JPH0446350B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for controlling the operation of a helium liquefaction/refrigeration system, and more specifically, the present invention relates to a method for controlling the operation of a helium liquefaction/refrigeration system, and in particular, it is possible to control the refrigeration output even when there is a sudden change in heat load in a cryogenic environment. The present invention relates to a method for controlling the operation of a helium liquefaction/refrigeration system that can maintain stable operating conditions without causing excess or deficiency.

[Prior art] Helium (hereinafter referred to as "He") liquefaction/refrigeration equipment uses high-pressure gas compressed to approximately 15 to 20 atmospheres.
By isentropically expanding a part of the He gas in an expander, cold is generated, and using this cold, the remaining He gas is gradually heated to a predetermined low temperature (so-called inversion temperature) by heat exchange action. After pre-cooling, the He gas is passed through a Joel-Thomson (hereinafter referred to as JT) valve, and the He gas is liquefied by the cooling action utilizing the JT effect, thereby achieving a liquid He temperature, that is, an extremely low temperature. If the liquid He obtained in this way is taken out as a product, it will become a liquefaction device, but on the other hand, the liquid He will be circulated in a closed circuit without being taken out, and the latent heat of the liquid He will be used to make use of the latent heat of the liquid He. If it absorbs the heat load of the object to be cooled in the load section and maintains the temperature of the environment constant, it becomes a refrigeration system. In other words, the difference between refrigeration equipment and liquefaction equipment is that in liquefaction equipment, the low-pressure side He
(Return side He) gas flow rate is high pressure side He (inlet side He)
In contrast, in a refrigeration system, the liquefied He also evaporates and returns to the low-pressure side, so the He gas flow rate on the high-pressure side and the low-pressure side becomes equal. For this reason, liquefaction equipment and refrigeration equipment differ only in the temperature distribution of the heat exchanger and expander within the equipment body, and their thermal designs are different; there is no essential difference in the structure of the equipment. . Therefore, a He refrigeration system will be described below as a representative example.

As such a He refrigerating device, for example, one having a configuration as schematically illustrated in FIG. 3 is known. That is, in FIG. 3, the refrigeration system 1 includes heat exchangers 5a to 5.
e, a device body 2 in which expanders 7a, 7b, JT valve 6, etc. are built-in, a compressor 3 and a purifier 4 connected to the inlet side of the device body 2, and a cryogenic environment connected to the outlet side of the device body 2; It consists of parts 10 and the like. After the He gas is pressurized by the compressor 3, it passes through the first to fifth heat exchangers 5a to 5e (hereinafter, this passage route is referred to as the "high pressure side route") and is cooled while undergoing heat exchange. , further adiabatically expands to near atmospheric pressure in the JT valve 6, partially liquefies He into a gas-liquid mixture state, that is, He mist (hereinafter simply referred to as "liquid He"), and then supplies He mist. tube 8
into the cryogenic environment section 10, and the environment section 10
The atmosphere is cooled to an extremely low temperature. A typical example of a specific use of the cryogenic environment section 10 is a cryogenic fatigue testing device for examining the mechanical properties of metal materials at cryogenic temperatures.
In this case, a condenser may be provided to re-condense the liquid He in the test device if it evaporates.

Now, the He gas that has been vaporized by taking away the heat of the object to be cooled existing in the cryogenic environment section 10 is returned to the main body of the apparatus.
The He gas passes through the heat exchangers 5a to 5e in the opposite direction (hereinafter, this passage path is referred to as the "low pressure side path"), and after cooling the He flowing through the counterflow high pressure side path, it becomes He gas at normal temperature and pressure. Return to compressor 3. By circulating He through this path, the cryogenic environment section 10 is continuously kept at a cryogenic temperature. In conventional He refrigerators like this, the throughput of the expander is manually adjusted and the amount of cold generated by the expander is controlled, so if there is a change in load or at startup, etc. , it was necessary to adjust the flow rate. In particular, multiple cryogenic environment departments (hereinafter sometimes referred to as users) for one He refrigerator
In a refrigeration system that connects multiple units in parallel (hereinafter referred to as a multi-user system), the load fluctuates widely, and if the expander throughput is not appropriately adjusted, energy may be wasted due to excessive cooling. be. In addition, when a user stops cooling one (or two or more) units during cooling operation or starts cooling again, the user
The operating conditions of a He refrigeration system vary, and conventional manual operation requires a high level of skill to maintain a constant temperature condition for the user during cooling operation.

Focusing on these circumstances, the present invention maintains the user's environmental temperature constant while suppressing the generation of excessive cold in the expander, and furthermore, in a multi-user system, the cooling of one (or two or more) users is stopped. As a result of conducting various researches in an attempt to provide a He liquefaction/refrigeration system that can properly perform recooling without adversely affecting the operating conditions of other users, the technology disclosed in Japanese Patent Application No. 169998/1983 was developed. developed.

That is, FIG. 4 is a schematic overall view showing the He refrigerating apparatus according to the disclosed invention, in which 13 indicates a temperature control controller, 14 indicates a pressure control controller, 15 indicates a temperature measurement point, and 16 indicates a pressure detection point.

A part of the high-pressure He gas in system _L2 on the He gas discharge side of the compressor 3 is cooled by the expanders 7a and 7b, and the remaining He gas cooled by this cold is
It passes through the JT valve 6 and generates He mist due to the JT effect, thereby cooling the atmosphere in the cryogenic environment section 10 to a cryogenic temperature. Here, He gas G ₁ discharged from the expander 7b on the low temperature side and return gas from the cryogenic environment section 10
Temperature measurement point 15 is installed downstream from the confluence with G ₂ ,
The temperature value at the temperature measurement point 15 is input to the temperature control controller 13, and the throughput of the low temperature side expander 7b is adjusted depending on the level of the temperature value. In other words, if the measured temperature value is higher than the set value, it means that the amount of cold generated by the expander 7b is insufficient, so the temperature control controller 13 sends a command to increase the output to the expander 7b and processes the expander 7b. The amount of cold generation is increased by increasing the amount of cold generated, thereby lowering the temperature at the temperature measuring point 15. On the other hand, if the measured temperature value is lower than the set value, it means that the amount of cold generated by the expander 7b is excessive.
A command to reduce the output is sent to the expander 7b to reduce the throughput of the expander 7b, thereby reducing the amount of cold generation, thereby increasing the temperature at the temperature measuring point 15. In this way, temperature measurement point 1
5 temperature is held constant. As a result, in the heat exchanger 5d, the high-pressure side He gas, which is a refrigerant, receives a stable cooling effect by the low-pressure side He gas, which is a refrigerant that has a constant set temperature, so that the temperature after heat exchange remains at a predetermined temperature. The temperature can be maintained, thereby maintaining the cryogenic environment 10 at a constant temperature regardless of fluctuations in operating conditions. The temperature measurement point 15 shall be provided between the confluence point and the inlet of the heat exchanger immediately after (including the inlet), and between the confluence point and the temperature measurement point 15, the discharge gas G ₁ and the return gas G ₂ are connected. A mixer may be provided to improve mixing.

However, if the discharge amount of the compressor 3 is constant, even if the throughput of the expander 7b is changed according to the refrigeration load.
The required power of He refrigeration equipment does not change, but the energy consumption rate decreases, especially when the refrigeration load decreases. In order to prevent this drop, in the He refrigeration system, the discharge pressure of the compressor 3 is detected at the pressure detection point 16, and the discharge amount of the compressor 3 is adjusted by the pressure controller 14 so as to keep this pressure constant. It is arranged like this. If the refrigeration load decreases as a result, if only the JT valve is throttled down, the throughput of the expander 7b will decrease in accordance with the refrigeration load, so the pressure control controller will keep the discharge pressure of the compressor 3 constant. 14
By reducing the discharge air volume due to the effect of , it is possible to prevent a decrease in the energy unit cost and perform energy-saving operation.

[Problems to be Solved by the Invention] However, the temperature at the measurement point downstream of the confluence of the He gas G ₁ fed from the low-temperature side expander and the return gas G ₂ from the cryogenic environment section is as follows. The change occurs with a slight delay after the heat load fluctuation occurs in the cryogenic environment, and with the above control method, if the heat load changes suddenly in the cryogenic environment, there will be a delay in control. Moreover, in order to maintain the cold state stably despite heat load fluctuations in the cryogenic environment section, simply controlling the throughput of the expander is insufficient; If the cold supply amount is unexpected, the cooling state of the cryogenic environment section will become unstable, and conversely, if the cold supply amount from the JT valve to the cryogenic environment section is too large, there will be excessive cooling and the purpose of energy saving will not be achieved. .

Under such circumstances, even if the heat load in the cryogenic environment section suddenly changes, the present invention can quickly and appropriately control the amount of cold generated by the refrigeration system in accordance with the sudden change. The purpose is to provide an operation control method that can stably maintain the cold in the environment.

[Means for Solving the Problems] The configuration of the operation control method of the present invention that can achieve the above objectives is obtained by isentropic expansion of helium gas, as shown in FIG. 4, for example. Helium liquefaction is a process in which helium gas at room temperature and high pressure is precooled step by step using a heat exchange action that uses cold, and then liquefied by passing it through a Joel-Thomson valve.
In a method for controlling the operation of a refrigeration equipment, a heat load fluctuation detector is provided in the cryogenic environment section, and the discharge gas of the expander installed in the high-pressure helium gas supply circuit in the helium liquefaction/refrigeration equipment and the return gas from the cryogenic environment section are A temperature measuring device is provided downstream of the confluence of the above, and the required amount of cold generation from the expander is calculated and controlled based on the heat load fluctuation of the cryogenic environment section determined by the heat load fluctuation detector. At the same time,
In addition to correcting this control based on the temperature measurement results from the temperature measuring device, the refrigerant flow rate required to stabilize the cold in the cryogenic environment is calculated based on the heat load fluctuations, and the opening degree of the Joel-Thomson valve is adjusted. The gist lies in the fact that it does.

[Function] As will be made clear in the examples below, the basic cooling control device of the present invention is similar to the technology shown in FIG. 4, but in the present invention, as in the example of FIG. The amount of cold generation (discharged gas amount) from the expander installed in the high-pressure He gas supply circuit is adjusted according to the temperature change of the return gas from the cryogenic environment section, which changes due to the heat load fluctuation in the low-temperature environment section. Instead of controlling, as an essential control element, heat load fluctuations are directly detected by a heat load fluctuation detector (for example, liquid He level, gas pressure, etc.) installed in the cryogenic environment part, and this heat load fluctuation is Based on this, the required amount of cold generation from the expander is calculated and controlled. Furthermore, the amount of refrigeration consumed in the cryogenic environment section is calculated based on the detected heat load fluctuations, and the amount of refrigerant supplied necessary to stabilize the cold state in the cryogenic environment section is determined, and the JT valve is automatically controlled appropriately. It is something to do.
That is, the present invention directly detects heat load fluctuations in the cryogenic environment to control the cooling efficiency of the cold generation device of the He liquefaction/refrigeration equipment, and also controls the amount of cold supplied to the cryogenic environment. , the fourth
Compared to the method shown in the figure, the response to changes in heat load is extremely fast, and even if there is a sudden change in heat load, there will be no delay on the He liquefaction/refrigeration equipment side. In addition, the amount of refrigeration consumed in the cryogenic environment section is immediately calculated based on the fluctuations in the heat load, and the opening of the JT valve is adjusted so that the amount of refrigerant that can stably maintain the cooling capacity is supplied to the cryogenic environment section. Since the system is configured to automatically control the temperature, there is no possibility that the cooling capacity of the cryogenic environment section will decrease, resulting in a decrease in cooling efficiency, or that there will be no loss due to excessive cooling.

Also in the present invention, a temperature measuring device is provided downstream of the confluence of the discharge gas of the expander installed in the high-pressure He gas supply circuit and the return gas from the cryogenic environment section, and the temperature measurement results are sent to the expander. However, in view of the fact that if this temperature measurement result is used as the main control element, the response to heat load fluctuations will be delayed as described above, in the present invention, the temperature measurement result is calculated from the heat load fluctuation. It is used as a confirmation element to check whether the necessary cold generation amount control value is appropriate, and by correcting the necessary cold generation amount control value, the control can be performed more accurately. There is.

In this way, it has become possible to control the operation of the He liquefaction/refrigeration equipment extremely quickly and accurately in response to changes in the heat load in the cryogenic environment.

[Example] Figure 1 is a schematic flow diagram showing an example of the present invention, and the basic configuration is the same as the example in Figure 4, so the same parts are given the same reference numerals. . In this example as well, the He gas that has been pressurized by the compressor 3 and then purified by the purifier 4 is sent from the run L ₂ to the liquefaction/refrigeration device main body 2, and sequentially passes through the heat exchangers 5a to 5e along the high-pressure side path. After being gradually cooled down, a portion of the fluid is liquefied by adiabatic expansion in the JT valve 6 and supplied to the cryogenic environment section 10. Cryogenic environment department 10
In this case, some of the liquefied He gas is vaporized under the cold load caused by, for example, a cryogenic fatigue test, and this low-pressure He gas flows again in the opposite direction through the heat exchangers 5a to 5e of the device main body 2, and is converted into a countercurrent high-pressure He gas. After cooling the He gas flowing through the side path, it returns to the compressor 3 from the line _L1 as He gas at room temperature and pressure. Here, in order to compensate for the lack of cooling in the device main body 2, a part of the He gas in the high pressure side path is bypassed and the expander 7a,
7b to the low-pressure side path, and in order to prevent the pressure drop of He gas in the high-pressure side path, the discharge pressure of the compressor 3 is detected at the pressure detection point 1.
This is similar to the prior art example shown in FIG. 4 in that the compressor is configured so that the discharge amount of the compressor can be adjusted by the pressure controller 14 so as to detect the pressure at 6 and keep the pressure constant.

In such a He liquefaction/refrigeration system, if the heat load on the cryogenic environment section 10 fluctuates, as described above, the cooling efficiency in the main body 2 of the apparatus will be insufficient or too high, and the cooling capacity in the cryogenic environment section 10 may decrease. The section 10 may become supercooled, resulting in economic loss. Therefore, in the present invention, as shown in the figure, a liquid level gauge 17 is attached to the cryogenic environment section 10 and connected to a liquid level indicating regulator 18, and fluctuations in the liquid level that occur with changes in the heat load in the cryogenic environment section 10 are provided. Detect immediately.
In this part, the return gas is adjusted to match the fluctuations in the liquid level.
Estimate the calorific value fluctuation of the gas at G ₂ and the temperature measurement point 15, calculate the processing amount (discharged gas amount) of the expander 7b according to it, and send the signal to the calculator 19,
A command to increase or decrease the throughput is issued from the computing unit 19 to the expander 7b.

In the present invention, estimation of heat load fluctuation by liquid level detection as described above, and expansion machine 7 according to the liquid level fluctuation are performed.
As long as the increase/decrease calculation and command of the processing amount b are performed properly, the temperature inside the device main body 2 can be properly controlled with only the above configuration, but in this example, the processing amount of the expander 7b is controlled more accurately. Therefore, the following correction operations are also used. That is, the cryogenic environment section 10
A temperature measuring device is installed at a temperature measuring point 15 downstream of the confluence of the return gas G ₂ from the expander _7b and _the discharge gas G ₁ from the expander 7b.
In order to keep the mixed gas temperature as constant as possible, the temperature control controller 13 calculates the throughput of the expander 7b and sends it to the computing unit 19. A device that compares and calculates the calculated value sent from the temperature control controller 13 and the calculated value sent from the liquid level control controller 18, determines the optimal throughput in the expander 7b, and instructs the expander 7b. It is.
That is, in the present invention, the control result of the expander 7b throughput calculated and instructed by the liquid level control controller 18 and the computing unit 19 is confirmed by the temperature measurement point 15 and the temperature control controller 13, and then fed back to the computing unit 19. Since the control value is corrected, the control precision can be significantly improved. Moreover, expander 7
The instructions for the required processing amount in b are given by the cryogenic environment section 1.
0 heat load fluctuation is detected directly by the liquid level gauge 17 and the liquid level control controller 18, and then immediately issued via the calculator 19, so even if there is a sudden heat load fluctuation, there will be no delay in control. There will be no fear.

By the way, if the opening degree of the JT valve 6 in the device main 2 is fixed, even if the He liquid level fluctuates due to changes in the heat load in the cryogenic environment section 10, the function to adjust it will not be activated, and the He liquid The He liquid level may drop and the cooling capacity may become insufficient, or the liquefaction/refrigeration device 2 may be in an overoperating state and the He liquid level may rise excessively.
Therefore, in the present invention, in order to minimize such fluctuations in the He liquid level and maintain a constant cooling capacity, the cryogenic environment part 10 is controlled based on the liquid level fluctuation value detected by the liquid level gauge 17. Calculate the amount of liquid He that should be replenished,
A signal for controlling the opening degree of the JT valve 6 is transmitted from the liquid level controller 18. As a result, the amount of liquid He in the cryogenic environment section 10 corresponds to the fluctuation of the He liquid level.
is replenished, and the cooling capacity of the cryogenic environment section 10 can be kept as constant as possible.

FIG. 2 is a flowchart showing another embodiment of the present invention, and shows an example of application to a recondensing He refrigerator. In this example, the refrigerant He is used in the compressor 3.
A closed circuit is formed between the heat exchangers 5a to 5e, the recondenser 20 in the cryogenic environment section 10, and the heat exchangers 5a to 5e, and the JT valve 6 liquefies He, and the recondenser 2
This part uses the latent heat of vaporization of He to absorb the heat load of the object to be cooled in the cryogenic environment section 10, and maintains the cryogenic environment section 10 in a cryogenic state. In this case, the cryogenic environment section 1 constituting the freezing room
0 has a sealed structure, and the cryogenic environment section 10
If there is a change in the heat load within the
This appears as pressure fluctuations within the body. Therefore, in the present invention, a pressure detector 21 is attached to the cryogenic environment section 10, and the pressure fluctuation is constantly detected and inputted to the computer 22. Then, the computer 22 generates return gases G ₂ and 1 corresponding to the gas pressure (thermal load) fluctuations in the cryogenic environment section 10.
Estimate the heat amount fluctuation of the gas at five points, calculate the processing amount (discharged gas amount) of the expander 7b according to it, send the signal to the calculator 19, and increase or decrease the processing amount from the calculator 19 to the expander 7b. command is issued.

This command is immediately calculated and transmitted using the pressure fluctuations caused by heat load fluctuations in the cryogenic environment section 10 as input data, so it takes less time to control the throughput of the expander 7b as in the example shown in FIG. There is no risk of any delays. However, in this example as well, in order to more accurately estimate the heat load fluctuations and calculate and control the required processing amount of the expander 7b, the first
Similar to the example shown in the figure, correction is performed based on the actually measured gas temperature at the temperature measuring point 15.

That is, a temperature measuring device is installed at a temperature measuring point 15 downstream of the confluence of the return gas G ₂ from the recondenser 20 and the discharge gas G ₁ from the expander 7b, and at this point G ₁ The temperature of the mixed gas and G ₂ is measured, and the temperature controller 13 calculates the required throughput of the expander 7b and sends it to the calculator 19 so that the mixed gas temperature can be kept as constant as possible. In the computing unit 19,
The calculated value sent from the temperature control controller 13 and the calculated value sent from the computer 22 are compared and calculated, and the optimal discharge gas amount in the expander 7b is determined and instructed to the expander 7b. That is, in this example as well, the control result of the expansion machine 7b throughput calculated by the computer 22 based on the pressure fluctuation from the pressure detector 21 is confirmed by the temperature measurement point 15 and the temperature control controller, and then fed back to the calculator 19. Since the control value is corrected based on the value, highly accurate control is possible.

Further, with only the above configuration, when a sudden change in heat load occurs in the cryogenic environment section 10, it is not possible to maintain the inside of the section 10 in a stable cold state, and a state of insufficient cooling or excessive cooling may occur. Therefore, in this example,
The amount of liquid He fed to the recondenser 20 is automatically adjusted based on the pressure fluctuation detected by the pressure detector 21, thereby increasing the cooling capacity of the cryogenic environment section 10 to the level before the heat load fluctuation. We are trying to get back to normal condition immediately. That is, the flow rate of the refrigerant supplied to the recondenser 20 is measured at the flow rate measurement point 24, and the flow rate control controller 23 controls the JT so that the flow rate becomes a predetermined amount.
However, in the present invention, this flow rate measurement value is input into the computer 22, and when there is a heat load fluctuation in the cryogenic environment section 10, an amount of refrigerant commensurate with the fluctuation is regenerated. An opening adjustment signal is sent from the computer 22 to the JT valve 6 via the flow rate controller 23 so that the fluid is fed into the condenser 20. As a result, the cold state in the cryogenic environment section 10 immediately returns to the state before the heat load change, and a stable cryogenic state is maintained.

In the present invention, when the discharge amount of the compressor 3 is constant, even if the processing amount of the expander 7b is changed according to the heat load, the required power of the He liquefaction/refrigeration system does not change. If it decreases, there will be excessive cooling and the energy consumption rate will decrease. Therefore, in order to avoid such waste, as shown in FIG.
It is preferable to have a configuration in which the discharge amount of the compressor 3 can be adjusted by the pressure control controller 14 so as to detect this pressure at a constant value. By doing so, even if the heat load is reduced, there is no fear that the main body of the apparatus will be in an over-operating state, and energy-saving operation becomes possible.

The present invention is roughly configured as described above, but its greatest feature is that it directly detects heat load fluctuations in the cryogenic environment by liquid level fluctuations, pressure fluctuations, etc., and based on the measured values, (a) In addition to calculating the required amount of cold generation from the expander in the He liquefaction/refrigeration equipment body and controlling the expander, (b) based on the measured value, the amount of cold generated necessary for stabilizing the cold in the cryogenic environment section. The structure is such that the opening degree of the JT valve is adjusted by calculating the refrigerant flow rate, and various changes can be made within the range where these characteristics can be enjoyed. For example, the first
Although FIG. 2 shows an example in which five heat exchangers are combined, the number of heat exchangers is of course not limited to that shown and can be increased or decreased as appropriate. Further, although the figure shows an example in which only the discharge amount of the low temperature section side expander 7b is controlled, the discharge amount of the high temperature section side expander 7a can also be controlled in the same manner. Furthermore, all the illustrations are for one unit.
Although we have shown an example in which one cryogenic environment section is connected to a He liquefaction/refrigeration machine, a refrigeration system (multi-user Of course, it is also possible to apply it to a system). In particular, the present invention has the advantage of being able to respond quickly to sudden changes in heat load, and to maintain a cryogenic environment in a stable cold state despite sudden changes in heat load. For example, it can be said that its characteristics can be most effectively exhibited when applied to the multi-user system, etc., where the heat load is likely to change suddenly due to a change in the operating number of the cryogenic environment section.

[Effects of the Invention] The present invention is configured as described above, and its effects can be summarized as follows.

(1) Since this method directly detects and controls heat load fluctuations in the cryogenic environment, the response is extremely fast and there is no delay in control.

(2) Since this method performs feedback control while correcting the value calculated from the heat load fluctuation value with the value obtained from the actual measured value after control, there is no risk of erroneous control and the control accuracy is high.

(3) In the conventional example, fluctuations in the cooling capacity of the cryogenic environment section caused by heat load fluctuations were not strictly controlled, but in the present invention, the cooling capacity of the cryogenic environment section is simultaneously controlled before the heat load change. The state can be restored. Therefore, it is possible to maintain the cooling capacity stably despite heat load fluctuations, and problems such as insufficient cooling or excessive cooling do not occur.

[Brief explanation of the drawing]

1 and 2 are flow diagrams showing embodiments of the present invention,
3 and 4 are flowcharts for explaining a known He liquefaction/refrigeration system and its operation control method. 2...Refrigerating device main body, 3...Compressor, 5a-5
e... Heat exchanger, 6... JT valve, 7a... High temperature side expansion machine, 7b... Low temperature side expansion machine, 10... Cryogenic environment section (user), 13... Temperature control controller, 14... Pressure control controller, 15...Temperature measurement point, 16...Pressure detection point, 17...Liquid level gauge, 1
8... Liquid level control controller, 19... Arithmetic unit,
20... Recondenser, 21... Pressure detector, 22...
...Computer, 23...Flow rate control controller.

Claims (1)

[Scope of Claims] 1 Helium gas at room temperature and high pressure is precooled in stages by a heat exchange action that utilizes the cold obtained by isentropic expansion of helium gas, and then passed through a Joel-Thomson valve. In the operation control method of a helium liquefaction/refrigeration equipment, a heat load fluctuation detector is provided in the cryogenic environment part, and
A temperature measuring device is installed downstream of the confluence of the discharge gas of the expander installed in the high-pressure helium gas supply circuit of the helium liquefaction/refrigeration equipment and the return gas from the cryogenic environment section, and the thermal load fluctuation detector described above is installed. In addition to calculating and controlling the required amount of cold generation from the expander based on the heat load fluctuation of the cryogenic environment section, which is determined by A method for controlling the operation of a helium liquefaction/refrigeration system, characterized in that the flow rate of refrigerant necessary for stabilizing cooling in a cryogenic environment is calculated based on fluctuations, and the opening degree of a Juul-Thomson valve is adjusted. 2. The operation control method according to claim 1, wherein the pressure on the discharge side of the compressor that supplies helium gas at room temperature and high pressure is detected and the compressor is controlled so that the detected value is constant.