WO2023233655A1

WO2023233655A1 - Refrigeration cycle device

Info

Publication number: WO2023233655A1
Application number: PCT/JP2022/022626
Authority: WO
Inventors: 駿哉行徳
Original assignee: 三菱電機株式会社
Priority date: 2022-06-03
Filing date: 2022-06-03
Publication date: 2023-12-07

Abstract

A refrigeration cycle device (200) is provided with a switching mechanism (60) which switches a mode of a connection of a heat exchanger (80) between a first mode and a second mode. The switching mechanism (60) switches the connection of the heat exchanger (80) such that a refrigerant which has passed through a heat exchanger (20) and is heading to an expansion valve (30) and a refrigerant which has passed through an expansion valve (72) and is heading to a compressor (10) exchange heat in the heat exchanger (80) in a first mode and the refrigerant which has been discharged from the compressor (10) and is heading to the heat exchanger (20) and the refrigerant which has not yet passed through the expansion valve (30) or has passed through the expansion valve (30) exchange heat in the heat exchanger (80) in a second mode.

Description

Refrigeration cycle equipment

The present disclosure relates to a refrigeration cycle device.

In water heaters that produce hot water at a low temperature (for example, outside temperature -20°C) and hot water output at a high temperature (for example, 70°C), the difference between the condensing temperature and the evaporation temperature tends to be large, and the difference between the low-pressure part and the high-pressure part during the refrigeration cycle tends to be large. A high differential pressure operation with a large differential pressure is executed.

Under these conditions, the expansion valve opening is smaller in the low load state than under standard conditions (for example, outside temperature 7°C, hot water exit 45°C). If a general linear expansion valve whose opening changes linearly with respect to the manipulated variable is used at such a low opening, the change in the amount of refrigerant circulation with respect to the unit manipulated variable corresponding to one pulse of the control signal becomes large. As a result, precise control cannot be performed using the expansion valve, and the amount of refrigerant circulation ends up hunting, making the outlet temperature unstable.

To address these issues, Japanese Patent No. 5984747 (Patent Document 1) discloses an electronic expansion valve that can be used with air conditioners of various capacities.

Patent No. 5984747

The electronic expansion valve disclosed in Japanese Patent No. 5984747 (Patent Document 1) employs a three-stage structure in which each needle portion has a different taper. In this electronic expansion valve, by changing the needle taper angle of the expansion valve, it is possible to reduce the change in opening degree with respect to a unit operation amount of the expansion valve in a region where the amount of refrigerant circulation is low. However, since the needle part requires high processing precision and is expensive, it is not widely available. Therefore, most water heaters often use linear expansion valves whose opening degree changes linearly with the amount of operation of the expansion valve.

An object of the present disclosure is to provide a refrigeration cycle device that uses a linear expansion valve and is capable of stable operation even when the amount of refrigerant circulation is small.

The present disclosure relates to a refrigeration cycle device. The refrigeration cycle device includes a refrigerant circuit and a bypass flow path. The refrigerant circuit includes a compressor, a first heat exchanger, a first expansion valve, and a second heat exchanger. The refrigerant circuit is configured such that refrigerant circulates through the compressor, the first heat exchanger, the first expansion valve, the second heat exchanger, and back to the compressor. The bypass passage includes a second expansion valve and is configured to send the refrigerant that has passed through the first heat exchanger to the compressor through the second expansion valve. The refrigeration cycle device includes a first passage and a second passage, and a third heat exchanger configured to exchange heat between the refrigerant passing through the first passage and the refrigerant passing through the second passage; The apparatus further includes a switching mechanism that switches the connection of the third heat exchanger between the first mode and the second mode. In the first mode, the third heat exchanger exchanges heat between refrigerant that passes through the first heat exchanger and heads toward the first expansion valve, and refrigerant that passes through the second expansion valve and heads toward the compressor. In the second mode, heat is exchanged between the refrigerant discharged from the compressor and directed to the first heat exchanger, and the refrigerant before passing through the first expansion valve or after passing through the first expansion valve. It is composed of

According to the refrigeration cycle device of the present disclosure, the fluctuation range of the refrigerant circulation amount is suppressed during low load heating, etc., and the hot water supply temperature etc. are stabilized.

1 is a diagram showing the basic configuration of a refrigerant circuit to which this embodiment is applied. It is a figure shown about Cv value characteristic of a linear expansion valve. FIG. 3 is a ph diagram for explaining flow path switching according to the first embodiment. FIG. 2 is a diagram showing the configuration of the refrigeration cycle device of Embodiment 1 and the flow of refrigerant in normal heating mode. FIG. 3 is a diagram showing the flow of refrigerant in the low-load heating mode of the refrigeration cycle device according to the first embodiment. 3 is a flowchart for explaining control in a low-load heating mode of the refrigeration cycle device according to the first embodiment. It is a figure showing the composition of the refrigeration cycle device of Embodiment 2, and the flow of a refrigerant in normal heating mode. FIG. 7 is a diagram showing the flow of refrigerant in the low-load heating mode of the refrigeration cycle device according to the second embodiment. It is a flow chart for explaining control in low load heating mode of the refrigeration cycle device of Embodiment 2. FIG. 7 is a ph diagram for explaining flow path switching in Embodiment 3. FIG. It is a figure which shows the structure of the refrigeration cycle apparatus of Embodiment 3, and the flow of a refrigerant|coolant in normal heating mode. FIG. 7 is a diagram showing the flow of refrigerant in the low-load heating mode of the refrigeration cycle device according to the third embodiment. 12 is a flowchart for explaining control in a low-load heating mode of the refrigeration cycle device according to the third embodiment. It is a figure showing the composition of the refrigeration cycle device of Embodiment 4, and the flow of a refrigerant in normal heating mode. FIG. 7 is a diagram showing the flow of refrigerant in the low-load heating mode of the refrigeration cycle device according to the fourth embodiment. It is a flow chart for explaining control in low load heating mode of the refrigeration cycle device of Embodiment 4. It is a figure showing the composition of the refrigeration cycle device of Embodiment 5, and the flow of a refrigerant in normal heating mode. FIG. 7 is a diagram showing the flow of refrigerant in the low-load heating mode of the refrigeration cycle device according to the fifth embodiment. It is a flow chart for explaining control in low load heating mode of the refrigeration cycle device of Embodiment 5.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Although a plurality of embodiments will be described below, it has been planned from the beginning of the application to appropriately combine the configurations described in each embodiment. In addition, the same reference numerals are attached to the same or corresponding parts in the drawings, and the description thereof will not be repeated. Note that in the following figures, the size relationship of each component may differ from the actual one.

Embodiment 1.
FIG. 1 is a diagram showing the basic configuration of a refrigerant circuit to which this embodiment is applied. The following embodiments 1 to 5 are applied to such a refrigeration cycle device. A refrigeration cycle device is, for example, a water heater or a heating device that heats a heat medium in a refrigeration cycle that uses a refrigerant. Further, it may be provided with an air-conditioning mode in which the heat medium is cooled in a refrigeration cycle and used for air-conditioning.

This refrigeration cycle device includes a refrigerant circuit C and a bypass flow path 70.
The refrigerant circuit C includes a compressor 10, a heat exchanger 20, and an expansion valve 30. In the refrigerant circuit C, the refrigerant circulates in order to return to the compressor 10 via the compressor 10, piping 51, heat exchanger 20, piping 52, expansion valve 30, piping 54, heat exchanger 40, and piping 55. It is configured as follows. The compressor has a discharge port, a suction port, and an intermediate port.

The heat exchanger 20 is configured to exchange heat between a heat medium such as water or brine and a refrigerant. The heat medium heated or cooled by the heat exchanger 20 serves as a heat source for generating hot water in a water heater or for heating and cooling. The heat medium heated or cooled by the heat exchanger 20 returns to the heat exchanger 20 via the piping 121, the pump WP, the piping 122, the heat exchanger 123, and the piping 124. The heat exchanger 123 is a user-side device such as a water heater, an air conditioning unit, or a floor heating unit.

The bypass flow path 70 includes an expansion valve 72. The bypass passage 70 branches part of the refrigerant that has passed through the heat exchanger 20 through a pipe 71 . The bypass passage 70 is configured to pass through the expansion valve 72 and the piping 73 and to be sent to the intermediate port of the compressor 10 . As a result, the liquid or two-phase refrigerant is injected, so the discharge temperature of the compressor 10 can be lowered, and the temperature of the discharged refrigerant can be prevented from exceeding the allowable temperature limit of members such as the motor.

In a refrigeration cycle device with such a basic configuration, a linear expansion valve is generally used as the expansion valve 30. The linear expansion valve is given a pulse signal as a control signal, and the manipulated variable x is indicated by the number of pulses.

FIG. 2 is a diagram showing the Cv value characteristics of the linear expansion valve. As shown in FIG. 2, when the manipulated variable x (pulse) is the proportional coefficient A, the Cv value indicating the expansion valve opening is expressed as Cv=Ax.

When using a linear expansion valve exhibiting such characteristics, the rate of change in the amount of refrigerant circulation per unit operation amount will be examined. The refrigerant circulation amount Gr and the Cv value indicating the expansion valve opening have a relationship as shown in the following equation (1). Here, ΔP indicates the differential pressure before and after the expansion valve, and ρ indicates the refrigerant density at the inlet of the expansion valve.
Gr=27.1Cv√(ρΔP)…(1)
Here, it is assumed that the unit operation amount Δx is the operation amount x of the expansion valve. The rate of change in the refrigerant circulation amount per unit operation amount is expressed by the following equation (2) by substituting the above equation (1). Note that A indicates a proportionality coefficient.
(Gr+ΔGr)/Gr
= (27.1Cv√(ρΔP)+27.1ΔCv√(ρΔP))/(27.1Cv√(ρΔP))
=(Cv+ΔCv)/Cv
=1+AΔx/Cv…(2)
This indicates that when the expansion valve opening degree is small, that is, when the Cv value is small, the change in the refrigerant circulation amount with respect to the unit operation amount Δx becomes large. Therefore, the expansion valve becomes too sensitive when the load is small and the refrigerant flow rate is low, causing hunting in the refrigerant flow rate. As a result, problems such as unstable hot water temperature in water heaters and the like arise.

Therefore, in this embodiment, even when the load is small, the sensitivity to the manipulated variable is set to an appropriate state by not using the region where the opening degree of the expansion valve is small. For this purpose, the flow path is switched to change the insertion position of the internal heat exchanger in the refrigerant circuit.

FIG. 3 is a ph diagram for explaining flow path switching in the first embodiment. In the first embodiment, in the normal heating mode, an operation is performed along the ph diagram shown in cycle C0 in FIG. 3. In cycle C0, heat is exchanged between the refrigerant flowing through the pipe 53 and the refrigerant flowing through the pipe 73 in FIG. 1 by the internal heat exchanger.

On the other hand, in the first embodiment, in the low-load heating mode, the operation is performed along the ph diagram shown in cycle C1 in FIG. 3. In cycle C1, the expansion valve 72 is closed and no refrigerant flows into the bypass passage 70. Instead, heat exchange of ΔH1 is performed between the refrigerant flowing through the pipe 51 and the refrigerant flowing through the pipe 53 in FIG. 1 by the internal heat exchanger. As a result, the enthalpy difference in the heat exchanger 20 becomes smaller than in the normal heating mode. Since heating capacity is expressed as enthalpy difference x amount of refrigerant circulation, in low load heating mode, the amount of refrigerant circulation can be increased more than in normal heating mode even under low load. Therefore, low-load heating can be performed without using the region where the opening degree of the expansion valve 30 is small, where changes in the refrigerant circulation amount are sensitive to the operation amount.

In other words, in the ph diagram of FIG. 3, the enthalpy at the inlet of the expansion valve increases in cycle C1 more than in cycle C0. Therefore, the refrigerant density at the expansion valve inlet decreases. As the refrigerant density at the expansion valve inlet decreases, the expansion valve opening degree increases.

FIG. 4 is a diagram showing the configuration of the refrigeration cycle device of Embodiment 1 and the flow of refrigerant in normal heating mode.

The refrigeration cycle device 200 shown in FIG. 4 includes a compressor 10, a heat exchanger 20, an expansion valve 30, a heat exchanger 40, an expansion valve 72, a heat exchanger 80, a refrigerant circuit C, and a bypass flow 70.

The refrigerant circuit C is configured so that the refrigerant circulates through the compressor 10, the heat exchanger 20, the expansion valve 30, and the heat exchanger 40, and returns to the compressor 10.

The bypass passage 70 is configured to send the refrigerant that has passed through the heat exchanger 20 to the compressor 10 through the expansion valve 72.

The heat exchanger 80 includes a first passage R1 and a second passage R2, and is configured to exchange heat between the refrigerant passing through the first passage R1 and the refrigerant passing through the second passage R2.

The refrigeration cycle device 200 further includes a switching mechanism 60 that switches the connection of the heat exchanger 80 between the first mode and the second mode. The first mode is a normal heating mode, and the second mode is a low-load heating mode. Note that in addition to the first and second modes, a cooling mode or the like may be provided.

In the first mode (normal heating mode), the heat exchanger 80 allows the refrigerant to pass through the heat exchanger 20 and go to the expansion valve 30, and the refrigerant to pass through the expansion valve 72 and go to the compressor 10, as shown by the arrow in FIG. It is set to exchange heat with the refrigerant headed for.

FIG. 5 is a diagram showing the flow of refrigerant in the low-load heating mode of the refrigeration cycle device of Embodiment 1. As shown by the arrow in FIG. 5, in the second mode, the switching mechanism 60 switches the refrigerant discharged from the compressor 10 toward the heat exchanger 20 and the refrigerant before passing through the expansion valve 30 into the heat exchanger 80. The connection of the heat exchanger 80 is switched to exchange heat.

In the second mode (low-load heating mode), the heat exchanger 80 exchanges heat between the refrigerant discharged from the compressor 10 and heading toward the heat exchanger 20 and the refrigerant passing through the heat exchanger 20 and heading toward the expansion valve 30. Configured to be exchanged.

The refrigeration cycle device 200 further includes a control device 100 that controls the switching mechanism and the expansion valve 72.

The control device 100 includes a CPU (Central Processing Unit) 101, a memory 102 (ROM (Read Only Memory) and RAM (Random Access Memory)), an input/output buffer (not shown), and the like. The CPU 101 expands a program stored in the ROM into a RAM or the like and executes the program. The program stored in the ROM is a program in which the processing procedure of the control device 100 is written. Control device 100 executes control of each device in refrigeration cycle device 200 according to these programs. This control is not limited to processing by software, but can also be performed by dedicated hardware (electronic circuit).

The switching mechanism 60 includes a first four-way valve 61 having first to fourth ports, and a second four-way valve 62 having fifth to eighth ports. P1 to P8 in FIG. 4 indicate the first to eighth ports of the four-way valve, respectively.

The first port is connected to the discharge port of the compressor 10 by a pipe 83. The second port is connected to the eighth port by piping 82. The third port is connected to the downstream side of the expansion valve 72 by a pipe 73A. The first passage R1 of the heat exchanger 80 is connected by a pipe 81 between the fourth port and the sixth port. The fifth port is connected to the intermediate port of the compressor 10 by a pipe 73B. The seventh port is connected to the refrigerant inlet of the heat exchanger 20 by a pipe 51B.

The first four-way valve 61 has a first port and a second port communicating with each other in the first mode (normal heating mode), a third port and a fourth port communicating with each other, and a second mode (low-load heating mode). The second port and the third port communicate with each other, and the fourth port and the first port communicate with each other.

In the second four-way valve 62, in the first mode (normal heating mode), the fifth port and the sixth port communicate with each other, and the seventh port and the eighth port communicate with each other, and in the second mode (low-load heating mode). In this case, the sixth port and the seventh port communicate with each other, and the eighth port and the fifth port communicate with each other.

FIG. 6 is a flowchart for explaining control in the low-load heating mode of the refrigeration cycle device of Embodiment 1. According to the flowchart of FIG. 6, the control device 100 closes the expansion valve 72 when the opening degree of the expansion valve 30 becomes equal to or less than the determination value in the second mode.

Further, when the opening degree of the expansion valve 30 becomes equal to or less than the determination value in the second mode, the control device 100 adjusts the operating frequency of the compressor 10 based on the temperature of the heat medium that has passed through the heat exchanger 20. Control.

First, in step S1, the control device 100 determines whether the opening degree of the expansion valve 30 is less than or equal to the threshold value dt. If the opening degree is less than or equal to the threshold value dt (YES in S1), the control device 100 advances the process to step S2.

In step S2, the control device 100 determines whether the operating frequency of the compressor 10 is equal to or lower than the threshold value ft. If the operating frequency is equal to or less than the threshold value ft (YES in S2), the control device 100 advances the process to step S3.

When the process progresses to step S3, the load of the heating operation has become small. Therefore, the control device 100 switches the switching mechanism 60 to switch the operating cycle from the cycle C0 shown in FIG. 3 to the cycle C1. Specifically, in step S3, the control device 100 closes the expansion valve 72. In step S4, the control device 100 sets the state of the switching mechanism 60 (four-way valves 61, 62) to the low-load heating mode shown in FIG. If the normal heating mode has been in effect until then, switching is performed, but if it is in the low-load heating mode, the state of the switching mechanism 60 is maintained. Note that the four-

way valves

61 and 62 may be switched in any order.

After that, in step S5, the control device 100 determines whether the temperature (water temperature) T1 at the heat medium outlet of the heat exchanger 20 is equal to the target water temperature T1t. If the temperature T1 is not equal to the target temperature T1t (NO in S5), in step S6, the control device 100 determines whether the temperature T1 is lower than the target temperature T1t. If the temperature T1 is lower than the target temperature T1t (YES in S6), the control device 100 increases the operating frequency of the compressor 10 in step S7. This increases the heating capacity of the heat exchanger 20. On the other hand, if the temperature T1 is not lower than the target temperature T1t, that is, if the temperature T1 is too high (NO in S6), the control device 100 reduces the operating frequency of the compressor 10 in step S8. This reduces the heating capacity of the heat exchanger 20.

Note that if the determination is NO in steps S1 and S2 and YES in step S5, and if the processing in steps S7 and S8 is completed, the process exits from the flowchart of FIG. The processing in the flowchart of FIG. 6 is executed.

As explained above, in Embodiment 1, the injection flow path is closed during low-load heating, and the position of the heat exchanger 80, which is an internal heat exchanger that exchanges heat between refrigerants, in the refrigerant circuit is changed by the mechanism. Changed by 60. Thereby, the refrigeration cycle is switched from cycle C0 in FIG. 3 to cycle C1, and the enthalpy difference caused by the heat exchanger 20 is reduced. This makes it possible to increase the amount of refrigerant circulation even during low-load heating.

Increasing the amount of refrigerant circulation eliminates the need to use the low opening range of the expansion valve 30, which is a linear expansion valve where changes in the amount of refrigerant circulation are sensitive to unit operation amount. Then, the change in the refrigerant circulation amount with respect to the unit operation amount of the expansion valve 30 can be reduced. Therefore, the range of increase/decrease in the amount of refrigerant circulation during low-load heating can be kept small. This stabilizes the hot water temperature.

Embodiment 2.
In the first embodiment, the switching mechanism is configured with two four-way valves, but in the second embodiment, an example will be described in which the switching mechanism is implemented with one six-way valve.

FIG. 7 is a diagram showing the configuration of the refrigeration cycle device of Embodiment 2 and the flow of refrigerant in normal heating mode. FIG. 8 is a diagram showing the flow of refrigerant in the low-load heating mode of the refrigeration cycle device according to the second embodiment.

A refrigeration cycle device 201 according to the second embodiment includes a six-way valve 160 in place of the four-

way valves

61 and 62 in the configuration of the refrigeration cycle device 200 shown in FIG. Regarding the configuration of other parts, the refrigeration cycle device 201 is the same as the refrigeration cycle device 200, so the description will not be repeated.

In addition, in the second mode, the heat exchanger 80 whose connection is switched by the six-way valve 160 serving as a switching mechanism in the second embodiment is configured to switch between the refrigerant discharged from the compressor 10 and directed toward the heat exchanger 20, and the heat exchanger 20. It is the same as the switching mechanism 60 of the first embodiment in that it is configured to exchange heat with the refrigerant passing through and heading toward the expansion valve 30.

In the second embodiment, the switching mechanism is a six-way valve 160 having first to sixth ports. P1 to P6 in FIG. 7 indicate the first to sixth ports of the six-way valve 160, respectively. The first port of the hexagonal valve 160 is connected to the discharge port of the compressor 10 by a pipe 83, and the second port is connected to the refrigerant inlet of the heat exchanger 20 by a pipe 51B. The fourth port of the six-way valve 160 is connected to the downstream side of the expansion valve 72 by a pipe 73A, the first passage R1 of the heat exchanger 80 is connected between the third port and the sixth port by a pipe 81, and the fifth The port is connected to the intermediate port of compressor 10 by piping 73B.

In the six-way valve 160, in the first mode (normal heating mode), the first port and the second port communicate with each other, the third port and the fourth port communicate with each other, and the fifth port and the sixth port communicate with each other. It is configured as follows. In the six-way valve 160, in the second mode (low-load heating mode), the second port and the third port communicate with each other, the fourth port and the fifth port communicate with each other, and the sixth port and the first port communicate with each other. configured to do so.

FIG. 9 is a flowchart for explaining control in the low-load heating mode of the refrigeration cycle device according to the second embodiment. The flowchart in FIG. 9 includes step S11 instead of step S4 in the flowchart in FIG. Since the other steps have been explained using the flowchart of FIG. 6, only step S11 will be explained here, and other explanations will not be repeated.

In step S11, the control device 100 sets the state of the hexagonal valve 160 to the low-load heating mode shown in FIG. 8. Therefore, if the normal heating mode has been in effect until then, switching is performed, but if it is in the low-load heating mode, the state of the six-way valve 160 is maintained.

In Embodiment 2, as in Embodiment 1, the effect of suppressing hunting in the amount of refrigerant circulation can be obtained by increasing the amount of refrigerant circulation. This stabilizes the hot water temperature. Furthermore, the number of parts can be reduced.

Embodiment 3.
In the first and second embodiments, it has been explained that the expansion valve opening degree is increased during low-load heating to reduce the change in the refrigerant circulation amount with respect to the unit operation amount.

Here, the heating capacity is expressed as the enthalpy difference of the condenser x the amount of refrigerant circulation. Therefore, in order to reduce the change in the refrigerant circulation amount with respect to the unit operation amount during low-load heating, two approaches can be considered.

The first approach is to reduce the enthalpy difference in the condenser by exchanging heat between the discharged refrigerant and the condenser outlet refrigerant using the heat exchanger 80, as shown in Embodiments 1 and 2. The goal is to increase the amount of circulation.

The second approach is to reduce the enthalpy difference in the condenser by exchanging heat between the discharged refrigerant and the evaporator inlet refrigerant using the heat exchanger 80, as shown in Embodiment 3 and thereafter. The goal is to increase

FIG. 10 is a ph diagram for explaining flow path switching in the third embodiment. In the third embodiment, in the normal heating mode, an operation is performed along the ph diagram shown in cycle C0 in FIG. 10. In cycle C0, heat is exchanged between the refrigerant flowing through the pipe 53 and the refrigerant flowing through the pipe 73 in FIG. 1 by the internal heat exchanger.

On the other hand, in the third embodiment, in the low-load heating mode, the operation is performed along the ph diagram shown in cycle C2 in FIG. 10. In cycle C2, the expansion valve 72 is closed and no refrigerant flows into the bypass passage 70. Instead, heat exchange of ΔH2 is performed between the refrigerant flowing through the pipe 51 and the refrigerant flowing through the pipe 54 in FIG. 1 by the internal heat exchanger. As a result, the enthalpy difference in the heat exchanger 20 becomes smaller than in the normal heating mode. Since heating capacity is expressed as enthalpy difference x amount of refrigerant circulation, in low load heating mode, the amount of refrigerant circulation can be increased more than in normal heating mode even under low load. Therefore, low-load heating can be performed without using the region where the opening degree of the expansion valve 30 is small, where changes in the refrigerant circulation amount are sensitive to the operation amount.

FIG. 11 is a diagram showing the configuration of the refrigeration cycle device of Embodiment 3 and the flow of refrigerant in normal heating mode. FIG. 12 is a diagram showing the flow of refrigerant in the low-load heating mode of the refrigeration cycle device according to the third embodiment.

In the third embodiment, a switching mechanism for switching the refrigerant circuit in the refrigeration cycle device 202 is configured by a four-way valve 261, a four-way valve 262, and a four-way valve 263. The heat exchanger 80 whose connection has been switched by this switching mechanism is in the second mode in which low-load heating is performed. The refrigerant is configured to exchange heat with the refrigerant.

The switching mechanism includes a first four-way valve 261 having first to fourth ports, a second four-way valve 262 having fifth to eighth ports, and a third four-way valve 263 having ninth to twelfth ports. . P1 to P12 in FIG. 11 correspond to the first to twelfth ports of these four-way valves, respectively.

The first port is connected to the discharge port of the compressor 10 through a pipe 83, a four-way valve 50, and a pipe 51A. Between the second port and the fourth port, the refrigerant flow path of the heat exchanger 20 and the first passage R1 of the heat exchanger 80 are connected in series by

pipes

51B and 52A. The third port is connected to the upstream side of the expansion valve 30 and the upstream side of the expansion valve 72 by a pipe 52B.

The fifth port is connected to the downstream side of the expansion valve 30 by a pipe 54A. The sixth port is connected to the refrigerant inlet of the heat exchanger 40 by a pipe 54B. The seventh port is connected to the ninth port by piping 85.

A second passage R2 of the heat exchanger 80 is connected by a pipe 84 between the eighth port and the tenth port. The eleventh port is connected to the intermediate port of the compressor 10 by a pipe 73B. The twelfth port is connected to the downstream side of the expansion valve 72 by a pipe 73A.

In the first mode (normal heating mode) shown in FIG. 11, the first four-way valve 261 has a first port and a second port communicating with each other, a third port and a fourth port communicating with each other, and a fourth port shown in FIG. In the 2 mode (low load heating mode), the second port and the third port communicate with each other, and the fourth port and the first port communicate with each other.

In the first mode (normal heating mode) shown in FIG. 11, the second four-way valve 262 has a fifth port and a sixth port communicating with each other, a seventh port and an eighth port communicating with each other, and a fourth port shown in FIG. In the 2 mode (low load heating mode), the sixth port and the seventh port communicate with each other, and the eighth port and the fifth port communicate with each other.

In the first mode (normal heating mode) shown in FIG. 11, the third four-way valve 263 has a 10th port and an 11th port communicating with each other, a 12th port and a 9th port communicating with each other, and In the 2nd mode (low load heating mode), the 9th port and the 10th port communicate with each other, and the 11th port and the 12th port communicate with each other.

FIG. 13 is a flowchart for explaining control in the low-load heating mode of the refrigeration cycle device according to the third embodiment. The flowchart in FIG. 13 includes steps S21 and S22 instead of step S4 in the flowchart in FIG. Since the other steps have been explained using the flowchart of FIG. 6, steps S21 and S22 will be explained here, and other explanations will not be repeated.

In step S21, the control device 100 sets the four-

way valves

261 and 263 to the low-load heating mode shown in FIG. 12. Note that the four-

way valves

261 and 263 may be switched in any order. After that, the control device 100 sets the state of the four-way valve 262 to the low-load heating mode shown in FIG. 12.

Therefore, if the normal heating mode has been in effect until then, the four-way valves are switched in steps S21 and S22, but if the low-load heating mode is in effect, the states of the four-

way valves

261, 262, and 263 are maintained. be done.

In Embodiment 3, as in Embodiment 1, by increasing the refrigerant circulation amount, the effect of suppressing hunting in the refrigerant circulation amount can be obtained. This stabilizes the hot water temperature. In addition, when a non-azeotropic mixed refrigerant is used, the temperature at the refrigerant inlet of the evaporator increases, which also makes it possible to suppress frost formation.

Embodiment 4.
In the third embodiment, the switching mechanism is configured with three four-way valves, but in the fourth embodiment, an example will be described in which the switching mechanism is implemented with four four-way valves. Note that the ph diagram in FIG. 10 is the same in Embodiment 4, so a description thereof will be omitted.

FIG. 14 is a diagram showing the configuration of the refrigeration cycle device of Embodiment 4 and the flow of refrigerant in normal heating mode. FIG. 15 is a diagram showing the flow of refrigerant in the low-load heating mode of the refrigeration cycle device according to the fourth embodiment.

In the fourth embodiment, the heat exchanger 80 whose connection is switched by the switching mechanism that switches the refrigerant circuit in the refrigeration cycle device 203 is configured to connect the refrigerant discharged from the compressor 10 and directed to the heat exchanger 20 in the second mode, and expand the refrigerant. It is configured to exchange heat with the refrigerant that passes through the valve 30 and heads toward the heat exchanger 40 .

The switching mechanism includes a first four-way valve 261 having first to fourth ports, a second four-way valve 262 having fifth to eighth ports, a third four-way valve 263 having ninth to twelfth ports, and a third four-way valve 263 having ninth to twelfth ports. and a fourth four-way valve 264 having 13th to 16th ports. P1 to P16 in FIG. 14 correspond to the first to sixteenth ports of these four-way valves, respectively.

The first port is connected to the discharge port of the compressor 10 through a pipe 83, a four-way valve 50, and a pipe 51A. A refrigerant flow path of the heat exchanger 20 is connected between the second port and the 16th port by

pipes

51B and 52A. The third port is connected to the fifteenth port via piping 52B. A first passage R1 of the heat exchanger 80 is connected between the fourth port and the fourteenth port by a pipe 86.

The thirteenth port is connected to the upstream side of the expansion valve 30 and the upstream side of the expansion valve 72 via the piping 52B.

In the fourth four-way valve 264, in the first mode (normal heating mode) shown in FIG. 11, the 13th port and the 14th port communicate with each other, the 15th port and the 16th port communicate with each other, and the In the 2 mode (low load heating mode), the 14th port and the 15th port communicate with each other, and the 16th port and the 13th port communicate with each other.

FIG. 16 is a flowchart for explaining control in the low-load heating mode of the refrigeration cycle device according to the fourth embodiment. The flowchart in FIG. 16 includes steps S31 and S32 instead of step S4 in the flowchart in FIG. Since the other steps have been explained using the flowchart of FIG. 6, steps S31 and S32 will be explained here, and other explanations will not be repeated.

In step S31, the control device 100 sets the four-

way valves

261, 263, and 264 to the low-load heating mode shown in FIG. 15. Note that the four-

way valves

261, 263, and 264 may be switched in any order. After that, the control device 100 sets the state of the four-way valve 262 to the low-load heating mode shown in FIG. 15.

Therefore, if the normal heating mode had been in effect until then, the four-way valves would be switched in steps S31 and S32, but if the low-load heating mode had been in effect, the states of the four-way valves 261 to 264 would be maintained. .

In Embodiment 4, as in Embodiment 1, by increasing the refrigerant circulation amount, the effect of suppressing hunting in the refrigerant circulation amount can be obtained. This stabilizes the hot water temperature. In addition, when a non-azeotropic mixed refrigerant is used, the temperature at the refrigerant inlet of the evaporator increases, which also makes it possible to suppress frost formation.

Embodiment 5.
In the fourth embodiment, the switching mechanism is configured with four four-way valves, but in the fifth embodiment, an example will be described in which the switching mechanism is implemented with two six-way valves. Note that the ph diagram in FIG. 10 is the same in the fifth embodiment, so a description thereof will be omitted.

FIG. 17 is a diagram showing the configuration of the refrigeration cycle device of Embodiment 5 and the flow of refrigerant in normal heating mode. FIG. 18 is a diagram showing the flow of refrigerant in the low-load heating mode of the refrigeration cycle device according to the fifth embodiment.

In the second mode, the heat exchanger 80 whose connection has been switched by the switching mechanism of the fifth embodiment transfers the refrigerant discharged from the compressor 10 to the heat exchanger 20 and the refrigerant that passes through the expansion valve 30 to the heat exchanger 40. It is configured to exchange heat with the oncoming refrigerant.

The switching mechanism of the fifth embodiment includes a first six-way valve 361 having first to sixth ports and a second six-way valve 362 having seventh to twelfth ports. P1 to P12 in FIG. 17 respectively indicate the first port to the twelfth port of the two hexagonal valves.

The first port is connected to the discharge port of the compressor 10. The second port is connected to the refrigerant inlet of the heat exchanger 20 by a pipe 51B. The expansion valve 30 is connected between the fourth port and the tenth port by pipes 53B and 54A. The first passage R1 of the heat exchanger 80 is connected by a pipe 87 between the third port and the sixth port. The fifth port is connected to the refrigerant outlet of the heat exchanger 20 and the upstream side of the expansion valve 72 by a pipe 53A.

The seventh port is connected to the intermediate port of the compressor 10 by a pipe 73B. A second passage R2 of the heat exchanger 80 is connected by a pipe 84 between the eighth port and the eleventh port. The ninth port is connected to the refrigerant inlet of the heat exchanger 40 by a pipe 54B. The twelfth port is connected to the downstream side of the expansion valve 72 by a pipe 73A.

In the first hexagonal valve 361, in the first mode (normal heating mode), the first port and the second port communicate with each other, the third port and the fourth port communicate with each other, and the fifth port and the sixth port communicate with each other. communication, and in the second mode (low-load heating mode), the second port and the third port communicate, the fourth port and the fifth port communicate, and the sixth port and the first port communicate. It is composed of

In the second six-way valve 362, in the first mode (normal heating mode), the 7th port and the 8th port communicate with each other, the 9th port and the 10th port communicate with each other, and the 11th port and the 12th port communicate with each other. However, in the second mode (low load heating mode), the 8th port and the 9th port communicate with each other, the 10th port and the 11th port communicate with each other, and the 12th port and the 7th port communicate with each other. configured.

FIG. 19 is a flowchart for explaining control in the low-load heating mode of the refrigeration cycle device of Embodiment 5. The flowchart in FIG. 19 includes step S41 instead of step S4 in the flowchart in FIG. Since the other steps have been explained using the flowchart of FIG. 6, only step S41 will be explained here, and other explanations will not be repeated.

In step S41, the control device 100 sets the states of the hexagonal valves 361 and 362 to the low-load heating mode shown in FIG. 18. Therefore, if the normal heating mode has been in effect until then, switching is performed, but if the low-load heating mode is in effect, the states of the six-way valves 361 and 362 are maintained. Note that the hexagonal valves 361 and 362 may be switched in any order.

In Embodiment 5, as in Embodiment 1, by increasing the refrigerant circulation amount, the effect of suppressing hunting in the refrigerant circulation amount can be obtained. This stabilizes the hot water temperature. In addition, when a non-azeotropic mixed refrigerant is used, the temperature at the refrigerant inlet of the evaporator increases, which also makes it possible to suppress frost formation.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the claims rather than the description of the embodiments described above, and it is intended that all changes within the meaning and range equivalent to the claims are included.

10 Compressor, 20, 40, 80, 123 Heat exchanger, 30, 72 Expansion valve, 50, 61, 62, 261-264 Four-way valve, 60 Switching mechanism, 70 Bypass flow path, 100 Control device, 101 CPU, 102 Memory, 160, 361, 362 six-way valve, 200-204 refrigeration cycle device, C refrigerant circuit, R1 first passage, R2 second passage, WP pump.

Claims

A refrigeration cycle device,
Equipped with a refrigerant circuit and a bypass flow path,
The refrigerant circuit includes a compressor, a first heat exchanger, a first expansion valve, and a second heat exchanger; The refrigerant is configured to circulate back to the compressor via the expansion valve and the second heat exchanger;
The bypass flow path includes a second expansion valve, and is configured to send the refrigerant that has passed through the first heat exchanger to the compressor through the second expansion valve,
The refrigeration cycle device includes:
a third heat exchanger including a first passage and a second passage and configured to exchange heat between a refrigerant passing through the first passage and a refrigerant passing through the second passage;
further comprising a switching mechanism that switches the connection of the third heat exchanger between a first mode and a second mode,
In the first mode, the third heat exchanger is arranged between refrigerant that passes through the first heat exchanger and heads toward the first expansion valve, and refrigerant that passes through the second expansion valve and heads toward the compressor. and in the second mode, the refrigerant discharged from the compressor and headed for the first heat exchanger and the refrigerant before passing through the first expansion valve or after passing through the first expansion valve. A refrigeration cycle device configured to exchange heat with a subsequent refrigerant.
further comprising a control device that controls the switching mechanism and the second expansion valve,
The refrigeration cycle device according to claim 1, wherein the control device closes the second expansion valve when the opening degree of the first expansion valve becomes equal to or less than a determination value in the second mode.
The first heat exchanger is configured to exchange heat between a heat medium and a refrigerant,
When the opening degree of the first expansion valve becomes equal to or less than the determination value in the second mode, the control device controls the compressor based on the temperature of the heat medium that has passed through the first heat exchanger. The refrigeration cycle device according to claim 2, wherein the operating frequency of the refrigeration cycle device is controlled.
The third heat exchanger is configured to, in the second mode, refrigerant discharged from the compressor and directed to the first heat exchanger, and refrigerant passing through the first heat exchanger and directed to the first expansion valve. configured to exchange heat between
The switching mechanism is
a first four-way valve having first to fourth ports;
a second four-way valve having fifth to eighth ports;
The first port is connected to the discharge port of the compressor, the second port is connected to the eighth port, the third port is connected to the downstream side of the second expansion valve, and the fourth port is connected to the outlet of the compressor. A first passage of the third heat exchanger is connected between and the sixth port, the fifth port is connected to an intermediate port of the compressor, and the seventh port is connected to the first passage of the third heat exchanger. connected to the refrigerant inlet of
In the first mode, the first four-way valve communicates with the first port and the second port, and in the second mode, the first port and the fourth port communicate with each other, and in the second mode, the second port communicates with the first port. configured such that the port and the third port communicate with each other, and the fourth port and the first port communicate with each other,
In the second four-way valve, the fifth port and the sixth port communicate with each other in the first mode, the seventh port and the eighth port communicate with each other, and the second four-way valve communicates with the sixth port in the second mode. The refrigeration cycle device according to claim 1, wherein the port and the seventh port communicate with each other, and the eighth port and the fifth port communicate with each other.
The third heat exchanger is configured to, in the second mode, refrigerant discharged from the compressor and directed to the first heat exchanger, and refrigerant passing through the first heat exchanger and directed to the first expansion valve. configured to exchange heat between
The switching mechanism includes a six-way valve having first to sixth ports,
The first port is connected to a discharge port of the compressor, the second port is connected to a refrigerant inlet of the first heat exchanger, and the fourth port is connected to a downstream side of the second expansion valve. a first passage of the third heat exchanger is connected between the third port and the sixth port, and the fifth port is connected to an intermediate port of the compressor;
In the first mode, the hexagonal valve is configured such that the first port and the second port communicate with each other, the third port and the fourth port communicate with each other, and the fifth port and the sixth port communicate with each other. communication, and in the second mode, the second port and the third port communicate, the fourth port and the fifth port communicate, and the sixth port and the first port communicate. The refrigeration cycle device according to claim 1, configured as follows.
The third heat exchanger is configured to, in the second mode, refrigerant discharged from the compressor and directed to the first heat exchanger, and refrigerant passing through the first expansion valve and directed to the second heat exchanger. configured to exchange heat between
The switching mechanism is
a first four-way valve having first to fourth ports;
a second four-way valve having fifth to eighth ports;
a third four-way valve having ninth to twelfth ports;
the first port is connected to a discharge port of the compressor,
A refrigerant flow path of the first heat exchanger and a first passage of the third heat exchanger are connected in series between the second port and the fourth port,
The third port is connected to the upstream side of the first expansion valve and the upstream side of the second expansion valve,
The fifth port is connected to the downstream side of the first expansion valve,
the sixth port is connected to a refrigerant inlet of the second heat exchanger,
the seventh port is connected to the ninth port,
A second passage of the third heat exchanger is connected between the eighth port and the tenth port,
the eleventh port is connected to an intermediate port of the compressor,
the twelfth port is connected to the downstream side of the second expansion valve,
In the first mode, the first four-way valve communicates with the first port and the second port, and in the second mode, the first port and the fourth port communicate with each other, and in the second mode, the second port communicates with the first port. configured such that the port and the third port communicate with each other, and the fourth port and the first port communicate with each other,
In the second four-way valve, the fifth port and the sixth port communicate with each other in the first mode, the seventh port and the eighth port communicate with each other, and the second four-way valve communicates with the sixth port in the second mode. The port is configured to communicate with the seventh port, and the eighth port and the fifth port communicate with each other,
In the third four-way valve, in the first mode, the tenth port and the eleventh port communicate with each other, and in the second mode, the tenth port and the ninth port communicate with each other, and in the second mode, the third four-way valve communicates with the tenth port and the eleventh port. The refrigeration cycle device according to claim 1, wherein the port and the tenth port communicate with each other, and the eleventh port and the twelfth port communicate with each other.
The third heat exchanger is configured to, in the second mode, refrigerant discharged from the compressor and directed to the first heat exchanger, and refrigerant passing through the first expansion valve and directed to the second heat exchanger. configured to exchange heat between
The switching mechanism is
a first four-way valve having first to fourth ports;
a second four-way valve having fifth to eighth ports;
a third four-way valve having ninth to twelfth ports;
a fourth four-way valve having 13th to 16th ports,
the first port is connected to a discharge port of the compressor,
A refrigerant flow path of the first heat exchanger is connected between the second port and the 16th port,
the third port is connected to the fifteenth port,
A first passage of the third heat exchanger is connected between the fourth port and the fourteenth port,
The fifth port is connected to the downstream side of the first expansion valve,
the sixth port is connected to a refrigerant inlet of the second heat exchanger,
the seventh port is connected to the ninth port,
A second passage of the third heat exchanger is connected between the eighth port and the tenth port,
the eleventh port is connected to an intermediate port of the compressor,
the twelfth port is connected to the downstream side of the second expansion valve,
The thirteenth port is connected to the upstream side of the first expansion valve and the upstream side of the second expansion valve,
In the first mode, the first four-way valve communicates with the first port and the second port, and in the second mode, the first port and the fourth port communicate with each other, and in the second mode, the second port communicates with the first port. configured such that the port and the third port communicate with each other, and the fourth port and the first port communicate with each other,
In the second four-way valve, the fifth port and the sixth port communicate with each other in the first mode, the seventh port and the eighth port communicate with each other, and the second four-way valve communicates with the sixth port in the second mode. The port is configured to communicate with the seventh port, and the eighth port and the fifth port communicate with each other,
In the third four-way valve, in the first mode, the tenth port and the eleventh port communicate with each other, and in the second mode, the tenth port and the ninth port communicate with each other, and in the second mode, the third four-way valve communicates with the tenth port and the eleventh port. configured such that the port and the tenth port communicate with each other, and the eleventh port and the twelfth port communicate with each other,
In the fourth four-way valve, in the first mode, the thirteenth port and the fourteenth port communicate with each other, and in the second mode, the fourteenth port communicates with the thirteenth port, and the fifteenth port and the sixteenth port communicate with each other. The refrigeration cycle device according to claim 1, wherein the port and the fifteenth port communicate with each other, and the sixteenth port and the thirteenth port communicate with each other.
The third heat exchanger is configured to, in the second mode, refrigerant discharged from the compressor and directed to the first heat exchanger, and refrigerant passing through the first expansion valve and directed to the second heat exchanger. configured to exchange heat between
The switching mechanism is
a first six-way valve having first to sixth ports;
a second six-way valve having seventh to twelfth ports;
The first port is connected to the discharge port of the compressor, the second port is connected to the refrigerant inlet of the first heat exchanger, and the first port is connected to the refrigerant inlet of the first heat exchanger, and the 1 expansion valve is connected, a first passage of the third heat exchanger is connected between the third port and the sixth port, and the fifth port is the refrigerant outlet of the first heat exchanger and the first passage of the third heat exchanger. connected to the upstream side of the second expansion valve;
The seventh port is connected to the intermediate port of the compressor, the second passage of the third heat exchanger is connected between the eighth port and the eleventh port, and the ninth port is connected to the intermediate port of the compressor. connected to a refrigerant inlet of a second heat exchanger, the twelfth port being connected to the downstream side of the second expansion valve,
In the first mode, the first six-way valve communicates with the first port and the second port, communicates with the third port and communicates with the fourth port, and communicates with the fifth port and the sixth port. are in communication, and in the second mode, the second port and the third port are in communication, the fourth port and the fifth port are in communication, and the sixth port and the first port are in communication. configured to communicate,
In the second hexagonal valve, in the first mode, the seventh port and the eighth port communicate with each other, the ninth port and the tenth port communicate with each other, and the eleventh port and the twelfth port communicate with each other. are in communication, and in the second mode, the eighth port and the ninth port are in communication, the tenth port and the eleventh port are in communication, and the twelfth port and the seventh port are in communication. The refrigeration cycle device according to claim 1, configured to communicate with each other.