EP4729854A1

EP4729854A1 - Refrigeration cycle device

Info

Publication number: EP4729854A1
Application number: EP25739693.7A
Authority: EP
Inventors: Kanoko TSUKA; Kei Takenaka; Shun Yoshioka; Yuu HARAGUCHI; Shouta AGOU; Masato Okuno
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2024-08-21
Filing date: 2025-04-24
Publication date: 2026-04-22
Also published as: JP2026036980A; WO2026042342A1

Abstract

A refrigeration cycle apparatus (100) includes a bridge circuit (40). The bridge circuit (40) keeps a traveling direction of a refrigerant (R) the same in both a cold heat utilization operation and a hot heat utilization operation. The bridge circuit (40) includes a first flow path (AB), a second flow path (BC), a third flow path (DC), a fourth flow path (AD), and a first check valve (41), and a second check valve (42), a third check valve (43), and a fourth check valve (44) provided in the first flow path (AB), the second flow path (BC), the third flow path (DC), and the fourth flow path (AD), respectively. A flow path resistance of the fourth flow path (AD) is larger than a flow path resistance of the first flow path (AB), or a flow path resistance of the third flow path (DC) is larger than a flow path resistance of the second flow path (BC).

Description

TECHNICAL FIELD

The present disclosure relates to a refrigeration cycle apparatus including a heat exchanger that handles a non-azeotropic mixed refrigerant and achieves therein a counterflow in which a traveling direction of air faces a traveling direction of the non-azeotropic mixed refrigerant.

BACKGROUND ART

The refrigeration cycle apparatus disclosed in Patent Literature 1 ( JP 2009-222362 A ) includes a bridge circuit. Such a bridge circuit may be mounted on a refrigeration cycle apparatus that handles a non-azeotropic mixed refrigerant. In this case, the bridge circuit functions to always keep the same traveling direction of a refrigerant flowing through a heat source heat exchanger regardless of which one of a cold heat utilization operation and a hot heat utilization operation the refrigeration cycle apparatus performs, and thus achieves the counterflow of the heat source heat exchanger.

SUMMARY OF THE INVENTION

The bridge circuit is provided with a check valve to keep a direction in which the refrigerant flows the same. However, when the circulation amount of the refrigerant in the refrigeration cycle apparatus decreases, the pressure of the refrigerant may not greatly differ at both ends of the check valve. In this case, depending on the structure of the check valve, the check valve may not perform a normal opening and closing operation, and there is a possibility that the function of the bridge circuit for handling the non-azeotropic mixed refrigerant is impaired.

A refrigeration cycle apparatus according to a first aspect includes a compressor, an expansion valve, a four-way switching valve, a first heat exchanger, a second heat exchanger, and a bridge circuit. The compressor compresses a refrigerant. The expansion valve decompresses the refrigerant. The four-way switching valve switches between a first operation and a second operation. The first heat exchanger includes a refrigerant inlet and a refrigerant outlet. The first heat exchanger functions as a condenser in the first operation and functions as an evaporator in the second operation. The second heat exchanger functions as an evaporator in the first operation and functions as a condenser in the second operation. In both the first operation and the second operation, the bridge circuit causes the refrigerant to enter the first heat exchanger at the refrigerant inlet and exit the first heat exchanger at the refrigerant outlet.
The bridge circuit includes a first node, a second node, a third node, a fourth node, a first flow path, a second flow path, a third flow path, a fourth flow path, a first check valve, a second check valve, a third check valve, and a fourth check valve.
The first flow path extends from the first node to the second node. The second flow path extends from the second node to the third node. The third flow path extends from the fourth node to the third node. The fourth flow path extends from the first node to the fourth node. The first check valve causes the refrigerant to flow from the first node to the second node. The second check valve causes the refrigerant to flow from the second node to the third node. The third check valve causes the refrigerant to flow from the fourth node to the third node. The fourth check valve causes the refrigerant to flow from the first node to the fourth node.
The first node is connected to the refrigerant outlet. The second node is connected to the compressor via the four-way switching valve. The third node is connected to the refrigerant inlet. The fourth node is connected to the expansion valve.
The flow path resistance of the fourth flow path is larger than the flow path resistance of the first flow path, or the flow path resistance of the third flow path is larger than the flow path resistance of the second flow path.
In this configuration, the flow path resistance of the third flow path or the fourth flow path is large. Therefore, even when incomplete operation of the third check valve or the fourth check valve can occur due to, for example, a small circulation amount of the refrigerant, since the magnitude of the flow path resistance of the third flow path increases the pressure difference between the refrigerants at both ends of the fourth check valve, or the magnitude of the flow path resistance of the fourth flow path increases the pressure difference between the refrigerants at both ends of the third check valve, malfunction of the third check valve or the fourth check valve is less likely to occur.
A refrigeration cycle apparatus according to a second aspect is the refrigeration cycle apparatus according to the first aspect, in which a flow path sectional area of the fourth flow path is smaller than a flow path sectional area of the first flow path, or a flow path sectional area of the third flow path is smaller than a flow path sectional area of the second flow path.
In this configuration, the flow path sectional area of the third flow path or the fourth flow path is small. As a result, since the flow path resistance of the third flow path or the fourth flow path can be increased, malfunction of the third check valve or the fourth check valve is less likely to occur.
A refrigeration cycle apparatus according to a third aspect is the refrigeration cycle apparatus according to the first or second aspect, in which a flow path sectional area of the third flow path is smaller than a flow path sectional area of the second flow path.
In this configuration, the flow path sectional area of the third flow path is small. As a result, since the flow path resistance of the third flow path can be increased, malfunction of the third check valve is less likely to occur.
A refrigeration cycle apparatus according to a fourth aspect is the refrigeration cycle apparatus according to any one of the first to third aspects, in which a flow path sectional area of the fourth flow path is smaller than a flow path sectional area of the first flow path.
In this configuration, the flow path sectional area of the fourth flow path is small. As a result, since the flow path resistance of the fourth flow path can be increased, malfunction of the fourth check valve is less likely to occur.
A refrigeration cycle apparatus according to a fifth aspect is the refrigeration cycle apparatus according to any one of the first to fourth aspects, in which a flow path sectional area of the third flow path is smaller than 55% of a flow path sectional area of the second flow path.
In this configuration, the flow path resistance of the third flow path is smaller than 55% of the flow path sectional area of the second flow path. As a result, since the flow path resistance of the third flow path can be significantly increased, malfunction of the third check valve is efficiently suppressed.
A refrigeration cycle apparatus according to a sixth aspect is the refrigeration cycle apparatus according to any one of the first to fifth aspects, in which a flow path sectional area of the fourth flow path is smaller than 55% of a flow path sectional area of the first flow path.
In this configuration, the flow path sectional area of the fourth flow path is smaller than 55% of the flow path sectional area of the first flow path. As a result, since the flow path resistance of the fourth flow path can be significantly increased, malfunction of the fourth check valve is efficiently suppressed.
A refrigeration cycle apparatus according to a seventh aspect is the refrigeration cycle apparatus according to any one of the first to sixth aspects, in which the first heat exchanger is a heat source heat exchanger, and the second heat exchanger is a utilization heat exchanger.
In this configuration, the first heat exchanger is the heat source heat exchanger. Therefore, the heat source heat exchanger can achieve a counterflow in which traveling directions of the refrigerant and air face each other.
A refrigeration cycle apparatus according to an eighth aspect is the refrigeration cycle apparatus according to any one of the first to sixth aspects, in which the first heat exchanger is a utilization heat exchanger, and the second heat exchanger is a heat source heat exchanger.
In this configuration, the first heat exchanger is the utilization heat exchanger. Therefore, the utilization heat exchanger can achieve a counterflow in which the traveling directions of the refrigerant and the air face each other.
A refrigeration cycle apparatus according to a ninth aspect is the refrigeration cycle apparatus according to any one of the first to eighth aspects, in which the refrigerant includes a non-azeotropic mixed refrigerant.
The refrigerant includes a non-azeotropic mixed refrigerant in this configuration. In this case, the bridge circuit can also achieve a counterflow in which the traveling directions of the refrigerant and the air face each other regardless of an operating mode. Therefore, a decrease in performance of the refrigeration cycle apparatus is suppressed.
A refrigeration cycle apparatus according to a tenth aspect is the refrigeration cycle apparatus according to any one of the first to ninth aspects, in which a minimum value obtainable as a circulation amount of the refrigerant in the refrigeration cycle apparatus in the first operation or the second operation is less than 35.00 kg/h.
In this configuration, a small minimum value of the circulation amount of the refrigerant can cause incomplete operation of the third check valve or the fourth check valve. Even in this case, since the flow path resistance of the third flow path or the fourth flow path is large, malfunction of the third check valve or the fourth check valve can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a configuration of a refrigeration cycle apparatus 100 according to a first embodiment.
FIG. 2 is a schematic diagram showing a configuration of a heat source heat exchanger 13.
FIG. 3 is a schematic diagram showing a configuration of a heat exchanger body 60.
FIG. 4 is a schematic diagram showing a counterflow between a refrigerant R and an air flow AF in the heat source heat exchanger 13.
FIG. 5 is a schematic diagram showing an operation of the refrigeration cycle apparatus 100 in a cold heat utilization operation.
FIG. 6 is a schematic diagram showing an operation of the refrigeration cycle apparatus 100 in a hot heat utilization operation.
FIG. 7 is a graph showing temperature changes of the refrigerant R and the air flow AF in the cold heat utilization operation.
FIG. 8 is a graph showing temperature changes of the refrigerant R and the air flow AF in the hot heat utilization operation.
FIG. 9 is a sectional view showing a structure of a check valve 47.
FIG. 10 is a schematic diagram showing a configuration of a refrigeration cycle apparatus 100A according to a second embodiment.
FIG. 11 is a schematic diagram showing a configuration of a refrigeration cycle apparatus 100B according to a third embodiment.

DESCRIPTION OF EMBODIMENTS

(1) Overall configuration

FIG. 1 shows a configuration of a refrigeration cycle apparatus 100 according to a first embodiment. The refrigeration cycle apparatus 100 provides cold heat or hot heat acquired from a heat source to a user by circulating the refrigerant R. The refrigeration cycle apparatus 100 provides cold heat to the user in a cold heat utilization operation. The refrigeration cycle apparatus 100 provides cold heat to the user in a hot heat utilization operation. The refrigeration cycle apparatus 100 can be configured as an air conditioner, a refrigerator, a freezer, a water heater, a floor heating device, or the like. When the refrigeration cycle apparatus 100 is an air conditioner, the cold heat utilization operation and the hot heat utilization operation correspond to a cooling operation and a heating operation, respectively. The refrigeration cycle apparatus 100 includes a heat source unit 10, a utilization unit 20, and a connection pipe group 30.

(2) Detailed configuration

(2-1) Refrigerant R

A refrigerant R includes a non-azeotropic mixed refrigerant. The non-azeotropic mixed refrigerant is a refrigerant produced by mixing a plurality of refrigerant components having different boiling points. The refrigerant R is, for example, R454C. R454C is a mixture of R32 and R1234yf.
The non-azeotropic mixed refrigerant shows a remarkable temperature glide. The temperature glide is a range of temperature change appearing in a process in which the refrigerant R evaporates or condenses. In the process in which the non-azeotropic mixed refrigerant evaporates, a low-boiling-point component evaporates first, and then a high-boiling-point component evaporates later. In the process in which the non-azeotropic mixed refrigerant condenses, a high-boiling-point component condenses first, and then a low-boiling-point component condenses later. The presence of such a plurality of boiling points causes a large temperature glide.

(2-2) Heat source unit 10

The heat source unit 10 acquires cold heat or hot heat from air, which is a heat source. The heat source unit 10 includes a compressor 11, a four-way switching valve 12, a heat source heat exchanger 13, a heat source fan 14, a bridge circuit 40, a heat source expansion valve 15, an accumulator 16, a liquid shutoff valve 17, and a gas shutoff valve 18.

(2-2-1) Compressor 11

The compressor 11 includes a suction pipe 11a and a discharge pipe 11b. The compressor 11 sucks the refrigerant R in a low-pressure gas state from the suction pipe 11a, compresses the refrigerant R, and discharges the refrigerant R in a high-pressure gas state from the discharge pipe 11b.

(2-2-2) Four-way switching valve 12

The four-way switching valve 12 switches between the cold heat utilization operation and the hot heat utilization operation by switching a traveling direction of the refrigerant R. When the cold heat utilization operation is performed, the four-way switching valve 12 achieves a connection indicated by a solid line in FIG. 1 and causes the refrigerant R to travel in a direction indicated by an arrow CO. When the hot heat utilization operation is performed, the four-way switching valve 12 achieves a connection indicated by a broken line in FIG. 1 and causes the refrigerant R to travel in a direction indicated by an arrow HO.

(2-2-3) Heat source heat exchanger 13 and heat source fan 14

(2-2-3-1) Functions

The heat source heat exchanger 13 causes the refrigerant R to acquire cold heat or hot heat by exchanging heat between air, which is a heat source, and the refrigerant R. When the cold heat utilization operation is performed, the heat source heat exchanger 13 functions as a condenser or a heat radiator for the refrigerant R, and causes the refrigerant R to acquire cold heat. When the hot heat utilization operation is performed, the heat source heat exchanger 13 functions as an evaporator or a heat absorber for the refrigerant R, and causes the refrigerant R to acquire hot heat.
The heat source heat exchanger 13 includes a refrigerant inlet 13a and a refrigerant outlet 13b. The refrigerant R enters the heat source heat exchanger 13 at the refrigerant inlet 13a and exits from the heat source heat exchanger 13 at the refrigerant outlet 13b. The heat source fan 14 generates an air flow passing through the heat source heat exchanger 13 to promote heat exchange between air and the refrigerant R. Hereinafter, the term "condenser" can include use as a heat radiator without phase transition of the refrigerant R, and the term "evaporator" can include use as a heat absorber without phase transition of the refrigerant R.

(2-2-3-2) Structure

FIG. 2 shows a structure of the heat source heat exchanger 13. The heat source heat exchanger 13 includes a diverger 50, a heat exchanger body 60, and a converger 70 in addition to the refrigerant inlet 13a and the refrigerant outlet 13b.
The diverger 50 includes a diverger body 51 to which a pipe constituting the refrigerant inlet 13a is connected, and a plurality of diverger pipes 56 extending from the diverger body 51. The diverger body 51 has one intake port 53 and a plurality of exhaust ports 54. The refrigerant inlet 13a is connected to the intake port 53. The plurality of diverger pipes 56 are connected to the respective exhaust ports 54. The refrigerant R flowing into the refrigerant inlet 13a is diverged into the plurality of diverger pipes 56.
The heat exchanger body 60 is a portion that exchanges heat between the refrigerant R and air. The heat exchanger body 60 has a plurality of refrigerant paths 61 through which the refrigerant R flows. The plurality of refrigerant paths 61 includes a lowest path 61L arranged at the lowest height and a highest path 61H disposed at the highest height. Each of the refrigerant paths 61 has a refrigerant path inlet 62 and a refrigerant path outlet 63. Each of the plurality of refrigerant path inlets 62 is connected to the respective diverger pipe 56.
The converger 70 includes a plurality of converger pipes 75 and a converger body 76. Each converger pipe 75 connects one refrigerant path outlet 63 and the converger body 76. The converger body 76 has an outlet pipe connecting portion 77 to which a pipe constituting the refrigerant outlet 13b is connected. The converger 70 converges the refrigerant R received from the plurality of refrigerant paths 61 and exhausts the refrigerant R to the refrigerant outlet 13b.
FIG. 3 shows a configuration of the heat exchanger body 60. The heat exchanger body 60 includes a plurality of heat transfer tubes 65 and a plurality of fins 67. Each of the heat transfer tubes 65 is inserted into through holes of all the fins 67. Ends of two adjacent heat transfer tubes 65 are connected by a U-shaped tube 66. One refrigerant path 61 includes the plurality of heat transfer tubes 65 and a plurality of the U-shaped tubes 66.

(2-2-3-3) Counterflow

FIG. 4 schematically shows a counterflow achieved in the heat source heat exchanger 13 and the heat source fan 14. The counterflow means that the traveling direction of the refrigerant R is opposite to a traveling direction of an air flow AF. Achieving the counterflow in the heat source heat exchanger 13 is important for heat exchange of the refrigerant R having a large temperature glide.
The refrigerant R flows into the heat source heat exchanger 13 from the refrigerant inlet 13a, is diverged by the diverger 50, passes through the plurality of refrigerant paths 61, converges at the converger 70, and flows out of the heat source heat exchanger 13 from the refrigerant outlet 13b. Each of the refrigerant paths 61 has a plurality of heat transfer tubes 65, and includes the heat transfer tubes 65 disposed in a first row L1 closer to a fin front end 671 of the heat source heat exchanger 13 and the heat transfer tubes 65 disposed in a second row L2 closer to a fin rear end 672. After flowing in from the refrigerant inlet 13a, the refrigerant R always first passes through the heat transfer tubes 65 in the first row L1, then passes through the heat transfer tubes 65 in the second row L2, and finally flows out from the refrigerant outlet 13b. In other words, the refrigerant R travels from the fin front end 671 toward the fin rear end 672.
In contrast, the air flow AF generated by the heat source fan 14 passes between the adjacent fins 67 while traveling from the fin rear end 672 toward the fin front end 671.

(2-2-4) Bridge circuit 40

Referring to FIG. 1 again, the bridge circuit 40 always achieves the counterflow between the refrigerant R and the air flow AF in the heat source heat exchanger 13. In a refrigerant circuit without the bridge circuit 40, the direction of the refrigerant R flowing through the heat exchanger is reversed every time the cold heat utilization operation and the hot heat utilization operation are switched. In the refrigeration cycle apparatus 100 according to the present embodiment, the bridge circuit 40 always keeps the same traveling direction of the refrigerant R in the heat source heat exchanger 13 regardless of which one of the cold heat utilization operation and the hot heat utilization operation is performed. The bridge circuit 40 causes the refrigerant R to always enter the heat source heat exchanger 13 at the refrigerant inlet 13a and always exit the heat source heat exchanger 13 at the refrigerant outlet 13b regardless of which one of the direction indicated by the arrow CO and the direction indicated by the arrow HO the traveling direction of the refrigerant R is.
The bridge circuit 40 includes a first node A, a second node B, a third node C, and a fourth node D. The first node A is connected to the refrigerant outlet 13b. The second node B is connected to the compressor 11 via the four-way switching valve 12. The third node C is connected to the refrigerant inlet 13a. The fourth node D is connected to the heat source expansion valve 15.
The bridge circuit 40 further includes a first flow path AB extending from the first node A to the second node B, a second flow path BC extending from the second node B to the third node C, a third flow path DC extending from the fourth node D to the third node C, and a fourth flow path AD extending from the first node A to the fourth node D.
The bridge circuit 40 includes a first check valve 41, a second check valve 42, a third check valve 43, and a fourth check valve 44. These check valves keep the same traveling direction of the refrigerant R in the flow path where it is installed and prevent backflow of the refrigerant R. The first check valve 41 is provided in the first flow path AB and allows the refrigerant R to flow only in a direction from the first node A toward the second node B. The second check valve 42 is provided in the second flow path BC, and allows the refrigerant R to flow only in a direction from the second node B toward the third node C. The third check valve 43 is provided in the third flow path DC, and allows the refrigerant R to flow only in a direction from the fourth node D toward the third node C. The fourth check valve 44 is provided in the fourth flow path AD, and allows the refrigerant R to flow only in a direction from the first node A toward the fourth node D.

(2-2-5) Heat source expansion valve 15

The heat source expansion valve 15 decompresses the refrigerant R. The heat source expansion valve 15 is constituted by an electric valve having an adjustable opening degree. When the opening degree of the heat source expansion valve 15 is set to be small, the amount of the refrigerant R that can pass through the heat source expansion valve 15 decreases, and the pressure of the refrigerant R after passing through the heat source expansion valve 15 decreases.

(2-2-6) Accumulator 16

The accumulator 16 stores only a liquid component contained in the refrigerant R therein, and allows only a gas component to pass therethrough. The accumulator 16 is connected to the suction pipe 11a of the compressor 11, and restrains the liquid component of the refrigerant R from damaging the compressor 11.

(2-2-7) Liquid shutoff valve 17 and gas shutoff valve 18

The liquid shutoff valve 17 and the gas shutoff valve 18 manually shut off movement of the refrigerant R. The liquid shutoff valve 17 and the gas shutoff valve 18 are manually opened or closed by an installation operator of the refrigeration cycle apparatus 100.

(2-3) Utilization unit 20

The utilization unit 20 provides the user with cold heat or hot heat acquired from the heat source by the heat source unit 10. The utilization unit 20 includes a utilization heat exchanger 23 and a utilization fan 24.

(2-3-1) Utilization heat exchanger 23

The utilization heat exchanger 23 provides cold heat or hot heat to the user by exchanging heat between the refrigerant R and air in an environment where the user is present or water used by the user. When the cold heat utilization operation is performed, the utilization heat exchanger 23 functions as an evaporator of the refrigerant R and provides cold heat to the user. When the hot heat utilization operation is performed, the utilization heat exchanger 23 functions as a condenser of the refrigerant R and provides hot heat to the user. As described above, here, the term "condenser" can include use as a heat radiator without phase transition of the refrigerant R, and the term "evaporator" can include use as a heat absorber without phase transition of the refrigerant R.

(2-3-2) Utilization fan 24

The utilization fan 24 is provided in the case where a user uses cold heat or hot heat via air. The utilization fan 24 generates an air flow passing through the utilization heat exchanger 23 to promote heat exchange between air and the refrigerant R.

(2-4) Connection pipe group 30

The connection pipe group 30 constitutes a circulation path of the refrigerant R by connecting the heat source unit 10 and the utilization unit 20. The connection pipe group 30 includes a liquid connection pipe 31 and a gas connection pipe 32. The liquid connection pipe 31 mainly allows the refrigerant R in a liquid state or a gas-liquid two-phase state to pass therethrough. The liquid connection pipe 31 connects the liquid shutoff valve 17 and the utilization heat exchanger 23. The gas connection pipe 32 mainly allows the refrigerant R in the high-pressure gas state or in the low-pressure gas state to pass therethrough. The gas connection pipe 32 connects the gas shutoff valve 18 and the utilization heat exchanger 23.

(3) Overall operation

(3-1) Cold heat utilization operation

FIG. 5 shows an operation of the refrigeration cycle apparatus 100 in the cold heat utilization operation. The four-way switching valve 12 achieves a connection indicated in this drawing and causes the refrigerant R to travel in the direction indicated by the arrow CO.
The compressor 11 sucks the refrigerant R in the low-pressure gas state from the suction pipe 11a, and discharges the refrigerant R in the high-pressure gas state from the discharge pipe 11b. The refrigerant R in the high-pressure gas state passes through the four-way switching valve 12 and reaches the second node B of the bridge circuit 40. Thereafter, the refrigerant R passes through the second check valve 42 and reaches the third node C. The refrigerant R then enters the heat source heat exchanger 13 at the refrigerant inlet 13a. The heat source heat exchanger 13 condenses the refrigerant R by using cold heat of air to generate the refrigerant R in a high-pressure liquid state. The refrigerant R in the high-pressure liquid state exits the heat source heat exchanger 13 from the refrigerant outlet 13b, and then reaches the first node A. Thereafter, the refrigerant R passes through the fourth check valve 44 and reaches the fourth node D. Then, the refrigerant R in the high-pressure liquid state is decompressed by the heat source expansion valve 15 to become the refrigerant R in the gas-liquid two-phase state. After that, the refrigerant R passes through the liquid shutoff valve 17 and the liquid connection pipe 31 and reaches the utilization heat exchanger 23. The utilization heat exchanger 23 evaporates the refrigerant R in the gas-liquid two-phase state to provide the user with cold heat carried by the refrigerant R and generate the refrigerant R in the low-pressure gas state. Thereafter, the refrigerant R passes through the gas connection pipe 32, the gas shutoff valve 18, the four-way switching valve 12, and the accumulator 16 in that order, and then is sucked into the compressor 11 through the suction pipe 11a.

(3-2) Hot heat utilization operation

FIG. 6 shows an operation of the refrigeration cycle apparatus 100 in the hot heat utilization operation. The four-way switching valve 12 achieves a connection indicated in this drawing and causes the refrigerant R to travel in the direction indicated by the arrow HO.
The compressor 11 sucks the refrigerant R in the low-pressure gas state from the suction pipe 11a, and discharges the refrigerant R in the high-pressure gas state from the discharge pipe 11b. The refrigerant R in the high-pressure gas state passes through the four-way switching valve 12, the gas shutoff valve 18, and the gas connection pipe 32 in that order and reaches the utilization heat exchanger 23. The utilization heat exchanger 23 condenses the refrigerant R in the high-pressure gas state to provide the user with hot heat carried by the refrigerant R and generate the refrigerant R in the high-pressure liquid state. Thereafter, the refrigerant R passes through the liquid connection pipe 31 and the liquid shutoff valve 17, and reaches the heat source expansion valve 15. Then, the refrigerant R in the high-pressure liquid state is decompressed by the heat source expansion valve 15 to become the refrigerant R in the gas-liquid two-phase state. Thereafter, the refrigerant R passes through the fourth node D, the third check valve 43, and the third node C in that order. The refrigerant R then enters the heat source heat exchanger 13 at the refrigerant inlet 13a. The heat source heat exchanger 13 evaporates the refrigerant R by using hot heat of air to generate the refrigerant R in a low-pressure gas state. The refrigerant R in the low-pressure gas state exits the heat source heat exchanger 13 from the refrigerant outlet 13b, and then reaches the first node A. Thereafter, the refrigerant R passes through the first check valve 41 and reaches the second node B. Thereafter, the refrigerant R passes through the four-way switching valve 12 and the accumulator 16 in that order, and then is sucked into the compressor 11 through the suction pipe 11a.

(3-3) Effects of counterflow in heat source heat exchanger 13

FIGS. 7 and 8 are examples of temperature changes of the refrigerant R and the air flow AF in the heat source heat exchanger 13. The horizontal axis represents a position y in a y direction. A position y1 is the position of the fin rear end 672, and y2 is the position of the fin front end 671. The vertical axis represents a temperature T of the refrigerant R and the air flow AF. The numerical value of the temperature T shown in the drawing is merely an example.
FIG. 7 shows temperature changes in the cold heat utilization operation. In this drawing, it is assumed that the heat source heat exchanger 13 achieves a counterflow between the refrigerant R and the air flow AF. The air flow AF proceeds from the position y1 of the fin rear end 672 to the position y2 of the fin front end 671. In contrast, the refrigerant R proceeds from the position y2 of the fin front end 671 to the position y1 of the fin rear end 672.
The heat source heat exchanger 13 functions as a condenser. In the heat source heat exchanger 13, the refrigerant R is deprived of heat by the air flow AF. Therefore, the temperature of the refrigerant R decreases as the refrigerant R proceeds from the position y2 to the position y1. Since the air flow AF receives heat from the refrigerant R, the temperature of the air flow AF increases as the air flow AF proceeds from the position y1 to the position y2.
A temperature difference ΔT1 between the refrigerant R and the air flow AF at the position y1 and a temperature difference ΔT2 between the refrigerant R and the air flow AF at the position y2 both ensure a sufficient magnitude. Therefore, heat is transferred from the refrigerant R to the air flow AF without any trouble in an entire region of the heat source heat exchanger 13.
FIG. 8 shows temperature changes in the hot heat utilization operation. The heat source heat exchanger 13 functions as an evaporator. Since the refrigerant R receives heat from the air flow AF in the heat source heat exchanger 13, the temperature of the air flow AF decreases as the air flow AF proceeds from the position y1 to the position y2.
The refrigerant R receives heat from the air flow AF. Therefore, the temperature of the refrigerant R increases as the refrigerant R proceeds through the heat source heat exchanger 13. In this drawing, two types of temperature changes of the refrigerant R are shown.
An arrow Rn indicates a temperature change in a comparative example. In the comparative example, it is assumed that the bridge circuit 40 does not exist in the refrigerant circuit and the refrigerant R proceeds in a direction opposite to that of the cold heat utilization operation. At this time, similarly to the air flow AF, the refrigerant R proceeds from the position y1 of the fin rear end 672 to the position y2 of the fin front end 671.
An arrow Rc indicates a temperature change in the heat source heat exchanger 13 according to the present embodiment. The refrigerant circuit includes the bridge circuit 40, and counterflow can be achieved in the heat source heat exchanger 13 similarly to the cold heat utilization operation. At this time, the refrigerant R proceeds from the position y2 of the fin front end 671 to the position y1 of the fin rear end 672, contrary to the air flow AF.
In the comparative example indicated by the arrow Rn, a temperature difference ΔT3 between the refrigerant R and the air flow AF at the position y1 is greatly different from a temperature difference ΔT4 between the refrigerant R and the air flow AF at the position y2. The temperature difference ΔT4 cannot secure a sufficient magnitude. This indicates that the transfer of heat from the air flow AF to the refrigerant R can be inhibited near the fin front end 671.
On the other hand, in the present embodiment indicated by the arrow Rc, a temperature difference ΔT5 between the refrigerant R and the air flow AF at the position y1 and a temperature difference ΔT6 between the refrigerant R and the air flow AF at the position y2 both ensure a sufficient magnitude. It is therefore understood that the heat is transferred from the air flow AF to the refrigerant R without any problem in the entire region of the heat source heat exchanger 13 according to the present embodiment.
When the refrigerant R having a large temperature glide, such as a non-azeotropic mixed refrigerant, is used, it tends to be difficult to secure a sufficient temperature difference between the refrigerant R and the air flow AF at an outlet of the refrigerant R in the heat exchanger. When a small value such as the temperature difference ΔT4 is generated, the heat exchange performance of the heat source heat exchanger 13 deteriorates. This problem can be improved by mounting the bridge circuit 40 to always achieve a counterflow between the refrigerant R and the air flow AF in the heat source heat exchanger 13.

(3-4) Circulation amount of refrigerant R

The circulation amount of the refrigerant R in the refrigeration cycle apparatus 100 varies depending on an operation situation, and increases or decreases in a range from a minimum value to a maximum value. In the refrigeration cycle apparatus 100, the circulation amount of the refrigerant R may become significantly small. In both the cold heat utilization operation and the hot heat utilization operation, the minimum value of the circulation amount of the refrigerant R in the refrigeration cycle apparatus 100 is less than 35.00 kg/h.

(4) Detailed structure of bridge circuit 40

(4-1) Check valve

FIG. 9 shows a detailed structure of the check valve 47 used in the bridge circuit 40. The check valve 47 is the first check valve 41, the second check valve 42, the third check valve 43, or the fourth check valve 44. The check valve 47 is installed in a pipe P forming a flow path such as the first flow path AB, the second flow path BC, the third flow path DC, or the fourth flow path AD.
The check valve 47 includes a guide member 471, a valve body 472, a valve seat 473, and a seal member 474. The guide member 471 has a cylindrical shape and guides the valve body 472. The guide member 471 is provided with an outflow port 471a. The valve body 472 is movable in the guide member 471 and includes a valve portion 472a and a blade portion 472b. The blade portion 472b comes into contact with an inner peripheral surface of the guide member 471 to stabilize the valve portion 472a. The valve seat 473 closes the flow path by coming into contact with the valve portion 472a. The valve seat 473 is provided with an inflow port 473a. The seal member 474 seals a gap between the check valve 47 and the pipe P.
When the pressure of the refrigerant R at the inflow port 473a is higher than the pressure of the refrigerant R at the outflow port 471a, the check valve 47 opens the flow path and allows the refrigerant R to pass therethrough. When the pressure of the refrigerant R at the inflow port 473a is smaller than the pressure of the refrigerant R at the outflow port 471a, the valve body 472 moves toward the valve seat 473, and thus, the check valve 47 closes the flow path and shuts off the refrigerant R. In order to close the check valve 47, the valve portion 472a needs to be pressed against the valve seat 473 with a certain degree of force. To achieve this, the pressure difference between the refrigerant R at the inflow port 473a and the outflow port 471a needs to be larger than a predetermined value. If a sufficient pressure difference of the refrigerant R cannot be obtained, the check valve 47 may be incompletely closed, and there is a possibility that the refrigerant R passes between the inflow port 473a and the outflow port 471a.

(4-2) Flow path

The flow path resistances of the first flow path AB, the second flow path BC, the third flow path DC, and the fourth flow path AD shown in FIG. 1 are set to be different from each other. Specifically, the flow path resistance of the fourth flow path AD is set to be larger than the flow path resistance of the first flow path AB, or the flow path resistance of the third flow path DC is set to be larger than the flow path resistance of the second flow path BC. Preferably, the flow path resistance of the fourth flow path AD is set to be larger than the flow path resistance of the first flow path AB, and the flow path resistance of the third flow path DC is set to be larger than the flow path resistance of the second flow path BC.
The difference in flow path resistance is achieved by a difference in flow path sectional area. The flow path sectional areas of the first flow path AB, the second flow path BC, the third flow path DC, and the fourth flow path AD are set to be different from each other. Specifically, the flow path sectional area of the fourth flow path AD is set to be smaller than the flow path sectional area of the first flow path AB, or the flow path sectional area of the third flow path DC is set to be smaller than the flow path sectional area of the second flow path BC. For example, the flow path sectional area of the fourth flow path AD is set to be smaller than 55% of the flow path sectional area of the first flow path AB, or the flow path sectional area of the third flow path DC is set to be smaller than 55% of the flow path sectional area of the second flow path BC.
Preferably, the flow path sectional area of the fourth flow path AD is set to be smaller than the flow path sectional area of the first flow path AB, and the flow path sectional area of the third flow path DC is set to be smaller than the flow path sectional area of the second flow path BC.
In order to reduce the flow path sectional area of any one of the first flow path AB, the second flow path BC, the third flow path DC, or the fourth flow path AD, the diameter of the pipe P constituting the flow path shown in FIG. 9 may be set to be small. Alternatively, in order to reduce the flow path sectional area, the flow path may be configured by an electromagnetic valve or a capillary. For example, by installing an electric valve having an adjustable opening degree in the flow path, the flow path sectional area can be reduced by electrical control. Alternatively, the flow path sectional area can be reduced by installing a capillary in the flow path or configuring the flow path itself with a capillary.

(5) Defective closing of check valve

(5-1) Defective closing of fourth check valve 44

The fourth check valve 44 is required to be closed in the hot heat utilization operation. Both ends of the fourth check valve 44 are the first node A and the fourth node D. As shown in FIG. 6, in the hot heat utilization operation, the refrigerant R in the low-pressure gas state exists at the first node A, and the refrigerant R in the gas-liquid two-phase state exists at the fourth node D. The refrigerant R in the gas-liquid two-phase state, which contains a gas component and a liquid component, makes the operation of the fourth check valve 44 unstable. Therefore, the closing of the fourth check valve 44 tends to be incomplete.
When the refrigerant R leaks at the fourth check valve 44 to be closed, the refrigerant R in the gas-liquid two-phase state leaks from the fourth node D to the first node A. The refrigerant R in the gas-liquid two-phase state, which contains a liquid component, has a large density. Therefore, the mass of the refrigerant R leaking through the fourth check valve 44 is large.
As described above, there is a possibility that the malfunction of the fourth check valve 44 in the hot heat utilization operation significantly adversely affects the operation of the refrigerant circuit.

(5-2) Defective closing of third check valve 43

The third check valve 43 is required to be closed in the cold heat utilization operation. Both ends of the third check valve 43 are the third node C and the fourth node D. As shown in FIG. 5, in the cold heat utilization operation, the refrigerant R in the high-pressure gas state exists at the third node C, and the refrigerant R in the high-pressure liquid state exists at the fourth node D. Since the refrigerant R in the gas-liquid two-phase state does not exist at both ends of the third check valve 43, the risk that the closing of the third check valve 43 becomes unstable is not as large as that of the fourth check valve 44 in the hot heat utilization operation.
If the refrigerant R leaks at the third check valve 43 to be closed, the refrigerant R in the high-pressure gas state leaks from the third node C to the fourth node D. The refrigerant R in a gas state has a small density. Therefore, the mass of the refrigerant R leaking through the third check valve 43 is small.
As described above, it can be said that the malfunction of the third check valve 43 in the cold heat utilization operation is less likely to occur, and does not significantly adversely affect the operation of the refrigerant circuit.

(5-3) Defective closing of second check valve 42

The second check valve 42 is required to be closed in the hot heat utilization operation. Both ends of the second check valve 42 are the second node B and the third node C. As shown in FIG. 6, in the hot heat utilization operation, the refrigerant R in the low-pressure gas state exists at the second node B, and the refrigerant R in the gas-liquid two-phase state exists at the third node C. The refrigerant R in the gas-liquid two-phase state, which contains a gas component and a liquid component, makes the operation of the second check valve 42 unstable. Therefore, the closing of the second check valve 42 tends to be incomplete.
When the refrigerant R leaks at the second check valve 42 to be closed, the refrigerant R in the gas-liquid two-phase state leaks from the third node C to the second node B. The refrigerant R in the gas-liquid two-phase state, which contains a liquid component, has a large density. Therefore, a large amount of refrigerant R flows backward through the second check valve 42.
As described above, there is a possibility that the malfunction of the second check valve 42 in the hot heat utilization operation significantly adversely affects the operation of the refrigerant circuit.

(5-4) Defective closing of first check valve 41

The first check valve 41 is required to be closed in the cold heat utilization operation. Both ends of the first check valve 41 are the first node A and the second node B. As shown in FIG. 5, in the cold heat utilization operation, the refrigerant R in the high-pressure liquid state exists at the first node A, and the refrigerant R in the high-pressure gas state exists at the second node B. Since the refrigerant R in the gas-liquid two-phase state does not exist at both ends of the first check valve 41, the risk that the closing of the first check valve 41 becomes unstable is not as large as that of the fourth check valve 44 in the hot heat utilization operation.
If the refrigerant R leaks at the first check valve 41 to be closed, the refrigerant R in the high-pressure gas state leaks from the second node B to the first node A. The refrigerant R in a gas state has a small density. Therefore, the mass of the refrigerant R flowing backward through the first check valve 41 is small.
As described above, the malfunction of the first check valve 41 in the cold heat utilization operation is less likely to occur, and does not significantly adversely affect the operation of the refrigerant circuit.

(6) Characteristics

(6-1) (6-1-1) Setting of flow path resistance

In the bridge circuit 40, the flow path sectional area of the third flow path DC or the fourth flow path AD is small. Preferably, the flow path sectional area of the third flow path DC is smaller than 55% of the flow path sectional area of the second flow path BC, or the flow path sectional area of the fourth flow path AD is smaller than 55% of the flow path sectional area of the first flow path AB.
Thus, the flow path resistance of the third flow path DC or the fourth flow path AD is set to be large.

(6-1-2) Effects of setting flow path resistance of third flow path DC to be large

When the flow path resistance of the third flow path DC is increased, the pressure difference of the refrigerant R at both ends of the fourth check valve 44 to be closed can be increased in the hot heat utilization operation shown in FIG. 6. This is because the pressure difference at both ends of the fourth check valve 44 is not just the pressure difference at both ends of the heat source heat exchanger 13, but a value obtained by adding together it and a significant pressure difference appearing at both ends of the third flow path DC. Therefore, in the hot heat utilization operation, the fourth check valve 44 disposed in the fourth flow path AD can be more firmly closed.
Similarly, by increasing the flow path resistance of the first flow path AB, the pressure difference between the refrigerant R at both ends of the second check valve 42 to be closed can be increased to more firmly close the second check valve 42 in the hot heat utilization operation. However, the second flow path BC including the second check valve 42 has a role of supplying all the refrigerant R discharged from the compressor 11 to the refrigerant circuit at a subsequent stage in the cold heat utilization operation shown in FIG. 5. Therefore, if the flow path resistance of the first flow path AB is increased, performance of the entire refrigerant circuit can be deteriorated. For that reason, in the present embodiment, the flow path resistance of the first flow path AB is not increased.
On the other hand, as an adverse effect of increasing the flow path resistance of the third flow path DC, when a problem occurs in which the pressure of the refrigerant R at the third node C becomes excessively small in the hot heat utilization operation shown in FIG. 6, it is possible to alleviate the decrease in pressure at the third node C by adjusting the opening degree of the heat source expansion valve 15 to be slightly large. For the above reasons, increasing the flow path resistance of the third flow path DC is prioritized over increasing the flow path resistance of the first flow path AB.

(6-1-3) Effects of setting flow path resistance of fourth flow path AD to be large

When the flow path resistance of the fourth flow path AD is increased, the pressure difference of the refrigerant R at both ends of the third check valve 43 to be closed can be increased in the cold heat utilization operation shown in FIG. 5. This is because the pressure difference at both ends of the third check valve 43 is not just the pressure difference at both ends of the heat source heat exchanger 13, but a value obtained by adding together it and a significant pressure difference appearing at both ends of the fourth flow path AD. Therefore, in the cold heat utilization operation, the third check valve 43 disposed in the third flow path DC can be more firmly closed.
As described above, a defective closing of the third check valve 43 is less likely to occur, and does not significantly adversely affect the operation of the refrigerant circuit. However, it is useful to take a measure for ensuring the closing of third check valve 43 in order to reduce dysfunction of the refrigeration cycle apparatus 100.
Similarly, by increasing the flow path resistance of the second flow path BC, the pressure difference between the refrigerant R at both ends of the first check valve 41 to be closed can be increased to more firmly close the first check valve 41 in the cold heat utilization operation. However, the first flow path AB including the first check valve 41 has a role of guiding all the refrigerant R sent from the refrigerant circuit at a preceding stage to the compressor 11 in the hot heat utilization operation shown in FIG. 6. Therefore, if the flow path resistance of the second flow path BC is increased, performance of the entire refrigerant circuit can be deteriorated. For that reason, in the present embodiment, the flow path resistance of the second flow path BC is not increased.
On the other hand, as an adverse effect of increasing the flow path resistance of the fourth flow path AD, when a problem occurs in which the pressure of the refrigerant R at the fourth node D becomes excessively small in the cold heat utilization operation shown in FIG. 5, it is possible to alleviate the decrease in pressure in the refrigerant circuit at a stage subsequent to the heat source expansion valve 15 by adjusting the opening degree of the heat source expansion valve 15 to be slightly large. For the above reasons, increasing the flow path resistance of the fourth flow path AD is prioritized over increasing the flow path resistance of the second flow path BC.
(6-2)
The bridge circuit 40 is provided so that the direction of the refrigerant R in the heat source heat exchanger 13 is always the same. Therefore, the heat source heat exchanger 13 can achieve a counterflow in which the traveling directions of the refrigerant R and the air flow AF face each other.
(6-3)
The refrigerant R includes a non-azeotropic mixed refrigerant having a large temperature glide. For example, the refrigerant R is R454C which is a mixture of R32 and R1234yf. In this case, the bridge circuit 40 can also achieve a counterflow in which the traveling directions of the refrigerant R and the air flow AF face each other regardless of which one of the cold heat utilization operation and the hot heat utilization operation the refrigeration cycle apparatus 100 performs. Therefore, a decrease in performance of the refrigeration cycle apparatus is suppressed.
(6-4)
In both the cold heat utilization operation and the hot heat utilization operation, the minimum value obtainable as the circulation amount of the refrigerant R in the refrigeration cycle apparatus 100 is less than 35.00 kg/h. Therefore, a small minimum value of the circulation amount of the refrigerant R can cause incomplete operation of the third check valve 43 or the fourth check valve 44. Even in this case, since the flow path resistance of the third flow path DC or the fourth flow path AD is large, malfunction of the third check valve 43 or the fourth check valve 44 can be suppressed.

(7) Modifications

(7-1)
In the above embodiment, the flow path resistances and the flow path sectional areas are set so that the flow path resistance of the fourth flow path AD is set to be larger than the flow path resistance of the first flow path AB, or the flow path resistance of the third flow path DC is set to be larger than the flow path resistance of the second flow path BC. Alternatively, the flow path resistances may be set so that the flow path resistance of the fourth flow path AD is set to be larger than the flow path resistance of the second flow path BC, or the flow path resistance of the third flow path DC is set to be larger than the flow path resistance of the first flow path AB.
Furthermore, the flow path sectional area may be determined so that the flow path sectional area of the fourth flow path AD is smaller than the flow path sectional area of the second flow path BC, or the flow path sectional area of the third flow path DC is smaller than the flow path sectional area of the first flow path AB.
Furthermore, the flow path sectional area may be determined so that the flow path sectional area of the third flow path DC is smaller than 55% of the flow path sectional area of the first flow path AB, or the flow path sectional area of the fourth flow path AD is smaller than 55% of the flow path sectional area of the second flow path BC.
(7-2)
The refrigeration cycle apparatus 100 according to the above embodiment includes one heat source unit 10 and one utilization unit 20. Alternatively, the refrigeration cycle apparatus 100 may include one heat source unit 10 and a plurality of utilization units 20. The refrigeration cycle apparatus 100 may further include a plurality of heat source units 10.

(1) Overall configuration

FIG. 10 shows a configuration of a refrigeration cycle apparatus 100A according to a second embodiment. The refrigeration cycle apparatus 100A is different from the refrigeration cycle apparatus 100 according to the first embodiment in that the heat source unit 10 does not include the bridge circuit 40 and the utilization unit 20 includes a bridge circuit 80.

(2) Detailed configuration

The refrigeration cycle apparatus 100A includes the utilization heat exchanger 23 and the bridge circuit 80.

(2-1) Utilization heat exchanger 23 and utilization fan 24

Unlike the first embodiment, the utilization heat exchanger 23 has a refrigerant inlet 23a and a refrigerant outlet 23b. The refrigerant R enters the utilization heat exchanger 23 at the refrigerant inlet 23a and exits from the utilization heat exchanger 23 at the refrigerant outlet 23b. The utilization fan 24 generates the air flow AF passing through the utilization heat exchanger 23 to promote heat exchange between air and the refrigerant R.

(2-2) Bridge circuit 80

The bridge circuit 80 always keeps the traveling direction of the refrigerant R in the utilization heat exchanger 23 the same. The function of the bridge circuit 80 causes the refrigerant R to always enter the utilization heat exchanger 23 at the refrigerant inlet 23a and always exit the utilization heat exchanger 23 at the refrigerant outlet 23b regardless of which one of the direction indicated by the arrow CO and the direction indicated by the arrow HO the traveling direction of the refrigerant R is.
The bridge circuit 80 includes a first node A', a second node B', a third node C', and a fourth node D'. The first node A' is connected to the refrigerant outlet 23b. The second node B' is connected to the compressor 11 via the four-way switching valve 12. The third node C' is connected to the refrigerant inlet 23a. The fourth node D' is connected to the heat source expansion valve 15.
The bridge circuit 80 further includes a first flow path A'B' extending from the first node A' to the second node B', a second flow path B'C' extending from the second node B' to the third node C', a third flow path D'C' extending from the fourth node D' to the third node C', and a fourth flow path A'D' extending from the first node A' to the fourth node D'.
The bridge circuit 80 includes a first check valve 81, a second check valve 82, a third check valve 83, and a fourth check valve 84. These check valves keep the traveling direction of the refrigerant R the same in the flow path where it is installed and prevent backflow of the refrigerant R. The first check valve 41 is provided in the first flow path A'B' and allows the refrigerant R to flow only in a direction from the first node A' toward the second node B'. The second check valve 42 is provided in the second flow path B'C', and allows the refrigerant R to flow only in a direction from the second node B' toward the third node C'. The third check valve 43 is provided in the third flow path D'C', and allows the refrigerant R to flow only in a direction from the fourth node D' toward the third node C'. The fourth check valve 44 is provided in the fourth flow path A'D', and allows the refrigerant R to flow only in a direction from the first node A' toward the fourth node D'.

(3) Characteristics

The bridge circuit 80 is provided so that the direction of the refrigerant R in the utilization heat exchanger 23 is always the same. Therefore, the utilization heat exchanger 23 can achieve a counterflow in which the traveling directions of the refrigerant R and the air flow AF face each other.

(4) Modifications

The modifications of the first embodiment may be applied to the present embodiment.

(1) Overall configuration

FIG. 11 shows a configuration of a refrigeration cycle apparatus 100B according to a third embodiment. The refrigeration cycle apparatus 100B is different from the refrigeration cycle apparatus 100 according to the first embodiment and the refrigeration cycle apparatus 100A according to the second embodiment in that the heat source unit 10 and the utilization unit 20 include the bridge circuit 40 and the bridge circuit 80, respectively. The configurations of the bridge circuit 40 and the bridge circuit 80 are similar to those of the first embodiment or the second embodiment.

(2) Characteristics

The bridge circuit 40 and the bridge circuit 80 are provided so that the directions of the refrigerant R in the heat source heat exchanger 13 and the utilization heat exchanger 23 are always the same. Therefore, both the heat source heat exchanger 13 and the utilization heat exchanger 23 can achieve a counterflow in which the traveling directions of the refrigerant R and the air flow AF face each other.

(3) Modifications

The modifications of the first or second embodiment may be applied to the present embodiment.

The embodiments of the present disclosure have been described. It is understood that various changes to modes and details should be available without departing from the gist and the scope of the present disclosure recited in the claims.

REFERENCE SIGNS LIST

10: heat source unit
11: compressor
12: four-way switching valve
13: heat source heat exchanger (first heat exchanger, second heat exchanger)
13a: refrigerant inlet
13b: refrigerant outlet
14: heat source fan
15: heat source expansion valve (expansion valve)
20: utilization unit
23: utilization heat exchanger (second heat exchanger, first heat exchanger)
23a: refrigerant inlet
23b: refrigerant outlet
24: utilization fan
30: connection pipe group
40, 80: bridge circuit
41, 81: first check valve
42, 82: second check valve
43, 83: third check valve
44, 84: fourth check valve
47: check valve
50: diverger
60: heat exchanger body
70: converger
100, 100A, 100B: refrigeration cycle apparatus
A, A': first node
B, B': second node
C, C': third node
D, D': fourth node
AB, A'B': first flow path
BC, B'C': second flow path
DC, D'C': third flow path
AD, A'D': fourth flow path
R: refrigerant
AF: air flow

CITATION LIST

PATENT LITERATURE

Patent Literature 1: JP 2009-222362 A

Claims

A refrigeration cycle apparatus (100) comprising:
a compressor (11) that compresses a refrigerant (R);

an expansion valve (15) that decompresses the refrigerant;

a four-way switching valve (12) that switches between a first operation and a second operation;

a first heat exchanger (13) that has a refrigerant inlet (13a) and a refrigerant outlet (13b), functions as a condenser in the first operation, and functions as an evaporator in the second operation;

a second heat exchanger (23) that functions as an evaporator in the first operation and functions as a condenser in the second operation; and

a bridge circuit (40) that causes the refrigerant to enter the first heat exchanger at the refrigerant inlet and to exit from the first heat exchanger at the refrigerant outlet in both the first operation and the second operation,

wherein the bridge circuit includes
a first node (A),

a second node (B),

a third node (C),

a fourth node (D),

a first flow path (AB) extending from the first node (A) to the second node (B),

a second flow path (BC) extending from the second node (B) to the third node (C),

a third flow path (DC) extending from the fourth node (D) to the third node (C),

a fourth flow path (AD) extending from the first node (A) to the fourth node (D),

a first check valve (41) that causes the refrigerant to flow from the first node (A) to the second node (B),

a second check valve (42) that causes the refrigerant to flow from the second node (B) to the third node (C),

a third check valve (43) that causes the refrigerant to flow from the fourth node (D) to the third node (C), and

a fourth check valve (44) that causes the refrigerant to flow from the first node (A) to the fourth node (D),

the first node (A) is connected to the refrigerant outlet (13b),

the second node (B) is connected to the compressor (11) via the four-way switching valve (12),

the third node (C) is connected to the refrigerant inlet (13a),

the fourth node (D) is connected to the expansion valve (15), and

a flow path resistance of the fourth flow path (AD) is larger than a flow path resistance of the first flow path (AB), or a flow path resistance of the third flow path (DC) is larger than a flow path resistance of the second flow path (BC).
The refrigeration cycle apparatus according to claim 1, wherein
a flow path sectional area of the fourth flow path (AD) is smaller than a flow path sectional area of the first flow path (AB), or a flow path sectional area of the third flow path (DC) is smaller than a flow path sectional area of the second flow path (BC).
The refrigeration cycle apparatus according to claim 1 or 2, wherein
a flow path sectional area of the third flow path (DC) is smaller than a flow path sectional area of the second flow path (BC).
The refrigeration cycle apparatus according to any one of claims 1 to 3, wherein
a flow path sectional area of the fourth flow path (AD) is smaller than a flow path sectional area of the first flow path (AB).
The refrigeration cycle apparatus according to any one of claims 1 to 4, wherein
a flow path sectional area of the third flow path (DC) is smaller than 55% of a flow path sectional area of the second flow path (BC).
The refrigeration cycle apparatus according to any one of claims 1 to 5, wherein
a flow path sectional area of the fourth flow path (AD) is smaller than 55% of a flow path sectional area of the first flow path (AB).
The refrigeration cycle apparatus according to any one of claims 1 to 6, wherein
the first heat exchanger is a heat source heat exchanger (13), and the second heat exchanger is a utilization heat exchanger (23).
The refrigeration cycle apparatus according to any one of claims 1 to 6, wherein
the first heat exchanger is a utilization heat exchanger (23), and the second heat exchanger is a heat source heat exchanger (13).
The refrigeration cycle apparatus according to any one of claims 1 to 8, wherein
the refrigerant includes a non-azeotropic mixed refrigerant.
The refrigeration cycle apparatus according to any one of claims 1 to 9, wherein
a minimum value obtainable as a circulation amount of the refrigerant in the refrigeration cycle apparatus in the first operation or the second operation is less than 35.00 kg/h.