Refrigeration cycle device, corrosion detection method, program, and storage medium

Abstract

This refrigeration cycle device includes: a refrigeration cycle having a heat exchanger; a corrosion sensor provided on the surface of the heat exchanger; and a control unit. The control unit acquires log data of a corrosion current during a first period, determines, on the basis of the log data, whether or not a vibration component is continuously generated in the corrosion current throughout a second period shorter than the first period, and, if it has been determined that the vibration component is continuously generated in the corrosion current throughout the second period, detects that pass-through caused by corrosion is occurring in the heat exchanger.

Description

Refrigeration cycle device, corrosion detection method, program, and storage medium

[0001] The present disclosure relates to a refrigeration cycle device, a corrosion detection method, a program, and a storage medium.

[0002] As a refrigeration cycle device, for example, Patent Document 1 discloses an absorption chiller capable of detecting localized corrosion. The absorption chiller is provided with a corrosion detection means. The corrosion detection means detects localized corrosion of the constituent material of the inner wall of the chiller using a pair of electrodes immersed in the absorption liquid inside the device.

[0003] JP 2008-286441 A

[0004] Conventional absorption chillers and their corrosion detection means can detect localized corrosion, but cannot detect when corrosion has progressed to the point where penetration has occurred.

[0005] An object of the present disclosure is to provide a refrigeration cycle device, a corrosion detection method, a program, and a storage medium that can detect penetration due to corrosion in a heat exchanger of the refrigeration cycle device.

[0006] In order to solve the above-mentioned problems, the present disclosure provides a refrigeration cycle device, a corrosion detection method, a program, and a storage medium.

[0007] A refrigeration cycle apparatus according to one aspect of the present disclosure includes a refrigeration cycle having a heat exchanger, a corrosion sensor provided on a surface of the heat exchanger, and a control unit that controls the refrigeration cycle and acquires a corrosion current from the corrosion sensor. The control unit acquires log data of the corrosion current for a first time period, and determines, based on the log data, whether an oscillatory component is continuously generated in the corrosion current for a second time period that is shorter than the first time period. If it is determined that an oscillatory component is continuously generated in the corrosion current for the second time period, the control unit detects that the heat exchanger has been penetrated by corrosion.

[0008] Another aspect of the present disclosure provides a corrosion detection method for detecting corrosion occurring in a heat exchanger of a refrigeration cycle of a refrigeration cycle apparatus, the corrosion detection method including the steps of acquiring log data of a corrosion current for a first time period using a corrosion sensor provided on a surface of the heat exchanger, determining based on the log data whether an oscillatory component is continuously occurring in the corrosion current for a second time period shorter than the first time period, and detecting that penetration due to corrosion has occurred in the heat exchanger if it is determined that an oscillatory component is continuously occurring in the corrosion current for the second time period.

[0009] A program according to another aspect of the present disclosure is a computer program for causing a refrigeration cycle apparatus to execute the corrosion detection method described above.

[0010] Another aspect of the present disclosure is a storage medium that is non-transitory and computer-readable and stores a computer program that, when executed by a processor, realizes the corrosion detection method described above.

[0011] According to the refrigeration cycle device, corrosion detection method, program, and storage medium described in the present disclosure, it is possible to detect penetration due to corrosion in the heat exchanger of the refrigeration cycle device.

[0012] FIG. 1 is a block diagram showing an example of a schematic configuration of a refrigeration cycle device according to embodiment 1; FIG. 2 is a diagram showing an example of a schematic configuration of a corrosion sensor according to embodiment 1; FIG. 3 is a flowchart of an example of a corrosion detection method according to embodiment 1; FIG. 4 is a schematic diagram showing the SCC generation process in a copper pipe containing phosphorus to which internal pressure is applied; FIG. 5 is a schematic diagram showing the SCC generation process in a copper pipe containing phosphorus to which internal pressure is applied; FIG. 6 is a diagram showing an example of a measurement result of stress corrosion cracking (SCC) according to embodiment 1;

[0013] <Technical Concept> Before describing specific embodiments of a refrigeration cycle device, a corrosion detection method, a program, and a storage medium capable of detecting corrosion penetration in a heat exchanger of a refrigeration cycle device according to the present disclosure, the technical concept described in the present disclosure will first be described using an example. In the present disclosure, the refrigeration cycle device includes a refrigeration cycle, a corrosion sensor provided on the surface of the heat exchanger, and a control unit that controls the refrigeration cycle and acquires a corrosion current from the corrosion sensor. The refrigeration cycle device is, for example, an air conditioner or a refrigerator, and is a device that includes a refrigeration cycle. The refrigeration cycle includes two heat exchangers, a compressor, and an expansion mechanism. The corrosion sensor outputs a corrosion current depending on the corrosion state of the heat exchanger surface.

[0014] The pipes of a heat exchanger through which a refrigerant flows are formed, for example, from a material primarily composed of copper. When formaldehyde contained in adhesives used as building materials oxidizes around the pipes, ant nest corrosion, which creates cavities within the pipes, is likely to occur. Furthermore, the presence of ammonia around parts of the pipes where bending stress is applied is likely to cause stress corrosion cracking (SCC). The corrosion resistance can be changed by the amount of phosphorus added to the copper of the pipes; increasing the amount of phosphorus added increases the resistance to ant nest corrosion, which creates cavities within the pipes. However, copper pipes containing phosphorus are prone to SCC in an ammonia atmosphere.

[0015] When corrosion penetration occurs in the piping of a heat exchanger, the refrigerant inside the piping leaks through the hole (i.e., a gas leak occurs). If the refrigerant is toxic or flammable, the gas leak may pose a risk to the health and safety of users. In the early stages of penetration, the hole is small and only a small amount of refrigerant leaks. However, as corrosion progresses and the hole becomes larger, the refrigerant suddenly leaks out of the pipe, increasing the risk. Therefore, there is a need for early detection of corrosion penetration in heat exchangers.

[0016] The inventors of the present disclosure have discovered that the process of SCC occurrence involves at least three stages: a stage in which a water film forms on the surface of a heat exchanger pipe, a stage in which localized corrosion occurs, and a stage in which penetration due to corrosion occurs and cracks progress to penetrate the pipe.The inventors have also discovered that when penetration due to corrosion occurs, an oscillatory component is continuously generated in the corrosion current output by a corrosion sensor.

[0017] Based on this finding, the refrigeration cycle apparatus and corrosion detection method of the present disclosure acquire log data of the corrosion current and determine whether an oscillatory component is continuously occurring in the corrosion current for a certain period of time based on the log data. If it is determined that an oscillatory component is continuously occurring in the corrosion current for a certain period of time, for example, five minutes, the refrigeration cycle apparatus and corrosion detection method detect that penetration due to corrosion has occurred in the heat exchanger.

[0018] Each of the embodiments described below represents an example of the present disclosure. The numerical values, shapes, configurations, steps, and step orders shown in each of the following embodiments are examples and do not limit the present disclosure. Among the components in the following embodiment 1, components that are not described in the independent claims that represent the highest concept are described as optional components.

[0019] In each of the embodiments described below, certain elements may be modified, and other elements may be appropriately combined with any configuration, and the combined configurations will provide the respective effects. In the embodiments, the respective combinations of the configurations of the respective modifications will provide the respective effects of the respective modifications.

[0020] In the following detailed description, terms such as "first," "second," etc. are used for descriptive purposes only and should not be understood as expressing or implying relative importance or ranking of technical features. Features qualified as "first" and "second" expressly or imply the inclusion of one or more of that feature.

[0021] First Embodiment A first embodiment of a refrigeration cycle device, a corrosion detection method, a program, and a storage medium according to the present disclosure will be described in detail below with reference to the accompanying drawings as appropriate.

[0022] FIG. 1 is a block diagram showing an example of a schematic configuration of a refrigeration cycle device according to a first embodiment.

[0023] 1 , the refrigeration cycle apparatus 10 includes a refrigeration cycle 11, a corrosion sensor 12, a storage unit 13, and a control unit 14. The refrigeration cycle apparatus 10 may be, for example, an air conditioner, a refrigerator, or another apparatus including a refrigeration cycle. In this disclosure, an air conditioner is often used as an example of the refrigeration cycle apparatus 10, but the refrigeration cycle apparatus 10 is not limited to an air conditioner.

[0024] The refrigeration cycle apparatus 10 may further include at least one sensor for corrosion detection. For example, the refrigeration cycle apparatus 10 may include at least one of a humidity sensor 15, a temperature sensor 16, and an acoustic emission sensor (AE sensor) 17. The humidity sensor 15 and the temperature sensor 16 are used to detect the humidity and temperature around the heat exchanger that is the target of corrosion detection. The humidity sensor 15 and the temperature sensor 16 may be provided on the surface of the heat exchanger, near the corrosion sensor 12, or away from the corrosion sensor 12, for example.

[0025] The refrigeration cycle apparatus 10 may also include at least one sensor to perform its unique function. For example, if the refrigeration cycle apparatus 10 is an air conditioner, the refrigeration cycle apparatus 10 may include an indoor temperature sensor, an outdoor temperature sensor, and an indoor humidity sensor.

[0026] The refrigeration cycle apparatus 10 may include a communication unit 18 for communicating with a terminal device 20 or a server 30. For example, the refrigeration cycle apparatus 10 may be connected to the terminal device 20, which is a user's smartphone, via the Internet, or may be connected to the terminal device 20, which is a remote controller for the refrigeration cycle apparatus 10, via infrared rays. Similarly, the refrigeration cycle apparatus 10 may be connected to a server 30 related to the refrigeration cycle apparatus 10 via the Internet.

[0027] The refrigeration cycle apparatus 10 may include an input unit for receiving input from a user. The refrigeration cycle apparatus 10 may include a display, a speaker, or a light-emitting diode (LED) for presenting a notification regarding corrosion or a detection error to the user.

[0028] <Refrigeration cycle 11> The refrigeration cycle 11 includes two heat exchangers, a compressor, and an expansion mechanism. Pipes through which a refrigerant flows connect these elements to circulate the refrigerant. When the refrigeration cycle device 10 is an air conditioner, the two heat exchangers are an indoor heat exchanger and an outdoor heat exchanger. When the refrigeration cycle device 10 is a refrigerator, the two heat exchangers are an evaporator inside the refrigerator and a condenser outside the refrigerator.

[0029] <Corrosion sensor 12> The corrosion sensor 12 outputs a corrosion current according to the corrosion state of the surface of the heat exchanger. In one example, the corrosion sensor is an atomic corrosion monitor (ACM) sensor that detects the corrosion current. The corrosion sensor 12 measures and outputs the corrosion current at a predetermined sampling interval. The sampling interval may be, for example, 1 second, 3 seconds, or 10 seconds. The output of the corrosion sensor 12 is accumulated in the memory unit 13 as log data of the corrosion current.

[0030] FIG. 2 is a diagram illustrating an example of a schematic configuration of the corrosion sensor 12 according to the first embodiment. The corrosion sensor 12 illustrated in FIG. 2 includes a copper tube 121 as a working electrode, epoxy 122 as an insulating layer, carbon 123 as a counter electrode, and two coated copper wires 124 connected to the working electrode and the counter electrode, respectively. A gas-sealed space is provided inside the copper tube 121 as the working electrode. The gas pressure inside the copper tube 121 is higher than atmospheric pressure. The epoxy 122 as an insulating layer is disposed on the surface of the copper tube 121 so that an exposed portion, which is a portion of the surface of the copper tube 121, is exposed. The carbon is disposed on the epoxy and has a more noble potential than the copper tube.

[0031] When a water film is formed on the exposed portion of the working electrode and the working electrode and counter electrode are electrically connected via the water film, the dissolved oxygen in the water film acts as an oxidizing agent, causing copper ions to oxidize and elute from the working electrode, thereby reducing the solution resistance of the water film. At this time, a local cell is formed between the working electrode and counter electrode via the water film, and a corrosion current begins to flow. The corrosion sensor 12 outputs the detected corrosion current via the coated copper wire 124.

[0032] <Storage Unit 13> The storage unit 13 is a recording medium that records various information and control programs, and may be a memory that functions as a work area for the control unit 14. The storage unit 13 is realized, for example, by a flash memory, a RAM (Random Access Memory), a ROM (Read Only Memory), or other storage device, or by an appropriate combination of these.

[0033] The storage unit 13 stores information and thresholds for executing the corrosion detection method, and can store standards and thresholds for specific functions of the refrigeration cycle apparatus 10. The storage unit 13 may also store information acquired from various sensors, the terminal device 20, or the server 30. This information can be read out by the control unit 14 when executing the corrosion detection method or when executing the functions of the refrigeration cycle apparatus 10.

[0034] The storage unit 13 may also store a computer program for causing the control unit 14 to execute the corrosion detection method. The storage unit 13 may be a non-transitory computer-readable storage medium in which the computer program is stored.

[0035] <Control unit 14> The control unit 14 is a controller that controls at least some of the functions of the refrigeration cycle apparatus 10. The control unit 14 includes a general-purpose processor such as a CPU, MPU, MCU, FPGA, DSP, or ASIC that executes a program to realize predetermined functions. The control unit 14 can realize various controls in the refrigeration cycle apparatus 10 by calling and executing a control program stored in the storage unit 13. The control unit 14 can also read and write data stored in the storage unit 13 in cooperation with the storage unit 13. The control unit 14 is not limited to a controller that realizes predetermined functions through cooperation between hardware and software, and may be a hardware circuit designed specifically to realize the predetermined functions.

[0036] <Communication Unit 18> The communication unit 18 can communicate with the terminal device 20 or the server 30, for example, by transmitting and receiving internet packets. The communication unit 18 may communicate between the refrigeration cycle apparatus 10, the terminal device 20, and the server 30 in accordance with standards such as Wi-Fi (registered trademark), IEEE 802.2, IEEE 802.3, 3G, and LTE, and transmit and receive data. The communication unit 18 may communicate via the internet, an intranet, an extranet, a LAN, ISDN, a VAN, a CATV communication network, a virtual private network, a telephone line network, a mobile communication network, a satellite communication network, infrared, Bluetooth (registered trademark), or RFID (registered trademark). The control unit 14 can transmit notifications regarding corrosion and detection errors to the terminal device 20 or the server 30 via the communication unit 18.

[0037] <Terminal Device 20> The terminal device 20 is a device related to the refrigeration cycle apparatus 10. For example, the terminal device 20 may be a controller for the refrigeration cycle apparatus 10, or may be a controller capable of simultaneously managing and controlling multiple types of home appliances. Furthermore, the terminal device 20 may be an information terminal capable of performing data communication with the refrigeration cycle apparatus 10, such as a smartphone, a mobile phone, a tablet, a wearable device, or a computer equipped with a dedicated related application 22.

[0038] <Server 30> The server 30 may be a management server of a manufacturer of the refrigeration cycle apparatus 10 for managing or collecting data on at least one refrigeration cycle apparatus 10. For example, the terminal device 20 is a user's smartphone, and an associated application 22 for managing the refrigeration cycle apparatus 10 is installed in the terminal device 20. In this case, the server 30 can transfer notifications about corrosion or detection errors received from the refrigeration cycle apparatus 10 to the terminal device 20 and present the notifications, etc. to the user via the associated application 22.

[0039] <Corrosion Detection Method> The refrigeration cycle apparatus 10 executes a corrosion detection method using the above-described configuration. Figure 3 is a flowchart of an example of the corrosion detection method according to embodiment 1, and the corrosion detection method includes steps S110 to S130. In one example, the refrigeration cycle apparatus 10 periodically executes the corrosion detection method.

[0040] In the corrosion detection method, first, the control unit 14 of the refrigeration cycle apparatus 10 acquires log data of the corrosion current for a first time period (step S110). The first time period may be, for example, 30 minutes, 1 hour, 2 hours, or 3 hours. For example, the control unit 14 executes the corrosion detection method every hour and acquires log data for the immediately preceding hour in step S110.

[0041] Next, the control unit 14 determines, based on the log data, whether an oscillatory component is continuously present in the corrosion current for a second time period shorter than the first time period (step S120). As will be described later, the corrosion current includes a background current and may further include noise, spikes (large noise that meets specific conditions), oscillatory components, etc., depending on the corrosion state. The control unit 14 determines whether the corrosion current includes a continuous oscillatory component.

[0042] In this disclosure, the term "oscillating component" refers to a current component that occurs continuously and has a relatively large amplitude, rather than a single pulse. Such an oscillatory component can also be observed in the corrosion current waveform, where the waveform of the background current and the oscillatory component overlap.

[0043] The second time period may be, for example, 3 minutes, 5 minutes, 10 minutes, or 15 minutes. The second time period can be set based on the material of the heat exchanger piping and test data or simulation results regarding corrosion.

[0044] If it is determined that the oscillatory component has been continuously generated in the corrosion current for the second time period, the control unit 14 detects that the heat exchanger has been penetrated by corrosion (step S130). In this case, there is a duration during the first time period during which the oscillatory component of the corrosion current continues to be generated for a period longer than the second time period. After detecting the penetration by corrosion, the refrigeration cycle apparatus 10 can notify the user of the detection or control the refrigeration cycle 11 to delay the corrosion.

[0045] <Principle of penetration detection> The inventors conducted an SCC test by attaching a corrosion sensor 12 to the surface of a copper pipe used as piping for a heat exchanger, assuming an environment in which an air conditioner would be used. The SCC occurrence process discovered by the inventors in a phosphorus-containing copper pipe to which internal pressure was applied will be described below with reference to Figures 4A to 4D. In addition, the relationship between the vibration component of the corrosion current and penetration due to corrosion will be described with reference to Figures 5 to 7.

[0046] In the tests, a highly corrosion-resistant copper (phosphorus concentration: 0.28 mass%, tempering code: OL, bottom wall thickness: 0.23 mm, outer diameter: 6.35 mm) spirally grooved tube was used as the copper tube used for the working electrode of the corrosion sensor. One end of the copper tube was sealed with a flare cap, and a digital pressure gauge (GC61, manufactured by Nagano Keiki) and a valve were attached to the other end. Helium gas was then filled into the copper tube to an internal pressure of approximately 4 MPa (the design pressure of the refrigerant piping of an air conditioner). In other words, the copper tube forming the working electrode was a phosphorus-containing copper tube to which internal pressure had been applied.

[0047] To determine the timing of SCC occurrence, an AE sensor was attached to the copper pipe and fixed in contact with it, and the AE signal generated during the test was measured. The AE signal was amplified at 70 dB and filtered to count AE waves with a frequency of 20 kHz or higher and with a strength higher than the environmental noise.

[0048] In the test, the working electrode (exposed portion of the copper tube) and counter electrode (carbon) of the corrosion sensor were sealed in a polyethylene container (400 mL volume) with 100 mL of 1% by mass aqueous ammonia solution and atmospheric air, and exposed to the gas phase. The copper tube was positioned so that the surfaces of the working electrode and counter electrode were perpendicular to the water surface. In this state, the copper tube was cooled using a Peltier element, causing condensed water to form on the surface of the working electrode.

[0049] The potential of the working electrode and the current flowing through the external circuit between the working electrode and counter electrode were measured using a zero-resistance ammeter (SZRA 204, manufactured by Sylinx). The direction in which the anodic reaction occurred at the working electrode was considered positive. These parameters, as well as the pipe temperature and internal pressure, were read using a data logger (GL240, manufactured by Graphtec). All of the above-mentioned measurement parameters and AE signals were measured at sampling intervals of 1 second. The test was continued until cracks appeared in the copper pipe and the internal pressure decreased. After the test, the working electrode was immediately removed from the vessel, thoroughly removed of water droplets, and allowed to air dry. After drying, the surface of the working electrode and the cross section of the SCC initiation site were observed. For cross-sectional observation, the test specimens were cut perpendicular to the longitudinal direction, embedded in resin, and mirror-polished to expose the cut surface. An optical microscope (VHX-6000, manufactured by Keyence) was used for observation.

[0050] 4A to 4D are schematic diagrams showing the SCC development process of a phosphorus-containing copper tube subjected to internal pressure. FIG. 4A shows the state of the working electrode (copper tube) at the beginning of the test. At the beginning of the test, a water film forms on the surface of the working electrode in the ammonia aqueous solution, covering the working electrode and the counter electrode (carbon). Ammonia gas dissolves in the water film, and copper ions are oxidized and eluted from the working electrode using dissolved oxygen as an oxidizer, reducing the solution resistance of the water film. A local cell is formed between the working electrode and the counter electrode, and a corrosion current (galvanic current) begins to flow. In other words, FIG. 4A corresponds to the stage at which a water film forms on the surface of the heat exchanger piping of the refrigeration cycle 11.

[0051] 4B shows that localized corrosion such as intergranular corrosion occurs even in copper pipes containing phosphorus, and a film precipitates as copper ions become concentrated. FIG. 4B corresponds to a stage in which localized corrosion occurs on the surface of the heat exchanger pipe of the refrigeration cycle 11. At this stage, pitting corrosion growth and repassivation within the pits occur repeatedly. During the pitting corrosion process, destruction of the passive film creates an active new surface, and a dissolution reaction occurs again on the new surface, regenerating the film. Note that, in the present disclosure, localized corrosion refers to a state in which a localized portion of the pipe is corroded, but the corrosion has not yet penetrated the pipe wall.

[0052] Figure 4C shows that as corrosion progresses, SCC occurs, forming small holes in the copper pipe, resulting in a continuous slow leak of helium gas from the copper pipe. Figure 4C corresponds to the initial stage of penetration, when penetration due to corrosion begins. When bubbles due to gas leakage form in the holes or cracks, the amount of dissolved oxygen supplied to the surface of the cathode electrode (counter electrode) increases due to the stirring of the condensed water (water film) and fluctuations in the water surface (fluctuations in water film thickness). Furthermore, the generation of bubbles reduces the contact area between the working electrode and the condensed water, and the contact area also fluctuates over time. In other words, when gas leakage occurs due to penetration, the gas bubbles cause fluctuations in the water film thickness and contact area.

[0053] Figure 4D shows that the corrosion progresses further, causing the perforations to grow larger and more numerous. The perforations cause continuous gas leaks, increasing the flow rate of leaking gas and significantly reducing the internal pressure of the copper tube. Figure 4D corresponds to the later stage of perforation, where the corrosion perforation progresses further and the refrigerant suddenly escapes the tube. At this stage, it may not be possible to maintain a continuous water film between the working electrode and the counter electrode. As the internal pressure of the copper tube decreases, the generation of bubbles slows, and a continuous water film is again formed between the working electrode and the counter electrode. In this way, the water film is vigorously agitated by the bubbles.

[0054] Next, the relationship between the oscillatory component of the corrosion current and penetration due to corrosion, which was discovered by the inventors based on the above-described SCC generation process, will be described with reference to Figures 5 to 7. Figure 5 is a diagram showing an example of measurement results for SCC according to the first embodiment, and Figures 6 and 7 are partial enlarged views of the measurement results in Figure 5.

[0055] 5 shows the corrosion current ("Current"), the potential of the working electrode ("Potential"), the number of AE waves counted ("AE count"), and the pressure inside the copper tube ("Pressure") measured during the test period. For the purpose of explaining the test period step by step, the test period is divided into four sections: Section I (0 h to 1.6 h), Section II (1.6 h to 21 h), Section III (21 h to 38.7 h), and Section IV (38.7 h to 41.1 h). Sections I to IV correspond to the stages shown in FIGS. 4A to 4D, respectively.

[0056] In section I, a water film is formed on the surfaces of the working electrode (copper tube) and the counter electrode (carbon), and the potential of the working electrode and the corrosion current flowing are weak. In section I, the corrosion current gradually increases from 0 to 0.23 μA. At this stage, neither corrosion nor gas leakage has occurred, no AE waves are generated, and there is almost no change in the internal pressure of the copper tube.

[0057] In Section II, localized corrosion such as intergranular corrosion occurs on the surface of the copper pipe. When destruction of the copper pipe surface or passive film occurs, copper ions concentrate, causing spikes in the corrosion current. In Section II, a background current of approximately 1.0 μA occurs, and numerous spike-shaped current noises (hereinafter sometimes abbreviated as "spikes") are observed on the anode side. Each spike-shaped current noise has a waveform that increases sharply and then gradually decays.

[0058] The rise in current value in the current noise corresponds to the fall in potential in the potential noise, and the potential noise has a waveform that shifts sharply to the negative side and then gradually recovers. At this stage, localized corrosion has occurred, and the first AE occurred 20.987 hours after the start of the test, with subsequent AEs occurring continuously. Because no gas leaks have occurred yet, there is almost no change in the internal pressure of the copper pipe.

[0059] In section III, penetration due to corrosion begins, and helium gas in the copper tube also begins to leak. As shown in Figure 6, in the section from 21 to 25 hours after the start of the test, the background current of the corrosion current gradually increases from 0.8 μA to approximately 2.5 μA. Then, in the section from 25 to 38.7 hours after the start of the test, the background current gradually decreases to approximately 1.5 μA, and oscillations with an amplitude of approximately 0.05 μA are also observed. As mentioned above, the cause of the continuous oscillation component of this corrosion current is thought to be fluctuations in the water film thickness and contact area caused by gas bubbles when a gas leak occurs.

[0060] The relatively strong spike-like current noise observed in section II is also observed in section III. For example, as shown in Fig. 7, spike-like current noise is observed 28.49 hours and 28.66 hours after the start of the test, and the potential also shifts to the negative side in response to these current noises.

[0061] During the test period from 25 hours to 38.7 hours, the internal pressure gradually decreased from 3.91 MPa to 3.63 MPa due to gas leakage. AEs occurred continuously throughout Section III. In other words, when penetration due to corrosion occurred, physical vibrations also occurred on the copper pipe surface.

[0062] In Section IV, in the later stages of penetration, the flow rate of leaking gas increases, and the internal pressure of the copper pipe drops sharply from 3.63 MPa to 0. In the section from 38.7 hours to 40.0 hours after the start of the test, both the corrosion current and potential are near 0, and immediately thereafter, there is a rise in the corrosion current and a drop in the potential. In Section IV, at 38.7 hours after the start of the test, the internal pressure of the copper pipe dropped to nearly 0, and a large AE was observed.

[0063] From the above test results and explanation, it will be understood that when corrosion penetration occurs (section III), an oscillatory component is continuously generated in the corrosion current. Based on this knowledge, the refrigeration cycle apparatus 10 and the corrosion detection method determine that corrosion penetration has occurred in the heat exchanger if it is determined that an oscillatory component is continuously generated in the corrosion current for the second time period.

[0064] Hereinafter, a more detailed description will be given of how the refrigeration cycle apparatus 10 determines whether an oscillatory component is continuously occurring in the corrosion current.

[0065] <Detection of penetration by dispersion of corrosion current> Fig. 8 is a flowchart of an example of the corrosion detection method according to embodiment 1. The corrosion detection method shown in Fig. 8 includes steps S110 to S140, and steps S110 to S130 in Fig. 8 are the same as steps S110 to S130 in Fig. 3, and therefore will not be described in detail here.

[0066] Fluctuations in the corrosion current can be caused by small noises, spikes (large noises), oscillatory components, and fluctuations in the background current. In the embodiment of Fig. 8, the refrigeration cycle apparatus 10 determines whether an oscillatory component is occurring based on the variance of the corrosion current. The refrigeration cycle apparatus 10 further determines whether the oscillatory component is occurring continuously.

[0067] After acquiring the log data of the corrosion current, the control unit 14 of the refrigeration cycle apparatus 10 calculates the variance of the corrosion current every third hour based on the log data (step S140). The variance of the corrosion current is a mathematical and statistical index that represents the degree of variation in the log data of the corrosion current, and is the average of the squares of the differences between the current value of each corrosion current in the log data and the average value.

[0068] The third time period is longer than the sampling interval of the corrosion sensor 12 and shorter than the second time period. For example, the third time period may be 3, 5, 10, 15, 30, or 60 times the sampling interval, or may be 2%, 3%, 5%, or 10% of the first time period.

[0069] The variance may be calculated by using a moving average, weighted average, median, or mode of the corrosion current values ​​as the mean value. Instead of the variance, penetration detection may be performed using a standard deviation, which indicates the degree of variation in the data.

[0070] If the fluctuation in the corrosion current is due to a single occurrence or a small number of noises or spikes, the variance is relatively low. Similarly, if the fluctuation in the corrosion current is due to fluctuations in the background current, the average value fluctuates according to the background current, and the variance is relatively low. Therefore, when the variance exceeds a predetermined first threshold, the control unit 14 determines that an oscillatory component is occurring in the corrosion current.

[0071] In step S120, the control unit 14 determines whether the duration during which the variance continues to exceed the first threshold exceeds the second time. In one example, the control unit 14 divides the first time into a plurality of divided time periods in units of four time periods. A variance exceeding the first threshold exists in all divided time periods within the duration. In other words, divided time periods in which a variance exceeding the first threshold exists occur consecutively, and the sum of these divided time periods exceeds the second time period. If the control unit 14 determines that the duration during which the variance continues to exceed the first threshold exceeds the second time period, it determines that an oscillatory component has continuously occurred in the corrosion current over the second time period.

[0072] In another example, the control unit 14 counts the number of times the variance exceeds the first threshold for each divided time period, and determines that an oscillatory component occurs in the divided time period when the number of times exceeds a predetermined threshold. In this case, the number of times that the variance exceeds the first threshold is equal to or greater than the predetermined threshold for all divided time periods within the duration.

[0073] The fourth time period may be the same as the third time period, or may be longer than the third time period and shorter than the second time period. For example, the fourth time period may be 1, 2, 3, or 5 times the third time period. The third and fourth times may be set based on the material of the heat exchanger piping and test data or simulation results regarding corrosion.

[0074] By using the variance in this way, it is possible to eliminate corrosion current fluctuations due to other causes and detect the occurrence of an oscillatory component.

[0075] <Detection of Penetration Using Variance and Moving Average of Corrosion Current> Figure 9 is a flowchart of another example of the corrosion detection method according to embodiment 1. This example corrosion detection method includes steps S110 to S150. Steps S110 to S140 in Figure 9 are the same as steps S110 to S140 in Figure 8.

[0076] 9, the refrigeration cycle apparatus 10 determines whether an oscillatory component is occurring continuously based on the variance and moving average of the corrosion current. In this embodiment, the control unit 14 further calculates the moving average of the corrosion current every third hour based on the log data (step S150). Then, in step S140, the control unit 14 calculates the variance of the corrosion current based on the moving average of the corrosion current.

[0077] In this embodiment, the control unit 14 may set the first threshold value based on the moving average. For example, the control unit 14 may set the first threshold value to 1%, 2%, 3%, or 5% of the moving average. The moving average of the corrosion current represents the magnitude of the background current contained in the corrosion current. Therefore, if the first threshold value for determining the presence of an oscillatory component is set based on the moving average, the determination of the presence or absence of an oscillatory component is not affected by fluctuations in the moving average itself, i.e., is not affected by fluctuations in the background current. In this way, the presence or absence of an oscillatory component can be determined more accurately.

[0078] <Detection of Penetration by Combined Use of AE Sensor 17> In one embodiment, the refrigeration cycle apparatus 10 includes an AE sensor 17 that detects AE signals generated in the heat exchanger of the refrigeration cycle 11. As described with reference to Figures 4C, 4D, 5, and 6, when penetration due to corrosion occurs, AE signals are continuously generated due to gas leakage. Therefore, the presence or absence and number of AE signals can be used to detect vibration components. For example, the control unit 14 may count the AE signals and add the fact that the AE signals exceed a certain number of times to the conditions for determining whether a vibration component is occurring.

[0079] <Detection of Penetration by Filtering Corrosion Current> In one embodiment, the refrigeration cycle apparatus 10 can detect penetration due to corrosion by filtering the corrosion current. According to the measurement results of the test shown in FIG. 5 , when penetration due to corrosion (zone III) occurs, the corrosion current is relatively large and noise occurs relatively frequently compared to when corrosion has not yet occurred (zone I) and when localized corrosion occurs (zone II). In one example, the control unit 14 filters the noise using a high-pass filter and counts noise with high-frequency components. If the number of counted noise components exceeds a predetermined number, the control unit 14 detects penetration due to corrosion. In another example, the control unit 14 sets a bandpass filter based on a moving average of the corrosion current. The control unit 14 filters the noise using the bandpass filter and counts noise components outside a set range. If the number of counted noise components exceeds a predetermined number, the control unit 14 detects penetration due to corrosion.

[0080] <Countermeasures in Response to Detection of Corrosion> The refrigeration cycle apparatus 10 of the present disclosure can also take various countermeasures in response to detection of corrosion. Figure 10 is a flowchart of an example of a corrosion detection method according to embodiment 1. This exemplary corrosion detection method includes steps S110 to S130 and step S170. Steps S110 to S130 in Figure 10 are the same as steps S110 to S130 in Figure 3.

[0081] 10 , after detecting penetration due to corrosion, the control unit 14 takes countermeasures for the heat exchanger (step S170). The countermeasures include, for example, at least one of sending an alert notification, causing the refrigeration cycle 11 to perform a dry operation, causing the refrigeration cycle 11 to perform a freezing operation, stopping the refrigeration cycle 11, and sending a notification suggesting that cathodic protection be performed on the refrigeration cycle 11.

[0082] The alert notification may include a notification that corrosion has occurred in the heat exchanger, that corrosion has caused perforation, or that there is a risk of a refrigerant leak. The alert notification and the notification suggesting cathodic protection can be presented to the user by the refrigeration cycle apparatus 10 or the terminal device 20. The notification can be sent via the terminal device 20 or the server 30 to a third party other than the user, such as a company responsible for maintaining the refrigeration cycle apparatus 10 or a person in charge of the location where the refrigeration cycle apparatus 10 is installed.

[0083] The heat exchanger can be dried by causing the refrigeration cycle 11 to perform a dry operation or a freeze operation. This measure can slow or stop the progression of corrosion occurring in the heat exchanger. Furthermore, the control unit 14 may stop the operation of the refrigeration cycle 11 in order to prevent the spread of refrigerant leakage through the heat exchanger as much as possible.

[0084] In one embodiment, the control unit 14 selects a countermeasure based on the corrosion state. For example, the memory unit 13 stores a comparison table of corrosion states and countermeasures to be taken. The control unit 14 determines the countermeasure to be taken by checking the comparison table with the corrosion state to be determined. The corrosion state may be, for example, no corrosion, localized corrosion, no penetration due to corrosion, or penetration due to corrosion. In one example, if it is determined that localized corrosion exists, the control unit 14 causes the refrigeration cycle 11 to perform a dry operation and presents an alert notification to the user. In another example, if it is determined that penetration due to corrosion exists, the control unit 14 stops the operation of the refrigeration cycle 11 and presents an alert notification to the person in charge of the location where the refrigeration cycle apparatus 10 is installed.

[0085] In one embodiment, the refrigeration cycle apparatus 10 includes a program used to execute the corrosion detection method described above. The program causes the refrigeration cycle apparatus 10 to execute the corrosion detection method.

[0086] This completes the process of corrosion detection, etc. The refrigeration cycle device, the corrosion detection method, the program, and the storage medium disclosed herein can detect penetration due to corrosion in the heat exchanger of the refrigeration cycle device.

[0087] <Embodiment 2> <Detection of Localized Corrosion> In Embodiment 2, the refrigeration cycle apparatus 10 can detect localized corrosion in the heat exchanger of the refrigeration cycle 11 under various circumstances. For example, the refrigeration cycle apparatus 10 can determine the presence or absence of localized corrosion when it determines that no penetration due to corrosion has occurred or when it detects a spike in the corrosion current.

[0088] As described with reference to FIGS. 4B and 5, when localized corrosion occurs, a spike-like current noise occurs in the corrosion current, which has a waveform that increases suddenly and then gradually decays.

[0089] Figure 11 is a partially enlarged view of the measurement results shown in Figure 5. As mentioned above, during the stage where localized corrosion is occurring (Figure 4B and section II in Figure 5), spike-like current noise that overlaps with the background current is observed in the corrosion current. Each of these spikes has a waveform that rapidly increases and then gradually decays. For example, at 5.09 hours after the start of the test, the corrosion current rapidly increases from 1.0 μA to 27 μA, then rapidly decays to 1.8 μA over approximately 300 seconds, and then gradually decays back to the original background over approximately 0.3 hours.

[0090] Based on this knowledge, in the embodiment of FIG. 12A, when the refrigeration cycle apparatus 10 determines that such a spike has occurred, it determines that localized corrosion has occurred in the heat exchanger.

[0091] 12A is a flowchart of an example of a corrosion detection method according to embodiment 2, which includes steps S110 to S150 and steps S210 to S240. Steps S110 to S150 in FIG. 12A are the same as steps S110 to S150 in FIG. 9, and therefore will not be described in detail here.

[0092] 12A, the control unit 14 determines whether an oscillatory component is continuously occurring in the corrosion current based on the variance and moving average of the corrosion current (steps S110 to S150). To determine whether a spike is occurring, the control unit 14 also determines whether the corrosion current is equal to or less than a second threshold (step S210). That is, the control unit 14 determines whether a relatively large current fluctuation is occurring.

[0093] In step S210, the control unit 14 sets a second threshold value based on the variance. For example, the control unit 14 determines whether the amplitude of the current fluctuation is greater than two, three, or five times the variance. In one example, the control unit 14 sets the second threshold value to the sum of the moving average and three times the variance. In another example, the control unit 14 obtains a predicted current for the background current based on test data or past detection data. Then, the control unit 14 sets the second threshold value to the sum of the predicted current and three times the variance.

[0094] If it is determined that the corrosion current is below the second threshold, i.e., no significant current fluctuations are occurring ("Yes" in step 210), the control unit 14 performs steps S120 and S130 in succession to perform penetration detection.

[0095] On the other hand, if it is determined that the corrosion current is not equal to or less than the second threshold ("NO" in step S210), the control unit 14 performs steps S220 and S230 in succession to detect localized corrosion. In this case, the control unit 14 obtains a predicted current related to the background current of the corrosion current (step S220) and obtains a predicted current range including the predicted current. As described above, the predicted current is a predicted value related to the background current obtained based on test data or past detection data. The predicted current range may be, for example, a range of "predicted current ± variance" or a range of "predicted current ± variance × 2."

[0096] Next, the control unit 14 determines whether the moving average over a certain time period includes a value outside the predicted current range that includes the predicted current (step S230). This determination is made to determine whether the current fluctuation detected in step S210 is a spike having characteristics corresponding to localized corrosion or is due to fluctuations in background current. Note that the "certain time period" in step S230 may be, for example, the fourth hour, third hour, first hour, or any other predetermined time. The "moving average" in step S230 may be the moving average calculated in step S150.

[0097] The presence of a value outside the predicted current range in the moving average indicates that the current fluctuation is a spike having a waveform that rapidly increases and then decays back into the predicted current range. Therefore, when it is determined that the moving average has a value outside the predicted current range, the control unit 14 detects that localized corrosion has occurred in the heat exchanger (step S240).

[0098] On the other hand, if it is determined that the moving average does not include a value outside the predicted current range ("No" in step 230), the control unit 14 determines that the background current of the corrosion current fluctuates and does not have a spike, i.e., that localized corrosion is not occurring in the heat exchanger.

[0099] The control unit 14 determines whether or not a spike having the waveform described above is present in the corrosion current through steps S210 to S230. If a waveform having characteristics corresponding to localized corrosion is detected, the control unit 14 determines that localized corrosion is occurring.

[0100] As described above, the refrigeration cycle apparatus 10 and the corrosion detection method can detect localized corrosion based on whether or not a spike having characteristics corresponding to localized corrosion is present in the corrosion current.

[0101] 12B is a flowchart of another example of the corrosion detection method according to embodiment 2. The flowchart shown in FIG. 12B differs from the flowchart shown in FIG. 12A in the processing performed when it is determined in step S210 that the corrosion current is greater than the second threshold. In the example shown in FIG. 12B , for example, if a spike is detected in the corrosion current ("NO" in step S210), it can be determined that localized corrosion is occurring.

[0102] Fig. 13A is a flowchart of an example of a corrosion detection method according to embodiment 2. Steps S110 to S140 and steps S220 to S240 included in the corrosion detection method of Fig. 13A are the same as steps S110 to S140 and steps S220 to S240 in Fig. 12A.

[0103] In the example shown in FIG. 13A , the control unit 14 determines whether an oscillatory component is continuously present in the corrosion current based on the variance and moving average of the corrosion current (steps S110 to S140). If it is determined that an oscillatory component is not continuously present in the corrosion current ("No" in step S120), the control unit 14 performs the above-described steps S220 to S240 to determine whether localized corrosion is occurring. If it is determined that no penetration due to corrosion has occurred, the control unit 14 further determines whether a spike satisfying a specific condition is present in the corrosion current. That is, in the example shown in FIG. 13A , the control unit 14 first determines whether the corrosion current has the current characteristics of the aforementioned section III, and then determines whether the corrosion current has the current characteristics of section II.

[0104] 13B is a flowchart of an example of a corrosion detection method according to embodiment 2. The flowchart shown in FIG. 13B differs from the flowchart shown in FIG. 13A in the processing performed when it is determined in step S120 that an oscillatory component is not continuously present in the corrosion current. In the example shown in FIG. 13B , for example, even if an oscillatory component is not continuously present in the corrosion current ("NO" in step S120), if an oscillatory component is detected, it is considered that localized corrosion is occurring.

[0105] This completes the process of detecting localized corrosion. In this way, it is possible to detect the occurrence of localized corrosion in the heat exchanger under various circumstances.

[0106] <Embodiment 3> <Operation Check and Preliminary Determination> In Embodiment 3, the refrigeration cycle apparatus 10 and the corrosion detection method can check whether the corrosion sensor 12 is operating correctly before performing corrosion detection. Furthermore, the refrigeration cycle apparatus 10 and the corrosion detection method can perform a simple determination of the presence or absence of corrosion before performing corrosion determination based on the log data of the corrosion current.

[0107] 14 is a flowchart of an example of a corrosion detection method according to embodiment 3, which includes steps S110 to S130 and steps S310 to S340. Steps S110 to S130 in FIG. 14 are the same as steps S110 to S130 in FIG. 3, and so details will not be repeated here.

[0108] 14, the refrigeration cycle apparatus 10 and the corrosion detection method check the operation of the corrosion sensor 12 before detecting corrosion. For example, if the corrosion sensor 12 detects a corrosion current in a dry environment where condensed water (a water film) does not form on the heat exchanger, the corrosion sensor 12 may not be operating correctly. Conversely, if the corrosion sensor 12 does not detect a corrosion current in a high-humidity environment where condensed water forms, the corrosion sensor 12 may also be operating incorrectly.

[0109] Before detecting corrosion, the control unit 14 of the refrigeration cycle apparatus 10 acquires the relative humidity around the heat exchanger using the humidity sensor 15 (step S310), and also acquires the corrosion current using the corrosion sensor 12 (step S320).

[0110] More specifically, if the humidity sensor 15 is a sensor that detects the relative humidity of the surrounding environment, the control unit 14 can directly obtain the relative humidity via the humidity sensor 15. On the other hand, if the humidity sensor 15 is a sensor that detects the absolute humidity, the control unit 14 also obtains the temperature around the heat exchanger via the temperature sensor 16. The control unit 14 calculates the relative humidity based on the absolute humidity and temperature around the heat exchanger.

[0111] The control unit 14 then determines whether the relative humidity is equal to or less than the sixth threshold and the corrosion current is greater than the seventh threshold, or whether the relative humidity is greater than the sixth threshold and the corrosion current is equal to or less than the seventh threshold (step S330). The sixth threshold is a relative humidity threshold that indicates an environment in which condensation is likely to occur. For example, the sixth threshold may be 75%, 80%, 85%, or 90%. The seventh threshold is a threshold for determining whether a corrosion current is flowing. For example, the seventh threshold may be from 0 to several nA.

[0112] If the relative humidity is equal to or less than the sixth threshold and the corrosion current is greater than the seventh threshold, or if the relative humidity is greater than the sixth threshold and the corrosion current is equal to or less than the seventh threshold, the control unit 14 presents a detection error related to the corrosion sensor 12 (step S340). The detection error includes information indicating that the corrosion sensor 12 may not be operating correctly. In step S340, the control unit 14 can present the detection error to, for example, the user, the server 30, or a maintenance technician for the refrigeration cycle apparatus 10.

[0113] On the other hand, if the relative humidity is equal to or less than the sixth threshold and the corrosion current is equal to or less than the seventh threshold, or if the relative humidity is higher than the sixth threshold and the corrosion current is higher than the seventh threshold, the corrosion sensor 12 is considered to be operating normally. Therefore, if the answer to step S330 is "No," the control unit 14 performs corrosion detection using the corrosion sensor 12 (steps S110 to S130).

[0114] This completes the process of checking the operation of the corrosion sensor 12. In this way, it is possible to check whether the corrosion sensor 12 is operating correctly before performing corrosion detection.

[0115] 15 is a flowchart of another example of the corrosion detection method according to embodiment 3, and the corrosion detection method includes steps S110 to S130, step S320, step S350, and step S360. Steps S110 to S130 and step S320 in FIG. 15 are the same as steps S110 to S130 and step S320 in FIG. 14.

[0116] 15 , before detecting corrosion based on the log data, the control unit 14 acquires the corrosion current (step S320) and determines whether the corrosion current is greater than a fifth threshold (step S350). The fifth threshold is set to be smaller than the second threshold ( FIGS. 12A and 12B ) used to detect spikes representing localized corrosion. For example, the fifth threshold may be 50 nA, 100 nA, 200 nA, 500 nA, or 1 μA.

[0117] The fifth threshold is a threshold for determining whether corrosion has occurred and can be set based on the material of the heat exchanger piping, test data related to corrosion, or simulation results. For example, according to the measurement results of the test shown in Figure 5, when localized corrosion (zone II) or corrosion penetration (zone III) occurs, the corrosion current is relatively large compared to when corrosion has not yet occurred (zone I).

[0118] Therefore, when it is determined that the corrosion current is greater than the fifth threshold, it can be determined that at least localized corrosion has occurred. In this case, the control unit 14 detects that corrosion has occurred in the heat exchanger and takes appropriate measures regarding the heat exchanger (step S360). For example, in response to the detection of corrosion by the simplified determination, the control unit 14 sends an alert notification and causes the refrigeration cycle 11 to perform drying operation, freezing operation, or stop operation.

[0119] If it is determined that the corrosion current is greater than the fifth threshold, the control unit 14 may further detect whether or not penetration due to corrosion has occurred (steps S110 to S130).In this case, the control unit 14 may further detect whether or not localized corrosion has occurred (steps S210 to S240 in FIGS. 12A to 13B).

[0120] On the other hand, if the control unit 14 determines that the corrosion current is equal to or less than the fifth threshold, the control unit 14 determines that corrosion has not yet occurred and ends the corrosion detection process. In this way, a simple determination of the presence or absence of corrosion can be made before determining corrosion based on the log data of the corrosion current.

[0121] (Other Embodiments) (Additional Notes) The above description of the embodiments discloses the following techniques.

[0122] (Technology 1) A refrigeration cycle device comprising: a refrigeration cycle having a heat exchanger; a corrosion sensor provided on the surface of the heat exchanger; and a control unit that controls the refrigeration cycle and acquires a corrosion current from the corrosion sensor, wherein the control unit acquires log data of the corrosion current for a first time period, and determines based on the log data whether an oscillatory component is continuously occurring in the corrosion current for a second time period that is shorter than the first time period; and if it determines that an oscillatory component is continuously occurring in the corrosion current for the second time period, detects that penetration due to corrosion has occurred in the heat exchanger.

[0123] In this way, it is possible to detect the occurrence of penetration of the heat exchanger due to corrosion.

[0124] (Technology 2) The control unit calculates the variance of the corrosion current every third hour, which is shorter than the second hour, based on the log data, and if it determines that the duration during which the variance continues to exceed the first threshold exceeds the second hour, it determines that an oscillatory component is continuously occurring in the corrosion current over the second hour.This is a refrigeration cycle device described in Technology 1.

[0125] In this way, it is possible to determine whether or not an oscillatory component is continuously occurring in the corrosion current based on the variance of the corrosion current.

[0126] (Technology 3) The refrigeration cycle device described in Technology 2, wherein the first time is divided into a plurality of divided times in units of a fourth time equal to or greater than the third time, and a variance exceeding the first threshold exists in all of the divided times within the duration.

[0127] In this way, it is possible to determine whether or not an oscillatory component is continuously occurring in the corrosion current based on the variance of the corrosion current.

[0128] (Technology 4) A refrigeration cycle device described in Technology 2 or 3, wherein the control unit calculates a moving average of the corrosion current every third hour based on the log data, and the first threshold value is set based on the moving average.

[0129] In this way, it is possible to more accurately determine whether an oscillatory component is continuously occurring in the corrosion current based on the variance and moving average of the corrosion current.

[0130] (Technology 5) A refrigeration cycle device described in any one of Technologies 2 to 4, wherein the control unit calculates a moving average of the corrosion current every third hour based on the log data, and if it determines that the corrosion current is less than or equal to a second threshold, it determines whether the variance exceeds the first threshold, and the second threshold is set based on the variance.

[0131] In this way, it is possible to more accurately determine whether an oscillatory component is continuously occurring in the corrosion current based on the variance and moving average of the corrosion current.

[0132] (Technology 6) When the control unit determines that the corrosion current is greater than a second threshold, it obtains a predicted current related to the background current of the corrosion current, determines whether the moving average contains a value outside a predicted current range including the predicted current, and when it determines that the moving average contains a value outside the predicted current range, detects that localized corrosion has occurred in the heat exchanger, in a refrigeration cycle device as described in Technology 5.

[0133] In this way, localized corrosion in the heat exchanger can be detected.

[0134] (Technology 7) A refrigeration cycle device according to Technology 5 or 6, wherein the control unit detects that localized corrosion has occurred in the heat exchanger when it determines that the corrosion current is greater than a second threshold value.

[0135] In this way, localized corrosion in the heat exchanger can be detected.

[0136] (Technology 8) The control unit calculates a moving average of the corrosion current every third hour based on the log data, and if it determines that the duration does not exceed the second hour, obtains a predicted current related to the background current of the corrosion current, determines whether the moving average contains a value outside a predicted current range that includes the predicted current, and if it determines that the moving average contains a value outside the predicted current range, detects that localized corrosion is occurring in the heat exchanger. This is a refrigeration cycle device described in any one of Technologies 2 to 7.

[0137] In this way, localized corrosion in the heat exchanger can be detected.

[0138] (Technology 9) A refrigeration cycle device described in any one of Technologies 2 to 8, wherein the control unit detects that localized corrosion has occurred in the heat exchanger when it determines that the duration does not exceed the second time.

[0139] In this way, localized corrosion in the heat exchanger can be detected.

[0140] (Technology 10) A refrigeration cycle device described in any one of Technologies 6 to 9, wherein the control unit counts the number of times that localized corrosion is detected, and if it determines that the number of times that localized corrosion is detected exceeds a third threshold, it takes appropriate measures regarding the heat exchanger.

[0141] In this way, countermeasures can be taken against the progression of localized corrosion.

[0142] (Technology 11) A refrigeration cycle apparatus as described in Technology 6 or 8, wherein the control unit calculates an amount of charge corresponding to localized corrosion based on the moving average and the predicted current, calculates an amount of corrosion corresponding to localized corrosion based on the amount of charge, and takes appropriate measures regarding the heat exchanger if it determines that the amount of corrosion exceeds a fourth threshold.

[0143] In this way, countermeasures can be taken depending on the amount of corrosion.

[0144] (Technology 12) A refrigeration cycle device described in any one of technologies 1 to 11, wherein the control unit determines whether the corrosion current is greater than a fifth threshold before acquiring the log data of the corrosion current for the first time, and if it determines that the corrosion current is greater than the fifth threshold, detects that corrosion has occurred in the heat exchanger and takes appropriate measures regarding the heat exchanger.

[0145] In this way, corrective action can be taken in response to the detection of corrosion.

[0146] (Technology 13) A refrigeration cycle device as described in Technology 12, wherein when the control unit determines that the corrosion current is greater than the fifth threshold, it acquires the log data of the corrosion current for the first time and detects the corrosion status of the heat exchanger.

[0147] In this way, corrosion can be detected more efficiently.

[0148] (Technology 14) A refrigeration cycle device described in any one of technologies 1 to 13, wherein the control unit takes appropriate measures regarding the heat exchanger in response to detecting that penetration due to corrosion has occurred in the heat exchanger.

[0149] In this way, countermeasures can be taken in response to the detection of penetration.

[0150] (Technology 15) The refrigeration cycle device described in Technology 14, wherein the response measures include at least one of sending an alert notification, running the refrigeration cycle in a dry operation, running the refrigeration cycle in a freezing operation, stopping the refrigeration cycle, and sending a notification suggesting that cathodic protection be applied to the refrigeration cycle.

[0151] Such countermeasures may notify the user of corrosion detection or may slow the progression of corrosion.

[0152] (Technology 16) The refrigeration cycle device further includes a humidity sensor for detecting the humidity around the heat exchanger, and the control unit acquires the relative humidity around the heat exchanger using the humidity sensor, and if the relative humidity is equal to or less than a sixth threshold and the corrosion current is greater than a seventh threshold, or if the relative humidity is higher than the sixth threshold and the corrosion current is equal to or less than the seventh threshold, the control unit presents a detection error related to the corrosion sensor.

[0153] In this way, it is possible to check whether the corrosion sensor is operating correctly before performing corrosion detection.

[0154] (Technology 17) A corrosion detection method for detecting corrosion occurring in a heat exchanger of a refrigeration cycle of a refrigeration cycle device, comprising the steps of: acquiring log data of corrosion current for a first time period using a corrosion sensor provided on the surface of the heat exchanger; determining, based on the log data, whether an oscillatory component is continuously occurring in the corrosion current for a second time period that is shorter than the first time period; and detecting that penetration due to corrosion has occurred in the heat exchanger if it is determined that an oscillatory component is continuously occurring in the corrosion current for the second time period.

[0155] (Technology 18) A program that causes a refrigeration cycle device to execute the corrosion detection method described in Technology 17.

[0156] (Technology 19) A non-transitory computer-readable storage medium on which a computer program is stored, the non-transitory computer-readable storage medium realizing the corrosion detection method described in Technology 17 when the computer program is executed by a processor.

[0157] The corrosion detection method, program, or storage medium makes it possible to detect the occurrence of corrosion penetration in a heat exchanger.

[0158] The above are merely specific embodiments of the present disclosure, and the scope of protection of the present disclosure is not limited thereto. The present disclosure includes the contents described above in the drawings and the specific embodiments described above, but the present disclosure is not limited thereto. Various disclosed embodiments or examples can be combined without departing from the scope or spirit of the present disclosure. Modifications that do not depart from the functional and structural principles of the present disclosure are within the scope of the claims.

[0159] REFRIGERATION CYCLE DEVICE 11 REFRIGERATION CYCLE 12 CORROSION SENSOR 121 COPPER PIPE 122 EPOXY 123 CARBON 124 COATED COPPER WIRE 13 MEMORY UNIT 14 CONTROL UNIT 15 HUMIDITY SENSOR 16 TEMPERATURE SENSOR 18 COMMUNICATION UNIT 20 TERMINAL DEVICE 22 RELATED APPLICATION 30 SERVER

Claims

1. A refrigeration cycle device comprising: a refrigeration cycle having a heat exchanger; a corrosion sensor provided on the surface of the heat exchanger; and a control unit that controls the refrigeration cycle and acquires a corrosion current from the corrosion sensor, wherein the control unit acquires log data of the corrosion current for a first time period; determines based on the log data whether an oscillatory component is continuously occurring in the corrosion current for a second time period that is shorter than the first time period; and if it determines that an oscillatory component is continuously occurring in the corrosion current for the second time period, detects that penetration due to corrosion has occurred in the heat exchanger.

2. The refrigeration cycle device of claim 1, wherein the control unit calculates the variance of the corrosion current every third time period shorter than the second time period based on the log data, and if it determines that the duration during which the variance continues to exceed the first threshold value exceeds the second time period, it determines that an oscillatory component is continuously occurring in the corrosion current over the second time period.

3. The refrigeration cycle device according to claim 2, wherein the first time period is divided into a plurality of divided times, each divided time being a fourth time period equal to or greater than the third time period, and a variance exceeding the first threshold exists in all of the divided times within the duration.

4. The refrigeration cycle device according to claim 2 or 3, wherein the control unit calculates a moving average of the corrosion current for each of the third hours based on the log data, and the first threshold value is set based on the moving average.

5. A refrigeration cycle device as described in any one of claims 2 to 4, wherein the control unit calculates a moving average of the corrosion current for each third hour based on the log data, and when it determines that the corrosion current is equal to or less than a second threshold, determines whether the variance exceeds the first threshold, and the second threshold is set based on the variance.

6. The refrigeration cycle device described in claim 5, wherein the control unit, when determining that the corrosion current is greater than the second threshold, obtains a predicted current related to the background current of the corrosion current, determines whether the moving average contains a value outside a predicted current range including the predicted current, and, when determining that the moving average contains a value outside the predicted current range, detects that localized corrosion has occurred in the heat exchanger.

7. The refrigeration cycle device according to claim 5 or 6, wherein the control unit detects that localized corrosion has occurred in the heat exchanger when it determines that the corrosion current is greater than the second threshold value.

8. The refrigeration cycle device according to any one of claims 2 to 7, wherein the control unit calculates a moving average of the corrosion current for each of the third hours based on the log data, obtains a predicted current for the background current of the corrosion current if it determines that the duration does not exceed the second hour, determines whether the moving average contains a value outside a predicted current range that includes the predicted current, and detects that localized corrosion has occurred in the heat exchanger if it determines that the moving average contains a value outside the predicted current range.

9. A refrigeration cycle device according to any one of claims 2 to 8, wherein the control unit detects that localized corrosion has occurred in the heat exchanger when it determines that the duration does not exceed the second time.

10. A refrigeration cycle device according to any one of claims 6 to 9, wherein the control unit counts the number of times that localized corrosion is detected, and when it determines that the number of times that localized corrosion is detected exceeds a third threshold, takes appropriate measures regarding the heat exchanger.

11. The refrigeration cycle apparatus according to claim 6 or 8, wherein the control unit calculates an amount of charge corresponding to localized corrosion based on the moving average and the predicted current, calculates a corrosion amount corresponding to localized corrosion based on the amount of charge, and takes appropriate measures regarding the heat exchanger if it determines that the corrosion amount exceeds a fourth threshold value.

12. A refrigeration cycle device as described in any one of claims 1 to 11, wherein the control unit, before acquiring the log data of the corrosion current for the first time, determines whether the corrosion current is greater than a fifth threshold value, and if it determines that the corrosion current is greater than the fifth threshold value, detects that corrosion has occurred in the heat exchanger and takes appropriate measures regarding the heat exchanger.

13. The refrigeration cycle device according to claim 12, wherein, when the control unit determines that the corrosion current is greater than the fifth threshold, the control unit acquires the log data of the corrosion current for the first time period and detects the corrosion status of the heat exchanger.

14. A refrigeration cycle device according to any one of claims 1 to 13, wherein the control unit takes corrective measures regarding the heat exchanger in response to detecting that penetration due to corrosion has occurred in the heat exchanger.

15. The refrigeration cycle device according to claim 14, wherein the countermeasure includes at least one of sending an alert notification, causing the refrigeration cycle to perform a dry operation, causing the refrigeration cycle to perform a freezing operation, causing the refrigeration cycle to stop operation, and sending a notification suggesting that cathodic protection be applied to the refrigeration cycle.

16. A refrigeration cycle device according to any one of claims 1 to 15, further comprising a humidity sensor for detecting the humidity around the heat exchanger, and wherein the control unit obtains the relative humidity around the heat exchanger using the humidity sensor, and indicates a detection error related to the corrosion sensor if the relative humidity is equal to or less than a sixth threshold and the corrosion current is greater than a seventh threshold, or if the relative humidity is higher than the sixth threshold and the corrosion current is equal to or less than the seventh threshold.

17. A corrosion detection method for detecting corrosion occurring in a heat exchanger of a refrigeration cycle of a refrigeration cycle device, comprising: a step of acquiring log data of corrosion current for a first time period using a corrosion sensor provided on the surface of the heat exchanger; a step of determining whether an oscillatory component is continuously occurring in the corrosion current for a second time period shorter than the first time period based on the log data; and a step of detecting that penetration due to corrosion has occurred in the heat exchanger when it is determined that an oscillatory component is continuously occurring in the corrosion current for the second time period.

18. A program for causing a refrigeration cycle device to execute the corrosion detection method according to claim 17.

19. A non-transitory computer-readable storage medium having a computer program stored thereon, the non-transitory computer-readable storage medium realizing the corrosion detection method of claim 17 when the computer program is executed by a processor.

Images