Refrigeration device, environment forming device, and refrigeration method

Abstract

The invention provides a refrigeration device, an environment forming device and a refrigeration method. A refrigeration device is provided with a main refrigeration circuit in which a first refrigerant is sealed, a supercooling refrigeration circuit in which a second refrigerant is sealed and which is connected to a supercooling heat exchanger, and a controller. The supercooling heat exchanger supercools the first refrigerant in the main refrigeration circuit. In the superheat degree setting control, the controller sets the target value of the superheat degree of the second refrigerant on the outlet side of the supercooling heat exchanger to a first value when the refrigeration demand degree is a first demand value, and sets the target value of the superheat degree to a second value greater than the first value when the refrigeration demand degree is a second demand value smaller than the first demand value. The controller controls the second expansion mechanism on the basis of a target value of the degree of superheat during the control of the degree of superheat. Accordingly, not only energy saving is achieved by using the supercooling heat exchanger, but also energy saving is further achieved.

Description

Technical Field

[0001] The invention relates to a refrigeration device, an environment forming device and a refrigeration method. Background Art

[0002] In the past, as disclosed in Japanese Patent Publication No. 54-31657, a refrigeration device having a refrigeration circuit provided with a subcooler is known. In this refrigeration device, a subcooler is provided between the condenser and the expansion valve in a main refrigeration circuit provided with a compressor, a condenser, an expansion valve and an evaporator. The subcooler is connected to a subcooling refrigeration circuit provided with other compressors, other condensers and other expansion valves. In addition, in the subcooler, since the refrigerant of the main refrigeration circuit is subcooled using the refrigerant of the subcooling refrigeration circuit, the refrigeration capacity of the main refrigeration circuit can be increased.

[0003] In the subcooler, if a structure is adopted in which the refrigerant of the subcooling refrigeration circuit is heat-exchanged with the refrigerant of the main refrigeration circuit, a compressor having a smaller compressor capacity than the compressor of the one refrigeration circuit can be used to exert the same refrigeration capacity as when only one refrigeration circuit is used to exert the same refrigeration capacity. Therefore, energy saving is achieved by providing a subcooler, but further energy saving is required. Summary of the invention

[0004] An object of the present invention is to provide a refrigeration device, an environment forming device and a refrigeration method, which can achieve not only energy saving by utilizing a supercooling heat exchanger but also further energy saving.

[0005] A refrigeration device according to one aspect of the present invention includes: a main refrigeration circuit in which a first refrigerant is sealed, and a first compressor, a first condenser, a subcooling heat exchanger, a first expansion mechanism, and a first evaporator are provided; a subcooling refrigeration circuit in which a second refrigerant is sealed, and a second compressor, a second condenser, and a second expansion mechanism are provided, and the subcooling heat exchanger is connected; and a controller capable of performing superheat setting control and superheat control. The subcooling heat exchanger is configured to evaporate the second refrigerant in the subcooling refrigeration circuit, thereby subcooling the first refrigerant in the main refrigeration circuit. In the superheat setting control, the controller sets a target value of the superheat of the second refrigerant at the outlet side of the subcooling heat exchanger to a first value when the refrigeration requirement is a first requirement value, and sets the target value of the superheat to a second value greater than the first value when the refrigeration requirement is a second requirement value less than the first requirement value. The controller controls the second expansion mechanism in the superheat control based on the target value of the superheat set in the superheat setting control.

[0006] Another aspect of the present invention relates to an environment forming device comprising: an environment chamber; and the refrigeration device, which is used to cool the environment chamber.

[0007] A refrigeration method according to another aspect of the present invention uses a refrigeration device, the refrigeration device comprising: a main refrigeration circuit, in which a first refrigerant is sealed, and a first compressor, a first condenser, a subcooling heat exchanger, a first expansion mechanism and a first evaporator are provided; and a subcooling refrigeration circuit, in which a second refrigerant is sealed, and a second compressor, a second condenser and a second expansion mechanism are provided, and the subcooling heat exchanger is connected to the subcooling heat exchanger. The refrigeration method performs the following steps: receiving a refrigeration requirement in the refrigeration device; and when the received refrigeration requirement is a first requirement value, , setting the target value of the superheat of the second refrigerant at the outlet side of the subcooling heat exchanger to a first value; in a case where the received refrigeration demand is a second demand value smaller than the first demand value, setting the target value of the superheat to a second value larger than the first value; based on the set target value of the superheat, controlling the second expansion mechanism; evaporating the second refrigerant in the subcooling heat exchanger into which the second refrigerant flows after the flow rate is adjusted by the second expansion mechanism, thereby subcooling the first refrigerant of the main refrigeration circuit.

[0008] According to the present invention, not only energy saving is achieved by utilizing the subcooling heat exchanger, but further energy saving is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram showing the structure of the refrigeration device according to the first embodiment.

[0010] Figure 2 is a schematic diagram showing a control device including a controller of the refrigeration device.

[0011] Figure 3 This is a diagram for explaining the relationship between the cooling requirement and the target superheat degree.

[0012] Figure 4 This is a diagram for explaining the relationship between the cooling requirement and the target superheat degree.

[0013] Figure 5 This is a diagram for explaining the relationship between the cooling requirement and the target superheat degree.

[0014] Figure 6 It is a diagram for explaining the operation of the refrigeration device.

[0015] Figure 7 It is a schematic diagram showing the structure of a refrigeration device according to a second embodiment.

[0016] Figure 8 It is a schematic diagram showing the configuration of a refrigeration apparatus according to a modified example of the second embodiment.

[0017] Fig. 9 It is a schematic diagram showing the structure of a refrigeration device according to a third embodiment.

[0018] Fig.10 It is a schematic diagram showing an environment forming device according to a fourth embodiment. DETAILED DESCRIPTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0020] (First embodiment)

[0021] like Figure 1 As shown, the refrigeration device 10 involved in the first embodiment includes a main refrigeration circuit 15 in which a first refrigerant is sealed and a subcooling refrigeration circuit 16 in which a second refrigerant is sealed. The first refrigerant can be, for example, a refrigerant such as R-449A, R-404A, or R-448A. The second refrigerant can be a refrigerant of the same type as the first refrigerant, or a refrigerant of a different type from the first refrigerant. The second refrigerant can be, for example, a refrigerant such as R-449A, R-404A, R-448A, R-134a, or R-513A.

[0022] The main refrigeration circuit 15 is provided with a first compressor 1, a first condenser 2, a heat exchanger 14 for subcooling, a first expansion mechanism 3 and a first evaporator 4 in sequence. The first compressor 1 operates so that the first refrigerant circulates in the main refrigeration circuit 15, thereby performing a vapor compression refrigeration cycle. The refrigeration device 10 can be used to cool the air in a freezer and / or a cold storage, or can be used to generate cooling water in a refrigerator. Alternatively, the refrigeration device 10 can also be used in an environment forming device such as an environmental test device that provides a temperature environment of a specified temperature. In addition, in the present embodiment, the refrigeration device 10 is used in a freezer.

[0023] The first compressor 1 is responsible for the compression step of the refrigeration cycle, and is constructed in a manner of sucking in and compressing the first refrigerant. The first compressor 1 includes, for example, a compression mechanism of a scroll type or a screw type, and is constructed so that the compression mechanism is driven by a motor with a constant speed. In addition, the first compressor 1 may also be constructed so that the speed of the motor can be adjusted by an inverter. In addition, the first compressor 1 may also be a structure including one unit compressor, or alternatively, may be a structure including two or more unit compressors of different capacities connected in parallel.

[0024] The first condenser 2 is responsible for the condensation step of the refrigeration cycle, and is configured to condense the first refrigerant by exchanging heat between the first refrigerant discharged from the first compressor 1 and a cooling medium such as air, water or refrigerant.

[0025] The first expansion mechanism 3 is responsible for the expansion step of the refrigeration cycle, and is configured to expand the liquid first refrigerant condensed in the first condenser 2. In addition, when the subcooling heat exchanger 14 functions, the first refrigerant flowing into the first expansion mechanism 3 becomes a state in which the degree of subcooling is further increased in the subcooling heat exchanger 14.

[0026] The first expansion mechanism 3 is formed of, for example, an electronic expansion valve. Therefore, by adjusting the valve opening of the first expansion mechanism 3, the flow rate of the first refrigerant flowing through the cooling heat exchanger 14 and the first evaporator 4 in the main refrigeration circuit 15 can be arbitrarily changed.

[0027] The first evaporator 4 is responsible for the evaporation step of the refrigeration cycle, and is configured so that the first refrigerant in a liquid state decompressed in the first expansion mechanism 3 exchanges heat with air to evaporate the first refrigerant. The first evaporator 4 cools the air (cooling object) supplied to the interior of the freezer (the interior to be cooled). In addition, when the refrigeration device 10 is provided in a refrigerator that generates cooling water, the first evaporator 4 becomes a configuration that evaporates the first refrigerant to cool the cooling water (cooling object).

[0028] The subcooling refrigeration circuit 16 is provided with a second compressor 11, a second condenser 12, a second expansion mechanism 13, and a subcooling heat exchanger 14 in sequence. When the second compressor 11 operates, the second refrigerant circulates in the subcooling refrigeration circuit 16, thereby performing a vapor compression refrigeration cycle.

[0029] The second compressor 11 is responsible for the compression step of the refrigeration cycle, and is constructed in a manner of sucking in and compressing the second refrigerant. The second compressor 11 includes, for example, a scroll-type, screw-type compression mechanism, and is constructed to be driven by a motor with a constant speed. In addition, the second compressor 11 may also be constructed to be able to adjust the speed of the motor using a converter. In addition, the second compressor 11 may also be a structure including one unit compressor, or alternatively, may be a structure including two or more unit compressors of different capacities connected in parallel.

[0030] The capacity of the second compressor 11 is smaller than the capacity of the first compressor 1. In addition, the size relationship between the capacities of the first compressor 1 and the second compressor 11 is not limited to this.

[0031] The second condenser 12 is responsible for the condensation step of the refrigeration cycle, and is configured to condense the second refrigerant by exchanging heat between the second refrigerant discharged from the second compressor 11 and a cooling medium such as air, water or refrigerant.

[0032] The second expansion mechanism 13 is responsible for the expansion step of the refrigeration cycle, and is configured in such a way as to expand the liquid second refrigerant condensed in the second condenser 12. The second expansion mechanism 13 is formed by, for example, an electronic expansion valve. Therefore, by adjusting the valve opening of the second expansion mechanism 13, the flow rate of the second refrigerant flowing through the cooling heat exchanger 14 in the subcooling refrigeration circuit 16 can be arbitrarily changed.

[0033] The subcooling heat exchanger 14 is configured to perform heat exchange between the first refrigerant flowing in the main refrigeration circuit 15 and the second refrigerant flowing in the subcooling refrigeration circuit 16. The second refrigerant whose flow rate is regulated by the second expansion mechanism 13 flows into the subcooling heat exchanger 14, and the liquid first refrigerant flowing out of the first condenser 2 flows into the subcooling heat exchanger 14. Then, the liquid first refrigerant is subcooled by evaporation of the second refrigerant in the subcooling heat exchanger 14.

[0034] The subcooling refrigeration circuit 16 is provided with an inlet temperature detector 21 for detecting the temperature of the second refrigerant flowing into the subcooling heat exchanger 14, and an outlet temperature detector 22 for detecting the temperature of the second refrigerant flowing out of the subcooling heat exchanger 14. The temperature detectors 21 and 22 output signals indicating the temperatures detected respectively.

[0035] The signals outputted by the temperature detectors 21 and 22 are inputted to the controller 100. The controller 100 is formed by a microcomputer or the like including a CPU for executing arithmetic processing, a ROM for storing a processing program and data, and a RAM for temporarily storing data. By executing the processing program stored in the controller 100, Figure 2 As shown, the controller 100 can be made to function as a receiving unit 101 , a superheat deriving unit 102 , a superheat setting unit 103 , a superheat control unit 104 , a compressor control unit 105 , and a cooling capacity control unit 106 .

[0036] The receiving unit 101 is configured to repeatedly receive the cooling requirement at each designated time and temporarily store the received cooling requirement. The cooling requirement is generated by the generator 120, and the cooling requirement generated by the generator 120 is input to the receiving unit 101. In addition, in the example shown in the figure, the generator 120 is configured independently of the controller 100, but the generator 120 of the cooling requirement may also be a function of the controller 100.

[0037] The generator 120 repeatedly receives signals from a sensor 121 for detecting the internal temperature (the temperature of the room to be cooled in the freezer), an input device 122 for inputting a set value of the internal temperature, etc., at each specified time, and calculates the refrigeration requirement each time. The refrigeration requirement is a value obtained by dedimensionalizing the refrigeration load in the freezer, for example, calculated based on the difference between the detected value and the set value of the internal temperature. Therefore, the greater the difference between the detected internal temperature and the set value of the internal temperature, the greater the refrigeration requirement. Since the refrigeration requirement may change from moment to moment, the generator 120 outputs the refrigeration requirement at each specified time.

[0038] The superheat deriving unit 102 is configured to derive the difference between the temperature detected by the outflow side temperature detector 22 and the temperature detected by the inflow side temperature detector 21 as the superheat of the second refrigerant on the outlet side of the subcooling heat exchanger 14. That is, in the subcooling refrigeration circuit 16, the liquid second refrigerant after being decompressed by the second expansion mechanism 13 is in a saturated state or a state close to a saturated state. Therefore, the temperature difference between the temperature of the gaseous second refrigerant flowing out of the subcooling heat exchanger 14 and the temperature of the liquid second refrigerant flowing into the subcooling heat exchanger 14 is equivalent to the superheat of the second refrigerant on the outlet side of the subcooling heat exchanger 14.

[0039] In addition, the superheat of the second refrigerant on the outlet side of the subcooling heat exchanger 14 can also be calculated by a method other than this method. For example, a temperature detector (outflow side temperature detector 22) and a pressure detector can also be arranged on the outlet side of the subcooling heat exchanger 14, and the superheat derivation unit 102 calculates the superheat of the second refrigerant using the saturated vapor temperature corresponding to the detection pressure detected by the pressure detector and the detection temperature detected by the temperature detector (outflow side temperature detector 22). In this case, the detection pressure detected by the pressure detector becomes the suction pressure of the second compressor 11, and therefore, the saturated vapor temperature corresponding to the suction pressure of the second compressor 11 can be obtained. This method of calculating the superheat is not limited to the refrigeration device 10 involved in the first embodiment, and can also be applied to the refrigeration device 10 involved in the second and third embodiments described later.

[0040] The superheat setting unit 103 is configured to set a target superheat, which is a target value of the superheat of the second refrigerant at the outlet side of the subcooling heat exchanger 14. That is, the controller 100 stores logic for setting the target superheat. Figure 3As shown, the logic is configured to set the target superheat to a value corresponding to the received refrigeration requirement. Specifically, when the received refrigeration requirement is above a preset threshold TV, the target superheat is set to a first value, and when the received refrigeration requirement is lower than the threshold TV, the target superheat is set to gradually increase from the first value as the refrigeration requirement decreases. That is, the controller 100 can perform superheat setting control, that is, setting the value of the target superheat when the received refrigeration requirement is the first requirement value to the first value, and on the other hand, when the received refrigeration requirement is the second requirement value, which is the refrigeration requirement less than the first requirement value, the target superheat is set to a second value greater than the first value. In addition, in the superheat setting control, when the received refrigeration requirement is lower than the threshold TV, the smaller the refrigeration requirement is, the larger the value of the target superheat is set.

[0041] Figure 3 The example in which the target superheat degree changes differently depending on whether the cooling demand is above or below the threshold value TV is shown, but the present invention is not limited thereto. Figure 4 As shown, the target superheat degree may be set to gradually increase as the cooling requirement decreases without setting the threshold TV. In this case, when the cooling requirement is the maximum required value, the target superheat degree also becomes the minimum value, and when the cooling requirement is less than the maximum required value, the target superheat degree may take a value higher than the minimum value. That is, when the cooling requirement is the maximum required value, the target superheat degree of the second refrigerant is set to the minimum value by the superheat degree setting unit 103, and when the cooling requirement is less than the maximum required value, the target superheat degree may be set to a value greater than the target superheat degree when the cooling requirement is the maximum required value. If the target superheat degree is set in this way, the threshold TV may be set or not.

[0042] Here, the maximum demand value refers to the demand value when the lowest set value that can be set and the highest value that the internal temperature can take is set when the refrigeration demand degree is calculated based on the difference between the detected value and the set value of the internal temperature, for example. In other words, the maximum demand value is the maximum value of the values ​​obtained under the conceivable conditions as the refrigeration demand degree.

[0043] In addition, if Figure 5 As shown in FIG. 1 , when a threshold value TV is set in advance, the target superheat degree may be set to gradually increase as the cooling requirement decreases when the threshold value TV is above the threshold value TV, and on the other hand, the target superheat degree may be set to be constant when the cooling requirement is below the threshold value TV. In this case, when the cooling requirement is the maximum requirement value, the target superheat degree also becomes the minimum value, and when the cooling requirement is less than the maximum requirement value, the target superheat degree may take a value higher than the minimum value.

[0044] The superheat control unit 104 is configured to control the second expansion mechanism 13 so that the superheat of the second refrigerant derived by the superheat deriving unit 102 reaches the target superheat set by the superheat setting unit 103. That is, the controller 100 can perform superheat control to control the second expansion mechanism 13 based on the target superheat.

[0045] If the opening of the second expansion mechanism 13 is reduced, the flow rate of the second refrigerant flowing in the subcooling refrigeration circuit 16 is reduced, and accordingly, in the subcooling heat exchanger 14, the second refrigerant is placed in a further superheated state, so that the superheat of the second refrigerant on the outlet side of the subcooling heat exchanger 14 is further increased. On the other hand, if the opening of the second expansion mechanism 13 is increased, the flow rate of the second refrigerant flowing in the subcooling refrigeration circuit 16 is increased. Accordingly, in the subcooling heat exchanger 14, the second refrigerant is placed in a state where it is not too superheated, so that the superheat of the second refrigerant on the outlet side of the subcooling heat exchanger 14 is further reduced. Therefore, the superheat control unit 104 controls the second expansion mechanism 13 in such a way that the superheat of the second refrigerant approaches the target superheat.

[0046] The compressor control unit 105 is configured to stop the second compressor 11 after the target superheat degree is increased to a predetermined maximum value. That is, the controller 100 can perform compressor control to stop the second compressor 11 after the target superheat degree is gradually increased.

[0047] When the target superheat is increased to the maximum value, the subcooling degree of the first refrigerant on the outlet side of the subcooling heat exchanger 14 decreases accordingly. Therefore, the refrigeration capacity exerted by the first evaporator 4 also decreases. Therefore, since the second compressor 11 is stopped in a state where the supercooling degree is reduced, even if the second compressor 11 is stopped, the occurrence of unstable temperature control in the freezer can be suppressed. In addition, the structure of stopping the second compressor 11 after the target superheat is increased to the maximum value can also be omitted.

[0048] The cooling capacity control unit 106 is configured to control the first expansion mechanism 3 so that the flow rate of the first refrigerant passing through the first expansion mechanism 3 is adjusted according to the cooling request received by the receiving unit 101. That is, the controller 100 can perform cooling capacity control for controlling the first expansion mechanism 3 based on the cooling request.

[0049] Specifically, information on the target evaporation temperature assigned to the received refrigeration demand is stored, and the refrigeration capacity control unit 106 controls the first expansion mechanism 3 so that the target evaporation temperature obtained according to the received refrigeration demand can be obtained. That is, the refrigeration capacity control unit 106 is configured to adjust the flow rate of the first refrigerant flowing into the first evaporator 4 according to the refrigeration demand.

[0050] In addition, the control of the first expansion mechanism 3 by the refrigeration capacity control unit 106 is not limited to the method of controlling in a manner that can obtain the target evaporation temperature. The target evaporation temperature is not specified, and the flow rate of the first refrigerant flowing into the first evaporator 4 is adjusted according to the received refrigeration demand. In this case, for example, information on the allocation of the opening degree of the first expansion mechanism 3 to the refrigeration demand may be stored, and the opening degree of the first expansion mechanism 3 may be set according to the refrigeration demand.

[0051] Here, refer to Figure 6 A refrigeration method using the refrigeration device 10 having the above-described configuration will be described.

[0052] After the target temperature of the in-store temperature (the temperature of the room to be cooled in the freezer, the temperature in the freezer) is set and the operation of the refrigeration device 10 starts, the controller 100 receives the refrigeration requirement generated by the generator 120 (step ST11), and receives the detected temperature detected by the inlet-side temperature detector 21 and the detected temperature detected by the outlet-side temperature detector 22 (step ST12). The refrigeration capacity control unit 106 of the controller 100 adjusts the opening of the first expansion mechanism 3 based on the received refrigeration requirement (step ST13). That is, the refrigeration capacity control unit 106 adjusts the opening of the first expansion mechanism 3 based on the refrigeration requirement so that the target evaporation temperature can be obtained. Accordingly, in the main refrigeration circuit 15, since the flow rate of the first refrigerant corresponding to the refrigeration requirement can be obtained, the required refrigeration capacity can be exerted.

[0053] On the other hand, in the subcooling refrigeration circuit 16, the superheat deriving unit 102 derives the difference between the temperature detected by the outflow-side temperature detector 22 and the temperature detected by the inflow-side temperature detector 21 as the superheat of the second refrigerant on the outlet side of the subcooling heat exchanger 14 (step ST14). In addition, the superheat setting unit 103 sets the target value of the superheat of the second refrigerant on the outlet side of the subcooling heat exchanger 14, that is, the target superheat, to a value corresponding to the cooling requirement (step ST15). Specifically, the superheat setting unit 103 sets the target superheat to a first value when the received cooling requirement is greater than a preset threshold value TV. On the other hand, when the received cooling requirement is lower than the threshold value TV, the superheat setting unit 103 sets the target superheat in such a way that the target superheat gradually increases from the first value as the cooling requirement decreases.

[0054] Next, the superheat control unit 104 controls the second expansion mechanism 13 so that the superheat of the second refrigerant derived by the superheat derivation unit 102 reaches the target superheat set by the superheat setting unit 103 (step ST16). At this time, if the received refrigeration requirement is above the threshold TV, the target superheat is set to the first value, and therefore, the second expansion mechanism 13 is controlled in such a way that the superheat reaches the first value. At this time, the target superheat is set to the first value regardless of whether the refrigeration requirement changes, but in the main refrigeration circuit 15, the first expansion mechanism 3 is controlled according to the refrigeration requirement. That is, in the main refrigeration circuit 15, the flow rate of the first refrigerant flowing through the first evaporator 4 changes according to the refrigeration requirement. Therefore, the second expansion mechanism 13 is adjusted according to the change in the flow rate of the first refrigerant. However, since the target superheat is set to a constant value, the control of the second expansion mechanism 13 does not become complicated.

[0055] On the other hand, when the received refrigeration requirement gradually decreases and the refrigeration requirement is lower than the threshold TV, the target superheat is set to a higher value. Therefore, the opening of the second expansion mechanism 13 is adjusted to an opening smaller than the opening when the refrigeration requirement is above the threshold TV. Moreover, in this case, the second expansion mechanism 13 is controlled so that the smaller the refrigeration requirement is, the higher the target superheat is. Therefore, the opening of the second expansion mechanism 13 further decreases as the refrigeration requirement decreases. Accordingly, the flow rate of the second refrigerant flowing through the cooling heat exchanger 14 is reduced, and therefore, the subcooling of the first refrigerant on the outlet side of the subcooling heat exchanger 14 is further reduced. Therefore, compared with the case where the superheat target value is maintained at a constant value, the subcooling of the first refrigerant is further reduced, and the refrigeration capacity exerted in the first evaporator 4 is reduced. Moreover, since the power of the first compressor 1 is also reduced, the energy consumption in the main refrigeration circuit 15 is reduced.

[0056] In addition, after the value of the refrigeration demand decreases and the target superheat increases to the maximum value, the second compressor 11 is stopped (ST17). Therefore, the energy consumption in the subcooling refrigeration circuit 16 is further reduced. At this time, since the refrigeration capacity exerted in the subcooling heat exchanger 14 becomes smaller, even if the second compressor 11 is stopped, the temperature control instability in the freezer can be suppressed.

[0057] In addition, the control for stopping the second compressor 11 (ST17) may be omitted. In addition, after the target superheat degree is increased to the maximum value, or when the target superheat degree reaches a specified ratio of the maximum value (i.e., the ratio at which the second refrigerant hardly flows), the second expansion mechanism 13 may be switched from the control based on the target superheat degree to the control corresponding to the cooling requirement. That is, the controller 100 may also be able to perform the subcooling adjustment control for controlling the second expansion mechanism 13 based on the cooling requirement.

[0058] As described above, in the present embodiment, in the subcooling heat exchanger 14, since the first refrigerant of the main refrigeration circuit 15 is subcooled by evaporation of the second refrigerant of the subcooling refrigeration circuit 16, the refrigeration capacity exerted by the main refrigeration circuit 15 increases accordingly. Therefore, compared with the case where the same refrigeration capacity is exerted by only one refrigeration circuit, a compressor with a smaller compressor capacity can be used to exert the same refrigeration capacity. In addition, when the value of the refrigeration demand is the second demand value (the value of the refrigeration demand is less than the first demand value), the target value of the superheat of the second refrigerant on the outlet side of the subcooling heat exchanger 14 is set to the second value (a value greater than the first value). And, the second expansion mechanism 13 is controlled based on the target value of the superheat of the second refrigerant on the outlet side of the subcooling heat exchanger 14. Accordingly, the flow rate of the second refrigerant circulating in the subcooling refrigeration circuit 16 is reduced compared with the flow rate based on the target value of the superheat when the refrigeration demand is the first demand value. As a result, the power of the second compressor 11 of the subcooling refrigeration circuit 16 is reduced compared to the case where the target superheat degree is controlled to be constant. Therefore, when the cooling demand is relatively small, further energy saving of the subcooling refrigeration circuit 16 can be achieved.

[0059] In addition, in the present embodiment, since the target superheat is set to the minimum value when the refrigeration demand is the maximum demand value, the second expansion mechanism 13 is controlled so as to achieve the target superheat, so that the flow rate of the second refrigerant circulating in the subcooling refrigeration circuit 16 becomes maximum. Therefore, the subcooling degree of the first refrigerant on the outlet side of the subcooling heat exchanger 14 in the main refrigeration circuit 15 is also increased. Therefore, a greater refrigeration capacity can be exerted.

[0060] In addition, in the present embodiment, when the cooling requirement is above a preset threshold value TV, the target superheat is set to the first value, and when the cooling requirement is below the threshold value TV, the value of the target superheat gradually increases from the first value as the cooling requirement decreases. Therefore, when the cooling requirement is above the threshold value TV, the specified cooling capacity is exerted, and on the other hand, when the cooling requirement is stable below the threshold value TV, further energy saving of the subcooling refrigeration circuit 16 can be achieved.

[0061] (Second embodiment)

[0062] like Figure 7 As shown, in the second embodiment, a bypass flow path 18 is provided in the subcooling refrigeration circuit 16. In addition, here, the same reference numerals are attached to the same components as those of the first embodiment, and detailed description thereof is omitted.

[0063] The bypass flow path 18 is a flow path for returning the second refrigerant flowing out of the second condenser 12 to the second compressor 11 without flowing through the cooling heat exchanger 14. One end of the bypass flow path 18 is connected to a portion between the second condenser 12 and the second expansion mechanism 13 in the subcooling refrigeration circuit 16, and the other end is connected to a portion between the subcooling heat exchanger 14 and the second compressor 11 in the subcooling refrigeration circuit 16.

[0064] The bypass expansion mechanism 17 and the bypass evaporator 5 are provided in the bypass flow path 18. The bypass evaporator 5 is arranged on the downstream side of the bypass expansion mechanism 17 in the bypass flow path 18, and makes the second refrigerant decompressed by the bypass expansion mechanism 17 exchange heat with the air supplied to the freezer (the room to be cooled). In addition, when the refrigeration device 10 is provided in a refrigerator that generates cooling water, the bypass evaporator 5 becomes a structure that evaporates the second refrigerant to cool the cooling water (cooling object).

[0065] The bypass expansion mechanism 17 is formed of, for example, an electronic expansion valve, and its opening degree is controlled by the controller 100. That is, the cooling capacity control unit 106 is configured to control the first expansion mechanism 3 and the bypass expansion mechanism 17 according to the cooling demand.

[0066] The controller 100 can perform, for example, a rapid cooling control in which both the first evaporator 4 and the bypass evaporator 5 function without allowing the subcooling heat exchanger 14 to function. In addition, the controller 100 can perform a subcooling control in which only the first evaporator 4 functions while the subcooling heat exchanger 14 functions. In addition, the controller 100 can perform an intercooling control in which only the first evaporator 4 functions while the subcooling heat exchanger 14 functions. In addition, the controller 100 can perform a weak cooling control in which only the bypass evaporator 5 functions. In addition, any one of the rapid cooling control, the intercooling control, and the weak cooling control can be omitted. In addition, controls other than these can also be performed.

[0067] In the rapid cooling control, the first expansion mechanism 3 and the bypass expansion mechanism 17 are controlled to have an opening degree corresponding to the refrigeration requirement. Therefore, the air supplied to the freezer is cooled by both the first evaporator 4 and the bypass evaporator 5. That is, the refrigeration capacity control unit 106 controls the first expansion mechanism 3 and the bypass expansion mechanism 17 according to the refrigeration requirement received by the receiving unit 101. In this rapid cooling control, in order to make the bypass evaporator 5 function, the second expansion mechanism 13 is closed. The rapid cooling control is performed when the refrigeration requirement is large and the temperature in the freezer is relatively high. In this rapid cooling control, the compressor power becomes larger, but a large refrigeration capacity can be exerted.

[0068] In the supercooling control, the first expansion mechanism 3 and the second expansion mechanism 13 are controlled to have an opening degree corresponding to the refrigeration requirement, and on the other hand, the bypass expansion mechanism 17 is closed. That is, in the supercooling control, the bypass evaporator 5 is not used, and the operation using the supercooling heat exchanger 14 is performed in the main refrigeration circuit 15. In this case, in the supercooling control, the same control as that described in the first embodiment is performed. In addition, in the supercooling control, it is also possible to control the bypass expansion mechanism 17 to open as the opening degree of the first expansion mechanism 3 decreases. In this case, the opening degree of the first expansion mechanism 3 decreases as the refrigeration requirement decreases, and the opening degree of the bypass expansion mechanism 17 increases, so that control instability can be suppressed when switching from the supercooling control or transferring to the weak cooling control.

[0069] That is, the refrigeration capacity control unit 106 controls the first expansion mechanism 3 so that the flow rate of the first refrigerant passing through the first evaporator 4 is adjusted according to the refrigeration requirement received by the receiving unit 101. In addition, the superheat control unit 104 controls the second expansion mechanism 13 so that the superheat of the second refrigerant derived by the superheat derivation unit 102 reaches the target superheat set by the superheat setting unit 103. At this time, the superheat setting unit 103 sets the value of the target superheat when the received refrigeration requirement is the first requirement value to the first value, and on the other hand, when the received refrigeration requirement is the refrigeration requirement that is smaller than the first requirement value, that is, the second requirement value, the target superheat is set to the second value that is larger than the first value. Therefore, in the supercooling control, Figure 3 (or Figure 4 , Figure 5 ) is set, and the second expansion mechanism 13 is controlled.

[0070] Intercooling control is performed when the refrigeration requirement is less than the refrigeration requirement that is the object of supercooling control. In the intercooling control, the first expansion mechanism 3 is controlled to an opening corresponding to the refrigeration requirement, and on the other hand, the bypass expansion mechanism 17 and the second expansion mechanism 13 are closed. In addition, the second compressor 11 is stopped. Therefore, the air supplied to the freezer is cooled only by the first evaporator 4. At this time, the first refrigerant is not supercooled by the supercooling heat exchanger 14, and therefore, the refrigeration capacity is reduced compared to the supercooling control.

[0071] In the intercooling control, the first expansion mechanism 3 is controlled according to the cooling requirement. Therefore, in the intercooling control, if the cooling requirement gradually decreases, the opening degree of the first expansion mechanism 3 also decreases accordingly. In addition, the first compressor 1 may be stopped when the first expansion mechanism 3 is reduced to the minimum opening degree (or a predetermined designated opening degree). However, if the first compressor 1 is stopped, it may cause unstable control. Therefore, a control valve 12 may be provided in the main refrigeration circuit 15. Figure 8The first bypass flow path 31 and the second bypass flow path 32 shown in the figure continue the operation of the first compressor 1. In this case, even in a state where the opening degree of the first expansion mechanism 3 is very small, the operation of the first compressor 1 can be continued.

[0072] The first bypass flow path 31 is a flow path for allowing the refrigerant (liquid refrigerant) flowing out of the first condenser 2 to flow into the first compressor 1 without passing through the first evaporator 4. The second bypass flow path 32 is a flow path for allowing the refrigerant (gas refrigerant) ejected from the first compressor 1 to flow into the first compressor 1 without passing through the first condenser 2 and the first evaporator 4. By providing the first bypass flow path 31 and the second bypass flow path 32, the suction pressure of the first compressor 1 will not be excessively reduced, and the liquid refrigerant will not be sucked into the first compressor 1 until the opening of the first expansion mechanism 3 is closed, so that the refrigerant flow rate flowing to the first evaporator 4 can be adjusted. A flow regulator 33 such as a temperature expansion valve or an electronic expansion valve is provided in the first bypass flow path 31, and a bypass valve 34 such as a suction pressure regulating valve or an electronic expansion valve is provided in the second bypass flow path 32.

[0073] The weak cooling control is executed when the cooling requirement is lower than the cooling requirement to be controlled by the intercooling control. That is, the subcooling control is executed when the received cooling requirement is the first requirement value and the second requirement value, and the weak cooling control is executed when the received cooling requirement is the third requirement value, which is a further smaller value.

[0074] In weak cooling control, the first expansion mechanism 3 and the second expansion mechanism 13 are closed, while the bypass expansion mechanism 17 is controlled to an opening corresponding to the cooling requirement. Therefore, the air supplied to the freezer is not cooled in the first evaporator 4, but only cooled by the bypass evaporator 5. In this case, the first compressor 1 is stopped. However, if the first compressor 1 is stopped, it may cause unstable control. Therefore, it is also possible to set Figure 8 The first bypass flow path 31 and the second bypass flow path 32 shown in the figure continue the operation of the first compressor 1. Thus, even when the first expansion mechanism 3 is closed, the first compressor 1 can be kept operating.

[0075] Therefore, in the present embodiment, when the refrigeration requirement is a third requirement value lower than the second requirement value, the flow rate of the second refrigerant circulating in the subcooling refrigeration circuit 16 is reduced compared to the flow rate based on the target superheat when the refrigeration requirement is the second requirement value. In this case, the bypass expansion mechanism 17 is controlled in such a way that the second refrigerant flows through the bypass flow path 18, and in the main refrigeration circuit 15, the first expansion mechanism 3 is controlled in such a way that the first refrigerant does not flow through the first evaporator 4. Accordingly, the refrigeration capacity exerted by the first evaporator 4 is reduced, and the refrigeration capacity is exerted in the bypass evaporator 5. At this time, since the capacity of the second compressor 11 is smaller than the capacity of the first compressor 1, the energy required to drive the compressors 1 and 11 can be saved. In addition, when the first compressor 1 is stopped, energy can be further saved.

[0076] In addition, descriptions of other structures, functions, and effects are omitted, and the descriptions of the first embodiment can be applied to the second embodiment.

[0077] (Third embodiment)

[0078] like Fig. 9 As shown, in the third embodiment, a low temperature refrigeration circuit 19 is connected to the main refrigeration circuit 15, thereby forming a so-called binary refrigeration circuit. In addition, here, the same reference numerals are attached to the same components as those in the first and second embodiments, and their detailed descriptions are omitted.

[0079] A cascade bypass flow path 35 is provided in the main refrigeration circuit 15. One end of the cascade bypass flow path 35 is connected between the subcooling heat exchanger 14 and the first expansion mechanism 3 in the main refrigeration circuit 15, and the other end is connected between the first evaporator 4 and the first compressor 1 in the main refrigeration circuit 15.

[0080] The cascade bypass flow passage 35 is provided with a cascade expansion mechanism 8 and a cascade heat exchanger 52. The cascade heat exchanger 52 is arranged on the downstream side of the cascade expansion mechanism 8 in the cascade bypass flow passage 35, and the first refrigerant after being decompressed in the cascade expansion mechanism 8 flows into the cascade heat exchanger 52.

[0081] The cascade expansion mechanism 8 is formed of, for example, an electronic expansion valve, and is controlled by the controller 100. In addition, the cascade expansion mechanism 8 is not limited to a structure formed of an electronic expansion valve. For example, the cascade expansion mechanism 8 may also be formed of a temperature-type expansion valve. In this case, the cascade expansion mechanism 8 is not controlled by the controller 100, but becomes a structure in which the opening degree is adjusted according to the temperature of the first refrigerant flowing in the cascade bypass flow path 35. In this case, the temperature detectors 28 and 29 described later are omitted.

[0082] The cascade bypass flow path 35 is provided with temperature detectors 28 and 29 located on the upstream side and the downstream side of the cascade heat exchanger 52 .

[0083] The cascade heat exchanger 52 is connected to the low temperature refrigeration circuit 19. A third refrigerant is sealed in the low temperature refrigeration circuit 19. The third refrigerant may be a refrigerant having a lower boiling point than the first refrigerant, such as R-473A, R-508A, or R-23.

[0084] The low-temperature refrigeration circuit 19 is provided with a low-temperature compressor 51 , a low-temperature precooler 56 , a cascade heat exchanger 52 , a low-temperature expansion mechanism 53 , and a low-temperature evaporator 6 in this order.

[0085] The cryogenic compressor 51 includes, for example, a scroll type, a screw type, or other compression mechanism, and is configured to be driven by a motor with a constant speed. In addition, the cryogenic compressor 51 may also be configured to be able to adjust the speed of the motor using a converter. In addition, the cryogenic compressor 51 may also be a structure including one unit compressor, or alternatively, may be a structure including two or more unit compressors with different capacities connected in parallel.

[0086] The low-temperature precooler 56 is configured to precool the third refrigerant by exchanging heat between the third refrigerant discharged from the low-temperature compressor 51 and a cooling medium such as air, water, or refrigerant.

[0087] The cascade heat exchanger 52 causes heat exchange between the first refrigerant having a low temperature in the cascade expansion mechanism 8 and the third refrigerant precooled in the low-temperature precooler 56. Thus, the third refrigerant is supercooled.

[0088] The low-temperature expansion mechanism 53 is configured to expand the third refrigerant condensed in the cascade heat exchanger 52 .

[0089] The low-temperature expansion mechanism 53 is formed of, for example, an electronic expansion valve. Therefore, by adjusting the valve opening of the low-temperature expansion mechanism 53, the flow rate of the third refrigerant flowing through the cascade heat exchanger 52 and the low-temperature evaporator 6 in the low-temperature refrigeration circuit 19 can be arbitrarily changed. The opening of the low-temperature expansion mechanism 53 is controlled by the controller 100. That is, the refrigeration capacity control unit 106 is configured to control the low-temperature expansion mechanism 53 according to the refrigeration requirement.

[0090] The low-temperature evaporator 6 is configured to evaporate the third refrigerant by exchanging heat between the third refrigerant in a liquid state after being decompressed by the low-temperature expansion mechanism 53 and the air in the freezer supplied thereto. In addition, when the refrigeration device 10 is provided in a refrigerator that generates cooling water, the low-temperature evaporator 6 is configured to evaporate the third refrigerant to cool the antifreeze solution.

[0091] The functions of the controller 100 include a second superheat degree deriving unit 107 that calculates the superheat degree of the first refrigerant flowing out of the cascade heat exchanger 52 based on the difference between the detected temperatures of the temperature detectors 28 and 29 .

[0092] In addition, the function of the controller 100 includes a cascade control unit 108 that controls the cascade expansion mechanism 8 based on the superheat of the first refrigerant obtained by the second superheat derivation unit 107. That is, the cascade control unit 108 controls the cascade expansion mechanism 8 in such a way that the superheat of the first refrigerant on the outlet side of the cascade heat exchanger 52 reaches the target superheat. The target superheat of the first refrigerant is set to a constant value. Accordingly, when the heat load on the low-temperature evaporator 6 is high and the heat load of the third refrigerant flowing through the cascade heat exchanger 52 becomes high, the cascade expansion mechanism 8 is controlled in such a way that the flow rate of the first refrigerant in the cascade bypass flow path 35 becomes larger.

[0093] The controller 100 determines whether to perform binary refrigeration operation or single refrigeration operation based on the set temperature and / or operating conditions. In the single refrigeration operation, since it operates as in the second embodiment, the description is omitted here. In the binary refrigeration operation, the first expansion mechanism 3 and the bypass expansion mechanism 17 are closed, so the first evaporator 4 and the bypass evaporator 5 do not function. In addition, the cascade heat exchanger 52 functions so that the main refrigeration circuit 15 becomes a cascade circuit, and the subcooling heat exchanger 14 functions so that the subcooling refrigeration circuit 16 becomes a subcooling circuit. In this case, the second expansion mechanism 13 and the low-temperature expansion mechanism 53 are controlled according to the refrigeration requirement. That is, the controller 100 controls the second expansion mechanism 13 and the low-temperature expansion mechanism 53 so that the opening of the second expansion mechanism 13 and the low-temperature expansion mechanism 53 decreases as the refrigeration requirement decreases. Therefore, the refrigerant circulation amount corresponding to the refrigeration requirement is obtained in the low-temperature refrigeration circuit 19 and the subcooling refrigeration circuit 16. In addition, after the opening degree of the second expansion mechanism 13 is reduced to the minimum opening, or when the second expansion mechanism 13 is closed, the second compressor 11 may be stopped.

[0094] In addition, descriptions of other structures, functions, and effects are omitted, and the descriptions of the first and second embodiments can be applied to the third embodiment.

[0095] (Fourth embodiment)

[0096] Fig.10 Here, the same components as those in the first to third embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0097] The fourth embodiment is an example in which the refrigeration device 10 is applied to an environment forming device 60 such as an environmental testing device. The environment forming device 60 has an environment chamber 61, and the interior of the environment chamber 61 is adjusted to a specified temperature environment. The environment forming device 60 also has an air conditioning chamber 62 for generating air with adjusted temperature, and the first evaporator 4 of the refrigeration device 10 is arranged in the air conditioning chamber 62. In addition, in the case of the refrigeration device 10 described in the second embodiment, the bypass evaporator 5 is also arranged in the air conditioning chamber 62, and in the case of the refrigeration device 10 described in the third embodiment, the bypass evaporator 5 and the low-temperature evaporator 6 are also arranged in the air conditioning chamber 62.

[0098] In the air conditioning room 62, a heater 64 for heating air and a blower 65 for blowing the temperature-adjusted air to the environmental room 61 are arranged to be located on the downstream side of the first evaporator 4. A sensor 121 for detecting the temperature of the cooling object (the indoor temperature of the environmental room 61) is provided in the environmental room 61. The input device 122 is used to input the set temperature of the temperature in the environmental room 61. The environment forming device 60 can also be a device that can set a wide range of temperatures such as a sub-zero temperature area, a normal temperature area, or a high temperature area, and has a program operation function that changes multiple temperatures in a stepwise or continuous manner.

[0099] In addition, the environment forming device 60 is configured to obtain not only a specified temperature environment but also a specified humidity environment. In this case, a humidifier (not shown) is provided. In this case, the first evaporator 4 can also function as a dehumidifier. In addition, in the refrigeration device 10 having the second evaporator 5, the second evaporator 5 can also function as a dehumidifier.

[0100] The generator 120 calculates the cooling requirement using the temperature detected by the sensor 121 and the set temperature from the input device 122 .

[0101] The output of the heater 64 is controlled based on the detected temperature of the sensor 121 and the set temperature from the input device 122. That is, the specified refrigeration capacity can be exerted by controlling the first expansion mechanism 3 and the second expansion mechanism 13 of the refrigeration device 10, but the detected temperature of the sensor 121 is sometimes lower than the set temperature. In this case, the indoor temperature of the environmental room 61 is finely adjusted by the heater 64. Therefore, if the overcooling of the refrigeration device 10 can be suppressed, not only the power of the refrigeration device 10 can be suppressed, but also the power of the heater 64 can be suppressed. In this regard, when the refrigeration demand is small, the refrigerant circulation amount can be further reduced by using the second expansion mechanism 13, so that the refrigeration capacity can be reduced. Therefore, the power of the heater 64 can also be suppressed, and further energy saving can be achieved. In addition, the target superheat of the second refrigerant on the outlet side of the subcooling heat exchanger 14 is changed by the superheat setting unit 103, and the superheat control unit 104 controls the second expansion mechanism 13 based on the target superheat, so that both the tracking property to the set temperature and the energy saving after the temperature is reached can be achieved, which is particularly suitable for the case of executing program operation. In addition, the heater 64 may be omitted.

[0102] In addition, the description of other structures, functions, and effects will be omitted, and the description of the first to third embodiments can be applied to the fourth embodiment.

[0103] (Other embodiments)

[0104] In addition, the embodiments disclosed this time are illustrative in all aspects and should not be considered as limiting. The present invention is not limited to the embodiments described above, and various changes and improvements can be made within the scope of the main purpose. For example, in the embodiments described above, the controller 100 controls the first expansion mechanism 3 based on the cooling demand, but, instead, the first expansion mechanism 3 can also be controlled based on the subcooling degree of the first refrigerant at the outlet of the subcooling heat exchanger 14.

[0105] In addition, although not shown in the figure, it is also possible to Figure 1 , Figure 7 , Figure 8 and Fig. 9 The subcooling refrigeration circuit 16 is also provided with the same functions as the first bypass flow path 31 and the second bypass flow path 32 of the main refrigeration circuit 15. In this case, energy saving can be further achieved. That is, a bypass flow path may be provided for allowing the refrigerant (liquid refrigerant) flowing out of the second condenser 12 to flow into the second compressor 11 without passing through the subcooling heat exchanger 14. In addition, a bypass flow path may be provided for allowing the refrigerant (gas refrigerant) ejected from the second compressor 11 to flow into the second compressor 11 without passing through the second condenser 12 and the bypass evaporator 5.

[0106] Furthermore, when the first compressor 1 is configured such that the rotation speed of the motor can be adjusted by an inverter, the controller 100 may control the rotation speed of the motor of the first compressor 1 based on the cooling demand instead of controlling the first expansion mechanism 3 .

[0107] Here, the above-mentioned embodiments will be briefly described.

[0108] (1) The refrigeration device according to the embodiment includes: a main refrigeration circuit in which a first refrigerant is sealed, and a first compressor, a first condenser, a subcooling heat exchanger, a first expansion mechanism, and a first evaporator are provided; a subcooling refrigeration circuit in which a second refrigerant is sealed, and a second compressor, a second condenser, and a second expansion mechanism are provided, and the subcooling heat exchanger is connected; and a controller capable of performing superheat setting control and superheat control. The subcooling heat exchanger is configured to evaporate the second refrigerant in the subcooling refrigeration circuit, thereby subcooling the first refrigerant in the main refrigeration circuit. In the superheat setting control, the controller sets a target value of superheat of the second refrigerant at the outlet side of the subcooling heat exchanger to a first value when the cooling demand is a first demand value, and sets the target value of superheat to a second value greater than the first value when the cooling demand is a second demand value smaller than the first demand value. The controller controls the second expansion mechanism in the superheat control based on the target value of the superheat set in the superheat setting control.

[0109] In the refrigeration device, in the subcooling heat exchanger, the second refrigerant of the subcooling refrigeration circuit evaporates, thereby supercooling the first refrigerant of the main refrigeration circuit. Therefore, the refrigeration capacity exerted by the main refrigeration circuit increases accordingly. Therefore, compared with the case where the same refrigeration capacity is exerted by only one refrigeration circuit, a compressor with a smaller compressor capacity can be used to exert the same refrigeration capacity. In addition, in the case where the value of the refrigeration requirement is the second requirement value (the value of the refrigeration requirement is less than the first requirement value), the target value of the superheat of the second refrigerant on the outlet side of the subcooling heat exchanger is set to the second value (a value greater than the first value). And, the second expansion mechanism is controlled based on the target value of the superheat of the second refrigerant on the outlet side of the subcooling heat exchanger. Accordingly, the flow rate of the second refrigerant circulating in the subcooling refrigeration circuit is reduced compared with the flow rate based on the target value of the superheat when the refrigeration requirement is the first requirement value. According to this, the power of the second compressor of the subcooling refrigeration circuit is reduced compared to the case where the target value of the superheat degree is controlled to be constant. Therefore, when the cooling demand is relatively small, further energy saving of the subcooling refrigeration circuit can be achieved.

[0110] (2) The controller may be configured to set the target value of the superheat degree to a minimum value when the cooling request degree is a maximum request value in the superheat degree setting control.

[0111] In this technical solution, when the refrigeration demand is the maximum demand value, the target value of the superheat becomes the minimum value, and therefore, the second expansion mechanism is controlled based on the target value of the superheat, so that the flow rate of the second refrigerant circulating in the subcooling refrigeration circuit becomes the maximum. Therefore, the subcooling degree of the first refrigerant on the outlet side of the subcooling heat exchanger in the main refrigeration circuit is also increased. Therefore, a greater refrigeration capacity can be exerted.

[0112] (3) The controller may also be configured such that, in the superheat setting control, when the degree of refrigeration requirement is above a preset threshold value, the target value of the superheat is set to the first value, and, when the degree of refrigeration requirement is less than the threshold value, the target value of the superheat is gradually increased from the first value as the degree of refrigeration requirement decreases.

[0113] In this technical solution, when the cooling requirement is above the threshold TV, the specified cooling capacity is exerted. On the other hand, when the cooling requirement is stable and is less than the threshold TV, further energy saving of the subcooling refrigeration circuit can be achieved as the cooling requirement decreases.

[0114] (4) The controller may be configured to gradually increase the target value of the superheat from the first value as the cooling requirement decreases during the superheat setting control. In this case, the controller may be configured to stop the second compressor after gradually increasing the target value of the superheat from the first value.

[0115] In this aspect, the second compressor is stopped when the cooling demand decreases, so that further energy saving can be achieved in the subcooling refrigeration circuit.

[0116] (5) The degree of superheat may be obtained based on a temperature difference between the second refrigerant located upstream and downstream of the subcooling heat exchanger in the subcooling refrigeration circuit.

[0117] (6) A bypass flow path for bypassing the subcooling heat exchanger may also be connected to the subcooling refrigeration circuit. In this case, a bypass expansion mechanism and a bypass evaporator may also be provided in the bypass flow path. In addition, the capacity of the second compressor may be smaller than the capacity of the first compressor. The controller may also be configured to control the first expansion mechanism in a manner that prevents the first refrigerant from flowing through the first evaporator, and to control the bypass expansion mechanism in a manner that allows the second refrigerant to flow through the bypass evaporator, when the refrigeration requirement is a third requirement value that is smaller than the second requirement value.

[0118] In this technical solution, when the refrigeration requirement is a third requirement value that is smaller than the second requirement value, the flow rate of the second refrigerant circulating in the subcooling refrigeration circuit is reduced compared to the flow rate based on the target value of the superheat when the refrigeration requirement is the second requirement value. In this case, the first expansion mechanism is controlled in such a way that the first refrigerant does not flow through the first evaporator in the main refrigeration circuit, and the bypass expansion mechanism is controlled in such a way that the second refrigerant flows through the bypass flow path of the cooling refrigeration circuit. Accordingly, the refrigeration capacity exerted by the first evaporator is reduced, and the refrigeration capacity is exerted in the bypass evaporator. At this time, since the capacity of the second compressor is smaller than the capacity of the first compressor, the energy required to drive the compressor can be saved.

[0119] (7) The environment forming device according to the above embodiment includes: an environment chamber; and the refrigeration device for cooling the environment chamber.

[0120] In the environment forming device, when the refrigeration demand is low, the target value of the superheat is increased in the refrigeration device, so that the flow rate of the second refrigerant in the subcooling refrigeration circuit is reduced. Therefore, the power of the second compressor of the subcooling refrigeration circuit is reduced compared with the case where the control is performed with the target value of the superheat constant. Moreover, the refrigeration capacity of the main refrigeration circuit is also reduced compared with the case where the control is performed with the target value of the superheat constant. Therefore, energy saving can be achieved.

[0121] (8) The environment forming device may also include: a heater, which operates when the temperature of the air in the environment room is lower than a specified temperature. In this technical solution, when the target value of superheat is increased when the refrigeration requirement is low, the flow rate of the second refrigerant in the subcooling refrigeration circuit is reduced. Therefore, the refrigeration capacity of the main refrigeration circuit is also reduced compared to the case where the target value of superheat is constant. Accordingly, the temperature of the air in the environment room can be suppressed from dropping excessively, so the output of the heater can be reduced. Therefore, further energy saving can be achieved.

[0122] (9) The refrigeration method involved in the embodiment uses a refrigeration device, which includes: a main refrigeration circuit, which is sealed with a first refrigerant and is provided with a first compressor, a first condenser, a subcooling heat exchanger, a first expansion mechanism and a first evaporator; and a subcooling refrigeration circuit, which is sealed with a second refrigerant and is provided with a second compressor, a second condenser and a second expansion mechanism, and is connected to the subcooling heat exchanger. The refrigeration method performs the following steps: receiving a refrigeration requirement in the refrigeration device; and when the received refrigeration requirement is a first requirement value, The target value of the superheat of the second refrigerant at the outlet side of the subcooling heat exchanger is set to a first value; when the received refrigeration requirement is a second requirement value smaller than the first requirement value, the target value of the superheat is set to a second value larger than the first value; based on the set target value of the superheat, the second expansion mechanism is controlled; in the subcooling heat exchanger into which the second refrigerant flows after the flow rate is adjusted by the second expansion mechanism, the second refrigerant is evaporated, thereby subcooling the first refrigerant of the main refrigeration circuit.

[0123] As described above, according to the above embodiment, not only energy saving is achieved by using the subcooling heat exchanger, but also further energy saving is achieved.

[0124] This application is based on Japanese patent application No. 2023-191756 filed on November 9, 2023, the contents of which are incorporated herein by reference. That is, this application claims priority to Japanese patent application (application number 2023-191756) filed on November 9, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A refrigeration device, characterized in that include: A main refrigeration circuit is sealed with a first refrigerant and is provided with a first compressor, a first condenser, a subcooling heat exchanger, a first expansion mechanism and a first evaporator; a subcooling refrigeration circuit enclosing a second refrigerant, provided with a second compressor, a second condenser and a second expansion mechanism, and connected to the subcooling heat exchanger; and A controller capable of performing superheat setting control and superheat control, wherein: The subcooling heat exchanger is configured to evaporate the second refrigerant in the subcooling refrigeration circuit to subcool the first refrigerant in the main refrigeration circuit. The controller sets a target value of the superheat of the second refrigerant at the outlet side of the subcooling heat exchanger to a first value in the superheat setting control when the cooling requirement is a first requirement value, and sets the target value of the superheat to a second value greater than the first value when the cooling requirement is a second requirement value smaller than the first requirement value. The controller controls the second expansion mechanism in the superheat control based on the target value of the superheat set in the superheat setting control.

2. The refrigeration device according to claim 1, characterized in that: The controller is configured to set the target value of the superheat degree to a minimum value when the cooling request degree is a maximum request value in the superheat degree setting control.

3. The refrigeration device according to claim 1, characterized in that: The controller is configured to: in the superheat setting control, when the cooling requirement is above a preset threshold value, set the target value of the superheat to the first value, and when the cooling requirement is less than the threshold value, gradually increase the target value of the superheat from the first value as the cooling requirement decreases.

4. The refrigeration device according to claim 1, characterized in that: The controller is configured to gradually increase the target value of the superheat degree from the first value as the cooling demand decreases during the superheat degree setting control, and The controller is configured to stop the second compressor after gradually increasing the target value of the superheat degree from the first value.

5. The refrigeration device according to claim 1, characterized in that: The degree of superheat is obtained based on a temperature difference between the second refrigerant located upstream and downstream of the subcooling heat exchanger in the subcooling refrigeration circuit.

6. The refrigeration device according to claim 1, characterized in that: The subcooling refrigeration circuit is connected to a bypass flow path for bypassing the subcooling heat exchanger. The bypass flow path is provided with a bypass expansion mechanism and a bypass evaporator. The capacity of the second compressor is smaller than the capacity of the first compressor, The controller is configured to control the first expansion mechanism in a manner that prevents the first refrigerant from flowing through the first evaporator when the cooling requirement is a third requirement value that is smaller than the second requirement value, and to control the bypass expansion mechanism in a manner that allows the second refrigerant to flow through the bypass evaporator.

7. An environment forming device, characterized in that include: Environmental chamber; as well as The refrigeration device according to any one of claims 1 to 6, used for cooling the environmental room.

8. The environment forming device according to claim 7, characterized in that Also includes: The heater operates when the temperature of the air in the environmental chamber is lower than a specified temperature.

9. A refrigeration method, characterized in that Using a refrigeration device, the refrigeration device comprising: a main refrigeration circuit in which a first refrigerant is sealed and provided with a first compressor, a first condenser, a subcooling heat exchanger, a first expansion mechanism, and a first evaporator; and The subcooling refrigeration circuit is filled with a second refrigerant and is provided with a second compressor, a second condenser and a second expansion mechanism, and is connected to the subcooling heat exchanger. The refrigeration method is performed as follows: receiving a refrigeration demand in the refrigeration device; When the received cooling request degree is a first request value, setting a target value of the superheat degree of the second refrigerant at the outlet side of the subcooling heat exchanger to a first value; When the received cooling request degree is a second request value that is smaller than the first request value, setting the target value of the superheat degree to a second value that is larger than the first value; controlling the second expansion mechanism based on the set target value of the degree of superheat; In the subcooling heat exchanger into which the second refrigerant having a flow rate adjusted by the second expansion mechanism flows, the second refrigerant is evaporated, thereby subcooling the first refrigerant in the main refrigeration circuit.

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