JPH0756420B2 - Ultra low temperature refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention sequentially connects a compressor, a condenser, a plurality of gas-liquid separators, a pressure reducing device and a cooler, and separates the gas-liquid separators. A cryogenic refrigeration system including a refrigeration cycle using a mixed refrigerant, wherein a cascade heat exchanger for exchanging heat between a decompressed refrigerant of a liquid refrigerant and a return gas refrigerant is provided, and particularly an improvement of the cascade heat exchanger. It is about.

(Prior Art) For example, in the case of the refrigerating apparatus of FIG. 3, the compressor 1, the condenser 2, the three gas-liquid separators 3, 4, 5, the decompressor 6 and the cooler 7 are sequentially connected by the pipes 8a to 8m. While forming a closed loop, the liquid refrigerant separated by the gas-liquid separators 3, 4, 5 is depressurized by the thin tubes 9, 10, 11, and the depressurized refrigerant and the tube 8l,
1 shows an ultra-low temperature refrigeration system including a refrigeration cycle using a mixed refrigerant, in which cascade heat exchangers 12, 13 and 14 are provided so as to be capable of exchanging heat with return gas refrigerants of 8k and 8j.

That is, the mixed refrigerant compressed by the compressor 1 and cooled by the condenser 2 is first separated into the liquefied high-boiling-point refrigerant and the residual gas refrigerant in the first gas-liquid separator 3. Then, the liquid refrigerant is decompressed in the narrow tube 9, flows into the pipe 8l outside the cascade heat exchanger 13, and the gas refrigerant separated in the gas-liquid separator 3 is heat-exchanged in the cascade heat exchanger 13, Cooling. The cooled gas refrigerant is separated into the liquefied medium-boiling-point refrigerant and the residual gas refrigerant in the second gas-liquid separator 4. Then, the liquid refrigerant is decompressed in the narrow tube 10, flows into the pipe 8k outside the cascade heat exchanger 14, and the gas refrigerant separated in the gas-liquid separator 4 is heat-exchanged in the cascade heat exchanger 14, Cooling. Further, the cooled gas refrigerant is separated into liquefied medium / low boiling point refrigerant and residual gas refrigerant (mainly ultra-low boiling point component) in the third gas-liquid separator 5. Then, the liquid refrigerant is decompressed by the narrow tube 11, flows into the tube 8j outside the cascade heat exchanger 15,
The gas refrigerant separated in the gas-liquid separator 5 is heat-exchanged in the cascade heat exchanger 15 and further cooled. The super-boiling point refrigerant is liquefied by this cooling, decompressed by the decompression device 6, flows into the cooler 7, and evaporates there. Due to this evaporation, the inside of a storage (not shown) having the cooler 7 is brought to an ultralow temperature.

By the way, the cascade heat exchangers 13, 14, which are double tubes,
Each of 15 is independent, and each inner pipe is connected by another pipe 8k, 8l. Therefore, there are many joints, there is a change in the cross-sectional area of the pipe, pressure loss increases, abnormal pressure rise of high pressure and abnormal pressure drop of low pressure occur, and at the same time, there is a problem that cooling performance deteriorates. In addition, the amount of proper refrigerant to be filled in the refrigeration cycle is large and the balance pressure becomes high, and the pressure resistance of the equipment must be taken into consideration.

(Problem to be Solved) The present invention is to provide an ultra-low temperature refrigerating apparatus including a cascade heat exchanger, in which the pressure loss of the refrigerant flow is small and the refrigerant filling amount is small.

(Means for Solving the Problem) The present invention has been made in view of the above circumstances,
In the cascade heat exchanger, a plurality of cascade heat exchangers are made into a series, that is, a double pipe of an integrated structure, with the refrigerant side being an inner tube and the supply side being an outer tube, and each gas-liquid separator is connected to the outer tube. It is an ultra-low temperature refrigerating device characterized in that the pipes are connected with a space.

(Operation) The gas refrigerant separated by each gas-liquid separator flows downstream in the outer pipe of the series of double pipes. In this case, the double pipe has few joints, changes in the cross-sectional area of the pipe are small, and pressure loss is reduced. In addition, since the number of connecting pipes is reduced, the amount of refrigerant enclosed can be reduced.

(Example) First, the cascade heat exchanger A of FIG. 1 is demonstrated.

21 corresponds to the pipe 8j from the cooler 7 in FIG. 3, and its pipe
A pipe 22 as an outer pipe is fitted and brazed to the 21 to form a double pipe. The pipe 22 is composed of four T-shaped joints 22a, 2
2b, 22c, 2d are arranged with a space, and adjacent joints are connected and brazed by pipes 22e, 22f, 22g. T-shaped joints 22a, 22d at both ends are brazed to the pipe 21. To be done. Reference numerals 23, 24, and 25 are gas-liquid separators, which correspond to the reference numerals 3, 4, and 5 in FIG. 3, and are connected and brazed to the lower ends of the T-shaped joints 22a, 22b, and 22c. Reference numeral 26 corresponds to the pipe 8b in FIG. 3, and is connected and brazed to the gas-liquid separator 23. 27 is the third
Corresponding to the piping 8h in the figure, it is connected and brazed to the T-shaped joint 22d. 28, 29, 30 correspond to the thin tubes 9, 10, 11 in FIG. 3,
One end thereof is connected to the bottom of the gas-liquid separators 23, 24, 25, and the other end thereof is connected to the pipe 21 through the T-shaped joints 22b, 22c, 22d and brazed.

Therefore, the gas refrigerant separated in the gas-liquid separator 23 is mainly in the pipe 22.
The gas refrigerant which is cooled when passing through e, and which is separated by the gas-liquid separator 24 is mainly cooled when passing through the pipe 22f,
Furthermore, the gas refrigerant separated by the gas-liquid separator 25 is mainly piped.
It will be cooled when passing 22g.

Next, the embodiment cascade heat exchanger A'of FIG. 2 will be described.

In the cascade heat exchanger A ', one outer tube 22' with both ends narrowed is fitted and inserted into the outer circumference of the inner tube 21, and both ends thereof are brazed to form a double tube. Then, openings are provided in the lower portion of the outer tube 22 'at intervals, and gas-liquid separators 23, 2 are provided in these openings.
4, 25 and pipe 27 are connected and brazed. Others are the same as those in the above-mentioned embodiment, and the description thereof will be omitted.

In addition, in all of the above-described embodiments, three cascade heat exchangers are integrated, but even if two are integrated,
It may be one in which four or more are integrated.

(Effect of the invention) Since a plurality of cascade heat exchangers have a series or integral double pipe structure as described above, the number of joint portions is smaller than that in the case where conventional independent ones are connected. ,
The change in the cross-sectional area of the pipeline is reduced, and the pressure loss can be reduced. Further, unlike the prior art, piping between adjacent cascade heat exchangers is not required, the liquid storage volume is reduced, the amount of refrigerant charged can be reduced, and the balance pressure at the time of operation stop can be lowered. Also, the entire cascade heat exchanger becomes compact,
Moreover, the number of brazing points is reduced, the reliability against refrigerant leakage is increased, and the productivity is improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a cascade heat exchanger portion of an ultra-low temperature refrigeration system according to an embodiment of the present invention, and FIG. 2 is a vertical sectional view of another embodiment cascade heat exchanger portion. FIG. 3 is a schematic diagram of a conventional ultra-low temperature refrigerator. 1 ... Compressor, 2 ... Condenser, 6 ... Pressure reducing device, 7 ...
Cooler, A, A '... Cascade heat exchanger, 21 ... Inner tube, 2
2,22 '... Outer tube, 23-25 ... Gas-liquid separator, 28-30 ... Thin tube.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Yamada 3-7-1, Minowa, Toyonaka-shi, Osaka Shinmeiwa Industrial Co., Ltd. Industrial Machinery Division Toru Uehara (56) Reference JP 62-233647 JP, A) Actual Kaihei 1-88271 (JP, U)

Claims (1)

[Claims] 1. A compressor, a condenser, a plurality of gas-liquid separators, a pressure reducing device and a cooler are sequentially connected, and a reduced pressure refrigerant and a return gas refrigerant of the liquid refrigerant separated by each of the gas liquid separators are connected. In a cryogenic refrigeration apparatus including a refrigeration cycle using a mixed refrigerant formed by interposing a cascade heat exchanger for heat exchange, the cascade heat exchanger has an inner tube on the return side of the refrigerant,
While the supply side is an outer tube and a plurality of the cascade heat exchangers in a series of double tubes, each gas-liquid separator is connected to the outer tube with a space, the ultra-low temperature refrigeration apparatus.