JP2017129320A - Freezer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a freezer which includes a compressor having multiple compression parts and enables reduction of a burden of a high pressure side compression part.SOLUTION: A freezer 1 includes a heat source unit 1a, a heat radiation unit 1b, and a cooling unit 1c. The heat source unit 1a includes a two-stage compressor 8, an oil separator 11, a receiver 12, an economizer 13, and an oil cooler 17. There is provided an injection pipeline 15, which is branched from a refrigerant circuit and connects with an intermediate pressure passage between a low stage compression part 9 and a high stage compression part 10 through an economizer expansion valve 14 and the economizer 13. In the oil cooler 17, a refrigeration oil is cooled by a refrigerant flowing in the refrigerant circuit. The refrigeration oil is sent from the oil separator 11 to the oil cooler 17 by an oil return pipeline 16 to be cooled and then is returned to the two-stage compressor 8.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a refrigeration apparatus, and more particularly to a refrigeration apparatus including a compressor having a plurality of compression units.

  Conventionally, there is a refrigeration apparatus including a two-stage compressor having a low-pressure stage compressor and a high-pressure stage compressor (Patent Document 1). In this type of refrigeration system, in order to lower the discharge temperature of the refrigerant discharged from the high-pressure stage compressor, the temperature of the refrigerating machine oil discharged together with the refrigerant is lowered, and the refrigerating machine oil whose temperature is lowered is used as the low-pressure stage compressor. And return to the high-pressure stage compressor.

  In the conventional refrigeration apparatus, the refrigeration oil is cooled by the refrigerant branched from the refrigerant circuit. The refrigerant that has cooled the refrigerating machine oil is returned to the intermediate pressure flow path between the low-pressure stage compressor and the high-pressure stage compressor. In such a conventional refrigeration apparatus, R404A is used as the refrigerant.

Japanese Patent Laid-Open No. 7-190520

  In recent years, it has been required to change the refrigerant in order to save energy. In the case of R404A, it is required to change to R410A.

  However, in the refrigeration apparatus using R410A as the refrigerant, the discharge temperature of the refrigerant discharged from the two-stage compressor (high-pressure stage side compressor) tends to be higher than when R404A is used. For this reason, in order to lower the temperature of the refrigerant to be discharged, it is necessary to branch more refrigerant from the refrigerant circuit and lower the temperature of the refrigerating machine oil discharged together with the refrigerant.

  The branched refrigerant is returned to the intermediate pressure flow path between the low pressure stage side compressor and the high pressure stage side compressor. As a result, there is a problem that the load on the high-pressure stage side compressor is increased as compared with the refrigeration apparatus using R404A as the refrigerant.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a refrigeration apparatus including a compressor having a plurality of compression units, in which the load on the compression unit on the high-pressure side is reduced. Is to provide.

  A refrigerating apparatus according to the present invention is a refrigerating apparatus including a refrigerant circuit in which a refrigerant circulates in the order of a compressor, an oil separator, a condenser, a receiver, an economizer, a first expansion unit, and a cooler, and the oil cooler And an oil return pipe and an injection pipe. The compressor has a plurality of compression units that sequentially compress the refrigerant. The oil cooler is provided in a first pipe connecting the condenser and the receiver in the refrigerant circuit, and performs heat exchange between the refrigeration oil separated in the oil separator and the refrigerant flowing through the first pipe. As a result, the refrigerator oil is cooled. The oil return pipe is connected from the oil separator to the compressor through the oil cooler. The injection pipe branches from the second pipe connecting the economizer and the first expansion section in the refrigerant circuit, and is connected to the intermediate pressure flow paths in the plurality of compression sections via the second expansion section and the economizer.

  According to the refrigerating apparatus according to the present invention, the refrigerating machine oil discharged from the compressor flows through the oil return pipe, and is cooled by the refrigerant flowing through the refrigerant circuit in the oil cooler, and then into the intermediate pressure flow paths in the plurality of compression units. Returned. Thereby, compared with the case where refrigeration oil is cooled with the refrigerant branched from the refrigerant circuit, it is possible to reduce the load on the high-pressure side compression unit higher than the intermediate pressure.

It is a figure containing the refrigerant circuit which shows the structure of the freezing apparatus which concerns on embodiment. In the same embodiment, it is a figure for demonstrating operation | movement of a freezing apparatus. In the embodiment, it is a graph which shows the Ph diagram of a freezing apparatus. It is a figure containing the refrigerant circuit which shows the structure of the freezing apparatus which concerns on a comparative example. It is a figure for demonstrating operation | movement of the freezing apparatus which concerns on a comparative example. It is a figure which shows the evaluation result of the quantity of the refrigerant | coolant branched in the embodiment.

  The refrigeration apparatus according to the embodiment will be described. FIG. 1 shows a refrigerant circuit of the refrigeration apparatus. As shown in FIG. 1, the refrigeration apparatus 1 includes a heat source unit 1a, a heat radiation unit 1b, and a cooling unit 1c. R410A is enclosed as a refrigerant in the refrigerant circuit. The heat source unit 1a, the heat radiating unit 1b, and the cooling unit 1c are arranged at a distance from each other.

  The heat source unit 1a includes a two-stage compressor 8, an oil separator 11, a receiver 12, an economizer 13, and an oil cooler 17. The heat source unit 1a is installed indoors, for example. The two-stage compressor 8 includes a low-stage compression unit 9 and a high-stage compression unit 10. In the oil separator 11, the refrigerating machine oil contained in the refrigerant discharged from the two-stage compressor 8 is separated. In the receiver 12, a surplus of the refrigerant sealed in the refrigerant circuit is stored.

  In the economizer 13, the refrigerant flowing through the refrigerant circuit is cooled by the refrigerant branched from the refrigerant circuit. The high-pressure liquid refrigerant is decompressed by the economizer expansion valve 14. Further, an injection pipe 15 branched from the refrigerant circuit and connected to an intermediate pressure flow path between the low-stage compression section 9 and the high-stage compression section 10 in the two-stage compressor 8 through the economizer expansion valve 14 and the economizer 13. Is provided. The branched refrigerant flows through the injection pipe 15 and is returned to the two-stage compressor 8.

  In the oil cooler 17, the refrigerating machine oil is cooled by the high-pressure liquid refrigerant flowing through the refrigerant circuit. The refrigerating machine oil is sent from the oil separator 11 to the oil cooler 17 through the oil return pipe 16. The refrigerating machine oil cooled in the oil cooler 17 is returned to the two-stage compressor 8. Further, a bypass pipe 18 and a bypass amount adjusting valve 19 are provided in parallel to the oil cooler 17.

  By adjusting the amount of the refrigerant flowing through the bypass pipe 18 by the bypass amount adjusting valve 19, the heat exchange between the liquid refrigerant and the refrigerating machine oil in the oil cooler 17 is adjusted. The amount of the refrigerant flowing through the bypass pipe 18 is adjusted by the control unit 2 based on the temperature of the refrigerant detected by the temperature sensor 4. The temperature sensor 4 is provided on the inlet side (heat radiation unit 1b side) of the oil cooler 17.

  The heat dissipation unit 1b includes an air-cooled condenser 24 and a heat dissipation fan 25. The heat radiation unit 1b is installed outdoors, for example. The heat dissipation unit 1b is connected to the heat source unit 1a by connection pipes 3a and 3b. The connection pipe 3 a connects the two-stage compressor 8 (oil separator 11) and the air-cooled condenser 24. The connection pipe 8 b connects the air-cooled condenser 24 and the oil cooler 17. The high-temperature gas refrigerant sent from the connection pipe 3 a is heat-exchanged with the outside air in the air-cooled condenser 24. The heat-exchanged refrigerant becomes liquid refrigerant, and flows through the connection pipe 3b and is sent to the oil cooler 17.

  The cooling unit 1 c includes an electromagnetic valve 20, a main expansion valve 21, a cooler 22, and a cooling fan 23. The cooling unit 1c is installed in a freezer or the like. The cooling unit 1c is connected to the heat source unit 1a by connection pipes 3c and 3d. The connection pipe 3 c connects the economizer 13 and the solenoid valve 20. The connection pipe 3 d connects the cooler 22 and the two-stage compressor 8. The cooling fan 23 adjusts heat exchange between the air in the freezer and the refrigerant flowing through the cooler 22. The refrigeration apparatus 1 according to the embodiment is configured as described above.

  Next, the cooling operation of the refrigeration apparatus 1 described above will be described. FIG. 2 shows the flow of refrigerant and the flow of refrigerating machine oil in the refrigeration apparatus 1. FIG. 3 shows a Ph diagram of the refrigeration cycle of the refrigeration apparatus 1. Moreover, the state of the refrigerant | coolant in each point (A point-J point) in a freezing apparatus is plotted on the Ph diagram.

  As shown in FIGS. 2 and 3, high-temperature and high-pressure gaseous refrigerant (gas refrigerant) is discharged from the two-stage compressor 8 (point C). The gas refrigerant flows into the oil separator 11. In the oil separator 11, the refrigerating machine oil discharged together with the refrigerant is recovered. The temperature of the gas refrigerant discharged from the two-stage compressor 8 is about 80 ° C. to 90 ° C., for example. The temperature of the separated refrigerating machine oil is also about 80 ° C to 90 ° C.

  The discharged gas refrigerant flows through the connection pipe 3a and flows into the heat radiating unit 1b (arrow Y1). In the heat radiating unit 1b, the air-cooled condenser 24 exchanges heat between the refrigerant flowing in and the air sent in by the heat radiating fan 25, and the high-temperature and high-pressure gas refrigerant is condensed to form a high-pressure liquid refrigerant ( Liquid refrigerant). The heat of the refrigerant is released to the outside air.

  The high-pressure liquid refrigerant (point D) sent out from the heat dissipation unit 1b flows through the connection pipe 3b and returns to the heat source unit 1a (arrow Y2). The liquid refrigerant returned to the heat source unit 1a flows through the oil cooler 17. In the oil cooler 17, the refrigerating machine oil separated in the oil separator 11 is cooled by the refrigerant. The cooling of the refrigerator oil will be described later.

  The refrigerant that has flowed through the oil cooler 17 flows into the receiver 12. In the receiver 12, the surplus refrigerant sealed in the refrigeration circuit is stored, so that the liquid refrigerant and the gas refrigerant coexist. For this reason, it becomes a saturated liquid before flowing into the receiver 12 (point E). Further, the liquid refrigerant before flowing into the oil cooler 17, that is, before being heated by the high-temperature refrigeration oil (D point) is a supercooled liquid.

  The liquid refrigerant sent out from the receiver 12 is sent to the economizer 13. In the economizer 13, the refrigerant flowing through the refrigerant circuit is cooled by the medium-pressure refrigerant obtained by reducing the pressure of the high-pressure liquid refrigerant branched from the refrigerant circuit. The high-pressure liquid refrigerant is depressurized by the economizer expansion valve 14 (point H).

  The branched refrigerant undergoes heat exchange with the high-pressure liquid refrigerant in the economizer 13 (point I). After the heat exchanged refrigerant flows through the injection pipe 15, it is returned to the intermediate pressure flow path between the low-stage compressor 9 and the high-stage compressor 10 in the two-stage compressor 8 (arrow Y5).

  The refrigerant cooled by the economizer 13 becomes a supercooled liquid (point F). The refrigerant that has become the supercooled liquid flows from the heat source unit 1a to the cooling unit 1c through the connection pipe 3c (arrow Y3). The high-pressure liquid refrigerant sent to the cooling unit 1c is depressurized by the main expansion valve 21 through the electromagnetic valve 20, and becomes a two-phase refrigerant of low-pressure gas refrigerant and liquid refrigerant (point G).

  The low-pressure two-phase refrigerant exchanges heat with the air in the freezer to be cooled in the cooler 22. The liquid refrigerant evaporates by heat exchange, and the two-phase refrigerant becomes a single-phase low-pressure gas refrigerant. Here, when the temperature in the freezer is, for example, −30 ° C., the evaporation temperature of the refrigerant is about −40 ° C.

  The low-pressure gas refrigerant flows through the connection pipe 3d and returns to the heat source unit 1a (arrow Y4). The low-pressure gas refrigerant (point A) returned to the heat source unit 1 a flows into the two-stage compressor 8, is compressed to become a high-temperature and high-pressure gas refrigerant, and is discharged from the two-stage compressor 8. Hereinafter, by repeating this cycle, the temperature in the freezer to be cooled is maintained at a predetermined temperature.

  Next, the operation | movement which cools the refrigerating machine oil of the freezing apparatus 1 is demonstrated. The refrigeration oil discharged together with the refrigerant from the two-stage compressor 8 is separated from the refrigerant in the oil separator 11. The temperature of the refrigerating machine oil separated in the oil separator 11 is about 80 ° C. to 90 ° C., for example. The refrigerating machine oil flows through the oil return pipe 16 and is sent to the oil cooler 17 (arrow Y6).

  In the oil cooler 17, heat exchange is performed between the fed refrigerating machine oil and the refrigerant sent out from the air-cooled condenser 24. By performing heat exchange, the temperature of the refrigerating machine oil is cooled to about 50 ° C., for example. The cooled refrigerating machine oil flows through the oil return pipe 16 and is returned to the two-stage compressor 8.

  In the refrigeration apparatus 1 described above, the refrigeration oil discharged from the two-stage compressor is cooled by the refrigerant flowing through the refrigerant circuit and returned to the two-stage compressor. Thereby, when R410A is used as a refrigerant | coolant, the load of the high stage compression part of a two-stage compressor can be reduced. This will be described in comparison with a refrigeration apparatus according to a comparative example.

  As shown in FIG. 4, the refrigeration apparatus 101 (refrigerant circuit) according to the comparative example includes a two-stage compressor 108, an oil separator / recoverer 111, a condenser 124, an economizer 113, a first expansion valve 120, an evaporator 122, A two expansion valve 114 and an oil cooler 117 are provided. R410A is enclosed as a refrigerant in the refrigerant circuit.

  Further, an economizer pipe 115 for returning the refrigerant branched from the refrigerant circuit to the two-stage compressor 108 (intermediate pressure flow path) through the second expansion valve 114 and the economizer 113 is provided. Furthermore, an oil return pipe 116 is provided for returning the refrigeration oil separated in the oil separator / collector 111 to the two-stage compressor 108 via the oil cooler 117.

  Next, the cooling operation of the refrigeration apparatus 101 according to the comparative example will be described. FIG. 5 shows the flow of refrigerant and the flow of refrigerating machine oil in the refrigeration apparatus 101. As shown in FIG. 5, the high-temperature and high-pressure refrigerant (gas refrigerant) discharged from the two-stage compressor 108 flows into the oil separator / recovery unit 111 (arrow YY1).

  The oil separator / collector 111 collects the refrigeration oil discharged together with the refrigerant. The temperature of the refrigerating machine oil separated from the gas refrigerant discharged from the two-stage compressor 108 is, for example, about 80 ° C. to 90 ° C. The gas refrigerant separated from the refrigerating machine oil flows into the condenser 124 (arrow YY1). In the condenser 124, heat exchange is performed between the flowing refrigerant and air, and the high-temperature and high-pressure gas refrigerant is condensed into a high-pressure liquid refrigerant (liquid refrigerant).

  The high-pressure liquid refrigerant sent out from the condenser 124 is sent to the economizer 113. In the economizer 113, the refrigerant flowing through the refrigerant circuit is cooled by the medium-pressure refrigerant obtained by reducing the pressure of the high-pressure liquid refrigerant branched from the refrigerant circuit. The branched high-pressure liquid refrigerant is decompressed by the second expansion valve 114 to become a low-pressure refrigerant.

  The low pressure refrigerant exchanges heat with the high pressure liquid refrigerant in the economizer 113. The low-pressure refrigerant that has undergone heat exchange flows through the economizer pipe 115, and then returns to the intermediate pressure flow path between the low-stage compressor 109 and the high-stage compressor 110 in the two-stage compressor 108 (arrow YY5). .

  On the other hand, the refrigerant cooled by the economizer 113 is decompressed by the first expansion valve 120 and becomes a two-phase refrigerant of a low-pressure gas refrigerant and a liquid refrigerant (arrow YY3). The low-pressure two-phase refrigerant is heat-exchanged with, for example, air in the evaporator 122. The liquid refrigerant evaporates by heat exchange, and the two-phase refrigerant becomes a single-phase low-pressure gas refrigerant.

  The low-pressure gas refrigerant flows through the pipe and into the two-stage compressor 108 (arrow YY4). The low-pressure gas refrigerant flowing into the two-stage compressor 108 is compressed again, becomes a high-temperature and high-pressure gas refrigerant, and is discharged from the two-stage compressor 108. Thereafter, this cycle is repeated.

  Next, the operation | movement which cools the refrigerating machine oil of the freezing apparatus 101 is demonstrated. The refrigeration oil discharged from the two-stage compressor 108 together with the refrigerant is separated from the refrigerant in the oil separator / collector 111. The refrigerating machine oil flows through the oil return pipe 116 and is sent to the oil cooler 117 (arrow YY6).

  In the oil cooler 117, heat exchange is performed between the refrigerating machine oil fed in and the refrigerant that has passed through the economizer 113. The heat-exchanged refrigeration oil flows through the oil return pipe 116 and is returned to the two-stage compressor 108.

  As already described, in the refrigeration apparatus, in order to save energy, it is required to change the refrigerant, and it is required to change from R404A to R410A. It is known that when R410A is used as the refrigerant, the refrigerant discharge temperature is higher than when R404A is used. For this reason, the discharge temperature of the refrigerating machine oil discharged together with the refrigerant (R410A) also becomes higher than when R404A is used, and is, for example, about 80 ° C. to 90 ° C.

  In the refrigerating apparatus 101 according to the comparative example, the refrigerating machine oil discharged and separated is cooled in the oil cooler 117 and returned to the two-stage compressor 108. In the oil cooler 117, the refrigeration oil is cooled by exchanging heat between the refrigeration oil and the refrigerant branched from the refrigerant circuit. For this reason, when the discharge temperature of refrigerator oil becomes high, in order to cool the temperature of refrigerator oil to desired temperature, it is necessary to increase the quantity of the refrigerant | coolant exchanged with refrigerator oil. That is, it is necessary to increase the amount of refrigerant branched from the refrigerant circuit.

  Here, as shown in FIGS. 2 and 5, the amount of refrigerant before branching from the refrigerant circuit is “1 + α”, the amount of refrigerant to be branched is “α”, and the refrigerant flows through the refrigerant circuit after branching. The amount of “1” is “1”. Note that “α” is referred to as an intermediate injection amount ratio (%) because the branched refrigerant is returned to the intermediate pressure flow path between the low-stage compression units 109 and 9 and the high-stage compression units 110 and 10. .

  The inventor evaluated the intermediate injection amount ratio for various conditions. As an evaluation result, FIG. 6 shows the amount of α when the refrigerant evaporation temperature is −30 ° C., −40 ° C., and −50 ° C. when the discharge temperature of the refrigerating machine oil is 83 ° C. As shown in FIG. 6, in the refrigeration apparatus according to the comparative example, α is 30% when the evaporation temperature is −30 ° C., and α is 56% when the evaporation temperature is −40 ° C. When the evaporation temperature was −50 ° C., α was found to be 100%.

  On the other hand, about the refrigeration apparatus 1 which concerns on embodiment, the intermediate injection amount ratio was evaluated similarly to the refrigeration apparatus 101 which concerns on a comparative example. As shown in FIG. 6, when the evaporation temperature is −30 ° C., α is 20%, and when the evaporation temperature is −40 ° C., α is 33% and the evaporation temperature is −50 ° C. In some cases, α was found to be 58%.

  In the refrigerating apparatus 101 according to the comparative example, the refrigerating machine oil is cooled by the refrigerant branched from the refrigerant circuit. For this reason, when the discharge temperature of the refrigerating machine oil increases with the change of the refrigerant (R404A → R410A), the amount of the refrigerant branched from the refrigerant circuit increases in order to cool the refrigerating machine oil. And the amount of refrigerant returned to the intermediate pressure flow path between the high-stage compression unit 110 increases. For this reason, the load of the high stage compression part 110 will increase.

  In addition, the state of the refrigerant | coolant in the AA point, JJ point, II point, BB point, CC point, and DD point shown by FIG. 5 is each plotted by Ph diagram shown by FIG. In the refrigeration apparatus 101 according to the comparative example, the refrigeration oil is cooled by the refrigerant flowing through the point II. Also, the DD point and the point corresponding to the E point before flowing into the economizer 113 substantially coincide with each other.

  On the other hand, in the refrigeration apparatus 1 according to the embodiment, the refrigeration oil is cooled by the refrigerant flowing through the refrigerant circuit. That is, the refrigerating machine oil is cooled while the refrigerant flows from point D to point E shown in FIG. For this reason, compared with the refrigerating apparatus 101 which concerns on a comparative example, the quantity of the refrigerant | coolant branched from a refrigerant circuit reduces significantly. That is, the amount of refrigerant flowing through the point II shown in FIG. 3 can be reduced to the amount of refrigerant flowing through the point I.

  Thereby, it is possible to reduce the amount of the refrigerant branched from the refrigerant circuit and returned to the intermediate pressure flow path between the low-stage compressor 9 and the high-stage compressor 10. As a result, it has been found that the amount of refrigerant flowing from point B to point C shown in FIG. 3 is reduced, and the load on the high-stage compression unit 10 of the two-stage compressor 8 can be suppressed.

  In the refrigeration apparatus 1 according to the embodiment, the refrigerant sent out from the air-cooled condenser 24 (heat radiation unit 1b) is in a state having a predetermined degree of supercooling. The refrigerant that cools the refrigerating machine oil is heated until the amount of heat of the supercooling is dissipated to become the saturated liquid (E point) from the state that becomes the supercooled liquid in the heat radiating unit 1b (D point).

  In general, the heat dissipation characteristic of the air-cooled condenser is the most efficient state in which the flow rate is adjusted so that the air flows out with a degree of supercooling that is about 1/2 of the difference between the outside air temperature and the condensation temperature. For this reason, the operation | movement more efficient than operating with a general high voltage | pressure receiver circuit can be performed.

  In addition, when the pressure loss of the connection pipe 3b is large, it may be assumed that the degree of supercooling of the refrigerant sent out from the air-cooled condenser 24 becomes excessive, and the original heat radiation performance cannot be sufficiently exhibited. In such a case, the amount of liquid refrigerant flowing through the oil cooler 17 is decreased by the bypass amount adjusting valve 19 to reduce the amount of cooling the refrigeration oil, and the supercooling of the refrigerant sent out from the air-cooled condenser 24 is reduced. Adjust to reduce the degree.

  Even in cases where the outside air temperature is low and both the condensing temperature and the discharge temperature are low, the amount of cooling of the refrigerating machine oil is reduced, the discharge temperature is raised to a predetermined temperature, and the heat dissipation characteristics are not lowered. To. That is, the bypass amount adjusting valve 19 has a function of adjusting the amount of cooling of the refrigerating machine oil so that the temperature of the refrigerant discharged from the two-stage compressor 8 becomes a predetermined temperature, for example, a constant discharge temperature of about 90 ° C. have.

  On the other hand, in the economizer expansion valve 14, the opening degree of the economizer expansion valve 14 is adjusted so that the degree of superheat at the low pressure side outlet (point I) of the economizer 13 is constant, for example, about 10 (K). Is done. Thereby, the branched liquid refrigerant is not unnecessarily returned to the intermediate pressure flow path between the low-stage compressor 9 and the high-stage compressor 10 in the two-stage compressor 8. Moreover, the superheat degree of the refrigerant | coolant of the low pressure side of the economizer 13 becomes excessive, and the malfunction which cannot fully cool the exit (F point) of a high voltage | pressure side can also be suppressed.

  Thus, in the refrigerating apparatus 1 according to the embodiment, the separated refrigerating machine oil is heat-exchanged with the refrigerant in the refrigerant circuit in the oil cooler 17 provided on the upstream side of the receiver 12. Thereby, it is not necessary to cool refrigeration oil with the refrigerant (intermediate pressure injection refrigerant) branched from the refrigerant circuit. Thereby, it can prevent that the quantity of intermediate pressure injection refrigerant | coolants increases and a coefficient of performance (COP: Coefficient Of Performance) deteriorates. Further, since the amount of the intermediate pressure injection refrigerant does not increase, the present invention can be applied to a low-temperature refrigeration system that is used under a condition where the evaporation temperature is −30 ° C. or lower.

  In the refrigeration apparatus 1 according to the embodiment, a refrigerant supercooling region is formed on the outlet side (downstream side) of the air-cooled condenser 24. For this reason, the refrigerant can be dissipated with higher efficiency than when the refrigerant is operated so as to become a saturated liquid on the outlet side of the air-cooled condenser 24. At this time, since a decompression device for adding a degree of supercooling to the refrigerant is not necessary, the refrigerant can be fed into the cooling unit 1c without substantially reducing the pressure of the high-pressure refrigerant. Thereby, even when the pressure loss of the connection pipe 3c is large, a sufficient differential pressure can be ensured before and after the main expansion valve 21 (upstream and downstream).

  The temperature of the liquid refrigerant used as the cooling heat source is a temperature that is always several degrees lower than the condensation temperature. For this reason, even under conditions where the outside air temperature is extremely different, the temperature change of the refrigerating machine oil returned to the two-stage compressor 8 is small. As a result, the temperature of the refrigerating machine oil is extremely lowered, the flow resistance of the circuit for returning the refrigerating machine oil to the two-stage compressor 8 is increased, and the amount of refrigerating machine oil to be returned can be prevented from being insufficient. .

  Furthermore, in the refrigeration apparatus 101 according to the comparative example, when the discharge gas temperature is sufficiently cooled only by the refrigeration oil returned to the two-stage compressor 108, the amount of the branched refrigerant decreases. . For this reason, it is assumed that the economizer 113 does not function sufficiently and the performance deteriorates. On the other hand, in the refrigeration apparatus 1 according to the embodiment, such a situation can be avoided.

  Note that the two-stage compressor 8 having the low-stage compressor 9 and the high-stage compressor 10 has been described as an example of the compressor of the refrigeration apparatus 1 described above. The compressor is not limited to a two-stage compressor, and can also be applied to a compressor having three or more stages of compression units.

  The embodiment disclosed this time is an example, and the present invention is not limited to this. The present invention is defined by the terms of the claims, rather than the scope described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is effectively used in a refrigeration apparatus including a compressor having a plurality of compression units.

  DESCRIPTION OF SYMBOLS 1 Refrigeration equipment, 1a Heat source unit, 1b Heat radiation unit, 1c Cooling unit, 2 Control part, 3a, 3b, 3c, 3d Connection piping, 4 Temperature sensor, 8 Two-stage compressor, 9 Low stage compression part, 10 High stage compression 11, oil separator, 12 receiver, 13 economizer, 14 economizer expansion valve, 15 injection pipe, 16 oil return pipe, 17 oil cooler, 18 bypass pipe, 19 bypass amount adjustment valve, 20 solenoid valve, 21 main expansion valve , 22 Cooler, 23 Cooling fan, 24 Air-cooled condenser, 25 Heat radiation fan, Y1, Y2, Y3, Y4, Y5, Y6 Arrows.

Claims (5)

The refrigerant is a refrigeration apparatus including a refrigerant circuit in which a compressor, an oil separator, a condenser, a receiver, an economizer, a first expansion unit, and a cooler are circulated in order.
The compressor has a plurality of compression units that sequentially compress the refrigerant,
In the refrigerant circuit, heat exchange is performed between the refrigerating machine oil separated in the oil separator and the refrigerant flowing in the first pipe, which is provided in a first pipe connecting the condenser and the receiver. An oil cooler for cooling the refrigerating machine oil,
An oil return pipe connected from the oil separator to the compressor via the oil cooler;
An injection pipe branching from a second pipe connecting between the economizer and the first expansion section in the refrigerant circuit and connected to intermediate pressure flow paths in the plurality of compression sections via the second expansion section and the economizer; A refrigeration apparatus comprising: A bypass pipe connected in parallel to the oil cooler;
The refrigeration apparatus according to claim 1, further comprising a flow rate adjusting unit that adjusts an amount of the refrigerant flowing through the bypass pipe.   The refrigeration apparatus according to claim 2, wherein the flow rate adjusting unit is adjusted according to a degree of supercooling of the refrigerant sent out from the condenser. The compressor, the oil separator, the oil cooler, the oil return pipe, the receiver, the economizer, and the injection pipe are heat source units,
The condenser is a heat dissipation unit,
The refrigeration apparatus according to any one of claims 1 to 3, wherein the first expansion section and the cooler are cooled units. The refrigeration apparatus according to claim 4, wherein the heat source unit and the heat radiating unit are spaced apart from each other.

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