JP2765243B2 - Air conditioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner in which a plurality of indoor units are connected in parallel to one outdoor unit, and more particularly to a measure for reducing the amount of refrigerant charged.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Utility Model Laid-Open No. 1-1266.
As disclosed in No. 1, a plurality of indoor units are arranged for one outdoor unit, and each device of the outdoor unit is connected by a main pipe, while each device of the indoor unit is connected by a branch pipe, A so-called multi-type air conditioner in which each branch pipe is connected in parallel to a main pipe to form a closed circuit refrigerant circuit is a known technique.

[0003]

By the way, in the above-mentioned conventional multi-type air conditioner, it is desirable that the state of the refrigerant immediately before the expansion valve in each indoor unit during the cooling operation is uniform, and furthermore, that each utilization side heat is used. In order for the exchanger to exhibit sufficient capacity, its refrigerant state needs to be within a certain range. For this reason, in order to minimize the pressure loss in the liquid pipe, a system is generally adopted in which the refrigerant pipe is sufficiently kept warm and the liquid refrigerant is circulated through the pipe in a single phase. However, in recent years, there has been a strong demand to reduce the amount of refrigerant used. However, when all the pipes are circulated in a liquid single-phase flow as described above, especially in a multi-type air conditioner, the pipe length reaches several tens of meters. Therefore, the amount of refrigerant charged becomes enormous, and it is difficult to reduce the amount of refrigerant charged.

[0004] On the other hand, it is conceivable to reduce the amount of refrigerant by flowing a gas-liquid two-phase flow through the main pipe on the liquid side. However, in the case of the multi-type air conditioner as described above, the main pipe is connected to the branch pipe. When the refrigerant is diverted into the two-phase flow, it is very difficult to distribute the gas-liquid ratio uniformly in the two-phase flow, that is, it is very difficult to distribute the void ratio to each branch pipe. There was a problem that a special device was required.

[0005] The present invention has been made in view of such a point, and an object thereof is to make a single-phase flow of only a liquid refrigerant in a main pipe, a gas-liquid two-phase flow in a branch pipe, and furthermore, in each indoor unit. An object of the present invention is to reduce the amount of charged refrigerant while maintaining a good air conditioning function by making the refrigerant state uniform.

[0006]

In order to achieve the above object, the means of the present invention is, as shown in FIG. 1, composed of a compressor (1), a heat source side heat exchanger (3) and an outdoor unit. A plurality of indoor units (A) having an indoor pressure reducing valve (6a) and a use-side heat exchanger (7a) are arranged with respect to the outdoor unit (X) provided with the pressure reducing valve (4), The devices (1), (3), (4) of the outdoor unit (X) are sequentially connected by the main pipe (9) of the refrigerant pipe, while the devices (6a) of the indoor units (A),. (7a),... Are connected by branch pipes (9a),.
It is assumed that the air conditioner includes a refrigerant circuit (10) in which the branch pipes (9a) are connected in parallel to the main pipe (9).

The branch pipes (9a),.
In the vicinity of the liquid side branch that branches off from the liquid pipe of the main pipe (9)
During the cooling operation, the refrigerant is depressurized and each branch pipe is
(9a), ... and the branch pipe (9a),
… Composed so that the longer the length, the lower the degree of decompression of the refrigerant
, The decompression mechanisms (20a),.
The configuration is as follows.

[0008] The means adopted by the invention of claim 2 is that, in the invention of claim 1, the degree of decompression of each decompression mechanism (20a),... Is determined by the use side heat exchanger (7) of the indoor unit (A),.
a),... are set lower as the capacity is larger.

The means adopted by the invention of claim 3 is the same as that of claim 1 or 2 except that each of the pressure reducing mechanisms (20a),.
Are set higher as the diameter of the branch pipes (9a),... Is larger.

[0010]

According to the first aspect of the present invention, during the cooling operation of the air conditioner, the refrigerant condensed and liquefied by the heat source side heat exchanger (3) flows through the main pipe (9) as a liquid single-phase flow. After that, it branches into each branch pipe (9a),... And flows into each indoor unit (A),. At that time, each branch pipe (9a) ~
The refrigerant is decompressed at the branch between (9c) and the main pipe (9),
Since the pressure reducing mechanisms (20a),... For flowing the liquid two-phase flow to the branch pipes (9a),... Are provided, a part of the liquid refrigerant is evaporated and liquefied, and then flows in a gas-liquid two-phase flow. Therefore,
The amount of refrigerant charged in the entire air conditioner is reduced.

In this case, the longer the length of the branch pipes (9a),..., The greater the pressure loss, and especially in the case of a gas-liquid two-phase flow,
The refrigerant state such as the pressure immediately before each indoor pressure reducing valve (6a),... Greatly changes due to the difference in pressure loss. In the present invention, the longer the length of the branch pipes (9a),.
Are set so as to reduce the degree of pressure reduction in the structures (20a),..., The difference in pressure loss in each branch pipe (9a),. Are made substantially uniform, and the capacity of each use-side heat exchanger (7a),. Therefore, the branch pipe (9
a), even if there is a difference in the piping length, the air conditioning function in each indoor unit (A),... by setting the degree of decompression of the pressure reducing mechanisms (9a),. , And the amount of refrigerant charged can be reduced.

According to the second aspect of the present invention, when there is a difference between the capacities of the use side heat exchangers (7a),... Of the indoor units (A),. However, the larger the capacity of the use side heat exchangers (7a),..., The lower the degree of decompression of each decompression mechanism (9a),. The air-conditioning capacity of each of the indoor units (A),... Is properly maintained.

According to the third aspect of the present invention, the branch pipes (9a),.
Are set higher as the diameter of the pressure reducing mechanisms (20a),... Is increased, the difference in pressure loss between the branch pipes (9a),. In conjunction with the adjustment of the pressure loss by the change, the indoor pressure reducing valve (6
a),... The refrigerant pressure immediately before is more finely equalized, and a smooth operation is ensured.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.
It will be described based on.

FIG. 1 shows a refrigerant piping system of an air conditioner according to an embodiment. A multi-unit in which three indoor units (A) to (C) are connected in parallel to one outdoor unit (X). It is configured in shape. In the outdoor unit (X),
A compressor (1) that compresses and discharges the sucked refrigerant, a four-way switching valve (2) whose connection switches as shown by the solid line in the cooling operation and a broken line in the heating operation as shown by the solid line in the cooling operation, and a condensate in the cooling operation A heat source side heat exchanger (3) that functions as an evaporator during the heating operation, and an outdoor electric expansion valve (4) that functions as an outdoor pressure reducing valve that reduces the pressure of the refrigerant during the heating operation.
And a receiver (5) for storing the liquid refrigerant and an accumulator (8) for removing the liquid refrigerant in the refrigerant sucked into the compressor (1). ,
The above devices are connected in series by a main pipe (9) of a refrigerant pipe.

On the other hand, each of the indoor units (A) to (C)
Have heat exchangers (7a) to (7c) having different capacities and functioning as an evaporator during the cooling operation and as a condenser during the heating operation, depressurizing the refrigerant during the cooling operation, and performing the heating operation during the heating operation. There are provided indoor electric expansion valves (6a) to (6c) as indoor pressure reducing valves for adjusting the flow rate of the refrigerant, and each device (6a) to (6c) of each of the indoor units (A) to (C) is provided. (7a) to (7c) are connected by branch pipes (9a) to (9c) of the refrigerant pipe, respectively. Further, the branch pipes (9a) to (9c) are connected to both ends of the main pipe (9). The liquid distributor (14) and the gas distributor (15) are connected in parallel with each other. That is, each of the main devices (1) to (8) of the air conditioner.
Is composed of a main pipe (9) and branch pipes (9a) to (9c).
A main refrigerant circuit (10) is sequentially connected to form a closed circuit and circulates refrigerant to generate heat transfer.

Here, as a characteristic of the present invention, each of the branch pipes (9a) to (9c) has a branch portion from the liquid distributor (14) (the inlet portion of the liquid refrigerant during the cooling operation). Capillary tubes (20a) to (20a) to (9a) to (9a) to (9a) to (9a) to (9a) to (9a) to (9a) to (7a) to (7a) to (7c). 2
0c) is provided. Each of the capillary tubes (2
0a), (20b) and (20c) are branch pipes (9a), (9b) and (9c) branching from a liquid flow divider (14) provided at the liquid side end of the main pipe (9) of the refrigerant pipe. Is provided at the inlet portion of the liquid refrigerant during the cooling operation, and the degree of decompression is set according to the inner diameter of each of the capillary tubes (20a), (20b), and (20c).
(B), (C) utilization side heat exchangers (7a), (7b),
(7c), each branch pipe (9a), (9b), (9
Table 1 below sets the diameter and length of c).

[0018]

[Table 1] However, in Table 1 above, L, LM, M, HM, and H indicate the degree of pressure reduction, and are described in order from the lower side. That is, as shown in Table 1 above, each capillary tube (2
0a), (20b), and (20c), the degree of decompression decreases as the length of the branch pipes (9a) to (9c) increases, and decreases as the capacity of the use-side heat exchangers (7a) to (7c) increases. The higher the diameter of the branch pipes (9a) to (9c), the higher the setting.

Therefore, in the above embodiment, during the cooling operation of the air conditioner, the refrigerant discharged from the compressor (1) flows through the main pipe (9) of the refrigerant pipe and condenses and liquefies in the heat source side heat exchanger (3). After being stored in the receiver (5), the liquid branches from the liquid distributor (14) to the branch pipes (9a) to (9c) and flows to the indoor units (A) to (C). After being throttled by each of the electric expansion valves (6a) to (6c) and evaporated by each of the use-side heat exchangers (7a) to (7c), the gas diverter (15)
, Flow into the outdoor unit (X), and accumulate
Return to the compressor (1) via the compressor (8). By repeating this circulation, the heat absorbed by the heat exchange with the indoor air in each of the use-side heat exchangers (7a) to (7c) is released to the outdoor air by the heat-source-side heat exchanger (3), and each of the indoor heat exchangers (7a) to (7c) is released. Perform air conditioning.

At this time, each of the branch pipes (9a) to (9)
Capillary tubes (20a) to (c) functioning as decompression mechanisms for decompressing the refrigerant to the branch pipes (9a) to (9c) respectively near the branching point with the liquid flow divider (14).
Since the liquid refrigerant (20c) is provided, part of the liquid refrigerant flowing in the liquid single-phase flow to the liquid flow divider (14) evaporates and liquefies,
Thereafter, it flows in a gas-liquid two-phase flow. Here, for example, in a building such as a building, branch pipes (9a) to (9a) of refrigerant pipes reaching each room.
Since the length of c) reaches several tens of meters, if the branch pipes (9a) to (9c) are filled with the liquid refrigerant as in the prior art, the amount of the refrigerant becomes enormous, and the amount of refrigerant used is reduced. We cannot respond to requests. On the other hand, as in the above-described embodiment, by flowing the gas through the branch pipes (9a) to (9c) in a gas-liquid two-phase flow, the refrigerant charging amount of the entire air conditioner can be reduced.

In this case, when the main pipe (9) up to the liquid distributor (14) is circulated in a gas-liquid two-phase flow, each branch pipe (9)
Although the distribution to a) to (9c) becomes difficult, such a problem does not occur because the liquid is a single-phase flow in the main pipe (9) on the liquid side as in the above embodiment.

Then, each of the above capillary tubes (20
a) A branch pipe (9a) in which the degree of reduced pressure of (20c) is arranged
The longer the length of ~ (9c) is, the lower it is set,
The difference in pressure loss in each of the branch pipes (9a) to (9c) is reduced. That is, the longer the length of the branch pipes (9a) to (9c), the greater the pressure loss. Particularly, in the case of a gas-liquid two-phase flow, the difference between the pressure losses causes the pressure in each of the indoor electric expansion valves (6a) to (6a) to
(6b) The refrigerant state (refrigerant pressure) immediately before changes greatly. For example, if the length of the branch pipes (9a) to (9c) is as long as 50 m or more, if the pipe length is long, the refrigerant pressure immediately before the electric expansion valve (6a) becomes extremely low due to pressure loss, and If the refrigerant pressure immediately before the use-side heat exchangers (9a) to (9c) is high, the flow rate of the refrigerant will drastically decrease. Therefore, the capacity of the use side heat exchangers (7a) to (7c) cannot be sufficiently exhibited. On the other hand, the branch pipe (9a)
By adjusting the degree of pressure reduction as described above according to the length of (9c) to (9c), the difference in pressure loss is compensated, and the refrigerant pressure of each indoor electric expansion valve (6a) to (6c) is made substantially uniform. hand,
The capacity of each use side heat exchanger (7a) to (7c) is properly exhibited. Therefore, the refrigerant charging amount can be reduced while maintaining the air conditioning function in each of the indoor units (A) to (C) satisfactorily.

In particular, such a difference in pressure loss due to the difference in refrigerant pipe length can be achieved by changing the pipe diameter. However, preparing refrigerant pipes having various types of diameters increases costs. Connect. On the other hand, by compensating for the difference in pressure loss with the degree of reduced pressure that can be easily adjusted by the difference in inner diameter and length of the capillary tubes (20a) to (20c), cost increase is suppressed. .

When there is a difference in capacity between the use side heat exchangers (7a) to (7c) of the indoor units (A) to (C),
The greater the capacity of each of the utilization side heat exchangers (7a) to (7c), the greater the amount of refrigerant circulation required to maintain the same refrigerant state. Therefore, each use side heat exchanger (7a) to (7a)
By reducing the degree of decompression as the volume of c) increases,
The required amount of the refrigerant circulating in each of the use-side heat exchangers (7a) to (7c) is ensured, and the capacity is sufficiently exhibited.

Further, as the diameter of each of the branch pipes (9a) to (9c) increases, the pressure loss decreases. Therefore, as the diameter of each of the branch pipes (9a) to (9a) increases, the capillary tubes (20a) to (9a). By increasing the degree of pressure reduction in 20c), it is possible to compensate for the pressure loss difference between the branch pipes (9a) to (9c). In particular, branch pipes (9a) to (9c)
The pressure loss can be adjusted by changing the pipe diameter in accordance with the length of the pipe, but as described above, preparing many types of pipes whose diameters are slightly different from each other increases the cost, As shown in Table 1 above, while the pressure loss is roughly adjusted with several types of pipe diameters, the degree of decompression of each of the capillary tubes (20a) to (20c) is set.
Along with the adjustment by the pipe diameter, the difference in pressure loss can be finely compensated. Therefore, the indoor electric expansion valve (6a)-
(6c) The refrigerant pressure immediately before can be made more uniform, and smooth operation can be ensured.

In the above embodiment, an example was described in which the present invention was applied to an air conditioner of a so-called header-branch system in which flow splitters (14) and (15) were arranged at both ends of a main pipe (9). The present invention is not limited to such an embodiment. FIG. 3 shows a modification of the above embodiment, in which the present invention is applied to a so-called line type air conditioner in which each of the branch pipes (9a) to (9c) branches from the middle of the main pipe (9). It is the same as the above embodiment except that the points 14) and 15) are not provided.

Also in this modified example, as in the above embodiment, each of the branch pipes (9a) to (9b) depends on the length and diameter and the capacity of the use-side heat exchangers (7a) to (7c). By setting the degree of pressure reduction of the capillary tubes (20a) to (20c), the same effect as in the above embodiment can be obtained.

The pressure reducing mechanism of the present invention is not limited to the capillary tube, and FIG. 2 shows an example in which a nozzle is used as the pressure reducing mechanism. FIG. 4 shows a modified example thereof,
This is an example in which a branch pipe (9a) is divided at a large diameter part in the middle, and an outer diameter part of a capillary tube (20a) is fitted to each divided end. Also in this case, it is needless to say that the section of the liquid single-phase flow can be extremely short and the same effect of reducing the refrigerant charge as in the above embodiment can be exhibited.

[0029]

As described above, according to the first aspect of the present invention, each device of the outdoor unit of the air conditioner is connected to the main pipe while each device of the indoor unit is connected to the main pipe. On the other hand, the branch pipes are connected in parallel with each other to form a refrigerant circuit, and in the vicinity of the liquid side branch from the main pipe of each branch pipe , the refrigerant is depressurized during the cooling operation to form a gas-liquid two-phase flow.
A decompression mechanism for flowing into each branch pipe is provided, and the degree of decompression of each decompression mechanism is set to be lower as the length of the branch pipe is longer. Refrigerant charge can be reduced by flowing in a gas-liquid two-phase flow, and the refrigerant state immediately before each indoor pressure reducing valve is compensated by compensating for the difference in pressure loss based on the pipe length difference without finely changing the pipe diameter. Can be made substantially uniform, so that
The refrigerant charging amount can be reduced while maintaining the air-conditioning function of each indoor unit satisfactorily.

According to the second aspect of the present invention, in the first aspect of the present invention, the degree of decompression of each decompression mechanism is set to be lower as the capacity of the use side heat exchanger is larger. Even when there is a difference between the capacities of the side heat exchangers, the refrigerant state of each use side heat exchanger can be properly maintained, so that the air conditioning capacity of each indoor unit can be maintained well.

According to the third aspect of the present invention, in the first or second aspect of the present invention, the degree of pressure reduction of the pressure reducing mechanism is set to be higher as the diameter of the branch pipe becomes larger, so that the pressure is reduced as the diameter increases. The difference in pressure loss between each branch pipe is compensated,
Together with the adjustment of the pressure loss by changing the diameter, the refrigerant pressure immediately before the indoor pressure reducing valve can be more finely uniformed,
Therefore, a remarkable effect can be exhibited.

[Brief description of the drawings]

FIG. 1 is a refrigerant piping system diagram of an air conditioner according to an embodiment.

FIG. 2 is a longitudinal sectional view showing a structure when a nozzle is used for a pressure reducing mechanism.

FIG. 3 is a refrigerant piping system diagram of an air conditioner according to a modification of the embodiment.

FIG. 4 is a longitudinal sectional view showing a structure of a modified example when a nozzle is used for a pressure reducing mechanism.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 3 Heat source side heat exchanger 4 Outdoor electric expansion valve (outdoor decompression valve) 6 Indoor electric expansion valve (indoor decompression valve) 9 Main pipe 9a-9c Branch pipe 10 Refrigerant circuit 20a-20c Capillary tube (decompression mechanism)

Claims (3)

(57) [Claims] 1. An indoor pressure reducing valve (6a) and a use side heat are supplied to an outdoor unit (X) provided with a compressor (1), a heat source side heat exchanger (3) and an outdoor pressure reducing valve (4). Exchanger (7
a), a plurality of indoor units (A),... having the respective units (1), (3),
(4) are sequentially connected by the main pipe (9) of the refrigerant pipe, while the devices (6a) and (7a),... Of the indoor units (A),.
, And each of the branch pipes (9a),... Is connected to the main pipe (9) in parallel with each other.
0), the branch pipes (9a),... Of the liquid pipe section of the main pipe (9).
In the vicinity of the liquid side branch that branches from the
Is decompressed and flowed to each branch pipe (9a), ... in a gas-liquid two-phase flow.
And the longer the length of the branch pipe (9a),.
A pressure reducing mechanism (20) configured to reduce the degree of pressure reduction of the medium.
An air conditioner , wherein a),... are interposed . 2. The air conditioner according to claim 1, wherein the degree of pressure reduction of each of the pressure reducing mechanisms (20a),... Is such that the capacity of the use side heat exchangers (7a),. An air conditioner characterized by being set as low as possible. 3. The air conditioner according to claim 1, wherein the degree of pressure reduction of each pressure reducing mechanism (20a),.
a) An air conditioner characterized by being set higher as the diameter of... increases.