EP4317849A1

EP4317849A1 - Refrigeration cycle device

Info

Publication number: EP4317849A1
Application number: EP22781007.4A
Authority: EP
Inventors: Masaki Tanaka; Eiji Kumakura; Ikuhiro Iwata; Ryuhei Kaji; Atsushi Yoshimi; Hiroki Ueda; Takuro Yamada; Masaki Nakayama
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2021-03-31
Filing date: 2022-03-29
Publication date: 2024-02-07
Also published as: JP2023038281A; EP4317849A4; JP7568954B2; WO2022210796A1; JP2022157804A; JP7216308B2; US20240019178A1; CN117098959A

Abstract

Providing a refrigeration cycle apparatus capable of using a refrigerant of an appropriate composition in accordance with an operating condition. The refrigeration cycle apparatus (100) includes a main refrigerant circuit (50), a changing unit (70), and a controller (110). The main refrigerant circuit uses a non-azeotropic refrigerant mixture containing a first refrigerant and a second refrigerant. The changing unit changes a composition ratio between the first refrigerant and the second refrigerant in a refrigerant flowing through the main refrigerant circuit. The controller controls an operation of the changing unit. The controller executes a first mode and a second mode. The first mode is a mode in which the operation of the changing unit is controlled to cause substantially the second refrigerant alone to flow through the main refrigerant circuit. The second mode is a mode in which the operation of the changing unit is controlled to cause a refrigerant mixture of the first refrigerant and the second refrigerant to flow through the main refrigerant circuit.

Description

TECHNICAL FIELD

The present invention relates to a refrigeration cycle apparatus.

BACKGROUND ART

A refrigerant used in a refrigeration cycle apparatus is required to satisfy various requirements, such as high safety and low environmental burden, in addition to performance as a refrigerant. For example, PTL 1 ( Japanese Unexamined Patent Application Publication No. 2008-281326 ) describes using, in place of R134a, R1234yf that has a low global warming potential in a refrigeration cycle apparatus.

SUMMARY OF INVENTION

However, as there are various requirements for the refrigerant, it is generally difficult to select a refrigerant that is efficient and with which it is possible to obtain a sufficient capacity regardless of the operating conditions.

A refrigeration cycle apparatus according to a first aspect includes a refrigeration cycle, a changing unit, and a controller. The refrigeration cycle is configured to use a non-azeotropic refrigerant mixture containing a first refrigerant and a second refrigerant. The changing unit is configured to change a composition ratio between the first refrigerant and the second refrigerant in a refrigerant flowing through the refrigeration cycle. The controller is configured to control an operation of the changing unit. The controller is configured to execute a first mode and a second mode. The first mode is a mode in which the operation of the changing unit is controlled to cause substantially the second refrigerant alone to flow through the refrigeration cycle. The second mode is a mode in which the operation of the changing unit is controlled to cause a refrigerant mixture of the first refrigerant and the second refrigerant to flow through the refrigeration cycle.
In the refrigeration cycle apparatus of the first aspect, substantially the second refrigerant alone or a non-azeotropic refrigerant mixture containing the first refrigerant and the second refrigerant can be used. Therefore, a refrigerant having an appropriate composition can be used in accordance with an operating condition.
A refrigeration cycle apparatus according to a second aspect is the refrigeration cycle apparatus according to the first aspect, wherein, in the first mode, a refrigerant in which the concentration of the second refrigerant is more than or equal to 92 wt% is caused to flow through the refrigeration cycle.
A refrigeration cycle apparatus according to a third aspect is the refrigeration cycle apparatus according to the second aspect, wherein, in the first mode, a refrigerant in which the concentration of the second refrigerant is more than or equal to 98 wt% is caused to flow through the refrigeration cycle.
A refrigeration cycle apparatus according to a fourth aspect is the refrigeration cycle apparatus according to any one of the first to third aspects, further includes a detection section. The detection section is configured to detect a composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the refrigeration cycle. The controller is configured to control the operation of the changing unit so that the composition ratio between the first refrigerant and the second refrigerant detected by the detection section becomes a target composition ratio.
In the refrigeration cycle apparatus of the fourth aspect, because the composition ratio between the first refrigerant and the second refrigerant is changed while the composition ratio of the refrigerants is being detected, a refrigerant having an appropriate composition can be used in accordance with the operating condition.
A refrigeration cycle apparatus according to a fifth aspect is the refrigeration cycle apparatus according to any one of the first to fourth aspects, wherein a boiling point of the second refrigerant is higher than a boiling point of the first refrigerant.
A refrigeration cycle apparatus according to a sixth aspect is the refrigeration cycle apparatus according to the fifth aspect, wherein the refrigeration cycle includes a utilization heat exchanger configured to perform temperature adjustment of an object for temperature adjustment. When the utilization heat exchanger is utilized as an evaporator, the controller is configured to execute the first mode. When the utilization heat exchanger is utilized as a radiator, the controller is configured to execute the second mode.
In the refrigeration cycle apparatus of the sixth aspect, when the utilization heat exchanger is utilized as an evaporator, substantially the second refrigerant alone can be used to perform an operation that places importance on efficiency. On the other hand, during an operation in which the utilization heat exchanger is utilized as a radiator, where insufficient capacity is likely to occur, a necessary capacity can be obtained by using the non-azeotropic refrigerant mixture of the first refrigerant and the second refrigerant.
A refrigeration cycle apparatus according to a seventh aspect is the refrigeration cycle apparatus according to the sixth aspect, wherein, when the utilization heat exchanger is utilized as the radiator, the controller is configured to execute the first mode or the second mode in accordance with a capacity required of the refrigeration cycle apparatus.
In the refrigeration cycle apparatus of the seventh aspect, even when the utilization heat exchanger is utilized as a radiator, substantially the second refrigerant alone can be used to perform an operation that places importance on efficiency if it is not necessary to use the refrigerant mixture of the first refrigerant and the second refrigerant in terms of capacity.
A refrigeration cycle apparatus according to an eighth aspect is the refrigeration cycle apparatus according to the seventh aspect, wherein the refrigeration cycle includes a compressor. The controller is configured to further control a number of revolutions of the compressor. The controller is configured to execute the second mode if the required capacity cannot be obtained even when the number of revolutions of the compressor is increased to a predetermined number of revolutions during execution of the first mode.
In the refrigeration cycle apparatus of the eighth aspect, a necessary capacity can be obtained while suppressing a decrease in efficiency.
A refrigeration cycle apparatus according to a ninth aspect is the refrigeration cycle apparatus according to the sixth aspect or the seventh aspect, wherein the controller is configured to control, when executing the second mode, the operation of the changing unit to change the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the refrigeration cycle between a first composition ratio and a second composition ratio. The ratio of the first refrigerant is higher in the second composition ratio than in the first composition ratio.
In the refrigeration cycle apparatus of the ninth aspect, because the composition ratio between the first refrigerant and the second refrigerant is changed in a stepwise manner, a necessary capacity can be obtained while a decrease in efficiency is suppressed.
A refrigeration cycle apparatus according to a tenth aspect is the refrigeration cycle apparatus according to the ninth aspect, wherein the refrigeration cycle includes a compressor. The controller is further configured to control the number of revolutions of the compressor. The controller is configured to change either a number of revolutions of the compressor or a composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the refrigeration cycle, in accordance with a change in the capacity required of the refrigeration cycle apparatus.
In the refrigeration cycle apparatus of the tenth aspect, a necessary capacity can be obtained while a decrease in efficiency is suppressed.
A refrigeration cycle apparatus according to an eleventh aspect is the refrigeration cycle apparatus according to the tenth aspect, wherein, when the required capacity increases, the controller is configured to change one of the number of revolutions of the compressor and the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the refrigeration cycle that causes a smaller amount of increase in electric power of the compressor when being changed.
In the refrigeration cycle apparatus of the eleventh aspect, a necessary capacity can be obtained while a decrease in efficiency is suppressed.
A refrigeration cycle apparatus according to a twelfth aspect is the refrigeration cycle apparatus of the tenth aspect or the eleventh aspect, wherein, when the required capacity decreases, the controller is configured to control the changing unit to lower the ratio of the first refrigerant in the refrigerant flowing through the refrigeration cycle when the ratio of the first refrigerant in the refrigerant flowing through the refrigeration cycle is higher than a predetermined value, and to lower the number of revolutions of the compressor when the ratio of the first refrigerant in the refrigerant flowing through the refrigeration cycle is lower than or equal to the predetermined value.
In the refrigeration cycle apparatus of the twelfth aspect, a necessary capacity can be obtained while a decrease in efficiency is suppressed.
A refrigeration cycle apparatus according to a thirteenth aspect is the refrigeration cycle apparatus of any of the first through twelfth aspects, wherein the first refrigerant is CO₂. The second refrigerant is R1234Ze or R1234yf.
A refrigeration cycle apparatus according to a fourteenth aspect is the refrigeration cycle apparatus according to any one of the first to twelfth aspects, wherein the first refrigerant is R1132(E) or R1123. The second refrigerant is R1234Ze or R1234yf.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is a schematic configuration diagram of a refrigeration cycle apparatus according to an embodiment.
Fig. 2 is a diagram schematically showing a change in the COP when the number of revolutions of the motor of a compressor is changed to change capacity, and a change in the COP when the ratio of a first refrigerant in the refrigerant is changed to change capacity.
Fig. 3 is an example of a flowchart of control performed when the refrigeration cycle apparatus has insufficient capacity.
Fig. 4 is an example of a flowchart of control performed when the refrigeration cycle apparatus has excessive capacity.
Fig. 5 is a schematic configuration diagram of a refrigeration cycle apparatus according to Modification A.
Fig. 6 is a schematic configuration diagram of a refrigeration cycle apparatus according to Modification G.

DESCRIPTION OF EMBODIMENTS

Hereafter, embodiments of the refrigeration cycle apparatus of the present disclosure will be described with reference to the drawings.
The refrigeration cycle apparatus is an apparatus that performs at least one of cooling of an object for temperature adjustment and heating of the object for temperature adjustment by utilizing a vapor compression refrigeration cycle. The refrigeration cycle apparatus of the present disclosure uses a non-azeotropic refrigerant mixture as the refrigerant. As will be described later, the refrigeration cycle apparatus of the present disclosure changes the composition ratio of the refrigerant flowing through the refrigeration cycle in accordance with conditions.

(1) General outline

A refrigeration cycle apparatus 100 according to a first embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic configuration diagram of the refrigeration cycle apparatus 100.
Here, the refrigeration cycle apparatus 100 is an air conditioner that cools and heats air that is the object for temperature adjustment. However, this is not a limitation, and the refrigeration cycle apparatus 100 may be an apparatus that cools and heats a liquid (for example, water) as the object for temperature adjustment.
As shown in Fig. 1, the refrigeration cycle apparatus 100 mainly includes a main refrigerant circuit 50 as an example of a refrigeration cycle, a changing unit (changer) 70, a detection section 150, and a controller 110. The main refrigerant circuit 50 and a first bypass flow path 80 of the changing unit 70, which will be described later, connected to the main refrigerant circuit 50 are collectively referred to as a refrigerant circuit 200.
The refrigerant circuit 200 is filled with a non-azeotropic refrigerant mixture. In other words, the main refrigerant circuit 50 uses a non-azeotropic refrigerant mixture. The non-azeotropic refrigerant mixture is a mixture of at least two types of refrigerant. The refrigerant circuit 200 of the refrigeration cycle apparatus 100 of the first embodiment is filled with a non-azeotropic refrigerant mixture containing only two types of refrigerant (a first refrigerant and a second refrigerant). However, this is not a limitation, and the non-azeotropic refrigerant mixture may be a mixture of three or more types of refrigerant. For example, the second refrigerant may not be one type of refrigerant but may be an azeotropic refrigerant mixture or a near-azeotropic refrigerant mixture containing two or more types of refrigerant. In short, the non-azeotropic refrigerant mixture may be a refrigerant mixture of an azeotropic refrigerant mixture or a near-azeotropic refrigerant mixture containing two or more types of refrigerant as the second refrigerant, and the first refrigerant that is non-azeotropic with respect to the second refrigerant.
Specifically, but without limitation, the first refrigerant is CO₂ (carbon dioxide), and the second refrigerant is HFO (hydrofluoroolefin). HFO is a refrigerant having an extremely low global warming potential. Without limitation, a specific example of the HFO for use as the second refrigerant is R1234Ze (cis-1,3,3,3-tetrafluoropropene). Further, for example, instead of R1234Ze, R1234yf (2,3,3,3-tetrafluoropropene) may be used as the HFO of the second refrigerant. CO₂ is a refrigerant that has a relatively low boiling point, and R1234Ze and R1234yf are refrigerants that have relatively high boiling points. In other words, the boiling point of the second refrigerant is higher than the boiling point of the first refrigerant. Hereafter, the first refrigerant may be referred to as a low boiling-point refrigerant, and the second refrigerant may be referred to as a high boiling-point refrigerant.
The ratio of the total weight of the first refrigerant that is filled in the refrigerant circuit 200 to the total weight of all the refrigerants that is filled in the refrigerant circuit 200 of the refrigeration cycle apparatus 100 is preferably 20 wt% or less.
The main refrigerant circuit 50, the changing unit 70, the detection section 150, and the controller 110 will be briefly described.
As shown in Fig. 1, the main refrigerant circuit 50 mainly includes a compressor 10, a flow path switching mechanism 15, a heat-source heat exchanger 20, an expansion mechanism 30, and a utilization heat exchanger 40. The compressor 10, the flow path switching mechanism 15, the heat-source heat exchanger 20, the expansion mechanism 30, and the utilization heat exchangers 40 are connected by refrigerant pipes 52a to 52e, which will be described later, to constitute the main refrigerant circuit 50 (see Fig. 1). The refrigeration cycle apparatus 100 cools and heats air that is the object for temperature adjustment, by circulating the refrigerant in the main refrigerant circuit 50.
The changing unit 70 is a mechanism that changes the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50.
The detection section 150 detects the composition ratio of the refrigerant circulating in the main refrigerant circuit 50.
As indicated by long dashed double short-dashed lines in Fig. 1, the refrigeration cycle apparatus 100 includes a heat source unit 2 that has a casing (not shown), and a utilization unit 4 that has a casing (not shown) and is connected to the heat source unit 2 via refrigerant pipes. The heat source unit 2 is installed, for example, on a rooftop or in a machine chamber of a building in which the refrigeration cycle apparatus 100 is installed, or around the building in which the refrigeration cycle apparatus 100 is installed. The utilization unit 4 is disposed in a space to be air-conditioned or in a space in the vicinity of the space to be air-conditioned (for example, a space above the ceiling, a machine chamber, or the like). Without limitation, the casing of the heat source unit 2 mainly houses: the compressor 10, the flow path switching mechanism 15, the heat-source heat exchanger 20, and the expansion mechanism 30 of the main refrigerant circuit 50; the changing unit 70; and the detection section 150. The casing of the utilization unit 4 mainly houses the utilization heat exchanger 40 of the main refrigerant circuit 50.
The controller 110 controls operations of various components of the refrigeration cycle apparatus 100.
For example, the controller 110 controls the operation of the changing unit 70. The controller 110 executes a first mode and a second mode by controlling the operation of the changing unit 70. The first mode is a mode in which the operation of the changing unit 70 is controlled to cause substantially the second refrigerant alone to flow through the main refrigerant circuit 50. The second mode is a mode in which the operation of the changing unit 70 is controlled to cause a refrigerant mixture of the first refrigerant and the second refrigerant to flow through the main refrigerant circuit 50.
Note that, here, causing substantially the second refrigerant alone to flow is not limited to a state in which the second refrigerant not containing the first refrigerant is caused to flow, but includes a state in which the second refrigerant having a high concentration more than or equal to a predetermined concentration is caused to flow (a state in which substantially the second refrigerant alone is caused to flow). Specifically, the state in which substantially the second refrigerant alone is caused to flow through the main refrigerant circuit 50 includes a state in which the second refrigerant having a concentration of more than or equal to 92 wt% is caused to flow through the main refrigerant circuit 50. Note that, in the first mode, preferably a refrigerant in which the concentration of the second refrigerant is as high as possible (the refrigerant in which the concentration of the first refrigerant is low) is caused to flow through the main refrigerant circuit 50. Preferably, in the first mode, a refrigerant in which the concentration of the second refrigerant is more than or equal to 98 wt% is caused to flow through the main refrigerant circuit 50.

(2) Detailed configuration

(2-1) Main refrigerant circuit

As shown in Fig. 1, the main refrigerant circuit 50 mainly includes the compressor 10, the flow path switching mechanism 15, the heat-source heat exchanger 20, the expansion mechanism 30, and the utilization heat exchanger 40.
As shown in Fig. 1, the main refrigerant circuit 50 has a suction pipe 52a, a discharge pipe 52b, a first gas refrigerant pipe 52c, a liquid refrigerant pipe 52d, and a second gas refrigerant pipe 52e as pipes for connecting the compressor 10, the flow path switching mechanism 15, the heat-source heat exchanger 20, the expansion mechanism 30, and the utilization heat exchangers 40 (see Fig. 1). The suction pipe 52a connects a suction port 10b of the compressor 10 and the flow path switching mechanism 15. The discharge pipe 52b connects a discharge port 10c of the compressor 10 and the flow path switching mechanism 15. The first gas refrigerant pipe 52c connects the flow path switching mechanism 15 and a gas end of the heat-source heat exchanger 20. The liquid refrigerant pipe 52d connects a liquid end of the heat-source heat exchanger 20 and a liquid end of the utilization heat exchanger 40. The liquid refrigerant pipe 52d is provided with the expansion mechanism 30. The second gas refrigerant pipe 52e connects a gas end of the utilization heat exchanger 40 and the flow path switching mechanism 15.

(2-1-1) Compressor

The compressor 10 suctions a low-pressure refrigerant in the refrigeration cycle from the suction port 10b, compresses the refrigerant in a compression mechanism (not shown) and discharges a high-pressure refrigerant in the refrigeration cycle from the discharge port 10c. Although only one compressor 10 is depicted in Fig. 1, the main refrigerant circuit 50 may include a plurality of compressors 10 connected in series or in parallel.
The compressor 10 is, for example, a scroll compressor. However, this is not a limitation, and the compressor 10 may be a compressor of a type other than the scroll compressor, such as a rotary compressor. The type of the compressor 10 may be appropriately selected.
Without limitation, the compressor 10 is an inverter-controlled compressor in which the number of revolutions of the motor 10a is variable. A controller 110 that controls the operation of the compressor 10, as will be described later, controls the number of revolutions of the motor 10a of the compressor 10 in accordance with, for example, an air-conditioning load.

(2-1-2) Flow path switching mechanism

The flow path switching mechanism 15 is a mechanism that switches the flow direction of the refrigerant in the main refrigerant circuit 50 in accordance with the operation mode (cooling operation mode/heating operation mode) of the refrigeration cycle apparatus 100. The cooling operation mode is an operation mode of the refrigeration cycle apparatus 100 in which the heat-source heat exchanger 20 is caused to function as a radiator and the utilization heat exchanger 40 is caused to function as an evaporator. The heating operation mode is an operation mode of the refrigeration cycle apparatus 100 in which the utilization heat exchanger 40 is caused to function as a radiator and the heat-source heat exchanger 20 is caused to function as an evaporator.
In the cooling operation mode, the flow path switching mechanism 15 switches the flow direction of the refrigerant in the main refrigerant circuit 50 so that the refrigerant discharged by the compressor 10 is sent to the heat-source heat exchanger 20. Specifically, in the cooling operation mode, the flow path switching mechanism 15 causes the suction pipe 52a to communicate with the second gas refrigerant pipe 52e, and causes the discharge pipe 52b to communicate with the first gas refrigerant pipe 52c (see the solid lines in Fig. 1).
In the heating operation mode, the flow path switching mechanism 15 switches the flow direction of the refrigerant in the main refrigerant circuit 50 so that the refrigerant discharged by the compressor 10 is sent to the utilization heat exchanger 40. Specifically, in the heating operation mode, the flow path switching mechanism 15 causes the suction pipe 52a to communicate with the first gas refrigerant pipe 52c, and causes the discharge pipe 52b to communicate with the second gas refrigerant pipe 52e (see the dashed lines in Fig. 1).
The flow path switching mechanism 15 is, for example, a four-way switching valve. However, the flow path switching mechanism 15 may be realized by a mechanism other than a four-way switching valve. For example, the flow path switching mechanism 15 may be configured by combining a plurality of electromagnetic valves and pipes so as to realize the switching of the flow direction of the refrigerant.

(2-1-3) Heat-source heat exchanger

The heat-source heat exchanger 20 functions as a radiator of the refrigerant when the refrigeration cycle apparatus 100 is operated in the cooling operation mode, and functions as an evaporator of the refrigerant when the refrigeration cycle apparatus 100 is operated in the heating operation mode. Although only one heat-source heat exchanger 20 is depicted in Fig. 1, the main refrigerant circuit 50 may include a plurality of heat-source heat exchangers 20 arranged in parallel.
Without limitation, the heat-source heat exchanger 20 is a fin-and-tube type heat exchanger, for example, having a plurality of heat transfer tubes and a plurality of heat transfer fins.
As shown in Fig. 1, a first gas refrigerant pipe 52c is connected to one end of the heat-source heat exchanger 20. As shown in Fig. 1, the liquid refrigerant pipe 52d is connected to the other end of the heat-source heat exchanger 20.
When the refrigeration cycle apparatus 100 is operated in the cooling operation mode, the refrigerant flows into the heat-source heat exchanger 20 from the first gas refrigerant pipe 52c. The refrigerant that has flowed into the heat-source heat exchanger 20 from the first gas refrigerant pipe 52c dissipates heat by exchanging heat with air supplied by a fan (not shown), and at least a portion of the refrigerant condenses. The refrigerant that has dissipated heat in the heat-source heat exchanger 20 flows out to the liquid refrigerant pipe 52d.
When the refrigeration cycle apparatus 100 is operated in the heating operation mode, the refrigerant flows into the heat-source heat exchanger 20 from the liquid refrigerant pipe 52d. The refrigerant that has flowed from the liquid refrigerant pipe 52d into the heat-source heat exchanger 20 absorbs heat by exchanging heat with air supplied by a fan (not shown) in the heat-source heat exchanger 20 and evaporates. The refrigerant that has absorbed heat (that has been heated) in the heat-source heat exchanger 20 flows out to the first gas refrigerant pipe 52c.
In the present embodiment, in the heat-source heat exchanger 20, heat exchange is performed between the refrigerant flowing inside and the air as the heat source supplied to the heat-source heat exchanger 20. However, the heat-source heat exchanger 20 is not limited to a heat exchanger that performs heat exchange between air and the refrigerant. For example, the heat-source heat exchanger 20 may be a heat exchanger that performs heat exchange between a refrigerant flowing inside and a liquid as a heat source supplied to the heat-source heat exchanger 20.

(2-1-4) Expansion mechanism

The expansion mechanism 30 is a mechanism that decompresses the refrigerant and adjusts the flow rate of the refrigerant. In the present embodiment, the expansion mechanism 30 is an electronic expansion valve with an adjustable opening degree. The opening degree of the expansion mechanism 30 is appropriately adjusted according to the operating condition. Note that the expansion mechanism 30 is not limited to an electronic expansion valve, but may be a thermostatic expansion valve or a capillary tube.

(2-1-5) Utilization heat exchanger

The utilization heat exchanger 40 functions as an evaporator of the refrigerant when the refrigeration cycle apparatus 100 is operated in the cooling operation mode, and functions as a radiator of the refrigerant when the refrigeration cycle apparatus 100 is operated in the heating operation mode. When functioning as an evaporator, the utilization heat exchanger 40 cools the object for temperature adjustment (air in the present embodiment). When functioning as a radiator, the utilization heat exchanger 40 heats the object for temperature adjustment (air in the present embodiment).
Note that in the example shown in Fig. 1, the refrigeration cycle apparatus 100 includes only one utilization heat exchanger 40. However, this is not a limitation. The main refrigerant circuit 50 of the refrigeration cycle apparatus 100 may include a plurality of utilization heat exchangers 40 arranged in parallel. Then, each utilization unit 4 may include an expansion mechanism (for example, an electronic expansion valve with an adjustable opening degree), not shown, disposed on the liquid side of the utilization heat exchanger 40.
Without limitation, the utilization heat exchanger 40 is a fin-and-tube type heat exchanger, for example, having a plurality of heat transfer tubes and a plurality of heat transfer fins.
As shown in Fig. 1, the liquid refrigerant pipe 52d is connected to one end of the utilization heat exchanger 40. As shown in Fig. 1, the second gas refrigerant pipe 52e is connected to the other end of the utilization heat exchanger 40.
When the refrigeration cycle apparatus 100 is operated in the cooling operation mode, the refrigerant flows into the utilization heat exchanger 40 from the liquid refrigerant pipe 52d. The refrigerant that has flowed into the utilization heat exchanger 40 from the liquid refrigerant pipe 52d exchanges heat with air supplied by a fan (not shown), absorbs heat, and evaporates in the utilization heat exchanger 40. The refrigerant that has absorbed heat (that has been heated) in the utilization heat exchanger 40 flows out to the second gas refrigerant pipe 52e. The air as the object for temperature adjustment cooled by the utilization heat exchanger 40 is blown out into the space to be air-conditioned.
When the refrigeration cycle apparatus 100 is operated in the heating operation mode, the refrigerant flows into the utilization heat exchanger 40 from the second gas refrigerant pipe 52e. The refrigerant that has flowed into the utilization heat exchanger 40 from the second gas refrigerant pipe 52e dissipates heat by exchanging heat with air supplied by a fan (not shown) and at least a portion of the refrigerant condenses. The refrigerant that has dissipated heat in the utilization heat exchanger 40 flows out to the liquid refrigerant pipe 52d. The air that has been heated by the utilization heat exchanger 40 as the object for temperature adjustment is blown out into the space to be air-conditioned.

(2-2) Changing unit

The changing unit 70 is a mechanism that changes the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50.
The changing unit 70 includes a first bypass flow path 80, a refrigerant container 72, a heat source-side valve 82a, and a utilization-side valve 82b.
The first bypass flow path 80 is a pipe that connects a heat source-side end A of the main refrigerant circuit 50 and a utilization-side end B of the main refrigerant circuit 50. The heat source-side end A is a portion of the liquid refrigerant pipe 52d of the main refrigerant circuit 50 between the heat-source heat exchanger 20 and the expansion mechanism 30. The utilization-side end B is a portion of the liquid refrigerant pipe 52d of the main refrigerant circuit 50 between the utilization heat exchanger 40 and the expansion mechanism 30.
The refrigerant container 72, the heat source-side valve 82a, and the utilization-side valve 82b are disposed in the first bypass flow path 80.
The refrigerant container 72 is a container capable of storing the refrigerant therein.
The heat source-side valve 82a is disposed between the heat source-side end A and the changing unit 70. The utilization-side valve 82b is disposed between the utilization-side end B and the changing unit 70. The heat source-side valve 82a and the utilization-side valve 82b are electronic expansion valves with adjustable opening degrees.
A method in which the changing unit 70 changes the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50 will be described.
When the opening degrees of the heat source-side valve 82a and the utilization-side valve 82b are adjusted during operation of the refrigeration cycle apparatus 100, the ratio between the liquid phase and the gaseous phase of the refrigerant stored in the refrigerant container 72 can be increased or decreased in accordance with the opening degrees of the heat source-side valve 82a and the utilization-side valve 82b.
When an azeotropic refrigerant mixture or a near-azeotropic refrigerant mixture is present in a gas-liquid two-phase state, the composition ratio of the refrigerant in the gaseous phase and the composition ratio of the refrigerant in the liquid phase are approximately the same.
On the other hand, when a non-azeotropic refrigerant mixture of a low boiling-point refrigerant (first refrigerant) and a high boiling-point refrigerant (second refrigerant) is present in a gas-liquid two-phase state, the ratio of the high boiling-point refrigerant is higher in the liquid phase portion, and the ratio of the low boiling-point refrigerant is higher in the gas phase portion. Therefore, the amount of the first refrigerant stored in the refrigerant container 72 can be increased or decreased by adjusting the opening degrees of the heat source-side valve 82a and the utilization-side valve 82b to change the amount of the liquid-phase refrigerant and the amount of the gas-phase refrigerant that are stored in the refrigerant container 72. When the amount of the first refrigerant stored in the refrigerant container 72 is increased, the amount of the first refrigerant present in the main refrigerant circuit 50 is reduced. As a result, the ratio of the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50 can be increased. On the other hand, when the amount of the first refrigerant stored in the refrigerant container 72 is decreased, the amount of the first refrigerant present in the main refrigerant circuit 50 increases. As a result, the ratio of the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50 can be lowered (the ratio of the first refrigerant can be increased).

(2-3) Detection section

The detection section 150 detects the composition ratio between the first refrigerant and the second refrigerant in the refrigerant circulating in the main refrigerant circuit 50.
The detection section 150 includes a pipe 151 that connects a point between the heat-source heat exchanger 20 and the expansion mechanism 30 in the main refrigerant circuit 50 and a point between the utilization heat exchanger 40 and the expansion mechanism 30 in the main refrigerant circuit 50. Note that the pipe 151 is used to detect the composition of the refrigerant flowing through the main refrigerant circuit 50, and is not directly required for a vapor compression refrigeration cycle. The pipe 151 is a pipe having a diameter smaller than that of the liquid refrigerant pipe 52d, and a very small amount of refrigerant flows therethrough.
The detection section 150 includes a refrigerant container 152 and a valve 154 that are disposed in the pipe 151. The valve 154 includes a first valve 154a and a second valve 154b. The first valve 154a is disposed between the refrigerant container 152 and a portion of the pipe 151 connected to the liquid refrigerant pipe 52d between the heat-source heat exchanger 20 and the expansion mechanism 30. The second valve 154b is disposed between the refrigerant container 152 and a portion of the pipe 151 connected to the liquid refrigerant pipe 52d between the utilization heat exchanger 40 and the expansion mechanism 30. The first valve 154a and the second valve 154b are, for example, electronic expansion valves with variable opening degrees. However, this is not a limitation, and the first valve 154a and the second valve 154b may be, for example, capillary tubes. The detection section 150 includes a pressure sensor 156 that measures the pressure of the refrigerant in the refrigerant container 152, and a temperature sensor 158 that measures the temperature of the refrigerant in the refrigerant container 152.
The controller 110 opens the first valve 154a and the second valve 154b as necessary during a cooling operation or a heating operation, and controls the first valve 154a and the second valve 154b to predetermined opening degrees so that a two-phase (liquid-phase and gas-phase) refrigerant is present in the refrigerant container 152. For example, when performing an adsorption control and a desorption control, the controller 110 opens the first valve 154a and the second valve 154b, and controls the first valve 154a and the second valve 154b to predetermined opening degrees so that a two-phase refrigerant is stored in the refrigerant container 152.
In the non-azeotropic refrigerant mixture, the composition ratio thereof can be calculated when the type of refrigerant used in the non-azeotropic refrigerant mixture and the pressure and temperature of the two-phase refrigerant are known. Therefore, the detection section 150 can detect the composition ratio of the refrigerant in the refrigerant container 152, in other words, the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the liquid refrigerant pipe 52d of the main refrigerant circuit 50, based on the pressures of the two-phase refrigerant measured by the pressure sensor 156 and the temperature of the two-phase refrigerant measured by the temperature sensor 158.
The controller 110 may function as a part of the detection section 150 to detect (calculate) the composition ratio of the refrigerant circulating in the main refrigerant circuit 50 based on the measurement results of the pressure sensor 156 and the temperature sensor 158. Alternatively, the detection section 150 may be an apparatus independent of the controller 110 and detect the composition ratio of the refrigerant circulating in the main refrigerant circuit 50 based on the measurement results of the pressure sensor 156 and the temperature sensor 158.
In the present embodiment, the controller 110 detects the composition ratio of the refrigerant circulating in the main refrigerant circuit 50 based on the measurement results of the pressure sensor 156 and the temperature sensor 158. Specifically, memory (a storage section) of the controller 110 stores data (for example, a table or a relational expression) indicating, with respect to the non-azeotropic refrigerant mixture to be used, the relationship between the pressure and temperature of the two-phase refrigerant and the composition ratio of the non-azeotropic refrigerant mixture. The controller 110 detects the composition ratio of the refrigerant circulating in the main refrigerant circuit 50 based on the data stored in the memory indicating the relationship between the pressure and temperature of the two-phase refrigerant and the composition ratio of the non-azeotropic refrigerant mixture, and the measurement results of the pressure sensor 156 and the temperature sensor 158.
Note that the method of detecting the composition ratio of the refrigerant circulating in the main refrigerant circuit 50 need not be limited to the method exemplified here, and the detection section 150 may detect the composition ratio of the refrigerant circulating in the main refrigerant circuit 50 by another method or using a device different from that of the above-described method.

(2-4) Controller

The controller 110 is a control unit for controlling operations of various devices of the refrigeration cycle apparatus 100.
The controller 110 mainly includes, for example, a microcontroller unit (MCU) and various electric circuits and electronic circuits (not shown). The MCU includes a CPU, memory, an I/O interface, and the like. Various programs to be executed by the CPU of the MCU are stored in the memory of the MCU. Further, an FPGA or an ASIC may be used for the controller 110. Note that the various functions of the controller 110 need not be implemented by software, and may be implemented by hardware or by cooperation of hardware and software.
The controller 110 may be an apparatus independent of the heat source unit 2 and the utilization unit 4. Further, the controller 110 may not be an apparatus independent of the heat source unit 2 and the utilization unit 4. For example, a controller (not shown) mounted in the heat source unit 2 and a controller (not shown) mounted in the utilization unit 4 may cooperate to function as the controller 110.
The controller 110 is electrically connected to the compressor 10, the flow path switching mechanism 15, and the expansion mechanism 30 of the main refrigerant circuit 50, and controls the operations of the compressor 10, the flow path switching mechanism 15, and the expansion mechanism 30 (see Fig. 1). Further, the controller 110 is electrically connected to a fan (not shown) for supplying air to the heat-source heat exchanger 20 of the heat source unit 2, and is electrically connected to a fan (not shown) for supplying air to the utilization heat exchanger 40 of the utilization unit 4, so as to be able to control the operations of these fans. Further, the controller 110 is electrically connected to the heat source-side valve 82a and the utilization-side valve 82b of the changing unit 70, and controls the operations of the heat source-side valve 82a and the utilization-side valve 82b (see Fig. 1). In addition, the controller 110 is electrically connected to the first valve 154a and the second valve 154b of the detection section 150 so as to be able to control the operations of the first valve 154a and the second valve 154b. In addition, the controller 110 is electrically connected to the pressure sensor 156 and to the temperature sensor 158, and can acquire measurement values of the pressure sensor 156 and the temperature sensor 158. The controller 110 is also electrically connected to sensors (not shown) disposed in various places of the refrigeration cycle apparatus 100 other than the pressure sensor 156 and the temperature sensor 158, and can acquire measurement values of these sensors.
The controller 110 executes various types of control by, for example, the CPU executing a program stored in the memory. For example, when the refrigeration cycle apparatus 100 performs a cooling operation or a heating operation, the controller 110 controls the operations of various devices of the refrigeration cycle apparatus 100. In addition, the controller 110, in accordance with a capacity required of the refrigeration cycle apparatus 100, increases or decreases the number of revolutions of the compressor 10 or controls the operation of the changing unit 70 to change the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50.
Hereafter, basic operations of the various devices of the refrigeration cycle apparatus 100 during the cooling operation and the heating operation will be described without referring to the control by the changing unit 70 of the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50.
Thereafter, control of the number of revolutions of the compressor 10, and control of the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50 using the changing unit 70 (hereafter, referred to as composition ratio control in some cases to avoid complicated description) according to the capacity required of the refrigeration cycle apparatus 100 will be described.

(2-5-1) Cooling operation

The controller 110 executes the cooling operation when the execution of the cooling operation is instructed from a remote controller (not shown) or when it is determined that the execution of the cooling operation is necessary in view of the temperature of the space to be air-conditioned.
During the cooling operation, the controller 110 controls the operation of the flow path switching mechanism 15 so that the heat-source heat exchanger 20 functions as a radiator of the refrigerant and the utilization heat exchanger 40 functions as an evaporator of the refrigerant. In addition, the controller 110 starts the operation of the compressor 10 and fans (not shown) mounted in the heat source unit 2 and the utilization unit 4. Further, the controller 110 adjusts the number of revolutions of the motor 10a of the compressor 10, the number of revolutions of the fans mounted in the heat source unit 2 and the utilization unit 4, and the opening degree of the electronic expansion valve as the expansion mechanism 30, based on the measurement values of the various sensors of the refrigeration cycle apparatus 100, the target temperature of the space to be air-conditioned set by the user, and the like.

(2-5-2) Heating operation

The controller 110 executes the heating operation when an instruction to execute the heating operation is given from a remote controller (not shown), or when it is determined that the heating operation needs to be executed in view of the temperature of the space to be air-conditioned.
During the heating operation, the controller 110 controls the operation of the flow path switching mechanism 15 so that the heat-source heat exchanger 20 functions as an evaporator of the refrigerant and the utilization heat exchanger 40 functions as a radiator of the refrigerant. In addition, the controller 110 starts the operation of the compressor 10 and fans (not shown) mounted in the heat source unit 2 and the utilization unit 4. Further, the controller 110 adjusts the number of revolutions of the motor 10a of the compressor 10, the number of revolutions of the fans mounted in the heat source unit 2 and the utilization unit 4, and the opening degree of the electronic expansion valve as the expansion mechanism 30, based on the measurement values of the various sensors of the refrigeration cycle apparatus 100, the target temperature of the space to be air-conditioned set by the user, and the like.
Note that when frost formation on the heat-source heat exchanger 20 is detected during the heating operation, the controller 110 interrupts the heating operation, controls the operation of the flow path switching mechanism 15 so that the flow direction of the refrigerant in the main refrigerant circuit 50 is switched to the same direction as during the cooling operation, and performs a defrosting operation (reverse cycle defrosting operation). The defrosting operation is an operation for removing frost on the heat-source heat exchanger 20. Because the defrosting operation of the refrigeration cycle apparatus is generally known, the defrosting operation will not be described in detail.

(2-5-3) Control of compressor and changing unit according to required capacity

Hereafter, control of the compressor 10 and the changing unit 70 according to the capacity required of the refrigeration cycle apparatus 100, which is executed by the controller 110, will be described.
Before describing the control of the compressor 10 and the changing unit 70 according to the capacity required of the refrigeration cycle apparatus 100, the reason why the controller 110 switches execution between the first mode in which substantially the second refrigerant alone is caused to flow through the main refrigerant circuit 50, and the second mode in which the refrigerant mixture of the first refrigerant and the second refrigerant is caused to flow through the main refrigerant circuit 50, will be described.
When the second refrigerant (high boiling-point refrigerant) such as R1234Ze or R1234yf is used, the refrigeration cycle apparatus 100 can be operated relatively efficiently. However, when a high boiling-point refrigerant is used, insufficient capacity may occur when a heating operation is performed at a low outside-air temperature. In this regard, the insufficient capacity can be compensated for by using a non-azeotropic refrigerant mixture in which the first refrigerant (low boiling-point refrigerant), such as CO₂, is mixed with the high boiling-point refrigerant. However, when the non-azeotropic refrigerant mixture in which the first refrigerant is mixed with the second refrigerant is used, there is a problem of a decrease in efficiency compared to when the second refrigerant alone is used.
Thus, the controller 110 switches a mode between the first mode in which substantially the second refrigerant alone is caused to flow through the main refrigerant circuit 50, and the second mode in which a refrigerant mixture of the first refrigerant and the second refrigerant is caused to flow through the main refrigerant circuit 50, in accordance with the capacity required of the refrigeration cycle apparatus 100.
Specifically, the controller 110 executes the first mode during the cooling operation in which the required capacity is relatively low and insufficient capacity is unlikely to occur even when substantially the second refrigerant alone is used. Here, the controller 110 does not execute the second mode during the cooling operation. In short, the controller 110 executes the first mode when the utilization heat exchanger 40 is utilized as an evaporator. Therefore, although a detailed description is omitted, after the execution of the second mode (for example, in a case where the composition ratio control for the first mode is not executed after the execution of the second mode during the heating operation), the controller 110 executes the composition ratio control for causing substantially the second refrigerant alone to flow through the main refrigerant circuit 50 at the start of the cooling operation.
On the other hand, the controller 110 executes the second mode during the heating operation in which the required capacity tends to be relatively large and insufficient capacity may occur in the first mode. In short, the controller 110 executes the second mode when the utilization heat exchanger 40 is utilized as a radiator.
As a control method, it is possible to always execute the second mode during the heating operation.
However, even during the heating operation, it may be more efficient to execute the first mode. Description will be made with reference to Fig. 2. Fig. 2 is a diagram schematically showing a change in the COP when the capacity is changed by changing the number of revolutions of the motor 10a of the compressor 10, and a change in the COP when the capacity is changed by changing the ratio of the first refrigerant in the refrigerant. The solid line in Fig. 2 indicates a change in the COP when the number of revolutions of the motor 10a of the compressor 10 is increased to increase the capacity of the refrigeration cycle apparatus 100. The dashed lines in Fig. 2 indicate a change in the COP when the capacity of the refrigeration cycle apparatus 100 is increased by increasing the ratio of the first refrigerant in the refrigerant flowing through the main refrigerant circuit 50. As can be seen from Fig. 2, up to a predetermined capacity value (see the long dashed double short-dashed line in Fig. 2), the COP is higher when the capacity is obtained by increasing the number of revolutions of the motor 10a of the compressor 10 than when the capacity is secured by performing the composition ratio control (control of the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50 using the changing unit 70).
Therefore, during the heating operation (in other words, when the utilization heat exchanger 40 is utilized as a radiator), the controller 110 preferably executes the first mode or the second mode in accordance with the capacity required of the refrigeration cycle apparatus 100, instead of always executing the second mode. Specifically, as will be described below with reference to Figs. 3 and 4, the controller 110 preferably executes the control of the number of revolutions of the motor 10a of the compressor 10 and the composition ratio control in combination. Fig. 3 is an example of a flowchart of control performed when the refrigeration cycle apparatus 100 has insufficient capacity. Fig. 4 is an example of a flowchart of control performed when the refrigeration cycle apparatus 100 has excessive capacity. The processes of Figs. 3 and 4 are executed in parallel.
As a prerequisite of the description, it is assumed that the number of revolutions (upper-limit number of revolutions) of the motor 10a of the compressor 10 at a position corresponding to the intersection of the line indicated by the long dashed double short-dashed line and the solid line (see Fig.2) is obtained in advance. The solid line illustrated in Fig. 2 indicates a change in the COP when the number of revolutions of the motor 10a is changed to change the capacity. The upper-limit number of revolutions may be obtained by an experiment using an actual machine, or may be obtained by simulation or theoretical calculation. A value of the upper-limit number of revolutions obtained in advance is stored in the memory of the controller 110.
When the required capacity increases during the heating operation and the required capacity cannot be achieved by the current operation (when the capacity is insufficient), the controller 110 performs the control of the number of revolutions of the motor 10a of the compressor 10 or the composition ratio control according to the flowchart of Fig. 3.
In step S1 of the flowchart of Fig. 3, it is determined whether the required capacity cannot be achieved by the current operation (whether the capacity is insufficient). The determination in step S1 is repeatedly executed until it is determined that the capacity is insufficient.
When it is determined that the capacity is insufficient, the process proceeds to step S2. In step S2, it is determined whether the current number of revolutions of the motor 10a of the compressor 10 is the upper-limit number of revolutions. If it is determined that the number of revolutions of the motor 10a of the compressor 10 has not reached the upper-limit number of revolutions, the process proceeds to step S3.
In step S3, the controller 110 increases the number of revolutions of the motor 10a of the compressor 10. In step S3, the controller 110 may increase the number of revolutions by a predetermined value, or may change the increment of the number of revolutions in accordance with an insufficient capacity with respect to the required capacity. After performing step S3, the process returns to step S 1.
On the other hand, if it is determined in step S2 that the number of revolutions of the motor 10a of the compressor 10 has reached the upper-limit number of revolutions, the process proceeds to step S4. In step S4, the controller 110 performs the composition ratio control to increase the ratio of the first refrigerant in the refrigerant flowing through the main refrigerant circuit 50. In short, if the required capacity cannot be obtained even when the number of revolutions of the compressor 10 is increased to a predetermined number of revolutions (upper-limit number of revolutions) during execution of the first mode, the controller 110 executes the second mode to control the changing unit 70 so that the refrigerant mixture of the first refrigerant and the second refrigerant flows through the main refrigerant circuit 50. In step S4, the controller 110 may increase the ratio of the first refrigerant by a predetermined value (for example, increase by 2 wt%), or may determine how much the ratio of the first refrigerant is to be increased in accordance with an insufficient capacity with respect to the required capacity.
Specifically, in step S4, the controller 110 controls the opening degrees of the heat source-side valve 82a and the utilization-side valve 82b of the changing unit 70 so that the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50 detected by the detection section 150 becomes a target composition ratio. When the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50 detected by the detection section 150 becomes the target composition ratio, the controller 110 closes the heat source-side valve 82a and the utilization-side valve 82b. After performing step S4, the process returns to step S1.
Note that when the process of step S4 is performed again after performing step S4, the controller 110 controls the operation of the changing unit 70 in the second mode to change the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50, between a first composition ratio and a second composition ratio. The ratio of the first refrigerant in the second composition ratio is higher than that in the first composition ratio. In this way, by changing the ratio of the first refrigerant in a stepwise manner, it is possible to secure a necessary capacity while a decrease in efficiency due to the use of a refrigerant containing the first refrigerant excessively is suppressed.
During the heating operation, the controller 110 executes the process described with the flowchart of Fig. 4 in parallel with the process described with the flowchart of Fig. 3. The controller 110 performs the control of the number of revolutions of the motor 10a of the compressor 10 or the composition ratio control in accordance with the flowchart of Fig. 4 when, during the heating operation, the required capacity decreases and the capacity of by the current operation is excessive (during excessive capacity).
In step S11 of the flowchart of Fig. 4, it is determined whether the capacity of the current operation is excessive with respect to the required capacity. The determination in step S11 is repeatedly executed until it is determined that the capacity is excessive.
When it is determined that the capacity is excessive, the process proceeds to step S12. In step S 12, it is determined whether the current ratio of the first refrigerant in the refrigerant flowing through the main refrigerant circuit 50 (in other words, the concentration of the first refrigerant) is a lower-limit value. The lower-limit value of the ratio of the first refrigerant is, for example, a concentration determined in advance at which the controller 110 determines that the refrigerant flowing through the main refrigerant circuit 50 is substantially the second refrigerant alone. In other words, in step S12, the controller 110 determines whether the mode being executed is the first mode.
If it is determined in step S12 that the current ratio of the first refrigerant in the refrigerant flowing through the main refrigerant circuit 50 is the lower-limit value (if it is determined that the first mode is being executed), the process proceeds to step S13. On the other hand, if it is determined that the current ratio of the first refrigerant in the refrigerant flowing through the main refrigerant circuit 50 is not the lower-limit value, the process proceeds to step S14.
In step S13, the controller 110 decreases the number of revolutions of the motor 10a of the compressor 10. In step S3, the controller 110 may decrease the number of revolutions by a predetermined value, or may change how much the number of revolutions is to be decreased in accordance with a capacity that is excessive with respect to the required capacity. After performing step 13, the process returns to step S 11.
In step S14, the controller 110 performs the composition ratio control to decrease the ratio of the first refrigerant in the refrigerant flowing through the main refrigerant circuit 50. In step S14, the controller 110 may decrease the ratio of the first refrigerant by a predetermined value, or may change how much the ratio of the first refrigerant is decreased in accordance with a capacity that is excessive with respect to the required capacity.
Specifically, in step S14, the controller 110 controls the opening degrees of the heat source-side valve 82a and the utilization-side valve 82b of the changing unit 70 so that the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50 detected by the detection section 150 becomes the target composition ratio. When the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50 detected by the detection section 150 becomes the target composition ratio, the controller 110 closes the heat source-side valve 82a and the utilization-side valve 82b. After performing step 14, the process returns to step S11.

(3) Features

(3-1) The refrigeration cycle apparatus 100 includes the main refrigerant circuit 50, the changing unit 70, and the controller 110. The main refrigerant circuit 50 uses a non-azeotropic refrigerant mixture including a first refrigerant and a second refrigerant. The changing unit 70 changes a composition ratio between the first refrigerant and the second refrigerant in a refrigerant flowing through the main refrigerant circuit 50. The controller 110 controls an operation of the changing unit 70. The controller 110 executes a first mode and a second mode. The first mode is a mode in which the operation of the changing unit 70 is controlled to cause substantially the second refrigerant alone to flow through the main refrigerant circuit 50. The second mode is a mode in which the operation of the changing unit 70 is controlled to cause a refrigerant mixture of the first refrigerant and the second refrigerant to flow through the main refrigerant circuit 50.
The refrigeration cycle apparatus 100 can use substantially the second refrigerant alone or the non-azeotropic refrigerant mixture containing the first refrigerant and the second refrigerant. Therefore, the refrigeration cycle apparatus 100 can use the refrigerant having an appropriate composition in accordance with the operating condition.
Preferably, in the refrigeration cycle apparatus 100, in the first mode, a refrigerant in which the concentration of the second refrigerant is more than or equal to 92 wt% is caused to flow through the main refrigerant circuit 50.
More preferably, in the refrigeration cycle apparatus 100, in the first mode, a refrigerant in which the concentration of the second refrigerant is more than or equal to 98 wt% is caused to flow through the main refrigerant circuit 50.
(3-2) The refrigeration cycle apparatus 100 includes the detection section 150. The detection section 150 detects the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50. The controller 110 controls the operation of the changing unit 70 so that the composition ratio between the first refrigerant and the second refrigerant detected by the detection section 150 becomes a target composition ratio.
In the refrigeration cycle apparatus 100, because the composition ratio between the first refrigerant and the second refrigerant is changed while the composition ratio of the refrigerants is being detected, a refrigerant having an appropriate composition can be used in accordance with the operating condition.
(3-3) In the refrigeration cycle apparatus 100, a boiling point of the second refrigerant is higher than a boiling point of the first refrigerant.
For example, the first refrigerant is CO₂. The second refrigerant is R1234Ze or R1234yf.
(3-4) In the refrigeration cycle apparatus 100, the main refrigerant circuit 50 includes the utilization heat exchanger 40 that performs temperature adjustment of the object for temperature adjustment. When the utilization heat exchanger 40 is utilized as an evaporator, the controller 110 executes the first mode. When the utilization heat exchanger 40 is utilized as a radiator, the controller 110 executes the second mode.
In the refrigeration cycle apparatus 100, when the utilization heat exchanger 40 is utilized as an evaporator, substantially the second refrigerant alone can be used to perform an operation that places importance on efficiency. On the other hand, during an operation in which the utilization heat exchanger 40 is utilized as a radiator, where insufficient capacity is likely to occur, a necessary capacity can be obtained by using the non-azeotropic refrigerant mixture of the first refrigerant and the second refrigerant.
(3-5) When the refrigeration cycle apparatus 100 utilizes the utilization heat exchanger 40 as a radiator, the controller 110 executes the first mode or the second mode in accordance with a capacity required of the refrigeration cycle apparatus 100.
Even when the utilization heat exchanger 40 is utilized as a radiator in the refrigeration cycle apparatus 100, substantially the second refrigerant alone can be used to perform an operation that places importance on efficiency if it is not necessary to use the refrigerant mixture of the first refrigerant and the second refrigerant in terms of capacity.
(3-6) In the refrigeration cycle apparatus 100, the main refrigerant circuit 50 includes the compressor 10. The controller 110 controls the number of revolutions of the compressor 10. The controller 110 executes the second mode if the required capacity cannot be obtained even when the number of revolutions of the compressor 10 is increased to a predetermined number of revolutions (upper-limit number of revolutions) during execution of the first mode.
In the refrigeration cycle apparatus 100, a necessary capacity can be obtained while a decrease in efficiency is suppressed.
(3-7) In the refrigeration cycle apparatus 100, when executing the second mode, the controller 110 controls the operation of the changing unit 70 to change the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50 between the first composition ratio and the second composition ratio. In the second composition ratio, the ratio of the first refrigerant is higher than that in the first composition ratio.
In the refrigeration cycle apparatus 100, because the composition ratio between the first refrigerant and the second refrigerant is changed in a stepwise manner, it is possible to obtain a necessary capacity while a decrease in efficiency is suppressed.
(3-8) In the refrigeration cycle apparatus 100, the main refrigerant circuit 50 includes the compressor 10. The controller 110 controls the number of revolutions of the compressor 10. The controller 110 changes either the number of revolutions of the compressor 10 or the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50, in accordance with a change in the capacity required of the refrigeration cycle apparatus 100.
In the refrigeration cycle apparatus 100, the necessary capacity can be obtained while the decrease in efficiency is suppressed.
(3-9) In the refrigeration cycle apparatus 100, when the required capacity decreases, the controller 110 controls the changing unit 70 to lower the ratio of the first refrigerant in the refrigerant flowing through the main refrigerant circuit 50 when the ratio of the first refrigerant in the refrigerant flowing through the main refrigerant circuit 50 is higher than a predetermined value (lower-limit value), and to lower the number of revolutions of the compressor 10 when the ratio of the first refrigerant in the refrigerant flowing through the main refrigerant circuit 50 is lower than or equal to the predetermined value (lower-limit value).
In the refrigeration cycle apparatus 100, the necessary capacity can be obtained while a decrease in efficiency is suppressed.

(4) Modifications

Modifications of the above-described embodiment will be described below. Note that the following modifications may be combined as appropriate as long as the modifications do not contradict each other.

(4-1) Modification A

The mechanism for changing the composition of the refrigerant flowing through the main refrigerant circuit 50 is not limited to a mechanism such as the changing unit 70 of the above embodiment. For example, as shown in Fig. 5, the refrigeration cycle apparatus 100 may include a changing unit 170 instead of the changing unit 70.
The changing unit 170 includes a container 172 filled with an adsorbent 172a, instead of the refrigerant container 72. Other components are similar to those of the changing unit 70 of the above-described embodiment.
The adsorbent 172a has a property to adsorb the first refrigerant. To be specific, in the refrigeration cycle apparatus 100 of the first embodiment, the adsorbent 172a has the property to adsorb CO₂.
Further, the adsorbent 172a has the property not to adsorb the second refrigerant. To be specific, in the refrigeration cycle apparatus 100 of the first embodiment, the adsorbent 172a does not adsorb R1234Ze or R1234yf used as the second refrigerant. Alternatively, the adsorbent 172a may have a property such that, while the second refrigerant is also adsorbed in addition to the first refrigerant, the adsorption performance for the second refrigerant is lower than the adsorption performance for the first refrigerant.
The adsorbent 172a is, for example, zeolite having high adsorption performance for CO₂. The adsorbent 172a may be a metal-organic framework (MOF) having high adsorption performance for CO₂. The type of the adsorbent 172a is not limited to the above-described adsorbent as long as it adsorbs the first refrigerant and it does not adsorb the second refrigerant or the adsorption performance for the second refrigerant is lower than that for the first refrigerant.
In the changing unit 170, when causing the adsorbent 172a to adsorb the first refrigerant, the heat source-side valve 82a and the utilization-side valve 82b are opened, and a portion of the refrigerant flowing through the main refrigerant circuit 50 flows into the container 172. When the refrigerant passes through the inside of the container 172, the first refrigerant is adsorbed by the adsorbent 172a, whereas the second refrigerant is not adsorbed or is hardly adsorbed by the adsorbent 172a. Therefore, the refrigerant that has passed through the container 172 becomes a refrigerant having a high ratio of the second refrigerant. By allowing this refrigerant to flow into the main refrigerant circuit 50, the ratio of the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50 can be increased.
When the first refrigerant is desorbed from the adsorbent 172a, the heat source-side valve 82a and the utilization-side valve 82b are also opened, and a portion of the refrigerant flowing through the main refrigerant circuit 50 flows into the container 172. Further, during desorption, the adsorbent 172a in the container 172 is heated by, for example, heat of the hightemperature refrigerant discharged from the compressor 10 or heat generated by a heater or the like (not shown). As a result, the first refrigerant is desorbed from the adsorbent 172a and is mixed into the refrigerant flowing through the container 172, so that the refrigerant flowing out of the container 172 becomes a refrigerant having a low ratio of the second refrigerant (the ratio of the second refrigerant is lower than when flowing into the container 172). By allowing this refrigerant to flow into the main refrigerant circuit 50, the ratio of the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50 can be decreased. In other words, by allowing this refrigerant to flow into the main refrigerant circuit 50, the ratio of the first refrigerant in the refrigerant flowing through the main refrigerant circuit 50 can be increased.
Further, the configuration of the changing unit is not limited to that which has been exemplified, and may be another configuration as long as the composition ratio of the refrigerant flowing through the main refrigerant circuit 50 can be changed. For example, the changing unit may utilize a refrigerant rectification column.

(4-2) Modification B

In the above embodiment, the refrigeration cycle apparatus that uses the non-azeotropic refrigerant mixture in which CO₂ is used as the first refrigerant and R1234Ze or R1234yf of the HFO refrigerant is used as the second refrigerant has been described. However, the types of the first refrigerant and the second refrigerant are not limited to the exemplified refrigerants. For example, the first refrigerant may be R1132(E)(trans-1,2-difluoroethylene) or R1123 (trifluoroethylene) of the HFO refrigerant. Even with such a combination of refrigerants, highly efficient operation can be realized by using substantially the second refrigerant alone, and the insufficient capacity can be compensated for by using the non-azeotropic refrigerant mixture of the first refrigerant and the second refrigerant when the capacity is insufficient in the case of using the second refrigerant alone.

(4-3) Modification C

In the above-described embodiment, the refrigeration cycle apparatus of the present disclosure has been described using the example of the refrigeration cycle apparatus 100 installed in a building or the like. However, the refrigeration cycle apparatus of the present disclosure is not limited to an apparatus installed in a building. The refrigeration cycle apparatus of the present disclosure may be, for example, an apparatus mounted on a vehicle, such as an automobile.

(4-4) Modification D

In the above embodiment, the refrigeration cycle apparatus of the present disclosure has been described by taking, as an example, the case where the refrigeration cycle apparatus 100 includes the heat source unit 2 and the utilization unit 4 connected to the heat source unit 2 by the refrigerant pipes. However, the refrigeration cycle apparatus of the present disclosure is not limited to such an apparatus. For example, the refrigeration cycle apparatus of the present disclosure may be an integrated apparatus in which all devices are mounted in one casing.

(4-5) Modification E

In the above embodiment, when the utilization heat exchanger 40 is utilized as an evaporator, the controller 110 executes the first mode in which substantially the second refrigerant alone is used. However, this is not a limitation, and the controller 110, even when the utilization heat exchanger 40 is utilized as an evaporator, may execute the second mode in which the non-azeotropic refrigerant mixture of the first refrigerant and the second refrigerant is used in addition to the first mode if there is a condition in which the insufficient capacity becomes a problem. In this case, the refrigeration cycle apparatus may be an apparatus that performs only an operation of cooling the object for temperature adjustment.

(4-6) Modification F

In the above embodiment, the refrigeration cycle apparatus 100 is an apparatus capable of switching between an operation in which the utilization heat exchanger 40 is utilized as an evaporator and an operation in which the utilization heat exchanger 40 is utilized as a radiator. However, this is not a limitation, and the refrigeration cycle apparatus 100 may be an apparatus that mainly performs only an operation in which the utilization heat exchanger 40 is utilized as a radiator.

(4-7) Modification G

In the above-described embodiment, when the capacity of the refrigeration cycle apparatus 100 is increased in response to a change in the required capacity, the controller 110 changes one of the number of revolutions of the motor 10a of the compressor 10 and the composition ratio of the refrigerant flowing through the main refrigerant circuit 50 with which it is possible to maintain a higher COP after the change. Alternatively, when the capacity of the refrigeration cycle apparatus 100 is increased in response to a change in the required capacity, the controller 110 may change one of the number of revolutions of the motor 10a of the compressor 10 and the composition ratio of the refrigerant flowing through the main refrigerant circuit 50 that has a lower power increase amount.
In order to perform such control, for example, the relationship between capacity and power consumption when the number of revolutions of the motor 10a of the compressor 10 is changed, and the relationship between capacity and power consumption when the ratio of the first refrigerant in the refrigerant flowing through the main refrigerant circuit 50 is changed may be obtained, and the upper-limit number of revolutions of the compressor may be determined as a threshold in advance. The upper-limit number of revolutions is stored in, for example, memory (a storage section) of the controller 110.
In another example, as shown in Fig. 6, a current meter or a watt-hour meter 10d may be provided in the compressor 10. Then, when the demand with respect to the refrigeration cycle apparatus 100 increases, the controller 110 may actually measure a change in current value when the number of revolutions of the motor 10a of the compressor 10 is changed without changing the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50, and a change in current value when the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50 is changed without changing the number of revolutions of the motor 10a of the compressor 10. Then, the controller 110 may select one of the two controls in which an increase in current value of the compressor 10 is actually smaller, as the control to be finally executed.

(4-8) Modification H

In the above embodiment, the composition ratio between the first refrigerant and the second refrigerant is changed in a stepwise manner in the second mode, but this is not a limitation. For example, in the second mode, the controller 110 may perform control so that the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the main refrigerant circuit 50 is always a predetermined (always the same) composition ratio.

<Notes>

Although embodiments and modifications of the present disclosure have been described above, it will be understood that various changes in form and detail may be made without departing from the spirit and scope of the present disclosure as set forth in the appended claims.

The present disclosure can be widely applied to a refrigeration cycle apparatus and is useful.

REFERENCE SIGNS LIST

10: Compressor
40: Utilization heat exchanger
50: Main refrigerant circuit (refrigeration cycle)
70: Changing unit
100: Refrigeration cycle apparatus
110: Controller
150: Detection section
170: Changing unit

Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No. 2008-281326

Claims

A refrigeration cycle apparatus (100) comprising:
a refrigeration cycle (50) configured to use a non-azeotropic refrigerant mixture containing a first refrigerant and a second refrigerant;

a changing unit (70, 170) configured to change a composition ratio between the first refrigerant and the second refrigerant in a refrigerant flowing through the refrigeration cycle; and

a controller (110) configured to control an operation of the changing unit,

the controller configured to execute a first mode in which the operation of the changing unit is controlled to cause substantially the second refrigerant alone to flow through the refrigeration cycle, and a second mode in which the operation of the changing unit is controlled to cause a refrigerant mixture of the first refrigerant and the second refrigerant to flow through the refrigeration cycle.
The refrigeration cycle apparatus according to claim 1, wherein,
in the first mode, a refrigerant in which a concentration of the second refrigerant is more than or equal to 92 wt% flows through the refrigeration cycle.
The refrigeration cycle apparatus according to claim 2, wherein,
in the first mode, a refrigerant in which a concentration of the second refrigerant is more than or equal to 98 wt% flows through the refrigeration cycle.
The refrigeration cycle apparatus according to any one of claims 1 to 3, further comprising a detection section (150) configured to detect a composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the refrigeration cycle,
wherein
the controller is configured to control the operation of the changing unit so that the composition ratio of the first refrigerant and the second refrigerant detected by the detection section becomes a target composition ratio.
The refrigeration cycle apparatus according to any one of claims 1 to 4, wherein
a boiling point of the second refrigerant is higher than a boiling point of the first refrigerant.
The refrigeration cycle apparatus according to claim 5, wherein
the refrigeration cycle includes a utilization heat exchanger (40) configured to perform a temperature adjustment of an object for temperature adjustment,

when the utilization heat exchanger is utilized as an evaporator, the controller is configured to execute the first mode, and

when the utilization heat exchanger is utilized as a radiator, the controller is configured to execute the second mode.
The refrigeration cycle apparatus according to claim 6, wherein,
when the utilization heat exchanger is utilized as the radiator, the controller is configured to execute the first mode or the second mode according to a capacity required of the refrigeration cycle apparatus.
The refrigeration cycle apparatus (100) according to claim 7, wherein
the refrigeration cycle includes a compressor (10),

the controller is further configured to control a number of revolutions of the compressor, and

the controller is configured to execute the second mode if the required capacity cannot be obtained even when the number of revolutions of the compressor is increased to a predetermined number of revolutions during execution of the first mode.
The refrigeration cycle apparatus according to claim 6 or 7, wherein
the controller is configured to control, when executing the second mode, the operation of the changing unit to change the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the refrigeration cycle between a first composition ratio and a second composition ratio in which a ratio of the first refrigerant is higher than in the first composition ratio.
The refrigeration cycle apparatus (100) according to claim 9, wherein
the refrigeration cycle includes a compressor (10),

the controller is further configured to control a number of revolutions of the compressor, and

the controller is configured to change either a number of revolutions of the compressor or a composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the refrigeration cycle, in accordance with a change in the capacity required of the refrigeration cycle apparatus.
The refrigeration cycle apparatus according to claim 10, wherein,
when the required capacity increases, the controller is configured to change one of the number of revolutions of the compressor and the composition ratio between the first refrigerant and the second refrigerant in the refrigerant flowing through the refrigeration cycle that causes a smaller amount of increase in electric power of the compressor when being changed.
The refrigeration cycle apparatus according to claim 10 or 11, wherein,
when the required capacity decreases, the controller is configured to control the changing unit to lower the ratio of the first refrigerant in the refrigerant flowing through the refrigeration cycle when the ratio of the first refrigerant in the refrigerant flowing through the refrigeration cycle is higher than a predetermined value, and to lower the number of revolutions of the compressor when the ratio of the first refrigerant in the refrigerant flowing through the refrigeration cycle is lower than or equal to the predetermined value.
The refrigeration cycle apparatus according to any one of claims 1 to 12, wherein
the first refrigerant is CO₂, and

the second refrigerant is R1234Ze or R1234yf.
The refrigeration cycle apparatus according to any one of claims 1 to 12, wherein
the first refrigerant is R1132(E) or R1123, and

the second refrigerant is R1234Ze or R1234yf.