Bubble rate sensor, flow meter using same, and pipette

Abstract

This bubble rate sensor is provided with: an insulating tube having a plurality of through-holes through which a liquid flows; and a plurality of electrodes positioned inside or on the outer surface of the insulating tube and facing each other with the plurality of through-holes interposed therebetween. The plurality of through holes have an elongated shape having a first direction and a second direction shorter than the first direction in a cross section perpendicular to the flow direction of the liquid. The plurality of electrodes face each other across the plurality of through holes in the second direction.

Description

Technical Field

[0001] The present disclosure relates to a void fraction sensor for measuring the void fraction of liquid such as liquid hydrogen, a flow meter using the void fraction sensor, and a pipette. Background Art

[0002] Recently, with the reduction of greenhouse gas emissions, the use of hydrogen as a powerful energy storage medium has attracted much attention. In particular, since liquid hydrogen has a high volumetric efficiency and can be stored for a long time, a variety of its utilization technologies have been developed. However, an accurate measurement method for the flow rate required for large-scale processing of liquid hydrogen has not yet been established in the industry. The main reason is that liquid hydrogen is a fluid that is very easy to gasify and the ratio of gas to liquid varies greatly.

[0003] That is, liquid hydrogen is a super-low temperature liquid (boiling point -253°C), and has the characteristic of generating bubbles (voids) immediately due to its extremely high heat conductivity and low latent heat. Therefore, liquid hydrogen becomes a so-called two-phase flow of gas-liquid mixture in the transfer pipe. Therefore, since the content ratio of bubbles varies greatly, in order to measure the flow rate of liquid hydrogen flowing through the transfer pipe, it is impossible to know the exact flow rate by only measuring the flow rate as with ordinary liquids.

[0004] Therefore, the development of a bubble fraction meter that measures the bubble fraction representing the gas phase volume ratio of a gas-liquid two-phase flow has been progressing. 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 capacitance.

[0005] Prior Art Literature

[0006] Non-patent literature

[0007] Non-patent document 1: Norihide MAENO, and five others, “Void Fraction Measurement of Cryogenic Two Phase Flow Using a Capacitance Sensor,” Trans. JSASS Aerospace Tech. Japan, Vol. 12, No.ists 29, pp. Pa_101-Pa_107, 2014 Summary of the invention

[0008] The bubble rate sensor disclosed in the present invention has an insulating tube and at least two electrodes. The insulating tube has a plurality of through holes for liquid to flow through. The at least two electrodes are respectively located inside or on the outer surface of the insulating tube, and are respectively opposed to each other with the plurality of through holes sandwiched therebetween. The plurality of through holes have an elongated shape in a cross section perpendicular to the flow direction of the liquid, and the elongated shape has a first side in a first direction and a second side in a second direction whose length is shorter than that in the first direction. The at least two electrodes are opposed in the second direction, and the plurality of through holes are located between the at least two electrodes.

[0009] The flow meter of the present disclosure measures the flow rate of the liquid flowing through the transfer tube. The flow meter has the bubble rate sensor and a flow meter. The flow meter can measure the flow rate of the liquid flowing through the through hole. Furthermore, the pipette of the present disclosure is equipped with the flow meter. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic perspective view showing an air bubble ratio sensor according to an embodiment of the present disclosure.

[0011] Figure 2 yes Figure 1 A schematic side view of an air bubble rate sensor is shown.

[0012] Figure 3 yes Figure 2 A cross-sectional view of the bubble rate sensor taken along line II-II is shown.

[0013] Figure 4 yes Figure 2 A cross-sectional view of the bubble rate sensor taken along line IV-IV is shown.

[0014] Figure 5 yes Figure 3 The VV line cross-sectional view of the air bubble rate sensor is shown.

[0015] Figure 6 yes Figure 3 An enlarged cross-sectional view of part P of the air bubble rate sensor is shown.

[0016] Fig. 7A It is shown Figure 3 , Figure 4 as well as Figure 5 A schematic perspective view of an insulating tube in the air bubble rate sensor shown.

[0017] Figure 7B yes Fig. 7A MM line cross-sectional view of the insulating tube shown.

[0018] Figure 7C yes Fig. 7A NN line cross-sectional view of the insulating tube shown.

[0019] Fig. 8A It is shown Figure 1 A schematic perspective view of a supply pipe and a discharge pipe in the air bubble rate sensor shown.

[0020] Figure 8B Observed from the opposite side Fig. 8A A schematic perspective view of the supply pipe and the discharge pipe is shown.

[0021] Figure 8C yes Fig. 8A And a longitudinal cross-sectional view of the supply pipe and the discharge pipe shown in 8B.

[0022] Fig.8D yes Figure 8C A cross-sectional view of the supply pipe and the discharge pipe taken along line ZZ is shown.

[0023] Fig. 9 yes Figure 2 A cross-sectional view of the air bubble rate sensor taken along line IX-IX is shown.

[0024] Fig.10 This is a schematic cross-sectional view showing an air bubble ratio sensor according to another embodiment of the present disclosure.

[0025] Fig.11 This is a schematic explanatory diagram showing an example of a pipette including the air bubble ratio sensor according to the present disclosure.

[0026] Fig.12 This is a schematic explanatory diagram showing the relationship between the air bubble ratio sensor and the transfer pipe.

[0027] Fig.13A This is a schematic explanatory diagram showing another example of a pipette including the air bubble ratio sensor according to the present disclosure.

[0028] Fig. 13B Observed from the direction of arrow Q Fig.13A Schematic side view of a pipette.

[0029] Fig.14 1 is a schematic side view showing another example of the pipette of the present disclosure. DETAILED DESCRIPTION

[0030] In the electrostatic capacitance porosimeter proposed in non-patent document 1, the cross-sectional shape of the tube through which liquid nitrogen flows is a perfect circle. Therefore, if the supply amount of liquids such as liquid nitrogen is to be increased, the diameter of the tube needs to be increased. However, if the diameter of the tube is increased, the distance between the electrodes that are opposite to each other while clamping the tube will also become longer. As a result, the intensity of the electrical signal decreases, so the measurement accuracy is reduced. In order to improve this situation, there is a method of increasing the area of ​​the electrode or increasing the applied voltage. However, if the electrode area is increased, damage caused by the bonding stress of the large electrode is likely to occur. Further, it is believed that if the voltage is increased, sufficient safety cannot be ensured.

[0031] Therefore, the present disclosure realizes a bubble ratio sensor capable of improving the measurement accuracy of the bubble ratio of liquid even at low temperatures without reducing the supply amount of liquid, and a flow meter and a pipette using the bubble ratio sensor.

[0032] Hereinafter, an air bubble ratio sensor according to an embodiment of the present disclosure will be described based on the drawings.

[0033] Figure 1 1 is a schematic perspective view showing an air bubble ratio sensor 1 according to an embodiment of the present disclosure. Figure 2 FIG. 1 is a schematic side view thereof. The bubble rate sensor 1 measures the bubble rate of the liquid. Figure 1 As shown, the air bubble rate sensor 1 has a liquid supply-side transfer pipe 2 and a liquid discharge-side transfer pipe 3 connected at both ends thereof.

[0034] Figure 3 yes Figure 2 The II-II line cross-sectional view of the air bubble rate sensor 1 is shown. Figure 4 yes Figure 2 The bubble rate sensor 1 has a vacuum container 4. The insulating tube 5 is located at the center of the vacuum container 4. The insulating tube 5 has two through holes 6a and 6b for passing liquid (see Figure 4 The liquid may be a cryogenic liquid or an ultra-cold liquid as long as it has the property of being able to store electric charge so as to measure the electrostatic capacitance. In the following description of the present disclosure, as an example, the liquid is sometimes referred to as a cryogenic liquid or an ultra-cold liquid. The electrodes 7a and 7b are located on the outer surface of the insulating tube 5 (see Figure 3 ). The electrode 7a and the electrode 7b are opposite to each other. The through holes 6a and 6b are located between the electrode 7a and the electrode 7b. The vacuum container 4 has a vacuum exhaust valve 12. The vacuum exhaust valve 12 can maintain the interior of the vacuum container 4 as a vacuum space 26. The vacuum space 26 functions as a heat insulating layer.

[0035] Use as Figure 3 VV line cross-sectional view Figure 5The structure of the insulating tube 5 is described in more detail. As described above, the insulating tube 5 has two through holes 6a and 6b for the ultra-low temperature liquid to flow through, and a pair of electrodes 7a and 7b facing each other with the through holes 6a and 6b sandwiched therebetween are located on the outer surface of the insulating tube 5. The through holes 6a and 6b are oriented in the direction of the flow of the ultra-low temperature liquid (i.e. Figure 5 The cross-section of the through holes 6a and 6b is slender in the first direction (the direction perpendicular to the paper surface). Figure 5 ) has the first side 6a1, 6b1, and in the second direction (in Figure 5 ) has a second side 6a2, 6b2 shorter than the first side 6a1. In addition, the second side 6a2, 6b2 can be defined as a side connecting two parallel first sides 6a1, 6b1, including a straight line and a curve.

[0036] The so-called elongated shape includes, for example, a rectangular shape, a flat oval shape, etc.

[0037] In this way, since the through holes 6a and 6b are elongated, the distance between the electrodes 7a and 7b can be shortened. Thus, the electrostatic capacitance accumulated between the electrodes 7a and 7b becomes larger, the measurement accuracy of the bubble rate of the ultra-low temperature liquid can be improved, and the supply amount of the ultra-low temperature liquid can be maintained. Furthermore, since the first partition wall 11 between the adjacent through holes 6a and 6b functions as a support, the withstand voltage performance of the insulating tube 5 is improved.

[0038] Furthermore, since the two through holes 6a and 6b are arranged along the first direction (x direction), it is possible to achieve a thinner insulating tube 5. The aspect ratio (major axis / minor axis) of the major axis parallel to the first direction (x direction) and the minor axis parallel to the second direction (y direction) is, for example, 5 or more and 8 or less. The major axis is an axis passing through the axis center of the through holes 6a and 6b and parallel to the first direction (x direction), and the minor axis is an axis passing through the axis center of the through holes 6a and 6b and parallel to the second direction (y direction).

[0039] like Figure 5 as well as Figure 6 ( Figure 3 As shown in the enlarged view of the P part of the embodiment, the electrodes 7a and 7b are opposed to each other in the second direction with the through holes 6a and 6b sandwiched therebetween. Each electrode 7a and 7b is individually connected to a conduction pin 8. The conduction pin 8, an insulating substrate 9 having a through hole, and a flange 10 together constitute an airtight terminal. The insulating substrate 9 is circular in shape, and the conduction pin 8 is fixed in the through hole by solder or the like. The flange 10 surrounds the insulating substrate 9. The flange 10 is fixed to the vacuum container 4. Therefore, the airtight terminal is connected to the vacuum container 4. The airtight terminal reduces the leakage of ultra-low temperature liquid from the bubble rate sensor 1 to the outside. As a result, the measurement accuracy of the bubble rate is improved.

[0040] like Figure 7A to Figure 7C As shown, the insulating tube 5 has two through holes 6a and 6b in the first direction and an opening 13 in the second direction for accommodating plate-shaped electrodes 7a and 7b. The electrodes 7a and 7b are located in a recess 131 located at the bottom of the opening 13.

[0041] The electrodes 7a and 7b include, for example, a copper film, an aluminum film, etc. In order to form the electrodes 7a and 7b on the bottom surface of each recess 131, for example, a vacuum evaporation method, a metallization method, or an active metal method can be used. In addition, a metal plate that becomes the electrodes 7a and 7b can also be bonded to the bottom surface of the recess 131. The thickness of the electrodes 7a and 7b can be 0.1 μm or more, preferably 20 μm or more, or 2 mm or less, preferably 1 mm or less.

[0042] The insulating tube 5 includes, for example, ceramics mainly composed of zirconium oxide, aluminum oxide, sapphire, aluminum nitride, silicon nitride, SiAlON, cordierite, mullite, yttrium oxide, silicon carbide, cermet, β-eucalyptite, etc. When the ceramic includes ceramics mainly composed of aluminum oxide, the ceramic may also include silicon, calcium, magnesium, sodium, etc. as oxides.

[0043] The so-called main component in ceramics refers to the component that accounts for 60% or more of the total 100% by mass of the components constituting the ceramics. In particular, the main component is preferably a component that accounts for 95% or more of the total 100% by mass of the components constituting the ceramics. The components constituting the ceramics can be obtained using an X-ray diffraction device (XRD). Regarding the content of each component, after the components are identified, a fluorescent X-ray analyzer (XRF) or an ICP emission spectrometer is used to obtain the content of the elements constituting the components, and it is converted into the identified components.

[0044] The insulating tube 5 preferably includes low thermal expansion ceramics. Low thermal expansion ceramics refer to ceramics whose linear expansion coefficient at 22°C is 0±20ppb / K or less when the temperature range for measuring the linear expansion coefficient is 0°C to 50°C. Since the linear expansion coefficient of low thermal expansion ceramics is low, the possibility of damage is reduced even if they are subjected to thermal shock due to ultra-low temperature liquid. The linear expansion coefficient of low thermal expansion ceramics can be obtained, for example, using an optical heterodyne optical interferometer.

[0045] Specifically, regarding low thermal expansion ceramics, it is preferred that the main crystalline phase is cordierite, and as a sub-crystalline phase, alumina, mullite and saponite are included, and an amorphous phase containing Ca is present in the grain boundary phase. The crystal phase ratio of the main crystalline phase can also be 95 mass % or more and 97.5 mass % or less, and the crystal phase ratio of the sub-crystalline phase can be 2.5 mass % or more and 5 mass % or less. The content of Ca relative to the total amount is converted to CaO as 0.4 mass % or more and 0.6 mass % or less, and zirconium oxide can also be further included, and the content of zirconium oxide relative to the total amount is 0.1 mass % or more and 1.0 mass % or less. Thus, even if the temperature of the ultra-low temperature liquid has a large change, the low thermal expansion ceramic is difficult to expand and contract, so it can be used for a long time. Such low thermal expansion ceramics are, for example, recorded in Japanese Patent Gazette No. 5430389.

[0046] The relative dielectric constant of the ceramic constituting the insulating tube 5 in the use temperature range is preferably 11 or less. Since the relative dielectric constant of the ultra-low temperature liquid is small, if the relative dielectric constant of the ceramic is small, it is close to the relative dielectric constant of the ultra-low temperature liquid, and the high-frequency characteristics become better, so the measurement accuracy of the bubble rate is further improved. In particular, if it is 11 or less, the measurement accuracy of the bubble rate of the ultra-low temperature liquid can be further improved. The so-called use temperature range refers to the temperature range of the ceramic constituting the insulating tube 5 when the ultra-low temperature liquid is transferred.

[0047] In addition, the insulating tube 5 may also include ceramics containing silicon nitride or SiAlON as a main component. These ceramics have high mechanical strength and thermal shock resistance, so even if they are subjected to thermal shock, the possibility of damage is reduced.

[0048] Specifically, the ceramic comprises calcium oxide, aluminum oxide and oxides of rare earth elements. With respect to 100 mass % of the total of calcium oxide, aluminum oxide and oxides of rare earth elements, the contents of calcium oxide and aluminum oxide are 0.3 mass % or more and 1.5 mass % or less, and 14.2 mass % or more and 48.8 mass % or less, respectively. The remainder is the oxide of the rare earth element. Silicon nitride is a composition formula consisting of Si 6-Z Al Z O Z N 8-Z The β-sialon represented by (z=0.1 to 1) has an average crystal grain size of 20 μm or less (except 0 μm). Such ceramics are described in, for example, Japanese Patent No. 5430389.

[0049] The arithmetic mean roughness Ra in the roughness curve of the inner wall surface in the direction parallel to the axis of the through holes 6a and 6b in at least the insulating tube 5 is preferably less than 0.2 μm. If the arithmetic mean roughness Ra in the roughness curve of the inner wall surface is less than 0.2 μm, the rise of the flow resistance of the ultra-cold liquid generated by the inner wall surface is reduced, so the flow velocity distribution of the ultra-cold liquid is stable. That is, since the deviation of the flow velocity is reduced, the measurement accuracy of the bubble rate of the ultra-cold liquid can be improved.

[0050] The arithmetic mean roughness Ra can be measured using a laser microscope (manufactured by KYENCE Co., Ltd., ultra-deep color 3D shape measurement microscope (VK-X1000 or its successor model)) in accordance with JIS B 0601:2001. The measurement conditions are as follows: the illumination method is set to coaxial illumination, the measurement magnification is set to 240 times, there is no cutoff value λs, the cutoff value λc is set to 0.08mm, there is a correction for the terminal effect, and the measurement range is set to 1425μm×1067μm. Within the measurement range, 4 lines set as the measurement object are drawn at approximately equal intervals, and the line roughness measurement is performed. The length of each line set as the measurement object is 1280μm.

[0051] The relative density of ceramics is, for example, 92% or more and 99.9% or less. The relative density is expressed as a percentage (ratio) of the apparent density of ceramics determined in accordance with JIS R1634-1998 to the theoretical density of ceramics.

[0052] The insulating tube 5 may also include a ceramic having a plurality of 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 centers of gravity of adjacent closed pores (hereinafter, this value is referred to as the interval between closed pores) is greater than 8 μm and 18 μm. The closed pores are independent of each other. When the interval between the closed pores is greater than 8 μm, the mechanical strength is increased because the closed pores exist in a relatively dispersed state. On the other hand, when the interval between the closed pores is less than 18 μm, even if hot and cold shocks are repeatedly applied, microcracks starting from the contour of the closed pores are generated, and the probability of their extension being blocked by the surrounding closed pores is increased. Therefore, if the interval between the closed pores is greater than 8 μm and less than 18 μm, the insulating tube 5 can be used for a long time.

[0053] The skewness of the equivalent circular diameter of the closed pores may be greater than the skewness of the distance between the centers of gravity of the closed pores. Here, the so-called skewness refers to how much the distribution deviates from the normal distribution, that is, it is an indicator (statistic) that indicates the left-right symmetry of the distribution. When the skewness is greater than 0, the hem of the distribution is toward the right. When the skewness is 0, the distribution is left-right symmetric. When the skewness is less than 0, the hem of the distribution is toward the left.

[0054] If the histograms of the equivalent circle diameter of the closed pores and the distance between the centers of gravity of the closed pores are overlapped, when the skewness of the equivalent circle diameter of the closed pores is larger than the skewness of the distance between the centers of gravity 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 centers of gravity. That is, there are more closed pores with smaller equivalent circle diameters, and these closed pores exist more sparsely, which can be set as a ceramic component with both mechanical strength and thermal shock resistance.

[0055] For example, the skewness of the closed pore equivalent circle diameter is 1 or more, and the skewness of the distance between the centers of gravity of the closed pores is 0.7 or less. The difference between the skewness of the closed pore equivalent circle diameter and the skewness of the distance between the centers of gravity of the closed pores is 0.3 or more.

[0056] In order to obtain the distance between the centers of gravity and the equivalent circle diameter of the closed pores, first, the average particle size D is used to calculate the distance between the centers of gravity and the equivalent circle diameter of the closed pores from one end surface of the insulating tube 5 made of ceramic toward the axial direction. 50 The diamond abrasive with an average particle size of 3 μm was ground on a copper disk. 50 By grinding on a tin plate with diamond abrasive grains of 0.5 μm, a polished surface having an arithmetic mean roughness Ra of 0.2 μm or less in a roughness curve can be obtained.

[0057] The arithmetic mean roughness Ra of the polished surface can be measured by the above-mentioned measurement method. The polished surface is observed at a magnification of 200 times to select the average range. For example, a CCD camera is used to observe an area of ​​7.2×10 4 μm 2 The observation image was obtained by photographing a range of 310 μm in the horizontal direction and 233 μm in the vertical direction. The observation image was used as the object, and the distance between the centers of gravity of the closed pores was obtained by the method of the distance between the centers of gravity of the dispersion measurement using the image analysis software "A-Zou Kun (ver2.52)" (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.). Hereinafter, the image analysis software "A-Zou Kun" means the image analysis software manufactured by Asahi Kasei Engineering Co., Ltd.

[0058] The setting conditions of this method may be, for example, as follows: the threshold value as an index indicating the brightness of the image is 165, the brightness is dark, and the small pattern removal area is 1 μm. 2 , no noise removal filter. In addition, the threshold can be adjusted according to the brightness of the observed image. When the brightness is set to dark, the binarization method is manual, and the small pattern removal area is 1μm 2And on the basis of the noise removal filter, adjust the threshold so that the mark appearing in the observation image is consistent with the shape of the closed pore. Taking the above observation image as the object, the equivalent circle diameter of the closed pore can be obtained by a method such as particle analysis. The setting conditions are the same as those used in the distance between the centers of gravity of the closed pore. The equivalent circle diameter of the closed pore and the skewness of the distance between the centers of gravity can be obtained using the function Skew of Excel (registered trademark, Microsoft Corporation).

[0059] An example of a method for manufacturing the insulating tube 5 made of such ceramic will be described. The case where the main component of the ceramic constituting the insulating tube 5 is alumina will be described.

[0060] Alumina powder (purity of 99.9% by mass or more) as the main component, magnesium hydroxide, silicon oxide, and calcium carbonate powders are placed in a pulverizer together with a solvent (ion exchange water). The pulverization is performed until the average particle size (D 50 ) becomes 1.5 μm or less, an organic binder and a dispersant for dispersing the alumina powder are added and mixed to obtain a slurry.

[0061] Here, the content of magnesium hydroxide powder in the total 100 mass% of the above powder is 0.3 mass% to 0.42 mass%, the content of silicon oxide powder is 0.5 mass% to 0.8 mass%, and the content of calcium carbonate powder is 0.06 mass% to 0.1 mass%. The remainder is aluminum oxide powder and inevitable impurities. The organic binder is acrylic emulsion, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, etc.

[0062] Next, after the slurry is spray-granulated to obtain granules, a uniaxial press or cold isostatic press is used to increase the forming pressure to 78 MPa or more and 118 MPa or less, thereby obtaining a columnar formed body. In the formed body, a depression that becomes the concave portion 131 after firing is formed by cutting as needed. The formed body is fired at a firing temperature of 1580° C. or more and 1780° C. or less, and a holding time of 2 hours or more and 4 hours or less, thereby obtaining an insulating tube 5.

[0063] In order to obtain an insulating tube 5 in which the interval between closed pores is 8 μm or more and 18 μm, the firing temperature is set to 1600°C or more and 1760°C or less, and the holding time is set to 2 hours or more and 4 hours or less to fire the formed body. In order to obtain an insulating tube 5 in which the deviation of the equivalent circular diameter of the closed pores is larger than the deviation of the distance between the centers of gravity of the closed pores, the firing temperature can be set to 1600°C or more and 1760°C or less, and the holding time can be set to 2 hours or more and 4 hours or less to fire the formed body obtained by pressurizing the forming pressure to 96 MPa or more and 118 MPa or less. The inner wall surfaces of the through holes 6a and 6b of the insulating tube 5 can also be ground. In addition, the bottom surface of the recess 131 on which the electrodes 7a and 7b are mounted can also be ground.

[0064] As described above, the insulating tube 5 has two elongated through holes 6a and 6b. On the other hand, the cross-section of the flow path of the supply-side transfer pipe 2 and the discharge-side transfer pipe 3 connected to the bubble rate sensor 1 preferably has a circular shape. Therefore, in order to allow the ultra-low temperature liquid to flow from the supply-side transfer pipe 2 to the discharge-side transfer pipe 3 via the insulating tube 5, it is necessary to change the cross-sectional shape of the flow path.

[0065] For this reason, Figure 3 as well as Figure 4 As shown, the supply-side converter 14 and the discharge-side converter 15 for converting the cross-sectional shape of the flow path are located on both sides (i.e., the supply side and the discharge side) of the insulating tube 5 in the vacuum container 4. The supply-side converter 14 and the discharge-side converter 15 have flow holes 14a and 15a through which ultra-low temperature liquid flows. The cross-sectional shape of one end 141a and 151a of the flow holes 14a and 15a is a circle to which the circular supply-side transfer pipe 2 and the discharge-side transfer pipe 3 are connected. The cross-sectional shape of the other end 141b and 151b is a second direction (i.e., the second direction) of the insulating tube 5. Figure 5 The length of the insulating tube 5 in the y direction (shown in the y direction) is greater than the length of the insulating tube 5 in the first direction (i.e. Figure 5 The length of the ultra-low temperature liquid is small (in the x direction shown). Thus, the supply amount of the ultra-low temperature liquid can be maintained without reducing it.

[0066] The supply side converter 14 and the discharge side converter 15 may also be directly connected to the insulating tube 5, but in this embodiment, Figure 3 , Figure 4 As shown, the supply-side converter 14 is connected to the insulating tube 5 via a supply tube 16 , and the discharge-side converter 15 is connected to the insulating tube 5 via a discharge tube 17 .

[0067] Figures 8A to 8D A supply pipe 16 and a discharge pipe 17 are shown. Fig. 8A This is a perspective view of the supply pipe 16 and the discharge pipe 17 as viewed from the supply-side converter 14 and the discharge-side converter 15. Figure 8BThis is a perspective view viewed from the insulating tube 5 side. Figure 8C yes Fig. 8A , Figure 8B The longitudinal section view of the supply pipe 16 and the discharge pipe 17 is shown. Fig.8D yes Figure 8C The ZZ line cross-sectional view is shown.

[0068] Figure 4 The supply pipe 16 described in the figure is arranged on the supply side of the insulating tube 5 and has two supply holes 16a and 16b. The shape of each supply hole 16a and 16b in the cross section perpendicular to the flow direction of the ultra-low temperature liquid is an elongated shape that is the same as the shape of each of the plurality of through holes 6a and 6b in the cross section. The two supply holes 16a and 16b may also be opposite to the two through holes 6a and 6b of the insulating tube 5, respectively.

[0069] In this way, the two supply holes 16a, 16b are opposite to the two through holes 6a, 6b. As a result, the generation of bubbles can be reduced at the portion where the supply holes 16a, 16b are connected to the through holes 6a, 6b, and the measurement accuracy of the bubble rate of the ultra-low temperature liquid can be further improved. Further, between the adjacent supply holes 16a, 16b, there is a portion separating the two supply holes 16a, 16b as the second partition wall 18. Therefore, since the second partition wall 18 functions as a support, the pressure resistance of the supply pipe 16 is improved.

[0070] As described above, the portion of the insulating tube 5 that separates the adjacent through holes 6a and 6b from each other is formed as the first partition wall 11 (see Figure 5 ), and the portion of the supply pipe 16 that separates the adjacent supply holes 16a and 16b is set as the second partition wall 18. In this case, Figure 8C As shown, the second facing surface 18a of the second partition wall 18 on the insulating tube 5 side is non-contact with the first facing surface 11a of the first partition wall 11 on the supply tube 16 side, and a gap D1 is provided between the two facing surfaces 11a and 18a.

[0071] In this way, since the first opposing surface 11a and the second opposing surface 18a have a gap D1 and are non-joined, the stress generated on the first opposing surface 11a of the first partition wall 11 can be reduced. The gap D1 is preferably selected to be less than 1 mm (but not 0 mm). Thus, the stress generated on the first opposing surface 11a can be reduced, and the bubbles generated by the mixing of the ultra-low temperature liquid flowing through the adjacent through holes 6a, 6b can be reduced, so the measurement accuracy of the bubble rate of the ultra-low temperature liquid can be improved.

[0072] The discharge pipe 17 disposed on the side opposite to the supply pipe 16 has the same structure as the supply pipe 16, and has the same structure and function. Figure 8C That is, the discharge pipe 17 has two discharge holes 17a and 17b, and each discharge hole 17a and 17b is opposite to the two through holes 6a and 6b. Between two adjacent discharge holes 17a and 17b, a portion separating the two discharge holes 17a and 17b exists as a third partition wall 19, and the third partition wall 19 functions as a support.

[0073] The portion of the insulating tube 5 that separates the adjacent through holes 6a and 6b from each other is formed as a first partition wall 11 (see Figure 5 ), and the portion of the discharge pipe 17 that separates the adjacent discharge holes 17a and 17b is set as the third partition wall 19, as shown in FIG. Figure 8C As shown, the third opposing surface 19a of the third partition wall 19 on the insulating tube 5 side and the fourth opposing surface 11b of the first partition wall 11 on the discharge tube 17 side are non-contacting, and there is a gap D2 between the two opposing surfaces 11b and 19a. As with the gap D1, the gap D2 is also preferably 1 mm or less (but not 0 mm). The rest is the same as the supply tube 16, so detailed description is omitted.

[0074] A first covering portion including a metallized layer is provided on the end surface of the insulating tube 5 on the supply tube 16 side, except for the first facing surface 11a. The first facing surface 11a is excluded to reduce the unintended adhesion of the brazing material to the metallized layer on the first facing surface 11a when the insulating tube 5 and the supply tube 16 are joined by brazing. As a result, the first facing surface 11a can be less likely to be joined to the second facing surface 18a of the supply tube 16, thereby reducing the increase in stress generated on the first facing surface 11a of the first partition wall 11. Similarly, a second covering portion including a metallized layer is provided on the end surface of the insulating tube 5 on the discharge tube 17 side, except for the fourth facing surface 11b.

[0075] Fig. 9 yes Figure 2 IX-IX line cross-sectional view. As shown in the figure, both ends of the insulating tube 5 are connected to the supply pipe 16 and the discharge pipe 17 of the ultra-low temperature liquid. Further, the supply side converter 14 is connected to the upstream side of the supply pipe 16, and the discharge side converter 15 is connected to the downstream side of the discharge pipe 17. The supply pipe 16 and the discharge pipe 17 are formed of metal and brazed with the insulating tube 5. Specifically, the supply pipe 16 and the discharge pipe 17 are preferably formed of austenitic stainless steel (for example, SUS316L) with a nickel content of 10.4% by mass or more, Fenic alloy, Fe-Ni alloy, Fe-Ni-Cr-Ti-A1 alloy, Fe-Cr-A1 alloy, Fe-Co-Cr alloy, etc. The supply side converter 14 and the discharge side converter 15 are also preferably formed of the same metal.

[0076] Back to Figure 3 as well as Figure 4 The supply side transfer pipe 2 connected to the supply side converter 14 is surrounded by a supply side bellows 20 as a flexible pipe. When ultra-low temperature liquid flows, the supply side transfer pipe 2 is easy to shrink, while the vacuum container 4 itself is difficult to shrink. Therefore, the supply side bellows 20 has a function as a buffer material to alleviate the difference in their shrinkage. In addition, the discharge side transfer pipe 3 connected to the discharge side converter 15 is also surrounded by a discharge side bellows 21 that is the same as or similar to the supply side bellows 20.

[0077] The supply-side bellows 20 and the discharge-side bellows 21 are connected to both ends of the cylindrical vacuum container 4 via flanges 22. The connection is kept vacuum-tight. In addition, the upstream opening of the supply-side bellows 20 and the downstream opening of the discharge-side bellows 21 are sealed by bellows joints 23, respectively, and are kept vacuum-tight. In addition, it is preferred that at least any one of the outer peripheral surfaces of the supply-side transfer pipe 2 surrounded by the supply-side bellows 20, the supply-side converter 14, the discharge-side converter 15, the insulating tube 5, and the discharge-side transfer pipe 3 surrounded by the discharge-side bellows 21 is covered with a heat insulating material 27. The heat insulating material 27 is, for example, a film of polyester, polystyrene, polypropylene, or the like.

[0078] Fig.10 Another embodiment of the present disclosure is shown. As shown in the figure, the bubble rate sensor 1′ has a plurality of through holes 61 for flowing ultra-low temperature liquid in the insulating tube 51, and a plurality of electrodes 71 are arranged in the insulating tube 51, which are opposite to each other and sandwich the through holes 61. The plurality of through holes 61 are all elongated shapes having a first direction (x direction) and a second direction (y direction) in a cross section perpendicular to the flow direction of the ultra-low temperature liquid. In the second direction, the plurality of electrodes 71 are opposite to each other and sandwich the plurality of through holes 61. In addition, the plurality of through holes 61 are the same as the aforementioned embodiment, and are connected to the converters 14 and 15 via the supply pipe 16 and the discharge pipe 17, respectively. The rest is the same as the aforementioned embodiment.

[0079] Next, the flow meter involved in the embodiment of the present disclosure is described. The flow meter can measure the flow rate of the ultra-low temperature liquid flowing through the through holes 6a, 6b or the through hole 61. The flow meter includes the bubble rate sensor 1 or the bubble rate sensor 1' and a velocity meter not shown. The bubble rate sensor 1 or the bubble rate sensor 1' and the velocity meter are installed in the supply side transfer pipe 2 and / or the discharge side transfer pipe 3.

[0080] The cryogenic liquid flowing through the supply side transfer pipe 2 and the discharge side transfer pipe 3 becomes a two-phase flow of gas-liquid mixture. Therefore, the bubble rate is measured by the bubble rate sensor 1 or the bubble rate sensor 1', and the density d (kg / m 3). This is because the density d of the cryogenic liquid corresponds to the relative dielectric constant, and therefore also corresponds to the electrostatic capacitance measured by the bubble ratio sensor 1 or the bubble ratio sensor 1 ′.

[0081] The flow rate (m / s) of the ultracold liquid obtained by the flow meter is set as v, and the cross-sectional area (m 2 ) is set to a, the flow rate F (kg / sec) is calculated by the following formula.

[0082] F=d×v×a

[0083] In order to perform the above calculation, the flow meter further includes a calculation device connected to the bubble rate sensor 1 or bubble rate sensor 1' and a flow meter. Thus, since the flow rate of the ultra-cold liquid can be easily measured, management becomes easy when a large amount of ultra-cold liquid is transferred industrially.

[0084] Fig.11 An example of the transfer pipe 24 of the present disclosure provided with the above-mentioned flow meter is shown. Fig.11 An example in which the air bubble ratio sensor 1 or the air bubble ratio sensor 1 ′ in the flow meter is mounted on the bent transfer tube 24 is schematically shown. In the air bubble ratio sensor 1 or the air bubble ratio sensor 1 ′, the wiring 25 is connected to the conduction pin 8 .

[0085] At this time, if the supply side or the discharge side of the bent transfer tube 24 approaches the air bubble rate sensor 1 or the air bubble rate sensor 1', it may hinder the installation of the wiring 25. Fig.12 As shown in FIG. 1 , it is preferable to make the air bubble rate sensor 1 or the air bubble rate sensor 1 ′ inclined relative to the bent portion (hereinafter referred to as the bent portion) of the transfer tube 24. Fig.12 As shown, the inclination angle θ of the air bubble ratio sensor 1 or the air bubble ratio sensor 1 ′ is preferably 10° or more and 90° or less with respect to the axis of the bent portion of the transfer tube 24. The transfer tube 24 is, for example, a U-shaped tube or a J-shaped tube.

[0086] In particular, if Fig.13A , Fig. 13B As shown, when the insulating tube 51 is large as in the air bubble rate sensor 1 ′ according to another embodiment of the present disclosure, the wiring 25 may be inclined with respect to the transfer tube 24 . Fig. 13B Observed from the direction of arrow Q Fig.13A A schematic side view of the air bubble rate sensor 1' is shown. Fig. 13BIn the embodiment, the wiring 25 is inclined by 90° relative to the axis of the bent portion of the transfer tube 24, but the angle may be 10° or more and 90° or less. Fig.14 As shown, the wiring 25 may be arranged in the same direction as the bent portion of the transfer tube 24 .

[0087] In addition to liquid hydrogen (-253°C), ultra-cold liquids that can be measured by the bubble rate sensor 1 and bubble rate sensor 1′ of the present disclosure include 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, in the present disclosure, "ultra-cold liquid" means a liquid that is liquefied at an ultra-low temperature of -162°C or less.

[0088] As described above, according to the present disclosure, the plurality of through holes 6a, 6b, 61 located in the insulating tubes 5, 51 have an elongated shape having a first side in the first direction and a second side in the second direction whose length is shorter than the first side in a cross section perpendicular to the flow direction of the liquid. Furthermore, the plurality of electrodes 7a, 7b or the electrode 71 are opposed to each other in the second direction with the plurality of through holes 6a, 6b or the through hole 61 sandwiched therebetween. Therefore, the distance between the electrodes 7a, 7b or the electrode 71 can be shortened. As a result, the electrostatic capacitance accumulated between the electrodes 7a, 7b or the electrode 71 becomes larger, and as a result, the measurement accuracy of the bubble rate of the liquid can be improved, and the supply amount of the liquid can be maintained.

[0089] As mentioned above, although embodiment of this disclosure was demonstrated, the air bubble rate sensor of this disclosure is not limited to the said embodiment, Various changes and / or improvements are possible within the scope of this disclosure.

[0090] -Explanation of symbols-

[0091] 1. 1′ Bubble rate sensor

[0092] 2 Supply side transfer pipe

[0093] 3 Discharge side transfer pipe

[0094] 4 Vacuum container

[0095] 5.51 Insulation tube

[0096] 6a, 6b, 61 through holes

[0097] 6a1, 6b1 Side 1

[0098] 6a2, 6b2 Side 2

[0099] 7a, 7b, 71 electrodes

[0100] 8 conduction pin

[0101] 9 Insulation substrate

[0102] 10 Flange

[0103] 11 1st partition wall

[0104] 11a First opposing surface

[0105] 11b Fourth opposing surface

[0106] 12 Vacuum exhaust valve

[0107] 13 Opening

[0108] 131 recess

[0109] 14 Supply-side converter

[0110] 14a Flow hole

[0111] 141a One end

[0112] 141b The other end

[0113] 15 Discharge side converter

[0114] 15b Flow hole

[0115] 151a One end

[0116] 151b The other end

[0117] 16 Supply pipe

[0118] 16a Supply hole

[0119] 17 Discharge pipe

[0120] 17a Discharge hole

[0121] 18 Second partition wall

[0122] 18a Second opposing surface

[0123] 19 The third partition wall

[0124] 19a The third opposing surface

[0125] 20 Supply side bellows

[0126] 21 Discharge side bellows

[0127] 22 Flange

[0128] 23 Bellows connector

[0129] 24 Transfer tube

[0130] 25 Wiring

[0131] 26 Vacuum Space

[0132] 27 Insulation Materials

[0133] D1, D2 gap.

Claims

1. A bubble rate sensor, comprising: an insulating tube having a plurality of through holes for passing a liquid; and At least two electrodes are located inside or outside the insulating tube and face each other with the plurality of through holes interposed therebetween. The plurality of through holes have an elongated shape in a cross section perpendicular to the flow direction of the liquid, the elongated shape having a first side in a first direction and a second side in a second direction that is shorter than the first side. The at least two electrodes are opposed to each other in the second direction, and the plurality of through holes are present between the at least two electrodes.

2. The air bubble rate sensor according to claim 1, wherein: The plurality of through holes are arranged in the first direction.

3. The air bubble rate sensor according to claim 1, wherein: The plurality of through holes are arranged in the second direction.

4. The air bubble rate sensor according to any one of claims 1 to 3, wherein: A supply pipe having a plurality of supply holes is arranged on the supply side of the insulating pipe. The plurality of supply holes each have the same shape as the cross-section of each of the plurality of through holes in a cross section perpendicular to the flow direction of the liquid, and each of the supply holes faces the plurality of through holes.

5. The air bubble rate sensor according to claim 4, wherein: When the portion of the insulating tube that separates adjacent through holes is set as the first partition wall, and the portion of the supply tube that separates adjacent supply holes is set as the second partition wall, the second opposing surface of the second partition wall on the insulating tube side is non-contact with the first opposing surface of the first partition wall on the supply tube side.

6. The air bubble rate sensor according to claim 5, wherein: A gap between the first opposing surface and the second opposing surface is 1 mm or less.

7. The air bubble rate sensor according to claim 5 or 6, wherein: The first covering portion including the metallized layer is located on the supply tube side end surface of the insulating tube, excluding the first opposing surface.

8. The air bubble rate sensor according to any one of claims 1 to 7, wherein: A discharge pipe having a plurality of discharge holes is arranged on the discharge side of the insulating tube, The plurality of discharge holes each have the same shape as the cross-section of each of the plurality of through holes in a cross section perpendicular to the flow direction of the liquid, and each of the plurality of discharge holes faces the plurality of through holes.

9. The air bubble rate sensor according to claim 8, wherein: When the portion of the insulating tube that separates the adjacent through holes is set as the first partition wall, and the portion of the discharge pipe that separates the adjacent through holes is set as the third partition wall, the third opposing surface of the third partition wall on the insulating tube side and the fourth opposing surface of the first partition wall on the discharge pipe side are non-contacting.

10. The air bubble rate sensor according to claim 9, wherein: A gap between the third opposing surface and the fourth opposing surface is 1 mm or less.

11. The air bubble rate sensor according to claim 9 or 10, wherein: The second covering portion including the metallized layer is located on the discharge pipe side end surface of the insulating tube, excluding the fourth opposing surface. 12 . A flow meter comprising: the air bubble ratio sensor according to claim 1 ; and a flow meter for measuring a flow rate of the liquid flowing through the through hole, wherein the flow meter measures the flow rate of the liquid flowing through the through hole.

13. A pipette comprising the flow meter according to claim 12.

Images