REFRIGERATION APPARATUS, ENVIRONMENT FORMING APPARATUS, AND REFRIGERATION METHOD

Abstract

 A refrigeration apparatus includes a main circuit that includes a compressor, a condenser, an expansion valve, and an evaporator and circulates a refrigerant, a bypass flow path that includes a flow rate adjusting valve, branches from the main circuit, and causes a refrigerant liquefied in the condenser to be lowered in temperature by the flow rate adjusting valve and to be suctioned into the compressor without passing through the evaporator, an expansion control unit that controls the expansion valve according to a refrigeration request degree, a superheating degree control unit that controls the flow rate adjusting valve so that a degree of superheat with respect to a saturation temperature corresponding to a suction pressure of the compressor becomes a target value, and a changing unit that changes the target value of the degree of superheat.

Description

Field of the Invention

[0001] The present invention relates to a refrigeration apparatus, an environment forming apparatus, and a refrigeration method.

Background Art

[0002] Conventionally, as disclosed in JP H06-4560 U, a refrigeration apparatus including a refrigeration circuit having a bypass flow path for suction injection is known. The bypass flow path is connected to a main circuit of the refrigeration circuit provided with a compressor, a condenser, an expansion valve, and an evaporator. The bypass flow path is a flow path for lowering a temperature and a pressure of a part of a high-pressure liquid refrigerant obtained by the condenser, and returning the refrigerant to a suction port of the compressor while bypassing the expansion valve and the evaporator. By causing the refrigerant flowing through the bypass flow path to be suctioned into the compressor, a discharge pipe temperature of the compressor can be lowered.

[0003] In the configuration in which the bypass flow path is connected to the main circuit as in the refrigeration apparatus disclosed in Japanese Utility Model Laid-Open No. H06-4560 U, the discharge pipe temperature of the compressor can be lowered, so that the compressor can be protected. On the other hand, when the refrigerant having a constant flow rate continues to flow through the bypass flow path, the refrigerant having a predetermined flow rate flows through the bypass flow path even when cooling of the compressor is not originally necessary. Accordingly, the amount of the refrigerant flowing through the evaporator decreases, and thus the refrigeration capacity of the evaporator decreases. Therefore, the refrigeration capacity may be sacrificed while the compressor is excessively protected.

Summary of the Invention

[0004] An object of the present invention is to provide a refrigeration apparatus, an environment forming apparatus, and a refrigeration method capable of adjusting refrigeration capacity of an evaporator while stably driving a compressor by suction injection using a bypass flow path.

[0005] A refrigeration apparatus according to one aspect of the present invention includes a main circuit that includes a compressor, a condenser, an expansion valve, and an evaporator and is configured to circulate a refrigerant, a bypass flow path that includes a flow rate adjusting valve, branches from the main circuit between the condenser and the expansion valve, and causes a refrigerant liquefied in the condenser to be lowered in temperature by the flow rate adjusting valve and to be suctioned into the compressor without passing through the evaporator, an expansion control unit configured to control the expansion valve according to a refrigeration request degree, a superheating degree control unit configured to control the flow rate adjusting valve so that a degree of superheat with respect to a saturation temperature corresponding to a suction pressure of the compressor becomes a target value, and a changing unit configured to change the target value of the degree of superheat.

[0006] An environment forming apparatus according to one aspect of the present invention includes an environment chamber and the refrigeration apparatus for cooling the environment chamber.

[0007] A refrigeration method according to one aspect of the present invention is a refrigeration method using a refrigeration apparatus, the refrigeration apparatus including a main circuit that includes a compressor, a condenser, an expansion valve, and an evaporator and configured to circulate a refrigerant; a bypass flow path that includes a flow rate adjusting valve, branches from the main circuit between the condenser and the expansion valve, and causes a refrigerant liquefied in the condenser to be lowered in temperature by the flow rate adjusting valve and to be suctioned into the compressor without passing through the evaporator; and a reception unit, the refrigeration method including receiving a refrigeration request degree received by the reception unit, controlling the expansion valve according to the refrigeration request degree received by the reception unit, changing a target value of a degree of superheat with respect to a saturation temperature corresponding to a suction pressure of the compressor according to the refrigeration request degree or an opening degree of the expansion valve, and controlling the flow rate adjusting valve so that the degree of superheat becomes the changed target value.

Brief Description of the Drawings

[0008] 

Fig. 1 is a diagram schematically illustrating a configuration of a refrigeration apparatus according to a first embodiment.

Fig. 2 is a diagram schematically illustrating a control device including a controller of the refrigeration apparatus.

Fig. 3 is a diagram for describing a relationship between an in-freezer temperature and a target value of a degree of superheat.

Fig. 4 is a diagram for describing a control flow of the refrigeration apparatus.

Fig. 5 is a diagram schematically illustrating a configuration of a refrigeration apparatus according to a modification of the first embodiment.

Fig. 6 is a diagram schematically illustrating a configuration of a refrigeration apparatus according to a second embodiment.

Fig. 7 is a diagram schematically illustrating a configuration of a refrigeration apparatus according to a modification of the second embodiment.

Fig. 8 is a diagram schematically illustrating a control device including a controller of the refrigeration apparatus.

Fig. 9 is a diagram schematically illustrating an environment forming apparatus according to a third embodiment.

Description of Embodiments

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First Embodiment)

[0010] As illustrated in Fig. 1, a refrigeration apparatus 10 according to a first embodiment includes a main circuit 15 in which a refrigerant is sealed, and a bypass flow path 16 connected to the main circuit 15. The refrigerant may be a low GWP refrigerant such as R-449A or R-448A.

[0011] The main circuit 15 is provided with a compressor 1, a condenser 2, an expansion valve 3, and an evaporator 4 in this order. When the compressor 1 operates, the refrigerant circulates in the main circuit 15, thereby performing a vapor compression refrigeration cycle. The refrigeration apparatus 10 may be used to cool air inside a freezer or a refrigerator, or may be used to generate cooling water in a chiller. Alternatively, the refrigeration apparatus 10 may be used in an environment forming apparatus such as an environment testing apparatus for providing a temperature environment of a predetermined temperature. Note that, in the present embodiment, it is assumed that the refrigeration apparatus 10 is used in a freezer.

[0012] The compressor 1 is responsible for a compression process of a refrigeration cycle, and is configured to suction and compress the refrigerant. The compressor 1 includes, for example, a compression mechanism of a scroll type, a screw type, or the like, and a motor for driving the compression mechanism. The compressor 1 is configured to drive the motor at a constant rotation speed, but may alternatively be configured to be able to adjust the rotation speed of the motor by an inverter. The compressor 1 may include one unit compressor, but alternatively, include two unit compressors having the same capacity or different capacities which are connected in parallel.

[0013] The condenser 2 is responsible for a condensation process of the refrigeration cycle, and is configured to exchange heat of the refrigerant discharged from the compressor 1 with a cooling medium such as air, water, or a refrigerant to condense the refrigerant.

[0014] The expansion valve 3 is responsible for an expansion process of the refrigeration cycle, and is configured to expand the liquid refrigerant condensed in the condenser 2.

[0015] The expansion valve 3 is configured by, for example, an electronic expansion valve. Thus, by adjusting the valve opening degree of the expansion valve 3, it is possible to arbitrarily change the flow rate of the liquid refrigerant flowing through the evaporator 4 in the main circuit 15.

[0016] The evaporator 4 is responsible for an evaporation process of the refrigeration cycle, and is configured to exchange heat between the liquid refrigerant having a low pressure by the expansion valve 3 and air to evaporate the liquid refrigerant. That is, the evaporator 4 cools the air supplied into the cooling room of the freezer.

[0017] The bypass flow path 16 branches from the main circuit 15 on the downstream side of the condenser 2. That is, one end of the bypass flow path 16 is connected to the main circuit 15 between the condenser 2 and the expansion valve 3. The other end of the bypass flow path 16 is connected to the main circuit 15 between the evaporator 4 and the compressor 1. Thus, the refrigerant flowing through the bypass flow path 16 merges with the refrigerant evaporated in the evaporator 4 and is then suctioned into the compressor 1.

[0018] A flow rate adjusting valve 11 is disposed on the bypass flow path 16. The flow rate adjusting valve 11 is configured by an electronic expansion valve. Thus, by adjusting the opening degree of the flow rate adjusting valve 11, the flow rate of the refrigerant flowing through the bypass flow path 16 is adjusted.

[0019] The bypass flow path 16 includes a bypass temperature detector 21 for detecting the temperature of the refrigerant flowing through the bypass flow path 16 on the downstream side of the flow rate adjusting valve 11. The bypass temperature detector 21 outputs a signal indicating the detected temperature.

[0020] The main circuit 15 includes a suction temperature detector 22 for detecting the temperature of the refrigerant suctioned into the compressor 1. The suction temperature detector 22 outputs a signal indicating the detected temperature.

[0021] The signals output from the detectors 21 and 22 are input to the controller 100. The controller 100 is configured by a microcomputer including a CPU that executes arithmetic processing, a ROM that stores a processing program, data, and the like, and a RAM that temporarily stores data. By executing the processing program stored in the controller 100, as illustrated in Fig. 2, the controller 100 can function as a reception unit 101, an expansion control unit 102, a superheating degree calculation unit 103, a superheating degree control unit 104, and a changing unit 105.

[0022] The reception unit 101 is configured to repeatedly receive the refrigeration request degree at predetermined time intervals, and temporarily store the received refrigeration request degree. The refrigeration request degree is generated by a generator 120, and the refrigeration request degree generated by the generator 120 is input to a reception unit 101. Note that, in the example of Fig. 2, the generator 120 is configured separately from the controller 100, but the generator 120 of the refrigeration request degree may be one function of the controller 100.

[0023] For example, the generator 120 repeatedly receives signals from a sensor 121 that detects the in-freezer temperature (or the temperature of the room to be cooled in the freezer), an input device 122 that inputs the set value of the in-freezer temperature, and the like at predetermined time intervals, and calculates the refrigeration request degree each time. The refrigeration request degree indicates the refrigeration load in the freezer as a dimensionless numerical value, and is calculated from, for example, a difference value between a detection value and a set value of an in-freezer temperature. Thus, the larger the difference between the detection value of the in-freezer temperature from the set value of the in-freezer temperature, the larger the refrigeration request degree. Since the refrigeration request degree can change from moment to moment, the generator 120 outputs the refrigeration request degree every predetermined time.

[0024] The expansion control unit 102 is configured to adjust the opening degree of the expansion valve 3 according to the received refrigeration request degree every time the reception unit 101 receives the refrigeration request degree. That is, the expansion control unit 102 controls the expansion valve 3 so that the opening degree of the expansion valve 3 increases as the refrigeration request degree increases, and controls the expansion valve 3 so that the opening degree of the expansion valve 3 decreases as the refrigeration request degree decreases. Thus, the flow rate of the refrigerant flowing through the evaporator 4 can be set to a flow rate according to the refrigeration request degree, so that the refrigeration capacity according to the refrigeration request degree can be obtained.

[0025] The superheating degree calculation unit 103 is configured to derive a difference value between the temperature detected by the suction temperature detector 22 and the temperature detected by the bypass temperature detector 21 as the degree of superheat of the refrigerant suctioned into the compressor 1. That is, in the bypass flow path 16, the liquid refrigerant decompressed by the flow rate adjusting valve 11 is saturated or nearly saturated. The liquid refrigerant merges with a gas refrigerant evaporated in the evaporator 4 to thereby increase in temperature, and is suctioned into the compressor 1. Thus, the temperature difference between the temperature of the gas refrigerant suctioned into the compressor 1 and the temperature of the liquid refrigerant on the downstream side of the flow rate adjusting valve 11 in the bypass flow path 16 corresponds to the degree of superheat of the refrigerant suctioned into the compressor 1. In other words, the difference of the temperature of the gas refrigerant suctioned into the compressor 1 with respect to the temperature of the liquid refrigerant on the downstream side of the flow rate adjusting valve 11 in the bypass flow path 16 is a degree of superheat with respect to a saturation temperature corresponding to a suction pressure of the compressor 1.

[0026] The degree of superheat of the refrigerant suctioned into the compressor 1 can also be calculated by other methods. For example, a pressure detector (not illustrated) that detects the pressure of the refrigerant suctioned into the compressor 1 is provided, and the degree of superheat of the refrigerant suctioned into the compressor 1 can be calculated using the saturated vapor temperature corresponding to the detected pressure and the detection temperature by the suction temperature detector 22.

[0027] The superheating degree control unit 104 is configured to control the flow rate adjusting valve 11 so that the degree of superheat of the gas refrigerant derived by the superheating degree calculation unit 103 becomes a target value. That is, when the opening degree of the flow rate adjusting valve 11 is reduced, the flow rate of the refrigerant flowing through the bypass flow path 16 is reduced, so that the ratio of the flow rate of the refrigerant passing through the bypass flow path 16 to the flow rate of the refrigerant passing through the evaporator 4 is reduced. In this case, the degree of superheat of the refrigerant becomes larger. On the other hand, when the opening degree of the flow rate adjusting valve 11 is increased, the flow rate of the refrigerant flowing through the bypass flow path 16 increases, so that the ratio of the flow rate of the refrigerant passing through the bypass flow path 16 to the flow rate of the refrigerant passing through the evaporator 4 increases. In this case, the degree of superheat of the refrigerant becomes smaller. Therefore, by adjusting the opening degree of the flow rate adjusting valve 11, the degree of superheat of the gas refrigerant can be brought close to the target value.

[0028] The changing unit 105 is configured to change a target value of the degree of superheat of the refrigerant suctioned into the compressor 1 according to the refrigeration request degree received by the reception unit 101. The changing unit 105 sets the superheating degree target value as the first value when the received refrigeration request degree is the first refrigeration request degree, and sets the superheating degree target value as the second value lower than the first value when the received refrigeration request degree is the second refrigeration request degree which is a refrigeration request degree lower than the first refrigeration request degree.

[0029] As illustrated in Fig. 3, an upper limit value and a lower limit value are set as the superheating degree target value, and the superheating degree target value takes a value between an upper limit value and a lower limit value according to the refrigeration request degree. The superheating degree target value is set to be higher as the refrigeration request degree is higher, and to be lower as the refrigeration request degree is lower. In a case where the refrigeration request degree is indicated by a value of 0% to 100%, the superheating degree target value is set to the upper limit value when the refrigeration request degree is 100%, and the superheating degree target value is set to the lower limit value when the refrigeration request degree is 0%.

[0030] The upper limit value of the superheating degree target value includes, but is not limited to, an area that changes according to the in-freezer temperature (or the temperature of the room to be cooled in the freezer) and an area that is constant regardless of the in-freezer temperature. The upper limit value of the superheating degree target value may be set to be higher as the in-freezer temperature is higher over the entire possible temperature range of the in-freezer temperature. Alternatively, the upper limit value of the superheating degree target value may be set to the same value over the entire possible temperature range of the in-freezer temperature. Note that, in a case where the refrigeration apparatus 10 is configured as a chiller, the "in-freezer temperature" can be replaced with the temperature of the coolant introduced into the evaporator 4.

[0031] The lower limit value of the superheating degree target value is constant over the entire possible temperature range of the in-freezer temperature, but may be set to include a region in which the lower limit value of the superheating degree target value is higher as the in-freezer temperature is higher. Further, the lower limit value of the superheating degree target value may be set to be higher as the in-freezer temperature is higher over the entire possible temperature range of the in-freezer temperature.

[0032] Here, a refrigeration method using the refrigeration apparatus 10 having the above configuration will be described.

[0033] When the target temperature of the in-freezer temperature is set and the operation of refrigeration apparatus 10 is started, the controller 100 receives the refrigeration request degree generated by the generator 120 as illustrated in Fig. 4 (step ST11). Further, the controller 100 also receives a suction temperature that is a value detected by the suction temperature detector 22 and receives a bypass temperature that is a value detected by the bypass temperature detector 21 (step ST12). The refrigeration request degree, the suction temperature, and the bypass temperature are repeatedly received by the controller 100 at predetermined time intervals.

[0034] The superheating degree calculation unit 103 of the controller 100 calculates the degree of superheat of the refrigerant suctioned into the compressor 1 using the suction temperature (or the value detected by the suction temperature detector 22) and the bypass temperature (or the value detected by the bypass temperature detector 21) (step ST13).

[0035] The expansion control unit 102 of the controller 100 adjusts the opening degree of the expansion valve 3 based on the received refrigeration request degree (step ST14). The refrigeration request degree changes from moment to moment, and the generator 120 outputs the refrigeration request degree every predetermined time. Thus, the expansion control unit 102 adjusts the opening degree of the expansion valve 3 every time the refrigeration request degree is received. In this case, the expansion control unit 102 controls the expansion valve 3 so that the opening degree of the expansion valve 3 is larger as the refrigeration request degree is higher, and that the opening degree of the expansion valve 3 is smaller as the refrigeration request degree is lower. Thus, the refrigerant of the flow rate according to the refrigeration request degree flows through the evaporator 4, so that the refrigeration capacity according to the refrigeration request degree is exhibited in the evaporator 4.

[0036] The refrigeration request degree is also used to set the target value of the degree of superheat of the refrigerant suctioned into the compressor 1. That is, the changing unit 105 changes the target value of the degree of superheat of the refrigerant suctioned into the compressor 1 according to the refrigeration request degree received by the reception unit 101 (step ST15). At this time, the superheating degree target value is changed so that the higher the refrigeration request degree, the higher the superheating degree target value, and the lower the refrigeration request degree, the lower the superheating degree target value.

[0037] The superheating degree control unit 104 controls the flow rate adjusting valve 11 so that the degree of superheat becomes the changed target value (step ST16). Specifically, when the refrigeration request degree is high, the superheating degree target value is changed to be higher than the current value, and thus the superheating degree control unit 104 controls the flow rate adjusting valve 11 so that the opening degree of the flow rate adjusting valve 11 becomes small. That is, when the refrigeration request degree is high, the flow rate adjusting valve 11 is tightened. Thus, the flow rate of the refrigerant flowing through the bypass flow path 16 decreases. Accordingly, the flow rate of the refrigerant flowing into the evaporator 4 can be increased. That is, although the opening degree of the expansion valve 3 is set to a value according to the refrigeration request degree by the expansion control unit 102, the flow rate of the refrigerant flowing through the evaporator 4 can be increased as the flow rate adjusting valve 11 is throttled. Therefore, the refrigeration capacity exhibited by the evaporator 4 can be increased as compared with a case where the target value of the superheating degree is fixed.

[0038] On the other hand, when the refrigeration request degree is low, the superheating degree target value is changed to be lower than the current value. Thus, the superheating degree control unit 104 controls the flow rate adjusting valve 11 so that the valve opening degree of the flow rate adjusting valve 11 becomes larger. That is, when the refrigeration request degree is low, the opening degree of the expansion valve 3 is throttled, and the circulation flow rate of the main circuit 15 is smaller, so that it is difficult to obtain the cooling effect of the compressor 1. Accordingly, by controlling the flow rate adjusting valve 11 so as to increase the valve opening degree of the flow rate adjusting valve 11, the flow rate of the refrigerant flowing through the bypass flow path 16 can be increased. Thus, the flow rate of the refrigerant suctioned into the compressor 1 can be increased, so that the cooling effect of the compressor 1 can be enhanced. On the other hand, as the flow rate of the refrigerant in the bypass flow path 16 increases, the flow rate of the refrigerant flowing into the evaporator 4 further decreases under the opening degree of the expansion valve 3 controlled by the expansion control unit 102. Therefore, the refrigeration capacity exhibited by the evaporator 4 can be further reduced as compared with a case where the target value of the superheating degree is fixed.

[0039] As described above, in the present embodiment, the expansion valve 3 is adjusted by the expansion control unit 102 according to the refrigeration request degree. Thus, the flow rate of the refrigerant flowing through the evaporator 4 is adjusted according to the refrigeration request degree. Accordingly, the evaporator 4 can exhibit the refrigeration capacity according to the refrigeration request degree. On the other hand, a part of the refrigerant condensed in the condenser 2 is suctioned into the compressor 1 through the bypass flow path 16 without passing through the evaporator 4. Thus, while the cooling effect of the compressor 1 (the effect of lowering the discharge pipe temperature) can be obtained, the refrigeration capacity exhibited by the evaporator 4 can be lowered. However, since the target value of the degree of superheat of the refrigerant suctioned into the compressor 1, the target value being the control target of the flow rate adjusting valve 11 of the bypass flow path 16, can be changed by the changing unit 105, the flow rate of the refrigerant flowing through the bypass flow path 16 can be adjusted. Accordingly, the valve opening degree of the flow rate adjusting valve 11 is adjusted according to a target value change amount of the degree of superheat, so that the decrease amount of the flow rate of the refrigerant flowing to the evaporator 4 can be changed according to the refrigeration request degree. Therefore, the refrigeration capacity of the evaporator 4 can be adjusted while the discharge pipe temperature of the compressor 1 is adjusted, and the imbalance between the protection of the compressor 1 and the refrigeration capacity can be suppressed.

[0040] Moreover, since the target value of the degree of superheat is changed according to the refrigeration request degree, the valve opening degree of the flow rate adjusting valve 11 can be adjusted according to the refrigeration request degree. That is, the expansion valve 3 is adjusted to the opening degree according to the refrigeration request degree, while the flow rate adjusting valve 11 is adjusted so as to obtain the superheating degree target value according to the refrigeration request degree. Thus, while the opening degree of the expansion valve 3 is adjusted so as to exhibit the refrigeration capacity according to the refrigeration request degree, the refrigerant flow rate of the evaporator 4 obtained by the adjustment of the expansion valve 3 also changes with the adjustment of the valve opening degree of the flow rate adjusting valve 11. Thus, even if the flow rate of the refrigerant flowing to the evaporator 4 decreases as the refrigerant flows to the bypass flow path 16, the decrease amount of the refrigeration capacity can be adjusted by adjusting the valve opening degree of the flow rate adjusting valve 11.

[0041] Further, in the present embodiment, the changing unit 105 decreases the target value of the degree of superheat when the refrigeration request degree is low. That is, when the refrigeration request degree is low, the target value of the degree of superheat is lowered to further increase the valve opening degree of the flow rate adjusting valve 11. Thus, the flow rate (suction injection flow rate) of the refrigerant flowing through the bypass flow path 16 increases as compared with the case where the superheating degree target value is fixed. On the other hand, when the refrigeration request degree is low, the opening degree of the expansion valve 3 decreases to lower the refrigeration capacity exerted by the evaporator 4, and thus the flow rate of the refrigerant circulating through main circuit 15 decreases. Therefore, as the refrigerant circulation flow rate decreases, it tends to be difficult to obtain the cooling effect of the compressor 1. However, since the suction injection flow rate increases, it is possible to avoid a situation where it is difficult to obtain the cooling effect of the compressor 1. Since the target value of the degree of superheat is not adjusted based on the discharge pipe temperature of the compressor 1, the opening degree of the flow rate adjusting valve 11 is adjusted regardless of whether or not the discharge pipe temperature rises. Therefore, the refrigeration capacity of the evaporator 4 can be more appropriately adjusted according to the refrigeration request degree.

[0042] Moreover, since the flow rate of the refrigerant flowing through the bypass flow path 16 further increases as the valve opening degree of the flow rate adjusting valve 11 further increases, the flow rate of the refrigerant in the evaporator 4 at the opening degree of the expansion valve 3 set to a value according to the refrigeration request degree by the expansion control unit 102 can be further reduced. Thus, the refrigeration capacity of the evaporator 4 can be further reduced. Accordingly, compared to a case where the target value of the degree of superheat is fixed, the refrigeration capacity of the evaporator 4 adjusted according to the refrigeration request degree can be further reduced. Thus, it is possible to suppress the occurrence of a situation in which the refrigeration capacity becomes excessive when the state in which the refrigeration request degree is low continues.

[0043] Further, in the present embodiment, in the region where the in-freezer temperature is low, the upper limit value of the target value of the degree of superheat is set to decrease as the in-freezer temperature decreases. Thus, the cooling effect of the compressor 1 can be further enhanced. For example, in a case where the in-freezer temperature is low at a certain refrigeration request degree, the evaporation temperature needs to be lower as compared to a case where the in-freezer temperature is high with respect to the same refrigeration request degree, so that the expansion valve 3 tends to be throttled. Thus, the refrigerant circulation flow rate tends to decrease as the in-freezer temperature decreases, so that it is difficult to obtain the cooling effect of the compressor 1. Accordingly, the flow rate adjusting valve 11 is further opened by setting the upper limit value of the target value of the degree of superheat to decrease as the in-freezer temperature decreases. Thus, even when the expansion valve 3 is in a throttled state, it is possible to easily obtain a cooling effect of the compressor 1.

[0044] Note that, in the present embodiment, the changing unit 105 changes the target value of the degree of superheat with respect to the saturation temperature corresponding to the suction pressure of the compressor 1 according to the refrigeration request degree, but alternatively, the target value of the degree of superheat may be changed according to the opening degree of the expansion valve 3. In this case, the target value of the degree of superheat changes according to the opening degree of the expansion valve 3, and the valve opening degree of the flow rate adjusting valve 11 is adjusted accordingly. That is, since the opening degree of the expansion valve 3 is adjusted to the opening degree according to the refrigeration request degree, the target value of the degree of superheat is changed according to the opening degree of the expansion valve 3, whereby the valve opening degree of flow rate adjusting valve 11 is adjusted to the opening degree according to the refrigeration request degree. In this case, the changing unit 105 decreases the target value of the degree of superheat when the opening degree of the expansion valve 3 is small. That is, when the opening degree of the expansion valve 3 is small, the suction pressure to compressor 1 decreases, and accordingly, the discharge pipe temperature of the compressor 1 tends to increase. In this case, since the target value of the degree of superheat is lowered by the changing unit 105, the superheating degree control unit 104 controls the flow rate adjusting valve 11 so as to increase the valve opening degree of the flow rate adjusting valve 11. Therefore, since the flow rate (suction injection flow rate) of the refrigerant flowing through the bypass flow path 16 increases, an increase in the discharge pipe temperature can be suppressed.

[0045] In the above embodiment, the upper limit value of the superheating degree target value changes according to the in-freezer temperature, but is not limited thereto. For example, a region where the upper limit value of the superheating degree target value decreases as the outlet temperature of the evaporator 4 or the evaporation temperature of the refrigerant decreases, instead of the in-freezer temperature, may be provided. In addition, over the entire possible range of the outlet temperature of the evaporator 4 or the evaporation temperature of the refrigerant, the upper limit value of the superheating degree target value may be set to be smaller as these temperatures are lower. Even in these cases, the cooling effect of the compressor 1 can be easily obtained.

[0046] In addition, the upper limit value of the superheating degree target value may be set to decrease as the detection temperature by the bypass temperature detector 21 (that is, the temperature on the outlet side of the flow rate adjusting valve 11 in the bypass flow path 16) decreases, instead of the in-freezer temperature. That is, since the detection temperature of the bypass temperature detector 21 depends on the suction pressure to the compressor 1 (or low pressure in the main circuit 15), the detection temperature of the bypass temperature detector 21 decreases as the opening degree of the expansion valve 3 decreases. Thus, when the upper limit value of the target value of the degree of superheat is set to decrease as the detection temperature of the bypass temperature detector 21 decreases, an effect equivalent to that of decreasing the upper limit value of the target value of the degree of superheat as the opening degree of the expansion valve 3 decreases can be obtained. Therefore, the cooling effect of the compressor 1 can be easily obtained.

[0047] In addition, by referring to a plurality of temperatures out of the in-freezer temperature, the outlet temperature of the evaporator 4, the evaporation temperature of the refrigerant, and the detection temperature of the bypass temperature detector 21, the upper limit value of the superheating degree target value may be set to decrease when a value obtained as a result of predetermined processing (for example, average processing) of the plurality of temperatures decreases.

[0048] Further, in the present embodiment, the superheating degree calculation unit 103 derives a difference value between the temperature detected by the suction temperature detector 22 and the temperature detected by the bypass temperature detector 21 as the degree of superheat of the refrigerant suctioned into the compressor 1, but the present embodiment is not limited thereto. For example, as illustrated in Fig. 5, the bypass temperature detector 21 may be omitted, and the pressure detector 31 that detects the pressure of the refrigerant suctioned into the compressor 1 may be provided. The superheating degree calculation unit 103 may derive a difference value between the temperature detected by the suction temperature detector 22 and the saturated vapor temperature corresponding to the pressure detected by the pressure detector 31 as the degree of superheat of the suction refrigerant.

(Second Embodiment)

[0049] As illustrated in Fig. 6, the refrigeration apparatus 10 according to the second embodiment includes a hot gas bypass flow path 17. Note that, here, the same components as those of the first embodiment are denoted by the same reference numerals, and the detailed description thereof will be omitted.

[0050] The hot gas bypass flow path 17 is a flow path through which a part of the refrigerant discharged from the compressor 1 is suctioned into the compressor 1 without passing through the condenser 2, the expansion valve 3, and the evaporator 4. One end of the hot gas bypass flow path 17 is connected to a portion of the main circuit 15 between the compressor 1 and the condenser 2. The other end of the hot gas bypass flow path 17 is connected to a portion of the main circuit 15 between the evaporator 4 and the compressor 1.

[0051] The hot gas bypass flow path 17 is provided with a hot gas valve 12 including a mechanical expansion valve. Thus, the hot gas valve 12 is always opened in a state of being set to a predetermined opening degree. Note that the hot gas valve 12 is not limited thereto and may be controlled to open and close by the controller 100 as illustrated in Figs. 7 and 8. That is, the hot gas valve 12 may be controlled to be opened when the suction pressure of the compressor 1 can be equal to or lower than the set pressure, such as when the expansion valve 3 is closed (or the opening degree becomes very small), and to be closed otherwise. The set pressure may be a pressure determined from design conditions of the compressor 1 set as a range in which the compressor 1 can be stably operated.

[0052] In the present embodiment, the hot gas control unit 106 of the controller 100 controls the hot gas valve 12 so that the suction pressure of the compressor 1 does not become equal to or lower than the set pressure. That is, when the opening degree of the expansion valve 3 decreases, the suction pressure of the compressor 1 decreases accordingly, and thus, when the opening degree of the expansion valve 3 is closed (or made very small) to reduce the refrigeration capacity as much as possible, the suction pressure of the compressor 1 may excessively decrease, and there is a possibility that stable operation cannot be performed. Accordingly, when the suction pressure is likely to become equal to or lower than the set pressure, the hot gas control unit 106 opens the hot gas valve 12. Thus, since the hot gas is suctioned into the compressor 1 through the hot gas bypass flow path 17, the suction pressure can be prevented from becoming equal to or lower than the set pressure. Therefore, it is possible to minimize the refrigeration capacity of the evaporator 4 as much as possible while ensuring the stable operation of the compressor 1.

[0053] When the hot gas valve 12 is opened, the degree of superheat of the refrigerant suctioned into the compressor 1 increases, and accordingly, the superheating degree control unit 104 further increases the valve opening degree of the flow rate adjusting valve 11 so that the degree of superheat approaches the target value. Therefore, even if the hot gas valve 12 is opened, the degree of superheat of the suctioned refrigerant does not become excessively high.

[0054] Note that the hot gas valve 12 may be configured by an electronic expansion valve. In this case, the hot gas control unit 106 is configured to control the opening degree of the hot gas valve 12. For example, the hot gas control unit 106 may perform control of adjusting the opening degree of the hot gas valve 12 in conjunction with the opening degree control of the expansion valve 3 by the expansion control unit 102 or according to the refrigeration request degree. In this case, the hot gas control unit 106 performs control to open the hot gas valve 12 at least when the expansion valve 3 is closed. Thus, the refrigeration capacity of the evaporator 4 can be reduced as much as possible. Further, when the hot gas valve 12 is controlled according to the refrigeration request degree, the hot gas valve 12 is controlled so that the opening degree of the hot gas valve 12 becomes larger as the refrigeration request degree decreases. Thus, the suction pressure of the compressor 1 can be secured. Further, in a case where the pressure sensor 31 that detects the pressure of the refrigerant suctioned into the compressor 1 is provided, it is also possible to control the hot gas valve 12 so that the suction pressure of the compressor 1 does not decrease to a predetermined pressure or less.

[0055] Although descriptions of other configurations, operations, and effects are omitted, the description of the first embodiment can be applied to the description of the second embodiment.

(Third Embodiment)

[0056] Fig. 9 illustrates a third embodiment. Note that, here, the same components as those of the first or second embodiment are denoted by the same reference numerals, and the detailed description thereof will be omitted.

[0057] The third embodiment is an example in which the refrigeration apparatus 10 is applied to an environment forming apparatus 50 such as an environment testing apparatus. The refrigeration apparatus 10 may be any of the refrigeration apparatuses according to the first embodiment and the second embodiment.

[0058] The environment forming apparatus 50 includes an environment chamber 51 and adjusts the inside of the environment chamber 51 to a predetermined temperature environment. The environment forming apparatus 50 further includes an air conditioning chamber 52 for generating air whose temperature is adjusted, and the evaporator 4 of the refrigeration apparatus 10 is disposed in the air conditioning chamber 52.

[0059] In the air conditioning chamber 52, a heater 54 for heating the air and a blower 55 for blowing out the temperature-adjusted air to the environment chamber 51 are disposed on the downstream side of the evaporator 4. In the environment chamber 51, the sensor 121 for detecting a room temperature is installed. The input device 122 is used to input a set temperature of the temperature in the environment chamber 51. Note that, in the present embodiment, the "in-freezer temperature" in the first and second embodiments is replaced with the "room temperature". That is, the sensor 121 detects the air temperature in the room to which the air cooled by the evaporator 4 is supplied.

[0060] The generator 120 calculates the refrigeration request degree using the detection temperature by the sensor 121 and the set temperature from the input device 122.

[0061] The output of the heater 54 is controlled based on the detection temperature by the sensor 121 and the set temperature from the input device 122. That is, the expansion valve 3 of the refrigeration apparatus 10 is controlled based on the refrigeration request degree, so that a predetermined refrigeration capacity is exhibited. At this time, since the detection temperature by the sensor 121 may be lower than the set temperature, the room temperature is finely adjusted by the heater 54. Thus, if excessive cooling by the refrigeration apparatus 10 can be suppressed, not only the power of the refrigeration apparatus 10 can be suppressed, but also the power of the heater 54 can be suppressed. In this regard, when the refrigeration request degree is small, the changing unit 105 lowers the target value of the degree of superheat, and thus the flow rate adjusting valve 11 is controlled so that the opening degree of the flow rate adjusting valve 11 becomes larger accordingly. Accordingly, the flow rate of the refrigerant flowing into the evaporator 4 can be further reduced under the opening degree of the expansion valve 3 controlled by the expansion control unit 102. Therefore, as compared with a case where the target value of the degree of superheat is fixed, the refrigeration capacity exhibited by the evaporator 4 can be reduced, so that the power of the heater 54 can also be suppressed, and further energy saving can be achieved. Note that the heater 54 can be omitted.

[0062] Further, the upper limit value of the target value of the degree of superheat is set to decrease as the room temperature decreases. Thus, when the refrigeration request degree is 100%, the lower the room temperature is, the more the expansion valve 3 tends to be throttled and the more the flow rate adjusting valve 11 is opened. Thus, the flow rate of the refrigerant flowing into the evaporator 4 is further reduced, so that the cooling capacity of the evaporator 4 can be further reduced. Therefore, since the output of the heater 54 can be suppressed, energy saving of the environment forming apparatus 50 can be achieved.

[0063] Note that, although descriptions of other configurations, operations, and effects are omitted, the description of the first or second embodiment can be applied to the third embodiment.

(Other Embodiments)

[0064] It should be understood that the embodiment disclosed herein is illustrative in all respects and is not restrictive. The present invention is not limited to the above embodiments, and various modifications, improvements, and the like can be made without departing from the gist of the present invention.

[0065] Here, the embodiments will be outlined.

(1) A refrigeration apparatus according to the embodiment includes a main circuit that includes a compressor, a condenser, an expansion valve, and an evaporator and is configured to circulate a refrigerant, a bypass flow path that includes a flow rate adjusting valve, branches from the main circuit between the condenser and the expansion valve, and causes a refrigerant liquefied in the condenser to be lowered in temperature by the flow rate adjusting valve and to be suctioned into the compressor without passing through the evaporator, an expansion control unit configured to control the expansion valve according to a refrigeration request degree, a superheating degree control unit configured to control the flow rate adjusting valve so that a superheating degree with respect to a saturation temperature corresponding to a suction pressure of the compressor becomes a target value, and a changing unit configured to change the target value of the degree of superheat.
In the refrigeration apparatus, the expansion valve of the main circuit is adjusted by the expansion control unit according to the refrigeration request degree. Thus, the flow rate of the refrigerant flowing through the evaporator is adjusted according to the refrigeration request degree. Therefore, the evaporator can exhibit the refrigeration capacity according to the refrigeration request degree. On the other hand, since a part of the refrigerant condensed by the condenser is suctioned into the compressor through the bypass flow path without passing through the evaporator, a cooling effect of the compressor (the effect of lowering the discharge pipe temperature) can be obtained, and the refrigeration capacity exhibited by the evaporator can be deteriorated. However, since the valve opening degree of the flow rate adjusting valve provided in the bypass flow path can be adjusted, the flow rate of the refrigerant flowing through the bypass flow path can be adjusted. Moreover, the target value of the degree of superheat of the refrigerant suctioned into the compressor, the target value being the control target of the flow rate adjusting valve, can be changed by the changing unit. Accordingly, the valve opening degree of the flow rate adjusting valve is adjusted in accordance with a target value change amount of the degree of superheat, so that the decrease amount of the flow rate of the refrigerant flowing to the evaporator can be changed. Therefore, the refrigeration capacity of the evaporator can be adjusted while the compressor is stably driven, and the imbalance between the protection of the compressor and the refrigeration capacity can be suppressed.

(2) The changing unit may be configured to change the target value of the degree of superheat according to the refrigeration request degree.
In this aspect, since the target value of the degree of superheat is changed according to the refrigeration request degree, the valve opening degree of the flow rate adjusting valve can be adjusted according to the refrigeration request degree. That is, while the expansion valve is adjusted to the opening degree according to the refrigeration request degree, the flow rate adjusting valve is adjusted so as to obtain the superheating degree target value according to the refrigeration request degree. Thus, the opening degree of the expansion valve is adjusted so that the refrigeration capacity according to the refrigeration request degree is exhibited. At this time, the refrigerant flow rate of the evaporator obtained by this adjustment of the expansion valve also changes with the adjustment of the valve opening degree of the flow rate adjusting valve. Thus, even if the flow rate of the refrigerant flowing to the evaporator decreases as the refrigerant flows to the bypass flow path, the decrease amount of the refrigeration capacity can be adjusted by adjusting the valve opening degree of the flow rate adjusting valve.

(3) The changing unit may be configured to change the target value of the degree of superheat according to an opening degree of the expansion valve.
In this aspect, since the target value of the degree of superheat changes according to the opening degree of the expansion valve, the valve opening degree of the flow rate adjusting valve is adjusted accordingly. That is, the opening degree of the expansion valve is adjusted to the opening degree according to the refrigeration request degree, and the refrigerant flow rate of the evaporator obtained by this adjustment of the expansion valve also changes with the adjustment of the valve opening degree of the flow rate adjusting valve. Thus, even if the flow rate of the refrigerant flowing to the evaporator decreases as the refrigerant flows to the bypass flow path, the decrease amount of the refrigeration capacity can be adjusted by adjusting the valve opening degree of the flow rate adjusting valve.

(4) An upper limit value of the target value of the degree of superheat may be set to decrease as a temperature of a room to be cooled, an outlet temperature of the evaporator, an evaporation temperature of the refrigerant or a temperature on an outlet side of the flow rate adjusting valve, or a value obtained by subjecting a plurality of the temperatures to predetermined processing decreases.

[0066] In this aspect, the cooling effect of the compressor can be further enhanced. For example, in a case where the temperature of the room to be cooled is low at a certain refrigeration request degree, the evaporation temperature needs to be lower as compared to a case where the temperature of the room to be cooled is high with respect to the same refrigeration request degree, so that the expansion valve tends to be throttled. Thus, the refrigerant circulation flow rate tends to decrease as the temperature of the room to be cooled decreases, so that it is difficult to obtain the cooling effect of the compressor. Accordingly, the flow rate adjusting valve is further opened by setting the upper limit value of the target value of the degree of superheat to decrease as the temperature of the room to be cooled decreases. This makes it possible to easily obtain the cooling effect of the compressor even when the expansion valve is in a throttled state. The same applies to a case where the outlet temperature of the evaporator and the evaporation temperature of the refrigerant decrease.

[0067] Since the temperature on the outlet side of the flow rate adjusting valve depends on the suction pressure to the compressor (or low pressure of the refrigeration circuit), this temperature decreases as the opening degree of the expansion valve decreases. Therefore, when the upper limit value of the target value of the degree of superheat is set to decrease as the temperature decreases, it is possible to obtain an effect equivalent to reducing the upper limit value of the target value of the degree of superheat as the opening degree of the expansion valve decreases. Therefore, the cooling effect of the compressor can be easily obtained.

[0068] (5) The refrigeration apparatus may further include a bypass temperature detector that is disposed on the bypass flow path and is configured to detect a temperature of the refrigerant on a downstream side of the flow rate adjusting valve, and a suction temperature detector that is disposed on the main circuit and is configured to detect a temperature of the refrigerant suctioned into the compressor. In this case, the degree of superheat may be obtained from a temperature difference between a detection temperature of the suction temperature detector and a detection temperature of the bypass temperature detector.

[0069] The detection temperature by the bypass temperature detector is a saturation temperature corresponding to the suction pressure. Thus, the degree of superheat of the refrigerant suctioned into the compressor is obtained from the temperature difference between the suction temperature detector that detects the temperature of the refrigerant suctioned into the compressor where the refrigerant from the bypass flow path and the refrigerant passing through the evaporator merge and the bypass temperature detector.

[0070] (6) The refrigeration apparatus may further include a hot gas bypass flow path that includes a hot gas valve, branches from a portion of the main circuit between the compressor and the condenser, and causes a refrigerant compressed by the compressor to be suctioned into the compressor without passing through the evaporator, and a hot gas control unit configured to open the hot gas valve so that a pressure of the refrigerant suctioned into the compressor does not become equal to or lower than a set pressure.

[0071] In this aspect, the hot gas flow rate adjusting valve is controlled by the hot gas control unit so that the suction pressure of the compressor does not become equal to or lower than the set pressure. That is, when the opening degree of the expansion valve decreases, the suction pressure of the compressor decreases accordingly, and thus, when the opening degree of the expansion valve is made very small to reduce the refrigeration capacity as much as possible, the suction pressure of the compressor may excessively decrease, and there is a possibility that stable operation cannot be performed. Accordingly, when the suction pressure is likely to become equal to or lower than the set pressure, the hot gas is suctioned into the compressor through the hot gas bypass flow path, whereby the suction pressure can be prevented from becoming equal to or lower than the set pressure. Therefore, it is possible to minimize the refrigeration capacity while ensuring the stable operation of the compressor.

[0072] (7) The hot gas control unit may be configured to control the hot gas valve according to the refrigeration request degree.

[0073] In this aspect, when the refrigeration request degree is low and the expansion control unit performs control to throttle the expansion valve, the hot gas control unit can perform control to further open the hot gas valve. Therefore, when the refrigeration request degree is low, the refrigeration capacity can be reduced as much as possible. Furthermore, by suctioning the hot gas into the compressor through the hot gas bypass flow path, the suction pressure can be prevented from becoming equal to or lower than the set pressure. Therefore, it is possible to minimize the refrigeration capacity while ensuring the stable operation of the compressor.

[0074] (8) The environment forming apparatus according to the embodiment includes an environment chamber and the refrigeration apparatus for cooling an inside of the environment chamber.

[0075] In the environment forming apparatus, for example, when the target value of the degree of superheat is lowered in the refrigeration apparatus, the opening degree of the flow rate adjusting valve is controlled to be larger. Thus, the flow rate of the refrigerant flowing into the evaporator can be further reduced. Therefore, the refrigeration capacity exhibited by the evaporator can be reduced as compared with a case where the target value of the degree of superheat is fixed.

[0076] (9) A refrigeration method according to the embodiment is a refrigeration method using a refrigeration apparatus, the refrigeration apparatus including a main circuit that includes a compressor, a condenser, an expansion valve, and an evaporator and is configured to circulate a refrigerant; a bypass flow path that includes a flow rate adjusting valve, branches from the main circuit between the condenser and the expansion valve, and causes a refrigerant liquefied in the condenser to be lowered in temperature by the flow rate adjusting valve and to be suctioned into the compressor without passing through the evaporator: and a reception unit, the refrigeration method including receiving a refrigeration request degree received by the reception unit, controlling the expansion valve according to the refrigeration request degree received by the reception unit, changing a target value of a degree of superheat with respect to a saturation temperature corresponding to a suction pressure of the compressor according to the refrigeration request degree or an opening degree of the expansion valve, and controlling the flow rate adjusting valve so that the degree of superheat becomes the changed target value.

[0077] (10) In a case where the refrigeration apparatus further includes a bypass temperature detector that is disposed in the bypass flow path and is configured to detect a temperature of the refrigerant on a downstream side of the flow rate adjusting valve, and a suction temperature detector that is disposed on the main circuit and is configured to detect a temperature of the refrigerant suctioned into the compressor, in the refrigeration method, the degree of superheat may be obtained from a temperature difference between a temperature detected by the suction temperature detector and a temperature detected by the bypass temperature detector.

[0078] (11) In a case where the refrigeration apparatus further includes a hot gas bypass flow path that includes a hot gas valve, branches from a portion of the main circuit between the compressor and the condenser, and is configured to cause a refrigerant compressed by the compressor to be suctioned into the compressor without passing through the evaporator, in the refrigeration method, the hot gas valve may be opened so that a pressure of the refrigerant suctioned into the compressor does not become equal to or lower than a set pressure.

[0079] As described above, the refrigeration capacity of the evaporator can be adjusted while the compressor is stably driven by suction injection using the bypass flow path.

[0080] This application is based on Japanese Patent Application No. 2023-146286 filed with the Japan Patent Office on September 8, 2023, the contents of which are incorporated herein by reference.

Claims

1. A refrigeration apparatus (10) comprising:

a main circuit (15) that includes a compressor (1), a condenser (2), an expansion valve (3), and an evaporator (4) and is configured to circulate a refrigerant;

a bypass flow path (16) that includes a flow rate adjusting valve (11), branches from the main circuit (15) between the condenser (2) and the expansion valve (3), and causes a refrigerant liquefied in the condenser (2) to be lowered in temperature by the flow rate adjusting valve (11) and to be suctioned into the compressor (1) without passing through the evaporator (4);

an expansion control unit (102) configured to control the expansion valve (3) according to a refrigeration request degree;

a superheating degree control unit (104) configured to control the flow rate adjusting valve (11) so that a degree of superheat with respect to a saturation temperature corresponding to a suction pressure of the compressor (1) becomes a target value; and

a changing unit (105) configured to change the target value of the degree of superheat.

2. The refrigeration apparatus (10) according to claim 1, wherein the changing unit (105) is configured to change the target value of the degree of superheat according to the refrigeration request degree.

3. The refrigeration apparatus (10) according to claim 1, wherein the changing unit (105) is configured to change the target value of the degree of superheat according to an opening degree of the expansion valve (3).

4. The refrigeration apparatus (10) according to any one of claims 1 to 3, wherein an upper limit value of the target value of the degree of superheat is set to decrease as a temperature of a room to be cooled, an outlet temperature of the evaporator (4), an evaporation temperature of the refrigerant or a temperature on an outlet side of the flow rate adjusting valve (11), or a value obtained by subjecting a plurality of the temperatures to predetermined processing decreases.

5. The refrigeration apparatus (10) according to any one of claims 1 to 4, further comprising:

a bypass temperature detector (21) that is disposed on the bypass flow path (16) and is configured to detect a temperature of the refrigerant on a downstream side of the flow rate adjusting valve (11); and

a suction temperature detector (22) that is disposed on the main circuit (15) and is configured to detect a temperature of the refrigerant suctioned into the compressor (1),

wherein the degree of superheat is obtained from a temperature difference between a detection temperature of the suction temperature detector (22) and a detection temperature of the bypass temperature detector (21).

6. The refrigeration apparatus (10) according to any one of claims 1 to 5, further comprising:

a hot gas bypass flow path (17) that includes a hot gas valve (12), branches from a portion of the main circuit (15) between the compressor (1) and the condenser (2), and causes a refrigerant compressed by the compressor (1) to be suctioned into the compressor (1) without passing through the evaporator (4); and

a hot gas control unit (106) configured to open the hot gas valve (12) so that a pressure of the refrigerant suctioned into the compressor (1) does not become equal to or lower than a set pressure.

7. The refrigeration apparatus (10) according to claim 6, wherein the hot gas control unit (106) is configured to control the hot gas valve (12) according to the refrigeration request degree.

8. An environment forming apparatus (50) comprising:

an environment chamber (51); and

the refrigeration apparatus (10) according to any one of claims 1 to 7 for cooling an inside of the environment chamber (51).

9. A refrigeration method using a refrigeration apparatus (10), the refrigeration apparatus (10) including:

a main circuit (15) that includes a compressor (1), a condenser (2), an expansion valve (3), and an evaporator (4) and is configured to circulate a refrigerant;

a bypass flow path (16) that includes a flow rate adjusting valve (11), branches from the main circuit (15) between the condenser (2) and the expansion valve (3), and causes a refrigerant liquefied in the condenser (2) to be lowered in temperature by the flow rate adjusting valve (11) and to be suctioned into the compressor (1) without passing through the evaporator (4), and

a reception unit (101),

the refrigeration method comprising:

receiving a refrigeration request degree received by the reception unit (101),

controlling the expansion valve (3) according to the refrigeration request degree received by the reception unit (101),

changing a target value of a degree of superheat with respect to a saturation temperature corresponding to a suction pressure of the compressor (1) according to the refrigeration request degree or an opening degree of the expansion valve (3), and

controlling the flow rate adjusting valve (11) so that the degree of superheat becomes the changed target value.

10. The refrigeration method according to claim 9, wherein
the refrigeration apparatus (10) further includes:

a bypass temperature detector (21) that is disposed on the bypass flow path (16) and is configured to detect a temperature of the refrigerant on a downstream side of the flow rate adjusting valve (11); and

a suction temperature detector (22) that is disposed on the main circuit (15) and is configured to detect a temperature of the refrigerant suctioned into the compressor (1), and, the method further comprises

obtaining the degree of superheat from a temperature difference between a temperature detected by the suction temperature detector (22) and a temperature detected by the bypass temperature detector (21).

11. The refrigeration method according to claim 9 or 10, wherein

the refrigeration apparatus (10) further includes

a hot gas bypass flow path (17) that includes a hot gas valve (12), branches from a portion of the main circuit (15) between the compressor (1) and the condenser (2), and is configured to cause a refrigerant compressed by the compressor (1) to be suctioned into the compressor (1) without passing through the evaporator (4), and the method further comprises

opening the hot gas valve (12) so that a pressure of the refrigerant suctioned into the compressor (1) does not become equal to or lower than a set pressure.

Drawing