JPH0429338Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an ultra-low temperature refrigeration device using a non-azeotropic refrigerant mixture.

(Prior art) A refrigeration system that uses a non-azeotropic mixed refrigerant to generate ultra-low temperatures repeatedly cools the refrigerant and separates gas and liquid, ultimately separating and extracting the liquid with low boiling point components. Ultra-low temperature is obtained by latent heat of vaporization. On the other hand, there is currently no lubricating oil used in compressors that does not solidify at extremely low temperatures. For this reason, lubricating oil (hereinafter referred to as oil) contained in the refrigerant discharged from the compressor
reaches the low-temperature section of the refrigeration cycle, where it loses its fluidity and adheres to the walls of the passages. As the amount of adhesion increases, the pressure loss in the flow of refrigerant increases, which not only reduces the suction pressure of the compressor and causes inefficient operation, but also impedes heat transfer through the pipe wall and significantly reduces cooling performance. There was a drawback.

For this reason, in the case of refrigeration equipment that does not necessarily require continuous operation, it is recommended to stop operation as appropriate, wait until the temperature of the ultra-low temperature part reaches or exceeds the pour point of the oil, and then restart operation to compress the clogged oil. It was sent back to the aircraft to improve the flow of refrigerant and restore cooling performance. However, this method has a problem in that cooling performance is hindered if the operation is stopped too often or if the recovery of oil fluidity is slow and the operation has to be stopped for a long time.

For this reason, oil separators are installed in the pipes through which the refrigerant flows, or high-temperature uncondensed refrigerants are intermittently passed to the ultra-low temperature section through bypass pipes consisting of pipes and solenoid valves (especially Although it is unavoidable for refrigeration equipment that requires continuous operation, it is uneconomical because the equipment becomes complicated in other cases.

(Problems to be Solved) The present invention has been made in view of the above-mentioned drawbacks, and can be used in the above-mentioned refrigeration equipment, especially those that can stop operation intermittently, without making the equipment complicated. The purpose of the present invention is to provide an ultra-low temperature refrigeration system that is capable of high performance and economical operation, and whose performance is not inhibited by a decrease in the fluidity of oil.

(Means and effects for solving the problem) The present invention sequentially separates the non-azeotropic mixed refrigerant, and finally extracts the low boiling point refrigerant as a liquid component, which is depressurized and cooled by a cooler. This is a refrigeration system that generates ultra-low temperatures.The low-pressure side pipe line on which lubricating oil adheres has a downward slope structure toward the suction part of the compressor, so that during intermittent shutdowns, the lubricating oil, which has regained fluidity due to the rise in temperature, is It is designed to be collected into a compressor by natural fall.

(Example) Hereinafter, an example in which the present invention is implemented in a cryostat refrigeration device will be described using FIG. 1. 1st
The figure is a substantial connection diagram that not only shows the connections of the devices that make up this refrigeration system, but also shows the positional relationship in the height direction.

In FIG. 1, the refrigeration system includes a compressor 1, a condenser 2, a first gas-liquid separator 3, a first cascade heat exchanger 4, a first capillary 5, a second gas-liquid separator 6, and a second cascade heat exchanger. It is composed of a container 7, a second thin tube 8, a pressure reducing device 9, a cooler 10, and a pipe line connecting these.

Here, the cooler 10 is a piping welded to the outer surface of a stainless steel inner box of a low-temperature chamber (not shown) in a regularly meandering manner. Furthermore, the first and second cascade heat exchangers 4 and 7 have a double tube structure, and the flow directions of the refrigerant flowing through the inner tubes 4'' and 7'' and the outer tubes 4' and 7' are opposite to each other. connected like this.

The discharge side of the compressor 1 is connected to an inlet of a condenser 2 by piping, and the outlet of the condenser 2 is connected to an inlet of a first gas-liquid separator 3 by piping. The gas outlet of the first gas-liquid separator 3 connects to the first cascade heat exchanger 4
The outlet of the outer tube 4' is connected to the inlet of the second gas-liquid separator 6 by piping. The gas outlet of the second gas-liquid separator 6 is connected to the inlet of the outer tube 7' of the second cascade heat exchanger 7, and the outlet of the outer tube 7' is connected to the cooler 10 through the pressure reducing device 9.
The pipe is connected to the inlet of the And cooler 1
The outlet of 0 connects the inner tube 7'' of the second cascade heat exchanger 7 and the inner tube 4'' of the first cascade heat exchanger 4 to a flow opposite to the refrigerant flow in the respective outer tubes 7' and 4'. The piping is connected to the suction side of the compressor 1 via sequentially in the opposite direction as shown in FIG. Further, the liquid reservoir section of the second gas-liquid separator 6 and the liquid reservoir section of the first gas-liquid separator 3 are connected to piping and pipes from the outlet of the cooler 10 to the inner pipe 7'' of the second cascade heat exchanger 7, respectively. The pipes from the inner pipe 7'' of the second cascade heat exchanger 7 to the inner pipe 4'' of the first cascade heat exchanger 4 are also connected by thin tubes 8 and 5.

The cooler 10, the pipe 11, the inner pipe 7'' of the second cascade heat exchanger 7, the pipe 12, the inner pipe 4'' of the first cascade heat exchanger 4, the pipe 13, and the suction part of the compressor 1 are As shown in Figure 1, they are arranged sequentially from high to low positions and are connected to piping. That is, the low-pressure side pipe line leading from the cooler 10 to the pipe 13 is arranged at a downward slope toward the suction part of the compressor 1.

In addition, the control device (not shown) for operating this refrigeration equipment does not operate completely continuously, but is designed to be able to stop operation intermittently when oil that has lost fluidity becomes clogged in the ultra-low temperature section. .

In the refrigeration cycle formed in this way, a plurality of refrigerants having different evaporation temperatures (for example, R
1, R12, R13, etc.) are enclosed.

The operation of this refrigeration cycle will be explained below. The refrigerant compressed in the compressor 1 is cooled in the condenser 2, and a part of the refrigerant in the mixed refrigerant, here the component with the highest evaporation temperature, is mainly liquefied and sent to the first gas-liquid separator in a gas-liquid mixed state. 3, where it is separated into a high boiling point component that becomes a liquid refrigerant and the remaining gas refrigerant. The liquid refrigerant is depressurized in the first capillary tube 5 and flows into the inner tube 4'' from the outside of the end of the first cascade heat exchanger 4, while the gas refrigerant separated in the first gas-liquid separator 3 is The refrigerant flows into the outer pipe 4' of the cascade heat exchanger 4 and heat exchange is performed.The refrigerant flowing through the outer pipe 4' of the first cascade heat exchanger 4 is a part of the refrigerant, and here the evaporation temperature is medium temperature. The components are mainly liquefied and flow into the second gas-liquid separator 6 in a gas-liquid mixed state, where they are separated into a medium-boiling point component, which has become a liquid refrigerant, and a gas refrigerant (mainly a low-boiling point component). The gas refrigerant flows into the inner tube 7'' from the outside of the end of the second cascade heat exchanger 7 through the thin tube 8, and the gas refrigerant flows into the outer tube 7' of the second cascade heat exchanger 7 to exchange heat with each other. The low boiling point refrigerant flowing in the outer pipe 7 is completely liquefied and reduced in pressure by the pressure reducing device 9, and then flows into the cooler 10, where it evaporates and generates an extremely low temperature. Due to this evaporation, the cryogenic chamber (not shown) provided with the cooler 10 becomes extremely low temperature. The refrigerant evaporated in the cooler 10 is transferred to the second cascade heat exchanger 7 together with the refrigerant guided through the second thin tube 8.
The refrigerant flows into the inner tube 7'' of the first cascade heat exchanger 4 after joining with the refrigerant guided through the first thin tube 5, and then flows into the inner tube 4'' of the first cascade heat exchanger 4. Return.

In such a device, if the refrigeration operation continues, the cooler 10, piping 11, and second cascade heat exchanger 7
The low pressure side pipe line consisting of the inner pipe 7'' of the first cascade heat exchanger 4, the pipe 12, the inner pipe 4" of the first cascade heat exchanger 4, and the pipe 13,
The lubricating oil contained in the refrigerant gas discharged from the compressor 1 gradually solidifies and adheres to the refrigerant gas. As a result,
The pressure loss in the pipeline increases, and the cooling performance gradually decreases. However, this low-pressure side pipe line has a downward slope with respect to the suction section of the compressor 1. Therefore, once the operation is stopped due to intermittent operation, the adhered oil regains fluidity as the temperature rises and is returned to the compressor 1 by gravity. Therefore, at the time of restart, the pipe resistance is also eliminated and highly efficient cooling operation can be performed. In this embodiment, gas and liquid are separated twice, but the present invention is not limited to this, and can also be applied to a refrigeration cycle in which gas and liquid are separated once or n times.

Furthermore, the cascade heat exchanger is not limited to a double tube structure, and may be of various types, such as a parallel tube type or one in which a coiled pipe is built into a container. Although it is possible not to pass the refrigerant from the cooler through the cascade heat exchanger, it is advantageous to do so. The pressure reducing device may be a capillary tube or the like in addition to a pressure reducing valve. In addition to the cryostat, it can also be used as a cooling device for cold traps and other applications. Also,
The refrigerant used may also be a mixed refrigerant other than those in the above embodiments.

(Effects) The present invention is a refrigeration system that uses a non-azeotropic mixed refrigerant and generates ultra-low temperatures by repeatedly cooling the refrigerant and separating gas and liquid. This method is very effective in that it is possible to remove lubricating oil accumulation in ultra-low temperature parts without complicating the structure of the device, and it is possible to continue highly efficient cooling operation at all times.

[Brief explanation of the drawing]

The drawings illustrate embodiments of the invention,
FIG. 1 is a physical connection diagram of the refrigeration circuit. In the drawings, 1... Compressor, 2... Condenser, 3... First gas-liquid separator, 4... First cascade heat exchanger, 5...
First capillary, 6... Second gas-liquid separator, 7... Second cascade heat exchanger, 8... Second capillary, 9... Pressure reducing device, 10... Cooler, 4', 7'... Outer tube, 4″,
7″……Inner tube.

Claims (1)

[Scope of utility model registration request] A first gas-liquid separator 3 that compresses a non-azeotropic mixed refrigerant with a compressor, cools it with a condenser, and separates the partially condensed gas-liquid mixed refrigerant into a liquefied high-boiling point refrigerant and a residual gas refrigerant. and a first cascade heat exchanger 4 in which the low-temperature refrigerant after depressurizing the liquid refrigerant separated in the first gas-liquid separator and the gas refrigerant separated similarly exchange heat, and a first cascade heat exchanger 4 that passes through the first cascade heat exchanger. A second gas-liquid separator 6 separates the gas refrigerant into a liquefied medium-boiling point refrigerant and a residual gas refrigerant, and separates the liquid refrigerant separated in the second gas-liquid separator in the same way as the low-temperature refrigerant after depressurization. The remaining low boiling point component gas passes through the second cascade heat exchanger 7, where the gas refrigerant exchanges heat, and the remaining low boiling point component gas passes through the same gas-liquid separator and cascade heat exchanger in sequence, and then passes through the n-th cascade heat exchanger at the final stage. Completely liquefy the refrigerant, reduce the pressure with a pressure reducing device, and guide it to the cooler.
The cooler is connected to the compressor suction in a refrigeration cycle, and has a path in which the refrigerant flowing into each cascade heat exchanger and cooler under reduced pressure returns to the compressor so as to obtain a desired cold temperature; A refrigeration system in which a low-pressure side pipe line including a cascade heat exchanger is formed in a downward slope structure with respect to the compressor.