JPH05223378A - Helium liquefying/freezing apparatus and operation thereof - Google Patents

Abstract

PURPOSE:To provide a helium liquefying/freezing apparatus and a method of operation of the same which demonstrates a great difference between freezing capability required in stationary operation and maximum freezing capability required in operation, and which is suitable for cooling an article to be cooled in which the time the maximum freezing capability is needed is shorter than the time of the stationary operation. CONSTITUTION:In a helium liquefying/freezing apparatus, a gas holder 26 is connected to an article cooling part 25 via a valve 33 which is opened when pressure in a cooling part 25 is raised. There is further provided means for forcing helium gas stored in the gas holder 26 to join with circulated helium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helium liquefying refrigerating apparatus and an operating method thereof, and more particularly to a helium liquefying refrigerating apparatus suitable for cooling a cooled object whose refrigeration load fluctuates greatly and an operating method thereof.

[0002]

2. Description of the Related Art A helium liquefaction refrigerating apparatus for generating supercritical helium having a good thermal conductivity has been conventionally used as a means for cooling an object to be cooled such as a superconducting magnet to an extremely low temperature of several K. As shown in FIG. 2, this helium liquefaction refrigeration system generally includes a circulation compressor 1, a heat exchanger group including a plurality of heat exchangers 2, a JT valve 3, a liquid helium storage tank 4, and an expansion turbine (not shown). The helium liquefier 5 is composed of the helium liquefier 5 and the cooled member cooling section 6 to which the liquid helium in the liquid helium storage tank 4 is supplied.

In the helium liquefier 5, circulation amount control valves 8a and 9a are provided on the discharge side and the suction side of the circulation compressor 1, respectively, as paths for keeping the amount of helium circulating in the system constant. A pressure regulator 1 for measuring the discharge pressure of the circulation compressor 1 and a buffer tank 10 connected through the channels 8 and 9 that are provided to open and close the circulation amount regulating valves 8a and 9a.
1 is provided, and as a path for keeping the suction pressure of the circulation compressor 1 constant, a path 12 that connects the discharge side and the suction side of the circulation compressor 1 via a bypass valve 12a,
The bypass valve 12 is measured by measuring the suction pressure of the circulation compressor 1.
A pressure controller 13 for adjusting the opening degree of a is provided. Further, the liquid helium storage tank 4 is provided with a heater 14 and a liquid level controller 15 for keeping the amount of liquid helium in the storage tank 4 constant.

[0004]

The refrigerating capacity of the helium liquefaction refrigerating apparatus having such a structure is usually designed according to the maximum refrigerating load required by the object to be cooled. For example, SMES (Super conductin) applied to electric power storage, etc.
g magnet energy strage), etc., is always maintained in a superconducting state, but changes in the magnetic field occur in a short time during operation, so AC loss occurs and a large refrigeration load is required. In such an SMES, for example, the refrigerating capacity required in the steady state is 100 W, and it is possible that the required refrigerating capacity at the peak time reaches 2000 W.
At this time, the refrigerating capacity required for the helium liquefaction refrigerating apparatus is 2100W. Therefore, during the steady operation, the refrigerating capacity of 2000 W is wasted.

That is, at the time of steady operation, the above-mentioned chilling amount corresponding to 2000 W becomes excessive, and the amount of liquid helium generated becomes excessive. Therefore, the heater 14 is installed in the liquid helium storage tank 4 and the heat input thereof Liquid helium must be evaporated to generate a predetermined amount of return gas to maintain a steady state, resulting in waste of power.

[0006] In particular, the period in which a large heat load is required due to the AC loss as described above is not so long, and it may be practical, for example, to think about 20 seconds a day. In such a case, Most of the operating time of a day is spent to generate unnecessary cold.

Therefore, according to the present invention, the object to be cooled has a large difference between the refrigerating capacity required during steady operation and the maximum refrigerating capacity required during operation, and the time required for the maximum refrigerating capacity is shorter than the steady operation time. It is an object of the present invention to provide a helium liquefaction refrigerating apparatus suitable for cooling air and its operating method.

[0008]

In order to achieve the above object, a helium liquefaction refrigerating apparatus of the present invention comprises a compressor for circulating helium, a heat exchanger for cooling compressed helium by heat exchange with return helium, Helium after cooling J
JT valve for T expansion, liquid helium storage tank for storing helium liquefied by JT expansion, cooled part to be cooled to which liquid helium in the liquid helium storage tank is supplied, helium gas vaporized in the cooling part, and liquid helium storage tank In a helium liquefaction refrigerating apparatus having a path for circulating the helium gas in the helium as return helium to the compressor through the heat exchanger, in the cooled part to be cooled, when the pressure in the cooling part rises. It is characterized in that a gas holder is connected in series through a valve that opens, and a means for merging the helium gas stored in the gas holder with the circulating helium is provided.

Further, in the device of the present invention, in the above-mentioned structure, a buffer tank is connected to the suction side and the discharge side of the compressor through paths having circulation amount control valves, respectively, and both circulation amount control valves are connected. It is characterized in that a pressure regulator that opens and closes according to the discharge pressure of the compressor is provided, and the means for merging the helium gas stored in the gas holder with the circulating helium is compressed by the compressor. The ejector is configured to suck the helium gas in the gas holder by using the helium gas as a driving source, and the path for circulating the helium gas after the ejector is led to the suction side of the compressor.

In addition, as a control means for performing a stable operation in the helium liquefaction refrigerating apparatus configured as described above, a path connecting the discharge side and the suction side of the compressor through a bypass valve, and the bypass valve. A pressure regulator that opens and closes according to the suction pressure of the compressor, a pressure regulator that opens and closes a valve provided between the cooling unit and the gas holder according to the pressure of the cooling unit, and the pressure inside the gas holder. According to the pressure controller for adjusting the flow rate of the compressed helium gas as a drive source of the ejector, and the flow rate of the helium gas sucked from the gas holder to the ejector according to the amount of helium gas in the gas holder. And a liquid for adjusting the amount of liquid helium by operating a heater provided in the liquid helium storage tank according to the amount of liquid helium in the storage tank. It is characterized by comprising a control.

Further, in the method for operating the helium liquefaction refrigerating apparatus of the present invention, compressed helium is cooled by heat exchange with return helium, liquefied by JT expansion and stored in the liquid helium storage tank, and stored in the liquid helium storage tank. In a method of operating a helium liquefaction refrigerating apparatus for deriving a predetermined amount of liquid helium as a cooling source for an object to be cooled, heating the helium after cooling the object to be cooled, and compressing and circulating again. When the cooling load increases, the amount of liquid helium discharged from the liquid helium storage tank is increased, and the helium after cooling the cooled object corresponding to the increased amount is temporarily stored in a gas holder, and then merged with the circulating helium. Is characterized by.

[0012]

[Operation] If the cooling load of the cooled object increases and the amount of helium vaporized in the cooled part of the cooled object increases, and the pressure of the cooled part of the cooled object rises due to the increase in the evaporated amount, it is connected to the gas holder. The valve opens to let the helium gas, which is in excess of the normal return gas, flow out to the gas holder, and the liquid helium in the liquid helium storage tank is supplied to the cooled part of the cooled object to keep the cooled object at a predetermined temperature. To do.

As described above, a large amount of helium gas in the cooled portion of the object to be cooled, which is generated in a large amount as compared with that in the normal operation, is stored in the gas holder to cope with a large cooling load without increasing the amount of helium in the circulation system. can do. Therefore, by using a helium refrigerator having a surplus refrigerating capacity slightly larger than the refrigerating capacity (helium liquefaction amount) required during normal operation, the amount of liquid helium required at the maximum load due to the surplus refrigerating capacity is changed to liquid helium. By storing the liquid helium in the storage tank at the maximum load, the liquid helium in the storage tank can be supplied to the cooling target cooling unit to keep the cooling target at a predetermined temperature.

The surplus refrigerating capacity is set according to the ratio of the high load operation to the normal operation and the required refrigerating capacity, but the difference from the required capacity at the maximum load operation is large and the maximum load operating time is short. In this case, it suffices to add a slightly larger refrigerating capacity than that required for normal operation,
The refrigerating capacity can be made smaller than that of a helium refrigerator designed according to the maximum refrigerating load.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below based on an embodiment shown in FIG.

The helium liquefaction refrigerating apparatus shown in FIG. 1 has a circulation compressor 21, a heat exchanger group 22 including a plurality of heat exchangers, a JT valve 23, as in the conventional apparatus shown in FIG.
Connected to the helium liquefier portion composed of the liquid helium storage tank 24 and an expansion turbine (not shown), the cooled body cooling section 25 to which the liquid helium in the liquid helium storage tank 24 is supplied, and the cooled body cooling section 25. The gas holder 26, the recovery path 27 for recovering the helium gas in the gas holder 26 to the circulation system of the helium liquefier, and the helium gas and the liquid helium storage tank 24 which are vaporized in the cooling target cooling part 25 during the steady operation Helium gas circulating compressor 2
1, the paths 28, 29, etc. for returning to the suction side.

In the helium liquefier portion, as in the conventional case, the helium gas compressed by the circulation compressor 21 is heat-exchanged with the return gas in the heat exchanger group 22 to be cooled, and JT expanded by the JT valve 23 to be liquid. Liquid helium is generated in the helium storage tank 24, and the helium gas in the liquid helium storage tank 24 is led to the path 29 as a low-temperature return gas and passes through the heat exchanger group 22 to remove the compressed helium gas. After cooling, it is sucked into the circulation compressor 21 and compressed again.

Further, the liquid helium supplied as a cooling source to the cooled body cooling part 25 is vaporized into a helium gas by cooling the cooled body, and merges with the return gas from the path 28 from the path 28. And is sucked into the circulation compressor 21.

On the other hand, in the path 31 connecting the cooled part 25 to be cooled and the gas holder 26, the cooled part 2 to be cooled is provided.
A valve 33 that is opened and closed by a pressure regulator 32 that measures the pressure in the valve 5 and a heater 34 that heats the helium gas toward the gas holder 26 are provided.

The pressure adjuster 32 causes the valve 33 to operate when the cooling load of the object to be cooled increases and the amount of helium vaporized increases, and the pressure inside the object to be cooled 25 rises above a set pressure. It is opened, so that it operates so that the helium gas in the cooled part 25 to be cooled flows into the gas holder 26. Further, when the helium gas flowing into the gas holder 26 is kept at a low temperature, the heater 34 needs to provide a heat insulating structure to the gas holder and take into consideration heat expansion and contraction. This is for heating to about room temperature so that a general gas holder can be used. It should be noted that the heater 34 may be of the air temperature type, which does not require operating cost.

The type of the gas holder 26 is not particularly limited, but it is necessary to select one that does not mix water, nitrogen, oxygen, etc. with the helium gas stored therein, and to be cooled. In order for the helium gas in the cooling unit 25 to smoothly flow in, it is necessary to have a structure capable of keeping the internal pressure lower than the pressure in the cooling target member cooling unit 25. As such a gas holder, for example, a type in which a partition plate that can be vertically moved in an airtight manner is provided in a tank and the partition plate is suspended by a balancer can be mentioned.

The recovery passage 27 is provided with the circulation compressor 2
1, a recovery circulation path 41 extending from the discharge side to the suction side, and an ejector 42 and a flow rate control valve 4 provided in the circulation path 41.
3, a suction passage 44 that connects the gas holder 26 and the suction side of the ejector 42, and a flow rate control valve 45 provided in the suction passage 44.

That is, the recovery passage 27 is provided with the circulation compressor 2
The ejector 42 driven by the high-pressure helium gas discharged from No. 1 sucks the helium gas in the gas holder 26 and collects it on the suction side of the circulation compressor 21. The gas amount detector 46 provided in the gas holder 26 and the pressure adjuster 47 provided in the suction passage 44 adjust the opening degree of the flow rate adjusting valves 43 and 45.

Further, according to the present invention, when the pressure in the cooled part 25 to be cooled rises, a part of the vaporized helium gas is temporarily stored in the gas holder 26. When the amount of helium circulating in the machine part decreases, while the helium gas in the gas holder 26 is recovered by the recovery path 27, the amount of circulating helium increases.

If the amount of circulating helium fluctuates greatly as described above, stable operation of the device may be hindered.
The circulation amount control valve 5 is provided on each of the discharge side and the suction side of the circulation compressor 211 as a path for keeping the circulation helium amount substantially constant.
A buffer tank 53 connected via paths 51 and 52 having 1a and 52a, and a pressure controller 54 that measures the discharge pressure of the circulation compressor 21 to open and close the circulation amount control valves 51a and 52a are provided. Further, in order to keep the suction pressure of the circulation compressor 21 substantially constant, a path 55 connecting the discharge side and the suction side of the circulation compressor 21 via a bypass valve 55a.
And a pressure adjuster 56 for adjusting the opening of the bypass valve 55a by measuring the suction pressure of the circulation compressor 21.

Furthermore, in the present invention, the required amount of liquid nitrogen required at the time of maximum load is stored in the liquid helium storage tank 24. However, in order to keep the maximum level of the stored amount substantially constant,
In the liquid helium storage tank 24, a liquid level controller 57 for measuring the amount of liquid helium in the storage tank 24, and the liquid level controller 57.
And a heater 58 operated by

Next, in the helium liquefaction refrigerating apparatus having the above-mentioned structure, the refrigerating capacity required in the steady state is 100 as in the above.
A description will be given of an example of cooling an object to be cooled, which has a required refrigerating capacity of 2000 W for a peak time of 2000 W and the time is about 20 seconds per day.

First, since the amount of liquid helium vaporized by cooling the object to be cooled at the peak is about 100 g / sec, it becomes about 2 kg in 20 seconds, which is 16 liters of liquid helium and 7. Equivalent to 2 m ³ . Therefore, by using the gas holder 26 having a capacity of about 10 m ³ , the helium gas generated at the peak can be completely taken in.

At the peak, the liquid helium storage tank 2
The liquid helium of 4 liters is supplied from 4 to the cooled body cooling part 25, and the liquid helium in the liquid helium storage tank 24 is reduced. Therefore, it is necessary to replenish the reduced amount of 16 liters of liquid helium, but this replenishment of liquid helium may be performed during a steady operation other than the peak time. This steady operation time is 23 hours 59 minutes 40 seconds after subtracting the above peak time from one day, but even if it is possible to complete replenishment in 12 hours with a margin, 1.3 liters per hour It would be good if there was an extra liquefaction capacity. Therefore, in the liquefaction capacity required during normal operation,
It is sufficient to add a liquefaction capacity of 1.3 liters / hour. In this case, a liquefaction capacity of about 110 W is sufficient.

That is, 16 liters of liquid helium required at the peak time is 1.
The liquid helium storage tank 24 is replenished at a rate of 3 liters, and the necessary amount is replenished in about 12 hours.
When a predetermined amount of liquid helium is stored in the liquid helium storage tank 24 and the liquid level height becomes equal to or higher than a set level,
The heater 58 is operated by the liquid level controller 57 to evaporate the excess amount and keep the amount of liquid helium substantially constant.
Keep the circulating helium volume constant.

The helium gas of 7.2 m ³ vaporized in the cooled portion 25 of the object to be cooled at the peak time causes the valve 33 opened by the pressure controller 32 which detects the pressure increase in the cooled portion 25 of the object to be cooled. As it is, it is heated by the heater 34 and flows into the gas holder 26. At the same time, in the helium liquefier portion, the circulating helium amount is reduced by 7.2 m ^{3 and} the suction pressure of the circulating compressor 21 is lowered, so that the pressure regulator 56 operates and the bypass valve 55a is opened. Open,
Since the suction pressure is maintained above the set pressure and the discharge pressure decreases, the pressure regulator 54 operates to open the circulation amount regulation valve 52a and introduce the helium gas in the buffer tank 53 into the circulation system. To do.

When the amount of gas in the gas holder 26 exceeds the set value, the gas amount detector 46 opens the flow rate adjusting valve 45 and increases the pressure due to the inflow of helium gas from the cooled part 25 to be cooled. The pressure gauge 47 detects and opens the flow control valve 43. As a result, the high-pressure helium gas compressed by the circulation compressor 21 is introduced into the recovery passage 27, and the helium gas in the gas holder 26 is sucked by the ejector 42 using the gas as a driving source to suck the circulation compressor 21. Be recovered to the side.

Further, the pressure regulator 54 detects the pressure increase accompanying the increase in the amount of helium in the circulation system due to the recovery of the helium gas from the gas holder 26, and opens the circulation amount control valve 51a to open the circulation system. The excess helium gas is introduced into the buffer tank 53.

In the initial stage of the steady operation after the peak, the liquid helium is replenished in the liquid helium storage tank 24 as described above, so that the heater 58 does not operate and the liquid level is adjusted when the set amount is reached. The vessel 57 operates the heater 58 to vaporize the replenishment amount, that is, liquid helium at a rate of 1.3 liters per hour.

As described above, the refrigerating capacity, which was conventionally required to be 2100 W, can be increased to about 110 W, and the heat input amount by the heater 58 can be significantly reduced. Can be significantly reduced.

Furthermore, since the helium gas stored in the gas holder 26 can be recovered by using the ejector 42, there is almost no possibility of impurities being mixed in, and almost no power is required, so that low-cost operation is possible. However, since the suction side pressure of the circulation compressor 21 is low, it is possible to return the helium gas from the gas holder 26 to the circulation compressor 21 suction side with a simple compressor.

The configuration of each part in the helium liquefier part, for example, the number of expansion turbines for generating cold, their capacity, temperature range, etc. are set appropriately according to the required cold amount, and each heat is used. The exchanger can also be appropriately divided according to the installation conditions of the expansion turbine.

[0038]

As described above, according to the present invention,
The refrigerating capacity of the helium liquefying refrigerating device for cooling the cooled object whose refrigerating load fluctuates greatly can be made significantly smaller than the conventional one, and the facility cost and the operating cost can be greatly reduced.

Therefore, it is suitable as an apparatus for cooling a cooled object such as a superconducting magnet to an extremely low temperature, and the cost required for these experiments can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a helium liquefaction refrigeration system of the present invention.

FIG. 2 is a system diagram showing an example of a conventional helium liquefaction refrigeration system.

[Explanation of symbols]

21 ... Circulation compressor 22 ... Heat exchanger group 23 ... JT
Valve 24 ... Liquid helium storage tank 25 ... Cooling target cooling part 26 ... Gas holder 27 ... Recovery path 32, 47, 54, 56 ... Pressure controller 42 ... Ejector 46 ... Gas amount detector 53 ... Buffer tank 57 ... Liquid level adjustment Container 58 ... Heater

Claims (5)

[Claims] 1. A compressor for circulating helium, a heat exchanger for cooling compressed helium by heat exchange with return helium, a JT valve for JT expanding helium after cooling, and a JT.
Liquid helium storage tank for storing helium liquefied by expansion, cooled part to be cooled to which liquid helium in the liquid helium storage tank is supplied, helium gas vaporized in the cooling part and helium gas returned in the liquid helium storage tank As a helium liquefaction refrigerating apparatus having a path to circulate to the compressor via the heat exchanger, the cooled body to be cooled is provided with a valve that opens when the pressure in the cooling section rises. A helium liquefaction refrigerating apparatus, characterized in that a gas holder is provided in series and a means for merging the helium gas stored in the gas holder with the circulating helium is provided. 2. A buffer tank is connected to the suction side and the discharge side of the compressor through paths each having a circulation amount control valve, and both circulation amount control valves are opened / closed according to the discharge pressure of the compressor. The helium liquefaction refrigerating apparatus according to claim 1, further comprising a pressure controller for controlling the liquefaction and refrigeration. 3. The ejector for sucking the helium gas in the gas holder using the helium gas compressed by the compressor as a driving source, the means for joining the helium gas stored in the gas holder with the circulating helium. The helium liquefaction refrigerating apparatus according to claim 1, wherein the helium liquefied refrigerating apparatus is constituted by a path that circulates the helium gas after the ejection of the ejector to the suction side of the compressor. 4. A path connecting a discharge side and a suction side of the compressor via a bypass valve, a pressure controller for opening and closing the bypass valve according to suction pressure of the compressor, the cooling unit and a gas holder. And a pressure regulator that opens and closes a valve provided between and according to the pressure of the cooling unit, and a pressure regulator that adjusts the flow rate of the compressed helium gas that is the drive source of the ejector according to the pressure in the gas holder. According to the amount of liquid helium in the liquid helium storage tank, and a gas amount controller for adjusting the flow rate of the helium gas sucked from the gas holder to the ejector according to the amount of helium gas in the gas holder. The helium liquefaction refrigerating apparatus according to claim 3, further comprising: a liquid amount controller that operates a heater provided in the storage tank to adjust the amount of liquid helium. 5. An object to be cooled by cooling compressed helium by heat exchange with return helium, liquefying by JT expansion and storing in a liquid helium storage tank, and deriving a predetermined amount of liquid helium in the liquid helium storage tank. In the operating method of the helium liquefaction refrigerating apparatus, which uses as a cooling source of the helium after cooling the cooled object, raises the temperature of the cooled helium, and then compresses and circulates the helium again, when the cooling load of the cooled object increases, the helium is drawn from the liquid helium storage tank A method for operating a helium liquefier refrigerating apparatus, comprising increasing the amount of liquid helium, temporarily storing the cooled helium corresponding to the increased amount in a gas holder, and then joining the helium to the circulating helium.