JP2001235247A - Double-element freezer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a positive adjustment for a supplying amount of refrigerant to an evaporator for an upper stage freezing operation even in the case that a compressor with a fixed capacity is employed in a refrigerant circuit at a low temperature side of double-element type freezer. SOLUTION: A low temperature side refrigerant circuit (30) is provided with a bypassing circuit (40) and a refrigerant heat exchanger (50). A first passage (51) in the refrigerant heat exchanger (50) is connected between a compressor (38) and a cascade condenser (26) in a low temperature side refrigerant circuit (30). A second passage (52) in the refrigerant heat exchanger (50) is arranged at the middle part of the bypassing circuit (40). When one freezing device (13b) is thermally turned off, a bypassing solenoid valve (41) is opened to cause a part of a liquid refrigerant to be fed into the bypassing circuit (40). The refrigerant entered the bypassing circuit (40) is decreased in its pressure with a capillary tube (42), thereafter the refrigerant is fed into a second passage (52) of the refrigerant heat exchanger (50). Then, a part of discharged refrigerant at the compressor (38) is condensed at the first passage (51) of the refrigerant heat exchanger (50).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration system for performing a binary refrigeration cycle.

[0002]

2. Description of the Related Art Conventionally, a refrigeration system for performing a binary refrigeration cycle has been known as disclosed in Japanese Patent Application Laid-Open No. 9-210515. This type of refrigeration apparatus is used, for example, to maintain the inside of a freezer at a low temperature.

[0003] Specifically, the refrigerating apparatus is provided with a high-temperature side refrigerant circuit, a low-temperature side refrigerant circuit, and a cascade condenser. The high-temperature side refrigerant circuit and the low-temperature side refrigerant circuit are each configured as a closed circuit, in which the refrigerant circulates to perform a vapor compression refrigeration cycle. At this time, the refrigerant circulating in both refrigerant circuits exchanges heat with each other in the cascade condenser. The cascade condenser constitutes an evaporator of the high-temperature side refrigerant circuit and constitutes a condenser of the low-temperature side refrigerant circuit. For example, the evaporator of the low-temperature side refrigerant circuit is provided in the freezer, and the inside of the refrigerator is maintained at about minus several tens degrees by the operation of the refrigerating device.

In the refrigerating apparatus, a compressor having a fixed capacity is often used as a compressor of the low-temperature side refrigerant circuit. This is in consideration of operating conditions, cost, and the like in the low-temperature side refrigerant circuit. On the other hand, since the cooling load in the low-temperature side refrigerant circuit fluctuates, it is necessary to change the refrigerant circulation amount in the low-temperature side refrigerant circuit corresponding to this load fluctuation. In particular, in the case where a plurality of evaporators are provided in parallel in the low-temperature side refrigerant circuit and a plurality of freezers are individually cooled, since each of the freezers individually performs thermo-on / off, the refrigerant circulation in the low-temperature side refrigerant circuit is performed. The amount fluctuates greatly. Therefore, in such a case, it is essential to change the refrigerant circulation amount in the low-temperature side refrigerant circuit.

[0005] For this reason, in the low-temperature side refrigerant circuit of the refrigerating apparatus, the amount of refrigerant sent to the evaporator is changed by a so-called hot gas bypass. In other words, a circuit for guiding the refrigerant discharged from the compressor to the suction side of the compressor is provided, and the entire discharge gas is not sent to the cascade condenser, but a part of the discharge gas is depressurized and then returned to the compressor again. Was.

[0006]

However, in the low-temperature side refrigerant circuit of the refrigerating apparatus, since a part of the discharge gas is returned to the compressor as it is, the enthalpy of the refrigerant sucked by the compressor increases. For this reason, there has been a problem that the temperature and pressure of the discharged gas become excessive, and the refrigeration cycle operation in the low-temperature side refrigerant circuit becomes unstable. Further, in the hot gas bypass circuit, since the gaseous refrigerant flows at a relatively high flow velocity, there has been a problem that the noise generated thereby becomes excessive.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a low-temperature side refrigerant circuit while avoiding the above-mentioned problems even when a fixed-capacity compressor is employed. The purpose of the present invention is to reliably control the supply amount of the refrigerant to the evaporator.

[0008]

A first solution of the present invention is to provide a high-temperature refrigerant circuit (20) and a low-temperature refrigerant circuit (3).
0) and an intermediate heat exchanger (26).
The present invention is directed to a binary refrigeration apparatus that performs a binary refrigeration cycle by exchanging heat in an intermediate heat exchanger (26) between a refrigerant circulating in a low temperature side refrigerant circuit (30) and a refrigerant circulating in a low temperature side refrigerant circuit (30). And, in the low temperature side refrigerant circuit (30), a compressor (38),
Intermediate heat exchanger (26) and refrigerant expansion mechanism (35a, 35b)
And the evaporators (32a, 32b) are connected, and a part of the condensed refrigerant bypasses the evaporators (32a, 32b) to adjust the amount of refrigerant sent to the evaporators (32a, 32b). In addition, bypass means for condensing a part of the refrigerant compressed by the compressor (38) using the refrigerant bypassing the evaporator (32a, 32b) is provided.

According to a second aspect of the present invention, in the first aspect, a plurality of evaporators (32a, 32b) are connected in parallel to the low-temperature side refrigerant circuit (30). The bypass means is configured such that a part of the condensed refrigerant bypasses all of the evaporators (32a, 32b).

According to a third aspect of the present invention, in the first or second aspect, the bypass means is compressed by a compressor (38) with a refrigerant bypassing the evaporator (32a, 32b). And a refrigerant heat exchanger (50) for exchanging heat with the refrigerant.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the bypass means is configured such that a part of the refrigerant sent to the expansion mechanism (35a, 35b) after the condensation is removed from the evaporator (32a, 3b).
It has a bypass circuit (40) for inflowing to bypass 2b) and for decompressing a part of the inflowing refrigerant and introducing it to the refrigerant heat exchanger (50).

In the first solution, the refrigerant circulates in the high-temperature side refrigerant circuit (20) and the low-temperature side refrigerant circuit (30) while changing phase. In each of the refrigerant circuits (20, 30), a cycle including compression, condensation, expansion, and evaporation is repeated, and a vapor compression refrigeration cycle is performed. At that time, in the intermediate heat exchanger (26), the refrigerant circulating in the two refrigerant circuits (20, 30) exchange heat with each other. In the intermediate heat exchanger (26), the refrigerant in the low-temperature side refrigerant circuit (30) releases heat and condenses, while the refrigerant in the high-temperature side refrigerant circuit (20) absorbs heat and evaporates. That is, the intermediate heat exchanger (26) forms a so-called cascade condenser.

The low temperature side refrigerant circuit (30) is provided with bypass means. In the low-temperature side refrigerant circuit (30), the amount of the refrigerant supplied to the evaporators (32a, 32b) is adjusted by the operation of the bypass means. Specifically, a part of the condensed refrigerant flows so as to bypass the evaporator (32a, 32b). That is, in the refrigerant condensed in the refrigeration cycle operation, a part of the refrigerant flows by bypassing the evaporator (32a, 32b), and only the remaining refrigerant is sent to the evaporator (32a, 32b). Therefore, the amount of refrigerant supplied to the evaporators (32a, 32b) is reduced. At this time, the condensed high-pressure liquid refrigerant may bypass the evaporator (32a, 32b), and the refrigerant decompressed by the expansion mechanism (35a, 35b) may be supplied to the evaporator (32
a, 32b) may be bypassed.

In the bypass means, the evaporator (32a,
The refrigerant bypassing 32b) is used to condense a part of the high-pressure gas refrigerant discharged from the compressor (38). That is, the high-pressure gas refrigerant radiates heat to the refrigerant bypassing the evaporator (32a, 32b), and a part of the refrigerant condenses.
Accordingly, the amount of the high-pressure gas refrigerant in the low-temperature side refrigerant circuit (30) to be condensed in the intermediate heat exchanger (26) is reduced,
In the intermediate heat exchanger (26), the amount of heat to be absorbed by the refrigerant in the high-temperature side refrigerant circuit (20) also decreases. The refrigerant bypassing the evaporators (32a, 32b) is returned to the suction side of the compressor (38) after being used for condensation of the high-pressure gas refrigerant.

In the second solution, a plurality of evaporators (32a, 32b) are provided in the low-temperature side refrigerant circuit (30). Each evaporator (32a, 32b) is connected in parallel with each other. Then, the refrigerant circulating in the low-temperature side refrigerant circuit (30) is distributed to each evaporator (32a, 32b) and evaporates. Meanwhile, the evaporator (3
When adjusting the amount of refrigerant supplied to the evaporators (2a, 32b), a part of the condensed refrigerant flows by bypassing all the evaporators (32a, 32b) by the operation of the bypass means. That is, in this case, a part of the refrigerant before being distributed to each evaporator (32a, 32b) is diverted by the bypass means, and a part of the high-pressure gas refrigerant discharged from the compressor (38) is condensed. After being used, it is returned to the suction side of the compressor (38).

In the third solution, the refrigerant heat exchanger (50) is provided in the bypass means of the low-temperature side refrigerant circuit (30). The refrigerant heat exchanger (50) includes a refrigerant that bypasses the evaporator (32a, 32b) by bypass means, and a compressor (38).
The high-pressure gas refrigerant compressed in the above is introduced. In the refrigerant heat exchanger (50), both refrigerants exchange heat, and the high-pressure gas refrigerant radiates heat. Then, a part of the high-pressure gas refrigerant is condensed in the refrigerant heat exchanger (50). Meanwhile, evaporators (32a, 32b)
The refrigerant introduced into the refrigerant heat exchanger (50) by bypassing the refrigerant absorbs heat, evaporates, and is returned to the suction side of the compressor (38).

In the fourth solution, a bypass circuit (40) is provided in the bypass means of the low temperature side refrigerant circuit (30). This bypass circuit (40) has an expansion mechanism (35a, 35
Part of the refrigerant sent to b) flows in. That is, the high-pressure liquid refrigerant before being condensed and decompressed flows into the bypass circuit (40). Part of this high-pressure liquid refrigerant is supplied to the bypass circuit (4
0) bypasses the evaporator (32a, 32b) and reduces the amount of refrigerant sent to the evaporator (32a, 32b). The refrigerant flowing into the bypass circuit (40) is introduced into the refrigerant heat exchanger (50) after being decompressed. In the refrigerant heat exchanger (50), the decompressed refrigerant absorbs heat from the refrigerant compressed by the compressor (38) and evaporates. The refrigerant evaporated in the refrigerant heat exchanger (50) is thereafter returned to the suction side of the compressor (38).

[0018]

According to the present invention, the low-temperature side refrigerant circuit (30) is provided with bypass means so that a part of the circulating refrigerant is evaporated (32a, 32a).
The amount of refrigerant sent to the evaporator (32a, 32b) is adjusted by bypassing 32b). And the evaporator (32a, 32
A part of the refrigerant compressed by the compressor (38) is condensed using the refrigerant bypassing b). Therefore, the amount of refrigerant that needs to be condensed in the intermediate heat exchanger (26) can be reduced, and the amount of heat that the refrigerant in the high-temperature side refrigerant circuit (20) should absorb in the intermediate heat exchanger (26) can be reduced. As a result, the amount of heat to be processed in the high-temperature side refrigerant circuit (20) can be reduced, the energy required for the refrigeration cycle operation in the high-temperature side refrigerant circuit (20) can be reduced, and the energy required for the cooling operation can be reduced. .

In the bypass means of the present invention, the condensed refrigerant bypasses the evaporators (32a, 32b). That is, the high-pressure liquid refrigerant or the refrigerant in the gas-liquid two-phase state after the pressure reduction bypasses the evaporator (32a, 32b). For this reason, the flow velocity of the refrigerant flowing through the piping for the bypass can be reduced, and the noise caused by the flow of the refrigerant can be reduced as compared with the case where the circulation amount is adjusted by the hot gas bypass as in the related art.

Further, in the bypass means of the present invention, the refrigerant whose enthalpy has been reduced by condensation flows by bypassing the evaporators (32a, 32b), and is used to condense a part of the high-pressure gas refrigerant. It is returned to the suction side of (38). For this reason, it is possible to suppress an increase in the enthalpy of the refrigerant sucked by the compressor (38), as compared with the case where the circulation amount is adjusted by the hot gas bypass as in the related art. As a result, the temperature and pressure of the gas discharged from the compressor (38) are prevented from becoming excessive, and the evaporator (32a, 32
The amount of refrigerant sent to b) can be adjusted appropriately.

Therefore, according to the present invention, even when a fixed-capacity compressor is employed in the low-temperature side refrigerant circuit (30), generation of the above-described refrigerant noise and instability of the operation state are avoided. In addition, the amount of refrigerant supplied to the evaporators (32a, 32b) can be reliably adjusted.

[0022]

Embodiment 1 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

As shown in FIGS. 1 and 2, the binary refrigeration system (10) according to the present embodiment is installed in a supermarket to cool a freezer. This binary refrigeration system (10) includes one outdoor unit (11), one cascade unit (12), and two refrigeration units (13
a, 13b). The outdoor unit (11), the cascade unit (12), and the refrigeration units (13a, 13b) contain various types of equipment, and these equipment are connected by piping to connect the high-temperature side refrigerant circuit (20) and the low-temperature side refrigerant circuit ( 30) is configured.

The high-temperature side refrigerant circuit (20) includes a compression mechanism (21), an outdoor condenser (23), a receiver (24), an electric expansion valve (25), and a cascade condenser (26). It is connected. Among these, the compression mechanism (21), the outdoor condenser (23), the receiver (24), and the electric expansion valve (25) are provided in the outdoor unit (11). The cascade condenser (26) forms an intermediate heat exchanger, and is provided in the cascade unit (12).

The compression mechanism (2) of the high-temperature side refrigerant circuit (20)
1) is configured by connecting two compressors (22) in parallel. The compression mechanism (21) is configured to have a variable capacity by changing the number of operating compressors (22).
A check valve (CV) is provided on the discharge side of each compressor (22). The discharge side of each compressor (22) is connected to the inlet end of the outdoor condenser (23).

The outdoor condenser (23) is for condensing the refrigerant by heat exchange with outdoor air. The outdoor unit (11) is provided with an outdoor fan (14), and the outdoor fan (14) sends outdoor air to the outdoor condenser (23). The outlet end of this outdoor condenser (23) is connected to the receiver (24)
It is connected to the. The receiver (24) is an electric expansion valve (2
5) is connected to the high temperature side inlet end of the cascade capacitor (26). The cascade condenser (26) forms an evaporator in the high-temperature side refrigerant circuit (20). The outlet end on the high temperature side of the cascade condenser (26) is connected to the suction side of the compression mechanism (21), that is, each compressor (2
2) It is connected to the suction side.

The low temperature side refrigerant circuit (30) includes a compressor (38), a refrigerant heat exchanger (50), a cascade condenser (26), a receiver (31), and two refrigeration evaporators ( 32a, 32b) and an accumulator (33). Of these, the compressor (38) and the refrigerant heat exchanger (5
0), a cascade capacitor (26) and a receiver (3
1) and the accumulator (33) are provided in the cascade unit (12). In addition, refrigeration evaporator (32
a, 32b) are connected in parallel to each other, and each is provided in a separate refrigeration unit (13a, 13b).

A first passage (51) and a second passage (52) are defined in the refrigerant heat exchanger (50). A refrigerant is introduced into each of the first passage (51) and the second passage (52). The refrigerant heat exchanger (50) is configured to exchange heat between the refrigerant flowing through the first passage (51) and the refrigerant flowing through the second passage (52).

The compressor (38) has a fixed capacity. That is, control of the number of revolutions of the compressor motor by the inverter is not performed on the compressor (38). The discharge side of the compressor (38) is connected to the inlet end of the first passage (51) in the refrigerant heat exchanger (50). Refrigerant heat exchanger (5
The outlet end of the first passage (51) in (0) is connected to the lower end of the cascade condenser (26). An outlet end on the low-temperature side of the cascade capacitor (26) is connected to the receiver (31). Receiver (3
1) is connected to the inlet end of each freezing evaporator (32a, 32b). The outlet end of each refrigerating evaporator (32a, 32b) is connected to the suction side of a compressor (38) via an accumulator (33).

The part provided in the refrigeration units (13a, 13b) of the low-temperature side refrigerant circuit (30) is used in the utilization side circuit (34).
a, 34b). That is, each user side circuit (34a, 3
4b), one freezing evaporator (32a, 32b) is arranged. At the inlet side of the refrigerating evaporator (32a, 32b) in each use side circuit (34a, 34b), one thermosensitive expansion valve (35a, 35b) and one use side solenoid valve (37a, 37b) are connected in series. It is provided in. The temperature-sensitive cylinders (36a, 36b) of the temperature-sensitive expansion valves (35a, 35b)
Evaporator for refrigeration (32a, 32) in use side circuit (34a, 34b)
b) Installed on the exit side. The degree of opening of the temperature-sensitive expansion valves (35a, 35b) changes according to the pipe temperature at the outlet side of the refrigerating evaporator (32a, 32b) to which the temperature-sensitive cylinders (36a, 36b) are attached. This constitutes a refrigerant expansion mechanism in the low-temperature side refrigerant circuit (30).

The freezing evaporators (32a, 32b) evaporate the refrigerant by heat exchange with the air in the freezer. Each freezer unit (13a, 13b) is provided with a freezer fan (15a, 15b).
a, 15b) sends air inside the freezer to the freezing evaporator (32a, 32b).

A bypass circuit (40) is connected to the low-temperature side refrigerant circuit (30). This bypass circuit (40) is provided in the cascade unit (12). One end of the bypass circuit (40) is connected to the low-temperature side refrigerant circuit (3
0) Receiver (31) and refrigeration evaporator (32a, 32b)
, That is, one end is connected upstream of the refrigerating evaporator (32a, 32b). The other end of the bypass circuit (40) is located between the refrigerating evaporator (32a, 32b) and the accumulator (33) in the low-temperature side refrigerant circuit (30), that is, the refrigerating evaporator (32
The other end is connected downstream of a, 32b). The bypass circuit (40) is provided with a bypass solenoid valve (41), a capillary tube (42), and a refrigerant heat exchanger (50) in order from one end to the other end.

When the amount of refrigerant sent from the receiver (31) to the refrigerating evaporators (32a, 32b) is adjusted, one of the liquid refrigerant discharged from the receiver (31) is supplied to the bypass circuit (40). Department is introduced. The bypass circuit (40) depressurizes the introduced liquid refrigerant with the capillary tube (42), and then sends it to the second passage (52) of the refrigerant heat exchanger (50). Also,
The bypass circuit (40) converts the refrigerant flowing out of the second passage (52) of the refrigerant heat exchanger (50) into an accumulator (33).
That is, return to the suction side of the compressor (38). The bypass circuit (40) and the refrigerant heat exchanger (50) constitute bypass means.

-Operating operation- An operation during the cooling operation of the binary refrigeration system (10) will be described.

<< Operation in Normal Operation >> First, the operation in the normal operation of cooling the refrigerator air in both refrigeration units (13a, 13b) will be described.

In the low temperature side refrigerant circuit (30), the use side solenoid valves (37a, 37b) of each use side circuit (34a, 34b) are opened, and the bypass solenoid valve (41) is closed. When the compressor (38) is operated in this state, the low-temperature side refrigerant circulates in the low-temperature side refrigerant circuit (30) to perform a refrigeration cycle operation.

Specifically, the refrigerant discharged from the compressor (38) passes through the first passage (51) of the refrigerant heat exchanger (50) and flows into the cascade condenser (26). In normal operation, the refrigerant discharged from the compressor (38) simply passes through the refrigerant heat exchanger (50). Therefore, no heat exchange is performed in the refrigerant heat exchanger (50).

The refrigerant flowing into the cascade condenser (26) exchanges heat with the refrigerant in the high-temperature side refrigerant circuit (20), radiates heat and condenses. The condensed refrigerant once flows into the receiver (31), and is then split and separated into each of the refrigeration units (13a, 13b).
To the user side circuits (34a, 34b). As mentioned above,
The bypass solenoid valve (41) of the bypass circuit (40) is closed. Therefore, all of the liquid refrigerant flowing out of the receiver (31) is supplied to each of the use side circuits (34a, 34b).

The refrigerant flowing into each of the utilization side circuits (34a, 34b) is depressurized by the temperature-sensitive expansion valve (35a, 35b), and then flows into the refrigerating evaporator (32a, 32b). Evaporator for refrigeration (3
In 2a, 32b), the refrigerant absorbs heat from the air in the refrigerator and evaporates.
Thereby, the inside air is cooled. The refrigerant evaporated in the refrigeration evaporator (32a, 32b) is supplied to the accumulator (3
It is sucked into the compressor (38) again through 3). In the low-temperature side refrigerant circuit (30), the low-temperature side refrigerant circulates as described above to perform a refrigeration cycle.

In the high temperature side refrigerant circuit (20), the electric expansion valve (25) is adjusted to a predetermined opening. When both compressors (22) of the compression mechanism (21) are operated in this state, the high-temperature side refrigerant circulates in the high-temperature side refrigerant circuit (20), and the refrigeration cycle operation is performed.

Specifically, the refrigerant discharged from the compression mechanism (21) is sent to the outdoor condenser (23). Outdoor condenser (2
In 3), the refrigerant radiates heat and condenses due to heat exchange with outdoor air. The refrigerant condensed in the outdoor condenser (23) once flows into the receiver (31), and is then sent to the electric expansion valve (25). The refrigerant decompressed by the electric expansion valve (25) is sent to the cascade condenser (26).

In the cascade condenser (26), the inflowing refrigerant absorbs heat from the refrigerant in the low-temperature side refrigerant circuit (30) and evaporates. The refrigerant evaporated in the cascade condenser (26)
It is sent to the compression mechanism (21) and sucked into both compressors (22) again. In the high temperature side refrigerant circuit (20), the high temperature side refrigerant circulates as described above to perform a refrigeration cycle.

<< Operation at Thermo-Off >> Next, the operation when the second refrigeration unit (13b) is thermo-off will be described. When the air inside the freezer reaches the set temperature, the second freezing unit (13
b) Thermo-off.

In this case, in the low-temperature side refrigerant circuit (30), the use side solenoid valve (37b) of the thermo-off second refrigeration unit (13b) is closed, and the bypass solenoid valve (41) is opened. When the compressor (38) is operated in this state, the refrigerant circulates in the low-temperature side refrigerant circuit (30) to perform a refrigeration cycle. Hereinafter, points different from the operation during the normal operation will be described.

In the low-temperature side refrigerant circuit (30), a part of the liquid refrigerant flowing out of the receiver (31) is bypassed (4).
0). Therefore, only the remaining refrigerant is sent to the refrigeration evaporator (32a) of the first refrigeration unit (13a) that continues to operate. The refrigerant sent to the refrigeration evaporator (32a) is depressurized by the temperature-sensitive expansion valve (35a), flows into the refrigeration evaporator (32a), absorbs heat from the air in the refrigerator, evaporates, and then accumulates the refrigerant. 33). This point
Same as during normal operation.

On the other hand, the refrigerant flowing into the bypass circuit (40) is reduced in pressure while flowing through the capillary tube (42).
Thereafter, the refrigerant is introduced into the second passage (52) of the refrigerant heat exchanger (50). The high-pressure gas refrigerant discharged from the compressor (38) is introduced into the first passage (51) of the refrigerant heat exchanger (50) as in the normal operation. In the refrigerant heat exchanger (50), the refrigerant in the first passage (51) and the refrigerant in the second passage (52) exchange heat.

In the second passage (52) of the refrigerant heat exchanger (50), the refrigerant introduced after being decompressed by the capillary tube (42) absorbs heat and evaporates. This evaporated refrigerant is
It is sent to the accumulator (33). Then, in the accumulator (33), the refrigerant evaporated in the refrigerant heat exchanger (50) and the refrigerant evaporated in the refrigeration evaporator (32a) merge,
The joined refrigerant is sucked into the compressor (38).

In the first passage (51) of the refrigerant heat exchanger (50), the high-pressure gas refrigerant radiates heat and a part of the refrigerant condenses. Thereafter, the refrigerant in the first passage (51) is sent to the cascade condenser (26), radiates heat to the refrigerant in the high-temperature side refrigerant circuit (20), and is completely condensed. That is, in the cascade condenser (26), only the refrigerant not condensed in the refrigerant heat exchanger (50) releases heat and condenses. Therefore, the heat absorption amount of the refrigerant in the high-temperature side refrigerant circuit (20) in the cascade condenser (26) is reduced as compared with the normal operation.

-Effects of First Embodiment- In the first embodiment, a bypass circuit (40) is provided in the low-temperature side refrigerant circuit (30), and a part of the circulating refrigerant bypasses the refrigeration evaporators (32a, 32b). By doing so, the amount of refrigerant sent to the freezing evaporator (32a, 32b) is adjusted. The refrigerant that bypasses the refrigeration evaporators (32a, 32b) is introduced into the refrigerant heat exchanger (50), and is used to condense a part of the refrigerant compressed by the compressor (38). Therefore, the amount of refrigerant that must be condensed by the cascade condenser (26) can be reduced, and the amount of heat that the refrigerant in the high-temperature side refrigerant circuit (20) should absorb heat can be reduced by the cascade condenser (26).
As a result, the amount of heat to be processed in the high-temperature side refrigerant circuit (20) can be reduced, the input to the compressor (22) of the high-temperature side refrigerant circuit (20) can be reduced, and the energy required for the cooling operation can be reduced. .

The bypass circuit (40) of the first embodiment
In, the condensed refrigerant downstream of the cascade condenser (26) flows. For this reason, the flow velocity of the refrigerant flowing through the piping for the bypass can be reduced, and the noise caused by the flow of the refrigerant can be reduced as compared with the case where the circulation amount is adjusted by the hot gas bypass as in the related art.

The bypass circuit (40) of the first embodiment
In this case, the refrigerant whose enthalpy has decreased due to condensation flows by bypassing the refrigeration evaporators (32a, 32b), and the refrigerant heat exchanger (5
After being used to condense a part of the high-pressure gas refrigerant in 0), it is returned to the suction side of the compressor (38). For this reason, it is possible to suppress an increase in the enthalpy of the refrigerant sucked by the compressor (38), as compared with the case where the circulation amount is adjusted by the hot gas bypass as in the related art. As a result, while the temperature and pressure of the gas discharged from the compressor (38) are prevented from becoming excessively high and stable operation is performed, the refrigeration evaporator (32a,
The amount of refrigerant sent to 32b) can be adjusted appropriately.

Therefore, in this embodiment, the compressor (38) is configured to have a fixed capacity, but even in this case, the generation of the refrigerant noise and the instability of the operation state as described above are avoided. In addition, the amount of the refrigerant supplied to the refrigerating evaporator (32a, 32b) can be surely adjusted.

[0053]

[Embodiment 2] In Embodiment 2 of the present invention, three refrigeration units (13a, 13b, 13c) are provided in a binary refrigeration system (10), and the configuration of a bypass circuit (40) is accordingly changed. To change.

As shown in FIG. 3, each refrigeration unit (13a,
13b, 13c) have the same configuration as that of the first embodiment. That is, each refrigeration unit (13a, 13b, 13c) is provided with one refrigeration evaporator (32a, 32b, 32c). The refrigerating evaporators (32a, 32b, 32c) are connected to the low-temperature side refrigerant circuit (30) in parallel with each other. In addition, the use side circuit (34a, 34b, 3c) of each refrigeration unit (13a, 13b, 13c)
4c), one thermosensitive expansion valve (35a, 35b, 35c) and one use-side solenoid valve (37a, 37b, 37c) are provided. Furthermore,
Each refrigeration unit (13a, 13b, 13c) has a refrigeration evaporator (3
2a, 32b, 32c) Freezer fan (15a, 15)
b, 15c) are provided.

In the bypass circuit (40) according to the second embodiment, two capillary tubes (42a, 42b) are provided in parallel. Among them, a switching solenoid valve (43) is provided upstream of the second capillary tube (42b). This switching solenoid valve (43) is operated as follows.

For example, only the third refrigeration unit (13c) is turned off and the first and second refrigeration units (13a, 13c) are turned off.
In b), when the cooling operation is continued, the switching solenoid valve (43) is closed. In this state, the refrigerant corresponding to the amount sent to the refrigeration evaporator 3 of the third refrigeration unit (13c) that has been thermo-off flows into the bypass circuit (40). This refrigerant is depressurized only through the first capillary tube (42a), and then the second passage (5) of the refrigerant heat exchanger (50).
Introduced in 2).

On the other hand, the second and third refrigeration units (13b,
When the thermostat 13c is turned off and only the first refrigeration unit (13a) continues the cooling operation, the switching solenoid valve (43) is opened. In this state, the refrigerant corresponding to the amount sent to the refrigeration evaporators (32b, 32c) of the second and third refrigeration units (13b, 13c) that have been thermo-off flows into the bypass circuit (40). This refrigerant is supplied to both capillary tubes (42a, 42a).
After being distributed to b), the pressure is reduced in each of the capillary tubes (42a, 42b), and then introduced into the second passage (52) of the refrigerant heat exchanger (50).

That is, when the amount of the refrigerant flowing into the bypass circuit (40) increases, the pressure of the refrigerant is reduced using the first and second capillary tubes (42a, 42b). Thereby, the second passage (5) of the refrigerant heat exchanger (50)
The pressure of the refrigerant introduced into 2) is maintained appropriately.

[0059]

Other Embodiments In the first embodiment described above, the capillary tube (42) is provided in the bypass circuit (40) to reduce the pressure of the refrigerant. Alternatively, the following configuration may be adopted. Good. That is, as shown in FIG. 4, an electric expansion valve (44) of a bypass circuit (40) may be provided instead of the capillary tube (42). In this case, the amount of refrigerant sent to the refrigerating evaporator (32a, 32b) can be continuously adjusted instead of stepwise, and a cooling operation more suitable for operating conditions can be performed.

[Brief description of the drawings]

FIG. 1 is a piping diagram of a low-temperature side refrigerant circuit according to a first embodiment.

FIG. 2 is a piping system diagram of a high-temperature side refrigerant circuit according to Embodiment 1.

FIG. 3 is a piping diagram of a low-temperature side refrigerant circuit according to a second embodiment.

FIG. 4 is a piping diagram of a low-temperature side refrigerant circuit according to another embodiment.

[Explanation of symbols]

 (20) High-temperature side refrigerant circuit (26) Cascade condenser (intermediate heat exchanger) (30) Low-temperature side refrigerant circuit (32a, 32b, 32c) Refrigeration evaporator (evaporator) (35a, 35b, 35c) Thermal expansion Valve (expansion mechanism) (38) Compressor (40) Bypass circuit (50) Refrigerant heat exchanger

Claims (4)

[Claims] The refrigerant circuit includes a high-temperature side refrigerant circuit (20), a low-temperature side refrigerant circuit (30), and an intermediate heat exchanger (26). ) Is a binary refrigeration system that exchanges heat with the refrigerant circulating in the intermediate heat exchanger (26) to perform a binary refrigeration cycle, and the low-temperature side refrigerant circuit (30) includes a compressor (38) The intermediate heat exchanger (26), the refrigerant expansion mechanism (35a, 35b), and the evaporator (32a, 32b) are connected, and a part of the condensed refrigerant is removed from the evaporator (32a, 32b). The amount of refrigerant sent to the evaporator (32a, 32b) is adjusted by bypassing the refrigerant, and the refrigerant compressed by the compressor (38) using the refrigerant bypassing the evaporator (32a, 32b). Binary refrigeration system provided with bypass means for partially condensing. 2. The two-way refrigeration system according to claim 1, wherein the low-temperature side refrigerant circuit (30) includes a plurality of evaporators (32a, 32b).
Are connected in parallel with each other, while the bypass means is configured so that a part of the condensed refrigerant
a, 32b) A binary refrigeration system configured to bypass all of the above. 3. The binary refrigeration system according to claim 1, wherein the bypass means exchanges heat between the refrigerant bypassing the evaporator (32a, 32b) and the refrigerant compressed by the compressor (38). Binary refrigeration system equipped with a heat exchanger (50). 4. The two-way refrigeration system according to claim 3, wherein the bypass means flows a part of the refrigerant sent to the expansion mechanism (35a, 35b) after the condensation to bypass the evaporator (32a, 32b). And a bypass refrigeration system including a bypass circuit (40) for reducing the pressure of a part of the refrigerant flowing into the refrigerant heat exchanger (50).