Thermoacoustic device

Abstract

To increase fluid oscillation generated on the basis of a thermoacoustic phenomenon and improve output per volume.SOLUTION: A thermoacoustic device 1 includes: a heat accumulator 10 that generates a thermoacoustic phenomenon; and a flow passage 2 in which the heat accumulator 10 is provided between a first flow passage 3 and a second flow passage 4, and liquid flows in the first flow passage. In the heat accumulator, a temperature gradient is formed between a low-temperature part formed by cooling one end side to a first temperature region and a high-temperature part formed by heating the other side to a second temperature region higher than the first temperature region. During supply of liquid D from the first flow passage connected to one end side, when the liquid is moved from the low-temperature part side to the high-temperature part side, energy conversion of a heat flow and sound power is performed. At the same time, the liquid is heated to the second temperature region higher than a temperature of a boiling point depending on device internal pressure of the liquid, the liquid is vaporized on the basis of a phase change, and fluid oscillation on the basis of gas expansion is generated on the second flow passage side connected to the other end side. When the liquid reciprocates between the high-temperature part and the low-temperature part, fluid oscillation is generated, or fluid oscillation is amplified.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a thermoacoustic device that generates fluid vibrations.

Background Art

[0002] A thermoacoustic device is a device that utilizes the thermoacoustic phenomenon that enables mutual energy conversion between a heat flow and a working flow (acoustic power) to extract thermal energy or acoustic energy. The thermoacoustic device includes a regenerator that generates the thermoacoustic phenomenon. In the regenerator, for example, a large number of capillary flow paths that penetrate both ends are formed so that a working fluid capable of propagating sound circulates.

[0003] For example, by providing a low-temperature heat exchanger on one end side of the regenerator and a high-temperature heat exchanger on the other end side, when heat is input to the regenerator to give a temperature gradient, a thermoacoustic prime mover that converts thermal energy into acoustic energy, generates, or amplifies a working flow can be configured. Since the conversion between thermal energy and acoustic energy in the regenerator is a reversible reaction, a thermoacoustic heat pump that outputs thermal energy by the heat pump effect can be configured by inputting a working flow to the regenerator. That is, according to the thermoacoustic device, it is also possible to configure a thermoacoustic heater that outputs high-temperature heat based on the input of a working flow, and it is also possible to configure a thermoacoustic cooler that outputs low-temperature heat.

[0004] According to the thermoacoustic device, it is also possible to configure a thermoacoustic generator that outputs electric power based on the input of thermal energy by providing a generator that operates based on a vibrating flow such as sound as an output unit. According to the thermoacoustic device, an acoustically driven thermoacoustic heat pump that outputs thermal energy based on the input of a vibrating flow can also be configured by providing an acoustic driver that generates a vibrating flow in the thermoacoustic device. Further, according to the thermoacoustic device, it is also possible to combine a thermoacoustic prime mover and a thermoacoustic heat pump, and a thermoacoustic heat pump that operates based on the input of thermal energy can also be configured.

[0005] As heat sources for heating the thermoacoustic engine, various heat sources can be utilized, such as waste heat from factories, ships, etc., and heat collection from sunlight. Therefore, the thermoacoustic device is expected to be used as a waste heat recovery device. Since the thermoacoustic heat pump can use gases without a global warming potential, such as air, argon, and helium, as the working gas, an eco-friendly heat pump can be configured.

[0006] Conventionally, in a thermoacoustic device that uses both a gas column and a liquid column as the working fluid, it is known that a large pressure amplitude can be obtained in the working fluid by utilizing the phase change of the liquid. For example, Patent Document 1 describes a thermoacoustic device including a tubular flow path filled with a working fluid containing a mixture of a condensable fluid (liquid) and a non-condensable fluid (gas), and a regenerator provided in the flow path. Patent Document 1 proposes obtaining a high pressure amplitude of the working fluid by utilizing the high heat transfer rate of the phase change of the liquid by using a working fluid based on a mixture.

[0007] Patent Document 2 describes a thermoacoustic device including a loop tube filled with a working fluid containing a condensable fluid (liquid) and a non-condensable fluid (gas), a regenerator provided in the loop tube, an output section provided in a branch tube branched from the loop tube, and a heating section for heating the branch tube. Patent Document 1 proposes causing a gas-liquid phase change in the condensable fluid at the high-temperature part of the regenerator in a regenerator wetted with the condensable fluid, and preventing the condensable fluid from condensing by the heating section to prevent a decrease in acoustic power.

[0008] Patent Document 3 describes a thermoacoustic device including a loop tube filled with a condensable fluid as the working fluid and a regenerator provided in the loop tube. Patent Document 2 proposes preventing the capillary flow path in the regenerator from being blocked by the working fluid by adjusting the position of the liquid level so that the height of the working fluid is less than half of the regenerator, and stabilizing the operation.

Prior Art Documents

Patent Documents

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-074722 [Patent Document 2] Japanese Patent Application Laid-Open No. 2019-211129 [Patent Document 3] Japanese Patent Application Laid-Open No. 2020-118307 [Summary of the Invention] [Problems to be Solved by the Invention]

[0010] However, in conventional research on thermoacoustic phenomena, when using a regenerator in a wet state, it has been proposed to use a phase change phenomenon below the boiling point for energy conversion, but using a phase change phenomenon above the boiling point of the liquid in the regenerator for energy conversion has not yet been proposed.

[0011] As a result of intensive research, the inventors have found that in a thermoacoustic device using a liquid, when a liquid phase change phenomenon occurs in a temperature range above the boiling point of the liquid in a wet regenerator, the pressure vibration excited in the device may be larger than the pressure vibration generated at a temperature lower than the boiling point of the liquid.

[0012] An object of the present invention is to provide a thermoacoustic device capable of increasing fluid vibration generated based on the thermoacoustic phenomenon and improving the output per unit volume. [Means for Solving the Problems]

[0013] One aspect of the present invention includes a regenerator that generates a thermoacoustic phenomenon, a flow path in which the regenerator is provided between a first flow path and a second flow path, and a liquid flows through the first flow path. The regenerator has a temperature gradient formed between a low-temperature part whose one end side is cooled to a first temperature region and a high-temperature part whose other end side is heated to a second temperature region higher than the first temperature region. When the liquid is supplied from the first flow path connected to the one end side, when the liquid moves from the low-temperature part side to the high-temperature part side, while performing energy conversion between heat flow and acoustic power, the liquid is heated to the second temperature region above the boiling point temperature depending on the internal pressure of the liquid in the device, the liquid is vaporized based on a phase change, a fluid vibration based on gas expansion is generated on the second flow path side connected to the other end side, and when the liquid reciprocates between the high-temperature part and the low-temperature part, a fluid vibration is generated or the fluid vibration is amplified. It is a thermoacoustic device.

Effects of the Invention

[0014] According to the present invention, it is possible to increase fluid vibration generated based on the thermoacoustic phenomenon and improve the output per unit volume.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0016] As shown in FIG. 1, the thermoacoustic device 1 includes a flow path 2 through which a working fluid flows, and a regenerator 10 provided in the middle of the flow path 2. The flow path 2 is formed by, for example, a pipe with a circular cross section. The cross-sectional shape of the flow path 2 may be formed not only in a circular shape but also in other shapes such as a polygon. The flow path 2 is formed by a pair of first straight portions 2A and second straight portions 2B arranged along the vertical direction, and a bent portion 2C arranged in the horizontal direction and connected to the first straight portion 2A and the second straight portion 2B.

[0017] The end of the first straight portion 2A is open. The end of the first straight portion 2A may be closed. The end of the second straight portion 2B is open. The end of the second straight portion 2B may be closed. The end of the first straight portion 2A and the end of the second straight portion 2B may be connected, and a loop-shaped flow path 2 may be formed.

[0018] A regenerator 10 is provided in the middle of the first straight portion 2A. In the first straight portion 2A, one end side of the regenerator 10 is connected to the first flow path 3 arranged below. In the first straight portion 2A, the other end side of the regenerator 10 is connected to the second flow path 4 arranged above. A liquid D, which is a working fluid in which a gas-liquid phase change phenomenon occurs, is injected into the inside of the first flow path 3, the inside of the bent portion 2C connected to the first flow path 3, and the inside of the second straight portion 2B. The liquid D is subjected to the action of gravity (in the g direction in the figure) in a stationary state and is stored in the first flow path 3, the bent portion 2C, and the second straight portion 2B. As will be described later, the liquid D flows through the inside of the first flow path 3, the inside of the bent portion 2C, and the inside of the second straight portion 2B.

[0019] The liquid D is, for example, water. The liquid D may be any substance as long as it can cause a gas-liquid phase change, such as ethanol or ammonia, not just water. In the first straight portion 2A, the inside of the second flow path 4 is filled with a gas that serves as a working fluid. Above the water surface of the liquid D inside the second straight portion 2B, it is filled with a gas L that serves as a working fluid. The gas L is, for example, air. The gas L may be not only air but also helium, argon, nitrogen, etc.

[0020] When the end of the first straight portion 2A or the second straight portion 2B is open, the average atmospheric pressure of the gas L is maintained at atmospheric pressure. When the ends of the first straight portion 2A and the second straight portion 2B are closed, the gas L may be pressurized to a pressure higher than atmospheric pressure. A regenerator 10 is provided between the first flow path 3 and the second flow path 4.

[0021] In the regenerator 10, one to countless capillary flow paths 11 are formed. The one to countless capillary flow paths 11 are formed so as to penetrate from one end side on the downstream side to the other end side on the upstream side of the regenerator 10. The regenerator 10 is, for example, a honeycomb structure formed of porous ceramics. The regenerator 10 may be a structure in which one to countless capillary flow paths 11 are formed by laminating stainless steel mesh thin plates having countless holes. The regenerator 10 may have capillary flow paths 11 formed by randomly laminating mesh-like materials. The regenerator 10 may be made of any material that can form fine capillary flow paths 11 such as glass pipes and through which an oscillating flow can pass, and is not limited to these.

[0022] On one end side of the regenerator 10, a first heat exchanger 12 for heat exchange on the low-temperature side is provided. The first heat exchanger 12 is configured to maintain, for example, one end side of the regenerator 10 in a normal temperature region (first temperature region) as the ambient temperature. The first heat exchanger 12 is appropriately set to utilize the normal temperature heat energy obtained in the environment where the thermoacoustic device 1 is installed. Here, the normal temperature is, for example, a temperature stably obtained by the surrounding environment such as air, seawater, river water, lake water, pool water, and geothermal heat. The first heat exchanger 12 exchanges heat with normal temperature air through a heat medium, for example.

[0023] On the other end side of the regenerator 10, a second heat exchanger 13 for heat exchange on the high-temperature side is provided. The second heat exchanger 13 is configured to heat, for example, the other end side of the regenerator 10 through a heat medium to a high-temperature region (second temperature region) that is at a higher temperature than the normal-temperature region on the one end side. The second temperature region is, for example, a high-temperature region at a temperature equal to or higher than the boiling point temperature depending on the internal pressure of the liquid D in the apparatus. The second heat exchanger 13 heats the other end side of the regenerator 10 to a second temperature region that is higher than the boiling point temperature of the liquid D, and vaporizes the liquid D approaching the other end side of the regenerator 10 inside the regenerator 10.

[0024] The second heat exchanger 13 is appropriately set to utilize, for example, the thermal energy in the high-temperature region obtained in the environment where the thermoacoustic device 1 is installed. The second heat exchanger 13 may utilize, for example, unused thermal energy such as the exhaust heat of an internal combustion engine or factory exhaust heat. The second heat exchanger 13 may be absent as long as the other end side of the regenerator 10 is in a heated state. That is, the high-temperature part of the regenerator 10 may be realized by heating the other end side of the regenerator 10.

[0025] With the above configuration, a temperature gradient is formed in the regenerator 10 between the one end side maintained at the normal-temperature region by the first heat exchanger 12 and the other end side heated to the high-temperature region by the second heat exchanger 13. The regenerator 10 has at least the low-temperature side maintained in a wet state by the liquid D present in the first flow path 3. The regenerator 10 is configured as a thermoacoustic device that generates or amplifies a working flow (acoustic power) based on an oscillating flow in the direction of the second flow path 4 from the other end side on the high-temperature side. The regenerator 10 may be configured as a thermoacoustic device for power generation that utilizes the working flow. In the illustrated example, the regenerator 10 is configured as a two-phase thermoacoustic device for power generation that utilizes an oscillating flow of a gas-liquid phase change type by vaporization of the liquid D in the region including the high-temperature side.

[0026] As shown in FIG. 2, at least one end side of the heat accumulator 10 in a state where the liquid D is stationary is in a wet state by the liquid D. The liquid level D1 of the liquid D includes at least one end side of the heat accumulator 10. The liquid level D1 of the liquid D may be adjusted to a height inside the heat accumulator 10. The liquid level D1 of the liquid D is adjusted so as not to reach the second heat exchanger 13 on the other end side. When the second heat exchanger 13 is not provided in the heat accumulator 10, the liquid level D1 of the liquid D may be adjusted so as not to reach the heating region on the other end side of the heat accumulator 10. The liquid level D1 of the liquid D may be adjusted to a height that reaches the high-temperature side inside the heat accumulator during the vibration of the liquid D. Thereby, it is possible to prevent the high-temperature part and the low-temperature part of the heat accumulator 10 from being short-circuited by the liquid D and the temperature difference from decreasing, and it is possible to prevent the thermoacoustic phenomenon from occurring easily.

[0027] When one end side of the heat accumulator 10 is cooled to the first temperature region by the first heat exchanger 12, a low-temperature part is generated on one end side. When the other end side of the heat accumulator 10 is heated to the second temperature region by the second heat exchanger 13, a high-temperature part is generated on the other end side. A temperature gradient is formed between the low-temperature part and the high-temperature part in the heat accumulator 10. When the liquid D is supplied from the first flow path 3 connected to one end side of the heat accumulator 10, when the liquid D moves from the low-temperature part side to the high-temperature part side, energy conversion between the heat flow and the acoustic power is performed, and based on the thermoacoustic phenomenon, acoustic power (oscillating flow) is generated or amplified. At this time, the heat accumulator 10 in which at least one end side is in a wet state has the acoustic power amplified and output as compared with the heat accumulator 10 in a dry state.

[0028] The liquid D moves from the low-temperature part to the high-temperature part inside the heat accumulator 10, for example, by capillary action and the vibration of the liquid level D. The liquid D moves to the high-temperature part side and is heated to a second temperature region higher than the boiling point depending on the internal pressure of the liquid D in the high-temperature part, and vaporizes based on the phase change. When the heat accumulator 10 vaporizes the liquid D based on the phase change, it generates a fluid vibration based on the expansion of the gas on the second flow path 4 side connected to the other end side.

[0029] The regenerator 10 pushes down the liquid level D1 of the liquid D based on the oscillating flow generated inside the device and the downward reaction force generated by the expansion of the phase-changed gas. The regenerator 10 moves the liquid D from the high-temperature part side to the low-temperature part side based on the reaction force of the fluid oscillation. Since gravity acts on the liquid D in the U-shaped pipe, the liquid level D1 of the liquid D pushed down in the flow path 2 rises again. When the rising liquid level D1 of the liquid D rises in the regenerator 10 and approaches the high-temperature part, it is heated in the second temperature region, vaporizes based on the phase change, and the liquid level D1 of the liquid D is pushed down again. By repeating the above operation, the liquid level D1 of the liquid D reciprocates in the regenerator 10.

[0030] As shown in FIG. 3, when the liquid D reciprocates between the high-temperature part and the low-temperature part, the regenerator 10 generates or amplifies fluid oscillation. At this time, by adjusting the amount of heat input to the regenerator 10 based on the conditions of the device configuration, the regenerator 10 generates self-excited oscillation in the liquid D based on the fluid oscillation and reciprocates the liquid level D1 of the liquid D between the high-temperature part and the low-temperature part. At this time, the liquid level D1 of the liquid D may be adjusted not only to reciprocate between the high-temperature part and the low-temperature part of the regenerator 10 but also to reciprocate between the region below the high-temperature part of the regenerator 10 and the region below the low-temperature part. A driver for exciting the gas column and the liquid column inside the flow path 2 may be attached to the thermoacoustic device 1 to induce self-excited oscillation.

[0031] The above-described thermoacoustic device 1 can be converted into energy such as thermal energy, vibration energy, and electric power by providing an output unit. The output unit can be configured by another regenerator different from the regenerator 10 to constitute a thermoacoustic heater that outputs high-temperature heat based on the input of the working fluid flow, or a thermoacoustic cooler that outputs low-temperature heat. The thermoacoustic device 1 can also be configured as a thermoacoustic generator that outputs electric power based on the input of thermal energy by providing a generator that operates based on a vibration flow such as sound as the output unit. The thermoacoustic device 1 can also be configured as an acoustically driven thermoacoustic heat pump that outputs thermal energy based on the input of the vibration flow by providing an acoustic driver that generates the vibration flow. The thermoacoustic device 1 can also combine the above-described thermoacoustic prime mover and the thermoacoustic heat pump to constitute a thermoacoustic heat pump that operates based on the input of thermal energy.

[0032] FIG. 4 shows an experimental device 100 simulating the thermoacoustic device 1. In the following description, the same names and reference numerals are used for the same configurations as those of the thermoacoustic device 1, and repeated descriptions are omitted as appropriate. In the experimental device 100, water is used as the liquid D. In the stationary state of the experimental device 100, the gas L in the flow path 2 is atmospheric air. The experimental device 100 is provided with a pressure sensor S for detecting the pressure vibration of the liquid D in the flow path 2. In the stationary state of the experimental device 100, in order to perform energy conversion using a gas-liquid phase change phenomenon at a temperature equal to or higher than the boiling point of the liquid, the liquid level D1 of the liquid D is set at the position of the lower end of the regenerator 10 (the upper end of the first heat exchanger 12 on the low-temperature side). The pressure sensor S detects the pressure vibration at the position of the liquid D when self-excited vibration occurs in the experimental device 100.

[0033] FIG. 5 shows an experimental device 100A according to a comparative example. The experimental device 100A according to the comparative example has the same device configuration as the experimental device 100, but the height of the liquid level D1 of the liquid D is changed. In the experimental device 100A, the liquid level D1 of the liquid D is set at the position of the lower end of the first heat exchanger 12 on the low-temperature side.

[0034] In the experiments using the experimental apparatus 100 and the experimental apparatus 100A according to the comparative example, in the first heat exchanger 12 on the low-temperature side disposed at one end side of the heat accumulator 10, cooling water is circulated around the first heat exchanger 12 by a chiller. In this experiment, with the set temperature of the chiller being 20°C, cooling water was circulated around the first heat exchanger 12. Further, in the experimental apparatus 100 and the experimental apparatus 100A according to the comparative example, in the second heat exchanger 13 on the high-temperature side disposed at the other end side of the heat accumulator 10, a heater is wound around the periphery thereof.

[0035] The second heat exchanger 13 was heated based on the electric power supplied from a DC power source connected to the heater. The second heat exchanger 13 was heated based on the electric power of 337.6 W adjusted to an input voltage of 160.0 V and an input current of 2.11 A. In the experiment, the pressure vibration at the position of the liquid D when self-excited vibration occurred was measured in the experimental apparatus 100 and the experimental apparatus 100A according to the comparative example.

[0036] FIG. 6 shows the measurement results of the pressure vibration of the self-excited vibration occurring in the experimental apparatus 100 and the experimental apparatus 100A using the experimental apparatus 100 and the experimental apparatus 100A according to the comparative example. The measurement results show the time history of the pressure vibration detected by the pressure sensor S for 60 seconds. In the experimental apparatus 100, a pressure vibration of about 40 kPa was confirmed (see FIG. 6(A)). In contrast, in the experimental apparatus 100A, a pressure vibration of about 6 kPa was confirmed.

[0037] From the experimental results, it was confirmed that when the height of the liquid surface D1 of the liquid D in the stationary state is set to include at least the position of the lower end of the heat accumulator 10 (the upper end of the first heat exchanger 12 on the low-temperature side), the heat acoustic device 1 can increase the pressure vibration generated in the device as compared with the case where the height of the liquid surface D1 of the liquid D is set in the region below the position of the lower end of the heat accumulator 10.

[0038] As described above, according to the thermoacoustic device 1, based on the oscillatory flow generated in the regenerator 10 and the phase change of the liquid D, the fluid oscillation of the liquid D can be increased and the output per unit volume can be improved. According to the thermoacoustic device 1, by heating the liquid D in the high-temperature portion of the regenerator 10 to a second temperature region at a temperature equal to or higher than the boiling point, the fluid oscillation of the liquid D generated based on the thermoacoustic phenomenon can be increased.

Description of Reference Numerals

[0039] 1 Thermoacoustic device, 2 Flow path, 2A First straight portion, 2B Second straight portion, 2C Bending portion, 3 First flow path, 4 Second flow path, 4A Valve, 10 Regenerator, 11 Capillary flow path, 12 First heat exchanger, 13 Second heat exchanger, 100, 100A Experimental device, D Liquid, D1 Liquid level, L Gas, S Pressure sensor

Claims

1. A heat storage device that generates a thermoacoustic phenomenon; The heat accumulator is provided between a first flow path and a second flow path, and a flow path through which a liquid flows in the first flow path, The heat storage device is A temperature gradient is formed between a low-temperature section having one end cooled to a first temperature range and a high-temperature section having the other end heated to a second temperature range higher than the first temperature range, When the liquid is supplied from the first flow path connected to the one end side, the liquid moves from the low temperature section side to the high temperature section side, and at the same time, energy conversion between heat flow and acoustic power is performed, Heating the liquid to a second temperature range equal to or higher than a boiling point of the liquid, the second temperature range being dependent on the pressure inside the apparatus; The liquid is vaporized based on a phase change, and fluid vibration based on gas expansion is generated on a second flow path connected to the other end side, When the liquid moves back and forth between the high temperature part and the low temperature part, a fluid vibration is generated or the fluid vibration is amplified. Thermoacoustic device.

2. The heat accumulator moves the liquid from the high temperature section side to the low temperature section side based on a reaction force of the fluid vibration.

10. The thermoacoustic device of claim 1.

3. The heat storage device is In the first flow path formed in a U-shape, a self-excited vibration is generated in the liquid based on the fluid vibration, and the liquid is caused to reciprocate between the high temperature portion and the low temperature portion.

3. A thermoacoustic device as claimed in claim 2.

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