JP5686753B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner that reduces pressure loss in a gas side connection pipe, improves energy efficiency, and reduces the diameter of the gas side connection pipe.

  Patent Document 1 discloses a lubricating oil separation between an evaporator and a compressor that separates the lubricating oil contained in the refrigerant and circulated in the refrigeration apparatus and returns the separated lubricating oil to the compressor side. A refrigeration apparatus with a vessel is described. Since the separated lubricating oil is returned to the compressor, the lubricating oil in the refrigerant pipe between the evaporator and the compressor is reduced, so that the pressure loss between the evaporator and the compressor can be reduced.

  Further, in Patent Document 2, a bottle-shaped oil separator body having a flow passage enlarged portion, a gas discharge pipe arranged with an annular gap maintained between the inner wall of the oil separator body, and an opening near the bottom of the oil separator body. An oil separator with an oil discharge pipe is described. When a gas containing oil flows in the pipe, the gas flows fast in the center of the pipe, and the oil flows slowly along the pipe wall. As the oil goes from upstream to downstream, the oil is separated from the gas at the annular portion, flows down along the inner wall of the oil separator body, accumulates at the bottom, and is discharged through the oil discharge pipe.

Japanese Patent Laid-Open No. 3-17479 Japanese Utility Model Publication No. 1-82468

  Patent Document 1 does not disclose any configuration relating to a cooling / heating air conditioner in which the refrigerant flows in opposite directions during the cooling operation and the heating operation. That is, when a four-way switching valve is attached to the cycle configuration described in Patent Document 1 to form an air conditioning air conditioning apparatus, a short-circuit flow is formed in which the high-temperature high-pressure refrigerant at the condenser inlet flows to the compressor inlet at a low pressure, and the efficiency is greatly increased. descend.

  Moreover, the oil discharge pipe of the oil separator of Patent Document 2 does not assume that only the oil accumulated at the bottom of the oil separator body is discharged and the gas refrigerant is circulated.

  The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to provide an air conditioner that reduces the pressure loss of the gas-side connection pipe during cooling and heating.

A feature of the present invention that achieves the above object is that a compressor, a four-way valve, an outdoor heat exchanger, an expansion valve, a liquid side connection pipe, an indoor heat exchanger, and a gas side connection pipe are refrigerant pipes. In the connected air conditioner, an oil separator is provided between the indoor heat exchanger and the gas side connection pipe, and the oil return pipe of the oil separator is connected to the refrigerant pipe between the gas side connection pipe and the four-way valve. , During cooling operation, refrigeration oil and refrigerant are circulated from the oil return pipe of the oil separator to the refrigerant pipe between the gas side connection pipe and the four-way valve. It is made to distribute | circulate from the said refrigerant | coolant piping between a gas side connection piping and the said four-way valve to the said oil return piping of the said oil separator .

  ADVANTAGE OF THE INVENTION According to this invention, the pressure loss of the gas side connection piping at the time of cooling and heating can be reduced.

1 is a system diagram of an air conditioner according to a first embodiment of the present invention. FIG. 2 is a structural diagram of the oil separator of FIG. 1. FIG. 3 is a cross-sectional structure diagram of the oil separator of FIG. 2. It is a systematic diagram of the air conditioning apparatus which concerns on the 2nd Example of this invention. It is the pressure loss reduction rate with respect to the pipe diameter of the second gas side connection pipe. It is a pipe friction coefficient with respect to the pipe diameter of the second gas side connection pipe.

  Embodiments of the present invention will be described below.

  An embodiment of an air conditioner according to the present invention will be described with reference to FIGS. FIG. 1 is a system diagram of the air conditioner 100. The air conditioner 100 includes an outdoor unit 1 installed outside on the heat source side, an indoor unit 2 installed indoors on the usage side, and two gas side connection pipes (first gas side connection pipe 23, second gas Gas-side connection pipe 24) and one liquid-side connection pipe 15 are provided.

  R410A, R32, R1234yf, etc. are used as the refrigerant. Moreover, compatible oil is used as refrigerating machine oil.

  The compressor 11 that compresses the refrigerant is connected to a four-way valve 12 that switches the direction of the refrigerant flow between the cooling operation and the heating operation. One of the outdoor heat exchangers 13 for exchanging heat between the outdoor air sent by the outdoor fan 13a and the refrigerant is connected to the four-way valve 12, and the other is provided with an expansion valve 14 for reducing the pressure of the refrigerant whose opening degree can be adjusted. To the outdoor liquid side connection port 15a. The liquid side connection pipe 15 is connected to the outdoor liquid side connection port 15a and the indoor liquid side connection port 15b.

  One of the indoor liquid side pipes 16 is connected to the indoor liquid side connection port 15 b and the other is connected to the indoor heat exchanger 17. The indoor heat exchanger 17 performs heat exchange between the indoor air sent by the indoor fan 17b and the refrigerant.

  The oil separator 19 that separates the refrigerating machine oil from the refrigerant has a double pipe structure, the outer pipe 30 side is connected to the indoor heat exchanger 17 via the first indoor gas side pipe 18, and the inner pipe 31 side is The second indoor gas side pipe 20, the first indoor gas side connection port 23b, the first gas side connection pipe 23, and the first outdoor gas side connection port 23a are connected in this order. In addition, the oil return port 32 of the oil separator 19 is connected in the order of the indoor oil return pipe 21, the second indoor gas side connection port 24b, the second gas side connection pipe 24, and the second outdoor gas side connection port 24a. Is done.

  The first outdoor gas side connection port 23a is connected to the four-way valve 12 via the outdoor gas side piping 25, and the second outdoor gas side connection port 24a is connected to the Y of the outdoor gas side piping 25 via the outdoor oil return piping 26. It is connected by the character part 25a. When the Y-shaped portion 25a joins at the time of cooling and branches at the time of heating, the flow path is Y-shaped, so that the flow path loss can be reduced.

  Next, the structure and operation of the oil separator 19 will be described with reference to FIGS. FIG. 2 is a structural diagram of the oil separator 19, and FIG. 3 is a cross-sectional view taken along line AA and BB in FIG. 2. The oil separator 19 has a double pipe structure including an outer pipe 30 and an inner pipe 31 that have been subjected to drawing processing. The oil separator 19 fits between an enlarged portion 30a of the outer pipe 30 and a reduced portion 31b of the inner pipe 31, and an oil return port. The enlarged portion 30b and the oil return port 32 are fitted and brazed and joined. Of the gas refrigerant and the refrigerating machine oil flowing in from the outer pipe 30 side of the oil separator 19, the refrigerating machine oil that is liquid flows along the inner wall surface of the outer pipe 30, and the gas refrigerant that is a gas flows through the center of the outer pipe 30. . The refrigerating machine oil flowing along the inner wall surface of the outer tube 30 flows into the gap between the outer tube 30 and the inner tube 31 and flows out from the oil return port 32. On the other hand, the gas refrigerant mainly flows into the inner pipe 31 and flows out from the other end.

  Further, the length direction of the pipe of the oil separator 19 having a double pipe structure is the same as the length direction of the indoor gas side pipe 18, and the outer diameter shape of the oil separator 19 is the outer diameter shape of the gas side pipe 18. Therefore, it can be arranged compactly.

  When the oil separator is installed horizontally, the lower side of the refrigerating machine oil flowing along the inner wall surface of the outer tube 30 has a thick distribution due to the influence of gravity. Therefore, the oil return port 32 is positioned below the inner pipe 31 in the direction of gravity so that the refrigerating machine oil can flow more easily.

  The operation of the cooling operation and the heating operation in the above configuration will be described. First, the operation during the cooling operation will be described with reference to FIG. In the figure, solid arrows indicate the direction of refrigerant flow during cooling operation.

  During the cooling operation, the gas refrigerant compressed at the compressor 11 and having a high temperature and high pressure containing the refrigerating machine oil flows into the outdoor heat exchanger 13 through the four-way valve 12. This high-temperature and high-pressure gas refrigerant is cooled and condensed in the outdoor heat exchanger 13 by the outdoor air sent by the outdoor fan 13a. The high-pressure condensed refrigerant is depressurized by the expansion valve 14 to become a low-temperature low-pressure gas-liquid two-phase refrigerant, and flows into the indoor heat exchanger 17 through the liquid side connection pipe 15 and the indoor liquid side pipe 16. The gas-liquid two-phase refrigerant flowing through the indoor heat exchanger 17 is heated and evaporated by the indoor air sent by the indoor heat exchanger 17b, and becomes a low-pressure gas refrigerant. At this time, the room air is cooled by cooling the room air.

  The refrigerant in the indoor gas side pipe 18 on the outlet side of the indoor heat exchanger 17 contains refrigeration oil, the refrigeration oil flows along the wall surface of the pipe, and the gas refrigerant flows in the center of the pipe. The refrigerant composed of the gas refrigerant and the refrigerating machine oil is separated in an oil separator 19 having a double pipe structure, and the gas refrigerant separated from the oil flows into the indoor gas side pipe 20 and the first gas side connection pipe. 23, the outdoor gas side pipe 25 and the four-way valve 12 are returned to the compressor 11 again. The separated refrigerating machine oil flows into the indoor oil return pipe 21, passes through the second gas side connection pipe 24 and the outdoor oil return pipe 26, and merges with the gas refrigerant at the Y-shaped portion 25 a of the outdoor gas side pipe 25. To do. It should be noted that the second gas side connection pipe 24 is composed only of refrigerating machine oil so that the pressure loss between the first gas side connection pipe 23 side flow path and the second gas side connection pipe 24 side flow path is balanced. Gas refrigerant also flows.

  At this time, since the oil-separated gas refrigerant flows through the first gas side connection pipe 23, the pressure loss can be reduced. That is, when refrigerating machine oil is mixed in the gas refrigerant, the pressure loss is several times that of the pure refrigerant. Therefore, the gas refrigerant and the refrigerating machine oil are separated from each other by flowing the gas refrigerant mixed with the refrigerating machine oil through one pipe. The pressure loss can be greatly reduced by using each of the pipes. Thereby, energy efficiency can be improved.

  Next, operation during heating operation will be described. In FIG. 1, a broken-line arrow indicates the refrigerant flow direction during heating operation.

  During the heating operation, the gas refrigerant compressed by the compressor 11 and having a high temperature and high pressure passes through the four-way valve 12 and is diverted by the Y-shaped portion 25a of the outdoor gas side pipe 25, one of which is the first gas side connection pipe. 23, flows into the indoor gas side pipe 20 and the oil separator 19, and the other flows into the outdoor oil return pipe 26, the second gas side connection pipe 24, the indoor oil return pipe 21, and the oil separator 19. The flow rate ratio of the gas refrigerant in the first gas side connection pipe 23 side flow path and the second gas side connection pipe 24 side flow path is a flow rate ratio in which pressure loss is balanced. At this time, the oil separator 19 does not perform oil separation.

  The high-temperature and high-pressure gas refrigerant merged in the oil separator 19 flows into the indoor heat exchanger 17 through the indoor gas side pipe 18, and is cooled and condensed by the indoor air sent by the indoor fan 17b. At this time, the room air is heated by heating the room air. The high-pressure condensed refrigerant passes through the indoor liquid side pipe 16 and the liquid side connection pipe 15, is decompressed by the expansion valve 14, becomes a low-temperature low-pressure gas-liquid two-phase refrigerant, and flows into the outdoor heat exchanger 13. The gas-liquid two-phase refrigerant flowing in the outdoor heat exchanger 13 is heated and evaporated by the outdoor air sent by the outdoor fan 13a, and becomes a low-pressure gas refrigerant. The low-pressure gas refrigerant returns to the compressor 11 again through the four-way valve 12.

  At this time, since the gas refrigerant was also circulated through the second gas side connection pipe 24 side channel used as the oil return channel during the cooling operation, the gas refrigerant was circulated only through the first gas side connection pipe 23 side channel. In some cases, pressure loss can be reduced, and energy efficiency can be improved. Moreover, this invention can apply the pressure loss reduction part of gas side connection piping to diameter reduction of gas side connection piping.

The rated cooling capacity of the air conditioner 100 is 8 kW, the diameter of the first gas side connection pipe 23 is 12.7 mm, the diameter of the second gas side connection pipe 24 is 6.35 mm, and the liquid side connection pipe 15 The tube diameter is 9.52 mm. A conventional refrigeration air conditioner with a rated cooling capacity of 8 kW has a single gas side connection pipe with a pipe diameter of 15.88 mm (pipe wall thickness is 1 mm) and an inner diameter cross-section of 151 mm ² . The inner diameter cross-sectional area of the gas-side connection pipe 23 (pipe thickness is 0.8 mm) with a pipe diameter of 12.7 mm is 97 mm ² , and the inner diameter of the gas-side connection pipe 24 (pipe thickness is 0.8 mm) with a pipe diameter of 6.35 mm The sectional area is 18 mm ² , the total inner diameter sectional area is 115 mm ² , the refrigerant channel sectional area can be reduced, and the outer diameter sectional area of the piping is also reduced, so that the piping space can be reduced. Moreover, since the pipe diameter is small, the workability can be improved.

The conventional oil separator has a small diameter in the oil return pipe because only the refrigeration oil flows through the oil return pipe. For example, a pipe diameter of 3.18 mm (wall thickness of 0.8 mm) is used, the inner diameter cross-sectional area is 2 mm ² , and the first gas side connection pipe 23 has a pipe diameter of 12.7 mm (inner diameter cross-sectional area of 97 mm ² ). The ratio of the inner diameter cross-sectional area is about 2%.

At this time, it is assumed that only the gas refrigerant flows through the first gas side connection pipe and the oil return pipe, and the physical properties of the refrigerant (refrigerant: R410A, density: 40.22 kg / m ³ , kinematic viscosity: 3.07 × 10 ⁻⁷ m ² / s) and Nicklaus's equation (described later), the relationship between the flow rate and the pressure loss (total flow rate: 0.0483 kg / s) is calculated. For example, the refrigerant flowing in the oil return pipe having a tube diameter of 3.18 mm is Less than 1% of the total. As an effect of bypassing the gas refrigerant to the oil return pipe, the pressure loss reduction rate of the first gas side connection pipe is less than 1%.

  The pressure loss Δp can be expressed by (Formula 1).

Δp = λ × l / d × ρv 2/2 ......... ( Equation 1)
Further, the pipe friction coefficient λ can be expressed by the Nikrose expression of (Expression 2).

λ = 0.0032 + 0.221 / Re ^0.237 (Formula 2)
Patent Document 1 describes an example in which the refrigerant pipe is about 16 mm and the oil return pipe is about 4 to 5 mm, and the ratio of the inner diameter cross-sectional area is about 3 to 6%, which is slightly larger than 2%. However, the effect of bypassing the gas refrigerant is similarly small.

On the other hand, the ratio of the inner diameter cross-sectional area of the second gas-side connecting pipe 24 serving as the oil return flow path of the present embodiment to the first gas-side connecting pipe 23 having a pipe diameter of 6.35 mm (inner diameter cross-sectional area of 18 mm ² ) is 19%.

  At this time, the refrigerant flowing through the second gas side connection pipe 24 is about 10% of the total, and as an effect of bypassing the gas refrigerant to the second gas side connection pipe 24, the pressure loss of the first gas side connection pipe is reduced. The rate is 16% and the effect is great. When the pressure loss is reduced by 10%, the inner diameter cross-sectional area of the second gas side connection pipe 24 and the first gas side connection pipe 23 is 12%, and the effect of reducing the pressure loss of the gas refrigerant can be obtained. By flowing the gas refrigerant through the second gas side connection pipe 24, the amount of the gas refrigerant flowing through the first gas side connection pipe 23 can be reduced to reduce the pressure loss, and the energy efficiency can be improved. it can. The gas refrigerant is distributed to the first gas side connection pipe 23 side flow path and the second gas side connection pipe 24 side flow path so that the pressure loss is balanced.

  FIG. 5 shows the pressure loss reduction ratio with respect to the pipe diameter of the second gas side connection pipe when the pipe diameter of the first gas side connection pipe is 12.7 mm (wall thickness: 0.8 mm). FIG. 6 shows the pipe friction coefficient with respect to the pipe diameter of the second gas side connection pipe. As shown in FIG. 5, the pressure loss reduction rate is low when the diameter of the second gas side connection pipe 24 is 6 mm (thickness 0.8 mm) or less, and the pressure loss reduction rate is greatly improved when the pipe diameter exceeds 6 mm. To do. This is because, as shown in FIG. 6, when the pipe diameter of the second gas side connection pipe 24 is 6 mm or less, the pipe friction coefficient of the second gas side connection pipe 24 is large. Therefore, in order to obtain not only the refrigerating machine oil but also the gas refrigerant through the oil return flow path to obtain the effect of reducing the pressure loss, the inner diameter cross-sectional area of the second gas side connection pipe 24 is the first gas side connection. It is desirable to make it approximately 15% or more of the inner diameter cross-sectional area of the pipe 23.

  Another embodiment of the present invention will be described with reference to FIG. The air conditioner 101 shown in FIG. 4 is obtained by separating the oil separator 19 from the indoor unit 2. Equivalent parts are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 4 is a system diagram of the air conditioner 101. The outer pipe 30 of the oil separator 19 is connected to the indoor gas side connection port 40b of the indoor unit 2, and the inner pipe 31 is connected to the first gas side connection pipe 23 via the first oil separator gas side connection port 41a. The oil return port 32 is connected to the second gas side connection pipe 24 via the second oil separator gas side connection port 41b. Moreover, the Y-shaped tube 43 is connected to the first gas-side connecting pipe 23 via the first Y-shaped tube gas side connection port 42a, and via the second Y-shaped tube gas side connection port 42b. It is connected to the second gas side connection pipe 24 and is connected to the outdoor gas side pipe 25 through the outdoor gas side connection port 40a.

  During the cooling operation, the refrigerant in the indoor gas side pipe 18 on the outlet side of the indoor heat exchanger 17 contains refrigeration oil, the refrigeration oil flows along the wall surface of the pipe, and the gas refrigerant flows in the center of the pipe. The refrigerant composed of these gas refrigerant and refrigerating machine oil is oil-separated in an oil separator 19 having a double pipe structure arranged outside the indoor unit, and the gas refrigerant separated from the oil is supplied to the first gas side connection pipe. 23, the Y-shaped pipe 43, the outdoor gas side pipe 25, and the four-way valve 12 are returned to the compressor 11 again. The separated refrigerating machine oil passes through the second gas side connection pipe 24 and merges with the gas refrigerant at the Y-shaped pipe 43. It should be noted that the second gas side connection pipe 24 is composed only of refrigerating machine oil so that the pressure loss between the first gas side connection pipe 23 side flow path and the second gas side connection pipe 24 side flow path is balanced. Gas refrigerant also flows.

  During the heating operation, the gas refrigerant compressed by the compressor 11 and having become high temperature and high pressure passes through the four-way valve 12 and is divided by the Y-shaped pipe 43, one of which is the first gas side connection pipe 23 and the oil separator 19. The other flows into the second gas side connection pipe 24 and the oil separator 19. The flow rate ratio of the gas refrigerant in the first gas side connection pipe 23 side flow path and the second gas side connection pipe 24 side flow path is a flow rate ratio in which pressure loss is balanced. At this time, the oil separator 19 does not perform oil separation.

  At this time, since the oil separator 19 is provided separately from the indoor unit 2, an oil separator and a Y-shaped pipe are added to the conventional unit, and pressure loss is reduced by using two connecting pipes. , Energy efficiency can be improved.

  Further, by applying the reduced pressure loss of the gas side connection pipe to the diameter reduction of the gas side connection pipe, the piping space can be reduced and the workability can be improved since the pipe diameter is small.

  In the present embodiment, the oil separator having a double pipe structure has been described, but the present invention is not limited to this structure.

  The air conditioner of the present invention is an air in which a compressor, a four-way valve, an outdoor heat exchanger, an expansion valve, a liquid side connection pipe, an indoor heat exchanger, and a gas side connection pipe are connected by a refrigerant pipe. In the harmony device, an oil separator was provided between the indoor heat exchanger and the gas side connection pipe, and the oil return pipe of the oil separator was connected to the refrigerant pipe between the gas side connection pipe and the four-way valve.

  Further, the inner diameter cross-sectional area of the oil return pipe of the oil separator was set to about 15% or more of the inner diameter cross-sectional area of the gas side connection pipe.

  Further, during the cooling operation, the refrigeration oil and the refrigerant are circulated from the oil return pipe of the oil separator to the refrigerant pipe between the gas side connection pipe and the four-way valve, and during the heating operation, the refrigeration oil and the refrigerant are connected to the gas side connection pipe. The refrigerant pipe between the four-way valve is circulated to the oil return pipe of the oil separator.

  The oil separator has a double pipe structure, and the oil return pipe of the oil separator is an outer pipe having a double pipe structure.

DESCRIPTION OF SYMBOLS 1 Outdoor unit 2 Indoor unit 11 Compressor 12 Four-way valve 13 Outdoor heat exchanger 14 Expansion valve 15 Liquid side connection piping 17 Indoor heat exchanger 19 Oil separators 23 and 24 Gas side connection piping 43 Y-shaped pipes 100 and 101 Air conditioning Equipment λ Pipe friction coefficient l Length d Pipe inner diameter ρ Density v Speed Re Reynolds number

Claims (3)

In an air conditioner in which a compressor, a four-way valve, an outdoor heat exchanger, an expansion valve, a liquid side connection pipe, an indoor heat exchanger, and a gas side connection pipe are connected by a refrigerant pipe.
An oil separator is provided between the indoor heat exchanger and the gas side connection pipe,
Connecting an oil return pipe of the oil separator to a refrigerant pipe between the gas side connection pipe and the four-way valve ;
During cooling operation, refrigeration oil and refrigerant are circulated from the oil return pipe of the oil separator to the refrigerant pipe between the gas side connection pipe and the four-way valve,
An air conditioner in which refrigeration oil and refrigerant are circulated from the refrigerant pipe between the gas side connection pipe and the four-way valve to the oil return pipe of the oil separator during heating operation .   The air conditioner according to claim 1, wherein an inner diameter cross-sectional area of the oil return pipe of the oil separator is approximately 15% or more of an inner diameter cross-sectional area of the gas side connection pipe. The oil separator has a double pipe structure,
The air conditioner according to claim 1 or 2 , wherein the oil return pipe of the oil separator is an outer pipe having a double pipe structure.