JPWO2019053880A1 - Refrigeration air conditioner - Google Patents

Abstract

The refrigerating and air-conditioning system is configured such that a compressor, a condenser, a decompression device, and an evaporator are connected by pipes, and the refrigerant circulates therein. An injection circuit that allows a part of the refrigerant flowing out of the exchanger to flow into the compressor, an inlet temperature sensor that detects an inlet temperature of the refrigerant flowing into the subcooling heat exchanger, and an outlet of the refrigerant that flows out of the subcooling heat exchanger An outlet temperature sensor for detecting the temperature, and a control device for determining whether the amount of refrigerant flowing through the pipe is insufficient, the control device calculates an evaluation value based on the inlet temperature and the outlet temperature, an evaluation value calculation unit And a refrigerant amount determining unit that determines whether the refrigerant amount is insufficient based on a comparison result between the evaluation value and the set threshold.

Description

  TECHNICAL FIELD The present invention relates to a refrigeration / air-conditioning apparatus provided with a subcooling heat exchanger.

  2. Description of the Related Art Conventionally, in a refrigeration / air-conditioning apparatus, if the amount of refrigerant in the apparatus is excessive or deficient, it causes a decrease in capacity or damage to components. Therefore, it has been proposed to determine whether the amount of refrigerant charged in the refrigeration / air-conditioning apparatus is excessive or insufficient (for example, see Patent Document 1).

  Patent Literature 1 discloses a refrigeration / air-conditioning apparatus that calculates the temperature efficiency of a subcooling heat exchanger, estimates a refrigerant amount from the calculated temperature efficiency, and determines whether the refrigerant amount is excessive or insufficient. This refrigerating air conditioner measures the discharge pressure of the compressor by a pressure sensor provided on the discharge side of the compressor, and calculates the saturated gas temperature based on the measured discharge pressure. The refrigerating air conditioner calculates the temperature efficiency based on the calculated saturated gas temperature and the outside air temperature or the outlet temperature of the condenser. When the temperature efficiency is lower than the set threshold, the control device of the refrigeration / air-conditioning apparatus determines that the amount of the refrigerant is excessive or insufficient.

JP 2010-223542 A

  In the refrigeration and air-conditioning apparatus of Patent Document 1, the temperature efficiency of the subcooling heat exchanger is calculated based on the saturated gas temperature and the outside air temperature or the outlet temperature of the subcooling heat exchanger. In a refrigeration / air-conditioning system using a cooling device having a small pressure loss, such as a circular tube heat exchanger or a double tube coil, as a supercooling heat exchanger, it is not necessary to consider temperature fluctuation due to the pressure loss. Therefore, if a temperature change occurs, it can be said that the temperature change is caused by a refrigerant leak, so that an excess or deficiency of the refrigerant amount can be detected with the temperature efficiency described in Patent Document 1.

  However, when the temperature efficiency described in Patent Literature 1 is calculated in a refrigeration air conditioner using a cooling device having a large pressure loss such as a flat tube heat exchanger or a plate heat exchanger as a supercooling heat exchanger, the amount of supercooling is reduced. It is indistinguishable whether it is caused by pressure loss or refrigerant leakage. Therefore, it is difficult to detect the shortage of the refrigerant based on the temperature efficiency calculated as described in Patent Document 1.

  The present invention has been made in view of the above problems, and has as its object to provide a refrigeration / air-conditioning apparatus that can accurately determine a refrigerant amount without being affected by pressure loss.

  The refrigeration air conditioner of the present invention is a refrigeration air conditioner in which a compressor, a condenser, a decompression device, and an evaporator are connected by a pipe, and a refrigerant circulates through the pipe, between the condenser and the decompression device. A supercooling heat exchanger for supercooling the refrigerant flowing out of the condenser; and a refrigerant branched from the subcooling heat exchanger and the pressure reducing device and flowing out of the supercooling heat exchanger. An injection circuit for flowing a part into the compressor, an inlet temperature sensor for detecting an inlet temperature of the refrigerant flowing into the subcooling heat exchanger, and an outlet for detecting an outlet temperature of the refrigerant flowing out of the subcooling heat exchanger. A temperature sensor, and a control device for determining whether the amount of refrigerant flowing through the pipe is insufficient, the control device, based on the inlet temperature and the outlet temperature, the performance of the subcooling heat exchanger Show An evaluation value calculation unit for calculating a value, and has a refrigerant quantity determination unit that determines whether the amount of refrigerant is insufficient in accordance with the comparison result between the evaluation value and the preset threshold.

  According to the present invention, an evaluation value is calculated based on the inlet temperature and the outlet temperature of the subcooling heat exchanger, and it is determined whether the refrigerant amount is insufficient based on a comparison result between the evaluation value and the set threshold. Accordingly, the determination of the refrigerant amount can be accurately performed without being affected by the pressure loss.

FIG. 1 is a schematic diagram illustrating an example of a configuration of a refrigeration / air-conditioning apparatus according to Embodiment 1. FIG. 2 is a functional block diagram illustrating an example of a configuration of the control device in FIG. 1. FIG. 2 is a ph diagram when the proper amount of refrigerant is filled in the refrigeration / air-conditioning apparatus of FIG. 1. FIG. 2 is a ph diagram when the refrigerant amount of the refrigeration air conditioner of FIG. 1 is insufficient. 5 is a flowchart illustrating an example of a flow of a refrigerant amount determination process according to the first embodiment. FIG. 9 is a schematic diagram illustrating an example of a configuration of a refrigeration / air-conditioning apparatus according to Embodiment 2. FIG. 7 is a functional block diagram illustrating an example of a configuration of the control device in FIG. 6. FIG. 7 is a ph diagram when a pressure loss occurs in a condenser or a supercooling heat exchanger due to an excess or deficiency of a refrigerant amount in the refrigeration / air-conditioning apparatus of FIG. 13 is a flowchart illustrating an example of a flow of a refrigerant amount determination process in Embodiment 2.

Embodiment 1 FIG.
Hereinafter, a refrigeration / air-conditioning apparatus according to Embodiment 1 of the present invention will be described.
[Configuration of refrigeration / air-conditioning apparatus 100]
FIG. 1 is a schematic diagram illustrating an example of a configuration of a refrigeration / air-conditioning apparatus 100 according to Embodiment 1. As shown in FIG. 1, the refrigeration / air-conditioning apparatus 100 includes a heat source side unit 1 and a load side unit 2. In the refrigeration / air-conditioning apparatus 100, a refrigeration cycle is formed by connecting the heat source side unit 1 and the load side unit 2 with refrigerant pipes. Although one load-side unit 2 is provided in the example shown in FIG. 1, the present invention is not limited to this. For example, two or more load-side units 2 may be connected in parallel. When a plurality of load-side units 2 are provided, all of the load-side units 2 may have the same capacity or may have different capacities.

(Heat source side unit 1)
The heat source side unit 1 includes a compressor unit 1A, a condenser unit 1B, and a control device 3. The compressor unit 1A and the condenser unit 1B are connected by refrigerant pipes 10a and 10b. The notification device 4 is connected to the control device 3.

  The compressor unit 1A has a compressor 11, a receiver 13, a supercooling heat exchanger 14, and a flow control device 15. The condenser unit 1B has a condenser 12 and a fan 12a.

  The compressor 11 sucks low-temperature and low-pressure refrigerant, compresses the sucked refrigerant, and discharges the refrigerant at a high-temperature and high-pressure state. The compressor 11 is a scroll compressor, and is provided with an injection port at an intermediate pressure portion of a compression chamber. The injection port is connected to a bypass pipe 16 of the injection circuit 5 that is branched from the main circuit on the outlet side of the subcooling heat exchanger 14. In the example shown in FIG. 1, one compressor 11 is provided. However, the present invention is not limited to this. For example, two or more compressors 11 are connected in parallel according to the load of the load-side unit 2. May be.

  As the compressor 11, for example, an inverter compressor that can control a capacity that is a refrigerant delivery amount per unit time by changing a drive frequency is used. In this case, a compressor inverter board for changing the driving frequency is mounted on the heat source side unit 1, and the driving frequency of the compressor 11 is controlled by the control device 3.

  The condenser 12 is connected to the discharge side of the compressor 11 via the refrigerant pipe 10a, and performs heat exchange between a fluid such as air and the refrigerant. The condenser 12 radiates heat of the refrigerant to the fluid to condense the refrigerant. As the condenser 12, for example, a fin-and-tube heat exchanger having a heat transfer tube and a number of fins is used. In the condenser 12, the fluid that exchanges heat with the refrigerant is exemplified as air, but is not limited to this, and may be, for example, water, a refrigerant, or brine.

  The fan 12 a blows air to the condenser 12, and the rotation speed of the fan 12 a is controlled by the control device 3. The receiver 13 is connected to the outlet side of the condenser 12 of the condenser unit 1B via the refrigerant pipe 10b. The receiver 13 temporarily stores the refrigerant flowing out of the condenser 12 and separates the liquid refrigerant from the gas refrigerant.

  The supercooling heat exchanger 14 is connected to the condenser 12 via the refrigerant pipe 10b and the receiver 13, and supercools the refrigerant flowing out of the condenser 12. The supercooling heat exchanger 14 exchanges heat between the refrigerant flowing through the main circuit and the refrigerant flowing through the injection circuit 5 branched from the main circuit. As the supercooling heat exchanger 14, for example, a flat tube heat exchanger or a plate heat exchanger having a large pressure loss as compared with a circular tube heat exchanger is used.

  The flow rate adjusting device 15 adjusts the flow rate of the refrigerant branched from the outlet side of the subcooling heat exchanger 14 to the injection circuit 5 based on the control of the control device 3. As the flow control device 15, for example, an electronic expansion valve is used.

  Further, the heat source side unit 1 includes a discharge pressure sensor 41, a suction pressure sensor 42, an outside air temperature sensor 43, an inlet temperature sensor 44, an outlet temperature sensor 45, and an intermediate pressure sensor 46. The discharge pressure sensor 41 is provided on the discharge side of the compressor 11 and detects a discharge pressure value of the refrigerant discharged from the compressor 11. The suction pressure sensor 42 is provided on the suction side of the compressor 11 and detects a suction pressure value of the refrigerant drawn into the compressor 11. The outside air temperature sensor 43 detects the outside air temperature of the fluid sent to the condenser 12. The inlet temperature sensor 44 detects an inlet temperature Tin of the refrigerant flowing into the subcooling heat exchanger 14. The outlet temperature sensor 45 detects the outlet temperature Tout of the liquid refrigerant flowing out of the subcooling heat exchanger 14.

  The intermediate pressure sensor 46 is provided on the bypass pipe 16 forming the injection circuit 5, and detects an intermediate pressure of the refrigerant flowing into the injection port of the compressor 11. Note that the intermediate pressure sensor 46 is not necessarily provided. The intermediate pressure can be calculated using a known mathematical formula based on, for example, the discharge pressure value detected by the discharge pressure sensor 41 and the suction pressure value detected by the suction pressure sensor 42.

(Load side unit 2)
The load side unit 2 is connected to the compressor unit 1A of the heat source side unit 1 by refrigerant pipes 10c and 10d. The load side unit 2 has a pressure reducing device 21 and an evaporator 22.

  The decompression device 21 decompresses and expands the refrigerant supercooled by the subcooling heat exchanger 14, and adjusts the refrigerant flow rate. As the pressure reducing device 21, for example, an electronic expansion valve or a temperature expansion valve is used. In the example of FIG. 1, the pressure reducing device 21 is described as being provided in the load-side unit 2, but is not limited thereto, and may be provided in the heat-source-side unit 1.

  The evaporator 22 performs heat exchange between a fluid such as air and a refrigerant. The evaporator 22 absorbs and evaporates the refrigerant decompressed and expanded by the decompression device 21. As the evaporator 22, for example, a fin-and-tube heat exchanger having a heat transfer tube and a number of fins is used. In the evaporator 22, the fluid that exchanges heat with the refrigerant is mainly air, but is not limited thereto, and may be, for example, water, a refrigerant, or brine.

(Control device 3)
The control device 3 is configured by software executed on an arithmetic device such as a microcomputer, or hardware such as a circuit device such as an analog circuit or a digital circuit that realizes various functions. The control device 3 controls the operation of each component such as the compressor 11 based on the detection results of the various sensors.

  The control device 3 controls the driving frequency of the compressor 11 so that the evaporation temperature in the evaporator 22 becomes a target value. The control device 3 controls the rotation speed of the fan 12a such that the condensation temperature in the condenser 12 becomes a target value. The control device 3 adjusts the opening of the flow control device 15 based on the discharge temperature of the refrigerant converted from the discharge pressure of the compressor 11.

  Further, the control device 3 performs a refrigerant amount determination process of determining whether the refrigerant amount in the refrigeration cycle is insufficient based on the detection results of the various sensors. FIG. 2 is a functional block diagram showing an example of the configuration of the control device 3 of FIG. As illustrated in FIG. 2, the control device 3 includes an evaluation value calculation unit 31, a refrigerant amount determination unit 32, and an output control unit 33.

The evaluation value calculation unit 31 uses the equation (1) to perform supercooling heat exchange based on the inlet temperature Tin by the inlet temperature sensor 44, the outlet temperature Tout by the outlet temperature sensor 45, and the intermediate pressure Pm by the intermediate pressure sensor 46. The temperature efficiency of the vessel 14 is calculated as an evaluation value P. The evaluation value P is a value indicating the performance of the subcooling heat exchanger 14. The intermediate pressure saturation temperature in the equation (1) is obtained by converting the intermediate pressure Pm into a saturation temperature.
Evaluation value P = (Tin−Tout) / (Tin−intermediate pressure saturation temperature)
... (1)

The evaluation value P is not limited to this, and based on the inlet temperature Tin detected by the inlet temperature sensor 44, the outlet temperature Tout detected by the outlet temperature sensor 45, and the outside air temperature detected by the outside air temperature sensor 43, It can also be calculated using equation (2).
Evaluation value P = (Tin−Tout) / (Tin−outside air temperature) (2)

  When calculating the evaluation value P, each temperature used in the equation (1) or the equation (2) may be an instantaneous value detected at a certain point in time. The moving average of the evaluation value P may be obtained using a plurality of instantaneous values.

  The refrigerant amount determination unit 32 determines whether the refrigerant is insufficient based on the evaluation value P calculated by the evaluation value calculation unit 31. The refrigerant amount determination unit 32 compares the evaluation value P with the set threshold value Pref, and determines that the refrigerant amount is insufficient when the evaluation value P is smaller than the set threshold value Pref. The set threshold value Pref may be stored in advance, or may be input by an operator using an input unit (not shown) or the like. Further, the set threshold value Pref may be obtained by communication from outside such as a remote place.

  The output control unit 33 outputs information indicating the refrigerant shortage to the notification unit 4 when the refrigerant amount determination unit 32 determines that the refrigerant is short. The notification unit 4 performs notification indicating the refrigerant shortage based on the information indicating the refrigerant shortage output from the output control unit 33. As the notification unit 4, for example, an LED (Light Emitting Diode), a liquid crystal display, a speaker, or the like disposed on a substrate of the control device 3 is used.

  The output control unit 33 is not limited to this, and may communicate with an information output device provided outside, such as a remote place, and transmit information indicating a refrigerant shortage to the information output device by communication. Thus, it is possible to directly notify a service person or the like who manages the refrigeration / air-conditioning apparatus 100 at a remote place that the refrigerant is insufficient.

[Operation of refrigeration air conditioner 100]
FIG. 3 is a ph diagram when the refrigeration and air-conditioning apparatus 100 of FIG. 1 is filled with an appropriate amount of refrigerant. The operation of the refrigeration / air-conditioning apparatus 100 filled with an appropriate amount of refrigerant will be described with reference to FIGS.

  The low-temperature low-pressure refrigerant is compressed by the compressor 11 and discharged as a high-temperature high-pressure gas refrigerant (point A → point A1 → n → point B in FIG. 3). The high-temperature and high-pressure gas refrigerant discharged from the compressor 11 flows into the condenser 12 via the refrigerant pipe 10a. The high-temperature and high-pressure gas refrigerant flowing into the condenser 12 exchanges heat with the air taken in by the fan 12a, condenses, and flows out of the condenser 12 as a high-pressure liquid refrigerant (point B → point k).

  The high-pressure liquid refrigerant flowing out of the condenser 12 is separated into gas and liquid by the receiver 13 via the refrigerant pipe 10b, and then flows into the supercooling heat exchanger 14. The high-pressure liquid refrigerant flowing into the subcooling heat exchanger 14 exchanges heat with the refrigerant branched at the outlet side of the subcooling heat exchanger 14, is supercooled, and flows out of the subcooling heat exchanger 14 (point k → Point C). The high-pressure liquid refrigerant flowing out of the subcooling heat exchanger 14 branches off at the outlet side of the subcooling heat exchanger 14.

  The branched refrigerant flows into the pressure reducing device 21 via the refrigerant pipe 10c. The refrigerant flowing into the pressure reducing device 21 is decompressed by the pressure reducing device 21 to become a low-temperature low-pressure gas-liquid two-phase refrigerant, and flows into the evaporator 22 (point C → point D). The low-temperature and low-pressure gas-liquid two-phase refrigerant that has flowed into the evaporator 22 exchanges heat with air, absorbs heat and evaporates, and flows out of the evaporator 22 as a low-temperature and low-pressure gas refrigerant (point D → point A). The low-temperature low-pressure gas refrigerant flowing out of the evaporator 22 is sucked into the compressor 11 via the refrigerant pipe 10d.

  On the other hand, a part of the refrigerant branched on the outlet side of the supercooling heat exchanger 14 flows into the flow control device 15. The flow rate of the refrigerant flowing into the flow control device 15 is adjusted and the pressure is reduced, the heat is exchanged in the subcooling heat exchanger 14 to become an intermediate pressure refrigerant, and flows out of the subcooling heat exchanger 14 (point C → point). m). The intermediate-pressure refrigerant flowing out of the supercooling heat exchanger 14 flows into the injection port of the compressor 11 via the bypass pipe 16 of the injection circuit 5 (from point m to point n). The intermediate-pressure refrigerant that has flowed into the injection port lowers the refrigerant temperature on the discharge side of the compressor 11 that has a high pressure (point A1 → point n).

(Detection of refrigerant shortage)
FIG. 4 is a ph diagram when the refrigerant amount of the refrigeration / air-conditioning apparatus 100 of FIG. 1 is insufficient. When the refrigerant amount of the refrigeration / air-conditioning apparatus 100 is insufficient, the refrigerant flowing out of the condenser 12 is in a gas-liquid two-phase state (point k1). As a result, the enthalpy of the refrigerant flowing out of the subcooling heat exchanger 14 increases as compared with the case where the refrigerant amount is appropriate (point C1). Therefore, the degree of subcooling decreases, and the temperature efficiency of the subcooling heat exchanger 14 decreases.

  Here, it is conceivable to detect the shortage of the refrigerant based on the fluctuation of the degree of subcooling in the subcooling heat exchanger 14. However, the degree of supercooling fluctuates depending not only on the amount of the refrigerant but also on the operating conditions of the refrigeration / air-conditioning apparatus 100. Further, the degree of subcooling varies depending on the magnitude of the pressure loss in the subcooling heat exchanger 14. That is, the change in the degree of supercooling is not caused only by the change in the refrigerant amount. Therefore, it is difficult to detect the shortage of the refrigerant based on the degree of subcooling.

  On the other hand, the temperature efficiency of the subcooling heat exchanger 14 has less fluctuation due to operating conditions than the degree of subcooling. That is, it can be considered that the change in the temperature efficiency is caused by the change in the refrigerant amount. Therefore, in the first embodiment, the evaluation value P as the temperature efficiency of the subcooling heat exchanger 14 is calculated using Expression (1) or Expression (2), and the refrigerant amount is determined based on the calculated evaluation value P. Determine if there is a shortage. Thereby, even if the shortage of the refrigerant is small, the shortage of the refrigerant can be detected.

[Refrigerant amount determination processing]
FIG. 5 is a flowchart illustrating an example of the flow of the refrigerant amount determination process according to the first embodiment. With reference to FIG. 5, the refrigerant amount determination processing by the refrigeration and air-conditioning apparatus 100 will be described.

  In step S1, when the refrigeration / air-conditioning apparatus 100 is performing normal operation, the control device 3 performs control during normal operation based on detection results of various sensors. For example, the control device 3 calculates control values such as deviations of the condensing temperature and the evaporating temperature from target values based on the detection results of various sensors provided in each part of the refrigeration cycle. Then, the control device 3 controls the fan 12a, the flow rate adjusting device 15, and the pressure reducing device 21 based on the calculated control value.

  In step S2, the evaluation value calculation unit 31 calculates the evaluation value P based on Expression (1) or Expression (2). In step S3, the refrigerant amount determination unit 32 compares the evaluation value P calculated by the evaluation value calculation unit 31 with the set threshold Pref, and determines whether the evaluation value P is smaller than the set threshold Pref.

  When the evaluation value P is equal to or greater than the set threshold value Pref (Step S3; No), the refrigerant amount determination unit 32 determines that the refrigerant is not insufficient, and the process returns to Step S1. On the other hand, when the evaluation value P is smaller than the set threshold value Pref (Step S3; Yes), the refrigerant amount determination unit 32 determines that a refrigerant shortage has occurred. Then, in step S4, the output control unit 33 outputs information indicating the refrigerant shortage to the notification unit 4. Thereby, the notification means 4 notifies that the refrigerant is insufficient.

  Note that the refrigerant amount determination process is not limited to the normal operation, and is also applied to, for example, a refrigerant charging operation when the refrigeration / air-conditioning apparatus 100 is installed, or a case where the refrigerant is once discharged and refilled for maintenance. be able to. The refrigerant amount determination process is automatically performed during normal operation, but is not limited to this. For example, the refrigerant amount determination process may be performed by giving an instruction to the control device 3 to perform the refrigerant amount determination process from the outside.

  As described above, the refrigeration and air-conditioning apparatus 100 according to Embodiment 1 sets the inlet temperature Tin of the refrigerant flowing into the subcooling heat exchanger 14 and the outlet temperature Tout of the refrigerant flowing out of the subcooling heat exchanger 14. Based on this, an evaluation value P indicating the performance of the subcooling heat exchanger 14 is calculated. Then, the refrigeration / air-conditioning apparatus 100 determines whether the refrigerant amount is insufficient based on the comparison result between the evaluation value P and the set threshold value Pref. In particular, a heat exchanger having a large pressure loss, such as a flat tube heat exchanger or a plate heat exchanger, can be used as the condenser 12 or the supercooling heat exchanger 14. As a result, the evaluation value P corresponding to the refrigerant amount is calculated, so that the determination of the refrigerant amount can be accurately performed without being affected by the pressure loss.

  In addition, the refrigeration air conditioner 100 calculates the evaluation value P based on the inlet temperature Tin, the outlet temperature Tout, and the intermediate pressure saturation temperature obtained by converting the intermediate pressure Pm of the refrigerant flowing through the injection circuit 5 and flowing into the compressor 11. calculate. As a result, the evaluation value P, which is the temperature efficiency, is calculated according to the amount of the refrigerant, so that the determination of the amount of the refrigerant can be performed more accurately.

  Further, the refrigeration / air-conditioning apparatus 100 calculates the evaluation value P based on the inlet temperature Tin, the outlet temperature Tout, and the temperature of the fluid sent to the condenser 12. As a result, the evaluation value P, which is the temperature efficiency, is calculated according to the amount of the refrigerant, so that the determination of the amount of the refrigerant can be performed more accurately.

  Furthermore, the refrigeration / air-conditioning apparatus 100 includes a notifying unit 4 for notifying the shortage of the refrigerant when it is determined that the amount of the refrigerant flowing through the pipe is insufficient. Thereby, since the shortage of the refrigerant of the refrigeration / air-conditioning apparatus 100 is notified to the outside, the shortage of the refrigerant can be promptly notified to a service person or the like.

Embodiment 2 FIG.
Next, a refrigeration / air-conditioning apparatus according to Embodiment 2 of the present invention will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description will be omitted.

[Configuration of refrigeration / air-conditioning apparatus 200]
FIG. 6 is a schematic diagram illustrating an example of a configuration of a refrigeration and air-conditioning apparatus 200 according to Embodiment 2. As shown in FIG. 6, in the refrigeration / air-conditioning apparatus 200, the heat source side unit 1 includes a compressor unit 1C, a condenser unit 1D, and a control device 3. The compressor unit 1C has a pressure sensor 47 in addition to the configuration of the compressor unit 1A in the first embodiment. The condenser unit 1D has a temperature sensor 48 in addition to the configuration of the condenser unit 1B in the first embodiment.

  The pressure sensor 47 detects a supercooling pressure value of the refrigerant flowing out of the subcooling heat exchanger 14 and flowing into the pressure reducing device 21. The temperature sensor 48 is provided at an intermediate portion of the condenser 12 and detects a condenser intermediate temperature Tmid.

  FIG. 7 is a functional block diagram showing an example of the configuration of the control device 3 of FIG. As shown in FIG. 7, a discharge pressure sensor 41, a pressure sensor 47, an outlet temperature sensor 45, and a temperature sensor 48 are connected to the evaluation value calculation unit 31.

Based on the discharge pressure value detected by the discharge pressure sensor 41 and the supercooling pressure value detected by the pressure sensor 47, the evaluation value calculating unit 31 uses the equation (3) to calculate the condenser 12 or the supercooling heat exchange. The pressure loss in the vessel 14 is calculated as an evaluation value P.
Evaluation value P = Discharge pressure value-Supercooling pressure value (3)

In addition, the evaluation value calculation unit 31 uses the equation (4) to calculate the temperature of the condenser 12 or the temperature of the condenser 12 based on the outlet temperature Tout detected by the outlet temperature sensor 45 and the condenser intermediate temperature Tmid detected by the temperature sensor 48. The temperature difference due to the pressure loss in the cooling heat exchanger 14 is calculated as the evaluation value P.
Evaluation value P = Tmid-Tout (4)

  The refrigerant amount determination unit 32 determines whether the refrigerant is insufficient based on the evaluation value P calculated by the evaluation value calculation unit 31. The refrigerant amount determination unit 32 compares the evaluation value P with the set threshold value Pref, and determines that the refrigerant amount is insufficient when the evaluation value P is equal to or larger than the set threshold value Pref.

[Operation of refrigeration air conditioner 200]
FIG. 8 is a ph diagram when a pressure loss occurs in the condenser 12 or the supercooling heat exchanger 14 due to an excess or deficiency of the refrigerant amount in the refrigeration / air-conditioning apparatus 200 in FIG. The operation of the refrigeration / air-conditioning apparatus 200 when a pressure loss has occurred will be described with reference to FIGS.

  The low-temperature low-pressure refrigerant is compressed by the compressor 11 and discharged as a high-temperature high-pressure gas refrigerant (point A → point A1 → n → point B in FIG. 8). The high-temperature and high-pressure gas refrigerant discharged from the compressor 11 flows into the condenser 12 via the refrigerant pipe 10a. The high-temperature and high-pressure gas refrigerant flowing into the condenser 12 exchanges heat with the air taken in by the fan 12a, condenses, and flows out of the condenser 12 as a high-pressure liquid refrigerant.

  At this time, when a flat tube heat exchanger or a plate heat exchanger is used as the condenser 12 or the supercooling heat exchanger 14, the gas refrigerant flowing into the condenser 12 is caused by an insufficient refrigerant amount. As a result, a gas-liquid two-phase state is established. This also increases the pressure loss in the condenser 12. Therefore, the gas refrigerant flowing into the condenser 12 is depressurized by the pressure loss (point B → point k2). Therefore, a temperature difference due to pressure loss occurs between the inlet temperature of the condenser 12 and the outlet temperature of the subcooling heat exchanger 14.

  Therefore, in the second embodiment, the temperature difference between the inlet temperature of the condenser 12 and the outlet temperature of the subcooling heat exchanger 14 due to the pressure loss generated in the condenser 12 or the supercooling heat exchanger 14 or the pressure loss. It is determined whether or not the refrigerant amount is insufficient based on the above.

[Refrigerant amount determination processing]
FIG. 9 is a flowchart illustrating an example of a flow of a refrigerant amount determination process according to the second embodiment. With reference to FIG. 9, a refrigerant amount determination process performed by the refrigeration / air-conditioning apparatus 200 will be described. In the flowchart shown in FIG. 9, steps common to those in the flowchart of the first embodiment shown in FIG. 5 are denoted by the same reference numerals, and detailed description is omitted.

  In step S1, when the refrigeration / air-conditioning apparatus 200 is performing normal operation, the control device 3 performs control during normal operation based on detection results of various sensors. In step S12, the evaluation value calculation unit 31 calculates the evaluation value P based on Expression (3) or Expression (4).

  In step S13, the refrigerant amount determination unit 32 compares the evaluation value P calculated by the evaluation value calculation unit 31 with the set threshold value Pref, and determines whether the evaluation value P is equal to or larger than the set threshold value Pref.

  When the evaluation value P is smaller than the set threshold value Pref (Step S13; No), the refrigerant amount determination unit 32 determines that the refrigerant is not insufficient, and the process returns to Step S1. On the other hand, when the evaluation value P is equal to or larger than the set threshold value Pref (Step S13; Yes), the refrigerant amount determination unit 32 determines that a refrigerant shortage has occurred. Then, in step S4, the output control unit 33 outputs information indicating the refrigerant shortage to the notification unit 4. Thereby, the notification means 4 notifies that the refrigerant is insufficient.

  As described above, the refrigeration / air-conditioning apparatus 200 according to Embodiment 2 provides the condenser obtained by the difference between the discharge pressure value of the compressor 11 and the supercooling pressure value of the refrigerant flowing out of the supercooling heat exchanger 14. The pressure loss of 12 or the supercooling heat exchanger 14 is calculated as the evaluation value P. As a result, the evaluation value P, which is the pressure loss, is calculated according to the amount of the refrigerant, so that even if the pressure loss of the condenser 12 or the supercooling heat exchanger 14 is large, the refrigerant shortage can be accurately detected.

  In addition, the refrigeration / air-conditioning apparatus 200 calculates, as the evaluation value P, a temperature difference due to a pressure loss of the condenser 12 or the supercooling heat exchanger 14, which is obtained from a difference between the condenser intermediate temperature Tmid and the outlet temperature Tout. As a result, the evaluation value P, which is the temperature difference due to the pressure loss, is calculated according to the amount of the refrigerant, so that even when the pressure loss of the condenser 12 or the supercooling heat exchanger 14 is large, it is possible to accurately detect the refrigerant shortage. Can be.

Note that, as the refrigerant, a refrigerant having a low global warming potential (GWP) such as R410A, R32, or CO ₂ is used. The present invention is not limited to this, and a mixed refrigerant such as a non-azeotropic mixed refrigerant including at least one of the above-described refrigerants, or another type of refrigerant different from these refrigerants may be used.

Non-azeotropic mixed refrigerant, for example, R407C or R448A, R32, R125, R134a, a mixed refrigerant such as R1234yf and CO _2. The non-azeotropic refrigerant mixture, the proportion of R32 XR32, R125 proportion of XR125, the percentage of R134a XR134a proportion XCO ₂ percentage of R1234yf XR1234yf and CO ₂ are shown below (1) all of the conditions to (6) The refrigerant to be filled may be sufficient.
(1) 33 <XR32 [wt%] <39
(2) 27 <XR125 [wt%] <33
(3) 11 <XR134a [wt%] <17
(4) 11 <XR1234yf [wt%] <17
(5) 3 <XCO ₂ [wt%] <9
(6) The sum of XR32, XR125, XR134a, XR1234yf and XCO ₂ is 100

  Reference Signs List 1 heat source side unit, 1A, 1C compressor unit, 1B, 1D condenser unit, 2 load side unit, 3 control device, 4 notification means, 5 injection circuit, 10a, 10b, 10c, 10d refrigerant pipe, 11 compressor, REFERENCE SIGNS LIST 12 condenser, 12 a fan, 13 receiver, 14 supercooling heat exchanger, 15 flow control device, 16 bypass pipe, 21 decompression device, 22 evaporator, 31 evaluation value calculation unit, 32 refrigerant amount determination unit, 33 output control unit , 41 discharge pressure sensor, 42 suction pressure sensor, 43 outside air temperature sensor, 44 inlet temperature sensor, 45 outlet temperature sensor, 46 intermediate pressure sensor, 47 pressure sensor, 48 temperature sensor, 100, 200 refrigeration air conditioner.

The refrigerating air conditioner of the present invention is a refrigerating air conditioner in which a compressor, a condenser, a decompression device, and an evaporator are connected by piping, and a refrigerant circulates through the piping. A supercooling heat exchanger for supercooling the refrigerant flowing out of the condenser; and a refrigerant branched from the subcooling heat exchanger and the pressure reducing device and flowing out of the supercooling heat exchanger. An injection circuit for flowing a part into the compressor, an inlet temperature sensor for detecting an inlet temperature of the refrigerant flowing into the subcooling heat exchanger, and an outlet for detecting an outlet temperature of the refrigerant flowing out of the subcooling heat exchanger. A temperature sensor, a discharge pressure sensor for detecting a discharge pressure value of the refrigerant discharged from the compressor , and a pressure for detecting a supercooling pressure value of the refrigerant flowing out of the supercooling heat exchanger and flowing into the pressure reducing device. Sensor , And a determining controller whether the amount of coolant flowing through the pipe is insufficient, the control device, the condenser or the super obtained by difference between the supercooling pressure value and said discharge pressure value the pressure loss of the cooling heat exchanger, the evaluation value calculation unit which calculates as an evaluation value indicating the performance of the supercooling heat exchanger, or the amount of refrigerant according to a result of comparison between the evaluation value and the preset threshold is insufficient And a refrigerant amount judging unit for judging whether or not there is no refrigerant.

Claims (9)

A compressor, a condenser, a decompression device and an evaporator are connected by piping, and a refrigeration air conditioner in which a refrigerant circulates through the piping,
A supercooling heat exchanger that is provided between the condenser and the decompression device and supercools a refrigerant flowing out of the condenser.
An injection circuit that branches off from between the subcooling heat exchanger and the pressure reducing device and causes a part of the refrigerant flowing out of the subcooling heat exchanger to flow into the compressor;
An inlet temperature sensor for detecting an inlet temperature of the refrigerant flowing into the supercooling heat exchanger,
An outlet temperature sensor for detecting an outlet temperature of the refrigerant flowing out of the supercooling heat exchanger,
A control device for determining whether the amount of refrigerant flowing through the pipe is insufficient,
The control device includes:
An evaluation value calculation unit that calculates an evaluation value indicating the performance of the subcooling heat exchanger based on the inlet temperature and the outlet temperature,
A refrigeration / air-conditioning apparatus comprising: a refrigerant amount determination unit that determines whether a refrigerant amount is insufficient based on a comparison result between the evaluation value and a set threshold. Further comprising an intermediate pressure sensor that detects an intermediate pressure of the refrigerant flowing through the injection circuit and flowing into the compressor,
The evaluation value calculation unit,
The refrigeration air conditioner according to claim 1, wherein the evaluation value is calculated based on the inlet temperature, the outlet temperature, and an intermediate pressure saturation temperature obtained by converting the intermediate pressure. Further comprising an outside air temperature sensor for detecting the temperature of the fluid sent to the condenser,
The evaluation value calculation unit,
The refrigeration / air-conditioning apparatus according to claim 1, wherein the evaluation value is calculated based on the inlet temperature, the outlet temperature, and the temperature of the fluid. The refrigerant amount determination unit,
The refrigeration / air-conditioning apparatus according to any one of claims 1 to 3, wherein when the evaluation value is smaller than the set threshold, it is determined that the amount of refrigerant flowing through the pipe is insufficient. The condenser or the subcooling heat exchanger,
The refrigeration / air-conditioning apparatus according to claim 1, which is a flat tube heat exchanger or a plate heat exchanger. A discharge pressure sensor for detecting a discharge pressure value of the refrigerant discharged from the compressor,
A pressure sensor for detecting a supercooling pressure value of the refrigerant flowing out of the supercooling heat exchanger and flowing into the pressure reducing device,
The evaluation value calculation unit,
The refrigeration air conditioner according to claim 5, wherein a pressure loss of the condenser or the supercooling heat exchanger obtained from a difference between the discharge pressure value and the supercooling pressure value is calculated as the evaluation value. Further provided is a temperature sensor that is provided in an intermediate portion of the condenser and detects a condenser intermediate temperature,
The evaluation value calculation unit,
The refrigerating and air-conditioning apparatus according to claim 5, wherein a temperature difference due to a pressure loss of the condenser or the supercooling heat exchanger, which is obtained from a difference between the condenser intermediate temperature and the outlet temperature, is calculated as the evaluation value. The refrigerant amount determination unit,
The refrigeration / air-conditioning apparatus according to any one of claims 5 to 7, wherein when the evaluation value is equal to or greater than the set threshold, it is determined that the amount of refrigerant flowing through the pipe is insufficient. The refrigeration / air-conditioning apparatus according to any one of claims 1 to 8, further comprising a notification unit configured to notify a shortage of the refrigerant when it is determined that the amount of the refrigerant flowing through the pipe is insufficient.

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