JPH0450729A - Device for monitoring residual amount of refrigerant - Google Patents

Abstract

PURPOSE:To allow the omission of a heater, the extension of the period for replenishing helium and the sure announcement of the time for replenishing by providing means for measuring the flow rate of the gaseous refrigerant discharged by a heat insulating vessel, integrating this flow rate, calculating the residual amt. and displaying the same. CONSTITUTION:The flow rate of the gaseous helium from a helium evaporating port 6 is detected by an ammeter 12 and is subjected to A/D conversion 13. The converted signal is inputted to a CPU 14 where the flow rate signal is integrated. The integrated signal is stored in a memory device 15. The function to apply the liquid level value of the liquefied helium corresponding to the integrated value of the gaseous helium is stored in the device 15 and the residual amt. is thereby displayed on a monitor 16. The threshold value of the residual amt. of the liquefied helium is stored in the device 15 and an alarm is emitted when the residual amt. falls below this value. The omission of the heater, the extension of the time for replenishing the helium and the sure announcement of the time for replenishing are executed in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for monitoring the remaining amount of liquefied refrigerant used in a cooling device. The present invention relates to a remaining amount monitoring device.

[Prior Art] A refrigerant remaining amount monitoring device in a conventional cooling device installs a liquid level sensor in a refrigerant container, monitors and displays the refrigerant liquid level in the container, and further monitors and displays the refrigerant liquid level when the refrigerant liquid level reaches a predetermined value. It was designed to generate an alarm if it breaks.

FIG. 2 is a diagram showing an example of the liquid level sensor. When the superconducting wire 2 is immersed in the refrigerant in the container, the resistance value of the part of the superconducting wire 2 below the refrigerant liquid level becomes substantially zero, and the part above the refrigerant liquid level exhibits normal conductivity. Since it exhibits a high resistance value, the liquid level can be detected from the resistance value.

For example, liquefied helium is used as the refrigerant of the superconducting magnet for nuclear magnetic resonance apparatus, and the superconducting wire 2 has a normal conductivity resistance value of 2.
A wire of 225 Ω per 0 inch is used.

However, if left alone, the portion of the superconducting wire 2 above the refrigerant liquid level will also cool down and exhibit superconductivity, so a heater 3 is provided above the superconducting wire 2 as shown in FIG. At the time of measurement, this portion was heated by a constant current power source 1. As a result, the part of the superconducting wire 2 close to the heater 3 becomes normal conductive and heated by the above current, and the heat propagates to the lower part, makes it normal conductive and heats it, and finally ends up above the liquid level. Two parts of the superconducting wire had become normal conductive. Since the voltmeter 4 detects the voltage drop in the portion of the superconducting wire 2 substantially above the normal conductive liquid level, it is possible to know the refrigerant liquid level from this.

[Problems to be Solved by the Invention] In the above-mentioned prior art, the amount of liquefied helium evaporated due to the above-mentioned power consumption of the heater 3 is excessive, so there is a problem in that liquefied helium must be replenished frequently.

In one example of the cooling device for a superconducting magnet for a nuclear magnetic resonance apparatus, if the heater 3 is not heated, the amount of evaporation of the liquefied helium is approximately 0.003 m1/see, regardless of the liquid amount.
On the other hand, when the heater 3 is heated, as shown in Figure 3, when the container is full of liquefied helium,
1/sec, 6.1 when the container is almost empty
1 m 1 /'sec, which were both dominantly larger than when the heater 3 was not heated. However, FIG. 3 shows a case where a 20-inch superconducting wire 2 with a room temperature resistance value of 225Ω and a heater 3 with a resistance value of 3Ω are used.

In order to reduce evaporation of liquefied helium by the heater 3, the liquid level is detected intermittently, and the heating time is set to, for example,
Even if the time is set twice a day for 6 seconds each time, the effect is significant.For example, the period during which the liquefied helium in the cooling device for superconducting magnets is emptied is approximately 10 months, depending on the capacity of the container. Ta.

As is well known, when liquefied helium is depleted during energization of a superconducting magnet, the superconducting magnet current rapidly decays. - Once the superconducting magnet has stopped, it takes a lot of effort to readjust the magnetic properties before replenishing it with liquefied helium and energizing it again, so it is necessary to replenish the liquefied helium after energizing it so that it does not run out. Since the amount of work required for this replenishment is quite large, it is desirable to lengthen the replenishment period by 8, and at the same time make the above 10 months into a neat period such as 12 months, ie, one year. This is because if it is one year, replenishment can be done on a fixed day every year, which makes it easier to manage schedules and prevents forgetting to replenish.

Furthermore, since the amount of liquefied helium evaporated by the heater 3 increases at an accelerated rate as the remaining amount of liquefied helium decreases, there is a risk that the liquefied helium will be depleted without being noticed at the final stage. Therefore, it is necessary to reliably notify when it is time to replenish liquefied helium.

It is an object of the present invention to omit a heating device such as the heater 3 for detecting the liquid level of the liquefied helium, or to significantly reduce the heating frequency thereof, thereby extending the replenishment period of the liquefied helium, and further ensuring the timing of replenishment. An object of the present invention is to provide a refrigerant remaining amount monitoring device that can notify the user of the remaining amount of refrigerant.

[Means for Solving the Problems] In order to solve the above problems, the present invention detects and integrates the flow rate of the refrigerant gas exhausted by the heat insulating container to calculate the consumed amount or remaining amount of the liquefied refrigerant. and display this.

Further, the time-dependent change characteristic of the predicted value of the remaining amount of liquefied refrigerant is stored, and the predicted value of the remaining amount of liquefied refrigerant is read by a timer signal from the time when a predetermined amount of liquefied refrigerant is filled into the insulated container. Make it visible.

Further, an alarm is generated by a signal obtained by comparing a liquefied refrigerant remaining amount calculated from the integrated flow rate value of the refrigerant gas exhausted by the heat insulating container with a predicted liquefied refrigerant remaining amount in the storage device. Make it.

Furthermore, a liquid level sensor is inserted into the heat insulating container to detect the liquid level value of the liquefied refrigerant, and thereby the liquefied refrigerant remaining amount value calculated from the integrated flow rate value of the refrigerant gas and the liquefied refrigerant in the storage device. The remaining amount predicted value etc. will be corrected.

Further, an arithmetic formula or a calculation table for calculating the consumption amount or remaining amount of the liquefied refrigerant from the integrated flow rate value of the refrigerant gas is stored, and further, the arithmetic formula or calculation table is stored based on the detected value of the liquid level sensor. Modify the table to remember the results.

Further, the limit value of the remaining amount of the liquefied refrigerant is stored, and this is compared with the remaining amount of the refrigerant and the predicted value to generate an alarm.

[Function] The refrigerant remaining amount monitoring device of the present invention configured as described above calculates the consumption amount or remaining amount of the liquefied refrigerant from the flow rate of the refrigerant gas exhausted by the heat insulating container, and uses the conventional liquid level sensor. Omit or significantly reduce the frequency of heating.

Further, the liquefied refrigerant remaining amount value is read and displayed based on the temporal change characteristics of the liquefied refrigerant remaining amount predicted value.

Further, the liquefied refrigerant remaining amount value calculated from the integrated flow rate value of the refrigerant gas is compared with the liquefied refrigerant remaining amount predicted value, and if the difference exceeds a predetermined value, an alarm is generated.

Further, a conventional liquid level sensor is used in combination, and the liquefied refrigerant remaining amount value calculated from the flow rate integrated value of the refrigerant gas and the liquefied refrigerant remaining amount predicted value are corrected based on the liquid level value.

At the same time, based on the liquid level value detected by the liquid level sensor, the calculation formula for calculating the remaining amount of liquefied refrigerant from the integrated value of the refrigerant gas flow rate and the temporal change characteristics of the predicted value of the remaining amount of liquefied refrigerant are corrected and stored. Do it like this.

Furthermore, - each of the above-mentioned liquefied refrigerant remaining amount values is compared with its permissible limit value, and if this exceeds a predetermined range, an alarm is generated.

[Embodiment] FIG. 1 is a diagram showing an embodiment of a superconducting magnet cooling device equipped with a refrigerant remaining amount monitoring device according to the present invention.

In FIG. 1, 100 is a superconducting magnet section that houses a superconducting magnet and its cooling device, and its interior has a cross-sectional structure as shown in FIG. 4.

The structure shown in FIG. 4 has a donut shape as a whole, and first and second helium containers 91 and 92 are provided to surround the donut-shaped superconducting coil 8, and a nitrogen container 10 surrounds the outside of the helium container 92. is housed in the main body container 11.

Each of the containers described above has a heat insulating structure, and liquefied helium is filled into the first helium container 91 from the liquefied helium filling port 5, and liquefied nitrogen is filled into the nitrogen container 10 from the liquefied nitrogen filling lower.

In the conventional device, the helium liquid level was measured by a liquid level sensor shown in FIG. 2 inserted into the first helium container 91 from the liquefied helium filling port 5.

In contrast, in the present invention, the amount of helium gas coming out of the helium evaporation port 6 is measured to calculate the amount of liquefied helium consumed, and the liquid level sensor is necessary for auxiliary purposes such as calibration and confirmation. Please use it accordingly.

As shown in FIG.
/D converter 13 converts it into a digital signal and outputs CPt.
J (central processing unit) 14.

The CPtJ 14 integrates the helium gas flow rate signal and stores the result in the storage device 15.

Further, the storage device 15 stores a function that gives a liquid level value of liquefied helium corresponding to the integrated value of the helium gas as shown in FIG. Is displayed.

The storage device 15 also stores a limit value for the remaining amount of liquefied helium, and an alarm is generated when the remaining amount falls below this limit value. Then, the operator replenishes liquefied helium in response to the display on the monitor 16 or the above-mentioned alarm. Note that the function stored in the storage device 15 may be a function table other than an arithmetic expression.

Since the function shown in Figure S is a standard one, there will be an error between the liquefied helium level determined from this and the actual level. This error can be corrected by the liquid level sensor shown in FIG. 2 inserted through the liquefied helium filling port S. That is, when the integrated value of helium gas reaches a predetermined value, CPt, T14 issues a command to the refrigerant monitoring device 17 including the constant current power supply 1 and voltmeter shown in FIG. The liquid level sensor is operated to measure the liquid level of liquefied helium, the measurement result is digitized by the A/D converter 13, and the CPU performs calculations to correct the slope of the function shown in FIG. This corrected function is stored in the storage device 15 and used for subsequent calculation of the helium liquid level. The measurement by the liquid level sensor may be performed periodically.

In principle, it is sufficient to perform the above correction once during the time when liquefied helium is consumed, so that the amount of liquefied helium consumed due to heating of the liquid level sensor is negligible compared to conventional devices. Even when this measurement is performed periodically (for example, once a month), compared to conventional equipment,
The frequency of heating the liquid level sensor can be significantly reduced, and as a result, the amount of liquefied helium consumed by heating the liquid level sensor can be reduced to a negligible level.

Furthermore, if the limit value of the remaining amount of liquefied helium is set with a margin, even if there is a slight error in calculating the liquid level according to Fig. 5, the above-mentioned alarm will be issued before the liquefied helium is depleted. Therefore, the liquid level sensor can be omitted.

The solid line in FIG. 6 is a characteristic line showing the remaining amount of liquefied helium in the device of the present invention, and the dotted line is a characteristic line showing the remaining amount of liquefied helium in the device of the present invention.
This is the same characteristic line when the liquid level sensor shown in the figure is heated twice a day for 6 seconds each time.

From this, the consumption period of liquefied helium is approximately 10 years with conventional equipment.
It can be seen that while the period of time for the device of the present invention is approximately 12 months. Therefore, the liquefied helium filling period can be set to one year, and the filling can be done on a fixed day every year. Note that although FIG. 6 shows a case where the amount of liquefied helium filled is 80 liters, if this amount is increased, the filling period of one year can be set with plenty of time.

Next, other embodiments of the present invention will be described. As mentioned above, when the consumption of liquefied helium due to heating of the liquid level sensor becomes negligible, the remaining amount characteristic line of liquefied helium shown by the solid line in Figure 6 becomes approximately linear, and its variation decreases. .

Therefore, after filling the tank with liquefied helium to a predetermined amount, the timer device is activated to periodically read out and display the remaining amount of liquefied helium as shown by the solid line in Figure 6. It is also possible to issue an alarm.

In this case, the liquefied helium remaining amount characteristic curve shown by the solid line in FIG. 6 is stored in the storage device 15 shown in FIG. It is displayed on the monitor 16 or the above-mentioned alarm is generated. Therefore, detection of the amount of helium evaporation using the electric flowmeter 12 becomes unnecessary. Furthermore, the liquefied helium remaining amount characteristic shown by the solid line in FIG. 6 can also be calibrated using a liquid level sensor.

However, if the electric flow meter 12 is used to detect the amount of helium evaporation, an abnormality detection function as described below can also be provided.

For example, if a vacuum leak occurs in the first helium container 91 and its piping system, the actual remaining amount of liquefied helium will be far from the characteristics shown by the solid line in FIG.
The remaining amount of helium is calculated from the amount of helium evaporated in the path of the /D converter 13 and the CPU 14, and this is compared with the characteristics shown by the solid line in Figure 6. If the difference between the two exceeds a predetermined value, an alarm is issued. Let it happen. This alarm allows the operator to inspect the equipment and restore it to normal condition.

Although the above embodiments of the present invention have been explained with a focus on detecting the remaining amount of helium shown in FIG. 4, the present invention can also be applied to detecting the amount of liquefied nitrogen consumed, etc. to obtain similar effects. can.

[Effects of the Invention] According to the present invention, since the consumption amount or remaining amount of the liquefied refrigerant is calculated from the flow rate of the refrigerant gas exhausted by the heat insulating container, the conventional liquid level sensor can be omitted or its heating frequency can be reduced. This can significantly reduce the amount of liquefied refrigerant consumed.

In addition, the remaining amount of refrigerant can be calculated from the predicted aging characteristics of the remaining amount of liquefied refrigerant, and the conventional liquid level sensor can be omitted or its heating frequency can be significantly reduced, thereby reducing the amount of liquefied refrigerant consumed. can be reduced.

Furthermore, by comparing the predicted change characteristics of the remaining amount of liquefied refrigerant with the remaining amount of liquefied refrigerant calculated from the flow rate of the refrigerant gas, vacuum leaks and other abnormal situations can be detected and an alarm can be issued. .

Furthermore, the remaining amount of liquefied refrigerant is displayed 1. Moreover, when this becomes less than a predetermined amount, an alarm, q, can be generated to prevent the depletion of the liquefied refrigerant.

Furthermore, by using a conventional liquid level sensor in combination, the remaining amount of liquefied refrigerant can be corrected to a correct value.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of a liquid level detection device according to the present invention, FIG. 2 is a circuit diagram of a conventional liquid level sensor, and FIG. 3 is a diagram showing the amount of helium evaporated by a conventional liquid level sensor. FIG. 4 is a cross-sectional view of the superconducting magnet according to the present invention, FIG. 5 is a diagram showing the remaining amount of liquefied helium used in the present invention, and FIG. FIG. 1... constant current power supply, 2... superconducting wire, 3... heater, 4... voltmeter, 5... liquefied helium filling port, 6
... Helium evaporation port, 7... Liquid nitrogen filling port, 8.
...Superconducting coil, 91...First helium container, 92
...Second helium container, 10...Nitrogen container, 11.
...Main container, 12...Electric flow meter, 13...A/
D converter, 14... CPU, 15... Storage device, 6... Monitor, 17... Refrigerant monitoring device, 100... Superconducting magnet section.

Claims (1)

[Scope of Claims] 1. A cooling device that cools the inside of the insulating container using the latent heat of vaporization of a liquefied refrigerant filled in the insulating container, comprising: a gas flow rate measuring device that detects the flow rate of the refrigerant gas exhausted from the insulating container; , a refrigerant residue comprising: a calculation device that calculates the remaining amount of the liquefied refrigerant by integrating the flow rate of the refrigerant gas detected by the gas flow rate measuring device; and a display device for the remaining amount of the liquefied refrigerant. Quantity monitoring device. 2. A cooling device that cools the inside of the heat insulating container using the latent heat of vaporization of the liquefied refrigerant filled in the heat insulating container, comprising a timer device and a storage device that stores at least the temporal change characteristics of the remaining amount of the liquefied refrigerant; Remaining refrigerant amount monitoring characterized in that the timer device is activated when a predetermined amount of liquefied refrigerant is filled into the container, and the liquefied refrigerant remaining amount value is read out and displayed based on the time signal of the timer device. Device. 3. In a cooling device that cools the inside of the heat insulating container using latent heat of vaporization of a liquefied refrigerant filled in the heat insulating container, a gas flow rate measuring device for detecting the flow rate of the refrigerant gas exhausted by the heat insulating container, and the gas flow rate measuring device a calculation device that calculates the remaining amount of the liquefied refrigerant by integrating the flow rate of the refrigerant gas detected by the controller, a display device for the remaining amount of the liquefied refrigerant, a timer device, and at least a predicted value of the remaining amount of the liquefied refrigerant over time. A storage device for storing characteristics and an alarm device are provided, and the remaining amount of the liquefied refrigerant in the storage device is predicted based on a time signal from the timer device that is activated when a predetermined amount of liquefied refrigerant is filled into the insulated container. A refrigerant remaining amount monitoring device comprising means for reading a value and comparing it with the remaining amount of the liquefied refrigerant calculated by the arithmetic unit, and driving the alarm device based on the output of the comparing means. . 4. Any one of claims 1 to 3, further comprising a liquid level sensor inserted into the heat insulating container, wherein the liquid level value of the liquefied refrigerant detected by the liquid level sensor is calculated from the refrigerant gas flow rate. A refrigerant remaining amount monitoring device, characterized in that the amount of consumption or remaining amount of liquefied refrigerant and/or the time-varying characteristic value of the predicted value of the remaining amount of liquefied refrigerant stored in the storage device is corrected. 5. Claim 4, further comprising a storage device that stores an arithmetic expression or a calculation table for calculating the consumed amount or remaining amount of the liquefied refrigerant from the integrated flow rate value of the refrigerant gas, A refrigerant remaining amount monitoring device characterized in that the arithmetic expression or arithmetic table is corrected based on the liquid level value of the liquefied refrigerant detected by a surface sensor, and the result is stored in the storage device.