evaporator

Abstract

To inhibit increase in the size of an evaporator which generates steam through evaporation.SOLUTION: An evaporator includes: a passage formation part which has a pipe shape and forms a passage in which a fluid, an object to be evaporated, flows at the inner side of a pipe; and a structure which is disposed within the passage and connected to the passage formation part to enable heat exchange with the passage formation part and generates flow intersecting a fluid flow direction in the fluid flowing in the passage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an evaporator. [Background technology]

[0002] SOECs (Solid Oxide Electrolyzer Cells) are known that produce hydrogen by electrolyzing high-temperature steam (see, for example, Patent Document 1). In the hydrogen production device described in Patent Document 1, steam preheated by heat exchange with 900°C heat supplied from a nuclear reactor, which is an external heat source, is supplied to the SOEC. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-90425 Summary of the Invention [Problem to be solved by the invention]

[0004] When using a high-temperature heat source such as a nuclear reactor, steam can be generated from liquid water by boiling. However, when using an intermediate-temperature heat source, which is slightly higher than the boiling point, steam is generated from liquid water mainly through evaporation rather than boiling. Therefore, in an evaporator using an intermediate-temperature heat source, the flow path for generating steam from liquid water becomes long, resulting in a large evaporator.

[0005] The present invention has been made to solve at least part of the above-mentioned problems, and has an object to prevent an evaporator that generates steam by evaporation from becoming large in size. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following forms. An evaporator comprising: a flow path forming portion having a tubular shape and forming a flow path inside the tube through which a fluid to be evaporated flows; and a structure disposed within the flow path and connected to the flow path forming portion to enable heat exchange between the flow path forming portion and the flow path forming portion, the structure generating a flow that intersects with the flow direction of the fluid flowing through the flow path, the structure being a spiral fin that generates a swirling flow that intersects with the flow direction of the fluid flowing through the flow path, the structure being formed separately from the flow path forming portion and generating a force that urges the flow direction of the fluid toward the inner wall of the flow path forming portion. An evaporator comprising: a flow path forming portion having a tubular shape and forming a flow path inside the tube through which a fluid to be evaporated flows; and a structure arranged within the flow path and connected to the flow path forming portion to enable heat exchange between the flow path forming portion and the structure, which generates a flow in the fluid flowing through the flow path that intersects with the flow direction of the fluid, wherein the structure has: a first fin which generates a swirling flow in the fluid flowing through the flow path in a first direction that intersects the flow direction of the fluid; and a second fin which generates a swirling flow in a direction opposite to the first direction, the second fin being arranged downstream of the flow path relative to the first fin. An evaporator comprising: a flow path forming section having a tubular shape, which forms a flow path inside the tube through which a fluid to be evaporated flows; and a structure disposed within the flow path and connected to the flow path forming section, which is capable of heat exchange with the flow path forming section, and which generates a flow in the fluid flowing through the flow path that intersects with the flow direction of the fluid, wherein an inner wall of the flow path forming section upstream of the structure in the flow path is hydrophilically treated.an evaporator comprising: a flow path forming part having a tubular shape, forming a flow path inside the tube through which a fluid to be evaporated flows, the flow path forming part having an inner wall of the tube that has been hydrophilized; and a structure disposed within the flow path and connected to the flow path forming part to enable heat exchange between the flow path forming part and the flow path forming part, the structure causing the fluid flowing through the flow path to flow in a direction intersecting the flow direction of the fluid, the structure being a spiral fin that causes a swirling flow in the fluid flowing through the flow path that intersects the flow direction of the fluid, the structure being formed separately from the flow path forming part and generating a force that urges the flow direction of the fluid toward the inner wall of the flow path forming part.

[0007] (1) According to one aspect of the present invention, an evaporator includes a flow path forming portion having a tubular shape and forming a flow path inside the tube through which a fluid to be evaporated flows, and a structure disposed within the flow path and connected to the flow path forming portion to enable heat exchange between the flow path forming portion and the structure generating a flow that intersects the flow direction of the fluid flowing through the flow path.

[0008] According to this configuration, a structure is disposed within the flow path through which the fluid to be evaporated flows. When the fluid collides with the structure, the flow direction of the fluid flowing within the flow path is subjected to a force directed toward the inner wall of the flow path forming portion. As a result, the fluid is more likely to collide with the inner wall of the flow path forming portion or the structure compared to when no structure is disposed within the flow path. When the flow path forming portion is heated to evaporate the fluid, the structure connected to the flow path forming portion also rises in temperature. The fluid flowing within the flow path is more likely to collide with the heated inner wall or the structure of the flow path forming portion, and is therefore more likely to evaporate. As a result, by disposing a structure within the flow path, the generation of unevaporated droplets can be suppressed, shortening the length of the spray flow area and preventing the evaporator from becoming larger.

[0009] (2) In the evaporator according to the above aspect, the structure may generate a swirling flow in the fluid flowing through the flow path, the swirling flow intersecting the flow direction of the fluid. According to this configuration, a regular swirling flow is generated in the fluid flowing through the flow path. This allows the fluid to collide with the inner wall of the flow path forming portion or a structure while suppressing pressure loss for the fluid. As a result, the power required to flow the fluid (for example, pump power) can be suppressed. .

[0010] (3) In the evaporator of the above aspect, the structure may be a spiral fin that is disposed downstream of the flow path and generates a swirling flow in the same direction. With this configuration, the spiral fins generate a unidirectional swirling flow in the fluid flowing through the flow channel. This amplifies the velocity component within the cross section of the flow channel, making the liquid more likely to collide with the inner wall of the flow channel-forming section due to its momentum. With this configuration, when the flow channel-forming section is heated, the temperature of the inner wall of the flow channel-forming section becomes higher than the temperature of the fins. Particularly when the fluid temperature is low, droplet adhesion to the low-temperature fins can be suppressed while droplet collision with the higher-temperature inner wall of the flow channel-forming section can be promoted. This suppresses the accumulation of collected droplets and the occurrence of dripping on the low-temperature fins, and promotes droplet collection and evaporation on the high-temperature inner wall. As a result, the evaporator with this configuration can exhibit stable droplet evaporation performance even when the fluid temperature is low. In other words, the droplet distribution within the flow channel can be made heterogeneous with low pressure loss, allowing evaporation to be completed in a shorter spray region, enabling the evaporator to be made more compact.

[0011] (4) In the evaporator of the above aspect, the structure may have a first fin that generates a swirling flow in a first direction, and a second fin that generates a swirling flow in a direction opposite to the first direction, the second fin being positioned downstream of the flow path from the first fin. With this configuration, the swirling flows generated by the first fin and the second fin are oriented in opposite directions. Therefore, downstream of the first fin, the number of droplets colliding with the inner wall of the flow path forming section decreases, while the number of droplets colliding with the second fin increases. In particular, when the temperature of the inner wall is high, droplets colliding with the inner wall can cause the Leidenfrost phenomenon, in which the vapor generated from the droplets in the spray flow interferes with the flow. Therefore, when the temperature of the inner wall is high, the droplets in the spray flow are made to collide with the second fin, which is cooler than the inner wall, instead of the high-temperature inner wall. This allows the droplets to evaporate without causing the Leidenfrost phenomenon. As a result, the thermal conductivity can be improved and the length of the spray area can be reduced while suppressing droplets from passing through the outlet of the flow path.

[0012] (5) In the evaporator of the above aspect, the cross section of the flow path may be circular and have the same diameter throughout the entire flow direction of the fluid, and the thickness of each of the first fin and the second fin may depend on the length of the structure in the flow direction, the diameter of the cross section of the flow path, the thermal conductivity of the first fin and the second fin, and the proportion of steam to the total of liquid and steam in the fluid flowing upstream of the first fin. According to this configuration, the thicknesses of the first and second fins are determined based on parameters such as the length of the structure. When droplets collide with the second fin and evaporate, the temperature on the surface of the second fin drops. If the second fin is too thin, the temperature difference between the second fin and the saturated vapor temperature of the fluid may not be sufficient, and droplets may not evaporate on the surface of the second fin. In contrast, with this configuration, the thicknesses of the first and second fins are determined based on the proportion of steam flowing upstream of the first fin using the length of the structure in the flow direction, the diameter of the cross section of the flow path, and the thermal conductivity of the first and second fins. In other words, the necessary thicknesses of the first and second fins can be set based on the proportion of steam flowing upstream of the first fin to evaporate droplets that collide with the surfaces of the first and second fins.

[0013] (6) In the evaporator of the above aspect, an inner wall of the flow path forming portion on the upstream side of the structure in the flow path may be subjected to a hydrophilic treatment. According to this configuration, the inner wall of the flow path forming section upstream of the structure is hydrophilized, which changes the balance of three-phase interfacial tension formed by the solid, liquid, and gas on the inner wall, thereby reducing the contact angle. As a result, even if a dry patch occurs in which part of the liquid film on the inner wall breaks and exposes the inner wall, the liquid is transported to the dry patch area by tension from the liquid film or liquid slug around the dry patch, and a stable liquid film is formed on the entire inner wall. As a result, the occurrence of nucleate boiling and the steam shear force in the annular flow are prevented downstream of the flow path where the structure is located. This can suppress the direct generation of droplets, such as droplets formed from a liquid film due to the vaporization of the vapor. In other words, the generation of dry patches is suppressed, so the length of the flow path can be shortened and the size of the evaporator can be prevented from increasing.

[0014] (7) In the evaporator of the above aspect, the cross section of the flow path may be circular and have the same diameter throughout the entire flow direction of the fluid, and the diameter of the cross section of the flow path may depend on the number of capillaries, the flow velocity of the fluid flowing into the upstream side of the structure, and the thickness of the liquid film. This configuration allows the thickness of the liquid film of the fluid to be controlled to be determined using the cross-sectional diameter of the flow channel, the capillary number (determined by the viscosity and surface tension of the fluid), and the flow velocity of the fluid. The thinner the liquid film formed by slug flow and annular flow, the smaller the droplets generated by dry patches and the shear force of the steam flow can be. This configuration allows the thickness of the liquid film to be controlled to be set according to the use of the steam generated by the evaporator, and parameters such as the cross-sectional diameter of the flow channel can be set while suppressing increases in pressure loss.

[0015] The present invention can be realized in various forms, for example, an evaporator, a steam generating device, a hydrogen production system, an SOEC, a steam generating method, a method for designing an evaporator, a system including these devices, a computer program for executing these devices, a server device for distributing this computer program, a non-transitory storage medium storing the computer program, etc. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is an explanatory diagram of an evaporator according to an embodiment of the present invention; [Figure 2] FIG. [Figure 3] FIG. 10 is an explanatory diagram of the effect of the fins. [Figure 4] FIG. 2 is a schematic cross-sectional view of an evaporator of Comparative Example 1. [Figure 5] FIG. 10 is an explanatory diagram of an evaporator of Comparative Example 2. [Figure 6]FIG. 10 is an explanatory diagram of an evaporator of Comparative Example 2. [Figure 7] FIG. 6 is an explanatory diagram of an evaporator according to a second embodiment. [Figure 8] FIG. 10 is a schematic perspective view of a fin according to a second embodiment. [Figure 9] FIG. 10 is an explanatory diagram of the relationship between temperature difference and steam generation. [Figure 10] 10A and 10B are diagrams illustrating the effect of the fins of the second embodiment. [Figure 11] FIG. 10 is an explanatory diagram of a method for calculating the thickness of a fin. [Figure 12] FIG. 10 is an explanatory diagram of a method for calculating the thickness of a fin. [Figure 13] FIG. 10 is an explanatory diagram of the relationship between the steam quality at the inlet and the thickness of the fin. [Figure 14] FIG. 10 is an explanatory diagram of an evaporator according to a third embodiment. [Figure 15] FIG. 15 is a schematic enlarged view of the area in FIG. 14. [Figure 16] 10A and 10B are diagrams illustrating the effect of a flow path forming portion that has been subjected to a hydrophilic treatment. [Figure 17] FIG. 1 is a diagram illustrating the relationship between the capillary number and the dimensionless liquid thickness. [Figure 18] FIG. 10 is an explanatory diagram of the relationship between steam fluctuations that change depending on the representative diameter and the average heat flux. DETAILED DESCRIPTION OF THE INVENTION

[0017] First Embodiment 1. Evaporator configuration: FIG. 1 is an explanatory diagram of an evaporator 100 according to one embodiment of the present invention. The evaporator 100 of this embodiment generates steam from liquid water by heating a flow path forming section 10 that forms a flow path 11 through which water to be evaporated flows. Fins (structures) 20 are provided to generate a swirling flow in the water flowing in the flow path 11. The water that generates the swirling flow is more likely to collide with the heated inner wall 12 of the flow path forming section 10 and the fins 20 connected to the flow path forming section 10, and is more likely to evaporate. As a result, the water flowing in the flow path 11 is more likely to evaporate, and the size of the evaporator 100 is reduced. This suppresses the degradation of the oxidized material.

[0018] 1 shows a block diagram of a portion of the configuration of the evaporator 100 and a schematic cross-sectional view of the flow path 11. As shown in Fig. 1, the evaporator 100 includes a flow path forming unit 10, fins 20, a tank 40 that stores liquid water to be supplied to the flow path 11, a pump 50 that supplies water from the tank 40 to the flow path 11, a heater 30 that heats the flow path forming unit 10, and a control unit 60 that controls the heater 30 and the pump 50.

[0019] The flow path forming section 10 has a tubular shape with a circular cross section and a straight central axis. In this embodiment, the direction from the cylindrical inlet to the outlet formed by the flow path forming section 10 is defined as the flow direction of water flowing through the flow path 11. The circular cross section of the flow path 11 has the same diameter throughout the entire flow direction. Fins 20 are arranged in a portion of the downstream side of the flow path 11, as shown in FIG. 1.

[0020] FIG. 2 is a schematic perspective view of the fin 20. As shown in FIG. 2, the fin 20 is a spiral fin that generates a swirling flow DR1 (FIG. 1) in the same direction as the water flowing through the flow path 11. In other words, the fin 20 generates a swirling flow DR1 in the water flowing through the flow path 11, as a flow that intersects the flow direction. The fin 20 is connected to the inner wall 12 of the flow path forming portion 10 at a portion not shown in FIG. 1. Therefore, when the flow path forming portion 10 is heated by the heater 30, heat is transferred from the flow path forming portion 10 to the fin 20, and the temperature of the fin 20 increases. In other words, the fin 20 is a structure that can exchange heat with the flow path forming portion 10 by being connected to the flow path forming portion 10. In this embodiment, a Cartesian coordinate system CS is defined, which has a Z-axis parallel to the central axis OL of the flow path 11 and X- and Y-axes perpendicular to the Z-axis. The Cartesian coordinate system CS shown in FIG. 1 corresponds to the Cartesian coordinate systems CS shown in FIG. 2 and subsequent figures.

[0021] A portion of the flow path 11 shown in Figure 1 shows a two-phase region where liquid water and steam exist. Within the flow path 11, the region changes from a boiling region to a spray region from the upstream side. In this embodiment, the control unit 60 controls the pump 50 and the heater 30 so that the fins 20 are included in the downstream spray region. The fins 20 generate a swirling flow DR1 that flows along the central axis OL of the flow path 11. The swirling flow DR1 flows counterclockwise on the XY plane when viewed from the positive Z-axis direction.

[0022] The control unit 60 determines the amount of steam to be generated in the flow path 11 in response to a request from a steam utilization device (not shown in FIG. 1 ) that utilizes the steam generated in the evaporator 100. The control unit 60 generates steam from the water flowing in the flow path 11 by controlling the rotation of the pump 50 and the heating of the heater 30 in accordance with the determined amount of steam. The generated water vapor is supplied to the steam utilization device.

[0023] FIG. 3 is an explanatory diagram of the effect of the fins 20. In FIG. 3, when a fin 20 having a length of 120 mm in the flow direction is arranged and the temperature of the inner wall 12 is 200°C, the change C1 in the droplet collection efficiency in the flow path 11 is shown by a solid line, and the change C2 in the pressure drop (pressure drop) is shown by a dashed line. The droplet collection efficiency is the proportion of droplets that are collected downstream of the fin 20 out of the droplets that flow in from the upstream side of the fin 20. A smaller droplet collection efficiency indicates that more droplets are generated as vapor. The fin 20 completes one rotation around the central axis OL when it moves 40 mm along the central axis OL. If one rotation of the fin is considered to be one segment, a fin with a length of 120 mm is formed by three fin segments.

[0024] The horizontal axis in Fig. 3 represents the distance downstream when the position of the upstream end (negative Z-axis direction) of the fin 20 in the flow path 11 is set to zero. As shown by the change C1 in the droplet collection efficiency in Fig. 3, the droplet collection efficiency at a distance of about 40 mm is 10 -2 (1%), and the droplet collection rate at a distance of about 60 mm is 10 -3 (0.1%). In other words, at a distance of about 60 mm, 99.9% Vaporization into steam is complete. As shown by the change in pressure loss C2 in Figure 3, the pressure loss until the fluid passes through fin 20 is approximately 0.54 kPa. The values ​​shown in Figure 3 are based on the condition that the flow velocity Vz of the fluid in flow path 11 is 20 m / s.

[0025] FIG. 4 is a schematic cross-sectional view of an evaporator 100x of Comparative Example 1. FIG. 4 shows a schematic cross-section of a portion of the flow path forming unit 10, which is included in the configuration of the evaporator 100x of Comparative Example 1. The evaporator 100x of Comparative Example 1 differs from the evaporator 100 of the present embodiment only in that fins 20 are not arranged in the flow paths 11x. By providing the fins 20, the evaporator 100 of the present embodiment makes it easier for water flowing in the flow paths 11 to collide with the fins 20 and the inner wall 12 of the flow path forming unit 10, compared to the evaporator 100x that does not have the fins 20. Therefore, in the evaporator 100 of the present embodiment, the length of the flow paths 11 required to generate steam from water can be shortened, compared to the evaporator 100 of Comparative Example 1.

[0026] 5 and 6 are explanatory diagrams of an evaporator 100y of Comparative Example 2. FIG. 5 shows a schematic cross section of a portion of the flow path forming section 10 of the configuration of the evaporator 100y of Comparative Example 2. The evaporator 100y of Comparative Example 2 differs from the evaporator 100 of the present embodiment only in that it includes a filter 20y instead of the fin 20. The porosity ε of the filter 20y is 0.9. The filter 20y forms a square lattice with a side length of 100 μm in the XY plane. That is, the mesh size Dp of the filter 20y is 100 μm. The length of the flow path 11y of Comparative Example 2 is the same as the length of the flow path 11 of the above embodiment.

[0027] 6 shows the pressure loss depending on the thickness of the filter 20y under the same conditions as those shown in FIG. 3. As shown in FIG. 6, the pressure loss increases as the thickness of the filter 20y along the flow direction (Z-axis direction) increases to 5 mm, 10 mm, and 20 mm. In Comparative Example 2, the pressure loss is 13.1 kPa when the thickness of the filter 20y is 5 mm. On the other hand, in the evaporator 100 of this embodiment, the pressure loss until the fluid passes through the fins 20 is approximately 0.54 kPa, which is much smaller than that of Comparative Example 2.

[0028] As described above, the evaporator 100 of this embodiment includes fins 20 arranged in the flow path 11. The fins 20 are structures that are connected to the flow path forming portion 10 and enable heat exchange with the flow path forming portion 10. The fins 20 generate a flow that intersects the flow direction of water flowing through the flow path 11. In this embodiment, the water flowing in the flow path 11 collides with the fins 20, and the flow direction of the water is subjected to a force toward the inner wall 12 of the flow path forming portion 10. As a result, the water as a fluid is more likely to collide with the inner wall 12 of the flow path forming portion 10 or the fins 20 compared to when the fins 20 are not arranged in the flow path 11. When the flow path forming portion 10 is heated to evaporate the water, the fins 20 connected to the flow path forming portion 10 also rise in temperature. The water flowing in the flow path 11 is more likely to collide with the heated inner wall 12 of the flow path forming portion 10 or the fins 20, and is therefore more likely to evaporate. As a result, by disposing the fins 20 in the flow passage 11, the generation of non-evaporated droplets can be suppressed, the length of the spray area can be shortened, and the evaporator 100 can be prevented from becoming large.

[0029] Furthermore, the fins 20 in this embodiment are disposed downstream of the flow path 11. The fins 20 are spiral fins that generate a unidirectional swirling flow in the water flowing in the flow path 11. In this embodiment, a regular swirling flow is generated in the water flowing in the flow path 11. This allows the water to collide with the inner wall 12 of the flow path forming section 10 or the fins 20 while suppressing pressure loss in the water flow. As a result, the power required to flow the water (e.g., pump power) can be reduced. Furthermore, in this embodiment, a unidirectional swirling flow is generated in the water flowing in the flow path 11, amplifying the velocity component in the cross section of the flow path 11, and the momentum of the droplets makes them more likely to collide with the inner wall 12 of the flow path forming section 10. In this embodiment, when the flow path forming section 10 is heated, the temperature of the inner wall 12 of the flow path forming section 10 becomes higher than the temperature of the fins 20. In particular, when the water temperature is low, droplet adhesion to the low-temperature fins 20 can be suppressed while droplet collision with the higher-temperature inner wall 12 of the flow path forming portion 10 can be promoted. This suppresses the accumulation of collected droplets and the occurrence of dripping on the low-temperature fins 20, and promotes droplet collection and evaporation on the high-temperature inner wall 12. As a result, the evaporator 100 of this embodiment can exhibit stable droplet evaporation performance even when the water temperature is low. In other words, since the droplet distribution in the flow path 11 can be made non-uniform with low pressure loss, evaporation is completed in a shorter spray flow region, and the evaporator 100 can be made more compact.

[0030] Second Embodiment Fig. 7 is an explanatory diagram of an evaporator 100a according to a second embodiment. Fig. 7 shows a schematic cross-sectional view of a portion of a flow path forming portion 10 included in the evaporator 100a. In the second embodiment, the shape of the fins 20a arranged in the flow paths 11a is different from that of the fins 20 in the first embodiment. Therefore, in the second embodiment, the fins 20a and the influence of the fins 20a will be described, and a description of the same configuration as in the first embodiment will be omitted.

[0031] As shown in FIG. 7, the fin 20a of the second embodiment includes a first fin 21 and a second fin 22. The first fin 21 generates a swirling flow DR1 in the same direction as the fin 20 of the first embodiment. On the other hand, the second fin 22 generates a swirling flow DR2 in the opposite direction to the swirling flow DR1 generated by the first fin. In other words, when viewed from the positive Z-axis direction, the first fin 21 generates a counterclockwise flow on the XY plane, and the second fin 22 generates a clockwise flow on the XY plane. The direction of the swirling flow DR1 corresponds to the first direction, and the direction of the swirling flow DR2 corresponds to the second direction.

[0032] FIG. 8 is a schematic perspective view of a fin 20a of the second embodiment. The length of the fin 20a of the second embodiment along the Z axis is 120 mm, the same as that of the fin 20 of the first embodiment. The fin 20a is composed of three segments, each of which consists of a first fin 21 that rotates halfway around the central axis and a second fin 22 that is connected to the first fin 21 and rotates halfway around the central axis. Therefore, the length of one segment along the Z axis is 40 mm. When the fin 20a is arranged in the flow path 11, the first fin 21 is arranged downstream of the second fin 22 in each segment.

[0033] The amount of evaporation of liquid water into vapor varies depending on the temperature difference between the water flowing through the flow path 11a and the temperature of the inner wall 12 or the fins 20a of the flow path forming portion 10. FIG. 9 is an explanatory diagram of the relationship between the temperature difference ΔTs and vapor generation. FIG. 9 shows a boiling curve C3, where the horizontal axis represents the temperature difference ΔTs, calculated by subtracting the saturation temperature Ts (K) of water from the temperature Tw (K: Kelvin) of the inner wall 12, and the vertical axis represents the heat flux qw passing through the surface of the inner wall 12. As shown in FIG. 9, if the temperature difference ΔTs is within the range of nucleate boiling, the higher the temperature difference ΔTs, the greater the heat flux qw, which increases the amount of vapor generated from droplets through heat exchange with the inner wall 12. On the other hand, when the temperature difference ΔTs exceeds 100 K and the system transitions to vapor film boiling, the surface of the high-temperature inner wall 12 becomes more likely to be covered with vapor evaporated from the droplets, and the Leidenfrost phenomenon, which inhibits droplets from colliding with the inner wall 12, begins. Therefore, when the temperature transitions to vapor film boiling, even if the temperature difference ΔTs increases, the heat flux qw does not increase and the amount of vapor generated decreases. When the temperature rises above the Leidenfrost temperature at the Leidenfrost point Pl shown in Figure 9, the amount of vapor generated also increases as the temperature difference ΔTs increases.

[0034] The fins 20a of the second embodiment have a first fin 21 and a second fin 22 that generate swirling flows DR1 and DR2 in different directions. Therefore, the fins 20a make it easier for water flowing through the flow path 11a to collide with the fins 20a rather than with the inner wall 12. The temperature of the fins 20a is lower than the temperature of the inner wall 12 of the flow path forming section 10, which is directly heated. Therefore, when the temperature of the inner wall 12 of the flow path forming section 10 is high and the temperature difference ΔTs is large, the droplets collide with the low-temperature fins 20a instead of the inner wall 12, which makes it easier for the droplets to evaporate.

[0035] Fig. 10 is an explanatory diagram of the effect of the fin 20a of the second embodiment. Fig. 10 additionally shows, in addition to Fig. 3, a change C1a (solid line) in the droplet collection efficiency and a change C2a (dashed line) in the pressure loss of the second embodiment when the temperature of the inner wall 12 is 400°C. Note that in Fig. 10, the change C1 in the droplet collection efficiency and the change C2 in the pressure loss of the first embodiment are shown by thin lines.

[0036] As shown in Figure 10, droplet collection efficiency C1a is 10 -3 (less than 0.1%). That is, at a distance of about 30 mm, 99.9% of the water has been vaporized into steam. As shown by the change in pressure loss C2a in FIG. 10, the pressure loss until the water passes through the fins 20a is about 1.1 kPa, which is significantly smaller than when the filter 20y of Comparative Example 2 shown in FIG. 6 is installed.

[0037] Next, the thickness δ (mm) of the fin 20a was evaluated. To activate droplet collection and evaporation on the surface of the fin 20a instead of on the inner wall 12 of the flow path forming section 10, the cross section of the fin 20a must transport the necessary heat by thermal conduction with a high heat flux qw. For example, if the thermal conductivity of the fin 20a is low and the fin 20a does not have a sufficient thickness δ, the temperature of the fin 20a on the central axis OL side, where the droplet distribution is dense due to the swirling flows DR1 and DR2 flowing in different directions, may be low. In this case, a sufficient temperature difference ΔTs cannot be obtained on the central axis OL side of the fin 20a, and droplets collected on the surface of the fin 20a do not vaporize. Unevaporated droplets accumulate on the surface of the fin 20a and may move to and come into contact with the high-temperature inner wall 12, potentially causing steam instability such as bumping. Therefore, the thickness δ of the fin 20a must be at least a certain thickness.

[0038] 11 and 12 are explanatory diagrams of a method for calculating the thickness δ of the fin 20a. FIG. 11 shows a cross-sectional shape of a portion of a simplified model of the fin 20a for calculating the thickness δ of the fin 20a. In the simplified model shown in FIG. 11, the height H (=10 mm) of the fin 20a, which is the radial length of the fin 20a in the flow path 11a, and the thickness δ of the fin 20a are defined. In addition, in the second embodiment, the thermal conductivity λ is defined as 18 (W / m / K).

[0039] FIG. 12 shows an image of the heat quantity between the fin 20a and the droplets AD that evaporate upon impact with the fin 20a. In the second embodiment, the heat quantity Qw transferred from the flow path forming portion 10 to the fin 20a, the total latent heat quantity L of the droplets, and the total length of the fin 20a were defined as 120 mm, and the thickness δ was evaluated for inlet steam quality Xin of 0.6 and 0.8. The inlet steam quality Xin is the ratio of steam to the total of liquid water and steam flowing upstream of the fin 20a. That is, in the second embodiment, the thickness δ of each of the first fin 21 and the second fin 22 depends on the length of the fin 20a in the flow direction (120 mm), the height H as the diameter of the flow path 11, the thermal conductivity λ, and the inlet steam quality Xin.

[0040] FIG. 13 is an explanatory diagram of the relationship between the inlet steam quality Xin and the thickness δ of the fin 20a. FIG. 13 shows the temperature at each position on the fin 20a in the radial direction (height H direction) that changes according to the thickness δ of the fin 20a when a central temperature of 120°C is ensured. In FIG. 13, the temperature when the inlet steam quality Xin is 0.6 is shown by four types of thick straight lines connecting the black circles. Specifically, the temperature when the thickness δ is 2 mm is shown by the two-dot chain change line L62, the temperature when the thickness δ is 3 mm is shown by the dashed change line L63, the temperature when the thickness δ is 4 mm is shown by the solid change line L64, and the temperature when the thickness δ is 5 mm is shown by the dashed change line L65. Similarly, in FIG. 13, the temperature when the inlet steam quality Xin is 0.8 is shown by three types of thin straight lines connecting the black squares. Specifically, the temperature when the thickness δ is 3 mm is shown by the dashed change line L83, and the temperature when the thickness δ is 4 mm is shown by the solid change line L64. The temperature at a thickness δ of 5 mm is shown by a solid change line L84, and the temperature at a thickness δ of 5 mm is shown by a dashed change line L85. Note that the change line when the steam quality Xin is 0.8 and the thickness δ is 2 mm is almost the same as the change line L64, so it is not shown in the figure.

[0041] To prevent the Leidenfrost phenomenon from occurring on the surface of the fin 20a, it is preferable to keep the temperature of the fin 20a near the inner wall 12, where the temperature is highest, below 300°C, based on the boiling curve C3 in Fig. 9. As shown in Fig. 13, the temperature of the inner wall 12 exceeds 300°C on the change lines L62 and L63. Therefore, it is preferable that the thickness δ of the fin 20a be 4 mm or more.

[0042] As described above, the evaporator 100a of the second embodiment includes the fin 20a having the first fin 21 and the second fin 22. The second fin 22 is disposed downstream of the first fin 21 and generates a swirling flow DR2 in the opposite direction to the swirling flow DR1 generated by the first fin 21. Therefore, in the second embodiment, downstream of the first fin 21, the amount of droplets colliding with the inner wall 12 of the flow path forming portion 10 decreases, and the amount of droplets colliding with the second fin 22 increases. In particular, when the temperature of the inner wall 12 is high, if droplets collide with the inner wall 12, the Leidenfrost phenomenon occurs, in which the vapor generated from the droplets in the spray flow interferes with the droplets. Therefore, when the temperature of the inner wall 12 is high, the droplets in the spray flow collide with the second fin 22, which is cooler than the inner wall 12, instead of the high-temperature inner wall 12. This allows the droplets to evaporate without causing the Leidenfrost phenomenon. As a result, the blow-by of droplets from the outlet of the flow path 11 can be suppressed, while the thermal conductivity can be improved and the length of the spray area can be reduced.

[0043] In the second embodiment, the thickness δ of each of the first fin 21 and the second fin 22 depends on the length of the fin 20a in the flow direction (120 mm), the height H as the diameter of the flow path 11, the thermal conductivity λ, and the inlet steam quality Xin. In the second embodiment, when the droplets AD collide with the first fin 21 or the second fin 22 and evaporate, the temperature on the surface of the second fin 22 decreases. If the thickness δ of the fin 20a is small, the temperature difference ΔTs between the fin 20a and the saturated steam temperature of water cannot be obtained, and the droplets AD may not evaporate on the surface of the fin 20a. In contrast, in the second embodiment, the thickness δ of the fin 20a is determined using the length of the fin 20a in the flow direction, the height H of the fin 20a, and the thermal conductivity λ of the fin 20a according to the steam quality Xin flowing upstream of the fin 20a. That is, the thickness of the fins 20a required to evaporate the droplets AD that collide with the surfaces of the fins 20a can be set according to the steam quality Xin flowing upstream of the fins 20a.

[0044] Third Embodiment Fig. 14 is an explanatory diagram of an evaporator 100b of the third embodiment. Fig. 14 shows a schematic cross-sectional view of a flow path 11b upstream of the fins 20 in the flow path 11 of the flow path forming section 10 included in the evaporator 100 of the first embodiment. The third embodiment differs from the first embodiment in that the inner wall 12b of the flow path forming section 10b on the upstream side where the fins 20 are not arranged is hydrophilized. Therefore, in the third embodiment, only the hydrophilized inner wall 12b will be described, and a description of the same configuration as in the first embodiment will be omitted.

[0045] As shown in Figure 14, liquid water supplied to flow channel 11b is heated through inner wall 12b, generating a bubbly flow containing a bubble slug Sa as it flows downstream, and the slug flow generates an annular flow. Subsequently, fins 20 (not shown) generate steam from the droplets. To minimize pressure loss and achieve compact evaporators 100 and 100b, it is preferable to minimize the amount of droplets delivered to fins 20.

[0046] Fig. 15 is a schematic enlarged view of the region AR1 in Fig. 14. The flow path forming portion 10b of the third embodiment is made of a material in which the surface of a metallic porous body has been subjected to a hydrophilic treatment. Specifically, the flow path forming portion 10b is formed from a material obtained by coating a 0.5 mm thick, 60% porosity SUS316L metal fiber sintered body with a hydrophilic coating using an SiO2 based material.

[0047] Here, the amount of heat Q supplied to the water flowing in the flow path 11b is expressed as in the following formula (1) using the parameters shown in Fig. 15. The temperature difference ΔTs in formula (1) is expressed as in the following formula (2).

number

number

[0048] As the phase change occurs, the liquid film formed on the inner wall 12b becomes thinner. When a dry patch occurs in which the liquid film disappears and the temperature of the inner wall 12b rises, the liquid film area Af in the above formula (1) decreases, and the amount of heat Q supplied to the water from the inner wall 12b decreases. This can lead to the direct generation of droplets, such as the generation of boiling nuclei within the thin liquid film or droplet formation from the liquid film due to the vapor shear force in the annular flow. To address this issue, in the third embodiment, the flow path forming portion 10b changes the balance of tension at the three-phase interface formed by the solid, liquid, and gas, thereby reducing the contact angle (dynamic contact angle). As a result, even if a dry patch occurs, the liquid water is transported by the tension from the surrounding liquid film or liquid slug, and a stable liquid film is formed on the inner wall 12b.

[0049] 16 is an explanatory diagram of the effect of the flow path forming portion 10b that has been subjected to hydrophilic treatment. In FIG. 16, the mass rate (kg / m) that can be evaporated per unit length of the flow path 11b is shown. 2The graph shows the steam flow rate fluctuation (%) when the mass velocity (m / s) is changed. The steam flow rate fluctuation is an index obtained by detecting the amount of droplets as a flow rate fluctuation by evaporating the droplets flowing into the fins 20, 20a using a lattice filter. In other words, the larger the value of the steam flow rate fluctuation, the more droplets there are and the more dry patches occur on the inner wall 12b. The unit length of the flow path 11b is 100 mm in the flow direction. The higher the mass velocity, the easier it is for water to evaporate in the flow path 11b.

[0050] 16 shows plots of steam flow rate fluctuations for Example 1, which includes the flow path forming portion 10b of the third embodiment, and Comparative Example 3, which includes a metal inner wall that has not been hydrophilically treated. The four plots for Example 1 and Comparative Example 3 correspond to inner wall temperatures of 110°C, 120°C, 130°C, and 140°C. The temperatures corresponding to each plot are indicated by numbers in the graph. The plots for Example 1 are indicated by black circles, and the plots for Comparative Example 3 are indicated by black squares.

[0051] 16, comparing the area surrounded by the solid ellipse corresponding to Example 1 with the area surrounded by the dashed ellipse corresponding to Comparative Example 3, Example 1 has a higher mass velocity and a smaller fluctuation in steam flow rate. That is, in Example 1, the amount of droplets flowing into the fins 20, 20a arranged downstream of the flow path 11b is smaller than in Comparative Example 3.

[0052] The non-dimensional liquid film thickness (δw / de) obtained by dividing the liquid film thickness δw by the representative diameter de of the pipe of the flow path 11b is calculated by the viscosity coefficient μ L (Pa·s) and surface tension σ L (N / m) As shown in equation (3), when the physical property value and the liquid flow velocity (mass velocity) are constant, the smaller the diameter of the flow path 11b, the smaller the liquid film thickness Δw.

[0053]

number

[0054] FIG. 17 is an explanatory diagram of the relationship between the capillary number Ca and the dimensionless liquid thickness δw / de. FIG. 17 shows the dimensionless liquid thickness δw / de that changes depending on the capillary number Ca. The dimensionless liquid thickness δw / de is expressed as in the following equation (4) using constants α and β calculated by the least squares method. As shown in FIG. 17, the dimensionless liquid thickness δw / de increases as the capillary number Ca increases.

[0055]

number

[0056] In the third embodiment, the representative diameter de of the flow path 11b is calculated using the relationship shown in the above formulas (3) and (4). In other words, the representative diameter de is calculated by the number of capillaries Ca and the bubble velocity u of the water flowing through the upstream flow path 11b where the fins 20 and 20a are not arranged. b and the liquid film thickness δw.

[0057] FIG. 18 is an explanatory diagram of the relationship between steam fluctuations that change depending on the representative diameter de and the average heat flux. In FIG. 18, the horizontal axis represents steam fluctuations (%), and the vertical axis represents the average heat flux (W / m 2 ) are plotted for Example 2 and Comparative Example 4, where the representative diameter de is set to 1, 2, and 3 mm. The four plots in Example 2 and Comparative Example 4 correspond to inner wall temperatures of 110°C, 120°C, 130°C, and 140°C. In Example 2, the flow path forming portion 10b is formed of a porous body that has been hydrophilically treated, as in the third embodiment. On the other hand, in Comparative Example 4, the flow path forming portion has a metal inner wall that has not been hydrophilically treated, as in Comparative Example 3.

[0058] In Fig. 18, the plots for the representative diameter de of Example 2, where de is 1 mm, are shown by black triangles, the plots for the representative diameter de of 2 mm are shown by black circles, and the plots for the representative diameter de of 3 mm are shown by black squares. On the other hand, the plots for the representative diameter de of Comparative Example 4, where de is 1 mm, are shown by white triangles, the plots for the representative diameter de of 2 mm are shown by white circles, and the plots for the representative diameter de of 3 mm are shown by white squares. The solid line (1 mm) in Fig. 18 and the broken line Example 2, which is surrounded by the ellipses of the line (2 mm) and the dashed line (3 mm), has smaller steam fluctuations and a larger average heat flux than Comparative Example 4. That is, Example 2 can reduce the amount of droplets flowing into the downstream flow path 11 where the fins 20 are arranged more than Comparative Example 4.

[0059] As described above, in the evaporator 100b of the third embodiment, the inner wall 12b of the flow path forming portion 10b upstream of the fins 20 and 20a is hydrophilized. In the third embodiment, the hydrophilized inner wall 12b of the flow path forming portion 10b upstream of the fins 20 and 20a changes the balance of interfacial tension between solids, liquids, and gases on the inner wall 12b, thereby reducing the contact angle. Even if a dry patch occurs on the inner wall 12b, where a portion of the liquid film breaks and exposes the inner wall 12b, tension transports liquid water from the liquid film or liquid slug surrounding the dry patch to the dry patch, forming a stable liquid film over the entire inner wall 12b. As a result, direct droplet generation, such as nucleate boiling and droplet formation from the liquid film due to vapor shear forces in annular flow, can be suppressed downstream of the flow path 11b where the fins 20 and 20a are located. That is, since the occurrence of dry patches is suppressed, the length of the flow path 11b can be shortened, and the evaporator 100b can be prevented from becoming large.

[0060] Furthermore, in the third embodiment, the flow path forming portion 10b is formed of a porous material in addition to being hydrophilized. By forming the flow path forming portion 10b of a porous material, the contact angle of the inner wall 12b is further reduced. This further reduces the occurrence of dry patches on the inner wall 12b.

[0061] In the third embodiment, the representative diameter de of the flow path 11b is determined by the number of capillaries Ca and the velocity u of bubbles in the water flowing through the upstream flow path 11b where the fins 20 and 20a are not arranged. b and the liquid film thickness δw. With this configuration, the thinner the liquid film formed by the slug flow and the annular flow, the smaller the droplets that are generated due to the occurrence of dry patches and the shear force of the steam flow. In the third embodiment, the thickness of the liquid film to be controlled is set according to the use of the steam generated by the evaporator 100b, and parameters such as the diameter of the cross section of the flow path can be set while suppressing an increase in pressure loss.

[0062] <Modifications of the above embodiment> The present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the spirit of the present invention, including, for example, the following modifications: In the above-described embodiment, part of the configuration realized by hardware may be replaced by software, and conversely, part of the configuration realized by software may be replaced by hardware.

[0063] <Variation 1> The evaporators 100, 100a, 100b of the first to third embodiments can be modified as long as they include a structure that generates a flow that intersects with the flow direction of the flow path 11. For example, the evaporator 100 only needs to include a flow path forming unit 10 that forms the flow path 11 through which water flows as a fluid, and does not necessarily need to include the heater 30, the tank 40, the pump 50, and the control unit 60. The heater 30 and the like may be included in another device, and the other device may be connected to the evaporator 100.

[0064] In the first and second embodiments, the fin 20 that generates the swirling flow DR1 and the fin 20a that generates the swirling flows DR1 and DR2 have been described, but the flows generated in the flow path 11 do not have to be the swirling flows DR1 and DR2. For example, a metal plate inclined at a predetermined angle with respect to the central axis may be disposed as a structure in the flow path 11, connected to the flow path forming portion 10. In this case, when the fluid flowing along the flow direction collides with the metal plate, a flow that intersects the flow direction and is different from the swirling flows DR1 and DR2 occurs in the fluid. The crossing flows cause the fluid to collide with the inner wall 12 more frequently, which makes it easier for the fluid to evaporate.

[0065] The fins 20, 20a as structures are arranged on the downstream side of the flow path 11, but they may also be arranged on the upstream side or arranged throughout the entire flow path 11. In this case, the flow path forming section 10 on which the fins 20, 20a are arranged may be combined on the downstream side of another flow path forming section that forms a flow path different from the flow path 11 on which the fins 20, 20a are arranged. The number of segments (length in the flow direction) of the fins 20, 20a in the above embodiment and their radial size relative to the flow path 11 can be modified in various ways.

[0066] In the first to third embodiments, the flow path forming unit 10 forms the flow path 11 having a circular cross section and a linear central axis OL, but the shape of the flow path 11 can be modified. The cross section of the flow path 11 may be rectangular or a polygon such as an octagon. In this case, the pipe diameter may be the distance from the center of gravity of the cross section of the flow path 11 to each side. Furthermore, the central axis OL of the flow path 11 may not be linear, but may be curved, for example. In this case, the flow direction can be defined as a flow along the central axis connecting each cross section.

[0067] In the second embodiment, the thickness δ of the fin 20a was set using the length of the fin 20a in the flow direction, the height H as the diameter of the flow path 11, the thermal conductivity λ, and the steam quality Xin in order to evaporate the droplets AD that collide with the fin 20a, but it may be set using other methods. The fin 20a does not need to have a uniform thickness δ over its entirety, and may have a thickness δ of 0.2 mm or 0.3 mm as shown in FIG. 13. The thickness δ may be set appropriately depending on the steam quality Xin flowing upstream of the fin 20a, etc.

[0068] <Variation 2> In the third embodiment, the inner wall 12b of the flow path forming portion 10b on the upstream side, where the fins 20 and 20a are not disposed, is hydrophilized. However, the hydrophilized inner wall 12b is not limited to the upstream side, and the entire inner wall 12b may be hydrophilized. Structures such as the fins 20 and 20a may not be disposed in the flow path 11b on the upstream side of the hydrophilized inner wall 12b. Even in this case, the hydrophilized inner wall 12b can suppress the occurrence of dry patches in the flow path 11b where the slug flow transitions to the annular flow, thereby shortening the flow path 11b for generating steam.

[0069] In the third embodiment, the flow path forming portion 10b is formed of a porous body that has been hydrophilically treated. However, the flow path forming portion 10b may not be formed of a porous body, and for example, the surface of the inner wall of a metal may be hydrophilically treated. Furthermore, well-known techniques, such as inorganic film coating of alumina or inorganic film coating of silica, can be applied as the hydrophilic treatment applied to the flow path forming portion 10b. The porous body forming the flow path forming portion 10b is formed of a material that has been hydrophilically coated on SUS316L, but well-known porous body materials can be applied.

[0070] In the third embodiment, the representative diameter de of the flow path 11b is determined by the capillary number Ca and the bubble velocity u band the liquid film thickness δw, but it may be set by other methods. The representative diameter de may be set according to the steam generation capacity required of the evaporator, or the representative diameter de may be reduced by using a manifold or a filter.

[0071] Although the present aspect has been described above based on the embodiments and modifications, the above-described embodiments are intended to facilitate understanding of the present aspect and are not intended to limit the present aspect. The present aspect may be modified or improved without departing from the spirit and scope of the claims. In addition, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of symbols]

[0072] 10, 10b...flow path forming section 11, 11b, 11x...flow path 12,12b…Inner wall 20, 20a...Fin (structure) 20y...filter 21...First fin 22...Second fin 30...Heater 40...Tank 50...Pump 60...Control unit 100, 100a, 100b, 100x, 100y...Evaporator AD…droplet AR1…area Af: Liquid film area C1, C1a...Change in droplet collection rate C2, C2a...Change in pressure loss C3…Boiling curve CS...Cartesian coordinate system Ca: Number of capillaries DR1,DR2…Swirling flow σ L …surface tension μ L ...viscosity coefficient L…Total latent heat amount L62~L64, L83~L85...Variation line L63...Variable Line L64...Variation Line L65...Variation Line L83...Variable Line L84...Variation Line L85...Variation Line OL: Central axis of the flow path Pl…Leidenfrost point Q,Qw…heat amount qw…Heat flux ΔTs…Temperature difference Ts…Saturation temperature Tw: Temperature of the inner wall Vz…Flow velocity Xin...Steam quality de…Representative diameter u b …bubble velocity δw: Liquid film thickness δw / de: dimensionless liquid thickness

Claims

1. An evaporator comprising: a flow path forming portion having a tubular shape and forming a flow path inside the tube through which a fluid to be evaporated flows; a structure that is disposed in the flow path and is connected to the flow path forming portion to enable heat exchange between the structure and the flow path forming portion, the structure generating a flow that intersects with the flow direction of the fluid flowing through the flow path; Equipped with The structure is a spiral fin that generates a swirling flow in the fluid flowing through the flow path, the swirling flow intersecting the flow direction of the fluid, The flow path forming portion is formed separately from the flow path forming portion, An evaporator that generates a force that directs the flow direction of the fluid toward the inner wall of the flow path forming portion.

2. 10. The evaporator of claim 1, The structure is Located downstream of the flow path, An evaporator that generates a swirling flow in the same direction.

3. An evaporator, a flow path forming portion having a tubular shape and forming a flow path inside the tube through which a fluid to be evaporated flows; a structure that is disposed in the flow path and is connected to the flow path forming portion to enable heat exchange between the structure and the flow path forming portion, the structure generating a flow that intersects with the flow direction of the fluid flowing through the flow path; Equipped with The structure is a first fin that generates a swirling flow in a first direction intersecting a flow direction of the fluid flowing through the flow path; a second fin that generates a swirling flow in a direction opposite to the first direction, the second fin being disposed downstream of the first fin in the flow path; an evaporator having

4. 4. The evaporator according to claim 3, a cross section of the flow path is a circle having a constant diameter throughout the flow direction of the fluid, The thickness of each of the first fin and the second fin is The length of the structure in the flow direction; a diameter of the flow path at the cross section; the thermal conductivity of the first fin and the second fin; a ratio of vapor to the total of liquid and vapor in the fluid flowing upstream of the first fin; Depending on the evaporator.

5. An evaporator comprising: a flow path forming portion having a tubular shape and forming a flow path inside the tube through which a fluid to be evaporated flows; a structure that is disposed in the flow path and is connected to the flow path forming portion to enable heat exchange between the structure and the flow path forming portion, the structure generating a flow that intersects with the flow direction of the fluid flowing through the flow path; Equipped with An evaporator, wherein an inner wall of the flow path forming portion upstream of the structure in the flow path is subjected to a hydrophilic treatment.

6. 6. The evaporator according to claim 5, a cross section of the flow path is a circle having a constant diameter throughout the flow direction of the fluid, An evaporator, wherein the diameter of the flow path in the cross section depends on the number of capillaries and the flow rate and thickness of the liquid film of the fluid flowing into the upstream side of the structure.

7. An evaporator comprising: a flow path forming section having a tubular shape and forming a flow path inside the tube through which a fluid to be evaporated flows, the flow path forming section having an inner wall that has been subjected to a hydrophilic treatment; a structure that is disposed in the flow path and is connected to the flow path forming portion to enable heat exchange between the structure and the flow path forming portion, the structure generating a flow that intersects with the flow direction of the fluid flowing through the flow path; Equipped with The structure is a spiral fin that generates a swirling flow in the fluid flowing through the flow path, the swirling flow intersecting the flow direction of the fluid, The flow path forming portion is formed separately from the flow path forming portion, An evaporator that generates a force that directs the flow direction of the fluid toward the inner wall of the flow path forming portion.

8. 8. The evaporator of claim 7, a cross section of the flow path is a circle having a constant diameter throughout the flow direction of the fluid, An evaporator, wherein the diameter of the flow path in the cross section depends on the number of capillaries and the flow rate and thickness of the liquid film of the fluid flowing into the upstream side of the structure.

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