Refrigeration system

Abstract

This refrigeration system comprises: a refrigerated warehouse having a refrigerated space; and a refrigerator able to cool gas drawn in from the refrigerated space. The refrigerator comprises: an inlet line for guiding gas from the refrigerated space to a compressor; a compressed gas line for guiding gas from the compressor to a turbine; an outlet line for guiding gas from the turbine to the refrigerated space; a heat exchanger for exchanging heat between the gas flowing through the inlet line and the gas flowing through the compressed gas line; a bypass line for guiding gas flowing upstream of the heat exchanger in the compressed gas line in order to melt frost; and a flow path switching valve able to switch flow paths to achieve flow through the bypass line. The refrigeration system is further provided with a control device for controlling the flow path switching valve on the basis of a frosted state of the refrigerated space ascertained on the basis of the humidity, sensed by a humidity sensor, of circulating gas flowing downstream of the heat exchanger in the inlet line.

Description

Refrigeration system

[0001] The present disclosure relates to a refrigeration system. The present application claims priority based on Japanese Patent Application No. 2025-049478 filed with the Japan Patent Office on March 25, 2025, the content of which is incorporated herein by reference.

[0002] Patent Document 1 discloses a refrigerated warehouse having therein a refrigeration space that is an object to be cooled, and an air refrigerant refrigeration apparatus for cooling air extracted from the refrigeration space. Patent Document 1 discloses that in order to remove frost formed by condensation in an air refrigerant that is adiabatically expanded by an expansion turbine and cooled to a low temperature, a defroster is provided in a pipe connecting the expansion turbine and the refrigerated warehouse.

[0003] Japanese Patent No. 4241699

[0004] In an open cycle that circulates air extracted from a refrigeration space, when moisture in the air cools, it turns into ice (snow) and forms frost in the cycle, which may reduce the performance of the air refrigerant refrigeration apparatus. The invention described in Patent Document 1 removes ice (moisture) by causing frost to adhere to a defroster and then melting the adhered frost (defrosting). However, it is difficult to select an appropriate timing for performing defrosting. If defrosting is performed at an incorrect timing, performance degradation due to heat loss caused by heating the refrigerator becomes a problem.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a refrigeration system capable of automatically performing defrosting operation of a refrigerator.

[0006] A refrigeration system according to at least one embodiment of the present disclosure comprises a cold storage warehouse having a cold storage space to be cooled, and at least one chiller configured to cool a circulating gas drawn in from the cold storage space, wherein the chiller includes: a compressor configured to compress the circulating gas; a turbine configured to expand the circulating gas; an inlet line for leading the circulating gas from the cold storage space to the compressor; a compressed gas line for leading the compressed gas, which is the circulating gas compressed by the compressor, to the turbine; an outlet line for leading the circulating gas, which has been expanded by the turbine, to the cold storage space; a heat exchanger configured to perform heat exchange between the circulating gas flowing through the inlet line and the compressed gas flowing through the compressed gas line; and at least one bypass line for drawing out the circulating gas from the upstream side of the heat exchanger in the compressed gas line and leading it to at least one of the following: the downstream side of the heat exchanger in the compressed gas line, the outlet line, or the upstream side of the heat exchanger in the inlet line. The refrigeration system includes at least one flow path switching valve configured to switch the flow path of the circulating gas in the refrigerator so that the circulating gas flows through at least one bypass line, the refrigeration system further includes a humidity sensor configured to detect the humidity of the circulating gas flowing downstream of the heat exchanger in the inlet line, and a control device configured to control the at least one flow path switching valve based on the frost condition of the refrigerated space, which is determined based on the humidity of the circulating gas detected by at least the humidity sensor.

[0007] According to at least one embodiment of the present disclosure, a refrigeration system is provided that can automatically perform defrosting operations on a refrigerator.

[0008] This figure schematically shows a refrigeration system according to one embodiment of the present disclosure. This is a schematic configuration diagram schematically showing the configuration of the control device shown in Figure 1. This is an explanatory diagram for explaining the relationship between the internal temperature, internal humidity, and the frost condition of the refrigerated space. This is an explanatory diagram for explaining an example of a method for determining the frost condition of the refrigerated space using the compressor inlet humidity or internal humidity. This figure schematically shows a modified version of the refrigeration system shown in Figure 1. This is a schematic diagram for showing a modified version of the refrigeration system shown in Figure 1. This figure schematically shows a refrigeration system according to one embodiment of the present disclosure. This is a schematic configuration diagram schematically showing the configuration of the control device shown in Figure 7 or Figure 8. This figure schematically shows a refrigeration system according to one embodiment of the present disclosure. This is an explanatory diagram for explaining an example of a method for determining the frost condition of the refrigerated space using the compressor inlet humidity or internal humidity of multiple refrigerators.

[0009] Hereinafter, several embodiments of this disclosure will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the components described or shown in the drawings as embodiments are not intended to limit the scope of this disclosure, but are merely illustrative examples.

[0010] (Refrigeration System) Figure 1 is a schematic diagram showing a refrigeration system 1 according to one embodiment of the present disclosure. As shown in Figure 1, a refrigeration system 1 according to several embodiments comprises a cold storage warehouse 2 having a cold storage space 20 inside which to be cooled, and at least one refrigerator 3 configured to cool circulating gas drawn in from the cold storage space 20. The cold storage space 20 can accommodate the object to be cooled. The refrigerator 3 cools the cold storage space 20 by cooling the circulating gas drawn in from the cold storage space 20 and then returning it to the cold storage space 20.

[0011] The refrigeration system 1 can adjust the temperature of the gas inside the chamber (the gas present in the refrigerated space 20) using the refrigerator 3. In the following embodiment, the refrigerator 3 can set the temperature of the gas inside the chamber to an extremely low temperature (below -40°C and above -120°C, preferably below -80°C).

[0012] (Refrigeration Unit) The refrigerator unit 3, as shown in Figure 1, includes a compressor 41 configured to compress the circulating gas, a turbine 42 configured to expand the circulating gas, an inlet line 5, a compressed gas line 6, an outlet line 7, and a heat exchanger 8.

[0013] (Inlet line, compressed gas line, outlet line) The inlet line 5, as shown in Figure 1, is a flow path for guiding circulating gas from the refrigerated space 20 to the compressor 41. The compressed gas line 6, as shown in Figure 1, is a flow path for guiding the compressed gas, which is the circulating gas compressed by the compressor 41, to the turbine 42. The outlet line 7 is a flow path for guiding the circulating gas, which has been expanded by the turbine 42, back to the refrigerated space 20.

[0014] As shown in Figure 1, the inlet line 5 is provided in the refrigeration space 20 and has a suction port 51 (opening) for drawing circulating gas from the refrigeration space 20 into the interior of the inlet line 5. The suction port 51 is formed at the upstream end of the inlet line 5. The downstream end of the inlet line 5 is connected to the compressor 41.

[0015] The compressed gas line 6 is located outside the refrigeration space 20. The upstream end of the compressed gas line 6 is connected to the compressor 41, and the downstream end is connected to the turbine 42.

[0016] As shown in Figures 1 to 3, the outlet line 7 has an outlet 71 (opening) provided in the refrigeration space 20 for guiding circulating gas from inside the outlet line 7 into the refrigeration space 20. The outlet 71 is formed at the downstream end of the outlet line 7. The upstream end of the outlet line 7 is connected to the turbine 42.

[0017] (Turbomachinery) In the illustrated embodiment, the refrigerator 3 described above includes a turbomachinery 4, as shown in Figure 1. The turbomachinery 4 includes the compressor 41 described above, the turbine 42 described above, a rotating shaft 43, and an electric motor 44, as shown in Figure 1. The rotating shaft 43 is connected to the compressor 41 and the turbine 42. The electric motor 44 is configured to generate rotational force to rotate the compressor 41, the turbine 42, and the rotating shaft 43.

[0018] In the illustrated embodiment, the impeller of the compressor 41 is attached to one side of the rotating shaft 43, and the wheel (turbine wheel) of the turbine 42 is attached to the other side of the rotating shaft 43. The compressor 41 and the turbine 42 are arranged coaxially with each other via the rotating shaft 43, which is the output shaft of the electric motor 44, and are connected to the rotating shaft 43. The electric motor 44 is configured to transmit the rotational force it generates to the rotating shaft 43.

[0019] In the illustrated embodiment, the electric motor 44 is supplied with current from a power source such as a generator (not shown), and is driven by the current supplied from the power source to drive (rotate) the rotating shaft 43, the compressor 41, and the turbine 42.

[0020] By driving the compressor 41, the gas in the refrigerated space 20 is drawn into the inlet line 5 via the suction port 51 and guided to the compressor 41. The compressor 41 is configured to compress the circulating gas, which is the gas drawn in from the refrigerated space 20 via the suction port 51. The circulating gas compressed by the compressor 41 is heated and pressurized higher than before it was introduced into the compressor 41, becoming a gas of relatively high temperature and pressure.

[0021] The compressed gas, which is a circulating gas compressed by the compressor 41, is led to the turbine 42 via the compressed gas line 6. The turbine 42 is configured to expand the compressed gas that has been led to it. The circulating gas expanded by the turbine 42 is cooled and depressurized compared to before it was introduced into the turbine 42, becoming a relatively cold and low-pressure fluid. The circulating gas expanded in the turbine 42 is blown out into the refrigerated space 20 from the outlet line 7 via the outlet 71.

[0022] (Heat Exchanger) The heat exchanger 8 is configured to exchange heat between the circulating gas flowing through the inlet line 5 and the compressed gas flowing through the compressed gas line 6. The heat exchanger 8 is configured so that heat is transferred between two gases with different temperatures separated by a heat transfer wall. Through heat transfer in the heat exchanger 8, the compressed gas flowing through the compressed gas line 6 is cooled and the circulating gas flowing through the inlet line 5 is heated. The circulating gas heated by the heat exchanger 8 is introduced into the compressor 41. The compressed gas cooled by the heat exchanger 8 is introduced into the turbine 42.

[0023] (Cooler) In the illustrated embodiment, the refrigerator 3 described above further includes a cooler 9 configured to cool the compressed gas flowing upstream of the heat exchanger 8 (compressor 41 side) of the compressed gas line 6. The cooler 9 is configured to exchange heat between the compressed gas flowing upstream of the heat exchanger 8 of the compressed gas line 6 and a coolant (for example, water) that is colder than the compressed gas. The cooler 9 is configured so that two fluids with different temperatures (compressed gas and coolant) transfer heat across a heat transfer wall.

[0024] Heat transfer in the cooler 9 cools the compressed gas flowing upstream of the heat exchanger 8 in the compressed gas line 6. The compressed gas cooled by the cooler 9 is then introduced into the heat exchanger 8 through the compressed gas line 6.

[0025] In the illustrated embodiment, the refrigerator 3 includes a coolant line 91 for circulating coolant and a cooling device 92 for cooling the coolant flowing through the coolant line 91. The coolant line 91 is a passage for returning the coolant taken from the cooler 9 to the cooler 9. The coolant line 91 is provided with a coolant pump 93 for supplying coolant in the coolant line 91 and a radiator 94. The cooling device 92 includes a radiator 94 and a fan 95 for air-cooling the radiator 94.

[0026] The coolant, which has been heated by heat transfer in the cooler 9, is guided to the coolant line 91 by the coolant pump 93, cooled by the cooling system 92 including the radiator 94, and then guided back to the cooler 9.

[0027] The refrigerator 3 further includes at least one bypass line 11 and at least one flow path switching valve 12, as shown in Figure 1. The refrigeration system 1 further includes a humidity sensor 13 and a control device 14.

[0028] (Bypass line) The bypass line 11 is a flow path for extracting circulating gas from the upstream side of the heat exchanger 8 of the compressed gas line 6 and guiding it to at least one of the following: the downstream side of the heat exchanger 8 of the compressed gas line 6, the outlet line 7, or the upstream side of the heat exchanger 8 of the inlet line 5.

[0029] In the illustrated embodiment, the at least one bypass line 11 described above includes a heat exchanger-side bypass line 11A, as shown in Figure 1. The heat exchanger-side bypass line 11A is a flow path that extracts circulating gas from the upstream side of the heat exchanger 8 of the compressed gas line 6 and guides it to the downstream side of the heat exchanger 8 of the compressed gas line 6.

[0030] In the illustrated embodiment, the upstream end 111 of the heat exchanger-side bypass line 11A is connected upstream of the cooler 9 of the compressed gas line 6 (compressor 41 side). The downstream end 112 of the heat exchanger-side bypass line 11A is connected downstream of the heat exchanger 8 (turbine 42 side) of the compressed gas line 6. In this case, by connecting the upstream end 111 of the heat exchanger-side bypass line 11A upstream of the cooler 9 of the compressed gas line 6, the refrigeration system 1 can flow high-temperature circulating gas (warm air) through the heat exchanger-side bypass line 11A compared to when it is connected between the cooler 9 and the heat exchanger 8 of the compressed gas line 6, thereby promoting defrosting of the chiller 3 by the warm air. In some other embodiments, the upstream end 111 of the heat exchanger-side bypass line 11A may be connected between the cooler 9 and the heat exchanger 8 of the compressed gas line 6.

[0031] (Flow path switching valve) The flow path switching valve 12 is configured to switch the flow path of the circulating gas in the refrigerator 3 so that the circulating gas flows through at least one bypass line 11 as described above. The flow path switching valve 12 is configured to switch between the flow path (path) of the circulating gas during normal operation of the refrigerator 3 and the flow path (path) of the circulating gas during defrost operation to melt frost attached to the refrigerator 3.

[0032] During normal operation of the refrigerator 3, the circulating gas flows through the inlet line 5, the compressed gas line 6, and the outlet line 7 in that order, and does not flow through the bypass line 11. In contrast, during defrost operation of the refrigerator 3, the circulating gas is compressed gas compressed by the compressor 41 and guided through the bypass line 11 to the equipment and lines in the refrigerator 3 that are to be defrosted.

[0033] The refrigeration system 1 can automatically defrost the refrigerator 3 by switching the circulating gas flow path during normal operation of the refrigerator 3 to the circulating gas flow path during defrost operation of the refrigerator 3 using the flow path switching valve 12. After the defrosting of the refrigerator 3 is completed, the refrigeration system 1 can automatically return the refrigerator 3 to normal operation by switching the circulating gas flow path during normal operation of the refrigerator 3 from the circulating gas flow path during defrost operation of the refrigerator 3 to the circulating gas flow path during normal operation of the refrigerator 3.

[0034] In the illustrated embodiment, the at least one flow path switching valve 12 described above includes a first flow control valve 12A, as shown in Figure 1. The first flow control valve 12A is provided in the heat exchanger-side bypass line 11A and is configured to adjust the flow rate of the circulating gas flowing through the heat exchanger-side bypass line 11A. The first flow control valve 12A is configured to adjust the flow rate of the circulating gas that is led downstream of the first flow control valve 12A (towards the turbine 42) via the heat exchanger-side bypass line 11A by changing the opening degree of a valve body located in the heat exchanger-side bypass line 11A. The first flow control valve 12A may be an on-off valve whose opening degree can be adjusted to fully closed and fully open, or it may be an opening degree adjustment valve whose opening degree can be adjusted to fully closed, fully open and at least one intermediate opening degree between these.

[0035] (Opening and closing of valves during normal operation) During normal operation (steady-state operation) of the chiller 3, the first flow control valve 12A provided in the heat exchanger side bypass line 11A is closed. During normal operation (steady-state operation) of the chiller 3, the circulating gas flows through the inlet line 5, the compressed gas line 6, and the outlet line 7 without passing through the heat exchanger side bypass line 11A.

[0036] (Opening and closing of valves during defrost operation) During defrost operation of the chiller 3, the first flow control valve 12A, located in the heat exchanger-side bypass line 11A, is open. During defrost operation of the chiller 3, warm air (circulating gas) that has become relatively high temperature and pressure due to compression by the compressor 41 is guided through the heat exchanger-side bypass line 11A to the turbine 42 and outlet line 7. The warm air guided to the turbine 42 and outlet line 7 heats the turbine 42 and outlet line 7, melting any frost that has accumulated on them.

[0037] (Humidity Sensor) The humidity sensor 13 is configured to detect the humidity (relative humidity [RH (%)], compressor inlet humidity) H1 of the circulating gas flowing downstream of the heat exchanger 8 in the inlet line 5. The humidity sensor 13 detects the humidity of the circulating gas flowing downstream of the heat exchanger 8 in the inlet line 5 during the normal operation of the chiller 3. During the normal operation of the chiller 3, the temperature of the circulating gas flowing downstream of the heat exchanger 8 in the inlet line 5 is at ambient temperature (0°C to 40°C), making it suitable for humidity detection. In contrast, during the operation of the chiller 3, the temperature of the circulating gas flowing in the refrigerated space 20, upstream of the heat exchanger 8 in the inlet line 5, and in the outlet line 7 is relatively low (below 0°C), making it unsuitable for humidity detection. Furthermore, the circulating gas flowing in the compressed gas line 6 during the operation of the chiller 3 has different properties than before it was compressed by the compressor 41, and is therefore not suitable for understanding the frost condition of the refrigerated space 20.

[0038] (Control device) The control device 14 is configured to control at least one flow path switching valve 12 based on the frost condition of the refrigerated space 20, which is determined based on the humidity H1 of the circulating gas detected by at least the humidity sensor 13. Here, the frost condition of the refrigerated space 20 is information (parameters) indicating whether or not frost has formed in the refrigerated space 20.

[0039] Figure 2 is a schematic diagram illustrating the configuration of the control device 14 shown in Figure 1. The control device (controller) 14 is an electronic control unit for controlling the drive of equipment mounted on the refrigeration system 1, such as the flow path switching valve 12, the electric motor 44, and the notification device 21. As shown in Figure 2, the control device 14 may be configured as a microcomputer including an input device 141 (input interface), an output device 142 (output interface), a storage device 143 (memory such as ROM or RAM, external storage device, etc.), and an arithmetic unit 144 (CPU). The control device 14 achieves drive control of the flow path switching valve 12, the electric motor 44, and the notification device 21 by having the CPU operate (for example, perform data calculations, etc.) according to instructions of a program loaded into the main memory of the above-mentioned memory.

[0040] The control device 14 receives various signals from sensors installed in the refrigeration system 1, such as the humidity sensor 13, the internal temperature sensor 15, the compressor inlet temperature sensor 16, the outlet temperature sensor 18, and the inlet temperature sensor 19, via the input device 141 to the storage device 143 and the arithmetic unit 144. The storage device 143 stores the various signals from the sensors installed in the refrigeration system 1. The arithmetic unit 144 is configured to execute various controls according to the control programs stored in the storage device 143.

[0041] As shown in Figure 2, the control device 14 includes at least a storage humidity calculation unit 101 and a flow path switching valve control unit 102.

[0042] (Internal humidity calculation unit) The internal humidity calculation unit 101 is configured to calculate internal humidity H0, which is the humidity (relative humidity [RH (%)]) of the refrigeration space 20, based on at least the humidity of the circulating gas (relative humidity [RH (%)], compressor inlet humidity) H1 detected by the humidity sensor 13.

[0043] In some embodiments, the internal humidity calculation unit 101 is configured to calculate the internal humidity H0 from the measured value of the compressor inlet humidity H1 based on association information (first association information) in which at least the internal humidity H0 and the compressor inlet humidity H1 are associated with each other.

[0044] The first association information indicates the correspondence between the internal humidity H0 and the compressor inlet humidity H1, and only needs to be configured such that when the compressor inlet humidity H1 (measured value) is used as input information, the internal humidity H0 corresponding to the input information can be obtained as output information. The first association information includes lists, tables, maps, functions, machine learning models, strength analysis models, etc. that show the correspondence between the input information and the output information. The association information may be created based on numerical analysis results.

[0045] In some embodiments, the internal humidity calculation unit 101 is configured to calculate the internal humidity H0 from the measured value of the compressor inlet humidity H1 based on association information (second association information) in which the internal humidity H0, the compressor inlet humidity H1, the internal temperature T0, and the compressor inlet temperature T1 are associated with one another.

[0046] The second association information indicates the correspondence among the internal humidity H0, the compressor inlet humidity H1, the internal temperature T0, and the compressor inlet temperature T1, and only needs to be configured such that when the compressor inlet humidity H1 (measured value) is used as input information, the internal humidity H0 corresponding to the input information can be obtained as output information. Here, the internal temperature T0 is the temperature of the refrigeration space 20, and the compressor inlet temperature T1 is the temperature of the circulating gas flowing downstream of the heat exchanger 8 of the inlet line 5.

[0047] The internal humidity calculation unit 101 may use previously prepared values for the internal temperature T0 and the compressor inlet temperature T1, which are parameters used in the second association information. These previously prepared values may be set based on actual measured values obtained during past normal operation of the refrigerator 3 or actual measured values obtained during normal operation of a model of the refrigerator 3 that is the same type as refrigerator 3, or may be set based on numerical analysis results of the refrigerator 3. In this case, the refrigeration system 1 does not need to include an internal temperature sensor 15 (see FIG. 7) configured to measure the internal temperature T0, or a compressor inlet temperature sensor 16 (see FIG. 7) configured to measure the compressor inlet temperature T1. Therefore, the complication of the structure and control of the refrigeration system 1 can be suppressed, and an increase in the manufacturing cost of the refrigeration system 1 can also be suppressed.

[0048] The previously prepared values of the internal temperature T0 or the compressor inlet temperature T1 may be stored in the storage device 143 in a referable manner together with the second association information, and may be configured to be referred to by the internal humidity calculation unit 101. Alternatively, the previously prepared values of the internal temperature T0 or the compressor inlet temperature T1 may be stored in the storage device 143 in a referable manner in a state of being incorporated into the second association information, and may be configured to be used when the internal humidity calculation unit 101 refers to the second association information.

[0049] FIG. 3 is an explanatory diagram for explaining the relationship among the internal temperature T0, the internal humidity H0, and the frosting state of the freezing space 20. In FIG. 3, a graph is shown in which the horizontal axis represents the internal temperature T0, and the vertical axis represents absolute humidity AH [SH (kg / kg)], which is a parameter indicating the amount of water vapor contained in air. A curve L1 shown in FIG. 3 indicates that the internal humidity H0 is 100%.

[0050] The internal humidity H0 calculated by the internal humidity calculation unit 101 is a parameter that indicates the frost condition of the freezing space 20. As shown in Figure 3, when the internal humidity H0 is 100% or higher (belonging to the region 20A above curve L1 in Figure 3), the frost condition of the freezing space 20 can be considered to be a state where frost has formed in the freezing space 20 (subject to defrosting). Also, when the internal humidity H0 is less than 100% (belonging to the region 20B below curve L1 in Figure 3), the frost condition of the freezing space 20 can be considered to be a state where frost has not formed in the freezing space 20 (not subject to defrosting). In this embodiment, the freezing system 1 can determine the frost condition of the freezing space 20 by calculating the internal humidity H0 in the internal humidity calculation unit 101.

[0051] Furthermore, the threshold value indicating the boundary between the state in which frost has formed in the freezing space 20 and the state in which frost has not formed in the freezing space 20 is not limited to when the internal humidity H0 is 100%, but may be a predetermined humidity with a margin on the higher or lower side relative to 100%.

[0052] (Flow path switching valve control unit) The flow path switching valve control unit 102 of the control device 14 is configured to control at least one of the flow path switching valves 12 described above, based on the frost condition of the refrigerated space 20, which is determined based on the compressor inlet humidity H1 detected by the humidity sensor 13.

[0053] Specifically, the flow path switching valve control unit 102 is configured to instruct the flow path switching valve 12 to switch from the normal flow path of the circulating gas during normal operation of the chiller 3 (normal path) to the defrost flow path of the circulating gas during defrost operation of the chiller 3 when the frost state of the chiller 20 transitions from a state where there is no frost in the chiller 20 to a state where there is frost in the chiller 20.

[0054] In the embodiment shown in Figure 1, the flow path switching valve control unit 102 is configured to instruct the first flow control valve 12A to open when the frost condition of the refrigerated space 20 transitions from a state where there is no frost in the refrigerated space 20 to a state where there is frost in the refrigerated space 20. When the first flow control valve 12A is opened, the warm air (circulating gas) that has become relatively hot and high-pressure after being compressed by the compressor 41 flows through the defrost path, that is, through the heat exchanger side bypass line 11A and is guided to the turbine 42 and outlet line 7.

[0055] The flow path switching valve control unit 102 may be configured to instruct the flow path switching valve 12 to switch back (switch) from the defrost path to the normal path after a predetermined period has elapsed in which the defrosting of the refrigerator 3 can be considered complete, following the switching from the normal path to the defrost path by the flow path switching valve 12. In the embodiment shown in Figure 1, the flow path switching valve control unit 102 is configured to instruct the first flow rate control valve 12A to close after the above predetermined period has elapsed. When the first flow rate control valve 12A is closed, the warm air (circulating gas) that has become relatively high temperature and high pressure due to compression by the compressor 41 flows through the normal path.

[0056] The refrigeration system 1 according to this embodiment can determine the frost condition of the refrigerated space 20 based on the humidity of the circulating gas (compressor inlet humidity) H1 detected by at least the humidity sensor 13. When the frost condition of the refrigerated space 20 changes from a state where there is no frost in the refrigerated space 20 to a state where there is frost in the refrigerated space 20, the refrigeration system 1 can automatically perform defrost operation of the refrigerator 3 by switching the flow path of the circulating gas during normal operation of the refrigerator 3 (normal path) to the flow path of the circulating gas during defrost operation of the refrigerator 3 (defrost path) using the flow path switching valve 12. Such a refrigeration system (1) can improve its reliability.

[0057] Figure 4 is an explanatory diagram illustrating an example of a method for determining the frost condition of a refrigerated space 20 using compressor inlet humidity H1 or internal humidity H0. In Figure 4, a graph is shown with time (elapsed time) on the horizontal axis and compressor inlet humidity H1 or internal humidity H0 on the vertical axis.

[0058] In some embodiments of the refrigeration system 1, the flow path switching valve control unit 102 (control device 14) described above is configured to control at least one flow path switching valve 12 so that the circulating gas flows through at least one bypass line 11 when either the humidity H1 of the circulating gas detected by the humidity sensor 13, or the internal humidity H0 of the refrigerated space 20, which is determined based on the humidity H1 of the circulating gas detected by the humidity sensor 13 (compressor inlet humidity), exceeds a threshold TH1 (see Figure 4).

[0059] As described above, the humidity sensor 13 can determine the internal humidity H0 and the frost condition of the freezing space 20 from the humidity H1 of the circulating gas detected. The threshold TH1 indicates the boundary between the state in which frost has formed in the freezing space 20 and the state in which frost has not formed in the freezing space 20.

[0060] The information relating the internal humidity H0 to the frost condition of the freezing space 20 includes information on the internal humidity H0 corresponding to the boundary, and the internal humidity H0 corresponding to the boundary may be used as the threshold TH1.

[0061] By integrating the aforementioned association information (first association information or second association information) with the information relating the internal humidity H0 to the frost state of the freezing space 20, information relating the compressor inlet humidity H1 to the frost state of the freezing space 20 can be obtained. The information relating the compressor inlet humidity H1 to the frost state of the freezing space 20 includes the compressor inlet humidity H1 corresponding to the boundary, and the compressor inlet humidity H1 corresponding to the boundary may be used as the threshold TH1.

[0062] In this embodiment of the refrigeration system 1, if either the humidity H1 of the circulating gas detected by the humidity sensor 13, or the internal humidity H0 determined from this humidity H1, exceeds the threshold TH1, there is a high probability that frost is forming in the refrigerated space 20. When either the humidity H1 or the internal humidity H0 exceeds the threshold TH1, the refrigeration system 1 can automatically perform defrost operation of the refrigerator 3 by switching the flow path of the circulating gas with the flow path switching valve 12.

[0063] Figures 5 and 6 are schematic diagrams illustrating modified versions of the refrigeration system 1 shown in Figure 1. In some embodiments of the refrigeration system 1, as shown in Figure 5, the at least one bypass line 11 (11B) described above is a flow path for extracting circulating gas from the upstream side of the heat exchanger 8 in the compressed gas line 6 and guiding it to the upstream side of the heat exchanger 8 in the inlet line 5. The at least one flow path switching valve 12 (12B) described above is a flow control valve provided in the bypass line 11B and configured to adjust the flow rate of circulating gas flowing through the bypass line 11B.

[0064] In the illustrated embodiment, the upstream end 113 of the bypass line 11B is connected upstream of the cooler 9 of the compressed gas line 6 (towards the compressor 41). The downstream end 114 of the bypass line 11B is connected upstream of the heat exchanger 8 of the inlet line 5. Alternatively, the upstream end 113 of the bypass line 11B may be connected between the cooler 9 and the heat exchanger 8 of the compressed gas line 6.

[0065] In some embodiments of the refrigeration system 1, as shown in Figure 6, the above-described at least one bypass line 11 (11C) is a flow path for extracting circulating gas from the upstream side of the heat exchanger 8 of the compressed gas line 6 and guiding it to the outlet line 7. The above-described at least one flow path switching valve 12 (12C) is a flow control valve provided in the bypass line 11C and configured to adjust the flow rate of circulating gas flowing through the bypass line 11C.

[0066] In the illustrated embodiment, the upstream end 115 of the bypass line 11C is connected upstream of the cooler 9 of the compressed gas line 6 (towards the compressor 41). The downstream end 116 of the bypass line 11C is connected to the outlet line 7. Alternatively, the upstream end 115 of the bypass line 11C may be connected between the cooler 9 and the heat exchanger 8 of the compressed gas line 6.

[0067] Figures 7 and 8 are schematic diagrams showing a refrigeration system 1 according to one embodiment of the present disclosure. Figure 9 is a schematic configuration diagram showing the configuration of the control device 14 shown in Figure 7 or Figure 8. Refrigeration systems 1 according to several embodiments include, as shown in Figures 7 and 8, the above-described refrigerated warehouse 2, the above-described at least one refrigerator 3, the above-described humidity sensor 13, and the above-described control device 14.

[0068] In some embodiments of the refrigeration system 1, as shown in Figures 7 and 8, the above-described at least one bypass line 11 includes the heat exchanger-side bypass line 11A and the cold storage-side bypass line 11D for extracting circulating gas from the outlet line 7 and guiding it upstream of the heat exchanger 8 in the inlet line 5. The above-described flow path switching valve 12 includes the first flow rate control valve 12A and the second flow rate control valve 17 configured to adjust the flow rate of circulating gas flowing through the cold storage-side bypass line 11D.

[0069] (Cold Storage Warehouse Bypass Line) The cold storage warehouse bypass line 11D is a flow path for extracting circulating gas from the outlet line 7 and guiding it upstream of the heat exchanger 8 in the inlet line 5. In the illustrated embodiment, the cold storage warehouse bypass line 11D is located outside the cold storage warehouse 2 (cold storage space 20). The upstream end 117 of the cold storage warehouse bypass line 11D is connected to the outlet line 7, and the downstream end 118 is connected upstream of the heat exchanger 8 in the inlet line 5.

[0070] In the embodiment shown in Figure 7, the second flow control valve 17 is a central flow control valve 171 located in the middle of the cold storage warehouse side bypass line 11D. The central flow control valve 171 is configured to adjust the flow rate of circulating gas guided downstream of the central flow control valve 171 (towards the inlet line 5) via the cold storage warehouse side bypass line 11D by changing the opening degree of a valve body located in the cold storage warehouse side bypass line 11D. The central flow control valve 171 may be an on-off valve whose opening degree can be adjusted to fully closed and fully open, or it may be an opening degree adjustment valve whose opening degree can be adjusted to fully closed, fully open, and at least one intermediate opening degree between these.

[0071] In the embodiment shown in Figure 7, the chiller 3 includes an outlet flow control valve 172 and an inlet flow control valve 173. The outlet flow control valve 172 is located downstream of the connection point between the outlet line 7 and the cold storage bypass line 11D (on the outlet 71 side) and is configured to adjust the flow rate of the circulating gas flowing through the outlet line 7. The inlet flow control valve 173 is located upstream of the connection point between the inlet line 5 and the cold storage bypass line 11D (on the suction port 51 side) and is configured to adjust the flow rate of the circulating gas flowing through the inlet line 5.

[0072] In this embodiment, the refrigeration system 1 can melt frost attached to the turbine 42 and outlet line 7 by increasing the flow rate of circulating gas flowing through the heat exchanger-side bypass line 11A using the first flow rate control valve 12A. The refrigeration system 1 can also melt frost attached downstream of the connection between the heat exchanger 8 and the inlet line 5 and the cold storage-side bypass line 11D by increasing the flow rate of circulating gas flowing through the cold storage-side bypass line 11D using the second flow rate control valve 17.

[0073] (Opening and closing of valves during normal operation) During normal operation of the chiller 3, the first flow control valve 12A and the central flow control valve 171 are closed, and the inlet flow control valve 173 and the outlet flow control valve 172 are open. During normal operation of the chiller 3, the circulating gas flows through the inlet line 5, the compressed gas line 6 and the outlet line 7, without passing through the heat exchanger side bypass line 11A and the cold storage warehouse side bypass line 11D.

[0074] (Opening and closing of valves during defrost operation on the turbine side) During defrost operation on the turbine 42 side of the chiller 3, the central flow control valve 171 is closed, and the inlet flow control valve 173, the outlet flow control valve 172, and the first flow control valve 12A are open. During defrost operation on the turbine 42 side of the chiller 3, the circulating gas (compressed gas), which has become relatively high temperature and pressure due to compression by the compressor 41, is guided through the heat exchanger side bypass line 11A to the turbine 42 and the outlet line 7, thereby melting the frost attached to the turbine 42 and the outlet line 7.

[0075] (Opening and closing of valves during defrost operation on the heat exchanger side) During defrost operation on the heat exchanger 8 side of the chiller 3, the inlet flow control valve 173 and the outlet flow control valve 172 are closed, and the first flow control valve 12A and the central flow control valve 171 are open. During defrost operation on the heat exchanger 8 side of the chiller 3, the circulating gas (compressed gas), which has become relatively high temperature and pressure due to compression by the compressor 41, is guided to the heat exchanger 8 by passing through the heat exchanger side bypass line 11A and the cold storage warehouse side bypass line 11D, thereby melting the frost that has accumulated downstream of the connection between the heat exchanger 8 and the heat exchanger side bypass line 11A of the inlet line 5.

[0076] In the embodiment shown in Figure 7, the flow path switching valve control unit 102 is configured to instruct the first flow control valve 12A to open when the frost condition of the refrigerated space 20 transitions from a state where there is no frost in the refrigerated space 20 to a state where there is frost in the refrigerated space 20. When the first flow control valve 12A is opened, the warm air (circulating gas) that has become relatively hot and high-pressure due to compression by the compressor 41 flows through the defrost path on the turbine 42 side (turbine 42, outlet line 7).

[0077] The flow path switching valve control unit 102 switches from the normal path to the defrost path on the turbine 42 side using the flow path switching valve 12, and then, after a predetermined period has elapsed in which defrosting on the turbine 42 side can be considered complete, switches from the defrost path on the turbine 42 side to the defrost path on the heat exchanger 8 side using the flow path switching valve 12. Specifically, the flow path switching valve control unit 102 is configured to instruct the second flow control valve 17 (central flow control valve 171) to open after the predetermined period has elapsed. When the second flow control valve 17 is opened, the warm air (circulating gas) that has become relatively high temperature and high pressure due to compression by the compressor 41 flows through the turbine 42 and then through the cold storage warehouse side bypass line 11D to the defrost path on the heat exchanger 8 side (inlet line 5, heat exchanger 8).

[0078] The flow path switching valve control unit 102 may be configured to instruct the flow path switching valve 12 to return to the normal path (switch) after a predetermined period has elapsed in which the defrost path on the heat exchanger 8 side is deemed to be completed, following the switching of the flow path switching valve 12 from the defrost path on the turbine 42 side to the defrost path on the heat exchanger 8 side. In the embodiment shown in Figure 7, the flow path switching valve control unit 102 is configured to instruct the first flow control valve 12A and the second flow control valve 17 (central flow control valve 171) to close after a predetermined period has elapsed in which the defrost path on the heat exchanger 8 side is deemed to be completed. When the first flow control valve 12A and the second flow control valve 17 are closed, the warm air (circulating gas) that has become relatively high temperature and high pressure due to compression by the compressor 41 flows through the normal path.

[0079] In some embodiments of the refrigeration system 1, the second flow control valve 17 described above includes, as shown in Figure 8, an outlet-side three-way valve 174 provided at the connection point between the outlet line 7 and the upstream end 117 of the cold storage warehouse-side bypass line 11D, and an inlet-side three-way valve 175 provided at the connection point between the inlet line 5 and the downstream end 118 of the cold storage warehouse-side bypass line 11D.

[0080] During normal operation of the chiller 3 and during defrost operation on the turbine 42 side, the outlet three-way valve 174 connects the upstream and downstream sides of the outlet line 7 beyond the outlet three-way valve 174. During normal operation of the chiller 3 and during defrost operation on the turbine 42 side, the inlet three-way valve 175 connects the upstream and downstream sides of the inlet line 5 beyond the inlet three-way valve 175.

[0081] During defrost operation on the heat exchanger 8 side of the chiller 3, the outlet three-way valve 174, instructed by the flow path switching valve control unit 102, connects the cold storage warehouse side bypass line 11D to the upstream side of the outlet three-way valve 174 of the outlet line 7 (turbine 42 side). During defrost operation on the heat exchanger 8 side of the chiller 3, the inlet three-way valve 175, instructed by the flow path switching valve control unit 102, connects the cold storage warehouse side bypass line 11D to the downstream side of the inlet three-way valve 175 of the inlet line 5 (heat exchanger 8 side).

[0082] In this embodiment, the refrigeration system 1 can melt frost attached to the inlet-side three-way valve 175 by the circulating gas flowing through the cold storage-side bypass line 11D during the defrost operation of the refrigerator 3. If a flow control valve is provided upstream of the connection point between the inlet line 5 and the cold storage-side bypass line 11D, it will be difficult to melt frost attached to the flow control valve by the circulating gas flowing through the cold storage-side bypass line 11D during the defrost operation of the refrigerator 3.

[0083] The second flow control valve 17 may also include an inlet-side three-way valve 175, a central-side flow control valve 171, and an outlet-side flow control valve 172. In this case, the central-side flow control valve 171 and the outlet-side flow control valve 172 replace the outlet-side three-way valve 174. Alternatively, the second flow control valve 17 may also include an outlet-side three-way valve 174, a central-side flow control valve 171, and an inlet-side flow control valve 173. In this case, the central-side flow control valve 171 and the inlet-side flow control valve 173 replace the inlet-side three-way valve 175.

[0084] In some embodiments of the refrigeration system 1, as shown in Figures 7 and 8, an outlet temperature sensor 18 and an inlet temperature sensor 19 are included. The outlet temperature sensor 18 is configured to measure the outlet temperature T2, which is the temperature of the circulating gas flowing through the outlet line 7. The inlet temperature sensor 19 is configured to measure the inlet temperature T3, which is the temperature of the circulating gas flowing upstream of the heat exchanger 8 in the inlet line 5.

[0085] The cooling capacity of the refrigerator 3 can be determined from at least the outlet temperature T2 measured by the outlet temperature sensor 18 and the inlet temperature T3 measured by the inlet temperature sensor 19. For example, if the temperature difference between the outlet temperature T2 and the inlet temperature T3 is above a predetermined temperature, the cooling capacity of the refrigerator 3 can be fully utilized in the refrigerated space 20, and it can be considered that the cooling capacity of the refrigerator 3 has not decreased. On the other hand, if the temperature difference between the outlet temperature T2 and the inlet temperature T3 is below a predetermined temperature, the cooling capacity of the refrigerator 3 cannot be fully utilized in the refrigerated space 20, and it can be considered that the cooling capacity of the refrigerator 3 has decreased.

[0086] The cooling capacity of the refrigerator 3 may be calculated not only from the outlet temperature T2 and the inlet temperature T3, but also by adding the flow rate of the circulating gas flowing through the outlet line 7 or the flow rate of the circulating gas flowing upstream of the heat exchanger 8 in the inlet line 5. The cooling capacity of the refrigerator 3 may also be calculated by multiplying the temperature difference between the outlet temperature T2 and the inlet temperature T3 by either the flow rate of the circulating gas flowing through the outlet line 7 or the flow rate of the circulating gas flowing upstream of the heat exchanger 8 in the inlet line 5. The flow rate of the circulating gas flowing through the outlet line 7 or the flow rate of the circulating gas flowing upstream of the heat exchanger 8 in the inlet line 5 can be calculated from the pressure of the circulating gas flowing through the outlet line 7 or the pressure of the circulating gas flowing upstream of the heat exchanger 8 in the inlet line 5, which corresponds to the rotational speed of the refrigerator 3 (for example, the steady-state rotational speed).

[0087] By understanding the cooling capacity of the chiller 3 and the frost condition of the chilled space 20, the following case-by-case diagnosis becomes possible. If the cooling capacity of the chiller 3 has decreased and the chilled space 20 is covered in frost, it is necessary to perform a defrost operation on the heat exchanger 8 side. If the cooling capacity of the chiller 3 has decreased and the chilled space 20 is not covered in frost, a defrost operation on the turbine 42 side is sufficient. If the cooling capacity of the chiller 3 has not decreased and the chilled space 20 is covered in frost, there is a possibility of an abnormality other than defrosting of the chiller 3, so a defrost operation of the chiller 3 is not performed.

[0088] The control device 14 is configured to instruct the flow path switching valve 12 to perform defrost operation on the heat exchanger 8 side when the cooling capacity of the refrigerator 3 decreases and the frosted state of the frosted space 20 is reached.

[0089] The control device 14 is configured to instruct the flow path switching valve 12 to perform defrost operation on the turbine 42 side if the cooling capacity of the chiller 3 decreases and the frosted state of the refrigerated space 20 is no longer frosted.

[0090] The control device 14 is configured not to instruct the flow path switching valve 12 to perform defrost operation if the cooling capacity of the refrigerator 3 has not decreased and the frost condition of the refrigerated space 20 is such that frost has formed in the refrigerated space 20.

[0091] Furthermore, the control device 14 is configured not to instruct the flow path switching valve 12 to perform defrost operation if the cooling capacity of the refrigerator 3 has not decreased and the frost condition of the refrigerated space 20 is such that there is no frost in the refrigerated space 20.

[0092] In this embodiment of the refrigeration system 1, if frost adheres to at least one of the inlet line 5 or the outlet line 7, the inflow and outflow of circulating gas into and out of the refrigerated space 20 is obstructed, reducing the refrigeration performance of the chiller 3 and resulting in a small temperature difference between the inlet temperature T3 and the outlet temperature T2. By determining the refrigeration performance of the chiller 3 from the temperature difference between the inlet temperature T3 and the outlet temperature T2, the refrigeration system 1 can determine whether the abnormal humidity in the refrigerated space 20 is caused by frost adhering to the chiller 3. As a result, the refrigeration system 1 can suppress unnecessary defrosting operations of the chiller 3, thereby improving the reliability of the refrigeration system 1.

[0093] Figure 10 is a schematic diagram showing a refrigeration system 1 according to one embodiment of the present disclosure. In some embodiments of the refrigeration system 1, as shown in Figure 10, the above-described at least one refrigerator 3 includes a plurality of refrigerators 3 (3A, 3B, 3C, 3D) configured to cool circulating gas drawn in from the same refrigeration space 20.

[0094] As shown in Figure 10, the refrigeration system 1 is equipped with the aforementioned humidity sensors 13 provided for each refrigerator 3. The control device 14 is configured to control at least one flow path switching valve 12 based on either the relative difference in the humidity H1 of the circulating gas detected by the multiple humidity sensors 13, or the relative difference in the internal humidity H0, which is the humidity of the refrigerated space 20 determined based on the humidity H1 of the circulating gas detected by the multiple humidity sensors 13.

[0095] Figure 11 is an explanatory diagram illustrating an example of a method for determining the frost condition of a refrigerated space 20 using the compressor inlet humidity H1 or internal humidity H0 of multiple refrigerators 3. In Figure 11, a line L2 is shown representing the average value of the compressor inlet humidity H1 or internal humidity H0 of multiple refrigerators 3 (3A, 3B, 3C, 3D) on a graph with the compressor inlet humidity H1 or internal humidity H0 of multiple refrigerators 3 (3A, 3B, 3C, 3D) on the vertical axis.

[0096] The control device 14 calculates the average value of the compressor inlet humidity H1 (measured value) of multiple refrigerators 3, and refrigerators 3 whose compressor inlet humidity H1 is higher than a predetermined value compared to the average value can be considered to be subject to defrosting. The control device 14 is configured to instruct the flow path switching valve 12 of the refrigerator 3 subject to defrosting to switch the flow path from the normal path of the refrigerator 3 to the defrost path.

[0097] In this embodiment of the refrigeration system 1, among the multiple refrigerators 3, the refrigerator 3 in which the humidity H1 of the circulating gas detected by the humidity sensor 13, or the internal humidity H0 determined from this humidity H1, is significantly higher than that of the other refrigerators 3, is highly likely to have frost forming in the refrigerated space 20. The refrigeration system 1 can quickly determine the presence of frost in the refrigerated space 20 by comparing the above humidity H1 or internal humidity H0 of the multiple refrigerators 3, thereby improving the reliability of the refrigeration system 1.

[0098] In some of the above-described embodiments of the refrigeration system 1, the control device 14 includes an electric motor control unit 103 configured to control the rotation speed of the electric motor 44 based on the frost condition of the refrigerated space 20, which is determined based on the humidity H1 of the circulating gas detected by the humidity sensor 13.

[0099] The refrigeration system 1 can automatically perform defrost operation of the refrigerator 3 by switching the flow path of the circulating gas during normal operation of the refrigerator 3 to the flow path of the circulating gas during defrost operation of the refrigerator 3 using the flow path switching valve 12, based on the frost condition of the refrigerated space 20. The control device 14 can lower the rotation speed of the electric motor 44 compared to the rotation speed during normal operation (rated rotation speed) of the refrigerator 3 prior to defrost operation of the refrigerator 3 by controlling the rotation speed of the electric motor 44 based on the frost condition of the refrigerated space 20.

[0100] As a result, the refrigeration system 1 can prevent the temperature of the warm air (circulating gas) introduced to the equipment and lines to be defrosted from becoming too high during the defrost operation of the chiller 3, thereby suppressing heat-induced fatigue and damage to the equipment and lines to be defrosted. By suppressing heat-induced fatigue and damage to the equipment and lines to be defrosted, the reliability of the refrigeration system 1 can be improved.

[0101] In the refrigeration system 1 according to some embodiments described above, the control device 14 includes an electric motor control unit 103 configured to control the rotation speed of the electric motor 44 based on the refrigeration capacity of the refrigerator 3, which is determined based on the outlet temperature T2 measured by the outlet temperature sensor 18 and the inlet temperature T3 measured by the inlet temperature sensor 19, and the frost condition of the refrigerated space 20, which is determined based on the humidity H1 of the circulating gas detected by the humidity sensor 13.

[0102] The refrigeration system 1 can automatically perform defrost operation of the refrigerator 3 by switching the circulating gas flow path from the normal operation flow path of the refrigerator 3 to the defrost operation flow path of the refrigerator 3 using the flow path switching valve 12, based on the refrigeration capacity of the refrigerator 3 and the frost condition of the refrigerated space 20. The control device 14 can lower the rotation speed of the electric motor 44 compared to the rotation speed during normal operation (rated rotation speed) of the refrigerator 3 prior to defrost operation by controlling the rotation speed of the electric motor 44 based on the refrigeration capacity of the refrigerator 3 and the frost condition of the refrigerated space 20.

[0103] As shown in Figures 1, 2, 5 to 9, the refrigeration system 1 according to some of the embodiments described above further comprises a notification device 21 configured to provide notification by at least one of light, character display, vibration, or sound. The notification device 21 may be one of the following, or a combination of two or more: a notification light capable of illuminating or flashing light, a display device (e.g., a display) having a display screen on which character displays can be displayed, a vibration device capable of generating vibration, or a speaker capable of outputting sound or voice.

[0104] In some embodiments, the control device 14 described above includes a notification device control unit 104 configured to control notification by the notification device 21 based on the frost condition of the refrigerated space 20, which is determined based on the humidity H1 of the circulating gas detected by the humidity sensor 13.

[0105] The refrigeration system 1 can automatically perform defrost operation of the refrigerator 3 by switching the flow path of the circulating gas during normal operation of the refrigerator 3 to the flow path of the circulating gas during defrost operation of the refrigerator 3 using the flow path switching valve 12, based on the frost condition of the refrigerated space 20. The control device 14 can control the notification by the notification device 21 based on the frost condition of the refrigerated space 20, by providing notifications that frost has formed in the refrigerated space 20, notifications that the notification device 21 will start defrost operation prior to the defrost operation of the refrigerator 3, or notifications that the notification device 21 is in the process of defrost operation while the refrigerator 3 is in the process of defrost operation.

[0106] This allows the refrigeration system 1 to notify the notification device 21 so that the defrost operation of the refrigerator 3 can be performed at an appropriate time based on the frost condition of the refrigerated space 20. In addition, the refrigeration system 1 can notify the notification device 21 when the defrost operation of the refrigerator 3 is being performed or is being performed.

[0107] In the refrigeration system 1 according to some embodiments described above, the control device 14 includes a notification device control unit 104 configured to control notification by the notification device 21 based on the refrigeration capacity of the refrigerator 3, which is determined based on the outlet temperature T2 measured by the outlet temperature sensor 18 and the inlet temperature T3 measured by the inlet temperature sensor 19, and the frost condition of the refrigerated space 20, which is determined based on the humidity H1 of the circulating gas detected by the humidity sensor 13.

[0108] The refrigeration system 1 can automatically perform defrost operation of the refrigerator 3 by switching the flow path of the circulating gas during normal operation of the refrigerator 3 to the flow path of the circulating gas during defrost operation of the refrigerator 3 using the flow path switching valve 12, based on the refrigeration capacity of the refrigerator 3 and the frost condition of the refrigerated space 20. The control device 14 can control the notification by the notification device 21 based on the refrigeration capacity of the refrigerator 3 and the frost condition of the refrigerated space 20, thereby providing notifications such as: a notification that frost has formed in the refrigerated space 20; a notification by the notification device 21 to start defrost operation prior to the defrost operation of the refrigerator 3; or a notification by the notification device 21 to indicate that defrost operation is in progress while the defrost operation of the refrigerator 3 is in progress.

[0109] In this specification, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" shall not only describe such arrangements strictly, but also describe states of relative displacement with tolerances or angles or distances sufficient to achieve the same function. For example, expressions describing things being in an equal state such as "identical," "equal," and "homogeneous" shall not only describe states of being strictly equal, but also describe states where tolerances or differences exist to the extent that the same function is achieved. Furthermore, in this specification, expressions describing shapes such as quadrilaterals or cylindrical shapes shall not only describe geometrically precise quadrilaterals or cylindrical shapes, but also describe shapes including concave and concave parts, chamfered parts, etc., to the extent that the same effect is achieved. In addition, in this specification, expressions such as "equipment," "includes," or "possesses" a component are not exclusive expressions that exclude the existence of other components.

[0110] This disclosure is not limited to the embodiments described above, but also includes modified forms of the embodiments described above, as well as forms that combine these forms as appropriate.

[0111] The contents described in some of the embodiments above can be understood, for example, as follows:

[0112] [1] A refrigeration system (1) according to at least one embodiment of the present disclosure comprises: a cold storage warehouse (2) having a cold storage space (20) to be cooled inside; and at least one refrigerator (3) configured to cool a circulating gas drawn in from the cold storage space (20), wherein the refrigerator (3) comprises: a compressor (41) configured to compress the circulating gas; a turbine (42) configured to expand the circulating gas; an inlet line (5) for leading the circulating gas from the cold storage space (20) to the compressor (41); a compressed gas line (6) for leading the compressed gas, which is the circulating gas compressed by the compressor (41), to the turbine (42); and an outlet line (7) for leading the circulating gas, which has been expanded by the turbine (42), back into the cold storage space (20). The refrigeration system (1) includes: a heat exchanger (8) configured to perform heat exchange between the circulating gas flowing through the inlet line (5) and the compressed gas flowing through the compressed gas line (6); at least one bypass line (11) for extracting the circulating gas from the compressed gas line (6) upstream of the heat exchanger (8) and guiding it to at least one of the following: the compressed gas line (6) downstream of the heat exchanger (8), the outlet line (7), or the inlet line (5) upstream of the heat exchanger (8); and at least one flow path switching valve (12) configured to switch the flow path of the circulating gas in the refrigerator (3) so that the circulating gas flows through the at least one bypass line (11); the refrigeration system (1) includes: a humidity sensor (13) configured to detect the humidity (H1) of the circulating gas flowing downstream of the heat exchanger (8) in the inlet line (5); The system further includes a control device (14) configured to control at least one flow path switching valve (12) based on the frost condition of the refrigerated space (20), which is determined based on the humidity (H1) of the circulating gas detected by at least the humidity sensor (13).

[0113] According to the configuration described in [1] above, the refrigeration system (1) can determine the frost condition of the refrigerated space (20) based on the humidity (H1) of the circulating gas detected by at least the humidity sensor (13). When the frost condition of the refrigerated space (20) changes from a state where there is no frost in the refrigerated space (20) to a state where there is frost in the refrigerated space (20), the refrigeration system (1) can automatically perform defrost operation of the refrigerator (3) by switching the flow path (12) from the flow path of the circulating gas during normal operation of the refrigerator (3) (normal path) to the flow path of the circulating gas during defrost operation of the refrigerator (3). Such a refrigeration system (1) can improve its reliability.

[0114] [2] In some embodiments, the refrigeration system (1) described in [1] further comprises an internal temperature sensor (15) configured to measure the internal temperature (T0), which is the temperature of the refrigeration space (20), and the control device (14) is configured to determine the frost condition based on the internal temperature (T0) measured by the internal temperature sensor (15) and the humidity (H1) of the circulating gas detected by the humidity sensor (13).

[0115] According to the configuration described in [2] above, by using the internal temperature (T0) measured by the internal temperature sensor (15) as a parameter for determining the frost condition of the freezer space (20), the frost condition of the freezer space (20) can be determined with greater accuracy compared to using a pre-prepared internal temperature (T0).

[0116] [3] In some embodiments, the refrigeration system (1) described in [2] above, wherein the control device (14) includes an internal humidity calculation unit (141) that calculates the internal humidity (H0), which is the humidity of the refrigeration space (20), based on the internal temperature (T0) measured by the internal temperature sensor (15) and the humidity (H1) of the circulating gas detected by the humidity sensor (13), and is configured to grasp the frost condition based on the internal humidity (H0) calculated by the internal humidity calculation unit (141).

[0117] According to the configuration described in [3] above, the internal humidity (H0) in the internal humidity calculation unit (141) can be used to determine the frost condition of the freezing space (20).

[0118] [4] In some embodiments, the refrigeration system (1) described in [1] to [3] above, wherein the control device (14) is configured to control the at least one flow path switching valve (12) such that the circulating gas flows through the at least one bypass line (11) when either the humidity (H1) of the circulating gas detected by the humidity sensor (13) or the internal humidity (H0) of the refrigeration space (20) determined based on the humidity (H1) of the circulating gas detected by the humidity sensor (13) exceeds a threshold.

[0119] According to the configuration described in [4] above, if either the humidity of the circulating gas (H1) detected by the humidity sensor (13) or the internal humidity (H0) determined from this humidity (H1) exceeds a threshold, there is a high probability that frost is forming in the refrigerated space (20). The refrigeration system (1) can automatically perform defrost operation of the refrigerator (3) by switching the flow path of the circulating gas with the flow path switching valve (12) when either the humidity (H1) or the internal humidity (H0) exceeds a threshold.

[0120] [5] In some embodiments, the refrigeration system (1) described in [1] to [4] above, wherein the at least one refrigerator (3) includes a plurality of refrigerators (3) configured to cool the circulating gas drawn in from the same refrigeration space (20), the refrigeration system (1) includes the humidity sensor (13) provided for each refrigerator (3), and the control device (1) is configured to control the at least one flow path switching valve (12) based on either the relative difference in the humidity (H1) of the circulating gas detected by the plurality of humidity sensors (13), or the relative difference in the internal humidity (H0), which is the humidity of the refrigeration space (20) as determined based on the humidity (H1) of the circulating gas detected by the plurality of humidity sensors (13).

[0121] According to the configuration described in [5] above, among the multiple refrigerators (3), the refrigerator (3) in which the humidity of the circulating gas detected by the humidity sensor (13), or the internal humidity (H0) determined from this humidity (H1), is significantly higher than that of the other refrigerators (3), is highly likely to have frost forming in the refrigerated space (20). The refrigeration system (1) can quickly determine the presence of frost in the refrigerated space (20) by comparing the above humidity (H1) or internal humidity (H0) of the multiple refrigerators (3), thereby improving the reliability of the refrigeration system (1).

[0122] [6] In some embodiments, the refrigeration system (1) described in [1] to [4] above comprises: an outlet temperature sensor (18) configured to measure an outlet temperature (T2), which is the temperature of the circulating gas flowing through the outlet line (7); and an inlet temperature sensor (19) configured to measure an inlet temperature (T3), which is the temperature of the circulating gas flowing upstream of the heat exchanger (8) in the inlet line (5), wherein the control device (14) is configured to control the at least one flow path switching valve (12) based on the refrigeration capacity of the refrigerator (3) as determined based on at least the outlet temperature (T2) measured by the outlet temperature sensor (18) and the inlet temperature (T3) measured by the inlet temperature sensor (19), and the frost condition of the refrigerated space (20) as determined based on at least the humidity (H0) of the circulating gas detected by the humidity sensor (13).

[0123] According to the configuration described in [6] above, if frost adheres to at least one of the inlet line (5) or the outlet line (7), the inflow and outflow of circulating gas into and out of the refrigerated space (20) is obstructed, which reduces the refrigeration performance of the chiller (3) and results in a small temperature difference between the inlet temperature (T3) and the outlet temperature (T2). The refrigeration system (1) can determine whether the abnormal humidity in the refrigerated space (20) is caused by frost adhering to the chiller (3) by understanding the refrigeration performance of the chiller (3) from the temperature difference between the inlet temperature (T3) and the outlet temperature (T2). As a result, the refrigeration system (1) can suppress unnecessary defrosting of the chiller (3), thereby improving the reliability of the refrigeration system (1).

[0124] [7] In some embodiments, the refrigeration system (1) described in [6] above, wherein the refrigerator (3) includes an electric motor (44) configured to generate a rotational force to rotate the compressor (41), the electric motor (44) configured to have a variable rotational speed, and the control device (14) is configured to control the rotational speed of the electric motor (44) based on the refrigeration capacity of the refrigerator (3) as determined based on the outlet temperature (T2) measured by the outlet temperature sensor (18) and the inlet temperature (T3) measured by the inlet temperature sensor (19), and the frost condition of the refrigerated space (20) as determined based on the humidity (H1) of the circulating gas detected by the humidity sensor (13).

[0125] According to the configuration described in [7] above, the refrigeration system (1) can perform defrost operation of the refrigerator (3) at an appropriate time based on the refrigeration capacity of the refrigerator (3) and the frost condition of the refrigerated space (20), and can also reduce the rotational speed of the electric motor (44) prior to the defrost operation compared to the rotational speed (rated rotational speed) of the refrigerator (3) during normal operation. As a result, the refrigeration system (1) can prevent the temperature of the warm air (circulating gas) introduced to the equipment and lines to be defrosted from becoming too high during the defrost operation of the refrigerator (3), thereby suppressing thermal fatigue and damage to the equipment and lines to be defrosted. By suppressing thermal fatigue and damage to the equipment and lines to be defrosted, the reliability of the refrigeration system (1) can be improved.

[0126] [8] In some embodiments, the refrigeration system (1) described in [1] to [7] above, wherein the refrigerator (3) includes an electric motor (44) configured to generate a rotational force to rotate the compressor (41), the electric motor (44) configured to have a variable rotational speed, and the control device (14) is configured to control the rotational speed of the electric motor (44) based on the frost condition of the refrigerated space (20) as determined based on the humidity (H1) of the circulating gas detected by the humidity sensor (13).

[0127] According to the configuration described in [8] above, the refrigeration system (1) can perform defrost operation of the refrigerator (3) at an appropriate time, and can lower the rotational speed of the electric motor (44) prior to the defrost operation compared to the rotational speed (rated rotational speed) during normal operation of the refrigerator (3). As a result, the refrigeration system (1) can prevent the temperature of the warm air (circulating gas) introduced to the equipment and lines to be defrosted from becoming too high during the defrost operation of the refrigerator (3), thereby suppressing heat-induced fatigue and damage to the equipment and lines to be defrosted. By suppressing heat-induced fatigue and damage to the equipment and lines to be defrosted, the reliability of the refrigeration system (1) can be improved.

[0128] [9] In some embodiments, the refrigeration system (1) described in [1] to [8] further comprises a notification device (21) configured to provide notification by at least one of light, text display, vibration or sound, wherein the control device (14) is configured to control notification by the notification device (21) based on the refrigeration capacity of the refrigerator (3) as determined based on at least the outlet temperature (T2) measured by the outlet temperature sensor (18) and the inlet temperature (T3) measured by the inlet temperature sensor (19), and the frost condition of the refrigerated space (20) as determined based on at least the humidity (H1) of the circulating gas detected by the humidity sensor (13).

[0129] According to the configuration described in [9] above, the refrigeration system (1) can notify the notification device (21) so that the defrost operation of the refrigerator (3) can be performed at an appropriate time based on the refrigeration capacity of the refrigerator (3) and the frost condition of the refrigerated space (20). In addition, the refrigeration system (1) can notify the notification device (21) that the defrost operation of the refrigerator (3) is being performed or is being performed.

[0130]

[10] In some embodiments, the refrigeration system (1) described in [1] to [8] further comprises a notification device (21) configured to provide notification by at least one of light, text display, vibration or sound, wherein the control device (14) is configured to control notification by the notification device (21) based on the frost condition of the refrigerated space (20) as determined based on the humidity (H1) of the circulating gas detected by the humidity sensor (13).

[0131] According to the configuration described in

[10] above, the refrigeration system (1) can notify the notification device (21) so that the defrost operation of the refrigerator (3) can be performed at an appropriate time based on the frost condition of the refrigerated space (20). In addition, the refrigeration system (1) can notify the notification device (21) that the defrost operation of the refrigerator (3) is being performed or is being performed.

[0132]

[11] In some embodiments, the refrigeration system (1) described in [1] to

[10] above, wherein the at least one bypass line (11) includes a heat exchanger-side bypass line (11A) for withdrawing the circulating gas from the compressed gas line (6) upstream of the heat exchanger (8) and leading it downstream of the heat exchanger (8) in the compressed gas line (6), and the at least one flow path switching valve (12) includes a first flow control valve (12A) provided in the heat exchanger-side bypass line (11A) and configured to adjust the flow rate of the circulating gas flowing through the heat exchanger-side bypass line (11A).

[0133] According to the configuration described in

[11] above, when the chiller (3) is in defrost operation, the refrigeration system (1) opens the first flow control valve (12A) provided in the heat exchanger-side bypass line (11A), allowing warm air (circulating gas) that has been compressed by the compressor (41) to become relatively hot and high-pressure to pass through the heat exchanger-side bypass line (11A) and be guided to the turbine (42) and outlet line (7). The warm air guided to the turbine (42) and outlet line (7) heats the turbine (42) and outlet line (7), melting any frost that has accumulated on them.

[0134]

[12] In some embodiments, the refrigeration system (1) described in

[11] further comprises a cold storage side bypass line (11D) for extracting the circulating gas from the outlet line (7) and leading it upstream of the heat exchanger (8) in the inlet line (5), and the at least one flow path switching valve (12) further comprises a second flow control valve (17) configured to adjust the flow rate of the circulating gas flowing through the cold storage side bypass line (11D).

[0135] According to the configuration described in

[12] above, the refrigeration system (1) can melt frost attached to the turbine (42) and outlet line (7) by increasing the flow rate of circulating gas flowing through the heat exchanger-side bypass line (11A) using the first flow control valve (12A). The refrigeration system (1) can melt frost attached downstream of the connection between the heat exchanger (8) and the inlet line (5) and the cold storage-side bypass line (11D) by increasing the flow rate of circulating gas flowing through the cold storage-side bypass line (11D) using the second flow control valve (17).

[0136] 1 Refrigeration system 2 Cold storage warehouse 3 Refrigerator 4 Turbomachinery 5 Inlet line 6 Compressed gas line 7 Outlet line 8 Heat exchanger 9 Cooler 11 Bypass line 11A Heat exchanger side bypass line 11D Cold storage warehouse side bypass line 12 Flow path switching valve 12A First flow control valve 13 Humidity sensor 14 Control device 15 Internal temperature sensor 16 Compressor inlet temperature sensor 17 Second flow path switching valve 18 Outlet temperature sensor 19 Inlet temperature sensor 21 Notification device H0 Internal humidity H1 Compressor inlet humidity T0 Internal temperature T1 Compressor inlet temperature T2 Outlet temperature T3 Inlet temperature

Claims

1. A refrigeration system comprising: a cold storage warehouse having a cold storage space to be cooled inside; and at least one chiller configured to cool circulating gas drawn in from the cold storage space, wherein the chiller includes: a compressor configured to compress the circulating gas; a turbine configured to expand the circulating gas; an inlet line for leading the circulating gas from the cold storage space to the compressor; a compressed gas line for leading the compressed gas, which is the circulating gas compressed by the compressor, to the turbine; an outlet line for leading the circulating gas, which has been expanded by the turbine, to the cold storage space; a heat exchanger configured to perform heat exchange between the circulating gas flowing through the inlet line and the compressed gas flowing through the compressed gas line; and at least one bypass line for drawing out the circulating gas from the compressed gas line upstream of the heat exchanger and leading it to at least one of the following: the compressed gas line downstream of the heat exchanger, the outlet line, or the inlet line upstream of the heat exchanger. A refrigeration system comprising: at least one flow path switching valve configured to switch the flow path of the circulating gas in the refrigerator so that the circulating gas flows through at least one bypass line, the refrigeration system further comprising: a humidity sensor configured to detect the humidity of the circulating gas flowing downstream of the heat exchanger in the inlet line; and a control device configured to control the at least one flow path switching valve based on the frost condition of the refrigerated space, which is determined based on the humidity of the circulating gas detected by at least the humidity sensor.

2. The refrigeration system according to claim 1, further comprising an internal temperature sensor configured to measure the internal temperature, which is the temperature of the refrigerated space, wherein the control device is configured to determine the frost condition based on the internal temperature measured by the internal temperature sensor and the humidity of the circulating gas detected by the humidity sensor.

3. The refrigeration system according to claim 2, wherein the control device includes an internal humidity calculation unit that calculates the internal humidity, which is the humidity of the refrigerated space, based on the internal temperature measured by the internal temperature sensor and the humidity of the circulating gas detected by the humidity sensor, and is configured to determine the frost condition based on the internal humidity calculated by the internal humidity calculation unit.

4. The refrigeration system according to any one of claims 1 to 3, wherein the control device is configured to control at least one flow path switching valve so that the circulating gas flows through at least one bypass line when either the humidity of the circulating gas detected by the humidity sensor or the humidity inside the storage chamber, which is the humidity of the refrigerated space determined based on the humidity of the circulating gas detected by the humidity sensor, exceeds a threshold.

5. The refrigeration system according to any one of claims 1 to 3, wherein the at least one refrigerator includes a plurality of refrigerators configured to cool the circulating gas drawn in from the same refrigerated space, the refrigeration system comprises a humidity sensor provided for each refrigerator, and the control device is configured to control the at least one flow path switching valve based on either the relative difference in the humidity of the circulating gas detected by the plurality of humidity sensors, or the relative difference in the humidity inside the refrigerated space, which is the humidity of the refrigerated space as determined based on the humidity of the circulating gas detected by the plurality of humidity sensors.

6. A refrigeration system according to any one of claims 1 to 3, comprising: an outlet temperature sensor configured to measure the outlet temperature, which is the temperature of the circulating gas flowing through the outlet line; and an inlet temperature sensor configured to measure the inlet temperature, which is the temperature of the circulating gas flowing upstream of the heat exchanger in the inlet line, wherein the control device is configured to control at least one flow path switching valve based on the refrigeration capacity of the chiller, which is determined based on the outlet temperature measured by the outlet temperature sensor and the inlet temperature measured by the inlet temperature sensor, and the frost condition of the chilled space, which is determined based on the humidity of the circulating gas detected by at least the humidity sensor.

7. The refrigeration system according to claim 6, wherein the refrigerator includes an electric motor configured to generate a rotational force for rotating the compressor, the electric motor being configured to have a variable rotational speed, and the control device is configured to control the rotational speed of the electric motor based on the refrigeration capacity of the refrigerator, which is determined based on the outlet temperature measured by the outlet temperature sensor and the inlet temperature measured by the inlet temperature sensor, and the frost condition of the refrigerated space, which is determined based on the humidity of the circulating gas detected by the humidity sensor.

8. The refrigeration system according to any one of claims 1 to 3, wherein the refrigerator includes an electric motor configured to generate a rotational force for rotating the compressor, the electric motor being configured to have a variable rotational speed, and the control device is configured to control the rotational speed of the electric motor based on the frost condition of the refrigerated space, which is determined based on the humidity of the circulating gas detected by the humidity sensor.

9. The refrigeration system according to claim 6, further comprising a notification device configured to provide notification by at least one of light, text display, vibration or sound, wherein the control device is configured to control notification by the notification device based on the refrigeration capacity of the refrigerator, which is determined based on at least the outlet temperature measured by the outlet temperature sensor and the inlet temperature measured by the inlet temperature sensor, and the frost condition of the refrigerated space, which is determined based on at least the humidity of the circulating gas detected by the humidity sensor.

10. The refrigeration system according to any one of claims 1 to 3, further comprising a notification device configured to provide notification by at least one of light, text display, vibration or sound, wherein the control device is configured to control notification by the notification device based on the frost condition of the refrigerated space, which is determined based on the humidity of the circulating gas detected by the humidity sensor.

11. The refrigeration system according to any one of claims 1 to 3, wherein the at least one bypass line includes a heat exchanger-side bypass line for withdrawing the circulating gas from the compressed gas line upstream of the heat exchanger and leading it downstream of the heat exchanger in the compressed gas line, and the at least one flow path switching valve includes a first flow control valve provided in the heat exchanger-side bypass line and configured to adjust the flow rate of the circulating gas flowing through the heat exchanger-side bypass line.

12. The refrigeration system according to claim 11, wherein the at least one bypass line further includes a cold storage side bypass line for extracting the circulating gas from the outlet line and leading it upstream of the heat exchanger in the inlet line, and the at least one flow path switching valve further includes a second flow control valve configured to adjust the flow rate of the circulating gas flowing through the cold storage side bypass line.

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