Refrigeration device, environment formation device and refrigeration method

Abstract

To further save energy in addition to energy saving by using a supercooling heat exchanger.SOLUTION: A refrigeration device 10 includes: a main refrigeration circuit 15 filled with a first refrigerant; a supercooling refrigeration circuit 16 filled with a second refrigerant and connected to a supercooling heat exchanger 14; and a controller 100. The supercooling heat exchanger 14 supercools the first refrigerant in the main refrigeration circuit 15. In superheating degree setting control, the controller 100 sets a target value of a superheating degree of the second refrigerant on an outlet side of the supercooling heat exchanger 14 to a first value when a refrigeration request level is a first request value, and sets the target value of the superheating degree to a second value larger than the first value when the refrigeration request level is a second request value lower than the first request value. In the superheating degree setting control, the controller 100 controls a second expansion mechanism 13 on the basis of the target value of the superheating degree.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a refrigeration device, an environment creating device, and a refrigeration method. [Background technology]

[0002] Conventionally, as disclosed in Patent Document 1, a refrigeration system including a refrigeration circuit provided with a supercooler has been known. In this type of refrigeration system, a main refrigeration circuit including a compressor, a condenser, an expansion valve, and an evaporator has a supercooler provided between the condenser and the expansion valve. The supercooler is connected to a supercooling refrigeration circuit including a compressor, a condenser, and an expansion valve. In the supercooler, the refrigerant in the main refrigeration circuit is supercooled by the refrigerant in the supercooling refrigeration circuit, so that the refrigeration capacity in the main refrigeration circuit can be increased. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 54-31657 Summary of the Invention [Problem to be solved by the invention]

[0004] When the subcooler is configured to exchange heat between the refrigerant in the subcooling refrigeration circuit and the refrigerant in the main refrigeration circuit, the same refrigeration capacity can be achieved with a compressor having a smaller compressor capacity than the compressor in the single refrigeration circuit, compared to a case in which the same refrigeration capacity is achieved with only one refrigeration circuit. For this reason, energy savings are achieved by providing a subcooler, but further energy savings are required.

[0005] Therefore, the present invention has been made in consideration of the above-mentioned conventional technology, and its object is not only to achieve energy savings by using a supercooling heat exchanger, but also to achieve further energy savings. [Means for solving the problem]

[0006] In order to achieve the above object, the refrigeration device according to the present invention includes a main refrigeration circuit in which a first refrigerant is sealed and which is provided with a first compressor, a first condenser, a supercooling heat exchanger, a first expansion mechanism, and a first evaporator, a supercooling refrigeration circuit in which a second refrigerant is sealed and which is provided with a second compressor, a second condenser, and a second expansion mechanism and which is connected to the supercooling heat exchanger, and a controller capable of executing a superheat setting control and a superheat control. The supercooling heat exchanger is configured to supercool the first refrigerant of the main refrigeration circuit by evaporating the second refrigerant of the supercooling refrigeration circuit. In the superheat setting control, the controller sets a target value of the superheat degree of the second refrigerant at the outlet side of the supercooling heat exchanger to a first value when the refrigeration requirement is a first requirement value, and sets the target value of the superheat degree to a second value greater than the first value when the refrigeration requirement is a second requirement value lower than the first requirement value. In the degree of superheat control, the controller controls the second expansion mechanism based on the target value of the degree of superheat.

[0007] In the refrigeration device according to the present invention, the second refrigerant in the subcooling refrigeration circuit evaporates in the subcooling heat exchanger to subcool the first refrigerant in the main refrigeration circuit, and the refrigeration capacity exerted by the main refrigeration circuit increases accordingly. Therefore, compared to the case where the same refrigeration capacity is exerted by only one refrigeration circuit, the same refrigeration capacity can be exerted by a compressor having a smaller compressor capacity than the compressor of the one refrigeration circuit. Furthermore, when the value of the refrigeration requirement is the second requirement value (when the value of the refrigeration requirement is lower than the first requirement value), the target value of the superheat degree of the second refrigerant at the outlet side of the subcooling heat exchanger is set to a second value (a value larger than the first value). Then, the second expansion mechanism is controlled based on the target value of the superheat degree of the second refrigerant at the outlet side of the subcooling heat exchanger. As a result, 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 degree when the refrigeration requirement is the first requirement value. As a result, the power required by the second compressor of the supercooling refrigeration circuit is reduced compared to when the target value of the superheat degree is controlled to be constant, thereby achieving further energy savings in the supercooling refrigeration circuit when the required level of refrigeration is relatively small.

[0008] The controller may be configured, in the superheat degree setting control, to set the target value of the superheat degree to a minimum value when the required degree of refrigeration is at a maximum required value.

[0009] In this embodiment, when the required degree of refrigeration is at the maximum required value, the target value of the degree of superheat is at the minimum value, and therefore the flow rate of the second refrigerant circulating through the subcooling refrigeration circuit is maximized by controlling the second expansion mechanism based on the target value of the degree of superheat. As a result, the degree of subcooling of the first refrigerant at the outlet side of the subcooling heat exchanger in the main refrigeration circuit is also increased. As a result, a greater refrigeration capacity can be achieved.

[0010] The controller may be configured, in the superheat setting control, to set the target value of the superheat to the first value when the degree of refrigeration required is equal to or greater than a predetermined threshold, and to gradually increase the target value of the superheat from the first value as the degree of refrigeration required decreases when the degree of refrigeration required is less than the threshold.

[0011] In this aspect, when the degree of refrigeration demand is equal to or higher than the threshold value, a predetermined refrigeration capacity is exerted, while during stable times when the degree of refrigeration demand is below the threshold value, further energy savings can be achieved in the supercooling refrigeration circuit as the degree of refrigeration demand decreases.

[0012] The controller may be configured to gradually increase the target value of the superheat degree from the first value as the required degree of refrigeration decreases in the superheat degree setting control. In this case, the controller may be configured to stop the second compressor after gradually increasing the target value of the superheat degree from the first value.

[0013] In this embodiment, since the second compressor is stopped when the required degree of refrigeration decreases, further energy saving can be achieved in the supercooling refrigeration circuit.

[0014] The degree of superheat may be obtained from a temperature difference of the second refrigerant before and after the subcooling heat exchanger in the subcooling refrigeration circuit.

[0015] A bypass flow passage may be connected to the supercooling refrigeration circuit so as to bypass the supercooling heat exchanger. In this case, a bypass expansion mechanism and a bypass evaporator may be provided in the bypass flow passage. Furthermore, the capacity of the second compressor may be smaller than the capacity of the first compressor. The controller may be configured to control the first expansion mechanism so that a first refrigerant does not flow through the first evaporator and to control the bypass expansion mechanism so that a second refrigerant flows through the bypass evaporator when the refrigeration requirement level is a third requirement value lower than the second requirement value.

[0016] In this embodiment, when the refrigeration requirement is a third requirement value lower than the second requirement value, the flow rate of the second refrigerant circulating through the subcooling refrigeration circuit is reduced compared to the flow rate based on the target value of the degree of superheat when the refrigeration requirement is the second requirement value. In this case, the first expansion mechanism is controlled so that the first refrigerant does not flow through the first evaporator in the main refrigeration circuit, and the bypass expansion mechanism is controlled so that the second refrigerant flows through the bypass flow path of the subcooling refrigeration circuit. As a result, 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 is saved.

[0017] The environment creating device according to the present invention includes an environment chamber and the refrigeration device for cooling the inside of the environment chamber.

[0018] In the environment creating device according to the present invention, when the refrigeration demand is low, the target value of the superheat degree in the refrigeration device is increased, so the flow rate of the second refrigerant in the supercooling refrigeration circuit is reduced. This reduces the power of the second compressor in the supercooling refrigeration circuit compared to when the target value of the superheat degree is controlled to be constant. Moreover, the refrigeration capacity in the main refrigeration circuit is also reduced compared to when the target value of the superheat degree is controlled to be constant. This allows energy savings.

[0019] The environment forming device may include a heater that operates when the temperature of the air in the environment chamber is lower than a predetermined temperature. In the environment forming device, when the target value of the degree of superheat is increased when the refrigeration requirement is low, the flow rate of the second refrigerant in the subcooling refrigeration circuit decreases, and the refrigeration capacity in the main refrigeration circuit also becomes smaller than when the target value of the degree of superheat is controlled to be constant. This prevents the temperature of the air in the environment chamber from dropping too much, and the output of the heater can be reduced. This allows further energy savings.

[0020] The refrigeration method of the present invention is a refrigeration method using a refrigeration device including a main refrigeration circuit in which a first refrigerant is sealed and which 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 in which a second refrigerant is sealed and which is provided with a second compressor, a second condenser, and a second expansion mechanism and which is connected to the subcooling heat exchanger, the refrigeration method comprising the steps of: receiving a degree of refrigeration request; setting a target value of a degree of superheat of the second refrigerant at an outlet side of the subcooling heat exchanger to a first value when the received degree of refrigeration request is a first request value; setting a target value of the degree of superheat to a second value larger than the first value when the received degree of refrigeration request is a second request value smaller than the first request value; controlling the second expansion mechanism based on the set target value of the degree of superheat; and subcooling the first refrigerant in the main refrigeration circuit by evaporation of the second refrigerant in the subcooling heat exchanger into which the second refrigerant has flowed at a flow rate adjusted by the second expansion mechanism. Effect of the Invention

[0021] As described above, according to the present invention, not only can energy be saved by using a supercooling heat exchanger, but further energy savings can also be achieved. [Brief description of the drawings]

[0022] [Figure 1] 1 is a diagram illustrating a schematic configuration of a refrigeration device according to a first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a control device including a controller of the refrigeration apparatus. [Diagram 3] FIG. 4 is a diagram for explaining the relationship between a required degree of refrigeration and a target degree of superheat. [Figure 4] FIG. 4 is a diagram for explaining the relationship between a required degree of refrigeration and a target degree of superheat. [Diagram 5] FIG. 4 is a diagram for explaining the relationship between a required degree of refrigeration and a target degree of superheat. [Figure 6] FIG. 4 is a diagram for explaining the operation of the refrigeration device. [Figure 7] FIG. 6 is a diagram illustrating a schematic configuration of a refrigeration device according to a second embodiment. [Figure 8] FIG. 10 is a diagram illustrating a schematic configuration of a refrigeration device according to a modified example of the second embodiment. [Figure 9] FIG. 11 is a diagram illustrating a schematic configuration of a refrigeration device according to a third embodiment. [Figure 10] FIG. 13 is a diagram illustrating an environment forming device according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0024] (First embodiment) As shown in Fig. 1, the refrigeration device 10 according to 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 may be, for example, R-449A, R-404A, R448A, or the like. The second refrigerant may be the same type of refrigerant as the first refrigerant, or may be a different type of refrigerant from the first refrigerant. The second refrigerant may be, for example, R-449A, R-404A, R448A, R-134a, R-513A, or the like.

[0025] The main refrigeration circuit 15 is provided with a first compressor 1, a first condenser 2, a supercooling heat exchanger 14, a first expansion mechanism 3, and a first evaporator 4 in this order. When the first compressor 1 is operated, the refrigerant circulates in the main refrigeration circuit 15, thereby performing a vapor compression refrigeration cycle. The refrigeration device 10 may be used to cool the air inside a freezer or a refrigerator, or may be used to generate cooling water in a chiller. Alternatively, the refrigeration device 10 may be used in an environment forming device such as an environmental testing device for providing a temperature environment at a predetermined temperature. In this embodiment, the refrigeration device 10 is used in a freezer.

[0026] The first compressor 1 is responsible for the compression process of the refrigeration cycle, and is configured to suck in and compress the first refrigerant. The first compressor 1 is equipped with a compression mechanism, such as a scroll type or a screw type, and is configured to drive the compression mechanism by a motor with a constant rotation speed. The first compressor 1 may be configured so that the rotation speed of the motor can be adjusted by an inverter. The first compressor 1 may also be configured so that two or more compressors with different capacities are connected in parallel.

[0027] The first condenser 2 is responsible for the condensation process of the refrigeration cycle, and is configured to exchange heat between the first refrigerant discharged from the first compressor 1 and a cooling medium such as air, water, or a refrigerant, thereby condensing the first refrigerant.

[0028] 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. When the supercooling heat exchanger 14 is functioning, the first refrigerant flowing into the first expansion mechanism 3 is in a state in which the degree of supercooling is increased in the supercooling heat exchanger 14.

[0029] The first expansion mechanism 3 is configured by, for example, an electronic expansion valve. Therefore, by adjusting the valve opening degree of the first expansion mechanism 3, the flow rate of the first refrigerant flowing through the subcooling heat exchanger 14 and the first evaporator 4 in the main refrigeration circuit 15 can be changed arbitrarily.

[0030] The first evaporator 4 is responsible for the evaporation step of the refrigeration cycle, and is configured to evaporate the first refrigerant by exchanging heat with air and the first refrigerant in a low-pressure liquid state in the first expansion mechanism 3. The first evaporator 4 cools the air supplied to the inside of the freezer. When the refrigeration device 10 is provided in a chiller that generates cooling water, the first evaporator 4 is configured to evaporate the first refrigerant to cool the cooling water.

[0031] The supercooling refrigeration circuit 16 is provided with a second compressor 11, a second condenser 12, a second expansion mechanism 13, and a supercooling heat exchanger 14 in this order. When the second compressor 11 is operated, the second refrigerant circulates through the supercooling refrigeration circuit 16, thereby performing a vapor compression refrigeration cycle.

[0032] The second compressor 11 is responsible for the compression process of the refrigeration cycle, and is configured to suck in and compress the second refrigerant. The second compressor 11 is equipped with a compression mechanism, such as a scroll type or a screw type, and is configured to drive the compression mechanism by a motor with a constant rotation speed. The second compressor 11 may be configured so that the rotation speed of the motor can be adjusted by an inverter. The second compressor 11 may also be configured so that two or more compressors with different capacities are connected in parallel.

[0033] The capacity of the second compressor 11 is smaller than the capacity of the first compressor 1. However, the relationship in capacity between the first compressor 1 and the second compressor 11 is not limited to this.

[0034] The second condenser 12 is responsible for the condensation process of the refrigeration cycle, and is configured to exchange heat between the second refrigerant discharged from the second compressor 11 and a cooling medium such as air, water, or a refrigerant, thereby condensing the second refrigerant.

[0035] The second expansion mechanism 13 is responsible for the expansion step of the refrigeration cycle, and is configured to expand the liquid second refrigerant condensed in the second condenser 12. The second expansion mechanism 13 is configured, for example, by an electronic expansion valve. Therefore, by adjusting the valve opening degree of the second expansion mechanism 13, the flow rate of the second refrigerant flowing through the supercooling heat exchanger 14 in the supercooling refrigeration circuit 16 can be changed arbitrarily.

[0036] The supercooling heat exchanger 14 is configured to perform heat exchange between the first refrigerant flowing through the main refrigeration circuit 15 and the second refrigerant flowing through the supercooling refrigeration circuit 16. The second refrigerant, whose pressure has been reduced and whose flow rate has been adjusted by the second expansion mechanism 13, flows into the supercooling heat exchanger 14, and the first liquid refrigerant that has flowed out from the first condenser 2 flows into the supercooling heat exchanger 14. Then, in the supercooling heat exchanger 14, the second refrigerant evaporates, thereby supercooling the first liquid refrigerant.

[0037] The supercooling refrigeration circuit 16 is provided with an inflow side temperature detector 21 for detecting the temperature of the second refrigerant flowing into the supercooling heat exchanger 14, and an outflow side temperature detector 22 for detecting the temperature of the second refrigerant flowing out from the supercooling heat exchanger 14. The temperature detectors 21, 22 each output a signal indicating the detected temperature.

[0038] The signals output from the temperature detectors 21, 22 are input to the controller 100. The controller 100 is composed of a microcomputer including a CPU for executing arithmetic processing, a ROM for storing processing programs and data, and a RAM for temporarily storing data. By executing the processing programs stored in the controller 100, the controller 100 can function as a reception unit 101, a superheat degree derivation unit 102, a superheat degree setting unit 103, a superheat degree control unit 104, a compressor control unit 105, and a refrigeration capacity control unit 106, as shown in Fig. 2.

[0039] The reception unit 101 is configured to repeatedly receive the degree of freezing requirement at predetermined time intervals and temporarily store the received degree of freezing requirement. The degree of freezing requirement is generated by a generator 120, and the degree of freezing requirement generated by the generator 120 is input to the reception unit 101. Note that, although the illustrated example shows an example in which the generator 120 is configured separately from the controller 100, the generator 120 of the degree of freezing requirement may be one function of the controller 100.

[0040] Generator 120 repeatedly receives signals from, for example, sensor 121 that detects the inside temperature and input device 122 that inputs the set value of the inside temperature at predetermined time intervals, and calculates the required freezing degree each time. The required freezing degree indicates the refrigeration load inside the freezer as a dimensionless numerical value, and is calculated, for example, from the difference between the detected value of the inside temperature and the set value. For this reason, the greater the difference between the detected inside temperature and the set value of the inside temperature, the greater the required freezing degree. Since the required freezing degree can change from moment to moment, generator 120 outputs the required freezing degree at predetermined time intervals.

[0041] The superheat degree derivation unit 102 is configured to derive the difference value 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 degree of the second refrigerant at the outlet side of the supercooling heat exchanger 14. That is, in the supercooling refrigeration circuit 16, the liquid second refrigerant decompressed by the second expansion mechanism 13 is in a saturated state or a state close to it. Therefore, the temperature difference between the temperature of the gaseous second refrigerant flowing out from the supercooling heat exchanger 14 and the temperature of the liquid second refrigerant flowing into the supercooling heat exchanger 14 corresponds to the superheat degree of the second refrigerant at the outlet side of the supercooling heat exchanger 14.

[0042] The degree of superheat of the second refrigerant at the outlet side of the supercooling heat exchanger 14 can be calculated by other methods. For example, a temperature detector (outlet side temperature detector 22) and a pressure detector may be disposed at the outlet side of the supercooling heat exchanger 14, and the superheat degree derivation unit 102 may calculate the degree of superheat of the second refrigerant using a saturated vapor temperature equivalent to the pressure detected by the pressure detector and a temperature detected by the temperature detector (outlet side temperature detector 22). In this case, the pressure detected by the pressure detector is the suction pressure of the second compressor 11, so that a saturated vapor temperature equivalent to the suction pressure can be obtained. This method of calculating the degree of superheat is not limited to the refrigeration device 10 according to the first embodiment, but can also be applied to the refrigeration devices 10 according to second and third embodiments described later.

[0043] The superheat degree setting unit 103 is configured to set a target superheat degree, which is a target value of the superheat degree of the second refrigerant at the outlet side of the supercooling heat exchanger 14. As shown in FIG. 3, the target superheat degree is set to a value according to the received degree of required refrigeration. Specifically, the target superheat degree is set to a first value when the received degree of required refrigeration is equal to or higher than a preset threshold TV, and is set to gradually increase from the first value as the degree of required refrigeration decreases when the received degree of required refrigeration is less than the threshold TV. That is, the controller 100 can execute a superheat degree setting control in which the value of the target superheat degree is the first value when the received degree of required refrigeration is a first required value, and the target superheat degree is set to a second value higher than the first value when the received degree of required refrigeration is a second required value that is a degree of required refrigeration lower than the first required value.

[0044] FIG. 3 shows an example in which the target superheat degree changes depending on whether the refrigeration requirement is equal to or greater than the threshold TV or less than the threshold TV, but the present invention is not limited to this. For example, as shown in FIG. 4, the threshold TV may not be provided, and the target superheat degree may be set to gradually increase as the refrigeration requirement decreases. Even in this case, the target superheat degree becomes the minimum value when the refrigeration requirement is the maximum required value, and the target superheat degree can be a value higher than the minimum value when the refrigeration requirement is smaller than the maximum required value. That is, the threshold TV may or may not be set as long as the target superheat degree of the second refrigerant is set to the minimum value by the superheat degree setting unit 103 when the refrigeration requirement is the maximum required value, and the target superheat degree can be set to a value higher than the target superheat degree when the refrigeration requirement is the maximum required value when the refrigeration requirement is smaller than the maximum required value.

[0045] Here, the maximum required value means, for example, when the required degree of refrigeration is calculated by the difference between the detected value of the inside temperature and the set value, the required value when the set value is the lowest possible value and the inside temperature is the highest possible value. In other words, it is the maximum value that can be obtained as the required degree of refrigeration under the assumed conditions.

[0046] As shown in Fig. 5, the target superheat degree may be set such that a threshold TV is set in advance, and the target superheat degree gradually increases as the required degree of refrigeration decreases when the required degree of refrigeration is equal to or greater than the threshold TV, while the target superheat degree may be set constant when the required degree of refrigeration is less than the threshold TV. Even in this case, the target superheat degree becomes the minimum value when the required degree of refrigeration is the maximum required value, and the target superheat degree may be higher than the minimum value when the required degree of refrigeration is less than the maximum required value.

[0047] The superheat degree control unit 104 is configured to control the second expansion mechanism 13 so that the superheat degree of the second refrigerant derived by the superheat degree derivation unit 102 becomes the target superheat degree set by the superheat degree setting unit 103. In other words, the controller 100 is capable of executing superheat degree control for controlling the second expansion mechanism 13 based on the target superheat degree.

[0048] When the opening degree of the second expansion mechanism 13 is reduced, the flow rate of the second refrigerant flowing through the supercooling refrigeration circuit 16 is reduced, so that the second refrigerant is more superheated in the supercooling heat exchanger 14, and the degree of superheat of the second refrigerant at the outlet side of the supercooling heat exchanger 14 is increased. On the other hand, when the opening degree of the second expansion mechanism 13 is increased, the flow rate of the second refrigerant flowing through the supercooling refrigeration circuit 16 is increased. Therefore, the second refrigerant is not so superheated in the supercooling heat exchanger 14, and the degree of superheat of the second refrigerant at the outlet side of the supercooling heat exchanger 14 is reduced. Therefore, the superheat degree control unit 104 controls the second expansion mechanism 13 so that the degree of superheat of the second refrigerant approaches the target degree of superheat.

[0049] The compressor control unit 105 is configured to stop the second compressor 11 after the target degree of superheat is increased to a predetermined maximum value. That is, the controller 100 can execute compressor control to stop the second compressor 11 after the target value of the degree of superheat is gradually increased.

[0050] When the target degree of superheat is increased to the maximum value, the degree of supercooling of the first refrigerant at the outlet side of the supercooling heat exchanger 14 decreases accordingly. Therefore, the refrigeration capacity exerted by the first evaporator 4 also decreases. Therefore, even if the second compressor 11 is stopped in a state where the degree of supercooling is small, it is possible to suppress the occurrence of temperature disturbances in the freezer. Note that the configuration for stopping the second compressor 11 after the target degree of superheat is increased to the maximum value can be omitted.

[0051] The refrigeration 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 in accordance with the degree of required refrigeration received by the receiving unit 101. That is, the controller 100 is capable of executing refrigeration capacity control for controlling the first expansion mechanism 3 based on the degree of required refrigeration.

[0052] Specifically, a target evaporation temperature is assigned to the received degree of required freezing, and the refrigeration capacity control unit 106 controls the first expansion mechanism 3 so as to obtain the target evaporation temperature obtained from the received degree of required freezing. 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 in accordance with the degree of required freezing.

[0053] The control of the first expansion mechanism 3 by the refrigeration capacity control unit 106 is not limited to control so as to obtain a target evaporation temperature. It is sufficient if the flow rate of the first refrigerant flowing into the first evaporator 4 is adjusted in accordance with the received degree of required refrigeration without determining a target evaporation temperature. In this case, for example, the opening degree of the first expansion mechanism 3 may be set in accordance with the degree of required refrigeration.

[0054] Here, a refrigeration method using the refrigeration device 10 having the above-mentioned configuration will be described with reference to FIG.

[0055] When the target temperature of the inside of the refrigerator is set and the operation of the refrigeration device 10 is started, the controller 100 receives the degree of freezing requirement generated by the generator 120 (step ST11), and also receives the temperature detected by the inlet-side temperature detector 21 and the temperature detected by the outlet-side temperature detector 22 (step ST12). The refrigeration capacity control unit 106 of the controller 100 adjusts the opening degree of the first expansion mechanism 3 based on the received degree of freezing requirement (step ST13). That is, the refrigeration capacity control unit 106 adjusts the opening degree of the first expansion mechanism 3 based on the degree of freezing requirement so that the target evaporation temperature is obtained. As a result, the flow rate of the first refrigerant according to the degree of freezing requirement is obtained in the main refrigeration circuit 15, and the desired refrigeration capacity is exerted.

[0056] On the other hand, in the supercooling refrigeration circuit 16, the superheat degree derivation unit 102 derives the difference value between the temperature detected by the outlet side temperature detector 22 and the temperature detected by the inlet side temperature detector 21 as the superheat degree of the second refrigerant at the outlet side of the supercooling heat exchanger 14 (step ST14). In addition, the superheat degree setting unit 103 sets the target superheat degree, which is a target value of the superheat degree of the second refrigerant at the outlet side of the supercooling heat exchanger 14, to a value according to the required refrigeration degree (step ST15). Specifically, when the received required refrigeration degree is equal to or greater than a preset threshold TV, the superheat degree setting unit 103 sets the target superheat degree to a first value. On the other hand, when the received required refrigeration degree is less than the threshold TV, the superheat degree setting unit 103 sets the target superheat degree so that the target superheat degree gradually increases from the first value as the required refrigeration degree decreases.

[0057] Next, the superheat degree control unit 104 controls the second expansion mechanism 13 so that the superheat degree of the second refrigerant derived by the superheat degree derivation unit 102 becomes the target superheat degree set by the superheat degree setting unit 103 (step ST16). At this time, if the received refrigeration requirement is equal to or higher than the threshold value TV, the target superheat degree is set to the first value, and the second expansion mechanism 13 is controlled so that the superheat degree becomes the first value. At this time, the target superheat degree is set to the first value regardless of the change in the refrigeration requirement, 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 degree is set to a constant value, the control of the second expansion mechanism 13 does not become complicated.

[0058] On the other hand, when the received refrigeration requirement gradually decreases and becomes less than the threshold TV, the target superheat degree is set to a higher value. Therefore, the opening degree of the second expansion mechanism 13 is adjusted to a smaller opening degree than the opening degree when the refrigeration requirement is equal to or greater than the threshold TV. Moreover, in this case, the second expansion mechanism 13 is controlled so that the target superheat degree becomes higher as the refrigeration requirement becomes smaller. Therefore, the opening degree of the second expansion mechanism 13 becomes smaller as the refrigeration requirement becomes smaller. As a result, the flow rate of the second refrigerant flowing through the supercooling heat exchanger 14 is reduced, so that the degree of supercooling of the first refrigerant at the outlet side of the supercooling heat exchanger 14 becomes smaller. Therefore, compared to when the superheat degree target value is maintained at a constant value, the degree of supercooling of the first refrigerant becomes smaller, and the refrigeration capacity exerted in the first evaporator 4 is reduced. Moreover, the power of the first compressor 1 is also reduced, and the energy consumption in the main refrigeration circuit 15 is reduced.

[0059] Furthermore, after the value of the required degree of refrigeration is reduced and the target degree of superheat is increased to the maximum value, the second compressor 11 is stopped (step ST17). Therefore, the energy consumption in the supercooling refrigeration circuit 16 is further reduced. At this time, since the refrigeration capacity exerted in the supercooling heat exchanger 14 is reduced, even if the second compressor 11 is stopped, the occurrence of temperature disturbance in the freezer is suppressed.

[0060] Note that the control to stop the second compressor 11 (step ST17) can be omitted. Moreover, after the target degree of superheat is increased to the maximum value, or when the target degree of superheat reaches a predetermined percentage of the maximum value (i.e., the percentage at which the second refrigerant hardly flows), the second expansion mechanism 13 may be switched to control according to the required degree of refrigeration. That is, the controller 100 may be capable of executing a degree of supercooling adjustment control to control the second expansion mechanism 13 based on the required degree of refrigeration.

[0061] As described above, in the present embodiment, the second refrigerant in the supercooling refrigeration circuit 16 evaporates in the supercooling heat exchanger 14 to supercool the first refrigerant in the main refrigeration circuit 15, and the refrigeration capacity exerted by the main refrigeration circuit 15 is increased accordingly. Therefore, compared to the case where the same refrigeration capacity is exerted by only one refrigeration circuit, the same refrigeration capacity can be exerted by a compressor having a smaller compressor capacity than the compressor of the one refrigeration circuit. Furthermore, when the value of the refrigeration requirement is the second requirement value (when the value of the refrigeration requirement is smaller than the first requirement value), the target value of the superheat degree of the second refrigerant at the outlet side of the supercooling heat exchanger 14 is set to a second value (a value larger than the first value). Then, the second expansion mechanism 13 is controlled based on the target value of the superheat degree of the second refrigerant at the outlet side of the supercooling heat exchanger 14. As a result, the flow rate of the second refrigerant circulating in the supercooling refrigeration circuit 16 is reduced compared to the flow rate based on the target value of the superheat degree when the refrigeration requirement is the first requirement value. As a result, the power of the second compressor 11 of the subcooling refrigeration circuit 16 is reduced compared to when the target superheat degree is controlled at a constant level, thereby achieving further energy savings in the subcooling refrigeration circuit 16 when the required degree of refrigeration is relatively small.

[0062] Furthermore, in this embodiment, the target degree of superheat is set to the minimum value when the required degree of refrigeration is at the maximum required value, and therefore the second expansion mechanism 13 is controlled to achieve the target degree of superheat, thereby maximizing the flow rate of the second refrigerant circulating through the subcooling refrigeration circuit 16. As a result, the degree of subcooling of the first refrigerant at the outlet side of the subcooling heat exchanger 14 in the main refrigeration circuit 15 also becomes large. As a result, a greater refrigeration capacity can be achieved.

[0063] In this embodiment, when the degree of required refrigeration is equal to or higher than a preset threshold TV, the target degree of superheat is set to a first value, and when the degree of required refrigeration is less than the threshold TV, the value of the target degree of superheat is gradually increased from the first value as the degree of required refrigeration decreases. Therefore, when the degree of required refrigeration is equal to or higher than the threshold TV, a predetermined refrigeration capacity is exerted, while further energy saving of the supercooling refrigeration circuit 16 can be achieved during stable operation when the degree of required refrigeration is less than the threshold TV.

[0064] Second embodiment 7, in the second embodiment, a bypass flow path 18 is provided in a supercooling refrigeration circuit 16. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0065] The bypass flow passage 18 is a flow passage for returning the second refrigerant flowing out from the second condenser 12 to the second compressor 11 without flowing through the supercooling heat exchanger 14. One end of the bypass flow passage 18 is connected to a portion between the second condenser 12 and the second expansion mechanism 13 in the supercooling refrigeration circuit 16, and the other end is connected to a portion between the supercooling heat exchanger 14 and the second compressor 11 in the supercooling refrigeration circuit 16.

[0066] The bypass flow passage 18 is provided with a bypass expansion mechanism 17 and a bypass evaporator 5. The bypass evaporator 5 is disposed downstream of the bypass expansion mechanism 17 in the bypass flow passage 18, and exchanges heat between the second refrigerant decompressed by the bypass expansion mechanism 17 and the air supplied to the inside of the freezer. When the refrigeration device 10 is provided in a chiller that generates cooling water, the bypass evaporator 5 is configured to evaporate the second refrigerant to cool the cooling water.

[0067] The bypass expansion mechanism 17 is configured, for example, by an electronic expansion valve, and its opening degree is controlled by the controller 100. That is, the refrigeration capacity control unit 106 is configured to control the first expansion mechanism 3 and the bypass expansion mechanism 17 in accordance with the degree of refrigeration demand.

[0068] The controller 100 can execute, for example, rapid cooling control in which both the first evaporator 4 and the bypass evaporator 5 are operated while the supercooling heat exchanger 14 is not operated, supercooling control in which only the first evaporator 4 is operated while the supercooling heat exchanger 14 is operated, medium cooling control in which only the first evaporator 4 is operated while the supercooling heat exchanger 14 is not operated, and weak cooling control in which only the bypass evaporator 5 is operated. It is possible to omit any of the rapid cooling control, medium cooling control, and weak cooling control. Other controls are also possible.

[0069] In the rapid cooling control, the first expansion mechanism 3 and the bypass expansion mechanism 17 are controlled to an opening degree according to the degree of freezing demand, and the air supplied to the inside of 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 degree of freezing demand received by the reception unit 101. In this rapid cooling control, the second expansion mechanism 13 is closed to allow the bypass evaporator 5 to function. The rapid cooling control is executed when the degree of freezing demand is large and the inside temperature is relatively high. In the rapid cooling control, the compressor power becomes large, but a large refrigeration capacity can be exhibited.

[0070] In the supercooling control, the first expansion mechanism 3 and the second expansion mechanism 13 are controlled to an opening degree according to the refrigeration requirement, while the bypass expansion mechanism 17 is closed. That is, in the supercooling control, the bypass evaporator 5 is not used, and the operation is performed using the supercooling heat exchanger 14 in the main refrigeration circuit 15. In this case, in the supercooling control, the same control as that described in the first embodiment is executed. In addition, in the supercooling control, the bypass expansion mechanism 17 may be controlled to open as the opening degree of the first expansion mechanism 3 decreases. In this case, as the refrigeration requirement decreases, the opening degree of the first expansion mechanism 3 decreases and the opening degree of the bypass control mechanism 17 increases, so that it is possible to suppress control disturbance when switching or transitioning from the supercooling control to the weak cooling control.

[0071] 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 degree of required refrigeration received by the reception unit 101. The superheat degree control unit 104 also controls the second expansion mechanism 13 so that the degree of superheat of the second refrigerant derived by the degree of superheat derivation unit 102 becomes the target degree of superheat set by the degree of superheat setting unit 103. At this time, the superheat degree setting unit 103 sets the value of the target degree of superheat to a first value when the received degree of required refrigeration is a first required value, while setting the target degree of superheat to a second value higher than the first value when the received degree of required refrigeration is a second required value that is a degree of required refrigeration lower than the first required value. Therefore, in the supercooling control, the second expansion mechanism 13 is controlled while the target degree of superheat shown in FIG. 3 (or FIG. 4 or FIG. 5) is set.

[0072] The intermediate cooling control is executed when the freezing requirement is smaller than the freezing requirement that is the target of the supercooling control. In the intermediate cooling control, the first expansion mechanism 3 is controlled to an opening degree according to the freezing requirement, while 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 inside of the freezer is cooled only by the first evaporator 4, but 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.

[0073] In the intermediate cooling control, the first expansion mechanism 3 is controlled according to the refrigeration requirement. Therefore, when the refrigeration requirement gradually decreases in the intermediate cooling control, the opening degree of the first expansion mechanism 3 is accordingly reduced. Then, when the first expansion mechanism 3 is throttled to the minimum opening degree (or a preset predetermined opening degree), the first compressor 1 may be stopped. However, since stopping the first compressor 1 may induce control disturbance, the first bypass flow path 31 and the second bypass flow path 32 shown in FIG. 8 may be provided in the main refrigeration circuit 15 to keep the first compressor 1 operating. In this case, the operation of the first compressor 1 can be continued even when the first expansion mechanism 3 is extremely throttled.

[0074] The first bypass flow path 31 is a flow path for allowing the refrigerant (liquid refrigerant) flowing out from 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) discharged from the first compressor 1 to flow into the first compressor 1 without passing through the first condenser 2. By providing the first bypass flow path 31 and the second bypass flow path 32, the suction pressure of the first compressor 1 does not drop too much, and the liquid refrigerant is not sucked into the first compressor 1, and the refrigerant flow rate flowing into the first evaporator 4 can be adjusted until the aperture of the first expansion mechanism 3 is closed. The first bypass flow path 31 is provided with a flow rate regulator 33 such as a temperature-type expansion valve or an electronic expansion valve, and the second bypass flow path 32 is provided with a bypass valve 34 such as a suction pressure regulator valve or an electronic expansion valve.

[0075] The weak cooling control is executed when the required freezing level is lower than the required freezing level targeted by the medium cooling control. That is, the supercooling control is executed when the received required freezing level is the first required value and the second required value, but the weak cooling control is executed when the received required freezing level is the third required value, which is an even lower value.

[0076] In the 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 degree according to the refrigeration demand level. Therefore, the air supplied to the inside of the freezer is not cooled by the first evaporator 4, but only by the bypass evaporator 5. In this case, the first compressor 1 is stopped. However, since stopping the first compressor 1 may induce control disturbance, the operation of the first compressor 1 may be continued by providing a first bypass flow path 31 and a second bypass flow path 32 shown in FIG. 8. This makes it possible to continue the operation of the first compressor 1 even when the first expansion mechanism 3 is closed.

[0077] Therefore, in this embodiment, when the refrigeration requirement is the third requirement value lower than the second requirement value, the flow rate of the second refrigerant circulating through the subcooling refrigeration circuit 16 is reduced compared to the flow rate based on the target superheat degree when the refrigeration requirement is the second requirement value. In this case, the bypass expansion mechanism 17 is controlled so that the second refrigerant flows through the bypass passage 18, and the first expansion mechanism 3 is controlled in the main refrigeration circuit 15 so that the first refrigerant does not flow through the first evaporator 4. As a result, 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 compressor is saved. Furthermore, when the first compressor 1 is stopped, the energy is further saved.

[0078] It should be noted that the description of the other configurations, operations, and effects will not be repeated, but the description of the first embodiment can be applied to the second embodiment.

[0079] Third embodiment 9, in the third embodiment, a low-temperature refrigeration circuit 19 is connected to the main refrigeration circuit 15 to configure a so-called cascade refrigeration circuit. Note that the same components as those in the first and second embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0080] The main refrigeration circuit 15 is provided with a cascade bypass flow path 35. 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.

[0081] The cascade bypass passage 35 is provided with a cascade expansion mechanism 8 and a cascade heat exchanger 52. The cascade heat exchanger 52 is disposed downstream of the cascade expansion mechanism 8 in the cascade bypass passage 35, and the first refrigerant decompressed by the cascade expansion mechanism 8 flows into the cascade heat exchanger 52.

[0082] The cascade expansion mechanism 8 is, for example, an electronic expansion valve, and is controlled by the controller 100. The cascade expansion mechanism 8 is not limited to being configured by an electronic expansion valve. For example, the cascade expansion mechanism 8 may be configured by a thermostatic expansion valve. In this case, the cascade expansion mechanism 8 is not controlled by the controller 100, but is configured to be adjusted to an opening degree according to the temperature of the first refrigerant flowing through the cascade bypass flow path 35. In this case, the temperature detectors 28 and 29 described below are omitted.

[0083] The cascade bypass passage 35 is provided with temperature detectors 28 and 29 located upstream and downstream of the cascade heat exchanger 52 .

[0084] 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, R508A, or R-23.

[0085] 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.

[0086] The low-temperature compressor 51 is equipped with a compression mechanism, such as a scroll type or a screw type, and is configured to drive the compression mechanism by a motor with a constant rotation speed. The low-temperature compressor 51 may be configured so that the rotation speed of the motor can be adjusted by an inverter. The low-temperature compressor 51 may also be configured by connecting two or more compressors with different capacities in parallel.

[0087] The low-temperature precooler 56 is configured to exchange heat between the third refrigerant discharged from the low-temperature compressor 51 and a cooling medium such as air, water, or a refrigerant, thereby precooling the third refrigerant.

[0088] The cascade heat exchanger 52 causes heat exchange between the first refrigerant, which has been cooled in the cascade expansion mechanism 8, and the third refrigerant, which has been pre-cooled in the low-temperature pre-cooler 56. As a result, the third refrigerant becomes subcooled.

[0089] The low-temperature expansion mechanism 53 is configured to expand the third refrigerant condensed in the cascade heat exchanger 52.

[0090] The low-temperature expansion mechanism 53 is configured, for example, by 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 changed arbitrarily. 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 in accordance with the degree of refrigeration demand.

[0091] The low-temperature evaporator 6 is configured to evaporate the third refrigerant by exchanging heat with the air supplied to the inside of the freezer, the third refrigerant being in a low-pressure liquid state in the low-temperature expansion mechanism 53. When the refrigeration device 10 is provided in a chiller that generates cooling water, the low-temperature evaporator 6 is configured to evaporate the third refrigerant to cool the antifreeze liquid.

[0092] The functions of the controller 100 include a second superheat degree derivation unit 107 that calculates the degree of superheat of the first refrigerant flowing out from the cascade heat exchanger 52 from the difference between the temperatures detected by the temperature detectors 28 and 29.

[0093] The functions of the controller 100 also include a cascade control unit 108 that controls the cascade expansion mechanism 8 based on the superheat degree of the first refrigerant obtained by the second superheat degree derivation unit 107. That is, the cascade control unit 108 controls the cascade expansion mechanism 8 so that the superheat degree of the first refrigerant at the outlet side of the cascade heat exchanger 52 becomes a target superheat degree. This target superheat degree of the first refrigerant is set to a constant value. As a result, 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 so that the flow rate of the first refrigerant in the cascade bypass flow path 35 becomes large.

[0094] The controller 100 judges whether to perform a two-stage refrigeration operation or a single-stage refrigeration operation according to the set temperature and the operating conditions. In the single-stage refrigeration operation, the operation is the same as in the second embodiment, and therefore the description is omitted here. In the two-stage refrigeration operation, the first expansion mechanism 3 and the bypass expansion mechanism 17 are closed, so that 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 supercooling heat exchanger 14 functions, so that the supercooling refrigeration circuit 16 becomes a supercooling 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 degree of the second expansion mechanism 13 and the low-temperature expansion mechanism 53 decreases as the refrigeration requirement decreases. Therefore, in the low-temperature refrigeration circuit 19 and the supercooling refrigeration circuit 16, a refrigerant circulation amount according to the refrigeration requirement is obtained. After the opening degree of the second expansion mechanism 13 is reduced to the minimum opening degree, or when the second expansion mechanism 13 is closed, the second compressor 11 may be stopped.

[0095] It should be noted that the description of the other configurations, operations, and effects will not be repeated, but the description of the first embodiment can be applied to the second embodiment.

[0096] (Fourth embodiment) 10 shows the fourth embodiment. Note that the same components as those in the first to third embodiments are given 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 adjusts the inside of the environment chamber 61 to a predetermined temperature environment. The environment forming device 60 further includes an air conditioning chamber 62 for generating air whose temperature has been adjusted, and the first evaporator 4 of the refrigeration device 10 is disposed in the air conditioning chamber 62. In the case of the refrigeration device 10 described in the second embodiment, the bypass evaporator 5 is also disposed 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 disposed in the air conditioning chamber 62.

[0098] In the air-conditioning chamber 62, a heater 64 for heating air and a blower 65 for blowing the temperature-adjusted air into the environmental chamber 61 are disposed downstream of the first evaporator 4. In the environmental chamber 61, a sensor 121 for detecting the temperature of the object to be cooled (the room temperature of the environmental chamber 61) is disposed. The input device 122 is used to input the set temperature inside the environmental chamber 61. The environment forming device 60 can set a wide range of temperatures, such as a negative temperature range, a normal temperature range, or a high temperature range, and may have a program operation function for changing a plurality of temperatures in a stepwise or continuous manner.

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

[0100] The generator 120 calculates the required degree of refrigeration using the temperature detected by the sensor 121 and the set temperature from the input unit 122 .

[0101] The heater 64 is output-controlled based on the temperature detected by the sensor 121 and the set temperature from the input device 122. That is, a predetermined refrigeration capacity is achieved by controlling the first expansion mechanism 3 and the second expansion mechanism 13 of the refrigeration device 10, but since the temperature detected by the sensor 121 may fall below the set temperature, the heater 64 finely adjusts the room temperature of the environmental chamber 61. Therefore, if excessive cooling by the refrigeration device 10 can be suppressed, not only can the power of the refrigeration device 10 be suppressed, but also the power of the heater 64 can be suppressed. In this regard, when the refrigeration requirement is low, the second expansion mechanism 13 can further reduce the amount of refrigerant circulated, thereby reducing the refrigeration capacity. Therefore, the power of the heater 64 can also be suppressed, thereby achieving further energy saving. In addition, the target degree of superheat of the second refrigerant at 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 this target degree of superheat, so that it is possible to obtain both the ability to follow the set temperature and energy saving after the temperature is reached, which is particularly preferable when a programmed operation is performed. Note that the heater 54 can be omitted.

[0102] It should be noted that the explanations of the other configurations, operations and effects will be omitted, but the explanations of the first to third embodiments can be applied to the fourth embodiment.

[0103] (Other embodiments) It should be noted that the embodiments disclosed herein are illustrative in all respects and should not be considered restrictive. The present invention is not limited to the above-described embodiments, and various modifications and improvements are possible without departing from the spirit of the present invention. For example, in the above-described embodiments, the controller 100 controls the first expansion mechanism 3 based on the required degree of refrigeration, but instead, the controller 100 may control the first expansion mechanism 3 based on the degree of subcooling at the outlet of the subcooling heat exchanger 14.

[0104] Although not shown, the same functions as the first bypass flow path 31 and the second bypass flow path 32 of the main refrigeration circuit 15 may be provided in the subcooling refrigeration circuit 16 of Figs. 1, 7, 8 and 9. In this case, further energy saving is possible. 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. Also, a bypass flow path may be provided for allowing the refrigerant (gas refrigerant) discharged from the second compressor 11 to flow into the second compressor 11 without passing through the second condenser 12.

[0105] In addition, when the first compressor 1 is configured so that the motor rotation speed can be adjusted by an inverter, the controller 100 may control the motor rotation speed of the first compressor 1 based on the refrigeration requirement level, rather than controlling the first expansion mechanism 3. [Explanation of symbols]

[0106] 1: First compressor 2: First condenser 3: First expansion mechanism 4: First evaporator 5: Bypass evaporator 10: Refrigeration equipment 11: Second compressor 12: Second condenser 13: Second expansion mechanism 14: Heat exchanger for supercooling 15: Main refrigeration circuit 16:Refrigerating circuit for supercooling 17: Bypass expansion mechanism 18: Bypass flow path 60:Environment shaping device 61:Environmental room 64: Heater 100: Controller

Claims

1. a main refrigeration circuit in which a first refrigerant is sealed and which includes a first compressor, a first condenser, a subcooling heat exchanger, a first expansion mechanism, and a first evaporator; a subcooling refrigeration circuit in which a second refrigerant is sealed, which includes a second compressor, a second condenser, and a second expansion mechanism, and which is connected to the subcooling heat exchanger; A controller capable of executing superheat setting control and superheat control; Equipped with the subcooling heat exchanger is configured to subcool the first refrigerant in the main refrigeration circuit by evaporating the second refrigerant in the subcooling refrigeration circuit, the controller, in the superheat degree setting control, sets 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 required degree of refrigeration is a first required value, and sets the target value of the superheat degree to a second value larger than the first value when the required degree of refrigeration is a second required value lower than the first required value; The refrigeration apparatus, wherein the controller controls the second expansion mechanism based on a target value of the degree of superheat in the superheat degree control.

2. The refrigeration apparatus according to claim 1 , wherein the controller is configured to set the target value of the degree of superheat to a minimum value when the required degree of refrigeration is a maximum required value in the superheat degree setting control.

3. 2. The refrigeration device according to claim 1, wherein the controller is configured, in the superheat setting control, to set the target value of the superheat to the first value when the degree of refrigeration requirement is equal to or greater than a preset threshold, and to gradually increase the target value of the superheat from the first value as the degree of refrigeration requirement decreases when the degree of refrigeration requirement is less than the threshold.

4. The controller is configured to gradually increase the target value of the superheat degree from the first value as the refrigeration requirement decreases in the superheat degree setting control, 2. The refrigeration apparatus of claim 1, wherein the controller is configured to gradually increase the target superheat value from the first value and then shut down the second compressor.

5. 2. The refrigeration apparatus according to claim 1, wherein the degree of superheat is obtained from a temperature difference of the second refrigerant before and after the subcooling heat exchanger in the subcooling refrigeration circuit.

6. a bypass flow path is connected to the supercooling refrigeration circuit so as to bypass the supercooling 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, 2. The refrigeration device according to claim 1, wherein the controller is configured to, when the degree of refrigeration requirement is a third requirement value lower than the second requirement value, control the first expansion mechanism so that a first refrigerant does not flow through the first evaporator and control the bypass expansion mechanism so that a second refrigerant flows through the bypass evaporator.

7. An environmental chamber; A refrigeration device according to any one of claims 1 to 6 for cooling the inside of the environmental chamber; An environment forming device comprising:

8. The environment creating device according to claim 7, further comprising a heater that operates when the temperature of the air in the environmental chamber is lower than a predetermined temperature.

9. a main refrigeration circuit in which a first refrigerant is sealed and which includes a first compressor, a first condenser, a subcooling heat exchanger, a first expansion mechanism, and a first evaporator; A refrigeration method using a refrigeration device including a supercooling refrigeration circuit in which a second refrigerant is sealed, a second compressor, a second condenser, and a second expansion mechanism are provided, and the supercooling refrigeration circuit is connected to the supercooling heat exchanger, Receive the freezing requirements, setting a target value of the degree of superheat of the second refrigerant at the outlet side of the subcooling heat exchanger to a first value when the received refrigeration requirement is a first requirement value; When the received refrigeration requirement is a second requirement value smaller than the first requirement value, the target value of the degree of superheat is set to a second value larger than the first requirement value; controlling the second expansion mechanism based on the set target value of the degree of superheat; a subcooling heat exchanger into which a second refrigerant flows at a flow rate adjusted by the second expansion mechanism, and the first refrigerant in the main refrigeration circuit is subcooled by evaporation of the second refrigerant.

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