JPS61207957A - Heat loss measuring instrument - Google Patents

Abstract

PURPOSE:To obtain a heat loss measuring instrument which is very simple, and also has a high accuracy and a high sensitivity by constituting the device so that a cooling medium can be replaced by an evaporated gas of the cooling medium by exthothermic heat of a body to be measured, and providing a means which can measure the volume of its gas. CONSTITUTION:A gaseous helium which is evaporated by the exthothermic heat of a sample is replaced with a liquid helium in the liquid helium (in a cryostat), by which the volume is derived. This gaseous helium is maintained at a constant temperature of 4.2K, and the pressure is also scarcely varied and held in a constant state since the specific gravity of the liquid helium is small, therefore, the measuring accuracy is extremely high. For instance, a plug 7 is opened before a body to be measured is conducted electrically, and after a sample chamber 3 and a gas reservoir part 4 are filled completely with the liquid helium, the plug 7 is closed. Subsequently, the electric conduction is executed, and an evaporated gaseous helium by the generation of heat is replaced with a liquid helium collected in the gas reservoir part 4. When a prescribed time has elapsed, the electric conduction is stopped, and the height or the volume of a part 10 in which the gas has collected is measured by a suitable means. When the measurement is completed, the plug 7 is opened and the sample chamber 3 and the gas reservoir part 4 are filled with the liquid helium again.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a heat loss measuring device, and particularly to a heat loss measurement device for measuring heat loss caused by changing currents and changing magnetic fields in superconducting conductors, and in particular superconducting devices constructed using the same. The present invention relates to a heat loss measuring device suitable for measuring loss.

[The stomach view of invention]

Recently, there has been much research into making superconducting poloidal coils for nuclear fusion, but the key point in its development is to reduce AC losses due to the changing current flowing through the superconducting conductor or the changing magnetic field to which it is exposed. (hereinafter collectively referred to as heat loss) occurs, causing not only a loss of refrigerant but also a rise in the temperature of the superconducting conductor, resulting in the disappearance of the superconducting state t. Therefore, it is necessary to develop a superconducting conductor II with low heat loss. It is in. In the process of developing such superconducting conductors, a heat loss measuring device that can efficiently and conveniently evaluate heat loss is essential.

Methods for measuring heat loss in superconducting conductors and superconducting devices (typically superconducting magnets) made of them can be roughly divided into two types: electromagnetic methods and thermal methods. The former is an indirect method, and the latter is a direct method. Compared to the former, the latter requires more time to measure, but the accuracy and reliability of the measured values are superior.

Here, the latter measuring method, measuring device, problems related thereto, and the background of the present invention will be described.

FIG. 3 shows a typical example of a conventional measuring device using a thermal method. A cryostat (hereinafter, the vacuum insulation tank and liquid nitrogen insulation tank are omitted) containing a refrigerant (hereinafter represented by liquid helium at normal pressure 42) that can maintain the full superconducting state (the vacuum insulation tank and liquid nitrogen insulation tank are omitted) 1 is filled with liquid helium 2 to an excessive height. The sample chamber 3 is equipped with liquid helium supply and electric current to the sample chamber 3 at the bottom of the sample chamber 3. An opening 6 through which the lead wires 13, etc. are passed, and a conduit 14 that can be taken out from the ceiling to allow the vaporized liquid helium gas (Fry Ostara) due to heat loss in the object to be measured are installed. . The helium gas led outside of the Fly Ostara 1 is heated to a temperature of 30 degrees by a heat exchanger 16, measured by a flow meter 19, and then released into the atmosphere. - Helium gas that has been evaporated by heat entering cryostat 1 from the outside is transferred to conduit 1 at the top of cryostat 1.
The cryostat is led out of the cryostat 1 and released into the atmosphere through the on-off valve 17. These two conduits 14 and 1
A differential pressure gauge 18 is inserted between 5 and upstream of the flow meter 19. Consider a case where a varying current is applied to the object to be measured from the current lead wire 13. When the object to be measured generates heat due to this changing current, the liquid helium is vaporized and helium gas flows out through the conduit 14. In order to generate this flow t, it is necessary to maintain the inside of the cryostat 1 at a pressure higher than the pressure loss due to the conduit 14, the heat exchanger 16, and the flow meter 191c. Therefore, it is necessary to adjust the on-off valve 17 while monitoring the differential pressure gauge 18 in order to maintain the above-mentioned pressure constant at all times, taking into consideration heat intrusion from the outside into the cryostat 1 and pressure loss in the conduit 15. Become. Non-operation is extremely subtle and affects the reliability of measured values.

Since the ratio i of liquid helium is smaller than others, the height of the liquid level inside the conduit 14 changes greatly with a very small pressure difference, the temperature gradient (temperature distribution) inside this conduit 14 protrudes, and the volume of gas increases. As a result, the reading on the flowmeter 19 will fluctuate greatly, which will not only make measurement difficult but also cause loss of reliability. During the measurement, the liquid level in the conduit 14 is kept constant, preferably equal to or slightly higher than the liquid level in the cryostat 1. In addition, the measured helium gas is normally released into the atmosphere, and if it is connected to a helium gas recovery system, it will be affected by pressure fluctuations due to the recovery compressor and pressure loss up to the recovery system, making measurement impossible. Become. Therefore, we are in a situation where we have no choice but to release it into the atmosphere, which may be uneconomical.

In addition, immediately after filling the cryostat 1 with liquid helium 2, it takes an extremely long time for the entire device to reach a state of thermal equilibrium, which takes several hours, and during this period, the amount of liquid helium in the cryostat 1 fluctuates. However, the pressure inside the cryostat 1 also changes, making measurement impossible.

Incidentally, related devices of this type include, for example, [
Journal Application Physics (Jou
rnal Application Physics
) vow, 53, 41. (1982) p578, [
One example is uroda J.

[Purpose of the invention]

The present invention has been made in view of the above points, and its object is to provide an extremely simple, highly accurate, and highly sensitive heat loss measuring device.

[Summary of the Invention] The gist of the present invention is to determine the volume by replacing helium gas vaporized by heat generation in a sample with liquid helium in a liquid helium (inside a cryostat). This helium gas is kept at a constant temperature of 4.2 mm, and the pressure is kept constant at 4 M without any fluctuation, which is lower than the specific gravity of liquid helium, so the measured Sagara is extremely high.

[Embodiments of the invention]

The present invention will be explained below with reference to the embodiments shown in FIG. 8141 and FIG. FIG. 1 shows the basic configuration of the present invention.

As shown in the figure, a cryostat 1 is filled with liquid helium 2, a sample chamber 3 is submerged therein, and a superconducting conductor 8, which becomes the object to be measured, is placed in the sample chamber 3, and a superconducting magnet 9 made of the superconducting conductor 8 is placed inside the sample chamber 3. An opening 6 for replenishing liquid helium is provided at the bottom of the sample chamber 3, and a gas reservoir 4 for storing vaporized helium gas is provided at the ceiling. The opening 6 is the same as that for the third prisoner, or the gas reservoir 4 is located at the upper end or in liquid helium, and the upper end is provided with a stopper 7 that is tightly sealed to the extent that helium gas does not leak. It can be opened and closed from the outside using an operating rod 11. The operation will be explained using an example in which a changing current is applied to the object to be measured. Before energizing the object to be measured, the stopper 7t is opened, and after the sample chamber 3 and waste reservoir 4 are completely filled with liquid helium, the stopper 7 is closed. Next, electricity is applied, and the helium gas, which has been converted into fi due to heat generation, is stored in the gas reservoir section 4 and replaced with solid helium. After a certain period of time, the power is turned off,
The height or height yL of the 'fc portion 10 where debris accumulates is measured by an appropriate means. When the measurement is completed, the stopper 7 is used to refill the HV5 sample color 3 reservoir 4 with liquid helicum. That's 1
This marks the end of the measurement.

When the heat generation from the sample is 1 mW, the volume of helium gas at 1 atm is equivalent to 2.8 x 10-" sub-3/S. For example, if the gas reservoir is composed of a 54-t pipe and its diameter is
0 and 0, the height of the wound will be 8.56 after 10 minutes of energization. Needless to say, this height is quite high for observation. If this height is measured in hL of 5 inches, the heat value will have a sensitivity t-V of 0.05 mW in just 10 minutes, and no matter how long it takes with the conventional method, the measurement of 1 mW is reliable. This is a significant improvement compared to what was said to be no sex.

The specific gravity of liquid helium is O, 126g/at 1 atm 4.2
Cm", even if the liquid level in the gas reservoir 4 drops by 30 degrees, the pressure will be only 0.0037 atm, and re-liquefaction of the helium gas in 4.2 is unlikely to affect the measurement. There is no effect at all. Even if a volume change occurs for some reason, if the specie is collected using a known heating element under the same conditions, that concern will be resolved.

Even if the fly-oss foot 1 is not in thermal equilibrium, even if the conduit 15 is connected to the recovery system to recover the evaporated helium gas from inside the Takata cryostat 1, the gas reservoir 4
If you know the pressure inside the cryostat at the moment when you can read the liquid level inside the cryostat, you can calculate the correct heat loss just by making corrections. Therefore, the measurement time is significantly shortened, and expensive helium gas can be recovered without escaping into the atmosphere.

Not 1, but the opening/closing operation and structure of the stopper 7, and the waste storage part 4.
The dimensions of 2 and the relative positional relationship with the liquid level in the Iostat 1, especially including the case where the plug 7 is above the liquid level, may be deformed, but this is not a matter of concern. In addition, the method of applying a changing current, the method of applying a changing magnetic field, and the means of observing the liquid level in the gas reservoir 4 may also be carefully considered, and the present invention is not limited to these. In particular, regarding the means for observing the liquid level, (1) If the fly-oss foot 1 is made of glass, if a scale is attached to the waste reservoir 4, measurements can be made sufficiently by visual observation from the outside or by means such as a lens. (li) Even if the Flyos foot 1 is made of metal or glass, if the sample chamber 3 or gas reservoir s4 is covered with a superconducting magnet for applying an external magnetic field, It is also possible to measure the liquid level by placing an ultrasonic device in the stopper.

However, in this case, it is necessary to apply an element or method that does not involve heat generation, and to take care not to apply heat input into the sample chamber 3.

In this example, the object to be measured is a superconducting conductor or a superconducting device fi made of the same.
The object to be measured can be a normal conducting conductor or a device made of the same, and it becomes an extremely effective measuring device when heat loss at the temperature of the refrigerant used is negligible.

FIG. 2 shows another embodiment of the invention. In this method, multiple objects to be measured are placed in one cryostat, and the sample chamber 3
The sample chamber 3 is separated into a ceiling part and a lower part 5, and at the end of the measurement, the ceiling part of the sample chamber 3 (gas reservoir part 4, plug 7, operation vsllll
By moving the probe t' together and covering it with the next object to be measured, efficient measurement can be carried out. That is, the object to be measured is fixed to this bottom part 5, and a wall is provided around the periphery to prevent vaporized helium gas bubbles from flowing in from the outside. Place it so that it is covered.

Those skilled in the art are well aware that a large amount of liquid helium is consumed each time the sample chamber 3 is pulled out of the cryostat 1 and inserted for each measurement. In the present invention, the movement is performed by simply lifting only the ceiling to the height of the object to be measured, so the consumption of liquid helium is extremely small. This will be extremely effective in improving work efficiency.

〔Effect of the invention〕

The advantages of the present invention as described above include high efficiency due to the simplification of the measurement time and operation method, high reliability and high sensitivity of the defined value, and economical efficiency due to the recovery of liquid helium. In addition to improved performance, the biggest advantage is that the device itself is simple and inexpensive, and is used as an essential evaluation device for the development of superconducting conductors for nuclear fusion, energy storage, and accelerators. The industrial effect is extremely large.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing one embodiment of the heat loss measuring device of the present invention. heat loss measuring device fi
It is a schematic block diagram which shows t.

Claims (1)

[Scope of Claims] 1. A heat loss measuring device for measuring heat loss of a measured object placed in a refrigerant, configured so that the refrigerant can be replaced with vaporized gas of the refrigerant due to heat generated by the measured object. and a means for measuring the volume of the gas. 2. It has a container for storing the object to be measured, and has an opening at the bottom of the container to prevent gases vaporized from other causes from entering, and a ceiling part to prevent gases generated from the object to be measured from entering. Provide an opening with a stopper to prevent leakage;
The heat loss measuring device according to claim 1, characterized by having means capable of measuring the volume of vaporized gas accumulated in the ceiling portion or the height of the liquid level caused by replacing the refrigerant with the gas. . 3. Claims characterized in that the container for storing the object to be measured is separated into a bottom part and a ceiling part, the bottom part is fixed in the refrigerant container, and the ceiling part is detachable from the refrigerant container. The heat loss measuring device according to item 1.