Bubble rate sensor, flow meter using the same, and extremely low temperature liquid transfer tube

Abstract

This invention relates to a bubble rate sensor for measuring the bubble rate of a cryogenic liquid. The bubble rate sensor comprises: a piping having a conduit for the flow of the cryogenic liquid; and electrodes disposed on the outer peripheral surface of the piping for measuring the electrostatic capacitance of the cryogenic liquid flowing within the conduit. The piping is composed of a divisible even number of ceramic components, and the electrodes are respectively disposed on at least two of the even number of ceramic components that are opposite each other.

Description

Technical Field

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

[0002] Recently, with the reduction of greenhouse gas emissions, the utilization of hydrogen as a powerful energy storage medium has attracted attention. Liquid hydrogen, in particular, has high volumetric efficiency and can be stored for long periods, leading to the development of various technologies for its utilization. However, an accurate method for measuring the flow rate required for large-scale liquid hydrogen processing has not yet been established in industry. The main reason is that liquid hydrogen is very easily vaporized and is a fluid with a highly variable gas-to-liquid ratio.

[0003] In other words, 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 (voids). Therefore, liquid hydrogen in the piping used for transfer becomes a so-called two-phase flow of gas-liquid mixture.

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

[0005] Therefore, the development of bubble rate meters that measure the bubble rate representing the gas phase volume ratio in a gas-liquid two-phase flow has been promoted. As such a bubble rate meter, Non-Patent Document 1 proposes a capacitance-type void fraction sensor that uses a pair of electrodes to measure electrostatic capacitance. It describes that this capacitance-type void fraction sensor has an externally mounted electrode structure on a pipe integrally formed from acrylic resin or the like, with a pipe 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 AerospaceTech. 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. The bubble rate sensor comprises: a piping having a conduit for the flow of the cryogenic liquid; and electrodes disposed on the outer peripheral surface of the piping for measuring the electrostatic capacitance of the cryogenic liquid flowing within the conduit. The piping is composed of a divisible even number of ceramic components, and the electrodes are respectively disposed on at least two of the even number of ceramic components that are opposite each other.

[0010] Additionally, other bubble rate sensors disclosed herein include: an inner tube having a conduit for the flow of a cryogenic liquid; an outer tube covering the outer periphery of the inner tube; and electrodes disposed on the outer side of the inner tube for measuring the bubble rate of the cryogenic liquid flowing within the conduit. The inner tube is composed of a divisible even number of ceramic components, and the electrodes are respectively disposed on at least two of the even number of ceramic components that are opposite each other.

[0011] The flow meter disclosed herein measures the flow rate of a cryogenic liquid flowing in a piping system, wherein the flow meter comprises: the aforementioned bubble rate sensor; and a flow velocity meter that measures the flow velocity of the cryogenic liquid flowing in the piping system.

[0012] In addition, this disclosure provides a cryogenic liquid transfer tube that includes the aforementioned flow meter. Attached Figure Description

[0013] Figure 1 This is a schematic cross-sectional view illustrating a bubble rate sensor according to one embodiment of the present disclosure.

[0014] Figure 2 This is a schematic cross-sectional view illustrating another embodiment of the bubble rate sensor of this disclosure.

[0015] Figure 3A This is a schematic cross-sectional view illustrating a bubble rate sensor according to yet another embodiment of the present disclosure.

[0016] Figure 3B It is shown Figure 3A An explanatory diagram of the divisible ceramic components.

[0017] Figure 4A It is a schematic diagram used to illustrate that the distance between two electrodes is electrically equal.

[0018] Figure 4B It is a schematic diagram used to illustrate that the distance between two electrodes is electrically equal. Detailed Implementation

[0019] The bubble rate sensor according to embodiments of the present disclosure will now be described. It should be noted that the following description focuses on a bubble rate sensor used to measure the bubble rate when liquid hydrogen is used as the cryogenic liquid.

[0020] Figure 1 A bubble rate sensor 1 according to one embodiment of the present disclosure is shown. As shown in the figure, the bubble rate sensor 1 of this embodiment has a pipe 2. The pipe 2 is composed of two divisible ceramic components 21 and 22. Liquid hydrogen flows within a conduit 3 in the pipe 2.

[0021] In bubble rate sensors that capture changes in bubble rate as electrostatic capacitance, the piping 2 is preferably made of ceramic, which is less prone to thermal expansion than metal, in order to minimize the effects of thermal expansion. However, if the piping 2 is integrally formed with ceramic and has a large diameter, and liquid hydrogen, which is a cryogenic liquid, flows inside the piping, cracks are easily generated due to thermal shock.

[0022] In this disclosure, the piping 2 is composed of two divisible ceramic components 21 and 22. Therefore, even in an environment with flowing liquid hydrogen, cracking of the ceramic components 21 and 22 can be suppressed, and even if cracks do occur, crack propagation can be inhibited. Thus, the insulation properties of the ceramic components 21 and 22 can be maintained.

[0023] Ceramic components 21 and 22 are formed, for example, from ceramics whose main components are zirconium oxide, alumina, sapphire, aluminum nitride, silicon nitride, siliconium, cordierite, mullite, yttrium oxide, silicon carbide, cermet, β-nepheline, etc. When ceramic components 21 and 22 are composed of ceramics whose main component is alumina, the ceramic may also contain oxides such as silicon, calcium, magnesium, and sodium.

[0024] The main component in ceramics refers to the component that accounts for 60% or more by mass out of the total 100% mass of the components constituting the ceramic. In particular, the main component is preferably the component that accounts for 95% or more by mass out of the total 100% mass of the components constituting the ceramic. The components constituting the ceramic can be determined using an X-ray diffraction (XRD) apparatus. Regarding the content of each component, after identifying the components, the content of each element constituting the component is determined using an X-ray fluorescence (XRF) apparatus or an inductively coupled plasma optical emission spectrophotometer, and then converted into the identified component.

[0025] Furthermore, the inner diameter of pipe 2 is preferably 50 mm or more. Pipe 2 is composed of divisible ceramic components 21 and 22, which suppress the generation and propagation of cracks, thus allowing for an increase in the diameter of pipe 2. As a result, large quantities of liquid hydrogen can be transported.

[0026] like Figure 1As shown, recesses 5 and 6 are formed on the outer periphery of the pipe 2 at axially opposite locations across the flow path 3. Electrodes 41 and 42 for measuring electrostatic capacitance are respectively arranged opposite each other on the bottom surface of the recesses 5 and 6. Thus, because electrodes 41 and 42 are arranged on the bottom surface of the recesses 5 and 6, the mounting area and position of electrodes 41 and 42 can be determined with high precision, thereby improving the accuracy of measuring the bubble rate of liquid hydrogen.

[0027] Recesses 5 and 6 and electrodes 41 and 42 can be axially (with) the piping 2. Figure 1 It can be set along the entire length (vertically perpendicular to the paper surface) or only within a portion of the length. The bottom surfaces of recesses 5 and 6 are... Figure 1 The middle part is a flat surface, but the cross-section can also be an arc shape corresponding to flow path 3.

[0028] Electrodes 41 and 42 can be formed, for example, from copper foil or aluminum foil. To form electrodes 41 and 42 on the bottom surface of each recess 5 and 6, vacuum evaporation, metallization, or active metal deposition can be used, for example. Alternatively, metal plates that will become the first electrode 3A and the second electrode 3B can be bonded to the bottom surface of the recess 5 and 6 respectively.

[0029] The thickness of electrodes 41 and 42 is preferably 10 μm or more, preferably 20 μm or more and less than 1 mm, and preferably less than 2 mm.

[0030] The divisible ceramic components 21 and 22 have mutually abutting contact surfaces 21a and 22a. These contact surfaces 21a and 22a are mirror-finished to prevent leakage of liquid hydrogen flowing within the piping 2. The mirror finish is formed, for example, by grinding or lapping. The contact surfaces 21a and 22a preferably have an arithmetic mean roughness (Ra) of 0.4 μm or less, and more preferably 0.2 μm or less.

[0031] Arithmetic mean roughness (Ra) can be measured according to JIS B0601:2001 using a laser microscope (Keyence Corporation, Ultra-Deep Color 3D Shape Measurement Microscope (VK-X1000 or its successor)). As for the measurement conditions, the illumination mode is set to coaxial illumination, the measurement magnification is set to 240x, the cutoff value λs is set to none, the cutoff value λc is set to 0.08 mm, the end effect correction is set to yes, and the measurement range is set to 1425 μm × 1067 μm. Within the measurement range, four lines are drawn at approximately equal intervals as the measurement object for surface roughness measurement. The length of each line is 1280 μm.

[0032] Alternatively, ceramic components 21 and 22 can be bundled together by overlapping the abutting surfaces 21a and 22a of each other and then surrounding the outer periphery with the annular body described later.

[0033] Figure 2 A bubble rate sensor 11 according to another embodiment of this disclosure is shown. For example... Figure 2 As shown, the recesses 51 and 61 formed on the outer peripheral sides of ceramic components 21′ and 22′ have first recesses 7a and 8a that open outwards, and second recesses 7b and 8b disposed on the bottom surface of the first recesses 7a and 8a. The opening area of ​​the second recesses 7b and 8b is smaller than that of the first recesses 7a and 8a, and electrodes 41 and 42 are mounted on the bottom surface. This further improves the positioning accuracy of electrodes 41 and 42 and enhances the accuracy of measuring the bubble rate of liquid hydrogen.

[0034] Others Figure 1 The embodiments shown are the same, therefore the same reference numerals are used to label the same components and descriptions are omitted.

[0035] Next, based on Figure 3A , 3B A bubble rate sensor according to yet another embodiment of the present disclosure will be described. Figure 3A The bubble rate sensor 12 shown includes: an inner tube 9 having a conduit 31 for the flow of cryogenic liquid; an outer tube 10 covering the outer periphery of the inner tube 9; and electrodes 43a, 43b, 43c, and 43d located outside the inner tube 9 for measuring the bubble rate of the cryogenic liquid flowing within the conduit 31.

[0036] like Figure 3B As shown, the inner tube 9 is composed of four divisible ceramic components 91, 92, 93, and 94. These four ceramic components 91, ... 94 have recesses 71, 72, 73, and 74 formed on their outer peripheral sides. Electrodes 43a, ... 43d are respectively disposed on the bottom surface of each recess 71, ... 74. The ceramic components 91, ... 94 are made of the same material as the ceramic components 21 and 22 constituting the aforementioned piping 2.

[0037] The outer tube 10 is made of austenitic stainless steel such as SUS316 or SUS316L.

[0038] Electrostatic capacitance is measured between opposing electrodes 43a and 43d, and between 43b and 43d. To improve measurement accuracy, it is preferable that the distances between opposing electrodes 43a and 43d and between 43b and 43d are electrically equal.

[0039] Here, we will explain the meaning of "electrically equal distances". Figure 4A , 4BIt is a schematic diagram used to illustrate that the distance between two electrodes is electrically equal. Figure 4A The diagram schematically illustrates a case where the insulation layer constituting the inner tube 9 is relatively thick. Figure 4B The diagram illustrates the case where the insulating layer is relatively thin. It should be noted that in the following description, it is assumed that the total thickness of the inner tube 9 between electrodes 43a and 43c is greater than the total thickness of the inner tube 9 between electrodes 43b and 43d.

[0040] The total t is based on the average thickness of the inner tube 9 held by the two opposing electrodes 43a and 43c. 11 The resulting potential difference is set as E. 11 The average thickness t of the space A being measured, held by electrodes 43a and 43c, will be used as the basis for the measurement. 22 The resulting potential difference is set as E. 22 On the other hand, when the potential difference generated based on the total thickness t1 of the inner tube 9 held by the two opposing electrodes 43b and 43d is set as E1, and the potential difference generated based on the thickness t2 of the measured space B held by the electrodes 43b and 43d is set 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 said to be electrically equal is called the state in which the distance between the two electrodes is equal.

[0041] exist Figure 4A , 4B In the example shown, the total thickness t of the insulating ceramic, whose dielectric constant is greater than that of cryogenic liquids, is... 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. Potential differences E1, E... 22 E1 and E2 can be measured using an electrostatic capacitance meter.

[0042] The average thickness of the inner tube 9 held between electrodes 43a and 43c and between electrodes 43b and 43d can be calculated using the theorem of the average value of integrals. The average thickness t of the measured space A held by electrodes 43a and 43c is also calculated. 22 The total t is the difference between the interval between electrodes 43a and 43c and the average thickness of the inner tube 9 held by electrodes 43a and 43c. 11 The average thickness t2 of the measured space B, held by electrodes 43b and 43d, was also calculated in the same way.

[0043] Regarding internal tube 9, Figure 3AIn the inner tube 9, the cross-section is approximately quadrilateral, and its corners 13 are chamfered (C-face machining or R-face machining). Furthermore, annular bodies 14 for binding ceramic components 91, ... 94 are assembled on the outer circumferential surface of the inner tube 9. Examples of annular bodies 14 include strip-shaped flexible plastic films and metal strips. The two ends of the annular bodies 14 are joined by joining methods such as heat fusion or welding.

[0044] like Figure 3A As shown, the annular body 14 presses against each of the chamfered corners 13 in a roughly equal manner, thus securing each ceramic component 91, ... 94.

[0045] The inner circumferential surface of the inner tube 9 can also be a ground surface. If the inner circumferential surface of the inner tube 9 is a ground surface, it can achieve a state where the geometric tolerances such as roundness and cylindricity are superior to those of the fired surface, thereby improving the accuracy of bubble rate measurement.

[0046] Furthermore, an outer tube 10 is inserted around the outer periphery of the inner tube 9, which is bound by the annular body 14, thus covering the outer periphery of the inner tube 9. At this time, a gap 15 is formed between the inner tube 9 and the outer tube 10. By depressurizing within this gap 15, creating an insulating structure similar to vacuum-insulated piping, the vaporization of liquid hydrogen caused by heat can be suppressed, thereby improving the accuracy of the bubble rate measurement. The vacuum level within the gap 15 is, for example, 0.1 Pa or more and 100 Pa or less.

[0047] The relative density of the ceramic component is, for example, 92% or more and 99.9% or less. The relative density is expressed as the percentage (proportion) of the apparent density of the ceramic component relative to the theoretical density of the ceramic component, as determined based on JIS R 1634-1998.

[0048] At least one of the ceramic components has closed pores, the value obtained by subtracting the average equivalent circle diameter of the closed pores from the average distance between the centroids of adjacent closed pores (hereinafter referred to as the spacing between closed pores) is 8 μm or more and 18 μm. The closed pores are independent of each other.

[0049] When the spacing between closed pores is 8 μm or more, the closed pores exist in a relatively dispersed state, thus increasing the mechanical strength. On the other hand, when the spacing between closed pores is 18 μm or less, even if microcracks originating from the contours of the closed pores are generated by repeated thermal shocks, the probability of their propagation being blocked by the surrounding closed pores increases. Therefore, if the spacing between closed pores is 8 μm or more and 18 μm or less, ceramic components can be used for a long time.

[0050] The skewness of the equivalent circle diameter of a closed stomata can also be greater than the skewness of the distance between the centroids of the closed stomata. Here, skewness Sk refers to the index of how much the distribution deviates from the normal distribution, that is, an index (statistic) representing the left-right symmetry of the distribution. When the skewness is greater than 0, the tail of the distribution points to the right; when the skewness is 0, the distribution is symmetrical; and when the skewness is less than 0, the tail of the distribution points to the left.

[0051] When the histograms of the equivalent circle diameter of the closed pores and the distance between the centroids of the closed pores are superimposed, if the skewness of the equivalent circle diameter of the closed pores is greater than the skewness of the distance between the centroids of the closed pores, the mode of the equivalent circle diameter is located to the left (zero side) of the mode of the distance between the centroids. That is, there are more closed pores with smaller equivalent circle diameters, and these closed pores exist more sparsely, which can result in ceramic components that combine mechanical strength and resistance to thermal shock.

[0052] For example, the skewness of the equivalent circle diameter of the closed vent is 1 or more, and the skewness of the distance between the centroids of the closed vent is 0.6 or less. The difference between the skewness of the equivalent circle diameter of the closed vent and the skewness of the distance between the centroids of the closed vent is 0.4 or more.

[0053] To determine the distance between the centroids of closed pores and the equivalent circle diameter, firstly, starting from one end face of the ceramic component and moving axially, the average particle size D is used. 50 The grinding process involved using 3μm diamond abrasive grains and a copper disc. Then, the average grain size D was adjusted. 50 A polished surface with an arithmetic mean roughness (Ra) of less than 0.2 μm was obtained by polishing with 0.5 μm diamond abrasive grains using a tin disc. The arithmetic mean roughness Ra of the polished surface was determined using the same method as described above.

[0054] Observe the polished surface at 200x magnification, selecting an average area, for example, an area of ​​7.2 × 10⁻⁶ using a CCD camera. 4 μm 2 The observation image was obtained within a range of (310 μm horizontally and 233 μm vertically).

[0055] Using this observed image as an example, the distance between the centroids of the closed stomata can be determined by using image analysis software such as "A-Image-kun (ver2.52)" (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.) through a method such as the distance between the centroids measured by a dispersive spectroscopy meter. Hereinafter, when referred to as "A-Image-kun," it means image analysis software manufactured by Asahi Kasei Engineering Co., Ltd.

[0056] As a set condition for this method, for example, the threshold representing the brightness of the image is set to 165, brightness is set to dark, and the area to be removed for small graphics is set to 1 μm. 2Simply set the noise removal filter to "None". It should be noted that the threshold can be adjusted according to the brightness of the observed image. This includes setting the brightness to "Dark", the binarization method to "Manual", and the area to be removed for small images to 1μm. 2 Based on the noise removal filter, the threshold can be adjusted to ensure that the marks appearing in the observed image match the shape of the closed stomata. The equivalent circle diameter of the closed stomata can be determined using particle analysis on the observed image. The setting conditions are the same as those used to determine the distance between the centroids of the closed stomata.

[0057] The equivalent circle diameter of the closed pore and the skewness of the distance between the centroids can be calculated using the Skew function in Excel (registered trademark, Microsoft Corporation).

[0058] An example of a method for manufacturing such ceramic components will be described. The case where the main component of the ceramic component is alumina will be explained.

[0059] Alumina powder (purity ≥ 99.9% by mass), which is the main component, along with powders of magnesium hydroxide, silicon dioxide, and calcium carbonate, and a solvent (ion-exchanged water), are fed into a grinding mill and ground until the average particle size (D) of the powder is reached. 50 After the alumina powder is reduced to a particle size of less than 1.5 μm, an organic binder and a dispersant for dispersing the alumina powder are added and mixed to obtain a slurry.

[0060] Here, the total content of the above powders is 100% by mass, with magnesium hydroxide powder content of 0.3 to 0.42% by mass, silicon oxide powder content of 0.5 to 0.8% by mass, calcium carbonate powder content of 0.06 to 0.1% by mass, and the balance being aluminum oxide powder and unavoidable impurities.

[0061] Organic binders include acrylic emulsions, polyvinyl alcohol, polyethylene glycol, and polyethylene oxide.

[0062] Next, the slurry is spray-granulated to obtain granules, which are then pressurized using a uniaxial stamping or cold isostatic pressing device at a pressure of 78 MPa to 118 MPa to obtain a columnar molded body. If necessary, the molded body is machined to create recesses that will become concave sections after firing.

[0063] The molded body is fired at a temperature above 1580℃ and below 1780℃, and the holding time is above 2 hours and below 4 hours to obtain a ceramic component.

[0064] To obtain a ceramic component with a closed pore spacing of 8 μm or more and 18 μm, the molded body is fired at a firing temperature of 1600°C or more and 1760°C or less, and the holding time is 2 hours or more and 4 hours or less. Alternatively, the surface of the ceramic component opposite to pipes 3 and 31 can be ground to create a grinding surface. Additionally, the surface of the recessed portion where the electrode is located can be ground to create a bottom surface.

[0065] It should be noted that, in this disclosure, the cross-section of the inner tube is not limited to an approximate quadrilateral; the cross-sectional shape can also be circular or other polygonal. In this case, the number of ceramic components constituting the inner tube is an even number, such as 2, 4, 6, or 8. This is because, in order to measure electrostatic capacitance, a pair of opposing electrodes is required, with each electrode mounted on a separate ceramic component.

[0066] In addition, even if electrodes are not provided on all of the even number of ceramic components, electrodes can be provided only on at least two ceramic components that are opposite each other.

[0067] As described above, according to this disclosure, the piping 2 or inner pipe 9 is composed of a divisible even number of ceramic components. Therefore, even in environments with extremely low temperature liquid flow, the generation and propagation of cracks that are prone to form on the ceramic components can be suppressed, and electrical functions can be maintained. Thus, the bubble rate sensor of this disclosure exhibits excellent durability and high reliability.

[0068] Next, the flow meter according to an embodiment of this disclosure will be described. This flow meter is used to measure the flow rate of liquid hydrogen flowing within pipes 3 and 31, and includes the aforementioned bubble rate sensors 1, 11, and 12, and a velocity meter (not shown). The bubble rate sensors 1, 11, and 12, and the velocity meter are mounted in a liquid hydrogen transfer tube (hereinafter, sometimes simply referred to as the transfer tube). The velocity meter measures the flow velocity of the cryogenic liquid flowing within pipes 3 and 31.

[0069] The liquid hydrogen flowing in pipes 3 and 31 forms a two-phase flow of gas and liquid mixture. Therefore, the bubble rate is measured using bubble rate sensors 1, 11, and 12, and the density d (kg / m³) of the liquid hydrogen is calculated from this. 3 This is because the density d of liquid hydrogen corresponds to the specific permittivity, and therefore also to the electrostatic capacitance measured by the bubble rate sensors 1 and 11.

[0070] Furthermore, assuming the flow velocity of liquid hydrogen (m / s) determined by the flow meter is v, and the cross-sectional area (m²) of pipes 3 and 31 is... 2 When is set as a, the flow rate F (kg / s) can be calculated using the following formula.

[0071] F=d×v×a

[0072] To perform the above calculations, the flow meter can also be equipped with 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.

[0073] The above description describes bubble rate sensors 1, 11, and 12 for liquid hydrogen and flow meters using them, but the same principles apply to other cryogenic liquids, such as liquid nitrogen (-196°C), liquid helium (-269°C), liquefied natural gas (-162°C), and liquid argon (-186°C) (liquefaction temperature is indicated in parentheses). Therefore, cryogenic liquids in this disclosure refer to liquids liquefied at extremely low temperatures below -162°C.

[0074] 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 various changes and improvements can be made within the scope described in this disclosure.

[0075] Explanation of reference numerals in the attached figures:

[0076] 1, 11, 12... Bubble rate sensor;

[0077] 2...Piping;

[0078] 3, 31… Pipelines;

[0079] 5, 6, 51, 61...concave;

[0080] 6A, 6B...concave parts;

[0081] 7a, 8a...the first recess;

[0082] 7b, 8b...the second recess;

[0083] 9…inner tube;

[0084] 10…outer tube;

[0085] 13...corner;

[0086] 14… Circular bodies;

[0087] 15…gap;

[0088] 21, 22, 91, 92, 93, 94… Ceramic components;

[0089] 21a, 22a... contact surfaces;

[0090] Electrodes 41, 42, 43a, 43b, 44a, 44b...

[0091] 71, 72, 73, 74... concavities.

Claims

1. A bubble rate sensor for measuring the bubble rate of cryogenic liquids, wherein, The bubble rate sensor includes: Piping, having conduits for the flow of the cryogenic liquid; as well as An electrode, disposed on the outer periphery of the piping, is used to measure the electrostatic capacitance of the cryogenic liquid flowing within the piping. The piping is composed of an even number of ceramic components, each of which abuts against an adjacent ceramic component. The electrodes are respectively disposed on at least two of the even number of ceramic components that are opposite each other.

2. The bubble rate sensor according to claim 1, wherein, The ceramic component has recesses on its outer peripheral surface that open outwards, and the electrode is mounted on the bottom surface of the recesses.

3. The bubble rate sensor according to claim 2, wherein, The recess has: a first recess that opens to the outside; and a second recess disposed on the bottom surface of the first recess and having an opening area smaller than that of the first recess, wherein the electrode is mounted on the bottom surface of the second recess.

4. A bubble rate sensor for measuring the bubble rate of cryogenic liquids, wherein, The bubble rate sensor includes: The inner tube has a conduit for the flow of the cryogenic liquid; An outer tube that covers the outer periphery of the inner tube; and An electrode, disposed on the outside of the inner tube, is used to measure the bubble rate of the cryogenic liquid flowing within the tube. The inner tube is composed of an even number of ceramic components, each of which abuts against an adjacent ceramic component. The electrodes are respectively disposed on at least two of the even number of ceramic components that are opposite each other.

5. The bubble rate sensor according to claim 4, wherein, There is a reduced pressure gap between the inner tube and the outer tube.

6. The bubble rate sensor according to claim 4 or 5, wherein, An annular body for binding the ceramic component is assembled on the outer periphery of the inner tube.

7. The bubble rate sensor according to claim 4 or 5, wherein, The inner circumferential surface of the inner tube is a ground surface.

8. The bubble rate sensor according to any one of claims 1 to 5, wherein, At least one of the ceramic components has closed pores, and the value obtained by subtracting the average value of the equivalent circle diameter of the closed pores from the average value of the distance between the centroids of adjacent closed pores is 8 μm or more to 18 μm.

9. The bubble rate sensor according to claim 8, wherein, The deviation of the equivalent circle diameter of the closed vent is greater than the deviation of the distance between the centroids of the closed vent.

10. A flow meter for measuring the flow rate of a cryogenic liquid flowing in a piping or inner pipe of a pipeline, wherein, The flow meter has the following features: The bubble rate sensor according to any one of claims 1 to 9; and A flow meter that measures the flow rate of the cryogenic liquid flowing within the pipeline.

11. A cryogenic liquid transfer tube, wherein, The cryogenic liquid transfer tube is equipped with the flow meter as described in claim 10.

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