Bubble rate sensor and flow meter and cryogenic liquid transfer tube using the same

Abstract

A bubble rate sensor that measures a bubble rate of a liquid at an extremely low temperature, includes a pipe having a flow path through which a liquid at an extremely low temperature flows, a first electrode and a second electrode disposed outside the flow path, and at least one intermediate electrode disposed inside the flow path between the first electrode and the second electrode, the intermediate electrode being used to measure an electrostatic capacitance between the first electrode and / or the second electrode.

Description

Technical Field

[0001] This disclosure relates to a void fraction sensor for determining the void fraction of cryogenic liquids such as liquid hydrogen, and to a flow meter and cryogenic liquid transfer tube using the void fraction sensor. Background Technology

[0002] In recent years, with the reduction of greenhouse gas emissions, the utilization of hydrogen as a powerful energy storage medium has attracted attention. In particular, liquid hydrogen, due to its high volumetric efficiency and long-term storage capacity, has led to the development of various utilization technologies. However, an accurate method for measuring the required flow rate for large-scale liquid hydrogen processing has not yet been established in industry. The main reason for this is that liquid hydrogen is very easily vaporized, making it a fluid with a highly variable gas-to-liquid ratio.

[0003] That is, liquid hydrogen is a liquid at extremely low temperatures (boiling point -253°C), with very high thermal conductivity and low latent heat, thus exhibiting the characteristic of immediately generating bubbles (void). Therefore, liquid hydrogen in the piping used for transfer becomes a so-called two-phase flow consisting of a gas-liquid mixture.

[0004] Therefore, due to the large variation in the proportion of bubbles, it is impossible to determine the accurate flow rate of liquid hydrogen flowing in the piping simply by measuring the flow velocity as is the case for ordinary liquids.

[0005] Therefore, a bubble fraction meter is being developed to measure the bubble fraction representing the gas phase volume ratio in a gas-liquid two-phase flow. As such a bubble fraction meter, Non-Patent Document 1 proposes a capacitance-type void fraction sensor that uses a pair of electrodes to measure electrostatic capacitance. Non-Patent Document 1 reports the use of this void fraction sensor to measure the void fraction of liquid nitrogen. The piping used in this capacitance-type void fraction sensor is relatively small, with an inner diameter of 10.2 mm.

[0006] Prior art literature

[0007] Non-patent literature

[0008] Non-patent literature 1: Norihide MAENO et al., 5, “Void Fraction Measurement of Cryogenic Two Phase Flow Using a Capacitance Sensor”, Trans. JSASS Aerospace Tech. Japan, Vol. 12, No. ists29, pp. Pa_101-Pa_107, 2014 Summary of the Invention

[0009] The bubble rate sensor disclosed herein measures the bubble rate of cryogenic liquids, comprising: piping having a flow path for the cryogenic liquid to flow through; a first electrode and a second electrode disposed outside the flow path; and at least one intermediate electrode disposed within the flow path and between the first electrode and the second electrode for measuring electrostatic capacitance between the first electrode and / or the second electrode.

[0010] Another bubble rate sensor disclosed herein includes: piping having a flow path for the flow of cryogenic liquid; and at least one pair of electrodes for measuring electrostatic capacitance, the at least one pair of electrodes having an electrode disposed outside the flow path and an electrode disposed inside the flow path.

[0011] Another bubble rate sensor disclosed herein includes: piping having a flow path for the flow of cryogenic liquid; and at least one pair of electrodes for measuring electrostatic capacitance, the at least one pair of electrodes being disposed within the flow path.

[0012] The flow meter disclosed herein measures the flow rate of a cryogenic liquid flowing in a flow path of a piping system, and includes: the aforementioned bubble rate sensor; and a flow velocity meter for measuring the flow velocity of the cryogenic liquid flowing in the flow path.

[0013] In addition, this disclosure provides a cryogenic liquid transfer tube equipped with the above-mentioned flow meter. Attached Figure Description

[0014] Figure 1 This is a schematic cross-sectional view showing a bubble rate sensor according to one embodiment of the present disclosure.

[0015] Figure 2 This is a schematic cross-sectional view showing a bubble rate sensor according to other embodiments of this disclosure.

[0016] Figure 3A and Figure 3B It is a schematic diagram used to illustrate that the distance between two electrodes is electrically equal. Detailed Implementation

[0017] Hereinafter, a bubble rate sensor according to an embodiment of the present disclosure will be described. In the following description, a bubble rate sensor for measuring the bubble rate when liquid hydrogen is used as the cryogenic liquid will be used as an example.

[0018] Figure 1This figure illustrates a bubble rate sensor 1 according to an embodiment of the present disclosure. As shown, the bubble rate sensor 1 of this embodiment has a first electrode 3A and a second electrode 3B disposed outside a flow path 5 of a pipe 2. The pipe 2 has a flow path 5 for supplying liquid hydrogen, and an intermediate electrode 4 is disposed within the flow path 5 of the pipe 2. The intermediate electrode 4 is positioned between the first electrode 3A and the second electrode 3B and along the axial direction of the flow path 5 of the pipe 2 (within the direction of flow path 5). Figure 1 The flow path 5 (perpendicular to the paper surface) is opposite to the first electrode 3A and the second electrode 3B. The cross-section of the flow path 5, perpendicular to the axial direction, is circular through the intermediate electrode 4.

[0019] The first electrode 3A and the second electrode 3B are located outside the flow path 5. This means that the first electrode 3A and the second electrode 3B can also be located outside the flow path 5 as follows: Figure 1 It can be located on the outer periphery of pipe 2, or it can be located inside pipe 2 surrounding flow path 5. Specifically, as... Figure 1 As shown, the first electrode 3A and the second electrode 3B can be located on the outer periphery of the pipe 2. When the first electrode 3A and the second electrode 3B are located on the outer periphery of the pipe 2, the fabrication of the bubble rate sensor 1 becomes easier.

[0020] Furthermore, when there are multiple flow paths within a single pipe 2, these multiple flow path groups are considered as one flow path, and the first electrode 3A and the second electrode 3B are arranged outside the flow path group to sandwich the flow path group. In addition, in the case of multiple flow paths within a single pipe 2, the intermediate electrode 4 is located between the first electrode 3A and the second electrode 3B, and adjacent flow paths are positioned relative to each other.

[0021] Thus, since an intermediate electrode 4 is arranged in the flow path 5 of the piping 2, even if the inner diameter of the flow path 5 increases, the electrostatic capacitance can be measured between the first electrode 3A and the intermediate electrode 4 and between the second electrode 3B and the intermediate electrode 4. Therefore, the distance between the electrodes is shortened and the electrostatic capacitance increases.

[0022] Furthermore, by opposing the first electrode 3A and the second electrode 3B, the area of ​​the intermediate electrode 4 can be set to be larger, thus increasing the electrostatic capacitance accumulated between the electrodes and improving the accuracy of the measurement of the bubble rate of liquid hydrogen.

[0023] The first electrode 3A, the second electrode 3B, and the intermediate electrode 4 are all electrically connected to the electrostatic capacitance measuring machine 8, and the measured electrostatic capacitance value is displayed on the electrostatic capacitance measuring machine 8.

[0024] Pipe 2 is a cylindrical body with a flow path 5 for supplying liquid hydrogen, and is formed of insulating ceramic. Examples of such ceramics include those with zirconium oxide, alumina, sapphire, aluminum nitride, silicon nitride, silicon nitride, cordierite, mullite, yttrium oxide, silicon carbide, cermet, β-nepheline, etc.

[0025] Insulating ceramics are those with an inherent volume resistivity of 10 Ω·cm at 20°C. 10 Ceramics with an Ω·m or higher.

[0026] The principal component in ceramics refers to the component that accounts for more than 60% by mass out of the total 100% by mass of the components constituting the ceramic. Specifically, the principal component can be a component that accounts for more than 95% by mass out of the total 100% by mass of the components constituting the ceramic. The components constituting the ceramic can be determined using X-ray diffraction (XRD). After identifying the components, the content of each component is determined using X-ray fluorescence (XRF) or intracellular optical emission spectrophotometry (ICP-OES) to determine the content of each element, which can then be converted into the identified component.

[0027] The relative density of ceramics is, for example, 92% or more and 99.9% or less. Relative density is expressed as the percentage (proportion) of the apparent density of ceramics relative to the theoretical density of ceramics, as determined according to JIS R 1634-1998.

[0028] Ceramics can also have closed pores, with the value obtained by subtracting the average equivalent circle diameter of the closed pore from the average distance between the centroids of adjacent closed pores (hereinafter referred to as the spacing between closed pores) being 8 μm or more and 18 μm. The closed pores are independent of each other.

[0029] When the spacing between the closed pores is 8 μm or more, the pores exist in a relatively dispersed state, thus increasing the mechanical strength. On the other hand, when the spacing between the closed pores is 18 μm or less, repeated thermal shocks cause microcracks to form originating from the contours of the closed pores, increasing the probability that their propagation will be blocked through the surrounding closed pores. Therefore, if the spacing between the closed pores is 8 μm or more and 18 μm or less, the piping 2 made of this ceramic can be used for a long time.

[0030] The skewness of the equivalent circle diameter of the closed vent can be greater than the skewness of the distance between the centroids of the closed vent. Here, skewness is an indicator (statistic) representing how much the distribution is distorted from the normal distribution, that is, the left-right symmetry of the distribution. When the skewness is greater than 0, the lower edge of the distribution points to the right; when the skewness is 0, the distribution becomes left-right symmetrical; and when the skewness is less than 0, the lower edge of the distribution points to the left.

[0031] If the histograms of the equivalent circle diameters of the closed pores and the distances between the centers of gravity of the closed pores overlap, and if the skewness of the equivalent circle diameters of the closed pores is greater than the skewness of the distances between the centers of gravity of the closed pores, the most frequent value of the equivalent circle diameter is located on the left side (zero side) of the most frequent value of the distance between the centers of gravity. That is, there are many closed pores with small equivalent circle diameters, and these closed pores are more sparsely present, enabling the pipe 2 to have both mechanical strength and resistance to thermal shock.

[0032] For example, the skewness of the equivalent circle diameters of the closed pores is 1 or more, and the skewness of the distances between the centers of gravity of the closed pores is 0.6 or less. The difference between the skewness of the equivalent circle diameters of the closed pores and the skewness of the distances between the centers of gravity of the closed pores is 0.4 or more.

[0033] To find the distances between the centers of gravity and the equivalent circle diameters of the closed pores, first, use diamond abrasive grains with an average particle size D 50 of 3 μm to grind from one end face of the pipe forming the ceramic toward the axial direction through a copper disk. Then, use diamond abrasive grains with an average particle size D 50 of 0.5 μm to grind through a tin disk, thereby obtaining a grinding surface with an arithmetic mean roughness Ra of 0.2 μm or less in the roughness curve. The arithmetic mean roughness Ra of the grinding surface is the same as the above measurement method.

[0034] Observe the grinding surface at a magnification of 200 times, select an average range, for example, photograph an area of 7.2×10 4 μm 2 (the horizontal length is 310 μm and the vertical length is 233 μm) with a CCD camera to obtain an observation image.

[0035] Taking this observation image as an object, for example, using image analysis software "A-Image-kun (ver2.52)" (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.), the distance between the centers of gravity of the closed pores can be obtained by a method such as the center-of-gravity distance method measured by a dispersion meter. Hereinafter, when it is described as image analysis software "A-Image-kun", it means the image analysis software manufactured by Asahi Kasei Engineering Co., Ltd.

[0036] As the setting conditions for this method, for example, set the threshold value as an index representing the brightness and darkness of the image to 165, set the brightness to dark, set the area for removing small figures to 1 μm 2 , and set the noise removal filter to none. In addition, the threshold value can be adjusted according to the brightness of the observation image. As long as the brightness is set to dark, the binary method is set to manual, and the area for removing small figures is set to 1 μm 2And by setting the noise removal filter to "on" and adjusting the threshold to ensure that the marks appearing in the observed image match the shape of the closed vent, the equivalent circle diameter of the closed vent can be determined using the observed image as the object and a method such as particle analysis. The setting conditions are the same as those used to determine the distance between the centroids of the closed vent.

[0037] The equivalent circle diameter of the closed vent and the skewness of the distance between the centers of gravity can be calculated using the Skew function in Excel (registered trademark, Microsoft Corporation).

[0038] An example of a method for manufacturing pipes made from such ceramics will be described. The case where the main component of the ceramic forming the pipe is alumina will be explained.

[0039] Alumina powder (purity ≥ 99.9% by mass), magnesium hydroxide, silicon dioxide, and calcium carbonate powders, as the main components, are fed together with a solvent (e.g., deionized water) into a grinding mill and ground to an average particle size (D). 50 After the alumina powder is reduced to a particle size of less than 1.5 μm, an organic binder and a dispersant to disperse the alumina powder are added and mixed to obtain a slurry.

[0040] Here, the total 100% by mass of the above-mentioned powders contains 0.3 to 0.42% by mass of magnesium hydroxide powder, 0.5 to 0.8% by mass of silicon dioxide powder, 0.06 to 0.1% by mass of calcium carbonate powder, with the balance being alumina powder and unavoidable impurities. Organic binders include, for example, acrylic emulsions, polyvinyl alcohol, polyethylene glycol, and polyethylene oxide.

[0041] Next, the slurry is spray-granulated to obtain particles, and then a single-axis stamping forming device or a cold room hydrostatic stamping forming device is used to pressurize the particles by setting the forming pressure to above 78MPa and below 118MPa, thereby obtaining a columnar molded body.

[0042] In the molded body, a depression is formed by cutting as needed, which becomes a concave part after firing.

[0043] The firing temperature is set to above 1580℃ and below 1780℃, and the holding time is set to above 2 hours and below 4 hours. The molded body is fired to obtain a pipe made of ceramic.

[0044] To obtain ceramics with a pore spacing of 8μm or more and 18μm, for example, the firing temperature is set to 1600℃ or more and 1760℃ or less, and the holding time is set to 2 hours or more and 4 hours or less, and the molded body is fired.

[0045] Alternatively, the surface of the ceramic opposite the flow path can be ground to form a ground surface. Furthermore, the surface where the electrode is located can be ground to form a bottom surface.

[0046] Furthermore, the inner diameter of the flow path 5 is preferably 50 mm or more. In a bubble rate sensor with a pair of electrodes on the outer circumferential surface of the piping, increasing the diameter of the piping increases the distance between the electrodes, potentially reducing the electrostatic capacitance. However, as in this embodiment, by providing an intermediate electrode 4, the distance between the electrodes narrows, increasing the electrostatic capacitance and improving sensitivity. By providing the intermediate electrode 4, the inner diameter of the flow path 5 can be increased, thereby increasing the flow rate of liquid hydrogen.

[0047] The inner diameter of the flow path 5 refers to the maximum diameter of the flow path 5 in the direction perpendicular to the intermediate electrode 4. That is, the inner diameter of the flow path 5 also includes the thickness of the intermediate electrode 4 and the thickness of the support portion 7 that supports the intermediate electrode 4.

[0048] like Figure 1 As shown, the pipe 2 has recesses 6A and 6B formed opposite each other on the axis of the flow path 5. A first electrode 3A and a second electrode 3B are respectively disposed on the bottom surface of these recesses 6A and 6B. The recesses 6A and 6B, as well as the first electrode 3A and the second electrode 3B, can be provided along the entire axial length of the pipe 2, or only in a portion thereof. The bottom surface of the recesses 6A and 6B is... Figure 1 The middle part can be a flat surface, but it can also be an arc shape with a cross section corresponding to flow path 5.

[0049] The first electrode 3A, the second electrode 3B, and the intermediate electrode 4 can be formed, for example, from copper foil, aluminum foil, etc. To form the first electrode 3A and the second electrode 3B on the bottom surfaces of the recesses 6A and 6B, methods such as vacuum evaporation, metallization, and activated metal deposition can be used. Alternatively, metal plates that will become the first electrode 3A and the second electrode 3B can be bonded to the bottom surfaces of the recesses 6A and 6B, respectively.

[0050] The intermediate electrode 4 is preferably configured to connect two points on its radially opposed inner circumferential surfaces within the flow path 5. This allows for the segmentation of the liquid hydrogen flow path 5, thus shortening the distance between the electrodes and increasing the electrostatic capacitance. Consequently, the sensitivity of the bubble rate sensor 1 is increased, thereby improving the accuracy of the liquid hydrogen bubble rate measurement.

[0051] Pipe 2 has a plate-shaped support 7 within the flow path 5 for supporting the intermediate electrode 4, with the intermediate electrode 4 housed within the support 7. By supporting the intermediate electrode 4 with the support 7, the intermediate electrode 4 can be protected. In particular, since the intermediate electrode 4 is not exposed within the flow path 5, it is less susceptible to damage and can be used for a long time. The intermediate electrode 4 is arranged, for example, parallel to at least one of the first electrode 3A and the second electrode 3B.

[0052] The support portion 7 described above can be made of the same insulating ceramic as the pipe 2. Therefore, the support portion 7 and the pipe 2 can be integrally formed by extrusion molding or CIP (cold hydrostatic pressure) molding, for example. In order to embed the intermediate electrode 4 in the support portion 7, for example, the film of the intermediate electrode 4 can be inserted into the part forming the support portion 7 during molding.

[0053] Alternatively, a support portion 7 with an internal intermediate electrode 4 can be prefabricated instead of integral molding, and inserted orthogonally in the axial direction into the flow path 5.

[0054] Alternatively, the intermediate electrode 4 can be omitted from the internal structure, and instead, it can be assembled (layered) on one or both sides of the support portion 7, so as to be opposite to either or both of the first electrode 3A and the second electrode 3B. In this case, it can also be manufactured by integral molding, but the intermediate electrode 4 can also be glued on after integral molding.

[0055] The thickness of the first electrode 3A, the second electrode 3B, and the intermediate electrode 4 is 10 μm or more, preferably 20 μm or more, less than 2 mm, and preferably less than 1 mm.

[0056] The distance between the first electrode 3A and the intermediate electrode 4 can be electrically equal to the distance between the second electrode 3B and the intermediate electrode 4. By making the distance between these two electrodes electrically equal, the average thickness t of the measured space A (described later) is obtained. 22 The resulting potential difference becomes equal to the potential difference generated based on the thickness t2 of the measured space B, allowing the electrical evaluation of the bubble rate of the divided flow paths 5a and 5b to be set equal, thus simplifying control. The meaning of "the distance between the two electrodes is electrically equal" will be explained later.

[0057] like Figure 1 As shown, the first electrode 3A and the second electrode 3B are electrically connected to the electrostatic capacitance measuring machine 8. In addition, the electrostatic capacitance measuring machine 8 is also electrically connected to the intermediate electrode 4, forming the bubble rate sensor 1.

[0058] Next, based on Figure 2 Another embodiment of this disclosure will be described. Furthermore, regarding... Figure 1 Identical structural components are labeled with the same reference numerals, and detailed descriptions are omitted.

[0059] like Figure 2As shown, the bubble rate sensor 11 according to this embodiment includes a plurality of intermediate electrodes 41, 42, and 43, and the distance between each intermediate electrode 41, 42, and 43 is electrically equal. Thus, by including a plurality of intermediate electrodes 41, 42, and 43, the distance between each intermediate electrode 41, 42, and 43 can be shortened. Therefore, the electrostatic capacitance accumulated between each intermediate electrode 41, 42, and 43 increases, thereby improving the accuracy of the measurement of the bubble rate of liquid hydrogen.

[0060] At this point, as long as the distance between each intermediate electrode 41, 42, and 43 is electrically equal, the distance can be appropriately changed to alter the sensitivity.

[0061] Similar to the embodiment described above, intermediate electrodes 41, 42, and 43 are respectively housed within and supported by support portions 71, 72, and 73. Intermediate electrodes 41, 42, and 43 are arranged, for example, parallel to at least one of the first electrode 3A and the second electrode 3B.

[0062] The first electrode 3A, the second electrode 3B, and the intermediate electrodes 41, 42, and 43 are all electrically connected to the electrostatic capacitance measuring machine 8, and the measured electrostatic capacitance value is displayed on the electrostatic capacitance measuring machine 8.

[0063] Furthermore, depending on the conditions used, when gaseous hydrogen becomes a gas-liquid two-phase flow that gathers vertically above the flow path 5 in pipe 2, the overall accuracy of the measurement system can be improved by changing the evaluation weights by utilizing the sensitivity above the vertical and the sensitivity below the vertical with the liquid as the main component.

[0064] Based on improving measurement accuracy, it is preferable that the distance between the first electrode 3A and the intermediate electrode 41 closest to the first electrode 3A, and the distance between the second electrode 3B and the intermediate electrode 43 closest to the second electrode 3B, are electrically equal.

[0065] Similarly, at least one of the following must be electrically equal: the distance between each intermediate electrode 41, 42, 43; the distance between the intermediate electrode 41 closest to the first electrode 3A; and the distance between the second electrode 3B and the intermediate electrode 43 closest to the second electrode 3B.

[0066] Next, based on Figure 2 The bubble rate sensor 11 shown explains the meaning of "the distance between the two electrodes is electrically equal". Figure 3A , Figure 3B This is a schematic diagram illustrating that "the distance between the two electrodes is electrically equal". Figure 3A The diagram schematically illustrates a case where the insulating layer forming the piping 2 is relatively thick, as seen between the first electrode 3A and the intermediate electrode 41. Figure 3B The diagram schematically illustrates a case where the insulating layer is as thin as that between intermediate electrodes 41 and 42.

[0067] like Figure 3A As shown, the sum of the average thickness of the pipe 2 sandwiched between the first electrode 3A and the intermediate electrode 41 and the thickness of the support portion 71 is t. 11 The resulting potential difference is set as E. 11 The average thickness t of the space A to be measured, which is sandwiched between the first electrode 3A and the intermediate electrode 41, will be used as the basis for the measurement. 22 The resulting potential difference is set as E. 22 On the other hand, such as Figure 3B As shown, when the potential difference generated by the sum of the thicknesses t1 of the support portions 71 and 72 sandwiched by the intermediate electrodes 41 and 42 is defined as E1, and the potential difference generated by the thickness t2 of the measured space B sandwiched by the first electrode 3A and the intermediate electrode 41 is defined as E2, t 11 t 22 t1 and t2 are adjusted to E2 = E 22 The state in which the distance between the two electrodes is equal is called the electrical distance between them.

[0068] exist Figure 2 In the example shown, the total thickness t of the insulating ceramic with a dielectric constant greater than that of the cryogenic liquid 11 The thickness is greater than t1, therefore the average thickness t of the measured space A is... 22 It is shorter than the thickness t2 of the space B being measured.

[0069] Potential differences E1, E 22 E1 and E2 can be measured using an electrostatic capacitance measuring machine 8.

[0070] The average thickness of the pipe 2 sandwiched between the first electrode 3A and the intermediate electrode 41 can be calculated using the average value theorem of integration. The average thickness t of the measured space A sandwiched between the first electrode 3A and the intermediate electrode 41 is also calculated. 22 The sum t is the distance between the first electrode 3A and the intermediate electrode 41 minus the average thickness of the pipe 2 sandwiched between the first electrode 3A and the intermediate electrode 41 and the thickness of the support portion 71. 11 The value obtained.

[0071] In addition to the bubble rate sensors 1 and 11 described above, this disclosure may also include a bubble rate sensor consisting of a first electrode 3A or a second electrode 3B disposed on the outer periphery of the pipe 2 and an intermediate electrode 4 disposed within the flow path 5, used for measuring electrostatic capacitance. That is, the electrode disposed on the outer periphery of the pipe 2 may be only one of the aforementioned electrodes 3A and 3B. Even with such a pair of electrodes, the shorter distance between the electrodes results in a larger electrostatic capacitance accumulated between them, thus improving the accuracy of bubble rate measurement. Furthermore, a pair of electrodes may consist of two or more electrodes.

[0072] Furthermore, as another bubble rate sensor disclosed herein, a bubble rate sensor may be constructed from a pair of electrodes disposed within the flow path 5, without using the first electrode 3A or the second electrode 3B disposed outside the flow path 5. That is, it may also be composed of... Figure 2 A bubble rate sensor is formed by, for example, intermediate electrodes 41 and 43, intermediate electrodes 41 and 42, or intermediate electrodes 42 and 43, as shown in the diagram. Figure 2 As shown, a portion of each of the intermediate electrodes 41, 42, and 43 can also be located inside the inner circumferential surface surrounding the flow path 5.

[0073] Next, the flow meter according to the embodiments of this disclosure will be described. This flow meter measures the flow rate of liquid hydrogen flowing in the flow path 5, and includes the bubble rate sensors 1 and 11 and a flow velocity meter for measuring the flow velocity of a cryogenic liquid (not shown) flowing in the flow path 5. The bubble rate sensors 1 and 11 and the flow velocity meter are mounted in a liquid hydrogen transfer tube (not shown) (hereinafter sometimes simply referred to as the transfer tube).

[0074] The liquid hydrogen flowing within flow path 5 becomes a two-phase flow consisting of a gas-liquid mixture. Therefore, the electrostatic capacitance of the liquid hydrogen is measured by bubble rate sensors 1 and 11, and the density d (kg / m³) of the liquid hydrogen is calculated from this. 3 ).

[0075] Furthermore, setting the flow velocity of liquid hydrogen (m / s) obtained from the flow meter as v, and setting the cross-sectional area (m²) of flow path 5 as... 2 When is set as a, the flow rate F (kg / s) can be calculated using the following formula.

[0076] F=d×v×a

[0077] To perform the above calculations, the flow meter also includes a calculation device connected to bubble rate sensors 1 and 11 and a flow velocity meter. This allows for simple measurement of the flow rate of liquid hydrogen, thus simplifying management in industrial applications involving large-scale transfers of liquid hydrogen.

[0078] In the above description, bubble rate sensors 1 and 11 for liquid hydrogen and flow meters using them have been described. However, the same application can be made to other cryogenic liquids, such as liquid nitrogen (-196°C), liquid helium (-269°C), liquefied natural gas (-162°C), liquid argon (-186°C), etc. (the liquefaction temperature is indicated in parentheses). Therefore, cryogenic liquids in this disclosure refer to liquids that liquefy at extremely low temperatures below -162°C.

[0079] The embodiments of this disclosure have been described above, but the bubble rate sensor of this disclosure is not limited to the above embodiments and can be modified and improved in various ways within the scope described in this disclosure.

[0080] -Explanation of Figure Markers-

[0081] 1.11 Bubble Rate Sensor

[0082] 2 piping

[0083] 3A First Electrode

[0084] 3B Second Electrode

[0085] 4, 41, 42, 43 intermediate electrodes

[0086] 5 flow paths

[0087] 6A, 6B concave parts

[0088] 7, 71, 72, 73 Support sections

[0089] 8. Electrostatic capacitance tester.

Claims

1. A bubble rate sensor for measuring the bubble rate of cryogenic liquids. The bubble rate sensor includes: Piping having flow paths for the cryogenic liquid; The first electrode and the second electrode are disposed outside the flow path, sandwiching the flow path; and At least one intermediate electrode is disposed within the flow path and between the first electrode and the second electrode, the intermediate electrode being used to measure the electrostatic capacitance between the first electrode and / or the second electrode. The flow path is divided into at least two segments between the first electrode and the second electrode. The first electrode is opposite the intermediate electrode across one of the divided flow paths, and the second electrode is opposite the intermediate electrode across the other of the divided flow paths.

2. The bubble rate sensor according to claim 1, wherein, The intermediate electrode is disposed opposite to the first electrode and the second electrode along the axial direction of the flow path.

3. The bubble rate sensor according to claim 1 or 2, wherein, The intermediate electrode connects two points that are radially opposite each other and located on the inner circumferential surface within the flow path.

4. The bubble rate sensor according to claim 1 or 2, wherein, The distance between the first electrode and the intermediate electrode and the distance between the second electrode and the intermediate electrode are electrically equal.

5. The bubble rate sensor according to claim 1 or 2, wherein, There are multiple intermediate electrodes, and the distance between each intermediate electrode is electrically equal.

6. The bubble rate sensor according to claim 5, wherein, The distance between the first electrode and the intermediate electrode closest to the first electrode and the distance between the second electrode and the intermediate electrode closest to the second electrode are electrically equal.

7. The bubble rate sensor according to claim 5, wherein, The distance between each intermediate electrode, the distance between the first electrode and the intermediate electrode closest to the first electrode, and the distance between the second electrode and the intermediate electrode closest to the second electrode are at least electrically equal.

8. The bubble rate sensor according to claim 1 or 2, wherein, The piping includes a support portion that supports the intermediate electrode. The intermediate electrode is built into the support portion.

9. The bubble rate sensor according to claim 1 or 2, wherein, The piping includes a support portion that supports the intermediate electrode. The intermediate electrode is mounted on one or both sides of the support portion, such that it is opposite to either or both of the first electrode and the second electrode, and is covered by an insulating film.

10. The bubble rate sensor according to claim 8, wherein, The support portion is a component integrally formed with the piping.

11. The bubble rate sensor according to claim 1 or 2, wherein, The inner diameter of the flow path is 50 mm or more.

12. A flow meter for measuring the flow rate of a cryogenic liquid flowing within a piping path. The flow meter has the following features: The bubble rate sensor according to any one of claims 1 to 11; and A flow meter is used to measure the flow rate of the cryogenic liquid flowing within the flow path.

13. A cryogenic liquid transfer tube, The flow meter as described in claim 12 is provided.

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