Air conditioner, cooling unit, and refrigerant filling method

Abstract

In the present invention, during a cooling operation, a low-stage-side cycle (1) is formed in which a first refrigerant flows, in the given order, through: a first compressor (21); a first heat exchanger (22); a first expansion valve (24); a first piping (40a); a second heat exchanger (32); a second piping (40b); and the first compressor (21). An air conditioner (100) is configured so that a cooling unit (10) for cooling the first refrigerant can be connected to the air conditioner. The cooling unit (10) includes: a second compressor (11); a third heat exchanger (12); a second expansion valve (14); and a fourth heat exchanger (16). During the cooling operation, a high-stage-side cycle (2) is formed in which a second refrigerant flows, in the given order, through: the second compressor (11); the third heat exchanger (12); the second expansion valve (14); the fourth heat exchanger (16); and the second compressor (11). The fourth heat exchanger (16) performs heat exchange with the first refrigerant and the second refrigerant. The cooling unit (10) can be connected to the first piping (40a).

Description

Air conditioner, cooling unit, and refrigerant charging method

[0001] The present disclosure relates to an air conditioner, a cooling unit, and a refrigerant charging method.

[0002] A typical air conditioner consists of two components: an outdoor unit consisting of a compressor, an outdoor heat exchanger, a fan, and an expansion valve, and an indoor unit consisting of an indoor heat exchanger and a fan. The refrigeration cycle in a typical air conditioner is a single-stage refrigeration cycle, with a high-pressure condenser and a low-pressure evaporator. To meet the demand for air conditioners in regions with high outdoor temperatures, there is a demand for air conditioners that can maintain their performance even in these hot areas. When outdoor temperatures rise, the refrigerant condensation pressure increases to maintain the temperature difference between the refrigerant and the air, potentially causing the refrigerant pipes to burst. Therefore, in regions with high outdoor temperatures, where reliable thick-walled piping is not available, the system operates at a reduced capacity to prevent the refrigerant condensation pressure from increasing. Thus, in regions with high outdoor temperatures, where thick-walled piping is not available, the system operates at a reduced capacity to prevent the refrigerant condensation pressure from increasing. Thus, conventional single-stage refrigeration cycles can reduce their performance during cooling when thick-walled piping is not available.

[0003] In recent years, from the viewpoint of reducing environmental impact, there has been a demand for refrigerants with low GWP (Global Warming Potential) to be used in refrigeration cycles. ２ There are natural refrigerants such as R290 and CO ２ In Patent Document 1 (JP 2001-91074 A), a natural refrigerant (hydrocarbon-based refrigerant such as propane, or ammonia) is used as the refrigerant in the high-stage side circulation circuit, and a CO refrigerant is used as the refrigerant in the low-stage side circulation circuit. ２ A cascade type two-dimensional refrigeration circuit using the above method is disclosed.

[0004] Japanese Patent Application Laid-Open No. 2001-91074

[0005] The refrigeration device in Patent Document 1 (JP 2001-91074 A) is intended for refrigeration devices with evaporation temperatures of -30°C or lower, and is designed to provide stable CO ２However, when the refrigeration device of Patent Document 1 (JP 2001-91074 A) is applied to an air conditioner that mainly performs cooling operation with an evaporation temperature of about 0°C, the condensation pressure of the refrigerant may become high on the low-stage side.

[0006] An object of the present disclosure is to provide an air conditioner, a cooling unit, and a refrigerant charging method that enable stable cooling operation in areas where the outside air temperature is high.

[0007] An air conditioner according to the present disclosure includes an outdoor unit including a first compressor, a first heat exchanger, and a first expansion valve, an indoor unit including a second heat exchanger, and piping connecting the outdoor unit and the indoor unit and through which a refrigerant flows. The piping includes a first piping through which a first refrigerant in a first state flows and a second piping through which the first refrigerant in a second state flows. A first refrigerant circuit is configured in which the first refrigerant flows in the following order during cooling operation: the first compressor, the first heat exchanger, the first expansion valve, the first piping, the second heat exchanger, the second piping, and the first compressor. The air conditioner is configured to be connectable to a cooling unit that cools the first refrigerant. The cooling unit includes a second compressor, a third heat exchanger, a second expansion valve, and a fourth heat exchanger. A second refrigerant circuit is configured in which a second refrigerant flows in the following order during cooling operation: the second compressor, the third heat exchanger, the second expansion valve, the fourth heat exchanger, and the second compressor. The fourth heat exchanger exchanges heat between the first refrigerant and the second refrigerant. The cooling unit is connectable to the first pipe.

[0008] The present disclosure relates to a cooling unit connectable to a first refrigerant circuit through which a first refrigerant flows and constituting a second refrigerant circuit through which a second refrigerant flows. The cooling unit includes a second compressor, a third heat exchanger, a second expansion valve, a fourth heat exchanger, and the third expansion valve. The second refrigerant circuit is configured so that during cooling operation, the second refrigerant flows through the second compressor, the third heat exchanger, the second expansion valve, the fourth heat exchanger, and the second compressor in this order. The cooling unit also includes a third expansion valve located at a position through which the first refrigerant passes after flowing out of the fourth heat exchanger.

[0009] The refrigerant charging method according to the present disclosure includes the steps of connecting a cooling unit constituting a second refrigerant circuit to a first refrigerant circuit, and adding a first refrigerant corresponding to the volume of the fourth heat exchanger to the first refrigerant circuit after connecting the cooling unit.

[0010] According to the air conditioner, cooling unit, and refrigerant filling method disclosed herein, the configuration of the refrigerant circuit can be changed by connecting a cooling unit, making it possible to perform stable cooling operation even in areas where the outside air temperature is high.

[0011] It is a schematic diagram showing the configuration of an air conditioner in Embodiment 1. It is a ph diagram of the air conditioner in Embodiment 1. It is a diagram showing the connection flow of a cooling unit in Embodiment 1. It is a flowchart showing control during cooling operation in Embodiment 1.

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the embodiments described below, when numbers, quantities, etc. are mentioned, the scope of the present disclosure is not necessarily limited to those numbers, quantities, etc., unless otherwise specified. The same reference numerals are used for the same or equivalent parts, and redundant descriptions may not be repeated. It is intended from the beginning that the configurations in the embodiments may be used in appropriate combinations.

[0013] 1 is a schematic diagram showing the configuration of an air conditioner 100 in embodiment 1. The air conditioner 100 includes a cooling unit 10, an outdoor unit 20, an indoor unit 30, a first pipe 40a, a second pipe 40b, and a control device 60.

[0014] The outdoor unit 20 includes a first compressor 21, a first heat exchanger 22, a fan 23, and a first expansion valve 24. The indoor unit 30 includes a second heat exchanger 32 and a fan 33. The cooling unit 10 includes a second compressor 11, a third heat exchanger 12, a fan 13, a second expansion valve 14, a fourth heat exchanger 16, and a third expansion valve 15.

[0015] The outdoor unit 20 and the indoor unit 30 are connected via a first pipe 40a and a second pipe 40b. The cooling unit 10 is configured to be connectable to the first pipe 40a. When the cooling unit 10 is not connected to the first pipe 40a, the air conditioner 100 becomes a single-stage cycle in which the outdoor unit 20 and the indoor unit 30 are connected by the first pipe 40a and the second pipe 40b. When the cooling unit 10 is connected to the first pipe 40a, the air conditioner 100 becomes a multi-stage cycle composed of a low-stage cycle 1 including the outdoor unit 20 and the indoor unit 30, and a high-stage cycle 2 including the cooling unit 10.

[0016] The first compressor 21 draws in and compresses a low-temperature, low-pressure refrigerant and discharges it as a high-temperature, high-pressure gas refrigerant. The first compressor 21 is driven, for example, by an inverter, and its capacity (the amount of refrigerant discharged per unit time) is controlled. The first heat exchanger 22 exchanges heat between the refrigerant and air. The fan 23 is provided adjacent to the first heat exchanger 22 and blows air to the first heat exchanger 22. The first expansion valve 24 expands and reduces the pressure of the refrigerant. The first expansion valve 24 is, for example, an electronic expansion valve, and is a device whose opening degree can be controlled as desired.

[0017] The second heat exchanger 32 exchanges heat between the refrigerant and air. A fan 33 is provided adjacent to the second heat exchanger 32 and blows air toward the second heat exchanger 32. A gaseous or two-phase gas-liquid refrigerant flows through the first pipe 40a. A liquid or two-phase gas-liquid refrigerant flows through the second pipe 40b. The refrigerant flowing through the single-stage cycle and the low-stage cycle 1 (hereinafter also referred to as the first refrigerant) is, for example, R290, R32, or R410A. The first refrigerant may be a refrigerant other than those shown here.

[0018] The second compressor 11 draws in and compresses a low-temperature, low-pressure refrigerant and discharges it as a high-temperature, high-pressure gas refrigerant. The second compressor 11 is driven, for example, by an inverter, and its capacity (the amount of refrigerant discharged per unit time) is controlled. The third heat exchanger 12 exchanges heat between the refrigerant and air. The fan 13 is provided adjacent to the third heat exchanger 12 and blows air to the third heat exchanger 12. The second expansion valve 14 expands and reduces the pressure of the refrigerant. The second expansion valve 14 is, for example, an electronic expansion valve, and is a device whose opening can be controlled as desired.

[0019] The third expansion valve 15 expands and reduces the pressure of the refrigerant. The third expansion valve 15 is, for example, an electronic expansion valve, and is a device whose opening can be freely controlled. The third expansion valve 15 is disposed at a position through which the first refrigerant passes after flowing out of the fourth heat exchanger 16. The fourth heat exchanger 16 is a cascade heat exchanger. The fourth heat exchanger 16 exchanges heat between the refrigerant flowing between the first expansion valve 24 and the third expansion valve 15 in the low-stage cycle 1 and the refrigerant flowing between the second expansion valve 14 and the second compressor 11 in the high-stage cycle 2. The fourth heat exchanger 16 may be a double heat exchanger or a plate-type heat exchanger.

[0020] The refrigerant flowing through the high-stage cycle 2 (hereinafter also referred to as the second refrigerant) is, for example, R290. Compared to a single-stage cycle including the outdoor unit 20 and the indoor unit 30, the cooling unit 10 has a shorter overall piping length and uses a smaller amount of refrigerant. Because R290 (propane) is a flammable refrigerant, the amount of refrigerant that can be used is regulated by law. Because the cooling unit 10 can operate with a small amount of refrigerant, it can use R290, which has a low GWP within the regulated refrigerant amount range. Thus, even though the refrigerant amount is regulated by law, the cooling unit 10 uses a small capacity, making it possible to select a suitable refrigerant with a low GWP.

[0021] The flow of the first refrigerant in the low-stage cycle 1 during cooling operation is indicated by solid arrows in Fig. 1 . The flow of the second refrigerant in the high-stage cycle 2 during cooling operation is indicated by dashed arrows in Fig. 1 . As shown in Fig. 1 , during cooling operation, in the low-stage cycle 1, the first refrigerant circulates through the first compressor 21, the first heat exchanger 22, the first expansion valve 24, the fourth heat exchanger 16, the third expansion valve 15, the second heat exchanger 32, and the second compressor 11 in this order. As shown in Fig. 1 , during cooling operation, in the high-stage cycle 2, the refrigerant circulates through the second compressor 11, the third heat exchanger 12, the second expansion valve 14, the fourth heat exchanger 16, and the second compressor 11 in this order. The fourth heat exchanger 16 exchanges heat between the first refrigerant circulating in the low-stage cycle 1 and the second refrigerant circulating in the high-stage cycle 2.

[0022] The air conditioner 100 is provided with a plurality of sensors. A temperature sensor 51 is provided on the discharge side of the first compressor 21 to detect the temperature of the refrigerant discharged from the first compressor 21. A temperature sensor 52 is provided on the suction side of the first compressor 21 to detect the temperature of the refrigerant sucked into the first compressor 21. A temperature sensor 53 is provided at the air discharge position of the second heat exchanger 32 to detect the temperature of the cooled air. The temperature sensor 53 functions as a sensor that measures the blow-out temperature of the cooled air.

[0023] The control device 60 includes a control unit 61, a storage unit 62, and an input / output interface 63. These components are connected via a bus.

[0024] The control unit 61 is a computing entity that controls each actuator of the air conditioner 100 by executing various programs. The control unit 61 is composed of a computer such as a processor. The processor may be, for example, a microcontroller, a central processing unit (CPU), or a microprocessing unit (MPU). The processor has the function of executing various processes by executing programs, but some or all of these functions may be implemented using dedicated hardware circuits such as an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA). The term "processor" is not limited to a processor in the narrow sense that executes processes using a stored program, such as a CPU or MPU, but may also include hardwired circuits such as an ASIC or FPGA. Therefore, the term "processor" can also be interpreted as a processing circuitry whose processes are predefined by computer-readable code and / or hardwired circuits. The processor may be composed of a single chip or multiple chips. Furthermore, the processor and associated processing circuitry may be comprised of multiple computers interconnected by wire or wirelessly, such as via a local area network or a wireless network. The processor and associated processing circuitry may also be comprised of a cloud computer that performs remote calculations based on input data and outputs the results of the calculations to other devices at remote locations.

[0025] The memory unit 62 provides a storage area for storing program code, work memory, etc., when the processor of the control unit 61 executes various programs. The memory unit 62 may be one or more non-transitory computer-readable media. Examples of the memory unit 62 include volatile memory such as dynamic random access memory (DRAM) and static random access memory (SRAM), and non-volatile memory such as read-only memory (ROM) and flash memory. The memory unit 62 may also be one or more computer-readable storage media. Examples of the memory unit 62 include storage devices such as hard disk drives (HDDs) and solid-state drives (SSDs). The control unit 61 controls each actuator of the air conditioner 100 by executing the programs stored in the memory unit 62.

[0026] The input / output interface 63 acquires information related to temperatures from the temperature sensors 51, 52, and 53. The input / output interface 63 receives input signals from a user via an operation unit (not shown). The control device 60 may be provided in either the outdoor unit 20 or the indoor unit 30, or the outdoor unit 20 and the indoor unit 30 may have separate control devices. The control device 60 may also be provided in the cooling unit 10.

[0027] Figure 2 is a ph diagram of the air conditioner 100 according to the first embodiment. The dashed cycles at A1 to A4 in Figure 2 indicate single-stage cycles. The solid cycles at B1 to B4 in Figure 2 indicate low-stage cycle 1. The solid cycles at C1 to C4 in Figure 2 indicate high-stage cycle 2.

[0028] As shown in Figure 2, in a single-stage cycle during cooling operation, high-pressure, high-temperature refrigerant exchanges heat with air in the first heat exchanger 22 from A1 to A2. The refrigerant is then reduced in pressure by the first expansion valve 24 from A2 to A3, to become low-pressure. The refrigerant then exchanges heat with air in the second heat exchanger 32 from A3 to A4. The refrigerant is then compressed by the first compressor 21 from A4 to A1, to become high-pressure.

[0029] As shown in Fig. 2, in low-stage cycle 1 during cooling operation, high-pressure, high-temperature refrigerant exchanges heat with air in first heat exchanger 22 from B1 to B2, and also exchanges heat with refrigerant flowing in high-stage cycle 2 in fourth heat exchanger 16. Next, the refrigerant is decompressed to a low pressure by third expansion valve 15 from B2 to B3. Next, the refrigerant exchanges heat with air in second heat exchanger 32 from B3 to B4. Next, the refrigerant is compressed to a high pressure by first compressor 21 from B4 to B1. In low-stage cycle 1, because first expansion valve 24 of outdoor unit 20 is controlled to be fully open, the refrigerant pressure is not reduced by first expansion valve 24, but is reduced by third expansion valve 15.

[0030] As shown in Fig. 2, in the high-stage cycle 2 during cooling operation, high-pressure, high-temperature refrigerant exchanges heat with air in the third heat exchanger 12 from C1 to C2. Next, the refrigerant is decompressed to a low pressure by the second expansion valve 14 from C2 to C3. Next, the refrigerant exchanges heat with refrigerant flowing in the low-stage cycle 1 in the fourth heat exchanger 16 from C3 to C4. Next, the refrigerant is compressed by the second compressor 11 to a high pressure from C4 to C1.

[0031] 2, the air conditioner 100 can increase the degree of subcooling by changing from a single-stage cycle not connected to the cooling unit 10 to a multi-stage cycle (low-stage cycle 1 and high-stage cycle 2) connected to the cooling unit 10. By connecting the cooling unit 10, the degree of subcooling increases and the enthalpy difference in the condenser increases, thereby improving the cooling capacity of the air conditioner 100.

[0032] Next, the procedure for connecting the cooling unit will be described. FIG. 3 is a diagram showing the connection flow for the cooling unit 10 in the first embodiment. First, in step S (hereinafter simply referred to as "S") 1, the installer checks the installation guide for the cooling unit 10. The installation guide is a manual for the cooling unit that is sent from the control device 60 to the installer in a process executed by the control device 60, which will be described later. For example, the installation guide may be displayed on a terminal with a display screen owned by the installer. The installation guide may also be in the form of paper or the like. The installation guide may also be sent to the user of the air conditioner 100 rather than to the installer.

[0033] Next, the installer connects the cooling unit 10 constituting the high-stage cycle 2 to the first pipe 40a based on the installation guide (S2). The cooling unit 10 may be connected to the first pipe 40a using any installation method, such as a joint member for connecting pipes or welding. Next, the installer confirms the refrigerant charge amount of the first refrigerant to be additionally charged into the low-stage cycle 1 (S3). The refrigerant charge amount is the amount of the first refrigerant to be added after connecting the cooling unit 10. The refrigerant charge amount may be, for example, as indicated in the installation guide.

[0034] Next, the operator fills the low-stage cycle 1 with additional refrigerant based on the refrigerant filling amount in S3 (S4), and then ends the process. The operator fills the low-stage cycle 1 with the first refrigerant in an amount corresponding to the volume of the fourth heat exchanger 16. The first refrigerant can be filled into the low-stage cycle 1 from any point in the low-stage cycle 1, but it is preferable to provide a port on the low-pressure side where the pressure is low and to inject the first refrigerant from the low-pressure side.

[0035] In this way, the refrigerant charging method for adding the first refrigerant to the air conditioner 100 includes the steps of connecting the cooling unit 10 that constitutes the high-stage cycle 2 to the low-stage cycle 1, and adding the first refrigerant to the low-stage cycle 1 in an amount corresponding to the volume of the fourth heat exchanger 16 after connecting the cooling unit 10. By performing steps S1 to S4, the installer can charge the low-stage cycle 1 with an appropriate amount of the first refrigerant.

[0036] Next, a description will be given of the processing executed by the control device 60. Fig. 4 is a flowchart showing control during cooling operation in embodiment 1. The processing of the flowchart in Fig. 4 is repeatedly called and executed as a subroutine from the main routine in the control of the control device 60.

[0037] First, in step S11, the control device 60 determines whether or not the cooling unit 10 is connected to the first piping 40a of the low-stage cycle 1. The control device 60 may determine whether or not the cooling unit 10 is connected by, for example, receiving a connection signal for the cooling unit 10 input by an installer via the input / output interface 63. A detector that detects whether or not the cooling unit 10 is connected may be provided at the connection position of the first piping 40a with the cooling unit 10, and the control device 60 may determine whether or not the cooling unit 10 is connected based on the signal from the detector.

[0038] If the control device 60 determines in S11 that the cooling unit 10 is connected (YES in S11), it changes the opening degree of the first expansion valve 24 installed in the outdoor unit 20 so that it is fully open (S12). Next, the control device 60 detects the discharge temperature of the first refrigerant discharged from the first compressor 21 from the value of the temperature sensor 51 (S13). Note that in S13, the control device 60 may also detect the suction temperature of the first refrigerant sucked into the first compressor 21 from the value of the temperature sensor 52.

[0039] Next, the control device 60 changes the opening degree of the third expansion valve 15 of the cooling unit 10 according to the discharge temperature (or suction temperature) of the first refrigerant obtained in S13 (S14), and returns the processing from the subroutine to the main routine.

[0040] If the control device 60 determines in S11 that the cooling unit 10 is not connected (NO in S11), it detects the discharge temperature of the first refrigerant discharged from the first compressor 21 from the value of the temperature sensor 51 (S13). Note that in S13, the control device 60 may also detect the suction temperature of the first refrigerant sucked into the first compressor 21 from the value of the temperature sensor 52.

[0041] Next, the control device 60 changes the opening degree of the first expansion valve 24 of the outdoor unit 20 in accordance with the discharge temperature (or suction temperature) of the first refrigerant acquired in S15 (S15). Next, the control device 60 determines whether the capacity of the air conditioner 100 is within a predetermined normal operating range (S17). The control device 60 may determine that the capacity is not within the normal range, for example, if the detected value of the temperature sensor 53 does not drop to the target temperature even though the air conditioner 100 is operating at rated capacity. Whether the capacity is normal may also be determined based on whether a predetermined number of years has passed.

[0042] If the control device 60 determines in S17 that the capacity of the air conditioner 100 is normal (YES in S17), it returns the process from the subroutine to the main routine. If the control device 60 determines in S17 that the capacity of the air conditioner 100 is not normal (NO in S17), it issues installation instructions for the cooling unit 10 to the installer and returns the process from the subroutine to the main routine.

[0043] The air conditioner 100 can change the configuration of the refrigerant circuit by connecting the cooling unit 10, allowing it to perform stable cooling operation even in areas with high outdoor temperatures. When the cooling unit 10 is connected to the first pipe 40a, the control device 60, as shown in S12 and S14, increases the opening degree of the first expansion valve 24 greater than the opening degree of the third expansion valve 15. This causes the first refrigerant, after heat exchange with the high-stage cycle 2 in the fourth heat exchanger 16, to be decompressed by the third expansion valve 15, thereby increasing the degree of subcooling and improving cooling capacity.

[0044] As shown in S12 and S16, the control device 60 increases the opening degree of the first expansion valve 24 when the cooling unit 10 is connected to the first pipe 40a compared to the opening degree of the first expansion valve 24 when the cooling unit 10 is not connected to the first pipe 40a. This allows the air conditioning capacity to be changed depending on whether the cooling unit 10 is connected to the first pipe 40a or not.

[0045] In S17, the control device 60 determines that the capacity of the low-stage side cycle 1 has decreased below the reference capacity based on the temperature detected by the temperature sensor 53. As shown in S18, when the control device 60 determines that the capacity of the low-stage side cycle 1 has decreased below the reference capacity, it issues an installation guide, which is information for installing the cooling unit 10. This makes it possible to inform the installer of the situation in which it is necessary to improve the air conditioning capacity using the cooling unit 10.

[0046] Summary The air conditioner 100 of the present disclosure includes an outdoor unit 20 including a first compressor 21, a first heat exchanger 22, and a first expansion valve 24, an indoor unit 30 including a second heat exchanger 32, and piping connecting the outdoor unit 20 and the indoor unit 30 and through which a refrigerant flows. The piping includes a first piping 40a through which a gaseous first refrigerant flows and a second piping 40b through which a liquid first refrigerant flows. During cooling operation, a low-stage cycle 1 is formed in which the first refrigerant flows through the first compressor 21, the first heat exchanger 22, the first expansion valve 24, the first piping 40a, the second heat exchanger 32, the second piping 40b, and the first compressor 21 in this order. The air conditioner 100 is configured to be connectable to a cooling unit 10 that cools the first refrigerant. The cooling unit 10 includes a second compressor 11, a third heat exchanger 12, a second expansion valve 14, and a fourth heat exchanger 16. During cooling operation, a high-stage cycle 2 is formed in which a second refrigerant flows through the second compressor 11, the third heat exchanger 12, the second expansion valve 14, the fourth heat exchanger 16, and the second compressor 11 in this order. The fourth heat exchanger 16 exchanges heat between the first refrigerant and the second refrigerant. The cooling unit 10 is connectable to the first pipe 40a.

[0047] Preferably, the air conditioner 100 further includes a control device 60. The cooling unit 10 includes a third expansion valve 15 at a position through which the first refrigerant passes after flowing out of the fourth heat exchanger 16. The control device 60 makes the opening degree of the first expansion valve 24 larger than the opening degree of the third expansion valve 15 when the cooling unit 10 is connected to the first pipe 40a.

[0048] Preferably, the control device 60 sets the opening degree of the first expansion valve 24 when the cooling unit 10 is connected to the first piping 40a to be greater than the opening degree of the first expansion valve 24 when the cooling unit 10 is not connected to the first piping 40a.

[0049] Preferably, the indoor unit 30 further includes a temperature sensor 53 that measures the indoor temperature. The control device 60 determines that the capacity of the low-stage side cycle 1 has decreased below a reference capacity based on the temperature of the temperature sensor 53. When the control device 60 determines that the capacity of the low-stage side cycle 1 has decreased below the reference capacity, it outputs installation guidance, which is guidance information for installing the cooling unit 10.

[0050] Preferably, the second refrigerant used in the cooling unit 10 of the air conditioner 100 is R290.

[0051] The present disclosure relates to a cooling unit (10) connectable to a low-stage cycle (1) through which a first refrigerant flows and constituting a high-stage cycle (2) through which a second refrigerant flows. The cooling unit (10) includes a second compressor (11), a third heat exchanger (12), a second expansion valve (14), a fourth heat exchanger (16), and a third expansion valve (15). The high-stage cycle (2) is configured so that during cooling operation, the second refrigerant flows through the second compressor (11), the third heat exchanger (12), the second expansion valve (14), the fourth heat exchanger (16), and the second compressor (11) in this order. The fourth heat exchanger (16) exchanges heat between the first refrigerant and the second refrigerant. The cooling unit (10) includes the third expansion valve (15) at a position through which the first refrigerant passes after flowing out of the fourth heat exchanger (16).

[0052] The present disclosure relates to a refrigerant charging method for adding a first refrigerant to an air conditioner 100. The refrigerant charging method includes the steps of connecting a cooling unit 10 constituting a high-stage cycle 2 to a low-stage cycle 1, and adding, after connecting the cooling unit 10, the first refrigerant to the high-stage cycle 2 in an amount corresponding to the volume of a fourth heat exchanger 16.

[0053] Thus, according to the air conditioner 100, cooling unit 10, and refrigerant charging method of the present disclosure, the configuration of the refrigerant circuit can be changed by connecting the cooling unit 10, making it possible to perform stable cooling operation even in areas where the outside air temperature is high.

[0054] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0055] 1 Low-stage cycle, 2 High-stage cycle, 10 Cooling unit, 11 Second compressor, 12 Third heat exchanger, 13, 23, 33 Fan, 14 Second expansion valve, 15 Third expansion valve, 16 Fourth heat exchanger, 20 Outdoor unit, 21 First compressor, 22 First heat exchanger, 24 First expansion valve, 30 Indoor unit, 32 Second heat exchanger, 40a First piping, 40b Second piping, 51, 52, 53 Temperature sensor, 60 Control device, 61 Control unit, 62 Memory unit, 63 Input / output interface, 100 Air conditioner.

Claims

1. An air conditioner comprising an outdoor unit including a first compressor, a first heat exchanger, and a first expansion valve; an indoor unit including a second heat exchanger; and a pipe connecting the outdoor unit and the indoor unit and through which a refrigerant flows. The pipe includes a first pipe through which a first refrigerant in a first state flows and a second pipe through which the first refrigerant in a second state flows. During a cooling operation, a first refrigerant circuit is formed in which the first refrigerant flows in the order of the first compressor, the first heat exchanger, the first expansion valve, the first pipe, the second heat exchanger, the second pipe, and the first compressor. A cooling unit for cooling the first refrigerant is configured to be connectable. The cooling unit includes a second compressor, a third heat exchanger, a second expansion valve, and a fourth heat exchanger. During a cooling operation, a second refrigerant circuit is formed in which the second refrigerant flows in the order of the second compressor, the third heat exchanger, the second expansion valve, the fourth heat exchanger, and the second compressor. The fourth heat exchanger performs heat exchange between the first refrigerant and the second refrigerant. The cooling unit is connectable to the first pipe.

2. Further comprising a control device, wherein the cooling unit includes a third expansion valve at a position through which the first refrigerant flows after flowing out of the fourth heat exchanger, and the control device makes the opening degree of the first expansion valve larger than the opening degree of the third expansion valve when the cooling unit is connected to the first pipe. The air conditioner according to claim 1.

3. The control device makes the opening degree of the first expansion valve when the cooling unit is connected to the first pipe larger than the opening degree of the first expansion valve when the cooling unit is not connected to the first pipe. The air conditioner according to claim 2.

4. The indoor unit further includes a thermometer for measuring the indoor temperature. The control device determines that the capacity of the first refrigerant circuit has decreased below a reference capacity based on the temperature measured by the thermometer. When the control device determines that the capacity of the first refrigerant circuit has decreased below the reference capacity, the control device outputs guidance information for installing the cooling unit. The air conditioner according to claim 2 or claim 3.

5. The second refrigerant used in the cooling unit is R290. The air conditioner according to any one of claims 1 to 4.

6. A cooling unit that is connectable to a first refrigerant circuit through which a first refrigerant flows and that constitutes a second refrigerant circuit through which a second refrigerant flows, the cooling unit comprising a second compressor, a third heat exchanger, a second expansion valve, a fourth heat exchanger, and a third expansion valve, the second refrigerant circuit being configured such that the second refrigerant flows in the order of the second compressor, the third heat exchanger, the second expansion valve, the fourth heat exchanger, and the second compressor during a cooling operation, the fourth heat exchanger performing heat exchange between the first refrigerant and the second refrigerant, the cooling unit comprising the third expansion valve at a position through which the first refrigerant flows after flowing out of the fourth heat exchanger.

7. A refrigerant filling method for adding the first refrigerant to the air conditioner according to claim 1, the method comprising connecting the cooling unit that constitutes the second refrigerant circuit to the first refrigerant circuit, and adding the first refrigerant corresponding to the volume of the fourth heat exchanger to the first refrigerant circuit after connecting the cooling unit.

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