JPH0247674B2 - HERIUMUEKIKA * REITOSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a helium liquefaction and refrigeration system, and more particularly to fluctuations in refrigeration load due to cooling stoppage of one or more of multiple installed refrigeration load sections and subsequent recooling. The present invention relates to a helium liquefaction/refrigeration system that can maintain stable operating conditions without causing excess or deficiency in refrigeration output even under such conditions.

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 rates on the high-pressure side and the low-pressure side become 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 shown in FIG. 1 is known. That is, in FIG. 1, the refrigeration system 1 includes heat exchangers 5a to 5.
e, a device main 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 main body 2, a cryogenic environment connected to the outlet side of the device main body 2; It consists of parts 10 and the like. After the He gas is pressurized by the compressor 3, it descends through the first to fifth heat exchangers 5a to 5e (hereinafter, this descending 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 test 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 heat exchangers 5a to 5e are raised in the opposite direction (hereinafter, this ascending route is referred to as the "low-pressure side route"), and after cooling the He flowing through the counter-current high-pressure side route, the He gas becomes He gas at approximately room temperature and pressure. Then it returns 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 when there is a change in load or when starting up, etc. , it was necessary to adjust the flow rate. In particular, in a refrigeration system (hereinafter referred to as a multi-user system) in which multiple cryogenic environment units (hereinafter sometimes referred to as users) are connected in parallel to one He refrigerator, load fluctuations are large, and appropriate If expander throughput is not adjusted, excessive refrigeration generation can result in wasted energy. In addition, when a user stops cooling one unit (or two or more units) or starts cooling again during cooling operation, the operating conditions of the He refrigerator will change due to these operations, and the conventional manual In operation, a high level of skill is required to maintain the user's temperature conditions constant during cooling operation.

The present invention has been made with attention to these circumstances, and it is possible to maintain the user's environmental temperature constant while suppressing the generation of excessive cold in the expander. It is an object of the present invention to provide a He liquefaction/refrigeration system that allows a user to appropriately stop cooling and recool without adversely affecting the operating conditions of other users.

The He liquefaction/refrigeration system of the present invention, which has achieved the above object, precools He gas at normal temperature and high pressure in stages by a heat exchange action that utilizes the cold obtained by isenthalpic expansion of He gas, and then J.T.
In a He liquefaction/refrigeration system that generates liquefied He by passing it through a valve, the temperature is set downstream from the confluence of the discharge gas of the lowest temperature expander and the return gas from the cryogenic environment section. The gist lies in that the rotation speed of the expander is controlled and the amount of discharged gas is adjusted in accordance with the temperature detected by a measuring device.

The structure and effects of the present invention will be explained below with reference to the drawings, but the drawings are representative examples and do not limit the present invention.
Changes in the specific configuration and arrangement of the heat exchanger, expander, etc. built into the refrigeration equipment body, or in the structure of the cryogenic environment section, etc., are all within the technical scope of the present invention. It will be done.

FIG. 2 is a schematic overall diagram showing an embodiment of the He refrigeration system of the present invention, in which 13 is a temperature control controller;
4 is a pressure control controller, 15 is a temperature measurement point, 16
indicate pressure detection points, respectively.

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, a temperature measurement point 15 is provided downstream from the confluence of the He gas G1 discharged from the expander 7b on the low temperature side and the return gas G2 from the cryogenic environment section 10, and the temperature measurement value at the temperature measurement point 15 is measured. The temperature value 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 measured 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 the output of the expander 7b is increased. By increasing the number of rotations and increasing the amount of discharged gas (cold gas), the amount of cold generated is increased, 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, so the temperature control controller 13 sends a command to reduce the output to the expander 7b.
By lowering the rotational speed of b and reducing the amount of discharged gas (cold gas), the amount of cold generation is reduced, thereby increasing the temperature at the temperature measuring point 15. In this way, the temperature at the temperature measurement point 15 is maintained constant. As a result, in the heat exchanger 5d, the high-pressure He gas, which is a refrigerant, is on the low-pressure side, which is a refrigerant with a constant set temperature.
Since the He gas always receives a stable cooling effect, the temperature after heat exchange can be maintained at a predetermined temperature. As a result, the cryogenic environment section 10 can be easily maintained at a constant temperature regardless of fluctuations in operating conditions. The temperature measurement point 15 is 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 G1 and the return gas G2 are mixed. A mixer may also be provided to improve the quality.

However, when the discharge amount of the compressor 3 is constant, the required power of the He refrigeration system does not change even if the throughput of the expander 7b is changed according to the refrigeration load. The basic unit will decrease. In order to prevent this drop, in the He refrigeration system of the present invention, the discharge pressure of the compressor 3 is detected at the pressure detection point 16, and the rotation speed of the compressor 3 is controlled by the pressure controller 14 to keep this pressure constant. The discharge amount is controlled and adjusted. If the refrigeration load decreases as a result, just throttle the JT valve.
The throughput of the expander 7b also decreases according to the refrigeration load, and the discharge air volume is reduced by the action of the pressure control controller 14 so as to keep the discharge pressure of the compressor 3 constant, thereby preventing a decrease in the energy consumption rate. Energy saving operation can be performed.

FIG. 3 is a schematic overall diagram showing an example of a recondensing multi-user system according to the present invention, in which two users 10e and 10f each having recondensers 11e and 11f are connected to one refrigeration system 2. There is. Although the multi-user system according to the present invention includes a system in which many users are connected in parallel, the example in FIG. 3 illustrates a system with two users for ease of understanding.

Room temperature high pressure He supply system L ₂ on the He discharge side of compressor 3
is system L ₄ leading to the expander and JT valve 6 for user 10e.
It is branched into systems Le and Lf, which are introduced into the JT valve 6f for He and user 10f, respectively, and in the normal temperature section of each latter system, stop valves 17e and 17f and flow rate controllers 12e and 12f are installed along the flow direction of He. 12
f is provided respectively. The opening degree of the JT valve is adjusted by flow rate controllers 12e and 12f.
And return gas G1 from users 10e and 10f
A temperature measuring point 15b is provided downstream from the point where the gas G2 discharged from the low-temperature side expander 7b joins, and in this example, the temperature measuring point 15b is provided at the downstream side of the point where the gas G2 discharged from the low-temperature side expander 7b joins, and in this example, the combined gas G3 and the high-temperature side expander 7a
A temperature measurement point 15a is also provided downstream from the confluence point with the gas G4 discharged from the temperature measurement point 15a, and temperature control controllers 13b and 13a are provided corresponding to the temperature measurement points 15b and 15a, respectively. Of course, the temperature measuring point 15a can also be omitted. Further, as in the previous example, a pressure detection point 16 is provided on the discharge side of the compressor 3, and a pressure control controller 14 corresponding to the pressure detection point 16 is provided.

In the multi-user system with the above configuration, 2
When only one of the users, for example, the user 10f, is operated, when the stop valve 17e is closed, the high-pressure He refrigerant is no longer supplied to the user 10e, and the refrigeration load is reduced to a predetermined 1/2. Therefore, the expander 7
When the processing amount of b, 7a is a predetermined amount, the amount of cold generation becomes excessive, and the temperature of the temperature measurement points 15b, 15a decreases compared to the predetermined value, so the temperature control controller 13b, 13a is activated to lower the rotational speed of the expanders 7b and 7a to reduce the amount of discharged gas. The above operation reduces the predetermined amount of high-pressure He gas in the He refrigerator, so the pressure controller 14 operates to adjust the discharge air volume of the compressor 3 so as to keep the pressure at the pressure detection point 16 constant.

As mentioned above, in a multi-user system, if you want to suspend some users, just close the stop valve (17e in the above example) for that system, and the cold generation amount and compressor discharge amount will be automatically adjusted, making it easy. Energy savings can be achieved by always operating under optimal conditions.

In addition, when cooling the user 10e to an extremely low temperature while the user 10f is being cooled, the stop valve 17e is gradually opened after the user 10e is precooled with liquid nitrogen, and refrigerant He is supplied. Since the temperature at points 15b and 15a increases,
Detecting this temperature rise, the temperature control controller 1
3b and 13a, the rotational speed of the expanders 7b and 7a is increased to increase the amount of discharged gas, thereby increasing the amount of cold generated and maintaining the temperature at the temperature measurement points 15b and 15a at a predetermined value. Due to the above operation, the predetermined amount of high-pressure He gas in the He refrigerator increases, so the pressure controller 14 operates to adjust the discharge air volume of the compressor 3 so as to keep the pressure at the pressure detection point 16 constant.

As mentioned above, in a multi-user system,
When recooling a user that is inactive, simply open the stop valve (17e in the above example) of that system gradually, and the amount of cold generation can be reduced without disturbing the normal operation of the other user 10f who is operating. The discharge amount of the compressor is automatically adjusted and recooling can be easily performed.

The present invention is configured as described above, and can obtain the effects summarized below.

(1) The amount of cold generated by the expander is increased or decreased to keep it optimal in response to operating conditions such as fluctuations in refrigeration load, so the best operating conditions can be maintained and the temperature of the cryogenic environment section can be maintained at a predetermined value. It is possible to operate with the lowest energy consumption while maintaining the

(2) In a multi-user system, one (or two or more) of a plurality of operating users can easily stop and restart the system without disturbing the operating status of other users.

[Brief explanation of drawings]

Figure 1 is a schematic overall diagram showing a conventional He refrigeration system.
FIG. 2 is a schematic overall view showing a He refrigerating device according to the present invention, and FIG. 3 is a schematic overall view showing a He refrigerating device of a multi-user system according to the present invention. 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, 13a, 13b... Temperature control controller , 14...Pressure control controller, 15, 15a, 15b...Temperature measurement point, 16...
...Pressure detection point.

Claims (1)

[Scope of Claims] 1 Helium gas at room temperature and high pressure is precooled stepwise 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 a helium liquefaction/refrigeration system that generates liquefied helium, the temperature measurement results from a temperature measuring device installed downstream of the confluence of the discharge gas of the lowest temperature expander and the return gas from the cryogenic environment section A helium liquefaction/refrigeration apparatus characterized in that the helium liquefaction/refrigeration apparatus is configured to control the rotation speed of the expander and adjust the amount of discharged gas accordingly. 2. In the apparatus according to claim 1, the pressure on the discharge side of the compressor for producing helium gas at room temperature and high pressure is detected, and the rotational speed of the compressor is controlled so that the detected value is constant. Helium liquefaction/refrigeration equipment configured to maintain constant pressure.