REFRIGERATION APPARATUS, ENVIRONMENT CREATING APPARATUS AND REFRIGERATION METHOD

Abstract

 A refrigeration apparatus includes: a first injection flow passage branching off from a main circuit to allow a refrigerant to pass through a subcooler and be injected into a region of a compressor that is midway through a compression process; a first injection regulating valve disposed upstream of the subcooler in the first injection flow passage; a first valve control unit configured to control the first injection regulating valve such that a degree of superheat of the refrigerant injected through the first injection flow passage reaches a target degree of superheat; a reception unit configured to receive a refrigeration request degree; and a target superheat degree control unit configured to set the target degree of superheat to a first value when the refrigeration request degree received by the reception unit is a first refrigeration request degree and set the target degree of superheat to a second value higher than the first value when the received refrigeration request degree is a second refrigeration request degree lower than the first refrigeration request degree.

Description

Field of the Invention

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

Background Art

[0002] A refrigeration apparatus that has a flow passage for injecting a gas refrigerant into a medium pressure part of a compressor disposed in a refrigeration circuit has conventionally been known, as disclosed in JP 2010-60179 A. Specifically, the refrigeration apparatus includes a main circuit that has the compressor, a condenser, an economizer heat exchanger, an expansion valve, and an evaporator in this order to circulate a refrigerant and an intermediate injection circuit connected to the main circuit. The refrigerant in liquid form that has been condensed by the condenser flows into the intermediate injection circuit. In the intermediate injection circuit, after being decompressed by a second expansion valve, the liquid refrigerant is vaporized by passing through the economizer heat exchanger disposed in the main circuit. The vaporized refrigerant is injected into the medium pressure part of the compressor. The second expansion valve disposed in the intermediate injection circuit is controlled such that a superheat degree of the refrigerant in gas form discharged from the compressor reaches a predetermined superheat degree. This makes the refrigerant injected into the compressor through the intermediate injection circuit get into a saturation state and thereby prevents the compressor from being damaged.

[0003] In the refrigeration apparatus described in JP 2010-60179 A, the gas refrigerant is injected into the medium pressure part of the compressor. This makes it possible to control discharge pipe temperature. However, there remains room for improvement from an energy saving perspective. In other words, the injection of the gas refrigerant in the compressor causes an increase in motive power of the compressor. Thus, there is room for improvement from an energy saving perspective.

Summary of the Invention

[0004] It is an object of the present invention to enhance energy saving while enabling injection of a refrigerant into a region of a compressor that is midway through a compression process.

[0005] A refrigeration apparatus according to the present invention includes: a main circuit that has a compressor, a condenser, a subcooler, an expansion mechanism, and an evaporator to circulate a refrigerant; a first injection flow passage branching off from the main circuit at a point downstream of the condenser, the first injection flow passage being configured to allow the refrigerant to pass through the subcooler and be injected into a region of the compressor that is midway through a compression process; a first injection regulating valve disposed upstream of the subcooler in the first injection flow passage; a first valve control unit configured to control the first injection regulating valve such that a degree of superheat of the refrigerant injected into the compressor through the first injection flow passage reaches a target degree of superheat; a reception unit configured to receive a refrigeration request degree; and a target superheat degree control unit configured to set the target degree of superheat to a first value when the refrigeration request degree received by the reception unit is a first refrigeration request degree and set the target degree of superheat to a second value higher than the first value when the refrigeration request degree received by the reception unit is a second refrigeration request degree that is a refrigeration request degree lower than the first refrigeration request degree.

[0006] An environment creating apparatus according to the present invention includes: an environmental room and the refrigeration apparatus, the refrigeration apparatus being configured to cool inside the environmental room.

[0007] A refrigeration method according to the present invention is a refrigeration method using a refrigeration apparatus that includes: a main circuit that has a compressor, a condenser, a subcooler, an expansion mechanism, and an evaporator to circulate a refrigerant; a first injection flow passage branching off from the main circuit at a point downstream of the condenser, the first injection flow passage being configured to allow the refrigerant to pass through the subcooler and be injected into a region of the compressor that is midway through a compression process; a first injection regulating valve disposed upstream of the subcooler in the first injection flow passage; and a reception unit. The refrigeration method includes: receiving a refrigeration request degree by the reception unit; setting a target degree of superheat to a first value when the refrigeration request degree received by the reception unit is a first refrigeration request degree and setting the target degree of superheat to a second value higher than the first value when the refrigeration request degree received by the reception unit is a second refrigeration request degree that is a refrigeration request degree lower than the first refrigeration request degree; and controlling the first injection regulating valve such that a degree of superheat of the refrigerant injected into the compressor through the first injection flow passage reaches the target degree of superheat.

Brief Description of the Drawings

[0008] 

Fig. 1 is a schematic view showing a configuration of a refrigeration apparatus according to a first embodiment;

Fig. 2 is a schematic view showing a configuration of a refrigeration apparatus according to a modification of the first embodiment.

Fig. 3 is a schematic block diagram showing control equipment including a controller for the refrigeration apparatus;

Fig. 4 is a graph for illustrating a relationship between a refrigeration request degree and a target superheat degree;

Fig. 5 is a graph for illustrating a relationship between a refrigeration request degree and a target superheat degree;

Fig. 6 is a graph for illustrating a relationship between a refrigeration request degree and a target superheat degree;

Fig. 7 is a diagram for illustrating control flow for a first flow rate regulating valve in the refrigeration apparatus;

Fig. 8 is a schematic view showing a configuration of a refrigeration apparatus according to a second embodiment;

Fig. 9 is a schematic view showing a configuration of a refrigeration apparatus according to a modification of the second embodiment;

Fig. 10 is a schematic block diagram showing control equipment including a controller for the refrigeration apparatus;

Fig. 11 is a diagram for illustrating control flow for a first flow rate regulating valve in the refrigeration apparatus;

Fig. 12 is a diagram for illustrating control flow for a second flow rate regulating valve in the refrigeration apparatus; and

Fig. 13 is a schematic view showing an environment creating apparatus according to a third embodiment.

Description of Embodiments

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

(First embodiment)

[0010] As shown in Fig. 1, a refrigeration apparatus 10 according to a first embodiment includes a main circuit 15 in which a refrigerant is sealed and a first injection flow passage 16 connected to the main circuit 15. The refrigerant may be a refrigerant with a low global warming potential (GWP), such as R-449A or R-448A.

[0011] The main circuit 15 has a compressor 1, a condenser 2, a subcooler 12, an expansion mechanism 3, and an evaporator 4 in this order. The compressor 1 operates to circulate the refrigerant through the main circuit 15, and a refrigeration cycle of a vapor compression type is thereby performed. The refrigeration apparatus 10 may be used to cool air inside a freezer or a refrigerator or may be used to generate cooling water by a chiller. Alternatively, the refrigeration apparatus 10 may be used for an environment creating apparatus such as an environmental testing apparatus to provide a temperature environment at a predetermined temperature. In the present embodiment, the refrigeration apparatus 10 is used for a freezer.

[0012] The compressor 1 is responsible for a compression process in the refrigeration cycle and is configured to suction and compress the refrigerant. The compressor 1 has a compression mechanism of a scroll type or a screw type, for example, and is configured to drive the compression mechanism by a motor with a constant rotation rate. The compressor 1 may be configured such that the rotation rate of the motor is adjustable by an inverter. The compressor 1 may include one compressor unit or may alternatively include two compressor units that are connected in parallel and that have different capacities.

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

[0014] The expansion mechanism 3 is responsible for an expansion process in the refrigeration cycle and is configured to expand the refrigerant in liquid form that has condensed through the condenser 2. If the subcooler 12 is functioning, the refrigerant flowing into the expansion mechanism 3 is in such a state that a degree of subcooling has increased through the subcooler 12.

[0015] The expansion mechanism 3 is constituted by an electronic expansion valve, for example. Thus, an opening degree of the valve may be adjusted to freely change a flow rate of the liquid refrigerant flowing through the subcooler 12 and the evaporator 4 in the main circuit 15.

[0016] The evaporator 4 is responsible for an evaporation process in the refrigeration cycle and is configured to allow the liquid refrigerant to evaporate by causing the liquid refrigerant that decreases in pressure through the expansion mechanism 3 to exchange heat with air. The evaporator 4 cools air supplied into the freezer.

[0017] The first injection flow passage 16 branches off from the main circuit 15 at a point downstream of the condenser 2. In other words, one end of the first injection flow passage 16 is connected to the main circuit 15 through a point between the condenser 2 and the expansion mechanism 3. In Fig. 1, one end of the first injection flow passage 16 is connected to the main circuit 15 through a point between the condenser 2 and the subcooler 12. However, as shown in Fig. 2, the one end may be connected to the main circuit 15 through a point between the subcooler 12 and the expansion mechanism 3.

[0018] Another end of the first injection flow passage 16 is connected to a region of the compressor 1 that is midway through a process of compressing the refrigerant. In other words, the refrigerant is compressed in a compression space (not shown) in the compressor 1. The first injection flow passage 16 is connected so as to be opened to the compression space that is midway through the compression process. Hence, the refrigerant flowing through the first injection flow passage 16 is injected into the compression space, which is midway through the compression process, in the compressor 1.

[0019] A first flow rate regulating valve 11 (or a first injection regulating valve) is disposed on the first injection flow passage 16. The first flow regulating valve 11 is constituted by an electronic expansion valve. Thus, an opening degree of the first flow regulating valve 11 may be adjusted to regulate a flow rate of the refrigerant flowing through the first injection flow passage 16.

[0020] The first injection flow passage 16 passes through the subcooler 12 located downstream of the first flow rate regulating valve 11. Thus, in the subcooler 12, heat is exchanged between the liquid refrigerant flowing in the main circuit 15 and the liquid refrigerant flowing in the first injection flow passage 16. As a result, the liquid refrigerant that has decreased in temperature by being decompressed by the first flow rate regulating valve 11 in the first injection flow passage 16 evaporates by being heated by the liquid refrigerant in the main circuit 15. On the other hand, the liquid refrigerant in the main circuit 15 is cooled and gets into a supercooled state.

[0021] The first injection flow passage 16 has an inlet temperature detector 22 for detecting a temperature of the refrigerant flowing into the subcooler 12 and an outlet temperature detector 23 for detecting the temperature of the refrigerant flowing out from the subcooler 12. The inlet and outlet temperature detectors 22 and 23 output signals indicating the detected temperatures, respectively.

[0022] The main circuit 15 has a discharge pipe temperature detector 21 for detecting a discharge pipe temperature of the compressor 1 (or the temperature of the refrigerant discharged from the compressor 1). The discharge pipe temperature detector 21 outputs a signal indicating the detected temperature.

[0023] The signals output from the detectors 22, 23, and 21 are input into a controller 100. The controller 100 is constituted by, for example, a microcomputer that includes a central processing unit (CPU) to execute arithmetic processing, a read only memory (ROM) to store processing programs and other data, and a random access memory (RAM) to temporarily store data. As shown in Fig. 3, processing programs stored in the controller 100 are executed to enable the controller 100 to function as a reception unit 101, a target superheat degree control unit 102, a superheat degree calculator 103, a first valve control unit 104, and an expansion control unit 105.

[0024] The reception unit 101 is configured to receive a refrigeration request degree each at predetermined time intervals and temporarily store the received refrigeration request degree. A generator 120 generates a refrigeration request degree, and the refrigeration request degree generated by the generator 120 is input into the reception unit 101. The drawing shows an example in which the generator 120 is separate from the controller 100. However, the generator 120 of refrigeration request degree may be a function of the controller 100.

[0025] The generator 120 receives, for example, signals from a sensor 121 that detects an inside temperature of the freezer and an input device 122 used to input a set value for the inside temperature of the freezer each at predetermined time intervals and calculates a refrigeration request degree each at the time intervals. The refrigeration request degree indicates a refrigeration load inside the freezer in terms of dimensionless numbers and is calculated based on, for example, a difference value between a value of the detected inside freezer temperature and the set value for the inside freezer temperature. Hence, the refrigeration request degree increases along with an increase in difference between the detected inside freezer temperature and the set value for the inside freezer temperature. Since the refrigeration request degree can change every moment, the generator 120 outputs a refrigeration request degree each at predetermined time intervals.

[0026] The target superheat degree control unit 102 is configured to set a target degree of superheat that is a target value of a degree of superheat of the refrigerant injected into the compressor 1 through the first injection flow passage 16. When the received refrigeration request degree is a first refrigeration request degree, the target superheat degree control unit 102 sets the target degree of superheat to a first value. When the received refrigeration request degree is a second refrigeration request degree that is a refrigeration request degree lower than the first refrigeration request degree, the target superheat degree control unit 102 sets the target degree of superheat to a second value higher than the first value.

[0027] As shown in Fig. 4, a range of the target degree of superheat may include a region in which the target degree of superheat is set to a value that increases with a decrease in refrigeration request degree as well as a region in which the target degree of superheat is a constant value regardless of the refrigeration request degree. As shown in Fig. 5, the target degree of superheat may be set so as to increase along with a decrease in refrigeration request degree throughout a range from a minimum value to a maximum value of the refrigeration request degree. Furthermore, as shown in Fig. 6, the target degree of superheat may be set so as to increase stepwise along with a decrease in refrigeration request degree. In these cases, the target degree of superheat gradually increases with a decrease in value of the refrigeration request degree. This allows the subcooler 12 to lower the degree of subcooling (closer to a saturation temperature) along with a decrease in value of the refrigeration request degree.

[0028] The superheat degree calculator 103 is configured to derive a degree of superheat of the refrigerant, which is injected into the compressor 1 through the first injection flow passage 16, from a value of difference between the temperature detected by the outlet temperature detector 23 and the temperature detected by the inlet temperature detector 22. In other words, in the first injection flow passage 16, the liquid refrigerant decompressed by the first flow rate regulating valve 11 (or the liquid refrigerant flowing into the subcooler 12) is in a saturation state or a state close to the saturation state. Thus, the difference in temperature between the temperature of the gas refrigerant flowing from the subcooler 12 and the temperature of the liquid refrigerant flowing into the subcooler 12 is equivalent to the degree of superheat of the refrigerant injected into the compressor 1. It is assumed that the refrigerant injected into the compressor 1 through the first injection flow passage 16 is fully gasified. However, in a region of small super heat degrees, such as in a case of a lowest superheat degree, the injected refrigerant may include the refrigerant in liquid form.

[0029] The degree of superheat of the injected refrigerant may be calculated by a method other than the above method. For instance, the degree of superheat may be calculated using values detected by a temperature detector disposed downstream of the subcooler 12 (or the outlet temperature detector 23) and a pressure detector (not shown) in the first injection flow passage 16.

[0030] The first valve control unit 104 is configured to control the first flow rate regulating valve 11 such that the degree of superheat of the gas refrigerant derived by the superheat degree calculator 103 reaches the target degree of superheat. In other words, when the opening degree of the first flow rate regulating valve 11 gets smaller, the flow rate of the refrigerant flowing through the first injection flow passage 16 decreases. As a result, the refrigerant is superheated to an increased degree by the subcooler 12, and the degree of superheat of the injected refrigerant increases. On the other hand, when the opening degree of the first flow rate regulating valve 11 gets larger, the flow rate of the refrigerant flowing through the first injection flow passage 16 increases. As a result, the refrigerant is not superheated much by the subcooler 12, and the degree of superheat of the injected refrigerant decreases. Thus, the opening degree of the first flow rate regulating valve 11 can be adjusted to make the degree of superheat of the gas refrigerant closer to the target degree of superheat.

[0031] The first valve control unit 104 controls the first flow rate regulating valve 11 with reference to the value detected by the discharge pipe temperature detector 21. In other words, in response to a decrease in flow rate of the refrigerant injected into the compressor 1 through the first injection flow passage 16, a cooling effect of the compressor 1 diminishes and thus the temperature of the gas refrigerant discharged from the compressor 1 is likely to increase. This makes it possible to suppress an excessive rise in discharge pipe temperature by controlling the first flow rate regulating valve 11 with reference to the discharge pipe temperature. In other words, by controlling the first flow rate regulating valve 11 while monitoring the discharge pipe temperature, the first valve control unit 104 avoids an excessive rise in discharge pipe temperature caused by a decrease in flow rate of the refrigerant injected into the compressor 1 and concurrently achieves a reduction in motive power of the compressor 1 through a decrease in flow rate of the injected refrigerant.

[0032] The expansion control unit 105 is configured to adjust an opening degree of the expansion mechanism 3 in response to the refrigeration request degree received by the reception unit 101. In other words, the expansion control unit 105 is configured to adjust the flow rate of the refrigerant flowing into the evaporator 4 in response to the refrigeration request degree.

[0033] The refrigeration apparatus 10 may further include an evaporation temperature detector to detect the temperature (or an evaporation temperature) of the refrigerant flowing into the evaporator 4 to allow the expansion control unit 105 to adjust the expansion mechanism 3 in response to the evaporation temperature in addition to the refrigeration request degree.

[0034] A refrigeration method using the refrigeration apparatus 10 configured as described above will now be described.

[0035] When a temperature target for the inside freezer temperature is set and operation of the refrigeration apparatus 10 starts, the controller 100 receives a discharge pipe temperature, that is a value detected by the discharge pipe temperature detector 21, and a refrigeration request degree generated by the generator 120. The controller 100 also receives a value detected by the inlet temperature detector 22 and a value detected by the outlet temperature detector 23. The expansion control unit 105 of the controller 100 adjusts the opening degree of the expansion mechanism 3 based on the received refrigeration request degree. In other words, a target opening degree for the expansion mechanism 3 or a target evaporation temperature is set based on the refrigeration request degree, and the expansion control unit 105 adjusts the opening degree of the expansion mechanism 3 based on either of these target values. This enables the subcooler 12 to receive a flow rate of the refrigerant in response to the refrigeration request degree. If the target evaporation temperature is set, an evaporation temperature is obtained in the evaporator 4 in response to the refrigeration request degree.

[0036] As shown in Fig. 7, the controller 100 determines whether or not the received discharge pipe temperature is lower than a managed reference temperature range (step ST12). The managed reference temperature range is a predetermined temperature range, and the controller 100 controls the discharge pipe temperature such that the discharge pipe temperature falls within the temperature range. If the result determined in step ST12 is NO, the controller 100 transitions to step ST13 and executes control for target discharge pipe temperature. In this control, when the value detected by the discharge pipe temperature detector 21 is within the managed reference temperature range, the opening degree of the first flow rate regulating valve 11 is maintained. On the other hand, if the value detected by the discharge pipe temperature detector 21 exceeds the managed reference temperature range, the controller 100 controls the first flow rate regulating valve 11 such that the opening degree of the first flow rate regulating valve 11 gets larger. As a result of this, the discharge pipe temperature is adjusted to fall within or below the managed reference temperature range.

[0037] If the received discharge pipe temperature is lower than the managed reference temperature range, the controller 100 transitions to step ST14, and the target superheat degree control unit 102 sets a target degree of superheat. In other words, the reception unit 101 receives a refrigeration request degree each at predetermined time intervals, and whenever the refrigeration request degree is received, the target superheat degree control unit 102 derives a target degree of superheat in response to the received refrigeration request degree.

[0038] Meanwhile, the superheat degree calculator 103 calculates a degree of superheat of the refrigerant injected into the compressor 1 through the first injection flow passage 16 using signals from the inlet and the outlet temperature detectors 22 and 23. Then, control for target superheat degree is executed (step ST15). In other words, control for target superheat degree is executed on condition that the discharge pipe temperature of the compressor 1 does not exceed a threshold level.

[0039] In the control for target superheat degree, the first valve control unit 104 controls the first flow rate regulating valve 11 such that the degree of superheat of the refrigerant calculated by the superheat degree calculator 103 approaches the target degree of superheat set in step ST14. When the received refrigeration request degree at this time is the first refrigeration request degree, the target degree of superheat is set to the first value. When the received refrigeration request degree is the second refrigeration request degree lower than the first refrigeration request degree, the target degree of superheat is set to the second value higher than the first value. Hence, when a low cooling load is carried and the value of the refrigeration request degree is low, the target degree of superheat increases. As a result, the opening degree of the first flow rate regulating valve 11 is lowered, and the flow rate of the refrigerant injected into the region of the compressor 1, which is midway through a compression process, decreases. This contributes to a reduction in motive power of the compressor 1.

[0040] While the control for target superheat degree is executed, the controller returns to step ST12 again to monitor the discharge pipe temperature and as necessary controls again the opening degree of the first flow rate regulating valve 11 (step ST13). For instance, in response to a decrease in refrigeration request degree, the target degree of superheat goes up and thus the opening degree of the first flow rate regulating valve 11 gets smaller and the discharge pipe temperature is likely to increase. Nevertheless, control for target discharge pipe temperature (step ST13) can be executed again to adjust and make the discharge pipe temperature fall within the managed reference temperature range. As a result, even if the amount of the injected refrigerant gas is reduced in step ST15, the controller 100 prevents an excessive rise in discharge pipe temperature.

[0041] In the present embodiment, as described above, the first injection flow passage 16 passes through the subcooler 12. This makes it possible to supercool the refrigerant flowing in the main circuit 15 by the refrigerant flowing in the first injection flow passage 16. Moreover, the first injection flow passage 16 is a flow passage designed to inject the refrigerant into the region of the compressor 1, which is midway through a compression process. This allows the refrigerant to circulate through the main circuit 15 without a reduction in flow rate of the refrigerant flowing into the evaporator 4, even in a case in which the refrigerant flows from the main circuit 15 to the first injection flow passage 16. By changing the opening degree of the first flow rate regulating valve 11, the flow rate of the refrigerant flowing through the first injection flow passage 16 can be changed to change the degree of subcooling of the refrigerant passing through the subcooler 12 in the main circuit 15. This makes it possible to adjust refrigeration capacity in response to the changed degree of subcooling.

[0042] Meanwhile, with the first flow rate regulating valve 11 being controlled, the degree of superheat of the refrigerant injected into the compressor 1 through the first injection flow passage 16 also changes. The first valve control unit 104 controls the first flow rate regulating valve 11 such that the degree of superheat of the refrigerant reaches the target degree of superheat. When the refrigeration request degree received by the reception unit 101 is the first refrigeration request degree, the first value is assigned to the target degree of superheat. When the received refrigeration request degree is the second refrigeration request degree, which is a refrigeration request degree lower than the first refrigeration request degree, the second value higher than the first value is assigned to the target degree of superheat. In other words, when the refrigeration request degree is relatively low (the second refrigeration request degree) compared with a case in which the refrigeration request degree is relatively high (the case of the first refrigeration request degree), the target degree of superheat is set such that the target degree of superheat is high. Hence, compared with a case in which the target degree of superheat is maintained at a constant value, the first flow rate regulating valve 11 is controlled so as to have a smaller opening degree when the refrigeration request degree is relatively low. This decreases the flow rate of the refrigerant injected into the region of the compressor 1, which is midway through a compression process, through the first injection flow passage 16. This makes it possible to decrease the flow rate of the injected refrigerant and thus decrease a workload (the motive power) of the compressor 1 compared with a case in which the target degree of superheat is maintained at a constant value. This helps to decrease the motive power of the compressor 1 and enhance energy saving when the refrigeration request degree is relatively low.

[0043] In the present embodiment, the degree of superheat of the refrigerant is controlled to reach the target degree of superheat on condition that the discharge pipe temperature of the compressor 1 does not exceed a threshold level. In other words, control for target discharge pipe temperature (step ST13) takes precedence over control for target degree of superheat (step ST15). This prevents an excessive rise in discharge pipe temperature when the refrigeration request degree is relatively low and thus helps to enhance energy saving while lessening an adverse effect on the compressor 1.

(Second embodiment)

[0044] Fig. 8 shows a second embodiment. For the second embodiment, components identical to those of the first embodiment are denoted by the same numerals or symbols, and detailed descriptions thereof are omitted.

[0045] In the second embodiment, a second injection flow passage 17 is added. The second injection flow passage 17 is a flow passage that allows a refrigerant sent from a condenser 2 to be injected into a region of a compressor 1 that is midway through a compression process without passing through a subcooler 12. One end of the second injection flow passage 17 is connected to a point between the condenser 2 and the subcooler 12 in a main circuit 15. Another end of the second injection flow passage 17 is connected to a point between the subcooler 12 and the compressor 1 in a first injection flow passage 16. The refrigerant in liquid form flowing in the second injection flow passage 17 may flow in a fully liquid state or may get into a mixed gas-liquid state by being decompressed by a second flow rate regulating valve 13 described later. When the liquid refrigerant flowing through the second injection flow passage 17 joins the refrigerant flowing in the first injection flow passage 16, the liquid refrigerant may be partially or wholly gasified.

[0046] The one end of the second injection flow passage 17 may not be connected to the point between the condenser 2 and the subcooler 12 in the main circuit 15. As shown in Fig. 9, the one end of the second injection flow passage 17 may be connected to a point between the subcooler 12 and an expansion mechanism 3 in the main circuit 15.

[0047] The second flow rate regulating valve 13 (or a second injection regulating valve) is disposed on the second injection flow passage 17. The second flow rate regulating valve 13 is constituted by an electronic expansion valve. Thus, an opening degree of the second flow rate regulating valve 13 may be adjusted to regulate a flow rate of the refrigerant flowing through the second injection flow passage 17.

[0048] As shown in Fig. 10, functions of a controller 100 include a second valve control unit 106. The second valve control unit 106 is configured to control the second flow rate regulating valve 13 in response to a result detected by a discharge pipe temperature detector 21. In other words, the second valve control unit 106 controls the second flow rate regulating valve 13 such that the discharge pipe temperature falls within the managed reference temperature range. Hence, in the second embodiment, a first valve control unit 104, in a way different from that in the first embodiment, controls a first flow rate regulating valve 11 without reference to the value detected by the discharge pipe temperature detector 21.

[0049] In other words, in the second embodiment, control for target superheat degree shown in Fig. 11 and control for target discharge pipe temperature shown in Fig. 12 are executed separately and independently from each other.

[0050] Regarding control for target superheat degree, when a temperature target for the inside freezer temperature is set and operation of a refrigeration apparatus 10 starts, a target superheat degree control unit 102 sets a target degree of superheat (step ST22). In other words, a reception unit 101 receives a refrigeration request degree each at predetermined time intervals, and the target superheat degree control unit 102 derives a target degree of superheat in response to the refrigeration request degree received by the reception unit 101. A superheat degree calculator 103 calculates a degree of superheat of the refrigerant injected into the compressor 1 through the first injection flow passage 16. In the control for target superheat degree in step ST23, the first valve control unit 104 controls the first flow rate regulating valve 11 such that the calculated degree of superheat of refrigerant approaches the target degree of superheat set in step ST22. As shown in Figs. 4 to 6 and others, the target degree of superheat is set such that the value (the second value) for the lower refrigeration request degree (the second refrigeration request degree) is higher than the value (the first value) for the higher refrigeration request degree (the first refrigeration request degree). Hence, when a low cooling load is carried and the value of the refrigeration request degree is low, the target degree of superheat increases. As a result, the flow rate of the refrigerant injected into a region of the compressor 1 that is midway through a compression process decreases. Setting a target degree of superheat (step ST22) and control for the target superheat degree (step ST23) are repeated whenever a refrigeration request degree is received by the reception unit 101. Thus, with an increase in degree of approach of the inside freezer temperature to the set temperature, the flow rate of the refrigerant injected into the compressor 1 decreases.

[0051] Meanwhile, when a temperature target for the inside freezer temperature is set and operation of the refrigeration apparatus 10 starts, the controller 100, as shown in Fig. 12, receives a discharge pipe temperature that is a value detected by the discharge pipe temperature detector 21. The controller 100 determines whether or not the received discharge pipe temperature is within the managed reference temperature range (step ST32). When the value detected by the discharge pipe temperature detector 21 is within the managed reference temperature range, the opening degree of the second flow rate regulating valve 13 is maintained. The discharge pipe temperature is within the managed reference temperature range at a start of operation, for example, and thus the second flow rate regulating valve 13 is maintained in a closed state.

[0052] If the controller determines NO in step ST32 as a result of a change in detected discharge pipe temperature, control for target discharge pipe temperature is executed (step ST33). In this control, if the value detected by the discharge pipe temperature detector 21 exceeds the managed reference temperature range, the opening degree of the second flow rate regulating valve 13 gets larger. On the other hand, if the value detected by the discharge pipe temperature detector 21 is lower than the managed reference temperature range, the opening degree of the second flow rate regulating valve 13 gets smaller. As a result of this, the discharge pipe temperature is adjusted to fall within the managed reference temperature range. The control for target discharge pipe temperature (step ST33) is repeatedly executed whenever the controller 100 receives a detection signal from the discharge pipe temperature detector 21.

[0053] This makes it possible, in the second embodiment, to decrease the discharge pipe temperature of the compressor 1 with improved effectiveness, since the refrigerant is injected into the region of the compressor 1, which is midway through a compression process, through the second injection flow passage 17.

[0054] Moreover, the second flow rate regulating valve 13 is controlled in response to the result detected by the discharge pipe temperature detector 21. This allows the refrigeration apparatus 10 to regulate the flow rate of the refrigerant in the second injection flow passage 17 independently from adjustment of the degree of subcooling at the subcooler 12 by regulating the flow rate of the refrigerant flowing through the first injection flow passage 16. This makes it possible to optimize the flow rate of the refrigerant through the second injection flow passage 17.

[0055] In the control for target superheat degree (step ST23), the first flow rate regulating valve 11 may be controlled so as to stop the injection of the refrigerant into the compressor 1 through the first injection flow passage 16. In other words, when the refrigeration request degree received by the reception unit 101 is a third refrigeration request degree that is a refrigeration request degree lower than the second refrigeration request degree, the flow rate of the refrigerant injected through the first injection flow passage 16 decreases. Thus, the discharge pipe temperature of the compressor 1 is likely to rise. In this case, since the refrigerant is injected into the compressor 1 through the second injection flow passage 17 by the control for target discharge pipe temperature (step ST33), the injection of the refrigerant from a first flow rate regulating valve 11 side through the first injection flow passage 16 may be stopped. In this case, the compressor 1 is efficiently cooled, and this contributes to a reduction in motive power of the compressor 1.

[0056] In this case, the target superheat degree control unit 102 may set the value of the target degree of superheat such that the target degree of superheat gradually increases along with a decrease in value of the refrigeration request degree. For instance, the value of the target degree of superheat is set so as to change linearly or in a curved manner. This helps to prevent occurrence of an irregularity in control of the degree of subcooling through the subcooler 12, even when the injection of the refrigerant from the first flow rate regulating valve 11 side through the first injection flow passage 16 is stopped.

[0057] Although descriptions of other configurations, action, and effects are omitted, descriptions thereof in the first embodiment can be cited as those in the second embodiment.

(Third embodiment)

[0058] Fig. 13 shows a third embodiment. For the third embodiment, components identical to those of the first or the second embodiment are denoted by the same numerals or symbols, and detailed descriptions thereof are omitted.

[0059] The third embodiment is an example in which a refrigeration apparatus 10 is applied to an environment creating apparatus 50 such as an environmental testing apparatus. The refrigeration apparatus 10 may be any one of the refrigeration apparatuses in the first and the second embodiments.

[0060] The environment creating apparatus 50 has an environmental room 51 and is designed to provide a predetermined temperature environment inside the environmental room 51 through adjustment. The environment creating apparatus 50 further includes an air-conditioning room 52 to generate air at an adjusted temperature. The evaporator 4 of the refrigeration apparatus 10 is disposed in the air-conditioning room 52. In other words, the refrigeration apparatus 10 is configured to cool an inside the environmental room 51.

[0061] The air-conditioning room 52 has a heater 54 for heating air and a fan 55 for blowing out air at an adjusted temperature to the environmental room 51. The heater 54 and the fan 55 are disposed downstream of the evaporator 4. In the environmental room 51, the sensor 121 is installed to detect a temperature inside the environmental room 51. The input device 122 is used to input a set temperature for the temperature inside the environmental room 51. The environment creating apparatus 50 may be designed to set a wide temperature range, such as a negative temperature range, a normal temperature range or a high temperature range, and may have a program operating function to change the temperature between a plurality of set temperatures stepwise or continuously.

[0062] The generator 120 calculates a refrigeration request degree using the temperature detected by the sensor 121 and the set temperature from the input device 122.

[0063] Output of the heater 54 is controlled based on the temperature detected by the sensor 121 and the set temperature from the input device 122. In other words, a predetermined degree of subcooling is given and predetermined refrigeration capacity is displayed through control of the expansion mechanism 3 in the refrigeration apparatus 10. However, the temperature detected by the sensor 121 can fall below the set temperature, and in this case, the room temperature is fine-tuned by the heater 54. Hence, an ability to avoid excessive cooling by the refrigeration apparatus 10 would make it possible to not only reduce electricity required for the refrigeration apparatus 10 but also reduce electricity required for the heater 54. In this regard, when the refrigeration request degree is low, the flow rate of the refrigerant injected through the first injection flow passage 16 decreases. This decreases the refrigeration capacity and thus helps to reduce electricity required for the heater 54 and further enhance energy saving. The controller 100 controls such that the target superheat degree control unit 102 changes the target degree of superheat. This provides both adaptivity to the set temperature and enhanced energy saving after the temperature is reached. As a result, the refrigeration apparatus 10 is suitable particularly for a case in which a program operation is performed to change the temperature between a plurality of set temperatures stepwise or continuously.

[0064] Although descriptions of other configurations, action, and effects are omitted, descriptions thereof in the first or the second embodiment can be cited as those in the third embodiment.

[0065] In order to express the present invention, the present invention has been appropriately and fully described above through the embodiments with reference to the drawings. However, it is to be understood that various changes and/or modifications to the above-described embodiments will be apparent to those skilled in the art. Therefore, unless the changes or modifications implemented by those skilled in the art are at a level that departs from the scope of the appended claims, the changes or modifications should be construed as being included within the scope of the appended claims.

[0066] An outline of the above embodiments will now be given.

(1) A refrigeration apparatus according to the embodiment described above includes: a main circuit that has a compressor, a condenser, a subcooler, an expansion mechanism, and an evaporator to circulate a refrigerant; a first injection flow passage branching off from the main circuit at a point downstream of the condenser, the first injection flow passage being configured to allow the refrigerant to pass through the subcooler and be injected into a region of the compressor that is midway through a compression process; a first injection regulating valve disposed upstream of the subcooler in the first injection flow passage; a first valve control unit configured to control the first injection regulating valve such that a degree of superheat of the refrigerant injected into the compressor through the first injection flow passage reaches a target degree of superheat; a reception unit configured to receive a refrigeration request degree; and a target superheat degree control unit configured to set the target degree of superheat to a first value when the refrigeration request degree received by the reception unit is a first refrigeration request degree and set the target degree of superheat to a second value higher than the first value when the refrigeration request degree received by the reception unit is a second refrigeration request degree that is a refrigeration request degree lower than the first refrigeration request degree.

[0067] In the refrigeration apparatus described above, the first injection flow passage passes through the subcooler. This makes it possible to supercool the refrigerant flowing in the main circuit by the refrigerant flowing in the first injection flow passage. Moreover, the first injection flow passage is a flow passage designed to inject the refrigerant into the region of the compressor, which is midway through a compression process. This allows the refrigerant to circulate through the main circuit without a reduction in flow rate of the refrigerant flowing into the evaporator, even in a case in which the refrigerant flows from the main circuit to the first injection flow passage. By changing an opening degree of the first injection regulating valve, the flow rate of the refrigerant flowing through the first injection flow passage can be changed to change the degree of subcooling of the refrigerant passing through the subcooler in the main circuit. This makes it possible to adjust refrigeration capacity in response to the changed degree of subcooling.

[0068] Meanwhile, the degree of superheat of the refrigerant injected into the compressor through the first injection flow passage also changes. The first valve control unit controls the first injection regulating valve such that the degree of superheat of the refrigerant reaches the target degree of superheat. When the refrigeration request degree received by the reception unit is the first refrigeration request degree, the target superheat degree control unit assigns the first value to the target degree of superheat. When the received refrigeration request degree is the second refrigeration request degree, which is a refrigeration request degree lower than the first refrigeration request degree, the second value higher than the first value is assigned to the target degree of superheat. In other words, when the refrigeration request degree is relatively low (the second refrigeration request degree) compared with a case in which the refrigeration request degree is relatively high (the case of the first refrigeration request degree), the target degree of superheat is set such that the target degree of superheat is high. Hence, compared with a case in which the target degree of superheat is maintained at a constant value, the first injection regulating valve is controlled so as to have a smaller opening degree when the refrigeration request degree is relatively low. This decreases the flow rate of the refrigerant injected into the region of the compressor, which is midway through a compression process, through the first injection flow passage. This makes it possible to decrease the flow rate of the injected refrigerant and thus decrease a workload (motive power) of the compressor compared with a case in which the target degree of superheat is maintained at a constant value. This helps to decrease the motive power of the compressor and enhance energy saving when the refrigeration request degree is relatively low.

[0069] (2) In the refrigeration apparatus described above, the first valve control unit may be configured to control the first injection regulating valve such that the degree of superheat of the refrigerant reaches the target degree of superheat on condition that a discharge pipe temperature of the compressor does not exceed a threshold level.

[0070] In this aspect, the degree of superheat of the refrigerant is controlled to reach the target degree of superheat on condition that the discharge pipe temperature of the compressor does not exceed a threshold level. In other words, control for the discharge pipe temperature takes precedence over control for the target degree of superheat. This prevents an excessive rise in discharge pipe temperature when the refrigeration request degree is relatively low and thus helps to enhance energy saving while lessening an adverse effect on the compressor.

[0071] (3) The refrigeration apparatus described above may further include a second injection flow passage branching off from the main circuit at a point downstream of the condenser to allow the refrigerant sent from the condenser to be injected into the region of the compressor that is midway through a compression process.

[0072] In this aspect, the refrigerant is injected into the region of the compressor, which is midway through a compression process, through the second injection flow passage. This makes it possible to decrease the discharge pipe temperature of the compressor with improved effectiveness.

[0073] (4) The refrigeration apparatus described above may include: a second injection regulating valve disposed in the second injection flow passage to regulate a flow rate of the refrigerant; a discharge pipe temperature detector configured to detect a discharge pipe temperature of the compressor; and a second valve control unit configured to control the second injection regulating valve in response to a result detected by the discharge pipe temperature detector.

[0074] In this aspect, the second injection regulating valve is controlled in response to the result detected by the discharge pipe temperature detector. This allows the refrigeration apparatus to regulate the flow rate of the refrigerant in the second injection flow passage independently from adjustment of the degree of subcooling at the subcooler in the first injection flow passage. This makes it possible to optimize the flow rate of the refrigerant through the second injection flow passage.

[0075] (5) The target superheat degree control unit may be configured to set a value of the target degree of superheat such that the target degree of superheat gradually increases along with a decrease in value of the refrigeration request degree received by the reception unit.

[0076] In this aspect, the target degree of superheat gradually increases along with a decrease in value of the refrigeration request degree. Thus, the first injection regulating valve is controlled such that the flow rate of the refrigerant in the first injection flow passage gradually decreases. This allows the subcooler to lower the degree of subcooling (closer to a saturation temperature) along with a decrease in value of the refrigeration request degree. This allows the evaporator to provide decreased refrigeration capacity. This helps to display appropriate refrigeration capacity and further enhance energy saving in such a case when the refrigeration load is low.

[0077] (6) The refrigeration apparatus described above may include a second injection flow passage branching off from the main circuit at a point downstream of the condenser to allow the refrigerant sent from the condenser to be injected into the region of the compressor that is midway through a compression process. In this case, the first valve control unit may be configured to control the first injection regulating valve so as to stop injection of the refrigerant into the compressor through the first injection flow passage when the refrigeration request degree received by the reception unit is a third refrigeration request degree that is a refrigeration request degree lower than the second refrigeration request degree.

[0078] In the embodiment, the flow rate of the refrigerant in the first injection flow passage gradually decreases along with a decrease in value of the refrigeration request degree, and when the refrigeration request degree is the third refrigeration request degree, the first injection regulating valve is controlled so as to stop injection of the refrigerant through the first injection flow passage. In other words, the refrigeration apparatus is able to stop injection of the refrigerant through the first injection flow passage after a gradual reduction in flow rate of the refrigerant in the first injection flow passage. This helps to prevent occurrence of an irregularity in control of the degree of subcooling through the subcooler when the injection of the refrigerant through the first injection flow passage is stopped. Moreover, when the control unit for the second injection regulating valve is functioning, the refrigerant can be injected into the compressor to suppress a rise in discharge pipe temperature of the compressor.

[0079] (7) The environment creating apparatus may include: an environmental room; and the refrigeration apparatus, the refrigeration apparatus being configured to cool inside the environmental room.

[0080] (8) A refrigeration method according to the embodiment described above is a refrigeration method using a refrigeration apparatus that includes: a main circuit that has a compressor, a condenser, a subcooler, an expansion mechanism, and an evaporator to circulate a refrigerant; a first injection flow passage branching off from the main circuit at a point downstream of the condenser, the first injection flow passage being configured to allow the refrigerant to pass through the subcooler and be injected into a region of the compressor that is midway through a compression process; a first injection regulating valve disposed upstream of the subcooler in the first injection flow passage; and a reception unit. The refrigeration method includes: receiving a refrigeration request degree by the reception unit; setting a target degree of superheat to a first value when the refrigeration request degree received by the reception unit is a first refrigeration request degree and setting the target degree of superheat to a second value higher than the first value when the refrigeration request degree received by the reception unit is a second refrigeration request degree that is a refrigeration request degree lower than the first refrigeration request degree; and controlling the first injection regulating valve such that a degree of superheat of the refrigerant injected into the compressor through the first injection flow passage reaches the target degree of superheat.

[0081] As described above, the present embodiment enables injection of a refrigerant into a region of a compressor that is midway through a compression process and helps to enhance energy saving.

Claims

1. A refrigeration apparatus (10) comprising:

a main circuit (15) that has a compressor (1), a condenser (2), a subcooler (12), an expansion mechanism (3), and an evaporator (4) to circulate a refrigerant;

a first injection flow passage (16) branching off from the main circuit (15) at a point downstream of the condenser (2), the first injection flow passage (16) being configured to allow the refrigerant to pass through the subcooler (12) and be injected into a region of the compressor (1) that is midway through a compression process;

a first injection regulating valve (11) disposed upstream of the subcooler (12) in the first injection flow passage (16);

a first valve control unit (104) configured to control the first injection regulating valve (11) such that a degree of superheat of the refrigerant injected into the compressor (1) through the first injection flow passage (16) reaches a target degree of superheat;

a reception unit (101) configured to receive a refrigeration request degree; and

a target superheat degree control unit (102) configured to set the target degree of superheat to a first value when the refrigeration request degree received by the reception unit (101) is a first refrigeration request degree and set the target degree of superheat to a second value higher than the first value when the refrigeration request degree received by the reception unit (101) is a second refrigeration request degree that is a refrigeration request degree lower than the first refrigeration request degree.

2. The refrigeration apparatus (10) according to claim 1, wherein the first valve control unit (104) is configured to control the first injection regulating valve (11) such that the degree of superheat of the refrigerant reaches the target degree of superheat on condition that a discharge pipe temperature of the compressor (1) does not exceed a threshold level.

3. The refrigeration apparatus (10) according to claim 1 or 2, further comprising a second injection flow passage (17) branching off from the main circuit (15) at a point downstream of the condenser (2) to allow the refrigerant sent from the condenser (2) to be injected into the region of the compressor (1) that is midway through a compression process.

4. The refrigeration apparatus (10) according to claim 3, comprising:

a second injection regulating valve (13) disposed in the second injection flow passage (17) to regulate a flow rate of the refrigerant;

a discharge pipe temperature detector (21) configured to detect a discharge pipe temperature of the compressor (1); and

a second valve control unit (106) configured to control the second injection regulating valve (13) in response to a result detected by the discharge pipe temperature detector (21).

5. The refrigeration apparatus (10) according any one of claims 1 to 4, wherein the target superheat degree control unit (102) is configured to set a value of the target degree of superheat such that the target degree of superheat gradually increases along with a decrease in value of the refrigeration request degree received by the reception unit (101).

6. The refrigeration apparatus (10) according to claim 5, comprising a second injection flow passage (17) branching off from the main circuit (15) at a point downstream of the condenser (2) to allow the refrigerant sent from the condenser (2) to be injected into the region of the compressor (1) that is midway through a compression process,
wherein the first valve control unit (104) is configured to control the first injection regulating valve (11) so as to stop injection of the refrigerant into the compressor (1) through the first injection flow passage (16) when the refrigeration request degree received by the reception unit (101) is a third refrigeration request degree that is a refrigeration request degree lower than the second refrigeration request degree.

7. An environment creating apparatus (50) comprising:

an environmental room (51); and

the refrigeration apparatus (10) according any one of claims 1 to 6, the refrigeration apparatus (10) being configured to cool inside the environmental room (51).

8. A refrigeration method using a refrigeration apparatus that comprises:

a main circuit (15) that has a compressor (1), a condenser (2), a subcooler (12), an expansion mechanism (3), and an evaporator (4) to circulate a refrigerant;

a first injection flow passage (16) branching off from the main circuit (15) at a point downstream of the condenser (2), the first injection flow passage (16) being configured to allow the refrigerant to pass through the subcooler (12) and be injected into a region of the compressor (1) that is midway through a compression process;

a first injection regulating valve (11) disposed upstream of the subcooler (12) in the first injection flow passage (16); and

a reception unit (101), the refrigeration method comprising:

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

setting a target degree of superheat to a first value when the refrigeration request degree received by the reception unit (101) is a first refrigeration request degree and setting the target degree of superheat to a second value higher than the first value when the refrigeration request degree received by the reception unit (101) is a second refrigeration request degree that is a refrigeration request degree lower than the first refrigeration request degree; and

controlling the first injection regulating valve (11) such that a degree of superheat of the refrigerant injected into the compressor (1) through the first injection flow passage (16) reaches the target degree of superheat.

Drawing