JPWO2014045394A1 - Refrigeration equipment - Google Patents

Abstract

The refrigeration apparatus 100 includes a first refrigerant circuit 50 and a second refrigerant circuit 60, and the cascade condenser 15 is configured by the first evaporator 4 of the first refrigerant circuit 50 and the second condenser 7 of the second refrigerant circuit 60. Refrigeration equipment. The second refrigerant circuit 60 of the refrigeration apparatus 100 is connected to the receiver 8 provided between the second condenser 7 and the second expansion valve 10 and the second compressor 5, and surplus of the second compressor 5. The refrigerating machine oil 18 is stored to adjust the amount of the refrigerating machine oil 18 in the second compressor 5, the bypass circuit 13 that connects the receiver 8 and the tank 14, and the bypass circuit 13, A bypass valve 13a that opens the bypass circuit 13 when the high pressure of the refrigerant circuit 60 becomes equal to or higher than a predetermined pressure, and closes the bypass circuit 13 when the high pressure of the second refrigerant circuit 60 becomes lower than the predetermined pressure. .

Description

  The present invention relates to a refrigeration apparatus, and more particularly to a binary refrigeration apparatus that includes a first refrigerant circuit and a second refrigerant circuit, and in which a cascade condenser is configured by an evaporator of the first refrigerant circuit and a condenser of the second refrigerant circuit. It is.

As a conventional refrigerator, a binary refrigeration apparatus including a first refrigerant circuit and a second refrigerant circuit, and a cascade condenser formed by an evaporator of the first refrigerant circuit and a condenser of the second refrigerant circuit has been proposed. Such a conventional binary refrigeration apparatus includes an expansion tank 65 connected to a pipe 20S on the suction side of the compressor 20 via a capillary tube 66 in the second refrigerant circuit, and in parallel with the capillary tube 66. A check valve 67 is connected, and a configuration having a configuration of “the forward direction of the check valve is set to the direction of the expansion tank 65” has been proposed (see Patent Document 1).
Such a refrigeration apparatus normally increases the pressure in the second refrigerant circuit by quickly collecting the refrigerant in the second refrigerant circuit into the expansion tank via the check valve when the compressor of the second refrigerant circuit is stopped. To prevent this. In addition, such a refrigeration apparatus gradually starts the compressor of the second refrigerant circuit by returning the refrigerant from the expansion tank into the second refrigerant circuit through the decompression device after the compressor of the second refrigerant circuit is started. The load is reduced.

JP 2007-303792 (Summary, FIG. 6)

  In the binary refrigeration apparatus, when the ambient temperature of the second refrigerant circuit is higher than the saturation temperature on the high pressure side of the second refrigerant circuit during operation (saturation temperature of the refrigerant flowing through the circuit portion on the high pressure side) during operation, When the compressor stops, the pressure in the second refrigerant circuit increases to a pressure corresponding to the ambient temperature. In such a case, the conventional binary refrigeration apparatus collects the refrigerant in the second refrigerant circuit in the expansion tank as described above, and prevents the pressure in the second refrigerant circuit from increasing.

  Here, in the second refrigerant circuit of the operating dual refrigeration system, the circuit portion on the high pressure side (compressor) is compared with the circuit portion on the low pressure side (circuit portion from the decompression device to the compressor inlet). The circuit density from the discharge port to the decompression device) has a higher refrigerant density. For this reason, when the compressor of the second refrigerant circuit is stopped, the pressure of the circuit portion on the high pressure side becomes higher than that of the circuit portion on the low pressure side. However, in the conventional binary refrigeration apparatus, the expansion tank is connected to the suction side piping of the compressor of the second refrigerant circuit, that is, the low pressure side circuit portion of the second refrigerant circuit. For this reason, the conventional binary refrigeration apparatus has a problem that when the compressor of the second refrigerant circuit is stopped, an abnormal increase in pressure may not be avoided in the circuit portion on the high pressure side of the second refrigerant circuit. .

  An on-off valve (a high pressure side circuit portion and a low pressure side circuit portion) prevents the refrigerant from flowing into the evaporator when the compressor of the second refrigerant circuit stops upstream of the evaporator of the second refrigerant circuit. May be provided. When such an on-off valve is provided, since the flow path through which the refrigerant flows from the high pressure side circuit portion of the second refrigerant circuit to the low pressure side circuit portion is further reduced, in the high pressure side circuit portion of the second refrigerant circuit The above-mentioned problem that an abnormal increase in pressure may not be avoided is even more remarkable.

  Further, in the binary refrigeration apparatus, even when the compressor of the second refrigerant circuit is stopped, the abnormal pressure rise of the second refrigerant circuit can be avoided by operating the first refrigerant circuit and cooling the second refrigerant circuit. . For this reason, the expansion tank does not perform its function except when a power failure occurs and the first refrigerant circuit cannot be operated. Therefore, since the conventional binary refrigeration apparatus includes an expansion tank that does not know whether to use it, there is a problem that the cost of the binary refrigeration apparatus increases.

  The present invention solves at least one of the problems as described above, and when the compressor of the second refrigerant circuit stops, an abnormal increase in pressure occurs in the high pressure side circuit portion of the second refrigerant circuit. It aims at providing the freezing apparatus which can prevent generating.

  The refrigeration apparatus according to the present invention includes a first refrigerant circuit in which a first compressor, a first condenser, a first decompression device, and a first evaporator are sequentially connected by piping, a second compressor, a second condenser, And a second condenser circuit in which a decompression device and a second evaporator are sequentially connected by a pipe, and a cascade condenser between the first evaporator of the first refrigerant circuit and the second condenser of the second refrigerant circuit A receiver that is connected between the second condenser of the second refrigerant circuit and the second decompression device and stores excess refrigerant, and the second refrigerant circuit. A tank connected to the two compressors, storing a surplus refrigerating machine oil of the second compressor and adjusting an amount of the refrigerating machine oil in the second compressor, a bypass circuit connecting the receiver and the tank; The high pressure of the second refrigerant circuit provided in the bypass circuit There opens the bypass circuit and equal to or higher than a predetermined pressure, in which the high pressure of the second refrigerant circuit is provided with a first opening and closing valve closing the bypass circuit to become smaller than the predetermined pressure.

  In the refrigeration apparatus according to the present invention, when the second compressor of the second refrigerant circuit is stopped and the high pressure of the second refrigerant circuit becomes equal to or higher than a predetermined pressure, from the receiver provided in the circuit portion on the high pressure side, The refrigerant in the second refrigerant circuit is stored in the tank via the bypass circuit and the first on-off valve. For this reason, when the 2nd compressor of the 2nd refrigerant circuit stops, the refrigerating device concerning the present invention can prevent that the abnormal rise of a pressure occurs in the high pressure side circuit part of the 2nd refrigerant circuit.

  In the refrigeration apparatus according to the present invention, the tank that functions as the expansion tank of the conventional refrigeration apparatus also functions as the oil tank of the second compressor during the operation of the second refrigerant circuit. For this reason, the refrigeration apparatus according to the present invention can also prevent the second compressor from being damaged due to exhaustion of the refrigeration oil.

It is a refrigerant circuit diagram which shows the structure of the freezing apparatus which concerns on Embodiment 1 of this invention. It is a Mollier diagram which shows the operation state of the freezing apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the relationship between the refrigerant density of the 2nd refrigerant | coolant which concerns on Embodiment 1 of this invention, refrigerant temperature, and a refrigerant | coolant pressure. The internal volume of each component of the second refrigerant circuit in the refrigeration apparatus according to Embodiment 1 of the present invention, the amount of refrigerant stored in each component (amount of the second refrigerant), the refrigerant density in the second refrigerant circuit, It is a figure which shows the relationship between a refrigerant | coolant pressure. It is a refrigerant circuit diagram which shows the tank vicinity of the 2nd refrigerant circuit which concerns on Embodiment 1 of this invention. It is a refrigerant circuit figure which shows the structure of the freezing apparatus which concerns on Embodiment 2 of this invention. It is a refrigerant circuit figure which shows the structure of the freezing apparatus which concerns on Embodiment 3 of this invention.

Embodiment 1 FIG.
FIG. 1 is a refrigerant circuit diagram showing a configuration of a refrigeration apparatus according to Embodiment 1 of the present invention.
As shown in FIG. 1, the refrigeration apparatus 100 according to the first embodiment is a binary refrigeration apparatus, and includes a first refrigerant circuit 50 and a second refrigerant circuit 60.

The first refrigerant circuit 50 is a refrigerant circuit through which the first refrigerant circulates. The first refrigerant circuit 1, the first condenser 2, the first expansion valve 3, and the first evaporator 4 are sequentially connected by piping. Yes. The first compressor 1 sucks the first refrigerant in a gas phase at a low pressure and compresses the first refrigerant in a gas phase at a high pressure. The first condenser 2 causes the first refrigerant compressed in the high-pressure gas phase state by the first compressor 1 to exchange heat with a heat exchange target such as air, and condenses it into a high-pressure liquid phase state. The first expansion valve 3 expands and depressurizes the first refrigerant condensed in the high-pressure liquid phase state by the first condenser 2 to form a low-pressure gas-liquid two-phase state. The first evaporator 4 exchanges heat with the second refrigerant flowing through the second condenser 7 of the second refrigerant circuit 60, with the first refrigerant expanded and decompressed in a low-pressure gas-liquid two-phase state by the first expansion valve 3. Evaporates into a low-pressure gas phase. That is, in the refrigeration apparatus 100 according to the first embodiment, the first evaporator 4 of the first refrigerant circuit 50 and the second condenser 7 of the second refrigerant circuit 60 constitute a cascade condenser 15.
Here, the first expansion valve 3 corresponds to the first pressure reducing device of the present invention. A capillary tube or the like may be used as the first decompression device. The “high pressure” and “low pressure” used in the description of the first refrigerant circuit 50 and the “high pressure” and “low pressure” used in the following description of the first refrigerant circuit 50 are the same in the first refrigerant circuit 50. It shows the relative pressure of the first refrigerant at, and does not show the absolute pressure of the first refrigerant.

The second refrigerant circuit 60 is a refrigerant circuit in which the second refrigerant circulates, and is configured by sequentially connecting the second compressor 5, the second condenser 7, the second expansion valve 10, and the second evaporator 11 by piping. Yes. The second compressor 5 sucks the second refrigerant in a gas phase at a low pressure and compresses the second refrigerant in a gas phase at a high pressure. The second condenser 7 exchanges heat between the second refrigerant compressed in the high-pressure gas phase state by the second compressor 5 with the first refrigerant flowing through the first evaporator 4 of the first refrigerant circuit 50, It is condensed to a liquid phase state or a gas-liquid two phase state. The second expansion valve 10 expands and depressurizes the second refrigerant condensed by the second condenser 7 into a high-pressure liquid phase state or a gas-liquid two-phase state to make a low-pressure gas-liquid two-phase state. The second evaporator 11 heat-exchanges the second refrigerant expanded and depressurized by the second expansion valve 10 into a low-pressure gas-liquid two-phase state with a heat exchange target such as air, and evaporates it into a low-pressure gas-phase state. It is.
Here, the second expansion valve 10 corresponds to a second pressure reducing device of the present invention. A capillary tube or the like may be used as the second decompression device. The “high pressure” and “low pressure” used in the description of the second refrigerant circuit 60 and the “high pressure” and “low pressure” used in the following description of the second refrigerant circuit 60 are the same in the second refrigerant circuit 60. It shows the relative pressure of the second refrigerant at, and does not show the absolute pressure of the second refrigerant.

  The second refrigerant circuit 60 according to the first embodiment is also provided with an oil separator 6, a receiver 8, an on-off valve 9, an accumulator 12, a bypass circuit 13, a bypass valve 13a, and a tank 14.

  The oil separator 6 is provided between the second compressor 5 and the second condenser 7 and separates refrigeration oil mixed in the second refrigerant discharged from the second compressor 5. . The oil separator 6 is provided with an oil return pipe 6a. The oil return pipe 6 a is connected to the suction side of the second compressor 5, and the refrigeration oil separated by the oil separator 6 is returned to the suction side of the second compressor 5. The receiver 8 is provided between the second condenser 7 and the second expansion valve 10 and stores excess second refrigerant. Further, when the gas-liquid two-phase second refrigerant flows out of the second condenser 7, the receiver 8 separates the second refrigerant into a gas-phase second refrigerant and a liquid-phase second refrigerant. Also, the second refrigerant in the liquid phase is supplied to the second expansion valve 10.

The on-off valve 9 is provided between the receiver 8 and the second expansion valve 10 and opens and closes a circuit between them. That is, the on-off valve 9 prevents the second refrigerant from flowing into the second evaporator 11. In other words, the on-off valve 9 includes a circuit portion on the high pressure side of the second refrigerant circuit 60 (circuit portion from the discharge port of the second compressor 5 to the second expansion valve 10) and a circuit portion on the low pressure side (second expansion valve). 10 to the circuit portion from the suction port of the second compressor 5).
Here, the on-off valve 9 corresponds to a second on-off valve of the present invention.

  The accumulator 12 is provided between the second evaporator 11 and the second compressor 5. The accumulator 12 separates the second refrigerant flowing out of the second evaporator 11 into a second refrigerant in a gas phase and a second refrigerant in a liquid phase, and the second refrigerant in the gas phase is converted into a second compressor. 5 is sucked in to prevent the occurrence of liquid back in the second compressor 5. In addition, the accumulator 12 also functions to store excess second refrigerant. In addition, the 2nd refrigerant circuit 60 which concerns on this Embodiment 1 is also provided with the receiver 8 as a structure which fulfill | performs the function which stores an excess 2nd refrigerant | coolant. For this reason, the accumulator 12 may not be provided when there is no concern that liquid back may occur in the second compressor 5.

The tank 14 performs the same function as an expansion tank of a conventional refrigeration apparatus (more specifically, a binary refrigeration apparatus). The tank 14 is connected to the receiver 8 by a bypass circuit 13. That is, the refrigeration apparatus 100 according to the first embodiment has a configuration in which the tank 14 that functions as an expansion tank is connected to a circuit portion on the high-pressure side of the second refrigerant circuit 60. Further, the bypass circuit 13 is provided with a bypass valve 13 a that opens and closes the bypass circuit 13. The bypass valve 13a is in a closed state (a state in which the bypass circuit 13 is closed) during normal operation. The bypass valve 13a is in an open state (a state in which the bypass circuit 13 is opened) when the second compressor 5 is stopped and the pressure on the high pressure side of the second refrigerant circuit 60 becomes equal to or higher than a predetermined pressure. It is. That is, the refrigeration apparatus 100 according to Embodiment 1 has a configuration in which the second refrigerant of the second refrigerant circuit 60 is stored in the tank 14 when the pressure on the high-pressure side of the second refrigerant circuit 60 becomes equal to or higher than a predetermined pressure. It has become.
Here, the bypass valve 13a corresponds to the first on-off valve of the present invention.
The predetermined pressure is, for example, a pressure higher than a high pressure assumed during normal operation (a pressure of a circuit portion on the high pressure side of the second refrigerant circuit 60), and prevents the second refrigerant circuit 60 from being broken. Therefore, the pressure is lower than the set allowable pressure. Further, the high pressure of the second refrigerant circuit 60 is detected by, for example, a pressure sensor (not shown) provided in a circuit portion on the high pressure side of the second refrigerant circuit 60.

  The refrigeration apparatus 100 configured as described above operates as follows.

FIG. 2 is a Mollier diagram showing the operating state of the refrigeration apparatus according to Embodiment 1 of the present invention.
First, the operation of the first refrigerant circuit 50 will be described. In the first refrigerant circuit 50, the first refrigerant (point A) in a low pressure and gas phase is sucked into the first compressor 1 and compressed, and in the first refrigerant circuit 50, the high pressure gas phase (point B). And discharged from the first compressor 1. The first refrigerant (point B) discharged from the first compressor 1 flows into the first condenser 2 and is cooled and condensed by a heat exchange target such as air (in other words, the heat exchange target such as air is changed). The first refrigerant circuit 50 becomes a high-pressure and liquid first refrigerant (point C). The first refrigerant flows out from the first condenser 2 and then flows into the first expansion valve 3 to be decompressed and expanded to become a low-pressure gas-liquid two-phase refrigerant (point D) in the first refrigerant circuit 50. Then, the first refrigerant flowing out from the first expansion valve 3 flows into the first evaporator 4 (that is, the cascade condenser 15), and is heated by the second refrigerant flowing through the second condenser 7 of the second refrigerant circuit 60. Evaporates (in other words, the second refrigerant flowing through the second condenser 7 of the second refrigerant circuit 60 is cooled), and the first refrigerant circuit 50 becomes a first refrigerant (point A) in a gas phase at a low pressure. . Thereafter, the first refrigerant is sucked into the first compressor 1 again. The first refrigerant circuit 50 repeats such an operation.

  Subsequently, the operation of the second refrigerant circuit 60 will be described. In the second refrigerant circuit 60, the second refrigerant in a gas phase at a low pressure (point E) is sucked into the second compressor 5 and compressed, and in the second refrigerant circuit 60 in a gas phase in a high pressure (point F). And discharged from the second compressor 5. The second refrigerant (point F) discharged from the second compressor 5 flows into the second condenser 7 (that is, the cascade condenser 15) after the refrigeration oil is separated by the oil separator 6, and the first refrigerant. In the second refrigerant circuit 60, the first refrigerant flowing through the first evaporator 4 of the circuit 50 is cooled and condensed (in other words, the first refrigerant flowing through the first evaporator 4 of the first refrigerant circuit 50 is heated). Becomes a second refrigerant in a liquid state at high pressure (point G). The second refrigerant flows out of the second condenser 7 and then flows into the second expansion valve 10 via the receiver 8 and the on-off valve 9 and is decompressed / expanded. In the second refrigerant circuit 60, the low-pressure gas-liquid is discharged. It becomes a two-phase refrigerant (point H). Then, the second refrigerant that has flowed out of the second expansion valve 10 is heated by a heating target such as air and is evaporated (in other words, a heat exchange target such as air is cooled), and the second refrigerant circuit 60 has a low pressure. It becomes the 1st refrigerant | coolant (point E) of a gaseous-phase state. Thereafter, the second refrigerant passes through the accumulator 12 and is then sucked into the second compressor 5 again. The second refrigerant circuit 60 repeats such an operation.

  In the refrigeration apparatus 100 that operates as described above, when the second evaporator 11 of the second refrigerant circuit 60 is used as a use-side heat exchanger, that is, for example, air in a storage space in which an object to be cooled is stored is second. When cooling with the evaporator 11, the ability exhibited by the second evaporator 11 is the product of the enthalpy difference from the point H to the point E and the amount of the second refrigerant flowing through the second evaporator 11. Further, in the refrigeration apparatus 100 according to the first embodiment, when the second evaporator 11 needs to be cooled, the on-off valve 9 is opened so that the second refrigerant flows into the second evaporator 11, and the second evaporator 11 is opened. The compressor 5 is operated. The first refrigerant circuit is also operated in the same manner. When the cooling of the second evaporator 11 is no longer necessary, the on-off valve 9 is closed to stop the flow of the second refrigerant, stop the second compressor 5, and similarly stop the first refrigerant circuit. I am doing so.

Here, when the ambient temperature of the second refrigerant circuit 60 is higher than the saturation temperature on the high pressure side of the second refrigerant circuit 60 during operation (saturation temperature of the second refrigerant flowing in the circuit portion on the high pressure side) during operation, the second refrigerant circuit When the 60 second compressor 5 stops, the pressure in the second refrigerant circuit 60 rises to a pressure corresponding to the ambient temperature.
For example, in the refrigeration apparatus 100 according to Embodiment 1, it is assumed that a CO ₂ refrigerant is used as the second refrigerant. Then, it is assumed that the operation as the saturation temperature of the high pressure side during operation of the second refrigerant circuit 60 becomes a temperature lower than the critical temperature (31.1 [℃]) of CO ₂ refrigerant. In such a case, the pressure in the 2nd refrigerant circuit 60 at the time of a stop becomes as shown in FIG.

FIG. 3 is a diagram showing a relationship among the refrigerant density, the refrigerant temperature, and the refrigerant pressure of the second refrigerant according to Embodiment 1 of the present invention. In FIG. 3, the horizontal axis indicates the temperature of the second refrigerant, and the vertical axis indicates the pressure of the second refrigerant. Also, the straight lines “150”, “230”, “260”, “350”, “400”, “450”, “500”, “550” shown in FIG. Refrigerant amount [kg]) / volume [m ³ ]) are 150 [kg / m ³ ], 230 [kg / m ³ ], 260 [kg / m ³ ], 350 [kg / m ³ ], 400 [kg / The relationship between the refrigerant temperature and the pressure at m ³ ], 450 [kg / m ³ ], 500 [kg / m ³ ], and 550 [kg / m ³ ] is shown.

As shown in FIG. 3, the higher the temperature of the second refrigerant, the higher the pressure of the second refrigerant. Further, the higher the refrigerant density of the second refrigerant, the higher the pressure of the second refrigerant. For example, when the refrigerant density of the second refrigerant is about 350 [kg / m ³ ] and the temperature is 60 [° C.], the pressure of the second refrigerant is 10.894 [MPa].

  Therefore, in the first embodiment, even when the second refrigerant circuit 60 stops, the ambient temperature of the second refrigerant circuit 60 increases, and the pressure in the second refrigerant circuit 60 increases, the second refrigerant circuit 60 The internal volume of the tank 14 is determined so that the internal pressure is less than or equal to the allowable pressure.

FIG. 4 shows the internal volume of each component of the second refrigerant circuit in the refrigeration apparatus according to Embodiment 1 of the present invention, the amount of refrigerant stored in each component (amount of the second refrigerant), and the inside of the second refrigerant circuit It is a figure which shows the relationship between the refrigerant density of this, and a refrigerant | coolant pressure. The internal volume of each component of the second refrigerant circuit 60 shown in FIG. 4 is a case where the second refrigerant circuit 60 corresponding to 10 horsepower ([Hp] = × 745.7 [W]) is assumed. Further, the amount of refrigerant stored in each component of the second refrigerant circuit 60 shown in FIG. 4 indicates the amount of refrigerant stored in each component during the operation of the second refrigerant circuit 60 equivalent to 10 horsepower. . Here, the “discharge pipe” shown in FIG. 4 is a pipe from the discharge port of the second compressor 5 to the second condenser. The “liquid pipe” is a pipe from the second condenser 7 to the second expansion valve 10. The “suction pipe” is a pipe from the second evaporator 11 to the suction port of the second compressor 5. In addition, since the piping from the 2nd expansion valve 10 to the 2nd evaporator 11 is short and the internal volume and refrigerant | coolant storage amount are small, description in FIG. 4 is abbreviate | omitted.
Also,

In the case of the second refrigerant circuit 60 shown in FIG. 4, the total internal volume of the second refrigerant circuit 60 is 0.084 [m ³ ], and the amount of refrigerant is 19.36 [kg]. 6 [kg / m ³ ]. When the ambient temperature at this refrigerant density is 43 [° C.], the pressure in the second refrigerant circuit 60 is about 7.696 [MPa] from FIG. At this time, if the pressure in the second refrigerant circuit 60 is set to about 6.2 [MPa] or less, which is a refrigerant pressure smaller than the allowable pressure (6.2 + α [MPa]), the refrigerant in the second refrigerant circuit 60 The density needs to be 150 [kg / m ³ ] or less. That is, if the amount of the second refrigerant in the second refrigerant circuit 60 does not change (assuming the amount of second refrigerant 19.36 [kg] is a fixed value), the required internal volume of the second refrigerant circuit 60 is 0. 1291 [m ³ ]. That is, the tank 14 needs an internal volume of 0.0451 [m ³ ] (= 0.1291-0.084).

  The internal volume of the expansion tank of the conventional refrigeration apparatus (binary refrigeration apparatus) is determined in the same manner as described above.

  Here, as shown in FIG. 4, in the second refrigerant circuit 60 in operation, the circuit density on the high pressure side has a higher refrigerant density than the circuit part on the low pressure side. For this reason, when the 2nd compressor 5 of the 2nd refrigerant circuit 60 stops and the 2nd refrigerant in the 2nd refrigerant circuit 60 rose to equivalent to ambient temperature, the circuit part by the side of high pressure is lower than the circuit part by the side of low pressure. Even the pressure becomes higher. This is because the refrigerant density is high between the outlet of the second condenser 7 (cascade condenser 15) on the high pressure side and the second expansion valve 10 due to the large amount of the second refrigerant in the liquid phase, and the outlet of the second evaporator 11 on the low pressure side. This is because the refrigerant density is low between the second compressor 5 and the second compressor 5 due to the large amount of the second refrigerant in the gas phase. For this reason, in the conventional refrigeration apparatus that guides the refrigerant from the low pressure side circuit portion into the expansion tank, the high pressure side circuit portion of the second refrigerant circuit 60 becomes higher than the allowable pressure of the second refrigerant circuit. was there. In particular, when the on-off valve 9 that opens and closes the circuit between the receiver 8 and the second expansion valve 10 is provided as in the first embodiment, the second compressor 5 is operated when the on-off valve 9 is closed. When stopped, the flow path through which the second refrigerant flows from the circuit portion on the high pressure side of the second refrigerant circuit 60 to the circuit portion on the low pressure side further decreases, so that an abnormal increase in pressure occurs in the circuit portion on the high pressure side of the second refrigerant circuit 60. The above-mentioned problem that there are cases where it is not possible to avoid the problem becomes even more remarkable.

  For this reason, the second refrigerant circuit 60 according to the first embodiment connects the tank 14 functioning as an expansion tank to the receiver 8 disposed in the circuit portion on the high pressure side via the bypass circuit 13 and the bypass valve 13a. It is configured. When the high pressure portion of the second refrigerant circuit 60 reaches a predetermined pressure or higher, the bypass valve 13a is opened so that the high pressure side second refrigerant flows into the low pressure side tank 14 and the high pressure side pressure is lowered. .

  If the second compressor 5 is stopped in a normal operation in which power is supplied, the on-off valve 9 is opened to cause the high-pressure side refrigerant to flow to the low-pressure side, By operating the first refrigerant circuit 50, it is possible to cool the high pressure of the second refrigerant circuit 60 and lower the pressure. For this reason, it is preferable that the bypass valve 13a operates even in an environment where the on-off valve 9 and the first refrigerant circuit 50 cannot be operated, such as during a power failure. Therefore, the bypass valve 13a is preferably an on-off valve that mechanically opens and closes based on the high pressure of the second refrigerant circuit 60.

  Thus, the tank 14 functions as an expansion tank. That is, the tank 14 is intended to suppress the circuit pressure when the operation of the second refrigerant circuit 60 is stopped to an allowable pressure or less. However, for example, the tank 14 is used less frequently for stopping the second refrigerant circuit 60 due to a power failure and reducing the pressure in the refrigerant circuit.

  Therefore, in the first embodiment, the tank 14 that functions as an expansion tank is used as an oil tank during normal operation.

FIG. 5 is a refrigerant circuit diagram showing the vicinity of the tank of the second refrigerant circuit according to Embodiment 1 of the present invention.
As shown in FIG. 5, the 2nd compressor 5 and the tank 14 are arrange | positioned at the same bottom face part, for example, and the bottom face of the 2nd compressor 5 and the tank 14 is the same height. A refrigerating machine oil 18 is stored in the tank 14. The second compressor 5 and the tank 14 are connected by two pipes 17. Specifically, one pipe 17 connects a place where the refrigerating machine oil 18 of the second compressor 5 and the tank 14 exists near the bottom face (for example, near the bottom face). The other is connected to a place where the second compressor 5 and the refrigerating machine oil 18 of the tank 14 do not exist (for example, a place filled with a second refrigerant in a gas phase state such as the upper surface side of the tank 14).
Further, as shown in FIG. 1, an oil return pipe 6 a of the oil separator 6 is also connected to the tank 14, and the refrigerating machine oil 18 separated by the oil separator 6 is returned to the tank 14. Yes.

  By connecting the second compressor 5 and the tank 14 in this way, the oil level in the second compressor 5 (the upper surface portion of the refrigerating machine oil 18) and the oil level in the tank 14 can be made the same height. . For this reason, when the refrigerating machine oil in the 2nd compressor 5 reduces, refrigerating machine oil is replenished from the tank 14, and the refrigerating machine oil 18 in the 2nd compressor 5 increases (when the surplus refrigerating machine oil 18 generate | occur | produces). ) Can adjust the fluctuation of the amount of the refrigerating machine oil 18 in the second compressor 5 by discharging the refrigerating machine oil 18 to the tank 14, and the oil due to the oil depletion of the second compressor 5 and the oil amount increase. Compression can be avoided.

  Depending on the operating conditions and configuration of the second refrigerant circuit 60, the amount of the refrigerating machine oil 18 stored in the configuration other than the second compressor 5 during the operation of the second refrigerant circuit 60, that is, the piping portion (discharge piping) , Liquid pipe, suction pipe, etc.), oil separator 6, second condenser 7, receiver 8, second evaporator 11 and accumulator 12, the amount of refrigerating machine oil 18 is the maximum, the second compression The amount of refrigerating machine oil that can be stored in the machine 5 may be approximately the same. For example, in the example of the second refrigerant circuit 60 corresponding to 10 horsepower ([Hp] = × 745.7 [W]) shown in FIG. 4, the amount of refrigerating machine oil that can be stored in the second compressor 5 is about 3 [ L]. In this case, depending on the operating conditions of the second refrigerant circuit 60, the amount of the refrigerating machine oil 18 stored in the configuration other than the second compressor 5 may be about 3 [L] at the maximum. For this reason, in order to reliably prevent the oil depletion from occurring in the second compressor 5, the amount of the refrigerating machine oil 18 that can be stored in the tank 14 is the amount of the refrigerating machine oil 18 that can be stored in the second compressor 5. It is preferable to set it twice or more. Further, the heights of the bottom surfaces of the second compressor 5 and the tank 14 are not necessarily the same, and the tank 14 has a volume, shape, and possession with respect to a target oil amount during operation of the second compressor 5. It is good also as the height of the bottom according to the amount of oil. In FIG. 1, the refrigeration oil separated by the oil separator 6 of the second refrigerant circuit 60 is returned to the tank 14, but the connection destination of the oil return pipe 6 a of the oil separator 6 is the second compressor 5. If it is the suction side, it is not limited to the tank 14.

  As described above, in the refrigeration apparatus 100 configured as in the first embodiment, when the second compressor 5 of the second refrigerant circuit 60 is stopped and the high pressure of the second refrigerant circuit 60 becomes equal to or higher than a predetermined pressure. The second refrigerant in the second refrigerant circuit 60 is stored in the tank 14 from the receiver 8 provided in the circuit portion on the high-pressure side via the bypass circuit 13 and the bypass valve 13a. For this reason, in the refrigeration apparatus 100 configured as in the first embodiment, when the second compressor 5 of the second refrigerant circuit 60 stops, the pressure in the circuit portion on the high pressure side of the second refrigerant circuit 60 is reduced. Abnormal rise can be prevented.

  In the refrigeration apparatus 100 configured as in the first embodiment, the tank 14 that functions as an expansion tank of the conventional refrigeration apparatus is an oil tank of the second compressor 5 during the operation of the second refrigerant circuit 60. Also works. For this reason, in the refrigeration apparatus 100 configured as in the first embodiment, it is possible to prevent the second compressor 5 from being broken due to exhaustion of the refrigeration oil 18 or the like.

Embodiment 2. FIG.
In the first embodiment, the refrigeration apparatus 100 having the second refrigerant circuit 60 provided with one second compressor 5 has been described. However, the second refrigerant circuit 60 may include a plurality of second compressors 5. Good. In such a case, the cost of the refrigeration apparatus 100 can be suppressed by configuring the tank 14 as follows. Note that a configuration not particularly described in the second embodiment is the same as that of the first embodiment, and the same function and configuration are described using the same reference numerals.

FIG. 6 is a refrigerant circuit diagram illustrating a configuration of the refrigeration apparatus according to Embodiment 2 of the present invention.
Unlike the first embodiment, the refrigeration apparatus 100 according to the second embodiment includes two second compressors 5 in the second refrigerant circuit 60. Each of the two second compressors 5 is connected to one tank 14 via a pipe 17.

By configuring the refrigeration apparatus 100 as in the second embodiment, the same effect as in the first embodiment can be obtained.
Further, by configuring the refrigeration apparatus 100 as in the second embodiment, it is possible to configure the refrigeration apparatus with a smaller number of tanks 14 than the number of the second compressors 5, thus increasing the cost of the refrigeration apparatus 100. Can also be suppressed.

  In the second embodiment, the refrigeration apparatus 100 including the two second compressors 5 has been described. However, the refrigeration apparatus 100 including three or more second compressors 5 may be used as a matter of course. In this case, all the second compressors 5 may be connected to one tank 14, or a plurality of tanks 14 may be provided, and a plurality of second compressors 5 may be connected to each of these tanks 14. When a plurality of tanks 14 are provided, it is of course possible that a part of the tanks 14 is connected to one second compressor 5.

Embodiment 3 FIG.
When the second refrigerant circuit 60 has the function of an accumulator, the tank 14 shown in the first and second embodiments may be configured like the tank 16 shown below. Note that a structure not particularly described in the third embodiment is the same as that in the first or second embodiment, and the same function or structure is described using the same reference numeral.

FIG. 7 is a refrigerant circuit diagram illustrating a configuration of the refrigeration apparatus according to Embodiment 3 of the present invention.
Similar to the first and second embodiments, the tank 16 according to the third embodiment is connected to the second compressor 5 via the pipe 17 and via the bypass circuit 13 and the bypass valve 13a. The receiver 8 is connected.

Furthermore, the tank 16 according to the third embodiment is also connected to the second evaporator 11 and the suction port of the second compressor 5 via the refrigerant pipe. As a result, the tank 16 according to the third embodiment separates the second refrigerant flowing out of the second evaporator 11 into the second refrigerant in the gas phase and the second refrigerant in the liquid phase. The second refrigerant can be sucked into the second compressor 5 to prevent the occurrence of liquid back in the second compressor 5.
That is, the tank 16 according to the third embodiment has the function of the accumulator 12 shown in the first and second embodiments in addition to the function of the tank 14 shown in the first and second embodiments. It has a combined structure.

By configuring the refrigeration apparatus 100 as in the third embodiment, the same effects as in the first and second embodiments can be obtained.
Further, by configuring the refrigeration apparatus 100 as in the third embodiment, the tank 16 can fulfill the function of an accumulator, so there is no need to provide an accumulator separately, and an increase in the cost of the refrigeration apparatus 100 is suppressed. You can also

  DESCRIPTION OF SYMBOLS 1 1st compressor, 2 1st condenser, 3 1st expansion valve, 4th 1st evaporator, 5 2nd compressor, 6 Oil separator, 6a Oil return piping, 7 2nd condenser, 8 Receiver, 9 On-off valve, 10 second expansion valve, 11 second evaporator, 12 accumulator, 13 bypass circuit, 13a bypass valve, 14 tank, 15 cascade condenser, 16 tank, 17 piping, 18 refrigerating machine oil, 50 first refrigerant circuit, 60 Second refrigerant circuit, 100 refrigeration apparatus.

Claims (6)

A first refrigerant circuit in which a first compressor, a first condenser, a first pressure reducing device, and a first evaporator are sequentially connected by piping;
A second refrigerant circuit in which a second compressor, a second condenser, a second pressure reducing device, and a second evaporator are sequentially connected by piping;
With
A refrigeration apparatus comprising a cascade condenser by the first evaporator of the first refrigerant circuit and the second condenser of the second refrigerant circuit,
A receiver connected between the second condenser of the second refrigerant circuit and the second decompression device and storing excess refrigerant;
A tank that is connected to the second compressor of the second refrigerant circuit, stores excess refrigeration oil in the second compressor, and adjusts the amount of refrigeration oil in the second compressor;
A bypass circuit connecting the receiver and the tank;
A first circuit is provided in the bypass circuit, and opens when the high pressure of the second refrigerant circuit exceeds a predetermined pressure, and closes the bypass circuit when the high pressure of the second refrigerant circuit becomes smaller than the predetermined pressure. An on-off valve;
A refrigeration apparatus comprising: A plurality of the second compressors;
2. The refrigeration apparatus according to claim 1, wherein the tank is connected to at least two of the second compressors, and adjusts an amount of refrigeration oil in the second compressors. Connecting the outlet of the second evaporator and the tank;
Connecting a position above the refrigerating machine oil in the tank and the suction port of the second compressor;
The refrigeration apparatus according to claim 1 or 2, wherein the tank is also used as an accumulator. An oil separator provided between the second compressor and the second condenser;
The refrigeration apparatus according to any one of claims 1 to 3, wherein an oil return pipe of the oil separator is connected to a pipe on the suction side of the tank or the compressor.   5. The refrigeration apparatus according to claim 1, wherein the first on-off valve is an on-off valve that mechanically opens and closes based on a high pressure of the second refrigerant circuit.   The refrigeration apparatus according to any one of claims 1 to 5, further comprising a second on-off valve that opens and closes a circuit between the receiver and the second decompression device. .

Images