cooled by absorption of heat by sound waves is taken out and used as a cooling device.
- the heat / sonic transducer 10 is a device that increases the sound pressure energy of the sound wave Sw input to the heat / sonic wave conversion component with the heat / sonic wave conversion component and outputs a sound wave having increased sound pressure energy.
- the heat / sonic converter 10 increases the sound wave Sw having a small sound pressure energy by the heat / sonic wave conversion component, circulates the sound wave having the increased sound pressure energy, and further inputs the sound wave to the heat / sonic wave conversion component. By increasing the pressure energy, it is possible to output a sound wave having a very large sound pressure energy.
- the heat / sonic converter 10 uses the circulation to convert a part of the noise component of the sound in the conduit 14 to the heat / sonic converter. It is selectively amplified as a sound wave having a frequency determined by 10 shape dimensions and the like. Thereby, the sound wave Sw having the small sound pressure energy is formed by self-excitation.
- the heat / sonic converter 10 mainly includes a heat / sonic conversion component 12, a conduit 14, and heat exchange units 15 and 23.
- the heat / sonic wave conversion component 12 is a component that converts the energy of sound waves and heat between the fluid through which the sound wave Sw propagates and the wall in contact with the fluid. As will be described later, the propagation path of the sound wave Sw.
- the heat / sonic wave conversion component 12 is made of, for example, metal, ceramic, or resin.
- the conduit 14 includes a fluid in the conduit 14, forms a propagation path for the sound wave Sw of the fluid, and transmits the sound wave Sw along the extending direction of the through hole of the thermal / sonic conversion component 12. Sw is guided to the through hole.
- the conduit 14 is, for example, a metal tube.
- a gas is preferably used as a fluid, and for example, hydrogen or helium gas is used.
- the gas is sealed in the conduit 14 after being adjusted to a predetermined pressure in the range of, for example, several atmospheres to several tens of atmospheres, more specifically 21 to 40 atmospheres.
- the conduit 14 is configured to form a circulation path 36 through which the sound wave Sw circulates through the heat / sonic wave conversion component 12 as indicated by a broken line in FIG.
- the conduit 14 has an output end 14a connected to a converter 40 that converts the sound wave energy obtained by amplifying the sound wave energy into energy other than sound pressure energy.
- a converter 40 that converts the sound wave energy obtained by amplifying the sound wave energy into energy other than sound pressure energy.
- the heat exchanging unit 15 is a low-temperature unit that is provided at one end of the heat / sonic wave conversion component 12 and lowers the end of the heat / sonic wave conversion component 12.
- the heat exchange unit 15 is referred to as a low temperature unit 15 with the same reference numeral.
- the heat exchanging unit 23 is a high-temperature unit that is provided at the other end of the heat / sonic wave conversion component 12 and raises the end of the heat / sonic wave conversion component 12.
- the heat exchange unit 23 is referred to as the high temperature unit 23 with the same reference numeral.
- the low temperature part 15 and the high temperature part 23 are along the wall surface of the through-hole provided in the heat / sonic wave conversion component 12 between both ends of the heat / sonic wave conversion component 12, that is, in the extending direction of the through hole.
- a temperature gradient is formed along.
- the low temperature section 15 is provided between a supply pipe 16 for supplying a medium such as low temperature gas or liquid to the low temperature section 15, a discharge pipe 18 for discharging the medium from the low temperature section 15, and between the supply pipe 16 and the discharge pipe 18.
- the supply pipe 16 is connected to a low heat source (not shown).
- the annular pipe 20 is connected to the supply pipe 16 and the discharge pipe 18.
- the annular tube 20 is in contact with a metal member 21 having a high thermal conductivity, and the metal member 21 is in contact with the heat / sonic wave conversion component 12. Therefore, heat is exchanged with the end of the heat / sonic wave conversion component 12 through the metal member 21, and heat flows from the end of the heat / sonic wave conversion component 12 to the low temperature portion 15, thereby the metal of the heat / sonic wave conversion component 12.
- the end in contact with the member 21 is cooled.
- the low temperature part 15 is provided with cooling fins 22 for cooling the fluid in the conduit 14. Since the cooling fins 22 are connected to the annular pipe 20, the cooling fins 22 absorb the heat of the fluid located in the low temperature part 15 and reduce the temperature of the fluid.
- the high temperature section 23 includes a supply pipe 24 that supplies a medium such as a high-temperature gas or liquid to the high temperature section 23, a discharge pipe 26 that discharges the medium from the high temperature section 23, and a gap between the supply pipe 24 and the discharge pipe 26. And an annular tube 28 that annularly surrounds the propagation path of the sound wave Sw.
- the supply pipe 24 is connected to a high heat source (not shown).
- the annular tube 28 is connected to the supply tube 24 and the discharge tube 26.
- the annular tube 28 is in contact with a metal member 29 having a high thermal conductivity, and the metal member 29 is in contact with the heat / sonic wave conversion component 12.
- the end of the heat / sonic wave conversion component 12 exchanges heat with the high temperature portion 23 via the metal member 29, and heat flows from the high temperature portion 23 to the end of the heat / sonic wave conversion component 12 to be heated.
- the high-temperature portion 23 is provided with heating fins 30 for heating the fluid in the conduit 14. Since the heating fin 30 is connected to the annular tube 28, heat is supplied to the fluid located in the high temperature portion 23, and the temperature of the fluid located in the heating fin 30 is increased.
- An interference member 32 that suppresses the heat transfer of the heat / sonic wave conversion component 12 is provided on the outer periphery of the heat / sonic wave conversion component 12.
- a casing 34 is provided on the outer periphery of the interference member 32 via a gap. Therefore, the heat / sonic wave conversion component 12 can maintain the temperature gradient formed by the low temperature member 15 and the high temperature member 23. Details of the operation of the heat / sonic wave conversion component 12 in the heat / sonic wave converter 10 will be described later.
- FIG. 2 is a diagram illustrating an example of a configuration of a heat / sonic transducer 110 that is an embodiment different from the heat / sonic transducer 10.
- the thermal / sonic converter 110 shown in FIG. 2 is a device that converts sound pressure energy of a sound wave propagating in a conduit into thermal energy.
- the heat / sonic converter 110 mainly includes a heat / sonic conversion component 112, a conduit 114, a heat conversion unit 123, and a heat output unit 115.
- the heat output unit 115 is a part that extracts a temperature having a temperature difference from the temperature of the heat exchange unit 123, that is, a part that outputs a cooled cooling medium (gas or liquid).
- the heat / sound converter 110 is connected to the above-described heat / sound converter 10 that outputs sound waves via a conduit 114.
- the heat / sonic wave converter 110 of the present embodiment is configured to be connected to the heat / sonic wave converter 10 described above, but may be an apparatus that generates other sound waves.
- the conduit 114 and the heat conversion section 123 have the same configuration as the conduit 14 and the heat conversion section 23 shown in FIG.
- the conduit 114 includes a fluid in the conduit 114, forms a propagation path of the sound wave of the fluid, and heats the sound wave so that the sound wave propagates along the extending direction of the through hole of the heat / sonic wave conversion component 112. Lead to the through hole of the sound wave conversion component 112.
- the conduit 114 is, for example, a metal tube.
- a gas is used as a fluid, for example, hydrogen or helium gas. The gas is adjusted to a predetermined pressure of, for example, several atmospheres to several tens of atmospheres and enclosed in the conduit 114.
- the conduit 114 is configured to form a circulation path 136 through which sound waves circulate through the heat / sonic wave conversion component 112.
- the conduit 114 forms the circulation path 136, but the conduit 114 does not necessarily form the circulation path.
- the heat exchanging unit 123 includes a supply pipe 124 that supplies a medium such as a gas or a liquid having a constant temperature to the heat exchanging unit 123, a discharge pipe 126 that discharges the medium from the heat conversion unit 123, a supply pipe 124, and a discharge pipe. 126, and an annular tube 128 that annularly surrounds the sound wave propagation path.
- the supply pipe 124 is connected to a heat source having a constant temperature (not shown).
- the annular pipe 128 is connected to the supply pipe 124 and the discharge pipe 126.
- the annular tube 128 is in contact with a metal member 129 having a high thermal conductivity, and the metal member 129 is in contact with the heat / sonic wave conversion component 12.
- the end of the heat / sonic wave conversion component 12 exchanges heat with the heat exchange unit 123 via the metal member 129, and the end of the heat / sonic wave conversion component 112 becomes the same temperature as the temperature of the heat exchange unit 123.
- the heat conversion unit 123 is provided with fins 130 for keeping the fluid in the conduit 114 at a constant temperature. Since the fin 130 is connected to the annular pipe 128, heat is supplied to the fluid located in the heat conversion unit 123, and the temperature of the fluid located in the fin 130 is made constant.
- An interference member 132 that suppresses heat transfer of the heat / sonic wave conversion component 112 is provided on the outer periphery of the wave / heat conversion component 112.
- a casing 134 is provided on the outer periphery of the interference member 132 via a gap. Therefore, the heat / sonic wave conversion component 112 can maintain a temperature gradient formed by the sound wave. Details of the operation of the heat / sonic wave conversion component 112 that converts sound waves and heat in the heat / sonic wave converter 110 will be described later.
- the heat output unit 115 is provided at one end of the heat / sonic wave conversion component 112.
- the heat output unit 115 extracts a temperature having a temperature difference from the temperature of the heat exchange unit 123 from the temperature gradient formed on the heat / sonic wave conversion component 112 by the propagation of sound waves.
- the temperature gradient is a temperature gradient formed between a certain temperature of the heat conversion unit 123.
- the heat output section 115 is provided between a supply pipe 116 for supplying a medium such as gas or liquid, a discharge pipe 118 for discharging the medium from the heat output section 115, and between the supply pipe 116 and the discharge pipe 118.
- an annular tube 120 surrounding the propagation path in an annular shape.
- the annular pipe 120 is connected to the supply pipe 116 and the discharge pipe 118.
- the annular tube 120 is in contact with a metal member 121 having a high thermal conductivity, and the metal member 121 is in contact with the heat / sonic wave conversion component 112. Accordingly, the annular pipe 120 is annularly exchanged with the end of the heat / sonic wave conversion component 112 through the metal member 121 and heat flows from the heat output unit 115 to the end of the heat / sonic wave conversion component 112.
- Tube 120 is cooled. For this reason, the medium flowing through the annular tube 12 becomes a cooling medium, and the cooling medium is output. Such a cooling medium is used for a cooling device.
- the heat output unit 115 is provided with cooling fins 122 for cooling the fluid in the conduit 114. Since the cooling fins 122 are connected to the annular pipe 120, the cooling fins 122 absorb the heat of the fluid located in the heat output unit 115 and reduce the temperature.
- the heat / sonic wave converter 110 converts sound pressure energy of sound waves into heat energy, and this conversion is performed by the heat / sonic wave conversion component 112.
- the operation of the heat / sonic wave conversion component 12 and the heat / sonic wave conversion component 112 that is, the conversion of sound pressure energy and heat energy will be described.
- FIG. 3 is an external perspective view of the heat / sonic wave conversion component 12.
- the heat / sonic wave conversion component 12 is provided with a plurality of through holes 12a configured to extend in one direction and penetrate the heat / sonic wave conversion component 12 to form a propagation path of the sound wave.
- the thermal / sonic wave conversion component 12 includes a wall 12b formed around each of the plurality of through holes 12a and extending in the extending direction of the through hole 12a (X direction in FIG. 3).
- the wall 12b is configured to exchange heat with a fluid as will be described later.
- the wall 12b is simplified by a line.
- the heat / sonic wave conversion component 12 is constituted by a single body.
- the integrated object does not include a structure in which a plurality of structures such as pipes are bundled, and refers to an integrated object composed of one structure, that is, an integrated structure.
- the heat / sonic wave conversion component 12 is formed by forming a partition wall that defines a through hole serving as a fluid flow path extending from one end surface to the other end surface with the same material, that is, as an integral structure.
- the structure is made of a scale-like structure because the through-hole 12a having a uniform cross-sectional shape can be formed and the wall 12b around the through-hole 12a can be thinned. More preferably, the long structure is made of the same material and a homogeneous material.
- the heat / sonic wave conversion component 12 is, for example, an extrusion-molded product obtained by extruding a material so that the extending direction of the through hole 12a is the extrusion direction.
- the length in the X direction of the heat / sonic wave conversion component 12 is set according to the wavelength of the sound wave formed in the conduit 14 or the longitudinal displacement due to the vibration of the fluid, and is preferably 10 mm or more and less than 500 mm, for example.
- the frequency of the sound wave is not particularly limited, but is a frequency in the range of 50 Hz to 200 kHz, for example.
- FIGS. 4A and 4B are diagrams for explaining the conversion between the sound pressure energy and the heat energy in the heat / sonic wave conversion component 12 and the transfer of heat between the wall 12b and the fluid.
- a fluid is a medium that propagates sound waves and vibrates longitudinally.
- a description will be given using a fluid element that defines a very small region of the fluid.
- the fluid element in the fluid When the sound wave is a traveling wave and the sound wave propagates in the fluid, the fluid element in the fluid repeatedly undergoes compression and expansion.
- the position in the X direction along the wall 12b of the fluid element to be compressed and the position in the X direction along the wall 12b of the fluid element to be compressed differ depending on the longitudinal vibration of the fluid.
- FIG. 4A one cycle of compression and expansion in a traveling wave in which the sound pressure of the sound wave and the phase of the fluctuation of the fluid element are shifted by a quarter cycle is shown.
- One end (position I) of the wall 12b is heated from the outside, one end (position II) is cooled from the outside, and the wall 12b has a temperature gradient as shown in FIG.
- the fluid element receives heat from the wall 12b during the expansion process, and the wall 12b can remove heat from the fluid element during the compression process, thereby increasing the compression and expansion of the fluid element. That is, the heat / sonic wave conversion component 12 can increase the sound pressure energy of the sound wave propagating to the heat / sonic wave conversion component 12 by forming a temperature gradient in the wall 12b in advance.
- the heat / sonic wave conversion component 112 can extract a low temperature or a high temperature using a temperature gradient formed by the sound pressure energy of the sound wave propagating to the heat / sonic wave conversion component 112. For example, a temperature gradient is formed on the wall 12b between the position I and the position II by sound waves.
- the temperature gradient is adjusted to a certain temperature.
- a temperature with a temperature difference can be taken out. That is, the heat / sonic wave conversion component 112 can extract a low temperature or a high temperature using a temperature gradient formed by the sound pressure energy of the sound wave propagating to the heat / sonic wave conversion component 112.
- traveling waves have been described as examples. In the traveling wave, the cycle of fluid compression and expansion and the cycle of fluctuation of the fluid element are shifted by a quarter period. For this reason, energy conversion between sound waves and heat is realized.
- the conversion can be realized by setting the frequency of the sound wave in order to use the conversion delay that occurs when energy conversion is performed between the fluid and the wall.
- the wavelength of the standing wave is determined according to the length of the conduits 14 and 114 or the circulation paths 36 and 136, and the frequency of the sound wave is determined by this wavelength. , 136 is adjusted.
- the delay in energy conversion is determined by the thermal conductivity of the fluid, the density of the fluid, the specific heat of the constant pressure of the fluid, and the size of the through hole.
- the through holes for transmitting sound waves of the heat / sonic wave conversion component 12 and the heat / sonic wave conversion component 112 of the present embodiment include a through hole having a hydraulic diameter of 0.4 mm or less.
- the aperture ratio of the plurality of through holes in the acoustic wave conversion component 112 is 60% or more.
- the number of through holes having a hydraulic diameter of 0.4 mm or less is preferably 80% or more of the total number of through holes that transmit sound waves in the sound wave conversion component 12 and the heat / sonic wave conversion component 112, and the heat / sonic wave conversion component. It is most preferable that the hydraulic diameters of the through holes for propagating the sound waves of 12 and the heat / sonic wave conversion component 112 are 0.4 mm or less. Furthermore, the thermal conductivity of the heat / sonic wave conversion component 12 and the heat / sonic wave conversion component 112 in the fluid atmosphere is 0.4 [W / m / K] or less at 25 ° C., and the heat / sonic wave in the fluid atmosphere. The heat capacities at 400 ° C. of the conversion component 12 and the heat / sonic conversion component 112 are adjusted to be larger than 0.5 [J / cc / K] (the heat capacity per cc of the heat / sonic conversion component 112).
- the reason why the hydraulic diameter of the through hole is 0.4 mm or less is that the upper limit of the thickness of the fluid that contributes when energy is converted between the wall around the through hole and the fluid is 0.2 mm. For this reason, in order to improve the energy conversion efficiency, the hydraulic diameter of the through hole is set to 0.4 mm or less.
- the hydraulic diameter is the cross-sectional shape of the through-hole when cut in a direction perpendicular to the extending direction of the through-hole, and the circumference of the outer periphery of the cross-sectional shape is L [mm], and the cross-sectional area is S [mm 2 ]. Is a dimension represented by 4 ⁇ S / L [mm].
- the hydraulic diameter of the through hole is preferably 0.2 to 0.3 mm.
- the hydraulic diameter of the through hole is smaller than 0.1 mm, it is not preferable because the frictional resistance increases between the fluid and the wall of the through hole. In this respect, it is preferable that the hydraulic diameter of the through hole is 0.1 mm or more.
- the reason why the opening ratio of the through holes of the heat / sonic wave conversion component 12 and the heat / sonic wave conversion component 112 is 60% or more is to provide more places for energy conversion between the fluid and the wall through which the sound wave propagates. It is.
- the aperture ratio is the ratio of the sum of the cross-sectional areas of the through holes to the area surrounded by the outer periphery of the cross-sectional shape cut in the direction orthogonal to the X direction of the heat / sonic wave conversion component 12 and the heat / sonic wave conversion component 112.
- the aperture ratio is preferably 70% or more, and more preferably 80% or more.
- the upper limit of the aperture ratio is 93%, for example.
- the heat / sonic wave conversion component 12 and the heat / sonic wave conversion component 112 have a honeycomb structure in which the wall 12b can be thinned.
- An example of the honeycomb structure is an extruded product of a honeycomb structure in which a material is extruded so that the extending direction of the through holes 12a is the extrusion direction.
- the aperture ratio is obtained by photographing the cross section (polished surface) of the heat / sonic wave conversion component 12 and the heat / sonic wave conversion component 112 perpendicular to the through-hole with a microscope, and from the photographed image of the cross section at this time, the material partial area S1 And void portion area S2 is obtained, and S2 / (S1 + S2) is obtained using S1 and S2.
- the thermal conductivity is the thermal conductivity in a fluid atmosphere.
- thermal conductivity in the case of a ceramic porous body, it is not the thermal conductivity in the material, but in addition to the material, voids such as pores and through holes (voids containing fluid) ).
- Such thermal conductivity is adjusted by adjusting the cell density, the porosity, or the opening ratio of the above-mentioned through-holes in addition to the thermal conductivity which is a characteristic of the material, so that the thermal conductivity at 25 ° C. is 0.4. [W / m / K] or less.
- the thermal conductivity is preferably 0.3 [W / m / K] or less from the viewpoint of making the temperature gradient steeper.
- the thermal conductivity is more preferably 0.2 [W / m / K] or less.
- the lower limit of the thermal conductivity is, for example, 0.005 [W / m / K].
- the thermal conductivity is obtained by the following temperature gradient method (steady method). That is, a plate-like test sample to be measured for thermal conductivity is sandwiched between spacers with known thermal conductivity, and one side is heated to a temperature of 30 ° C. to 200 ° C., and the opposite side is set to 20 ° C. to 25 ° C. Cooling to a certain temperature provides a steady state temperature gradient in the thickness direction of the test sample. The heat flow that propagates at this time is obtained from the temperature gradient in the spacer, and the heat conductivity is calculated by dividing the heat flow by the temperature difference.
- steady method steady method
- the heat / sonic wave conversion part 12 or the heat / sonic wave conversion part 112 having a diameter of 30 mm and a bowl thickness of 30 mm is used as a test sample, and a spacer made of stainless steel or copper having a diameter of 30 mm and a bowl length of 150 mm is used.
- a spacer made of stainless steel or copper having a diameter of 30 mm and a bowl length of 150 mm is used.
- the density of the through holes is 1600 cpsi (number of through holes per square inch (number of cells)) or more, and preferably 9000 cpsi or less.
- the porosity of the material constituting the heat / sonic wave conversion component 12 and the heat / sonic wave conversion component 112 is preferably 35% or less, and more preferably 27% or less. Considering the range that can be substantially manufactured, it is preferably 0.5% to 35%. It is preferable that the heat capacity of the structure at 400 ° C.
- the temperature gradient in the heat / sonic wave conversion component 12 and the heat / sonic wave conversion component 112 in the fluid atmosphere is larger than 0.5 [J / cc / K].
- the temperature gradient can be stably maintained while the temperature of the wall varies due to the transfer of heat between the wall and the fluid.
- the heat capacity of the structure is 0.5 [J / cc / K] or less, the temperature of the wall rapidly decreases or rapidly increases due to the transfer of heat between the wall and the fluid. Is not preferable for maintaining a stable state.
- the heat capacity of the structure at 400 ° C.
- the heat capacities of the heat / sonic wave conversion component 12 and the heat / sonic wave conversion component 112 are obtained as follows. First, the heat capacity per unit mass of the material itself is obtained. Specifically, the heat capacity per unit mass of the material itself is determined from the relationship between the input heat and the temperature rise using an adiabatic calorimeter, using a material obtained by pulverizing the above material as a sample.
- the heat capacity per unit volume (1 cc) as a structure is obtained by multiplying the mass per volume of the material before grinding used as a sample.
- the thermal expansion coefficient along the extending direction of the through hole between 20 ° C. and 800 ° C. in the heat / sonic conversion component 12 and the heat / sonic conversion component 112 is preferably 6 [ppm / K] or less. Thereby, the thermal stress of the heat / sonic wave conversion component 12 and the heat / sonic wave conversion component 112 can be reduced, and the breakage due to thermal strain can be suppressed.
- the thermal expansion coefficient along the extending direction of the through hole between 20 ° C. and 800 ° C.
- the coefficient of thermal expansion along the extending direction of the through hole is determined in accordance with “Measurement method of thermal expansion by thermomechanical analysis of fine ceramics” described in JIS R1618-2002.
- the heat / sonic wave conversion component 12 and the heat / sonic wave conversion component 112 are mainly composed of a component selected from cordierite, mullite, aluminum titanate, alumina, zirconia, silicon nitride, silicon carbide, and synthetic resin.
- a material is used.
- a main component means that the content rate of the said material is 80 mass% or more, and a content rate may be 100 mass%.
- Cordierite, mullite, aluminum titanate, alumina, zirconia, silicon nitride, and silicon carbide are ceramics, and a ceramic porous body is preferably used.
- a polyimide is illustrated.
- the cross-sectional shape of the through holes provided in the heat / sonic wave conversion component 12 and the heat / sonic wave conversion component 112 is, for example, a polygonal shape including a triangle, a quadrangle, and a hexagon. Or it is the shape which combined this polygonal shape. Also, a through hole 12a having a cross-sectional shape as shown in FIG. 5 can be used.
- FIG. 5 is a diagram illustrating an example of a cross-sectional shape of the through hole 12 a provided in the heat / sonic wave conversion component 12 and the heat / sonic wave conversion component 112.
- a rib 12c protruding toward the inner side of the cross section of the through hole 12a is provided along the extending direction of the through hole 12a.
- the length of the heat / sonic transducer 10 in the X direction was 30 mm, and helium gas was sealed in the conduit 14 to 10 atm.
- the temperature of the low temperature part 15 and the high temperature part 23 was determined so that the end on the low temperature part 15 side of the heat / sonic wave conversion component 12 was 100 ° C. and the end on the high temperature part 23 side was 450 ° C.
- Example 1 to 10 and Comparative Examples 1 to 12 the coefficient of thermal expansion along the extending direction of the through hole between 20 ° C. and 800 ° C. was 1 [ppm / K].
- the hydraulic diameters of Examples 11 and 12 and Comparative Examples 13 and 14 were each 0.3 [mm], the aperture ratio was 80 [%], and the above-mentioned thermal expansion coefficient was changed variously by changing the material.
- the thermal endurance pass / fail was examined based on the presence or absence of breakage of the heat / sonic wave conversion component when continuously used for 5 hours under the conditions for measuring the conversion efficiency. It was.
- Tables 1 and 2 below show the specifications and the results of energy conversion efficiency at that time.
- the hydraulic diameter, aperture ratio, thermal conductivity, heat capacity at 400 ° C., and thermal expansion coefficient between 20 ° C. and 800 ° C. in Tables 1 and 2 are the parameters already described.
- the heat capacity is preferably 0.61 [J / cc / K] or more.
- the hydraulic diameter of the through hole of the heat / sonic wave conversion component 12 is set to 0.4 mm or less
- the opening ratio of the through hole in the heat / sonic wave conversion component 12 is set to 60% or more
- the heat / sonic wave conversion component 12 in the fluid atmosphere is set to be greater than 0.5 [J / cc / K]. It can be seen that the energy conversion efficiency can be increased.
Abstract
Description
熱・音変換技術を利用した熱・音響システムの例として、固体とガス間で十分な接触頻度を持つ装置において、固体の一端を加熱しつつ、熱の一部を音波のエネルギに変換し、この音波を発電装置に供給するシステムが挙げられる。このシステムでは、上記装置中の固体に形成される温度勾配がキーとなるが、この装置では音波へのエネルギの変換効率が十分ではなかった。これは、熱エネルギを音圧エネルギに変換する役割を持つ熱・音波変換部品が、好ましい構造、物性を持っていなかったことに起因する。
当該熱音響装置用スタックは、複数の貫通孔が形成されており、熱伝導率が10[W/m・K]未満の材料から構成されている。これにより、スタックの長さを短くしても温度勾配をスケーリング(比例縮小)することが可能となるので、臨界温度勾配を達成するのに必要な高温側熱交換器の温度を低くすることができる。
音波が伝播する流体と、前記流体と接する壁との間で、音波のエネルギを熱のエネルギに変換する、あるいは熱のエネルギを音波のエネルギに変換する熱・音波変換部品である。当該熱・音波変換部品は、一方向に延在して前記熱・音波変換部品を貫通し音波の伝播経路を形成するように構成された複数の貫通孔それぞれの周りに形成され、前記貫通孔の延在方向に延び、前記流体との間で熱の授受を行なうように構成された壁、を備える。
前記貫通孔は、水力直径が0.4mm以下の貫通孔を含み、前記熱・音波変換部品における前記複数の貫通孔の開口率は60%以上である。
前記流体雰囲気中における前記熱・音波変換部品における熱伝導率は0.4[W/m/K]以下であり、前記流体雰囲気中における前記熱・音波変換部品における400℃における熱容量は0.5[J/cc/K]より大きい。
前記熱・音波変換部品における20℃~800℃間の前記貫通孔の延在方向に沿った熱膨張率は6[ppm/K]以下である、形態1に記載の熱・音波変換部品。
前記貫通孔の延在方向と直交する方向に前記熱・音波変換部品を切断したときの前記貫通孔それぞれの断面形状は、多角形状である、形態1または形態2に記載の熱・音波変換部品。
前記貫通孔それぞれと接する前記壁の内壁面には、前記貫通孔それぞれの断面の内側に向かって突出したリブが前記貫通孔の延在方向に沿って設けられている、形態1または形態2に記載の熱・音波変換部品。
また、前記流体雰囲気中における前記熱・音波変換部品における400℃における熱容量は0.75[J/cc/K]以上である、形態1~4のいずれか1つに記載の熱・音波変換部品。
一体構造物で構成されている、形態1~5のいずれか1つに記載の熱・音波変換部品。
一方の端面から他方の端面に延在する、流体の流路となる貫通孔を区画する隔壁を、同一材料で一体構造物として形成した長尺状の構造体で構成されている、形態1~5のいずれか1つに記載の熱・音波変換部品。
前記熱・音波変換部品は、コージェライト、ムライト、アルミニウムチタネート、アルミナ、ジルコニア、窒化珪素、炭化珪素、及び、合成樹脂の中から選択された成分を80質量%以上含む材料を用いて構成される、形態1~7のいずれか1つに記載の熱・音波変換部品。
流体の音波エネルギを、前記流体に接する壁の熱を用いて増幅する熱・音波変換部品を備えた熱・音波変換器であって、
前記熱・音波変換部品と、
前記流体の音波の伝播経路を形成し、前記熱・音波変換部品の前記貫通孔の延在方向に沿って前記音波が伝播するように、前記音波を前記貫通孔に導くように構成された導管と、
前記熱・音波変換部品の両端に設けられ、前記熱・音波変換部品の前記両端の間で前記延在方向に沿って温度勾配を形成させるように構成された一対の熱交換部と、を有し、
前記導管は、前記温度勾配を用いて音波エネルギが増幅された音波を出力ように構成され、出力した音波を用いて、前記増幅した音波エネルギを別のエネルギに変換するように構成された変換器に接続される出力端を有する、ことを特徴とする熱・音波変換器。
流体に接する壁に、前記流体の音波エネルギを用いて温度勾配をつくる熱・音波変換部品を備えた熱・音波変換器であって、
前記熱・音波変換部品と、
前記流体の音波の伝播経路を形成し、前記熱・音波変換部品の前記貫通孔の延在方向に沿って前記音波が伝播するように、前記音波を前記貫通孔に導くように構成された導管と、
前記熱・音波変換部品の両端のうち第1の端に設けられた一定の温度を有するように構成された熱交換部と、
前記熱・音波変換部品の前記第1の端と異なる第2の端に設けられる熱出力部であって、前記音波の伝播によって、前記熱交換部との間で前記熱・音波変換部品上に形成される温度勾配から、前記熱交換部の温度と温度差を有する温度を取り出すように構成された熱出力部と、を有することを特徴とする熱・音波変換器。
図1は、本実施形態の熱・音波変換部品を適用した本実施形態の熱・音波変換器10の構成の一例を示す図である。図1に示す熱・音波変換器10は、導管内を伝播する音波の音圧エネルギを増大し、増大した音圧エネルギを、他のエネルギに変換する変換装置40に供給する装置である。変換装置40は、例えば、音波エネルギを電気エネルギに変換する発電機や音波エネルギを熱エネルギに変換する装置が挙げられる。上記発電機では、音波によって発電素子であるコイルや磁石等を振動させることにより電磁誘導を発生させて起電力を生じさせる。音波エネルギを熱エネルギに変換する変換装置では、例えば音波に熱が吸収されて冷却された冷却媒体を取り出して、冷却装置として用いられる。
熱・音波変換器10は、熱・音波変換部品に入力した音波Swの音圧エネルギを熱・音波変換部品で増大させ、音圧エネルギの増大した音波を出力する装置である。熱・音波変換器10は、例えば、小さな音圧エネルギの音波Swを熱・音波変換部品で増大させ、音圧エネルギの増大した音波を循環して、さらに熱・音波変換部品に入力させて音圧エネルギを増大させることにより、極めて大きな音圧エネルギの音波を出力することができる。このとき、小さな音圧エネルギの音波Swを形成する初期段階では、熱・音波変換器10は、上記循環を利用して、導管14内の音のノイズ成分の一部を、熱・音波変換器10の形状寸法等によって定まる周波数を持つ音波として選択的に増幅する。これにより、上記小さな音圧エネルギの音波Swが自励的に形成される。
熱・音波変換部品12は、音波Swが伝播する流体と、この流体と接する壁との間で、音波と熱のエネルギの変換を行う部品であって、後述するように、音波Swの伝播経路を形成する一方向に延在した管状の複数の貫通孔を備える。すなわち、熱・音波変換部品12は円柱や角柱等の柱形状を成し、柱形状の軸方向に沿って、多数の貫通孔が互いに平行に設けられている。熱・音波変換部品12は、例えば、金属、セラミック、あるいは樹脂によって構成される。
低温部15は、低温のガスや液体等の媒体を低温部15に供給する供給管16と、上記媒体を低温部15から排出する排出管18と、供給管16と排出管18の間に設けられ、音波Swの伝播経路の周りを環状に囲む環状管20と、を有する。供給管16は、図示されない低熱源と接続されている。環状管20は、供給管16と排出管18に接続されている。また、環状管20は、熱伝導率の高い金属部材21と当接し、この金属部材21が熱・音波変換部品12と当接している。したがって、上記金属部材21を介して熱・音波変換部品12の端との間で熱交換して熱・音波変換部品12の端から低温部15に熱が流れて熱・音波変換部品12の金属部材21と接する端は冷却される。また、低温部15は、導管14内の流体を冷却するための冷却フィン22が設けられている。この冷却フィン22は、環状管20と接続されているので、低温部15に位置する流体の熱を吸収し、流体の温度を低下させる。
したがって、熱・音波変換部品12は、低温部材15及び高温部材23によって形成される温度勾配を維持することができる。このような熱・音波変換器10における熱・音波変換部品12の作用についての詳細は後述する。
図2は、熱・音波変換器10とは別の実施形態である熱・音波変換器110の構成の一例を示す図である。図2に示す熱・音波変換器110は、導管内を伝播する音波の音圧エネルギを熱エネルギに変換する装置である。
熱・音波変換器110は、図2に示すように、熱・音波変換部品112と、導管114と、熱変換部123と、熱出力部115と、を主に有する。熱出力部115が熱交換部123の温度と温度差を有する温度を取り出す、すなわち、冷却された冷却媒体(ガスあるいは液体)を出力する部分である。
熱・音波変換器110は、導管114を介して、音波を出力する上述した熱・音波変換器10に接続されている。本実施形態の熱・音波変換器110では、上述した熱・音波変換器10に接続される構成であるが、これ以外の音波を発生させる装置であってもよい。
導管114は、流体を導管114内に含み、この流体の音波の伝播経路を形成するとともに、熱・音波変換部品112の貫通孔の延在方向に沿って音波が伝播するように、音波を熱・音波変換部品112の貫通孔に導く。導管114は、例えば、金属製の管である。導管114内では、流体としてガスが用いられ、例えば水素やヘリウムガスが用いられる。ガスは、例えば数気圧~数十気圧の所定の圧力に調整されて導管114に封入されている。導管114は、図2に示すように、音波が熱・音波変換部品112を循環する循環経路136を形成するように構成される。本実施形態の導管114は、循環経路136を形成するが、導管114は必ずしも循環経路を形成しなくてもよい。
熱出力部115は、ガスや液体等の媒体を供給する供給管116と、上記媒体を熱出力部115から排出する排出管118と、供給管116と排出管118の間に設けられ、音波の伝播経路の周りを環状に囲む環状管120と、を有する。環状管120は、供給管116と排出管118に接続されている。また、環状管120は、熱伝導率の高い金属部材121と当接し、この金属部材121が熱・音波変換部品112と当接している。したがって、環状管120は、上記金属部材121を介して熱・音波変換部品112の端との間で熱交換をして熱・音波変換部品112の端に熱出力部115から熱が流れて環状管120は冷却される。このため、環状管12を流れる媒体は冷却媒体となり、冷却媒体が出力される。このような冷却媒体は、冷却装置に用いられる。また、熱出力部115は、導管114内の流体を冷却するための冷却フィン122が設けられている。この冷却フィン122は、環状管120と接続されているので、熱出力部115に位置する流体の熱を吸収し、温度を低下させる。
このように熱・音波変換器110では、音波の音圧エネルギを熱エネルギに変換するが、この変換は熱・音波変換部品112によって行われる。以下、熱・音波変換部品12及び熱・音波変換部品112の作用、すなわち音圧エネルギ及び熱エネルギの変換について説明する。
熱・音波変換部品12及び熱・音波変換部品112は同一の構成を有するので、熱・音波変換部品12を代表して説明する。図3は、熱・音波変換部品12の外観斜視図である。
熱・音波変換部品12には、一方向に延在して熱・音波変換部品12を貫通し、音波の伝播経路を形成するように構成された複数の貫通孔12aが設けられている。熱・音波変換部品12は、複数の貫通孔12aそれぞれの周りに形成されて貫通孔12aの延在方向(図3中のX方向)に延びる壁12bを備える。壁12bは、後述するように流体との間で熱の授受を行なうように構成されている。図3では壁12bは線で簡略化して記されている。熱・音波変換部品12は、一体物で構成されていることが好ましい。一体物は、パイプ等の複数の構造体を束ねた形態のものを含まず、1つの構造体で構成された一体物、すなわち一体構造物をいう。また、熱・音波変換部品12は、一方の端面から他方の端面に延在する、流体の流路となる貫通孔を区画する隔壁を、同一材料で一体物、すなわち一体構造物として形成した長尺状の構造体で構成されていることが、均一な断面形状を有する貫通孔12aをつくることができ、かつ貫通孔12a周りの壁12bを薄くできる点で好ましい。長尺状の構造体は、同一材料でかつ均質な材料で構成されていることがより好ましい。熱・音波変換部品12は、例えば、貫通孔12aの延在方向が押し出し方向となるように材料を押し出し成形した押出成形品である。
熱・音波変換部品12のX方向の長さは、導管14内に形成させる音波の波長や流体の振動による縦変位に応じて設定され、例えば10mm以上500mm未満であることが好ましい。この範囲にあるとき、音波の縦振動による流体要素の変位に一致し、効率のよいエネルギ変換を実現できる。音波の周波数は、特に制限されないが、例えば50Hz~200kHzの範囲の周波数である。
流体は、音波を伝播させる媒体であり縦振動する。この縦振動による流体の変位と流体の圧縮と膨張との関係を説明するために、流体のごく一部の領域を定めた流体要素を用いて説明する。
図4(a)に示す例では、音波の音圧と流体要素の変動の位相が4分の1周期ずれる進行波における圧縮、膨張の1サイクルを示している。予め壁12bの一端(位置I)を外部より加熱し、一端(位置II)を外部より冷却して壁12bに図4(b)に示すように温度勾配をつけてある状態で、流体要素が、壁12bの位置Iで膨張過程の状態Aにある。この状態で膨張をつづけながら状態Bに移行する。このとき、流体要素は温度が高い壁12bから熱の供給を受ける。次に、状態Bから流体要素は変位を開始して、壁12bの位置IIに向かって移動し最も膨張した状態B’に移行する。この状態B’において、音波により圧縮を開始し、状態Dに移行する。このとき、温度の低い壁12bに熱を供給する。次に、状態Dから流体要素は変位を開始して、位置Iに向かって移動し、最も圧縮されたD’にいたるまでの間壁12bへの熱の供給を続ける。このように、膨張過程で流体要素が壁12bから熱を受け、壁12bが圧縮過程で流体要素から熱を奪うことができ、流体要素の圧縮と膨張を増大させることができる。すなわち、熱・音波変換部品12は、熱・音波変換部品12に伝播する音波の音圧エネルギを、壁12bに温度勾配を予め形成しておくことにより増大させることができる。
以上のようなサイクルを1サイクルとして複数サイクルを繰り返し行うために、循環経路36,136を形成することが好ましい。
なお、上記説明では、進行波を例に挙げて説明した。進行波は、流体の圧縮及び膨張のサイクルと、流体要素の変動のサイクルが4分の1周期ずれている。このため、音波と熱のエネルギ変換が実現される。これに対して、定在波では、流体の圧縮及び膨張のサイクルと、流体要素の変動のサイクルが同位相であるため、エネルギ変換は発生し難い。しかし、定在波の場合、流体と壁との間でエネルギ変換を行うときに生じる変換の遅れを利用するために、音波の周波数を設定することにより、上記変換を実現することができる。定在波の波長は、導管14,114あるいは循環経路36,136の長さに応じて定まり、この波長によって音波の周波数は定まるので、音波の周波数の設定は、導管14,114あるいは循環経路36,136の長さを調整することにより行われる。なお、エネルギ変換の遅れは、流体の熱伝導度、流体の密度、流体の定圧比熱、及び貫通孔の大きさによって定まる。
この点で、本実施形態の熱・音波変換部品12及び熱・音波変換部品112の音波を伝播する貫通孔は水力直径が0.4mm以下の貫通孔を含み、熱・音波変換部品12及び熱・音波変換部品112における複数の貫通孔の開口率は60%以上である。水力直径が0.4mm以下の貫通孔の数は、音波変換部品12及び熱・音波変換部品112における音波を伝播する貫通孔全体の数の80%以上であることが好ましく、熱・音波変換部品12及び熱・音波変換部品112の音波を伝播する貫通孔の水力直径はいずれも0.4mm以下であることが最も好ましい。さらに、流体雰囲気中における熱・音波変換部品12及び熱・音波変換部品112における熱伝導率は、25℃において、0.4[W/m/K]以下であり、流体雰囲気中における熱・音波変換部品12及び熱・音波変換部品112における400℃における熱容量は0.5[J/cc/K](熱・音波変換部品112の1cc当たりの熱容量)より大きく調整されている。
熱・音波変換部品12及び熱・音波変換部品112の貫通孔の開口率を60%以上とするのは、音波が伝播する流体と壁との間でエネルギの変換を行う場所をより多数設けるためである。開口率は、熱・音波変換部品12及び熱・音波変換部品112のX方向に直交する方向に切断した断面形状の外周で囲まれる面積に対する貫通孔の断面積の総和の比率である。上記開口率が60%未満である場合、熱・音波変換部品12及び熱・音波変換部品112の内の伝播経路が急激に狭くなり、音波による流体要素の粘性による散逸エネルギが増加し易い。この点で上記開口率は、70%以上であることが好ましく、80%以上であることがより好ましい。上記開口率の上限は、例えば93%である。上記開口率を高めるために、熱・音波変換部品12及び熱・音波変換部品112は、壁12bを薄くできるハニカム構造体であることが好ましい。ハニカム構造体として、例えば、貫通孔12aの延在方向が押し出し方向となるように材料を押し出し成形したハニカム構造体の押出成形品が挙げられる。なお、上記開口率は、貫通孔に垂直な熱・音波変換部品12及び熱・音波変換部品112の断面(研磨面)を顕微鏡で撮影し、このときの断面の撮影画像から、材料部分面積S1と空隙部分面積S2を求め、S1とS2を用いてS2/(S1+S2)として求められる。
また、熱・音波変換部品12及び熱・音波変換部品112を構成する材料の気孔率は35%以下であることが好ましく、27%以下であることがさらに好ましい。実質、作製可能な範囲を考えると、0.5%~35%であることが好ましい。
流体雰囲気中における熱・音波変換部品12及び熱・音波変換部品112における400℃における構造体としての熱容量を0.5[J/cc/K]より大きくすることが好ましい。これにより、壁と流体との間の熱の授受によって壁の温度が変動しながらも、温度勾配を安定して維持することができる。構造体としての熱容量が0.5[J/cc/K]以下である場合、壁と流体との間の熱の授受によって、壁の温度は急激に冷え、あるいは急激に大きくなるため、温度勾配を安定して維持する上で好ましくない。400℃における構造体としての熱容量は0.61[J/cc/K]以上、さらには0.75[J/cc/K]以上であることが、熱勾配をより安定させる点で好ましい。400℃における構造体としての熱容量の上限は、例えば3[J/cc/K]である。
熱・音波変換部品12及び熱・音波変換部品112の上記熱容量は以下のように求められる。まず、材料自体の単位質量当たりの熱容量を求める。具体的には、上記材料を粉砕して粉末状にした材料をサンプルとして、断熱型熱量計を用いて投入熱と温度上昇の関係から、材料自体の単位質量当たりの熱容量を求める。その後、サンプルとして用いた粉砕前の材料の体積あたりの質量を掛け算して構造体としての単位体積(1cc)あたり熱容量を求める。
また、熱・音波変換部品12及び熱・音波変換部品112における20℃~800℃間の貫通孔の延在方向に沿った熱膨張率は、6[ppm/K]以下であることが好ましい。これにより、熱・音波変換部品12及び熱・音波変換部品112の熱応力を小さくして熱歪みによる破壊を抑制することができる。熱・音波変換部品12及び熱・音波変換部品112における20℃~800℃間の貫通孔の延在方向に沿った熱膨張率は、3[ppm/K]以下であることがより好ましい。上記熱膨張率の下限は、例えば0.2[ppm/K]である。なお、貫通孔の延在方向に沿った上記熱膨張率は、JIS R1618-2002に記載される「ファインセラミックスの熱機械分析による熱膨張の測定方法」に準拠して求められる。
本実施形態の熱・音波変換部品における音波が伝播する流体と壁との間でエネルギ変換を効率よく行うことを確認するために、種々の熱・音波変換部品を作製した。
エネルギの変換効率の算出のために、図1に示す熱・音波変換器10の出力端14aにおいて、リニア発電気により音波を電気に変換し、その発電量W[J/秒]を測定した。一方、高温度側熱交換器における本システムへの投入熱量Q(J/秒)を、高温側の熱変換部の入り口、出口間のガスの温度差(ΔT)と その流量M(kg/秒)とガスの比熱Cp(J/kg/K)よりQ= ΔT・Cp・Mとして求めた。変換効率ηは、η=W/Qとして求めた。変換効率は、20%以上を合格品とした。
熱・音波変換器10のX方向の長さは30mmとし、導管14内にヘリウムガスを密封し、10気圧とした。熱・音波変換部品12の、低温部15側の端は100℃となり、高温部23側の端は450℃となるように、低温部15及び高温部23の温度を定めた。
実施例1~10及び比較例1~12における20℃~800℃間の貫通孔の延在方向に沿った熱膨張率は1[ppm/K]であった。実施例11,12及び比較例13,14の水力直径はいずれも0.3[mm]とし、開口率はいずれも80[%]とし、材料を変更して上記熱膨張率を種々変えた。実施例11,12及び比較例13,14では、上記変換効率を測定する条件で、5時間連続使用したときの熱・音波変換部品の破損の有無により、熱耐久性の合格、不合格を調べた。
これより、熱・音波変換部品12の貫通孔の水力直径を0.4mm以下とし、熱・音波変換部品12における貫通孔の開口率を60%以上とし、流体雰囲気中における熱・音波変換部品12における熱伝導率を0.4[W/m/K]以下とし、流体雰囲気中における熱・音波変換部品12における400℃における熱容量を0.5[J/cc/K]より大きくする、ことにより、エネルギの変換効率を高めることができることがわかる。
12,112 熱・音波変換部品
12a 貫通孔
12b 壁
14,114 導管
14a 出力端
15 熱交換部(低温部)
16,24,116,124 供給管
18,26,118,126 排出管
20,28,120,128 環状管
21,29,121,129 金属部材
22,122 冷却フィン
23 熱交換部(高温部)
30 加熱フィン
32,132 干渉材
34,134 ケーシング
36,136 循環経路
40 変換装置
115 熱出力部
123 熱変換部
130 フィン
Claims (10)
- 音波が伝播する流体と、前記流体と接する壁との間で、音波のエネルギを熱のエネルギに変換する、あるいは熱のエネルギを音波のエネルギに変換する熱・音波変換部品であって、
前記熱・音波変換部品は、一方向に延在して前記熱・音波変換部品を貫通し音波の伝播経路を形成するように構成された複数の貫通孔それぞれの周りに形成されて前記貫通孔の延在方向に延び、前記流体との間で熱の授受を行なうように構成された壁、を備え、
前記貫通孔は、水力直径が0.4mm以下の孔を含み、
前記熱・音波変換部品における前記複数の貫通孔の開口率は60%以上であって、
前記流体雰囲気中における前記熱・音波変換部品における熱伝導率は0.4[W/m/K]以下であり、
前記流体雰囲気中における前記熱・音波変換部品における400℃における熱容量は0.5[J/cc/K]より大きい、ことを特徴とする熱・音波変換部品。 - 前記熱・音波変換部品における20℃~800℃間の前記貫通孔の延在方向に沿った熱膨張率は6[ppm/K]以下である、請求項1に記載の熱・音波変換部品。
- 前記貫通孔の延在方向と直交する方向に前記熱・音波変換部品を切断したときの前記貫通孔それぞれの断面形状は、多角形状である、請求項1または2に記載の熱・音波変換部品。
- 前記貫通孔それぞれと接する前記壁の内壁面には、前記貫通孔それぞれの断面の内側に向かって突出したリブが前記貫通孔の延在方向に沿って設けられている、請求項1または2に記載の熱・音波変換部品。
- 前記流体雰囲気中における前記熱・音波変換部品における400℃における熱容量は0.75[J/cc/K]以上である、請求項1~4のいずれか1項に記載の熱・音波変換部品。
- 一体構造物で構成されている、請求項1~5のいずれか1項に記載の熱・音波変換部品。
- 一方の端面から他方の端面に延在する、流体の流路となる貫通孔を区画する隔壁を、同一材料で一体構造物として形成した長尺状の構造体で構成されている、請求項1~5のいずれか1項に記載の熱・音波変換部品。
- 前記熱・音波変換部品は、コージェライト、ムライト、アルミニウムチタネート、アルミナ、ジルコニア、窒化珪素、炭化珪素、及び、合成樹脂の中から選択された成分を80質量%以上含む材料を用いて構成される、請求項1~7のいずれか1項に記載の熱・音波変換部品。
- 流体の音波エネルギを、前記流体に接する壁の熱を用いて増幅する熱・音波変換部品を備えた熱・音波変換器であって、
熱・音波変換部品と、
前記流体の音波の伝播経路を形成し、前記熱・音波変換部品の前記貫通孔の延在方向に沿って前記音波が伝播するように、前記音波を前記貫通孔に導くように構成された導管と、
前記熱・音波変換部品の両端に設けられ、前記熱・音波変換部品の前記両端の間で前記延在方向に沿って温度勾配を形成させるように構成された一対の熱交換部と、を有し、
前記導管は、前記温度勾配を用いて音波エネルギが増幅された音波を出力ように構成され、出力した音波を用いて、前記増幅した音波エネルギを別のエネルギに変換するように構成された変換器に接続される出力端を有し、
前記熱・音波変換部品は、一方向に延在して前記熱・音波変換部品を貫通し音波の伝播経路を形成するように構成された複数の貫通孔それぞれの周りに形成されて前記貫通孔の延在方向に延び、前記流体との間で熱の授受を行なうように構成された壁、を備え、
前記貫通孔は、水力直径が0.4mm以下の孔を含み、
前記熱・音波変換部品における前記複数の貫通孔の開口率は60%以上であって、
前記流体雰囲気中における前記熱・音波変換部品における熱伝導率は0.4[W/m/K]以下であり、
前記流体雰囲気中における前記熱・音波変換部品における400℃における熱容量は0.5[J/cc/K]より大きい、ことを特徴とする熱・音波変換器。 - 流体に接する壁に、前記流体の音波エネルギを用いて温度勾配をつくる熱・音波変換部品を備えた熱・音波変換器であって、
熱・音波変換部品と、
前記流体の音波の伝播経路を形成し、前記熱・音波変換部品の前記貫通孔の延在方向に沿って前記音波が伝播するように、前記音波を前記貫通孔に導くように構成された導管と、
前記熱・音波変換部品の両端のうち第1の端に設けられた一定の温度を有するように構成された熱交換部と、
前記熱・音波変換部品の前記第1の端と異なる第2の端に設けられる熱出力部であって、前記音波の伝播によって、前記熱交換部との間で前記熱・音波変換部品上に形成される温度勾配から、前記熱交換部の温度と温度差を有する温度を取り出すように構成された熱出力部と、を有し、
前記熱・音波変換部品は、一方向に延在して前記熱・音波変換部品を貫通し音波の伝播経路を形成するように構成された複数の貫通孔それぞれの周りに形成されて前記貫通孔の延在方向に延び、前記流体との間で熱の授受を行なうように構成された壁、を備え、
前記貫通孔は、水力直径が0.4mm以下の孔を含み、
前記熱・音波変換部品における前記複数の貫通孔の開口率は60%以上であって、
前記流体雰囲気中における前記熱・音波変換部品における熱伝導率は0.4[W/m/K]以下であり、
前記流体雰囲気中における前記熱・音波変換部品における400℃における熱容量は0.5[J/cc/K]より大きい、ことを特徴とする熱・音波変換器。
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