WO2022079763A1

WO2022079763A1 - Refrigeration cycle device, air conditioner, and heat exchanger

Info

Publication number: WO2022079763A1
Application number: PCT/JP2020/038481
Authority: WO
Inventors: 良太湯浅; 宗希石山
Original assignee: 三菱電機株式会社
Priority date: 2020-10-12
Filing date: 2020-10-12
Publication date: 2022-04-21
Also published as: EP4227607A1; US20230288149A1; JPWO2022079763A1; CN116249870A; EP4227607A4

Abstract

An air conditioner (1) is a refrigeration cycle device in which incompatible oil is used as refrigerator oil, and comprises: a compressor (10) that compresses a refrigerant; a first heat exchanger (30) that condenses the refrigerant output from the compressor; a decompression device (40) that decompresses the refrigerant output from the first heat exchanger; and a second heat exchanger (50) that evaporates the refrigerant output from the decompression device and outputs the evaporated refrigerant to the compressor. The second heat exchanger includes a heat exchanger tube with a groove formed in the inner surface of the tube. The groove in the heat exchanger tube is formed so that the tube inner surface area on the downstream side of the heat exchanger tube is smaller than the tube inner surface area on the upstream side of the heat exchanger tube.

Description

Refrigeration cycle equipment, air conditioners, and heat exchangers

This disclosure relates to refrigeration cycle devices, air conditioners, and heat exchangers.

International Publication No. 2019/180817 (Patent Document 1) discloses a heat exchanger used in a refrigeration cycle apparatus. In this heat exchanger, a groove is provided on the inner surface of the heat transfer tube. As a result, the surface area on the inner surface of the pipe is increased, the fluid is agitated, and the heat transfer performance of the heat exchanger is improved (see Patent Document 1).

Further, Japanese Patent Application Laid-Open No. 4-45753 (Patent Document 2) also discloses such a heat exchanger. In this heat exchanger, at least two types of spiral grooves having different groove depths are provided on the inner surface of the heat transfer tube, and the groove depth is reduced on the fluid inlet side of the heat transfer tube in consideration of heat transfer performance and pressure loss. , It is enlarged on the exit side (see Patent Document 2).

International Publication No. 2019/180817 Pamphlet Japanese Unexamined Patent Publication No. 4-45753

By using refrigerating machine oil (hereinafter referred to as "incompatible oil") having weak compatibility with liquid refrigerant, the amount of refrigerant dissolved in the refrigerating machine oil is suppressed, and the amount of refrigerant enclosed in the refrigerating cycle is reduced. be able to. The incompatible oil is a refrigerating machine oil that has a small amount of mutual dissolution with a refrigerant and is easy to separate into two layers, as opposed to a "phase-dissolved oil" having a large amount of mutual dissolution with a refrigerant. Although it is difficult to define a clear boundary, those skilled in the art can understand that an incompatible oil is an oil in which the amount of mutual dissolution with a refrigerant is clearly smaller than that of a compatible oil.

In the heat exchanger (evaporator) on the low pressure side, the flow mode of the refrigerant becomes a circular flow or a circular spray flow on the downstream side where the dryness of the refrigerant becomes high, and the liquid phase is pushed by the wall surface and flows along the pipe wall. , The gas phase flows through the center of the tube. Therefore, when incompatible oil is used in the refrigeration cycle apparatus, the oil separated into two layers on the downstream side may form an oil film on the pipe wall and stay there due to its high viscosity. When an oil film is formed on the tube wall, the heat transfer performance of the heat exchanger is lowered and the pressure loss is increased.

The present disclosure has been made to solve such a problem, and an object of the present disclosure is to reduce the heat transfer performance of the low pressure side heat exchanger in a refrigeration cycle apparatus in which incompatible oil is used as the refrigerating machine oil. It is to suppress the increase in pressure loss.

The refrigerating cycle apparatus of the present disclosure is a refrigerating cycle apparatus in which an incompatible oil is used for the refrigerating machine oil, and includes a compressor that compresses the refrigerant and a first heat exchanger that condenses the refrigerant output from the compressor. A decompression device for depressurizing the refrigerant output from the first heat exchanger and a second heat exchanger for evaporating the refrigerant output from the decompression device and outputting the refrigerant to the compressor are provided. The second heat exchanger includes a heat transfer tube having a groove formed on the inner surface of the tube. The groove of the heat transfer tube is formed so that the surface area inside the tube per unit length on the downstream side of the heat transfer tube is smaller than the surface area inside the tube per unit length on the upstream side of the heat transfer tube.

According to this refrigeration cycle device, it is possible to suppress a decrease in heat transfer performance and an increase in pressure loss of the second heat exchanger (low pressure side heat exchanger).

It is an overall block diagram of the air conditioner shown as an example of the refrigeration cycle apparatus according to Embodiment 1. FIG. It is a figure which showed the flow of the refrigerant in an air conditioner. It is a figure which showed the flow of the refrigerant at the time of a heating operation. It is a figure which shows roughly the influence of the oil circulation rate on the capacity ratio of a refrigeration cycle. It is a figure which shows typically the state of the refrigerant and the refrigerating machine oil flowing through the heat transfer tube of a low pressure side heat exchanger when an incompatible oil is used as a refrigerating machine oil. It is a Baker diagram which shows the flow mode of the gas-liquid two-phase refrigerant flowing through a heat transfer tube. It is a figure which conceptually explains the internal structure of the heat transfer tube in the indoor heat exchanger shown in FIG. 1. It is a figure which shows an example of the cross section in the 1st part of a heat transfer tube. It is a figure which shows an example of the cross section in the 2nd part of a heat transfer tube. It is a figure which shows an example of the specific structure of the room heat exchanger shown in FIG. It is a block diagram which shows an example of the hardware composition of a control device. It is a flowchart explaining an example of the process executed by the control device in Embodiment 2. It is a flowchart explaining an example of the process executed by the control apparatus in the modification 1 of Embodiment 2. It is a flowchart explaining an example of the process executed by the control device in the modification 2 of Embodiment 2. It is a figure which shows the arrangement of the sensor which detects the flow mode of the refrigerant in the room heat exchanger in Embodiment 3 and the variation | embodiment.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

Embodiment 1.
FIG. 1 is an overall configuration diagram of an air conditioner shown as an example of a refrigeration cycle apparatus according to the first embodiment. With reference to FIG. 1, the air conditioner 1 includes an outdoor unit 2 and an indoor unit 3. The indoor unit 3 is installed in a target space (indoor) where air conditioning is performed by the air conditioner 1, and the outdoor unit 2 is installed outside the target space (for example, outdoors).

The outdoor unit 2 includes a compressor 10, a four-way valve 20, an outdoor heat exchanger 30, a fan 32, a decompression device 40, pipes 62 to 66, 72, temperature sensors 81 to 84, and a control device 90. including. The indoor unit 3 includes an indoor heat exchanger 50, a fan 52, and

temperature sensors

85 and 86. The outdoor unit 2 and the indoor unit 3 are connected to each other through

pipes

68 and 70.

The pipe 62 connects the discharge port of the compressor 10 and the port p1 of the four-way valve 20. The pipe 64 connects the port p2 of the four-way valve 20 and the outdoor heat exchanger 30. The pipe 66 connects the outdoor heat exchanger 30 and the decompression device 40. The pipe 68 connects the decompression device 40 and the indoor heat exchanger 50. The pipe 70 connects the indoor heat exchanger 50 and the port p3 of the four-way valve 20. The pipe 72 connects the port p4 of the four-way valve 20 and the suction port of the compressor 10.

The compressor 10 compresses the refrigerant sucked from the pipe 72 and outputs it to the pipe 62. The compressor 10 is configured so that the operating frequency can be adjusted according to the control signal from the control device 90. The output of the compressor 10 is adjusted by adjusting the operating frequency of the compressor 10. Various types of compressors 10 can be adopted, and for example, rotary type, reciprocating type, scroll type, screw type and the like can be adopted.

The four-way valve 20 communicates port p1 and port p2, and communicates port p3 and port p4. As a result, the pipe 62 and the pipe 64 are connected, and the pipe 70 and the pipe 72 are connected. The four-way valve 20 can switch the connection state of the ports p1 to p4 according to the control signal from the control device 90. That is, during the heating operation, the four-way valve 20 communicates the port p1 and the port p3, and communicates the port p2 and the port p4. As a result, during the heating operation, the pipe 62 and the pipe 70 are connected, and the pipe 64 and the pipe 72 are connected.

The outdoor heat exchanger 30 is configured such that the refrigerant flowing through the heat transfer tube provided inside exchanges heat with the outside air. In the outdoor heat exchanger 30, the high-temperature and high-pressure superheated steam (refrigerant) flowing from the pipe 64 is condensed and liquefied by exchanging heat (heat dissipation) with the outside air, and the liquid refrigerant is output to the pipe 66. During the heating operation, the refrigerant flowing from the pipe 66 into the outdoor heat exchanger 30 evaporates by exchanging heat (heat absorption) with the outside air in the outdoor heat exchanger 30, and becomes superheated steam, which is output to the pipe 64. To. The fan 32 is attached to the outdoor heat exchanger 30 and blows outside air to the outdoor heat exchanger 30.

The pressure reducing device 40 is composed of, for example, an electronic expansion valve, and the opening degree Op is adjusted according to a control signal from the control device 90. When the opening degree Op changes in the closing direction, the refrigerant pressure on the exit side of the decompression device 40 decreases, and the dryness of the refrigerant increases. When the opening degree Op changes in the opening direction, the refrigerant pressure on the exit side of the decompression device 40 increases, and the dryness of the refrigerant decreases. The decompression device 40 decompresses the refrigerant output from the outdoor heat exchanger 30 to the pipe 66 and outputs the refrigerant to the pipe 68. During the heating operation, the decompression device 40 decompresses the refrigerant output from the indoor heat exchanger 50 to the pipe 68 and outputs the refrigerant to the pipe 66.

The indoor heat exchanger 50 is configured such that the refrigerant flowing through the heat transfer tube provided inside exchanges heat with the air in the target space. In the indoor heat exchanger 50, the refrigerant flowing from the pipe 68 evaporates by performing heat exchange (endothermic) with the air in the target space to become superheated steam, which is output to the pipe 70. During the heating operation, the high-temperature and high-pressure superheated steam (refrigerator) flowing from the pipe 70 into the indoor heat exchanger 50 is condensed by exchanging heat (heat dissipation) with the air in the target space in the indoor heat exchanger 50. And liquefies, and the liquid refrigerant is output to the pipe 68. The fan 52 is attached to the indoor heat exchanger 50 and blows air to the indoor heat exchanger 50.

The temperature sensor 81 detects the temperature T1 of the refrigerant on the inlet side (exit side in the heating operation) of the outdoor heat exchanger 30, and outputs the detected value to the control device 90. The temperature sensor 82 detects the temperature T2 of the refrigerant on the outlet side (inside in the heating operation) of the outdoor heat exchanger 30, and outputs the detected value to the control device 90. The temperature sensor 83 detects the temperature T3 (condensation temperature in the cooling operation and evaporation temperature in the heating operation) of the heat transfer tube of the outdoor heat exchanger 30 and outputs the detected value to the control device 90.

Further, the temperature sensor 84 detects the temperature T4 (outside air temperature) of the place where the outdoor unit 2 (outdoor heat exchanger 30) is installed, and outputs the detected value to the control device 90. The temperature sensor 85 detects the temperature T5 (evaporation temperature in the cooling operation and the condensation temperature in the heating operation) of the heat transfer tube of the indoor heat exchanger 50, and outputs the detected value to the control device 90. The temperature sensor 86 detects the temperature T6 (indoor temperature) of the target space in which the indoor unit 3 (indoor heat exchanger 50) is installed, and outputs the detected value to the control device 90.

The control device 90 controls each device in the air conditioner 1. As the main control executed by the control device 90, the control device 90 sets the operating frequency of the compressor 10 and the operating frequency of the compressor 10 so that the air conditioner 1 performs the desired air conditioning operation based on the detected values of the temperature sensors 81 to 86 and the like. The opening degree Op of the decompression device 40 is controlled. Further, the control device 90 switches the state of the four-way valve 20 depending on whether the cooling operation or the heating operation is executed.

FIG. 2 is a diagram showing the flow of the refrigerant in the air conditioner 1. FIG. 2 shows the flow of the refrigerant during the cooling operation. With reference to FIG. 2, the refrigerant brought into a high-temperature and high-pressure steam state by the compressor 10 is supplied to the outdoor heat exchanger 30 via the four-way valve 20. Then, the refrigerant is condensed (liquefied) by exchanging heat (dissipating) with the outside air in the outdoor heat exchanger 30, and becomes a high-pressure liquid refrigerant.

The refrigerant that has passed through the outdoor heat exchanger 30 is decompressed by the decompression device 40, becomes a low-temperature low-pressure refrigerant, and is supplied to the indoor heat exchanger 50. Then, in the indoor heat exchanger 50 (low pressure side heat exchanger), the refrigerant evaporates (vaporizes) by exchanging heat (heat absorption) with the air in the target space to become a low pressure gas refrigerant. After that, the refrigerant is sucked into the compressor 10 again via the four-way valve 20.

During the heating operation, as shown in FIG. 3, the four-way valve 20 is switched so that the flow of the refrigerant is in the opposite direction to that during the cooling operation. Therefore, in this case, the indoor heat exchanger 50 is on the high pressure side and the outdoor heat exchanger 30 is on the low pressure side. 1), and the indoor heat exchanger 50 will be referred to as a low pressure side heat exchanger (second heat exchanger).

In the refrigeration cycle device, by providing a groove (unevenness) on the inner surface of the heat transfer tube of the heat exchanger, the surface area per unit length of the tube inner surface (hereinafter referred to as "tube inner surface area") is increased, and the heat exchanger is used. The heat transfer performance can be improved.

Further, in the refrigeration cycle device, oil (refrigerator oil) exists in the compressor in order to ensure the lubricity of the compressor. During the operation of the compressor, the refrigerating machine oil is taken out to the refrigerant circuit together with the flow in which the refrigerant is output from the compressor to the refrigerant circuit. The oil taken out to the refrigerant circuit circulates in the refrigerant circuit together with the refrigerant and returns to the compressor.

By using an incompatible oil having a weak compatibility with the liquid refrigerant as this refrigerating machine oil, the amount of the refrigerant dissolved in the refrigerating machine oil can be suppressed, and the amount of the refrigerant sealed in the refrigerating cycle device can be reduced. Can be done.

However, when incompatible oil is used as the refrigerating machine oil, in the heat exchanger on the low pressure side, the oil brought out to the refrigerant circuit on the downstream side where the dryness of the refrigerant becomes high has an oil film on the pipe wall due to its high viscosity. As a result, the heat transfer performance of the heat exchanger may decrease and the pressure loss may increase. This point will be described in detail below.

FIG. 4 is a diagram schematically showing the effect of the oil circulation rate on the capacity ratio of the refrigeration cycle. The oil circulation rate is an index showing the amount of refrigerating machine oil brought out to the refrigerant circuit. For example, the weight ratio of the refrigerant circulating in the refrigerant circuit to the refrigerating machine oil (the weight of oil with respect to the weight of the refrigerant (wt%)). )). The higher the oil circulation rate, the more oil is taken out from the compressor to the refrigerant circuit. The capacity ratio is an index showing the degree of decrease in the capacity of the refrigeration cycle under certain operating conditions. In this example, the capacity of the refrigeration cycle when the oil circulation rate is 0 is set to 1, and the capacity ratio corresponds to the oil circulation rate. The capacity ratio of the refrigeration cycle is shown.

With reference to FIG. 4, as the oil circulation rate increases, the capacity ratio of the refrigeration cycle decreases. When incompatible oil is used as the refrigerating machine oil, the oil circulation rate becomes high, so that the refrigerating cycle capacity may decrease. The reason why the capacity ratio of the refrigeration cycle decreases when the oil circulation rate increases and the reason why the oil circulation rate increases when incompatible oil is used will be described later.

FIG. 5 is a diagram schematically showing the state of the refrigerant and the refrigerating machine oil flowing through the heat transfer tube of the low pressure side heat exchanger when the incompatible oil is used as the refrigerating machine oil. With reference to FIG. 5, in the heat transfer tube of the low pressure side heat exchanger, the refrigerant flows as a gas-liquid two-phase flow of the liquid refrigerant 102 and the gas refrigerant 104. The incompatible refrigerating machine oil becomes oil droplets 106 and exists in the liquid refrigerant 102.

On the upstream side of the heat transfer tube, heat exchange between the refrigerant and the outside air has not progressed so much, and the dryness of the refrigerant is low. When the refrigerant flows through the heat transfer tube, it exchanges heat (endothermic) with the outside air and evaporates (gasifies), and the dryness of the refrigerant is high on the downstream side of the heat transfer tube.

On the upstream side of the heat transfer tube (low dryness), the flow mode of the refrigerant is often slag flow or stratified flow. The flow mode represents the form of a flow that is judged to belong to the same category by visually classifying the flow of gas-liquid two-phase flow flowing through a pipe. When the flow mode is a slag flow or a stratified flow, the oil droplet 106 in the liquid refrigerant 102 is flowed toward the downstream together with the liquid refrigerant 102. Then, on the downstream side of the heat transfer tube, the dryness of the refrigerant increases, and the flow mode often changes to a circular flow or a circular spray flow.

FIG. 6 is a Baker diagram showing the flow mode of the gas-liquid two-phase refrigerant flowing through the heat transfer tube. In FIG. 6, the vertical axis indicates the amount corresponding to the flow rate of the refrigerant, and the horizontal axis indicates the amount corresponding to the ratio of the liquid phase flow to the gas phase flow.

With reference to FIG. 6, typical flow modes include bubble flow, slag flow, stratified flow, circular flow, circular spray flow, and the like. The point cloud 95 is a plot of the state of the refrigerant for each degree of dryness x of the refrigerant flowing through the heat transfer tube. In this example, it can be seen that when the dryness x is low, the refrigerant flows as a slag flow, and when the dryness x is high, the refrigerant flows as a circular flow. Then, in this example, it can be seen that the flow mode changes from the slag flow to the circular flow when the dryness x is about 0.2.

The degree of dryness in which the flow mode of the refrigerant changes can be calculated from, for example, the temperature of the heat exchanger (evaporation temperature), the flow rate of the refrigerant, the inner diameter of the heat transfer tube, and the like. Further, from the enthalpies of the saturated liquid and the saturated vapor at the evaporation temperature and the calculated dryness (dryness at which the flow mode changes), the region (position) where the flow mode changes in the heat transfer tube can be estimated. ..

With reference to FIG. 5 again, on the downstream side where the dryness of the refrigerant becomes high, the flow mode of the refrigerant becomes a circular flow or a circular spray flow, and the liquid refrigerant 102 is pushed by the wall surface and flows along the pipe wall. Therefore, when an incompatible oil is used as the refrigerating machine oil, the oil separated into two layers on the downstream side may form an oil film 108 on the pipe wall due to its high viscosity. In particular, when the groove provided on the inner surface of the heat transfer tube is deepened in order to enhance the heat transfer performance, the oil film 108 is likely to be formed on the tube wall.

The oil film 108 is formed on the pipe wall, so that the oil stays in the heat transfer pipe, and as a result, the amount of oil returned to the compressor decreases and the oil circulation rate increases. Further, the formed oil film 108 increases the pressure loss when the refrigerant flows, hinders the heat transfer property between the refrigerant and the heat transfer tube, and lowers the heat transfer efficiency. Further, since the amount of oil returned to the compressor is reduced, the lubricity and reliability of the compressor may be lowered. As described above, when incompatible oil is used as the refrigerating machine oil, the oil circulation rate becomes high, and as a result, the capacity ratio of the refrigerating cycle may be significantly lowered.

Therefore, in the air conditioner 1 according to the first embodiment, incompatible oil is used as the refrigerating machine oil, and in the heat transfer tube of the indoor heat exchanger 50 (low pressure side heat exchanger), the downstream side (highly dry) of the heat transfer tube is used. Grooves (unevenness) on the inner surface of the pipe are formed so that the inner surface of the pipe on the (degree side) side is smaller than the inner surface surface of the pipe on the upstream side (low dryness side).

More specifically, the heat transfer tube is composed of a first part on the upstream side and a second part on the downstream side, and the surface area inside the tube at the second part is smaller than the surface area inside the tube at the first part. Surface grooves are formed. The boundary between the first portion and the second portion is provided in a region where the flow mode of the refrigerant flowing through the heat transfer tube changes to a circular flow or a circular spray flow. As a result, even if an incompatible oil is used as the refrigerating machine oil, it is possible to prevent the oil separated into two layers from forming an oil film on the pipe wall in the indoor heat exchanger 50. Further, on the upstream side of the heat transfer tube, it is possible to secure the heat transfer efficiency by securing the surface area inside the tube.

The boundary between the first part and the second part is determined by the APF (Annual Performance Factor, year-round energy consumption efficiency) of the air conditioner 1 in consideration of the heat transfer performance and pressure loss of the indoor heat exchanger 50. It may be set to the maximum position. That is, where the boundary is provided in a region where the flow mode of the refrigerant changes, for example, the APF does not set the position of the boundary from the region when the air conditioner 1 is operated under predetermined outside air conditions. The position of the boundary may be set from the above region when the air conditioner 1 is operated under the maximum condition. This makes it possible to save energy in the air conditioner 1.

In the first embodiment, for example, alkylbenzene oil is used as the incompatible refrigerating machine oil (incompatible oil). However, the non-phase-dissolved oil that can be used is not limited to this, and other arts that can be understood by those skilled in the art as oils having a clearly smaller amount of mutual dissolution with the refrigerant than the phase-dissolved oil. Refrigerating machine oil may be used.

FIG. 7 is a diagram conceptually explaining the internal configuration of the heat transfer tube in the indoor heat exchanger 50 shown in FIG. FIG. 7 schematically shows a cross section of the heat transfer tube 100 along the refrigerant flow direction from the inlet 120 to the outlet 122 of the heat transfer tube 100.

With reference to FIG. 7, in the air conditioner 1 according to the first embodiment, the heat transfer tube 100 of the indoor heat exchanger 50 (low pressure side heat exchanger) is connected to the first portion 110 on the upstream side of the boundary 114. , A second site 112 downstream of the boundary 114. A groove is formed on the inner peripheral surface of the heat transfer tube 100 in order to enhance the heat transfer property between the refrigerant flowing through the heat transfer tube 100 and the outside air.

FIG. 8 is a diagram showing an example of a cross section of the heat transfer tube 100 at the first portion 110. Further, FIG. 9 is a diagram showing an example of a cross section of the second portion 112 of the heat transfer tube 100.

With reference to FIGS. 8 and 9, the depth of the groove 118 formed on the inner peripheral surface of the second portion 112 is shallower than the depth of the groove 116 formed on the inner peripheral surface of the first portion 110. .. By forming

such grooves

116 and 118, the surface area of the inner surface of the pipe in the second portion 112 is smaller than the surface area of the inner surface of the pipe in the first portion 110. The depth of the groove 118 formed on the inner peripheral surface of the second portion 112 may be substantially zero.

With reference to FIG. 7 again, the boundary 114 between the first portion 110 and the second portion 112 is provided in a region where the flow mode of the refrigerant changes from a slag flow, a stratified flow, or the like to a circular flow or a circular spray flow. .. As a result, it is possible to prevent the oil separated into two layers from forming an oil film on the pipe wall at the second portion 112 by changing the flow mode to a circular flow or a circular spray flow. As a result, it is possible to suppress an increase in pressure loss and a decrease in heat transfer efficiency due to the oil film. Further, since the decrease in the amount of oil returned to the compressor 10 is suppressed, it is possible to suppress the decrease in the lubricity and reliability of the compressor 10. On the other hand, in the first portion 110 whose flow mode is a slag flow, a stratified flow, or the like, the heat transfer efficiency can be ensured by securing the surface area of the inner surface of the pipe.

The position of the boundary 114 in the heat transfer tube 100 is set in a region where the flow mode of the refrigerant changes from a slag flow, a stratified flow, or the like to a circular flow or a circular spray flow. The region (position) where the flow mode of the refrigerant changes in the heat transfer tube 100 can be estimated as follows, for example. That is, the dryness of the refrigerant whose flow mode changes from the temperature T5 (evaporation temperature) of the heat transfer tube of the indoor heat exchanger 50 detected by the temperature sensor 85, the flow rate of the refrigerant flowing through the refrigerant circuit, the inner diameter of the heat transfer tube 100, and the like. Can be calculated. Then, the region where the flow mode of the refrigerant changes is estimated from the enthalpies of the saturated liquid and the saturated vapor at the temperature T5 (evaporation temperature) and the calculated dryness (dryness at which the flow mode changes). can do.

The heat transfer tube 100 is actually composed of a plurality of pipes connected in series, and the first portion 110 and the second portion 112 are composed of pipe units. That is, where the position of the boundary 114 between the first portion 110 and the second portion 112 is set in the region where the flow mode of the refrigerant changes, the piping group constituting the first portion 110 and the second portion A plurality of pipes are configured so that the connection portion (boundary 114) with the pipe group constituting the portion 112 is included in the region where the flow mode of the refrigerant changes. In other words, the plurality of pipes are configured so that the boundary 114 is located at the connection portion of the pipes rather than in the middle of any of the pipes. As a result, it is not necessary to prepare a pipe whose internal surface area changes in the middle of the pipe, and the cost of parts can be suppressed.

FIG. 10 is a diagram showing an example of a specific configuration of the indoor heat exchanger 50 shown in FIG. 1. With reference to FIG. 10, the indoor heat exchanger 50 includes a plurality of

pipes

124, 125, a plurality of connecting pipes 126, and a plurality of fins 128.

A plurality of

pipes

124 and 125 are arranged in parallel at regular intervals. The plurality of fins 128 are formed so as to surround each of the plurality of

pipes

124 and 125. The plurality of connecting pipes 126 connect the plurality of

pipes

124, 125 arranged side by side in series by connecting the

adjacent pipes

124 or 125 alternately on the left and right.

Of the plurality of

pipes

124 and 125, the plurality of pipes 124 on the upstream side correspond to the first portion 110 shown in FIG. 7, and the plurality of pipes 125 on the downstream side correspond to the second portion 110 shown in FIG. Corresponds to 112. That is, the surface area inside the pipe of each pipe 125 is smaller than the surface area inside the pipe of each pipe 124. The connecting pipe 126 connecting the most downstream pipe 124 among the plurality of pipes 124 and the most upstream pipe 125 among the plurality of pipes 125 corresponds to the boundary 114 shown in FIG. 7.

With such a configuration, in the heat transfer tube 100 constituting the indoor heat exchanger 50, it is not necessary to prepare a pipe whose internal surface area changes in the middle of the pipe, and the first portion 110 and the second portion 112 do not need to be prepared. Can be easily formed.

As described above, according to the first embodiment, it is possible to suppress a decrease in heat transfer performance and an increase in pressure loss of the indoor heat exchanger 50 (low pressure side heat exchanger).

Embodiment 2.
In the indoor heat exchanger 50 (low pressure side heat exchanger), when the ambient environment such as the outside air temperature changes, the region (position) where the flow mode of the refrigerant changes to the annular flow or the annular spray flow changes. When the region where the flow mode of the refrigerant changes changes, the position of the boundary 114 between the first portion 110 and the second portion 112 of the heat transfer tube 100 becomes inconsistent, and an oil film is formed on the tube wall. Problems can occur.

Therefore, in the second embodiment, the control device 90 controls the air conditioner 1 so that the region (position) where the flow mode of the refrigerant changes approaches the boundary 114 between the first portion 110 and the second portion 112. Control the operating condition.

FIG. 11 is a block diagram showing an example of the hardware configuration of the control device 90. With reference to FIG. 11, the control device 90 includes a CPU (Central Processing Unit) 132, a RAM (Random Access Memory) 134, a ROM (Read Only Memory) 136, an input unit 138, a display unit 140, and I. It is configured to include the / F portion 142. The RAM 134, ROM 136, input unit 138, display unit 140, and I / F unit 142 are connected to the CPU 132 via the bus 144.

The CPU 132 expands the program stored in the ROM 136 into the RAM 134 and executes it. The program stored in the ROM 136 is a program in which the processing procedure of the control device 90 is described. The air conditioner 1 executes control of each device in the air conditioner 1 according to these programs. It should be noted that these controls are not limited to processing by software, but can also be processed by dedicated hardware (electronic circuit).

FIG. 12 is a flowchart illustrating an example of processing executed by the control device 90. In this flowchart, an example of a control processing procedure for matching a region where the flow mode of the refrigerant changes with the boundary 114 is shown. The series of processes shown in this flowchart are repeatedly executed at a predetermined cycle during the operation of the air conditioner 1 (during the operation of the compressor 10).

With reference to FIG. 12, the control device 90 detects the flow mode of the refrigerant at the boundary 114 shown in FIG. 7 in the heat transfer tube 100 of the indoor heat exchanger 50 which is the heat exchanger on the low pressure side (step S10). ..

The flow mode of the refrigerant at the boundary 114 can be detected, for example, as follows. The temperature T1 of the refrigerant on the inlet side of the outdoor heat exchanger 30, the temperature T2 of the refrigerant on the outlet side of the outdoor heat exchanger 30, and the temperature T3 of the heat transfer tube of the outdoor heat exchanger 30 (condensation), which are detected by the temperature sensors 81 to 86, respectively. Temperature), the temperature T4 (outside air temperature) of the place where the outdoor unit 2 (outdoor heat exchanger 30) is installed, the temperature T5 (evaporation temperature) of the heat transfer tube 100 of the indoor heat exchanger 50, and the indoor unit 3 (indoor heat). From the temperature T6 (indoor temperature) of the target space in which the exchanger 50) is installed, the refrigerating cycle of the air conditioner 1 in the ph diagram (pressure-specific enthalpy diagram) can be obtained. From this refrigeration cycle (ph-h diagram), the dryness of the refrigerant at the position of the boundary 114 of the indoor heat exchanger 50 can be obtained. Then, by applying the obtained dryness to the Baker diagram shown in FIG. 6, the flow mode of the refrigerant at the boundary 114 can be detected (estimated).

When the flow mode of the refrigerant at the boundary 114 is detected in step S10, the control device 90 determines whether the detected flow mode is a circular flow or a circular spray flow (step S20). Then, when it is determined that the flow mode is a circular flow or a circular spray flow (YES in step S20), the control device 90 increases the valve opening degree of the decompression device 40 (step S30). When the flow mode of the refrigerant at the boundary 114 is a circular flow or a circular spray flow, the change point of the flow mode in the indoor heat exchanger 50 is on the upstream side of the boundary 114. In this case, by increasing the valve opening degree of the decompression device 40, the evaporation pressure in the indoor heat exchanger 50 increases, and the dryness of the refrigerant at the inlet of the indoor heat exchanger 50 decreases. As a result, the change point of the flow mode in the indoor heat exchanger 50 shifts to the downstream side and approaches the boundary 114.

On the other hand, if it is determined in step S20 that the flow mode is not a circular flow or a circular spray flow (NO in step S20), the control device 90 reduces the valve opening degree of the decompression device 40 (step S40). When the flow mode of the refrigerant at the boundary 114 is not a circular flow or a circular spray flow (that is, when the flow mode is a slag flow, a stratified flow, etc.), the change point of the flow mode in the indoor heat exchanger 50 is the boundary. It is on the downstream side of 114. In this case, by reducing the valve opening degree of the decompression device 40, the evaporation pressure in the indoor heat exchanger 50 decreases, and the dryness of the refrigerant at the inlet of the indoor heat exchanger 50 increases. As a result, the change point of the flow mode in the indoor heat exchanger 50 shifts to the upstream side and approaches the boundary 114.

In step S20, it may be determined whether the flow mode of the refrigerant is a slag flow or a stratified flow. When it is determined that the flow mode is a slag flow or a stratified flow, the process is shifted to step S40 to reduce the valve opening degree of the decompression device 40, and it is determined that the flow mode is not a slag flow or a stratified flow. If so, the process may be shifted to step S30 to increase the valve opening degree of the pressure reducing device 40.

As described above, according to the second embodiment, in the indoor heat exchanger 50 (low pressure side heat exchanger), the position of the boundary 114 between the first portion 110 and the second portion 112 of the heat transfer tube 100 , It is possible to suppress the deviation from the region (position) where the flow mode of the refrigerant changes to the annular flow or the annular spray flow.

Modification example of the second embodiment 1.
In the second embodiment described above, the region (position) where the flow mode of the refrigerant changes is brought closer to the boundary 114 by adjusting the valve opening degree of the decompression device 40, but instead of the decompression device 40, a compressor is used. The operating frequency of 10 may be adjusted.

FIG. 13 is a flowchart illustrating an example of the process executed by the control device 90 of the modified example 1. This flowchart corresponds to the flowchart shown in FIG.

With reference to FIG. 13, the processes executed in steps S110 and S120 are the same as the processes executed in steps S10 and S20 of FIG. 12, respectively.

Then, in step S120, when it is determined that the flow mode of the refrigerant is a circular flow or a circular spray flow (YES in step S120), the control device 90 lowers the operating frequency of the compressor 10 (step S130). As a result, the flow rate of the refrigerant flowing through the refrigerant circuit is reduced, and in the Baker diagram shown in FIG. 6, the point cloud 95 moves downward as a whole. As a result, the change point of the flow mode in the indoor heat exchanger 50 shifts to the downstream side and approaches the boundary 114.

On the other hand, if it is determined in step S120 that the flow mode is not a circular flow or a circular spray flow (NO in step S120), the control device 90 raises the operating frequency of the compressor 10 (step S140). As a result, the flow rate of the refrigerant flowing through the refrigerant circuit increases, and in the Baker diagram shown in FIG. 6, the point cloud 95 moves upward in the figure as a whole. As a result, the change point of the flow mode in the indoor heat exchanger 50 shifts to the upstream side and approaches the boundary 114.

Also for this modification 1, in step S120, it may be determined whether the flow mode of the refrigerant is a slag flow or a stratified flow. When it is determined that the flow mode is a slag flow or a stratified flow, the process is shifted to step S140 to raise the operating frequency of the compressor 10, and it is determined that the flow mode is not a slag flow or a stratified flow. If so, the process may be shifted to step S130 to lower the operating frequency of the compressor 10.

Modification example of the second embodiment 2.
In the second embodiment, the valve opening degree of the pressure reducing device 40 is adjusted, and in the first modification, the operating frequency of the compressor 10 is adjusted in order to bring the region (position) where the flow mode of the refrigerant changes closer to the boundary 114. However, instead of these, the capacity (rotational speed) of the fan 52 of the indoor heat exchanger 50 may be adjusted.

FIG. 14 is a flowchart illustrating an example of processing executed by the control device 90 of the modification 2. This flowchart also corresponds to the flowchart shown in FIG.

With reference to FIG. 14, the processes executed in steps S210 and S220 are the same as the processes executed in steps S10 and S20 of FIG. 12, respectively.

Then, when it is determined in step S220 that the flow mode of the refrigerant is a circular flow or a circular spray flow (YES in step S220), the control device 90 reduces the rotation speed of the fan 52 of the indoor heat exchanger 50 (YES in step S220). Step S230). When the rotation speed of the fan 52 is lowered, the air volume of the fan 52 decreases. The reduction in the air volume of the fan 52 has the same effect as the reduction in the flow rate of the refrigerant, that is, the reduction in the operating frequency of the compressor 10 has the same effect. Therefore, by lowering the rotation speed of the fan 52, the change point of the flow mode in the indoor heat exchanger 50 shifts to the downstream side and approaches the boundary 114.

On the other hand, if it is determined in step S220 that the flow mode is not a circular flow or a circular spray flow (NO in step S220), the control device 90 increases the rotation speed of the fan 52 of the indoor heat exchanger 50 (step S240). .. As a result, the change point of the flow mode in the indoor heat exchanger 50 shifts to the upstream side and approaches the boundary 114.

Also for this modification 2, in step S220, it may be determined whether the flow mode of the refrigerant is a slag flow or a stratified flow. When it was determined that the flow mode was a slag flow or a stratified flow, the process was shifted to step S240 to increase the rotation speed of the fan 52, and it was determined that the flow mode was not a slag flow or a stratified flow. In that case, the process may be shifted to step S230 to reduce the rotation speed of the fan 52.

Embodiment 3.
In the second embodiment and its modifications, the temperatures T1 to T6 detected by the temperature sensors 81 to 86 are used to detect the flow mode of the refrigerant at the boundary 114 of the heat transfer tube 100 of the indoor heat exchanger 50. bottom. In the third embodiment, a sensor capable of detecting the flow mode of the refrigerant is arranged at the boundary 114, and the flow mode of the refrigerant at the boundary 114 is directly detected.

FIG. 15 is a diagram showing an arrangement of sensors for detecting the flow mode of the refrigerant in the indoor heat exchanger 50 in the third embodiment. FIG. 15 corresponds to FIG. 7 described in the first embodiment.

With reference to FIG. 15, the configuration of the heat transfer tube 100 is the same as that of the heat transfer tube shown in FIG. Then, in the third embodiment, the luminous intensity sensor 150 is arranged at the boundary 114 between the first portion 110 and the second portion 112.

The luminous intensity sensor 150 is a sensor for detecting the flow mode of the refrigerant flowing through the boundary 114 based on the detected luminous intensity when the refrigerant (gas-liquid two-phase flow) flowing through the boundary 114 is irradiated with light. The detected luminous intensity may be the luminous intensity of transmitted light or the luminous intensity of reflected light. Utilizing the fact that the detected luminous intensity differs depending on the flow mode of the refrigerant, the flow mode of the refrigerant flowing through the boundary 114 is detected based on the detected luminous intensity. By evaluating the relationship between the detected luminous intensity and the flow mode in advance by experiments or the like in advance, and storing the relationship between the detected value of the luminous intensity sensor 150 and the flow mode of the refrigerant flowing through the boundary 114 in ROM 136 with a map or the like. , The flow mode of the refrigerant flowing through the boundary 114 can be easily obtained from the detection value of the luminous intensity sensor 150.

Then, based on the flow mode of the refrigerant flowing through the boundary 114 detected by using the luminous intensity sensor 150, the change point of the flow mode of the refrigerant approaches the boundary 114 according to the flowchart shown in FIG. 12, FIG. 13 or FIG. Be done.

As described above, also in the third embodiment, the flow mode of the refrigerant flowing through the boundary 114 is detected by using the detection value of the luminous intensity sensor 150, and the position of the boundary 114 and the region (position) where the flow mode changes. Can be suppressed from diverging.

Modification example of the third embodiment 1.
Instead of the luminous intensity sensor 150, the sound wave sensor 160 may be arranged at the boundary 114, and the sound wave sensor 160 may detect the flow mode of the refrigerant at the boundary 114.

With reference to FIG. 15 again, the sound wave sensor 160 is also arranged at the boundary 114 between the first portion 110 and the second portion 112. The sound wave sensor 160 is a sensor for detecting the flow mode of the refrigerant flowing through the boundary 114 based on the detection wave when the sound wave is irradiated toward the refrigerant (gas-liquid two-phase flow) flowing through the boundary 114. Utilizing the fact that the detection wave differs depending on the flow mode of the refrigerant, the flow mode of the refrigerant flowing through the boundary 114 is detected based on sound waves. By evaluating the relationship between the detected wave and the flow mode in advance by experiments or the like in advance, and storing the relationship between the detected value of the sound wave sensor 160 and the flow mode of the refrigerant flowing through the boundary 114 in ROM 136 with a map or the like. , The flow mode of the refrigerant flowing through the boundary 114 can be easily obtained from the detection value of the sound wave sensor 160.

In the second embodiment and its modification, the flow mode of the refrigerant at the boundary 114 is detected, and the decompression device 40 or the like is controlled so that the region (position) where the flow mode changes approaches the boundary 114. , The region (position) where the flow mode changes in the heat transfer tube 100 may be estimated, and the decompression device 40 or the like may be controlled so that the region approaches the boundary 114. As described above, the region where the flow mode of the refrigerant changes depends on the enthalpies of the saturated liquid and the saturated vapor at the temperature (evaporation temperature) of the heat transfer tube 100 and the dryness of the refrigerant whose flow mode changes. The changing region can be estimated. The dryness of the refrigerant whose flow mode changes can be calculated from the temperature of the heat transfer tube 100 (evaporation temperature), the flow rate of the refrigerant flowing through the refrigerant circuit, the inner diameter of the heat transfer tube 100, and the like.

Further, in each of the above embodiments and modifications, the air conditioner has been described as an example of the refrigeration cycle device, but the refrigeration cycle device according to the present disclosure is not limited to the air conditioner, and is not limited to the air conditioner, but is not limited to the air conditioner. It can also be applied to refrigeration cycle equipment used for cases and the like.

The embodiments disclosed this time should be considered to be exemplary in all respects and not restrictive. The technical scope set forth in the present disclosure is set forth by the claims rather than the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. ..

1 air conditioner, 2 outdoor unit, 3 indoor unit, 10 compressor, 20 four-way valve, 30 outdoor heat exchanger, 32,52 fan, 40 decompression device, 50 indoor heat exchanger, 62-72, 124, 125 piping , 81-86 temperature sensor, 90 controller, 95 point group, 100 heat transfer tube, 102 liquid refrigerant, 104 gas refrigerant, 106 oil droplets, 108 oil film, 110 first part, 112 second part, 114 boundary, 116 , 118 groove, 120 inlet 122 exit, 126 connection tube, 128 fins, 132 CPU, 134 RAM, 136 ROM, 138 input section, 140 display section, 142 I / F section, 144 bus, 150 luminous sensor, 160 sonic sensor.

Claims

A refrigeration cycle device that uses incompatible oil as refrigerating machine oil.
A compressor that compresses the refrigerant and
A first heat exchanger that condenses the refrigerant output from the compressor,
A decompression device that decompresses the refrigerant output from the first heat exchanger, and
A second heat exchanger that evaporates the refrigerant output from the decompression device and outputs the refrigerant to the compressor is provided.
The second heat exchanger includes a heat transfer tube having a groove formed on the inner surface of the tube.
The groove is formed so that the surface area inside the tube per unit length on the downstream side of the heat transfer tube is smaller than the surface area inside the tube on the upstream side of the heat transfer tube.
The heat transfer tube is
The first part and
Includes a second site downstream of the first site, including
The groove is formed so that the surface area inside the pipe at the second portion is smaller than the surface area inside the pipe at the first portion.
The refrigerating cycle apparatus according to claim 1, wherein the boundary between the first portion and the second portion is provided in a region where the flow mode of the refrigerant flowing through the heat transfer tube changes.
The first portion comprises at least one first pipe connected in series.
The second portion comprises at least one second pipe connected in series.
The at least one first pipe and the at least one second pipe are formed so that a connection portion between the at least one first pipe and the at least one second pipe is included in the region. The refrigeration cycle apparatus according to claim 2.
A temperature sensor for detecting the state of the refrigerant and
The refrigeration cycle apparatus according to claim 2 or 3, further comprising a detection unit that detects the flow mode of the refrigerant at the boundary by using the detection value of the temperature sensor.
The temperature sensor detects the inlet refrigerant temperature, the outlet refrigerant temperature, the heat transfer tube temperature and the ambient temperature of the first heat exchanger, and the ambient temperature and the heat transfer tube temperature of the second heat exchanger. Item 4. The refrigeration cycle apparatus according to Item 4.
The refrigerating cycle apparatus according to claim 2 or 3, further comprising a sensor arranged at the boundary and for detecting the flow mode of the refrigerant at the boundary.
The refrigeration cycle device according to claim 6, wherein the sensor includes a luminous intensity sensor that detects the state of the refrigerant at the boundary.
The refrigeration cycle device according to claim 6, wherein the sensor includes a sound wave sensor for detecting the state of the refrigerant at the boundary.
The pressure reducing device includes a pressure reducing valve, and the pressure reducing device includes a pressure reducing valve.
The refrigeration cycle device further includes a control device for controlling the opening degree of the pressure reducing valve.
The control device is
When the detected flow mode is a circular flow or a circular spray flow, the opening degree is increased.
The refrigeration cycle apparatus according to any one of claims 4 to 8, wherein the opening degree is reduced when the detected flow mode is not a circular flow or a circular spray flow.
Further equipped with a control device for controlling the operating frequency of the compressor,
The control device is
When the detected flow mode is a circular flow or a circular spray flow, the operating frequency is lowered.
The refrigeration cycle apparatus according to any one of claims 4 to 8, wherein the operating frequency is increased when the detected flow mode is not a circular flow or a circular spray flow.
The fan provided in the second heat exchanger and
Further equipped with a control device for controlling the rotation speed of the fan,
The control device is
When the detected flow mode is a circular flow or a circular spray flow, the rotation speed is reduced.
The refrigerating cycle apparatus according to any one of claims 4 to 8, wherein the rotational speed is increased when the detected flow mode is not a circular flow or a circular spray flow.
An air conditioner including the refrigeration cycle apparatus according to any one of claims 1 to 11.
A heat exchanger for refrigeration cycle equipment that uses incompatible oil as refrigerating machine oil.
Equipped with a heat transfer tube with a groove formed on the inner surface of the tube
The heat transfer tube is
The first part and
Includes a second site downstream of the first site, including
The groove is formed so that the surface area in the pipe per unit length at the second portion is smaller than the surface area inside the pipe at the first portion.
The boundary between the first portion and the second portion is a heat exchanger provided in a region where the flow mode of the refrigerant flowing through the heat transfer tube changes.
The first portion comprises at least one first pipe connected in series.
The second portion comprises at least one second pipe connected in series.
The at least one first pipe and the at least one second pipe are formed so that a connection portion between the at least one first pipe and the at least one second pipe is included in the region. The heat exchanger according to claim 13.