Refrigeration machine, control device, control method, and program

Abstract

To easily avoid deterioration of heat insulation efficiency of an expansion turbine with a simple equipment configuration.SOLUTION: A refrigerator 10 includes: a turbo type compressor 20; an expansion turbine 30; a first refrigerant line 11 for connecting an outlet 22 of the compressor 20 and an inlet 31 of the expansion turbine 30; a second refrigerant line 12 for connecting an outlet 32 of the expansion turbine 30 and an inlet 21 of the compressor 20; a main heat exchanger 40 for performing heat exchange of a refrigerant 13 between the first refrigerant line 11 and the second refrigerant line 12; a sub heat exchanger 50 for performing heat exchange between the refrigerant 13 and an outside fluid 14 on the downstream of the main heat exchanger 40 of the first refrigerant line 11; a sensor group 60 mounted at least on the first refrigerant line 11 and the second refrigerant line 12; and a control device 70 which adjusts rotational frequency of the compressor 20 according to the target of capability of cooling the fluid 14, and which adjusts rotational frequency of the expansion turbine 30 according to the rotational frequency of the compressor 20 and a sensor value acquired from the sensor group 60.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a refrigerator, a control device, a control method, and a program. [Background technology]

[0002] Patent Document 1 discloses a method for changing the nozzle flow area by mechanically operating nozzle vanes provided at the inlet of the impeller of an expansion turbine with an external actuator. Patent Document 2 discloses a method for changing the operating temperature of an expansion turbine by opening and closing a bypass valve. Patent Document 3 discloses a refrigerator used to cool superconducting power equipment. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-137101 [Patent Document 2] JP 2018-066511 A [Patent Document 3] JP 2022-109068 A Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, the refrigeration capacity of a chiller is adjusted by changing the compressor speed or the pressure within the system. The expansion turbine is always operated at its rated speed. However, the expansion turbine is designed to maximize its adiabatic efficiency at the flow rate and pressure at the rated operating point, and the adiabatic efficiency decreases under flow rate and pressure conditions that deviate from the design point. The adiabatic efficiency affects the amount of refrigeration generated by the expansion turbine. Therefore, if the adiabatic efficiency deteriorates, the refrigeration capacity decreases and the COP also decreases, causing the efficiency of the entire chiller to deteriorate. "COP" is an abbreviation for coefficient of performance.

[0005] When the rotation speed of the compressor changes due to fluctuations in the thermal load, it is possible to operate the chiller efficiently without reducing the adiabatic efficiency of the expansion turbine by changing the volumetric flow rate of the expansion turbine.

[0006] One possible method for changing the volumetric flow rate of the expansion turbine is to change the flow passage area of ​​the nozzle, as disclosed in Patent Document 1. However, this method involves the incorporation of components with moving parts, which complicates the internal structure and may lead to an increased risk of failure and maintenance frequency. For this reason, this method is not suitable for cooling superconducting power equipment used as part of infrastructure functions, for example.

[0007] As a method for changing the volumetric flow rate of the expansion turbine, it is possible to change the operating temperature of the expansion turbine, as disclosed in Patent Document 2. However, this method requires multiple low-temperature automatic valves for switching the flow paths, which may lead to a risk of failure and increased costs. Therefore, a simpler configuration is desired.

[0008] An object of the present disclosure is to make it easier to avoid a decrease in the adiabatic efficiency of an expansion turbine with a simple equipment configuration. [Means for solving the problem]

[0009] Several aspects of the disclosure are set forth below.

[0010] [1] A turbo compressor that compresses a refrigerant; an expansion turbine for expanding the refrigerant; a first refrigerant line connecting an outlet of the compressor and an inlet of the expansion turbine; a second refrigerant line connecting an outlet of the expansion turbine and an inlet of the compressor; a main heat exchanger that exchanges heat of the refrigerant between the first refrigerant line and the second refrigerant line; a secondary heat exchanger that performs heat exchange between the refrigerant and an external fluid, the secondary heat exchanger being located downstream of the main heat exchanger in the first refrigerant line or upstream of the main heat exchanger in the second refrigerant line; A group of sensors attached to at least the first refrigerant line and the second refrigerant line; a control device that adjusts a rotation speed of the compressor in accordance with a target capacity for cooling the fluid, and adjusts a rotation speed of the expansion turbine in accordance with the rotation speed of the compressor and the sensor values ​​obtained from the group of sensors; A refrigerator equipped with

[0011] [2] The control device acquires at least measured values ​​of the pressure and temperature at the inlet of the expansion turbine and measured values ​​of the pressure and temperature at the outlet of the expansion turbine as the sensor values, and adjusts the rotation speed of the expansion turbine by calculating a set value of the rotation speed of the expansion turbine with reference to the acquired measured values ​​and characteristic data that defines a volumetric flow rate when the pressure and temperature of the refrigerant are at a reference pressure and a reference temperature, respectively, for each combination of the rotation speed of the compressor and the pressure ratio at the inlet and outlet of the compressor.

[0012] [3] The control device calculates a volumetric flow rate Q at the outlet of the expansion turbine by referring to the measured values ​​of pressure and temperature at the outlet of the expansion turbine and the characteristic data, and calculates a theoretical adiabatic head H of the expansion turbine by referring to the measured values ​​of pressure and temperature at the inlet of the expansion turbine and the measured value of pressure or temperature at the outlet of the expansion turbine, and calculates N=(2πr√Q) / (H 0.75 The refrigerator according to [2], wherein r, at which a specific speed N expressed by the following equation is within a reference range, is calculated as a set value for the rotation speed of the expansion turbine.

[0013] [4] The refrigeration machine according to [3], wherein the control device further acquires a measured value of a pressure at an inlet of the compressor and a measured value of a pressure at an outlet of the compressor as the sensor values, and calculates a volumetric flow rate Q at the outlet of the expansion turbine in accordance with an equation Q=(Q1P1T2) / (T1P2), where Q1 is a volumetric flow rate defined in the characteristic data in correspondence with a combination of a ratio of the measured value of the pressure at the inlet of the compressor and the measured value of the pressure at the outlet of the compressor, P1 is the reference pressure, T1 is the reference temperature, and P2 and T2 are the measured values ​​of the pressure and temperature at the outlet of the expansion turbine, respectively.

[0014] [5] The control device calculates the enthalpy h of the expansion turbine from the measured values ​​of the pressure and temperature at the inlet of the expansion turbine. in_r and the entropy is estimated, and the theoretical enthalpy h at the outlet of the expansion turbine is calculated from the estimated entropy and the measured value of the pressure or temperature at the outlet of the expansion turbine. out_i Calculate H=h in_r -h out_i The refrigeration machine according to [3] or [4], wherein a theoretical adiabatic head H of the expansion turbine is calculated according to the following formula:

[0015] [6] The refrigerator according to any one of [3] to [5], wherein the reference range is 0.6 or more and 0.7 or less.

[0016] [7] The refrigeration machine according to any one of [2] to [6], wherein the control device calculates a set value of a rotation speed of the expansion turbine when the control device detects a fluctuation in a rotation speed of the compressor or when a certain time has elapsed since the fluctuation in the rotation speed of the compressor.

[0017] [8] A control device for controlling a refrigerant cycle including a turbo compressor that compresses a refrigerant, an expansion turbine that expands the refrigerant, a first refrigerant line that connects an outlet of the compressor and an inlet of the expansion turbine, a second refrigerant line that connects an outlet of the expansion turbine and an inlet of the compressor, a main heat exchanger that performs heat exchange of the refrigerant between the first refrigerant line and the second refrigerant line, and a secondary heat exchanger that performs heat exchange between the refrigerant and an external fluid downstream of the main heat exchanger of the first refrigerant line or upstream of the main heat exchanger of the second refrigerant line, A communication unit that communicates with at least a group of sensors attached to the first refrigerant line and the second refrigerant line; a control unit that adjusts a rotation speed of the compressor in accordance with a target capacity for cooling the fluid, and adjusts a rotation speed of the expansion turbine in accordance with the rotation speed of the compressor and a sensor value obtained from the group of sensors via the communication unit; A control device comprising:

[0018] [9] A control method for controlling a refrigerant cycle including a turbo compressor that compresses a refrigerant, an expansion turbine that expands the refrigerant, a first refrigerant line that connects an outlet of the compressor and an inlet of the expansion turbine, a second refrigerant line that connects an outlet of the expansion turbine and an inlet of the compressor, a main heat exchanger that performs heat exchange of the refrigerant between the first refrigerant line and the second refrigerant line, and a secondary heat exchanger that is located downstream of the main heat exchanger of the first refrigerant line or upstream of the main heat exchanger of the second refrigerant line and performs heat exchange between the refrigerant and an external fluid, Adjusting the rotation speed of the compressor according to a target capacity for cooling the fluid; acquiring sensor values ​​from a group of sensors attached to at least the first refrigerant line and the second refrigerant line; A control method for adjusting the rotation speed of the expansion turbine in accordance with the rotation speed of the compressor and the sensor values ​​obtained from the group of sensors.

[0019]

[10] A program for controlling a refrigerant cycle including a turbo compressor that compresses a refrigerant, an expansion turbine that expands the refrigerant, a first refrigerant line that connects an outlet of the compressor and an inlet of the expansion turbine, a second refrigerant line that connects an outlet of the expansion turbine and an inlet of the compressor, a main heat exchanger that performs heat exchange of the refrigerant between the first refrigerant line and the second refrigerant line, and a secondary heat exchanger that performs heat exchange between the refrigerant and an external fluid downstream of the main heat exchanger of the first refrigerant line or upstream of the main heat exchanger of the second refrigerant line, A computer that communicates with a group of sensors attached to at least the first refrigerant line and the second refrigerant line, A program that executes a process of adjusting the rotation speed of the compressor in accordance with a target capacity for cooling the fluid, and a process of adjusting the rotation speed of the expansion turbine in accordance with the rotation speed of the compressor and sensor values ​​obtained from the group of sensors. Effect of the Invention

[0020] According to the present disclosure, a reduction in the adiabatic efficiency of an expansion turbine can be easily avoided with a simple equipment configuration. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a refrigerator according to an embodiment of the present disclosure. [Diagram 2] 4 is a graph showing an example of characteristic data related to a compressor according to an embodiment of the present disclosure. [Diagram 3] FIG. 2 is a block diagram showing a configuration of a control device according to an embodiment of the present disclosure. [Figure 4] 5 is a flowchart illustrating an operation of a control device according to an embodiment of the present disclosure. [Diagram 5] FIG. 13 is a diagram illustrating a configuration of a refrigerator according to a modified example of the embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0023] In each drawing, the same or corresponding parts are denoted by the same reference numerals. In the description of this embodiment, the description of the same or corresponding parts will be omitted or simplified as appropriate.

[0024] The configuration of a refrigerator 10 according to this embodiment will be described with reference to FIG.

[0025] The chiller 10 includes a first refrigerant line 11 and a second refrigerant line 12, as well as a turbo compressor 20, an expansion turbine 30, a main heat exchanger 40, a secondary heat exchanger 50, a sensor group 60, a control device 70, and an adjustment mechanism 80.

[0026] The first refrigerant line 11 and the second refrigerant line 12 circulate the refrigerant 13. The first refrigerant line 11 connects the outlet 22 of the compressor 20 and the inlet 31 of the expansion turbine 30. The second refrigerant line 12 connects the outlet 32 ​​of the expansion turbine 30 and the inlet 21 of the compressor 20. The compressor 20 compresses the refrigerant 13. The expansion turbine 30 expands the refrigerant 13 to generate cold. The main heat exchanger 40 recovers cold by performing heat exchange of the refrigerant 13 between the first refrigerant line 11 and the second refrigerant line 12. The auxiliary heat exchanger 50 performs heat exchange between the refrigerant 13 upstream of the main heat exchanger 40 of the second refrigerant line 12 and an external fluid 14. In this embodiment, the fluid 14 circulates in the fluid line 15.

[0027] The sensor group 60 is attached to at least the first refrigerant line 11 and the second refrigerant line 12. In this embodiment, the sensor group 60 includes a first pressure gauge 61, a second pressure gauge 62, a third pressure gauge 63, a fourth pressure gauge 64, a first thermometer 65, a second thermometer 66, and a third thermometer 67.

[0028] The second pressure gauge 62, the third pressure gauge 63, and the first thermometer 65 are attached to the first refrigerant line 11. Specifically, the second pressure gauge 62 is provided between the outlet 22 of the compressor 20 and the main heat exchanger 40, and measures the pressure at the outlet 22 of the compressor 20. The third pressure gauge 63 is provided between the main heat exchanger 40 and the inlet 31 of the expansion turbine 30, and measures the pressure at the inlet 31 of the expansion turbine 30. The first thermometer 65 is also provided between the main heat exchanger 40 and the inlet 31 of the expansion turbine 30, and measures the temperature at the inlet 31 of the expansion turbine 30.

[0029] The first pressure gauge 61, the fourth pressure gauge 64, and the second thermometer 66 are attached to the second refrigerant line 12. Specifically, the first pressure gauge 61 is provided between the main heat exchanger 40 and the inlet 21 of the compressor 20, and measures the pressure of the inlet 21 of the compressor 20. The fourth pressure gauge 64 is provided between the outlet 32 ​​of the expansion turbine 30 and the auxiliary heat exchanger 50, and measures the pressure of the outlet 32 ​​of the expansion turbine 30. The second thermometer 66 is also provided between the outlet 32 ​​of the expansion turbine 30 and the auxiliary heat exchanger 50, and measures the temperature of the outlet 32 ​​of the expansion turbine 30.

[0030] The third thermometer 67 is attached to the fluid line 15. The third thermometer 67 measures the temperature of the fluid 14 in the fluid line 15 downstream of the secondary heat exchanger 50.

[0031] The control device 70 controls a refrigerant cycle including the first refrigerant line 11, the second refrigerant line 12, the compressor 20, the expansion turbine 30, the main heat exchanger 40, and the auxiliary heat exchanger 50. Specifically, the control device 70 adjusts the rotation speed of the compressor 20 in accordance with a target capacity for cooling the fluid 14, and adjusts the rotation speed of the expansion turbine 30 in accordance with the rotation speed of the compressor 20 and the sensor values ​​obtained from the sensor group 60. Thus, according to this embodiment, it is easy to avoid a decrease in the adiabatic efficiency of the expansion turbine 30 with a simple equipment configuration.

[0032] The adjustment mechanism 80 includes a first inverter 81 and a second inverter 82. The compressor 20 and the expansion turbine 30 can be operated and their rotation speeds can be adjusted by commands from the first inverter 81 and the second inverter 82, respectively. In this embodiment, the control device 70 supplies power to the first inverter 81 and performs control input / output. That is, the control device 70 adjusts the rotation speed of the compressor 20 via the first inverter 81. The control device 70 supplies power to the second inverter 82 and performs control input / output via the first inverter 81. That is, the control device 70 adjusts the rotation speed of the expansion turbine 30 via the first inverter 81 and the second inverter 82. The power supply and control input / output to the second inverter 82 may be performed directly from the control device 70 without passing through the first inverter 81. Alternatively, the power supply and control input / output to the second inverter 82 may be performed from another independent control device.

[0033] The first inverter 81 and the second inverter 82 may be built into the control device 70. That is, the adjustment mechanism 80 may be integrated into the control device 70.

[0034] In this embodiment, the refrigerator 10 is used to cool superconducting power equipment such as a power transmission cable, a current limiter, or a transformer. The refrigerator 10 cools the superconducting power equipment by utilizing a cryogenic refrigeration cycle that repeats adiabatic compression, isobaric cooling, adiabatic expansion, and isobaric heating. In cooling the superconducting power equipment, a fluid 14 is circulated through the superconducting power equipment. The fluid 14 is, for example, liquid nitrogen, liquid hydrogen, or liquid helium. The fluid 14 rises in temperature due to heat generation in the superconducting power equipment or heat entering the system, but is cooled to a desired temperature by the refrigerator 10. The refrigerator 10 is suitable for cases where a large capacity of refrigeration capacity is required. For example, neon gas or helium gas is used as the refrigerant 13 of the refrigerator 10.

[0035] The refrigeration capacity of the chiller 10 is adjusted by changing the rotation speed of the compressor 20. When the rotation speed of the compressor 20 changes, if the rotation speed of the expansion turbine 30 is constant, the adiabatic efficiency of the expansion turbine 30 decreases. The adiabatic efficiency affects the amount of refrigeration generated by the expansion turbine 30. Therefore, when the adiabatic efficiency deteriorates, the refrigeration capacity decreases and the COP also decreases, resulting in a deterioration in the efficiency of the chiller 10 as a whole.

[0036] The specific speed N is one of the indexes indicating the adiabatic efficiency of the expansion turbine 30. The specific speed N is expressed by the following formula 1. N = (2πr√Q) / (H 0.75 )...Equation 1 In Equation 1, r is the rotation speed [rps] of the expansion turbine 30, Q is the volumetric flow rate [m 3 / s], and H is the theoretical adiabatic head [J / kg].

[0037] The volumetric flow rate Q at the outlet 32 ​​of the expansion turbine 30 is expressed by the following equation 2 according to the ideal gas state equation. Q=(Q1P1T2) / (T1P2)=(101.35Q1T2) / (273.15P2)...Equation 2 In Equation 2, Q1 is the volumetric flow rate under standard conditions [m 3 / s (normal)], P1 is the pressure [kPa] under standard conditions, T1 is the temperature [K] under standard conditions, P2 is the pressure [kPa] at the outlet 32 ​​of the expansion turbine 30, and T2 is the temperature [K] at the outlet 32 ​​of the expansion turbine 30. The standard conditions refer to a state of 101.35 kPa and 273.15 K. The volumetric flow rate Q1 under the standard conditions can be obtained in advance as characteristic data as shown in Fig. 2 from the relationship between the rotation speed and pressure ratio of the turbo compressor 20. Here, calculations are performed for an ideal gas, but there is no practical problem since there is only an error of a few percent from calculations for an actual gas.

[0038] The theoretical adiabatic head H is expressed by the following equation 3 using the state quantities of the inlet 31 of the expansion turbine 30 and the state quantities of the outlet 32 ​​of the expansion turbine 30. H=h in_r -h out_i ...Formula 3 In equation 3, hin_r is the enthalpy [kJ / kg] at the inlet 31 of the expansion turbine 30, h out_i is the theoretical enthalpy [kJ / kg] at the outlet 32 ​​of the expansion turbine 30. The enthalpy h at the inlet 31 of the expansion turbine 30 in_r is estimated from the pressure and temperature at the inlet 31 of the expansion turbine 30. The theoretical enthalpy h at the outlet 32 ​​of the expansion turbine 30 out_i is estimated from the inlet entropy previously estimated from the pressure and temperature at the inlet 31 of the expansion turbine 30 and the pressure or temperature at the outlet 32 ​​of the expansion turbine 30.

[0039] The adiabatic efficiency is highest when the specific speed N is in the range of 0.6 to 0.7. When the adiabatic efficiency is high, the amount of cold generated by the expansion turbine 30 increases, and the refrigeration capacity and COP are improved.

[0040] For example, at the rated operating point, the rotation speed r of the expansion turbine 30 is 1000 rps, and the volumetric flow rate Q of the outlet 32 ​​of the expansion turbine 30 is 0.0197 m 3 / s, and the theoretical adiabatic head H is 15.0 kJ / kg, then from equation 1 the specific speed N is 0.65.

[0041] If it is desired to increase the refrigeration capacity from this state, the rotation speed of the compressor 20 is increased. As a result, the theoretical adiabatic head H increases due to an increase in the flow rate and the pressure ratio. If the volumetric flow rate Q at the outlet 32 ​​of the expansion turbine 30 is 0.021 m 3 If the rotation speed r of the expansion turbine 30 is increased to 1150 rps and the theoretical adiabatic head H is increased to 19.0 kJ / kg, the specific speed N will be 0.56, which is outside the ideal range and will result in a decrease in adiabatic efficiency. However, by increasing the rotation speed r of the expansion turbine 30 to 1150 rps, the specific speed N can be improved to 0.65.

[0042] Conversely, when it is desired to reduce the refrigeration capacity from the steady state, the rotation speed of the compressor 20 is reduced. As a result, the theoretical adiabatic head H is reduced due to a decrease in the flow rate and the pressure ratio. 3If the rotation speed r of the expansion turbine 30 is reduced to 900 rps and the theoretical adiabatic head H is reduced to 12.0 kJ / kg, the specific speed N will be 0.74, which is outside the ideal range and will result in a decrease in adiabatic efficiency. However, by reducing the rotation speed r of the expansion turbine 30 to 900 rps, the specific speed N can be improved to 0.66.

[0043] As described above, since the specific speed N of the expansion turbine 30 changes depending on the operating state of the compressor 20, a constant rotation speed r of the expansion turbine 30 leads to a decrease in adiabatic efficiency. In this embodiment, the rotation speed r of the expansion turbine 30 is varied in accordance with the operating state of the compressor 20, so that the specific speed N can be kept within an ideal range.

[0044] The internal components of the expansion turbine 30, such as the nozzle and diffuser, are designed to flow a rated flow rate at the design temperature. As a characteristic of the expansion turbine 30, when the refrigerant temperature is higher than the design temperature, the volumetric flow rate decreases and the specific speed N also decreases.

[0045] According to this embodiment, when the rotation speed of the turbo compressor 20 changes due to a fluctuation in the heat load during steady operation of the chiller 10, by changing the rotation speed r of the expansion turbine 30, it becomes possible to operate the chiller 10 efficiently without decreasing the adiabatic efficiency of the expansion turbine 30. In other words, while adopting a simple device configuration that does not include a variable nozzle or a low-temperature automatic valve, it becomes possible to set the adiabatic efficiency of the expansion turbine 30 to an optimal condition simply by changing the rotation speed r of the expansion turbine 30.

[0046] The configuration of the control device 70 according to this embodiment will be described with reference to FIG.

[0047] The control device 70 includes a control unit 71, a storage unit 72, and a communication unit 73.

[0048] The control unit 71 includes at least one processor, at least one programmable circuit, at least one dedicated circuit, or any combination thereof. The processor is a general-purpose processor such as a CPU or GPU, or a dedicated processor specialized for a specific process. "CPU" is an abbreviation for central processing unit. "GPU" is an abbreviation for graphics processing unit. The programmable circuit is, for example, an FPGA. "FPGA" is an abbreviation for field-programmable gate array. The dedicated circuit is, for example, an ASIC. "ASIC" is an abbreviation for application specific integrated circuit. The control unit 71 executes processes related to the operation of the control unit 70 while controlling each part of the control unit 70.

[0049] The storage unit 72 includes at least one semiconductor memory, at least one magnetic memory, at least one optical memory, or any combination thereof. The semiconductor memory is, for example, a RAM, a ROM, or a flash memory. "RAM" is an abbreviation for random access memory. "ROM" is an abbreviation for read only memory. The RAM is, for example, an SRAM or a DRAM. "SRAM" is an abbreviation for static random access memory. "DRAM" is an abbreviation for dynamic random access memory. The ROM is, for example, an EEPROM. "EEPROM" is an abbreviation for electrically erasable programmable read only memory. The flash memory is, for example, an SSD. "SSD" is an abbreviation for solid-state drive. The magnetic memory is, for example, an HDD. "HDD" is an abbreviation for hard disk drive. The storage unit 72 functions, for example, as a main storage device, an auxiliary storage device, or a cache memory. The storage unit 72 stores data used in the operation of the control device 70 and data obtained by the operation of the control device 70.

[0050] The communication unit 73 includes at least one communication interface. The communication interface is, for example, an interface compatible with a wired LAN communication standard such as Ethernet (registered trademark), a wireless LAN communication standard such as IEEE802.11, an interface compatible with a mobile communication standard such as LTE, 4G standard, or 5G standard, or an interface compatible with short-range wireless communication such as Bluetooth (registered trademark). "LAN" is an abbreviation for local area network. "IEEE" is an abbreviation for Institute of Electrical and Electronics Engineers. "LTE" is an abbreviation for Long Term Evolution. "4G" is an abbreviation for 4th generation. "5G" is an abbreviation for 5th generation. The communication unit 73 communicates with the sensor group 60 and the adjustment mechanism 80. The communication unit 73 receives data used in the operation of the control device 70 and transmits data obtained by the operation of the control device 70.

[0051] At least some of the functions of the control device 70 are realized by executing a program according to this embodiment on a processor serving as the control unit 71. That is, at least some of the functions of the control device 70 are realized by software. The program causes a computer to execute the operations of the control device 70, thereby causing the computer to function as the control device 70. That is, the computer functions as the control device 70 by executing the operations of the control device 70 in accordance with the program.

[0052] The program may be stored in a non-transitory computer-readable medium. Examples of the non-transitory computer-readable medium include a flash memory, a magnetic recording device, an optical disk, a magneto-optical recording medium, or a ROM. The program may be distributed, for example, by selling, transferring, or lending a portable medium such as an SD card, DVD, or CD-ROM on which the program is stored. "SD" is an abbreviation for Secure Digital. "DVD" is an abbreviation for digital versatile disc. "CD-ROM" is an abbreviation for compact disc read only memory. The program may be distributed by storing the program in the storage of a server and transferring the program from the server to another computer. The program may be provided as a program product.

[0053] A computer temporarily stores a program stored in a portable medium or transferred from a server in a main storage device. Then, the computer reads the program stored in the main storage device with a processor and executes processing according to the read program with the processor. The computer may read the program directly from a portable medium and execute processing according to the program. The computer may execute processing according to the received program each time a program is transferred from the server to the computer. Processing may be executed by a so-called ASP-type service that realizes functions only by execution instructions and result acquisition without transferring a program from the server to the computer. "ASP" is an abbreviation for application service provider. Programs include information used for processing by a computer and equivalent to a program. For example, data that is not a direct command to a computer but has the property of defining computer processing falls under " equivalent to a program.

[0054] A part or all of the functions of the control device 70 may be realized by a programmable circuit or a dedicated circuit as the control unit 71. In other words, a part or all of the functions of the control device 70 may be realized by hardware.

[0055] The operation of the control device 70 according to this embodiment will be described with reference to Fig. 4. This operation corresponds to the control method according to this embodiment.

[0056] The control unit 71 of the control device 70 adjusts the rotation speed of the compressor 20 in accordance with the target capacity for cooling the fluid 14, and adjusts the rotation speed of the expansion turbine 30 in accordance with the rotation speed of the compressor 20 and the sensor value obtained from the sensor group 60 via the communication unit 73.

[0057] The procedure for adjusting the rotation speed of the compressor 20 may be the same as that of the conventional method. For example, the control unit 71 of the control device 70 compares the measured temperature value input from the third thermometer 67 via the communication unit 73 with the set temperature value stored in advance in the storage unit 72 or input via the communication unit 73 to determine whether the target of the ability to cool the fluid 14 has been achieved. The control unit 71 increases or decreases the rotation speed of the compressor 20 via the first inverter 81 according to the obtained determination result, that is, so that the difference between the measured temperature value and the set temperature value is eliminated. For example, when the measured temperature value is higher than the set temperature value, the control unit 71 increases the refrigeration capacity by increasing the rotation speed of the compressor 20 via the first inverter 81, since it is necessary to promote cooling.

[0058] The procedure for adjusting the rotation speed of the expansion turbine 30 will be described below.

[0059] In steps S1 to S5, the control unit 71 of the control device 70 acquires at least the measured values ​​of the pressure and temperature at the inlet 31 of the expansion turbine 30 and the measured values ​​of the pressure and temperature at the outlet 32 ​​of the expansion turbine 30 as sensor values. The control unit 71 adjusts the rotation speed of the expansion turbine 30 by calculating the set value of the rotation speed of the expansion turbine 30 with reference to the acquired measured values ​​and the characteristic data. The characteristic data is data that defines the volumetric flow rate in the standard state for each combination of the rotation speed of the compressor 20 and the pressure ratio of the inlet 21 and the outlet 22 of the compressor 20. The volumetric flow rate in the standard state refers to the volumetric flow rate when the pressure and temperature of the refrigerant 13 are at the reference pressure and the reference temperature, respectively. In general, for a turbo compressor, the relationship between the rotation speed, the pressure ratio, and the volumetric flow rate is specified in an evaluation test or simulation before being installed in a refrigerator, and is recorded as characteristic data. This characteristic data is also necessary to avoid troubles such as a surge at the time of startup. FIG. 2 is a graph that shows a schematic relationship between the volumetric flow rate in the standard state of the compressor 20 and the pressure ratio and the rotation speed. In this embodiment, data defining the relationship as expressed by this graph is assumed to be stored in advance in the storage unit 72 of the control device 70 as characteristic data.

[0060] The processes from step S1 to step S5 are executed when the rotation speed of the compressor 20 fluctuates. That is, when the control unit 71 of the control device 70 detects a fluctuation in the rotation speed of the compressor 20, it calculates the set value of the rotation speed of the expansion turbine 30. Alternatively, the processes from step S1 to step S5 may be executed when a certain time has elapsed since the fluctuation in the rotation speed of the compressor 20. That is, the control unit 71 of the control device 70 may calculate the set value of the rotation speed of the expansion turbine 30 when a certain time has elapsed since the fluctuation in the rotation speed of the compressor 20.

[0061] The following describes the details of the processes from steps S1 to S5.

[0062] In step S1, the control unit 71 of the control device 70 acquires, as sensor values, the pressure measurement value at the inlet 21 of the compressor 20 and the pressure measurement value at the outlet 22 of the compressor 20. The control unit 71 identifies a volumetric flow rate in a standard state defined in the characteristic data in association with a combination of the ratio of the pressure measurement value at the inlet 21 of the compressor 20 to the pressure measurement value at the outlet 22 of the compressor 20 and the rotation speed of the compressor 20.

[0063] Specifically, the control unit 71 of the control device 70 acquires a measured value of the pressure at the inlet 21 of the compressor 20 from the first pressure gauge 61 via the communication unit 73. The control unit 71 acquires a measured value of the pressure at the outlet 22 of the compressor 20 from the second pressure gauge 62 via the communication unit 73. As for the rotation speed of the compressor 20, the control unit 71 acquires a set value calculated when adjusting the rotation speed of the compressor 20. Alternatively, the control unit 71 may acquire a measured value via the communication unit 73 from a sensor additionally provided to measure the rotation speed of the compressor 20. The control unit 71 calculates the ratio of the measured value of the pressure at the inlet 21 of the compressor 20 to the measured value of the pressure at the outlet 22 of the compressor 20 as the pressure ratio of the compressor 20. The control unit 71 refers to the characteristic data stored in advance in the storage unit 72 and calculates a volumetric flow rate in a standard state corresponding to a combination of the calculated value of the pressure ratio of the compressor 20 and the set value or measured value of the rotation speed of the compressor 20. That is, the control unit 71 estimates the volumetric flow rate in the standard state from the relationship between the pressure ratio and the rotation speed of the compressor 20.

[0064] In step S2, the control unit 71 of the control device 70 acquires, as sensor values, the measured values ​​of the pressure and temperature at the outlet 32 ​​of the expansion turbine 30. The control unit 71 calculates the volumetric flow rate Q at the outlet 32 ​​of the expansion turbine 30 in accordance with the formula Q=(Q1P1T2) / (T1P2), where Q1 is the volumetric flow rate in the standard state identified in step S1, P1 is the reference pressure, T1 is the reference temperature, and P2 and T2 are the measured values ​​of the pressure and temperature at the outlet 32 ​​of the expansion turbine 30, respectively.

[0065] Specifically, the control unit 71 of the control device 70 acquires the measured values ​​of the pressure and temperature at the outlet 32 ​​of the expansion turbine 30 from the fourth pressure gauge 64 and the second thermometer 66 via the communication unit 73. The control unit 71 calculates the volumetric flow rate Q at the outlet 32 ​​of the expansion turbine 30 using Equation 2 from the estimated value of the volumetric flow rate under standard conditions obtained in step S1 and the measured values ​​of the pressure and temperature at the outlet 32 ​​of the expansion turbine 30.

[0066] In step S3, the control unit 71 of the control device 70 acquires the measured values ​​of the pressure and temperature at the inlet 31 of the expansion turbine 30 as sensor values. The control unit 71 calculates the enthalpy h in_r The control unit 71 estimates the theoretical enthalpy h at the outlet 32 ​​of the expansion turbine 30 from the estimated entropy and the measured value of the pressure or temperature at the outlet 32 ​​of the expansion turbine 30 acquired in step S2. out_i The control unit 71 calculates H=h in_r -h out_i The theoretical adiabatic head H of the expansion turbine 30 is calculated according to the following formula:

[0067] Specifically, the control unit 71 of the control device 70 acquires the measured values ​​of the pressure and temperature at the inlet 31 of the expansion turbine 30 from the third pressure gauge 63 and the first thermometer 65 via the communication unit 73. The control unit 71 estimates the inlet enthalpy and the inlet entropy from the measured values ​​of the pressure and temperature at the inlet 31 of the expansion turbine 30. The control unit 71 estimates the ideal outlet enthalpy from the estimated value of the inlet entropy and the measured value of the pressure or temperature at the outlet 32 ​​of the expansion turbine 30 acquired in step S2. The control unit 71 calculates the theoretical adiabatic head H of the expansion turbine 30 by Equation 3 from the estimated value of the ideal outlet enthalpy and the estimated value of the inlet enthalpy. That is, the control unit 71 estimates the theoretical adiabatic head H by calculating the difference between the estimated value of the ideal outlet enthalpy and the estimated value of the inlet enthalpy.

[0068] In step S4, the control unit 71 of the control device 70 calculates N=(2πr√Q) / (H) from the volumetric flow rate Q of the outlet 32 ​​of the expansion turbine 30 calculated in step S1 and step S2 with reference to the measured values ​​of the pressure and temperature of the outlet 32 ​​of the expansion turbine 30 and the characteristic data, and the theoretical adiabatic head H of the expansion turbine 30 calculated in step S3 with reference to the measured values ​​of the pressure and temperature of the inlet 31 of the expansion turbine 30 and the measured value of the pressure or temperature of the outlet 32 ​​of the expansion turbine 30. 0.75 ) falls within a reference range, is calculated as the set value of the rotation speed of the expansion turbine 30. That is, the control unit 71 calculates the optimum rotation speed of the expansion turbine 30 by back-calculation using Equation 1 from the calculated value of the volumetric flow rate Q at the outlet 32 ​​of the expansion turbine 30 obtained in step S2, the calculated value of the theoretical adiabatic head H of the expansion turbine 30 obtained in step S3, and the reference range of the specific speed N. In this embodiment, the reference range is set in advance to be 0.6 or more and 0.7 or less, but may be changed as appropriate. The reference range may be set as a single reference value.

[0069] In step S5, the control unit 71 of the control device 70 adjusts the rotation speed of the expansion turbine 30 via the first inverter 81 and the second inverter 82 by outputting the set value of the rotation speed of the expansion turbine 30 calculated in step S4 to the first inverter 81 via the communication unit 73. Alternatively, the control unit 71 may adjust the rotation speed of the expansion turbine 30 via the second inverter 82 by directly outputting the set value of the rotation speed of the expansion turbine 30 calculated in step S4 to the second inverter 82 via the communication unit 73.

[0070] In this embodiment, the ideal rotation speed of the expansion turbine 30 for the reference specific speed in a certain operating state can be calculated by executing the processes from step S1 to step S4 in the control device 70. For example, if the reference value of the specific speed N is 0.65, the control device 70 can calculate the rotation speed at which the specific speed N becomes 0.65 by back-calculation using Equation 1. In step S5, the control device 70 outputs a rotation speed command to the second inverter 82, thereby automatically adjusting the rotation speed of the expansion turbine 30 to a rotation speed at which high efficiency can be obtained in accordance with the operating state of the compressor 20.

[0071] The configuration of a refrigerator 10a according to a modified example of this embodiment will be described with reference to FIG.

[0072] The configuration of the refrigerator 10a is similar to that of the refrigerator 10 shown in Fig. 1, except that the expansion turbine 30 is disposed between the outlet of the auxiliary heat exchanger 50 and the inlet of the main heat exchanger 40. In this modification, the auxiliary heat exchanger 50 exchanges heat between the refrigerant 13 downstream of the main heat exchanger 40 in the first refrigerant line 11 and an external fluid 14.

[0073] In the chiller 10 shown in Fig. 1, a third pressure gauge 63 and a first thermometer 65 are provided between the main heat exchanger 40 and the expansion turbine 30, whereas in the chiller 10a shown in Fig. 5, a third pressure gauge 63 and a first thermometer 65 are provided between the auxiliary heat exchanger 50 and the expansion turbine 30. In the chiller 10 shown in Fig. 1, a fourth pressure gauge 64 and a second thermometer 66 are provided between the expansion turbine 30 and the auxiliary heat exchanger 50, whereas in the chiller 10a shown in Fig. 5, a fourth pressure gauge 64 and a second thermometer 66 are provided between the expansion turbine 30 and the main heat exchanger 40.

[0074] The functions and operations of the turbo compressor 20, the expansion turbine 30, the main heat exchanger 40, the sub-heat exchanger 50, the sensor group 60, the control device 70, and the adjustment mechanism 80 are similar to those of the chiller 10 shown in FIG. 1, and therefore will not be described here.

[0075] The present disclosure is not limited to the above-described embodiments. For example, multiple blocks shown in the block diagram may be integrated, or one block may be divided. Instead of executing multiple steps shown in the flowchart in chronological order as described, each step may be executed in parallel or in a different order depending on the processing capacity of the device executing each step, or as necessary. Other modifications are possible without departing from the spirit of the present disclosure. [Explanation of symbols]

[0076] 10,10a Refrigeration machine 11 First refrigerant line 12 Second refrigerant line 13 Refrigerants 14 Fluid 15 Fluid Lines 20 Compressor 21 Entrance 22 Exit 30 Expansion turbine 31 Entrance 32 Exit 40 Main heat exchanger 50 Secondary heat exchanger 60 Sensors 61 No. 1 pressure gauge 62 Second pressure gauge 63 Third pressure gauge 64 4th pressure gauge 65 1st thermometer 66 2nd thermometer 67 Third thermometer 70 Control device 71 Control Unit 72 Memory section 73 Communications Department 80 Adjustment mechanism 81 First inverter 82 2nd inverter

Claims

1. A turbo compressor that compresses a refrigerant; an expansion turbine for expanding the refrigerant; a first refrigerant line connecting an outlet of the compressor and an inlet of the expansion turbine; a second refrigerant line connecting an outlet of the expansion turbine and an inlet of the compressor; a main heat exchanger that exchanges heat of the refrigerant between the first refrigerant line and the second refrigerant line; a secondary heat exchanger that performs heat exchange between the refrigerant and an external fluid, the secondary heat exchanger being located downstream of the main heat exchanger in the first refrigerant line or upstream of the main heat exchanger in the second refrigerant line; A group of sensors attached to at least the first refrigerant line and the second refrigerant line; a control device that adjusts a rotation speed of the compressor in accordance with a target capacity for cooling the fluid, and adjusts a rotation speed of the expansion turbine in accordance with the rotation speed of the compressor and the sensor values ​​obtained from the group of sensors; A refrigerator equipped with

2. 2. The refrigeration machine according to claim 1, wherein the control device acquires at least measured values ​​of the pressure and temperature at an inlet of the expansion turbine and measured values ​​of the pressure and temperature at an outlet of the expansion turbine as the sensor values, and adjusts the rotation speed of the expansion turbine by calculating a set value of the rotation speed of the expansion turbine with reference to the acquired measured values ​​and characteristic data that defines a volumetric flow rate when the pressure and temperature of the refrigerant are at a reference pressure and a reference temperature, respectively, for each combination of the rotation speed of the compressor and a pressure ratio at the inlet and outlet of the compressor.

3. The control device calculates a volumetric flow rate Q at the outlet of the expansion turbine by referring to the measured values ​​of pressure and temperature at the outlet of the expansion turbine and the characteristic data, and calculates a theoretical adiabatic head H of the expansion turbine by referring to the measured values ​​of pressure and temperature at the inlet of the expansion turbine and the measured value of pressure or temperature at the outlet of the expansion turbine, and calculates N=(2πr√Q) / (H ０．７５ 3. The refrigerator according to claim 2, wherein a value r that makes a specific speed N expressed by the formula: N=r / (r+r) / (r+r) falls within a reference range is calculated as a set value for the rotational speed of the expansion turbine.

4. The control device further acquires, as the sensor values, a measured value of the pressure at the inlet of the compressor and a measured value of the pressure at the outlet of the compressor, and calculates a volumetric flow rate defined in the characteristic data in correspondence with a combination of a ratio of the measured value of the pressure at the inlet of the compressor to the measured value of the pressure at the outlet of the compressor and a rotation speed of the compressor. １ , the reference pressure is P １ , the reference temperature is T １ , the measured pressure and temperature at the outlet of the expansion turbine are respectively P ２ and T ２ Then, Q = (Q １ P １ T ２ ) / (T １ P ２ 4. The refrigerator according to claim 3, wherein a volume flow rate Q at an outlet of the expansion turbine is calculated in accordance with the following formula:

5. The control device calculates the enthalpy h of the expansion turbine from the measured values ​​of the pressure and temperature at the inlet of the expansion turbine. ｉｎ＿ｒ and the entropy is estimated, and the theoretical enthalpy h at the outlet of the expansion turbine is calculated from the estimated entropy and the measured value of the pressure or temperature at the outlet of the expansion turbine. ｏｕｔ＿ｉ Calculate H = h ｉｎ＿ｒ -h ｏｕｔ＿ｉ 4. The refrigerator according to claim 3, wherein the theoretical adiabatic head H of the expansion turbine is calculated according to the following formula:

6. The refrigerator according to claim 3 , wherein the reference range is 0.6 or more and 0.7 or less.

7. 7. The refrigerator according to claim 2, wherein the control device calculates a set value of a rotation speed of the expansion turbine when the control device detects a fluctuation in a rotation speed of the compressor or when a certain time has elapsed since the fluctuation in the rotation speed of the compressor.

8. A control device for controlling a refrigerant cycle including a turbo compressor that compresses a refrigerant, an expansion turbine that expands the refrigerant, a first refrigerant line that connects an outlet of the compressor and an inlet of the expansion turbine, a second refrigerant line that connects an outlet of the expansion turbine and an inlet of the compressor, a main heat exchanger that performs heat exchange of the refrigerant between the first refrigerant line and the second refrigerant line, and a secondary heat exchanger that performs heat exchange between the refrigerant and an external fluid downstream of the main heat exchanger of the first refrigerant line or upstream of the main heat exchanger of the second refrigerant line, A communication unit that communicates with at least a group of sensors attached to the first refrigerant line and the second refrigerant line; a control unit that adjusts a rotation speed of the compressor in accordance with a target capacity for cooling the fluid, and adjusts a rotation speed of the expansion turbine in accordance with the rotation speed of the compressor and a sensor value obtained from the group of sensors via the communication unit; A control device comprising:

9. A control method for controlling a refrigerant cycle including a turbo compressor that compresses a refrigerant, an expansion turbine that expands the refrigerant, a first refrigerant line that connects an outlet of the compressor and an inlet of the expansion turbine, a second refrigerant line that connects an outlet of the expansion turbine and an inlet of the compressor, a main heat exchanger that performs heat exchange of the refrigerant between the first refrigerant line and the second refrigerant line, and a secondary heat exchanger that is located downstream of the main heat exchanger of the first refrigerant line or upstream of the main heat exchanger of the second refrigerant line and performs heat exchange between the refrigerant and an external fluid, Adjusting the rotation speed of the compressor according to a target capacity for cooling the fluid; acquiring sensor values ​​from a group of sensors attached to at least the first refrigerant line and the second refrigerant line; A control method for adjusting the rotation speed of the expansion turbine in accordance with the rotation speed of the compressor and the sensor values ​​obtained from the group of sensors.

10. A program for controlling a refrigerant cycle including a turbo compressor that compresses a refrigerant, an expansion turbine that expands the refrigerant, a first refrigerant line that connects an outlet of the compressor and an inlet of the expansion turbine, a second refrigerant line that connects an outlet of the expansion turbine and an inlet of the compressor, a main heat exchanger that performs heat exchange of the refrigerant between the first refrigerant line and the second refrigerant line, and a secondary heat exchanger that performs heat exchange between the refrigerant and an external fluid downstream of the main heat exchanger of the first refrigerant line or upstream of the main heat exchanger of the second refrigerant line, a computer that communicates with a group of sensors attached to at least the first refrigerant line and the second refrigerant line; A program that executes a process of adjusting the rotation speed of the compressor in accordance with a target capacity for cooling the fluid, and a process of adjusting the rotation speed of the expansion turbine in accordance with the rotation speed of the compressor and sensor values ​​obtained from the group of sensors.

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