JPH09101277A - Heat loss measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the vibration of a float so as to improve the measurement accuracy of a heat loss measuring instrument by forming a cylinder in an U-shaped pipe having a projecting section on the top side and using one side of the pipe for collecting a gas and the other side for measuring the quantity of the gas. SOLUTION: A heat loss measuring instrument is dipped in liquid helium 2 stored in a cryostat 1 and the helium gas naturally evaporated from the whole body of the instrument is discharged through a gas duct 16. A superconducting material 3 is surrounded with a sample chamber 4 and all of the helium gas 5 generated by an AC loss is collected to a U-shaped cylinder 6 having a projecting section on the top side. When the gas 5 is generated, the surface level of liquid helium in the cylinder 6 becomes lower at a fixed rate. When the gas 5 generated by a heat loss is collected, the gas 5 is collected to one side of the cylinder 6 and a float 10 is floated on the surface of the liquid helium on the other side. The float 10, namely, the surface level of the liquid helium is detected with photosensors containing light emitting and light receiving sections arranged in the vertical direction around the cylindrical pipe of the cylinder 10 on the float side 10. Therefore, the vibration of the float 10 can be reduce and the measurement accuracy of the heat loss measuring instrument can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat loss measuring device, and is particularly suitable for measuring a heat loss (AC loss) associated with a changing current, a changing magnetic field, etc. of a superconductor or a superconducting device constituted by the superconductor. Heat loss measuring device.

[0002]

2. Description of the Related Art Heat loss (also referred to as AC loss) generated when an alternating current or a pulsed changing current is applied to a superconducting conductor or when a changing magnetic field is applied causes a temperature rise of the superconducting conductor and, by necessity, a superconducting conductor. This will result in the destruction (quenching) of the state. Therefore, the development of superconductors with reduced AC loss is an important and essential issue in the development of stable superconducting equipment. The superconducting device mentioned here is a magnet for fusion, a coil for power storage, a superconducting generator, a superconducting transformer, a current limiting device, etc., which mainly performs AC or pulse-like operation. Therefore, in order to develop the superconducting conductor in which the AC loss is reduced as described above, a device for accurately and quickly evaluating the AC loss is indispensable. From that point of view, the heat loss measuring device described in JP-A-61-207957 was developed,
It has been shown that measurement efficiency is improved and accuracy is improved. The outline is shown below. The device has a sample chamber so as to surround the object to be measured, and collects the refrigerant gas generated by AC loss in a cylinder with a scale arranged in the upper part of the sample chamber, and measures the helium gas generation amount per unit time, The AC loss can be easily calculated using (Equation 1).

[0003]

(Equation 1)

Here, Q: AC loss (W) ΔV: Cylinder volume (cm ³ ) Δt: Time required for helium gas to be filled by ΔV (seconds) 0.354: Constant obtained from physical properties of refrigerant (helium) In order to measure the amount of generated gas, the change in the liquid level of the refrigerant in the cylinder with a scale is visually observed, so that the accuracy cannot be improved for the following reasons. (1) Since the liquid level change in the cylinder is visually observed, the error due to parallax is large. In addition, a cryogenic container made of glass is indispensable, and there is a safety problem with danger such as rupture of the cryogenic container.

(2) There are variations in measured values depending on the person who measures.

In order to improve the above points, the document "Calorime"
tric measurement of ac losses ”Cryogenics '91
The heat loss measuring device shown in Vol.31 May p.363-365 has been developed and used. A schematic diagram of the device is shown in FIG. Like the invention described above, the structure of the sample chamber, the cylinder for collecting gas, etc. is such that the float is floated on the liquid surface of the refrigerant in the cylinder that moves with the gas generation, and two sets of sensors are used to make a sensor between the two sets. It is a method of measuring how many seconds it has passed. The reason why the float is necessary is due to the small refractive index of liquid helium as a refrigerant. Since the refractive index of light of liquid helium is very small, it is impossible to directly detect the liquid surface using an optical sensor. Therefore, the float was floated on the liquid surface of the refrigerant (liquid helium) so that it could be detected by the optical sensor. The light sensor senses light when the float is passing, and light when it is not.

According to this method, the parallax and the measurement error by the measurer can be eliminated. Furthermore, since the liquid level of the refrigerant can be monitored without checking the inside of the cryocontainer from the outside, it is possible to use not only the glass cryocontainer but also a metal or non-metal cryocontainer. However, in this method, when collecting gas, vaporized helium gas bubbles generated by heat loss are accumulated in the cylinder across the float. As a result, the bubbles of helium gas collide against the bottom surface of the float and repel it, causing the float to vibrate. The vibration of the float directly affects the accuracy of the measurement, and when the vibration is large, the accuracy is significantly deteriorated.

[0008]

DISCLOSURE OF THE INVENTION The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to use a photosensor to measure the helium gas generation rate by using a method of detecting a float on the liquid surface to detect a heat loss. In order to provide a heat loss measuring device, the vibration of the float at the time of collecting the helium gas is reduced to improve the measurement accuracy.

[0009]

In order to solve the above problems, the present invention divides the roles of collecting and measuring helium gas in the cylinder. Specifically, the shape of the cylinder is a U-shaped tube having an upward convex shape, and one is used for collecting gas and the other is used for measuring the amount of gas to improve the accuracy of measurement.

When the upwardly convex U-shaped tube as described above is used, bubbles of helium gas do not collide with the float floating on the liquid surface, so that vibration of the float during measurement can be reduced. Therefore, the measurement accuracy can be improved.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present embodiment, the AC loss generated when an alternating current or a pulsed current flows in a superconducting conductor or a superconducting device in liquid helium, or when an alternating current or a pulsed magnetic field is applied. The apparatus according to the present invention will be described by taking measurement as an example.

FIG. 1 is a schematic diagram relating to the present invention. The measuring device of the present invention is immersed in liquid helium 2 stored in a cryostat 1. The helium gas that spontaneously evaporated from the entire equipment was fed to the cryostat 1 through the gas conduit 16.
It is discharged outside.

The superconductor 3 is surrounded by the sample chamber 4, and the helium gas 5 generated by the AC loss is collected in the upwardly convex U-shaped cylinder 6. As the helium gas 5 is generated, the helium liquid level in the upwardly convex U-shaped cylinder 6 drops at a constant speed. The helium gas 5 generated by heat loss is collected in one of the upwardly convex U-shaped cylinders 6, and the float 10 is floated on the liquid surface in the other. The upper liquid level detecting light emitting unit 11a, the upper liquid level detecting light receiving unit 11b, the lower liquid level detecting light emitting unit 12a, and the lower liquid level detecting light receiving unit 12b are convex U-shaped on the side where the float 10 is present. It is arranged around the cylindrical tube of the cylinder 6 along the upper and lower longitudinal directions. The position of the float 10, that is, the liquid surface can be detected by using an optical sensor (detailed description of FIG. 2) including the light projecting unit and the light receiving unit. Here, the upwardly convex U-shaped cylinder 6 is made of glass, and the change in the internal volume due to thermal contraction and the influence on the refractive index of light are made as small as possible.

When the measurement is finished and the measurement is started again, the upwardly convex U-shaped cylinder 6 is moved up and down around the cylinder reversing bearing 14 to lift the cylinder hanging thread 15.
It is possible to reverse the upward convex U-shaped cylinder 6 and discharge the helium gas collected at the time of measurement to the outside of the upward convex U-shaped cylinder 6 and set it again at a predetermined position to restart the measurement. ing.

FIG. 2 shows the connection status of the measurement system including the optical sensor. The upper liquid level detecting light emitting part 11a, the upper liquid level detecting light receiving part 11b, the lower liquid level detecting light emitting part 12a, and the lower liquid level detecting light receiving part 12b use the optical fiber part 8 for the upper liquid level detection. Light emitting unit 13a, lower liquid level detecting light emitting unit 13b,
The upper liquid level detecting light / electric conversion unit 18a and the lower liquid level detecting light / electric conversion unit 18b are respectively connected. When light is emitted by the upper liquid level detecting light emitting section 13a and the lower liquid level detecting light emitting section 13b, light is transmitted to the corresponding optical fiber section 8 in the figure, and the upper liquid level detecting light emitting section 11a and the lower liquid level detecting Projector 12
Light is projected toward the gas amount measuring side of the U-shaped cylinder 6 which is convex upward from a. Further, the upper liquid level detection light / electric conversion unit 18a and the lower liquid level detection light / electric conversion unit 18b are also connected to the sensor signal line 17, and the presence or absence of the float 10 described below, that is, the presence of the refrigerant liquid level. The sensor signal recording unit 9 converts the light blocking state and the light emitting state without light into an electric signal.
Can be entered. Floating upper liquid level detecting light emitting part 11a, upper liquid level detecting light receiving part 11b, lower liquid level detecting light emitting part 12a, lower liquid level detecting light receiving part 12b.
When it is not at the position, the upper liquid level detecting light receiving section 11b and the lower liquid level detecting light receiving section 12b are in a state of receiving light, and the upper liquid level detecting light / electric conversion section 18a, the lower liquid level detecting light / The electrical conversion unit 18b is set so that the sensor signal recording unit 9 does not generate a sensor voltage signal. Further, an upper liquid level detecting light emitting unit 11a, an upper liquid level detecting light receiving unit 11b, and a lower liquid level detecting light emitting unit 12 which are floated.
a, when it is at the position of the lower liquid level detecting light receiving part 12b, the upper liquid level detecting light receiving part 11b, the lower liquid level detecting light receiving part 12b
Is in a state of blocking light, and the upper liquid level detection light / electric conversion unit 18a and the lower liquid level detection light / electric conversion unit 18b are set so that a sensor voltage signal is generated in the sensor signal recording unit 9. Has become. Now, the upper liquid level detection floodlight 1
1a, an upper liquid level detecting light receiving section 11b, a lower liquid level detecting light projecting section 12a, and a lower liquid level detecting light receiving section 12b are convex U
Around the part (gas amount measurement side) 6'of the character-shaped cylinder, the volume in the cylinder is set to be ΔV in the up and down longitudinal direction. Therefore, the liquid level in the cylinder is from the installation position of the upper liquid level detection light emitting unit 11a and the upper liquid level detection light receiving unit 11b to the lower liquid level detection light emitting unit 12a and the lower liquid level detection light receiving unit 12b. The AC loss is obtained by measuring the time (Δt) at which the temperature decreases to ΔV and changes by ΔV.

FIG. 3 is a perspective view of the main part of the heat loss measuring apparatus of the present invention. When the AC loss is calculated by measuring the time (Δt) changing by ΔV, the measured Δt was used as it is in the conventional formula, but the internal volume for gas collection is also taken into consideration because the cylinder is U-shaped. There is a need. In the U-shaped cylinder shown in FIG. 3, the cylindrical tubes for collecting gas and measuring the gas amount have the same cross-sectional area and are constant in the vertical direction.
Further, the liquid level drops at the same speed in both the gas collecting cylindrical tube and the gas amount measuring cylindrical tube. For this reason, the conversion formula (Formula 1) for the AC loss that has been put forward is as shown in (Formula 2).

[0017]

(Equation 2)

A float stopper 7 is provided inside the gas measuring cylindrical tube of the cylinder, and an upper liquid level detecting projector 11 is provided.
a, provided on the upper side with respect to the upper liquid level detection light receiving portion 11b.
This is to prevent the float from jumping out of the measurement range when reversing the cylinder in order to restart the measurement. During the measurement, the refrigerant evaporates from time to time, so that the refrigerant portion vaporized and replaced is supplied into the sample chamber 4. Therefore, the opening of the refrigerant supply unit 19 is provided on the lower side surface of the sample chamber 4.

Further, the cylinder may have a shape as shown in FIG. The shape of the upper part was changed while maintaining the size of the cylindrical tube for collecting gas and measuring the amount of gas. If the inner diameter of the upper portion is made sufficiently smaller than the size of the float, re-measurement can be performed without the float stopper 7.

The shape of the cylinder may be as shown in FIG. The cross-sectional area of one cylindrical tube of the cylinder is different from the cross-sectional area of the other so that both have a constant cross-sectional area in the vertical direction. At this time, the AC loss can be calculated by the following (Equation 3).

[0021]

(Equation 3)

Here, A ₁ is the cross-sectional area of the gas amount measuring cylindrical tube, and A ₂ is the cross-sectional area of the gas collecting cylindrical tube.

The method of measuring and evaluating the AC loss using the U-shaped tube of the heat loss measuring device according to the present invention has been described above. According to the present invention, noise (sensor bubbles of helium gas) in the sensor output of the optical sensor, which appears in the conventional method shown in FIG. 6, and disturbance of the signal of the optical sensor due to the float vibration are reduced, and noise or noise is generated in the sensor output as shown in FIG. Disturbance does not appear, and it is possible to improve the measurement accuracy and reproducibility as compared with the conventional method. Needless to say, in this embodiment, the cryogenic container may be made of metal, non-metal, or conventional glass.

[0024]

According to the present invention, it has become possible to measure and evaluate the heat loss (AC loss), which is essential for the development of superconducting conductors and superconducting equipment, with high precision and efficiency. Therefore, it has a great effect on the development of superconducting equipment for pulse and AC.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a heat loss measuring device according to an embodiment of the present invention.

FIG. 2 is a schematic view showing connection of components of an optical sensor of a heat loss measuring device according to an embodiment of the present invention.

FIG. 3 is a perspective view of a main part of the heat loss measuring device of the present invention.

FIG. 4 is a perspective view showing an example of a cylinder in the configuration of the heat loss measuring apparatus according to the embodiment of the present invention.

FIG. 5 is a perspective view showing an example of a cylinder in the configuration of the heat loss measuring apparatus according to the embodiment of the present invention.

FIG. 6 is an output characteristic diagram when a conventional optical sensor is detected.

FIG. 7 is an output characteristic diagram when an optical sensor is detected in the present embodiment.

FIG. 8 is a schematic diagram showing a configuration of a conventional heat loss measuring device.

[Explanation of symbols]

1 ... Cryostat, 2 ... Refrigerant, 3 ... Superconductor, 4 ...
Sample chamber, 5 ... Refrigerant gas, 6 ... U-shaped cylinder convex upward, 6 '... Part of U-shaped cylinder convex upward, 7 ... Float stop portion, 8 ... Optical fiber portion, 9 ... Sensor signal Recording unit, 10 ... Float, 11a ... Upper refrigerant liquid level detecting light projecting unit, 11b ... Upper refrigerant liquid level detecting light receiving unit, 12a ... Lower refrigerant liquid level detecting light projecting unit, 12b ... Lower refrigerant liquid level detecting Light receiving part, 13a ... Light emitting part for detecting upper refrigerant liquid level, 13b ... Light emitting part for lower refrigerant liquid level, 14 ... Cylinder inversion bearing, 1
5 ... Cylinder suspension thread, 16 ... Gas conduit, 17 ... Sensor signal line, 18a ... Upper refrigerant liquid level detection optical / electrical conversion section, 18b ... Lower refrigerant liquid level detection optical / electrical conversion section, 19
... Refrigerant supply unit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryuyoshi Takahashi 7-1, 1-1 Omika-cho, Hitachi City, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Kiyoshi Yamaguchi 7-chome, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 Hitachi Ltd. Hitachi Research Laboratory

Claims (6)

[Claims] 1. A heat loss measuring device for measuring a heat loss of an object to be measured placed in a refrigerant, wherein vaporized gas of the refrigerant generated by heat generation of the object to be measured is placed in the refrigerant and convex. A heat loss measuring device characterized by being able to collect vaporized gas collected on one side of the U-shaped tube and vaporized on the other side. 2. The U-shaped tube according to claim 1, wherein a cylindrical tube for collecting gas and a cylindrical tube for measuring gas volume are combined, and the cylindrical tube is connected and communicated at an upper portion. Heat loss measuring device characterized by. 3. The cylindrical tube for collecting gas and measuring the gas volume of the U-shaped tube according to claim 1 or 2, wherein the cross-sectional area is constant in the vertical and longitudinal directions. Heat loss measuring device. 4. An object which floats on a refrigerant in a cylindrical tube for measuring the volume of vaporized gas in the U-shaped tube according to claim 1, and moves when heat loss occurs. A heat loss measuring device characterized by detecting light with an optical sensor. 5. A U-shaped tube according to any one of claims 1, 2, 3 and 4, wherein optical sensors are arranged around a cylindrical tube for measuring the volume of vaporized gas, vertically and longitudinally. A heat loss measuring device characterized in that 6. Two sets of the optical sensor according to claim 4 or 5 are used, and 1 is provided around a cylindrical tube for measuring the volume of vaporized gas in an upwardly convex U-shaped tube, along the vertical and longitudinal directions. It is possible to measure the amount of vaporized gas generated per unit time by measuring the time when the optical sensor detects the object floated on the refrigerant by arranging it at a distance from each other and detecting it with the other optical sensor. A heat loss measuring device characterized in that