JPH0641097Y2 - Low temperature refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a low temperature refrigeration system of a multi-source refrigeration system in which at least two or more independent refrigeration circuits are combined via a cascade condenser.

(Conventional Technology and Problems Thereof) FIG. 3 is a diagram showing a refrigeration circuit of a conventional low temperature refrigeration system of a dual refrigeration system. As shown in the figure, the low temperature refrigeration system 1 comprises a high temperature side refrigeration circuit 1h and a low temperature side refrigeration circuit 1. The high temperature side refrigeration circuit 1h includes a compressor 2h and a condenser 4
And a capillary tube 3h that constitutes a pressure reducer, and a cascade condenser 5 that functions as an evaporator in the high temperature side refrigeration circuit 1h.
And are closed loop connected. On the other hand, in the low temperature side refrigeration circuit 1, a compressor 2l, a cascade condenser 5 acting as a condenser in the low temperature side refrigeration circuit 1, a capillary tube 3l constituting a decompressor, and an evaporator 6 are connected in a closed loop. It is formed.

In this low temperature refrigeration system 1, in the high temperature side refrigeration circuit 1h,
The high pressure hot gas of the high temperature side refrigerant compressed by the compressor 2h radiates heat in the condenser 4 and is liquefied. This liquid refrigerant is squeezed and expanded by the capillary tube 3h and the high pressure hot gas of the low temperature side refrigerant is cascaded in the cascade condenser 5. It vaporizes by the heat of gas (details will be described later). On the other hand, in the low temperature side refrigeration circuit 1, the compressor
The high-pressure hot gas of the low-temperature side refrigerant compressed by 2 l radiates heat to the high-temperature side liquid refrigerant in the cascade condenser 5 and is liquefied. This liquid refrigerant is squeezed and expanded by the capillary tube 3 l and vaporized by the evaporator 6. . As a result, heat is taken from a load (not shown) and cooled.

By the way, normally, in such a low temperature refrigeration system 1, a high boiling point refrigerant (for example, R-12, R-22, R-50) on the high temperature side is used as the refrigerant.
2 etc.) and a low boiling point refrigerant (eg R-13, R-503
Etc.) are used. Lubricating oil is used in the compressors 2h and 2l to prevent the seizure, and the lubricating oil is mixed in the circulating refrigerant. However, this lubricating oil tends not to dissolve in the low temperature side refrigerant and tends to separate, while the capillary tube 3l of the low temperature side refrigeration circuit 1 is separated.
In the low temperature region (shown by the arrow P in FIG. 3) from the vicinity of the refrigerant outlet of the evaporator to the vicinity of the refrigerant outlet of the evaporator 6, the lubricating oil separated from the refrigerant has a low temperature of −85 ° C. to −90 ° C. There is a problem in that the flow of the refrigerant is frozen in the region P and the flow of the refrigerant is hindered, and thereby the circulation of the refrigerant is deteriorated and the temperature rises. Further, when the lubricating oil does not return to the compressor 2l due to the freezing of the lubricating oil, the amount of the lubricating oil in the compressor 2l decreases, and if left as it is, there is a problem that seizure may occur in the compressor 2l.

(Object of the Invention) The present invention has been made in order to solve the above-mentioned problems of the prior art, and it is possible to prevent freezing of the lubricating oil in the pressure reducer and the evaporator, and to prevent the compressor from seizing. It is an object of the present invention to provide a low temperature refrigerating device.

(Means for Achieving the Purpose) The present invention comprises a combination of at least two independent refrigeration circuits via a cascade condenser, wherein the low temperature side refrigeration circuit is a compressor, the cascade condenser, a decompressor and an evaporator. In order to achieve the above object, it is a low temperature refrigerating device of a multi-source refrigeration system formed by connecting closed loops in series with each other.
While using a high-boiling / low-boiling mixed refrigerant as the refrigerant for the low-temperature side refrigeration circuit, between the compressor and the cascade condenser, a condenser that liquefies only the high-boiling refrigerant, and a liquefied high-boiling refrigerant A gas-liquid separator that separates the refrigerant and the low-boiling-point refrigerant in the gas phase is interposed in series, and the refrigerant in the gas phase separated by the gas-liquid separator is guided to the cascade condenser. The liquid refrigerant is directly guided to the pressure reducer via a bypass path.

(Embodiment) FIG. 1 is a view showing a refrigerating circuit of a low temperature refrigerating apparatus which is an embodiment of the present invention. As shown in the figure, in the high temperature side refrigeration circuit 7h of the low temperature refrigeration system 7, the compressor 8h is connected to the condenser.
9, decompressor capillary tube 10h, cascade condenser 11
A refrigeration path is formed that returns to the compressor 8h via the heat exchanger 13. On the other hand, in the low temperature side refrigeration circuit 7l, a low boiling point refrigerant (for example, R-13, R-503, etc.) and a high boiling point refrigerant (for example, R-11, R-114, etc.) in which the lubricating oil melts well are used as the refrigerant. A mixed refrigerant prepared by mixing is used. The refrigerant outlet of the compressor 8l is connected to the inlet of the gas-liquid separator 14 via the heat exchanger 13. In this case, the heat exchanger 13 is a high temperature side refrigeration circuit.
Utilizing the cooling heat of the return refrigerant of 7h, it acts to condense only the high boiling point refrigerant of the mixed refrigerant of the low temperature side refrigeration circuit 7l, the gas-liquid separator 14, the liquefied high boiling point refrigerant and the gas phase It acts to separate the low boiling point refrigerant in the state. The gas phase outlet 14a of the gas-liquid separator 14 is connected to the cascade condenser 1
The liquid phase outlet 14b is directly connected to the capillary tube 10l via the bypass passage 15 provided with the solenoid valve 16 while being connected to the capillary tube 10l of the decompressor via 1. The outlet of the capillary tube 10l is connected to the compressor 8l via the evaporator 12. The solenoid valve 16 is a gas-liquid separator.
It is configured to open periodically according to the liquid level of the gas-liquid separator 14 so that the liquid amount of 14 does not increase too much.

Next, the operation of the low temperature refrigeration system 7 will be described.
In the high temperature side refrigeration circuit 7h, the liquid refrigerant liquefied in the condenser 9 is squeezed and expanded by the capillary tube 10h, and in the cascade condenser 11, heat is taken from the refrigerant in the low temperature side refrigeration circuit 7l to be vaporized, and further the heat exchanger. At 13 as well, heat is taken from the refrigerant in the low temperature side refrigeration circuit 7l and the temperature becomes high, and the temperature returns to the compressor 8h. That is, the cascade condenser 11 and the heat exchanger 13 both act as a condenser of the low temperature side refrigeration circuit 7l. On the other hand, in the low temperature side refrigeration circuit 7l, only the high boiling point refrigerant of the high boiling point / low boiling point mixed refrigerant hot gas compressed by the compressor 8l is condensed and liquefied by the heat exchanger 13. The high boiling point refrigerant and the low boiling point refrigerant in the vapor phase are separated by the gas-liquid separator 14. Then, the low boiling point refrigerant in the gas phase is the gas-liquid separator 14
Is sent to the cascade condenser 11 from the gas phase outlet 14a thereof, is condensed and liquefied there, and is further expanded by being squeezed by the capillary tube 10l and vaporized in the evaporator 12, whereby the load is cooled. On the other hand, the high-boiling-point refrigerant in the liquid phase separated by the gas-liquid separator 14 is opened by the solenoid valve 16 according to the liquid level in the gas-liquid separator 14 periodically, so that the liquid in the gas-liquid separator 14 is sequentially discharged. Capillary tube 10l from the phase outlet 14b through the bypass path 15 while being mixed with the low boiling point liquid refrigerant.
Sent to. In this case, bypass the gas-liquid separator 14
The high-boiling-point refrigerant that is directly guided to the capillary tube 10l through 15 is higher in temperature than the low-boiling-point refrigerant obtained through the cascade condenser 11 because it does not pass through the cascade condenser 11. Therefore, even if the compressor lubricating oil is frozen in the capillary tube 10l and the evaporator 12, the frozen lubricating oil is melted and returned to the compressor 8l by the sensible heat of the high-temperature high-boiling-point refrigerant. In this way, the capillary tube 10l,
Since the freezing of the lubricating oil in the evaporator 12 can be prevented, the refrigerant can be circulated smoothly, the temperature does not rise, and the compressor 8l can be prevented from seizing.

FIG. 2 shows a refrigerating circuit diagram of a low temperature refrigerating apparatus according to another embodiment of the present invention. The low-temperature refrigeration system 17 is different from the low-temperature refrigeration system 7 shown in FIG.
Then, in order to liquefy the high boiling point refrigerant of the low temperature side refrigeration circuit 7l, the heat exchanger 13 which uses the cooling heat of the return refrigerant of the high temperature side refrigeration circuit 7h is used, while in the low temperature refrigeration apparatus 17, the high temperature Condenser 2 that is independent of the side refrigeration circuit 17h
3 is independently arranged in the low temperature side refrigeration circuit 17l so as to observe the liquefaction of the high boiling point refrigerant. Other configurations are the same as those of the low temperature refrigeration system 7 shown in FIG. 1 and achieve the same effects. Therefore, the same or corresponding parts are designated by the same reference numerals and the description thereof is omitted.

In the above-mentioned embodiment, the invention is applied to the low temperature refrigeration system 7, 17 of the dual refrigeration system as an example, but the invention is applied to the low temperature refrigeration system of the multi-source refrigeration system of two or more sources. Is also applicable. In this case, the low temperature side refrigeration circuit refers to other than the highest temperature side refrigeration circuit.

(Effect of the Invention) As described above, according to the low temperature refrigerating apparatus of the multi-source refrigeration system of the present invention, a mixed refrigerant having a high boiling point and a low boiling point is used as the refrigerant in the cold side refrigeration circuit, and the compressor and the cascade condenser are combined. A condenser for liquefying only the high-boiling-point refrigerant is provided between them, and only the high-boiling-point liquid refrigerant liquefied by the condenser is directly passed to the decompressor by bypassing the cascade condenser, and the decompressor by its sensible heat, Since the frozen lubricating oil is dissolved in the evaporator, it is possible to prevent the lubricating oil of the pressure reducer and the evaporator from being frozen and to prevent seizure of the compressor.

[Brief description of drawings]

FIG. 1 is a diagram showing a refrigerating circuit of a low temperature refrigerating apparatus which is an embodiment of the present invention, FIG. 2 is a diagram showing a refrigerating circuit of a low temperature refrigerating apparatus which is another embodiment of the present invention, and FIG. It is a figure which shows the refrigeration circuit of the low temperature refrigeration equipment of. 7,17 …… Low temperature refrigeration equipment, 7l, 17l …… Low temperature side refrigeration circuit, 8l …… Compressor, 10l …… Capillary tube (pressure reducer), 11 …… Cascade condenser, 12 …… Evaporator, 13… … Heat exchanger (condenser), 14 …… Gas-liquid separator, 15 …… Bypass path, 23 …… Condenser

Claims (1)

[Scope of utility model registration request] 1. A combination of at least two independent refrigeration circuits via a cascade condenser, wherein a low temperature side refrigeration circuit comprises a compressor, the cascade condenser, a pressure reducer and an evaporator connected in series in a closed loop. In the low temperature refrigeration system of the formed multi-source refrigeration system, while using a high boiling point / low boiling point mixed refrigerant as the refrigerant of the low temperature side refrigeration circuit, between the compressor and the cascade condenser, only the high boiling point refrigerant is used. A condenser for liquefying, a gas-liquid separator for separating a liquefied high-boiling-point refrigerant and a low-boiling-point refrigerant in a gas phase state is interposed in series, and the gas phase separated by the gas-liquid separator The low temperature refrigeration system of the multi-source refrigeration system in which the refrigerant in the state is guided to the cascade condenser, while the liquid refrigerant is directly guided to the pressure reducer via a bypass path.