JPH047491Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a mixed refrigerant cycle that generates extremely low temperatures, and particularly to a refrigeration device suitable for rapid freezing.

(Prior Art) A mixed refrigerant refrigeration cycle that generates extremely low temperatures will be explained using a three-stage gas-liquid separation type mixed refrigerant cycle shown in FIG. A mixed refrigerant, which is a mixture of refrigerants with different boiling points, is used as the refrigerant. The gas refrigerant compressed by the compressor 1 is cooled by the condenser 2 and is partially condensed. Next, the generated liquid refrigerant is transferred to the first gas-liquid separator 3
to separate the gas refrigerant. The separated liquid refrigerant is depressurized and expanded by a first expansion means 4 such as a capillary tube, enters a first cascade condenser 5, cools the separated gas refrigerant, and further condenses a portion. The gas-liquid mixed refrigerant generated here is separated in a second gas-liquid separator 6, the liquid refrigerant is expanded under reduced pressure in a second expansion means 7, the gas refrigerant is cooled in a second cascade condenser 8, and a portion of the refrigerant is to condense. The gas-liquid mixed refrigerant generated here is transferred to the third gas-liquid separator 9
Then, the separated gas refrigerant is separated into a gas refrigerant and a liquid refrigerant, and in the third cascade condenser 11, the separated gas refrigerant is completely condensed into a liquid refrigerant.
This is then expanded under reduced pressure by the expansion means 12 and evaporated by the evaporator 13 to generate an extremely low temperature. However, the mixed refrigerant used here has a property that its evaporation temperature increases as it evaporates even if the evaporation pressure is the same.
Therefore, in reality, as shown in Figure 3, heat exchange between the refrigerant at the inlet of the compressor 1 and the outlet of the condenser 2, and the
3 outlet and the refrigerant at the cascade condenser 11 outlet, and the evaporation side first cascade condenser 5 inlet and second cascade condenser 8 outlet. By connecting the inlet of the condenser 11 and the outlet of the evaporator 13 to sufficiently recover heat from each refrigerant, very efficient operation can be achieved. However, when the cycle is stable, the auxiliary condenser 14, which exchanges heat between the evaporator 13 outlet and the condensing side outlet of the third cascade condenser 11, uses the low-temperature refrigerant at the evaporator outlet to replace the refrigerant before the fourth expansion means 12. , has the function of further supercooling and increasing the cooling capacity, but at the beginning of startup, since the evaporator 13 has a heat capacity, the temperature of the refrigerant at the outlet of the evaporator 13 is high, and conversely heats the liquid refrigerant in front of the expansion means 12, Reduce cooling capacity. As a result, cooling of the evaporator 13 is delayed,
The drawback was that it took a very long time to stabilize the cycle. This tendency is more pronounced in freezers and the like whose evaporators have a large heat capacity.

(Problems to be Solved) The present invention aims to shorten the operating time from startup to stabilization in the above-mentioned refrigeration system, and improve the operating efficiency of the system.

(Means for Solving Problems) The present invention provides that in the above-mentioned refrigeration system, a switching valve is connected to the liquid refrigerant outlet flow path of the final stage gas-liquid separator, and one outlet of this switching valve is connected to the The other outlet is connected to the inlet of the expansion means connected to the evaporator.

(Function) At startup, the switching valve is switched to the evaporator side, and the liquid refrigerant used as cooling power for condensing the final gas refrigerant is supplied to the evaporator to pre-cool the evaporator. This facilitates cooling of the evaporator at the beginning of startup, and speeds up the stabilization of the cycle.

(Example) An example in which the present invention is applied to a three-stage gas-liquid separation type mixed refrigerant refrigeration cycle will be explained with reference to FIG.

The outlet of the compressor 1 of this refrigeration system is connected to the inlet of the condenser 2, and the outlet of the condenser 2 is connected to the inlet of one flow path of the first auxiliary cascade condenser 15. The first auxiliary cascade condenser 15 pre-cools the refrigerant supplied to the first cascade condenser 5 as the first stage cascade condenser with the refrigerant from the outlet of the evaporator 13, and has a double pipe structure. The two outlets are piped to one inlet of the outer tube. The following cascade capacitors have the same structure and are connected by piping in the same way.

The outlet of this flow path of the first auxiliary cascade condenser 15 is connected by piping to the inlet of the first gas-liquid separator 3 as the first-stage gas-liquid separator, and the gas refrigerant outlet of the first gas-liquid separator 3 is connected to the first gas-liquid separator 3. The cascade condenser 5 is connected to the cascade condenser 5 through piping, with one port of the outer tube serving as an inlet. In addition, the liquid refrigerant outlet is connected to the inlet of a first capillary tube 4 as an initial stage expansion means, and the outlet of the first capillary tube 4 is connected to the inlet of the inner tube of the first cascade condenser 5 and the outlet of the outer tube. Piping is connected to one side.

The second and third stages are connected in the same way,
The outlet of the outer tube of the third cascade condenser 11 serving as the final stage cascade condenser is connected to the inlet of the outer tube of the second auxiliary cascade condenser 14 . Further, a liquid refrigerant outlet of the first gas-liquid separator 9 as a final stage gas-liquid separator is connected to an inlet of a switching valve 16, and one outlet of the switching valve 16 is connected to a third capillary as a final stage expansion means. The inlet of the inner pipe of the third cascade condenser 11 is connected via the tube 10 to the outlet of the outer pipe.

The outlet of the outer pipe of the second auxiliary cascade condenser 14 and the other outlet of the switching valve 16 are both connected to the inlet of a capillary tube 12 as an expansion means connected to the inlet of the evaporator 13 .

The outlet of the evaporator 13 is connected to the outlet of the inner tube on the outlet side of the outer tube of the second auxiliary cascade condenser 14 by piping, and the outlet of the inner tube of the second auxiliary cascade condenser 14 is connected to the outlet of the inner tube of the second auxiliary cascade condenser 14 . The third capillary tube 14 is connected to the inner pipe inlet with a connection from the third capillary tube 14 outlet.

Thereafter, connections between the inner tubes of the cascade capacitors in each stage are made in the same way, and the inner tube outlet of the first cascade condenser 5 is connected to the inner tube port on the outlet side of the outer tube of the first auxiliary cascade condenser 15. Connected by piping. The inner pipe outlet of the first auxiliary cascade condenser 5 is connected to the inlet of the compressor 1 by piping.

Furthermore, a temperature sensor 17 is provided on the outlet side of the evaporator 13.
is provided, and its output is connected to the control circuit 18. The control circuit 18 generates an electric signal that switches the switching valve to the starting position when the temperature sensor input is above a desired low temperature, and its output is connected to the switching valve.

The operation of the cycle is as described above, but since the switching valve 16 is provided, the refrigerant is switched to flow to the inlet of the evaporator 13 when the cycle is started. When it is detected by the refrigerant temperature at the outlet of the evaporator 13 that the evaporator 13 has been sufficiently cooled, the refrigerant is switched to flow to the evaporation side inlet of the third cascade condenser 11. As a result, until the evaporator 13 is cooled from room temperature to a desired low temperature, the liquid refrigerant at the previous stage is used instead of the final liquid refrigerant. Therefore, at the start of the cycle, the second
By using the liquid refrigerant directly separated by the three gas-liquid separators without using the final gas refrigerant that was heated inversely by the auxiliary condenser 14, efficiency is improved by eliminating heat loss lost in each heat exchanger. The evaporator 13 can be cooled well and the time required for stabilization can be shortened.

In other embodiments, a first auxiliary cascade capacitor is not necessary, but it may be more efficient to use it.

The expansion means is not limited to a capillary tube, but may be an expansion means or the like.

Each cascade condenser is not limited to being connected by piping so that the refrigerant from the condenser side is passed through the outer pipe and the refrigerant from the evaporator is passed through the inner pipe, but it is also possible to connect them in the opposite manner. Furthermore, each cascade condenser is not limited to a heat exchanger with a double-tube structure, but can also have a structure in which one tube is wound around the other tube in a coil shape, or other types. .

The refrigerant temperature on the evaporator outlet side can also be displayed on a visible thermometer and the switching valve can be operated manually.

(Effects of the invention) According to the invention, the heat loss caused by the auxiliary condenser etc. can be eliminated and the liquid refrigerant separated in the final gas-liquid separator can be directly used, which increases the cooling efficiency of the cycle and stabilizes the cycle. The time required can be reduced to approximately half of the conventional time.

[Brief explanation of the drawing]

FIG. 1 is a mixed refrigerant cycle diagram showing an embodiment of the present invention, and FIGS. 2 and 3 are conventional mixed refrigerant cycle diagrams. In the drawings, 1 is a compressor, 2 is a condenser, 3 is a first (first stage) gas-liquid separator, 4 is a first capillary tube (first stage expansion means), 5 is a first (first stage) cascade condenser, and 6 is a first stage cascade condenser. Second (next stage) gas-liquid separator,
7 is a second capillary tube (next stage expansion means);
8 is a second (next stage) cascade condenser, 9 is a third (final stage) gas-liquid separator, 10 is a third capillary tube (final stage expansion means), 11 is a third (final stage) cascade condenser, 12 13 is a capillary tube (expansion means), 13 is an evaporator, 14 is a second auxiliary condenser, 15 is a first auxiliary condenser, 16 is a switching valve, 17 is a temperature sensor, and 18 is a control circuit.

Claims (1)

[Scope of claim for utility model registration] (1) A mixed refrigerant made by mixing various types of refrigerants is compressed, cooled in a condenser, and partially condensed. This gas refrigerant is led to the next stage gas-liquid separator through one flow path of the first stage cascade condenser.
The liquid refrigerant passes through the first-stage expansion means and returns to the compressor through the other flow path of the first-stage cascade condenser together with the gas refrigerant from the other flow path of the next-stage cascade condenser. The refrigerant cooled by the final stage cascade condenser is further guided to one flow path of the auxiliary cascade condenser, and is also guided to the evaporator via expansion means, where the gas from the evaporator is In a refrigeration system in which the refrigerant is guided to the other flow path of the auxiliary cascade condenser, a switching valve is connected to the liquid refrigerant outlet flow path of the final stage gas-liquid separator, and one outlet of the switching valve is connected to the liquid refrigerant outlet flow path of the final stage gas-liquid separator. is connected to the final stage expansion means, and the other outlet is connected to the inlet of the expansion means connected to the evaporator. (2) The switching valve is operated by an electric signal and is connected to the output of a control circuit that inputs the output of a temperature sensor provided on the outlet side of the evaporator. Refrigeration equipment.