JP6828176B2 - Multi-type air conditioning system and indoor unit - Google Patents

Description

Embodiments of the present invention relate to multi-type air conditioning systems and indoor units.

For example, in a multi-type air conditioning system in which a plurality of indoor units are connected to one outdoor unit, the amount of refrigerant supplied to each indoor unit changes every moment depending on the room temperature or the usage status of the indoor units. Therefore, the refrigerant supplied from the outdoor unit to the indoor unit may change from a liquid phase flow to a gas-liquid two-phase flow state depending on the flow condition of the refrigerant with respect to the plurality of indoor units.

It is known that when a gas-liquid two-phase flow refrigerant flows into an expansion valve of an indoor unit, a jarring refrigerant flow noise is generated. That is, the refrigerant flow noise depends on the flow mode of the gas-liquid two-phase flow, and the slag flow or floss flow in which non-uniform bubbles are intermittently present in the refrigerant flow is an expansion valve accompanied by pressure pulsation. When it flows into the air, a loud abnormal noise is intermittently generated from the expansion valve.

In order to reduce the refrigerant flow noise generated by the expansion valve, in the conventional indoor unit, the diameter of the expansion valve may be smaller than the inner diameter of the refrigerant pipe, or the refrigerant pipe may be located upstream of the expansion valve. It has been tried to provide a branching / merging portion in which the flow of the refrigerant is once branched into a plurality of parts and then merged again.

According to this configuration, the flow of the refrigerant guided to the expansion valve shifts from the slag flow or the flog flow to a more stable continuous flow, and the refrigerant flow noise caused by the gas-liquid two-phase flow can be reduced.

Japanese Unexamined Patent Publication No. 9-292166 Japanese Unexamined Patent Publication No. 9-318198

However, for example, when the rotation speed of the compressor that sends the refrigerant to the indoor unit decreases, or when the operation shifts to the defrosting operation during the heating operation, the sudden pressure change in the refrigerant piping causes the refrigerant to become gas-liquid two-phase. It is undeniable that it is difficult to suppress the refrigerant flow noise by simply reducing the diameter of the expansion valve when the above occurs.

Further, when the flow velocity of the refrigerant flowing through the refrigerant pipe is not sufficient, for example, when the multi-type air conditioning system is started or when the defrosting operation is started during the heating operation, the branch junction located on the upstream side of the expansion valve It is expected that it will be difficult to mix the gas and liquid sufficiently.

An object of the present invention is to obtain a multi-type air conditioning system having an indoor unit capable of reducing the refrigerant flow noise generated when the refrigerant flows into the expansion valve in a gas-liquid two-phase flow state and capable of quiet operation. It is in.

According to the embodiment, in the multi-type air conditioning system, an outdoor unit having an outdoor heat exchanger that exchanges heat between the refrigerant compressed by the compressor and air, and the refrigerant that has passed through the outdoor heat exchanger flow in. A plurality of indoor units having an expansion valve and an indoor heat exchanger for exchanging heat between the refrigerant decompressed by the expansion valve and air, and the plurality of indoor units connected in parallel to the outdoor unit. A refrigerant pipe through which a refrigerant circulating between the outdoor unit and the indoor unit flows is provided.

The refrigerant pipe located in the indoor unit has a plurality of capillaries at locations on the upstream side of the expansion valve along the flow direction of the refrigerant, and the capillaries are connected in parallel to the refrigerant pipe. .. Further provided are a branch pipe portion that connects the upstream ends of the plurality of capillaries and the refrigerant pipe, and a merging pipe portion that connects the downstream ends of the plurality of capillaries and the refrigerant pipe. There is. The branch pipe portion and the merging pipe portion have a positional relationship parallel to and facing each other, and a plurality of the capillaries are bridged between the branch pipe portion and the merging pipe portion.

FIG. 1 is a circuit diagram showing a refrigeration cycle of the multi-type air conditioning system according to the embodiment. FIG. 2 is a perspective view of a wall-mounted indoor unit used in a multi-type air conditioning system. FIG. 3 is a cross-sectional view of a wall-mounted indoor unit. FIG. 4 is a plan view of the indoor unit showing the positional relationship between the indoor heat exchanger, the expansion valve, and the capillary portion. FIG. 5 is a cross-sectional view of an expansion valve used in a multi-type air conditioning system. FIG. 6 is an enlarged plan view showing the capillary portion of FIG.

Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing a refrigeration cycle of a multi-type air conditioning system 1 used in, for example, a medium-low-rise building or a store building. The multi-type air conditioning system 1 according to the present embodiment includes one outdoor unit 2, three indoor units 3, and a refrigerant pipe 4 through which a refrigerant circulating between the outdoor unit 2 and the indoor unit 3 flows.

Specifically, the outdoor unit 2 includes a closed compressor 5, a four-way valve 6, an outdoor heat exchanger 7, a first expansion valve 8, and an accumulator 9. As shown in FIG. 1, the discharge port of the closed compressor 5 is connected to the first port 6a of the four-way valve 6. The second port 6b of the four-way valve 6 is connected to the outdoor heat exchanger 7. The outdoor heat exchanger 7 is connected to the first expansion valve 8. Further, the third port 6c of the four-way valve 6 is connected to the accumulator 9. The accumulator 9 is connected to the suction port of the sealed compressor 5 via a suction cup 10.

The three indoor units 3 are connected in parallel between the fourth port 6d of the four-way valve 6 and the first expansion valve 8. Each indoor unit 3 has a second expansion valve 12 and an indoor heat exchanger 13. The second expansion valve 12 is interposed between the first expansion valve 8 and the indoor heat exchanger 13, and is connected to the first expansion valve 8 and the indoor heat exchanger 13. The indoor heat exchanger 13 is connected to the fourth port 6d of the four-way valve 6.

When the multi-type air conditioning system 1 performs cooling operation, the four-way valve 6 switches so that the first port 6a communicates with the second port 6b and the third port 6c communicates with the fourth port 6d. When the cooling operation is started, the high-temperature, high-pressure vapor-phase refrigerant compressed by the closed compressor 5 is discharged to the refrigerant pipe 4. The high-temperature and high-pressure vapor-phase refrigerant is guided to the outdoor heat exchanger 7 that functions as a condenser via the four-way valve 6.

The gas-phase refrigerant guided to the outdoor heat exchanger 7 is condensed by heat exchange with the outdoor air sent from the blower fan 11 and changed to a high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant is depressurized in the process of passing through the first expansion valve 8 and then distributed to the three indoor units 3.

That is, the refrigerant that has passed through the first expansion valve 8 is depressurized again in the process of passing through the second expansion valve 12 of each indoor unit 3 and changes to a low-pressure gas-liquid two-phase flow. The gas-liquid two-phase refrigerant is guided to an indoor heat exchanger 13 that functions as an evaporator. The gas-liquid two-phase refrigerant guided to the indoor heat exchanger 13 exchanges heat with the indoor air sent from the blower fan 14 in the process of passing through the indoor heat exchanger 13.

As a result, the gas-liquid two-phase refrigerant takes heat from the indoor air and evaporates, and changes into a low-temperature / low-pressure gas-phase refrigerant. The air passing through the indoor heat exchanger 13 is cooled by the latent heat of vaporization of the liquid phase refrigerant, becomes cold air, and is blown into the room to be cooled.

The low-temperature / low-pressure vapor-phase refrigerant that has passed through the indoor heat exchanger 13 is sucked into the closed compressor 5 from the four-way valve 6 via the accumulator 9 and the suction cup 10. The vapor phase refrigerant sucked into the closed compressor 5 is compressed again into the high temperature and high pressure vapor phase refrigerant and discharged to the refrigerant pipe 4.

On the other hand, when the multi-type air conditioning system 1 performs the heating operation, the four-way valve 6 switches so that the first port 6a communicates with the fourth port 6d and the second port 6b communicates with the third port 6c. When the heating operation is started, the high-temperature and high-pressure vapor-phase refrigerant compressed by the closed compressor 5 is distributed to the indoor heat exchangers 13 of the three indoor units 3 via the four-way valve 6 and condensed. In the process of passing through the indoor heat exchanger 13 that functions as a container, heat is exchanged with the indoor air sent from the blower fan 14.

As a result, the gas phase refrigerant passing through the indoor heat exchanger 13 condenses by exchanging heat with the indoor air and changes to a high-pressure liquid phase refrigerant. The air passing through the indoor heat exchanger 13 is heated by heat exchange with the gas phase refrigerant, becomes warm air, and is blown into the room to be heated.

The high-pressure liquid-phase refrigerant that has passed through the indoor heat exchanger 13 is depressurized in the process of passing through the second expansion valve 12 and the first expansion valve 8 to change to a low-pressure gas-liquid two-phase flow. The gas-liquid two-phase refrigerant is guided to the outdoor heat exchanger 7 that functions as an evaporator, and evaporates by heat exchange with the outdoor air sent from the blower 11 here, and changes to a low-temperature / low-pressure vapor-phase refrigerant. .. The low-temperature / low-pressure vapor-phase refrigerant that has passed through the outdoor heat exchanger 7 is sucked into the closed compressor 5 from the four-way valve 6 via the accumulator 9 and the suction cup 10 as in the cooling operation.

If frost adheres to the outdoor heat exchanger 7 during the heating operation, the operation shifts to the defrosting operation for removing the frost. In the defrosting operation, the four-way valve 6 is switched from the heating operation to the cooling operation, and the blower fan 11 is stopped. As a result, the high-temperature vapor-phase refrigerant compressed by the closed compressor 5 is guided to the outdoor heat exchanger 7, and the frost adhering to the outdoor heat exchanger 7 is melted.

As shown in FIGS. 2 and 3, the indoor unit 3 of the present embodiment is a wall-mounted type installed on the upper surface of the wall surface W of the room R to be air-conditioned, and has a housing 20 fixed to the wall surface W. ing. The housing 20 is a box-shaped element having a front panel 21, a back panel 22, and left and right side panels 23. The housing 20 projects from the wall surface W into the room R to be air-conditioned, and extends laterally along the wall surface W.

Further, the housing 20 has a suction port 24 and an outlet 25. The suction port 24 is opened on the upper surface of the housing 20. The air outlet 25 is opened on the lower surface of the housing 20. The outlet 25 has a horizontal louver 26 that changes the conditioned air blowing direction in the vertical direction of the housing 20, and a plurality of vertical louvers 27 that change the conditioned air blowing direction in the horizontal direction of the housing 20. (Only one is shown) is arranged.

As shown in FIG. 3, the inside of the housing 20 is divided into a heat exchange chamber 28 and a pipe accommodating chamber 29. The heat exchange chamber 28 occupies a large area inside the housing 20, and the suction port 24 and the air outlet 25 are communicated with the heat exchange chamber 28. The pipe accommodating chamber 29 is separated from the heat exchange chamber 28 by being surrounded by the cover 30. The pipe accommodating chamber 29 is displaced to one side along the width direction of the housing 20 with respect to the heat exchange chamber 28, and is located behind the upper part of the heat exchange chamber 28.

The indoor heat exchanger 13, the blower fan 14, and the filter 33 are housed in the heat exchange chamber 28. The indoor heat exchanger 13 is a plate-shaped element that stands behind the front panel 21, and includes a plurality of cooling fins 34 and a plurality of heat transfer tubes 35 through which a refrigerant flows.

The cooling fins 34 extend in the height direction of the housing 20 and are arranged in a row at intervals in the width direction of the housing 20. The heat transfer tubes 35 are arranged at intervals in the height direction and the depth direction of the housing 20, and define a plurality of independent refrigerant flow paths (paths). Further, the heat transfer tube 35 is thermally connected to the cooling fin 34.

The blower fan 14 is arranged horizontally behind the indoor heat exchanger 13 in the width direction of the housing 20. Therefore, in the present embodiment, the indoor heat exchanger 13 is interposed between the blower fan 14 and the suction port 24 of the housing 20, and the air outlet 25 having the horizontal louver 26 and the vertical louver 27 directly below the blower fan 14 is provided. It is located.

The filter 33 is detachably supported in the heat exchange chamber 28 so as to face the front panel 21 and the suction port 24 of the housing 20. When the blower fan 14 starts operation, the air in the chamber R to be air-conditioned is sucked into the heat exchange chamber 28 from the suction port 24. The air sucked into the heat exchange chamber 28 is filtered by the filter 33 and then guided to the indoor heat exchanger 13. The air that has passed through the indoor heat exchanger 13 is discharged from the air outlet 25 into the room R to be air-conditioned after the blowing direction is changed by the vertical louver 27 and the horizontal louver 26.

As shown in FIGS. 3 and 4, the second expansion valve 12 and the liquid side pipe 37 are housed in the pipe storage chamber 29 of the housing 20. The liquid side pipe 37 constitutes a portion of the refrigerant pipe 4 that connects the first expansion valve 8 and the indoor heat exchanger 13 of the indoor unit 3.

As shown in FIGS. 4 and 5, the second expansion valve 12 is connected to the intermediate portion of the liquid side pipe 37. The second expansion valve 12 divides the liquid side pipe 37 into an inlet pipe portion 37a and an outlet pipe portion 37b. The inlet pipe portion 37a and the outlet pipe portion 37b extend horizontally in the pipe accommodating chamber 29 in the width direction of the housing 20, and are arranged parallel to each other in the height direction of the housing 20. The downstream end of the inlet pipe portion 37a is bent upward at a right angle.

The second expansion valve 12 includes a valve body 40 and a drive unit 41. A refrigerant passage 42 is formed inside the valve body 40. The refrigerant passage 42 has a refrigerant introduction section 42a and a refrigerant lead-out section 42b. The downstream end of the inlet pipe portion 37a of the liquid side pipe 37 is connected to the refrigerant introduction portion 42a. The upstream end of the outlet pipe portion 37b of the liquid side pipe 37 is connected to the refrigerant lead-out portion 42b.

Further, the refrigerant introduction section 42a and the refrigerant lead-out section 42b intersect with each other inside the valve body 40. A valve seat 43 is formed at a position where the refrigerant introducing portion 42a and the refrigerant leading portion 42b intersect.

The valve body 40 of the present embodiment has a needle support portion 44 projecting toward the side opposite to the refrigerant lead-out portion 42b. A needle insertion hole 45 is formed inside the needle support portion 44. The needle insertion hole 45 is positioned coaxially with the refrigerant lead-out portion 42b.

The needle 47 as a valve body is slidably inserted into the needle insertion hole 45 in the axial direction. The needle 47 is movably supported by the needle support portion 44 between the fully closed position and the open position.

In the fully closed position, the tapered head 47a located at one end along the axial direction of the needle 47 is seated on the valve seat 43, blocking the communication between the refrigerant introduction portion 42a and the refrigerant lead-out portion 42b. In the open position, the head 47a of the needle 47 is separated from the valve seat 43, and the passage area between the head 47a and the valve seat 43 is increased or decreased. As a result, the flow rate of the refrigerant flowing from the refrigerant introduction section 42a toward the refrigerant lead-out section 42b is controlled.

The drive unit 41 of the second expansion valve 12 is an element that moves the needle 47 in the axial direction, and includes a motor 48 and an electromagnet 49 as main elements. The motor 48 is fixed to a tubular rotor portion 51 screwed into the outer peripheral surface of the needle support portion 44, a tubular spacer 52 fitted to the outer peripheral surface of the rotor portion 51, and an outer peripheral surface of the spacer 52. It has an electromagnet 53 and. The tip of the rotor portion 51 is connected to the end portion 47b of the needle 47 opposite to the head portion 47a via an engaging element 54.

Further, the motor 48 is covered with the case 55 together with the needle support portion 44. The electromagnet 49 surrounds the electromagnet 53 from the outside of the case 55.

The rotor portion 51 of the motor 48 rotates according to the amount of electricity applied to the electromagnet 49. Since the rotor portion 51 is screwed into the needle support portion 44, it moves in the axial direction of the needle support portion 44 by rotating. When the movement of the rotor portion 51 is transmitted to the needle 47, the needle 47 linearly moves between the fully closed position and the open position. As a result, the flow rate of the refrigerant flowing from the refrigerant introduction section 42a to the refrigerant lead-out section 42b is controlled.

As shown in FIGS. 4 and 6, a capillary portion 60 is provided in the middle of the inlet pipe portion 37a of the liquid side pipe 37. The capillary portion 60 is located on the upstream side of the second expansion valve 12 along the flow direction of the refrigerant during the cooling operation.

The capillary portion 60 includes two capillaries 61a and 61b, a branch pipe portion 62, and a merging pipe portion 63. The capillaries 61a and 61b are each composed of straight pipes having a predetermined length L and an inner diameter d2. In the present embodiment, the length L of the capillaries 61a and 61b is set to 80 mm, and the inner diameter d2 of the capillaries 61a and 61b is set to 2 mm.

The branch pipe portion 62 has one first connection port 64 to which the liquid side pipe 37 is connected, and a pair of second connection ports 65a and 65b branched from the first connection port 64 into two. Have. The merging pipe portion 63 has one third connection port 66 to which the inlet pipe portion 37a is connected, and a pair of fourth connection ports 67a and 67b branched from the third connection port 66. Have.

One capillary 61a is bridged between the second connection port 65a of the branch pipe portion 62 and the fourth connection port 67a of the merging pipe portion 63. The other capillary 61b is bridged between the second connection port 65b of the branch pipe portion 62 and the fourth connection port 67b of the merging pipe portion 63. Therefore, the capillaries 61a and 61b are arranged in parallel with the inlet pipe portion 37a of the liquid side pipe 37 so as to be parallel to each other with a gap in the height direction of the housing 20, for example.

In the present embodiment, the inner diameters d2 of the capillaries 61a and 61b are set to be equal to or larger than the diameter d1 of the refrigerant introduction portion 42a of the second expansion valve 12, and are set to be equal to or larger than the diameter d1 of the refrigerant introduction portion 42a. It is set smaller than the inner diameter d3 of the portion 37a. Further, d1, d2 and d3 are obtained when the number of capillaries 61a and 61b is n.
d1 <d2 × n <d3
It is desirable to satisfy the relationship of.

As shown in FIG. 4, the outlet pipe portion 37b of the liquid side pipe 37 is connected to a plurality of branch pipes 71 via a distributor 70. The branch pipe 71 corresponds to the number of a plurality of refrigerant flow paths (passes) included in the indoor heat exchanger 13, and the branch pipe 71 is connected to the inlet of the refrigerant flow path.

Further, the outlets of the plurality of refrigerant flow paths (paths) of the indoor heat exchanger 13 are merged into one by the header 72 and then connected to the gas side pipe 73 via the header 72. The gas side pipe 73 constitutes a portion of the refrigerant pipe 4 that connects the indoor heat exchanger 13 of the indoor unit 3 and the fourth port 6d of the four-way valve 6.

In a state in which the multi-type air conditioning system 1 is being cooled, the refrigerant that has passed through the first expansion valve 8 is in a flow mode in which non-uniform bubbles are intermittently contained in the flow, for example, a slag flow. If there is, an unpleasant refrigerant flow noise is generated when the refrigerant passes through the gap between the head portion 47a of the needle 47 of the second expansion valve 12 and the valve seat 43.

In the indoor unit 3 of the present embodiment, a capillary portion 60 having two capillaries 61a and 61b is provided upstream of the second expansion valve 12 along the flow direction of the refrigerant. Therefore, when the gas-liquid two-phase flow refrigerant containing non-uniform bubbles reaches the capillary portion 60, the refrigerant is branched into two flows at the branch pipe portion 62 and then flows into the capillaries 61a and 61b.

Since the inner diameter d2 of the capillaries 61a and 61b is smaller than the inner diameter d3 of the inlet pipe portion 37a of the liquid side pipe 37, the flow velocity of the refrigerant branched into the two flows increases due to the drawing effect of the capillaries 61a and 61b.

As a result, the flow of the refrigerant passing through the capillaries 61a and 61b is changed from the slag flow to the stable spray flow flow mode. That is, as the flow velocity increases, the flow of the refrigerant becomes continuous, and the intermittent flow of the refrigerant that causes the generation of the refrigerant flow noise is eliminated.

Further, the refrigerants that have transitioned to the continuous spray flow in the process of passing through the capillaries 61a and 61b merge with each other at the merging pipe portion 63. As a result, the mixing of gas and liquid contained in the refrigerant is promoted, and the bubbles contained in the refrigerant from the merging pipe portion 63 to the second expansion valve 12 can form a uniform flow of the refrigerant. it can.

As a result, when the refrigerant reaches the vicinity of the gap between the head 47a of the needle 47 of the second expansion valve 12 and the valve seat 43, the refrigerant has fine bubbles that are evenly continuous in the liquid. It is possible to shift to a flow mode in which the refrigerant is mixed in, and to suppress the pressure change when the refrigerant passes through the gap.

Therefore, even if the flow velocity of the gas-liquid two-phase flow refrigerant flowing through the liquid side pipe 37 is not sufficient, for example, when the multi-type air conditioning system 1 is started or when the heating operation is shifted to the defrosting operation, the indoor unit 3 The refrigerant flow noise generated by the second expansion valve 12 of the above can be efficiently reduced, and quiet operation becomes possible.

Moreover, in the present embodiment, the diameter of the second expansion valve 12 is d1, the inner diameters of the capillaries 61a and 61b are d2, the inner diameter of the inlet pipe portion 37a of the liquid side pipe 37 is d3, and the number of capillaries 61a and 61b is n. When you do
d1 <d2 × n <d3
Meet the relationship.

As a result, it is possible to sufficiently secure the total passage cross-sectional area of the capillaries 61a and 61b with respect to the diameter d1 of the second expansion valve 12, and to reduce unnecessary pressure loss when the refrigerant passes through the capillaries 61a and 61b. Can be prevented.

In addition, since the inner diameter d2 of the individual capillaries 61a and 61b is smaller than the inner diameter d3 of the inlet pipe portion 37a of the liquid side pipe 37, the effect of squeezing the refrigerant by the capillaries 61a and 61b can be sufficiently exerted. Therefore, the flow velocity of the refrigerant passing through the capillaries 61a and 61b increases, which is convenient for making the flow of the refrigerant guided to the second expansion valve 12 more uniform.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

For example, the number of outdoor units of a multi-type air conditioning system is not limited to one, and may be two or three, and the number of outdoor units and indoor units is not particularly limited.

Further, in the above-described embodiment, the number of capillaries is two, but there is no restriction on the number of capillaries. At the same time, the inner diameters of the capillaries do not have to be the same as each other, and the inner diameters of the plurality of capillaries may be different from each other as long as the inner diameter is smaller than the inlet pipe portion of the liquid side pipe.

In addition, the capillaries are not limited to being arranged horizontally, and if a sufficient space can be secured in the housing, for example, the capillaries may be erected in the housing.

1 ... Multi-type air conditioning system, 2 ... Outdoor unit, 3 ... Indoor unit, 4 ... Refrigerant piping, 5 ... Compressor (sealed compressor), 7 ... Outdoor heat exchanger, 12 ... Expansion valve (second expansion valve) ), 13 ... Indoor heat exchanger, 61a, 61b ... Capillary.

Claims (8)

An outdoor unit having an outdoor heat exchanger that exchanges heat between the refrigerant compressed by the compressor and air, and
It has an expansion valve into which the refrigerant that has passed through the outdoor heat exchanger flows in, and an indoor heat exchanger that exchanges heat between the refrigerant decompressed by the expansion valve and air, and is exposed in the room to be air-conditioned. With multiple indoor units
In a multi-type air conditioning system provided with a plurality of indoor units connected in parallel to the outdoor unit and a refrigerant pipe through which a refrigerant circulating between the outdoor unit and the indoor unit flows.
The refrigerant pipe located in the indoor unit has a plurality of capillaries at a location on the upstream side of the expansion valve along the flow direction of the refrigerant, and the capillaries are connected in parallel to the refrigerant pipe .
Further, a branch pipe portion connecting the upstream ends of the plurality of capillaries and the refrigerant pipes, and a merging pipe portion connecting the downstream ends of the plurality of capillaries and the refrigerant pipes are further provided.
The branch pipe portion and the confluence pipe portion have a positional relationship parallel to and facing each other.
The plurality of capillaries are a multi-type air conditioning system that is bridged between the branch pipe portion and the confluence pipe portion . The multi-type air conditioning system according to claim 1, wherein the capillary is a straight pipe having a predetermined overall length and increases the flow velocity of the refrigerant flowing toward the expansion valve. The multi-type air-conditioning system according to claim 2, wherein the indoor unit is a wall-mounted type exposed in a room to be air-conditioned, and a plurality of the capillaries are horizontally arranged at intervals from each other. When the diameter of the expansion valve is d1, the inner diameter of the capillary is d2, the inner diameter of the refrigerant pipe connected to the branch pipe is d3, and the number of capillaries is n.
d1 <d2 × n <d3
The multi-type air conditioning system according to claim 1 , which satisfies the above relationship. During the cooling operation and the defrosting operation, the flow of the refrigerant that has passed through the outdoor heat exchanger is branched into the plurality of capillaries, and the expansion valve is in a state where the refrigerants that have passed through the plurality of capillaries merge with each other. The multi-type air conditioning system according to claim 1, which is guided by the above. Expansion valve and
A refrigerant pipe that guides the refrigerant heat exchanged by the outdoor unit to the expansion valve,
It has an indoor heat exchanger that exchanges heat with the refrigerant decompressed by the expansion valve.
A plurality of capillaries connected in parallel to the refrigerant pipe are provided at a portion of the refrigerant pipe on the upstream side of the expansion valve along the flow direction of the refrigerant .
Further, a branch pipe portion connecting the upstream ends of the plurality of capillaries and the refrigerant pipes, and a merging pipe portion connecting the downstream ends of the plurality of capillaries and the refrigerant pipes are further provided.
The branch pipe portion and the confluence pipe portion have a positional relationship parallel to and facing each other.
The plurality of capillaries are indoor units that are bridged between the branch pipe portion and the confluence pipe portion . The indoor unit according to claim 6 , wherein the capillary is a straight pipe having a predetermined overall length, and increases the flow velocity of the refrigerant flowing toward the expansion valve. When the diameter of the expansion valve is d1, the inner diameter of the capillary is d2, the inner diameter of the refrigerant pipe connected to the branch pipe is d3, and the number of capillaries is n.
d1 <d2 × n <d3
6. The indoor unit according to claim 6 .

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