Refrigeration equipment

Abstract

To improve heat exchange efficiency.SOLUTION: A turbo refrigerator comprises a compressor for compressing a refrigerant, a condenser for condensing the refrigerant which is compressed by the compressor, an expansion valve for expanding the refrigerant which is condensed by the condenser, an evaporator 5 for evaporating the refrigerant which is expanded by the expansion valve, and an expansion valve control part for controlling an opening of the expansion valve. The evaporator 5 has: a pressure vessel 11 serving as an outer shell; a heat transfer pipe group 16 accommodated in the pressure vessel 11, and having a plurality of heat transfer pipes 16a which are arranged while being aligned in a vertical direction; a refrigerant tray 13 for supplying the refrigerant to the heat transfer pipe group 16 from above; and an eductor 10 for introducing the refrigerant which is stored at a lower part of the pressure vessel 11, and remains while being not fully evaporated at the heat transfer pipe group 16 to the refrigerant tray 13. The expansion valve control part controls an opening of the expansion valve so that a water level of the refrigerant which is stored at a lower part of a box body reaches a water level corresponding a refrigerant quantity which is changed depending on an operation condition of a turbo refrigerator, and made to circulate by the eductor 10.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to refrigeration devices. [Background technology]

[0002] For example, a turbo refrigeration unit used as a heat source for district heating and cooling is well known to include a turbo compressor that compresses a refrigerant, a condenser that condenses the compressed refrigerant, a control valve that expands the condensed refrigerant, and an evaporator that evaporates the expanded refrigerant. The evaporator has a pressure vessel that forms the outer shell and heat transfer tubes placed inside the pressure vessel, and evaporates the refrigerant by exchanging heat between the expanded refrigerant supplied into the pressure vessel and the refrigerant to be cooled that circulates inside the heat transfer tubes.

[0003] A known evaporator used in turbo refrigeration systems is a liquid film evaporator, which forms a liquid film of refrigerant on the surface of a heat transfer tube. In a liquid film evaporator, a liquid refrigerant is supplied from above to a heat transfer tube bank, which has a vertical and horizontal arrangement of heat transfer tubes and through which a cooled medium flows, and a liquid film of refrigerant is formed on the surface of each heat transfer tube. In such a liquid film evaporator, the liquid refrigerant that does not completely evaporate in the heat transfer tube bank and accumulates in the lower part of the pressure vessel may be recirculated to the upper part of the evaporator and supplied again to the heat transfer tube bank (see, for example, Patent Document 1).

[0004] Patent Document 1 describes an evaporator that includes a tube bundle housed in a shell and a distributor that supplies refrigerant to the tube bundle from above. The evaporator in Patent Document 1 uses a pump and an ejector to recirculate liquid refrigerant from the bottom of the shell to the distributor. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US Patent Application Publication No. 2011 / 0120181 Summary of the Invention [Problem to be solved by the invention]

[0006] In a liquid film evaporator, the only heat transfer surface that performs heat exchange is the portion of the heat transfer tube surface where a liquid film is formed. Therefore, if a portion of the heat transfer tube surface does not have a liquid film (hereinafter, the absence of a liquid film on the surface of the heat transfer tube is also referred to as "dryout"), heat exchange does not occur in the portion where dryout occurs, resulting in a problem of reduced heat exchange efficiency. In particular, in a liquid film evaporator, refrigerant is supplied to the heat transfer tube group from above, so the lower the heat transfer tube, the more likely it is that dryout will occur. Therefore, in order to prevent a decrease in heat exchange efficiency, it is necessary to supply refrigerant to the heat transfer tube group so that the refrigerant reaches sufficiently all the way to the heat transfer tubes located at the lowest level. However, the amount of refrigerant introduced into the evaporator varies depending on the operating conditions of the refrigeration device (for example, the load and temperature of the refrigeration device). For this reason, in an evaporator that does not take into account the operating conditions of the refrigeration device, such as the evaporator described in Patent Document 1, depending on the operating conditions of the refrigeration device, there is a possibility that a sufficient amount of refrigerant is not supplied to the heat transfer tube group, resulting in a decrease in heat exchange efficiency.

[0007] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a refrigeration device that can improve heat exchange efficiency. [Means for solving the problem]

[0008] In order to solve the above problems, the refrigeration device of the present disclosure employs the following measures. a heat transfer tube group housed inside the housing and having a plurality of heat transfer tubes arranged side by side in the vertical direction; a refrigerant supply unit that supplies the refrigerant to the heat transfer tube group from above; and a circulation unit that guides the refrigerant that has not completely evaporated in the heat transfer tube group and is stored in a lower part of the housing to the refrigerant supply unit. The expansion valve control unit controls the opening of the expansion valve so that the water level of the refrigerant stored in the lower part of the housing becomes a water level corresponding to the amount of refrigerant circulated by the circulation unit, which changes depending on the operating conditions of the refrigeration device. The circulation unit is connected to a downstream end of a first circulation pipe connected to the bottom of the evaporator and a downstream end of a branch pipe branching from an intermediate position of the refrigerant pipe connecting the bottom of the condenser and the expansion valve, into which the refrigerant flows, and is connected to an upstream end of a second circulation pipe connected to an intermediate position of the refrigerant pipe connecting the expansion valve and the evaporator, from which the refrigerant flows. do. [Effects of the Invention]

[0009] According to the present disclosure, the heat exchange efficiency of the evaporator can be improved. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a turbo refrigeration device according to a first embodiment of the present disclosure. [Figure 2] 1 is a vertical cross-sectional view showing an evaporator according to a first embodiment of the present disclosure. [Figure 3] 1 is a vertical cross-sectional view showing an evaporator according to a first embodiment of the present disclosure. [Figure 4] FIG. 4 is a vertical cross-sectional view showing an evaporator according to a modified example of the first embodiment of the present disclosure. [Figure 5] FIG. 4 is a schematic configuration diagram of a turbo refrigeration device according to a second embodiment of the present disclosure. [Figure 6] FIG. 4 is a Mollier diagram showing a turbo refrigeration device according to a second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of a refrigeration device according to the present disclosure will be described with reference to the drawings. [First embodiment] Hereinafter, a first embodiment of the present disclosure will be described with reference to FIGS. 1 to 3. FIG. As shown in Figure 1, the turbo refrigeration system (refrigeration system) 1 of this embodiment is configured as a unit and includes a turbo compressor (compressor) 2 that compresses a refrigerant, a condenser 3 that condenses the refrigerant compressed by the turbo compressor 2, an expansion valve 4 that expands the refrigerant condensed by the condenser 3, and an evaporator 5 that evaporates the refrigerant expanded by the expansion valve 4.

[0012] The turbo compressor 2 and the upper part of the condenser 3 are connected by a discharge pipe 6. The discharge pipe 6 guides the refrigerant compressed by the turbo compressor 2 to the condenser 3. The bottom of the condenser 3, the expansion valve 4, and the upper part of the evaporator 5 are connected by a refrigerant pipe 7. The refrigerant pipe 7 is provided with the expansion valve 4. The refrigerant pipe 7 guides the refrigerant condensed in the condenser 3 to the evaporator 5. The upper part of the evaporator 5 and the turbo compressor 2 are connected by a suction pipe 8. The suction pipe 8 guides the refrigerant evaporated in the evaporator 5 to the turbo compressor 2.

[0013] A branch pipe 17 branches off from a midpoint of the refrigerant pipe 7. The branch pipe 17 branches off from the refrigerant pipe 7 upstream of the expansion valve 4. The downstream end of the branch pipe 17 is connected to the eductor 10. The branch pipe 17 guides a portion of the refrigerant condensed in the condenser 3 to the eductor 10. The eductor 10 and the evaporator 5 are connected by a first circulation pipe 14. The upstream end of the first circulation pipe 14 is connected to the bottom of the pressure vessel 11 of the evaporator 5. The downstream end of the first circulation pipe 14 is connected to the eductor 10. The first circulation pipe 14 guides the liquid phase refrigerant stored in the lower part of the evaporator 5 to the eductor 10. The upstream end of a second circulation pipe 15 that discharges the refrigerant in the eductor 10 is connected to the eductor 10. The downstream end of the second circulation pipe 15 is connected to the refrigerant pipe 7 downstream of the expansion valve 4. The second circulation pipe 15 guides the refrigerant discharged from the eductor 10 to the evaporator 5 via the refrigerant pipe 7 .

[0014] The turbo compressor 2 is a known centrifugal turbine type that is rotationally driven by an electric motor 9, and is disposed above the evaporator 5 with its axis extending substantially horizontally. The electric motor 9 is driven by an inverter unit. As will be described later, the turbo compressor 2 compresses gaseous refrigerant that is supplied from the refrigerant outlet of the evaporator 5 via a suction pipe 8. For example, the refrigerant may be a low-pressure refrigerant such as R1233zd that is used at a maximum pressure of less than 0.2 MPaG. The medium It is used.

[0015] The condenser 3 and the evaporator 5 are formed in a cylindrical shell shape with high pressure resistance, and are arranged adjacent to each other in parallel with their central axes extending substantially horizontally. The condenser 3 may be arranged at a relatively higher position than the evaporator 5.

[0016] Eductor 10 draws in the liquid-phase refrigerant stored in the lower part of pressure vessel 11 by using the difference in flow velocity and pressure of the liquid-phase refrigerant flowing inside. Specifically, the liquid-phase refrigerant (refrigerant from condenser 3) guided from branch pipe 17 to eductor 10 flows through the main flow path inside eductor 10 and is discharged from eductor 10 to second circulation pipe 15. As a result, the connection portion with first circulation pipe 14, which is provided on the outer periphery of the main flow path, becomes low pressure, and the liquid-phase refrigerant in pressure vessel 11 is drawn into eductor 10 via first circulation pipe 14. The liquid-phase refrigerant drawn into eductor 10 is discharged to second circulation pipe 15 together with the refrigerant sprayed from the nozzle. In this way, eductor 10 circulates the refrigerant by using the pressure difference inside turbo chiller 1 (such as the difference in refrigerant pressure between the refrigerant in condenser 3 and the refrigerant pressure in evaporator 5).

[0017] The evaporator 5 will be described in detail below with reference to FIG. As shown in FIG. 2, the evaporator 5 has a pressure vessel (housing) 11 forming an outer shell, a refrigerant inlet pipe 12 for introducing a refrigerant into the pressure vessel 11, a refrigerant tray (refrigerant supply section) 13 provided below the refrigerant inlet pipe 12, a group of heat transfer tubes 16 housed inside the pressure vessel 11, and a refrigerant outlet pipe (not shown) for discharging the evaporated refrigerant from the pressure vessel 11.

[0018] The pressure vessel 11 integrally comprises a cylindrical portion 11a extending along a central axis and two tube plates (not shown) closing both ends of the cylindrical portion 11a in the direction along the central axis. As described above, the cylindrical portion 11a is arranged so that its central axis is approximately horizontal. Each tube plate is a disk-shaped plate material. In the following description, the direction along the central axis (the direction into the paper in FIG. 2) will be referred to as the longitudinal direction. The vertical direction will be simply referred to as the up-down direction. The direction intersecting the longitudinal direction and the up-down direction will be referred to as the lateral direction.

[0019] The refrigerant inlet pipe 12 is a cylindrical member that extends in the vertical direction and is formed in a substantially straight line. The refrigerant inlet pipe 12 is provided so as to penetrate the upper part of the cylindrical portion 11a in the vertical direction. The refrigerant inlet pipe 12 is provided at substantially the center in the direction along the central axis of the cylindrical portion 11a. The refrigerant inlet pipe 12 is connected to the refrigerant piping 7 (see FIG. 1). That is, the refrigerant expanded in the expansion valve 4 is guided into the pressure vessel 11 via the refrigerant piping 7 and the refrigerant inlet pipe 12.

[0020] The refrigerant tray 13 is a member in the shape of a substantially rectangular plate. The refrigerant tray 13 is arranged at the top inside the pressure vessel 11 so that its plate surface is substantially horizontal. The refrigerant tray 13 is also arranged so that its plate surface faces the lower end of the refrigerant inlet pipe 12. The refrigerant tray 13 is arranged so that both ends in the short side direction are spaced a predetermined distance from the inner circumferential surface of the cylindrical portion 11a of the pressure vessel 11. The refrigerant tray 13 is also arranged over substantially the entire length of the pressure vessel 11. Both ends in the long side direction of the refrigerant tray 13 are respectively tube The refrigerant tray 13 is fixed to a plate. A number of holes are formed in the refrigerant tray 13, penetrating it in the vertical direction. The number of holes is formed over almost the entire area of the refrigerant tray 13. The liquid refrigerant discharged from the refrigerant inlet pipe 12 is discharged onto the refrigerant tray 13. The refrigerant discharged onto the refrigerant tray 13 flows over the upper surface of the refrigerant tray 13, and then falls downward through the number of holes. In this way, the refrigerant tray 13 distributes the refrigerant supplied from the refrigerant inlet pipe 12 in the longitudinal and lateral directions.

[0021] The heat transfer tube group 16 is disposed inside the pressure vessel 11. The heat transfer tube group 16 is disposed below the refrigerant tray 13. The heat transfer tube group 16 is composed of a plurality of heat transfer tubes 16a extending in the longitudinal direction. The plurality of heat transfer tubes 16a are disposed substantially parallel to one another. The plurality of heat transfer tubes 16a are arranged in a line at predetermined intervals in the vertical direction and the lateral direction. More specifically, the plurality of heat transfer tubes 16a are arranged in a plurality of rows in the vertical direction and in a plurality of columns in the lateral direction. Water, which serves as a liquid to be cooled, flows through each heat transfer tube 16a. Each heat transfer tube 16a is formed linearly. Each heat transfer tube 16a extends from one longitudinal end to the other longitudinal end of the pressure vessel 11 and penetrates each tube plate.

[0022] The refrigerant outlet pipe is a cylindrical member extending in the vertical direction, and is provided so as to communicate with an opening (not shown) formed in the upper part of the cylindrical portion 11a. The refrigerant outlet pipe is connected to the suction pipe 8 (see FIG. 1). That is, the refrigerant evaporated in the evaporator 5 is discharged to the outside of the pressure vessel 11 via the refrigerant outlet pipe and the suction pipe 8 and is led to the turbo compressor 2.

[0023] The turbo refrigeration system 1 also includes a control device 18. The control device 18 has an expansion valve control unit that controls the opening degree of the expansion valve 4, and an IGV control unit (adjustment means control unit) that controls inlet guide vanes (IGVs) (not shown) that are provided in the turbo compressor 2.

[0024] The control device 18 is composed of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions is stored in a storage medium, for example, in the form of a program. The CPU reads this program into RAM and executes information processing and arithmetic operations to realize various functions. The program may be pre-installed in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Examples of computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0025] The expansion valve control unit can adjust the level of the refrigerant stored in the lower part of pressure vessel 11 by controlling the aperture of expansion valve 4. In addition, the expansion valve control unit controls the aperture of expansion valve 4 so that the level of the refrigerant stored in the lower part of pressure vessel 11 is a level that corresponds to the operating capacity of eductor 10 (the amount of refrigerant that eductor 10 can circulate), which changes depending on the operating conditions of turbo refrigeration unit 1 (for example, the load and temperature of turbo refrigeration unit 1). Specifically, for example, the expansion valve control unit may increase the refrigerant level when the operating capacity of the eductor 10 decreases. Also, the expansion valve control unit may decrease the refrigerant level when the operating capacity of the eductor 10 increases.

[0026] Specifically, the expansion valve control unit may adjust the refrigerant level so that the lowest heat transfer tube 16a among the heat transfer tubes 16a whose surfaces are sufficiently supplied with refrigerant due to the operating capacity of the eductor 10 is directly above the refrigerant liquid level. That is, as shown in Fig. 3, if the operating capacity of the eductor 10 is such that refrigerant can be sufficiently supplied to the first to fifth heat transfer tubes 16a from the top (see the liquid film type heat transfer tube group 16A in Fig. 3), the refrigerant level may be adjusted so that the fifth heat transfer tube 16a is directly above the refrigerant liquid level, and the sixth and seventh heat transfer tubes 16a from the top (see the liquid-flooded type heat transfer tube group 16B in Fig. 3) are positioned below the refrigerant liquid level. That is, the sixth and seventh heat transfer tubes 16a may be immersed in the refrigerant. On the other hand, as shown in FIG. 2, if the operating capacity of the eductor 10 is such that the refrigerant can be sufficiently supplied to all of the heat transfer tubes 16a, the refrigerant level may be adjusted so that it is below the seventh heat transfer tube 16a.

[0027] The IGV control unit can adjust the pressure of the refrigerant flowing from the condenser 3 to the eductor 10. By adjusting the pressure of the refrigerant flowing to the eductor 10, the amount of refrigerant circulated by the eductor 10 can be adjusted. The IGV control unit controls the opening of the IGV (circulation unit adjustment means) so that the amount of refrigerant circulated by the eductor 10 is greater than a predetermined amount. Specifically, for example, when the operating capacity of the eductor 10 is reduced due to the operating conditions of the turbo refrigeration system 1 or the like, the IGV control unit may increase the pressure of the refrigerant flowing from the condenser 3 to the eductor 10. Furthermore, when the operating capacity of the eductor 10 is increased, the IGV control unit may decrease the pressure of the refrigerant flowing from the condenser 3 to the eductor 10.

[0028] In particular, if the amount of refrigerant that can be circulated by the eductor 10 (operating capacity) is less than a predetermined amount, the IGV control unit may increase the pressure of the refrigerant flowing from the condenser 3 to the eductor 10, thereby increasing the amount of refrigerant that can be circulated by the eductor 10. The predetermined amount may be an amount of refrigerant that is sufficiently supplied to the surface of the heat transfer tubes 16a located in the lowest position among the heat transfer tubes 16a that need to be supplied with refrigerant from the refrigerant tray 13 (i.e., the heat transfer tubes 16a above the liquid level). The predetermined amount may also be an amount calculated in advance depending on the operating conditions of the turbo chiller 1, etc. The predetermined amount may also be the sum (q+Q) of the amount of refrigerant evaporating in the heat transfer tube group 16 and the amount Q of refrigerant that does not completely evaporate in the heat transfer tube group 16 and is stored in the lower part of the pressure vessel 11 and circulated by the eductor 10.

[0029] According to this embodiment, the following advantageous effects are achieved. The amount of refrigerant circulated by the eductor 10 (hereinafter sometimes referred to as the "operating capacity of the eductor 10") may vary depending on the operating conditions of the turbo chiller 1. For example, like the eductor 10 according to the present embodiment, the turbo chiller 1 may be a device that circulates the refrigerant by utilizing a pressure difference within the turbo chiller 1 (such as the difference between the refrigerant pressure in the condenser 3 and the refrigerant pressure in the evaporator 5). In this case, if the pressure difference within the turbo chiller 1 is small due to the operating conditions of the turbo chiller 1, the amount of refrigerant that the eductor 10 can circulate will decrease. If the amount of refrigerant that can be circulated decreases, the amount of refrigerant supplied from the refrigerant tray 13 to the heat transfer tube group 16 will also decrease. As a result, a sufficient amount of refrigerant cannot be supplied to the heat transfer tube group 16, and a state may occur in which the refrigerant does not sufficiently reach the surfaces of some of the heat transfer tubes 16a (particularly the heat transfer tubes 16a arranged at the bottom) (this state will be referred to as "dry out" below). On the other hand, in this embodiment, the expansion valve control unit controls the aperture of the expansion valve 4 so that the refrigerant level stored in the lower part of the pressure vessel 11 is maintained at a level corresponding to the operating capacity of the eductor 10, which varies depending on the operating conditions of the turbo chiller 1. This allows the refrigerant level to be maintained at a level corresponding to the operating capacity of the eductor 10. Therefore, for example, if the operating capacity of the eductor 10 decreases, the aperture of the expansion valve 4 is controlled to raise the water level, thereby making it possible to position the lower heat transfer tubes 16a of the heat transfer tube group 16 below the liquid level. In other words, the lower heat transfer tubes 16a of the heat transfer tube group 16 can be immersed in the stored refrigerant. This reduces the number of heat transfer tubes 16a to which refrigerant needs to be supplied from the refrigerant tray 13 (i.e., the heat transfer tubes 16a above the liquid level), thereby preventing dryout even with a small amount of refrigerant. In this way, in this embodiment, the refrigerant level can be maintained at a level corresponding to the operating capacity of the eductor 10, thereby improving the heat exchange efficiency of the evaporator 5.

[0030] In this embodiment, the adjustment means control unit controls the IGV so that the amount of refrigerant circulating through the eductor 10 is greater than a predetermined amount. This allows a sufficient amount of refrigerant to circulate and be supplied from the refrigerant tray 13 to the heat transfer tube group 16. This prevents dryout from occurring, improving the heat exchange efficiency of the evaporator 5.

[0031] [Variations] In the first embodiment, an example in which the eductor 10 is used as a circulating unit for circulating the refrigerant has been described, but the present disclosure is not limited to this. For example, as shown in Fig. 4, a pump 19 may be provided instead of the eductor 10. The pump 19 pressurizes the refrigerant stored in the lower part of the pressure vessel 11. The rotation speed of pump 19 can be changed by an inverter device (not shown) or the like. Control device 18 can adjust the rotation speed of pump 19 by controlling the inverter device. That is, control device 18 can adjust the operating capacity of pump 19 (the amount of refrigerant that pump 19 can circulate). Even with this configuration, the same effects as those of the first embodiment are achieved.

[0032] [Second embodiment] In the first embodiment described above, an example was described in which the refrigeration device of the present disclosure is applied to a single-stage compression turbo refrigeration device 1, but the present disclosure is not limited to this. Many It may be applied to a stage compression type turbo refrigeration device 21. A turbo chiller 21 according to this embodiment differs from the first embodiment in that it includes a low-stage compressor 2A and a high-stage compressor 2B, an intercooler 22 and the like, intermediate piping 23, and a low-pressure expansion valve 4A and a high-pressure expansion valve 4B. As other aspects are similar to those of the first embodiment, the same components are designated by the same reference numerals and detailed descriptions thereof will be omitted.

[0033] The refrigerant pipe 7 according to this embodiment is provided with, in this order from the upstream side, a high-pressure expansion valve 4B, an economizer 22, and a low-pressure expansion valve 4A. The low-pressure expansion valve 4A is provided downstream of the position where the branch pipe 17 branches off. The high-pressure expansion valve 4B and the economizer 22 are provided upstream of the position where the branch pipe 17 branches off. The intercooler 22 separates the refrigerant discharged from the condenser 3 into gas and liquid. The gas-phase refrigerant is guided to the suction side of the high-stage compressor 2B via the intermediate pipe 23. The liquid-phase refrigerant is guided to the suction side of the high-stage compressor 2B via the refrigerant pipe 7. etc. The air is led to the evaporator 5 by the

[0034] A method for adjusting the operating capacity of the eductor 10 in this embodiment will be described with reference to the Mollier diagram of FIG. First, the refrigerant in the case indicated by the solid line in FIG. 6 will be described. Gas refrigerant (a) discharged from the high-stage compressor 2B flows into the condenser 3. The refrigerant flowing into the condenser 3 is condensed by heat exchange with water in the condenser 3. High-temperature, high-pressure liquid refrigerant (b) discharged from the condenser 3 is expanded and decompressed (c) by the high-pressure expansion valve 4B, becoming a two-phase gas-liquid refrigerant and flowing into the economizer 22. The two-phase gas-liquid refrigerant flowing into the economizer 22 is separated into gas and liquid, and the liquid refrigerant (d) with low enthalpy is guided to the low-pressure expansion valve 4A. The liquid refrigerant (d) flows into the main flow path of the eductor 10 via branch pipe 17. Gas refrigerant with higher enthalpy than the liquid refrigerant flows toward the high-stage compressor 2B via intermediate pipe 23.

[0035] The liquid refrigerant that flows from the intercooler 22 into the low-pressure expansion valve 4A is expanded and decompressed (e) by the low-pressure expansion valve 4A to become a gas-liquid two-phase refrigerant, and flows into the evaporator 5. The liquid refrigerant that flows into the evaporator 5 and that has not completely evaporated in the heat transfer tube group 16 (e) is guided to the eductor 10 via the first circulation pipe 14. That is, in the eductor 10, the pressure difference (P1 in FIG. 6) between the liquid refrigerant (d) and the liquid refrigerant (e) serves as a driving force. In this embodiment, the gas-liquid two-phase refrigerant that has flowed into the evaporator 5 exchanges heat with water and evaporates, becoming gas refrigerant and flowing out of the evaporator 5. The gas refrigerant (f) that has flowed out of the evaporator 5 is drawn into the low-stage compressor 2A and compressed (g).

[0036] The gas refrigerant separated into gas and liquid by the intercooler 22 is sucked into a space between the low-stage compressor 2A and the high-stage compressor 2B via the intermediate piping 23, and then merges with the gas refrigerant compressed by the low-stage compressor 2A (h), and the merged refrigerant is compressed by the high-stage compressor 2B and discharged (a).

[0037] Next, a case will be described where the aperture of the IGV provided at the inlet of the high-stage compressor 2B is reduced, as indicated by the dashed line in Fig. 6. In this case, the pressure of the refrigerant (c') expanded and decompressed by the high-pressure expansion valve 4B becomes higher than that of the refrigerant (c). The refrigerant (c') becomes a two-phase gas-liquid refrigerant and flows into the economizer 22. The two-phase gas-liquid refrigerant that has flowed into the economizer 22 is separated into gas and liquid, and the liquid refrigerant (d') with low enthalpy is guided to the low-pressure expansion valve 4A. The liquid refrigerant (d') flows into the main flow path of the eductor 10 via the branch pipe 17. The gas refrigerant with higher enthalpy than the liquid refrigerant flows toward the high-stage compressor 2B via the intermediate pipe 23.

[0038] The liquid refrigerant that flows from the economizer 22 into the low-pressure expansion valve 4A is expanded and decompressed by the low-pressure expansion valve 4A (e'), becomes a gas-liquid two-phase refrigerant, and flows into the evaporator 5. The liquid refrigerant that flows into the evaporator 5 and has not completely evaporated in the heat transfer tube group 16 (e') is guided to the eductor 10 via the first circulation piping 14. That is, in the eductor 10, the pressure difference (P2 in FIG. 6) between the liquid refrigerant (d') and the liquid refrigerant (e') serves as a driving force. As shown in FIG. 6, the pressure difference P2 is greater than the pressure difference P1. That is, the operating capacity of the eductor 10 can be improved in the case shown by the dashed line in FIG. 6. In this way, the operating capacity of the eductor 10 can be adjusted by adjusting the aperture of the IGV.

[0039] In this embodiment, the gas-liquid two-phase refrigerant that has flowed into the evaporator 5 exchanges heat with water and evaporates, becoming gas refrigerant and flowing out of the evaporator 5. The gas refrigerant (f) that has flowed out of the evaporator 5 is drawn into the low-stage compressor 2A and compressed (g'). The gas refrigerant separated into gas and liquid by the intercooler 22 is sucked into a space between the low-stage compressor 2A and the high-stage compressor 2B via the intermediate piping 23, and then merges with the gas refrigerant compressed by the low-stage compressor 2A (h'). The merged refrigerant is compressed by the high-stage compressor 2B and discharged (a).

[0040] The present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure. For example, in each of the above embodiments, the control device 18 is an expansion valve control section and Although the example in which both the expansion valve control section and the IGV control section are provided has been described, the present disclosure is not limited to this example. The control device 18 may have only one of the expansion valve control section and the IGV control section.

[0041] The refrigeration apparatus according to the above-described embodiment can be understood, for example, as follows. A refrigeration device according to one aspect of the present disclosure is a refrigeration device (1) including a compressor (2) that compresses a refrigerant, a condenser (3) that condenses the refrigerant compressed by the compressor, an expansion valve (4) that expands the refrigerant condensed by the condenser, an evaporator (5) that evaporates the refrigerant expanded by the expansion valve, and an expansion valve control unit that controls an opening degree of the expansion valve, wherein the evaporator is provided with a housing (11) that forms an outer shell, and a plurality of conductors housed inside the housing and arranged side by side in the vertical direction. The refrigeration system includes a heat transfer tube group (16) having heat tubes (16a), a refrigerant supply unit (13) that supplies the refrigerant to the heat transfer tube group from above, and a circulation unit (10) that guides the refrigerant that has not completely evaporated in the heat transfer tube group and is stored in the lower part of the housing to the refrigerant supply unit, and the expansion valve control unit controls the opening of the expansion valve so that the water level of the refrigerant stored in the lower part of the housing becomes a water level corresponding to the amount of refrigerant circulated by the circulation unit, which changes depending on the operating conditions of the refrigeration system.

[0042] The amount of refrigerant circulated by the circulation unit (hereinafter, sometimes referred to as the "operating capacity of the circulation unit") may vary depending on the operating conditions of the refrigeration unit. For example, the circulation unit may be an eductor, which circulates the refrigerant by utilizing a pressure difference within the refrigeration unit (such as the difference between the refrigerant pressure in the condenser and the refrigerant pressure in the evaporator). In this case, if the pressure difference within the refrigeration unit is small due to the operating conditions of the refrigeration unit, the amount of refrigerant that the circulation unit can circulate decreases. If the amount of refrigerant that can be circulated decreases, the amount of refrigerant supplied from the refrigerant supply unit to the heat transfer tube group also decreases. As a result, the refrigerant cannot be supplied sufficiently to the heat transfer tube group, and the refrigerant may not be sufficiently distributed over the surfaces of some heat transfer tubes (especially the heat transfer tubes located at the bottom) (hereinafter, this condition is referred to as "dry out"). In the above configuration, the expansion valve control unit controls the aperture of the expansion valve so that the refrigerant level stored in the lower part of the housing is maintained at a level corresponding to the operating capacity of the circulation unit, which varies depending on the operating conditions of the refrigeration system. This allows the refrigerant level to be maintained at a level corresponding to the operating capacity of the circulation unit. Therefore, for example, when the operating capacity of the circulation unit decreases, the aperture of the expansion valve is controlled to raise the water level, thereby keeping the lower heat transfer tubes in the heat transfer tube group below the liquid level. In other words, the lower heat transfer tubes in the heat transfer tube group can be immersed in the stored refrigerant. This reduces the number of heat transfer tubes that require refrigerant supply from the refrigerant supply unit (i.e., heat transfer tubes above the liquid level), thereby preventing dryout even with a small amount of refrigerant. In this way, the above configuration allows the refrigerant level to be maintained at a level corresponding to the operating capacity of the circulation unit, thereby improving the heat exchange efficiency of the evaporator.

[0043] In addition, a refrigeration device according to one aspect of the present disclosure includes a circulation unit adjustment means for adjusting the amount of refrigerant circulated by the circulation unit and an adjustment means control unit for controlling the circulation unit adjustment means, and the adjustment means control unit controls the circulation unit adjustment means so that the amount of refrigerant circulated by the circulation unit is greater than a predetermined amount.

[0044] In the above configuration, the adjustment means control unit controls the circulation unit adjustment means so that the amount of refrigerant circulating through the circulation unit is greater than a predetermined amount. This allows a sufficient amount of refrigerant to circulate and be supplied to the heat transfer tube group from the refrigerant supply unit. This prevents dryout and improves the heat exchange efficiency of the evaporator. The predetermined amount may be an amount of refrigerant that is sufficient to supply the surface of the lowest heat transfer tube among the heat transfer tubes that need to be supplied with refrigerant from the refrigerant supply unit (i.e., the heat transfer tubes above the liquid level).The predetermined amount may also be an amount calculated in advance depending on the operating conditions of the refrigeration device, etc.

[0045] A refrigeration device according to one aspect of the present disclosure is a refrigeration device (1) including a compressor (2) that compresses a refrigerant, a condenser (3) that condenses the refrigerant compressed by the compressor, an expansion valve (4) that expands the refrigerant condensed by the condenser, and an evaporator (5) that evaporates the refrigerant expanded by the expansion valve, wherein the evaporator includes a housing (11) that forms an outer shell, and a heat transfer tube group (16) that is housed inside the housing and has a plurality of heat transfer tubes (16a) arranged side by side in the vertical direction. a refrigerant supply unit (13) that supplies the refrigerant to the heat transfer tube group from above, and a circulation unit (10) that guides the refrigerant that has not completely evaporated in the heat transfer tube group and is stored in the lower part of the housing to the refrigerant supply unit, and further includes a circulation unit adjustment means that adjusts the amount of refrigerant circulated by the circulation unit, and an adjustment means control unit that controls the circulation unit adjustment means, and the adjustment means control unit controls the circulation unit adjustment means so that the amount of refrigerant circulated by the circulation unit becomes greater than a predetermined amount.

[0046] In addition, in a refrigeration device according to one aspect of the present disclosure, the circulation unit has an eductor (10) that circulates the refrigerant by utilizing a pressure difference between the pressure of the refrigerant in the condenser and the pressure of the refrigerant in the evaporator.

[0047] In the above configuration, even if the circulation capacity of the eductor is reduced, the occurrence of dry-out can be suppressed, and the heat exchange efficiency of the evaporator can be improved.

[0048] In the refrigeration device according to one aspect of the present disclosure, the circulation unit includes a pump (19) that increases the pressure of the refrigerant stored in the lower part of the housing.

[0049] In the above configuration, the coolant can be circulated using a pump. [Explanation of symbols]

[0050] 1: Turbo refrigeration unit (refrigeration unit) 2: Turbo compressor (compressor) 2A: Low stage compressor 2B: High-stage compressor 3: Condenser 4: Expansion valve 4A: Low pressure expansion valve 4B: High-pressure expansion valve 5: Evaporator 6:Discharge piping 7: Refrigerant piping 8: Intake piping 9: Electric motor 10: Eductor (circulation section) 11: Pressure vessel (casing) 11a: Cylindrical part 12: Refrigerant inlet pipe 13: Refrigerant tray (refrigerant supply section) 14: 1st circulation piping 15:Second circulation piping 16: Heat transfer tube group 16A: Liquid film heat transfer tube group 16B: Flooded heat transfer tube bank 16a: Heat transfer tube 17: Branch piping 18: Control device 19: Pump 21: Turbo refrigeration unit 22: Intercooler 23: Intermediate piping

Claims

1. a compressor that compresses a refrigerant; a condenser that condenses the refrigerant compressed by the compressor; an expansion valve that expands the refrigerant condensed in the condenser; an evaporator that evaporates the refrigerant expanded by the expansion valve; An expansion valve control unit that controls the opening degree of the expansion valve, the evaporator includes a housing forming an outer shell, a heat transfer tube group housed inside the housing and having a plurality of heat transfer tubes arranged side by side in the vertical direction, a refrigerant supply unit that supplies the refrigerant to the heat transfer tube group from above, and a circulation unit that guides the refrigerant that has not completely evaporated in the heat transfer tube group and is stored in a lower part of the housing to the refrigerant supply unit, The expansion valve control unit controls the opening degree of the expansion valve so that the water level of the refrigerant stored in the lower part of the housing becomes a water level corresponding to the amount of refrigerant circulated by the circulation unit, which changes depending on the operating conditions of the refrigeration device; The circulation unit is connected to the downstream end of a first circulation pipe connected to the bottom of the evaporator and the downstream end of a branch pipe branching from an intermediate position of the refrigerant pipe connecting the bottom of the condenser and the expansion valve, so that the refrigerant flows in, and is connected to the upstream end of a second circulation pipe connected to an intermediate position of the refrigerant pipe connecting the expansion valve and the evaporator, so that the refrigerant discharges.

2. a circulation unit adjusting means for adjusting the amount of refrigerant circulated by the circulation unit; an adjusting means control unit that controls the circulation section adjusting means, 2. The refrigeration apparatus according to claim 1, wherein the adjusting means control section controls the circulation section adjusting means so that the amount of refrigerant circulating through the circulation section becomes greater than a predetermined amount.

3. a compressor that compresses a refrigerant; a condenser that condenses the refrigerant compressed by the compressor; an expansion valve that expands the refrigerant condensed in the condenser; an evaporator that evaporates the refrigerant expanded by the expansion valve, the evaporator includes a housing forming an outer shell, a heat transfer tube group housed inside the housing and having a plurality of heat transfer tubes arranged side by side in the vertical direction, a refrigerant supply unit that supplies the refrigerant to the heat transfer tube group from above, and a circulation unit that guides the refrigerant that has not completely evaporated in the heat transfer tube group and is stored in a lower part of the housing to the refrigerant supply unit, a circulation unit adjusting means for adjusting the amount of refrigerant circulated by the circulation unit; An adjusting means control unit that controls the circulation unit adjusting means, the adjusting means control unit controls the circulation unit adjusting means so that the amount of refrigerant circulating through the circulation unit is greater than a predetermined amount; The circulation unit is connected to the downstream end of a first circulation pipe connected to the bottom of the evaporator and the downstream end of a branch pipe branching from an intermediate position of the refrigerant pipe connecting the bottom of the condenser and the expansion valve, so that the refrigerant flows in, and is connected to the upstream end of a second circulation pipe connected to an intermediate position of the refrigerant pipe connecting the expansion valve and the evaporator, so that the refrigerant discharges.

4. a low-stage compressor and a high-stage compressor that compress a refrigerant; a condenser that condenses the refrigerant compressed by the low-stage compressor and the high-stage compressor; a high-stage expansion valve that expands the refrigerant condensed in the condenser; an intercooler that separates the refrigerant expanded by the high-stage expansion valve into gas and liquid; a low-stage expansion valve that expands the liquid phase refrigerant separated in the intercooler; An evaporator that evaporates the refrigerant expanded by the low-stage expansion valve, the evaporator includes a housing forming an outer shell, a heat transfer tube group housed inside the housing and having a plurality of heat transfer tubes arranged side by side in the vertical direction, a refrigerant supply unit that supplies the refrigerant to the heat transfer tube group from above, and a circulation unit that guides the refrigerant that has not completely evaporated in the heat transfer tube group and is stored in a lower part of the housing to the refrigerant supply unit, a circulation unit adjusting means for adjusting the amount of refrigerant circulated by the circulation unit; An adjusting means control unit that controls the circulation unit adjusting means, the adjusting means control unit controls the circulation unit adjusting means so that the amount of refrigerant circulating through the circulation unit is greater than a predetermined amount; the circulation unit is connected to the downstream end of a first circulation pipe connected to the bottom of the evaporator and to the downstream end of a branch pipe branching off from an intermediate position downstream of the condenser and upstream of the low-stage expansion valve, so that the refrigerant flows in, and to the upstream end of a second circulation pipe connected to an intermediate position of the refrigerant pipe connecting the low-stage expansion valve and the evaporator, so that the refrigerant discharges.

5. 5. The refrigeration device according to claim 1, wherein the circulation unit includes an eductor that circulates the refrigerant by utilizing a pressure difference between the pressure of the refrigerant in the condenser and the pressure of the refrigerant in the evaporator.

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