REFRIGERATION CYCLE APPARATUS

TECHNICAL FIELD

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

BACKGROUND ART

As an example of an existing heat exchanger, a heat exchanger including a gas-liquid separation mechanism that separates refrigerant into gas refrigerant and liquid refrigerant before the refrigerant flows into the heat exchanger has been proposed (see, for example, Patent Literature 1).

The heat exchanger disclosed in Patent Literature 1 includes a plurality of heat transfer tubes, a first header, a second header, a gas-liquid separation mechanism, a first outlet tube, and a second outlet tube. The first header and the second header each have an internal space extending in a specific horizontal direction. The second header is provided above the first header. The gas-liquid separation mechanism is provided above the second header. A first inlet at one of both ends of the first header in the specific direction is connected with the gas-liquid separation mechanism by the first outlet tube, and a second inlet at the other end is connected with the gas-liquid separation mechanism by the second outlet tube.

The heat exchanger disclosed in Patent Literature 1 is configured such that gas refrigerant flows into the first header from the gas-liquid separation mechanism through the first outlet tube, and liquid refrigerant flows into the first header from the gas-liquid separation mechanism through the second outlet tube.

CITATION LIST
Patent Literature

- Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2017-223386

SUMMARY OF INVENTION
Technical Problem

In the heat exchanger disclosed in Patent Literature 1, the flow rates of gas refrigerant and liquid refrigerant that flow into the first header depend on the separation state of two-phase gas-liquid refrigerant in the gas-liquid separation mechanism. Thus, for example, in the case where liquid refrigerant flows unevenly; that is, a larger amount of liquid refrigerant flows to some of the plurality of heat transfer tubes, it is not possible to properly distribute the refrigerant to the plurality of heat transfer tubes. In this case, the efficiency of the heat exchange is low.

The present disclosure is applied to solve the above problem, and relates to a refrigeration cycle apparatus that improves the efficiency of the heat exchange.

Solution to Problem

A refrigeration cycle apparatus according to one embodiment of the present disclosure includes: a first heat exchanger including a plurality of heat transfer tubes and a first header configured to distribute refrigerant that flows into the first heat exchanger via a refrigerant pipe to the plurality of heat transfer tubes; a gas-liquid separator configured to separate the refrigerant that flows into the first heat exchanger, into gas refrigerant and liquid refrigerant; a gas bypass circuit connecting the gas-liquid separator and the first header, and configured to cause the gas refrigerant to flow from the gas-liquid separator into the first header; a liquid bypass circuit connecting the gas-liquid separator and the first header, and configured to cause the liquid refrigerant to flow from the gas-liquid separator into the first header; and a bypass valve provided at at least one of the gas bypass circuit and the liquid bypass circuit. The gas bypass circuit is connected to the first header at a position which is located downward of a position where the liquid bypass circuit is connected to the first header, in a flow direction of the liquid refrigerant in the first header.

Advantageous Effects of Invention

According to one embodiment of the present disclosure, in the first header which serves as a distributor of the first heat exchanger, gas refrigerant is blown upward from a downstream side which is located downstream of liquid refrigerant, and the flow rate of liquid refrigerant or gas refrigerant that flows into the first header is adjusted by the bypass valve. Thus, the liquid refrigerant that flows into the first header is diffused in the first header, and gas-liquid two-phase refrigerant is evenly distributed to the plurality of heat transfer tubes. As a result, the efficiency of the heat exchange at the first heat exchanger is improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a refrigerant circuit diagram illustrating an example of the configuration of a refrigeration cycle apparatus according to Embodiment 1.

FIG. 2 is a side schematic view for use in describing the configuration of a first heat exchanger illustrated in FIG. 1.

FIG. 3 is a schematic diagram illustrating an example of the configuration of a gas bypass valve as illustrated in FIG. 1.

FIG. 4 is a state diagram of a refrigeration cycle circuit in the refrigeration cycle apparatus as illustrated in FIG. 1.

FIG. 5 is a refrigerant circuit diagram illustrating another example of the configuration of the refrigeration cycle apparatus according to Embodiment 1.

FIG. 6 is a side schematic view illustrating another installation example of the first heat exchanger as illustrated in FIG. 2.

FIG. 7 is a refrigerant circuit diagram illustrating an example of the configuration of a refrigeration cycle apparatus according to Embodiment 2.

FIG. 8 is a state diagram of a refrigeration cycle circuit in the refrigeration cycle apparatus as illustrated in FIG. 7.

FIG. 9 is a refrigerant circuit diagram illustrating an example of the configuration of a refrigeration cycle apparatus according to Embodiment 3.

FIG. 10 is a state diagram of a refrigeration cycle circuit in the refrigeration cycle apparatus as illustrated in FIG. 9.

FIG. 11 is a refrigerant circuit diagram illustrating an example of the configuration of a refrigeration cycle apparatus according to Embodiment 4.

FIG. 12 is a functional block diagram illustrating an example of the configuration of a controller illustrated in FIG. 11.

FIG. 13 is a hardware configuration diagram illustrating an example of the configuration of the controller as illustrated in FIG. 12.

FIG. 14 is a hardware configuration diagram illustrating another example of the configuration of the controller as illustrated in FIG. 12.

FIG. 15 is a flowchart indicating the procedure of a control method that is applied by the controller as illustrated in FIG. 12.

DESCRIPTION OF EMBODIMENTS
Embodiment 1

A configuration of a refrigeration cycle apparatus according to Embodiment 1 will be described. FIG. 1 is a refrigerant circuit diagram illustrating an example of the configuration of the refrigeration cycle apparatus according to Embodiment 1. As illustrated in FIG. 1, a refrigeration cycle apparatus 1 includes a compressor 2, a first heat exchanger 3, a gas-liquid separator 4, an expansion valve 5, and a second heat exchanger 6. Of refrigerant pipes 16 which connect the compressor 2, the first heat exchanger 3, the expansion valve 5, and the second heat exchanger 6, at the refrigerant pipe between the first heat exchanger 3 and the expansion valve 5, the gas-liquid separator 4 is provided. The compressor 2, the first heat exchanger 3, the expansion valve 5, and the second heat exchanger 6 are included in a refrigerant circuit 10 in which refrigerant circulates.

The compressor 2 compresses and discharges refrigerant sucked thereinto. The compressor 2 is, for example, a reciprocating compressor or 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 thermal expansion valve. It should be noted that two types of thermal expansion valves are present, and one of them is an external equalizing expansion valve and the other is an internal equalizing expansion valve. In the case where the expansion valve 5 is an external equalizing expansion valve, a temperature sensing tube (not illustrated) and a pressure equalizing tube (not illustrated) are connected to the expansion valve 5; and the temperature sensing tube is provided at the refrigerant pipe 16 between the first heat exchanger 3 and the compressor 2 and the pressure equalizing tube is connected to the refrigerant pipe 16 which is closer to the compressor 2 than the temperature sensing tube. The opening degree of the expansion valve 5 is automatically adjusted depending on the difference between the pressure of a substance (which has the same properties as the refrigerant) which is provided in the sealed temperature sensing tube and that of refrigerant that is input through the pressure equalizing tube (not illustrated).

FIG. 2 is a side schematic view for use in describing the configuration of the first heat exchanger as illustrated in FIG. 1. In FIG. 2, arrows indicating three axes (X-axis, Y-axis, and Z-axis) that define directions are indicated as a matter of convenience for explanation. The opposite direction to the direction indicated by the Z-axis arrow is the direction of gravity.

The first heat exchanger 3 includes a plurality of heat transfer tubes 11, a first header 12, and a second header 13. The plurality of heat transfer tubes 11 extend parallel to the Y-axis. Each of the first header 12 and the second header 13 is formed in the shape of a cylinder and a cuboid that extends parallel to the Z-axis. As illustrated in FIG. 2, the first heat exchanger 3 includes a plurality of heat transfer fins 17 provided between the first header 12 and the second header 13. The heat transfer fins 17 are arranged at regular intervals in the direction parallel to the Y-axis. Each of the heat transfer fins 17 is formed in the shape of a plate parallel to the XZ plane. The heat transfer tubes 11 penetrate the heat transfer fins 17. In the first heat exchanger 3 as illustrated in FIG. 1, illustration of the heat transfer fins 17 as illustrated in FIG. 2 is omitted.

Regarding Embodiment 1, the first heat exchanger 3 including the heat transfer fins 17 is described above with reference to FIG. 2; however, the first heat exchanger 3 may be a heat exchanger that includes no heat transfer fin 17.

The first header 12 serves as a distributor that distributes, to the plurality of heat transfer tubes 11, refrigerant that flows from the gas-liquid separator 4 into the first header 12 via the refrigerant pipe 16. The second header 13 serves as a combining device that combines refrigerant which flows through the plurality of heat transfer tubes 11, into single refrigerant and causes the single refrigerant to flow out therefrom to a refrigerant suction port of the compressor 2. Each of the first header 12 and the second header 13 has a hollow structure for storage of refrigerant that is to be distributed to the plurality of heat transfer tubes 11 or refrigerant that flows from the plurality of heat transfer tubes 11 into the header. The plurality of heat transfer tubes 11 are connected to the first header 12 at different positions in the direction of gravity. The second heat exchanger 6 has a similar configuration to that of the first heat exchanger 3, and its detailed description will thus be omitted.

The gas-liquid separator 4 separates, into gas refrigerant and liquid refrigerant, refrigerant that flows from the expansion valve 5 into the first heat exchanger 3. The gas-liquid separator 4 and the first header 12 are connected by a gas bypass circuit 7 that causes the gas refrigerant to flow from the gas-liquid separator 4 into the first header 12. In addition, the gas-liquid separator 4 and the first header 12 are also connected by a liquid bypass circuit 8 that causes the liquid refrigerant to flow from the gas-liquid separator 4 into the first header 12.

The liquid bypass circuit 8 is connected to upper part of the first header 12. The gas bypass circuit 7 is connected to lower part of the first header 12. In Embodiment 1, the first header 12 is configured such that the gas refrigerant flows from the lower part of the first header 12 into the first header 12 to blow upward the liquid refrigerant which flows from the upper part of the first header 12 into the first header 12. The gas bypass circuit 7 is provided with a gas bypass valve 14. The opening degree of the gas bypass valve 14 is adjusted depending on the flow rate of the liquid refrigerant which flows into the first header 12, to obtain a flow-passage resistance with which a flow rate of gas refrigerant that is required for blowing the liquid refrigerant upward is obtained. In the following, a configuration of the gas bypass valve 14 is specifically described.

In the case where the flow rate of liquid refrigerant that flows into the first header 12 is low, the liquid refrigerant more easily stays at the lower part of the first header 12 (in the opposite direction to the direction indicated by the Z-axis arrow in FIG. 2) than at the upper side of the first header 12 (in the direction indicated by the Z-axis arrow in FIG. 2) due to the effect of gravity, and does not easily flow to upper ones of the plurality of heat transfer tubes 11. Thus, a larger amount of liquid refrigerant flows through lower ones of the heat transfer tubes 11, and a smaller amount of liquid refrigerant flows through upper ones of the heat transfer tubes 11. In this case, the opening degree of the gas bypass valve 14 is increased such that the amount of gas refrigerant that blows the liquid refrigerant upward is increased. Thus, the liquid refrigerant also easily flows through the upper ones of the plurality of heat transfer tubes 11.

In contrast, in the case where the flow rate of liquid refrigerant that flows into the first header 12 is high, even under the effect of gravity, liquid refrigerant easily flows into not only the lower heat transfer tubes 11 (in the opposite direction to the direction indicated by the Z-axis arrow in FIG. 2) but also the upper heat transfer tubes 11 (in the direction indicated by the Z-axis arrow in FIG. 2) among the plurality of heat transfer tubes 11. Furthermore, in Embodiment 1, even when the flow rate of liquid refrigerant that flows from the upper part of the first header 12 into the first header 12 is high, the liquid refrigerant is blown upward by gas refrigerant supplied from the lower part of the first header 12 and is diffused in the first header 12. Thus, the liquid refrigerant is more easily and evenly distributed to the plurality of heat transfer tubes 11.

As described above, the gas bypass valve 14 adjusts the flow rate ratio of liquid refrigerant and gas refrigerant that flow into the first header 12, on the basis of the flow rate of liquid refrigerant that flows into the first header 12. The gas bypass valve 14 is a valve that keeps constant, the difference between the pressures of the refrigerant at the inlet port and outlet port for the refrigerant, for example. Assuming that the flow rate ratio between liquid refrigerant that flows out from the gas-liquid separator 4 and gas refrigerant that flows from the gas-liquid separator 4 is constant, when the flow rate of liquid refrigerant that flows into the first header 12 is high, the flow rate of gas refrigerant that flows into the first header 12 is also high. In the case where the gas bypass valve 14 is a valve that keeps constant, the difference between the pressures of the refrigerant at the inlet and outlet ports for the refrigerant, when the flow rate of the gas refrigerant is low, the difference between the pressures of the refrigerant at the inlet and outlet ports for the refrigerant is small, and the opening degree of the gas bypass valve 14 is thus automatically increased to keep the pressure difference constant.

As a specific example of the gas bypass valve 14, a valve that operates on the same principle as a thermal expansion valve is applied. The gas bypass valve 14 includes an adjustment valve (not illustrated) such as a diaphragm that detects the difference between the pressures of the refrigerant at the inlet and outlet ports for the refrigerant, and the opening degree of the gas bypass valve 14 is adjusted depending on the operation of the adjustment valve. In this case, a specific component such as a controller that controls the opening degree of the gas bypass valve 14 does not need to be provided.

An example of the configuration of the gas bypass valve 14 will be described. FIG. 3 is a schematic diagram illustrating an example of the configuration of the gas bypass valve as illustrated in FIG. 1. The gas bypass valve 14 has an inlet port 51 for the refrigerant that is connected with the gas-liquid separator 4 by the gas bypass circuit 7 and an outlet port 52 for the refrigerant that is connected with the first header 12 by the gas bypass circuit 7. The gas bypass valve 14 includes a diaphragm chamber 53, a pressure chamber 55, an orifice plate, and a needle 57. In the pressure chamber 55, a spring 54 is provided. In the orifice plate, an orifice 56 is provided to allow the refrigerant to flow from the inlet port 51 for the refrigerant to the outlet port 52 for the refrigerant. The needle 57 adjusts the opening degree of the orifice 56.

The diaphragm chamber 53 is connected to part of the gas bypass circuit 7 that is located close to the inlet port 51 for the refrigerant, by a first pressure equalizing tube 61. The pressure chamber 55 is connected to part of the gas bypass circuit 7 that is located close to the outlet port 52 for the refrigerant, by a second pressure equalizing tube 62. The diaphragm chamber 53 has a diaphragm 53a at the boundary between the diaphragm chamber 53 and the pressure chamber 55, and a shaft 58 is attached to the diaphragm 53a. The needle 57 is attached to an end of the shaft 58 that is located opposite to the diaphragm 53a. The diaphragm 53a is moved in the axial direction of the shaft 58 by the pressure difference ΔP between the pressures of the refrigerant at the inlet port 51 and the outlet port 52 for the refrigerant and the elastic force of the spring 54. When the diagraph 53a is moved in the axial direction of the shaft 58 to move the needle 57, the opening degree of the orifice 56 is adjusted. As a result, the flow rate of refrigerant that flows through the orifice 56 is adjusted, and the pressure difference ΔP is kept constant.

Next, an operation of a refrigeration cycle circuit of the refrigeration cycle apparatus 1 as illustrated in FIG. 1 will be described. This description is made with respect to the case where the first heat exchanger 3 operates as an evaporator. FIG. 4 is a state diagram of the refrigeration cycle circuit in the refrigeration cycle apparatus as illustrated in FIG. 1. In the state diagram of FIG. 4, the horizontal axis represents specific enthalpy h [KJ/kg], and the vertical axis represents pressure P [MPa]. P1 to P8 indicated in FIG. 4 represent the states of refrigerant at the positions p1 to p8 in the refrigerant circuit 10 as illustrated in FIG. 1.

The compressor 2 sucks gas refrigerant, and compresses and discharges the sucked gas refrigerant (see the position p1 in FIG. 4). The gas refrigerant discharged from the compressor 2 is condensed through heat exchange with air at the second heat exchanger 6 to change into liquid refrigerant, and the liquid refrigerant flows out from the second heat exchanger 6 (see the position p2 in FIG. 4). The liquid refrigerant that has flowed out from the second heat exchanger 6 is depressurized by the expansion valve 5 to change into gas-liquid two-phase refrigerant (see the position p3 in FIG. 4). When the gas-liquid two-phase refrigerant flows into the gas-liquid separator 4, the gas-liquid two-phase refrigerant is separated into liquid refrigerant (see the position p4 in FIG. 4) and gas refrigerant (see the position p5 in FIG. 4).

The liquid refrigerant reaches the first header 12 from the gas-liquid separator 4 through the liquid bypass circuit 8. The liquid refrigerant that has reached the first header 12 flows from the upper part of the first header 12 into the first header 12. The gas refrigerant separated in the gas-liquid separator 4 flows from the gas-liquid separator 4 into the gas bypass circuit 7. The gas refrigerant that flows in the gas bypass circuit 7 is depressurized by the gas bypass valve 14, adjusted in flow rate, and then flows from the lower part of the first header 12 into the first header 12 (see the position p6 in FIG. 4).

At the position p6 indicated in the FIG. 4, in the case where the flow rate of refrigerant that flows into the gas bypass valve 14 is low, the opening degree of the gas bypass valve 14 is increased to increase the flow rate of the gas refrigerant; and in the case where the flow rate of refrigerant that flows into the gas bypass valve 14 is high, the opening degree of the gas bypass valve 14 is decreased to decrease the flow rate of the gas refrigerant.

The gas refrigerant that has flowed from the lower part of the first header 12 into the first header 12 is mixed with the liquid refrigerant that has flowed from the upper part of the first header 12 into the first header 12, while blowing the liquid refrigerant upward (see the position p7 in FIG. 4), thereby obtaining gas-liquid two-phase refrigerant. The obtained gas-liquid two-phase refrigerant is distributed to the plurality of heat transfer tubes 11. The gas-liquid two-phase refrigerant that flows through the heat transfer tubes 11 evaporates through heat exchange with air and is gasified to change into gas refrigerant, and the gas refrigerant then flows into the second header 13 and joins each other therein to obtain single gas refrigerant. The single gas refrigerant obtained in the second header 13 flows into the compressor 2 through the refrigerant suction port of the compressor 2 (see the position p8 in FIG. 4).

In the above manner, an appropriate amount of gas refrigerant is blown upward from the lower part of the first header 12, depending on the flow rate of liquid refrigerant that flows from the upper part of the first header 12 of the first heat exchanger 3 into the first header 12. Thus, the flow rates of the refrigerant in the plurality of heat transfer tubes 11 can be equalized.

It should be noted that the following description regarding Embodiment 1 is made with respect to the case where a bypass valve that causes the flow rate ratio between liquid refrigerant and gas refrigerant that flow from the gas-liquid separator 4 into the first header 12 to be constant is provided in the gas bypass circuit 7; however, the bypass valve may be provided in the liquid bypass circuit 8. FIG. 5 is a refrigerant circuit diagram illustrating another example of the configuration of the refrigeration cycle apparatus according to Embodiment 1. As illustrated in FIG. 5, in the case where the liquid bypass circuit 8 includes a liquid bypass valve 15, when the flow rate of liquid refrigerant that flows into the liquid bypass circuit 8 is high, the opening degree of the liquid bypass valve 15 is decreased, and when the flow rate of liquid refrigerant that flows into the liquid bypass circuit 8 is low, the opening degree of the liquid bypass valve 15 is increased.

Although FIG. 1 illustrates a configuration in which the liquid bypass circuit 8 is connected to the upper part of the first header 12, and the gas bypass circuit 7 is connected to the lower part of the first header 12, the connection positions of these bypass circuits are not limited to the positions indicated in FIG. 1. It suffices that the gas bypass circuit 7 is connected to the first header 12 at a position which is located downward of a position where the liquid bypass circuit 8 is connected to the first header 12, in the flow direction of liquid refrigerant in the first header 12. Also, in this case, the liquid refrigerant that flows into the first header 12 is blown upward by gas refrigerant in the direction indicated by the Z-axis arrow in FIG. 2, from a downstream side which is located downstream of the liquid refrigerant in the first header 12 in the flow direction thereof.

Furthermore, in Embodiment 1, the first header 12 may also be provided in such a manner as to extend parallel to the Y-axis in FIG. 2. FIG. 6 is a side schematic view illustrating another installation example of the first heat exchanger as illustrated in FIG. 2. FIG. 6 illustrates a configuration for the case where the first heat exchanger 3 is installed such that the direction in which the first header 12 extends is parallel to the ground. In the installation example as illustrated in FIG. 6, of the plurality of heat transfer tubes 11, the outermost one of the heat transfer tubes in the opposite direction to the direction indicated by the Y-axis arrow will be referred to as a first heat transfer tube 21, and the outermost one of the heat transfer tubes in the direction indicated by the Y-axis arrow will be referred to as a second heat transfer tube 22.

In the installation example as illustrated in FIG. 6, the liquid refrigerant flows down to the first header 12 through the liquid bypass circuit 8. An inertia force of the liquid refrigerant that acts when the liquid refrigerant flows down causes the liquid refrigerant to more easily flow in the first header 12 in the direction indicated by the dashed arrow. Thus, in the case where the amount of refrigerant that flows into the first header 12 is small, the refrigerant more easily flows toward the second heat transfer tube 22 than toward the first heat transfer tube 21; however, the refrigerant is blown upward toward the first heat transfer tube 21 by gas refrigerant that flows through the gas bypass valve 14. In such a manner, the direction in which the first header 12 extends may be parallel to the ground. Furthermore, in the installation example as illustrated in FIG. 6, the first heat exchanger 3 may be inclined relative to the ground.

Furthermore, in Embodiment 1, the expansion valve 5 may be an electronic expansion valve, and the compressor 2 may be an inverter compressor that can be changed in capacity. In the case where the expansion valve 5 is an electronic expansion valve, and the compressor 2 is an inverter compressor, the refrigeration cycle apparatus 1 may be provided with a controller (not illustrated) that controls the opening degree of the expansion valve 5 and the operation frequency of the compressor 2.

The refrigeration cycle apparatus 1 according to Embodiment 1 includes the first heat exchanger 3, the gas-liquid separator 4, the gas bypass circuit 7, and the liquid bypass circuit 8. The first heat exchanger 3 includes the plurality of heat transfer tubes 11 and the first header 12. The first header 12 distributes, to the plurality of heat transfer tubes 11, refrigerant that flows into the first heat exchanger through the refrigerant pipe 16. The gas-liquid separator separates refrigerant that flows into the first heat exchanger 3, into gas refrigerant and liquid refrigerant. The gas bypass circuit 7 connects the gas-liquid separator 4 and the first header 12, and causes the gas refrigerant to flow from the gas-liquid separator 4 into the first header 12. The liquid bypass circuit 8 connects the gas-liquid separator 4 and the first header 12 and causes the liquid refrigerant to flow from the gas-liquid separator 4 into the first header 12. At least one of the gas bypass circuit 7 and the liquid bypass circuit 8 is provided with a bypass valve. The opening degree of the bypass valve is adjusted depending on the flow rate of refrigerant that flows into the one of the gas bypass circuit 7 and the liquid bypass circuit 8. The bypass valve is the gas bypass valve 14 or the liquid bypass valve 15. The gas bypass circuit 7 is connected to the first header 12 at a position which is located downward of a position where the liquid bypass circuit 8 is connected to the first header 12, in the flow direction of liquid refrigerant in the first header 12.

According to Embodiment 1, in the case where the bypass valve is the gas bypass valve 14, when the flow rate of gas refrigerant that flows into the gas bypass circuit 7 is low, the opening degree of the gas bypass valve 14 is adjusted such that the flow rate of gas refrigerant blown out from the downstream side which is located downstream of the liquid refrigerant in the first header 12 is increased. When the opening degree of the gas bypass valve 14 is increased, the liquid refrigerant is lifted upward in the first header 12 by the gas refrigerant blown upward from the downstream side. As a result, the liquid refrigerant flows easily into upper heat transfer tubes 11 (in the direction indicated by the Z-axis arrow in FIG. 2), and gas-liquid two-phase refrigerant that flows into the first header 12 is evenly distributed to the plurality of heat transfer tubes 11.

In contrast, in the case where the flow rate of gas refrigerant that flows into the gas bypass circuit 7 is high, liquid refrigerant easily flows into not only lower heat transfer tubes 11 (in the opposite direction to the direction indicated by the Z-axis arrow in FIG. 2) but also upper heat transfer tubes 11 (in the direction indicated by the Z-axis arrow in FIG. 2) among the plurality of heat transfer tubes 11. Furthermore, the liquid refrigerant is blown upward from the downstream side by gas refrigerant that flows through the gas bypass valve 14 and is easily diffused in the first header 12. As a result, the gas-liquid two-phase refrigerant that flows into the first header 12 is evenly distributed to the plurality of heat transfer tubes 11.

Furthermore, in Embodiment 1, in the case where the bypass valve is the liquid bypass valve 15, when the flow rate of liquid refrigerant that flows into the liquid bypass circuit 8 is low, the opening degree of the liquid bypass valve 15 is adjusted such that the flow rate of liquid refrigerant that flows into the first header 12 is increased. Thus, it is possible to reduce the probability that the liquid refrigerant will more easily stay at the lower part of the first header 12 (in the opposite direction to the direction indicated by the Z-axis arrow in FIG. 2) than at the upper side of the first header 12 (in the direction indicated by the Z-axis arrow in FIG. 2). Furthermore, in the case where the flow rate of the liquid refrigerant is low, the liquid refrigerant easily stays at the lower part of the first header 12, but is blown upward by gas refrigerant in the first header 12. The liquid refrigerant easily flows into heat transfer tubes 11 that adjoin the upper side of the first header 12. As a result, the gas-liquid two-phase refrigerant that flows into the first header 12 is evenly distributed to the plurality of heat transfer tubes 11.

In contrast, in the case where the flow rate of liquid refrigerant that flows into the liquid bypass circuit 8 is high, the liquid refrigerant easily flows into not only lower heat transfer tubes 11 (in the opposite direction to the direction indicated by the Z-axis arrow in FIG. 2) but also upper heat transfer tubes 11 (in the direction indicated by the Z-axis arrow in FIG. 2) among the plurality of heat transfer tubes 11. The liquid bypass valve 15 is thus fully opened; that is, the opening degree of the liquid bypass valve 15 is set to set to the maximum opening degree. Even when the flow rate of liquid refrigerant that flows from the upper part of the first header 12 into the first header 12 is high, the liquid refrigerant is blown upward by gas refrigerant that flows from the lower part of the first header 12 and is easily diffused in the first header 12. As a result, the gas-liquid two-phase refrigerant that flows into the first header 12 is evenly distributed to the plurality of heat transfer tubes 11.

It should be noted that when the flow rate of liquid refrigerant that flows into the liquid bypass circuit 8 is excessively high, the opening degree of the liquid bypass valve 15 may be adjusted such that the flow rate of liquid refrigerant that flows into the first header 12 is decreased. This is because when the flow rate of liquid refrigerant that flows into the liquid bypass circuit 8 is excessively high, the liquid refrigerant that flows into the first header 12 will have too much momentum and will be more likely to flow into some of the heat transfer tubes 11. In this case, when the opening degree of the liquid bypass valve 15 is decreased, the flow rate of the liquid refrigerant that flows into the first header 12 is adjusted to an appropriate value, and the liquid refrigerant is easily evenly distributed to the plurality of heat transfer tubes 11. As a result, the gas-liquid two-phase refrigerant that flows into the first header 12 is evenly distributed to the plurality of heat transfer tubes 11.

In such a manner, in the first header 12 which operates as a distributor of the first heat exchanger 3, the gas refrigerant is blown upward from the downstream side which is located downstream of the liquid refrigerant. The flow rate of liquid refrigerant or gas refrigerant that flows into the first header 12 is adjusted by the gas bypass valve 14 or the liquid bypass valve 15. Thus, the liquid refrigerant that flows into the first header 12 is diffused in the first header 12, and the gas-liquid two-phase refrigerant is evenly distributed to the plurality of heat transfer tubes 11. As a result, the efficiency of the heat exchange at the first heat exchanger 3 is improved.

Embodiment 2

In a refrigeration cycle apparatus according to Embodiment 2, bypass valves are provided in both the gas bypass circuit and the liquid bypass circuit. Regarding Embodiment 2, components that have the same configurations as those in Embodiment 1 will be denoted by the same reference signs and their detailed descriptions will thus be omitted.

A configuration of the refrigeration cycle apparatus according to Embodiment 2 will be described. FIG. 7 is a refrigerant circuit diagram illustrating an example of the configuration of the refrigeration cycle apparatus according to Embodiment 2. As illustrated in FIG. 7, a refrigeration cycle apparatus 1a according to Embodiment 2 has a liquid bypass valve 15 that is provided in the liquid bypass circuit 8, in addition to the configuration as illustrated in FIG. 1.

The liquid bypass valve 15 is a valve that increases the pressure difference between the gas-liquid separator 4 and the first header 12. The liquid bypass valve 15 is, for example, a pressure adjustment valve that increases the pressure difference between the gas-liquid separator 4 and the first header 12 to cause the pressure difference to exceed a predetermined pressure. By increasing the pressure difference between the gas-liquid separator 4 and the first header 12, the momentum of gas refrigerant that is blown upward from the gas bypass circuit 7 into the first header 12 can be increased.

Next, an operation of a refrigeration cycle circuit of the refrigeration cycle apparatus 1a as illustrated in FIG. 7 will be described. The following description is made with respect to the case where the first heat exchanger 3 operates as an evaporator. FIG. 8 is a state diagram of the refrigeration cycle circuit in the refrigeration cycle apparatus as illustrated in FIG. 7. In the state diagram of FIG. 8, the horizontal axis represents specific enthalpy h [KJ/kg], and the vertical axis represents pressure P [MPa]. P1 to P9 indicated in FIG. 8 represent the states of refrigerant at positions p1 to p9 in the refrigerant circuit 10 as illustrated in FIG. 7.

The compressor 2 sucks gas refrigerant, and compresses and discharges the sucked gas refrigerant (see the position p1 in FIG. 8). The gas refrigerant discharged from the compressor 2 is condensed through heat exchange with air at the second heat exchanger 6 to change into liquid refrigerant, and the liquid refrigerant flows out from the second heat exchanger 6 (see the position p2 in FIG. 8). The liquid refrigerant that has flowed from the second heat exchanger 6 is depressurized by the expansion valve 5 to change into gas-liquid two-phase refrigerant (see the position p3 in FIG. 8). When the gas-liquid two-phase refrigerant flows into the gas-liquid separator 4, the gas-liquid two-phase refrigerant is separated into liquid refrigerant (see the position p4 in FIG. 8) and gas refrigerant (see the position p5 in FIG. 8).

The liquid refrigerant flows from the gas-liquid separator 4 to the liquid bypass circuit 8. The liquid refrigerant that flows in the liquid bypass circuit 8 is depressurized by the liquid bypass valve 15 and adjusted in flow rate, and then flows from the upper part of the first header 12 into the first header 12 (see the position p6 in FIG. 8). In contrast, the gas refrigerant separated in the gas-liquid separator 4 flows from the gas-liquid separator 4 to the gas bypass circuit 7. The gas refrigerant that flows in the gas bypass circuit 7 is depressurized by the gas bypass valve 14 and adjusted in flow rate, and thereafter flows from the lower part of the first header 12 into the first header 12 (see the position p7 in FIG. 8).

The gas refrigerant that flows from the lower part of the first header 12 into the first header 12 is mixed with the liquid refrigerant that flows from the upper part of the first header 12 into the first header 12, while blowing the liquid refrigerant upward (see the position p8 in FIG. 8), thereby obtaining gas-liquid two-phase refrigerant. The obtained gas-liquid two-phase refrigerant is distributed to the plurality of heat transfer tubes 11. The gas-liquid two-phase refrigerant that flows through the heat transfer tubes 11 evaporate through heat exchange with air and are gasified to change into gas refrigerant, and thereafter joins each other in the second header 13 to combine into single gas refrigerant. The single gas refrigerant obtained in the second header 13 flows into the compressor 2 through the refrigerant suction port of the compressor 2 (see the position p9 in FIG. 8).

The liquid bypass valve 15 increases the pressure difference between the inside of the gas-liquid separator 4 and the inside of the first header 12. Thus, compared with Embodiment 1, the momentum of the gas refrigerant which is blown out to liquid refrigerant flowing into the first header 12, from a downstream side which is located downstream of the liquid refrigerant, is increased at the position p7 illustrated in FIG. 8.

In the refrigeration cycle apparatus 1a according to Embodiment 2, the liquid bypass circuit 8 is provided with the liquid bypass valve 15. The liquid bypass valve 15 is a valve that increases the pressure difference between the gas-liquid separator 4 and the first header 12. According to Embodiment 2, the liquid refrigerant can be more largely blown upward by the gas refrigerant. Thus, when the flow rate of the refrigerant is low, the liquid refrigerant can be made to reach higher positions in the first header 12.

Furthermore, in a gas bypass circuit, when the pressure difference between the refrigerant at the refrigerant inlet port of the gas bypass valve and the refrigerant at the outlet port of the gas bypass valve is small, the capacity coefficient (Cv value) required for causing the refrigerant to flow at 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 first header 12. Thus, the pressure difference between the refrigerant at the inlet port of the gas bypass valve 14 and the refrigerant at the outlet port of the gas bypass valve 14 is increased in the gas bypass circuit 7, and the Cv value required for the gas bypass valve 14 can be decreased. As a result, the gas bypass valve 14 can be made smaller.

Embodiment 3

In a refrigeration cycle apparatus according to Embodiment 3, a refrigerant circuit is provided with a four-way valve that switches the flow direction of refrigerant in the refrigerant circuit between a plurality of flow directions. In Embodiment 3, components that have the same configurations as those in Embodiment 1 and/or Embodiment 2 will be denoted by the same reference signs, and their detailed description will thus be omitted. The following description regarding Embodiment 3 is made with respect to the case where the four-way valve is added to the refrigeration cycle apparatus 1a according to Embodiment 2; however, the four-way valve may be added to the refrigeration cycle apparatus 1 according to Embodiment 1.

The configuration of a refrigeration cycle apparatus according to Embodiment 3 will be described. FIG. 9 is a refrigerant circuit diagram illustrating an example of the configuration of the refrigeration cycle apparatus according to Embodiment 3. As illustrated in FIG. 9, in a refrigeration cycle apparatus 1b according to Embodiment 3, a four-way valve 9 is added to the configuration which is provided as illustrated in FIG. 7.

The four-way valve 9 sets the flow direction of refrigerant discharged from the compressor 2 to a first flow direction or a second flow direction. The first flow direction is the flow direction of the refrigerant from the compressor 2 to the first heat exchanger 3. The second flow direction is the flow direction of the refrigerant from the compressor 2 to the second heat exchanger 6. In the case where the flow direction of the refrigerant discharged from the compressor 2 is set to the first flow direction, the first heat exchanger 3 operates as a condenser, and the second heat exchanger 6 operates as an evaporator. In the case where the flow direction of the refrigerant discharged from the compressor 2 is set to the second flow direction, the first heat exchanger 3 operates as an evaporator, and the second heat exchanger 6 operates as a condenser.

The liquid bypass valve 15 is made to be in an open state as in Embodiment 2 in the case where the first heat exchanger 3 operates as an evaporator, and is made to be in a closed state in the case where the first heat exchanger 3 operates as a condenser. The opening degree of the gas bypass valve 14 is set to an opening degree required for adjusting the gas flow rate as in Embodiments 1 and 2 in the case where the first heat exchanger 3 operates as an evaporator, and the gas bypass valve 14 is made to be in a fully open state in the case where the first heat exchanger 3 operates as a condenser. In Embodiment 3, the gas bypass circuit 7 is connected to the first header 12 at a position which is located lower than a position where the liquid bypass circuit 8 is connected to the first header 12, in the direction of gravity. In the case where the first heat exchanger 3 operates as a condenser, when the gas bypass valve 14 is made to be in the fully open state, liquid refrigerant that flows from the plurality of heat transfer tubes 11 into the first header 12 easily smoothly flow to the gas-liquid separator 4 through the gas bypass circuit 7.

Next, an operation of the refrigeration cycle circuit in the refrigeration cycle apparatus 1b as illustrated in FIG. 9 will be described. The following description concerning Embodiment 3 is made with respect to the case where the first heat exchanger 3 operates as a condenser. In the case where the first heat exchanger 3 operates as an evaporator, the refrigeration cycle circuit operates in the same manner as in Embodiment 2 and its detailed description will thus be omitted.

FIG. 10 is a state diagram of the refrigeration cycle circuit of the refrigeration cycle apparatus as illustrated in FIG. 9. In the state diagram of FIG. 10, the horizontal axis represents specific enthalpy h [KJ/kg], and the vertical axis represents pressure P [MPa]. Positions p1, p2, p5, and p8 to p10 indicated in FIG. 10 are indicated as representative positions of the positions p1 to p10 in the refrigerant circuit 10 as illustrated in FIG. 9, and the states of the refrigerant at p1, p2, p5, and p8 to p10 can be seen from FIG. 10.

The compressor 2 sucks gas refrigerant, and compresses and discharges the sucked gas refrigerant (see the position p1 in FIG. 10). The gas refrigerant discharged from the compressor 2 passes through the four-way valve 9 and flows toward the second header 13 (see the position p9 in FIG. 10). The gas refrigerant that has flowed into the second header 13 is distributed to the plurality of heat transfer tubes 11. In each of the plurality of heat transfer tubes 11, gas refrigerant is liquefied through heat exchange with air. The refrigerant liquefied in the plurality of heat transfer tubes 11 joins each other in the first header 12 (see the position p8 in FIG. 10).

The liquid refrigerant that has flowed from the plurality of heat transfer tubes 11 into the first header 12 flows toward the lower part of the first header 12 by its own weight. Since the gas bypass valve 14 is in the fully open state, the liquid refrigerant that flowed to the lower part of the first header 12 does not stay at the lower part of the first header 12 and flows to the gas-liquid separator 4 through the gas bypass circuit 7 (see the position p5 in FIG. 10). This reduces the probability that the liquid refrigerant will stay at the lower part of the first header 12. Since liquid refrigerant that flows through lower ones of the plurality of heat transfer tubes 11 does not stay at the lower part of the first header 12, the liquid refrigerant can smoothly flows out form the heat transfer tubes 11 and flow into the gas-liquid separator 4 through the gas bypass circuit 7.

When flowing from the gas-liquid separator 4 into the expansion valve 5, the liquid refrigerant is depressurized by the expansion valve 5 to change into gas-liquid two-phase refrigerant (see the position p2 in FIG. 10). The gas-liquid two-phase refrigerant flows into the second heat exchanger 6. The gas-liquid two-phase refrigerant evaporates and is gasified through heat exchange with air in the second heat exchanger 6, and thereafter flows out from the second heat exchanger 6. The gas refrigerant that has flowed out from the second heat exchanger 6 flows into the compressor 2 through the refrigerant suction port of the compressor 2 (see the position p10 in FIG. 10).

The refrigeration cycle apparatus 1b according to Embodiment 3 includes the four-way valve 9, which sets the flow direction of refrigerant in the refrigerant circuit 10 to the first flow direction or the second flow direction. The gas bypass valve 14 is made to be in the fully open state in the case where the flow direction of refrigerant is set to the second flow direction by the four-way valve 9.

In the case where the flow direction of the refrigerant in the refrigerant circuit is the first flow direction in which the refrigerant flows when the first heat exchanger operates as a condenser, the condensed liquid refrigerant stays at the lower part of the first header. When the liquid refrigerant stays at the lower part of the first header, the refrigerant outlets of heat transfer tubes to the first header are blocked by the liquid refrigerant. In this case, the refrigerant in heat transfer tubes which adjoin the lower part of the first header does not smoothly flow, and the efficiency of the heat exchange at the first heat exchanger is reduced. In contrast, according to Embodiment 3, in the case where the flow direction of the refrigerant is the first flow direction, the gas bypass valve 14 provided at the gas bypass circuit 7 connected to the lower part of the first header 12 is made to be in the fully open state. Thus, the liquid refrigerant easily flows from the lower part of the first header 12 to the gas-liquid separator 4 through the gas bypass circuit 7, and this reduces the probability that the liquid refrigerant will stay at the lower part of the first header 12. As a result, the refrigerant also easily flows through lower heat transfer tubes 11 of the first heat exchanger 3, thereby improving the efficiency of the heat exchange at the first heat exchanger 3.

Embodiment 4

A refrigeration cycle apparatus according to Embodiment 4 controls the opening degree of a bypass valve depending on the temperatures of refrigerant that flows through heat transfer tubes. Regarding Embodiment 4, components that have the same configurations as those in any of Embodiments 1 to 3 will be denoted by the same reference signs, and their detailed descriptions will thus be omitted. In the following description, although Embodiment 4 is described based on the refrigeration cycle apparatus according to Embodiment 3, Embodiment 4 may be applied to the refrigeration cycle apparatus according to Embodiment 1 or 2.

A configuration of the refrigeration cycle apparatus according to Embodiment 4 will be described. FIG. 11 is a refrigerant circuit diagram illustrating an example of the configuration of the refrigeration cycle apparatus according to Embodiment 4. In a refrigeration cycle apparatus 1c as illustrated in FIG. 11, a first temperature sensor 31, a second temperature sensor 32, and a controller 40 are added to the configuration which is provided as illustrated in FIG. 9. The first temperature sensor 31 and the second temperature sensor 32 detect temperatures of refrigerant. The first temperature sensor 31 and the second temperature sensor 32 are, for example, thermistors. The first temperature sensor 31, the second temperature sensor 32, the gas bypass valve 14, and the liquid bypass valve 15 are connected to the controller 40 by signal lines (not illustrated).

The first temperature sensor 31 is provided at the first heat transfer tube 21 which is the uppermost one of the plurality of heat transfer tubes 11 in the direction of gravity (opposite to the Z-axis arrow) indicated in FIG. 2. The second temperature sensor 32 is provided at the second heat transfer tube 22 which is the lowermost one of the plurality of heat transfer tubes 11 in the direction of gravity.

FIG. 12 is a functional block diagram illustrating an example of the configuration of the controller as illustrated in FIG. 11. The controller 40 is, for example, a microcomputer. The controller 40 includes a determination circuitry 42 and a valve control circuitry 43. The determination circuitry 42 calculates a temperature difference Td between a detection value obtained by the first temperature sensor 31 and a detection value obtained by the second temperature sensor 32. The determination circuitry 42 determines whether or not the temperature difference Td is greater than a predetermined threshold Tth, and transmits information regarding the result of this determination to the valve control circuitry 43.

In the case where the temperature difference Td is greater than the threshold Tth, the valve control circuitry 43 adjusts the opening degree of at least one of the gas bypass valve 14 and the liquid bypass valve 15 such that the temperature difference Td is less than or equal to the threshold Tth. A specific example of a method of adjusting the opening degree of the bypass valve using the valve control circuitry 43 will be described.

In the case where a heat exchanger operates as an evaporator, when the flow rate of refrigerant that flows through a heat transfer tube is low, the temperature of the refrigerant rises. For example, in the case where the first heat exchanger 3 operates as an evaporator, when the flow rate of refrigerant that flows through the second heat transfer tube 22 is lower than that of refrigerant that flows through the first heat transfer tube 21, the detection value obtained by the second temperature sensor 32 is greater than that obtained by the first temperature sensor 31. When the temperature difference Td between the detection value obtained by the first temperature sensor 31 and the detection value by the second temperature sensor 32 exceeds the threshold Tth, the valve control circuitry 43 decreases the opening degree of the gas bypass valve 14. As a result, the amount of gas refrigerant that is blown out is reduced. Thus, the liquid refrigerant easily flows down toward the lower part of the first header 12, and the flow rate of refrigerant that flows in a region adjoining the second heat transfer tube 22 increases. The valve control circuitry 43 may increase the opening degree of the liquid bypass valve 15. In this case, the flow rate of the liquid refrigerant increases, a larger amount of liquid refrigerant flows toward the lower part of the first header 12 against the blowing of gas refrigerant, and the flow rate of refrigerant that flows in the region adjoining the second heat transfer tube 22 increases. Furthermore, the valve control circuitry 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 rates of refrigerant that flows through the plurality of heat transfer tubes 11 are equalized.

In contrast, in the case where the heat exchanger operates as a condenser, when the flow rate of refrigerant that flows through a heat transfer tube is low, the temperature of the refrigerant lowers. For example, in the case where the first heat exchanger 3 operates as a condenser, when the flow rate of refrigerant that flows through the first heat transfer tube 21 is lower than that of refrigerant that flows through the second heat transfer tube 22, the detection value obtained by the first temperature sensor 31 is lower than that obtained by the second temperature sensor 32. When the temperature difference Td between the detection value obtained by the first temperature sensor 31 and the detection value by the second temperature sensor 32 exceeds the threshold Tth, the valve control circuitry 43 increases the opening degree of the gas bypass valve 14. As a result, the refrigerant that flows in the region adjoining the second heat transfer tube 22 more smoothly flows, and the flow rate of the refrigerant in the region adjoining the second heat transfer tube 22 can be increased as described regarding Embodiment 3. As a result, the flow rates of refrigerant that flows through the plurality of heat transfer tubes 11 are equalized.

It should be noted that the following description regarding Embodiment 4 is made with respect to the case where the first temperature sensor 31 is provided at the first heat transfer tube 21, and the second temperature sensor 32 is provided at the second heat transfer tube 22; however, it suffices that a temperature sensor is provided at one of the above heat transfer tubes. For example, in the case where it can be determined which of the plurality of heat transfer tubes 11 is a heat transfer tube through which the flow rate of the refrigerant is relatively low, it suffices that a temperature sensor is provided at the heat transfer tube through which the flow rate of refrigerant is low. In this case, the valve control circuitry 43 adjusts the opening degree of the gas bypass valve 14 or the liquid bypass valve 15 such that a detection value obtained by the temperature sensor falls within a predetermined range.

An example of a hardware configuration of the controller 40 as illustrated in FIG. 12 will be described below. FIG. 13 is a hardware configuration diagram illustrating a configuration example of the controller as illustrated in FIG. 12. In the case where various functions of the controller 40 are fulfilled by dedicated hardware, the hardware configuration of the controller 40 as illustrated in FIG. 12 is a processing circuit 80 as illustrated in FIG. 13. The functions of the determination circuitry 42 and the valve control circuitry 43 as illustrated in FIG. 12 are fulfilled by the processing circuit 80.

In the case where the functions are fulfilled by hardware, the processing circuit 80 corresponds to, for example, a single-component circuit, a composite circuit, a programmed processor, a parallel programmed processor, an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination of these circuits. The functions of the determination circuitry 42 and the valve control circuitry 43 may be fulfilled by respective processing circuits 80 or may be fulfilled by a single processing circuit 80.

An example of another hardware configuration of the controller 40 as illustrated in FIG. 12 will be described. FIG. 14 is a hardware configuration diagram illustrating another configuration example of the controller as illustrated in FIG. 12. In the case where various functions of the controller 40 are fulfilled by software, the controller 40 as illustrated in FIG. 12 includes a processor 81 such as a central processing unit (CPU) and a memory 82 as illustrated in FIG. 14. The functions of the determination circuitry 42 and the valve control circuitry 43 are fulfilled by the processor 81 and the memory 82. FIG. 14 illustrates the processor 81 and the memory 82 which are connected by a bus 83. The memory 82 stores the threshold Tth as data.

In the case where the functions are fulfilled by software, the functions of the determination circuitry 42 and the valve control circuitry 43 are fulfilled by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and are stored in the memory 82. The processor 81 fulfills the functions of each of the above circuits by reading out and executing an associated program stored in the memory 82.

As the memory 82, for example, a nonvolatile semiconductor memory is used. As the nonvolatile semiconductor memory, a read only memory (ROM), a flash memory, an erasable and programmable ROM (EPROM), and an electrically erasable and programmable ROM (EEPROM) can be used. Furthermore, a volatile semiconductor memory such as a random access memory (RAM) may also be used as the memory 82. Furthermore, a removable recording medium may also be used as the memory 82. In addition, as the memory 82, a removable recording medium such as a magnetic disk, a flexible disk, an optical disk, a compact disc (CDs), a MiniDisc (MD), or a digital versatile disc (DVD) may be used.

Next, the operation of the refrigeration cycle apparatus 1c according to Embodiment 4 will be described. FIG. 15 is a flowchart indicating the procedure of a control method that is applied by the controller as illustrated in FIG. 12. The following description is made with respect to the case where the first heat exchanger 3 operates as an evaporator. The controller 40 operates according to the flowchart of FIG. 15 at regular intervals.

The determination circuitry 42 acquires detection values obtained by the first temperature sensor 31 and the second temperature sensor 32 (step S101). The determination circuitry 42 calculates a temperature difference Td between the detection value obtained by the first temperature sensor 31 and the detection value obtained by the second temperature sensor 32. The determination circuitry 42 determines whether the temperature difference Td is greater than the threshold Tth or not (step S102). When it is determined in step S102 that the temperature difference Td is less than or equal to the threshold Tth, the controller 40 ends the processing.

In contrast, when it is determined in step S102 that the temperature difference Td is greater than the threshold Tth, the determination circuitry 42 transmits information regarding the above result of the determination to the valve control circuitry 43. When the valve control circuitry 43 receives, from the determination circuitry 42, information that the temperature difference Td is greater than the threshold Tth, the valve control circuitry 43 adjusts the opening degree of the gas bypass valve 14 or the liquid bypass valve 15 such that the temperature difference Td is less than or equal to the threshold Tth (step S103).

It should be noted that in the case where the first temperature sensor 31 is provided at the first heat transfer tube 21, but the second temperature sensor 32 is not provided at the second heat transfer tube 22, the controller 40 operates as follows in the flowchart of FIG. 15. In the case where the first heat exchanger 3 operates as a condenser, in step S101, the determination circuitry 42 acquires a detection value obtained by the first temperature sensor 31. In step S102, the determination circuitry 42 determines whether the detection value obtained by the first temperature sensor 31 falls within a first temperature range or not. When the detection value obtained by the first temperature sensor 31 does not fall within the first temperature range, in step S103, the valve control circuitry 43 adjusts the opening degree of the gas bypass valve 14 or the liquid bypass valve 15. For example, when it is determined in step S102 that the detection value obtained by the first temperature sensor 31 is less than the first temperature range, the flow rate of refrigerant that flows into the first heat transfer tube 21 is considered low. In this case, the valve control circuitry 43 increases the opening degree of the gas bypass valve 14, whereby it is possible to increase the flow rate of refrigerant that flows through the first heat transfer tube 21.

Furthermore, in the case where the first temperature sensor 31 is not provided at the first heat transfer tube 21, but the second temperature sensor 32 is provided at the second heat transfer tube 22, the controller 40 operates as follows in the flowchart of FIG. 15. When the first heat exchanger 3 operates as an evaporator, in step S101, the determination circuitry 42 acquires a detection value obtained by the second temperature sensor 32. In step S102, the determination circuitry 42 determines whether the detection value obtained by the second temperature sensor 32 falls within a second temperature range or not. When the detection value obtained by the second temperature sensor 32 does not fall within the second temperature range, in step S103, the valve control circuitry 43 adjusts the opening degree of the gas bypass valve 14 or the liquid bypass valve 1. For example, when it is determined in step S102 that the detection value obtained by the second temperature sensor 32 is greater than the second temperature range, the flow rate of refrigerant that flows into the second heat transfer tube 22 is considered low. In this case, the valve control circuitry 43 decreases the opening degree of the gas bypass valve 14 or increases the opening degree of the liquid bypass valve 15, whereby it is possible to increase the flow rate of refrigerant that flows through the second heat transfer tube 22.

Furthermore, in Embodiment 4, in the case where the expansion valve 5 is an electronic expansion valve, and the compressor 2 is an inverter compressor whose capacity can be changed, the controller 40 may control the opening degree of the expansion valve 5 and the operation frequency of the compressor 2.

The refrigeration cycle apparatus 1c according to Embodiment 4 includes the controller 40 and the temperature sensor provided at at least one of the first heat transfer tube 21 and the second heat transfer tube 22. The controller 40 adjusts the opening degree of the gas bypass valve 14 or the liquid bypass valve 15 such that a detection value obtained by the temperature sensor falls within the predetermined range.

According to Embodiment 4, since the opening degree of the gas bypass valve 14 or the liquid bypass valve 15 is adjusted such that the detection value obtained by the temperature sensor provided at the first heat transfer tube 21 or the second heat transfer tube 22 falls within the predetermined range, the refrigerant is more evenly distributed through the plurality of heat transfer tubes 11. Thus, the efficiency of the heat exchange at the first heat exchanger 3 is improved.

Furthermore, in Embodiment 4, the first temperature sensor 31 may be provided at the first heat transfer tube 21, and the second temperature sensor 32 may be provided at the second heat transfer tube 22. In this case, the controller 40 may adjust the opening degree of the gas bypass valve 14 or the liquid bypass valve 15 such that the temperature difference Td between a detection value obtained by the first temperature sensor 31 and a detection value obtained by the second temperature sensor 32 is less than or equal to the threshold Tth. The flow rates of refrigerant distributed to the plurality of heat transfer tubes 11 of the first heat exchanger 3 can be estimated with high accuracy, thereby further improving the efficiency of the heat exchange at the first heat exchanger 3.

REFERENCE SIGNS LIST

1, 1a to 1c: refrigeration cycle apparatus, 2: compressor, 3: first heat exchanger, 4: gas-liquid separator, 5: expansion valve, 6: second heat exchanger, 7: gas bypass circuit, 8: liquid bypass circuit, 9: four-way valve, 10: refrigerant circuit, 11: heat transfer tube, 12: first header, 13: second header, 14: gas bypass valve, 15: liquid bypass valve, 16: refrigerant pipe, 17: heat transfer fin, 21: first heat transfer tube, 22: second heat transfer tube, 31: first temperature sensor, 32: second temperature sensor, 40: controller, 42: determination circuitry, 43: valve control circuitry, 51: inlet port, 52: outlet port, 53: diaphragm chamber, 53a: diaphragm, 54: spring, 55: pressure chamber, 56: orifice, 57: needle, 58: shaft, 61: first pressure equalizing tube, 62: second pressure equalizing tube, 80: processing circuit, 81: processor, 82: memory, 83: bus

REFRIGERATION CYCLE APPARATUS

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CPC

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