steam generator

Abstract

To provide a steam generator for generating steam in a stable and highly responsive manner while using a low temperature heat source having a temperature a little higher than a boiling point.SOLUTION: The steam generator includes a spray evaporation section having a first flow path where fluid is distributed, and a structure arranged in the first fluid path, a fluid spraying section having a second flow path arranged on the upstream side of the first flow path, and a spraying part formed in the second flow path to make the cross section area of part of the second flow path smaller than the cross section area of the first flow path, and a heating section for heating fluid distributed in the first flow path and in the second flow path.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a steam generator. [Background technology]

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

[0003] [Patent Document 1] Japanese Patent Publication No. 2010-090425 [Overview of the project] [Problems that the invention aims to solve]

[0004] Using high-temperature heat sources such as nuclear reactors, it is possible to generate steam from a liquid by boiling. On the other hand, using low-temperature heat sources that are only slightly above the boiling point, steam generation mainly occurs by evaporation rather than boiling, making it difficult to generate steam stably and with high responsiveness in accordance with the requirements of the steam supply equipment. To achieve stable and highly responsive steam generation using low-temperature heat sources, it is necessary to enlarge the evaporator that generates the steam.

[0005] This invention was made to solve at least some of the problems described above, and aims to generate steam stably and with high responsiveness using a low-temperature heat source slightly above the boiling point. [Means for solving the problem]

[0006] The present invention has been made to solve at least some of the above-mentioned problems and can be realized in the following forms.A steam generator comprising: a spray evaporation section having a first flow path through which a fluid flows and a structure disposed within the first flow path; a fluid atomization section having a second flow path disposed upstream of the first flow path and an atomization section formed within the second flow path that makes the cross-sectional area of ​​a portion of the second flow path smaller than the cross-sectional area of ​​the first flow path; and a heating section that heats the fluid flowing through the first flow path and the second flow path, wherein the structure is a fin disposed along the extension direction of the flow path at a position including the center of the flow path cross-section of the first flow path and the second flow path, and generates a swirling flow with respect to the fluid, and the heating section heats the fluid by heating the first flow path, the second flow path and the fin. In addition, the present invention can also be realized in the following forms.

[0007] (1) According to one embodiment of the present invention, a steam generator is provided. This steam generator includes a spray evaporation unit having a first flow path through which a fluid flows and a structure disposed in the first flow path, a second flow path disposed upstream of the first flow path, and a fluid atomization unit having an atomization unit formed in the second flow path and reducing a cross-sectional area of a part of the second flow path to be smaller than a cross-sectional area of the first flow path, and a heating unit for heating the fluid flowing in the first flow path and the second flow path.

[0008] According to this configuration, since the cross-sectional area of a part of the second flow path is made smaller than the cross-sectional area of the first flow path by the atomization unit, the fluid passing through the atomization unit flows near the center in the cross-section rather than the inner peripheral part of the first flow path. The fluid flowing near the center of the first flow path is converted into droplets and is likely to collide with the structure disposed in the first flow path instead of the liquid film traveling along the inner peripheral part of the first flow path. As a result, it is possible to suppress the instability of steam generation due to the dryout fluctuation of the liquid film formed on the inner peripheral part of the first flow path.

[0009] (2) In the steam generator of the above aspect, the atomization unit may have an inclined portion in which the cross-sectional area of a part of the second flow path gradually decreases from the upstream side to the downstream side, and a step portion formed between the downstream end of the inclined portion and the inner peripheral portion so that the fluid flowing downstream from the downstream end of the inclined portion does not contact the inner peripheral portion of the first flow path. According to this configuration, due to the inclined portion, the cross-sectional area of the second flow path gradually decreases toward the downstream side, so that the pressure loss of the fluid flowing through the second flow path can be reduced. Further, due to the step portion, the fluid flowing from the second flow path to the first flow path changes into droplets and collides with the structure without traveling along the inner peripheral portion of the second flow path, so that steam can be generated more stably.

[0010] (3) In the steam generator of the above aspect, the structure may be a flow path forming member that forms a spiral flow path between the inner peripheral portion. According to this configuration, a swirling flow that intersects the direction in which the fluid flows through the flow path forming member is generated with respect to the fluid. Therefore, the fluid that has changed into droplets is likely to collide with the flow path forming member and the inner peripheral portion of the first flow path. As a result, due to heat transfer from the flow path forming member or the inner peripheral portion, the liquid is likely to evaporate, and vapor can be generated more stably.

[0011] (4) In the vapor generator according to the above aspect, the flow path forming member may include a first flow path forming portion that forms a spiral flow path between the inner main portion and the first flow path to generate a swirling flow in a first direction with respect to the fluid flowing in the first flow path, and a second flow path forming portion that is connected to the downstream side of the first flow path forming portion and forms a spiral flow path between the inner peripheral portion and the first flow path to generate a swirling flow in a direction opposite to the first direction. According to this configuration, the flow path forming member has a first flow path forming portion that generates swirling flows in different directions and a second flow path forming portion that is connected to the first flow path forming portion. Thereby, the fluid that passes through the first flow path forming portion and flows along the swirling flow in the first direction is likely to collide with the second flow path forming portion rather than the inner peripheral portion of the first flow path when it flows into the second flow path forming portion. If the inner peripheral portion is at a high temperature, droplets are less likely to evaporate even if they collide with the inner peripheral portion due to the Leidenfrost effect. According to this configuration, by causing the fluid to collide with the second flow path forming portion instead of the inner peripheral portion, vapor can be generated stably without being affected by the Leidenfrost effect.

[0012] (5) In the vapor generator according to the above aspect, further, a calculation unit that calculates the ratio of the flow rate of vapor to the total flow rate of liquid and vapor at the boundary where the annular flow changes to the spray flow in the first flow path and the second flow path, and a flow rate control unit that controls the flow rate of the fluid supplied to the vapor generator using the ratio calculated by the calculation unit so that the atomization unit is located upstream of the boundary may be provided. In this configuration, the ratio of steam flow rates calculated by the calculation unit is used to represent the boundary between the annular flow and the atomized flow in the first and second flow channels. The flow rate of the fluid supplied to the steam generator is controlled so that the atomizing unit is located upstream of this boundary. This allows the atomizing unit to guide the liquid film that travels along the inner circumference of the second flow channel in the annular flow region onto a streamline that collides with the structure, thereby enabling stable steam generation.

[0013] (6) In the steam generator according to the above embodiment, the calculation unit calculates an area ratio obtained by dividing the minimum cross-sectional area in the atomizing unit by the cross-sectional area of ​​the inlet on the upstream side of the second flow path, and in accordance with the flow rate of the fluid supplied to the steam generator, a range of area ratios in which no droplets flow out from the downstream side of the first flow path, and the flow rate control unit may control the flow rate of the fluid supplied to the steam generator in accordance with the area ratio, within a range in which no droplets flow out from the downstream side of the first flow path. In this configuration, the flow rate of the fluid supplied to the steam generator is controlled according to the area ratio. If the area ratio is large, that is, if the minimum cross-sectional area of ​​the flow path in the atomization section is large, the liquid film that travels along the inner circumference of the second flow path may travel along the inner circumference of the first flow path without evaporating and may flow out of the steam generator as droplets. On the other hand, if the area ratio is small, that is, if the minimum cross-sectional area of ​​the flow path in the atomization section is small, many of the droplets contained in the fluid flowing from the second flow path to the first flow path will collide with the structure, but because of the high velocity, relatively large droplets will blow through. As a result, there is a risk that not all of the droplets that collide with the structure will evaporate and may flow out of the steam generator as droplets. In this configuration, by controlling the flow rate of the fluid supplied to the steam generator within the range in which the upper and lower limits of the flow path area ratio are set, steam can be stably generated in the steam generator.

[0014] (7) The steam generator according to the above embodiment may further include: a temperature difference acquisition unit that acquires the temperature difference between the temperature of the center on the upstream side of the structure and the temperature of the pipe wall forming the first flow path which is located at the same position as the upstream side of the structure along the flow path length; a calculation unit that uses the thickness of the structure, the length of the structure along the flow path length, and the flow rate of the fluid supplied to the steam generator to calculate the decrease in the temperature of the structure when the structure evaporates a liquid fluid; and a flow rate control unit that controls the flow rate of the liquid supplied to the steam generator so that the decrease is smaller than the temperature difference acquired by the temperature difference acquisition unit. In this configuration, the calculation unit calculates the amount of heat required for the structure to evaporate the liquid supplied to the steam generator, using the temperature difference obtained by the temperature difference acquisition unit and the thickness and length of the structure. If the flow rate of the fluid supplied to the steam generator is high, the number of droplets that collide with the structure and evaporate increases, so the decrease in the temperature of the structure increases. In this configuration, the flow rate of the fluid supplied to the steam generator is controlled by comparing the decrease in the temperature of the structure with the temperature difference obtained by the temperature difference acquisition unit. As a result, the flow rate supplied to the steam generator is controlled to be within a range that can evaporate all droplets that collide with the structure, thus suppressing the outflow of droplets from the steam generator.

[0015] Furthermore, the present invention can be realized in various forms, for example, as a steam generator, steam generating device, water vapor generating device, hydrogen production system, SOEC, steam generation method, steam generation method, water vapor generation method, steam generator design method, and a system equipped with these devices, a computer program for executing these devices, a server device for distributing this computer program, a non-temporary storage medium storing the computer program, and so on. [Brief explanation of the drawing]

[0016] [Figure 1] This is a block diagram of a steam generator as one embodiment of the present invention. [Figure 2] This is a schematic perspective of the evaporator. [Figure 3] This is an explanatory diagram illustrating the process of water flowing through a channel until it vaporizes. [Figure 4] This is an explanatory diagram illustrating the effects of a steam generator. [Figure 5] This is an explanatory diagram illustrating the effects of a steam generator. [Figure 6] This is an explanatory diagram illustrating the effects of a steam generator. [Figure 7] This is an explanatory diagram illustrating the effects of a steam generator. [Figure 8] This is an explanatory diagram about steam quality. [Figure 9] This is an explanatory diagram illustrating the relationship between boundary steam quality and heat flux. [Figure 10] This is an explanatory diagram regarding the pipe diameter ratio at the edge. [Figure 11] This is an explanatory diagram regarding the pipe diameter ratio at the edge. [Figure 12] This is an explanatory diagram regarding the pipe diameter ratio at the edge. [Figure 13] This is an explanatory diagram regarding the pipe diameter ratio at the edge. [Figure 14] This is an explanatory diagram regarding the thickness of the fins. [Figure 15] This is a flowchart illustrating a method for controlling flow rate using temperature differences. [Figure 16] This is an explanatory diagram of the atomizing section in a modified example. [Figure 17] This is an explanatory diagram of the atomizing section in a modified example. [Modes for carrying out the invention]

[0017] <First Embodiment> Figure 1 is a block diagram of a steam generator (steam generator) 100 as one embodiment of the present invention. The steam generator 100 of this embodiment heats and vaporizes liquid water passing through the flow path FL and supplies the vaporized steam to other devices. In the steam generator 100 of this embodiment, the liquid water that has passed through the edge section (atomization section) 14 in the flow path FL, where the pipe diameter gradually decreases, evaporates not as a liquid film that travels along the pipe wall (inner circumference) WL, but as droplets that flow through the flow path FL together with the gas and collide with the fins FN. Therefore, the outflow of the liquid film that travels along the pipe wall WL as liquid water from the steam generator 100 can be suppressed, and steam can be stably generated by the steam generator 100 even at a low heating temperature.

[0018] As shown in Figure 1, the steam generator 100 includes an evaporator 10 that generates steam from liquid water, a heater (heating unit) 30 that heats the evaporator 10, a tank 40 that stores liquid water, a pump 50 that supplies water from the tank 40 to the evaporator 10, and a control device 20 that controls the heater 30 and the pump 40. Figure 1 also shows a schematic cross-sectional view of a part of the evaporator 10.

[0019] The evaporator 10 is a tube made of metal components that forms a water channel FL through which water flows. The shape of the channel FL will be described later. The heater 30 heats the outer surface of the metal tube that is the evaporator 10. The water flowing in the channel FL is heated by the heating of the heater 30. The water flowing in the channel FL vaporizes into water vapor when heated.

[0020] The control device 20 in this embodiment is composed of a personal computer (PC). As shown in Figure 1, the control device 20 includes a CPU (Central Processing Unit) 21 and a storage unit 22. The CPU 21 functions as a calculation unit 23, a flow rate control unit 24, and a heating control unit 25 by loading computer programs stored in ROM (Read Only Memory) into RAM (Random Access Memory) and executing them.

[0021] The calculation unit 23 calculates the flow rate of water supplied to the evaporator 10. Details of the water flow rate calculated by the calculation unit 23 will be described in the second embodiment. The flow rate control unit 24 controls the pump 50 to supply the water flow rate calculated by the calculation unit 23 to the evaporator 10. The heating control unit 25 controls the heater 30. The storage unit 22 is composed of a hard disk drive (HDD) or the like and stores various data.

[0022] As shown in Figure 1, the evaporator 10 has a flow path length along the central axis OL and a flow path FL formed by the pipe wall WL. The evaporator 10 comprises a first region 11, a second region (fluid atomization section) 12, a third region (spray evaporation section) 13, a first temperature sensor SS1, a second temperature sensor SS2, and a flow sensor SS3 that detects the flow rate m of water supplied to the evaporator 10. The temperatures detected by the first temperature sensor SS1 and the second temperature sensor SS2 will be explained along with the calculations performed by the calculation unit 23.

[0023] In the first region 11, an upstream flow path FL1 with the same cross-sectional area is formed. The second region 12 includes an intermediate flow path (second flow path) FL2 through which fluid flows, and an edge portion (atomizing portion) 14 formed within the intermediate flow path FL2, which makes the cross-sectional area of ​​a portion of the intermediate flow path FL2 smaller than the cross-sectional area of ​​the downstream flow path FL3. The third region 13 includes a downstream flow path (first flow path) FL3 through which water and water vapor flows, and a fin (flow path forming member) FN that generates a swirling flow in the water and water vapor flowing in the downstream flow path FL3, which forms a spiral flow path between itself and the pipe wall WL. The fin FN generates a swirling flow in the water and water vapor flowing in the downstream flow path FL3.

[0024] Figure 2 is a schematic perspective view of the evaporator 10. Figure 2 shows a cross-section of the evaporator 10 passing through the central axis OL. As shown in Figures 1 and 2, the edge portion 14 has a sloping portion 14I in which the cross-sectional area of ​​a part of the intermediate flow path FL2 gradually decreases from the upstream side to the downstream side, and a stepped portion 14U downstream of the sloping portion 14I in which the cross-sectional area of ​​the intermediate flow path FL2 increases. The stepped portion 14U is formed between the downstream end of the sloping portion 14I and the pipe wall WL so that the fluid flowing downstream from the downstream end of the sloping portion 14I does not come into contact with the pipe wall WL of the downstream flow path FL3. The edge angle, which is the angle that the sloping portion 14I makes with respect to a cross-section perpendicular to the central axis OL, is θ (Figure 1).

[0025] The fin FN includes a first fin (first flow path forming part) FN1 that generates a swirling flow around the central axis OL in a predetermined direction (first direction) for the fluid flowing within the third region 13, and a second fin (second flow path forming part) FN2 connected downstream of the first fin FN1. The first fin FN1 forms a spiral flow path between itself and the pipe wall WL that generates a swirling flow in a predetermined direction. The second fin FN2 forms a spiral flow path between itself and the pipe wall WL that generates a swirling flow rotating in the opposite direction to the predetermined direction. The first fin FN1 and the second fin FN2 are made of a metallic material. Since the fin FN is connected to the pipe wall WL, it is heated by the heater 30 via the pipe wall WL. As shown in Figure 2, the second fin FN2 is formed to generate a swirling flow around the central axis OL in the opposite direction (second direction) to the predetermined direction for the fluid in which the first fin FN1 is generating a swirling flow in a predetermined direction. In this embodiment, the first fin FN1 is formed to rotate 1.5 times around the central axis OL. Similarly, the second fin FN2 is formed to rotate 1.5 times around the central axis OL.

[0026] Figure 3 is an explanatory diagram of the state of water flowing through the channel FLx until it vaporizes. Figure 3 shows a schematic cross-sectional view of a part of the evaporator 10x of Comparative Example 1, which does not have an edge portion 14 relative to the evaporator 10 and does not have fins FN. As shown in Figure 3, liquid water supplied from the upstream side of the channel FLx changes as it flows downstream through the channel FLx to a liquid single-phase flow, a two-phase flow in which liquid and gas are mixed, and a gas single-phase flow in which gas is only. In the two-phase flow, the flow regions are composed in the order of bubble flow F1, slug flow F2, annular flow F3, and spray flow F4 from the upstream side to the downstream side. As shown in Figure 3, the upstream side including the annular flow F3 is the boiling region, and the downstream side including the spray flow F4 is the spray evaporation region. In other words, the boiling region is upstream of the boundary between the annular flow F3 and the spray flow F4, and the spray evaporation region is downstream of the boundary.

[0027] In the bubble flow region F1, a high heat transfer coefficient to the fluid is obtained due to the stirring effect of the thermal boundary layer caused by boiling nuclei (bubbles) generated near the pipe wall WL. In the slug flow region F2, a high heat transfer coefficient to the liquid film LF can be maintained due to the wide evaporation interface via the thin liquid film LF formed on the pipe wall WL. On the other hand, in the annular flow region F3, the steam quality, which is the steam flow rate relative to the total flow rates of liquid and steam, is high. Therefore, a strong steam shear force acts on the liquid film LF, and droplets LD originating from liquid film rupture are generated due to boiling within the thin liquid film LF. In the spray evaporation region, the gas phase is heated by gas-phase heat transfer through the pipe wall WL, and the droplets LD present in the steam undergo a phase change (evaporation) due to direct heat exchange between the gas and liquid phases at the droplet surface, becoming the gas phase (100% steam quality) at the outlet of the spray flow region.

[0028] Here, even if the heat transfer coefficient between the pipe wall WL and the gas phase is improved (by promoting turbulence, enhancing heat transfer through flow channel refinement, or increasing the heat transfer area), the evaporation rate stalls due to heat transfer at the droplet surface, increasing the required spray flow region length for complete vaporization. In particular, when the vapor flow velocity in the flow channel FLx is high, the product of the time until evaporation is complete and the flow velocity becomes the required spray flow region length. Therefore, the flow channel length for the droplet LD to change into vapor increases in proportion to the flow velocity, and the evaporator size increases. In addition, the pressure loss in the flow channel FLx also increases, and the energy consumption of pump 50 may reduce system efficiency.

[0029] The leakage of droplet LD from evaporators 10 and 10x is not a major problem if the device supplying steam from evaporators 10 and 10x is solely for cooling purposes. On the other hand, if the device supplying steam from evaporators 10 and 10x is a system that uses generated steam as a raw material, the droplet LD discharged from evaporators 10 and 10x may cause various malfunctions. For example, if the device supplying steam is a fuel reforming system that produces hydrogen from hydrocarbon fuels through steam reforming reactions, the ratio of steam to fuel may fluctuate, potentially leading to carbon deposition in the reformer. Furthermore, in the case of an SOEC (Solid Oxide Electrolyzer Cell) system that produces hydrogen from electricity using steam as a raw material, rapid temperature fluctuations and thermal shock, expansion and contraction caused by droplet collisions with the ceramic components of the SOEC stack may lead to component failure. Therefore, it is preferable to prevent the generation of droplet LD in the spray flow F4 region (to vaporize almost all of it).

[0030] On the other hand, in the boiling region, which includes the regions of bubble flow F1, slug flow F2, and annular flow F3, common heat transfer enhancement techniques include improving the foaming point density in the bubble flow F1 region and reducing the thickness of the liquid film LF in the annular flow F3 region (reducing liquid film thermal resistance) and stabilizing it (suppressing dry-out patches). Thus, since the heat transfer phenomenon differs greatly between the boiling region and the spray evaporation region depending on the flow conditions, individual flow path designs are necessary to reduce pressure loss and miniaturize the flow paths FL and FLx. For this reason, in the steam generator 100 of this embodiment, as shown in Figure 1, an edge portion 14 is formed in the intermediate flow path FL2, and fins FN are arranged in the downstream flow path FL3.

[0031] Figures 4 to 7 are explanatory diagrams illustrating the effects of the steam generator 100. Figure 4 shows a schematic cross-sectional view when the flow path FL downstream of the edge portion 14 of the evaporator 10 is divided into five regions P1 to P5. Region P1 is the region from the stepped portion 14U, which is the downstream end face of the edge portion 14, to the upstream tip of the first fin FN1. Region P2 is the region of one rotation of the first fin FN1. Region P3 is the region including 0.5 rotations downstream of the first fin FN1 and 0.5 rotations upstream of the second fin FN2. Region P4 is the region of one rotation downstream of the second fin FN2. Region P5 is the region near the outlet of the evaporator 10.

[0032] Figure 5 shows the flow rate of the mass of droplets LD entering region P5 in the evaporator 10x of Comparative Example 1. In other words, Figure 5 shows the mass of droplets LD flowing out of the evaporator 10x. The state shown in Figure 5 is the result when the flow rate of water supplied to the evaporators 10 and 10x is adjusted so that the stepped portion 14U of the edge portion 14 is located in the annular flow F3 (Figure 3), for the purpose of comparing the evaporator 10 of this embodiment with the evaporator 10x of Comparative Example 1. In the evaporator 10 of this embodiment, the mass of droplets LD flowing out of the evaporator 10 was zero due to the presence of the edge portion 14. Specifically, the liquid film LF that attempted to enter region P1 flowed into region P1 as droplets LD due to the edge portion 14. On the other hand, in the evaporator 10x of the comparative example, as shown in Figure 5, mainly the diameter was 1.0 × 10 -5 ~6.0×10-5 The LD droplets leaked out.

[0033] Figure 6 shows the in-plane integrated values ​​of the liquid film LF flowing into each region P1 to P5 in evaporators 10 and 10x. In Figure 6, the integrated value of evaporator 10 in this embodiment is shown by a broken line LN connecting white circles with straight lines, and the integrated value of evaporator 10x in Comparative Example 1 is shown by a broken line LNx connecting black circles with dashed lines. In Figure 6, the in-plane integrated value of the liquid film thickness on the Y axis is the integrated value of the liquid film thickness along the flow path length along the central axis OL. As shown by the broken line LNx in Figure 6, in evaporator 10x of Comparative Example 1, the thickness of the liquid film LF decreases as it moves to the downstream region, but some of the liquid film LF flows out of evaporator 10x while remaining in liquid form.

[0034] On the other hand, in the evaporator 10 of this actual configuration, the edge portion 14 causes a portion of the liquid film LF formed on the inclined portion 14I to enter region P1 as droplets LD via the stepped portion 14U. As a result, the integrated value in region P1 is smaller than that in Comparative Example 1. The integrated value in region P2 is higher than that in region P1 because the droplets LD that have changed from liquid film LF due to the edge portion 14 adhere to the first fin FN1. In region P2, in the evaporator 10x of Comparative Example 1, the droplets LD present in the vapor evaporated through direct heat exchange between the gas phase and the liquid phase, but in the evaporator 10 of this embodiment, the liquid film LF adhering to the first fin FN1 evaporates more easily. Furthermore, in region P3, since the swirling flow generated by the second fin FN2 is in the opposite direction to the swirling flow generated by the first fin FN1, the droplets LD that receive a force moving outward in the circumferential direction on the first fin FN1 are more likely to adhere to the second fin FN2 due to a force moving inward in the circumferential direction. As a result, in regions P3 and P4, the integrated value of droplets LD decreases, as shown by the broken line LN. Consequently, there is no liquid water flowing out of the evaporator 10 of this embodiment as droplets LD.

[0035] Figure 7 shows the change in liquid mass ratio between the first fin structure SF1, which includes a second fin FN2 that generates a reverse swirling flow, and the second fin structure SF2, which consists only of the first fin that generates a swirling flow in the same direction. The liquid mass ratio is the ratio of the liquid mass remaining as liquid droplets LD to the total mass. The first fin structure SF1 is a fin connected to a first fin FN1 with a central axis length of 40 mm for one rotation of the fin, a second fin FN2 with the same length as the first fin FN1 (40 mm) for one rotation of the fin, and another first fin FN1 for one rotation. On the other hand, the second fin structure SF2 is a fin connected to the first fin FN1 for three rotations. In other words, the fins in the second rotation (located at 40-80 mm) are different between the first fin FN1 and the second fin FN2 in the first fin structure SF1 and the second fin structure SF2.

[0036] In Figure 7, the horizontal axis shows the change in liquid mass ratio with respect to distance as the flow path length. The liquid mass ratio of the first fin structure SF1 is shown by the broken line LN1, and the liquid mass ratio of the second fin structure SF2 is shown by the dashed broken line LN1y. As shown in Figure 7, the first fin structure SF1 can collect more droplets LD than the second fin FN2 because it contains the second fin FN2, which generates a different swirling flow relative to the fluid. In other words, because droplets LD are evaporated upstream of the first fin structure SF1, the amount of droplets LD collected downstream of the first fin structure SF1 is reduced. As a result, as shown by the broken line LN1, the liquid mass ratio downstream of the first fin structure SF1 is lower than that downstream of the second fin structure SF2.

[0037] As described above, in the steam generator 100 of this embodiment, the second region 12 of the evaporator 10 includes an intermediate flow path FL2 through which fluid flows, and an edge portion 14 formed within the intermediate flow path FL2, which makes the cross-sectional area of ​​a portion of the intermediate flow path FL2 smaller than the cross-sectional area of ​​the downstream flow path FL3. The third region 13 includes a downstream flow path FL3 through which water and steam flow, and fins FN that generate a swirling flow in the water and steam flowing in the downstream flow path FL3. The water flowing in the flow path FL is heated by the heating of the heater 30. Therefore, in this embodiment, because the cross-sectional area of ​​a portion of the intermediate flow path FL2 is reduced by the edge portion 14, the fluid that has passed through the edge portion 14 flows near the central axis OL of the downstream flow path FL3 rather than the pipe wall WL. The fluid flowing near the center of the downstream flow path FL3 is converted into droplets LD rather than a liquid film LF that travels along the pipe wall WL of the downstream flow path FL3, and is more likely to collide with the fins FN arranged in the downstream flow path FL3. As a result, it is possible to suppress the instability of steam generation caused by the drying out of the liquid film LF formed on the pipe wall WL of the downstream flow path FL3.

[0038] Furthermore, the edge portion 14 of this embodiment has an inclined portion 14I in which the cross-sectional area of ​​a part of the intermediate flow path FL2 gradually decreases from the upstream side to the downstream side, and a stepped portion 14U downstream of the inclined portion 14I in which the cross-sectional area of ​​the intermediate flow path FL2 increases. The stepped portion 14U is formed between the downstream end of the inclined portion 14I and the pipe wall WL so that the fluid flowing downstream from the downstream end of the inclined portion 14I does not come into contact with the pipe wall WL of the downstream flow path FL3. In other words, because the cross-sectional area of ​​the intermediate flow path FL2 gradually decreases downstream due to the inclined portion 14I, the pressure loss of the fluid flowing through the intermediate flow path FL2 can be reduced. Moreover, because the stepped portion 14U causes the fluid flowing from the intermediate flow path FL2 to the downstream flow path FL3 to change into droplets LD without traveling along the pipe wall WL of the intermediate flow path FL2 and collide with the fins FN, steam can be generated more stably.

[0039] Furthermore, the fins FN in this embodiment generate a swirling flow in the water and steam flowing in the downstream channel FL3. As a result, the fins FN generate a swirling flow that intersects the direction of fluid flow. The fluid, now transformed into droplets LD, is more likely to collide with the fins FN and the tube wall WL of the downstream channel FL3. Consequently, heat transfer from the fins FN or the tube wall WL makes it easier for the droplets LD to evaporate, allowing the evaporator 10 to generate steam more stably.

[0040] Furthermore, in this embodiment, the fin FN includes a first fin FN1 that generates a swirling flow around a central axis OL in a predetermined direction (first direction) for the fluid flowing within the third region 13, and a second fin FN2 connected downstream of the first fin FN1. Therefore, when the fluid that passes through the first fin FN1 and flows along the swirling flow flows through the second fin FN2, it is more likely to collide with the second fin FN2 rather than the pipe wall WL of the downstream flow path FL3. If the pipe wall WL is at a high temperature, the Leidenfrost effect makes it difficult for droplets LD to evaporate even if they collide with the pipe wall WL. According to this embodiment, by causing the fluid to collide with the second fin FN2 instead of the pipe wall WL, steam can be stably generated without being affected by the Leidenfrost effect.

[0041] <Second Embodiment> In the second embodiment, the control device 20 controls the flow rate of water supplied to the evaporator 10 (Figure 1) of the first embodiment using various parameters, thereby supplying water vapor free of liquid droplets LD from the evaporator 10 to a predetermined device that supplies water vapor.

[0042] Figure 8 shows Steam Quality X bp This is an explanatory diagram. Figure 8 shows the vapor quality X at the boundary between the annular flow F3 and the spray flow F4. bp A test apparatus for investigating this is shown. Specifically, the latent heat of vaporization of a predetermined flow rate Q is applied to the upstream evaporator 101. LSupply water, and supply a heat quantity Q1 to the upstream evaporator 101. Further, with the upstream evaporator 101 and the downstream evaporator 102 connected so that the fluid flowing out from the upstream evaporator 101 can be supplied to the downstream evaporator 102, supply a heat quantity Q2 to the downstream evaporator 102. In FIG. 8, for the sake of convenience, a state where the upstream evaporator 101 and the downstream evaporator 102 are separated is shown. Note that the vapor quality X bp corresponds to the ratio of the flow rate of vapor to the total flow rate of liquid and vapor at the boundary where the flow changes from annular flow to spray flow.

[0043] A part of the downstream evaporator 102 is formed of glass. Observe the state of the downstream evaporator 102 transmitted through the glass by the camera CA. By the observation, the state of the fluid flowing through the downstream evaporator 102 (for example, the annular flow F3) was examined. By changing the flow rate of the water supplied to the upstream evaporator 101 and the heat quantities Q1 and Q2, the vapor quality X bp at the boundary between the annular flow F3 and the spray flow F4 was investigated. The vapor quality X bp at the boundary is expressed as in the following formula (1). In the test apparatus shown in FIG. 8, mainly by controlling the heat quantity Q1, the heat flux qw on the wall surface of the downstream evaporator 102 and the control of the vapor quality X bp at the boundary can be carried out independently.

[0044]

Equation

[0045] FIG. 9 is an explanatory diagram of the relationship between the vapor quality X bp at the boundary and the heat flux qw. In FIG. 9, when the mass velocity Gw of the fluid is 2.3 kg / (m 2 ·s), a broken line LN2 representing the change in the vapor quality X bp at the boundary according to the heat flux qw is shown. As shown in FIG. 9, when the mass velocity Gw of the fluid is constant, since the vapor quality X bp at the boundary changes according to the heat flux qw, the vapor quality X bpThis can be expressed as a function as shown in equation (2) below. As shown by the piecewise curve LN2, the heat flux qw is 1.0 × 10⁻⁶. 4 (W / m 2 If it is larger than ), Steam Quality X bp The rate of decrease will be larger.

[0046]

number

[0047] To efficiently generate steam using the evaporator 10, it is preferable to prevent dryout in the annular flow F3 (Figure 3) where a liquid film LF is generated. Furthermore, in order to prevent dryout, it is preferable to form an edge portion 14 in the annular flow F3 upstream of the spray evaporation region where no liquid film LF is generated. That is, the edge portion 14 is the steam quality X at the boundary between the spray evaporation region and the boiling region. bp Lower steam quality X set It is preferable that it be formed at the position shown.

[0048] On the other hand, if an edge portion 14 is formed at a location with too low steam quality, for example, at the location of bubble flow F1, the effect of efficient steam generation by generating droplet LD cannot be expected. In other words, the steam quality X at the location where the edge portion 14 is formed. set This includes the lower limit of steam quality X cr There exists a lower limit of vapor quality X that is the limit for atomization. cr This can be expressed numerically as shown in equation (3) below. As shown in equation (3) below, the lower limit of steam quality X cr It is expressed as a function of mass velocity, vapor flow velocity Ug, and edge angle θ. Figure 9 shows the lower limit of vapor quality X under the conditions of piecewise line LN2. cr The value =0.6 is shown with a dashed line.

number

[0049] As explained above, the steam quality X of the edge portion 14set However, the lower limit of steam quality X cr The above, and also, the steam quality of the boundary X bp It is preferable that the edge portion 14 is formed at the following positions.

[0050] Figures 10 to 13 are explanatory diagrams regarding the pipe diameter ratio of the edge section 14. As shown in Figures 1 and 2, the flow path area with a circular cross-section is reduced by the edge section 14. The relationship between the pipe diameter ratio Rd (=din / dout), which is the ratio of the outlet pipe diameter doout (which makes the flow path area of ​​the second region 12 smaller than other parts) to the inlet pipe diameter din (flow path diameter) on the upstream side of the inclined section 14I of the edge section 14I, i.e., before the flow path area becomes smaller, and the steam generation in the evaporator 10 was investigated.

[0051] Figure 10 shows a bar graph of the mass flow rate (kg / s) of droplet LDs according to the diameter of the droplets LDs that flowed out of evaporator 10y, which has a pipe diameter ratio Rd of 0.25 (=2mm / 8mm). Figure 11 shows a bar graph of the mass flow rate of droplet LDs according to the diameter of the droplets LDs that flowed out of evaporator 10z, which has the same flow path length as evaporator 10y and a pipe diameter ratio Rd of 0.75 (=6mm / 8mm). Note that the order of magnitude of the values ​​on the horizontal and vertical axes differs between Figure 10 and Figure 11. Evaporator 10 in this embodiment has a pipe diameter ratio Rd of 0.50 (=4mm / 8mm) and the same flow path length as evaporators 10y and 10z. No droplet LDs were detected flowing out of evaporator 10 in this embodiment. Note that since the flow path area can be determined from the pipe diameter ratio Rd, the pipe diameter ratio Rd may be considered as an area ratio.

[0052] Figures 10 and 11 and the evaporator 10 of this embodiment show that if the pipe diameter ratio is too small or too large, droplets LD will flow out of evaporators 10y and 10z. Specifically, in evaporator 10y with a pipe diameter ratio Rd of 0.25, larger droplets LD flow out compared to evaporator 10z with a pipe diameter ratio Rd of 0.75. This is because reducing the pipe diameter ratio Rd causes the fluid streamlines to become denser towards the radial center of the fin FN. In this case, if the fluid velocity is high, the adhesion of droplets LD to the center of the fin FN concentrates, increasing the length of the flow path required to evaporate the droplets LD. As a result, relatively large-diameter droplets LD that were not captured by the fin FN flow out of evaporator 10y.

[0053] On the other hand, in evaporator 10z with a pipe diameter ratio Rd of 0.75, small droplets LD are flowing out. This is because increasing the pipe diameter ratio Rd causes the fluid streamlines to disperse radially outward from the fins FN. In this case, some of the droplets LD that pass through the edges adhere to the pipe wall WL before reaching the fins FN. As a result, some of the liquid film LF that does not evaporate along the pipe wall WL flows out of evaporator 10z as small-diameter droplets LD.

[0054] Figure 12, like Figure 6, shows the in-plane integrated values ​​of the liquid film LF flowing into regions P1 to P5 in evaporators 10, 10x, 10y, and 10z. Note that the order of magnitude of the vertical axis in Figure 12 is different from that of Figure 6. In addition to Figure 6, Figure 12 shows the integrated value of evaporator 10y, where the pipe diameter ratio Rd is 0.25, as shown by the polyline LNy, which connects black triangles with a dashed line, and the integrated value of evaporator 10z, which connects black squares with a dashed line, as shown by the polyline LNz.

[0055] As shown by the broken line LNy, in evaporator 10y with a pipe diameter ratio Rd of 0.25, the edge angle θ at the edge is the largest, so the integrated value in region P1 is smaller than in the other evaporators 10, 10x, and 10z. On the other hand, an integrated value exists in region P5, meaning that some of the liquid film LF is flowing out of evaporator 10y in liquid form. As shown by the broken line LNz, in evaporator 10z with a pipe diameter ratio Rd of 0.75, as shown in Figure 12, no liquid film LF is flowing out of evaporator 10z. On the other hand, unlike evaporator 10 with a pipe diameter ratio Rd of 0.50, droplets LD are flowing out of evaporator 10z.

[0056] Figure 13 shows the fluid pressure drop, which varies with respect to the pipe diameter ratio Rd, as shown by a bar graph. As shown in Figure 13, the larger the pipe diameter ratio Rd, the greater the pressure drop. In particular, the pressure drop of evaporator 10y, where the pipe diameter ratio Rd is 0.25, is extremely high compared to evaporators 10 and 10z.

[0057] As explained using Figures 10-13, unlike the other evaporators 10x, 10y, and 10z, no droplet LD flowed out of evaporator 10 in this embodiment, where the pipe diameter ratio Rd is 0.50. When the pipe diameter ratio Rd was changed from 0.50, it was confirmed that no droplet LD flowed out of the evaporator when the pipe diameter ratio Rd was between 0.37 and 0.63. From the above, it can be seen that the presence or absence of droplet LD flowing out of evaporator 10 differs depending on the flow rate of water supplied to evaporator 10. In other words, the pipe diameter ratio Rd at which droplet LD does not flow out of evaporator 10 can be calculated according to the flow rate of water supplied to evaporator 10.

[0058] In the second embodiment, the calculation unit 23 (Figure 1) calculates the vapor quality X at the boundary between the spray evaporation region and the boiling region. bp The flow rate control unit 24 calculates the steam quality X at the formation position of the edge portion 14. set This is the vapor quality X at the boundary between the atomization evaporation region and the boiling region. bp Lower than, and the lower limit of steam quality X cr The flow rate of water supplied to the evaporator 10 is controlled to achieve the above. Therefore, in the second embodiment, the steam quality X calculated by the calculation unit 23 is used.bp The boundary between the annular flow F3 and the spray flow F4 in the intermediate channel FL2 and the downstream channel FL3 is represented using this. The flow rate of the fluid supplied to the evaporator 10 is controlled so that the edge portion 14 is located upstream of this boundary. This allows the edge portion 14 to guide the liquid film LF that travels along the pipe wall WL of the intermediate channel FL2 in the annular flow F3 region onto a streamline that collides with the fin FN, thereby enabling stable steam generation.

[0059] Furthermore, the calculation unit 23 calculates the range of pipe diameter ratio Rd in which droplets LD do not flow out of the evaporator 10, according to the flow rate of water supplied to the evaporator 10. The flow rate control unit 24 supplies water to the evaporator 10 at a flow rate within the range calculated by the calculation unit 23 in which droplets LD do not flow out of the evaporator 10, according to the pipe diameter ratio Rd of the evaporator 10. In other words, in the second embodiment, the flow rate of the fluid supplied to the evaporator 10 is controlled according to the pipe diameter ratio Rd. If the pipe diameter ratio Rd is large, that is, if the minimum cross-sectional area of ​​the flow path at the edge portion 14 is large, the liquid film LF that travels along the pipe wall WL of the intermediate flow path FL2 may travel directly to the pipe wall WL of the downstream flow path FL3 and may not evaporate, potentially flowing out of the evaporator 10 as droplets LD. On the other hand, when the pipe diameter ratio Rd is small, that is, when the minimum cross-sectional area of ​​the flow path at the edge portion 14 is small, many of the droplets LD contained in the fluid flowing from the intermediate flow path FL2 to the downstream flow path FL3 collide with the fin FN, but because of the high velocity, relatively large droplets LD are blown through. As a result, there is a risk that not all of the droplets LD that collide with the fin FN will evaporate and will flow out of the evaporator 10 as droplets LD. In the second embodiment, the flow rate of the fluid supplied to the evaporator 10 is controlled within a range in which the upper and lower limits of the pipe diameter ratio Rd of the flow path FL are set, thereby enabling stable steam generation within the evaporator 10.

[0060] <Third Embodiment> In the third embodiment, the flow rate control unit 24 controls the flow rate of water supplied to the evaporator 10 according to the temperature difference ΔTf between the upstream tip temperature Tf of the fin FN and the tube wall temperature Th of the tube wall WL. Figure 14 is an explanatory diagram of the thickness t of the fin FN. Figure 14 shows a schematic front view of a part of the fin FN. The thickness t of the fin FN in this embodiment is constant.

[0061] As shown in Figure 1, the first temperature sensor SS1 detects the tip temperature Tf of the upstream end of the fin FN. The second temperature sensor SS2 detects the wall temperature Th of the pipe wall WL at the same position as the upstream end of the fin FN along the length of the flow path. The calculation unit 23 obtains the tip temperature Tf and the pipe wall temperature Th and calculates the temperature difference ΔTf (=Th-Tf). The calculation unit 23, the first temperature sensor SS1, and the second temperature sensor SS2 correspond to the temperature difference acquisition unit.

[0062] The liquid film LF that has passed through the edge portion 14 adheres to the fin FN and evaporates due to the heat obtained from the fin FN. However, since only a small amount of liquid film LF adheres to the tip of the fin FN (because there is no radial heat flow due to the adhesion and evaporation of droplet LD), the temperature difference ΔTf between the tip temperature Tf of the fin FN and the tube wall temperature Th is small. On the other hand, when the liquid film LF adhering to the entire fin FN is evaporated, a temperature difference ΔTc is generated between the tip temperature Tf of the fin FN and the tube wall temperature Th due to heat conduction by the fin FN, as shown in equation (4) below. The amount of heat Q (W) required to evaporate the droplet LD in equation (4) is expressed by equation (5) below. The droplet collection efficiency α in equation (5) is the proportion of droplet LD that are evaporated by 0.5 rotations (1 segment) of a fin with a length h (m) along the flow direction.

[0063]

number

number

[0064] The calculation unit 23 calculates the temperature difference ΔTc of the fin FN that decreases due to heat conduction, using the thickness t of the fin FN, the length h of each segment of the fin FN, and the mass velocity Gw of the fluid supplied to the evaporator 10, as shown in equations (4) and (5) above. The flow rate control unit 24 in this embodiment controls the flow rate of the fluid supplied to the evaporator 10 so that the temperature difference ΔTc of the fin FN is smaller than the temperature difference ΔTf between the tip temperature Tf of the fin FN and the pipe wall temperature Th.

[0065] Figure 15 is a flowchart of a flow rate control method using temperature differences ΔTc and ΔTf. In the control flow shown in Figure 15, first, the control device 20 receives the required steam flow rate m from other devices to be generated in the evaporator 10. set The flow rate control unit 24 obtains the required steam flow rate (step S1). The flow rate control unit 24 sets the water supply flow rate to be supplied to the evaporator 10 (step S2). The initially set supply flow rate is the required steam flow rate m set The flow rate may be set according to the conditions, or it may be a preset initial flow rate stored in the memory unit 22.

[0066] When water is supplied to the evaporator 10, the flow rate m and temperature difference ΔTf are detected (step S3). The calculation unit 23 obtains the temperature difference ΔTf between the tip temperature Tf of the fin FN and the temperature Tf of the pipe wall WL from the temperatures detected by the first temperature sensor SS1 and the second temperature sensor SS2. The flow rate control unit 24 also obtains the supply flow rate to the evaporator 10 detected by the flow rate sensor SS3.

[0067] The flow rate control unit 24 determines whether the temperature difference ΔTf is smaller than the temperature difference ΔTc of the fins FN, which has been calculated in advance by the calculation unit 23 (step S4). If it is determined that the temperature difference ΔTf is smaller than the temperature difference ΔTc (step S4: YES), the flow rate control unit 24 reduces the flow rate m currently supplied to the evaporator 10 by Δm (step S5), and repeats the process from step S3 onward. The flow rate Δm that the flow rate control unit 24 reduces is calculated by the calculation unit 23 using the following formula (6).

[0068]

number

[0069] In the process of step S4, if it is determined that the temperature difference Tf is greater than or equal to the temperature difference ΔTc (step S4: NO), the current flow rate m is the required steam flow rate m. set Determine whether it is smaller than (step S6). Flow rate m is the required steam flow rate m set If it is determined that the flow rate is smaller than the specified value, the flow rate control unit 24 increases the flow rate from the flow rate m by Δm (step S7), and repeats the process from step S3 onward.

[0070] In the process of step S6, the flow rate m is the required steam flow rate m set If the above is determined (step S6: NO), the flow rate control unit 24 determines whether or not to terminate the control flow that supplies water to the evaporator 10 (step S8). The trigger for terminating the control flow may be, for example, a termination operation from the user to the control device 20. If it is determined not to terminate the control flow (step S8: NO), the processing from step S3 onwards is repeated. If it is determined to process the control flow (step S: YES), the control flow is terminated. Note that the determination of terminating the control flow may be received while processing other than step S8 is being performed.

[0071] As described above, the calculation unit 23 calculates the temperature difference ΔTc of the fin FN that decreases due to heat conduction, using the thickness t of the fin FN, the length h of each segment of the fin FN, and the mass velocity Gw of the fluid supplied to the evaporator 10, as shown in equations (4) and (5) above. The flow rate control unit 24 in this embodiment controls the flow rate of the fluid supplied to the evaporator 10 so that the temperature difference ΔTc of the fin FN is smaller than the temperature difference ΔTf between the tip temperature Tf of the fin FN and the tube wall temperature Th. That is, the calculation unit 23 calculates the amount of heat Q required for the fin FN to evaporate the liquid supplied to the evaporator 10 using the temperature difference ΔTf calculated by the calculation unit 23, and the thickness t and length h of the fin FN. If the flow rate of the fluid supplied to the evaporator 10 is high, the number of liquid droplets LD that collide with the fin FN and evaporate increases, so the temperature difference ΔTc, which represents the decrease in the temperature of the fin FN, increases. In the second embodiment, the flow rate of the fluid supplied to the evaporator 10 is controlled by comparing the temperature difference ΔTc due to the temperature drop of the fins FN with the temperature difference ΔTf calculated by the calculation unit 23. As a result, the flow rate supplied to the evaporator 10 is controlled to be within a range that can evaporate all of the droplets LD colliding with the fins FN, thereby suppressing the outflow of droplets LD from the evaporator 10.

[0072] <Modified examples of embodiments> The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit. For example, the following modifications are possible. Furthermore, in the above embodiments, some of the configurations implemented by hardware may be replaced with software, and conversely, some of the configurations implemented by software may be replaced with hardware.

[0073] <Example 1> In the first embodiment described above, a fin FN was given as an example of a structure placed in the downstream flow path FL3, but the structure may have a shape other than a fin FN. The structure may be rectangular or spherical, or it may have a shape that does not generate swirling flow. The shape of the structure can be deformed within a range in which it is positioned to collide with the fluid guided towards the central axis OL rather than the pipe wall WL by the edge portion 14. The fin FN had a second fin FN2 that generated a swirling flow in the opposite direction to the swirling flow generated by the first fin FN1, but the second fin FN2 is not required. In other words, the fin FN may consist only of the first fin, as in the second fin structure SF2.

[0074] The steam generator 100 of the first embodiment described above can be modified to include an evaporator 10 and a heater 30. The steam generator 100 may not include, for example, a control device 20. In the second embodiment described above, the flow rate supplied to the evaporator 10 was controlled according to the position of the edge portion 14. However, in other embodiments, if the amount of steam to be generated by the evaporator 10 is known in advance, the evaporator 10 may be designed such that the edge portion 14 is located upstream of the boundary between the annular flow F3 and the spray flow F4, according to the required amount of steam to be generated. The control by the control device 20 described in the second embodiment can also be rephrased as a method for designing the evaporator 10 based on known specifications.

[0075] <Modification 2> The edge portion 14 in the first embodiment described above is an example and is formed within the intermediate flow path FL2, and is deformable to the extent that the cross-sectional area of ​​a part of the intermediate flow path FL2 is smaller than that of other parts. Figure 16 is an explanatory diagram of a modified atomizing section 14a. Figure 16 shows a schematic cross-sectional view of a part of the modified evaporator 10a. In the modified evaporator 10a, as shown in Figure 16, the cross-sectional area of ​​the intermediate flow path FL2a upstream of the atomizing section 14a is constant. The cross-sectional area of ​​the downstream flow path FL3a is larger than the cross-sectional area of ​​the intermediate flow path FL2a upstream of the atomizing section 14a, and is constant. In this case, the pipe wall WLa of the intermediate flow path FL2a corresponds to the atomizing section 14a which is smaller than the cross-sectional area of ​​the downstream flow path FL3a. Due to the atomizing section 14a, the fluid that passes through the atomizing section 14a and flows into the downstream channel FL3a does not propagate along the pipe wall WLa of the downstream channel FL3a as a liquid film LF, but is more likely to collide with downstream structures, which are not shown in Figure 16.

[0076] Figure 17 is an explanatory diagram of the modified atomizing section 14b. Figure 17 shows a schematic cross-sectional view of a part of the modified evaporator 10b. In the modified evaporator 10b, as shown in Figure 17, the cross-sectional areas of the intermediate flow path FL2b and the downstream flow path FL3b are the same and constant. The atomizing section 14b, which has multiple through holes HL formed therein, is located in a part of the intermediate flow path FL2b. The fluid flowing through the intermediate flow path FL2b flows into the downstream flow path FL3b through the through holes HL of the atomizing section 14b. In this modified example, the cross-sectional area of ​​the intermediate flow path FL2b is made smaller than the cross-sectional area of ​​the downstream flow path FL3b by the atomizing section 14b. Due to the atomizing section 14b, the fluid that has passed through the atomizing section 14b and flowed into the downstream flow path FL3b does not propagate along the pipe wall WLb of the downstream flow path FL3b as a liquid film LF, but is more likely to collide with downstream structures that are not shown in Figure 17.

[0077] In the first embodiment described above, the edge portion 14 was formed over the entire circumference of the pipe wall WL, but it may also be formed over a portion of the circumferential direction (for example, in the range of 0 to 180°). Furthermore, the cross-section of the flow path FL may be rectangular rather than circular, and the edge portion 14 can be deformed to match the cross-sectional shape of the flow path FL.

[0078] The embodiments of this specification have been described above based on the embodiments and modifications described above. The embodiments described above are for the purpose of facilitating understanding of this specification and do not limit it. This specification may be modified and improved without departing from its spirit and the scope of the claims, and equivalents thereof are included in this specification. Furthermore, any technical features that are not described as essential in this specification may be deleted as appropriate.

[0079] The present invention can also be realized in the following forms. [Application Example 1] A steam generator, A spray evaporation unit having a first flow path through which a fluid flows, and a structure disposed within the first flow path, A fluid atomizing unit having a second flow path arranged upstream of the first flow path, and an atomizing section formed within the second flow path, which makes the cross-sectional area of ​​a portion of the second flow path smaller than that of other portions, A heating unit that heats the fluid flowing in the first channel and the second channel, A steam generator equipped with the following features. [Application Example 2] The steam generator described in Application Example 1, The atomizing section is a steam generator having a sloped section in which the cross-sectional area of ​​a portion of the second flow path gradually decreases from the upstream side to the downstream side, and a stepped section formed between the downstream end of the sloped section and the inner circumference of the first flow path so that the fluid flowing downstream from the downstream end of the sloped section does not come into contact with the inner circumference of the first flow path. [Application Example 3] A steam generator as described in Application Example 1 or Application Example 2, The aforementioned structure is a steam generator, which is a flow channel forming member that forms a spiral flow channel between itself and the inner circumference. [Application Example 4] A steam generator described in any one of the application examples 1 to 3, The aforementioned flow channel forming member is Between the inner circumference and the first channel forming portion, a first channel forming portion is provided which a spiral channel is formed that generates a swirling flow in a first direction for the fluid flowing in the first channel, A steam generator having a second flow path forming section connected to the downstream side of the first flow path forming section between itself and the inner circumference, and forming a spiral flow path that generates a swirling flow in the opposite direction to the first direction. [Application Example 5] A steam generator described in any one of Application Examples 1 to 4, further, A calculation unit that calculates the ratio of the vapor flow rate to the total vapor flow rate at the boundary where the flow changes from an annular flow to a spray flow within the first and second flow paths, The flow control unit controls the flow rate of the fluid supplied to the steam generator using the ratio calculated by the calculation unit, such that the atomizing unit is located upstream of the boundary. A steam generator equipped with the following features. [Application Example 6] A steam generator described in any one of the application examples 1 to 5, The calculation unit calculates an area ratio obtained by dividing the minimum cross-sectional area in the atomizing section by the cross-sectional area of ​​the inlet on the upstream side of the second flow path, and determines the range of the area ratio in which droplets do not flow out from the downstream side of the first flow path, according to the flow rate of the fluid supplied to the steam generator. The flow rate control unit controls the flow rate of the fluid supplied to the steam generator in accordance with the area ratio, within a range in which no droplets flow out from the downstream side of the first flow path. [Application Example 7] A steam generator described in any one of the application examples 1 to 6, further, A temperature difference acquisition unit that acquires the temperature difference between the temperature of the center on the upstream side of the flow path forming member and the temperature of the pipe wall forming the first flow path at the same position along the flow path length as the upstream side of the flow path forming member, A calculation unit that calculates the temperature drop of the flow channel forming member when the flow channel forming member evaporates a liquid fluid, using the thickness of the flow channel forming member, the length of the flow channel forming member along the length of the flow channel, and the flow rate of the fluid supplied to the steam generator, A flow control unit controls the flow rate of the liquid supplied to the steam generator so that the aforementioned decrease is smaller than the temperature difference obtained by the temperature difference acquisition unit, A steam generator equipped with the following features. [Explanation of symbols]

[0080] 10, 10a, 10b, 10x, 10y, 10z… Evaporator 11...First area 12...Second region (fluid atomization section) 13…Third region (spray evaporation section) 14…Edge section (atomization section) 14I…Slope part 14U... Stepped section 14a, 14b...Atomization part 20...Control device 21…CPU 22...Storage section 23...Calculation section 24…Flow Control Unit 25… Heating control unit 30... Heater (heating part) 40... Tank 50... Pump 100... Steam generator (steam generator) 101…Upstream evaporator 102… Downstream evaporator CA...Camera F1...bubble flow F2...Slug flow F3...Circular flow F4…Spray flow FL, FLx…flow channel FL1…Upstream flow path FL2, FL2a, FL2b... Intermediate channel FL3, FL3a, FL3b…Downstream flow path FN...Fin (channel forming member) FN1…First fin (first channel forming section) FN2…Second fin (second channel forming section) HL...Through hole LD…Droplet LF…Liquid film OL…center axis P1~P5…area Q,Q1,Q2…heat amount Rd…Pipe diameter ratio SF1…First fin structure SF2…Second fin structure SS1…First temperature sensor SS2…Second temperature sensor SS3…Flow sensor ΔTc…Temperature difference Tf... Fin tip temperature ΔTf…Temperature difference Th…Tube wall temperature WL, WLa, WLb…Pipe wall (inner periphery) ΔX…Amount of flow rate change X bp ...Boundary Steam Quality X cr ...lowest steam quality X set ...steam quality din…Inlet pipe diameter dout…Outlet pipe diameter m…Flow rate m set ...required steam flow rate

Claims

1. A steam generator, A spray evaporation unit having a first flow path through which a fluid flows, and a structure disposed within the first flow path, A fluid atomizing unit having a second flow path arranged upstream of the first flow path, and an atomizing section formed within the second flow path that makes the cross-sectional area of ​​a portion of the second flow path smaller than the cross-sectional area of ​​the first flow path, A heating unit that heats the fluid flowing through the first and second flow paths, Equipped with, The structure is a fin that is positioned along the extension direction of the flow path at a location including the center of the flow path cross-section of the first flow path and the second flow path, and generates a swirling flow with respect to the fluid. The heating unit is a steam generator that heats a fluid by heating the first flow path, the second flow path, and the fins.

2. A steam generator according to claim 1, The atomizing section is a steam generator having an inclined section in which the cross-sectional area of ​​a portion of the second flow path gradually decreases from the upstream side to the downstream side, and a stepped section formed between the downstream end of the inclined section and the inner circumference of the first flow path so that the fluid flowing downstream from the downstream end of the inclined section does not come into contact with the inner circumference of the first flow path.

3. A steam generator according to claim 2, The aforementioned fin is, Between the inner circumference and the first flow path forming part, a first flow path forming part forms a spiral flow path that generates a swirling flow in a first direction, A steam generator having a second flow path forming section connected downstream of the first flow path forming section, which forms a spiral flow path between itself and the inner circumference section that generates a swirling flow in the opposite direction to the first direction.

4. A steam generator according to any one of claims 1 to 3, further, A temperature difference acquisition unit that acquires the temperature difference between the temperature of the center on the upstream side of the fin and the temperature of the pipe wall forming the first flow path at the same position along the flow path length as the upstream side of the fin, A calculation unit that uses the thickness of the fin, the length of the fin along the length of the flow path, and the flow rate of the fluid supplied to the steam generator to calculate the temperature drop of the fin when the fin evaporates a liquid fluid, A flow control unit controls the flow rate of the liquid supplied to the steam generator so that the aforementioned decrease is smaller than the temperature difference obtained by the temperature difference acquisition unit, A steam generator equipped with the following features.

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