JP7196187B2 - Outdoor unit of refrigerating cycle device, refrigerating cycle device, and air conditioner - Google Patents

Description

The present disclosure relates to an outdoor unit of a refrigeration cycle device, a refrigeration cycle device, and an air conditioner.

WO2016/135904 discloses a refrigeration device. This refrigeration system includes a heat source side unit and a user side unit (indoor unit) connected to the heat source side unit by piping. The heat source side unit includes a compressor, a condenser, and a subcooler. The utilization side unit includes an expansion valve and an evaporator. In this refrigeration system, the temperature efficiency of the supercooler is used to determine whether the amount of refrigerant charged in the refrigerant circuit is appropriate. Thermal efficiency is the degree of subcooling of the refrigerant at the outlet of the subcooler divided by the maximum temperature difference of the subcooler. According to this refrigeration system, it is possible to detect the shortage of refrigerant in the refrigerant circuit (see Patent Document 1).

International Publication No. 2016/135904 pamphlet

In the refrigeration system described in Patent Document 1, unless the amount of decrease in the amount of refrigerant becomes large to some extent, the shortage of refrigerant does not appear significantly in the degree of supercooling or the temperature efficiency, so there is a possibility that the shortage of refrigerant cannot be detected with high accuracy. In addition, in operating conditions such as during overload operation where supercooling cannot be achieved even if the amount of refrigerant is normal, the above-described refrigeration system can accurately detect a decrease in the amount of refrigerant due to a decrease in the degree of supercooling. There is a possibility that the detection accuracy will decrease.

The present disclosure has been made to solve such problems, and an object of the present disclosure is to provide an outdoor unit of a refrigeration cycle device capable of accurately detecting shortage of refrigerant enclosed in a refrigerant circuit, and a refrigeration cycle including the same. It is to provide an apparatus as well as an air conditioner.

The outdoor unit of the present disclosure is an outdoor unit of a refrigeration cycle device, and includes a compressor that compresses a refrigerant, a condenser that condenses the refrigerant output from the compressor, a bypass circuit, a control device, and a gas-liquid separation. and a mechanism. The bypass circuit is branched from the outlet pipe of the condenser, and is configured to return part of the refrigerant flowing through the pipe to the compressor without passing through the indoor unit. The bypass circuit includes a detection circuit for detecting shortage of refrigerant enclosed in the refrigeration cycle device. The sensing circuit includes a flow rate adjusting section configured to adjust the flow rate of refrigerant flowing through the bypass circuit, and a heating section configured to heat the refrigerant that has passed through the flow rate adjusting section. The control device determines that the refrigerant enclosed in the refrigeration cycle device is insufficient when the refrigerant that has passed through the heating unit is superheated. The gas-liquid separation mechanism is configured to separate the gas refrigerant from the gas-liquid two-phase refrigerant and flow it into the bypass circuit when the gas-liquid two-phase refrigerant flows through the pipe at the branching portion where the bypass circuit branches from the pipe. be done.

In this outdoor unit, unless there is a shortage of refrigerant, the refrigerant flowing through the heating unit is in a gas-liquid two-phase state, so the refrigerant that has passed through the heating unit is less likely to be superheated. On the other hand, when there is a shortage of refrigerant, the refrigerant flowing through the heating unit evaporates and becomes a gas refrigerant (gas single-phase state), so the refrigerant passing through the heating unit is superheated. Therefore, in this outdoor unit, when the refrigerant that has passed through the heating unit is superheated, it is determined that the refrigerant is insufficient.

When the refrigerant is insufficient, condensation of the refrigerant does not progress in the condenser, and the refrigerant enters a gas-liquid two-phase state on the outlet side of the condenser. In this case, if the liquid refrigerant flows into the bypass circuit, even if the refrigerant passes through the heating unit, it may not evaporate completely, and the refrigerant that has passed through the heating unit may not be superheated. Therefore, in this outdoor unit, a gas-liquid separation mechanism is provided at the branch where the bypass circuit branches, and when there is a shortage of refrigerant, the gas refrigerant separated from the gas-liquid two-phase refrigerant flows into the bypass circuit. . As a result, when there is a shortage of refrigerant, gas refrigerant or extremely dry refrigerant flows into the bypass circuit, so that the refrigerant that has passed through the heating unit can be reliably superheated. Therefore, according to this outdoor unit, it is possible to suppress erroneous detection that a refrigerant shortage does not occur even though a refrigerant shortage has occurred.

If there is no shortage of refrigerant, the output side of the condenser will be liquid refrigerant, and the liquid refrigerant will flow into the bypass circuit, so it is possible that the degree of superheat will occur due to the evaporation of all the refrigerant that has passed through the heating unit. sex is low.

According to the outdoor unit, the refrigeration cycle device, and the air conditioner of the present disclosure, it is possible to accurately detect the shortage of the refrigerant enclosed in the refrigerant circuit.

1 is an overall configuration diagram of a refrigeration system using an outdoor unit according to Embodiment 1 of the present disclosure; FIG. FIG. 4 is a ph diagram showing the relationship between refrigerant pressure and enthalpy in normal times when refrigerant shortage does not occur. FIG. 4 is a ph diagram showing the state of refrigerant when there is a shortage of refrigerant; 2 is a diagram showing an example of the configuration of a gas-liquid separation mechanism according to Embodiment 1; FIG. FIG. 2 is a flow chart showing an example of a refrigerant shortage determination processing procedure executed by the control device shown in FIG. 1 ; FIG. FIG. 7 is a diagram showing an example of the configuration of a gas-liquid separation mechanism according to Embodiment 2; FIG. 10 is a diagram showing an example of the configuration of a gas-liquid separation mechanism according to Embodiment 3; FIG. 10 is a diagram showing an example of the configuration of a gas-liquid separation mechanism according to Embodiment 4; It is a figure which shows the other structure of a gas-liquid separation mechanism. It is a figure which shows the structure of the outdoor unit in a modification. 1 is an overall configuration diagram of an air conditioner provided with a refrigeration cycle in which an outdoor unit of the present disclosure is used; FIG.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

Embodiment 1.
FIG. 1 is an overall configuration diagram of a refrigeration system using an outdoor unit according to Embodiment 1 of the present disclosure. It should be noted that FIG. 1 functionally shows the connection relationship and arrangement configuration of each device in the refrigeration system, and does not necessarily show the arrangement in a physical space.

Referring to FIG. 1 , refrigerating apparatus 1 includes an outdoor unit 2 and an indoor unit 3 . The outdoor unit 2 includes a compressor 10, a condenser 20, a fan 22, and pipes 80,83,85. Outdoor unit 2 further includes pipes 86 and 87 , refrigerant shortage detection circuit 70 , pressure sensor 90 , and control device 100 . Indoor unit 3 includes an expansion valve 50 , an evaporator 60 , a fan 62 , and piping 84 . The indoor unit 3 is connected to the outdoor unit 2 through pipes 83 and 85 .

A pipe 80 connects the discharge port of the compressor 10 and the condenser 20 . A pipe 83 connects the condenser 20 and the expansion valve 50 . A pipe 84 connects the expansion valve 50 and the evaporator 60 . A pipe 85 connects the evaporator 60 and the suction port of the compressor 10 . A pipe 86 branches from a branch portion 88 of the pipe 83 and connects the pipe 83 and the refrigerant shortage detection circuit 70 . A pipe 87 connects the refrigerant shortage detection circuit 70 and the pipe 85 .

Compressor 10 compresses the refrigerant sucked from pipe 85 and outputs the compressed refrigerant to pipe 80 . Compressor 10 is configured to adjust the rotation speed according to a control signal from control device 100 . By adjusting the rotation speed of the compressor 10, the circulation amount of the refrigerant is adjusted, and the capacity of the refrigeration system 1 can be adjusted. Various types can be adopted for the compressor 10, for example, a scroll type, a rotary type, a screw type, and the like can be adopted.

The condenser 20 condenses the refrigerant output from the compressor 10 to the pipe 80 and outputs the condensed refrigerant to the pipe 83 . Condenser 20 is configured such that the high-temperature, high-pressure gas refrigerant output from compressor 10 exchanges heat (radiates heat) with the outside air. This heat exchange causes the refrigerant to condense and change to a liquid phase. The fan 22 supplies outside air to the condenser 20 with which the refrigerant exchanges heat in the condenser 20 . By adjusting the rotational speed of the fan 22, the refrigerant pressure (high-pressure side pressure) on the output side of the compressor 10 can be adjusted.

The expansion valve 50 decompresses the refrigerant output from the condenser 20 to the pipe 83 and outputs it to the pipe 84 . When the opening degree of the expansion valve 50 is changed in the closing direction, the pressure of the refrigerant on the outlet side of the expansion valve 50 decreases and the dryness of the refrigerant increases. When the opening degree of the expansion valve 50 is changed in the opening direction, the refrigerant pressure on the outlet side of the expansion valve 50 increases and the dryness of the refrigerant decreases.

The evaporator 60 evaporates the refrigerant output from the expansion valve 50 to the pipe 84 and outputs it to the pipe 85 . The evaporator 60 is configured such that the refrigerant decompressed by the expansion valve 50 exchanges heat (absorbs heat) with the air in the indoor unit 3 . The refrigerant passes through the evaporator 60 and evaporates into superheated vapor. Fan 62 supplies outside air to evaporator 60 with which the refrigerant exchanges heat in evaporator 60 .

Refrigerant shortage detection circuit 70 is provided between pipe 86 branching from pipe 83 and pipe 87 connected to pipe 85 . The pipe 86 , the refrigerant shortage detection circuit 70 , and the pipe 87 constitute a “bypass circuit” that returns part of the refrigerant on the outlet side of the condenser 20 to the compressor 10 without passing through the indoor unit 3 .

Refrigerant shortage detection circuit 70 includes capillary tube 71 , heater 72 , temperature sensor 73 , and solenoid valve 74 . The capillary tube 71 is connected between the pipe 86 and the pipe 87 and adjusts the flow rate of the refrigerant flowing through the bypass circuit. As the refrigerant passes through the capillary tube 71, the pressure of the refrigerant decreases. As a result, when liquid refrigerant is supplied from the pipe 86 (when the amount of refrigerant is normal), the refrigerant that has passed through the capillary tube 71 is in a gas-liquid two-phase state with low dryness. On the other hand, when a gas-liquid two-phase refrigerant is supplied from the pipe 86 (at the time of refrigerant shortage), the refrigerant that has passed through the capillary tube 71 is in a gas-liquid two-phase state with a high degree of dryness.

A heater 72 and a temperature sensor 73 are provided in the pipe 87 . The heater 72 heats the coolant that has passed through the capillary tube 71 . The refrigerant is heated by the heater 72 and the enthalpy increases. The heater 72 basically heats the refrigerant from the outside of the pipe 87, but may be installed inside the pipe 87 in order to more reliably transfer heat from the heater 72 to the refrigerant.

The temperature sensor 73 detects the temperature T of the refrigerant flowing through the pipe 87 downstream of the heating portion by the heater 72 and outputs the detected value to the control device 100 . The temperature sensor 73 is also installed outside the pipe 87, but may be installed inside the pipe 87 in order to more reliably detect the temperature of the refrigerant. The principle and method of refrigerant shortage detection by the refrigerant shortage detection circuit 70 will be described later in detail.

The solenoid valve 74 is provided in the piping 86 upstream of the capillary tube 71 and opens and closes according to instructions from the control device 100 . When the electromagnetic valve 74 is opened, refrigerant flows through the bypass circuit, and the shortage of refrigerant can be detected by the refrigerant shortage detection circuit 70 . When the electromagnetic valve 74 is in the closed state, the flow of refrigerant in the bypass circuit is cut off, so refrigerant shortage detection cannot be executed. Note that the electromagnetic valve 74 may be provided in the piping 87 downstream of the capillary tube 71 .

Pressure sensor 90 detects refrigerant pressure (low pressure side pressure) LP on the suction side of compressor 10 and outputs the detected value to control device 100 . Since the pipe 87 of the bypass circuit is connected to the pipe 85 on the suction side of the compressor 10, if there is no pressure loss at the connection between the pipe 87 and the pipe 85, the pressure sensor 90 detects the pressure inside the pipe 87 of the bypass circuit. of refrigerant pressure can be detected.

The control device 100 includes a CPU (Central Processing Unit) 102, a memory 104 (ROM (Read Only Memory) and RAM (Random Access Memory)), an input/output buffer (not shown) for inputting and outputting various signals, and the like. Consists of The CPU 102 expands a program stored in the ROM into the RAM or the like and executes it. The program stored in the ROM is a program in which processing procedures of the control device 100 are described. The control device 100 controls each device in the outdoor unit 2 according to these programs. This control is not limited to processing by software, and processing by dedicated hardware (electronic circuit) is also possible.

<Explanation of refrigerant shortage detection>
A method of detecting a refrigerant shortage using the refrigerant shortage detection circuit 70 will be described below. Insufficient refrigerant occurs when the initial amount of refrigerant charged into the refrigerant circuit is insufficient, or refrigerant leakage occurs after the start of use.

FIG. 2 is a ph diagram showing the relationship between the pressure of the refrigerant and the enthalpy in normal times when there is no shortage of refrigerant. In the following description, when there is no shortage of refrigerant and the amount of refrigerant is within an appropriate range, the amount of refrigerant is referred to as "normal." Referring to FIG. 2, the vertical axis indicates pressure p, and the horizontal axis indicates specific enthalpy h (kJ/kg) (hereinafter simply referred to as "enthalpy").

A solid line S1 connecting points P11 to P14 (hereinafter referred to as "cycle 1") indicates the state of the refrigerant when the amount of refrigerant is normal. In cycle 1, point P14→point P11 indicates refrigerant compression in compressor 10 (isentropic change), and point P11→point P12 indicates isobaric cooling in condenser 20. FIG. Also, the point P12 → point P13 indicates the pressure reduction in the expansion valve 50 , and the point P13 → point P14 indicates the equal pressure heating in the evaporator 60 .

Points A1, B1, and C1 respectively indicate the state of the refrigerant at points A, B, and C on the bypass circuit shown in FIG. 1 when the amount of refrigerant is normal. A dotted line L11 connecting points A1 and B1 indicates pressure reduction by the capillary tube 71 of the refrigerant shortage detection circuit 70 . A dotted line L12 connecting points B1 and C1 indicates equal pressure heating by the heater 72 of the refrigerant shortage detection circuit 70 . Since the pipe 87 on the outlet side of the bypass circuit is connected to the pipe 85 on the outlet side of the evaporator 60, the pressure on the outlet side of the capillary tube 71 (the pressure at point B1) is the same as the pressure at the evaporator 60 (point P13 pressure). The refrigerant downstream of the heater 72 (point C1) is in a gas-liquid two-phase state, and the degree of superheat SH is zero.

FIG. 3 is a ph diagram showing the state of the refrigerant when the refrigerant is insufficient. Referring to FIG. 3, a solid line S2 connecting points P21 to P24 (hereinafter referred to as "cycle 2") indicates the state of refrigerant when the amount of refrigerant is insufficient. In cycle 2, point P24→point P21 indicates compression of the refrigerant in compressor 10 (isentropic change), and point P21→point P22 indicates isobaric cooling in condenser 20. FIG. Also, the point P22→point P23 indicates pressure reduction in the expansion valve 50, and the point P23→point P24 indicates isobaric heating in the evaporator 60. FIG.

As shown in the figure, when the refrigeration system 1 is operated with an insufficient amount of refrigerant, condensation of the refrigerant does not progress in the condenser 20, the degree of supercooling of the refrigerant decreases, and the refrigerant on the outlet side of the condenser 20 becomes a gas-liquid two-phase state (point p22). Points A2, B2, and C2 respectively indicate the states of the refrigerant at points A, B, and C on the bypass circuit shown in FIG. 1 when the amount of refrigerant is insufficient. A dotted line L21 connecting point A2 and point B2 indicates pressure reduction by capillary tube 71 of refrigerant shortage detection circuit 70 . A dotted line L22 connecting point B2 and point C2 indicates equal pressure heating by heater 72 of refrigerant shortage detection circuit 70 .

As will be described in detail later, in the outdoor unit 2 of the present disclosure, a gas-liquid separation mechanism is provided at a branching portion 88 ( FIG. 1 ) where the bypass circuit branches from the pipe 83 on the outlet side of the condenser 20, and a shortage of refrigerant is detected. If so, the gas refrigerant (gas-phase refrigerant) separated from the gas-liquid two-phase refrigerant output from the condenser 20 flows into the bypass circuit. As a result, when there is a shortage of refrigerant, gas refrigerant or extremely dry refrigerant flows into the bypass circuit (point A2). The refrigerant on the outlet side (point B2) of the capillary tube 71 is also gas refrigerant or refrigerant with extremely high dryness. Therefore, the refrigerant downstream of the heater 72 (point C2) is heated by the heater 72 and reliably becomes a gas refrigerant having a degree of superheat SH (SH>0).

In this way, when the amount of refrigerant is insufficient, the degree of superheat SH occurs in the refrigerant that has passed through the heating portion of the heater 72 in the refrigerant shortage detection circuit 70 provided in the bypass circuit. On the other hand, when the amount of refrigerant is normal, the degree of superheat SH does not occur in the refrigerant that has passed through the heating unit (SH=0). Therefore, in this refrigerating apparatus 1, it is determined whether or not there is a refrigerant shortage based on the degree of superheat SH of the refrigerant that has passed through the heating portion of the refrigerant shortage detection circuit 70. FIG.

According to the outdoor unit 2, when the refrigerant becomes a gas-liquid two-phase state on the outlet side of the condenser 20 due to a shortage of refrigerant, the refrigerant passing through the heating portion of the refrigerant shortage detection circuit 70 has a degree of superheat SH. Therefore, the lack of refrigerant can be detected immediately. Further, even in an operating state in which supercooling cannot be achieved even if the amount of refrigerant is normal, such as during overload operation, the shortage of refrigerant can be detected based on the degree of superheat SH.

The degree of superheat SH of the refrigerant that has passed through the heating portion of the refrigerant shortage detection circuit 70 can be calculated from the detection value of the temperature sensor 73 and the detection value of the pressure sensor 90 . That is, the detected value of the temperature sensor 73 indicates the temperature of the coolant heated by the heater 72 . Also, the detected value of the pressure sensor 90 indicates the pressure of the refrigerant in the heating portion by the heater 72 . From this refrigerant pressure, the evaporation temperature of the refrigerant in the heating section (saturation temperature of the refrigerant on the low-pressure side in the refrigeration system 1) can be calculated. By subtracting the evaporation temperature calculated from the detection value of the pressure sensor 90 from the detection value of the temperature sensor 73, the degree of superheat SH of the refrigerant heated by the heater 72 can be calculated.

<Configuration of gas-liquid separation mechanism>
As described above, in the outdoor unit 2, shortage of refrigerant is detected based on the degree of superheat SH of the refrigerant that has passed through the heating section of the shortage detection circuit 70 of refrigerant. Specifically, if the degree of superheat SH of the refrigerant that has passed through the heating unit is 0, the amount of refrigerant is normal, and if the degree of superheat of the refrigerant that has passed through the heating unit is (SH>0), the refrigerant is insufficient. is determined to occur.

Therefore, in order to accurately detect the refrigerant shortage, it is necessary to ensure that the refrigerant heated by the heater 72 has the degree of superheat SH when the refrigerant shortage occurs. When there is a shortage of refrigerant, condensation of the refrigerant does not progress in the condenser 20 and the refrigerant enters a gas-liquid two-phase state on the outlet side of the condenser 20 . In this case, if the liquid refrigerant (liquid-phase refrigerant) flows into the bypass circuit, even if the refrigerant is heated by the heater 72, it may not evaporate at all, and the degree of superheat SH may not occur in the refrigerant heated by the heater 72. be.

Therefore, in the outdoor unit 2 according to the first embodiment, the bypass circuit is configured to branch upward from the pipe 83 at the branch portion 88 (FIG. 1) where the bypass circuit branches from the pipe 83 (gas-liquid separation mechanism). With such a configuration, when there is a shortage of refrigerant, the gas refrigerant can be separated from the gas-liquid two-phase refrigerant on the outlet side of the condenser 20 and flowed to the bypass circuit. Since a gas refrigerant or a refrigerant having an extremely high degree of dryness flows into the bypass circuit, when the refrigerant is heated by the heater 72, the degree of superheat SH is surely generated in the refrigerant. As a result, it is possible to prevent erroneous detection that the amount of refrigerant is normal because the refrigerant heated by the heater 72 does not reach the degree of superheat SH even though there is a shortage of refrigerant.

FIG. 4 is a diagram showing an example of the configuration of the gas-liquid separation mechanism according to Embodiment 1. FIG. In the drawing, the direction of arrow U indicates the vertically upward direction, and the direction of arrow D indicates the vertically downward direction. Referring to FIG. 4, the outlet pipe 83 of the condenser 20 is arranged sideways with respect to the vertical direction at least in the vicinity of a branch portion 88 where the bypass circuit (pipe 86) branches. A pipe 86 is connected to the pipe 83 so that the bypass circuit branches vertically upward from the pipe 83 at the branch portion 88 .

With such a configuration, when the gas-liquid two-phase refrigerant 76 composed of the liquid refrigerant and the gas refrigerant is flowing through the pipe 83 due to a shortage of refrigerant, the liquid refrigerant having a large specific gravity is suppressed from flowing into the pipe 86 due to gravity. At the same time, a gaseous refrigerant having a low specific gravity can flow to the pipe 86 . The gas refrigerant flows to the pipe 86 because the pipe 87 on the bypass circuit output side is connected to the suction side of the compressor 10, that is, to the low pressure side of the refrigeration system 1. is because negative pressure is generated.

Depending on the flow velocity of the refrigerant, part of the liquid refrigerant may flow into the pipe 86 along with the gas refrigerant. can be made higher than the dryness of the refrigerant flowing through the pipe 83 upstream of the branch 88 .

When gas-liquid two-phase refrigerant is flowing in the pipe 83 due to insufficient refrigerant, in order to suppress the liquid refrigerant from flowing into the pipe 86, it is preferable to make the inner diameter d of the pipe 86 larger than the reference inner diameter d0. . Here, the reference inner diameter d0 is the inner diameter d when the gas-liquid two-phase refrigerant flows through the pipe 83 and the flow velocity of the gas refrigerant flowing from the pipe 83 into the pipe 86 becomes zero penetration flow velocity. Zero penetration is a phenomenon in which liquid refrigerant rises along the pipe wall when gas-liquid two-phase refrigerant flows upward in a pipe. It is the flow velocity of the refrigerant when the refrigerant starts to rise up the tube wall. The zero penetration flow velocity can be calculated using a known method from the inner diameter of the pipe, the density of the gas refrigerant, and the density of the liquid refrigerant. By making the inner diameter d of the pipe 86 larger than the reference inner diameter d0, the flow velocity of the gas refrigerant flowing into the pipe 86 becomes lower than the zero penetration flow velocity, so that the liquid refrigerant can be suppressed from flowing into the pipe 86. .

By providing such a gas-liquid separation mechanism, when there is a shortage of refrigerant, gas refrigerant or extremely dry refrigerant flows into the bypass circuit. Superheat can be generated.

On the other hand, when the amount of refrigerant is normal, the liquid refrigerant that has been cooled to a supercooled state flows through the pipe 83. Therefore, even if the gas-liquid separation mechanism as described above is provided, the bypass circuit has no liquid refrigerant. flows in. Therefore, even if the refrigerant is heated by the heater 72 in the refrigerant shortage detection circuit 70, the refrigerant does not evaporate completely, and the refrigerant that has passed through the heating section is not superheated.

In the above description, the pipe 86 forming the bypass pipe branches vertically upward from the pipe 83, but the branching direction of the pipe 86 does not necessarily have to be the vertical direction. The branching direction of the pipe 86 may be upward to the extent that it is possible to suppress the liquid refrigerant having a large specific gravity from flowing into the pipe 86 due to gravity. By making the branching direction of the pipe 86 vertically upward, the gas refrigerant can be most effectively separated from the gas-liquid two-phase refrigerant using gravity.

FIG. 5 is a flowchart showing an example of a refrigerant shortage determination processing procedure executed by the control device 100 shown in FIG. A series of processes shown in this flowchart are repeatedly executed while the refrigeration system 1 is in steady operation.

Referring to FIG. 5, control device 100 determines whether or not it is time to execute refrigerant shortage determination control (step S10). The refrigerant shortage determination control is executed, for example, once a day. When it is determined that it is not time to execute refrigerant shortage determination control (NO in step S10), control device 100 shifts the process to RETURN without executing the subsequent series of processes. A series of processes after step S20 shown in the flowchart may be started when it is time to execute the refrigerant shortage determination control without providing such determination processing in the flowchart.

When it is determined in step S10 that it is time to execute refrigerant shortage determination control (YES in step S10), control device 100 turns on (opens) electromagnetic valve 74 (step S20), and turns on heater 72. (operation) (step S30).

Next, when a predetermined period of time sufficient for the heating of the refrigerant by heater 72 to reach a steady state has elapsed (YES in step S40), control device 100 acquires the detected value of temperature T from temperature sensor 73. At the same time, the detected value of the pressure LP is obtained from the pressure sensor 90 (step S50).

Then, the control device 100 calculates the degree of superheat SH of the refrigerant that has passed through the heating unit using the acquired detection values of the temperature T and the pressure LP (step S60). Specifically, the relationship between the refrigerant pressure and the evaporation temperature (saturation temperature) is stored in advance in the ROM of the memory 104 as a map, table, or the like. The evaporation temperature of the refrigerant in the heating unit is calculated from the detected value of the pressure LP that indicates the pressure of the refrigerant in . Then, the control device 100 calculates the degree of superheat SH of the refrigerant heated by the heater 72 by subtracting the calculated evaporation temperature from the temperature T obtained in step S50.

When degree of superheat SH of the refrigerant downstream of heater 72 is calculated, control device 100 determines whether or not degree of superheat SH is higher than threshold value SHth (step S70). The threshold value SHth is for determining whether or not the refrigerant heated by the heater 72 has the degree of superheat SH, and is appropriately set based on the calculation accuracy of the degree of superheat SH.

Then, when it is determined in step S70 that degree of superheat SH is higher than threshold value SHth (YES in step S70), control device 100 determines that the amount of refrigerant is insufficient (step S80), An alarm indicating that there is a shortage of refrigerant is output (step S90). Thereafter, the control device 100 turns off (stops) the heater 72 (step S100) and turns off (closes) the solenoid valve 74 (step S110). After that, the control device 100 shifts the process to return, and ends the refrigerant shortage determination process.

If it is determined in step S70 that degree of superheat SH is equal to or less than threshold value SHth (NO in step S70), control device 100 proceeds to step S100 without executing steps S80 and S90. , the heater 72 is turned off (stopped) and the electromagnetic valve 74 is turned off (closed). That is, in this case, it is determined that the amount of refrigerant is normal.

As described above, in the first embodiment, it is determined whether or not there is a refrigerant shortage based on the degree of superheat SH of the refrigerant heated by the heater 72 of the refrigerant shortage detection circuit 70 . As a result, when a refrigerant shortage occurs and the refrigerant enters a gas-liquid two-phase state on the outlet side of the condenser 20, the degree of superheat SH is generated, so that the shortage of refrigerant can be detected immediately. Further, even in an operating state in which supercooling cannot be achieved even if the amount of refrigerant is normal, such as during overload operation, the shortage of refrigerant can be detected based on the degree of superheat SH.

In the first embodiment, the bypass circuit (pipe 86) is configured to branch upward from the pipe 83. As shown in FIG. As a result, when there is a shortage of refrigerant, the gas refrigerant can be separated from the gas-liquid two-phase refrigerant on the outlet side of the condenser 20 and flowed to the bypass circuit. Since gas refrigerant or extremely dry refrigerant flows into the bypass circuit, the refrigerant heated by the heater 72 reliably generates a degree of superheat SH. As a result, it is possible to prevent erroneous detection that the amount of refrigerant is normal due to the fact that the degree of superheat SH does not occur despite the shortage of refrigerant.

Embodiment 2.
The second embodiment differs from the first embodiment in the configuration of the gas-liquid separation mechanism.

FIG. 6 is a diagram showing an example of the configuration of the gas-liquid separation mechanism according to the second embodiment. As in FIG. 4, the arrow U direction indicates a vertically upward direction, and the arrow D direction indicates a vertically downward direction. Referring to FIG. 6, piping 83 on the outlet side of condenser 20 includes a first portion 110 and a second portion 112 . The first part 110 is arranged laterally with respect to the vertical direction. The second portion 112 is provided downstream of the first portion 110 and is arranged to extend vertically downward from the branch portion 88 in the direction opposite to the piping 86 .

With such a configuration, when a gas-liquid two-phase refrigerant composed of a liquid refrigerant and a gas refrigerant flows through the pipe 83 due to a shortage of refrigerant, the liquid refrigerant having a large specific gravity easily flows to the second portion 112 due to gravity. . Thereby, gas-liquid separation is performed more effectively than the configuration shown in FIG. Therefore, the gas refrigerant can flow into the pipe 86 more significantly than in the first embodiment.

Also in this second embodiment, it is preferable to make the inner diameter d of the pipe 86 larger than the reference inner diameter d0. As a result, the flow velocity of the gas refrigerant flowing into the pipe 86 can be made lower than the zero penetration flow velocity, so that the flow of liquid refrigerant from the pipe 83 to the pipe 86 can be suppressed when there is a shortage of refrigerant. can be done.

Also in the second embodiment, when the amount of refrigerant is normal, the liquid refrigerant cooled to a supercooled state flows through the pipe 83, so the gas-liquid separation mechanism as described above is provided. Also, the liquid refrigerant flows into the bypass circuit. Therefore, even if the refrigerant is heated by the heater 72 in the refrigerant shortage detection circuit 70, the refrigerant will not evaporate completely, and the refrigerant that has passed through the heating section will not be superheated.

The configurations of the outdoor unit 2 according to the second embodiment and the refrigeration system 1 using the outdoor unit 2 are the same as those shown in FIG. 1 except for the configuration of the gas-liquid separation mechanism described above.

As described above, according to the second embodiment, when there is a shortage of refrigerant, the gas refrigerant can be more effectively separated from the gas-liquid two-phase refrigerant flowing through the pipe 83 and allowed to flow through the bypass circuit. . As a result, refrigerant shortage can be detected more stably without erroneous detection.

Embodiment 3.
The third embodiment further has a configuration in which the refrigerant flowing through the pipe 83 is caused to swirl at the branch portion 88 in the configuration of the gas-liquid separation mechanism in the second embodiment. As a result, when there is a shortage of refrigerant, gas-liquid separation is performed more effectively with the addition of centrifugal separation due to swirling flow, and the gas refrigerant can flow into the pipe 86 more remarkably.

FIG. 7 is a diagram showing an example of the configuration of the gas-liquid separation mechanism according to the third embodiment. FIG. 7 is a view of a branching portion 88 where a pipe 86 branches from a pipe 83 when viewed vertically from above. The configuration of the gas-liquid separation mechanism when viewing the branching portion 88 from the side is the same as that of the gas-liquid separation mechanism in the second embodiment shown in FIG.

Referring to FIG. 7, in the third embodiment, the center line O1 of the first portion 110 of the pipe 83 and the center line O2 of the second portion 112 of the pipe 83 are offset when the branch portion 88 is viewed from above. have. Therefore, when the refrigerant flows from the first portion 110 to the second portion 112 in the pipe 83, a swirling flow is generated around the center line O2.

As a result, when the gas-liquid two-phase refrigerant on the outlet side of the condenser 20 flows from the first portion 110 into the second portion 112 due to a lack of refrigerant, the liquid refrigerant with a high specific gravity moves into the second portion 112 due to centrifugal force. Flowing along the inner wall, the gaseous refrigerant gathers in the center of the pipe. In this manner, the gas refrigerant can be more effectively separated from the gas-liquid two-phase refrigerant by centrifugal separation due to swirling flow, and the separated gas refrigerant can flow into the pipe 86 .

According to the third embodiment, when there is a shortage of refrigerant, the gas refrigerant can be more effectively separated from the gas-liquid two-phase refrigerant flowing through the pipe 83 and allowed to flow through the bypass circuit. As a result, the refrigerant shortage can be detected more stably without erroneous detection.

Embodiment 4.
Even with the gas-liquid separation mechanism described in each of the above embodiments, part of the liquid refrigerant may become droplets and flow into the bypass circuit together with the gas refrigerant. Therefore, in the fourth embodiment, the pipe 86 is provided with a mesh-like member that captures droplets that have flowed into the bypass circuit together with the gas refrigerant from the branch portion 88 .

FIG. 8 is a diagram showing an example of the configuration of the gas-liquid separation mechanism according to the fourth embodiment. Referring to FIG. 8, this gas-liquid separation mechanism further includes mesh-like member 120 in the configuration of Embodiment 1 shown in FIG. The mesh-like member 120 is provided on the pipe 86 of the bypass circuit, and arranged at the rising portion of the pipe 86 from the branch portion 88 .

When gas-liquid two-phase refrigerant is flowing through the pipe 83 due to a lack of refrigerant, the mesh-like member 120 allows the gas refrigerant separated at the branching portion 88 to pass through the meshes of the mesh and unexpectedly fly from the branching portion 88. catch the incoming droplets. The mesh-like member 120 cannot capture all of the droplets flying from the branching portion 88, but can capture at least some of them. The trapped droplets form a mass and fall to the branch portion 88 as the amount of trapped droplets increases.

When the amount of refrigerant is normal and the liquid refrigerant flows from the pipe 83 to the pipe 86, the mesh member 120 allows the liquid refrigerant to pass through the eyes.

According to the fourth embodiment, by providing the mesh member 120, when the gas-liquid two-phase refrigerant is flowing through the pipe 83 due to a refrigerant shortage, the liquid refrigerant (droplets) is not detected in the refrigerant shortage detection circuit 70. It is possible to prevent the coolant that has flowed in and is heated by the heater 72 from having the degree of superheat SH.

In the above description, the configuration of the first embodiment shown in FIG. 4 is further provided with the mesh-like member 120. However, as shown in FIG. A mesh-like member 120 may be further provided in the configuration of Mode 3.

Other modifications.
In each of the above embodiments, the temperature sensor 73 is provided downstream of the heater 72, and the temperature T detected by the temperature sensor 73 and the evaporation temperature calculated from the pressure LP detected by the pressure sensor 90 are used to determine the degree of superheat. Although SH is calculated, a temperature sensor for detecting the evaporation temperature (low-pressure saturation temperature) is further provided between the capillary tube 71 and the heater 72, and the detected value of the temperature sensor is different from the detected value of the temperature sensor 73. The superheat SH may be measured by subtraction.

By providing such a temperature sensor, it is possible to improve the accuracy of measurement of the degree of superheat SH, and thus the accuracy of detection of refrigerant shortage. On the other hand, a refrigeration system is generally provided with a pressure sensor that detects the pressure on the suction side of the compressor. According to the above-described embodiments in which such a pressure sensor 90 is used to derive the degree of superheat SH, the existing pressure sensor 90 can be used without separately providing a temperature sensor between the capillary tube 71 and the heater 72. Refrigerant shortage detection can be performed.

Further, in each of the above embodiments, the bypass circuit is branched from the pipe 83 on the outlet side of the condenser 20, but as shown in FIG. If the exchanger 40 is further provided, a bypass circuit may be branched from the pipe 82 between the liquid reservoir 30 and the heat exchanger 40 .

A refrigeration system is generally provided with such a liquid reservoir and a heat exchanger in many cases. If the amount of refrigerant is normal, the liquid refrigerant is stored in the liquid reservoir 30, and the liquid refrigerant flows through the pipe 82 and the pipe 86 of the bypass circuit. On the other hand, when a refrigerant shortage occurs, the liquid refrigerant is no longer stored in the liquid reservoir 30, so that the gas-liquid two-phase or single gas-phase refrigerant flows through the pipe 86 of the bypass circuit. Therefore, even with such a configuration, the refrigerant shortage can be detected by the refrigerant shortage detection circuit 70 provided in the bypass circuit.

Further, in each of the above-described embodiments and modifications, the outdoor unit and the refrigeration apparatus mainly used in warehouses, showcases, etc. have been described as representatives. , the air conditioner 200 using a refrigeration cycle.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the description of the above-described embodiments, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

REFERENCE SIGNS LIST 1 refrigerating device 2 outdoor unit 3 indoor unit 10 compressor 20 condenser 22, 42, 62 fan 30 liquid reservoir 40 heat exchanger 50 expansion valve 60 evaporator 70 refrigerant shortage detection circuit , 71 capillary tube, 72 heater, 73 temperature sensor, 74 solenoid valve, 80 to 87 piping, 88 branching part, 90 pressure sensor, 100 control device, 102 CPU, 104 memory, 110 first part, 112 second part, 120 Mesh member, 200 Air conditioner.

Claims (6)

An outdoor unit of a refrigeration cycle device,
a compressor that compresses a refrigerant;
a condenser that condenses the refrigerant output from the compressor;
a bypass circuit branched from a pipe on the outlet side of the condenser and configured to return part of the refrigerant flowing through the pipe to the compressor without passing through the indoor unit;
The bypass circuit includes a detection circuit for detecting a shortage of refrigerant enclosed in the refrigeration cycle device,
The detection circuit is
a flow rate adjusting unit configured to adjust the flow rate of the refrigerant flowing through the bypass circuit;
a heating unit configured to heat the refrigerant that has passed through the flow rate adjusting unit; and
a control device that determines that the refrigerant enclosed in the refrigeration cycle device is insufficient when the refrigerant that has passed through the heating unit is superheated;
In a branching portion where the bypass circuit branches from the pipe, when the gas-liquid two-phase refrigerant flows in the pipe, the gas refrigerant is separated from the gas-liquid two-phase refrigerant and flowed to the bypass circuit. and a liquid separation mechanism,
In the gas-liquid separation mechanism, the bypass circuit is configured to branch upward from the pipe,
The outdoor unit of the refrigeration cycle apparatus, wherein the inner diameter of the bypass circuit is larger than a reference inner diameter indicating the inner diameter when the gas refrigerant flowing from the pipe into the bypass circuit has a zero penetration flow velocity. 2. The outdoor unit of the refrigeration cycle apparatus according to claim 1 , wherein in said gas-liquid separation mechanism, said pipe is arranged downward from said branch portion. An outdoor unit of a refrigeration cycle device,
a compressor that compresses a refrigerant;
a condenser that condenses the refrigerant output from the compressor;
a bypass circuit branched from a pipe on the outlet side of the condenser and configured to return part of the refrigerant flowing through the pipe to the compressor without passing through the indoor unit;
The bypass circuit includes a detection circuit for detecting a shortage of refrigerant enclosed in the refrigeration cycle device,
The detection circuit is
a flow rate adjusting unit configured to adjust the flow rate of the refrigerant flowing through the bypass circuit;
a heating unit configured to heat the refrigerant that has passed through the flow rate adjusting unit; and
a control device that determines that the refrigerant enclosed in the refrigeration cycle device is insufficient when the refrigerant that has passed through the heating unit is superheated;
In a branching portion where the bypass circuit branches from the pipe, when the gas-liquid two-phase refrigerant flows in the pipe, the gas refrigerant is separated from the gas-liquid two-phase refrigerant and flowed to the bypass circuit. and a liquid separation mechanism,
In the gas-liquid separation mechanism, the bypass circuit is configured to branch upward from the pipe,
In the gas-liquid separation mechanism, the pipe is arranged downward from the branch,
The piping is
a first portion disposed laterally;
a second portion connected to the first portion and arranged downward from the branch portion;
The outdoor unit of the refrigeration cycle apparatus, wherein the centerline of the first portion is offset with respect to the centerline of the second portion. 4. The refrigeration cycle according to any one of claims 1 to 3 , wherein said gas-liquid separation mechanism includes a mesh-shaped member configured to capture liquid droplets that have flowed into said bypass circuit from said branch. Equipment outdoor unit. The outdoor unit according to any one of claims 1 to 4 ;
and an indoor unit connected to the outdoor unit. An air conditioner comprising the refrigeration cycle device according to claim 5 .

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