Correction formula calculation method

Abstract

The objective is to easily and inexpensively calculate a calibration formula for a liquid hydrogen level gauge using a superconductor, without using expensive liquid hydrogen. [Solution] A calibration formula calculation method for calculating a calibration formula for a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level height in a container by voltage measurement, characterized in that the calibration formula is calculated from the relationship between the voltage value of the liquid hydrogen level gauge and the respective liquid level height at at least three points, each with a different liquid level height, while pouring a liquid at a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the container in which the liquid hydrogen level gauge is installed vertically.

Description

[Technical Field]

[0001] The present invention relates to a method for calculating a calibration formula for calibrating a liquid hydrogen level gauge using a superconductor. [Background technology]

[0002] In February 2023, Japan's "Basic Policy for Realizing GX (Green Transformation)" was approved by the Cabinet, and with the promotion of hydrogen introduction being advocated, there is a need for accurate measurement of liquid hydrogen levels in the transportation, storage, and consumption of liquid hydrogen. In this context, efforts are underway to develop liquid hydrogen level gauges using superconductors such as MgB2.

[0003] For a liquid hydrogen level gauge to be used in practice, calibration is required between the voltage measurement of the gauge and the actual liquid hydrogen level. However, using liquid hydrogen for calibration is costly, and constructing a liquid hydrogen facility in-house is impractical due to strict applicable laws such as the High Pressure Gas Safety Act, the Industrial Safety and Health Act (Explosion-Proof Structure Standards for Electrical Machinery and Equipment), and the Fire Service Act. On the other hand, there are very few test facilities capable of testing liquid hydrogen, making it difficult to easily obtain an environment for testing and calibrating liquid hydrogen level gauges.

[0004] Patent Document 1 describes a configuration for a liquid level gauge for liquefied gases such as liquid nitrogen, in which a superconductor and a non-superconductor are arranged in parallel. [Prior art documents] [Patent Documents]

[0005] Patent document 1: Japanese Patent Application Laid-Open No. 04-99923 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, Patent Document 1 does not describe how to calibrate the voltage measurement value in the liquid level gauge with the actual liquid level of the liquefied gas. If the liquefied gas is liquid hydrogen, as mentioned above, it is not only costly but also difficult to perform in-house calibration due to legal restrictions.

[0007] The present invention aims to solve the above problems and to easily calculate a calibration formula for calibrating a liquid hydrogen level gauge using a superconductor at low cost. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides a calibration formula calculation method for calculating a calibration formula for a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level height in a container by voltage measurement, characterized in that the calibration formula is calculated from the relationship between the voltage of the liquid hydrogen level gauge and the respective liquid level heights at at least three points where the liquid level heights are different, while injecting a liquid at a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the container in which the liquid hydrogen level gauge is installed vertically.

[0009] This configuration allows for the easy and low-cost calculation of a calibration formula for a liquid hydrogen level gauge using a superconductor, without the need for expensive liquid hydrogen. Furthermore, the calibration test can be performed using a conventional liquid hydrogen level gauge instead of visual inspection.

[0010] Furthermore, in order to solve the above problems, the present invention provides a calibration formula calculation method for calculating a calibration formula for a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level height in a container by voltage measurement, While pouring a liquid at a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the container in which the liquid hydrogen level gauge is installed vertically, The third voltage of the liquid hydrogen level gauge when the liquid level is 0% and the first voltage of the liquid hydrogen level gauge when the liquid level is 100% are measured, and the second voltage of the liquid hydrogen level gauge is measured at at least one liquid level height between 0% and 100%. The present invention provides a calibration formula calculation method characterized by calculating a calibration formula from the relationship between the values ​​of the first voltage, the second voltage, and the third voltage and their respective liquid level heights.

[0011] This configuration allows for the easy and low-cost calculation of a calibration formula for a liquid hydrogen level gauge using a superconductor, without the need for expensive liquid hydrogen. Furthermore, the calibration test can be performed using a conventional liquid hydrogen level gauge instead of visual inspection.

[0012] A calibration formula calculation method may be provided, wherein the liquid hydrogen level gauge includes a superconducting wire and a non-superconducting wire of the same length, the first voltage is the voltage at 100% liquid level of the non-superconducting wire, and the second voltage is the voltage obtained by subtracting the voltage at 100% liquid level of the superconducting wire and any liquid level between 100% and 0% from the voltage at 100% liquid level of the non-superconducting wire.

[0013] This configuration prevents measurement errors caused by temperature changes in the gas phase.

[0014] The calibration formula calculation method may be configured such that the liquid injected into the container is liquid nitrogen.

[0015] This configuration allows for the calculation of a calibration formula for easily and inexpensively calibrating a liquid hydrogen level gauge using a superconductor, utilizing readily available, easy-to-handle, and low-cost liquid nitrogen.

[0016] The calibration formula calculation method may be configured such that the second voltage is the voltage of the liquid hydrogen level gauge when the liquid level is 50%.

[0017] This configuration allows for the calculation of a more accurate calibration formula because the liquid level at which the second voltage is measured is midway between the 100% and 0% liquid levels.

Advantages of the Invention

[0018] According to the correction formula calculation method of the present invention, a correction formula for calibrating a liquid hydrogen level gauge using a superconductor can be easily calculated at a low cost. Moreover, although it is difficult to measure liquid hydrogen with a general other type of level gauge, by using easily handled liquid nitrogen, a comparative test with the liquid level height measured by other types of level gauges becomes possible.

Brief Description of the Drawings

[0019] [Figure 1] It is a diagram for explaining the installation state of the liquid hydrogen level gauge in Example 1 of the present invention. [Figure 2] It is a diagram for explaining the state when 50% of the liquid is injected into the container in Example 1 of the present invention. [Figure 3] It is a diagram for explaining the state when 100% of the liquid is injected into the container in Example 1 of the present invention. [Figure 4] It is a diagram for explaining the installation state of the liquid hydrogen level gauge in Example 2 of the present invention.

Modes for Carrying Out the Invention

Examples

[0020] Example 1 of the present invention will be described with reference to FIGS. 1 - 3. FIG. 1 is a diagram for explaining the installation state of the liquid hydrogen level gauge in Example 1 of the present invention. FIG. 2 is a diagram for explaining the state when 50% of the liquid is injected into the container in Example 1 of the present invention. FIG. 3 is a diagram for explaining the state when 100% of the liquid is injected into the container in Example 1 of the present invention.

[0021] (Liquid Hydrogen Level Gauge) First, the liquid hydrogen level gauge 10 in Example 1 will be described. The liquid hydrogen level gauge 10 has a superconducting wire 11 and a non-superconducting wire 12 that are provided in parallel and of the same length. By passing an electric current through each end and measuring the voltage, the liquid level height is detected from the measured voltage, taking advantage of the fact that the area below the liquid surface becomes superconducting and has zero resistance. Both the superconducting wire 11 and the non-superconducting wire 12 are long core wires with a length of approximately 1 m and a diameter of approximately 0.3 mm, and are covered with a metal coating. The superconductor contained in the superconductor 11 is made by mixing 1 part magnesium (Mg) (325 mesh, manufactured by alfa Aesar, particle size approximately 44 μm) with boron (B) with an average particle size of 14 μm in a molar ratio of 2 (mixing process), drawing the mixture in a wire drawing process, and then firing it in a calcination process to make it a MgB2 superconductor. In the wire drawing process, a powdered mixture of Mg and B obtained from the mixing process was placed in a single tube and drawn to create a long wire. The critical temperature (Tc) of the superconductor manufactured in this way is approximately 32K to 34K.

[0022] In Example 1, a long core wire with a length of approximately 1 m and a diameter of approximately 0.3 mm was formed, but this is not necessarily limited to this and can be changed as appropriate. For example, the length could be approximately 5 m or 0.5 m, and it should be prepared according to the depth of liquid hydrogen in the container. Also, in Example 1, the diameter was approximately 0.3 mm, but this is not necessarily limited to this and can be changed as appropriate. For example, it could be 0.5 mm or 0.2 mm, and the diameter may be selected in consideration of the critical temperature (Tc).

[0023] The coating metal can be any metal with high conductivity. In Example 1, a CuNi alloy was used, but other metals such as stainless steel may also be used.

[0024] The non-superconducting wire 12 is composed of a non-superconducting metal of the same length and thickness as the superconducting wire described above, and is covered with a CuNi alloy coating. In Example 1, any ordinary conductor can be used as the non-superconducting metal.

[0025] When 50% of liquid hydrogen is injected into container 20 as shown in Figure 2, the portion of the superconducting wire 11 submerged in liquid hydrogen becomes superconducting, and the voltage between AC and V AC When measuring, the voltage V between A and B, which are not superconducting, is found. AB This can measure and determine the liquid level. However, because the resistance changes with temperature changes in the non-superconducting gas phase, the voltage V can change even if the liquid level does not change. AB This changes the voltage Vac of the non-superconducting wire 12 to the voltage V of the superconducting wire 11. AC Subtracting this, we get the voltage V of the superconducting wire 11 where the gas phase portion has the same temperature distribution. AB The voltage at the same liquid level in the non-superconducting wire 12 cancels out, leaving only the voltage Vbc in the non-superconducting wire 12. Since the temperature in the liquid is constant, the liquid level can be detected by calculating the voltage Vbc.

[0026] (Calibration of a liquid hydrogen level gauge using liquid hydrogen) In order to accurately measure the liquid level using the liquid hydrogen level gauge 10, it is necessary to obtain a calibration formula that calibrates the difference between the voltage Vbc of the non-superconducting wire 12 (output voltage of the liquid hydrogen level gauge 10) and the actual liquid level. For this reason, the liquid hydrogen level gauge 10 is usually installed in a container that can be visually observed from the outside, liquid hydrogen (Tc=20~30K) is injected into the container, and as the liquid level drops due to evaporation, the liquid level is visually checked using the scale, and a calibration formula is calculated to calibrate the visually observed liquid level and the output voltage of the liquid hydrogen level gauge 10.

[0027] Calibrating this liquid hydrogen level gauge 10 using liquid hydrogen presents the following problems: • The cost of liquid hydrogen is extremely high. • There are very few testing facilities nationwide that can perform tests with liquid hydrogen. • Constructing a liquid hydrogen facility in-house is difficult in terms of time and cost due to the strict application of laws and regulations such as the High Pressure Gas Safety Act, the Industrial Safety and Health Act (Explosion-Proof Structure Standards for Electrical Machinery and Equipment), and the Fire Service Act.

[0028] Therefore, the applicant has found a method for calculating a calibration formula for calibrating the liquid hydrogen level gauge 10 using a liquid other than liquid hydrogen, which is low-cost and subject to fewer applicable regulations. Next, the calibration formula calculation method for calculating the calibration formula for calibrating the liquid hydrogen level gauge in Example 1 of the present invention will be described.

[0029] (Calibration value calculation method without using liquid hydrogen) First, as shown in FIG. 1, a liquid hydrogen level gauge 10 is installed vertically in a container 20. At this time, the liquid hydrogen level gauge 10 should be of such a length that the liquid level height can be measured even when 100% liquid is injected into the container 20.

[0030] Next, with the liquid not being injected (liquid level at 0%), a voltage is applied across both ends of the superconducting wire 11 to measure the voltage V AC between point A and point C. At this time, the voltage when the superconducting wire 11 is not in the superconducting state is measured. Then, when the voltage Vac of the non-superconducting wire is subtracted from the voltage V AC of the superconducting wire 11, the result is zero, and the measured voltage value at a liquid level height of 0% is zero.

[0031] Next, a liquid 30 at a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge 10 is injected into the container up to a height of 50% (point B in FIG. 2). The critical temperature (Tc) of the superconductor in Example 1 is about 32K to about 34K, and in Example 1, the liquid injected into the container 20 is liquid nitrogen (boiling point at 1 atm = 77K).

[0032] At this time, since the liquid is liquid nitrogen (boiling point at 1 atm = 77K), the superconducting wire 11 in the liquid phase part is not in the superconducting state. When measuring the voltage V AC , the voltage V BC between point B and point C of the superconducting wire 11 does not become zero, and the voltage in the non-superconducting state is measured. However, if V BC is intentionally set to zero, the same V AC as in the superconducting state can be measured. That is, if the voltage V AB between point A and point B of the superconducting wire 11 is subtracted from the voltage Vac between point a and point c of the non-superconducting wire 12, the voltage Vbc of the non-superconducting wire 12 can be obtained, and the result is the same as that when the part below the liquid level (liquid phase part) of the superconducting wire 11 is in the superconducting state.

[0033] Next, a liquid at a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge 10 is poured into the container to 100% of its height (point A in Figure 3). Then, the voltage Vac between points a and c of the non-superconducting wire 12 is measured.

[0034] Finally, a calibration formula, which is an approximation, is calculated using the least squares method or similar based on the relationship between three points: the voltage at 0% liquid level (third voltage), the voltage across non-superconducting wire 12 at 50% liquid level (second voltage) and the voltage across non-superconducting wire 12 at 100% liquid level (first voltage), and their respective liquid levels. The liquid level can be determined by measuring it with another liquid level gauge.

[0035] In Example 1, point B shown in Figure 2 was set to a height of 50% of the liquid level, but this is not necessarily limited to this and can be changed as appropriate. For example, it could be 30% of the liquid level, 70% of the liquid level, or any point at any height between 0% and 100% of the liquid level. Furthermore, there is no need to be just one point B; multiple points B can be set between 0% and 100% of the liquid level to calculate the calibration formula.

[0036] Furthermore, in Example 1, the calibration formula was calculated from the voltage at a liquid level of 0%, a liquid level of 100%, and a liquid level of 50%, but this is not necessarily limited to this and can be modified as appropriate. For example, the calibration formula may be calculated from the relationship between the voltage values ​​at any three points with different liquid levels between 0% and 100%, and their respective liquid levels, using an approximate formula.

[0037] Furthermore, in Example 1, the liquid 30 injected into the container 20 was liquid nitrogen, but it is not necessarily limited to this and can be changed as appropriate. For example, it could be a liquefied gas such as liquefied carbon dioxide, or water if the water temperature is stable, or any liquid at a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge 10.

[0038] Thus, in Example 1, the calibration formula calculation method is used to calculate a calibration formula for a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level height in a container by voltage measurement, While pouring a liquid at a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the container in which the liquid hydrogen level gauge is installed vertically, A calibration formula calculation method is characterized by calculating a calibration formula from the relationship between the voltage value of the liquid hydrogen level gauge at at least three points with different liquid level heights and the respective liquid level heights. This method allows for the easy and low-cost calculation of a calibration formula for a liquid hydrogen level gauge using a superconductor, without using expensive liquid hydrogen. Furthermore, while it is difficult to measure liquid hydrogen with other types of liquid level gauges, using easily handled liquid nitrogen makes it possible to compare liquid level measurements with those measured by other types of liquid level gauges.

[0039] Furthermore, a method for calculating a calibration formula for calibrating a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level height in a container by voltage measurement, While pouring a liquid at a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the container in which the liquid hydrogen level gauge is installed vertically, The third voltage of the liquid hydrogen level gauge when the liquid level is 0% and the first voltage of the liquid hydrogen level gauge when the liquid level is 100% are measured, and the second voltage of the liquid hydrogen level gauge at at least one liquid level between 0% and 100% is measured. A calibration formula calculation method, characterized by calculating a calibration formula from the relationship between the values ​​of the first, second, and third voltages and their respective liquid level heights, allows for the easy and low-cost calculation of a calibration formula for calibrating a liquid hydrogen level gauge using a superconductor, without the need for expensive liquid hydrogen. Furthermore, while measuring liquid hydrogen with other types of general-purpose level gauges is difficult, using easily handled liquid nitrogen makes it possible to perform comparative tests with liquid level heights measured by other types of level gauges. [Examples]

[0040] The liquid hydrogen level gauge 110 in Embodiment 2 of the present invention differs from that in Embodiment 1 in that it is composed solely of superconducting wires and does not have non-superconducting wires. Embodiment 2 will be described with reference to Figure 4. Figure 4 is a diagram illustrating the installation state of the liquid hydrogen level gauge in Embodiment 2 of the present invention.

[0041] The liquid hydrogen level gauge 110 in Example 2 does not include a non-superconducting wire but has a superconducting wire 111. The superconducting wire 111 has the same configuration as in Example 1 and detects the liquid hydrogen level by measuring the voltage. Because the liquid hydrogen level gauge 110 does not have a non-superconducting wire, there is a risk of errors due to temperature changes in the gas phase portion. Therefore, it is mainly used in environments where the temperature of the gas phase portion can be kept constant.

[0042] The method for calculating the calibration formula will now be explained. First, as shown in Figure 4, the liquid hydrogen level gauge 110 is installed vertically in the container 20. At this time, the liquid hydrogen level gauge 110 should be long enough to measure the liquid level even when the container 20 is filled with 100% liquid.

[0043] Next, the voltage V across both ends of the superconducting wire 111 when no liquid is injected (liquid level 0%). AC We do not measure it and consider it to be zero.

[0044] Next, a liquid at a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge 110 is poured into the container to a height of 50% (point B). In Example 2, the critical temperature (Tc) of the superconductor is approximately 32K to 34K. The liquid poured into the container 20 is liquid nitrogen (77K), but it is not necessarily limited to this and can be changed as appropriate. For example, a liquefied gas such as liquefied carbon dioxide may be used, or water may be used if the water temperature is stable, as long as the liquid is at a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge 110.

[0045] In this case, since the liquid is liquid nitrogen, the superconducting wire 111 in the liquid phase is not superconducting, and the voltage V between point A and point C AC When measured, the voltage V of the superconducting wire 111 between point B and point C isBC The voltage is not zero, and the voltage in the non-superconducting state is measured, but V BC If we intentionally set V to zero, then V is the same as in the superconducting state. AC This can be measured. In other words, the voltage V of the superconducting wire 111 at liquid surface point B. AB Measure.

[0046] Next, a liquid at a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge 110 is poured into the container to 100% of its height (point A). Then, the voltage V between points A and C of the superconducting wire 111 is measured. AC Measure the voltage. When measuring the voltage, it is advisable to connect an appropriate current source.

[0047] Finally, the voltage is zero when the liquid level is 0%, and the voltage V between points A and B of the superconducting wire 111 when the liquid level is 50% (point B). AB The voltage V between point A and point C of the superconducting wire 111 when the liquid level is 100% (point A) AC The calibration formula for calibration is calculated by approximating it using the least squares method or similar, based on the relationship between the voltage values ​​at the three points and their respective liquid levels.

[0048] In Example 2, point B shown in Figure 4 was set to a height of 50% of the liquid level, but this is not necessarily limited to this and can be changed as appropriate. For example, it could be 30% of the liquid level, 70% of the liquid level, or any height between 0% and 100% of the liquid level. Furthermore, there is no need to be just one point B; multiple points B can be set between 0% and 100% of the liquid level to calculate the calibration formula.

[0049] Furthermore, in Example 2, the calibration formula was calculated from the voltage at a liquid level of 0%, a liquid level of 100%, and a liquid level of 50%, but this is not necessarily limited to this and can be modified as appropriate. For example, the calibration formula may be calculated from the relationship between the voltage values ​​at any three points with different liquid levels between 0% and 100% liquid levels and their respective liquid levels.

[0050] Thus, in Example 2, the calibration formula calculation method is used to calculate a calibration formula for a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level height in a container by voltage measurement, While pouring a liquid at a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the container in which the liquid hydrogen level gauge is installed vertically, A calibration formula calculation method is characterized by calculating a calibration formula from the relationship between the voltage value of the liquid hydrogen level gauge at at least three points with different liquid level heights and the respective liquid level heights. This method allows for the easy and low-cost calculation of a calibration formula for a liquid hydrogen level gauge using a superconductor, without using expensive liquid hydrogen. Furthermore, while it is difficult to measure liquid hydrogen with other types of liquid level gauges, using easily handled liquid nitrogen makes it possible to compare liquid level measurements with those measured by other types of liquid level gauges.

[0051] Furthermore, a method for calculating a calibration formula for calibrating a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level height in a container by voltage measurement, While pouring a liquid at a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the container in which the liquid hydrogen level gauge is installed vertically, The third voltage of the liquid hydrogen level gauge when the liquid level is 0% and the first voltage of the liquid hydrogen level gauge when the liquid level is 100% are measured, and the second voltage of the liquid hydrogen level gauge is measured at at least one point in the liquid level between 0% and 100%. A calibration formula calculation method, characterized by calculating a calibration formula from the relationship between the values ​​of the first, second, and third voltages and their respective liquid level heights, allows for the easy and low-cost calculation of a calibration formula for calibrating a liquid hydrogen level gauge using a superconductor, without the need for expensive liquid hydrogen. Furthermore, while measuring liquid hydrogen with other types of general-purpose level gauges is difficult, using easily handled liquid nitrogen makes it possible to perform comparative tests with liquid level heights measured by other types of level gauges. [Industrial applicability]

[0052] The calibration formula calculation method in this invention can be widely applied to the field of liquid hydrogen level gauges. [Explanation of Symbols]

[0053] 10: Liquid hydrogen level gauge 11:Superconducting wire 12: Non-superconducting wire 20: Container 30:Liquid 110: Liquid hydrogen level gauge 111:Superconducting wire

Claims

1. A method for calculating a calibration formula for a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level height in a container by voltage measurement, While pouring a liquid at a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the container in which the liquid hydrogen level gauge is installed vertically, A calibration formula calculation method characterized by calculating a calibration formula from the relationship between the voltage value of the liquid hydrogen level gauge and the respective liquid level at at least three points, each with a different liquid level.

2. A method for calculating a calibration formula for a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level height in a container by voltage measurement, While pouring a liquid at a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the container in which the liquid hydrogen level gauge is installed vertically, The third voltage of the liquid hydrogen level gauge when the liquid level is 0% and the first voltage of the liquid hydrogen level gauge when the liquid level is 100% are measured, and the second voltage of the liquid hydrogen level gauge is measured at at least one liquid level between 0% and 100%. A calibration formula calculation method characterized by calculating a calibration formula from the relationship between the values ​​of the first voltage, the second voltage, and the third voltage and their respective liquid level heights.

3. The calibration formula calculation method according to claim 2, characterized in that the liquid hydrogen level gauge includes a superconducting wire and a non-superconducting wire of the same length, the first voltage is the voltage at 100% liquid level of the non-superconducting wire, and the second voltage is the voltage obtained by subtracting the voltage at any liquid level between 100% liquid level and 0% liquid level of the superconducting wire from the voltage at 100% liquid level of the non-superconducting wire.

4. The calibration formula calculation method according to any one of 1-3, characterized in that the liquid injected into the container is liquid nitrogen.

5. The calibration formula calculation method according to claim 2 or 3, characterized in that the second voltage is the voltage of the liquid hydrogen level gauge when the liquid level is 50%.

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