JP2024011228A - refrigeration system - Google Patents

Abstract

To stably supply oil to all compressors in a plurality of compressor units.SOLUTION: A refrigeration system includes: a plurality of compressor units connected in parallel; and an oil equalizing pipe for connecting the plurality of compressor units with each other. The compressor unit includes: a low pressure compressor; a high pressure compressor for compressing a refrigerant compressed in the low pressure compressor; an oil separator for separating oil from the refrigerant; an oil tank for storing oil; a low pressure oil line for delivering the oil circulating in a main oil line for discharging the oil stored in the oil tank to the low pressure compressor; and a high pressure oil line for delivering the oil circulating in the main oil line to the high pressure compressor. The oil equalizing pipe connects main oil lines in the different compressor units with each other. Each compressor unit further includes: a low pressure valve arranged in the low pressure oil line; and a high pressure valve arranged in the high pressure oil line.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD This disclosure relates to refrigeration systems.

A refrigeration system equipped with a plurality of compressors has a structure in which each compressor is connected by an oil equalizing pipe. Oil equalizing pipes connected to multiple compressors supply refrigeration oil from the compressor with a large amount of refrigeration oil to the compressor with a small amount of refrigeration oil, thereby reducing the amount of refrigeration oil in each compressor. The amount of oil is evened out.

For example, in Patent Document 1, in a refrigeration system in which two multi-stage compressors each having a high-pressure compression element and a low-pressure compression element are connected in parallel, there is a structure having an oil return pipe as an oil equalizing pipe to suppress unevenness of the oil level. Are listed. The oil return pipe of Patent Document 1 returns refrigerating machine oil discharged from one compressor to the suction side of the other compressor. As a result, if there is an imbalance between the amounts of refrigerating machine oil accumulated in the compressor, more refrigerating machine oil discharged from one compressor will be returned to the compressor with less refrigerating machine oil. As a result, unevenness in the amount of refrigerating machine oil accumulated in the compressor is suppressed.

Japanese Patent Application Publication No. 2011-214757

By the way, not only the compressor but also a compressor unit having an oil tank and a compressor may be connected in parallel. In such a structure, oil does not circulate through each compressor or each oil tank in sequence. Therefore, differences in the operating conditions of the compressors in each compressor unit may cause differences in the amount of oil stored in the oil tanks. As a result, some oil tanks run out of oil to be supplied to the compressor, making it difficult to stably and continuously operate multiple compressor units.

The present disclosure has been made in order to solve the above problems, and aims to provide a refrigeration system that can stably supply oil to all compressors in a plurality of compressor units. do.

In order to solve the above problems, a refrigeration system according to the present disclosure includes a plurality of compressor units and an oil equalizing pipe that connects the plurality of compressor units to each other, and each compressor unit has a low-pressure compressor that compresses refrigerant. a high-pressure compressor that compresses the refrigerant compressed by the low-pressure compressor, an oil separator that separates lubricating oil from the refrigerant compressed by the high-pressure compressor, and the lubricating oil separated by the oil separator. an oil tank for storing the oil, a main oil line connected to the oil tank and discharging the oil stored in the oil tank, and a main oil line connected to the low pressure compressor to store the main oil. A low-pressure oil line that sends the oil flowing through the line to the low-pressure compressor, and a high-pressure line that connects the main oil line and the high-pressure compressor to send the oil flowing through the main oil line to the high-pressure compressor. an oil line, the oil equalizing pipe connects the main oil lines in different compressor units to each other, and each compressor unit has a low pressure valve disposed in the low pressure oil line and a low pressure valve disposed in the high pressure oil line. and a high pressure valve disposed.

According to the refrigeration system of the present disclosure, oil can be stably supplied to all compressors in a plurality of compressor units.

1 is a diagram showing a schematic configuration of a refrigeration system according to a first embodiment of the present disclosure. It is a diagram showing a schematic configuration of a refrigeration system according to a second embodiment of the present disclosure.

Hereinafter, embodiments for implementing a refrigeration system according to the present disclosure will be described with reference to the accompanying drawings. However, the present disclosure is not limited to this embodiment.

<First embodiment>
(Refrigerating system configuration)
As shown in FIG. 1, the refrigeration system 1 includes a plurality of (two in this embodiment) compressor units 2 that compress refrigerant. The refrigeration system 1 circulates refrigerant compressed by a compressor unit 2 between a cooling supply target such as an indoor unit, for example. In this embodiment, the refrigerant is, for example, carbon dioxide (CO2). Note that the refrigerant may be other than carbon dioxide.

In addition to the plurality of compressor units 2, the refrigeration system 1 includes a condenser 8 that condenses the refrigerant compressed by the compressor unit 2, an evaporator 9 that evaporates the recovered refrigerant, an oil equalization pipe 10, and a control unit 200. It is mainly equipped with. Moreover, in the refrigeration system 1, the plurality of compressor units 2 are connected in parallel. Therefore, the plurality of compressor units 2 can be operated not only under the same operating conditions but also under different operating conditions at the same time.

In this embodiment, the refrigeration system 1 includes a first compressor unit 2A and a second compressor unit 2B as the plurality of compressor units 2. The first compressor unit 2A and the second compressor unit 2B have the same configuration. Therefore, the first compressor unit 2A and the second compressor unit 2B are hereinafter simply referred to as compressor unit 2 and will be explained.

The compressor unit 2 of this embodiment includes a low pressure compressor 3, an intercooler 4, a high pressure compressor 5, an oil separator 6, an oil tank 7, a main oil line 70, a low pressure oil line 30, and a high pressure It mainly includes an oil line 50, a low pressure valve 39, and a high pressure valve 59.

In the compressor unit 2 , the refrigerant flows from the low-pressure compressor 3 toward the oil separator 6 . In the following, in the refrigerant flow direction in the compressor unit 2, the side where the low pressure compressor 3 is arranged with respect to the intercooler 4 is the upstream side, and the side where the high pressure compressor 5 is arranged with respect to the intercooler 4. is the downstream side.

The low-pressure compressor 3 compresses the gas refrigerant supplied from the evaporator 9 in multiple stages (two stages in this embodiment). In this embodiment, the low-pressure compressor 3 is a two-stage compressor that includes a low-pressure rotary compression mechanism 31 and a low-pressure scroll compression mechanism 32 in series. The low-pressure rotary compression mechanism 31 compresses gas refrigerant supplied from the outside of the low-pressure compressor 3. The low-pressure scroll compression mechanism 32 further compresses the refrigerant compressed by the low-pressure rotary compression mechanism 31. The refrigerant compressed by the low-pressure scroll compression mechanism 32 is sent to the intercooler 4. Furthermore, the low pressure compressor 3 further includes a low pressure oil level sensor (oil sensor) 33. The low pressure oil level sensor 33 is a sensor that can measure the amount of oil (refrigerating machine oil) stored inside the low pressure compressor 3. The low pressure oil level sensor 33 detects the height of the oil level inside the casing (not shown) of the low pressure compressor 3. The low-pressure oil level sensor 33 issues a signal to the control unit 200 when the oil level reaches the detectable range or goes out of the detectable range.

Intercooler 4 is arranged between low pressure compressor 3 and high pressure compressor 5. Intercooler 4 is arranged downstream of low-pressure compressor 3 in the refrigerant flow direction. The intercooler 4 cools the refrigerant compressed by the low pressure compressor 3. In this embodiment, the intercooler 4 is, for example, an air-cooled type.

High-pressure compressor 5 is arranged downstream of intercooler 4 in the refrigerant flow direction. The high-pressure compressor 5 further compresses the gas refrigerant, which has been compressed by the low-pressure compressor 3 and then cooled by the intercooler 4, in multiple stages (in this embodiment, two stages). In this embodiment, the high-pressure compressor 5 is a two-stage compressor that includes a high-pressure rotary compression mechanism 51 and a high-pressure scroll compression mechanism 52 in series. The high-pressure rotary compression mechanism 51 compresses refrigerant supplied from the outside of the high-pressure compressor 5. The high-pressure scroll compression mechanism 52 further compresses the refrigerant compressed by the high-pressure rotary compression mechanism 51. The refrigerant compressed by the high-pressure rotary compression mechanism 51 is sent to the oil separator 6. Furthermore, the high-pressure compressor 5 further includes a high-pressure oil level sensor (oil sensor) 53. The high-pressure oil level sensor 53 is a sensor that can measure the amount of oil (refrigerating machine oil) stored inside the high-pressure compressor 5. The high pressure oil level sensor 53 detects the height of the oil level inside the casing (not shown) of the high pressure compressor 5. The high-pressure oil level sensor 53 issues a signal to the control unit 200 when the oil level reaches the detectable range or goes out of the detectable range.

The oil separator 6 is disposed on the downstream side of the high-pressure compressor 5 in the refrigerant flow direction. The oil separator 6 separates oil (refrigerating machine oil) contained in the refrigerant from the refrigerant compressed by the high-pressure compressor 5. The refrigerant that has passed through the oil separator 6 is sent to a condenser 8 that is disposed downstream of the compressor unit 2 in the flow direction.

The oil tank 7 is disposed on the downstream side of the oil separator 6 in the refrigerant flow direction. The oil separated by the oil separator 6 is discharged into an oil tank 7. The oil tank 7 stores oil sent from the oil separator 6.

The main oil line 70 is a pipe connected to the oil tank 7. The main oil line 70 is connected to the bottom of the oil tank 7 and discharges the oil stored in the oil tank 7 to the outside of the oil tank 7. The main oil line 70 is directly connected to the bottom of the oil tank 7.

The low pressure oil line 30 is a pipe that connects the main oil line 70 and the low pressure compressor 3. The low pressure oil line 30 sends oil flowing through the main oil line 70 to the low pressure compressor 3. Low pressure oil line 30 is directly connected to main oil line 70.

The high pressure oil line 50 is a pipe connecting the main oil line 70 and the high pressure compressor 5. The low pressure oil line 30 sends oil flowing through the main oil line 70 to the high pressure compressor 5. High pressure oil line 50 is directly connected to main oil line 70. The low pressure oil line 30, the high pressure oil line 50, and the main oil line 70 are connected at a connection position C.

Low pressure valve 39 is arranged in low pressure oil line 30. The low pressure valve 39 is capable of switching the opening degree of the low pressure oil line 30 based on a signal from the control unit 200. The low pressure valve 39 of this embodiment is an on-off valve that can be switched between a fully open state in which oil flowing through the low pressure oil line 30 is allowed to flow toward the low pressure compressor 3 and a fully closed state in which the oil is not allowed to flow. The low pressure valve 39 is disposed on the downstream side in the flow direction (a position close to the low pressure compressor 3) with respect to the connection position C.

High pressure valve 59 is arranged in high pressure oil line 50. The high pressure valve 59 is capable of switching the opening degree of the high pressure oil line 50 based on a signal from the control unit 200. The high-pressure valve 59 of this embodiment is an on-off valve that can be switched between a fully open state that allows oil flowing through the high-pressure oil line 50 to flow toward the high-pressure compressor 5 and a fully closed state that prevents the oil from flowing. The high-pressure valve 59 is disposed on the downstream side in the flow direction (a position close to the high-pressure compressor 5) with respect to the connection position C.

The condenser 8 is a condenser that condenses the refrigerant compressed by the compressor unit 2. The condenser 8 is disposed on the downstream side of the oil separator 6 in the refrigerant flow direction. In this embodiment, only one capacitor 8 is disposed for each of the plurality of compressor units 2. The condenser 8 is, for example, an air-cooled heat exchanger that exchanges heat between external air and a refrigerant. The high-temperature, high-pressure gas refrigerant generated by the high-pressure compressor 5 passes through the condenser 8 and is condensed to become a high-temperature, high-pressure liquid refrigerant. The refrigerant condensed in the condenser 8 is sent to the evaporator 9 via a receiver (not shown), an expansion valve (not shown), and the like.

The evaporator 9 is an evaporator that generates a low-temperature, low-pressure gas refrigerant to be supplied to the compressor unit 2 . The evaporator 9 is disposed upstream of the low-pressure compressor 3 in the refrigerant flow direction. In this embodiment, the evaporator 9 is arranged separately for the plurality of compressor units 2. That is, two evaporators 9 in this embodiment are arranged, the same number as the compressor units 2. The evaporator 9 is, for example, an air-cooled heat exchanger that exchanges heat between external air and a refrigerant. The low-temperature, low-pressure liquid refrigerant that has passed through the expansion valve etc. evaporates by exchanging heat with external air when passing through the evaporator 9, and becomes a low-temperature, low-pressure gas refrigerant. The low-temperature, low-pressure gas refrigerant is supplied to the low-pressure compressor 3 of the compressor unit 2 .

The oil equalizing pipe 10 connects the plurality of compressor units 2 to each other. Specifically, the oil equalizing pipe 10 connects the main oil lines 70 in different compressor units 2 to each other between the connection position C and the oil tank 7. Therefore, the oil equalizing pipe 10 of this embodiment connects the main oil line 70 of the first compressor unit 2A and the main oil line 70 of the second compressor unit 2B. A first end (one end) of the oil equalizing pipe 10 is connected between a connection position C in the first compressor unit 2A and the oil tank 7. The second end (the end opposite to the first end) of the oil equalizing pipe 10 is connected between the connection position C in the second compressor unit 2B and the oil tank 7. Thereby, the oil equalizing pipe 10 is located downstream in the flow direction with respect to the oil tank 7 with respect to the first compressor unit 2A and the second compressor unit 2B, and with respect to the low pressure oil line 30 and the high pressure oil line 50. Connected on the upstream side in the flow direction. The oil equalizing pipe 10 of this embodiment is a pipe that extends linearly with the same diameter.

The control unit 200 adjusts the opening degrees of the low pressure valve 39 and the high pressure valve 59 based on information from the low pressure oil level sensor 33 and the high pressure oil level sensor 53. The control unit 200 of this embodiment collectively controls the first compressor unit 2A and the second compressor unit 2B. Specifically, the control unit 200 controls the low pressure oil level sensor 33 and high pressure oil level sensor 53 of the first compressor unit 2A, and the low pressure oil level sensor 33 and high pressure oil level sensor 53 of the second compressor unit 2B. Information on the position of the oil level in each compressor is acquired as information on the low pressure oil level sensor 33 and the high pressure oil level sensor 53. Based on the obtained oil level position information, the control unit 200 sets the low pressure valve 39 and high pressure valve 59 corresponding to the compressor in which the sensor that sent the information is disposed to either a fully open state or a fully closed state. Switch to Here, "corresponding" means that the low pressure oil level sensor 33 or the high pressure oil level sensor 53 that sent the information is arranged.

More specifically, the control unit 200 responds to signals sent from the low-pressure oil level sensor 33 and the high-pressure oil level sensor 53 when the oil level reaches the detectable range or goes out of the detectable range. Based on this information, information on the oil level positions inside the low-pressure compressor 3 and high-pressure compressor 5 is acquired. If the obtained oil level position information is information indicating that the oil level position has reached the detectable range, the control unit 200 causes the corresponding low pressure valve 39 or high pressure valve 59 to be fully closed. Send instructions. If the obtained oil level position information is information that indicates that the oil level position is out of the detectable range, the control unit 200 instructs the corresponding low pressure valve 39 or high pressure valve 59 to be fully open. send.

(effect)
In the refrigeration system 1 having the above configuration, a plurality of compressor units 2 are connected in parallel. In each compressor unit 2 , gas refrigerant generated in an evaporator 9 is supplied to a low-pressure compressor 3 . The gas refrigerant supplied to the low pressure compressor 3 flows through the low pressure rotary compression mechanism 31 and the low pressure scroll compression mechanism 32 in this order, and is compressed in two stages. The gas refrigerant compressed by the low pressure compressor 3 is sent to the intercooler 4 and cooled. Furthermore, the gas refrigerant cooled by the intercooler 4 is supplied to the high pressure compressor 5. The gas refrigerant supplied to the high-pressure compressor 5 flows through the high-pressure rotary compression mechanism 51 and the high-pressure scroll compression mechanism 52 in this order, and is compressed in two stages. The gas refrigerant compressed by the high-pressure compressor 5 is sent to an oil separator 6, where oil contained in the gas refrigerant is separated. The gas refrigerant from which the oil has been separated is sent to the condenser 8 and supplied to the refrigerant supply target. The refrigerant that has undergone heat exchange with the refrigerant supply target is returned to the compressor unit 2 and sent to the evaporator 9 via a receiver (not shown), an expansion valve (not shown), and the like. The refrigerant sent to the evaporator 9 evaporates and becomes a low-temperature, low-pressure gas refrigerant. The low-temperature, low-pressure gas refrigerant is again supplied to the low-pressure compressor 3 of the compressor unit 2. In this way, refrigerant is circulated in the refrigeration system 1 to the compressor unit 2.

Further, the oil separated by the oil separator 6 is sent to an oil tank 7 and stored therein. The oil sent to the oil tank 7 is returned to the low pressure compressor 3 through the main oil line 70 and the low pressure oil line 30 only when the low pressure valve 39 is fully open. Further, a portion of the oil passing through the main oil line 70 is returned to the high-pressure compressor 5 through the main oil line 70 and the high-pressure oil line 50 only when the high-pressure valve 59 is fully open. Further, the oil passing through the main oil line 70 is sent to another main oil line 70 through the oil equalizing pipe 10. That is, a part of the oil passing through the main oil line 70 of the first compressor unit 2A is sent to the main oil line 70 of the second compressor unit 2B through the oil equalizing pipe 10. Further, a part of the oil passing through the main oil line 70 of the second compressor unit 2B is sent to the main oil line 70 of the first compressor unit 2A through the oil equalizing pipe 10.

In this way, in the refrigeration system 1 of this embodiment, the main oil line 70 of the first compressor unit 2A and the main oil line 70 of the second compressor unit 2B are connected by the oil equalizing pipe 10. Therefore, the oil accumulated in the oil tank 7 of the first compressor unit 2A can flow not only into the main oil line 70 of the first compressor unit 2A but also into the main oil line 70 of the second compressor unit 2B. Similarly, the oil accumulated in the oil tank 7 of the second compressor unit 2B can flow not only into the main oil line 70 of the second compressor unit 2B but also into the main oil line 70 of the first compressor unit 2A. . In addition, in each compressor unit 2, a low pressure valve 39 is arranged in the low pressure oil line 30, and a high pressure valve 59 is arranged in the high pressure oil line 50. Therefore, the amount (flow state) of oil flowing into the low pressure compressor 3 from the main oil line 70 and the low pressure oil line 30 can be adjusted by the low pressure valve 39. Similarly, the amount (flow state) of oil flowing into the high-pressure compressor 5 from the main oil line 70 and the high-pressure oil line 50 can be adjusted by the high-pressure valve 59. With these, oil stored in different oil tanks 7 can be supplied to any compressor by switching the opening degrees of the low pressure valve 39 and the high pressure valve 59. Therefore, regardless of the operating status of the plurality of compressors, it is possible to stop supplying oil to a compressor with a large amount of oil, and to start supplying oil to a compressor with a low amount of oil. Thereby, oil can be stably supplied to all the compressors in the plurality of compressor units 2.

The control unit 200 also switches the opening degrees of the low pressure valve 39 and the high pressure valve 59 based on the oil level position information from the low pressure oil level sensor 33 and high pressure oil level sensor 53 of each compressor unit 2. There is. Therefore, if there is a low-pressure compressor 3 or a high-pressure compressor 5 that lacks oil in each compressor unit 2, oil is supplied to the low-pressure compressor 3 or high-pressure compressor 5 that lacks oil. The low pressure valve 39 and high pressure valve 59 can be opened automatically. Similarly, if there is a low-pressure compressor 3 or a high-pressure compressor 5 in which an excessive amount of oil has accumulated in each compressor unit 2, the low-pressure compressor 3 or high-pressure compressor 5 in which an excessive amount of oil has accumulated is The low pressure valve 39 and the high pressure valve 59 for supplying can be automatically closed. In this way, the amount of oil in each compressor can be automatically adjusted by the control unit 200. Therefore, in the plurality of compressor units 2, oil can be supplied to all the compressors so that the amount of oil stored therein is approximately uniform.

<Second embodiment>
Next, a second embodiment of the refrigeration system 1B according to the present disclosure will be described. In addition, in the second embodiment described below, the same reference numerals are given to the same components in the figures as in the first embodiment, and the explanation thereof will be omitted. The second embodiment differs from the first embodiment in that it includes an adjustment on-off valve 101.

The refrigeration system 1B of the second embodiment further includes an adjustment on-off valve 101 disposed in the middle of the oil equalizing pipe 10. The adjustment on-off valve 101 is capable of switching the opening degree of the oil equalizing pipe 10 based on a signal from the control section 200B. The adjustment on-off valve 101 of this embodiment is an on-off valve that can be switched between a fully open state that allows oil to flow through the oil equalizing pipe 10 and a fully closed state that prevents it from flowing.

The control unit 200B of the second embodiment adjusts the opening degree of not only the low pressure valve 39 and the high pressure valve 59 but also the adjustment valve 101 based on information from the low pressure oil level sensor 33 and the high pressure oil level sensor 53. The control unit 200B receives information from the low-pressure oil level sensor 33 and high-pressure oil level sensor 53 of the first compressor unit 2A and the low-pressure oil level sensor 33 and high-pressure oil level sensor 53 of the second compressor unit 2B in each compressor. Obtain information on oil level position. Based on the acquired oil level position information, the control unit 200B provides information on the total amount of oil in the low-pressure compressor 3 and high-pressure compressor 5 in the first compressor unit 2A and the second compressor unit. Information on the amount of oil in the low pressure compressor 3 and high pressure compressor 5 in the unit 2B as a whole is acquired. The control unit 200B causes the adjustment valve 101 to be fully open when the amount of oil in either compressor unit 2 is small or excessive, based on the information on the amount of oil in each compressor unit 2 as a whole. send instructions to do so. Further, when the amount of oil in all the compressor units 2 is appropriate, the control section 200B sends an instruction to the adjustment on-off valve 101 to be in a fully closed state.

(effect)
In the refrigeration system 1B having the above configuration, the oil distribution state in the oil equalizing pipe 10 is switched by the adjustment on-off valve 101. Therefore, the supply of oil between the first compressor unit 2A and the second compressor unit 2B can be stopped. Therefore, when it is desired to operate only one compressor unit 2, it is possible to prevent oil from being supplied to a compressor unit 2 that is not in operation. Thereby, in the plurality of compressor units 2, even only some of the compressor units 2 can be stably operated.

(Other embodiments)
Although the embodiment of the present disclosure has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes design changes within the scope of the gist of the present disclosure. .

Note that in the refrigeration systems 1 and 1B, the configurations other than the compressor unit 2 are not limited in any way, and the configurations can be changed as appropriate.

Further, the low pressure compressor 3 and the low pressure compressor 3 are not limited to being two-stage compressors. The low pressure compressor 3 and the high pressure compressor 5 may be multi-stage compressors with three or more stages, or may be single-stage compressors with only one stage. The low pressure compressor 3 and the high pressure compressor 5 are not limited to having a structure including a rotary compression mechanism and a scroll compression mechanism. For example, the low pressure compressor 3 and the high pressure compressor 5 may have only a rotary compression mechanism in multiple stages, or may have only a scroll compression mechanism in multiple stages.

In addition, the compressor unit 2 and the refrigeration systems 1 and 1B include a receiver (not shown) that recovers liquid refrigerant from the refrigerant condensed in the condenser 8, and a receiver that adiabatically expands and depressurizes the liquid refrigerant recovered by the receiver. , an expansion valve (not shown) which is an expander that converts the refrigerant into a gas-liquid two-phase state by evaporating a part of the liquid; It may further include an economizer (not shown), which is a device for separating the liquid phase and the liquid phase.

Further, the low pressure valve 39 and the high pressure valve 59 are not limited to being on/off valves or electromagnetic valves. The low pressure valve 39 and the high pressure valve 59 may be valves whose opening degrees can be adjusted arbitrarily, or may be valves whose opening degrees are adjusted manually instead of by the control units 200 and 200B. When the low pressure valve 39 and the high pressure valve 59 are not on-off valves but are valves that can be adjusted to arbitrary opening degrees, the control units 200 and 200B may send instructions to appropriate the opening degrees of the valves.

Further, the evaporator 9 is not limited to being arranged separately for the plurality of compressor units 2. For example, only one evaporator 9 may be disposed for a plurality of compressor units 2.

Further, the number of capacitors 8 is not limited to that only one is disposed for each of the plurality of compressor units 2. For example, the capacitor 8 may be arranged separately for the plurality of compressor units 2.

<Additional notes>
The refrigeration systems 1 and 1B described in each embodiment are understood as follows, for example.

(1) The refrigeration system 1, 1B according to the first aspect includes a plurality of compressor units 2 connected in parallel and an oil equalizing pipe 10 that connects the plurality of compressor units 2 to each other, and each compressor unit 2 includes a low-pressure compressor 3 that compresses refrigerant, a high-pressure compressor 5 that compresses the refrigerant compressed by the low-pressure compressor 3, and an oil separator that separates oil from the refrigerant compressed by the high-pressure compressor 5. 6, an oil tank 7 for storing the oil separated by the oil separator 6, a main oil line 70 connected to the oil tank 7 and discharging the oil stored in the oil tank 7, A low-pressure oil line 30 that connects the main oil line 70 and the low-pressure compressor 3 and sends the oil flowing through the main oil line 70 to the low-pressure compressor 3, and the main oil line 70 and the high-pressure compressor. 5, and a high-pressure oil line 50 that sends the oil flowing through the main oil line 70 to the high-pressure compressor 5. 70 are connected to each other, and each compressor unit 2 further includes a low pressure valve 39 disposed in the low pressure oil line 30 and a high pressure valve 59 disposed in the high pressure oil line 50.

Thereby, the main oil line 70 of one compressor unit 2 and the main oil line 70 of the other compressor unit 2 are connected to the oil equalizing pipe 10. Therefore, the oil accumulated in the oil tank 7 of one compressor unit 2 can flow not only into the main oil line 70 of that compressor unit 2 but also into the main oil line 70 of another compressor unit 2. In addition, in each compressor unit 2, a low pressure valve 39 is arranged in the low pressure oil line 30, and a high pressure valve 59 is arranged in the high pressure oil line 50. Therefore, the amount (flow state) of oil flowing into the low pressure compressor 3 from the low pressure oil line 30 can be adjusted by the low pressure valve 39. Similarly, the amount of oil flowing into the high-pressure compressor 5 from the high-pressure oil line 50 (flow state) can be adjusted by the high-pressure valve 59. With these, oil stored in different oil tanks 7 can be supplied to any compressor by switching the opening degrees of the low pressure valve 39 and the high pressure valve 59. Therefore, regardless of the operating status of a plurality of compressors, it is possible to stop supplying oil to a compressor with a large amount of oil, and to start supplying oil to a compressor with a low amount of oil. Thereby, oil can be stably supplied to all the compressors in the plurality of compressor units 2.

(2) The refrigeration system 1, 1B according to the second aspect is the refrigeration system 1, 1B of (1), in which the low pressure compressor 3 and the high pressure compressor 5 reduce the amount of oil stored therein. It further includes control units 200 and 200B that have a measurable oil sensor and adjust the opening degrees of the low pressure valve 39 and the high pressure valve 59 based on information from the oil sensor.

As a result, if there is a low-pressure compressor 3 or a high-pressure compressor 5 that lacks oil in each compressor unit 2, oil is supplied to the low-pressure compressor 3 or high-pressure compressor 5 that lacks oil. The low pressure valve 39 and high pressure valve 59 can be opened automatically. Similarly, if there is a low-pressure compressor 3 or a high-pressure compressor 5 in which an excessive amount of oil has accumulated in each compressor unit 2, the low-pressure compressor 3 or high-pressure compressor 5 in which an excessive amount of oil has accumulated is The low pressure valve 39 and the high pressure valve 59 for supplying can be automatically closed. In this way, the amount of oil in each compressor can be automatically adjusted by the control units 200, 200B. Therefore, in the plurality of compressor units 2, oil can be supplied to all the compressors so that the amount of oil stored therein is approximately uniform.

(3) The refrigeration system 1 according to the third aspect is the refrigeration system 1 or 1B of (1) or (2), and further includes an adjustment on-off valve 101 disposed in the middle of the oil equalizing pipe 10.

Thereby, the supply of oil between the plurality of compressor units 2 can be stopped. Therefore, when it is desired to operate only one compressor unit 2, it is possible to prevent oil from being supplied to a compressor unit 2 that is not in operation. Thereby, in the plurality of compressor units 2, even only some of the compressor units 2 can be stably operated.

1, 1B... Refrigeration system 2... Compressor unit 3... Low pressure compressor 31... Low pressure rotary compression mechanism 32... Low pressure scroll compression mechanism 33... Low pressure oil level sensor 4... Intercooler 5... High pressure compressor 51... High pressure rotary compression mechanism 52 …High pressure scroll compression mechanism 53…High pressure oil level sensor 6…Oil separator 7…Oil tank 70…Main oil line 30…Low pressure oil line 50…High pressure oil line 39…Low pressure valve 59…High pressure valve C…Connection position 2A…First Compressor unit 2B...Second compressor unit 10...Oil equalizing pipe 8...Condenser 9...Evaporator 200, 200B...Control section 101...Adjustment on-off valve

Claims (3)

multiple compressor units connected in parallel;
Equipped with an oil equalizing pipe that connects multiple compressor units to each other,
Each compressor unit is
a low-pressure compressor that compresses refrigerant;
a high-pressure compressor that compresses the refrigerant compressed by the low-pressure compressor;
an oil separator that separates oil from the refrigerant compressed by the high-pressure compressor;
an oil tank that stores the oil separated by the oil separator;
a main oil line connected to the oil tank and discharging the oil stored in the oil tank;
a low-pressure oil line that connects the main oil line and the low-pressure compressor and sends the oil flowing through the main oil line to the low-pressure compressor;
a high-pressure oil line that connects the main oil line and the high-pressure compressor and sends the oil flowing through the main oil line to the high-pressure compressor;
The oil equalizing pipe connects the main oil lines in different compressor units to each other,
Each compressor unit further includes a low pressure valve disposed in the low pressure oil line and a high pressure valve disposed in the high pressure oil line. The low-pressure compressor and the high-pressure compressor have an oil sensor capable of measuring the amount of oil stored therein,
The refrigeration system according to claim 1, further comprising a control unit that adjusts opening degrees of the low pressure valve and the high pressure valve based on information from the oil sensor. The refrigeration system according to claim 1 or 2, further comprising an adjustment on-off valve disposed in the middle of the oil equalizing pipe.

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