CN117693655A

CN117693655A - Refrigeration cycle device

Info

Publication number: CN117693655A
Application number: CN202180100905.4A
Authority: CN
Inventors: 梁池悟
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2021-08-03
Filing date: 2021-08-03
Publication date: 2024-03-12
Also published as: WO2023012899A1; JPWO2023012899A1

Abstract

A refrigeration cycle device is provided with: a 1 st heat exchanger having a plurality of heat transfer tubes and a 1 st header distributing refrigerant to the plurality of heat transfer tubes; a gas-liquid separator that separates the refrigerant flowing into the 1 st heat exchanger into a gas refrigerant and a liquid refrigerant; a gas bypass circuit for flowing a gas refrigerant from the gas-liquid separator into the 1 st header; a liquid bypass circuit for flowing liquid refrigerant from the gas-liquid separator into the 1 st header; and a bypass valve provided in at least one of the gas bypass circuit and the liquid bypass circuit, the gas bypass circuit being connected to the 1 st header at a position downstream in the flow direction of the liquid refrigerant from a position where the liquid bypass circuit is connected to the 1 st header, with respect to the flow direction of the liquid refrigerant in the 1 st header.

Description

Refrigeration cycle device

Technical Field

The present disclosure relates to a refrigeration cycle apparatus having a refrigerant circuit.

Background

As an example of a conventional heat exchanger, a heat exchanger having a gas-liquid separation mechanism for separating a refrigerant into a gas refrigerant and a liquid refrigerant before the refrigerant flows into the heat exchanger has been proposed (for example, see patent literature 1).

The heat exchanger disclosed in patent document 1 has a plurality of heat transfer tubes, a 1 st header, a 2 nd header, a gas-liquid separation mechanism, a 1 st outlet tube, and a 2 nd outlet tube. The 1 st header and the 2 nd header have an inner space extending in a specific direction of the horizontal. The 2 nd header is disposed above the 1 st header. The gas-liquid separation mechanism is disposed above the 2 nd header. The 1 st inlet at one of the two ends of the 1 st header in the specific direction is connected to the gas-liquid separation mechanism via the 1 st outlet pipe, and the 2 nd inlet at the other end is connected to the gas-liquid separation mechanism via the 2 nd outlet pipe.

The heat exchanger disclosed in patent document 1 is configured such that a gas refrigerant flows from the gas-liquid separation mechanism into the 1 st header through the 1 st outlet pipe, and a liquid refrigerant flows from the gas-liquid separation mechanism into the 1 st header through the 2 nd outlet pipe.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2017-223386

Disclosure of Invention

Problems to be solved by the invention

In the heat exchanger disclosed in patent document 1, the flow rates of the gas refrigerant and the liquid refrigerant flowing into the 1 st header are affected by the separation state of the gas-liquid two phases in the gas-liquid separation mechanism. Therefore, for example, when the liquid refrigerant flows toward a part of the plurality of heat transfer tubes, the refrigerant cannot be appropriately distributed to the plurality of heat transfer tubes. In this case, the heat exchange efficiency is lowered.

The present disclosure has been made to solve the above-described problems, and provides a refrigeration cycle device that improves heat exchange efficiency.

Means for solving the problems

The refrigeration cycle device of the present disclosure includes: a 1 st heat exchanger having a 1 st header and a plurality of heat transfer tubes, the 1 st header distributing refrigerant flowing in through refrigerant piping to the plurality of heat transfer tubes; a gas-liquid separator that separates the refrigerant flowing into the 1 st heat exchanger into a gas refrigerant and a liquid refrigerant; a gas bypass circuit connecting the gas-liquid separator to the 1 st header, and allowing the gas refrigerant to flow from the gas-liquid separator into the 1 st header; a liquid bypass circuit connecting the gas-liquid separator to the 1 st header, and allowing the liquid refrigerant to flow from the gas-liquid separator into the 1 st header; and a bypass valve provided in at least one of the gas bypass circuit and the liquid bypass circuit, wherein the gas bypass circuit is connected to the 1 st header at a position downstream in the flow direction from a position where the liquid bypass circuit is connected to the 1 st header, with respect to the flow direction of the liquid refrigerant in the 1 st header.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present disclosure, in the 1 st header functioning as the distributor of the 1 st heat exchanger, the gas refrigerant is blown from the downstream side of the liquid refrigerant, and the flow rate of the liquid refrigerant or the gas refrigerant flowing into the 1 st header is adjusted by the bypass valve. Therefore, the liquid refrigerant flowing into the 1 st header diffuses in the 1 st header, and the gas-liquid two-phase refrigerant is equally distributed to the plurality of heat transfer tubes. As a result, the heat exchange efficiency of the 1 st heat exchanger is improved.

Drawings

Fig. 1 is a refrigerant circuit diagram showing an example of a configuration of a refrigeration cycle apparatus according to embodiment 1.

Fig. 2 is a schematic side view for explaining the structure of the 1 st heat exchanger shown in fig. 1.

Fig. 3 is a schematic view showing a structural example of the gas bypass valve shown in fig. 1.

Fig. 4 is a state diagram of the refrigeration cycle performed by the refrigeration cycle apparatus shown in fig. 1.

Fig. 5 is a refrigerant circuit diagram showing another configuration example of the refrigeration cycle apparatus according to embodiment 1.

Fig. 6 is a schematic side view showing another arrangement example of the 1 st heat exchanger shown in fig. 2.

Fig. 7 is a refrigerant circuit diagram showing an example of the structure of the refrigeration cycle apparatus according to embodiment 2.

Fig. 8 is a state diagram of the refrigeration cycle performed by the refrigeration cycle apparatus shown in fig. 7.

Fig. 9 is a refrigerant circuit diagram showing an example of the structure of the refrigeration cycle apparatus according to embodiment 3.

Fig. 10 is a state diagram of the refrigeration cycle performed by the refrigeration cycle apparatus shown in fig. 9.

Fig. 11 is a refrigerant circuit diagram showing an example of the structure of the refrigeration cycle apparatus according to embodiment 4.

Fig. 12 is a functional block diagram showing a configuration example of the controller shown in fig. 11.

Fig. 13 is a hardware configuration diagram showing an example of the configuration of the controller shown in fig. 12.

Fig. 14 is a hardware configuration diagram showing another configuration example of the controller shown in fig. 12.

Fig. 15 is a flowchart showing steps of a control method performed by the controller shown in fig. 12.

Detailed Description

Embodiment 1.

The configuration of the refrigeration cycle apparatus according to embodiment 1 will be described. Fig. 1 is a refrigerant circuit diagram showing an example of a configuration of a refrigeration cycle apparatus according to embodiment 1. As shown in fig. 1, the refrigeration cycle apparatus 1 includes a compressor 2, a 1 st heat exchanger 3, a gas-liquid separator 4, an expansion valve 5, and a 2 nd heat exchanger 6. In the refrigerant piping 16 connecting the compressor 2, the 1 st heat exchanger 3, the expansion valve 5, and the 2 nd heat exchanger 6, the gas-liquid separator 4 is provided between the 1 st heat exchanger 3 and the expansion valve 5. The compressor 2, the 1 st heat exchanger 3, the expansion valve 5, and the 2 nd heat exchanger 6 constitute a refrigerant circuit 10 in which a refrigerant circulates.

The compressor 2 compresses and discharges a sucked refrigerant. The compressor 2 is, for example, a reciprocating compressor and a rotary compressor. The expansion valve 5 is an expansion device that decompresses and expands the refrigerant. The expansion valve 5 is, for example, a temperature type expansion valve. The temperature-type expansion valve has 2 types of an external pressure equalizing type expansion valve and an internal pressure equalizing type expansion valve. When the expansion valve 5 is an external pressure equalizing type expansion valve, a temperature sensing tube (not shown) provided in the refrigerant pipe 16 between the 1 st heat exchanger 3 and the compressor 2 and a pressure equalizing tube (not shown) connected to the refrigerant pipe 16 on the compressor 2 side of the temperature sensing tube are connected to the expansion valve 5. The expansion valve 5 automatically adjusts the opening degree according to a pressure difference between a pressure of a substance (substance having the same characteristic as the refrigerant) enclosed in the temperature sensing tube (not shown) and a pressure of the refrigerant inputted through the pressure equalizing tube (not shown).

Fig. 2 is a schematic side view for explaining the structure of the 1 st heat exchanger shown in fig. 1. In fig. 2, arrows defining 3 axes (X-axis, Y-axis, and Z-axis) of directions are shown for convenience of explanation. The opposite direction of the Z-axis arrow is referred to as the gravitational direction.

The 1 st heat exchanger 3 has a plurality of heat transfer tubes 11, a 1 st header 12, and a 2 nd header 13. The plurality of heat transfer tubes 11 extend parallel to the Y axis. The 1 st header 12 and the 2 nd header 13 are each of a cylindrical shape or a rectangular parallelepiped shape extending parallel to the Z axis. As shown in fig. 2, in the 1 st heat exchanger 3, a plurality of heat radiating fins 17 are provided between the 1 st header 12 and the 2 nd header 13. Each heat dissipation fin 17 is disposed at equal intervals in a direction parallel to the Y axis from the adjacent heat dissipation fin 17. Each of the heat radiating fins 17 has a plate-like structure parallel to the XZ plane. The plurality of heat transfer pipes 11 penetrate the plurality of heat radiating fins 17. In the 1 st heat exchanger 3 shown in fig. 1, the heat radiating fins 17 shown in fig. 2 are omitted.

In embodiment 1, the structure in which the 1 st heat exchanger 3 has the heat radiating fins 17 is described with reference to fig. 2, but the 1 st heat exchanger 3 may be a heat exchanger having no heat radiating fins 17.

The 1 st header 12 functions as a distributor for distributing the refrigerant flowing in from the gas-liquid separator 4 via the refrigerant piping 16 to the plurality of heat transfer tubes 11. The 2 nd header 13 functions as a combiner that combines the refrigerants flowing through the plurality of heat transfer tubes 11 and flows out to the refrigerant suction port of the compressor 2. The 1 st header 12 and the 2 nd header 13 have hollow structures in which the refrigerant branched to the plurality of heat transfer tubes 11 or the refrigerant flowing in from the plurality of heat transfer tubes 11 is retained, respectively. The plurality of heat transfer tubes 11 are connected at positions different in height with respect to the 1 st header 12 with respect to the gravitational direction. The 2 nd heat exchanger 6 has the same structure as the 1 st heat exchanger 3, and a detailed description thereof is omitted.

The gas-liquid separator 4 separates the refrigerant flowing from the expansion valve 5 into a gas refrigerant and a liquid refrigerant in the 1 st heat exchanger 3. The gas-liquid separator 4 and the 1 st header 12 are connected via a gas bypass circuit 7 through which the gas refrigerant flows from the gas-liquid separator 4 to the 1 st header 12. The gas-liquid separator 4 and the 1 st header 12 are connected via a liquid bypass circuit 8 through which the liquid refrigerant flows from the gas-liquid separator 4 to the 1 st header 12.

The liquid bypass circuit 8 is connected to the upper portion of the 1 st header 12. The gas bypass circuit 7 is connected to the lower portion of the 1 st header 12. In embodiment 1, the 1 st header 12 is a structure in which the gas refrigerant flows in from the lower portion of the 1 st header 12 so as to blow up the liquid refrigerant flowing in from the upper portion of the 1 st header 12. A gas bypass valve 14 is provided in the gas bypass circuit 7. The gas bypass valve 14 adjusts the opening degree to obtain a flow path resistance of the flow rate of the gas refrigerant required for blowing in, in accordance with the flow rate of the liquid refrigerant flowing into the 1 st header 12. The structure of the gas bypass valve 14 will be specifically described below.

When the flow rate of the liquid refrigerant flowing into the 1 st header 12 is small, the liquid refrigerant tends to stagnate on the lower side (opposite direction to the Z-axis arrow in fig. 2) of the 1 st header 12 than on the upper side (direction of the Z-axis arrow in fig. 2) of the 1 st header 12 due to the influence of gravity, and is less likely to flow to the heat transfer tubes 11 on the upper side of the plurality of heat transfer tubes 11. Therefore, the liquid refrigerant mostly flows to the heat transfer tube 11 on the relatively lower side among the plurality of heat transfer tubes 11, and the liquid refrigerant flowing to the heat transfer tube 11 on the upper side decreases. In this case, the gas bypass valve 14 increases the opening degree so that the amount of the gas refrigerant blowing up the liquid refrigerant becomes larger. Thereby, the liquid refrigerant also easily flows to the heat transfer tube 11 on the upper side among the plurality of heat transfer tubes 11.

On the other hand, when the flow rate of the liquid refrigerant flowing into the 1 st header 12 is large, the liquid refrigerant flows into the heat transfer tubes 11 on the lower side (the direction opposite to the Z-axis arrow in fig. 2) and also flows into the heat transfer tubes 11 on the upper side (the direction of the Z-axis arrow in fig. 2) of the plurality of heat transfer tubes 11 because the flow rate is large even when the liquid refrigerant is influenced by gravity. In embodiment 1, even if the flow rate of the liquid refrigerant flowing into the 1 st header 12 from the upper side of the 1 st header 12 is large, the liquid refrigerant is blown up from the lower side of the 1 st header 12 by the gas refrigerant, and the liquid refrigerant is diffused in the 1 st header 12. Therefore, the liquid refrigerant is easily more equally split into the plurality of heat transfer pipes 11.

As described above, the gas bypass valve 14 adjusts the flow rate ratio of the liquid refrigerant and the gas refrigerant flowing into the 1 st header 12 based on the flow rate of the liquid refrigerant flowing into the 1 st header 12. The gas bypass valve 14 is, for example, a valve that keeps a refrigerant pressure difference between an inflow port and an outflow port of the refrigerant constant. When the flow rate ratio of the liquid refrigerant flowing out of the gas-liquid separator 4 to the gas refrigerant flowing out of the gas-liquid separator 4 is considered to be fixed, if the flow rate of the liquid refrigerant flowing into the 1 st header 12 is large, the flow rate of the gas refrigerant flowing into the 1 st header 12 is also large. In the case where the gas bypass valve 14 is a valve that keeps the pressure difference between the refrigerant in the inlet and the refrigerant out of the inlet to be constant, when the flow rate of the gas refrigerant is small, the pressure difference between the refrigerant in the inlet and the refrigerant in the outlet is small, and therefore, the gas bypass valve 14 automatically increases the opening degree to keep the pressure difference between the refrigerant constant.

A specific example of the configuration of the gas bypass valve 14 is a valve that operates on the same principle as a temperature expansion valve. The gas bypass valve 14 has an adjustment valve (not shown) such as a diaphragm for detecting a refrigerant pressure difference between the inlet and the outlet of the refrigerant, and the opening degree is adjusted according to the operation of the adjustment valve. In this case, a special structure such as a controller for controlling the opening degree of the gas bypass valve 14 is not required.

An example of the structure of the gas bypass valve 14 will be described. Fig. 3 is a schematic view showing a structural example of the gas bypass valve shown in fig. 1. In the gas bypass valve 14, the refrigerant inflow port 51 side is connected to the gas-liquid separator 4 via the gas bypass circuit 7, and the refrigerant outflow port 52 side is connected to the 1 st header 12 via the gas bypass circuit 7. The gas bypass valve 14 includes a diaphragm chamber 53, a pressure chamber 55 provided with a spring 54, an orifice plate provided with an orifice 56 for allowing the refrigerant to flow from the refrigerant inflow port 51 to the refrigerant outflow port 52, and a valve needle 57 for adjusting the opening degree of the orifice 56.

The diaphragm chamber 53 is connected to the gas bypass circuit 7 on the refrigerant inflow port 51 side via the 1 st pressure equalizing pipe 61. The pressure chamber 55 is connected to the gas bypass circuit 7 on the refrigerant outflow port 52 side via a 2 nd pressure equalizing pipe 62. The diaphragm 53a is provided on a boundary surface between the diaphragm chamber 53 and the pressure chamber 55, and a shaft 58 is attached to the diaphragm 53 a. A needle 57 is attached to an end of the shaft 58 on the opposite side of the diaphragm 53 a. The diaphragm 53a moves in the axial direction of the shaft 58 by the refrigerant pressure difference Δp between the refrigerant inflow port 51 and the refrigerant outflow port 52 and the elastic force of the spring 54. The valve needle 57 is moved in accordance with the axial movement of the shaft 58 of the diaphragm 53a, whereby the opening degree of the orifice 56 is adjusted. As a result, the flow rate of the refrigerant flowing through the orifice 56 is adjusted, and the refrigerant pressure difference Δp is kept constant.

Next, the operation of the refrigeration cycle apparatus 1 shown in fig. 1 will be described. The case where the 1 st heat exchanger 3 functions as an evaporator will be described. Fig. 4 is a state diagram of the refrigeration cycle performed by the refrigeration cycle apparatus shown in fig. 1. In the state diagram shown in FIG. 4, the horizontal axis represents specific enthalpy h [ kJ/kg ], and the vertical axis represents pressure P [ MPa ]. P1 to P8 shown in fig. 4 represent the states of the refrigerants at positions P1 to P8 in the refrigerant circuit 10 shown in fig. 1.

The compressor 2 sucks in the gas refrigerant, compresses the sucked gas refrigerant, and discharges the compressed gas refrigerant (see a position p1 in fig. 4). The gas refrigerant discharged from the compressor 2 is condensed by heat exchange with air in the 2 nd heat exchanger 6, becomes a liquid refrigerant, and flows out of the 2 nd heat exchanger 6 (see a position p2 in fig. 4). The liquid refrigerant flowing out of the 2 nd heat exchanger 6 is depressurized by the expansion valve 5 to become a gas-liquid two-phase refrigerant (see position p3 in fig. 4). The gas-liquid two-phase refrigerant flows into the gas-liquid separator 4, and is separated into a liquid refrigerant (see a position p4 in fig. 4) and a gas refrigerant (see a position p5 in fig. 4).

Liquid refrigerant passes from the gas-liquid separator 4 to the 1 st header 12 via the liquid bypass circuit 8. The liquid refrigerant reaching the 1 st header 12 flows into the 1 st header 12 from the upper portion of the 1 st header 12. The gas refrigerant separated by the gas-liquid separator 4 flows through the gas bypass circuit 7 from the gas-liquid separator 4. The gas refrigerant flowing through the gas bypass circuit 7 is depressurized by the gas bypass valve 14 and then adjusted in flow rate, and then flows into the 1 st header 12 from the lower portion of the 1 st header 12 (see position p6 in fig. 4).

In the position p6 shown in fig. 4, when the flow rate of the refrigerant flowing into the gas bypass valve 14 is small, the gas bypass valve 14 increases the opening degree, and the flow rate of the gas refrigerant increases. When the flow rate of the refrigerant flowing into the gas bypass valve 14 is large, the gas bypass valve 14 reduces the opening degree, and reduces the flow rate of the gas refrigerant.

The gas refrigerant flowing into the 1 st header 12 from the lower portion of the 1 st header 12 mixes with the liquid refrigerant while blowing up the liquid refrigerant flowing into the 1 st header 12 from the upper portion of the 1 st header 12 (see position p7 in fig. 4). The mixed gas-liquid two-phase refrigerant is branched to the plurality of heat transfer pipes 11. The gas-liquid two-phase refrigerant flowing through each heat transfer tube 11 exchanges heat with air to evaporate, and after evaporation, merges in the 2 nd header 13. The gas refrigerant merged in the 2 nd header 13 flows into the compressor 2 from the refrigerant suction port of the compressor 2 (see position p8 in fig. 4).

In this way, an appropriate amount of gas refrigerant is blown from the lower portion of the 1 st header 12 in accordance with the flow rate of the liquid refrigerant flowing in from the upper portion of the 1 st header 12 of the 1 st heat exchanger 3. Therefore, the flow rate of the refrigerant in each heat transfer pipe 11 of the plurality of heat transfer pipes 11 can be equalized.

In embodiment 1, the explanation was given of the case where the bypass valve for fixing the flow rate ratio of the liquid refrigerant and the gas refrigerant flowing from the gas-liquid separator 4 to the 1 st header 12 is provided on the gas bypass circuit 7 side, but the bypass valve may be provided on the liquid bypass circuit 8 side. Fig. 5 is a refrigerant circuit diagram showing another configuration example of the refrigeration cycle apparatus according to embodiment 1. As shown in fig. 5, when the liquid bypass valve 15 is provided in the liquid bypass circuit 8, the liquid bypass valve 15 decreases the opening degree when the flow rate of the liquid refrigerant flowing into the liquid bypass circuit 8 is large, and increases the opening degree when the flow rate of the liquid refrigerant flowing into the liquid bypass circuit 8 is small.

Fig. 1 shows a structure in which the liquid bypass circuit 8 is connected to the upper portion of the 1 st header 12 and the gas bypass circuit 7 is connected to the lower portion of the 1 st header 12, but the connection positions of these bypass circuits are not limited to those shown in fig. 1. The gas bypass circuit 7 may be connected to a position downstream of the position where the liquid bypass circuit 8 is connected to the 1 st header 12 in the flow direction of the liquid refrigerant, with respect to the flow direction of the liquid refrigerant in the 1 st header 12. In this case, the liquid refrigerant flowing into the 1 st header 12 is blown up from the downstream side in the flow direction of the liquid refrigerant in the 1 st header 12 to the direction of the Z-axis arrow shown in fig. 2 by the gas refrigerant.

In embodiment 1, the 1 st header 12 may be arranged to extend parallel to the Y axis shown in fig. 2. Fig. 6 is a schematic side view showing another arrangement example of the 1 st heat exchanger shown in fig. 2. Fig. 6 shows a configuration in which the 1 st heat exchanger 3 is disposed such that the extending direction of the 1 st header 12 is parallel to the ground. In the example of the arrangement shown in fig. 6, the heat transfer tube in the direction opposite to the direction of the arrow closest to the Y-axis among the plurality of heat transfer tubes 11 is referred to as the 1 st heat transfer tube 21, and the heat transfer tube in the direction closest to the arrow closest to the Y-axis is referred to as the 2 nd heat transfer tube 22.

In the case of the installation example shown in fig. 6, the liquid refrigerant flows down to the 1 st header 12 via the liquid bypass circuit 8, but the liquid refrigerant easily flows in the direction indicated by the broken line arrow in the 1 st header 12 due to the inertial force at the time of the flow down. Therefore, when the amount of refrigerant flowing into the 1 st header 12 is small, the refrigerant easily flows toward the 2 nd heat transfer pipe 22 side than the 1 st heat transfer pipe 21, but is blown up toward the 1 st heat transfer pipe 21 side by the gas refrigerant flowing through the gas bypass valve 14. Thus, the extending direction of the 1 st header 12 may be a direction parallel to the ground. In the example shown in fig. 6, the 1 st heat exchanger 3 may be inclined with respect to the ground.

In embodiment 1, the expansion valve 5 may be an electronic expansion valve, and the compressor 2 may be a variable-frequency compressor with variable capacity. In the case where the expansion valve 5 is an electronic expansion valve and the compressor 2 is a variable frequency compressor, a controller (not shown) for controlling the opening degree of the expansion valve 5 and the operating frequency of the compressor 2 may be provided in the refrigeration cycle apparatus 1.

The refrigeration cycle apparatus 1 according to embodiment 1 includes a 1 st heat exchanger 3, a gas-liquid separator 4, a gas bypass circuit 7, and a liquid bypass circuit 8. The 1 st heat exchanger 3 includes a plurality of heat transfer tubes 11, and a 1 st header 12 for distributing the refrigerant flowing in through the refrigerant pipe 16 to the plurality of heat transfer tubes 11. The gas-liquid separator separates the refrigerant flowing into the 1 st heat exchanger 3 into a gas refrigerant and a liquid refrigerant. The gas bypass circuit 7 connects the gas-liquid separator 4 to the 1 st header 12, and allows the gas refrigerant to flow from the gas-liquid separator 4 into the 1 st header 12. The liquid bypass circuit 8 connects the gas-liquid separator 4 to the 1 st header 12, and allows the liquid refrigerant to flow from the gas-liquid separator 4 into the 1 st header 12. A bypass valve is provided in at least one of the gas bypass circuit 7 and the liquid bypass circuit 8. The bypass valve adjusts the opening degree in accordance with the flow rate of the refrigerant flowing into one of the bypass circuits. The bypass valve is a gas bypass valve 14 or a liquid bypass valve 15. The gas bypass circuit 7 is connected to the 1 st header 12 at a position downstream of the position where the liquid bypass circuit 8 is connected to the 1 st header 12 in the flow direction of the liquid refrigerant, based on the flow direction of the liquid refrigerant in the 1 st header 12.

According to embodiment 1, when the bypass valve is the gas bypass valve 14, and when the flow rate of the gas refrigerant flowing into the gas bypass circuit 7 is small, the gas bypass valve 14 adjusts the opening degree so that the flow rate of the gas refrigerant blown out from the downstream side of the liquid refrigerant in the 1 st header 12 increases. When the opening degree of the gas bypass valve 14 increases, the liquid refrigerant is lifted upward from the 1 st header 12 by the gas refrigerant blown up from the downstream side. As a result, the liquid refrigerant easily flows to the heat transfer tubes 11 on the upper side (in the direction of the Z-axis arrow in fig. 2), and the gas-liquid two-phase refrigerant flowing into the 1 st header 12 is equally split into the plurality of heat transfer tubes 11.

On the other hand, when the flow rate of the gas refrigerant flowing into the gas bypass circuit 7 is large, the liquid refrigerant easily flows into not only the lower heat transfer tube 11 (the direction opposite to the Z-axis arrow in fig. 2) but also the upper heat transfer tube 11 (the direction of the Z-axis arrow in fig. 2) among the plurality of heat transfer tubes 11. The liquid refrigerant is blown up from the downstream side by the gas refrigerant flowing through the gas bypass valve 14, and is likely to diffuse into the 1 st header 12. As a result, the gas-liquid two-phase refrigerant flowing into the 1 st header 12 is equally split into the plurality of heat transfer tubes 11.

In embodiment 1, when the bypass valve is the liquid bypass valve 15, the liquid bypass valve 15 adjusts the opening degree so that the flow rate of the liquid refrigerant flowing into the 1 st header 12 increases when the flow rate of the liquid refrigerant flowing into the liquid bypass circuit 8 is small. This can prevent the liquid refrigerant from easily stagnating on the lower side (opposite direction to the Z-axis arrow in fig. 2) of the 1 st header 12 than on the upper side (Z-axis arrow direction in fig. 2) of the 1 st header 12. In addition, when the flow rate is small, the liquid refrigerant tends to stagnate below the 1 st header 12, but is blown up by the gas refrigerant to the upper side in the 1 st header 12. The liquid refrigerant easily flows to the heat transfer tubes 11 on the upper side of the 1 st header 12. As a result, the gas-liquid two-phase refrigerant flowing into the 1 st header 12 is equally split into the plurality of heat transfer tubes 11.

On the other hand, when the flow rate of the liquid refrigerant flowing into the liquid bypass circuit 8 is large, the liquid bypass valve 15 is set to be fully opened because the liquid refrigerant easily flows into not only the lower heat transfer tube 11 (the direction opposite to the Z-axis arrow in fig. 2) but also the upper heat transfer tube 11 (the direction opposite to the Z-axis arrow in fig. 2) among the plurality of heat transfer tubes 11. Even if the flow rate of the liquid refrigerant flowing into the 1 st header 12 from the upper side of the 1 st header 12 is large, the liquid refrigerant is blown up by the gas refrigerant from the lower side of the 1 st header 12, and the liquid refrigerant is likely to spread in the 1 st header 12. As a result, the gas-liquid two-phase refrigerant flowing into the 1 st header 12 is equally split into the plurality of heat transfer tubes 11.

In addition, when the flow rate of the liquid refrigerant flowing into the liquid bypass circuit 8 is excessive, the opening degree of the liquid bypass valve 15 may be adjusted so that the flow rate of the liquid refrigerant flowing into the 1 st header 12 is reduced. This is because, when the flow rate of the liquid refrigerant flowing into the liquid bypass circuit 8 is too high, the momentum of the liquid refrigerant flowing into the 1 st header 12 is too high, and the tendency of the liquid refrigerant flowing into a part of the heat transfer tubes 11 becomes high. In this case, the opening degree is reduced by the liquid bypass valve 15, so that the flow rate of the liquid refrigerant flowing into the 1 st header 12 becomes appropriate, and the liquid refrigerant is easily and uniformly branched to the plurality of heat transfer tubes 11. As a result, the gas-liquid two-phase refrigerant flowing into the 1 st header 12 is equally split into the plurality of heat transfer tubes 11.

In this way, in the 1 st header 12 functioning as a distributor of the 1 st heat exchanger 3, the gas refrigerant is blown from the downstream side of the liquid refrigerant. The flow rate of the liquid refrigerant or the gas refrigerant flowing into the 1 st header 12 is adjusted by the gas bypass valve 14 or the liquid bypass valve 15. Therefore, the liquid refrigerant flowing into the 1 st header 12 diffuses in the 1 st header 12, and the gas-liquid two-phase refrigerant is equally distributed to the plurality of heat transfer tubes 11. As a result, the heat exchange efficiency of the 1 st heat exchanger 3 is improved.

Embodiment 2.

The refrigeration cycle apparatus according to embodiment 2 is configured such that a bypass valve is provided in both the gas bypass circuit and the liquid bypass circuit. In embodiment 2, the same components as those described in embodiment 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

The configuration of the refrigeration cycle apparatus according to embodiment 2 will be described. Fig. 7 is a refrigerant circuit diagram showing an example of the structure of the refrigeration cycle apparatus according to embodiment 2. As shown in fig. 7, the refrigeration cycle apparatus 1a of embodiment 2 is provided with a liquid bypass valve 15 in the liquid bypass circuit 8 in addition to the configuration shown in fig. 1.

The liquid bypass valve 15 is a valve that increases the pressure difference between the gas-liquid separator 4 and the 1 st header 12. The liquid bypass valve 15 is, for example, a pressure adjustment valve that makes the pressure difference between the gas-liquid separator 4 and the 1 st header 12 larger than a predetermined pressure. By increasing the pressure difference between the gas-liquid separator 4 and the 1 st header 12, the momentum of the gas refrigerant blown up from the gas bypass circuit 7 into the 1 st header 12 can be increased.

Next, the operation of the refrigeration cycle apparatus 1a shown in fig. 7 will be described. The case where the 1 st heat exchanger 3 functions as an evaporator will be described. Fig. 8 is a state diagram of the refrigeration cycle performed by the refrigeration cycle apparatus shown in fig. 7. In the state diagram shown in FIG. 8, the horizontal axis represents specific enthalpy h [ kJ/kg ], and the vertical axis represents pressure P [ MPa ]. P1 to P9 shown in fig. 8 represent the states of the refrigerants at positions P1 to P9 in the refrigerant circuit 10 shown in fig. 7.

The compressor 2 sucks in the gas refrigerant, compresses the sucked gas refrigerant, and discharges the compressed gas refrigerant (see a position p1 in fig. 8). The gas refrigerant discharged from the compressor 2 is condensed by heat exchange with air in the 2 nd heat exchanger 6, becomes a liquid refrigerant, and flows out of the 2 nd heat exchanger 6 (see a position p2 in fig. 8). The liquid refrigerant flowing out of the 2 nd heat exchanger 6 is depressurized by the expansion valve 5 to become a gas-liquid two-phase refrigerant (see position p3 in fig. 8). The gas-liquid two-phase refrigerant flows into the gas-liquid separator 4, and is separated into a liquid refrigerant (see a position p4 in fig. 8) and a gas refrigerant (see a position p5 in fig. 8).

The liquid refrigerant flows from the gas-liquid separator 4 through the liquid bypass circuit 8. The liquid refrigerant flowing through the liquid bypass circuit 8 is depressurized by the liquid bypass valve 15 and then flows into the 1 st header 12 from the upper portion of the 1 st header 12 after the flow rate is adjusted (see position p6 in fig. 8). On the other hand, the gas refrigerant separated by the gas-liquid separator 4 flows from the gas-liquid separator 4 through the gas bypass circuit 7. The gas refrigerant flowing through the gas bypass circuit 7 is depressurized by the gas bypass valve 14 and then adjusted in flow rate, and then flows into the 1 st header 12 from the lower portion of the 1 st header 12 (see position p7 in fig. 8).

The gas refrigerant flowing into the 1 st header 12 from the lower portion of the 1 st header 12 blows up the liquid refrigerant flowing into the 1 st header 12 from the upper portion of the 1 st header 12 and mixes with the liquid refrigerant (see position p8 in fig. 8). The mixed gas-liquid two-phase refrigerant is branched to the plurality of heat transfer pipes 11. The gas-liquid two-phase refrigerant flowing through each heat transfer tube 11 is evaporated and gasified by heat exchange with air, and then merges in the 2 nd header 13. The gas refrigerant merged in the 2 nd header 13 flows into the compressor 2 from the refrigerant suction port of the compressor 2 (see position p9 in fig. 8).

By the liquid bypass valve 15, the pressure difference between the inside of the gas-liquid separator 4 and the inside of the 1 st header 12 becomes large. Therefore, compared with embodiment 1, at the position p7 shown in fig. 8, the potential of the gas refrigerant blown out from the downstream side of the liquid refrigerant flowing into the 1 st header 12 to the liquid refrigerant increases.

The refrigeration cycle apparatus 1a of embodiment 2 is provided with a liquid bypass valve 15 in the liquid bypass circuit 8, and the liquid bypass valve 15 is a valve that increases the pressure difference between the gas-liquid separator 4 and the 1 st header 12. According to embodiment 2, since the liquid refrigerant is further blown up by the gas refrigerant, the liquid refrigerant can be made to reach a higher direction in the 1 st header 12 when the flow rate of the refrigerant is small.

In the gas bypass circuit, when the pressure difference between the inlet and the outlet of the refrigerant in the gas bypass valve is small, the capacity coefficient (Cv value) required for circulating the refrigerant having the same flow rate is increased. In contrast, in embodiment 2, the liquid bypass valve 15 increases the pressure difference between the inside of the gas-liquid separator 4 and the inside of the 1 st header 12. Therefore, in the gas bypass circuit 7, the pressure difference between the front and rear of the gas bypass valve 14 increases, and the Cv value required for the gas bypass valve 14 can be reduced. As a result, the gas bypass valve 14 can be miniaturized.

Embodiment 3.

The refrigeration cycle apparatus according to embodiment 3 is configured such that a four-way valve is provided in a refrigerant circuit, and the four-way valve switches the flow direction of refrigerant in the refrigerant circuit. In embodiment 3, the same components as those described in embodiments 1 and 2 are denoted by the same reference numerals, and detailed description thereof is omitted. In embodiment 3, the description is given of the case where the four-way valve is added to the refrigeration cycle apparatus 1a of embodiment 2, but the four-way valve may be added to the refrigeration cycle apparatus 1 of embodiment 1.

The configuration of the refrigeration cycle apparatus according to embodiment 3 will be described. Fig. 9 is a refrigerant circuit diagram showing an example of the structure of the refrigeration cycle apparatus according to embodiment 3. As shown in fig. 9, the refrigeration cycle apparatus 1b according to embodiment 3 is configured by adding a four-way valve 9 to the configuration shown in fig. 7.

The four-way valve 9 sets the flow direction of the refrigerant discharged from the compressor 2 to be the 1 st flow direction or the 2 nd flow direction, wherein the 1 st flow direction is the flow direction from the compressor 2 to the 1 st heat exchanger 3, and the 2 nd flow direction is the flow direction from the compressor 2 to the 2 nd heat exchanger 6. When the flow direction of the refrigerant discharged from the compressor 2 is set to the 1 st flow direction, the 1 st heat exchanger 3 functions as a condenser and the 2 nd heat exchanger 6 functions as an evaporator. When the flow direction of the refrigerant discharged from the compressor 2 is set to the 2 nd flow direction, the 1 st heat exchanger 3 functions as an evaporator, and the 2 nd heat exchanger 6 functions as a condenser.

The liquid bypass valve 15 has the following structure: when the 1 st heat exchanger 3 functions as an evaporator, the state is opened as in embodiment 2, but when the 1 st heat exchanger 3 functions as a condenser, the state is closed. The gas bypass valve 14 has the following structure: when the 1 st heat exchanger 3 functions as an evaporator, the opening degree of the flow rate of the gas is adjusted in the same manner as in embodiments 1 and 2, but when the 1 st heat exchanger 3 functions as a condenser, the full open state is achieved. In embodiment 3, the gas bypass circuit 7 is connected to the 1 st header 12 at a position lower than the liquid bypass circuit 8 with respect to the height based on the gravity direction. When the 1 st heat exchanger 3 functions as a condenser, the liquid refrigerant flowing from the plurality of heat transfer tubes 11 into the 1 st header 12 easily flows smoothly into the gas-liquid separator 4 through the gas bypass circuit 7 when the gas bypass valve 14 is in the fully opened state.

Next, the operation of the refrigeration cycle apparatus 1b shown in fig. 9 will be described. In embodiment 3, a case will be described in which the 1 st heat exchanger 3 functions as a condenser. The operation of the refrigeration cycle in the case where the 1 st heat exchanger 3 functions as an evaporator is the same as that described in embodiment 2, and therefore, a detailed description thereof is omitted.

Fig. 10 is a state diagram of the refrigeration cycle performed by the refrigeration cycle apparatus shown in fig. 9. In the state diagram shown in FIG. 10, the horizontal axis represents specific enthalpy h [ kJ/kg ], and the vertical axis represents pressure P [ MPa ]. The positions p1, p2, p5, and p8 to p10 shown in fig. 10 represent the states of the refrigerant at representative positions among the positions p1 to p10 in the refrigerant circuit 10 shown in fig. 9.

The compressor 2 sucks in the gas refrigerant, compresses the sucked gas refrigerant, and discharges the compressed gas refrigerant (see a position p1 in fig. 10). The gas refrigerant discharged from the compressor 2 flows through the four-way valve 9 to the 2 nd header 13 (see position p9 in fig. 10). The gas refrigerant flowing into the 2 nd header 13 is branched to the plurality of heat transfer tubes 11. In each heat transfer tube 11 of the plurality of heat transfer tubes 11, the gas refrigerant is liquefied by exchanging heat with air. The refrigerant liquefied in each of the heat transfer tubes 11 of the plurality of heat transfer tubes 11 merges in the 1 st header 12 (see position p8 in fig. 10).

The liquid refrigerant flowing from the plurality of heat transfer tubes 11 into the 1 st header 12 flows toward the lower side of the 1 st header 12 by the dead weight. Since the gas bypass valve 14 is in the fully opened state, the liquid refrigerant flowing to the lower portion of the 1 st header 12 does not remain in the lower portion of the 1 st header 12, but flows through the gas bypass circuit 7 to the gas-liquid separator 4 (see position p5 in fig. 10). Therefore, the liquid refrigerant is suppressed from stagnating in the lower portion of the 1 st header 12. Since the liquid refrigerant does not remain in the lower portion of the 1 st header 12, the liquid refrigerant flowing through the heat transfer tube 11 located at a lower position among the plurality of heat transfer tubes 11 smoothly flows out of the heat transfer tube 11, and can flow into the gas-liquid separator 4 through the gas bypass circuit 7.

After flowing from the gas-liquid separator 4 into the expansion valve 5, the liquid refrigerant is depressurized by the expansion valve 5 to become a gas-liquid two-phase refrigerant (see position p2 in fig. 10). The gas-liquid two-phase refrigerant flows into the 2 nd heat exchanger 6. In the 2 nd heat exchanger 6, the gas-liquid two-phase refrigerant is evaporated by heat exchange with air, gasified, and then flows out of the 2 nd heat exchanger 6. The gas refrigerant flowing out of the 2 nd heat exchanger 6 flows into the compressor 2 from the refrigerant suction port of the compressor 2 (see a position p10 in fig. 10).

The refrigeration cycle apparatus 1b according to embodiment 3 includes a four-way valve 9 that sets the flow direction of the refrigerant in the refrigerant circuit 10 to the 1 st flow direction or the 2 nd flow direction. The gas bypass valve 14 is configured to be fully opened when the flow direction of the refrigerant is set to the 2 nd flow direction by the four-way valve 9.

When the flow direction of the refrigerant in the refrigerant circuit is the 1 st flow direction in which the 1 st heat exchanger functions as a condenser, the condensed liquid refrigerant stays in the lower portion of the 1 st header. When the liquid refrigerant stagnates in the lower portion of the 1 st header, the refrigerant outlet of the heat transfer tube to the 1 st header is blocked by the liquid refrigerant. In this case, the flow of the refrigerant of the heat transfer tube in the lower portion of the 1 st header becomes poor, and the heat exchange efficiency of the 1 st heat exchanger decreases. In contrast, according to embodiment 3, when the flow direction of the refrigerant is the 1 st flow direction, the gas bypass valve 14 provided in the gas bypass circuit 7 connected to the lower side of the 1 st header 12 is in the fully opened state. Therefore, the liquid refrigerant easily flows from the lower portion of the 1 st header 12 to the gas-liquid separator 4 via the gas bypass circuit 7, and stagnation of the liquid refrigerant in the lower portion of the 1 st header 12 is suppressed. As a result, the refrigerant also easily flows into the heat transfer tube 11 on the lower side of the 1 st heat exchanger 3, and the heat exchange efficiency of the 1 st heat exchanger 3 increases.

Embodiment 4.

The refrigeration cycle apparatus according to embodiment 4 controls the opening degree of the bypass valve in accordance with the temperature of the refrigerant flowing through the heat transfer tube. In embodiment 4, the same components as those described in embodiments 1 to 3 are denoted by the same reference numerals, and detailed description thereof is omitted. In embodiment 4, the refrigeration cycle apparatus of embodiment 3 is described as a base, but embodiment 4 may be applied to the refrigeration cycle apparatus of embodiment 1 or 2.

The configuration of the refrigeration cycle apparatus according to embodiment 4 will be described. Fig. 11 is a refrigerant circuit diagram showing an example of the structure of the refrigeration cycle apparatus according to embodiment 4. The refrigeration cycle apparatus 1c shown in fig. 11 is configured by adding the 1 st and 2 nd temperature sensors 31 and 32 for detecting the temperature of the refrigerant and the controller 40 to the configuration shown in fig. 9. The 1 st temperature sensor 31 and the 2 nd temperature sensor 32 are, for example, thermistors. The 1 st temperature sensor 31, the 2 nd temperature sensor 32, the gas bypass valve 14, and the liquid bypass valve 15 are connected to the controller 40 via signal lines (not shown).

The 1 st temperature sensor 31 is provided in the 1 st heat transfer pipe 21, which is the highest heat transfer pipe among the plurality of heat transfer pipes 11, with respect to the height with respect to the gravitational direction (the direction opposite to the Z-axis arrow) shown in fig. 2. The 2 nd temperature sensor 32 is provided in the 2 nd heat transfer pipe 22, which is the lowest heat transfer pipe among the plurality of heat transfer pipes 11, with reference to the gravitational direction.

Fig. 12 is a functional block diagram showing a configuration example of the controller shown in fig. 11. The controller 40 is, for example, a microcomputer. The controller 40 has a determination unit 42 and a valve control unit 43. The determination unit 42 calculates a temperature difference Td between the detection value of the 1 st temperature sensor 31 and the detection value of the 2 nd temperature sensor 32. The determination unit 42 determines whether the temperature difference Td is greater than a predetermined threshold value Tth, and sends information of the determination result to the valve control unit 43.

When the temperature difference Td is greater than the threshold value Tth, the valve control unit 43 adjusts the opening degree of at least one of the gas bypass valve 14 and the liquid bypass valve 15 so that the temperature difference Td becomes equal to or less than the threshold value Tth. A specific example of the method for adjusting the opening degree of the bypass valve by the valve control unit 43 will be described below.

When the heat exchanger functions as an evaporator, the flow rate of the refrigerant flowing through the heat transfer tube decreases, and the temperature of the refrigerant increases. For example, when the 1 st heat exchanger 3 functions as an evaporator, the flow rate of the refrigerant flowing through the 2 nd heat transfer pipe 22 is smaller than the flow rate of the refrigerant flowing through the 1 st heat transfer pipe 21, and the detection value of the 2 nd temperature sensor 32 is larger than the detection value of the 1 st temperature sensor 31. When the temperature difference Td between the detection value of the 1 st temperature sensor 31 and the detection value of the 2 nd temperature sensor 32 is greater than the threshold value Tth, the valve control unit 43 decreases the opening degree of the gas bypass valve 14. As a result, the amount of blown out gas refrigerant decreases, the liquid refrigerant easily flows down to the lower portion side of the 1 st header 12, and the flow rate of the refrigerant flowing through the 2 nd heat transfer tube 22 increases. Further, the valve control unit 43 may increase the opening degree of the liquid bypass valve 15. In this case, the flow rate of the liquid refrigerant increases, and the amount of the refrigerant flowing through the 2 nd heat transfer tube 22 increases in opposition to the flow of the gas refrigerant flowing further toward the lower portion side of the 1 st header 12. The valve control unit 43 may decrease the opening degree of the gas bypass valve 14 and increase the opening degree of the liquid bypass valve 15. In either case, the flow rate of the refrigerant flowing through the plurality of heat transfer tubes 11 is equalized.

On the other hand, when the heat exchanger functions as a condenser, the refrigerant flowing through the heat transfer pipe becomes low in temperature when the flow rate of the refrigerant is small. For example, when the 1 st heat exchanger 3 functions as a condenser, the flow rate of the refrigerant flowing through the 1 st heat transfer pipe 21 is smaller than the flow rate of the refrigerant flowing through the 2 nd heat transfer pipe 22, and the detection value of the 1 st temperature sensor 31 is smaller than the detection value of the 2 nd temperature sensor 32. When the temperature difference Td between the detection value of the 1 st temperature sensor 31 and the detection value of the 2 nd temperature sensor 32 is greater than the threshold value Tth, the valve control unit 43 increases the opening degree of the gas bypass valve 14. As a result, as described in embodiment 3, the refrigerant flowing through the 2 nd heat transfer pipe 22 flows more smoothly, and the flow rate of the refrigerant on the 2 nd heat transfer pipe 22 side can be increased. As a result, the flow rate of the refrigerant flowing through the plurality of heat transfer tubes 11 is equalized.

In embodiment 4, the case where the 1 st temperature sensor 31 is provided in the 1 st heat transfer pipe 21 and the 2 nd temperature sensor 32 is provided in the 2 nd heat transfer pipe 22 is described, but the temperature sensor may be provided in either one of the heat transfer pipes. For example, if the heat transfer tubes having a relatively small flow rate of the refrigerant among the plurality of heat transfer tubes 11 are known in advance, a temperature sensor may be provided for the heat transfer tube having a small flow rate of the refrigerant. In this case, the valve control unit 43 adjusts the opening degree of the gas bypass valve 14 or the liquid bypass valve 15 so that the detection value of the temperature sensor falls within a predetermined range.

Here, an example of the hardware configuration of the controller 40 shown in fig. 12 will be described. Fig. 13 is a hardware configuration diagram showing an example of the configuration of the controller shown in fig. 12. When the various functions of the controller 40 are executed by dedicated hardware, the controller 40 shown in fig. 12 is constituted by a processing circuit 80 as shown in fig. 13. The respective functions of the determination unit 42 and the valve control unit 43 shown in fig. 12 are realized by a processing circuit 80.

Where the functions are performed by hardware, the processing circuitry 80 corresponds, for example, to a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit: application specific integrated circuit), an FPGA (Field-Programmable Gate Array: field programmable gate array), or a combination thereof. The functions of the respective units of the determination unit 42 and the valve control unit 43 may be realized by the processing circuit 80. Further, the functions of the respective units of the determination unit 42 and the valve control unit 43 may be realized by 1 processing circuit 80.

An example of another hardware configuration of the controller 40 shown in fig. 12 will be described. Fig. 14 is a hardware configuration diagram showing another configuration example of the controller shown in fig. 12. When various functions of the controller 40 are executed by software, the controller 40 shown in fig. 12 is configured by a processor 81 such as a CPU (Central Processing Unit: central processing unit) and a memory 82 as shown in fig. 14. The respective functions of the determination unit 42 and the valve control unit 43 are realized by a processor 81 and a memory 82. Fig. 14 shows that the processor 81 and the memory 82 are connected via a bus 83. The memory 82 stores a threshold value Tth.

In the case where each function is performed by software, the functions of the determination unit 42 and the valve control unit 43 are implemented by software, firmware, or a combination of software and firmware. The software and firmware are described in the form of programs and stored in the memory 82. The processor 81 realizes the functions of the respective units by reading out and executing programs stored in the memory 82.

As the Memory 82, for example, a nonvolatile semiconductor Memory such as ROM (Read Only Memory), flash Memory, EPROM (Erasable and Programmable ROM: erasable programmable ROM), and EEPROM (Electrically Erasable and Programmable ROM: electrically erasable programmable ROM) is used. Further, as the memory 82, a volatile semiconductor memory which is a RAM (Random Access Memory: random access memory) may be used. As the memory 82, a removable recording medium such as a magnetic disk, a flexible disk, an optical disk, a CD (Compact Disc), an MD (Mini Disc), and a DVD (Digital Versatile Disc: digital versatile Disc) may be used.

Next, an operation of the refrigeration cycle apparatus 1c according to embodiment 4 will be described. Fig. 15 is a flowchart showing steps of a control method performed by the controller shown in fig. 12. Here, the case where the 1 st heat exchanger 3 functions as an evaporator will be described. The controller 40 operates in accordance with the flow shown in fig. 15 at a fixed cycle.

The determination unit 42 obtains the detection values from the 1 st temperature sensor 31 and the 2 nd temperature sensor 32 (step S101). The determination unit 42 calculates a temperature difference Td between the detection value of the 1 st temperature sensor 31 and the detection value of the 2 nd temperature sensor 32. Then, the determination unit 42 determines whether the temperature difference Td is greater than the threshold value Tth (step S102). As a result of the determination in step S102, when the temperature difference Td is equal to or less than the threshold value Tth, the controller 40 ends the process.

On the other hand, as a result of the determination in step S102, when the temperature difference Td is greater than the threshold value Tth, the determination unit 42 sends information of the determination result to the valve control unit 43. Upon receiving the information indicating that the temperature difference Td is greater than the threshold value Tth from the determination unit 42, the valve control unit 43 adjusts the opening degree of the gas bypass valve 14 or the liquid bypass valve 15 so that the temperature difference Td becomes equal to or less than the threshold value Tth (step S103).

In the case where the 1 st temperature sensor 31 is provided in the 1 st heat transfer pipe 21 and the 2 nd temperature sensor 32 is not provided in the 2 nd heat transfer pipe 22, the controller 40 operates as follows in the flow chart shown in fig. 15. When the 1 st heat exchanger 3 functions as a condenser, the determination unit 42 obtains a detection value from the 1 st temperature sensor 31 in step S101. In step S102, the determination unit 42 determines whether the detection value of the 1 st temperature sensor 31 is within a predetermined 1 st temperature range. In the case where the detection value of the 1 st temperature sensor 31 is not within the 1 st temperature range, in step S103, the valve control unit 43 adjusts the opening degree of the gas bypass valve 14 or the liquid bypass valve 15. For example, in the determination in step S102, when the detection value of the 1 st temperature sensor 31 is smaller than the 1 st temperature range, it is considered that the flow rate of the refrigerant flowing into the 1 st heat transfer pipe 21 is small. In this case, the valve control unit 43 increases the opening degree of the gas bypass valve 14. This can increase the flow rate of the refrigerant flowing through the 1 st heat transfer pipe 21.

In the case where the 1 st temperature sensor 31 is not provided in the 1 st heat transfer pipe 21 but the 2 nd temperature sensor 32 is provided in the 2 nd heat transfer pipe 22, the controller 40 operates as follows in the flow chart shown in fig. 15. When the 1 st heat exchanger 3 functions as an evaporator, the determination unit 42 obtains a detection value from the 2 nd temperature sensor 32 in step S101. In step S102, the determination unit 42 determines whether the detection value of the 2 nd temperature sensor 32 is within a predetermined 2 nd temperature range. In the case where the detection value of the 2 nd temperature sensor 32 is not within the 2 nd temperature range, in step S103, the valve control unit 43 adjusts the opening degree of the gas bypass valve 14 or the liquid bypass valve 15. For example, in the determination in step S102, when the detection value of the 2 nd temperature sensor 32 is larger than the 2 nd temperature range, it is considered that the flow rate of the refrigerant flowing into the 2 nd heat transfer pipe 22 is small. In this case, the valve control unit 43 decreases the opening degree of the gas bypass valve 14 or increases the opening degree of the liquid bypass valve 15. This can increase the flow rate of the refrigerant flowing through the 2 nd heat transfer tube 22.

In embodiment 4, when the expansion valve 5 is an electronic expansion valve and the compressor 2 is a variable frequency compressor capable of varying the capacity, the controller 40 may control the opening degree of the expansion valve 5 and the operating frequency of the compressor 2.

The refrigeration cycle apparatus 1c according to embodiment 4 includes a temperature sensor provided in at least one of the 1 st heat transfer pipe 21 and the 2 nd heat transfer pipe 22, and a controller 40. The controller 40 adjusts the opening degree of the gas bypass valve 14 or the liquid bypass valve 15 so that the detection value of the temperature sensor is within a predetermined range.

According to embodiment 4, the opening degree of the gas bypass valve 14 or the liquid bypass valve 15 is adjusted so that the detection value of the temperature sensor provided in the 1 st heat transfer pipe 21 or the 2 nd heat transfer pipe 22 falls within a predetermined range, and therefore the refrigerant flows more uniformly to the plurality of heat transfer pipes 11. Therefore, the heat exchange efficiency of the 1 st heat exchanger 3 is improved.

In embodiment 4, the 1 st temperature sensor 31 may be provided in the 1 st heat transfer pipe 21, and the 2 nd temperature sensor 32 may be provided in the 2 nd heat transfer pipe 22. In this case, the controller 40 may adjust the opening degree of the gas bypass valve 14 or the liquid bypass valve 15 so that the temperature difference Td between the detection value of the 1 st temperature sensor 31 and the detection value of the 2 nd temperature sensor 32 becomes equal to or smaller than the threshold value Tth. The flow rate of the refrigerant branched to the plurality of heat transfer tubes 11 of the 1 st heat exchanger 3 can be estimated with high accuracy, and the heat exchange efficiency of the 1 st heat exchanger 3 can be further improved.

Description of the reference numerals

1. The 1a to 1c refrigeration cycle apparatus, 2 compressors, 3 st heat exchanger, 4 gas-liquid separator, 5 expansion valve, 6 nd heat exchanger, 7 gas bypass circuit, 8 liquid bypass circuit, 9 four-way valve, 10 refrigerant circuit, 11 heat transfer pipe, 12 st header, 13 nd header, 14 gas bypass valve, 15 liquid bypass valve, 16 refrigerant piping, 17 heat radiating fin, 21 st heat transfer pipe, 22 nd heat transfer pipe, 31 st temperature sensor, 32 nd temperature sensor, 40 controller, 42 judgment unit, 43 valve control unit, 51 refrigerant inflow port, 52 refrigerant outflow port, 53 diaphragm chamber, 53a diaphragm, 54 spring, 55 pressure chamber, 56 orifice, 57 valve, 58 shaft, 61 st pressure equalizing pipe, 62 nd pressure equalizing pipe, 80 processing circuit, 81 processor, 82 memory, 83 bus.

Claims

1. A refrigeration cycle apparatus, wherein,

the refrigeration cycle device comprises:

a 1 st heat exchanger having a 1 st header and a plurality of heat transfer tubes, the 1 st header distributing refrigerant flowing in through refrigerant piping to the plurality of heat transfer tubes;

a gas-liquid separator that separates the refrigerant flowing into the 1 st heat exchanger into a gas refrigerant and a liquid refrigerant;

A gas bypass circuit connecting the gas-liquid separator to the 1 st header, and allowing the gas refrigerant to flow from the gas-liquid separator into the 1 st header;

a liquid bypass circuit connecting the gas-liquid separator to the 1 st header, and allowing the liquid refrigerant to flow from the gas-liquid separator into the 1 st header; and

a bypass valve provided in at least one of the gas bypass circuit and the liquid bypass circuit,

the gas bypass circuit is connected to the 1 st header at a position downstream of a position where the liquid bypass circuit is connected to the 1 st header in the flow direction, with respect to the flow direction of the liquid refrigerant in the 1 st header.

2. The refrigeration cycle apparatus according to claim 1, wherein,

the bypass valve is a valve that keeps the pressure difference of the refrigerant with respect to the refrigerant flowing in and out of the bypass valve fixed.

3. A refrigeration cycle apparatus according to claim 1 or 2, wherein,

the refrigeration cycle device includes a gas bypass valve provided in the gas bypass circuit and a liquid bypass valve provided in the liquid bypass circuit as the bypass valve.

4. A refrigeration cycle apparatus according to claim 3, wherein,

the liquid bypass valve is a valve that increases the pressure difference between the gas-liquid separator and the 1 st header.

5. A refrigeration cycle apparatus according to any one of claims 1 to 4, wherein,

the plurality of heat transfer tubes are connected to the 1 st header at positions having heights different from each other with reference to the direction of gravity,

the gas bypass circuit is connected to the 1 st header at a position lower than a position where the liquid bypass circuit is connected to the 1 st header.

6. The refrigeration cycle apparatus according to claim 5, wherein,

the refrigeration cycle device comprises:

a compressor that compresses and discharges the refrigerant;

a 2 nd heat exchanger for exchanging heat between the refrigerant discharged from the compressor and air;

an expansion valve that expands the refrigerant flowing out of the 2 nd heat exchanger and that causes the expanded refrigerant to flow out to the gas-liquid separator; and

a four-way valve that sets a flow direction of the refrigerant discharged from the compressor to a 1 st flow direction or a 2 nd flow direction, wherein the 1 st flow direction is a flow direction from the compressor to the 1 st heat exchanger, and the 2 nd flow direction is a flow direction from the compressor to the 2 nd heat exchanger,

The 1 st heat exchanger has a 2 nd header, and when the flow direction of the refrigerant is set to the 1 st flow direction by the four-way valve, the 2 nd header distributes the refrigerant flowing in from the four-way valve to the plurality of heat transfer tubes,

the bypass valve is provided in the gas bypass circuit, and is in a fully opened state when the flow direction of the refrigerant is set to the 2 nd flow direction by the four-way valve.

7. A refrigeration cycle apparatus according to claim 1 or 2, wherein,

the refrigeration cycle device further includes:

a temperature sensor that detects a temperature of the refrigerant; and

a controller that adjusts the opening degree of the bypass valve so that the detection value of the temperature sensor is within a predetermined range,

the temperature sensor is provided in at least one of a 1 st heat transfer pipe which is a heat transfer pipe located at a highest position and a 2 nd heat transfer pipe which is a heat transfer pipe located at a lowest position among the plurality of heat transfer pipes.

8. The refrigeration cycle apparatus according to claim 7, wherein,

The refrigeration cycle device has a 1 st temperature sensor provided to the 1 st heat transfer pipe and a 2 nd temperature sensor provided to the 2 nd heat transfer pipe, as the temperature sensors,

the controller adjusts the opening degree of the bypass valve so that a temperature difference between the detection value of the 1 st temperature sensor and the detection value of the 2 nd temperature sensor is equal to or smaller than a predetermined threshold value.