JPS61235648A - Helium refrigerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a helium refrigeration device for obtaining cryogenic temperatures.

(Prior Art) In recent years, development of helium refrigeration equipment for obtaining extremely low temperatures has been progressing, and for example, a cryogenic refrigeration equipment as described in Japanese Patent Publication No. 58-21186 has been proposed. That is, in the Joule-Thomson circuit (hereinafter referred to as J-T circuit), high-pressure helium gas discharged from one compressor is cooled by low-pressure helium gas returning to the compressor and a separate precooler, and then the Joule-Thomson The pressure is reduced by a valve (hereinafter referred to as J-T valve) to obtain a cryogenic helium gas-liquid mixed state, and the latent heat of vaporization of helium in this gas-liquid mixed state is used for cryogenic cooling. .

(Problem to be solved by the invention) Generally, in helium refrigeration equipment, the J-T to the compressor is
The return pressure of the circuit is approximately 1 atm, but the discharge pressure is required to be approximately 20 atm. Therefore, when compressing helium gas with one gas compressor as in the above-mentioned known example, the load on the compressor is The problem is that it becomes too large.

Therefore, attempts have been made to reduce the load on each compressor by connecting two gas compressors with different capacities in series to compress helium gas.

However, in a helium refrigerator before startup, each pressure is equal, and the capacities of both compressors connected in series are significantly different (for example, the capacity of the lower stage compressor is different from that of the higher stage compressor). Therefore, if both compressors are started at the same time, the amount of gas discharged from the low-stage compressor immediately after startup will be considerably larger than during steady operation. As a result, the suction volume of the small-capacity high-stage compressor could not keep up, and eventually,
An abnormal situation occurs in which the suction pressure of the high-stage compressor becomes higher than the discharge pressure, making normal operation impossible.

In particular, when using a Rokuri compressor as the compressor,
The back pressure of the blade decreases, making normal compression operation impossible, resulting in continued operation under abnormal pressure conditions.

The present invention has been made in view of the above problems, and an object of the present invention is to enable smooth startup of two compressors on the J-T circuit side in a helium refrigeration system.

(Means for solving the problems) In the present invention, as means for solving the above problems,
As shown in FIG. 1, a J-T has a pre-cooling refrigeration circuit 1 having a pre-cooling compressor 3 and an expander 6, and a large-capacity low-stage compressor 8 and a small-capacity high-stage compressor 10 connected in series. circuit 2, in which the high-pressure refrigerant gas flowing through the J-T circuit 2 is cooled by the pre-cooling refrigeration circuit 1, the low-stage compressor 8 is delayed for a predetermined period after the activation of the high-stage compressor IO. Control means 43 for controlling operation to start
is attached.

(Function) In the present invention, by the above means, the small capacity high stage compressor 10 is operated first at startup, and the equal pressure level of the low stage compressor 8 is lowered (that is, the high stage compressor 10 is lowered). The effect is that the low stage compressor 8 is started after waiting for the discharge amount of the low stage compressor 8 to be suppressed immediately after the start-up.

(Embodiment) =3- Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

This helium refrigeration system includes a precooling refrigeration circuit 1, a J-T circuit 2, and a control means 43.

The pre-cooling refrigeration circuit 1 includes a pre-cooling compressor 3 for compressing helium gas for pre-cooling, an oil separator 4, an adsorber 5, an expander 6 and a surge bolt 7, which will be described in detail later, through a refrigerant gas pipe (
That is, the high pressure refrigerant gas pipe 23 and the low pressure refrigerant gas pipe 2
4). Here, the precooling compressor 3, the oil separator 4, the adsorber 5, and the surge bolt 7 constitute a precooling compressor unit A.

On the other hand, the J-T circuit 2 includes a large-capacity low-stage compressor 8, an oil separator 9, a small-capacity high-stage compressor 101, an oil separator 11, an adsorber 12, and a first Joule-Thomson heat exchanger (hereinafter referred to as , J-
(referred to as T heat exchanger)+3, adsorber 14, first precooler I5
, second J-T heat exchanger 16, adsorber 17, second precooler 1
8, third J-T heat exchanger 19, adsorber 20, J-T valve 21, cooling-4 = vessel 22, the third, second and first J-T heat exchangers 19
．． 16 and 13 are sequentially connected by refrigerant gas pipes (ie, high pressure refrigerant gas pipe 25 and low pressure refrigerant gas pipe 26). Here, the low-stage and high-stage compressors 8.10, the oil separator 9.11, the adsorber 12, and the gas ballast tank 37 described later constitute a J-T side compressor unit B.

The pre-cooling compressor 3, low stage and low stage compressors 8 and I
Cooling water coils 27, 28 and 29 are attached to O, respectively, and these cooling water coils 27, 28, 29
By the respective discharge gas coil 30.31.32
It is also configured to cool the injection oil coils 33, 34, and 35.

Each of the oil separators 4, 9. The oil separated in II is injected into the suction side of each compressor 3, 8.10.

Each of the adsorbers 5. +2.14. ．． 17.20 has the effect of removing impurities in helium gas in each state.

The surge bolt 7 has the function of reducing pulsation of the low-pressure helium gas returned to the pre-cooling compressor 3.

Furthermore, in the J-T circuit 2, a high pressure control valve 36, a gas ballast tank 37, and an intermediate pressure control valve are installed between the high pressure refrigerant gas pipe 25 on the outlet side of the adsorber 12 and the suction side of the high stage compressor 10. A bypass circuit 39 with 38 is provided. The gas ballast tank 37 is controlled by opening and closing the high pressure control valve 3G or the intermediate pressure control valve 38.
It has the function of adjusting the amount of helium scum circulating in the J-T circuit 2.

The expander 6, J-T heat exchangers 13, 16, 19, precoolers 15, 18, J-T valve 21, and cooler 22 are housed in a vacuum container 40 maintained at a high degree of vacuum, and Second
, third J-T heat exchanger 16, 19, second precooler 18, J
- The T valve 21 and the cooler 22 are surrounded by a radiation shield 41 and constitute a cryostat C. Reference numeral 42 is a thermometer that detects the temperature of the cooler 22. The expander 6
The high-pressure side inlet 61 is connected to the discharge side of the pre-cooling compressor 3, and the low-pressure side outlet 62 is connected to the suction side of the pre-cooling compressor 3, so that cooling is performed by the expansion stroke of high-pressure helium gas inside the expander 6. The helium gas flowing through the J-T circuit 2 is precooled in first and second precoolers 15.18 provided on the outer peripheries of the first and second heat station sections 70.71.

As a feature of the present invention, in this helium refrigeration system, the low stage compressor 8 in the J-T circuit 2 is replaced with the high stage compressor I.
A control means 43 (for example, a timer, etc.) is provided for controlling the operation so that the start-up is delayed by a predetermined time (for example, about 10 seconds) after the start-up of the O. Note that the control means 43
The operation of the compressor 3 of the pre-cooling refrigeration circuit 1 is also controlled, and the compressor 3 is started at the same time as the high-stage compressor 10 of the J-T circuit 2.

Next, the operation of the helium refrigeration system of the illustrated embodiment will be explained.

At the start of operation, the compressor 3 of the pre-cooling refrigeration circuit 1 and the high-stage compressor IO of the J-T circuit 2 are started at the same time by a command from the control means 43, and the low-stage compressor 8 is stopped. be done. Therefore, the expander 6 in the precooling refrigeration circuit 1
Each heat stencil 70.71 decreases in temperature.

On the other hand, in the J-T circuit 2, only the high-stage compressor IO is operated, so that the equal pressure level of the low-stage compressor 8 decreases, and approximately 10 seconds after the high-stage compressor 10 is started, This is the suction pressure of the high stage compressor IO. Therefore, when the low stage compressor 8 is started according to a command from the control means 43,
The discharge amount of the low-stage compressor 8 immediately after startup is suppressed, and there is no significant difference from the suction amount of the high-stage compressor 10. Therefore, the pressure reversal that occurs when the meat compressors 8 and 10 are started simultaneously does not occur, and the meat compressors 8 and 10 can be started without any problem.

Furthermore, by starting the meat compressors 8 and 10 at different times, the discharge amount of the low-stage compressor 8 immediately after starting is suppressed, and the meat compressors 8 and 10 can be started smoothly, and the The starting current is also significantly reduced.

Next, when the steady operating state is reached, the low-stage compressor 8 sucks and compresses the J-T circuit return helium gas from the cryostat C, and the cooling water coil 28 cools the helium gas to room temperature 30.
After cooling to 0K and separating oil in an oil separator 9, this helium gas is sucked and compressed by a high-stage compressor 10. after that,
After cooling to room temperature 300K with cooling water in a cooling water coil 29 and separating oil in an oil separator 11, impurities are adsorbed in an absorber 12, and clean high-pressure helium gas is supplied to a cryostat C.

The high-pressure helium gas supplied to the cryostat C side enters the primary side of the first J-T heat exchanger 13 and exchanges heat with the low-pressure helium gas on the secondary side that returns to the J-T side compressor unit B. It is cooled down to about 70K, and the expander 6
The heat enters the first precooler 15 provided on the outer periphery of the first heat station 70 (50 to 60K), is cooled to approximately 55K by the first heat station 70, and enters the primary side of the second J-T heat exchanger 16. , J-T side compressor unit B
Return to Heat exchange with low pressure helium gas on the secondary side to about 20K
The second heat station 71 of the expander 6
(15-20K) enters the second precooler 18 provided on the outer periphery of the J-T, is cooled down to about 15K by the second heat stain 71, further enters the primary side of the third J-T heat exchanger 19, and enters the primary side of the third J-T heat exchanger 19. It exchanges heat with the low-pressure helium gas on the secondary side that returns to the T-side compressor unit B, and is cooled to about 5K, and the J-T valve 2
It reaches 1. In addition, during the step 2, on the outlet side of each J-T heat exchanger 13, 16, 19, the absorber +4°17
．． 20, impurity gases such as nitrogen, oxygen, and hydrogen are adsorbed at a low temperature to produce cleaner helium gas to prevent clogging of the J-T valve 21 and each precooler 15, 18.

The high-pressure helium gas is then throttled by the J-T valve 21, subjected to Joule-Thomson expansion, and supplied to the cooler 22 as helium in a gas-liquid mixed state of 1 atmosphere and 4.2 degrees. In the cooler 22, the latent heat of vaporization of the liquid portion of helium is used for liquefying or recondensing other helium gas or cooling an object to be cooled.

As a result, the low pressure helium gas returning from the cooler 22 to the secondary side of the third J-T heat exchanger 19 becomes a saturated gas of about 42%. This low-pressure helium gas is then applied to the second and first
The high-pressure helium scum on the primary side is cooled in the J-T heat exchanger 16.13, the temperature rises to about 300 K, and it returns to the J-T side compressor unit B. Thereafter, similar cycles are repeated to perform the refrigeration operation.

(Effect of the invention) As described above, according to the present invention, in the J-T circuit 2,
Since the low-stage compressor 8 is started after a predetermined time delay after the high-stage compressor 10 is started, the discharge amount of the low-stage compressor 8 immediately after startup is suppressed, and the output of the high-stage compressor 10 is reduced. The amount corresponds to the suction amount, and has the excellent effect of eliminating troubles at startup that occur when two compressors are connected in series.

Also, two compressors8. By starting the IO in a staggered manner, there is also the effect that the starting current for the refrigeration system can be reduced to a large iJ.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a helium refrigeration system according to an embodiment of the present invention. l... Pre-cooling refrigeration circuit 2... Joule-Thomson circuit 3... Pre-cooling compressor 8... Low-stage compressor 10... High-stage compressor 43...・Control means

Claims (1)

[Claims] 1. It has a precooling refrigeration circuit (1) having a precooling compressor (3) and an expander (6), and a large capacity low stage compressor (8) and a small capacity high stage compressor (10) connected in series. The high-pressure refrigerant gas flowing through the Joule-Thompson circuit (2) is pre-cooled into a refrigeration circuit (1).
In a helium refrigeration system for cooling, a control means (43) controls the operation of the low-stage compressor (8) so as to start the low-stage compressor (8) with a predetermined time delay after the startup of the high-stage compressor (10).
A helium refrigeration device characterized by being attached with.