Refrigeration system

Abstract

This refrigeration system comprises a refrigerated warehouse that has a refrigeration space and a refrigerator that is capable of cooling a gas which is taken in from the refrigeration space. The refrigerator includes: an inlet line that guides gas from the refrigeration space to a compressor; a compressed gas line that guides the gas from the compressor to a turbine; an outlet line that guides the gas from the turbine to the refrigeration space; and a heat exchanger that exchanges heat between the gas which flows through the inlet line and the gas which flows through the compressed gas line. The refrigeration system further comprises: a humidity sensor that is configured to detect compressor inlet humidity, which is the humidity of circulated gas which flows through the inlet line downstream of the heat exchanger; and a frost formation detection section that is configured to detect the presence or absence of frost formation in the refrigeration space on the basis of at least the compressor inlet humidity detected by the humidity sensor.

Description

Refrigeration system

[0001] The present disclosure relates to a refrigeration system. The present application claims priority based on Japanese Patent Application No. 2025-049468 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 refrigeration warehouse having a refrigeration space, which is an object to be cooled, inside thereof, and an air refrigerant refrigeration apparatus for cooling air extracted from the refrigeration space. Patent Document 1 discloses that a defroster is provided in a pipe connecting an expansion turbine and a refrigeration warehouse in order to remove frost formed by condensation in an air refrigerant that has been adiabatically expanded by the expansion turbine and cooled to a low temperature.

[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 melting the adhered frost (defrosting), but 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 detecting the presence or absence of frost formation in a refrigeration space.

[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 inside, and a 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, and 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 further comprises a humidity sensor configured to detect compressor inlet humidity, which is the humidity of the circulating gas flowing downstream of the heat exchanger in the inlet line, and a frost detection unit configured to detect the presence or absence of frost in the cold storage space based at least on the compressor inlet humidity detected by the humidity sensor.

[0007] According to at least one embodiment of the present disclosure, a refrigeration system is provided that can detect the presence or absence of frost in a refrigerated space.

[0008] This is a schematic diagram illustrating a refrigeration system according to one embodiment of the present disclosure. This is a schematic configuration diagram illustrating 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 frost formation in the refrigerated space. This is an explanatory diagram for explaining the relationship between the internal temperature, compressor inlet temperature, compressor inlet humidity, and frost formation in the refrigerated space. This is an explanatory diagram for explaining an example of rotational speed control of a refrigeration system according to one embodiment of the present disclosure. This is an explanatory diagram for explaining an example of rotational speed control of a refrigeration system according to one embodiment of the present disclosure. This is a schematic perspective view of a refrigeration system (refrigerated container) according to one embodiment of the present disclosure.

[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 a refrigerator 3 configured to cool circulating gas (for example, air) 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] Some embodiments of the refrigeration system 1 further include a humidity sensor 11 and a control device 30, as shown in Figure 1.

[0028] (Humidity Sensor) The humidity sensor 11 is configured to detect the compressor inlet humidity H1 (relative humidity [RH (%)]), which is the humidity of the circulating gas flowing downstream of the heat exchanger 8 in the inlet line 5. The humidity sensor 11 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. The compressor inlet temperature T1, which is the temperature of the circulating gas flowing downstream of the heat exchanger 8 in the inlet line 5 during the normal operation of the chiller 3, is at ambient temperature (0°C to 40°C), making it suitable for humidity detection. In contrast, the temperature of the circulating gas flowing in the chilled space 20, upstream of the heat exchanger 8 in the inlet line 5, and in the outlet line 7 during the operation of the chiller 3 is relatively low (below 0°C), making it unsuitable for humidity detection. Furthermore, the circulating gas flowing through the compressed gas line 6 during the operation of the refrigerator 3 has different properties than before it was compressed by the compressor 41, and therefore is not suitable for understanding the frost formation state in the refrigerated space 20.

[0029] (Control device) The control device 30 is configured to detect whether or not frost has formed in the refrigerated space 20 based on the compressor inlet humidity H1 detected by at least the humidity sensor 11. Here, whether or not frost has formed in the refrigerated space 20 is information (parameter) indicating whether or not frost has formed in the refrigerated space 20.

[0030] Figure 2 is a schematic diagram illustrating the configuration of the control device 30 shown in Figure 1. The control device (controller) 30 is an electronic control unit for controlling the drive of equipment mounted on the refrigeration system 1, such as the electric motor 44 and the notification device 21. As shown in Figure 2, the control device 30 may be configured as a microcomputer including an input device 301 (input interface), an output device 302 (output interface), a storage device 303 (memory such as ROM or RAM, external storage device, etc.), and an arithmetic unit 304 (CPU). The control device 30 achieves drive control of 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.

[0031] The control device 30 receives various signals from sensors installed in the refrigeration system 1, such as the humidity sensor 11, the internal temperature sensor 12, the compressor inlet temperature sensor 13, the turbine inlet temperature sensor 14, and the turbine outlet temperature sensor 15, via the input device 301 to the storage device 303 and the arithmetic unit 304. The storage device 303 stores various signals from the sensors installed in the refrigeration system 1. The storage device 303 also stores information used when executing various controls in the arithmetic unit 304. The arithmetic unit 304 is configured to execute various controls according to the control programs stored in the storage device 303.

[0032] In the illustrated embodiment, the control device 30 includes a frost detection unit 101, a rotation speed control unit 102, and a notification control unit 103, as shown in Figure 2.

[0033] (Frost detection unit) In some embodiments, the frost detection unit 101 is configured to calculate the internal humidity H0 (relative humidity [RH (%)]), which is the humidity of the freezing space 20, based on the compressor inlet humidity H1 (relative humidity [RH (%)]), which is the humidity of the circulating gas detected by the humidity sensor 11.

[0034] The frost detection unit 101 may be configured to calculate the internal humidity H0 from the measured value of the compressor inlet humidity H1, based on association information (first association information) which associates at least the internal humidity H0 and the compressor inlet humidity H1.

[0035] The first association information indicates the correspondence between the internal humidity H0 and the compressor inlet humidity H1. It is sufficient if, 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 may include lists, tables, maps, functions, machine learning models, intensity analysis models, etc., that show the correspondence between the above input information and the above output information. The above association information may also be created based on numerical analysis results.

[0036] The frost detection unit 101 may be configured to calculate the internal humidity H0 from the measured value of the compressor inlet humidity H1, based on association information (second association information) which associates the internal humidity H0, the compressor inlet humidity H1, the internal temperature T0, and the compressor inlet temperature T1.

[0037] The second association information shows the correspondence between the internal humidity H0, the compressor inlet humidity H1, the internal temperature T0, and the compressor inlet temperature T1. It is sufficient 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 refrigerated space 20, and the compressor inlet temperature T1 is the temperature of the circulating gas flowing downstream of the heat exchanger 8 in the inlet line 5. The second association information may include lists, tables, maps, functions, machine learning models, intensity analysis models, etc., that show the correspondence between the above input information and the above output information. The above association information may also be created based on numerical analysis results.

[0038] The frost detection unit 101 may use pre-defined values ​​for the internal temperature T0 and compressor inlet temperature T1, which are parameters used in the second association information. These pre-defined values ​​may be set based on actual measured values ​​during normal operation of the refrigerator 3 in the past or actual measured values ​​during normal operation of the same model of refrigerator 3, or they may be set based on the numerical analysis results of the refrigerator 3. In this case, the refrigeration system 1 does not need to be equipped with an internal temperature sensor 12 (see Figure 1) configured to measure the internal temperature T0, or a compressor inlet temperature sensor 13 (see Figure 1) configured to measure the compressor inlet temperature T1. This can suppress the complexity of the structure and control of the refrigeration system 1, as well as the increase in the manufacturing cost of the refrigeration system 1.

[0039] The pre-prepared values ​​for the internal temperature T0 or compressor inlet temperature T1 may be stored in the storage device 303 for reference along with the second association information, and may be referenced by the frost detection unit 101. Alternatively, the pre-prepared values ​​for the internal temperature T0 or compressor inlet temperature T1 may be stored in the storage device 303 for reference while incorporated into the second association information, and may be used when the frost detection unit 101 references the second association information.

[0040] Figure 3 is an explanatory diagram illustrating the relationship between the internal temperature T0, internal humidity H0, and the frost formation state in the freezing space 20. Figure 3 shows a graph with the internal temperature T0 on the horizontal axis and absolute humidity AH [SH (kg / kg)], a parameter indicating the amount of water vapor contained in the circulating gas, on the vertical axis. Curve L1 shown in Figure 3 represents an internal humidity H0 of 100%.

[0041] The internal humidity H0 calculated by the frost detection unit 101 is a parameter that indicates the frost state of the freezing space 20. As shown in Figure 3, when the internal humidity H0 is 100% (the threshold for internal humidity) or higher (belonging to the region 20A above curve L1 in Figure 3), the frost state of the freezing space 20 can be considered to be a state where frost has formed in the freezing space 20 (defrosting required). In this case, the frost detection unit 101 detects frost in the freezing space 20.

[0042] When the internal humidity H0 is less than 100% (belonging to region 20B below curve L1 in Figure 3), the frost condition of the freezing space 20 can be considered as a state where there is no frost in the freezing space 20 (not subject to defrosting). In this case, the frost detection unit 101 does not detect frost in the freezing space 20. In this embodiment, the freezing system 1 can determine the frost condition (presence or absence of frost) of the freezing space 20 by calculating the internal humidity H0 in the frost detection unit 101.

[0043] 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%.

[0044] The refrigeration system 1 according to the present embodiment can detect the presence or absence of frost formation in a refrigeration space 20 based on at least the compressor inlet humidity H1 detected by a humidity sensor 11. Since such a refrigeration system 1 can perform defrosting of the refrigerator 3 at an appropriate timing, it can suppress performance degradation caused by heat loss that occurs when the refrigerator 3 is heated during defrosting.

[0045] A refrigeration system 1 according to some embodiments includes an internal temperature sensor 12 configured to measure an internal temperature T0. The frost formation detection unit 101 described above is configured to detect the presence or absence of frost formation in the refrigeration space 20 based on the measured value of the compressor inlet humidity H1 detected by the humidity sensor 11 and the measured value of the internal temperature T0 measured by the internal temperature sensor 12.

[0046] In the present embodiment, the measured value of the internal temperature sensor 12 is used as the internal temperature T0, which is a parameter used in the second association information. Further, a value prepared in advance is used as the compressor inlet temperature T1, which is a parameter used in the second association information.

[0047] The refrigeration system 1 according to the present embodiment uses the internal temperature T0 measured by the internal temperature sensor 12 as a parameter for grasping the frost formation state in the refrigeration space 20, so that the frost formation state in the refrigeration space 20 can be grasped more accurately than when using a pre-prepared internal temperature T0.

[0048] A refrigeration system 1 according to some embodiments includes a compressor inlet temperature sensor 13 configured to measure a compressor inlet temperature T1. The frost formation detection unit 101 described above is configured to detect the presence or absence of frost formation in the refrigeration space 20 based on the measured value of the compressor inlet humidity H1 detected by the humidity sensor 11 and the measured value of the compressor inlet temperature T1 measured by the compressor inlet temperature sensor 13.

[0049] In this embodiment, the compressor inlet temperature T1, a parameter used in the second association information, is set to use the measurement value from the compressor inlet temperature sensor 13. Furthermore, the internal temperature T0, another parameter used in the second association information, is set to use a pre-defined value.

[0050] In this embodiment, the refrigeration system 1 uses the compressor inlet temperature T1 measured by the compressor inlet temperature sensor 13 as a parameter for understanding the frost formation state of the refrigerated space 20. Compared to using a pre-prepared compressor inlet temperature T1, this allows for a more accurate understanding of the frost formation state of the refrigerated space 20.

[0051] In some embodiments of the refrigeration system 1, the frost detection unit 101 described above is configured to detect the presence or absence of frost in the refrigerated space 20 based on the measured value of the compressor inlet humidity H1 detected by the humidity sensor 11, the measured value of the internal temperature T0 measured by the internal temperature sensor 12, and the measured value of the compressor inlet temperature T1 measured by the compressor inlet temperature sensor 13.

[0052] In this embodiment, the internal temperature T0 parameter used in the second association information is the measurement value from the internal temperature sensor 12. Also, the compressor inlet temperature T1 parameter used in the second association information is the measurement value from the compressor inlet temperature sensor 13.

[0053] The refrigeration system 1 according to this embodiment uses the internal temperature T0 measured by the internal temperature sensor 12 and the compressor inlet temperature T1 measured by the compressor inlet temperature sensor 13 as parameters for understanding the frost state of the refrigerated space 20. Compared to using pre-prepared internal temperature T0 and compressor inlet temperature T1, this system can understand the frost state of the refrigerated space 20 with greater accuracy.

[0054] As described above, the humidity sensor 11 can determine the internal humidity H0 and the frost formation state of the freezing space 20 from the humidity H1 of the circulating gas detected. The information that associates the internal humidity H0 with the frost formation state of the freezing space 20 includes the boundary between the state in the freezing space 20 where frost has formed and the state where frost has not formed, and the internal humidity H0 corresponding to this boundary.

[0055] By integrating the aforementioned association information (first association information or second association information) with the information relating the internal humidity H0 to the frost formation state of the freezing space 20, information directly relating the compressor inlet humidity H1 to the frost formation state of the freezing space 20 can be obtained. This information directly relating the compressor inlet humidity H1 to the frost formation state of the freezing space 20 may include not only the humidity H1 of the circulating gas detected by the humidity sensor 11, but also at least one of the internal temperature T0 measured by the internal temperature sensor 12 or the compressor inlet temperature T1 measured by the compressor inlet temperature sensor 13 as additional input information.

[0056] The frost detection unit 101 may be configured to obtain whether or not frost has formed in the refrigerated space 20 from at least the humidity H1 of the circulating gas detected by the humidity sensor 11, based on information that directly correlates the compressor inlet humidity H1 with the frost state in the refrigerated space 20.

[0057] Figure 4 is an explanatory diagram illustrating the relationship between the internal temperature T0, the compressor inlet temperature T1, the compressor inlet humidity H1, and the frost formation state in the freezing space 20. In Figure 4, a graph is shown with the temperature difference between the compressor inlet temperature T1 and the internal temperature T0 on the horizontal axis and the compressor inlet humidity H1 on the vertical axis. Curves L2, L3, and L4 shown in Figure 4 represent a compressor inlet humidity H1 of 100% for each compressor inlet temperature T1. Curve L3 shows a compressor inlet temperature T1 higher than curve L2, and curve L4 shows a compressor inlet temperature T1 lower than curve L2.

[0058] As shown in Figure 4, when the compressor inlet humidity H1 is 100% or higher, the frost condition in the refrigerated space 20 can be considered to be a state where frost has formed in the refrigerated space 20 (defrosting required). In this case, the frost detection unit 101 detects frost in the refrigerated space 20.

[0059] If the compressor inlet humidity H1 is less than 100%, the frost condition in the freezing space 20 can be considered as a state where there is no frost in the freezing space 20 (not subject to defrosting). In this case, the frost detection unit 101 does not detect frost in the freezing space 20. In this embodiment, the freezing system 1 can determine the frost condition (presence or absence of frost) in the freezing space 20 without the frost detection unit 101 calculating the internal humidity H0.

[0060] In some embodiments of the refrigeration system 1, the frost detection unit 101 described above is configured to detect the presence or absence of frost in the refrigerator 3 based on information (see Figure 4) showing the correlation between the temperature difference between the compressor inlet temperature T1 and the internal temperature T0 for each compressor inlet temperature T1, and the compressor inlet humidity H1.

[0061] The frost detection unit 101 can detect the presence or absence of frost in the freezing space 20 from the compressor inlet temperature T1, the internal temperature T0, and the compressor inlet humidity H1 by using information that shows the correlation between the temperature difference between the compressor inlet temperature T1 and the internal temperature T0 for each compressor inlet temperature T1, and the compressor inlet humidity H1.

[0062] The refrigeration system 1 according to this embodiment can improve detection accuracy by detecting the frost state of the refrigerated space 20 based on information showing the correlation between the temperature difference between the compressor inlet temperature T1 and the internal temperature T0 for each compressor inlet temperature T1, and the compressor inlet humidity H1. Furthermore, the refrigeration system 1 according to this embodiment can reduce the computational load when detecting the frost state of the refrigerated space 20 by simplifying the logic for detecting the frost state of the refrigerated space 20.

[0063] In some embodiments, the electric motor 44 described above is configured to have a variable rotational speed. The refrigeration system 1 includes a rotational speed control unit 102 for controlling the rotational speed of the electric motor 44, which is configured to reduce the rotational speed of the electric motor 44 when frost formation on the refrigerator 3 is detected.

[0064] In this embodiment, the refrigeration system 1 can reduce the amount of frost drawn into the turbomachinery 4, including the compressor 41 and turbine 42, by lowering the rotation speed of the electric motor 44 when frost formation in the refrigerated space 20, thereby suppressing ice formation on the turbomachinery 4.

[0065] Figure 5 is an explanatory diagram illustrating an example of rotational speed control of a refrigeration system 1 according to one embodiment of the present disclosure. Figure 5 shows a graph with time elapsed on the horizontal axis and compressor inlet humidity H1 or internal humidity H0 on the vertical axis. In some embodiments of the refrigeration system 1, the rotational speed control unit 102 described above is configured to reduce the rotational speed of the electric motor 44 when the amount of increase over time of the compressor inlet humidity H1 (increase per unit time), or the amount of increase over time of the internal humidity H0, which is the humidity of the refrigerated space 20 as determined from the compressor inlet humidity H1 (increase per unit time), exceeds a predetermined amount, as shown in Figure 5.

[0066] The refrigeration system 1 according to this embodiment can improve the accuracy of detecting the presence or absence of frost on the refrigerator 3 by monitoring the increase in compressor inlet humidity H1 over time, or the increase in internal humidity H0 over time. The refrigeration system 1 detects that if the increase in compressor inlet humidity H1 over time, or the increase in internal humidity H0 over time, exceeds a predetermined amount, there is a high probability that frost has formed in the refrigerated space 20. For this reason, the refrigeration system 1 suppresses ice formation on the turbomachinery 4 by reducing the rotation speed of the electric motor 44.

[0067] In some embodiments of the refrigeration system 1, the rotational speed control unit 102 described above is configured to reduce the rotational speed of the electric motor 44 when the turbine inlet humidity H2, which is the humidity of the circulating gas flowing downstream of the heat exchanger 8 in the compressed gas line 6 and is calculated based on the measurement value H1 of the humidity sensor 11, is equal to or greater than the threshold TH2 of the turbine inlet humidity (for example, 100%). The rotational speed control unit 102 may calculate the turbine inlet humidity H2 from the measurement value H1 of the humidity sensor 11 based on information (for example, a conversion formula) that shows the correlation between the compressor inlet humidity H1 and the turbine inlet humidity H2. The threshold TH2 is not limited to the case where the turbine inlet humidity H2 is 100%, but may be a predetermined humidity with a margin on the high humidity side or low humidity side relative to 100%.

[0068] In this embodiment of the refrigeration system 1, when the turbine inlet humidity H2 is equal to or greater than the threshold TH2, there is a high probability that frost will form in the refrigerated space 20 located downstream of the turbine 42 in the flow direction of the circulating gas. For this reason, the refrigeration system 1 suppresses ice formation on the turbomachinery 4 by reducing the rotational speed of the electric motor 44. In this embodiment of the refrigeration system 1, the computational load when detecting the frost state in the refrigerated space 20 can be reduced by simplifying the logic for detecting the frost state in the refrigerated space 20.

[0069] In some embodiments of the refrigeration system 1, the rotational speed control unit 102 described above is configured to reduce the rotational speed of the electric motor 44 when the turbine outlet humidity H3, which is the humidity of the circulating gas flowing through the outlet line 7 calculated based on the measurement value H1 of the humidity sensor 11, is equal to or greater than a threshold TH3 for the turbine outlet humidity (for example, 100%). The rotational speed control unit 102 may calculate the turbine outlet humidity H3 from the measurement value H1 of the humidity sensor 11 based on information (for example, a conversion formula) that shows the correlation between the compressor inlet humidity H1 and the turbine outlet humidity H3. The threshold TH3 is not limited to the case where the turbine outlet humidity H3 is 100%, but may be a predetermined humidity with a margin on the high humidity side or low humidity side relative to 100%.

[0070] In this embodiment of the refrigeration system 1, when the turbine outlet humidity H3 is equal to or greater than the threshold TH3, there is a high probability that frost will form in the refrigerated space 20 located downstream of the turbine 42 in the flow direction of the circulating gas. For this reason, the refrigeration system 1 suppresses ice formation on the turbomachinery 4 by reducing the rotational speed of the electric motor 44. In this embodiment of the refrigeration system 1, the computational load when detecting the frost state in the refrigerated space 20 can be reduced by simplifying the logic for detecting the frost state in the refrigerated space 20.

[0071] Figure 6 is an explanatory diagram illustrating an example of rotational speed control of a refrigeration system according to one embodiment of the present disclosure. In some embodiments of the refrigeration system 1, as shown in Figure 1, a turbine inlet temperature sensor 14 is configured to measure the turbine inlet temperature T2, which is the temperature of the circulating gas flowing downstream of the heat exchanger 8 in the compressed gas line 6. As shown in Figure 6, the rotational speed control unit 102 described above is configured to set the rotational speed of the electric motor 44 to a rotational speed lower than the rated rotational speed (step S2) when the turbine inlet humidity H2, calculated based on the measured value H1 of the humidity sensor 11, is equal to or greater than the threshold turbine inlet humidity TH2 (e.g., 100%) and the measured value of the turbine inlet temperature T2 is equal to or greater than the threshold turbine inlet temperature TT2 (e.g., 0°C) ("Yes" in step S1 of Figure 6).

[0072] The threshold TH2 is not limited to the case where the turbine inlet humidity H2 is 100%, but may be a predetermined humidity with a margin on the higher or lower side relative to 100%. The threshold TT2 is not limited to the case where the turbine inlet temperature T2 is 0°C, but may be a predetermined temperature with a margin on the higher or lower side relative to 0°C.

[0073] In this embodiment of the refrigeration system 1, if the turbine inlet humidity H2 is greater than or equal to the threshold TH2 and the measured value of the turbine inlet temperature T2 is greater than or equal to the threshold TT2, there is a high possibility that frost will form in the refrigerated space 20 located downstream of the turbine 42 in the direction of circulating gas flow. For this reason, the refrigeration system 1 suppresses ice formation on the turbomachinery 4 by setting the rotational speed of the electric motor 44 to a rotational speed lower than the rated rotational speed.

[0074] As shown in Figure 6, the rotational speed control unit 102 described above is configured to set the rotational speed of the electric motor 44 to the rated rotational speed (step S3) when the turbine inlet humidity H2 is less than the turbine inlet humidity threshold TH2 (e.g., 100%) or the measured value of the turbine inlet temperature T2 is less than the turbine inlet temperature threshold TT2 (e.g., 0°C) (indicated as "No" in step S1 of Figure 6).

[0075] In this embodiment, the refrigeration system 1 is configured such that if the turbine inlet humidity H2 is less than the threshold TH2, or the measured turbine inlet temperature T2 is less than the threshold TT2, the moisture in the circulating gas is likely to be in a liquid state. Therefore, the refrigeration system 1 is configured to suppress ice formation on the turbomachinery 4 by setting the rotation speed of the electric motor 44 to its rated speed and quickly sending liquid to the downstream side of the turbine 42.

[0076] Figure 7 is an explanatory diagram illustrating an example of rotational speed control of a refrigeration system 1 according to one embodiment of the present disclosure. In some embodiments of the refrigeration system 1, as shown in Figure 1, the above-mentioned turbine inlet temperature sensor 14 and a turbine outlet temperature sensor 15 configured to measure the turbine outlet temperature T3, which is the temperature of the circulating gas flowing through the outlet line 7. The above-mentioned rotational speed control unit 102 is configured to increase the rotational speed of the electric motor 44 when the turbine outlet conditions are met, such that the turbine outlet humidity H3, which is the humidity of the circulating gas flowing through the outlet line 7 calculated based on the measurement value H1 of the humidity sensor 11, is equal to or greater than the turbine outlet humidity threshold TH3 (e.g., 100%), and the measured value of the turbine outlet temperature T3 is equal to or greater than the turbine outlet temperature threshold TT3 (e.g., 0°C) ("Yes" in step S10 of Figure 7) (step S20).

[0077] The threshold TH3 is not limited to the case where the turbine outlet humidity H3 is 100%, but may be a predetermined humidity with a margin on the higher or lower side relative to 100%. The threshold TT3 is not limited to the case where the turbine outlet temperature T3 is 0°C, but may be a predetermined temperature with a margin on the higher or lower side relative to 0°C.

[0078] In this embodiment of the refrigeration system 1, when the turbine outlet humidity H3 is equal to or greater than the threshold TH3 and the measured value of the turbine outlet temperature T3 is equal to or greater than the threshold TT3, there is a high probability that the moisture in the circulating gas is in a liquid state. Therefore, the refrigeration system 1 increases the rotational speed of the electric motor 44 to quickly send liquid to the downstream side of the turbine 42, thereby suppressing ice formation on the turbomachinery 4.

[0079] The rotational speed control unit 102 described above is configured to reduce the rotational speed of the electric motor 44 when the turbine outlet conditions are not met (No in step S10 of Figure 7), and when the turbine inlet humidity H2, which is the humidity of the circulating gas flowing downstream of the heat exchanger 8 in the compressed gas line 6 calculated based on the measurement value H1 of the humidity sensor 11, is equal to or greater than the turbine inlet humidity threshold TH2 (e.g., 100%), and the measured value of the turbine inlet temperature T2 is equal to or greater than the turbine inlet temperature threshold TT2 (e.g., 0°C) (Yes in step S30) (step S40).

[0080] The threshold TH2 is not limited to the case where the turbine inlet humidity H2 is 100%, but may be a predetermined humidity with a margin on the higher or lower side relative to 100%. The threshold TT2 is not limited to the case where the turbine inlet temperature T2 is 0°C, but may be a predetermined temperature with a margin on the higher or lower side relative to 0°C.

[0081] In this embodiment of the refrigeration system 1, if the turbine inlet humidity H2 is greater than or equal to the threshold TH2 and the measured value of the turbine inlet temperature T2 is greater than or equal to the threshold TT2, there is a high possibility that frost will form in the refrigerated space 20 located downstream of the turbine 42 in the direction of circulating gas flow. For this reason, the refrigeration system 1 is configured to suppress ice formation on the turbomachinery 4 by reducing the rotational speed of the electric motor 44.

[0082] The rotational speed control unit 102 described above is configured to increase the rotational speed of the electric motor 44 when the turbine outlet conditions are not met (No in step S10 of Figure 7), and when the turbine inlet humidity H2, which is the humidity of the circulating gas flowing downstream of the heat exchanger 8 in the compressed gas line 6 calculated based on the measurement value H1 of the humidity sensor 11, is less than the turbine inlet humidity threshold TH2 (e.g., 100%), or when the measured value of the turbine inlet temperature T2 is less than the turbine inlet temperature threshold TT2 (e.g., 0°C) (No in step S30) (step S50).

[0083] In this embodiment, the refrigeration system 1 suppresses ice formation on the turbomachinery 4 by setting the rotation speed of the electric motor 44 to its rated speed and quickly sending circulating gas to the downstream side of the turbine 42 when the measured value of the turbine inlet humidity H2 is less than the threshold TH2, or the measured value of the turbine inlet temperature T2 is less than the threshold TT2 for the turbine inlet temperature.

[0084] Figure 8 is a schematic perspective view of a refrigeration system 1 (refrigerated container 1A) according to one embodiment of the present disclosure. In some embodiments of the refrigeration system 1, as shown in Figure 8, the above-mentioned refrigerated warehouse 2 is the container body 2A of the refrigerated container 1A, and the above-mentioned refrigeration unit 3 is configured to be housed in the container body 2A having an internal space (refrigerated space 20) with a width of 2.3 m and a height of 2.9 m.

[0085] As shown in Figure 1, the container body 2A has a plurality of walls 201 to 204 and is formed in a rectangular cylindrical shape that extends along the longitudinal direction of the container body 2A. Hereinafter, the horizontal direction perpendicular to the longitudinal direction of the container body 2A is defined as the width direction of the container body 2A. The plurality of walls 201 to 204 include a ceiling wall 201 that extends along a direction perpendicular to the height direction of the container body 2A, a bottom wall 202 that extends below the ceiling wall 201 along a direction perpendicular to the height direction of the container body 2A, and a pair of long side walls 203, 204 that are spaced apart from each other and each connects the ceiling wall 201 and the bottom wall 202.

[0086] The refrigerated space 20 is defined by the inner surfaces of multiple walls 201 to 204. The refrigerated space 20 can accommodate cargo, etc. The container body 2A may be a transport container used for transporting cargo, etc. The container body 2A may be a standard transport container such as a 10ft container, a 20ft container, or a 40ft container.

[0087] 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, text display, vibration, or sound, as shown in Figures 1 and 2. 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 text can be displayed, a vibration device capable of generating vibration, or a speaker capable of outputting sound or voice.

[0088] In some embodiments, the control device 30 described above includes a notification control unit 103 configured to control notification by the notification device 21 based on the frost formation state of the refrigerated space 20, which is determined based on the humidity H1 of the circulating gas detected by the humidity sensor 11.

[0089] In this embodiment, the refrigeration system 1 can have the notification control unit 103 notify the notification device 21 so that when frost formation in the refrigerated space 20 is detected, the defrost operation of the refrigerator 3 can be performed quickly.

[0090] 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.

[0091] 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.

[0092] The contents described in some of the embodiments above can be understood, for example, as follows:

[0093] [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 a 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), and further comprises a humidity sensor (11) configured to detect a compressor inlet humidity (H1), which is the humidity of the circulating gas flowing downstream of the heat exchanger (8) in the inlet line (5), and a frost detection unit (101) configured to detect the presence or absence of frost in the refrigerated space (20) based at least on the compressor inlet humidity (H1) detected by the humidity sensor (11).

[0094] According to the configuration described in [1] above, the refrigeration system (1) can detect the presence or absence of frost in the refrigerated space (20) based on the compressor inlet humidity (H1) detected by at least the humidity sensor (11). Such a refrigeration system (1) can defrost the refrigerator (3) at an appropriate time, thereby suppressing performance degradation due to heat loss caused by heating the refrigerator (3) during defrosting.

[0095] [2] In some embodiments, the refrigeration system (1) described in [1] further comprises an internal temperature sensor (12) configured to measure the internal temperature (T0), which is the temperature of the refrigeration space (20), wherein the frost detection unit (101) is configured to detect whether or not frost has formed on the refrigeration unit based on the measured value of the compressor inlet humidity (H1) and the measured value of the internal temperature (T0).

[0096] According to the configuration described in [2] above, the refrigeration system (1) can grasp the frost state of the refrigerated space (20) with greater accuracy by using the internal temperature (T0) measured by the internal temperature sensor (12) as a parameter for grasping the frost state of the refrigerated space (20), compared to using a pre-prepared internal temperature (T0).

[0097] [3] In some embodiments, the refrigeration system (1) described in [2] further comprises a compressor inlet temperature sensor (13) configured to measure the compressor inlet temperature (T1), which is the temperature of the circulating gas flowing downstream of the heat exchanger (8) in the inlet line (5), wherein the frost detection unit (101) is configured to detect whether or not frost has formed on the refrigerator (3) based on information showing the correlation between the temperature difference between the compressor inlet temperature (T1) and the internal temperature (T0) and the compressor inlet humidity (H1) for each compressor inlet temperature (T1).

[0098] According to the configuration described in [3] above, the refrigeration system (1) can improve detection accuracy by detecting the frost state of the refrigerated space (20) based on information showing the correlation between the temperature difference between the compressor inlet temperature (T1) and the internal temperature (T0) and the compressor inlet humidity (H1) for each compressor inlet temperature (T1). Furthermore, the refrigeration system (1) can reduce the computational load when detecting the frost state of the refrigerated space (20) by simplifying the logic for detecting the frost state of the refrigerated space (20).

[0099] [4] In some embodiments, the refrigeration system (1) described in any of [1] to [3] 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) being configured to have a variable rotational speed, and the refrigeration system (1) further comprises a rotational speed control unit (102) for controlling the rotational speed of the electric motor (44), the rotational speed control unit (102) being configured to reduce the rotational speed of the electric motor (44) when frost formation on the refrigerator (3) is detected.

[0100] According to the configuration described in [4] above, when the refrigeration system (1) detects frost formation in the refrigerated space (20), it can reduce the amount of frost drawn into the turbomachinery (4), including the compressor (41) and turbine (42), by lowering the rotation speed of the electric motor (44), thereby suppressing ice formation on the turbomachinery (4).

[0101] [5] In some embodiments, the refrigeration system (1) described in any of [1] to [3] above, wherein the rotational speed control unit (102) is configured to reduce the rotational speed of the electric motor (44) when the amount of increase over time of the compressor inlet humidity (H1), or the amount of increase over time of the internal humidity (H0), which is the humidity of the refrigeration space (20) as determined from the compressor inlet humidity (H1), is greater than or equal to a predetermined amount.

[0102] According to the configuration described in [5] above, the refrigeration system (1) can improve the accuracy of detecting the presence or absence of frost on the refrigerator (3) by monitoring the increase in the compressor inlet humidity (H1) over time, or the increase in the internal humidity (H0) over time. The refrigeration system (1) determines that if the increase in the compressor inlet humidity (H1) over time, or the increase in the internal humidity (H0) over time, exceeds a predetermined amount, there is a high probability that frost has formed in the refrigerated space (20). For this reason, the refrigeration system (1) suppresses ice formation on the turbomachinery (4) by reducing the rotational speed of the electric motor (44).

[0103] [6] In some embodiments, the refrigeration system (1) described in [4] above, wherein the rotational speed control unit (102) is configured to reduce the rotational speed of the electric motor (44) when the turbine inlet humidity (H2), which is the humidity of the circulating gas flowing downstream of the heat exchanger (8) in the compressed gas line (6) calculated based on the measurement value (H1) of the humidity sensor (11), is equal to or greater than the turbine inlet humidity threshold (TH2).

[0104] According to the configuration described in [6] above, if the turbine inlet humidity (H2) is above a threshold (TH2), the refrigeration system (1) is likely to experience frost formation in the refrigerated space (20) located downstream of the turbine (42) in the direction of circulating gas flow. For this reason, the refrigeration system (1) suppresses ice formation on the turbomachinery (4) by reducing the rotational speed of the electric motor (44). According to the configuration described in [6] above, the refrigeration system (1) can reduce the computational load when detecting the frost formation state in the refrigerated space (20) by simplifying the logic for detecting the frost formation state in the refrigerated space (20).

[0105] [7] In some embodiments, the refrigeration system (1) described in [4] or [6] above, wherein the rotational speed control unit (102) is configured to reduce the rotational speed of the electric motor (44) when the turbine outlet humidity (H3), which is the humidity of the circulating gas flowing through the outlet line (7) calculated based on the measurement value (H1) of the humidity sensor (11), is equal to or greater than the turbine outlet humidity threshold (TH3).

[0106] According to the configuration described in [7] above, if the turbine outlet humidity (H3) is above a threshold (TH3), the refrigeration system (1) is likely to experience frost formation in the refrigerated space (20) located downstream of the turbine (42) in the direction of circulating gas flow. For this reason, the refrigeration system (1) suppresses ice formation on the turbomachinery (4) by reducing the rotational speed of the electric motor (44). According to the configuration described in [7] above, the refrigeration system (1) can reduce the computational load when detecting the frost formation state in the refrigerated space (20) by simplifying the logic for detecting the frost formation state in the refrigerated space (20).

[0107] [8] In some embodiments, the refrigeration system (1) described in [4] above includes a turbine inlet temperature sensor (14) configured to measure the turbine inlet temperature (T2), which is the temperature of the circulating gas flowing downstream of the heat exchanger (8) in the compressed gas line (6), and the rotational speed control unit (102) is configured to set the rotational speed of the electric motor (44) to a rotational speed lower than the rated rotational speed when the turbine inlet humidity (H2), which is the humidity of the circulating gas flowing downstream of the heat exchanger (8) in the compressed gas line (6) calculated based on the measurement value (H1) of the humidity sensor (11), is equal to or greater than the threshold value (TH2) of the turbine inlet humidity, and the measurement value of the turbine inlet temperature (T2) is equal to or greater than the threshold value (TT2) of the turbine inlet temperature.

[0108] According to the configuration described in [8] above, if the turbine inlet humidity (H2) is above a threshold (TH2) and the measured turbine inlet temperature (T2) is above a threshold (TT2), there is a high probability that frost will form in the refrigerated space (20) located downstream of the turbine (42) in the direction of circulating gas flow. For this reason, the refrigeration system (1) suppresses ice formation on the turbomachinery (4) by setting the rotational speed of the electric motor (44) to a rotational speed lower than the rated rotational speed.

[0109] [9] In some embodiments, the refrigeration system (1) described in [8] above, wherein the rotational speed control unit (102) is configured to set the rotational speed of the electric motor (44) to the rated rotational speed when the turbine inlet humidity (H2) is less than the threshold (TH2) of the turbine inlet humidity, or when the measured value of the turbine inlet temperature (T2) is less than the threshold (TT2) of the turbine inlet temperature.

[0110] According to the configuration described in [9] above, the refrigeration system (1) is configured such that if the turbine inlet humidity (H2) is below the threshold (TH2) or the measured turbine inlet temperature (T2) is below the threshold (TT2), the moisture in the circulating gas is likely to be in a liquid state. For this reason, the refrigeration system (1) is configured to suppress ice formation on the turbomachinery (4) by setting the rotational speed of the electric motor (44) to its rated speed and quickly sending liquid to the downstream side of the turbine (42).

[0111]

[10] In some embodiments, the refrigeration system (1) described in [4] above is further equipped with a turbine outlet temperature sensor (15) configured to measure the turbine outlet temperature (T3), which is the temperature of the circulating gas flowing through the outlet line (7), and the rotational speed control unit (102) is configured to increase the rotational speed of the electric motor (44) when the turbine outlet conditions are met, which include the turbine outlet humidity (H3), which is the humidity of the circulating gas flowing through the outlet line (7) calculated based on the measurement value (H1) of the humidity sensor (11), being equal to or greater than the threshold value (TH3) of the turbine outlet humidity, and the measurement value of the turbine outlet temperature (T3) being equal to or greater than the threshold value (TT3) of the turbine outlet temperature.

[0112] According to the configuration described in

[10] above, the refrigeration system (1) is configured such that if the turbine outlet humidity (H3) is above a threshold (TH3) and the measured turbine outlet temperature (T3) is above a threshold (TT3), the moisture in the circulating gas is likely to be in a liquid state. For this reason, the refrigeration system (1) increases the rotational speed of the electric motor (44) to quickly send liquid to the downstream side of the turbine (42) in order to suppress ice formation on the turbomachinery (4).

[0113]

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

[10] above includes a turbine inlet temperature sensor (14) configured to measure the turbine inlet temperature (T2), which is the temperature of the circulating gas flowing downstream of the heat exchanger (8) in the compressed gas line (6), and the rotational speed control unit (102) is configured to reduce the rotational speed of the electric motor (44) when the turbine outlet conditions are not met, at least when the turbine inlet humidity (H2), which is the humidity of the circulating gas flowing downstream of the heat exchanger (8) in the compressed gas line (6), calculated based on the measurement value (H1) of the humidity sensor (11), is equal to or greater than the threshold value (TH2) of the turbine inlet humidity, and the measurement value of the turbine inlet temperature (T2) is equal to or greater than the threshold value (TT2) of the turbine inlet temperature.

[0114] According to the configuration described in

[11] above, if the turbine inlet humidity (H2) is above a threshold (TH2) and the measured turbine inlet temperature (T2) is above a threshold (TT2), there is a high probability that frost will form in the refrigerated space (20) located downstream of the turbine (42) in the direction of circulating gas flow. For this reason, the refrigeration system (1) is configured to suppress ice formation on the turbomachinery (4) by reducing the rotational speed of the electric motor (44).

[0115]

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

[10] or

[11] above includes a turbine inlet temperature sensor (14) configured to measure the turbine inlet temperature (T2), which is the temperature of the circulating gas flowing downstream of the heat exchanger (8) in the compressed gas line (6), and the rotational speed control unit (102) is configured to increase the rotational speed of the electric motor (44) when the turbine outlet conditions are not met, and the turbine inlet humidity (H2), which is the humidity of the circulating gas flowing downstream of the heat exchanger (8) in the compressed gas line (6), calculated based on the measurement value (H1) of the humidity sensor (11), is less than the threshold value (TH2) of the turbine inlet humidity, or the measurement value of the turbine inlet temperature (T2) is less than the threshold value (TT) of the turbine inlet temperature.

[0116] According to the configuration described in

[12] above, the refrigeration system (1) suppresses ice formation on the turbomachinery (4) by setting the rotational speed of the electric motor (44) to its rated speed and quickly sending circulating gas to the downstream side of the turbine (42) when the measured value of the turbine inlet temperature (T2) is less than the threshold (TT2), or when the measured value of the turbine inlet temperature (T2) is less than the threshold (TT) of the turbine inlet temperature.

[0117]

[13] In some embodiments, the refrigeration system (1) described in any of [1] to

[12] above is configured such that the refrigerated warehouse (2) is the container body (2A) of a refrigerated container (1A), and the refrigeration unit (3) is configured to be housed in the container body (2A) having an internal space of 2.3 m in width and 2.9 m in height.

[0118] According to the configuration described in

[13] above, the cold storage warehouse (2) of the cold storage system (1) is the container body (2A) of a cold storage container (1A) on which a cold storage unit (3) can be mounted.

[0119]

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

[13] further comprises a notification device (21) configured to provide notification by at least one of light, text display, vibration or sound, wherein the notification device (21) is configured to provide notification when the frost detection unit (101) detects frost in the refrigeration space (20).

[0120] According to the configuration described in

[14] above, the refrigeration system (1) can cause the notification device (21) to notify the notification device (21) so that when frost formation in the refrigerated space (20) is detected, the defrost operation of the refrigerator (3) can be performed quickly.

[0121] 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 (Compressor inlet) Humidity sensor 12 Internal temperature sensor 13 Compressor inlet temperature sensor 14 Turbine inlet temperature sensor 15 Turbine outlet temperature sensor 20 Refrigerated space 21 Notification device 30 Control device 41 Compressor 42 Turbine 43 Rotating shaft 44 Electric motor 101 Frost detection unit 102 Rotation speed control unit 103 Notification control unit H0 Internal humidity H1 Compressor inlet humidity H2 Turbine inlet humidity H3 Turbine outlet humidity T0 Internal temperature T1 Compressor inlet temperature T2 Turbine inlet temperature T3 Turbine outlet temperature

Claims

1. A refrigeration system comprising: a cold storage warehouse having a cold storage space to be cooled inside; and a 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; and 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, wherein the refrigeration system further comprises: a humidity sensor configured to detect compressor inlet humidity, which is the humidity of the circulating gas flowing downstream of the heat exchanger in the inlet line; and a frost detection unit configured to detect the presence or absence of frost in the cold storage space based at least on the compressor inlet humidity detected by 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 frost detection unit is configured to detect the presence or absence of frost in the refrigerator based on the measured value of the compressor inlet humidity and the measured value of the internal temperature.

3. The refrigeration system according to claim 2, further comprising a compressor inlet temperature sensor configured to measure the compressor inlet temperature, which is the temperature of the circulating gas flowing downstream of the heat exchanger in the inlet line, wherein the frost detection unit is configured to detect the presence or absence of frost in the refrigerator based on information showing the correlation between the temperature difference between the compressor inlet temperature and the internal temperature of the refrigerator and the compressor inlet humidity for each compressor inlet temperature.

4. 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, and the electric motor is configured to have a variable rotational speed, and the refrigeration system further comprises a rotational speed control unit for controlling the rotational speed of the electric motor, which is configured to reduce the rotational speed of the electric motor when frost formation in the refrigerator is detected.

5. The refrigeration system according to claim 4, wherein the rotation speed control unit is configured to reduce the rotation speed of the electric motor when the increase in the humidity at the compressor inlet over time, or the increase in the humidity inside the storage chamber, which is the humidity of the refrigerated space as determined from the humidity at the compressor inlet, over time is greater than or equal to a predetermined amount.

6. The refrigeration system according to claim 4, wherein the rotational speed control unit is configured to reduce the rotational speed of the electric motor when the turbine inlet humidity, which is the humidity of the circulating gas flowing downstream of the heat exchanger in the compressed gas line calculated based on the measurement value of the humidity sensor, is equal to or greater than a threshold for the turbine inlet humidity.

7. The refrigeration system according to claim 4, wherein the rotational speed control unit is configured to reduce the rotational speed of the electric motor when the turbine outlet humidity, which is the humidity of the circulating gas flowing through the outlet line calculated based on the measurement value of the humidity sensor, is equal to or greater than a threshold for the turbine outlet humidity.

8. The refrigeration system according to claim 4, comprising a turbine inlet temperature sensor configured to measure the turbine inlet temperature, which is the temperature of the circulating gas flowing downstream of the heat exchanger in the compressed gas line, wherein the rotational speed control unit is configured to set the rotational speed of the electric motor to a rotational speed lower than the rated rotational speed when the turbine inlet humidity, which is the humidity of the circulating gas flowing downstream of the heat exchanger in the compressed gas line calculated based on the measurement value of the humidity sensor, is equal to or greater than a threshold value for the turbine inlet humidity, and the measurement value of the turbine inlet temperature is equal to or greater than the threshold value for the turbine inlet temperature.

9. The refrigeration system according to claim 8, wherein the rotational speed control unit is configured to set the rotational speed of the electric motor to the rated rotational speed when the turbine inlet humidity is less than the threshold for the turbine inlet humidity, or when the measured value of the turbine inlet temperature is less than the threshold for the turbine inlet temperature.

10. The refrigeration system according to claim 4, comprising a turbine outlet temperature sensor configured to measure the turbine outlet temperature, which is the temperature of the circulating gas flowing through the outlet line, wherein the rotational speed control unit is configured to increase the rotational speed of the electric motor when the turbine outlet conditions are met, which are the turbine outlet humidity, which is the humidity of the circulating gas flowing through the outlet line calculated based on the measurement value of the humidity sensor, being equal to or greater than a threshold for the turbine outlet humidity, and the measured value of the turbine outlet temperature being equal to or greater than a threshold for the turbine outlet temperature.

11. The refrigeration system according to claim 10, comprising a turbine inlet temperature sensor configured to measure the turbine inlet temperature, which is the temperature of the circulating gas flowing downstream of the heat exchanger in the compressed gas line, wherein the rotational speed control unit is configured to reduce the rotational speed of the electric motor when the turbine outlet conditions are not met, and the turbine inlet humidity, which is the humidity of the circulating gas flowing downstream of the heat exchanger in the compressed gas line calculated based on the measurement value of the humidity sensor, is equal to or greater than a threshold value for the turbine inlet humidity, and the measured value of the turbine inlet temperature is equal to or greater than a threshold value for the turbine inlet temperature.

12. The refrigeration system according to claim 10, comprising a turbine inlet temperature sensor configured to measure the turbine inlet temperature, which is the temperature of the circulating gas flowing downstream of the heat exchanger in the compressed gas line, wherein the rotational speed control unit is configured to increase the rotational speed of the electric motor when the turbine outlet condition is not met, at least when the turbine inlet humidity, which is the humidity of the circulating gas flowing downstream of the heat exchanger in the compressed gas line calculated based on the measurement value of the humidity sensor, is less than a threshold for the turbine inlet humidity, or when the measured value of the turbine inlet temperature is less than a threshold for the turbine inlet temperature.

13. The refrigeration system according to any one of claims 1 to 3, wherein the cold storage warehouse is the container body of a refrigerated container, and the refrigeration unit is configured to be housed in the container body having an internal space of 2.3 m in width and 2.9 m in height.

14. A 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 frost detection unit is configured to provide notification when it detects frost in the refrigerated space.

Images