Refrigeration system

Abstract

To reduce the installation area of a refrigeration system having two compressors.SOLUTION: A refrigeration system 1 includes a low stage side compressor 11, a high stage side compressor 12, an oil separator 13, a condenser 14, and as vaporizer 16. The high stage side compressor 12 is arranged on the lower side of the low stage side compressor 11. The oil separator 13 is arranged on one side in the longitudinal direction of the high stage side compressor 12. The vaporizer 16 is arranged on the upper side of the oil separator 13 and on one side in the longitudinal direction of the low stage side compressor 11. The high stage side compressor 12, the oil separator 13, the condenser 14 and the vaporizer 16 are arranged to be fit in the width of the low stage side compressor 11.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a refrigeration system.

Background Art

[0002] A refrigeration system includes a compressor for performing the compression step of the refrigeration cycle. For example, Patent Document 1 discloses a screw compressor composed of two compressors, a first compressor and a second compressor, as an example of a compressor applicable to a refrigeration system. The first compressor and the second compressor are fluidly connected in series, while being arranged side by side in terms of layout.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding a refrigeration system provided with two compressors, there is room for improvement in the installation area.

[0005] An object of the present invention is to reduce the installation area of a refrigeration system provided with two compressors.

Means for Solving the Problems

[0006] One aspect of the present invention provides a refrigeration system comprising: a low-stage compressor for compressing a refrigerant; a high-stage compressor for further compressing the refrigerant compressed by the low-stage compressor; an oil separator for separating oil from the refrigerant compressed by the high-stage compressor; a condenser for condensing the refrigerant separated from the oil by the oil separator; and an evaporator for evaporating the refrigerant condensed by the condenser, wherein the high-stage compressor is positioned below the low-stage compressor, the oil separator is positioned on one side in the longitudinal direction of the high-stage compressor, and the evaporator is positioned above the oil separator and on one side in the longitudinal direction of the low-stage compressor, and the high-stage compressor, the oil separator, the condenser, and the evaporator are arranged to fit within the width of the low-stage compressor.

[0007] In the above configuration, the two compressors, the low-stage compressor and the high-stage compressor, are arranged in a vertical line. Furthermore, the main devices constituting the refrigeration system—namely, the oil separator, condenser, and evaporator—are arranged together with the high-stage compressor so that they fit within the width of the low-stage compressor. Therefore, the installation area of ​​the refrigeration system can be reduced.

[0008] The condenser may be located below the high-stage compressor, between the high-stage compressor and the oil separator in the longitudinal direction of the high-stage compressor.

[0009] With the above configuration, the installation area in the longitudinal direction of the compressor can be reduced compared to the case where the condenser is located on the opposite side of the high-stage compressor from the oil separator.

[0010] The refrigeration system further comprises a compressor intermediate piping that connects a low-stage discharge port provided in the low-stage compressor for discharging the refrigerant to a high-stage intake port provided in the high-stage compressor for drawing in the refrigerant, wherein the low-stage discharge port is provided at the lower part of the low-stage compressor and the high-stage intake port is provided at the upper part of the high-stage compressor.

[0011] With the above configuration, the piping connecting the two compressors (intermediate compressor piping) can be shortened.

[0012] At least one of the lower-stage compressor and the upper-stage compressor is a screw compressor having a male rotor and a female rotor, and in the screw compressor, the male rotor and the female rotor may be arranged vertically.

[0013] According to the above configuration, when a screw compressor is used, the width of the compressor is reduced, and consequently, the installation area of ​​the refrigeration system can be reduced in the width direction.

[0014] The high-stage compressor may be narrower than the low-stage compressor, and the axis of the high-stage compressor may be offset in the width direction with respect to the axis of the low-stage compressor such that on one side in the width direction, the outer circumference position of the high-stage compressor is closer to the outer circumference position of the low-stage compressor.

[0015] With the above configuration, space is created below the lower-stage compressor and on the other side in the width direction of the upper-stage compressor. This space can be used to arrange devices or piping that constitute the refrigeration system. [Effects of the Invention]

[0016] According to the present invention, the installation area of ​​a refrigeration system equipped with two compressors can be reduced. [Brief explanation of the drawing]

[0017] [Figure 1] Circuit diagram of a refrigeration system according to an embodiment. [Figure 2] A side view of a refrigeration system according to an embodiment. [Figure 3] Front view of a refrigeration system according to an embodiment. [Figure 4] A plan view of the refrigeration system according to this embodiment. [Figure 5] Front view of a modified refrigeration system. [Modes for carrying out the invention]

[0018] Hereinafter, embodiments will be described with reference to the drawings. Note that the same or corresponding elements are denoted by the same reference numerals throughout the drawings, and redundant detailed descriptions are omitted.

[0019] Referring to FIG. 1, the refrigeration system 1 according to the embodiment is a so-called unit type. The refrigeration system 1 includes a refrigerant circuit 10 and an oil circulation circuit 30. The refrigerant is not particularly limited. As an example, R23 (CHF3) or R32 (CH2F2) can be preferably used as the refrigerant.

[0020] The refrigerant circuit 10 has a low-stage compressor 11, a high-stage compressor 12, an oil separator 13, a condenser 14, an expansion valve 15, and an evaporator 16. The refrigerant circulates in this order within the refrigerant circuit 10.

[0021] The low-stage compressor 11 gradually compresses the gaseous refrigerant. The high-stage compressor 12 further gradually compresses the gaseous refrigerant compressed by the low-stage compressor. The oil separator 13 separates oil from the high-temperature and high-pressure gaseous refrigerant compressed by the high-stage compressor 12. The condenser 14 condenses the high-temperature and high-pressure gaseous refrigerant separated from the oil by the oil separator 13. The expansion valve 15 expands the medium-temperature and high-pressure liquid refrigerant condensed by the condenser 14. The evaporator 16 evaporates the low-temperature and low-pressure liquid refrigerant expanded by the expansion valve 15. The low-temperature and low-pressure gaseous refrigerant obtained by the evaporator 16 is returned to the low-stage compressor 11.

[0022] The refrigerant circuit 10 has a plurality of piping members that connect the devices (devices) constituting the refrigerant circuit 10 in order to circulate the refrigerant. The piping members include, for example, a compressor suction pipe 21, a compressor intermediate pipe 22, a compressor discharge pipe 23, a condenser supply pipe 24, and a liquid-phase pipe 25.

[0023] The compressor suction piping 21 connects the refrigerant outlet 16B of the evaporator 16 to the suction port 11A of the low-stage compressor 11. The compressor intermediate piping 22 connects the discharge port 11B of the low-stage compressor 11 to the suction port 12A of the high-stage compressor 12, thereby connecting the low-stage compressor 11 and the high-stage compressor 12 in series. The compressor discharge piping 23 connects the discharge port 12B of the high-stage compressor 12 to the refrigerant inlet 13A of the oil separator 13. The condenser supply piping 24 connects the refrigerant outlet 13B of the oil separator 13 to the refrigerant inlet 14A of the condenser 14. The liquid phase piping 25 connects the refrigerant outlet 14B of the condenser 14 to the refrigerant inlet 16A of the evaporator 16. The expansion valve 15 is interposed on the liquid phase piping 25.

[0024] More specifically, the low-stage compressor 11 and the high-stage compressor 12 are two-stage, oil-cooled screw compressors. The low-stage compressor 11 has a first-stage compression section 11a and a second-stage compression section 11b. The high-stage compression section 12 has a first-stage compression section 12a and a second-stage compression section 12b. Each compression section 11a, 11b, 12a, and 12b is composed of a male and female pair of rotors (see Figure 3).

[0025] The low-stage compressor 11 and the high-stage compressor 12 are driven by separate motors 11c and 12c, respectively. The motor 11c of the low-stage compressor 11 drives the first-stage compression section 11a and the second-stage compression section 11b. The motor 12c of the high-stage compressor 12 is separate from motor 11c and drives the first-stage compression section 12a and the second-stage compression section 12b. Motors 11c and 12c are AC motors and can operate independently of each other. The rotational speeds of the low-stage compressor 11 and the high-stage compressor 12 are controlled independently of each other. Furthermore, the low-stage compressor 11 and the high-stage compressor 12 have the first compression sections 11a, 12a and the second compression sections 11b, 12b housed in series, giving them an elongated appearance in the depth direction. By using such a compressor, it is possible to construct an ultra-low temperature refrigerator (for example, one that can lower the brine temperature to around -80°C) while reducing the installation area of ​​the refrigeration system.

[0026] The low-stage compressor 11 is provided with an inlet 11A for drawing refrigerant into the low-stage compressor 11 from the compressor suction pipe 21, and a discharge port 11B for discharging refrigerant from the low-stage compressor 11 to the compressor intermediate pipe 22. The high-stage compressor 12 is provided with an inlet 12A for drawing refrigerant into the high-stage compressor 12 from the compressor intermediate pipe 22, and a discharge port 12B for discharging refrigerant from the high-stage compressor 12 to the compressor discharge pipe 23.

[0027] The refrigerant from the evaporator 16 is drawn into the low-stage compressor 11 via the compressor suction pipe 21 and suction port 11A, and is sequentially compressed as it passes through the first-stage compression section 11a and the second-stage compression section 11b in that order, and is discharged from the low-stage compressor 11 via the discharge port 11B. The discharged refrigerant is drawn into the high-stage compressor 12 via the compressor intermediate pipe 22 and suction port 12A, and is sequentially compressed as it passes through the first-stage compression section 12a and the second-stage compression section 12b in that order, and is discharged from the high-stage compressor 12 via the discharge port 12B. The discharged refrigerant is mixed with lubricating and cooling oil supplied to the compressors 11 and 12.

[0028] The oil separator 13 has a vertically elongated casing 13a. The casing 13a is provided with a refrigerant inlet 13A for introducing refrigerant, a refrigerant outlet 13B for discharging the refrigerant separated from the oil, and an oil outlet 13C for discharging the oil separated from the refrigerant. The refrigerant inlet 13A is located on the side of the casing 13a. The refrigerant outlet 13B is located at the top of the casing 13a. The oil outlet 13C is located at the bottom of the casing 13a.

[0029] The refrigerant from the high-stage compressor 12 flows into the oil separator 13 via the compressor discharge pipe 23 and the refrigerant inlet 13A, where it is separated from the oil within the casing 13a. The oil is stored at the bottom of the casing 13a. The refrigerant separated from the oil flows out of the oil separator 13 through the refrigerant outlet 13B.

[0030] The condenser 14 has a refrigerant passage 14a through which the refrigerant flows, and a coolant passage 14b through which the coolant flows. One end of the refrigerant passage 14a is a refrigerant inlet 14A, and the other end of the refrigerant passage 14a is a refrigerant outlet 14B. The expansion valve 15 is configured to allow adjustment of its opening degree. The evaporator 16 has a refrigerant passage 16a through which the refrigerant flows, and a brine passage 16b through which the brine flows. One end of the refrigerant passage 16a is a refrigerant inlet 16A, and the other end of the refrigerant passage 16a is a refrigerant outlet 16B.

[0031] The refrigerant from the oil separator 13 flows into the refrigerant passage 14a via the condenser supply piping 24 and the refrigerant inlet 14A. In the condenser 14, as it flows through the refrigerant passage 14a, it is cooled and condensed by heat exchange with the coolant, and then flows out of the condenser 14 through the refrigerant outlet 14B. The refrigerant from the condenser 14 expands and cools down due to the action of the expansion valve 15 as it flows through the liquid phase piping 25, flows into the evaporator via the refrigerant inlet, and in the evaporator 16, as it flows through the refrigerant passage 16a, it is heated and evaporates by heat exchange with the brine, and then flows out of the evaporator 16 through the refrigerant outlet 16B. The evaporator 16 acts as a cooler, cooling the brine with the cold energy of the refrigerant. For example, the evaporator 16 acting as a cooler can lower the brine temperature to an ultra-low temperature of -80°C. The brine is used to cool an object (not shown).

[0032] The oil circulation circuit 30 includes an oil separator 13, an oil return line 31, and an oil cooler 32. The oil return line 31 connects its oil outlet 13C to the compressors 11 and 12, supplying the oil separated by the oil separator 13 to the compressors 11 and 12. The oil cooler 32 is interposed on the oil return line 31 and cools the oil before supplying it to the compressors 11 and 12.

[0033] Next, the shapes and arrangement of the components of the refrigeration system 1 will be described with reference to Figures 2 to 4.

[0034] The refrigeration system 1 is installed, for example, on a plot of land S secured within a factory. The plot of land S is, for example, a long, narrow rectangle, with a relatively long required dimension X in the depth direction and a relatively short required dimension Y in the width direction. "Requirements" refers to a request from the user of the refrigeration system 1 to the provider of the refrigeration system 1, which requires that the refrigeration system 1 be designed to fit within the plot of land S. For the sake of explanation, the plot of land S is assumed to be horizontal, but the directions described below may be appropriately changed depending on the slope of the plot of land S.

[0035] The lower-stage compressor 11 is a semi-enclosed compressor. More specifically, the lower-stage compressor 11 has a casing 41 that is elongated in the axial direction. The casing 41 is roughly cylindrical with a stepped shape. The casing 41 has a relatively small diameter on one side in the longitudinal direction (axial direction) (left side of the paper in Figures 2 and 4), while it has a relatively large diameter on the other side in the longitudinal direction (right side of the paper in Figures 2 and 4). Detailed illustrations are omitted in Figures 2 to 4, but the motor 11c (see Figure 1), the first-stage compression section 11a (see Figure 1), and the second-stage compression section 11b (see Figure 1) are housed in the casing 41 in this order from the other side to the one side in the longitudinal direction.

[0036] The casing 41 has a motor housing section 41a at the other end in the longitudinal direction for housing the motor 11c. The motor housing section 41a has the largest diameter within the casing 41. The low-stage compressor 11 is installed on site S with its longitudinal or axial direction oriented horizontally and facing the depth direction of the site S. Therefore, the diameter of the motor housing section 41a of the casing 41 corresponds to the maximum width W11 of the casing 41.

[0037] The high-stage compressor 12 has the same structure as the low-stage compressor 11. The casing 51 of the high-stage compressor 12 also has a motor housing section 51a at the other end in its longitudinal direction, which houses the motor 12c (see Figure 1).

[0038] The high-stage compressor 12 is smaller than the low-stage compressor 11. The maximum width W12 of the high-stage compressor 12 is smaller than the maximum width W11 of the low-stage compressor 11. The length L12 of the high-stage compressor 12 is shorter than the length L11 of the low-stage compressor 11.

[0039] The lower-stage compressor 11 and the upper-stage compressor 12 are arranged vertically. The upper-stage compressor 12 is positioned below the lower-stage compressor 11. The upper-stage compressor 12 is supported on the site S via a support frame (not shown), floating above the ground of the site S. The lower-stage compressor 11 is also positioned above the upper-stage compressor 12 and supported on the site S via a support frame (not shown). In both the lower-stage compressor 11 and the upper-stage compressor 12, the axial direction is horizontal. The axis C11 of the lower-stage compressor 11 is located above the axis C12 of the upper-stage compressor 12. In a plan view, the axes C11 and C12 completely overlap. In other words, the axes C11 and C12 are in the same position in the width direction (of the site S).

[0040] The casing 41 of the low-stage compressor 11 has a compression section housing 41b that houses the compression sections 11a and 11b. The compression section housing 41b is gourd-shaped, and the male rotor 42 and female rotor 43 constituting each of the compression sections 11a and 11b are housed in a meshed state. The male rotor 42 is coaxial with the motor 11c. That is, the male rotor 42 constituting the first compression section 11a, the male rotor 42 constituting the second compression section 11b, and the motor shaft of the motor 11c are coaxial. The axis C11 of the low-stage compressor 11 corresponds to the common axis of the motor 11c and the male rotor 42. The central axis A43 of the female rotor 43 is parallel to the central axis A42 (axis C11) of the male rotor 42. In this embodiment, the central axis A43 of the female rotor 43 is directly below the central axis A42 of the male rotor 42, and the male rotor 42 and female rotor 43 are arranged vertically. The same applies to the high-stage compressor 12. The casing 51 has a compression section housing section 51b that houses the male rotor 52 and female rotor 53 constituting each compression section 12a and 12b in a meshed state. The male rotor 52 and female rotor 53 are arranged vertically, and the central axis A53 of the female rotor 53 is directly below the central axis A52 of the male rotor 52 (the axis C12 of the high-stage compressor 12). Furthermore, the male rotor 52 is coaxial with the motor 12c. That is, the male rotor 52 constituting the first compression section 12a, the male rotor 52 constituting the second compression section 12b, and the motor shaft of the motor 12c are coaxial.

[0041] The lower-stage compressor 11 and the upper-stage compressor 12 are positioned towards the other side of the site S in the depth direction (right side of the page in Figures 2 and 4). The motor housings 41a and 51a are located at the other end of the site S in the depth direction and are arranged vertically.

[0042] In contrast, the oil separator 13, condenser 14, expansion valve 15, and evaporator 16 are clustered together on one side of the site S in the depth direction (left side of Figures 2 and 4). In other words, the oil separator 13, condenser 14, expansion valve 15, and evaporator 16 are located on one side of the low-stage compressor 11 in the longitudinal direction (left side of Figures 2 and 4), or on one side of the high-stage compressor 12 in the longitudinal direction (left side of Figures 2 and 4).

[0043] The oil separator 13 is positioned near the ground of the site S, similar to the high-stage compressor 12, and is located on one side of the longitudinal direction of the high-stage compressor 12. The casing 13a of the oil separator 13 is supported on the site S with its axial direction oriented vertically. The axial dimension of the oil separator 13, i.e., its height H13, is considerably larger than its diameter φ13. The lower end of the oil separator 13 is located below the lower end of the high-stage compressor 12. The upper end of the oil separator 13 is located above the upper end of the high-stage compressor 12, while being located below the lower end of the low-stage compressor 11.

[0044] The evaporator 16 is rectangular in shape, square in plan view, and rectangular in side and front view, with its longer sides oriented in the height direction. The refrigerant passage 16a and brine passage 16b of the evaporator 16 are oriented vertically. The evaporator 16 is positioned above the oil separator 13. The evaporator 16 is positioned above the ground of the site S, similar to the low-stage compressor 11, and is located on one side of the low-stage compressor 11 in the longitudinal direction.

[0045] The condenser 14 is a low-profile panel and has a rectangular shape in plan view. The condenser 14 is positioned below the high-stage compressor 12. Furthermore, the condenser 14 is positioned on one side of the high-stage compressor 12 in the longitudinal direction, while it is positioned on the other side of the high-stage compressor 12 in the longitudinal direction relative to the oil separator 13. The other end of the condenser 14 enters the space formed between the ground of the site S and the lower end of the low-stage compressor 11. In other words, in plan view, the condenser 14 partially overlaps with the low-stage compressor 11.

[0046] The suction port 11A of the low-stage compressor 11 is located at the top of the casing 41 and is directed upward. The discharge port 11B of the low-stage compressor 11 is located at the bottom of the casing 41 and is directed downward. The suction port 12A of the high-stage compressor 12 is located at the top of the casing 51 and is directed upward. The discharge port 12B of the high-stage compressor 12 is located at the bottom of the casing 51 and is directed downward.

[0047] The suction ports 11A and 12A are located in the longitudinal center of the corresponding casings 41 and 51. The discharge ports 11B and 12B are located at one longitudinal end of the corresponding casings 41 and 51. The suction port 12A of the high-stage compressor 12 is located below and on the other longitudinal side of the discharge port 11B of the low-stage compressor 11.

[0048] The compressor intermediate piping 22 connects the discharge port 11B of the lower-stage compressor 11 to the suction port 12A of the higher-stage compressor 12. The compressor intermediate piping 22 extends slightly downward from the discharge port 11B, is bent at a right angle toward the other side in the longitudinal direction, and is bent at another right angle downward to reach the suction port 12A.

[0049] The refrigerant inlet 13A of the oil separator 13 is oriented horizontally and faces the high-stage compressor 12. The compressor discharge pipe 23 extends slightly downward from the discharge port 11B of the high-stage compressor 12, is bent at a right angle toward one side in the longitudinal direction, bent at a right angle toward upward, and then bent at a right angle toward one side in the longitudinal direction again, until it reaches the refrigerant inlet 13A.

[0050] The refrigerant outlet 13B of the oil separator 13 is located at the upper end of the oil separator 13 and is directed upward. The refrigerant inlet 14A of the condenser 14 is located on the upper side of the condenser 14 and is directed upward. The refrigerant inlet 14A is located below the refrigerant outlet 13B of the oil separator 13. In a plan view, the refrigerant inlet 14A is not covered from above by the high-stage compressor 12 and is located between the oil separator 13 and the high-stage compressor 12 in the depth direction of the site S.

[0051] The condenser supply piping 24 connects the refrigerant outlet 13B of the oil separator 13 to the refrigerant inlet 14A of the condenser 14. The condenser supply piping 24 extends slightly upward from the refrigerant outlet 13B of the oil separator 13, is bent at a right angle toward the other side in the longitudinal direction, and is then bent at a right angle downward to reach the refrigerant inlet 14A.

[0052] The refrigerant outlet 14B of the condenser 14 is located on the lower side of the condenser 14 and is directed downward. The refrigerant inlet 16A of the evaporator 16 is located at the lower end of the evaporator 16, is directed horizontally, and faces the low-stage compressor 11. The refrigerant inlet 16A of the evaporator 16 is positioned above the refrigerant outlet 14B of the condenser 14 and is located on one side in the depth direction of the site S.

[0053] The liquid phase piping 25 connects the refrigerant outlet 14B of the condenser 14 to the refrigerant inlet 16A of the evaporator 16. The liquid phase piping 25 extends slightly downward from the refrigerant outlet 14B, extends perpendicularly to one side in the longitudinal direction, extends perpendicularly upward, and is bent perpendicularly to one side in the longitudinal direction again to reach the refrigerant inlet 16A of the evaporator 16. The vertically extending portion of the liquid phase piping 25 is located between the oil separator 13 and the condenser 14 in the depth direction of the site S. The expansion valve 15 is interposed in this portion of the liquid phase piping 25.

[0054] The refrigerant outlet 16B of the evaporator 16 is located at the upper end of the evaporator 16, is oriented horizontally, and faces the low-stage compressor 11. The arrangement of the suction port 11A of the low-stage compressor 11 is as described above. The refrigerant outlet 16B is located above the suction port 11A. The compressor suction piping 21 extends from the refrigerant outlet 16B of the evaporator 16 to the other longitudinal side, is bent downwards at a right angle, and reaches the suction port 11A.

[0055] As mentioned above, the maximum width W11 of the low-stage compressor 11 is greater than the maximum width W12 of the high-stage compressor 12. Furthermore, the maximum width W11 of the low-stage compressor 11 is greater than the diameter φ13 of the oil separator 13, greater than the width W14 of the condenser 14, and greater than the width W16 of the evaporator 16. The high-stage compressor 12, oil separator 13, condenser 14, and evaporator 16 are arranged to fit within the width of the low-stage compressor 11. "The high-stage compressor 12 fits within the width of the low-stage compressor 11" means that, in a plan view, the high-stage compressor 12 is completely contained between the two ends of the low-stage compressor 11 in the width direction. The same applies to the oil separator 13, condenser 14, and evaporator 16 as to the high-stage compressor 12.

[0056] Furthermore, the maximum width W11 of the lower stage compressor 11 is less than the required width dimension Y of the site S (Y > W11). Therefore, the refrigeration system 1 as a whole fits within the site S in the width direction.

[0057] Furthermore, the low-stage compressor 11 and the evaporator 16 are arranged in the longitudinal direction of the low-stage compressor 11, i.e., in the depth direction of the site S. The sum of the length L11 of the low-stage compressor 11 and the length L16 of the evaporator 16 is less than the required dimension X in the depth direction of the site S (X > L11 + L16). The high-stage compressor 12 and the oil separator 13 are arranged in the longitudinal direction of the high-stage compressor 12, i.e., in the depth direction of the site S. The sum of the length L12 of the high-stage compressor 12 and the diameter φ13 of the oil separator 13 is less than the required dimension X in the depth direction of the site S (X > L12 + φ13). Therefore, the refrigeration system 1 as a whole fits within the site S in the depth direction.

[0058] As described above, in this embodiment, the two compressors, the low-stage compressor 11 and the high-stage compressor 12, are arranged in a vertical line. Furthermore, the main devices constituting the refrigeration system 1, namely the oil separator 13, the condenser 14, and the evaporator 16, are arranged together with the high-stage compressor 12 so as to fit within the width of the low-stage compressor 11. Therefore, the installation area of ​​the refrigeration system 1 can be reduced, and the refrigeration system 1 can be installed on a narrow site S.

[0059] The condenser 14 is positioned below the high-stage compressor 12 and between the high-stage compressor 12 and the oil separator 13 in the longitudinal direction of the high-stage compressor 12. Compared to the case where the condenser 14 is positioned on the opposite side of the high-stage compressor 12 from the oil separator 13, the installation area of ​​the refrigeration system 1 in the longitudinal direction of the compressors 11 and 12 can be reduced.

[0060] The discharge port 11B of the lower-stage compressor 11 is located at the bottom of the lower-stage compressor, and the suction port 11A of the upper-stage compressor 12 is located at the top of the upper-stage compressor 12. This allows the intermediate compressor piping 22 connecting the two compressors 11 and 12 to be shortened.

[0061] Furthermore, in this embodiment, the compressor suction pipe 21, compressor intermediate pipe 22, compressor discharge pipe 23, condenser supply pipe 24, and liquid phase pipe 25 are all bent at a right angle at least once. This is beneficial in that it can suppress thermal expansion of the piping components.

[0062] In the screw compressors, the lower-stage compressor 11 and the upper-stage compressor 12 have their respective male rotors 42 and 52 and their corresponding female rotors 43 and 53 arranged vertically. This reduces the width of the compressors 11 and 12, and consequently reduces the installation area of ​​the refrigeration system 1 in the width direction.

[0063] Figure 5 shows a modified refrigeration system 1. In this modified example, the axis C12 of the high-stage compressor 12 is offset to one side in the width direction (left side of Figure 5) relative to the axis C11 of the low-stage compressor 11. On one side in the width direction, the outer circumference of the high-stage compressor 12 is brought closer to the outer circumference of the low-stage compressor 11.

[0064] The high-stage compressor 12 is smaller and narrower than the low-stage compressor 11. Therefore, a larger space S1 is secured on the other side of the high-stage compressor 12 in the width direction compared to the other side of the low-stage compressor 11 in the width direction. This space S1 can be used to arrange other devices of the refrigeration system 1. For example, the refrigeration system 1 may include an economizer between the condenser 14 and the expansion valve 15. In that case, the space S1 can be used to arrange the economizer.

[0065] While embodiments have been described so far, the above configuration can be modified as appropriate within the scope of the present invention. For example, the high-stage compressor 12 may be arranged in the opposite direction in the longitudinal direction. That is, the high-stage compressor 12 may be arranged such that a motor housing 51a housing a motor 12c (see Figure 1) is located on one side of the high-stage compressor 12 in the longitudinal direction, and a compression housing 52b is located on the other side of the high-stage compressor 12 in the longitudinal direction, i.e., the left and right sides are reversed in Figure 2.

[0066] This disclosure may include the following aspects: (Aspect 1) A low-stage compressor that compresses the refrigerant, A high-stage compressor further compresses the refrigerant that has been compressed by the low-stage compressor, An oil separator for separating oil from the refrigerant compressed by the aforementioned high-stage compressor, A condenser for condensing the refrigerant separated from the oil in the oil separator, An evaporator for evaporating the refrigerant condensed in the condenser, Equipped with, The aforementioned high-stage compressor is positioned below the aforementioned low-stage compressor. The oil separator is positioned on one side in the longitudinal direction of the high-stage compressor. The evaporator is positioned above the oil separator and on one side in the longitudinal direction of the lower stage compressor. The high-stage compressor, the oil separator, the condenser, and the evaporator are arranged to fit within the width of the low-stage compressor. Refrigeration system. (Aspect 2) The condenser is located below the high-stage compressor and between the high-stage compressor and the oil separator in the longitudinal direction of the high-stage compressor. The refrigeration system described in Embodiment 1. (Aspect 3) The compressor further comprises a compressor intermediate piping that connects a low-stage discharge port, provided in the low-stage compressor for discharging the refrigerant, to a high-stage suction port, provided in the high-stage compressor for drawing in the refrigerant. The lower-stage discharge port is provided at the lower part of the lower-stage compressor, and the upper-stage suction port is provided at the upper part of the upper-stage compressor. A refrigeration system according to embodiment 1 or 2. (Aspect 4) At least one of the lower-stage compressor and the upper-stage compressor is a screw compressor having a male rotor and a female rotor. In the screw compressor, the male rotor and the female rotor are arranged vertically. A refrigeration system according to any one of embodiments 1 to 3. (Aspect 5) The aforementioned high-stage compressor is narrower than the aforementioned low-stage compressor. The axis of the high-stage compressor is offset in the width direction with respect to the axis of the low-stage compressor such that on one side in the width direction, the outer circumference position of the high-stage compressor approaches the outer circumference position of the low-stage compressor. A refrigeration system according to any one of embodiments 1 to 4. [Explanation of Symbols]

[0067] 1. Refrigeration System 10 Refrigerant Circuit 11. Low-stage compressor 12. High-stage compressor 11A, 12A Inlet 11B,12B Discharge port 11a, 12a First stage compression section 11b, 12b Second stage compression section 11c, 12c motor 13 Oil separator 13A Refrigerant Inlet 13B Refrigerant outlet 13C Oil Outlet 13a Casing 14 Condenser 14A Refrigerant Inlet 14B Refrigerant outlet 14a Refrigerant passage 14b Coolant passage 15 Expansion valve 16 Evaporator 16A Refrigerant Inlet 16B Refrigerant outlet 16a Refrigerant passage 16b Blind passage 21 Compressor suction piping 22 Compressor Intermediate Piping 23 Compressor discharge piping 24 Condenser supply piping 25 Liquid phase piping 30 Oil circulation circuit 31 Oil return line 32 Oil cooler 41, 51 Casing 41a, 51a Motor housing 41b, 51b Compression section housing 42,52 Male rotor 43,53 Female rotor S site S1 Space X Required dimensions in the depth direction Required dimensions in the Y width direction A42, A52 Male rotor central axis A43, A53 Female rotor central axis C11 Lower stage compressor shaft C12 High-stage compressor shaft H13 Height of oil separator L11 Length of the lower stage compressor L12 Length of the high-stage compressor L16 Evaporator length W11 Maximum width of the low-stage compressor W12 Maximum width of high-stage compressor W14 Condenser width W16 Evaporator width φ13 Diameter of the oil separator

Claims

1. A low-stage compressor that compresses the refrigerant, A high-stage compressor further compresses the refrigerant that has been compressed by the low-stage compressor, An oil separator for separating oil from the refrigerant compressed by the aforementioned high-stage compressor, A condenser for condensing the refrigerant separated from the oil in the oil separator, An evaporator for evaporating the refrigerant condensed in the condenser, Equipped with, The aforementioned high-stage compressor is positioned below the aforementioned low-stage compressor. The oil separator is positioned on one side in the longitudinal direction of the high-stage compressor. The evaporator is positioned above the oil separator and on one side in the longitudinal direction of the lower stage compressor. The high-stage compressor, the oil separator, the condenser, and the evaporator are arranged to fit within the width of the low-stage compressor. Refrigeration system.

2. The condenser is positioned below the high-stage compressor and between the high-stage compressor and the oil separator in the longitudinal direction of the high-stage compressor. The refrigeration system according to claim 1.

3. The compressor further comprises a compressor intermediate piping that connects the low-stage discharge port, provided in the low-stage compressor for discharging the refrigerant, to the high-stage suction port, provided in the high-stage compressor for drawing in the refrigerant. The lower-stage discharge port is provided at the lower part of the lower-stage compressor, and the upper-stage suction port is provided at the upper part of the upper-stage compressor. The refrigeration system according to claim 1 or 2.

4. At least one of the lower-stage compressor and the upper-stage compressor is a screw compressor having a male rotor and a female rotor. In the screw compressor, the male rotor and the female rotor are arranged vertically. The refrigeration system according to claim 1 or 2.

5. The aforementioned high-stage compressor is narrower than the aforementioned low-stage compressor. The axis of the high-stage compressor is offset in the width direction with respect to the axis of the low-stage compressor such that on one side in the width direction, the outer circumference position of the high-stage compressor approaches the outer circumference position of the low-stage compressor. The refrigeration system according to claim 1 or 2.

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