Liquid flow generation device

Abstract

A liquid flow generation device (100, 200, 300, 400) comprises a container (10) in which a working fluid (12) is sealed, and one or more heating bodies (20). Each of the one or more heating bodies has a first surface (20a) and a second surface (20b) that is on the side opposite from the first surface, and each of the one or more heating bodies is attached to the container so that the second surface is in contact with the working fluid. The first surface has a heating part (20aa). The second surface has a first portion (20ba) on the side opposite from the heating part. Each of the one or more heating bodies heats the heating part, thereby generating steam microbubbles (13) in the working liquid such that the steam microbubbles are in contact with the first portion. Air microbubbles (14) are discharged from the steam microbubbles. The working fluid is selected so that force (F2) in a direction away from the steam microbubbles acts on the air microbubbles.

Description

Liquid flow generator

[0001] The present disclosure relates to a liquid flow generating device.

[0002] For example, Japanese Patent Laid-Open Publication No. 2008-116381 (Patent Document 1) describes a micropump. The micropump described in Patent Document 1 includes a microchannel and a light absorber. A flow path is formed in the microchannel. A liquid is sealed in the flow path. The light absorber has a first surface and a second surface opposite to the first surface. The light absorber is attached to the microchannel so that the first surface faces the inner wall surface of the flow path. That is, the light absorber is attached to the microchannel so that the second surface is in contact with the liquid sealed in the flow path. When a laser is irradiated onto the first surface of the light absorber, bubbles are generated in the liquid so that the bubbles are in contact with the second surface. The Marangoni force of the bubbles generates a flow of liquid in the flow path.

[0003] JP 2008-116381 A

[0004] However, the micropump of Patent Document 1 leaves room for improvement in the flow rate of the liquid that generates bubbles. The present disclosure has been made in consideration of such problems in the prior art. More specifically, the present disclosure provides a liquid flow generating device that can improve the flow rate of the working liquid.

[0005] The liquid flow generating device of the present disclosure includes a container in which a working liquid is sealed and at least one heating element. Each of the at least one heating element has a first surface and a second surface opposite the first surface, and is attached to the container so that the second surface is in contact with the working liquid. The first surface has a heating portion. The second surface has a first portion opposite the heating portion. Each of the at least one heating element generates vapor microbubbles in the working liquid in contact with the first portion by heating the heating portion. Air microbubbles are released from the vapor microbubbles. The working liquid is selected so that a force acts on the air microbubbles in a direction away from the vapor microbubbles.

[0006] According to the liquid flow generating device of the present disclosure, it is possible to increase the flow velocity of the working liquid.

[0007] 1 is a cross-sectional view of a liquid flow generating device 100. FIG. 2 is a first cross-sectional view of a liquid flow generating device 100A. FIG. 3 is a second cross-sectional view of a liquid flow generating device 100A. FIG. 4 is a flow field generated by vapor microbubbles 13 when a 3 mass percent ethanol aqueous solution is used as the working liquid 12. FIG. 5 is a graph showing the relationship between the concentration of ethanol in the working liquid 12 and the flow velocity of the working liquid 12. FIG. 6 is a cross-sectional view of a liquid flow generating device 200. FIG. 7 is a cross-sectional view of a liquid flow generating device 300. FIG. 8 is a cross-sectional view of a liquid flow generating device 400. FIG. 9 is a plan view of a liquid flow generating device 400 according to a modified example.

[0008] The details of the embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and redundant descriptions will not be repeated.

[0009] Embodiment 1 A liquid flow generating device according to embodiment 1 will be described. The liquid flow generating device according to embodiment 1 is referred to as liquid flow generating device 100.

[0010] (Configuration of Liquid Flow Generating Device 100) The configuration of the liquid flow generating device 100 will be described below.

[0011] The liquid flow generating device 100 is used, for example, as a cooling device. Fig. 1 is a cross-sectional view of the liquid flow generating device 100. As shown in Fig. 1, the liquid flow generating device 100 includes a container 10 and a heating element 20.

[0012] The container 10 has an internal space 11. A working liquid 12 is sealed in the internal space 11. Details of the working liquid 12 will be described later. The material constituting the container 10 is not particularly limited as long as it can seal the working liquid 12. The shape of the container 10 (the shape of the internal space 11) is not particularly limited as long as it can seal the working liquid 12.

[0013] The container 10 is made of, for example, a metal material or a resin material. Specific examples of metal materials that can be used to make the container 10 include copper, copper alloys, aluminum, aluminum alloys, and stainless steel. To reduce the thermal resistance of the container 10, it is preferable that the thickness of the container 10 be small. The thickness of the container 10 is, for example, 1000 μm or less. The thickness of the container 10 may also be 500 μm or less.

[0014] The heating element 20 has a first surface 20 a and a second surface 20 b. The second surface 20 b is the surface opposite to the first surface 20 a. The heating element 20 is attached to the container 10 so that the second surface 20 b is in contact with the working liquid 12.

[0015] The first surface 20a has a heating portion 20aa. The heating portion 20aa is heated by a heating source 21 (not shown). The heating source 21 is, for example, a laser beam. The heating source 21 may be an electrode or a microheater. The heating source 21 may be a laser element or a semiconductor device to be cooled by the liquid flow generating device 100. The amount of heat generated by the heating source 21 is, for example, about 30 mW.

[0016] The second surface 20b has a first portion 20ba. The first portion 20ba is located on the opposite side of the heating portion 20aa. When the heating portion 20aa is heated by the heat source 21, the temperature of the first portion 20ba is increased. As a result, vapor microbubbles 13 are formed in the working liquid 12 so as to be in contact with the heating portion 20aa. The vapor microbubbles 13 are microbubbles composed of vapor of the working liquid 12. The microbubbles are bubbles (gas bubbles) with a diameter of 20 μm or less.

[0017] The heater 20 is made of, for example, a metal material. Specific examples of the metal material that makes up the heater 20 include copper, copper alloy, aluminum, aluminum alloy, stainless steel, etc. The thermal conductivity of the material that makes up the heater 20 is preferably higher than the thermal conductivity of the material that makes up the container 10. When the material that makes up the container 10 is stainless steel, the material that makes up the container 10 is, for example, copper, copper alloy, aluminum, aluminum alloy, etc.

[0018] Air microbubbles 14 are released from the steam microbubbles 13. The air microbubbles 14 are microbubbles made of air. The working liquid 12 is selected so that a force (force F2, described later) acts on the air microbubbles 14 in a direction away from the steam microbubbles 13. The working liquid 12 does not have to be degassed. That is, the working liquid 12 may contain air.

[0019] The working liquid 12 may be a mixture of multiple liquids. Each of the multiple liquids has a different surface tension. One of the multiple liquids is, for example, water. Another of the multiple liquids is a water-soluble liquid. A specific example of a water-soluble liquid is alcohol. The surface tension of alcohol is lower than that of water. Examples of alcohol include ethanol (ethyl alcohol), 1-propanol (normal propyl alcohol), and 2-propanol (isopropyl alcohol). Other specific examples of alcohol include methanol (methyl alcohol), 1-butanol (normal butyl alcohol), 2-butanol (isobutyl alcohol), and benzyl alcohol. When the alcohol is ethanol, the concentration of ethanol in the working liquid 12 is preferably 1 mass percent or more and 40 mass percent or less, and more preferably 1 mass percent or more and 10 mass percent or less.

[0020] One of the multiple types of liquids constituting the working liquid 12 may include a ketone, a glycol ether, or an ester. Specific examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl hexyl ketone, diisobutyl ketone, cyclohexanone, diacetone alcohol, and isophorone. Specific examples of glycol ethers include butyl glycol, methyl diglycol, ethyl diglycol, butyl diglycol, and tetrahydrofuran. Specific examples of esters include ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, and isopropyl acetate. Three or more types of liquids may be used to constitute the working liquid 12.

[0021] (Effects of Liquid Flow Generating Device 100) The effects of the liquid flow generating device 100 will be described below.

[0022] The surface tension of the working liquid 12 changes with temperature. For example, if the working liquid 12 is a mixture of water and alcohol, the surface tension of the working liquid 12 decreases as the temperature increases. The temperature of the working liquid 12 decreases as the working liquid 12 moves away from the heater 20. Therefore, a Marangoni force MF1, which is a shear force caused by the difference in surface tension between the high-temperature portion and the low-temperature portion (i.e., caused by the high-temperature portion pulling the low-temperature portion), occurs at the interface between the vapor microbubbles 13 and the working liquid 12. This Marangoni force MF1 causes a flow in the working liquid 12 (see the dotted arrow in the figure).

[0023] The vapor microbubbles 13 grow as they are heated in the first portion 20ba, but if they grow too large, the internal temperature and pressure decrease, causing them to shrink. The vibration of the vapor microbubbles 13 caused by this cycle of volume change further strengthens the flow of the working liquid 12.

[0024] Because the working liquid 12 is not degassed, air in the working liquid 12 is released from the vapor microbubbles 13 to form air microbubbles 14. A liquid flow generator 100A according to a comparative example is shown in FIG. 2A . FIG. 2A is a first cross-sectional view of the liquid flow generator 100A. The liquid flow generator 100A has the same configuration as the liquid flow generator 100, except that the working liquid 12 is not a mixture of multiple liquids. As described above, the temperature of the working liquid 12 decreases with increasing distance from the heating element 20. Therefore, in the liquid flow generator 100A, as shown in FIG. 2A , a Marangoni force MF2 is generated at the interface between the working liquid 12 and the air microbubbles 14 along the interface in a direction away from the heating element 20 (vapor microbubbles 13) (a downward-to-upward direction in FIG. 2A ). A force F1 is generated in the air microbubbles 14 in a direction toward the vapor microbubbles 13 as a reaction force to the Marangoni force MF2.

[0025] 2B is a second cross-sectional view of the liquid flow generator 100A. As shown in FIG. 2B, when a force F1 is applied to the air microbubbles 14, the air microbubbles 14 move toward the vapor microbubbles 13 and merge with the vapor microbubbles 13 to form microbubbles 15. Unlike the vapor microbubbles 13, the microbubbles 15 do not vibrate, and generate a flow of the working liquid 12 only by the Marangoni force MF3. Therefore, the flow velocity of the working liquid 12 is low in the liquid flow generator 100A.

[0026] On the other hand, in the liquid flow generator 100, since the working liquid 12 is a mixture of multiple liquids, the Marangoni force MF2 is affected not only by the temperature gradient but also by the concentration gradient. More specifically, when the working liquid 12 is a mixture of water and ethanol, ethanol, which has a low surface tension, is vaporized preferentially, and the concentration of ethanol in the working liquid 12 decreases as the working liquid 12 approaches the heater 20 (vapor microbubbles 13). Therefore, in the liquid flow generator 100, a Marangoni force MF2 is generated at the interface between the working liquid 12 and the air microbubbles 14 in a direction toward the heater 20 (vapor microbubbles 13) along the interface (from top to bottom in FIG. 1 ). As a result, a force F2 is generated in the air microbubbles 14 in a direction away from the vapor microbubbles 13 as a reaction force to the Marangoni force MF2.

[0027] Therefore, in the liquid flow generator 100, the force F2 prevents the air microbubbles 14 from approaching and integrating with the steam microbubbles 13, and both the Marangoni force MF1 and the vibration of the steam microbubbles 13 contribute to the flow of the working liquid 12. This improves the flow rate of the working liquid 12, thereby enabling the cooling target of the liquid flow generator 100 to be efficiently cooled.

[0028] Fig. 3 shows the flow field generated by vapor microbubbles 13 when a 3 mass percent ethanol aqueous solution is used as the working liquid 12. In Fig. 3, the flow field is visualized using polystyrene spheres. In Fig. 3, the vapor microbubbles 13 are formed by heating a heating element 20 made of ferrosilicon (FeSi) with laser light. As shown in Fig. 3, when the vapor microbubbles 13 are formed in the working liquid 12, a strong flow is generated in the working liquid 12.

[0029] 4 is a graph showing the relationship between the concentration of ethanol in the working liquid 12 and the flow rate of the working liquid 12. In each sample plotted in FIG. 4, the working liquid 12 was a mixture of water and ethanol or pure water. In each sample, the concentration of ethanol in the working liquid 12 was varied. In samples with an ethanol concentration of 0 mass percent (samples in which the working liquid 12 was pure water), the working liquid 12 was degassed, while in the other samples, the working liquid 12 was not degassed.

[0030] 4, in samples in which the concentration of ethanol in the working liquid 12 was 1 mass percent or more and 40 mass percent or more, the flow velocity of the working liquid 12 was equal to or greater than that of the sample in which the working liquid 12 was degassed pure water. In samples in which the concentration of ethanol in the working liquid 12 was 1 mass percent or more and 10 mass percent or less, the flow velocity of the working liquid 12 was further improved. This shows that the flow velocity of the working liquid 12 can be further improved by setting the concentration of ethanol in the working liquid 12 to 1 mass percent or more and 40 mass percent or less (1 mass percent or more and 10 mass percent or less).

[0031] Embodiment 2 A liquid flow generating device according to embodiment 2 will be described. The liquid flow generating device according to embodiment 2 is referred to as liquid flow generating device 200. Here, differences from liquid flow generating device 100 will be mainly described, and overlapping descriptions will not be repeated.

[0032] (Configuration of Liquid Flow Generating Device 200) The configuration of the liquid flow generating device 200 will be described below.

[0033] Fig. 5 is a cross-sectional view of the liquid flow generator 200. As shown in Fig. 5, the liquid flow generator 200 has a container 10 and a heating element 20. A working liquid 12 is sealed in an internal space 11. The working liquid 12 is selected so that a force is applied to the air microbubbles 14 in a direction away from the steam microbubbles 13. In these respects, the configuration of the liquid flow generator 200 is common to the configuration of the liquid flow generator 100.

[0034] The liquid flow generating device 200 has a plurality of heating elements 20. Therefore, in the liquid flow generating device 200, a plurality of vapor microbubbles 13 are generated in the working liquid 12. In this respect, the configuration of the liquid flow generating device 200 differs from the configuration of the liquid flow generating device 100. The number of heating elements 20 is not particularly limited. The number of multiple heating elements 20 is also not particularly limited. For example, the multiple heating elements 20 may be arranged on the same surface of the internal space 11, or may be arranged on opposing surfaces of the internal space 11. The multiple heating elements 20 may or may not be arranged in a straight line.

[0035] (Effects of Liquid Flow Generating Device 200) The effects of the liquid flow generating device 200 will be described below.

[0036] Since the liquid flow generating device 200 has a plurality of heating bodies 20, a plurality of vapor microbubbles 13 are generated in the working liquid 12 sealed in the internal space 11. Therefore, the liquid flow generating device 200 can generate a larger-scale flow in the working liquid 12 than the liquid flow generating device 100.

[0037] Embodiment 3 A liquid flow generating device according to embodiment 3 will be described. The liquid flow generating device according to embodiment 3 is referred to as liquid flow generating device 300. Here, differences from liquid flow generating device 100 will be mainly described, and overlapping descriptions will not be repeated.

[0038] (Configuration of Liquid Flow Generating Device 300) The configuration of the liquid flow generating device 300 will be described below.

[0039] Fig. 6 is a cross-sectional view of the liquid flow generator 300. As shown in Fig. 6, the liquid flow generator 300 has a container 10 and a heating element 20. In the liquid flow generator 300, a working liquid 12 is sealed in an internal space 11. In the liquid flow generator 300, a force is selected so that the working liquid 12 acts on the air microbubbles 14 in a direction away from the vapor microbubbles 13. In these respects, the configuration of the liquid flow generator 300 is common to the configuration of the liquid flow generator 100.

[0040] The liquid flow generator 300 is used, for example, as a pump. In the liquid flow generator 300, the internal space 11 forms a flow path 16. The flow path 16 has, for example, a closed loop shape. In the liquid flow generator 300, the first surface 20a has a non-heated portion 20ab, and the second surface 20b has a second portion 20bb. The non-heated portion 20ab is not heated by the heating source 21. The second portion 20bb is located on the opposite side of the non-heated portion 20ab. Therefore, when the heating portion 20aa is heated by the heating source 21, the temperature of the second portion 20bb becomes lower than the temperature of the first portion 20ba. However, at this time, the temperature of the second portion 20bb becomes higher than the temperature of the container 10. The first portion 20ba and the second portion 20bb are aligned in the direction in which the flow path 16 extends.

[0041] (Effects of Liquid Flow Generating Device 300) The effects of the liquid flow generating device 300 will be described below.

[0042] In the liquid flow generator 300, the heater 20 has the second portion 20bb, which causes the temperature distribution around the vapor microbubbles 13 to be asymmetric. More specifically, the temperature of the second portion 20bb is higher than the temperature of the container 10 on the opposite side of the vapor microbubbles 13. This causes the direction of the Marangoni bath (Marangoni force MF1) acting at the interface between the working liquid 12 and the vapor microbubbles 13 to approach the direction from the second portion 20bb to the first portion 20ba, i.e., the direction of the flow path 16. As a result, driven by the Marangoni force MF1, the working liquid 12 flows along the direction of the flow path 16. Similarly, the flow of the working liquid 12 caused by the vibration of the vapor microbubbles 13 also follows the direction of the flow path 16. This allows the liquid flow generator 300 to function as a pump.

[0043] Embodiment 4 A liquid flow generating device according to embodiment 4 will be described. The liquid flow generating device according to embodiment 4 is referred to as liquid flow generating device 400. Here, differences from liquid flow generating device 300 will be mainly described, and overlapping descriptions will not be repeated.

[0044] FIG. 7 is a cross-sectional view of the liquid flow generator 400. FIG. 8 is a plan view of the liquid flow generator 400. As shown in FIGS. 7 and 8, the liquid flow generator 400 includes a container 10 and a heater 20. The internal space 11 is filled with a working liquid 12. In the liquid flow generator 400, a force is selected to apply to the air microbubbles 14 in a direction that moves the working liquid 12 away from the vapor microbubbles 13. In the liquid flow generator 400, the internal space 11 forms a flow path 16. In the liquid flow generator 400, the first surface 20a has a non-heated portion 20ab, and the second surface 20b has a second portion 20bb. In these respects, the configuration of the liquid flow generator 400 is common to that of the liquid flow generator 300.

[0045] In the liquid flow generating device 400, the number of heating elements 20 is two. Note that, although the number of heating elements 20 is two in the examples shown in Figures 7 and 8, the number of heating elements 20 is not limited to this. In the liquid flow generating device 400, a plurality of heating elements 20 are arranged in a row along the direction in which the flow path 16 extends. In these respects, the configuration of the liquid flow generating device 400 differs from the configuration of the liquid flow generating device 300.

[0046] (Effects of Liquid Flow Generating Device 400) The effects of the liquid flow generating device 400 will be described below.

[0047] Since the liquid flow generator 400 has a plurality of heating elements 20, a plurality of vapor microbubbles 13 are generated in the working liquid 12 sealed in the flow path 16. Therefore, the liquid flow generator 400 can generate a larger-scale flow in the working liquid 12 than the liquid flow generator 300.

[0048] (Modification) Fig. 9 is a plan view of a liquid flow generating device 400 according to a modification. In the examples shown in Figs. 7 and 8, the multiple heating elements 20 are arranged in a single row, but as shown in Fig. 9, the multiple heating elements 20 may be arranged in multiple rows (in an array). In this case, the heat source 21 may be flat. With this configuration, planar cooling is possible. In the examples shown in Figs. 7 and 8, the multiple heating elements 20 are arranged on the same surface of the flow path 16, but the multiple heating elements 20 may be arranged on opposing surfaces of the flow path 16.

[0049] [Appendix] Various aspects of the present disclosure are summarized as appendices.

[0050] <Supplementary Note 1> A liquid flow generating device comprising: a container in which a working liquid is sealed; and at least one heating element; each of the at least one heating element has a first surface and a second surface opposite to the first surface, and is attached to the container so that the second surface is in contact with the working liquid; the first surface has a heating part; and the second surface has a first part opposite to the heating part; each of the at least one heating element heats the heating part to generate vapor microbubbles in the working liquid so that the vapor microbubbles are in contact with the first part; air microbubbles are released from the vapor microbubbles; and the working liquid is selected so that a force acts on the air microbubbles in a direction away from the vapor microbubbles.

[0051] <Supplementary Note 2> The liquid flow generating device according to Supplementary Note 1, wherein the at least one heating element is a plurality of heating elements.

[0052] <Supplementary Note 3> The liquid flow generating device according to Supplementary Note 1 or Supplementary Note 2, wherein the first surface further has a non-heated portion, and the second surface further has a second portion located on the opposite side to the non-heated portion.

[0053] <Supplementary Note 4> The liquid flow generating device according to Supplementary Note 3, wherein the working liquid is sealed in a flow path formed in the container, and the first portion and the second portion are aligned along an extending direction of the flow path.

[0054] <Supplementary Note 5> The liquid flow generating device according to Supplementary Note 4, wherein the at least one heating element is a plurality of heating elements, and the plurality of heating elements are arranged in a row along the direction in which the flow path extends.

[0055] <Supplementary Note 6> The liquid flow generating device according to Supplementary Note 4 or Supplementary Note 5, wherein the flow path is formed in a closed loop shape.

[0056] <Supplementary Note 7> The liquid flow generating device according to any one of Supplementary Note 1 to Supplementary Note 6, wherein the working liquid is a mixture of a plurality of liquids.

[0057] <Supplementary Note 8> The liquid flow generating device according to Supplementary Note 7, wherein one of the plurality of liquids is water, and another of the plurality of liquids is a water-soluble liquid.

[0058] <Supplementary Note 9> The liquid flow generating device according to Supplementary Note 8, wherein the water-soluble liquid is alcohol.

[0059] <Supplementary Note 10> The liquid flow generating device according to Supplementary Note 9, wherein the alcohol is any one of ethanol, 1-propanol, and 2-propanol.

[0060] <Supplementary Note 11> The liquid flow generating device according to Supplementary Note 9, wherein the alcohol is ethanol, and the concentration of the ethanol in the working liquid is 1 mass percent or more and 40 mass percent or less.

[0061] <Supplementary Note 12> The liquid flow generating device according to Supplementary Note 9, wherein the alcohol is ethanol, and a concentration of the ethanol in the working liquid is 1 mass percent or more and 10 mass percent or less.

[0062] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of this application is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0063] 100 Liquid flow generator, 10 Container, 11 Internal space, 12 Working liquid, 13 Steam microbubbles, 14 Air microbubbles, 15 Microbubbles, 16 Flow path, 20 Heating body, 20a First surface, 20aa Heated portion, 20ab Non-heated portion, 20b Second surface, 20ba First portion, 20bb Second portion, 21 Heat source, 100A Liquid flow generator, 200, 300, 400 Liquid flow generator, F1, F2 Force, MF1, MF2, MF3 Marangoni force.

Claims

1. a container filled with a working liquid; and at least one heating element, each of the at least one heating element has a first surface and a second surface opposite to the first surface, and is attached to the container such that the second surface is in contact with the working liquid, the first surface has a heating portion, the second surface has a first portion on the side opposite to the heating portion, each of the at least one heating element generates vapor microbubbles in the working liquid by heating the heating portion so as to contact the first portion, air microbubbles are released from the vapor microbubbles, the working liquid is a liquid flow generating device selected such that a force in a direction away from the vapor microbubbles acts on the air microbubbles.

2. The liquid flow generating device according to claim 1, wherein the at least one heating element is a plurality of heating elements.

3. The first surface further has a non-heating portion, The liquid flow generating device according to claim 1, wherein the second surface further has a second portion on the side opposite to the non-heating portion.

4. The working liquid is enclosed in a flow path formed in the container, The liquid flow generating device according to claim 3, wherein the first portion and the second portion are arranged side by side along the direction in which the flow path extends.

5. The at least one heating element is a plurality of heating elements, The liquid flow generating device according to claim 4, wherein the plurality of heating elements are arranged in a row along the direction in which the flow path extends.

6. The liquid flow generating device according to claim 4, wherein the flow path is formed in a closed loop.

7. The liquid flow generating device according to any one of claims 1 to 6, wherein the working liquid is a mixture of a plurality of liquids.

8. One of the plurality of liquids is water, The liquid flow generating device according to claim 7, wherein the other one of the plurality of liquids is a water-soluble liquid.

9. The liquid flow generating device according to claim 8, wherein the water-soluble liquid is alcohol.

10. The liquid flow generating device according to claim 9, wherein the alcohol is any one of ethanol, 1-propanol, and 2-propanol.

11. The alcohol is ethanol, The liquid flow generating device according to claim 9, wherein the concentration of the ethanol in the working liquid is 1 mass percent or more and 40 mass percent or less.

12. The alcohol is ethanol, The liquid flow generating device according to claim 9, wherein the concentration of the ethanol in the working liquid is 1 mass percent or more and 10 mass percent or less.