Refrigeration cycle device and method for controlling same

Abstract

A refrigeration cycle device (100) comprises a refrigeration cycle circuit. The refrigeration cycle circuit comprises: a compressor (1); a gas-liquid separator (2) disposed on the suction side of the compressor (1); and a condenser (3) that condenses refrigerant discharged from the compressor 1. The refrigeration cycle circuit circulates a mixed refrigerant containing a plurality of types of refrigerant each having a different evaporation temperature. The refrigeration cycle device (100) is provided with a bypass circuit (7) that returns the refrigerant from the discharge side of the compressor (1) to the suction side of the compressor (1), bypassing the condenser (3). The refrigeration cycle device (100) includes a control device (17). The control device (17) carries out control in which the control device: determines, before the compressor (1) starts up, whether or not the internal temperature of the gas-liquid separator (2) is no more than a threshold value; opens the bypass circuit (7) if the internal temperature is no more than the threshold value; and starts up the compressor (1) at a lower speed than a normal region.

Description

Refrigeration cycle device and control method thereof

[0001] The present invention relates to a refrigeration cycle device and a control method thereof.

[0002] To prevent global warming, there is a continuous demand for a shift from refrigerants with high global warming potential (GWP) to refrigerants with low GWP. Among various refrigerants, ethylene-based fluorocarbon refrigerants such as R1123, R1132(E), and R1132a are known for their high performance. These ethylene-based refrigerants are known to undergo disproportionation reactions (autolysis reactions) under high-temperature and high-pressure conditions when used alone. Therefore, they are often mixed with higher-boiling refrigerants, such as R1234yf, to reduce the risk of disproportionation reactions. Examples of such mixed refrigerants include R474B refrigerant, which has a component composition of R1132(E) / R1234yf=31.5 / 68.5. R474B refrigerant is non-toxic and has a GWP AR4 (Fourth Assessment Report) value of approximately 3 and a GWP AR6 value of approximately 0.34. It is expected to be a next-generation low-GWP refrigerant.

[0003] International Publication No. 2015 / 140884 (Patent Document 1) is known in relation to disproportionation reactions. Patent Document 1 discloses a technology aimed at providing a safe and high-performance refrigeration cycle system by preventing conditions under which a refrigerant that undergoes a disproportionation reaction is placed in the refrigeration cycle system, even when the refrigerant is used as one of non-azeotropic refrigerant mixtures in which a disproportionation reaction occurs. The prior art disclosed in Patent Document 1 is a refrigeration cycle system that uses a non-azeotropic refrigerant mixture containing a first refrigerant and a second refrigerant having a higher boiling point than the first refrigerant at the same pressure as the working refrigerant. The first refrigerant has a characteristic that causes a disproportionation reaction. In the initial state after startup of the compressor, the temperature or pressure of the refrigerant discharged from the compressor is suppressed compared to normal operation based on the amount of liquid refrigerant in the gas-liquid separator. Patent Document 1 also discloses a configuration in which a refrigerant pipe passes through the accumulator, heating the liquid refrigerant with the heat of the gas refrigerant in the pipe, or a heating means such as an electric heater attached to the outer surface of the accumulator.

[0004] In the prior art of Patent Document 1, in order to avoid the risk of disproportionation reactions, the compressor is operated at a low speed and the accumulator is heated using discharge gas after startup. Therefore, the prior art of Patent Document 1 can mitigate the refrigerant property conditions that make disproportionation likely to occur immediately after startup. However, the prior art of Patent Document 1 does not address cases where the refrigeration cycle circuit is stopped for a long period of time. That is, when the refrigeration cycle circuit is stopped for a long period of time, the temperature in the gas-liquid separator drops when the compressor is started, and the refrigerant property inside the gas-liquid separator is already biased. In this case, the prior art of Patent Document 1 returns the refrigerant directly to the compressor, which can become an ignition source, upon startup, which is insufficient in addressing the risk of disproportionation reactions.

[0005] International Publication No. 2015 / 140884

[0006] The present disclosure has been made in consideration of the above points, and aims to provide a refrigeration cycle device and a control method for the refrigeration cycle device that can further reduce the risk of disproportionation reactions caused by imbalances in refrigerant properties due to a decrease in the internal temperature of a gas-liquid separator when the refrigeration cycle circuit is stopped for an extended period of time.

[0007] In order to solve the above-mentioned problems, the present disclosure provides a refrigeration cycle apparatus having the following characteristics. The refrigeration cycle apparatus includes a compressor, a gas-liquid separator provided on the suction side of the compressor, and a condenser that condenses refrigerant discharged from the compressor, and includes a refrigeration cycle circuit in which a mixed refrigerant containing multiple types of refrigerants with different evaporation temperatures circulates. The refrigeration cycle apparatus also includes a bypass circuit that returns refrigerant from the discharge side of the compressor to the suction side of the compressor, bypassing the condenser. The refrigeration cycle apparatus further includes a control device that, before starting the compressor, determines whether the internal temperature of the gas-liquid separator is equal to or lower than a threshold value, and if the internal temperature is equal to or lower than the threshold value, opens the bypass circuit and controls the compressor to start at a speed lower than the normal range.

[0008] The above configuration makes it possible to further reduce the risk of disproportionation reactions caused by deviations in the physical properties of the refrigerant due to a drop in the internal temperature of the gas-liquid separator when the refrigeration cycle circuit is stopped for an extended period of time.

[0009] In addition, a control method executed by the above-described refrigeration cycle apparatus is provided.

[0010] Fig. 1 is a diagram showing the overall configuration of a refrigerator according to an embodiment of the present disclosure, Fig. 2 is a diagram showing the configuration of a gas-liquid separator in a refrigeration cycle circuit of a refrigerator according to an embodiment of the present disclosure, and Fig. 3 is a flowchart showing startup control executed by a refrigerator according to an embodiment of the present disclosure.

[0011] One or more embodiments of the present disclosure will be described below with reference to the drawings, but the embodiments of the present disclosure are not limited to the specific embodiments described below. Note that the same reference numerals throughout the drawings indicate the same or corresponding parts.

[0012] The present disclosure relates to a refrigeration cycle apparatus and a control method thereof. A refrigeration cycle apparatus according to an embodiment of the present disclosure includes a compressor, a gas-liquid separator provided on the suction side of the compressor, and a condenser that condenses refrigerant discharged from the compressor. The refrigeration cycle apparatus includes a refrigeration cycle circuit through which a mixed refrigerant containing multiple types of refrigerants with different evaporation temperatures circulates (under the same pressure). The refrigeration cycle apparatus also includes a bypass circuit that returns refrigerant from the discharge side of the compressor to the suction side of the compressor, bypassing the condenser. The refrigeration cycle apparatus further includes a control device that, before starting the compressor, determines whether an internal temperature of the gas-liquid separator is equal to or lower than a threshold value. If the internal temperature is equal to or lower than the threshold value, the control device opens the bypass circuit and controls the compressor to start at a speed lower than the normal range.

[0013] As described above, in a refrigeration cycle circuit in which a mixed refrigerant containing multiple types of refrigerants with different evaporation temperatures circulates, if the operation is stopped for an extended period of time, a temperature drop can cause imbalances in the refrigerant properties inside the gas-liquid separator before the compressor draws in. The above configuration further reduces the risk of disproportionation reactions caused by imbalances in the refrigerant properties that accompany a drop in the internal temperature of the gas-liquid separator during a long period of shutdown. Furthermore, because the compressor is started at a lower rotation speed than normal operation, the refrigerant circulates at a lower pressure, further reducing the risk of disproportionation reactions during compressor startup.

[0014] In a preferred embodiment, the control device further evaluates the stop time during which the refrigeration cycle circuit is stopped and determines whether or not the evaluation result of the stop time satisfies a condition in addition to the internal temperature being equal to or lower than a threshold value. By using the evaluation result of the stop time during which the refrigeration cycle circuit is stopped as a condition in addition to the internal temperature as a condition, it is possible to reliably condition the state inside the gas-liquid separator that requires action before the compressor is started.

[0015] In a specific embodiment, at least one refrigerant in the mixed refrigerant is a refrigerant that undergoes a disproportionation reaction, and the (local) refrigerant composition in the gas-liquid separator is changed by opening the bypass circuit and allowing the refrigerant to flow from the bypass circuit into the gas-liquid separator.

[0016] Oil is stored inside the gas-liquid separator, and some of the refrigerant dissolves in the oil. The mixed refrigerant inside the gas-liquid separator has a set composition (concentration) when the refrigeration cycle is operating. However, if the refrigeration cycle is shut down for an extended period of time, the difference in vapor pressure between the various refrigerants in the mixed refrigerant can change the way the refrigerant dissolves in the oil, resulting in changes to the composition of the gas refrigerant inside the gas-liquid separator, potentially resulting in imbalances in the refrigerant properties over time and at different temperatures. This can increase the ratio of refrigerants with low evaporation temperatures and refrigerants that undergo disproportionation reactions. If the refrigeration cycle is started while the ratio of refrigerant properties that cause disproportionation reactions is elevated, disproportionation reactions are more likely to occur even at low pressures and temperatures after the compressor starts. Therefore, by opening the bypass circuit and allowing refrigerant to flow from the bypass circuit into the gas-liquid separator, the refrigerant composition inside the gas-liquid separator can be adjusted to a composition closer to the set concentration, further reducing the risk of disproportionation reactions.

[0017] In a specific embodiment, the refrigeration cycle device includes a timer that accumulates time since operation was stopped. The stop time of the refrigeration cycle circuit is evaluated based on the accumulated time accumulated by the timer. The above-mentioned condition includes a time threshold for the accumulated time.

[0018] In another specific embodiment, the refrigeration cycle device includes an outside air temperature sensor that measures the outside air temperature and a refrigerant temperature sensor that measures a refrigerant temperature associated with the refrigeration cycle circuit (e.g., the internal temperature of a gas-liquid separator). The stop time of the refrigeration cycle circuit is evaluated based on the temperature difference between the outside air temperature and the refrigerant temperature. The condition includes a temperature difference threshold for the temperature difference. This is because, as the stop time of the refrigeration cycle circuit increases, the refrigerant temperature of the refrigeration cycle circuit gradually approaches the outside air temperature from the temperature range of the operating state, and therefore the difference between the refrigerant temperature and the outside air temperature is a good indicator of the stop time of the refrigeration cycle circuit.

[0019] In a specific embodiment, the control device starts the compressor in a low-speed state, then closes the bypass circuit, and transitions the compressor to normal operation. In a specific embodiment, the closing of the bypass circuit and the operation of the compressor in the normal operation range are performed after a predetermined time has elapsed.

[0020] In a particular embodiment, the bypass circuit includes a pipe extending from the discharge side of the compressor to the inlet of the gas-liquid separator, and an electromagnetic valve that opens and closes the flow path of the pipe.

[0021] According to an embodiment of the present disclosure, there is also provided a control method executed by a refrigeration cycle apparatus. The refrigeration cycle apparatus includes a refrigeration cycle circuit in which a mixed refrigerant containing multiple types of refrigerants with different evaporation temperatures circulates (under the same pressure), and a control device. The control method includes a step in which the control device determines whether an internal temperature of a gas-liquid separator provided before the compressor in the refrigeration cycle circuit on the suction side of the compressor is equal to or lower than a threshold. The control method also includes a step in which the control device, when the internal temperature is equal to or lower than the threshold, opens a bypass circuit that returns refrigerant from the discharge side of the compressor to the suction side of the compressor, bypassing the condenser, and starts the compressor at a speed lower than the normal range.

[0022] The above configuration makes it possible to further reduce the risk of disproportionation reactions caused by deviations in refrigerant properties due to a decrease in the internal temperature of the gas-liquid separator when the system is not in operation for a long period of time.

[0023] In a specific embodiment, the determining step includes a step of evaluating a stop time during which the refrigeration cycle circuit is stopped and a step of determining whether the evaluation result of the stop time satisfies a condition. The opening step and the starting step are performed when the internal temperature is equal to or lower than a threshold and the evaluation result of the stop time satisfies the condition. By using the evaluation result of the stop time during which the refrigeration cycle circuit is stopped in addition to the internal temperature as a condition, it is possible to reliably condition the state inside the gas-liquid separator that requires action before starting the compressor.

[0024] In a specific embodiment, the control method further includes a step of causing the control device to operate a timer that accumulates time in response to a command to stop operation. The evaluating step includes a step of evaluating a stop time of the refrigeration cycle circuit based on the accumulated time accumulated by the timer in response to a command to start operation. The condition includes a time threshold for the accumulated time.

[0025] Hereinafter, a refrigeration cycle apparatus and a control method thereof according to an embodiment of the present disclosure will be described in more detail with reference to FIGS.

[0026] 1 is a diagram showing the overall configuration of a refrigerator 100 as a refrigeration cycle apparatus according to an embodiment of the present disclosure. The refrigerator 100 is also called a condensing unit.

[0027] First, a refrigeration cycle circuit of the refrigerator 100 shown in Fig. 1 will be described below. In Fig. 1, the refrigeration cycle circuit of the refrigerator 100 is indicated by solid lines, and the flow of refrigerant is indicated by solid arrows. As shown in Fig. 1, the refrigerator 100 includes a compressor 1 that draws in refrigerant gas, compresses the drawn refrigerant, and discharges the compressed refrigerant, and a condenser 3 into which the refrigerant discharged from the compressor 1 flows.

[0028] The compressor 1 is a compressor of any type, such as a screw type, scroll type, reciprocating type, rotary type, or turbo type. The condenser 3 is a heat exchanger that condenses the refrigerant discharged from the compressor 1 by exchanging heat with a fluid such as air. The condenser 3 shown in Fig. 1 is an air-cooled heat exchanger, and the refrigerator 100 is provided with a blower 9 for blowing air to the condenser 3. The blower 9 blows air drawn in from the outside toward the condenser 3, or draws air from the outside through the condenser 3, thereby blowing air to the condenser 3.

[0029] 1 further includes a subcooler 5 into which the condensed refrigerant from the condenser 3 flows and which subcools the refrigerant that has flowed in. The subcooler 5 is provided with a subcooling expansion valve 6, and a portion of the refrigerant is decompressed by the subcooling expansion valve 6 and enters the subcooler 5, where it exchanges heat with the refrigerant from the condenser 3 to subcool the refrigerant from the condenser 3, and is then returned to the compressor 1.

[0030] The refrigerator 100 further includes an evaporator 12 and an expansion valve 13. The refrigerant delivered from the condenser 3 and supercooled by the supercooler 5 is decompressed by the expansion valve 13, which serves as an expansion mechanism, and supplied to the evaporator 12. In the evaporator 12, the refrigerant absorbs heat from a fluid, such as air, and evaporates. The refrigerant gas is then discharged from the evaporator 12 to the compressor 1. The refrigerator 100 shown in FIG. 1 also includes a blower 14 for blowing air to the evaporator 12. The blower 14 blows air drawn in from the outside toward the evaporator 12, or draws air from the outside through the evaporator 12 to blow air to the evaporator 12. The fluid is not limited to air and may be water. In the configuration shown in FIG. 1, the evaporator 12 and expansion valve 13, enclosed by dotted lines, are typically external components of the refrigerator 100 that are prepared by the user and constitute a showcase, refrigerator / freezer, unit cooler, chiller, ice maker, or the like.

[0031] The embodiment shown in FIG. 1 further includes a gas-liquid separator 2 provided between the evaporator 12 and the compressor 1, which separates the refrigerant liquid mixed in the gas refrigerant and allows only the gas refrigerant to be sucked into the compressor 1.

[0032] In the embodiment shown in Fig. 1, as described above, the gas-liquid separator 2, compressor 1, condenser 3, expansion valve 13, and evaporator 12 are connected in sequence to form a refrigeration cycle circuit. In the example shown in Fig. 1, a pressure shutoff valve HP is provided on the discharge side of the compressor 1, and a check valve V1 is provided between the compressor 1 and the condenser 3. In addition, a strainer S1 is provided on the inlet side of the gas-liquid separator 2, and a valve V2 is provided between the gas-liquid separator 2 and the evaporator 12.

[0033] A mixed refrigerant containing multiple types of refrigerants with different evaporation temperatures is circulated through the refrigeration cycle circuit under the same pressure. The refrigerant used in the refrigerator 100 can be a mixture of a first refrigerant capable of undergoing a disproportionation reaction and a second refrigerant with a higher boiling point and evaporation temperature than the first refrigerant. The first refrigerant is not particularly limited, but can be an ethylene-based fluorohydrocarbon refrigerant such as 1,1,2-trifluoroethylene (R1123), trans-1,2-difluoroethylene (R1132(E)), 1,1-difluoroethylene (R1132a), cis-1,2-difluoroethylene (R1132(Z)), or fluoroethylene (R1141). The second refrigerant with a high boiling point can be a propylene-based fluorohydrocarbon refrigerant such as 2,3,3,3-tetrafluoropropene (R1234yf). By using a mixture of a first ethylene-based refrigerant and a second refrigerant with a higher evaporation temperature, the risk of disproportionation reactions of the ethylene-based refrigerant can be reduced. The mixed refrigerant is not particularly limited, but is preferably a two-type mixed refrigerant. Known examples of such two-type mixed refrigerants include R474B refrigerant, which has a component composition of R1132(E) (boiling point = -52.5°C) / R1234yf (boiling point = -30°C) = 31.5 / 68.5. Using a refrigerant with a low GWP (Global Warming Potential) can reduce the impact on global warming caused by refrigerant leakage from a refrigerator.

[0034] The above-described chiller 100 further includes a bypass circuit 7 in addition to the above-described refrigeration cycle circuit, which returns refrigerant from the discharge side of the compressor 1 to the suction side of the compressor 1, bypassing the condenser 3. In the embodiment shown in Fig. 1 , the bypass circuit 7 includes a pipe that bypasses from the discharge side of the compressor 1 to the inlet side (before the strainer S1) of the gas-liquid separator 2 provided on the suction side of the compressor 1, and an electromagnetic valve 8 provided in the pipe for opening and closing the bypass circuit. Note that the bypass method of the bypass circuit 7 is not particularly limited, and may be a bypass to the inlet side of the gas-liquid separator provided before the suction port of the compressor 1 as shown in Fig. 1 , a bypass to the outlet of the evaporator 12, or a bypass to the inlet of the evaporator 12.

[0035] The chiller 100 further includes various sensors, various actuators, and a control device 17. More specifically, the various sensors include a temperature sensor 15 that measures the temperature inside the gas-liquid separator 2 and an outside air temperature sensor 16 that is provided in the condenser 3. The various actuators include blowers 9, 14 and a solenoid valve 8. In addition, the chiller 100 shown in FIG. 1 is provided with a high-pressure side pressure sensor PSH on the discharge side of the compressor 1, and a low-pressure side pressure sensor PSL on the inlet side of the gas-liquid separator 2.

[0036] The control device 17 performs overall control of the chiller 100. Based on signals from various sensors, the control device 17 controls the rotation speed of the compressor 1, the rotation speed of the blower 9, the opening degree of the expansion valve 13, or the rotation speed of the blower 14 of the evaporator 12. Based on signals from the various sensors, the control device 17 also controls the drive of the motor of the blower 9 to control the volume of air sent to the condenser 3. Based on signals from the various sensors, the control device 17 also controls the drive of the motor of the blower 14 to control the volume of air sent to the evaporator 12.

[0037] As described above, when a refrigeration cycle circuit in which a mixed refrigerant containing multiple types of refrigerants with different evaporation temperatures is used, if the refrigeration cycle circuit is stopped for an extended period of time, a deviation in the physical properties of the refrigerant may occur in the portion before the intake of the compressor 1, more specifically, in the gas-liquid separator 2 provided between the evaporator 12 and the compressor 1. Such a deviation in the physical properties of the refrigerant may cause a disproportionation reaction under lower temperature and pressure conditions.

[0038] 2 is a diagram illustrating the configuration of a gas-liquid separator 2 in a refrigeration cycle circuit of a refrigerator 100 according to an embodiment of the present disclosure. The gas-liquid separator 2 includes a housing 2a serving as a container, a pipe 2b connected to the evaporator 12 side, and a U-shaped tube 2c connected to the compressor 1 side. A mixed gas refrigerant G is present inside the gas-liquid separator 2, and refrigeration oil O is also stored therein. A small hole 2d is provided at the bottom of the internal U-shaped tube 2c, and liquid is returned to the compressor 1 little by little through the small hole 2d.

[0039] In the gas-liquid separator 2, the mixed gas refrigerant G inside has a set composition (concentration) when the refrigeration cycle circuit is operating. However, if the refrigeration cycle circuit is stopped for an extended period of time, the temperature drops below that of the operating state. Due to differences in vapor pressure between the various refrigerants, the dissolution rate of the refrigerant into the refrigeration oil O varies. This changes the composition of the mixed gas refrigerant G inside the gas-liquid separator 2, potentially resulting in deviations in the refrigerant properties over time and at different temperatures. Because ethylene-based refrigerants are mixed with refrigerants with high boiling points, the proportion of ethylene-based refrigerants, which have relatively low evaporation temperatures, may increase if the refrigerant cools down after a long period of shutdown. When the compressor 1 starts, the mixed gas refrigerant G inside the gas-liquid separator 2 is drawn into the compressor 1. Therefore, disproportionation reactions are more likely to occur immediately after the compressor starts, even at low pressures and temperatures.

[0040] Therefore, in the chiller 100 according to the embodiment of the present disclosure, the control device 17 determines whether the internal temperature of the gas-liquid separator 2 measured by the temperature sensor 15 is equal to or lower than a threshold value before starting the compressor 1, and if the internal temperature is equal to or lower than the threshold value, opens the electromagnetic valve 8, opens the bypass circuit 7, and controls the compressor 1 to start at a speed lower than the normal range. More preferably, in order to more reliably detect a state requiring measures due to a long-term shutdown, the control device 17 can evaluate the shutdown time during which the refrigeration cycle circuit was stopped and determine whether the evaluation result of the shutdown time satisfies the conditions in addition to the internal temperature being equal to or lower than the threshold value.

[0041] Before starting the compressor 1 of the refrigeration cycle circuit, the bypass circuit 7 is opened as necessary to allow refrigerant to flow from the bypass circuit 7 into the gas-liquid separator 2. This can change the refrigerant composition in the gas-liquid separator 2 to a composition closer to the set concentration. Because the refrigeration cycle circuit has been stopped for a long period of time, the refrigerant flowing in is in a relatively high-pressure state on the discharge side of the compressor 1, although the temperature range remains the same. By introducing such relatively high-pressure refrigerant, the composition of the mixed gas refrigerant G in the gas-liquid separator 2 is changed to approach the set composition. This alleviates the condition in which disproportionation reactions are likely to occur in the low-pressure, low-temperature range when the refrigeration cycle circuit is started with an elevated ethylene-based refrigerant property ratio, further reducing the risk of disproportionation reactions due to imbalances in the refrigerant properties during a long period of shutdown. Furthermore, starting the refrigeration cycle circuit at a speed slower than normal operation can further reduce the risk of disproportionation reactions due to imbalances in the refrigerant properties during a long period of shutdown.

[0042] Here, the normal region for operation of the compressor 1 refers to a possible region (range) of the frequency or rotation speed of the compressor 1 when performing an operation in which the rotation speed of the compressor 1, the rotation speed of the blower 9, the opening of the expansion valve 13, or the rotation speed of the blower 14 of the evaporator 12 is controlled so as to achieve a target discharge refrigerant temperature and pressure corresponding to the target capacity of the chiller 100. Starting at a speed lower than normal operation means starting at a rotation speed lower than the rotation speed region of such normal operation.

[0043] Regarding the state of the refrigeration cycle circuit, since the risk is due to differences in the way the oil dissolves due to the temperature being lower than in the operating state, first, it is determined whether the internal temperature of the gas-liquid separator 2 measured by the temperature sensor 15 is equal to or lower than a threshold value. If the internal temperature of the gas-liquid separator 2 is lower than the predetermined threshold value, the bypass circuit described above is not opened.

[0044] In addition, in order to more reliably determine the condition that requires action in response to a long-term shutdown, it is determined whether the evaluation result of the shutdown time of the refrigeration cycle circuit satisfies the condition in addition to whether the internal temperature is below a threshold. The shutdown time of the refrigeration cycle circuit can be evaluated using several methods.

[0045] The first method is to directly measure the stop time. As shown in FIG. 1 , the control device 17 includes a timer function 18. The timer function 18 is used to accumulate the time since the operation has been stopped. For example, a timer may be activated when the operation is stopped to measure the time, or time information at the time of the operation stop (such as the time on a real-time clock (RTC) or the time elapsed since a reference time) may be recorded and compared with the current time information when the compressor 1 is started to evaluate the stop time. In this way, the stop time of the refrigeration cycle circuit may be evaluated based on the accumulated time accumulated by the timer. When determining whether the condition is satisfied, if the accumulated time exceeds a predetermined time threshold, it can be evaluated as a time stop requiring action.

[0046] The second method is to indirectly evaluate the shutdown time based on the difference between the readings of the temperature sensor 15 in the refrigeration cycle circuit and the readings of the outside air temperature sensor 16. As the shutdown time of the refrigeration cycle circuit increases, the refrigerant temperature of the refrigeration cycle circuit gradually approaches the outside air temperature from the operating temperature range. Therefore, the temperature difference between the refrigerant temperature and the outside air temperature is a good indicator of the shutdown time of the refrigeration cycle circuit. The temperature difference is calculated and compared with a preset temperature difference threshold. If the temperature difference between the refrigerant temperature and the outside air temperature falls within a certain range, it can be evaluated that the refrigeration cycle circuit has been shut down for a period of time requiring action. In this way, the shutdown time of the refrigeration cycle circuit may be evaluated based on the temperature difference between the outside air temperature and the refrigerant temperature.

[0047] After the bypass circuit 7 is opened and the compressor 1 is started in the low-speed state, the bypass circuit can be closed at an appropriate timing to transition the compressor 1 to operation in the normal range. For example, the control device 17 may close the bypass circuit 7 and operate the compressor 1 in the normal range after a predetermined time has elapsed. The start of the compressor 1 in the low-speed state after the bypass circuit 7 is opened can also be delayed by a predetermined delay time.

[0048] FIG. 3 is a flowchart showing the startup control executed by the control device 17 provided in the refrigerator 100 according to this embodiment.

[0049] 3 starts from step S100. At this point, the compressor 1 is not operating, and the refrigeration cycle circuit is in a stopped state. Also, the bypass circuit 7 is closed if it was open during the previous stop. At this point, the bypass circuit is closed.

[0050] In step S101, the control device 17 receives an instruction to start operation. Here, the instruction to start operation may be issued manually by a user such as an administrator of the chiller 100, or may be issued according to a schedule set in advance by the administrator.

[0051] In step S102, the control device 17 measures the temperature inside the gas-liquid separator 2 using the temperature sensor 15. In step S103, the control device 17 acquires the accumulated time since the previous shutdown using the timer function 18. Here, it is assumed that the timer recorded the time information when the refrigeration cycle circuit was previously shut down. In this case, in step S103, the control device 17 acquires the current time information and calculates the accumulated time from the difference between the recorded time information at the time of shutdown and the current time information.

[0052] In step S104, the control device 17 determines whether the internal temperature is equal to or lower than the temperature threshold and the stop time is equal to or higher than the time threshold. If it is determined in step S104 that the internal temperature is equal to or lower than the temperature threshold and the stop time is equal to or higher than the time threshold (YES), control branches to step S105. In step S105, the control device 17 opens the electromagnetic valve 8 and opens the bypass circuit 7. In step S106, the control device 17 starts operation of the compressor 1 at a low rotation frequency and circulates the refrigerant at a low pressure. A predetermined delay time may be provided between steps S105 and S106.

[0053] In step S107, the control device 17 shifts the rotation frequency of the compressor 1 to the normal region, and in step S108, the operation shifts to normal operation. At this time, the control device 17 may close the electromagnetic valve 8 and close the bypass circuit 7. In addition, a predetermined delay time is provided between step S106 and step S107.

[0054] On the other hand, if it is determined in step S104 that the internal temperature is not equal to or lower than the temperature threshold value, or that the stop time is not equal to or higher than the time threshold value, or both (NO), the control proceeds directly to step S108. In step S108, the control device 17 sets the rotation frequency of the compressor 1 to the normal region, starts the operation of the compressor 1, and transitions to normal operation in step S108.

[0055] After the transition to normal operation, the timer will be reset as necessary in response to an instruction to stop operation, and will be restarted and time information will be recorded. When operation is stopped, the electromagnetic valve 8 will be closed and the bypass circuit 7 will be closed.

[0056] As described above, according to an embodiment of the present disclosure, a refrigeration cycle device and a control method thereof are provided that can further reduce the risk of disproportionation reactions caused by imbalances in refrigerant properties due to a decrease in the internal temperature of the gas-liquid separator when the refrigeration cycle circuit is stopped for an extended period of time.

[0057] As described above, in a refrigeration cycle circuit in which a mixed refrigerant containing multiple types of refrigerants with different evaporation temperatures circulates, if the operation is stopped for an extended period of time, a temperature drop can cause an imbalance in the composition of the gas refrigerant inside the gas-liquid separator before the compressor's intake due to differences in the ease of dissolving the refrigerant in oil due to differences in evaporation temperatures. The above configuration further reduces the risk of disproportionation reactions caused by imbalances in refrigerant properties due to a drop in the internal temperature of the gas-liquid separator during an extended period of shutdown. Furthermore, because the compressor is started at a lower rotation speed than normal operation, the refrigerant circulates at a lower pressure, further reducing the risk of disproportionation reactions when the compressor is started.

[0058] Furthermore, since the refrigerant flows in from the bypass circuit on the discharge side of the compressor, it acts to increase the pressure inside the gas-liquid separator, but it is expected that the advantage of the flowing in refrigerant is that it will adjust the refrigerant composition inside the gas-liquid separator to the normal side.

[0059] Furthermore, the conventional technology of Patent Document 1 mentioned above discloses measures to be taken after the compressor is started, but such a configuration is not capable of dealing with a situation in which the temperature inside the gas-liquid separator drops when the compressor is started, such as when the refrigeration cycle circuit is stopped for an extended period of time, and the physical properties of the refrigerant inside the gas-liquid separator have already become unbalanced.

[0060] In the above-described embodiment, the refrigerator 100 has been described as an example of a refrigeration cycle apparatus according to an embodiment of the present disclosure. However, the refrigeration cycle apparatus is not limited to a refrigerator and may include what is also called a refrigeration air-conditioning apparatus. Here, the term refrigeration air-conditioning apparatus collectively refers to devices that use a refrigerant and a refrigeration cycle, such as the refrigerator described above, air conditioners, and refrigerators. More specifically, examples of refrigeration air-conditioning apparatus include heat source equipment such as the refrigerator and chilling unit described above, air conditioners such as package air conditioners and multi-air conditioners for buildings, commercial refrigerators such as showcases, refrigerator-freezers, unit coolers, and ice makers, transportation refrigeration equipment such as car air conditioners, and heat pump water heaters.

[0061] It should be noted that the embodiments of the present invention are not limited to the above-described embodiments and may include various modifications. For example, the above-described embodiments have been described in detail for ease of understanding, and are not necessarily limited to those including all of the described features. Furthermore, some of the features of one embodiment may be replaced with features of another embodiment, or features of one embodiment may be added to features of another embodiment. Furthermore, some of the features of each embodiment may be added to, deleted from, or replaced with other features.

[0062] 100...refrigerating machine, 1...compressor, 2...gas-liquid separator, 3...condenser, 5...supercooler, 6...expansion valve, 7...bypass circuit, 8...solenoid valve, 9, 14...blower, 12...evaporator, 13...expansion valve, 15...internal temperature sensor, 16...outside air temperature sensor, 17...control device, 18...timer function

Claims

1. A refrigeration cycle device comprising: a refrigeration cycle circuit including a compressor, a gas-liquid separator provided on the suction side of the compressor, and a condenser for condensing refrigerant discharged from the compressor, in which a mixed refrigerant containing multiple types of refrigerants with different evaporation temperatures circulates; a bypass circuit for returning refrigerant from the discharge side of the compressor to the suction side of the compressor, bypassing the condenser; and a control device that determines whether an internal temperature of the gas-liquid separator is equal to or lower than a threshold value before starting the compressor, and if the internal temperature is equal to or lower than the threshold value, opens the bypass circuit and controls the compressor to start at a speed lower than a normal range.

2. The refrigeration cycle device according to claim 1, wherein the control device further evaluates the stop time during which the refrigeration cycle circuit is stopped, and determines whether the evaluation result of the stop time satisfies the condition in addition to the internal temperature being below a threshold value.

3. The refrigeration cycle device according to claim 2, wherein at least one type of refrigerant in the mixed refrigerant is a refrigerant that undergoes a disproportionation reaction, and the refrigerant composition in the gas-liquid separator is changed by opening the bypass circuit and allowing refrigerant to flow from the bypass circuit into the gas-liquid separator.

4. The refrigeration cycle device according to claim 2, further comprising a timer that accumulates time since operation has stopped, wherein the stop time of the refrigeration cycle circuit is evaluated based on the accumulated time accumulated by the timer, and the condition includes a time threshold value for the accumulated time.

5. A refrigeration cycle device as described in claim 2, further comprising: an outside air temperature sensor that measures the outside air temperature; and a refrigerant temperature sensor that measures the refrigerant temperature associated with the refrigeration cycle circuit, wherein the stop time of the refrigeration cycle circuit is evaluated based on a temperature difference between the outside air temperature and the refrigerant temperature, and the condition includes a temperature difference threshold for the temperature difference.

6. The refrigeration cycle device according to claim 2, wherein the control device closes the bypass circuit after starting the compressor in the low speed state, and transitions the compressor to operation in the normal range.

7. The refrigeration cycle device according to claim 6, wherein the bypass circuit is closed and the compressor is operated in the normal range after a predetermined time has elapsed.

8. The refrigeration cycle device according to claim 2, wherein the bypass circuit includes a pipe extending from the discharge side of the compressor to the inlet of the gas-liquid separator, and an electromagnetic valve for opening and closing the flow path of the pipe.

9. A control method executed by a refrigeration cycle device, the refrigeration cycle device including a refrigeration cycle circuit in which a mixed refrigerant containing multiple types of refrigerants with different evaporation temperatures circulates, and a control device, the control method including the control device executing the following steps: before starting a compressor of the refrigeration cycle circuit, determining whether the internal temperature of a gas-liquid separator provided on the suction side of the compressor is below a threshold value; if the internal temperature is below the threshold value, opening a bypass circuit that returns refrigerant from the discharge side of the compressor to the suction side of the compressor, bypassing a condenser; and starting the compressor at a speed lower than the normal range.

10. A control method as described in claim 9, wherein the determining step includes a step of evaluating a stop time during which the refrigeration cycle circuit has been stopped, and a step of determining whether or not the evaluation result of the stop time satisfies a condition, and the opening step and the starting step are executed when the internal temperature is equal to or lower than a threshold value and the evaluation result of the stop time satisfies the condition.

11. The control method according to claim 10, further comprising a step in which the control device operates a timer that accumulates time in response to a stop of operation, and the evaluating step comprises a step in which, in response to an instruction to start operation, the control device evaluates the stop time of the refrigeration cycle circuit based on the accumulated time accumulated by the timer, and the condition includes a time threshold value for the accumulated time.

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