JP2013164250A - Refrigerating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerating apparatus configured to prevent unnecessary increase in amount of refrigerant returning to a two-stage compressor and repetition of operation and stop of the two-stage compressor.SOLUTION: A refrigerating apparatus R includes: a two-stage compressor 11; an intercooler 20 having an entrance connected to a low-stage side discharge port 16 of the two-stage compressor 11 and having an exit connected to a high-stage side suction port 17 of the two-stage compressor 11; a gas cooler 30 having an entrance connected to a high-stage side discharge port 18 of the two-stage compressor 11; and an intermediate heat exchanger 40 which is connected to an exit of the gas cooler 30 and which supercools refrigerant flowing thereinto after passing through the gas cooler 30 with refrigerant decompressed by an expansion valve 35 after passing through the gas cooler 30. The refrigerating device also includes a control means C which changes a target value of a supercooling degree of the intermediate heat exchanger 40 on the basis of an outside temperature, and controls a valve opening degree of the expansion valve 35 on the basis of the changed target value of the supercooling degree.

Description

  The present invention relates to a refrigeration apparatus including a two-stage compressor, a gas cooler, a throttle means, and an evaporator in a refrigerant circuit.

  A two-stage compressor, an intercooler that cools the refrigerant discharged from the first stage of the two-stage compressor, a gas cooler that cools the refrigerant discharged from the second stage of the two-stage compressor, and an intermediate connected to the outlet of the gas cooler Conventionally, a refrigeration apparatus having a heat exchanger, an evaporator into which a refrigerant cooled by an intermediate heat exchanger flows, and a control unit that controls the valve opening degree of an expansion valve is known (for example, Patent Document 1). reference).

  The intermediate heat exchanger cools one refrigerant flowing through the gas cooler by the other refrigerant flowing after the gas cooler is further decompressed by the expansion valve. In addition, the refrigerant that has passed through the intermediate exchanger after being decompressed is returned to the second stage of the two-stage compressor. Furthermore, the control means controls the valve opening degree of the expansion valve so that one refrigerant is cooled by the intermediate heat exchanger according to a predetermined target value of the degree of supercooling set regardless of the temperature of the outside air. It is supposed to be. Since the refrigerant flowing to the evaporator side is cooled with a sufficient degree of supercooling, the cooling efficiency of the refrigeration apparatus has been improved.

JP 2011-137557 A

  In the above refrigeration apparatus, the target value of the degree of supercooling in the intermediate heat exchanger is set so that the space can be cooled without any problem even in the summer, compared to the temperature setting of the space cooled by the evaporator. On the other hand, when the outside air temperature is lowered, such as in winter, when the subcooling degree of the refrigerant is taken according to the target value of the subcooling degree set regardless of the outside air temperature in the intermediate heat exchanger, the following problems occur: Will occur.

For example, when carbon dioxide, which has a low critical point, is used as a refrigerant, the refrigerant in a properly condensed state is evaporated in an intermediate heat exchanger without securing a large degree of supercooling in situations where the outside air temperature is low. Can be supplied to the vessel. In other words, when the outside air temperature is low, it is not necessary to increase the degree of supercooling of one of the refrigerants discharged from the intermediate heat exchanger to the evaporator. Since the valve opening is opened, the amount of refrigerant returning to the second stage of the two-stage compressor is unnecessarily increased. This unnecessarily increases the work of the two-stage compressor.
Further, even under a condition where the outside air temperature is low, the refrigerant cooled with a predetermined degree of supercooling is supplied to the evaporator. For this reason, if the driving of the two-stage compressor is continued, the space cooled by the evaporator is excessively cooled. Therefore, conventionally, the temperature of the space to be cooled is adjusted by repeating the driving and stopping of the two-stage compressor. However, the two-stage compressor needs to be opened and closed due to the driving and stopping. The load on equipment such as an expansion valve has increased.

  The present invention has been made to solve the above-described problem, and can avoid an unnecessary increase in the amount of refrigerant returning to the two-stage compressor and can suppress the repetition of operation and stop of the two-stage compressor. The object is to obtain a refrigeration system.

  To achieve the above object, the present invention provides a two-stage compressor, an inlet connected to a first-stage refrigerant discharge section of the two-stage compressor, and a second-stage refrigerant suction section of the two-stage compressor. An intercooler to which an outlet is connected; a gas cooler having an inlet connected to a second-stage refrigerant discharge portion of the two-stage compressor; and a refrigerant that is connected to an outlet of the gas cooler and flows through the gas cooler. In the refrigeration apparatus including the intermediate heat exchanger that is supercooled by the refrigerant reduced in pressure through the expansion valve, the target value of the degree of supercooling of the intermediate heat exchanger is changed according to the outside air temperature. In addition, control means for controlling the opening degree of the expansion valve based on the changed target value of the degree of supercooling is provided.

  In the refrigeration apparatus according to the present invention, the control unit includes a storage unit that stores target value setting data in which the target value of the degree of supercooling is uniquely associated with the value of the outside air temperature. It is characterized by that.

  Further, in the refrigeration apparatus according to the present invention, the target value setting data is configured such that a value in the outside air temperature fluctuation region and a target value of the supercooling degree are associated with each other in a proportional relationship. Features.

  In the refrigeration apparatus according to the present invention, the target value setting data may be obtained by dividing the outside temperature fluctuation region into a plurality of regions and associating a predetermined degree of subcooling with each of the divided outside air temperature ranges. It is configured.

  Further, the present invention is the refrigeration apparatus, wherein the control means is configured such that the pressure of the refrigerant flowing into the first-stage refrigerant suction portion of the two-stage compressor is lower than a lower limit of a target range by a predetermined value or more. When the compressor is driven at the lowest compression capacity of the refrigerant, the opening degree of the expansion valve is reduced.

  Further, in the refrigeration apparatus according to the present invention, the control means includes a difference between a refrigerant temperature discharged from a second-stage refrigerant discharge portion of the two-stage compressor and a refrigerant temperature at an outlet of the gas cooler. In the case where is less than or equal to a predetermined threshold, priority is given to control for reducing the valve opening of the expansion valve.

  According to the refrigeration apparatus of the present invention, the expansion valve opening / closing control is performed so as to be appropriately changed according to the outside air temperature, so that the amount of refrigerant returned from the intermediate heat exchanger to the intermediate pressure region increases unnecessarily. You can avoid that. Furthermore, since it is not necessary to perform the cooling performance of the refrigeration apparatus by the refrigerant by operating and stopping the two-stage compressor, it is possible to reduce the burden on each device of the refrigeration apparatus that operates in conjunction with the driving and stopping of the two-stage compressor.

It is a refrigerant circuit figure of the refrigerating device which has a cooling unit concerning the embodiment of the present invention. It is a system block diagram of a freezing apparatus. It is a flowchart explaining control of the valve opening degree of the expansion valve at the normal time. It is a figure explaining the example of the target value of the supercooling degree according to outside temperature. It is a figure which shows the other example of target value setting data.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a refrigerant circuit diagram of a refrigeration apparatus according to an embodiment of the present invention, and FIG. 2 is a system configuration diagram of the refrigeration apparatus.
In FIG. 1, the refrigeration apparatus R in the present embodiment includes a refrigeration unit 2, a showcase unit 80 as a cooling unit having an evaporator 82, and control means C, and the refrigeration unit 2 and the showcase unit 80. Are connected by refrigerant pipes 7 and 9 to constitute a predetermined refrigerant circuit 1.
In the refrigeration cycle performed by the refrigerant circuit 1, carbon dioxide whose refrigerant pressure (high pressure) on the high pressure side is equal to or higher than the critical pressure (supercritical) is used as the refrigerant. This carbon dioxide refrigerant is a natural refrigerant that is friendly to the global environment and takes into consideration flammability and toxicity.

The control means C is constituted by a general-purpose microcomputer.
The control means C has a storage unit C1 that stores target value setting data to be described later.
The refrigerator unit 2 includes a two-stage compressor 11, an intercooler 20, a gas cooler 30, and an intermediate heat exchanger 40.
The refrigerator unit 2 also includes a refrigerant amount adjustment tank 60 for storing the refrigerant recovered from the refrigerant circuit 1 and returning the refrigerant to the refrigerant circuit 1 as necessary.
The two-stage compressor 11 is an internal intermediate pressure type multistage compression rotary compressor, and includes a cylindrical sealed container 12 made of a steel plate, an electric motor 19 disposed and housed in the inner space of the sealed container 12, and an electric motor 19, respectively. It has the 1st rotation compression element 13 and the 2nd rotation compression element 14 which are rotationally driven. In the present embodiment, the rotational speed (rotational speed) of the electric motor 19 is controlled by inverter control under the control of the control means C that also serves as the rotational speed control means. The operating frequency of AC power used for inverter control can be changed between 35 Hz and 70 Hz.
The rotational speed of the first rotary compression element 13 and the second rotary compression element 14 can be controlled by changing the rotational speed of the electric motor 19.
The first rotary compression element 13 is used on the lower pressure side than the second rotary compression element 14. The first rotary compression element 13 constitutes a first stage compressor in the two-stage compressor 11, and the second rotary compression element 14 constitutes a second stage compressor in the two-stage compressor 11.

The hermetic container 12 includes a low-stage suction port 15 serving as a refrigerant suction unit for the first rotary compression element 13, a low-stage discharge port 16 serving as a refrigerant discharge unit from the first rotary compression element 13, and a second A high-stage suction port 17 serving as a refrigerant suction portion to the rotary compression element 14 and a high-stage discharge port 18 serving as a refrigerant discharge portion from the second rotary compression element 14 are formed.
Further, the low-stage discharge port 16 of the two-stage compressor 11 and the inlet of the intercooler 20 are connected via an intermediate pressure discharge pipe 61. Further, the outlet of the intercooler 20 and the high-stage suction port 17 are connected via an intermediate pressure suction pipe 62. The high-stage discharge port 18 and the inlet of the gas cooler 30 are connected via a high-pressure refrigerant pipe 63. The intermediate heat exchanger 40 has a first flow path 40A and a second flow path 40B. The outlet of the gas cooler 30 and one end of the first flow path 40 </ b> A of the intermediate heat exchanger 40 are connected via a high-pressure refrigerant pipe 64. The other end (exit) of the first flow path 40 </ b> A is connected to the showcase unit 80 via the refrigerant pipe 7.

A strainer 8 is provided at a portion of the refrigerant pipe 7 located on the outlet side of the first flow path 40A. A predetermined portion of the refrigerant pipe 7 and one end of the second flow path 40 </ b> B are connected by a first split refrigerant pipe 65. Thereby, the refrigerant flow path branched from the refrigerant pipe 7 and reaching one end of the second flow path 40B is configured. The first split refrigerant pipe 65 is provided with an expansion valve 35.
Further, the refrigerant flow path returning from the intercooler 20 to the high-stage side suction port 17 and the other end of the second flow path 40 </ b> B are connected by a second split refrigerant pipe 66. An auxiliary refrigerant branched from the refrigerant pipe 7 by the first split refrigerant pipe 65 and the second split refrigerant pipe 66 and reaching the refrigerant flow path on the outlet side of the intercooler 20 via the second flow path 40B of the intermediate heat exchanger 40. A circuit is formed.

The refrigerant pipe 7 and the upper part of the refrigerant quantity adjustment tank 60 are connected via a first communication path 71 (first communication refrigerant pipe). The first communication passage 71 is provided with a recovery expansion valve 72 as a first valve device. By opening the recovery expansion valve 72, the high-pressure refrigerant flowing through the refrigerant pipe 7 can be recovered in the refrigerant amount adjustment tank 60.
Further, the portion of the first split refrigerant pipe 65 extending from the expansion valve 35 to the second flow path 40B and the lower part in the refrigerant amount adjustment tank 60 are connected via a second communication path 73 (second communication refrigerant pipe). ing. The second communication path 73 is provided with a solenoid valve 75 and a second valve device 74 having a capillary tube 76 having a throttling function. In addition, you may comprise the 2nd valve apparatus 74 by an expansion valve.

  Further, the intermediate pressure region of the refrigerant circuit 1 and the upper part in the refrigerant amount adjustment tank 60 are connected by a third communication path (third communication refrigerant pipe) 77. The intermediate pressure region is a region from the low-stage discharge port 16 of the two-stage compressor 11 to the high-stage suction port 17 of the two-stage compressor 11 via the intercooler 20. In the present embodiment, a predetermined portion of the intermediate pressure suction pipe 62 and the upper part in the refrigerant amount adjustment tank 60 are connected via the third communication passage 77. The third communication passage 77 is provided with an electromagnetic valve 78 as a third valve device.

The intermediate pressure region and the low pressure side of the refrigerant circuit 1 are connected via a bypass communication path (bypass pipe) 54. More specifically, the third communication path 77 and the refrigerant pipe 9 through which the refrigerant discharged from the outlet of the evaporator 82 flows are connected via the bypass communication path 54. The bypass communication path 54 is provided with an electromagnetic valve 55.
Here, the gas cooler 30 and the intercooler 20 are disposed in the same air passage 41, and a blower 42 for air-cooling the gas cooler 30 and the intercooler 20 is disposed.

A high-pressure sensor (high-pressure detector) 43 is provided at the outlet of the gas cooler 30 and detects the pressure of the high-pressure refrigerant discharged from the second rotary compression element 14.
In addition, a discharge temperature sensor (discharge temperature detection means) 44 is provided in the high-pressure refrigerant pipe 63 located in the vicinity of the high-stage discharge port 18 of the two-stage compressor 11, and the refrigerant discharged from the second rotary compression element 14. Detect the discharge temperature.
A unit outlet side pressure sensor (unit outlet side pressure detecting means) 45 is provided in the first communication path 71 branched from the refrigerant pipe 7 and detects the pressure of the high-pressure refrigerant flowing through the refrigerant pipe 7.
Further, an intermediate pressure sensor (intermediate pressure detection means) 46 is provided at a portion of the intermediate pressure suction pipe 62 located on the outlet side of the intercooler 20 and detects the pressure of the refrigerant flowing in the intermediate pressure region of the refrigerant circuit 1. To do. In addition, the pressure of a refrigerant | coolant is the same at the exit of the 2nd flow path 40B, and the exit of the intercooler 20. FIG. Further, a split outlet temperature sensor 47 is provided at a portion of the second split refrigerant pipe 66 located on the outlet side of the second flow path 40B, and detects the temperature of the refrigerant flowing through the intermediate pressure region of the refrigerant circuit 1.

Further, a low pressure sensor (suction pressure detection means) 48 is provided in the bypass communication path 54 connected to the refrigerant pipe 9, and the low pressure sucked from the evaporator 82 into the low stage suction port 15 of the two-stage compressor 11. The refrigerant pressure is detected.
Further, a gas cooler outlet temperature sensor (gas cooler outlet temperature detecting means) 49 is provided at a portion of the high-pressure refrigerant pipe 64 located on the outlet side of the gas cooler 30 and detects the temperature (GCT) of the refrigerant that has exited the gas cooler 30.
Further, a unit outlet temperature sensor (unit outlet temperature detection means) 50 is provided in the refrigerant pipe 7, and the temperature of the refrigerant supplied from the refrigerator unit 2 to the showcase unit 80, in other words, the intermediate heat exchanger 40 The temperature (LT) of the refrigerant discharged from the first flow path 40A is detected.
Further, a unit inlet temperature sensor (inlet temperature detecting means) 51 is provided in the refrigerant pipe 9 and sucked into the first rotary compression element 13 in other words, the temperature of the refrigerant introduced into the refrigerator unit 2 from the showcase unit 80. The temperature of the refrigerant to be detected is detected.
The air passage 41 is provided with an outside air temperature sensor (outside air temperature detecting means) 52 for detecting the outside air temperature at the location where the refrigerator unit 2 is disposed.
An intermediate pressure discharge temperature sensor 53 is provided in the intermediate pressure discharge pipe 61 and detects the discharge temperature of the refrigerant discharged from the first rotary compression element 13.

  The showcase unit 80 is installed in a store, for example, and is connected to the refrigerant pipe 7 and the refrigerant pipe 9. The showcase unit 80 includes a cooling unit side expansion valve 81 as a throttle means connected to the refrigerant pipe 7, and an evaporator 82 connected to the refrigerant pipe 7 through the cooling unit side expansion valve 81. Yes. The outlet of the evaporator 82 is connected to one end of the refrigerant pipe 9. Further, the showcase unit 80 is provided with a cool air circulation blower (not shown) that blows air to the evaporator 82. The other end of the refrigerant pipe 9 is connected to the low-stage suction port 15. The refrigerant pipe 9 is provided with a check valve 27 and a strainer 28. Thereby, in the refrigerant circuit 1, the refrigerant main circuit circulating through the evaporator 82, the first rotary compression element 13, the intercooler 20, the second rotary compression element 14, the gas cooler 30, and the intermediate heat exchanger 40 is provided. It is formed.

Next, the system configuration of the refrigeration apparatus R will be described.
The control means C is connected to the electric motor 19 of the two-stage compressor 11 as shown in FIG. 2, and the control means C performs drive control of the electric motor 19 and can detect (acquire) its operating frequency. Yes.
The control means C is connected to the fan motor 42M of the blower 42 and can control the driving of the fan motor 42M.
The control means C includes a high pressure sensor (high pressure detector) 43, a discharge temperature sensor 44, a unit outlet side pressure sensor 45, an intermediate pressure sensor 46, a split outlet temperature sensor 47, a low pressure sensor 48, and a gas cooler outlet. A temperature sensor 49, a unit outlet temperature sensor 50, and a unit inlet temperature sensor 51 are connected, and the control means C recognizes the outputs of these sensors.
The control means C is connected to the expansion valve 35, the electromagnetic valve 55, the recovery expansion valve 72, the electromagnetic valve 75, and the electromagnetic valve 78, and can control the opening and closing of these valves.

Next, the flow of the refrigerant in the refrigeration apparatus R will be described.
The first rotary compression element 13 compresses the low-pressure refrigerant sucked from the low-pressure side of the refrigerant circuit 1 through the refrigerant pipe 9, raises it to an intermediate pressure, and discharges it. The refrigerant discharged from the first rotary compression element 13 flows into the intercooler 20 through the intermediate pressure discharge pipe 61 and is air-cooled by the intercooler 20. The refrigerant that has passed through the intercooler 20 is sucked into the second rotary compression element 14 from the high-stage suction port 17 through the intermediate pressure suction pipe 62. The second rotary compression element 14 compresses the sucked intermediate pressure refrigerant to increase the pressure to a high pressure, and discharges it from the high-stage discharge port 18.

The high-pressure refrigerant discharged from the high-stage discharge port 18 flows into the gas cooler 30 via the high-pressure refrigerant pipe 63 and is cooled by the gas cooler 30. The refrigerant flow discharged from the outlet of the gas cooler 30 is directed to the first flow path 40A via the high-pressure refrigerant pipe 64 of the intermediate heat exchanger 40 and to the second flow path 40B via the first split refrigerant pipe 65. Divided into what is going.
In the intermediate heat exchanger 40, the refrigerant that has passed through the first flow path 40 </ b> A flows into the cooling unit side expansion valve 81 through the refrigerant pipe 7 and is depressurized. The decompressed refrigerant is evaporated by the evaporator 82 and then returns to the first rotary compression element 13 through the refrigerant pipe 9.

Further, a split cycle described below using the intermediate heat exchanger 40 is formed in the refrigerant circuit of the refrigeration apparatus R.
In the split cycle, the refrigerant that is diverted from the high-pressure side refrigerant flow path and depressurized by the expansion valve 35 is appropriately combined with the refrigerant from the refrigerant amount adjustment tank 60 via the third communication passage 77, and the refrigerant from the gas cooler 30. Is a cycle for exchanging heat. Note that the high-pressure side refrigerant flow path is a refrigerant flow path from the gas cooler 30 to the evaporator 82 of the showcase unit 80 through the intermediate heat exchanger 40. The intermediate-pressure (MP) refrigerant gas sucked into the second rotary compression element 14 from the high-stage side suction port 17 is compressed in the second stage by the second rotary compression element 14, so that the high-temperature and high-pressure (HP: normal) The refrigerant gas has a supercritical pressure of about 12 MPa in the operating state. That is, the high-pressure refrigerant that has reached the supercritical pressure flows through the high-pressure side refrigerant flow path.

Further, as described above, the refrigerant amount adjusting tank 60 is connected to the refrigerant pipe 7 constituting the high-pressure side refrigerant flow path so that the refrigerant in the refrigerant pipe 7 can be collected. The refrigerant collected in the refrigerant quantity adjustment tank 60 accumulates in the lower part of the refrigerant quantity adjustment tank 60. Details of the refrigerant recovery operation will be described later.
The refrigerant discharged from the outlet of the gas cooler 30 and flowing into the first split refrigerant pipe 65 is appropriately expanded by the expansion valve 35 under the control of the control means C, and then proceeds to the second flow path 40B. When the solenoid valve 75 that opens and closes the second communication path 73 is open, the refrigerant from the refrigerant quantity adjustment tank 60 expands in the capillary tube 76 and then flows through the first split refrigerant pipe 65. After being merged, it flows into the second flow path 40B.
Then, heat exchange is performed between the refrigerant flowing through the first flow path 40A and the refrigerant flowing through the second flow path 40B, and the refrigerant flowing through the second flow path 40B flows through the second split refrigerant pipe 66 to the intermediate pressure. Returned to area.

In the split cycle as described above, when heat is exchanged between the refrigerant flowing through the first flow path 40A of the intermediate heat exchanger 40 and the refrigerant flowing through the second flow path 40B, the refrigerant in the first flow path 40A. Is sufficiently cooled by the refrigerant in the second flow path 40B. Thereby, in the showcase unit 80, the cooling performance of the space cooled by the evaporator 82 is enhanced.
In addition, the other end of the second flow path 40B joins the refrigerant flow path that returns from the intercooler 20 to the high-stage suction port 17. For this reason, it is possible to smoothly merge the refrigerant flow from the intermediate heat exchanger 40 into the intermediate pressure region of the refrigerant main circuit while preventing pressure loss in the intercooler 20.

Next, control of the refrigerator unit 2 by the control means (control means) C will be described.
First, the operation frequency control of the two-stage compressor 11 will be described.
In the control means C, the target range of the pressure of the low-pressure refrigerant sucked into the first rotary compression element 13 is stored in advance according to the target set temperature in the showcase unit 80. If the pressure of the refrigerant discharged from the evaporator 82 of the showcase unit 80 is within the target range of the set pressure even when the outside air temperature is high, the target range of the pressure of the low-pressure refrigerant is the showcase unit 80. It is set so that the cooling performance required by the specifications can be considered satisfactory.

  Here, when the pressure of the low-pressure refrigerant is lower than the lower limit value of the target range, it means that the cooling performance in the showcase unit 80 is exhibited more than necessary. The control means C monitors the low-pressure sensor 48 and repeats the control to lower the operating frequency of the two-stage compressor 11 by a predetermined amount when the pressure of the low-pressure refrigerant is lower than the lower limit value of the target range. In addition, when the pressure of the low-pressure refrigerant is higher than the upper limit value of the target range, it means that the cooling performance in the showcase unit 80 is insufficient. The control means C monitors the low pressure sensor 48 and repeats control to increase the operating frequency of the two-stage compressor 11 by a predetermined amount when the pressure of the low pressure refrigerant is higher than the upper limit value of the target range. As a result, the low-pressure refrigerant pressure changes in a direction that falls within the set target range of pressure.

The control means C can adjust the valve opening degree of the expansion valve 35 by a step motor.
Hereinafter, control of the valve opening degree of the expansion valve 35 at the normal time will be described.
FIG. 3 is a flowchart for explaining the control of the opening degree of the expansion valve at the normal time, and FIG. 4 is an example of target value setting data in which the target value of the degree of supercooling is uniquely associated with the value of the outside air temperature. FIG.
The control means C refers to the output of the outside air temperature sensor 52, acquires the outside air temperature T, refers to the target value setting data in the storage unit C1, and sets the target value ΔKa of the degree of supercooling of the intermediate heat exchanger 40. Then, it is changed (set) according to the outside air temperature T (S101).

The target value setting data uniquely associates the target value of the degree of supercooling with the value of the outside air temperature T. For example, as shown by the solid line in FIG. 4, the target value ΔKa of the degree of supercooling is constant at the minimum value Ao (about 0 to 5) ° C. when the outside air temperature T is 0 ° C. or less. The outside air temperature T and the target value ΔKa of the degree of supercooling are associated with each other so as to increase in proportion to the increase from 0 ° C. For example, ΔKa when the outside air temperature T is 20 ° C. is 10 ° C., and ΔKa when the outside air temperature T is 40 ° C. is 20 ° C.
Note that the target value setting data is not limited to this, and for example, as shown by a broken line in FIG. 4, all values in the fluctuation region of the outside air temperature T and the target value ΔKa of the degree of supercooling are proportional to each other. It may be configured in association with. At this time, the proportionality coefficient is set as a positive value. Thus, the target value ΔKa is set to be a large value for a high outside temperature and a small value for a low outside temperature.
Next, the control means C determines the actual subcooling degree ΔKb (GCT) of the intermediate heat exchanger 40 from the refrigerant temperature (LT) detected by the unit outlet temperature sensor 50 and the refrigerant temperature (GCT) detected by the gas cooler outlet temperature sensor 49. -LT) is calculated (S102).

  The control means C determines whether or not the actual supercooling degree ΔKb in the intermediate heat exchanger 40 is larger than the valve expansion index value (= target value ΔKa + predetermined value α) (S103). α is equal to the target value ΔKa if the difference between ΔKb and ΔKa is within α, even if the actual degree of supercooling ΔKb and the target value ΔKa are different. It is set as appropriate within a range that does not vary greatly compared to when it is present.

When the actual degree of supercooling ΔKb is larger than the valve expansion index value (S103: YES), the control means C considers that the degree of supercooling in the intermediate heat exchanger 40 is sufficient and opens the valve opening of the expansion valve 35. Is reduced by a predetermined amount (S104), and the process returns to S101. Further, when the actual supercooling degree ΔKb is smaller than the valve expansion index value (S103: NO), the control means C has the actual supercooling degree ΔKb smaller than the valve reduction index value (= ΔKb−α). It is determined whether or not (S105).
When the actual degree of supercooling ΔKb is smaller than the valve reduction index value, the control means C considers that the degree of supercooling in the intermediate heat exchanger 40 is insufficient and increases the valve opening of the expansion valve 35 by a predetermined amount. (S106) and return to S101.
Further, when the actual degree of supercooling ΔKb is larger than the valve reduction index value, the control means C maintains the current valve opening of the expansion valve 35 (S107), and returns to S101.
In addition, the control cycle of the valve opening degree of the expansion valve 35 is repeated at predetermined intervals.

  When the control of the valve opening degree of the expansion valve 35 is summarized, the control means C changes the target value of the degree of supercooling of the intermediate heat exchanger 40 according to the outside air temperature T, and the changed subcooling. The valve opening degree of the expansion valve 35 is controlled based on the target value ΔKa of the degree. At this time, the actual degree of supercooling ΔKb in the intermediate heat exchanger 40 is controlled so as to be within a predetermined range (± α) from the target value ΔKa.

  As in the present embodiment, for example, when carbon dioxide having a low critical point is used as a refrigerant, when the outside air temperature T is high (for example, close to 40 ° C.), the degree of supercooling in the intermediate heat exchanger 40 is increased. If not taken sufficiently, the supercritical refrigerant that is not completely liquefied will be supplied to the showcase unit 80. For this reason, when the outside air temperature T is high, it is necessary to increase the degree of supercooling in the intermediate heat exchanger 40. On the other hand, when the outside air temperature T is low (for example, 0 ° C.), even the carbon dioxide refrigerant is sufficiently condensed, so it is necessary to supply the showcase unit 80 with a refrigerant having a large degree of supercooling in the intermediate heat exchanger 40. Sex is lost.

  Here, if the target value ΔKa of the supercooling degree in the intermediate heat exchanger 40 is set to be constant, the following problems occur. As described above, the target value ΔKa of the degree of supercooling needs to be set to a large value so that the cooling performance in the showcase unit 80 is ensured even when the outside air temperature T is high. Under this condition, when the outside air temperature T is lowered, the degree of supercooling in the intermediate heat exchanger 40 is taken more than necessary. That is, the amount of refrigerant flowing into the intermediate heat exchanger 40 after being diverted from the high-pressure side refrigerant flow path and reduced in pressure by the expansion valve 35 becomes unnecessarily large. In other words, since the amount of refrigerant returned from the intermediate heat exchanger 40 to the intermediate pressure region becomes unnecessarily large, the refrigerant pressure in the intermediate pressure region increases, and accordingly, the burden on the two-stage compressor 11 increases. The In addition, since the refrigerant whose degree of supercooling is taken more than necessary is supplied to the showcase unit 80, the temperature of the showcase unit 80 is lowered more than necessary, and the temperature in the showcase unit 80 is reduced by two stages. Adjustments must be made by repeatedly driving and stopping the compressor 11. In conjunction with driving and stopping of the two-stage compressor 11, a load is applied to the expansion valve 35 and the like that must be repeatedly opened and closed.

  On the other hand, in the present embodiment, the target value ΔKa of the subcooling degree in the intermediate heat exchanger 40 is changed according to the outside air temperature T, and the intermediate heat exchanger 40 changes according to the changed target value ΔKa of the subcooling degree. The degree of supercooling is controlled. For this reason, the amount of refrigerant returned from the intermediate heat exchanger 40 to the intermediate pressure region becomes unnecessarily large, or the cooling in the showcase unit 80 is excessively performed. Repeated driving and stopping are avoided.

  Normally, the valve opening degree of the expansion valve 35 is controlled as described above. However, if any of the following first to third conditions is satisfied, the control means C has priority over the above control. The emergency expansion valve control for adjusting the valve opening degree of the expansion valve 35 is performed.

The first condition is a case where the temperature difference (DT−GCT) between the refrigerant temperature DT discharged from the second rotary compression element 14 and the refrigerant temperature GCT passed through the gas cooler 30 is lower than a predetermined value TDT.
Here, the predetermined value TDT differs depending on whether the high-pressure side pressure HP is in the supercritical region or the saturation region of the refrigerant. The control means C determines whether the high pressure side pressure HP is in the supercritical region or the saturation region based on the outside air temperature T output from the outside air temperature sensor 52. Then, the control means C sets the predetermined value TDT to be lowered when it is determined as the supercritical region, and increases the predetermined value TDT when it is determined as the saturation region. In the present embodiment, the predetermined value TDT is 10 ° C. in the supercritical region and 35 ° C. in the saturation region.

  When the temperature difference (DT-GCT) is lower than the predetermined value TDT, the control means C reduces the valve opening of the expansion valve 35 or closes the expansion valve 35. As a result, it is avoided that the extremely cooled refrigerant returns to the intermediate pressure region, so that the liquid back is suppressed from proceeding in the intermediate pressure region.

The second condition is that the refrigerant temperature DT discharged from the second rotary compression element 14 has risen above a temperature DT0 that is slightly lower than a limit temperature (for example, + 100 ° C.) that enables proper operation of the two-stage compressor 11. Is the case.
In this case, the control means C controls to increase the valve opening degree of the expansion valve 35, suppresses the temperature rise of the two-stage compressor 11, and prevents the two-stage compressor 11 from reaching the limit temperature. Yes. Take control. An example of DT0 is about + 95 ° C.

  The third condition is that the refrigerant temperature GCT passed through the gas cooler 30 detected by the gas cooler outlet temperature sensor 49 and the refrigerant flow passed through the first flow path 40A of the intermediate heat exchanger 40 detected by the unit outlet temperature sensor 50. This is a case where the temperature difference (GCT−LT) from the temperature LT is smaller than the predetermined value SP. When the control means C determines that the temperature difference (GCT-LT) is smaller than the predetermined value SP, the control means C acts in a direction to increase the valve opening of the expansion valve 35.

Here, the predetermined value SP is different depending on whether the high-pressure side pressure HP is in the supercritical region or the saturation region of the refrigerant. In the present embodiment, whether the high-pressure side pressure HP is in the supercritical region or the saturation region is determined by the outside air temperature T detected by the outside air temperature sensor 52. When the outside air temperature T is high, for example, at + 31 ° C. or higher, it is determined that the high pressure side pressure HP is in the supercritical region, and when the outside air temperature T is low, for example, below + 31 ° C., the high pressure side pressure HP is in the saturation region. It is judged that it is. If the supercritical region is determined, the predetermined value SP is set to be increased, and if the saturated region is determined, the predetermined value SP is set to be decreased. In the present embodiment, the predetermined value SP is 35 ° C. in the supercritical region and 20 ° C. in the saturation region.
Thereby, even when the high-pressure side pressure HP is in the saturation region, the intermediate heat exchanger 40 can reliably ensure the degree of superheat of the refrigerant returned to the two-stage compressor 11, and the two-stage compressor 11 can be avoided. Further, when the high-pressure side pressure HP is in the supercritical region, such a liquid back hardly occurs.

Next, adjustment control of the refrigerant amount of the refrigerant circuit 1 will be described.
A case of performing recovery control for recovering the refrigerant in the refrigerant circuit 1 will be described. The control means C determines whether or not the detected pressure of the unit outlet side pressure sensor 45 exceeds a predetermined recovery threshold value, or a predetermined recovery protection value in which the detected pressure of the unit outlet side pressure sensor 45 is lower than the previous recovery threshold value. And whether the rotational speed of the blower 42 is the maximum value is determined.
In the present embodiment, since the intermediate pressure (MP) of the refrigerant circuit 1 has an appropriate value of about 8 MPa as an example, the value is set as a recovery protection value, and the recovery threshold is set to about 9 MPa, for example. Moreover, the maximum value of the rotation speed of the air blower 42 is set to 800 rpm as an example. Moreover, it is good also as a condition that predetermined time passes, after the rotation speed of the air blower 42 becomes the maximum value.
Thereby, the control means C exceeds the recovery protection value of 8 MPa when the detected pressure of the unit outlet side pressure sensor 45 exceeds the recovery threshold value of 9 MPa, or even if the detected pressure is not more than the recovery threshold value, and When the rotational speed of the blower 42 is the maximum value of 800 rpm, it is determined that the high-pressure side pressure has abnormally increased due to the circulation of excess gas refrigerant in the refrigerant circuit 1, and the refrigerant recovery Perform the action.

In this refrigerant recovery operation, the control means C opens the recovery expansion valve 72 and the electromagnetic valve 78 with the electromagnetic valve 75 closed. Thereby, a part of the refrigerant cooled in the intermediate heat exchanger 40 and flowing in the refrigerant pipe 7 toward the showcase unit 80 flows into the refrigerant amount adjustment tank 60 via the first communication path 71. To do.
At this time, since the electromagnetic valve 78 is opened, the pressure in the refrigerant quantity adjustment tank 60 can be released to the outside of the tank via the third communication passage 77. For this reason, even when the refrigerant in the refrigerant circuit 1 is in a gas cycle operation in which the refrigerant in the refrigerant circuit 1 is not liquefied, such as when the outside air temperature becomes high, the pressure in the refrigerant amount adjustment tank 60 decreases. The refrigerant flowing in is liquefied and collected in the tank 60. That is, when the pressure in the refrigerant amount adjustment tank 60 drops below the supercritical pressure, the refrigerant changes from the gas region to the saturation region, and the liquid level can be secured.

As a result, the refrigerant in the refrigerant circuit 1 can be recovered quickly and efficiently in the refrigerant amount adjustment tank 60. Therefore, it is possible to eliminate the inconvenience of an abnormally high pressure due to the excess refrigerant on the high-pressure side in the refrigerant circuit 1, and it is possible to prevent the overload operation of the two-stage compressor 11 due to the high-pressure abnormality.
In particular, unlike the case where the upper part of the refrigerant amount adjusting tank 60 and the intermediate pressure region of the refrigerant circuit 1 are communicated with each other via the third communication passage 77, the low pressure side pressure is reduced. It is possible to avoid a decrease in cooling efficiency due to the increase.

  Further, in the present embodiment, even if the pressure on the high pressure side detected by the unit outlet side pressure sensor 45 is equal to or lower than the recovery threshold, the predetermined recovery protection value is exceeded, and the blower 42 that air-cools the gas cooler 30 is provided. When the rotational speed is the maximum value, the refrigerant recovery operation is performed, so that the operation state of the blower 42 is also taken into consideration, and the efficiency reduction due to the state in which the high pressure side of the refrigerant circuit 1 becomes abnormally high continues. It becomes possible to prevent.

Next, a case where the state is changed from the state in which the refrigerant recovery control is performed to the first holding control for holding the refrigerant amount in the refrigerant circuit 1 will be described.
The control means C determines whether or not the pressure on the high pressure side detected by the unit outlet side pressure sensor 45 has become a recovery protection value, which is 8 MPa or less in the present embodiment. The operation is terminated and the operation proceeds to the refrigerant holding operation. In this refrigerant holding operation, the control means C maintains the electromagnetic valve 75 in a closed state, closes the electromagnetic valve 78, and maintains the valve opening of the recovery expansion valve 72 at the valve opening in the previous refrigerant recovery operation. To do.

Next, the discharge control for discharging the refrigerant to the refrigerant circuit 1 will be described.
And the control means C, when the detection pressure of the unit outlet side pressure sensor 45 falls below a predetermined release threshold (in this embodiment, about 7 MPa) lower than the recovery protection value (in this case, about 8 MPa), or It is determined whether or not the detected pressure of the unit outlet side pressure sensor 45 is equal to or lower than the previous recovery protection value and the rotational speed of the blower 42 is equal to or lower than a predetermined specified value lower than the maximum value. In the present embodiment, the predetermined specified value is about 3/8 of the maximum value, that is, about 300 rpm when the maximum value is 800 rpm. Moreover, it is good also as a condition that predetermined time passes, after the rotation speed of the air blower 42 becomes below a predetermined regulation value.
As a result, the control means C, when the detected pressure of the unit outlet side pressure sensor 45 falls below the discharge threshold of 7 MPa, or the detected pressure becomes 8 MPa or less which is the recovery protection value, and the rotational speed of the blower 42 Is equal to or less than a predetermined specified value (300 rpm in this case), it is determined that the refrigerant in the refrigerant circuit 1 has become insufficient, and the refrigerant discharge operation is executed.

  In this refrigerant discharge operation, the control means C closes the recovery expansion valve 72 and the electromagnetic valve 78 and opens the electromagnetic valve 75 of the second valve device 74. Thereby, the liquid refrigerant accumulated in the refrigerant quantity adjustment tank 60 is discharged to the refrigerant circuit 1 through the second communication path 73 connected to the lower part of the tank 60. Therefore, unlike the case where the gas refrigerant is mixed from the upper part of the refrigerant quantity adjustment tank 60 and discharged to the refrigerant circuit 1, the refrigerant in the refrigerant quantity adjustment tank 60 can be quickly released to the refrigerant circuit 1. As a result, the refrigeration apparatus R can be operated with high efficiency.

Next, a case will be described in which the state is shifted from the state in which the refrigerant discharge control is performed to the second holding control in which the refrigerant amount in the refrigerant circuit 1 is held.
The control means C determines whether or not the pressure on the high pressure side detected by the unit outlet side pressure sensor 45 has reached the recovery protection value, which is 8 MPa or more in this embodiment. The operation is terminated and the operation proceeds to the refrigerant holding operation as described above. Thereafter, by repeatedly executing the recovery control-first holding control-release control-second holding control based on the high pressure side pressure of the refrigerant circuit 1, the refrigerant recovery / release can be controlled based on the high pressure side pressure, High pressure protection and overload operation can be prevented accurately. Thereby, the cooling capacity of the refrigeration apparatus R can be ensured, and the COP can be optimized.

In the refrigeration apparatus R having the split cycle as described above, when the refrigerant is discharged from the refrigerant quantity adjustment tank 60, it is expanded by the capillary tube 76 and then merged with the refrigerant after decompression flowing through the first split refrigerant pipe 65. Then, it flows into the intermediate heat exchanger 40 and heat exchange is performed with the refrigerant from the gas cooler.
The refrigerant discharged from the refrigerant amount adjustment tank 60 is reliably warmed by the intermediate heat exchanger 40 and returned to the intermediate pressure region. That is, the warmed refrigerant is joined to the intermediate pressure region from the intercooler 20 to the high-stage suction port 17 of the two-stage compressor 11 and then into the second rotary compression element 14 from the high-stage suction port 17. Inflow. Thus, since the refrigerant discharged from the refrigerant amount adjustment tank 60 and flowing into the second flow path 40B is warmed and then returned to the intermediate pressure region, the refrigerant in the intermediate pressure region may be in the liquid back state. It is suppressed.

Next, the startability improvement control of the two-stage compressor 11 will be described.
When restarting the two-stage compressor 11 after the operation of the two-stage compressor 11 is stopped, the control means C is from the start of the two-stage compressor 11 until it rises to a predetermined operating frequency. The electromagnetic valve 55 is opened to open the flow path of the bypass circuit 84. The predetermined operating frequency is an operating frequency at which the two-stage compressor 11 can perform effective torque control. In the present embodiment, the predetermined operating frequency is set to 35 Hz as an example.
As a result, the electromagnetic valve 55 is opened until the two-stage compressor 11 is started from the stopped state and rises to the predetermined operating frequency, whereby the intermediate pressure discharge pipe 61 is discharged from the low-stage discharge port 16. The refrigerant in the intermediate pressure region after being discharged through the intercooler 20 flows into the low pressure side region of the refrigerant circuit 1 via the bypass circuit 84. Thereby, the pressure in the intermediate pressure region and the low pressure side region of the refrigerant circuit 1 is equalized.

Therefore, at the time of starting from the start of the two-stage compressor 11 to the increase to the predetermined operating frequency, a predetermined torque cannot be ensured. During this time, the intermediate pressure region and the low pressure side region are equalized, so that the outside air Even in a situation where the intermediate pressure tends to increase due to the high temperature, the inconvenience that the intermediate pressure approaches a high pressure can be solved.
Therefore, it is possible to avoid a starting failure due to the pressure in the intermediate pressure region and the pressure in the high pressure region approaching while the torque shortage at the time of starting the two-stage compressor 11 occurs. In addition, highly efficient operation can be realized. The control means C closes the solenoid valve 55 and closes the flow path of the bypass circuit 84 after the detected operating frequency of the two-stage compressor 11 has risen to a predetermined operating frequency. Perform a normal refrigeration cycle.

  In the refrigeration apparatus R according to the present invention, the inlet is connected to the two-stage compressor 11 and the low-stage discharge port 16 of the two-stage compressor 11, and the outlet is connected to the high-stage suction port 17 of the two-stage compressor 11. The intercooler 20, the gas cooler whose inlet is connected to the high-stage discharge port 18 of the two-stage compressor 11, and the refrigerant that is connected to the outlet of the gas cooler 30 and flows through the gas cooler 30, passes through the gas cooler 30, And an intermediate heat exchanger 40 that is supercooled by the refrigerant depressurized via the expansion valve 35. Furthermore, the refrigeration apparatus R changes the target value ΔKa of the subcooling degree of the intermediate heat exchanger 40 according to the outside air temperature T, and the expansion valve 35 based on the changed target value ΔKa of the subcooling degree. The control means C which controls the valve opening degree of this is provided.

  Therefore, according to the refrigeration apparatus R, since the degree of supercooling in the intermediate heat exchanger 40 is controlled according to the target value ΔKa of the degree of supercooling changed according to the outside air temperature T, the intermediate heat exchanger 40 An unnecessary increase in the amount of refrigerant returned to the intermediate pressure region can be avoided. Furthermore, since it is not necessary to perform the cooling performance of the refrigeration apparatus with the refrigerant by operating and stopping the two-stage compressor 11, the refrigerating apparatus R such as the expansion valve 35 that operates in conjunction with the driving and stopping of the two-stage compressor 11 is used. The burden on each device can be reduced.

In addition, the control means C has a storage unit C1 that stores target value setting data in which the target value ΔKa of the degree of supercooling is uniquely associated with the value of the outside air temperature T.
For this reason, since the control means C can determine the target value ΔKa of the degree of supercooling corresponding to the outside air temperature T only by referring to its own storage unit C1 without accessing the outside, the control speed is improved.

  The target value setting data is configured such that the outside air temperature T and the target value ΔKa of the degree of supercooling are associated with each other in a proportional relationship in the main range within the outside air temperature fluctuation region. For this reason, the control means C automatically calculates the target value ΔKa simply by storing in the storage unit C1 of the control means C an expression showing the relationship between the value in the fluctuation region of the outside air temperature T and the target value ΔKa. can do.

Further, the control means C is used when the difference between the temperature of the refrigerant discharged from the high-stage discharge port 18 of the two-stage compressor 11 and the temperature of the refrigerant discharged from the outlet of the gas cooler 30 is equal to or less than a predetermined threshold value. The control for reducing the valve opening of the expansion valve 35 is prioritized.
Thereby, since the very cooled refrigerant | coolant is avoided from returning to an intermediate pressure area | region, it can suppress that a liquid back | bag progresses in an intermediate pressure area | region.
Carbon dioxide is used as the refrigerant. Carbon dioxide is easy to manage refrigerant without toxicity or flammability.

In the above embodiment, the two-stage compressor 11 employs a two-stage compression rotary compressor in which the first rotary compression element 13, the second rotary compression element 14, and the electric motor 19 are incorporated in the sealed container 12. However, in addition to this, it may be of a type in which the refrigerant can be taken out and introduced from the intermediate pressure section with two single-stage rotary compressors or other types of compressors.
The first split refrigerant pipe 65 has been described as connecting the refrigerant pipe 7 through which the refrigerant having passed through the intermediate heat exchanger 40 flows and one end of the second flow path 40B. However, the outlet of the gas cooler 30 and the intermediate heat exchanger are described. It is good also as what connects the high pressure refrigerant | coolant pipe | tube 64 between 40 and the 2nd flow path 40B.

Further, as shown in FIG. 4, the target value setting data includes the outside air temperature T and the supercooling so that the supercooling degree target value ΔKa also changes continuously with respect to the continuous change in the outside air temperature T. In the above description, the degree target value ΔKa is associated with each other. However, the target value setting data may be set as shown in FIG.
FIG. 5 is a diagram showing another example of the target value setting data.
In FIG. 5, the target value setting data is divided into a plurality of fluctuation ranges of the outside air temperature T, and a predetermined supercooling degree target value ΔKa is associated with each of the divided outside air temperature ranges.
For example, the target value ΔKa of the degree of supercooling is set to the minimum value A ₀ (about 0 to 5 ° C.) when the outside air temperature T is less than 20 ° C., and when the outside air temperature T is 20 ° C. or more and less than 40 ° C., When the outside air temperature T is 40 ° C or higher, the temperature is set to 20 ° C. By setting in this way, the target value ΔKa of the degree of supercooling does not fluctuate little by little, so the frequency of changing the valve opening degree of the expansion valve 35 can be reduced.

Moreover, although the case where the carbon dioxide was used was mentioned as an example as a refrigerant | coolant, the effect of this application can be acquired even if it uses another refrigerant | coolant.
Further, the first split refrigerant pipe 65 constituting the auxiliary refrigerant circuit is branched from the refrigerant pipe 7 so as to reach the second flow path 40B of the intermediate heat exchanger 40. However, the high pressure refrigerant pipe 64 is used. It may be configured to branch from to the second flow path 40B. That is, the first split refrigerant pipe 65 may be configured to branch from a predetermined portion of the high-pressure side refrigerant flow path that has passed through the gas cooler 30 to reach the second flow path 40B.

R refrigeration unit C control means C1 storage unit 11 two-stage compressor 15 low-stage suction port (first-stage refrigerant suction unit of the two-stage compressor)
16 Low-stage discharge port (first-stage refrigerant discharge section of a two-stage compressor)
17 High-stage inlet (second-stage refrigerant suction part of the two-stage compressor)
18 High-stage outlet (second-stage refrigerant discharge part of two-stage compressor)
20 Intercooler 30 Gas cooler 35 Expansion valve 40 Intermediate heat exchanger

Claims (4)

A two-stage compressor, an intercooler having an inlet connected to a first-stage refrigerant discharge portion of the two-stage compressor, and an outlet connected to a second-stage refrigerant suction portion of the two-stage compressor; and the two-stage compressor A gas cooler having an inlet connected to a second-stage refrigerant discharge portion of the compressor, and a refrigerant that is connected to an outlet of the gas cooler and flows in through the gas cooler is decompressed through an expansion valve after passing through the gas cooler. In a refrigeration apparatus comprising an intermediate heat exchanger that is supercooled by a refrigerant,
Control means for changing the target value of the degree of supercooling of the intermediate heat exchanger according to the outside air temperature, and controlling the valve opening degree of the expansion valve based on the changed target value of the degree of supercooling. A refrigeration apparatus comprising the refrigeration apparatus. The said control means has a memory | storage part which memorize | stores the target value setting data with which the target value of the said supercooling degree is matched with the value of the said outside temperature uniquely. Refrigeration equipment. The refrigeration apparatus according to claim 2, wherein the target value setting data is configured by associating a value in the outside air temperature fluctuation region and a target value of the supercooling degree in a proportional relationship. . The target value setting data is configured to divide the outside temperature fluctuation region into a plurality of ranges and associate a target value of a predetermined supercooling degree for each of the divided outside air temperature ranges. Item 3. The refrigeration apparatus according to Item 2.

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