Calibration apparatus and calibration method for mass flow meters for cryogenic liquefied gases

Abstract

To provide a calibration device and calibration system for calibrating a flow measuring device that measures the flow rate of cryogenic liquefied gases. [Solution] A calibration device for a mass flow meter comprising: a first container capable of containing cryogenic liquefied gas; a weighing device for measuring the mass of the first container; a first pipe connecting the first container and the device under test; a second pipe connected to the device under test; and a second container connected to the second pipe. The calibration device is arranged in the order of the first container, the first pipe, the device under test, and the second container from the upstream side.

Description

[Technical Field]

[0001] This disclosure relates to a calibration apparatus and calibration method for a mass flow meter for cryogenic liquefied gases. [Background technology]

[0002] In order to widely commercialize cryogenic liquefied gases such as liquefied hydrogen in society, a measuring device is needed to accurately measure the amount of cryogenic liquefied gas supplied from storage tanks to the recipient. As a technology for calibrating liquid flow meters, for example, Patent Document 1 discloses a liquid flow meter calibration device. In the device of Patent Document 1, liquid stored in a storage tank is supplied to the flow meter under test at a stable flow rate, and the liquid that has passed through the flow meter under test flows into a weighing tank. Calibration is performed by comparing the change in mass of the weighing tank with the reading of the flow meter under test. The device of Patent Document 1 enables more accurate calibration by devising the shape of the diverter installed downstream of the flow meter under test.

[0003] Patent Document 2 discloses a flow rate measurement system. The system of Patent Document 2 is a flow rate measurement system for equipment through which cryogenic liquefied gas flows, and comprises a supercooling device, a flow meter and a flow control unit installed downstream thereof, with the entire system housed in a cold chamber. Cryogenic liquefied gas supplied from a storage tank passes through the supercooling device and then through the flow meter. The cryogenic liquefied gas passing through the flow meter is cooled by the supercooling device and is a liquid free from gaseous phase contamination. Therefore, the amount of cryogenic liquefied gas passing through the flow meter can be accurately measured. Furthermore, since the flow meter is housed in a cold chamber, there is no need to make the flow meter itself an insulated structure, and maintenance of the flow meter is easy.

[0004] Patent Document 3 discloses a calibration method for a Coriolis flow meter. The apparatus used for the calibration method of Patent Document 3 includes a resonant tube provided to cover the outer circumference of the flow tube of the Coriolis flow meter, a drive circuit capable of oscillating vibrations at a constant frequency, and a resonant frequency detection circuit. In the calibration method of Patent Document 3, a coefficient for calibrating the instrument error of the Coriolis flow meter is calculated by measuring the resonant frequency when the inside of the flow tube is under vacuum and the resonant frequency when the flow tube is filled with a liquid of known density. Water with a density of 1.0 (at 4°C) is given as an example of a fluid of known density used for calibration. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 4604243 [Patent Document 2] Japanese Patent Publication No. 2008-291872 [Patent Document 3] Japanese Patent Publication No. 2002-168672 [Overview of the project] [Problems that the invention aims to solve]

[0006] Cryogenic liquefied gases such as liquefied hydrogen readily vaporize due to heat input from the surrounding environment and frictional heat with piping. Therefore, within pipes and equipment through which cryogenic liquefied gases flow, the liquid phase (liquefied hydrogen) and gaseous phase (hydrogen gas) coexist, resulting in fluids of varying densities. To handle such fluids, a measuring device capable of accurately measuring flow rate regardless of fluid density is required. Furthermore, to ensure the accuracy of the measuring device, a calibration device capable of calibrating the device using the cryogenic liquefied gas fluid is desirable.

[0007] However, applying conventional calibration devices to cryogenic liquefied gases has not always been appropriate. For example, in the liquid flow meter calibration device described in Patent Document 1, the flow meter under test and the weighing tank located downstream are open and separated. However, in the case of cryogenic liquefied gases, if heat or gas is released outside the device between the flow meter under test and the weighing tank, accurate weighing becomes impossible. On the other hand, if the flow meter under test and the weighing tank are connected by piping without opening them, the weight of the piping is applied to the weighing tank, and other effects occur, making it impossible to accurately measure the mass of the weighing tank. Furthermore, Patent Document 2 does not disclose a calibration method for measuring devices. Patent Document 3 does not disclose the calibration of flow meters using fluids with a wide range of density variations. In view of this situation, one of the objectives of the present invention is to provide a calibration device and calibration system for calibrating a flow measuring device that measures the flow rate of cryogenic liquefied gases. [Means for solving the problem]

[0008] The calibration apparatus for a mass flow meter according to this disclosure comprises a first container capable of containing cryogenic liquefied gas, a weighing device for measuring the mass of the first container, a first pipe connecting the first container and the device under test, a second pipe connected to the device under test, and a second container connected to the second pipe. The calibration apparatus is arranged in the order of the first container, the first pipe, the device under test, and the second container from the upstream side.

[0009] A calibration method for a mass flow meter according to this disclosure comprises a first container containing cryogenic liquefied gas, a weighing device for measuring the mass of the first container, a first pipe connecting the first container and the device under test, a second pipe connected to the device under test, and a second container connected to the second pipe. This method is performed in a calibration device for a mass flow meter equipped with the following: In this method, the actual flow rate M measured by the weighing device r , the measured density ρ in the device under test m and measured flow rate M m From this, we obtain the correction coefficient C, which is expressed by the following equation (1).

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[0010] According to the present invention, a calibration device and a calibration system are provided for calibrating a flow rate measuring device for measuring the flow rate of cryogenic liquefied gas. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram showing the piping system of a calibration device according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a schematic diagram showing the piping system of a calibration device according to one embodiment of the present disclosure. [Figure 3] Figure 3 is a schematic diagram showing the piping system of a calibration device according to one embodiment of the present disclosure. [Figure 4] Figure 4 shows a graph as an example of a calibration method according to one embodiment of the present disclosure, in which the measured density measured in the device under test is changed, with the flow rate correction coefficient C on the vertical axis. [Figure 5] Figure 5 shows a graph as an example of a calibration method according to one embodiment of the present disclosure, in which the measured density measured in the device under test is changed on the horizontal axis and the density correction coefficient D is changed on the vertical axis. [Modes for carrying out the invention]

[0012] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described. The calibration apparatus for a mass flow meter according to this disclosure comprises a first container capable of containing cryogenic liquefied gas, a weighing device for measuring the mass of the first container, a first pipe connecting the first container and the device under test, a second pipe connected to the device under test, and a second container connected to the second pipe. The calibration apparatus is arranged in the order of the first container, the first pipe, the device under test, and the second container from the upstream side.

[0013] According to the calibration apparatus described herein, cryogenic liquefied gas contained in a first container is supplied to the device under test through a first pipe, and measurement values ​​of the device under test can be obtained. At this time, the amount of cryogenic liquefied gas discharged from the first container is determined as the decrease in the mass of the first container. Cryogenic liquefied gas easily gasifies due to heat input from outside the pipe or frictional heat with the pipe, and its density changes. However, according to the calibration apparatus described herein, the amount discharged can be confirmed from the change in mass of the first container installed upstream of the device under test, so the flow rate that flowed into the device under test can be determined more accurately.

[0014] In the calibration apparatus, the first piping may be provided with a support to support the first piping, thereby reducing the influence of the mass of the first piping on the measurement value of the weighing device. Because the first piping is provided with a support, even if, for example, a piping made of a heavy material with high thermal insulation is used as the first piping, the change in mass of the first container can be grasped more accurately. The provision of a support for the first piping increases the degree of freedom in the design and installation of the calibration apparatus, and allows for more accurate calibration.

[0015] The calibration device may further include a gas supply line connected to the first piping and a flow meter provided in or near the first container. By supplying gas to the first piping through the gas supply line, a wide range of fluid flow conditions (gas-liquid mixing ratio and flow rate) can be arbitrarily and easily configured as the fluid supplied to the device under test. Furthermore, by providing a flow meter in or near the first container, the amount of cryogenic liquefied fluid flowing from the first container to the device under test can be determined more accurately.

[0016] The calibration device may further include a bubble sensor capable of measuring the density of the fluid flowing in the first pipe. By providing the bubble sensor, it becomes possible to measure the density of the fluid flowing into the test device, and while referring to the measured value of the bubble sensor, it is possible to adjust the gas-liquid mixing ratio and the flow rate of the fluid flowing in the first pipe.

[0017] The calibration device may further include a cryogenic chamber filled with a cryogenic liquefied gas and a third pipe drawn from the outside to the inside of the cryogenic chamber. A part of the first pipe may be disposed in the cryogenic chamber, and the third pipe may be connected to the first pipe in the cryogenic chamber. According to this configuration, the cryogenic fluid flowing through the first pipe can be recooled and reliquefied in the cryogenic chamber. Further, another type of gas having a lower liquefaction temperature can be mixed into the liquefied cryogenic liquefied gas through the third pipe. If a flow rate control device is provided in the third pipe, the flow rate of the gas flowing through the third pipe can be accurately controlled. By configuring in this way, a fluid having an arbitrary gas-liquid mixing ratio can be constituted, and the calibration of the test device can be carried out more easily and accurately. In the calibration device, the cryogenic liquefied gas flowing through the first pipe may be liquefied hydrogen, and the gas flowing through the third pipe may be helium gas. Further, in the calibration device, the cryogenic liquefied gas flowing through the first pipe may be liquefied nitrogen, and the gas flowing through the third pipe may be hydrogen gas.

[0018] The calibration method of the mass flowmeter according to the present disclosure is a method performed in a calibration device of a mass flowmeter including a first container containing a cryogenic liquefied gas, a weighing device for measuring the mass of the first container, a first pipe connecting between the first container and the test device, a second pipe connecting to the test device, and a second container connecting to the second pipe. By this calibration method, the actual flow rate M r measured by the weighing device, the measured density ρ m and the measured flow rate M m are used to obtain a correction coefficient C represented by the following formula (1) for measuring the actual flow rate M r flowing into the test device.

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[0019] According to the calibration method, the instrument error of the measuring device can be corrected, and a correction coefficient C can be obtained to accurately determine the mass flow rate from the mass measurement value in the device under test. The calibration method uses the mass decrease of the first container installed upstream of the device under test to determine the actual flow rate M r The measured density ρ in the device under test is m and measured flow rate M m Calibration is performed by comparison. By measuring the mass decrease of the first container upstream of the device under test as the actual flow rate, the device under test can be accurately calibrated even when measuring the mass of cryogenic liquefied gas.

[0020] In the calibration method described above, the correction coefficient C is the measured flow rate M, which is expressed by the following formula (2). m The linear function of and the measured density ρ m It can be expressed as the product of quadratic functions.

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[0021] The calibration method for a mass flow meter according to this disclosure is a method performed in a calibration apparatus for a mass flow meter comprising: a first container containing a cryogenic liquefied gas; a weighing device for measuring the mass of the first container; a first pipe connecting the first container and a device under test, which is a Coriolis flow meter; a second pipe connected to the device under test; and a second container connected to the second pipe, further comprising a bubble sensor in the first pipe. In this calibration method, the measured density ρ in the device under test is... m and measured flow rate M m Therefore, the actual density ρ of the fluid flowing through the device under test rTo calculate this, we determine the correction coefficient D, which is expressed by the following equation (3).

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[0022] According to the calibration method, the instrument error of the measuring device can be corrected, and a correction coefficient D can be obtained for calculating an accurate density measurement from the density measurement value in the device under test. The calibration method is based on the actual density ρ of the fluid supplied to the device under test. r And the measured density ρ in the device under test m and measured flow rate M m Calibration is performed by comparison. According to the calibration apparatus of this disclosure, it is possible to supply fluids of a wide range of densities to the device under test, and the device under test can be accurately calibrated even when measuring cryogenic liquefied gases.

[0023] In the calibration method described above, the correction coefficient D is the measured flow rate M, which is expressed by the following formula (4). m The linear function of and the measured density ρ m It can be expressed as the product of quadratic functions.

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[0024] In the calibration method described above, the calibration apparatus for the mass flow meter may further include a cryogenic chamber filled with cryogenic liquefied gas and a third pipe drawn from outside to inside the cryogenic chamber, wherein a portion of the first pipe is located inside the cryogenic chamber, the third pipe is connected to the first pipe inside the cryogenic chamber, and the third pipe may be equipped with a flow control device. In the calibration method described above, the actual density ρ r However, the gas flow rate M of the flow rate control device gAnd the liquid flow rate M of the weighing device. l Therefore, it can be calculated using the following formula (5).

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[0025] [Specific examples of embodiments] Next, an example of a specific embodiment of the calibration apparatus and configuration method according to this disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated. In this specification, the flow direction of the fluid circulating in the piping when the calibration method is performed will be referred to as the "upstream side" and the "downstream side." In the operation of the apparatus, the direction of fluid flow may be temporarily switched for maintenance or other reasons, and of course, there will be times when no fluid flows through the apparatus.

[0026] (Cryogenic liquefied gas) The calibration apparatus and calibration method described herein are suitable for calibrating mass flow meters used to measure the flow rate of cryogenic liquefied gases. In this specification, "cryogenic" means a temperature range of 100K (-173°C) or lower, and cryogenic liquefied gases include liquefied nitrogen with a boiling point of -196°C at atmospheric pressure, liquefied oxygen with a boiling point of -183°C, liquefied argon with a boiling point of -186°C, liquefied hydrogen with a boiling point of -253°C, and liquefied helium with a boiling point of -269°C. In particular, the calibration apparatus and calibration method described herein are useful for calibrating flow meters used for measuring the flow rate of liquefied hydrogen. The following description will explain an example in which liquefied hydrogen is used as the cryogenic liquefied gas.

[0027] (calibration device) (First embodiment) Figure 1 shows a calibration device 1 according to this disclosure. Figure 1 shows the device under test 20 incorporated into the calibration device 1. The device under test 20 is a mass flow meter, more specifically, a Coriolis flow meter. A Coriolis flow meter is a flow meter capable of measuring mass flow rate and density. For example, when a Coriolis flow meter is used as a flow meter in a liquefied hydrogen supply facility, the amount of liquefied hydrogen supplied to the recipient can be accurately determined from the mass flow rate and density. On the other hand, Coriolis flow meters have instrument errors, and it is desirable to perform calibration considering the influence of fluid density on the measured flow rate. In particular, by calibrating the flow meter using a fluid that easily vaporizes, such as liquefied hydrogen, and in which air bubbles are mixed into the liquid, causing large density fluctuations, the reliability of the flow meter when measuring liquefied hydrogen can be further improved. Note that the device under test 20 to which calibration is performed using the calibration device 1 according to this disclosure is not limited to a Coriolis flow meter, but may be, for example, a flow measurement system combining a densimeter and a volumetric flow meter. The densimeter may be a capacitive densimeter, a gamma-ray densimeter, etc. The volumetric flow meter may be a throttle flow meter, a turbine flow meter, an ultrasonic flow meter, etc.

[0028] Referring to Figure 1, the calibration apparatus 1 comprises a first container 11, a weighing device 12, a flow meter 13, a first pipe 14, a second pipe 15, and a second container 16. In the calibration apparatus 1, the first container 11, the first pipe 14, the device under test 20, the second pipe 15, and the second container 16 are arranged in this order from upstream. The device under test 20 is connected between the first pipe 14 and the second pipe 15.

[0029] Liquid hydrogen is contained in the first container 11. The liquid hydrogen discharged from the first container 11 flows through the first pipe 14 to the test apparatus 20. The material of the first container 11 is not limited as long as the effects of the invention are obtained, but it is preferably a highly insulated container, and more specifically, a double-shell vacuum insulated container in which multi-layer insulation (MLI) is incorporated into the vacuum layer. The weighing device 12 is capable of measuring the mass of the first container 11. The weighing device 12 is, for example, a scale (mass meter). Based on the measurement value of the weighing device 12, the mass (kg) of liquid hydrogen discharged from the first container 11 can be determined. The flow meter 13 is installed near the connection between the first container 11 and the first pipe 14. The flow meter 13 is, for example, a Coriolis flow meter, or a flow measurement system combining a densimeter and a volumetric flow meter. The densimeter may be a capacitive densimeter or a gamma-ray densimeter, and the volumetric flowmeter may be a throttled flowmeter, a turbine flowmeter, an ultrasonic flowmeter, etc. From the measurement value of the flowmeter 13, the mass flow rate (e.g., kg / min) of liquefied hydrogen discharged from the first container 11 can be determined. The flowmeter 13 may be installed in the first container 11, or it may be installed near the first container 11 in the first piping 14 as described later. With this configuration, the mass flow rate of liquefied hydrogen discharged from the first container 11 can be accurately determined. The calibration device 1 can accurately determine the mass of liquefied hydrogen flowing from the first container 11 to the device under test 20 based on the measurement values ​​of the weighing device 12 and the flowmeter 13.

[0030] The first piping 14 is a line connecting the first container 11 and the device under test 20. Figure 1 schematically shows the first piping 14, but the first piping 14 may be connected to multiple pipes, and valves and measuring devices may be provided along it. For example, a flow meter 13 may be provided along the first piping 14 and near the first container 11, and thermometers, sensors, etc. (not shown) may also be provided. The material of the first piping 14 is not particularly limited as long as it is suitable for transferring liquefied hydrogen, but it is preferable that it be a pipe with heat insulation properties in order to reduce the heat input to the liquefied hydrogen through the pipe, and more specifically, it is preferable that at least a part of it be made of a flexible tube for vacuum piping. Flexible tubes for vacuum piping have excellent vibration absorption properties and can reduce the influence on measurement values ​​even when the device under test 20 is a device that is susceptible to vibration (e.g., a Coriolis flow meter).

[0031] The first pipe 14 is suspended and supported by a chain 18 acting as a support. The chain 18 may be suspended from, for example, the ceiling to support the first pipe 14, or it may be suspended from a support column or the like. The support supports the first pipe 14, suppressing the influence of the mass of the first pipe 14 on the measurement values ​​of the weighing device 12. This configuration allows for more accurate calibration. The specific configuration of the support is not limited to a chain, as long as the influence of the mass of the first pipe 14 on the measurement values ​​of the weighing device 12 can be reduced; for example, a support stand may be used as shown in Figure 2.

[0032] The second pipe 15 is connected to the device under test 20 and carries the liquefied hydrogen discharged from the device under test 20 to the second container 16. The material of the second pipe 15 is not particularly limited, but for example, SUS316L can be used. The second container 16 is a receiving container and receives the liquefied hydrogen that has passed through the device under test 20. The second container 16 is equipped with a vent line 17 for discharging gas.

[0033] Calibration device 1 includes pipes 31A, 31B, and 31C, which are pipes for supplying liquefied hydrogen or hydrogen gas to calibration device 1 from outside calibration device 1. Pipe 31A is connected to the lower part of the first container 11, and pipe 31B is connected to the upper part of the first container 11. Liquefied hydrogen can be supplied to the first container 11 through pipe 31A as needed. Hydrogen gas can also be supplied to the first container 11 through pipe 31B. This allows the pressure of the first container 11 to be adjusted as needed. Pipe 31C is connected to the first pipe 14, and hydrogen gas is supplied to the first pipe 14 through pipe 31C. If the mass of hydrogen gas supplied from pipe 31C is significantly less than the mass of liquefied hydrogen supplied from the first container 11, the amount of gas supplied through pipe 31C may be ignored, and the amount of fluid flowing to the device under test 20 may be calculated based on the measurements of the weighing device 12 and / or flow meter 13. Pipe 31C may also be equipped with flow control equipment. The flow control device may be a mass flow controller or a combination of a gas flow meter and a valve. In this case, the amount of fluid flowing through the device under test 20 may be calculated based on the sum of the measurements from the weighing device 12 and / or the flow meter 13 and the measurements from the flow control device. These configurations make it easy to create fluids with different gas-liquid mixing ratios, in other words, fluids with different densities.

[0034] (First proofreading method) This section describes the calibration method for the device under test 20 using the calibration device 1. A Coriolis flow meter is used as the device under test 20. The on / off valve (not shown) provided in the first container 11 and / or the first piping 14 is opened, and liquefied hydrogen is supplied from the first container 11 to the device under test 20. Hydrogen gas is also supplied from piping 31C, and the mixing ratio of liquefied hydrogen (liquid phase) and hydrogen gas (gas phase) flowing into the device under test 20 is adjusted to a predetermined ratio. By adjusting the valve opening or gas flow rate, a fluid with a predetermined mixing ratio (i.e., a predetermined density) can be formed. At this time, the actual flow rate M is determined from the measurements of the weighing device 12 and / or the flow meter 13. rThe (kg / min) can be determined. The actual density ρr may be measured by a measuring device, or it may be calculated from the mixing ratio of the liquid phase and the gas phase. The range of the actual flow rate and actual density can be adjusted according to the device under test and is not particularly limited, but for example, the actual flow rate M r The flow rate was increased from 0.5 kg / min to 20 kg / min, and the actual density was increased to 1.3 kg / m³. 3 ~70.8 kg / m 3 It can be changed up to this point. The measured flow rate M in the test apparatus 20 when a fluid with each actual flow rate and actual density flows through it. m , measured density ρ m Measure it.

[0035] Next, the measured density ρ m and measured flow rate M m Based on flow rate M r The measured density ρ for calculating m and measured flow rate M m A correction factor C, which is a function of , is determined. The correction factor C may be determined for each individual device under test, or for each group of devices under test (e.g., by lot, by model number, etc.).

[0036] Figure 4 shows the measured density ρ measured in the test apparatus when a two-phase fluid with a predetermined flow rate and density was supplied, using water as the liquid phase and nitrogen gas as the gas phase as a model system. m (kg / m 3 The graph shows the flow rate on the horizontal axis and the correction coefficient C on the vertical axis. The fluid flow rate is approximately 0.5 to 2.0 kg / min, and the density is approximately 26 kg / m³. 3 ~997 kg / m 3 The range was defined as follows:

[0037] The test was repeated three times, and the symbols indicate each test series. Each flow rate shown in the graph represents the measured flow rate M. m (kg / min). In the graph, the measured flow rate M mThe measured density ρ for flow rates of 0.5 kg / min (plots are represented by a diamond shape ◇, and the approximation curve is shown as a dotted line), 1.0 kg / min (plots are represented by a square shape □, and the approximation curve is shown as a dashed line), 1.5 kg / min (plots are represented by a circle ●, and the approximation curve is shown as a dashed line), and 2.0 kg / min (plots are represented by a triangle ▲, and the approximation curve is shown as a solid line). m (kg / m 3 This shows an approximation curve illustrating the correlation between () and the correction coefficient C.

[0038] As shown in Figure 4, in all cases where the measured flow rate is 0.5 kg / min, 1.0 kg / min, 1.5 kg / min, and 2.0 kg / min, the correction coefficient C is a quadratic curve with respect to the measured density, and the slope of the approximation curve is steeper as the flow rate decreases. Therefore, the measured flow rate M m A linear function of and the measured density ρ m By expressing it as the product of a quadratic function, the correction coefficient C can be accurately represented.

[0039] In other words, the relationship between the actual flow rate Mr and the measured flow rate Mm can be expressed by the following equation (1).

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[0040] (Second embodiment) Figure 2 shows the calibration apparatus 2 according to this disclosure. Components similar to those in calibration apparatus 1 are denoted by the same reference numerals and their descriptions are omitted. The main differences between calibration apparatus 1 and calibration apparatus 2 are that calibration apparatus 2 is further equipped with a bubble sensor 21 and a thermometer 22 in the first piping 14, and that the first piping 14 has a support base 19 instead of a chain 18 as a support.

[0041] The bubble sensor 21 detects bubbles contained in the fluid flowing through the first pipe 14. The bubble sensor 21 is installed near the device under test 20 and detects bubbles in the fluid just before it is introduced into the device under test 20. Preferably, the bubble sensor 21 can detect the presence or absence of bubbles and the proportion of bubbles in the fluid. The bubble sensor 21 can detect the density of the two-phase liquefied hydrogen flow introduced into the device under test 20. Specifically, the bubble sensor 21 may be, for example, a capacitive void fraction meter. A capacitive void fraction meter is a device that measures the capacitance of a two-phase flow by applying high frequency to electrodes installed in the pipe, and can measure bubble mixing ratios from 0% to 100%. By referring to the detected value of the bubble sensor 21, the amount of gas in the fluid flowing through the first pipe 14 can be adjusted, for example, by adjusting the amount of hydrogen gas supplied from pipe 31C, thereby creating a fluid of a desired density. The bubble sensor 21 is not limited to a capacitive void fraction meter, but may be a gamma-ray densimeter, an optical fiber densimeter, or the like.

[0042] The support stand 19 is a support stand installed on the floor and supports the first pipe 14. The support stand 19 suppresses the influence of the mass of the first pipe 14 on the weighing device 12. The specific configuration of the support stand 19 is not particularly limited. Also, there is no limit to the number of support stands 19 installed; there may be one or multiple.

[0043] (Second proofreading method) This section describes a calibration method for the device under test 20 using the calibration device 2. The device under test 20 is a Coriolis flow meter. By using the calibration device 2, it is possible to calibrate not only the measured flow rate but also the measured density of the Coriolis flow meter.

[0044] The on / off valve (not shown) provided in the first container 11 and / or the first piping 14 is opened, and liquefied hydrogen is supplied from the first container 11 to the device under test 20. Hydrogen gas is also supplied from piping 31C, and the mixing ratio of liquefied hydrogen (liquid phase) and hydrogen gas (gas phase) flowing into the device under test 20 is adjusted to a predetermined ratio. By adjusting the valve opening or gas flow rate, a fluid with a predetermined mixing ratio (i.e., a predetermined density) can be formed. From the measurements of the weighing device 12 and / or the flow meter 13, the actual flow rate M is determined. r (kg / min) can be determined. If a flow rate adjustment device is installed in the piping 31C, the actual flow rate M can be calculated from the sum of the weighing device 12 and / or the flow meter 13 and the flow rate setting value of the flow rate adjustment device. r The (kg / min) may be determined. The flow rate control device may be, for example, a mass flow controller. From the measurement value of the bubble sensor 21, the actual density ρ r (kg / m 3 ) can be grasped. Real density ρ r This may be calculated from the mixing ratio of the liquid phase and the gas phase, and a separate measuring device may be provided to measure the actual density. The range of the actual flow rate and actual density can be adjusted according to the device under test and is not particularly limited, but for example, the actual flow rate M r The flow rate was increased from 0.5 kg / min to 20 kg / min, and the actual density was increased to 1.3 kg / m³. 3 ~70.8 kg / m 3 It can be varied up to each actual flow rate M r and actual density ρ r The measured flow rate M in the test apparatus 20 when a fluid containing the specified fluid flows through it. m , measured density ρ m Measure it.

[0045] Next, the measured density ρ m and measured flow rate M m The density of the fluid ρ is based on r The measured density ρ for calculating m and measured flow rate M m The correction factor D, which is a function of , is determined. The correction factor D may be determined for each individual device under test, or for each group of devices under test (e.g., by lot, by model number, etc.).

[0046] Figure 5 shows the measured density ρ measured in the test device when a two-phase fluid having a predetermined flow rate and a predetermined density is supplied using water as the liquid phase and nitrogen gas as the gas phase as the model system. m (kg / m 3 ) is plotted on the horizontal axis, and the correction coefficient D is plotted on the vertical axis. The flow rate of the fluid was in the range of about 0.5 to 2.0 kg / min, and the density was in the range of about 26 kg / m 3 to 997 kg / m 3 .

[0047] The test was repeated three times. Each flow rate shown in the graph is the measured flow rate M m (kg / min). The measured flow rate M m is 0.5 kg / min (the plot is a diamond ◇ symbol, and the approximate curve is shown as a dotted line), 1.0 kg / min (the plot is a square □ symbol, and the approximate curve is shown as a dashed-dotted line), 1.5 kg / min (the plot is a circle ● symbol, and the approximate curve is shown as a dashed line), and 2.0 kg / min (the plot is a triangle ▲ symbol, and the approximate curve is shown as a solid line). The approximate curve shows the correlation between the measured density ρ m (kg / m 3 ) and the correction coefficient D.

[0048] As shown in Figure 5, in all cases where the measured flow rate is 0.5 kg / min, 1.0 kg / min, 1.5 kg / min, or 2.0 kg / min, the correction coefficient D is a quadratic curve with respect to the measured density, and the slope of the approximate curve is larger when the flow rate is lower. Therefore, the correction coefficient D can be accurately expressed by the product of a linear function of the measured flow rate M m and a quadratic function of the measured density ρ m .

[0049] That is, it can be said that the relationship between the actual density ρr and the measured density ρm is expressed by the following formula (3).

Equation

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[0050] (Third Embodiment) FIG. 3 shows a calibration device 3 according to the present disclosure. The same components as those of the calibration device 1 and the calibration device 2 are denoted by the same reference numerals and the description thereof is omitted. The main difference between the calibration device 2 and the calibration device 3 is that the calibration device 3 further includes a cryogenic chamber 30, a third pipe 33, and a flow rate control device 34 provided in the middle of the third pipe 33.

[0051] The cryogenic chamber 30 is an immersion device filled with an extremely low temperature liquefied gas such as liquefied hydrogen. A part of the first pipe 14 is disposed in the cryogenic chamber 30 and immersed in the extremely low temperature liquefied gas. Also, the third pipe 33 is connected to the first pipe 14 inside the cryogenic chamber 30. The amount of fluid flowing through the third pipe 33 is adjusted by the flow rate control device ۳۴, and a known amount of fluid is supplied from the third pipe 33. Gas can be supplied from the third pipe 33. That is, the third pipe 33 is a gas supply line.

[0052] It is preferable to use a fluid with a lower liquefaction temperature than the cryogenic liquefied gas supplied from the first container 11 as the fluid supplied from the third pipe 33. For example, liquefied hydrogen can be used as the cryogenic liquefied gas supplied from the first container 11, and helium gas can be supplied from the third pipe 33. The liquefied hydrogen supplied from the first container 11 and flowing through the first pipe 14 is cooled to below its liquefaction temperature in the low-temperature chamber 30, becoming a liquid that does not contain gas. On the other hand, helium gas is supplied to the first pipe 14 through the third pipe 33. The liquefaction temperature of helium is even lower than that of hydrogen, and it does not liquefy even when cooled to the temperature of liquefied hydrogen. Therefore, when supplied to the first pipe 14, helium remains as a gas without liquefying. By adjusting the flow rate of liquefied hydrogen and the flow rate of helium gas, the gas-liquid mixture state of the fluid flowing through the first pipe 14 can be adjusted arbitrarily and accurately.

[0053] The combination of cryogenic liquefied gas contained in the first container 11 and the gas supplied from the third pipe 33 is not limited to the above example. For example, liquid nitrogen may be used as the cryogenic liquefied gas contained in the first container 11, and hydrogen gas or helium gas may be supplied as the gas supplied from the third pipe 33. As a preferred example, liquid nitrogen may be used as the liquid phase supplied from the first container 11, and hydrogen gas may be used as the shared gas phase from the third pipe 33. In this case, it is preferable to fill the cryogenic chamber with liquid nitrogen so that a portion of the first pipe 14 used as a liquid nitrogen supply line is immersed in the liquid nitrogen.

[0054] (Variations of the proofreading method) Calibration of the device under test 20 using calibration device 3 can be performed in substantially the same manner as using calibration device 2. When using calibration device 3, as described above, a mixed fluid of liquid and gas phases can be created by using the cryogenic liquefied gas supplied from the first container 11 as the liquid phase and the gas supplied from the third pipe 33 as the gas phase. The amount of cryogenic liquefied gas supplied from the first container 11 (i.e., the amount of liquid phase) can be determined from the measurements of the weighing device 12 and the flow meter 13. In addition, the amount of gas supplied from the third pipe 33 can be adjusted with the flow control device 34. Therefore, the actual flow rate and actual density of the fluid supplied to the device under test 20 can be adjusted more accurately and arbitrarily.

[0055] When using this method, the actual density ρ of the fluid supplied to the device under test r This is the gas flow rate M set by the flow rate control device 34. g The liquid flow rate M measured by the weighing device 12 or flow meter 13 l Therefore, it is calculated using the following formula (5).

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[0056] The embodiments disclosed herein should be understood in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended. [Explanation of Symbols]

[0057] 1, 2, 3 Calibration device, 11 First container, 12 Weighing device, 13 Flow meter, 14 First piping, 15 Second piping, 16 Second container, 17 Vent line, 18 Chain, 19 Support stand, 20 Test device, 21 Bubble sensor, 22 Thermometer, 30 Low-temperature chamber, 31A, 31B, 31C Piping, 33 Third piping, 34 Flow control device.

Claims

1. A first container capable of containing cryogenic liquefied gas, A weighing device for measuring the mass of the first container, A first pipe connecting the first container and the device under test, which is a mass flow meter, A second pipe connected to the device under test, A second container connected to the second piping, Equipped with, The first container, the first piping, the device under test, and the second container are arranged in this order from the upstream side. Calibration device for mass flow meters.

2. The first piping includes a support that supports the first piping in such a way as to reduce the influence of the mass of the first piping on the measurement of the weighing device. Calibration apparatus for a mass flow meter according to claim 1.

3. Furthermore, a gas supply line connected to the first piping, A flow meter provided in or near the first container, including, Calibration apparatus for a mass flow meter according to claim 1.

4. Furthermore, the first pipe is equipped with a bubble sensor capable of measuring the density of the fluid flowing through the first pipe. Calibration apparatus for a mass flow meter according to any one of claims 1 to 3.

5. Furthermore, a cryogenic chamber filled with cryogenic liquefied gas, A third pipe is drawn from the outside to the inside of the aforementioned low-temperature chamber, Equipped with, A portion of the first piping is placed inside the low-temperature chamber. The third pipe is connected to the first pipe within the low-temperature chamber. Calibration apparatus for a mass flow meter according to any one of claims 1 to 3.

6. The cryogenic liquefied gas flowing through the first pipe is liquefied hydrogen, and the gas flowing through the third pipe is helium gas. Calibration apparatus for a mass flow meter according to claim 5.

7. The cryogenic liquefied gas flowing through the first pipe is liquid nitrogen, and the gas flowing through the third pipe is hydrogen gas. Calibration apparatus for a mass flow meter according to claim 5.

8. A first container containing cryogenic liquefied gas, A weighing device for measuring the mass of the first container, A first pipe connecting the first container and the device under test, which is a mass flow meter, A second pipe connected to the device under test, A second container connected to the second piping, Equipped with, The calibration is performed in a mass flow meter calibration apparatus in which the first container, the first piping, the device under test, and the second container are arranged in this order from the upstream side. A method for calibrating a mass flow meter, The actual flow rate M measured by the weighing device ｒ , the measured density ρ in the device under test ｍ and the measured flow rate M ｍ From this, we find the correction coefficient C expressed by the following equation (1): Calibration method for mass flow meters. [Math 1] (In equation (1), C(ρ ｍ M ｍ ) is where C is measured density ρ ｍ and the measured flow rate M ｍ (This shows that it is a function of [the function].)

9. The correction coefficient C is the product of a linear function of the measured flow rate M represented by the following formula (2) and a quadratic function of the measured density ρ ｍ and ｍ is represented by [Math 2] (In equation (2), v, w, x, y, and z are constants.) A method for calibrating a mass flow meter according to claim 8.

10. The first piping is further equipped with a flow meter, and the actual flow rate M ｒ A method for calibrating a mass flow meter according to claim 8 or claim 9, wherein the measurement value is obtained from the flow meter and / or the weighing device.

11. A first container containing cryogenic liquefied gas, A weighing device for measuring the mass of the first container, A first pipe connects the first container and the device under test, which is a Coriolis flow meter, A second pipe connected to the device under test, A second container connected to the second piping, Equipped with, The first container, the first piping, the device under test, and the second container are arranged in this order from the upstream side. Furthermore, in a calibration device for a mass flow meter equipped with a bubble sensor in the first piping, A method for calibrating a mass flow meter, The measured density ρ in the device under test ｍ and the measured flow rate M ｍ Therefore, the actual density ρ of the fluid flowing through the device under test r To calculate this, we find the correction coefficient D expressed by the following equation (3): Calibration method for mass flow meters. [Math 3] (In equation (3), D(ρ ｍ M ｍ ) is where D is the measured density ρ ｍ and the measured flow rate M ｍ (This shows that it is a function of [the function].)

12. The correction coefficient D is the measured flow rate M, which is expressed by the following formula (4). ｍ The linear function of and the measured density ρ ｍ It can be expressed as the product of quadratic functions, [Math 4] (In equation (4), v', w', x', y', and z' are constants.) The method for calibrating a mass flow meter according to claim 11.

13. Furthermore, a cryogenic chamber filled with cryogenic liquefied gas, A third pipe is drawn from the outside to the inside of the aforementioned low-temperature chamber, Equipped with, A portion of the first piping is placed inside the low-temperature chamber. The third pipe is connected to the first pipe within the low-temperature chamber. The pre-3 piping is equipped with a flow control device. The actual density ρ r However, the gas flow rate M of the flow rate control device ｇ And the liquid flow rate M of the weighing device. ｌ From this, the following formula (5) is used to calculate: [Math 5] (In equation (5), ρ ｌ and ρ ｇ (These represent liquid density and gas density, respectively.) A method for calibrating a mass flow meter according to claim 11 or claim 12.

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