JP2626912B2 - Refrigeration equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultra-low-temperature refrigeration apparatus suitable for cryopreservation of living organisms and microbial cells.

(Prior art) With the development of technology in the fields of medical and biotechnology, refrigeration equipment for cryopreservation of living organisms and microorganisms has been used for longer term storage, as long as cells during cryopreservation are not destroyed as much as possible. Since what can be done is desired, a refrigerating device that can obtain an extremely low temperature is required.

In order to meet such needs, various measures have been taken, but a refrigerant mixture comprising a plurality of types of refrigerants having different boiling points is sequentially condensed from a refrigerant having a higher boiling point to a refrigerant having a lower boiling point. A so-called mixed refrigerant type refrigeration for finally evaporating a refrigerant having a low evaporation temperature to obtain a desired ultra-low temperature is performed.

However, since there is a limit to the ultra-low temperature obtained by such a device, a first refrigeration circuit and a second refrigeration circuit filled with a mixed refrigerant comprising a plurality of types of refrigerants are provided, and an evaporator of the first refrigeration circuit and a second refrigeration circuit are provided. By using a dual refrigerating system refrigeration circuit so that heat is exchanged with the condenser of the refrigeration circuit, it is possible to obtain an ultra-low temperature with a small size, good controllability of temperature, and high heat exchange efficiency. It is disclosed in JP-A-62-73046. And, in the second refrigeration circuit, R21, R13, R1, R14, R
A mixed refrigerant consisting of four refrigerants such as 59
It has a very low temperature of 150 ° C.

On the other hand, the refrigeration system of the mixed refrigerant system sequentially performs gas-liquid separation and heat exchange, and obtains a desired low temperature by finally performing evaporation. Therefore, the refrigerant that evaporates and performs the cooling action tends to become considerably high in temperature due to a heat load corresponding to the heat capacity of cooling. When such high-temperature gas refrigerant passes through the cascade heat exchanger before returning to the compressor, the heat exchange there becomes unstable, so not only the cooling by the cooler becomes unstable, but also the rising Deteriorate. Further, when the high-temperature gas refrigerant returns directly to the compressor, the compressor is overheated, so that not only the above-mentioned instability of cooling and the poor start-up but also an anxiety about failure of the device.

(Problems to be Solved by the Invention) However, the conventional ultra-low-temperature refrigeration system employs a two-dimensional refrigeration system, which requires two compressors, which not only complicates the configuration of the refrigeration system, but also increases Since a control device for exchanging heat between refrigeration circuits is required,
The refrigeration system becomes complicated from the viewpoint of control. There is also a problem that operation is unstable at the time of startup in the mixed refrigerant system.

Therefore, the present invention eliminates such a refrigeration apparatus having a complicated configuration, is simple in terms of both configuration and control, can obtain an extremely low temperature of -150 ° C., and can perform stable cooling from the beginning of startup. It is an object to obtain an ultra-low temperature refrigeration system.

(Means for Solving the Problems) In the present invention, the refrigeration apparatus is a single-unit refrigeration system of a mixed refrigerant system, and the mixed refrigerant to be enclosed is such that the evaporation temperature differences of a plurality of types of mixed refrigerants are sequentially reduced. This is a predetermined interval.

Then, between the compressor and the cooler, a condenser is first provided, and then the gas refrigerant is separated from the gas-liquid separator and the cascade heat exchanger in the same manner as the residual gas refrigerant separated by the gas-liquid separator. Are connected so as to exchange heat with the refrigerant in a gas-liquid mixed state by reducing the pressure, and these are sequentially connected from the first stage to the fourth stage, and further, the fourth cascade heat in the final stage is provided. A sub-cooler for liquefying the residual gas refrigerant from the exchanger is provided. The sub-cooler is connected so that a part of the low-boiling refrigerant that has been cooled and liquefied is depressurized and heat-exchanged with the residual gas refrigerant from the fourth cascade heat exchanger. The refrigerant flowing out of the main cooler and the sub-cooler after being cooled is connected from the fourth cascade heat exchanger to the compressor via the first cascade heat exchanger.

In other words, the refrigeration apparatus of the present invention is characterized in that a mixed refrigerant composed of a plurality of types of refrigerant having a predetermined difference in boiling point temperature is sequentially sealed from a high boiling point to a low boiling point, and the compressed refrigerant is compressed. A refrigerant that cools the mixed refrigerant compressed by the compressor; a first gas-liquid separator that mainly separates the cooled mixed refrigerant into a high-boiling liquid refrigerant and a residual gas refrigerant; A first cascade heat exchanger for exchanging heat between the residual gas refrigerant separated by the gas-liquid separator and a high-boiling liquid refrigerant which is similarly separated and then decompressed; The second, third, and fourth gas-liquid separators that separate the exchanged residual gas refrigerant into a liquid refrigerant and a residual gas refrigerant in the same manner in order from a refrigerant having a higher boiling point, and Residues separated by the third and fourth gas-liquid separators , Third, and fourth cascade heat exchangers for exchanging heat between the liquid refrigerant and the decompressed liquid refrigerant, respectively, after being separated, and the residual low-boiling gas from the fourth cascade heat exchanger The subcooler that liquefies the refrigerant by exchanging heat with the decompressed refrigerant, which is part of the refrigerant that has exited from its own outlet, and of the refrigerant that has exited from the outlet of the subcooler. A main cooler that evaporates the remaining and depressurized refrigerant, and sequentially transfers the refrigerant that has been cooled by the main cooler and the sub-cooler from the fourth cascade heat exchanger to the first cascade heat exchanger. The compressor is configured to return to the compressor via an exchanger.

(Operation) The gaseous mixed refrigerant compressed by the compressor is cooled by the condenser, becomes a mixed state of the liquefied high-boiling refrigerant and the residual gas, and is separated by the first gas-liquid separator. The separated residual gas refrigerant is heat-exchanged in the first cascade heat exchanger with the decompressed liquid refrigerant, which is also divided here, and is supplied to the second-stage second gas-liquid separator. Hereinafter, in the same manner, the refrigerant mainly from the middle boiling point to the low boiling point is separated into gas and liquid in the second, third and fourth gas-liquid separators in sequence.
Heat is exchanged in the third and fourth cascade heat exchangers, respectively.

The low-boiling gas refrigerant that has exited the fourth cascade heat exchanger in the final stage enters the subcooler and is liquefied. In the sub-cooler, heat is exchanged between a part of the low-boiling refrigerant that has exited the outlet and a low-boiling gas refrigerant that enters the sub-cooler, and the low-boiling gas refrigerant is completely liquefied.

Most of the low-boiling liquid refrigerant leaving the sub-cooler is depressurized and enters the main cooler, where it evaporates to produce ultra-low temperatures.

The low-boiling gas refrigerant evaporated in the main cooler and the low-boiling gas refrigerant cooled in the sub-cooler are sequentially sent to the compressor via the fourth, third, second, and first cascade heat exchangers. At that time, the liquid refrigerant separated at the fourth, third, second, and first gas-liquid separators sequentially merges with the decompressed liquid refrigerant.

Thus, in the present invention, the refrigeration circuit is integrated,
The number of stages of the combination of the gas-liquid separator and the cascade heat exchanger is set to four, and the mixed refrigerant composed of a plurality of types of refrigerants having different boiling points is sequentially subjected to gas-liquid separation from those having a high boiling point to those having a low boiling point. Heat exchange (cooling) is performed, and a refrigerant finally liquefied with the lowest boiling point is evaporated in the main cooler to obtain an ultra-low temperature. Therefore, the discharge pressure of the compressor can be reduced, and unlike the secondary refrigeration system, only one compressor is required, and no device for controlling the operation between the two refrigeration circuits is required. The compressors that can be used here are the same as those used for ordinary air conditioning and refrigeration.

In addition, as the refrigerant that is a component of the mixed refrigerant, a refrigerant having a difference in boiling point temperature sequentially and at substantially a predetermined interval is selected, and for each stage of gas-liquid separation and heat exchange, the refrigerant is sequentially cooled at approximately equal intervals. Go,
By evaporating the refrigerant having the lowest boiling point finally, efficient cooling without waste is achieved, so that an extremely low temperature is obtained.

Furthermore, after the low-boiling-point gas refrigerant from the fourth cascade heat exchanger, which is the final stage, is liquefied in the sub-cooler, a part of the gas refrigerant is used for cooling in the sub-cooler, but is not used in the main cooler. It joins with the low-boiling gas refrigerant after the cooling action.
For this reason, immediately after the start of the refrigerating apparatus, when the temperature of the main cooler is not sufficiently lowered, even if the temperature of the low-boiling-point gas refrigerant flowing out due to the cooling action of the main cooler is abnormally high, Can be reduced. Therefore, the heat exchange in each cascade heat exchanger is stable even when the apparatus is started, and the cooling in the main cooler can be stabilized.

(Embodiment) An embodiment of a refrigeration apparatus for an ultra-low temperature storage which obtains an ultra-low temperature of -150 ° C by using a mixed refrigerant composed of six types of refrigerants having different boiling point temperatures will be described with reference to the drawings.

The components of the mixed refrigerant enclosed in the refrigeration apparatus are as follows.

Model Molar ratio (%) Boiling point (℃) R11 25 ± 5 23.82 R12 20 ± 5 − 29.79 R13 15 ± 5 −81.4 R14 15 ± 5 −127.96 R50 15 ± 5 −161.6 R740 10 ± 5 −185.7 However, the above boiling point is At atmospheric pressure.

FIG. 1 shows the connection between the components of the refrigeration system. The discharge side of the compressor 1 is connected to the inlet of the condenser 2 by a pipe, and the outlet of the condenser 2 is connected to the first gas-liquid separator. A pipe is connected to the inlet of the vessel 3. Since the first gas-liquid separator 3 allows a relatively large amount of mixed refrigerant to flow, the first gas-liquid separator 3 is larger than the latter one. And the gas phase part 3a of the first gas-liquid separator 3
Is connected to the outer pipe inlet of the first cascade heat exchanger 4, and the liquid phase part 3 b is connected to the inner pipe inlet of the first cascade heat exchanger 4 via the first thin pipe 5 as depressurizing means. Piping is connected. The first cascade heat exchanger 4 is formed of a double pipe, and the outer pipe inlet is connected to the inner pipe in order to effectively perform heat exchange between the refrigerant flowing through the outer pipe and the refrigerant flowing through the inner pipe. At the same end as the outlet, it is located at the same other end as the outer tube outlet and the inner tube inlet, respectively, so that the flows of the refrigerant in the inner and outer tubes are opposite to each other. In this way, a first stage of gas-liquid separation and heat exchange is formed, which mainly functions for liquefaction and separation of R11 and R12 and thereby heat exchange.

Hereinafter, similarly, the second gas-liquid separator 6 and the second cascade heat exchanger 7, the third gas-liquid separator 9 and the third cascade heat exchanger 10, and the fourth gas-liquid separator 12 and the fourth cascade. The heat exchanger 13 is connected, the outer pipe outlet of the first cascade heat exchanger 4 is connected to the inlet of the second gas-liquid separator 6, and the outer pipe outlet of the second cascade heat exchanger 7 is connected to the third gas-liquid separator. 9 and the outer tube outlet of the third cascade heat exchanger 10 is a fourth gas-liquid separator
Twelve inlets are connected to respective pipes to form second to fourth stages of gas-liquid separation and heat exchange.

The sub-cooler 15 is also a double-pipe heat exchanger, and its outer pipe inlet is connected to the outer pipe outlet of the fourth cascade heat exchanger 13 by piping. One is connected to the inner pipe inlet of the subcooler 15 via a fifth thin pipe 16 as a pressure reducing means. The other branch is connected to the inlet of a main cooler 18 provided in an ultra-low temperature storage (not shown) via a sixth thin tube 17 as a pressure reducing means.

Then, the piping from the outlet of the main cooler 18 and the sub-cooler 15
The pipes from the inner pipe outlet merge with the pipe from the fourth thin pipe 14 to the inner pipe inlet of the fourth cascade heat exchanger 13. Hereinafter, similarly, the inner pipe outlet of the fourth cascade heat exchanger 13 is connected to the inner building inlet of the third cascade heat exchanger 10 by the third pipe.
The inner pipe outlet of the cascade heat exchanger 10 is connected to the inner pipe inlet of the second cascade heat exchanger 7, and the inner pipe outlet of the second cascade heat exchanger 7 is connected to the inner pipe inlet of the first cascade heat exchanger 4. Is done. The inner pipe outlet of the first cascade heat exchanger 4 is connected to the suction port of the compressor 1 by piping.

During the steady operation, the suction pressure of the compressor 1 is 1.75 kg / cm ² G and the discharge pressure is 16.9 kg / cm ² G, and the mixed refrigerant discharged therefrom is in a high-temperature gas state of about 94 ° C. And condenser 2
At about 27 ° C, mainly with R1
Most of 1 and a considerable portion of R12 liquefy, and the other portions enter a gas-liquid mixed state in a gaseous state. And the gas refrigerant separated and separated by the first gas-liquid separator 3 is the first gas-liquid separator 3.
About −34 ° C. in the cascade heat exchanger 4, mainly R12
Is liquefied and a substantial portion of R13 is liquefied, and the remaining refrigerant is in a gas-liquid mixed state in a gaseous state. Then, these are separated in the second gas-liquid separator 6, and the separated gas refrigerant is converted to about −64 in the second cascade heat exchanger 7.
° C, mainly most of R13 and part of R14 are liquefied, and the remaining refrigerant is in a gas-liquid mixed state in a gaseous state. These are separated in the third gas-liquid separator 9, and the separated gas refrigerant is liquefied in the third cascade heat exchanger 10 at about −89 ° C., mainly a portion of R14 and a portion of R50 are liquefied. Is in a gas-liquid mixed state where the refrigerant is in a gaseous state.

These are separated in the fourth gas-liquid separator 12, and the separated gas refrigerant is supplied to the fourth cascade heat exchanger 13
At -109 ° C, a considerable part of R50 and a part of R740 liquefied,
The remaining refrigerant enters a gas-liquid mixed state in a gas state.

The remaining gas-liquid mixed refrigerant mainly composed of R740 is
In the subcooler 15, a part of the refrigerant flowing out of the outer tube outlet and heat exchange with the refrigerant decompressed by the fifth thin tube 16 become a complete liquefied state at about -123 ° C, The remainder of the refrigerant flowing out of the outer tube outlet of the sub-cooler 15 is decompressed in the sixth thin tube 17 and then flows into the main cooler 18 at about -155 ° C and evaporates. Cool to very low temperatures.

By the way, at the time of startup, this extremely low temperature cannot be obtained at once. Since the cooler 18 is often at substantially the same temperature as the surrounding environment, the temperature of the gas refrigerant flowing out of the main cooler 18 will be much higher than about -148 ° C during steady operation. However, it merges with the liquid refrigerant at about −110 ° C. flowing out of the subcooler 15, is mixed therewith and cooled, and flows into the fourth cascade heat exchanger 14.
Therefore, there is no adverse effect on the heat exchange in the preceding stage, and stable start-up can be performed.

As described above, the combination of gas-liquid separation and heat exchange is sequentially divided into four stages, the liquid refrigerant cooled in the previous stage is separated, the pressure is reduced to lower the temperature, and the next stage is cooled, Since the temperature difference between each stage is substantially uniform and not so large, cooling efficiency can be maintained high,
The compressor 1 does not generate a particularly large pressure ratio (discharge pressure / suction pressure), but may be a compressor for ordinary air conditioning.

Each mixed refrigerant has only a high boiling point in each stage,
Not only those with medium boiling points or those with low boiling points are liquefied and separated into gas and liquid, but those with high boiling points also remain, and the residual amount gradually decreases in each stage. R11, R1
2, R13, R14 and R50 slightly remain. Further, in consideration of heat loss in the process of generating a low temperature, the component ratio is increased as the boiling point increases, and the component ratio is decreased as the boiling point decreases.

Although the above is one of the preferred embodiments, if there is a large change in the size of each component device, for example, an additional device such as providing a flow control valve in the piping, or if the device capacity of each part fluctuates, The component ratio of the refrigerant may change. The refrigerant to be mixed may be another refrigerant as long as the refrigerants are combined so that the boiling point temperature differences are substantially the same.

Cooling in the condenser is not limited to cooling water, but may be air. The temperature is also determined appropriately. The cascade heat exchanger is not limited to the double tube type, but may be various types such as a parallel tube type or a coiled pipe in a vessel. The decompression means is not limited to the thin tube,
It may be a pressure reducing valve or an expansion valve. Further, the connection between the constituent devices may be configured such that the gas-liquid separator and the cascade heat exchanger are connected by piping and unitized to be sequentially connected. Furthermore, the cooling device can be used as a cold trap, a cooling device, or any other device that requires an extremely low temperature.

(Effects of the Invention) As described above, according to the present invention, since a single system is used, the number of components including a compressor can be reduced, and complicated control unlike a dual system is not required. Furthermore, since a four-stage gas-liquid separation system is used, a compressor for air conditioning or refrigeration having a low discharge pressure can be used, so that the configuration and control are both simplified, downsized, and efficiently. An ultra-low temperature of 150 ° C can be obtained, and a refrigeration apparatus with good stability at startup can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram showing an embodiment of the present invention. 1 ... Compressor, 2 ... Condenser, 3 ... First gas-liquid separator,
4 first cascade heat exchanger, 6 second gas-liquid separator, 7 second cascade heat exchanger, 9 third gas-liquid separator, 10 third cascade heat exchanger, 12: 4th stage liquid separator, 13: 4th cascade heat exchanger, 15: sub-cooler, 18: main cooler.

Claims (1)

(57) [Claims] 1. A compressor for compressing a refrigerant mixture comprising a plurality of types of refrigerants having a predetermined difference in boiling point temperature sequentially from a high boiling point to a low boiling point. A condenser that cools the mixed refrigerant compressed by the compressor; a first gas-liquid separator that mainly separates the cooled mixed refrigerant into a high-boiling liquid refrigerant and a residual gas refrigerant; and a first gas-liquid separator. A first cascade heat exchanger for exchanging heat between the residual gas refrigerant separated in step 1 and a high-boiling-point liquid refrigerant decompressed and then decompressed, and a residual heat exchanged in the first cascade heat exchanger. A second, a third and a fourth gas-liquid separator for separating the gaseous refrigerant into a liquid refrigerant and a residual gaseous refrigerant in the same order, starting from the refrigerant having a higher boiling point, 4 Residual gas refrigerant separated by gas-liquid separator Second, third, and fourth cascade heat exchangers for performing heat exchange with the depressurized liquid refrigerant after being separated, and a residual low-boiling gas refrigerant from the fourth cascade heat exchanger. A sub-cooler that liquefies by exchanging heat with a part of the refrigerant that has exited from the outlet and the depressurized refrigerant; and a remaining part of the refrigerant that has exited from the outlet of the sub-cooler and has been depressurized. And a main cooler for evaporating the refrigerant that has been cooled by the main cooler and the sub-cooler.
A refrigeration apparatus characterized in that the refrigeration apparatus is configured to sequentially return to the compressor from the fourth cascade heat exchanger via the first cascade heat exchanger.