JPH04332356A - Air conditioner - Google Patents

Abstract

PURPOSE:To flow ga-liquid two phase flow to each of dividing pipes of a refrigerant pipe in a multi-type air conditioner and to reduce a charging amount of refrigerant. CONSTITUTION:A plurality of branch pipes 9a,... for connecting an indoor electric expansion valve 6a,... and a utilization side heat exchanger 7a of each of indoor devices A are connected in parallel with a main pipe 9 of the refrigerant pipe to connect a compressor 1, a heat exchanger 3 at a heat source and an outdoor electric expansion valve 4 within an outdoor device X. A pressure reducing mechanism 20a,... are disposed near the branch part of each of the branch pipes 9a with the main pipe 9. With such an arrangement, the flow is changed to a liquid single phase flow at the main pipe 9, ga-liquid two-phase flow at the branch pipe so as to reduce an amount of refrigerant charging. Then, a degree of decreasing pressure of each of pressure reducing mechanisms 20a,... is lowered as a length of the branch pipe 9a is elongated more. As a capacity of the utilization side heat exchanger 7a is high, it is lowered, and as a diameter of the branch pipe 9a is high, its value is set high. With such an arrangement, a difference in pressure loss and a capacity difference at the utilization side heat exchanger are accommodated.

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 particularly relates to measures for reducing the amount of refrigerant charged.

0002

[Prior Art] Conventionally, for example, Utility Model Application Publication No. 1-10266
As disclosed in Publication No. 1, a plurality of indoor units are arranged for one outdoor unit, each device of the outdoor unit is connected by a main pipe, and each device of the indoor unit is connected by a branch pipe, A so-called multi-type air conditioner in which a closed refrigerant circuit is formed by connecting branch pipes in parallel to a main pipe is a well-known technology.

0003

[Problems to be Solved by the Invention] By the way, in the conventional multi-type air conditioner described above, it is desirable that the refrigerant state immediately before the expansion valve in each indoor unit be uniform during cooling operation, and furthermore, it is desirable to In order for the exchanger to exhibit sufficient capacity, the refrigerant condition must fall within a certain range. For this reason, in order to minimize the pressure loss in the liquid pipes, a method is generally adopted in which the refrigerant pipes are sufficiently heat-insulated and sealed, and a single phase of liquid refrigerant is allowed to flow through the pipes. However, in recent years, there has been a strong demand to reduce the amount of refrigerant used, but if a single-phase liquid flow is used in all piping as described above, the length of the piping can reach tens of meters, especially in multi-type air conditioners. Therefore, the amount of refrigerant charged becomes enormous, and it is difficult to reduce the amount of refrigerant charged.

On the other hand, it is possible to reduce the amount of refrigerant charged by circulating a gas-liquid two-phase flow in the main pipe on the liquid side. When dividing the refrigerant into two-phase flow, it is very difficult to distribute the gas-liquid ratio uniformly, that is, to distribute the void ratio uniformly to each branch pipe, resulting in uneven flow. There was a problem that special equipment was required.

[0005] The present invention has been made in view of the above, and its purpose is to provide a single-phase flow of only liquid refrigerant in the main pipe, while a gas-liquid two-phase flow in the branch pipe, and to provide a gas-liquid two-phase flow in each indoor unit. The objective is to reduce the amount of refrigerant charged while maintaining good air conditioning function by uniformizing the refrigerant state.

[0006]

[Means for Solving the Problem] In order to achieve the above object, the means taken by the invention of claim 1 are as shown in FIG.
Compressor (1), heat source side heat exchanger (3), and outdoor pressure reducing valve (
4), a plurality of indoor units (A), ... each having an indoor pressure reducing valve (6a) and a user-side heat exchanger (7a) are arranged for the outdoor unit (X) in which the above-mentioned outdoor unit is installed. Each device (1), (3), (4) of (X) is connected sequentially through the main pipe (9) of the refrigerant piping, while each device (6a) and (7a) of each indoor unit (A), ... , ... are connected by branch pipes (9a), ... of refrigerant piping, respectively, and each of the branch pipes (9a), ... is connected in parallel to the main pipe (9). It is assumed that an air conditioner is installed.

[0007]The branch pipes (9a), . . . have respective branch pipes (9a), .
A pressure reducing mechanism (20a),... is provided to reduce the pressure of the refrigerant to..., and the degree of pressure reduction of each pressure reducing mechanism (20a),... is set lower as the length of the branch pipe (9a),... is longer. It is configured to do this.

The means taken by the invention of claim 2 is that in the invention of claim 1, the degree of pressure reduction of each pressure reducing mechanism (20a), ... is adjusted to the user side heat exchanger (7) of the indoor unit (A), ...
The larger the capacity of a), . . . is, the lower the value is set.

The means taken by the invention of claim 3 is that in the invention of claim 1 or 2, each pressure reducing mechanism (20a),...
The degree of pressure reduction is set higher as the diameter of the branch pipe (9a), . . . becomes larger.

0010

[Operation] With the above configuration, in the invention of claim 1, during the cooling operation of the air conditioner, the refrigerant condensed and liquefied in the heat source side heat exchanger (3) flows in the main pipe (9) in a liquid single-phase flow. After that, it branches into each branch pipe (9a),... and connects each indoor unit (A).
, flows to... At that time, each branch pipe (9a) to (9c)
Since the pressure reducing mechanism (20a), . Therefore, the amount of refrigerant charged in the entire air conditioner is reduced.

[0011] In that case, the longer the length of the branch pipes (9a),...
Although the refrigerant state such as the pressure immediately before each indoor pressure reducing valve (6a), etc. changes greatly due to the difference in pressure loss, in the present invention, the degree of pressure reduction in each pressure reducing mechanism (20a),...
9a) The longer the length of..., the lower the setting is, so
The difference in pressure loss in each branch pipe (9a), ... is compensated for, the refrigerant pressure immediately before each indoor pressure reducing valve (6a), ... is approximately equalized, and the capacity of each user-side heat exchanger (7a), ... will be properly secured. Therefore, even if there is a difference in the length of the branch pipes (9a), ..., each indoor unit (A) ,... while maintaining good air conditioning function, it is possible to reduce the amount of refrigerant charged.

[0012] In the invention of claim 2, each indoor unit (A
),... If there is a difference in the capacity of the user-side heat exchanger (7a), ..., the larger the capacity, the more refrigerant circulation is required, but the capacity of the user-side heat exchanger (7a), ... The larger the value, the lower the degree of pressure reduction of each pressure reduction mechanism (9a), ... is set, so the capacity of the user side heat exchanger (7a), ... is properly secured, and the air conditioning in each indoor unit (A), ... Capacity will be maintained well.

[0013] In the invention of claim 3, the branch pipes (9a),...
The degree of pressure reduction in the pressure reducing mechanism (20a),... is set higher as the diameter of the branch tube (9a) increases. In addition to adjusting the pressure loss by changing the indoor pressure reducing valve (6
a),...The refrigerant pressure just before is made more finely uniform, and smooth operation is ensured.

[0014]

[Example] The following is an example of the present invention in FIGS. 1 to 4.
The explanation will be based on.

FIG. 1 shows a refrigerant piping system of an air conditioner according to an embodiment, in which three indoor units (A) to (C) are connected in parallel to one outdoor unit (X). organized into shapes. The above outdoor unit (X) includes:
A compressor (1) compresses and discharges the sucked refrigerant, a four-way switching valve (2) that switches connections as shown in the solid line in the figure during cooling operation and as shown in the broken line in the figure during heating operation, and condenses during cooling operation. They include a heat source side heat exchanger (3) that functions as an evaporator during heating operation, an outdoor electric expansion valve (4) that functions as an outdoor pressure reducing valve that reduces the pressure of the refrigerant during heating operation, and a A receiver (5) and an accumulator (8) for removing liquid refrigerant from the refrigerant sucked into the compressor (1) are arranged as main equipment, and each of the above equipment is connected to the main pipe of the refrigerant pipe. (9) are connected in series.

On the other hand, each of the above indoor units (A) to (C)
The use side heat exchangers (7a) to (7c) have different capacities and function as evaporators during cooling operation and as condensers during heating operation. Indoor electric expansion valves (6a) to (6c) are provided as indoor pressure reducing valves that adjust the refrigerant flow rate, and each of the equipment (
6a) to (6c), (7a) to (7c) are connected by branch pipes (9a) to (9c) of the refrigerant piping, respectively, and each branch pipe (9a) to (9c) is connected to the above-mentioned branch pipes (9a) to (9c). A liquid flow divider (14) and a gas flow divider (15) provided at both ends of the main pipe (9) are connected in parallel to each other. That is, each main equipment (1) to (8) of the air conditioner is as follows:
The main pipe (9) and branch pipes (9a) to (9c) are connected in sequence to form a closed circuit, and constitute a main refrigerant circuit (10) in which refrigerant circulates to cause heat transfer.

[0017] Here, as a feature of the present invention, each branch pipe (9a) to (9c) is connected to the branch part (the inlet part of the liquid refrigerant during cooling operation) from the liquid flow divider (14), respectively. Capillary tubes (20a) to (20a) to (20a) as pressure reduction mechanisms having a degree of pressure reduction corresponding to the length and diameter of branch pipes (9a) to (9c) and the capacity of each user-side heat exchanger (7a) to (7c). 2
0c) is provided. Each capillary tube (2
0a), (20b), and (20c) are the main pipes (
The liquid refrigerant is provided at the inlet portion of the branch pipes (9a), (9b), and (9c) branching from the liquid flow divider (14) provided at the liquid side end of the liquid refrigerant during cooling operation. Depending on the inner diameter of the capillary tubes (20a), (20b), and (20c), the degree of pressure reduction varies between each indoor unit (A) and (B).
, (C) user-side heat exchangers (7a), (7b), (7c)
), the diameter and length of each branch pipe (9a), (9b), (9c) are set as shown in Table 1 below.

[0018]

[Table 1]

However, in Table 1 above, L, LM, M
, HM, H indicate the degree of reduced pressure, and are listed in order from the lowest side. That is, as shown in Table 1 above, the degree of pressure reduction of each capillary tube (20a), (20b), (20c) is lower as the length of the branch pipes (9a) to (9c) is longer;
The larger the capacity of the utilization side heat exchangers (7a) to (7c) is, the lower the value is, and the larger the diameter of the branch pipes (9a) to (9c) is, the higher the value is set.

Therefore, in the above embodiment, during cooling operation of the air conditioner, the refrigerant discharged from the compressor (1) flows through the main pipe (9) of the refrigerant piping, and is condensed and liquefied in the heat source side heat exchanger (3). After being stored in the receiver (5), the liquid is branched from the liquid flow divider (14) to each of the branch pipes (9a) to (9c) and flows to each of the indoor units (A) to (C). Then, after being throttled by each electric expansion valve (6a) to (6c) and evaporated by each use-side heat exchanger (7a) to (7c), the gas flow divider (15)
and flows into the outdoor unit (X), accumulator.
It returns to the compressor (1) via the compressor (8). By repeating this circulation, the heat absorbed through heat exchange with the indoor air in each user side heat exchanger (7a) to (7c) is released to the outdoor air in the heat source side heat exchanger (3), and each indoor Perform air conditioning.

At that time, each of the branch pipes (9a) to (9c)
Capillary tubes (20a) to (20a) to (20a), which function as pressure reduction mechanisms for reducing the pressure of the refrigerant to each of the branch pipes (9a) to (9c), are installed near the branching part between the liquid flow divider (14) and the liquid flow divider (14).
20c), a part of the liquid refrigerant that has flowed in a liquid single-phase flow to the liquid flow divider (14) is evaporated and liquefied, and then flows in a gas-liquid two-phase flow. Here, for example, in a building such as a building, branch pipes (9a) to (9c) of refrigerant piping leading to each room are used.
) is several tens of meters in length, so if liquid refrigerant were to be filled into these branch pipes (9a) to (9c) as in the past, the amount of refrigerant would be enormous, and there was a demand to reduce the amount of refrigerant used. cannot respond to On the other hand, as in the above-mentioned embodiment, by circulating the gas-liquid two-phase flow through each of the branch pipes (9a) to (9c), it is possible to reduce the amount of refrigerant charged in the entire air conditioner.

In that case, the main pipe (
9) When a gas-liquid two-phase flow is caused to flow through each branch pipe (9a)
Although distribution to (9c) becomes difficult, such a problem does not occur because the flow is a liquid single phase in the main pipe (9) on the liquid side as in the above embodiment.

[0023] Then, each capillary tube (20
Branch pipe (9a) in which pressure reduction degrees of a) to (20c) are arranged
~(9c) is set lower as the length is longer, so
The difference in pressure loss in each branch pipe (9a) to (9c) is alleviated. That is, the longer the length of the branch pipes (9a) to (9c), the greater the pressure loss, and especially in the case of gas-liquid two-phase flow, the difference in pressure loss causes each indoor electric expansion valve (6a) to
(6b) The immediately preceding refrigerant state (refrigerant pressure) changes significantly. For example, the length of the branch pipes (9a) to (9c) can be as long as 50 m or more, so if the pipe length is long, the refrigerant pressure just before the electric expansion valve (6a) will be extremely low due to pressure loss, and other When the refrigerant pressure immediately before the use-side heat exchangers (9a) to (9c) is high, the refrigerant flow rate is drastically reduced. Therefore, the capacity of the utilization side heat exchangers (7a) to (7c) cannot be fully demonstrated. On the other hand, branch pipe (9a)
By adjusting the degree of pressure reduction as described above according to the length of ~ (9c), the difference in pressure loss is compensated, and the refrigerant pressures of the indoor electric expansion valves (6a) ~ (6c) are approximately equalized. hand,
The capacity of each user-side heat exchanger (7a) to (7c) is properly exhibited. Therefore, it is possible to reduce the amount of refrigerant charged while maintaining the air conditioning function of each of the indoor units (A) to (C) well.

In particular, the difference in pressure loss caused by the difference in refrigerant pipe length can be corrected by changing the pipe diameter, but preparing refrigerant pipes with many different diameters increases costs. Connect. On the other hand, by compensating for the difference in pressure loss with the degree of pressure reduction that can be easily adjusted by changing the inner diameter and length of the capillary tubes (20a) to (20c), cost increases can be suppressed. .

[0025] Furthermore, if there is a difference in capacity between the user-side heat exchangers (7a) to (7c) of the indoor units (A) to (C),
The larger the capacity of each of the user-side heat exchangers (7a) to (7c) is, the larger the amount of refrigerant circulation required to maintain the same refrigerant state is. Therefore, each user side heat exchanger (7a) to (7
By lowering the degree of pressure reduction as the capacity of c) increases,
The necessary amount of refrigerant circulation is ensured in each of the user-side heat exchangers (7a) to (7c), and their capabilities are effectively exhibited.

Furthermore, the larger the diameter of each branch pipe (9a) to (9c), the smaller the pressure loss.
By increasing the degree of pressure reduction of the capillary tubes (20a) to (20c) as the diameters of the capillary tubes (9a) to (9a) become larger, the pressure loss difference between each branch pipe (9a) to (9c) is compensated for. Can be done. In particular, pressure loss can be adjusted by changing the pipe diameter according to the length of the branch pipes (9a) to (9c), but as mentioned above, many types of pipes with slightly different diameters can be used. Since preparation would increase costs, as shown in Table 1 above, while roughly adjusting the pressure loss with several pipe diameters, it is necessary to set the degree of pressure reduction for each capillary tube (20a) to (20c). This makes it possible to finely compensate for differences in pressure loss in conjunction with adjustment by pipe diameter. Therefore, the indoor electric expansion valves (6a) to (
6c) The pressure of the refrigerant immediately before can be made more uniform, and smooth operation can be ensured.

[0027] In the above embodiment, the present invention is carried out by the host (9).
), the present invention is not limited to such an embodiment. FIG. 3 shows a modification of the above embodiment, in which the main pipe (9)
An example of application to a so-called line-type air conditioner in which branch pipes (9a) to (9c) branch out from the middle of the flowchart is shown, and the above implementation is shown except that the flow dividers (14) and (15) are not provided. Similar to the example.

In this modification, as in the above embodiment, the length and diameter of each branch pipe (9a) to (9b) and the capacity of the utilization side heat exchanger (7a) to (7c) are determined. By setting the degree of pressure reduction of the capillary tubes (20a) to (20c), the same effects as in the above embodiment can be obtained.

Further, the pressure reducing mechanism of the present invention is not limited to a 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,
This is an example in which the branch pipe (9a) is divided at a large diameter part in the middle, and the outer diameter part of the capillary tube (20a) is fitted into each of the divided ends. In this case as well, it is possible to limit the section of the liquid single-phase flow to an extremely short length, and it goes without saying that the same effect of reducing the amount of refrigerant charged as in the above embodiment can be achieved.

[0030]

As explained above, according to the invention of claim 1, each device of the outdoor unit of an air conditioner is connected to the main pipe, while each device of the indoor unit is connected to the main pipe by the branch pipe. In contrast, the branch pipes are connected in parallel to each other to form a refrigerant circuit, and a pressure reduction mechanism is provided near the liquid side branch from the main pipe of each branch pipe, and the degree of pressure reduction of each pressure reduction mechanism is adjusted to the degree of pressure reduction of the branch pipe. The longer the length, the lower the setting, so part of the liquid refrigerant evaporates and liquefies and flows through the branch pipe in a gas-liquid two-phase flow, reducing the amount of refrigerant charged. It is possible to compensate for the difference in pressure loss due to the difference in piping length without having to change the refrigerant state to approximately equalize the refrigerant state immediately before the pressure reducing valve in each room. It is possible to reduce the amount of refrigerant charged.

According to the invention of claim 2, in the invention of claim 1, the degree of pressure reduction of each pressure reduction mechanism is set to be lower as the capacity of the user-side heat exchanger is larger, so that each indoor unit is used more efficiently. Even when there is a difference in the capacity of the side heat exchangers, the refrigerant state of each user side heat exchanger can be maintained appropriately, and therefore, the air conditioning capacity of each indoor unit can be maintained satisfactorily.

According to the invention of claim 3, in the invention of claim 1 or 2, the degree of pressure reduction of the pressure reduction mechanism is set higher as the diameter of the branch pipe increases, so that the degree of pressure reduction decreases as the diameter increases. The difference in pressure loss of each branch pipe is compensated for,
Together with adjusting the pressure loss by changing the diameter, the refrigerant pressure just before the indoor pressure reducing valve can be made more finely uniform.
Therefore, it can be highly effective.

[Brief explanation of the drawing]

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

FIG. 2 is a longitudinal sectional view showing the structure when a nozzle is used in the pressure reduction 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 cross-sectional view showing a structure of a modified example when a nozzle is used in the pressure reduction mechanism.

[Explanation of symbols]

1 Compressor 3 Heat source side heat exchanger 4 Outdoor electric expansion valve (outdoor pressure reducing valve) 6 Indoor electric expansion valve (indoor pressure reducing valve) 9 Main pipes 9a to 9c Branch pipes 10 Refrigerant circuit

Claims (3)

[Claims] [Claim 1] Compressor (1), heat source side heat exchanger (3)
and an outdoor unit (X) equipped with an outdoor pressure reducing valve (4)
In contrast, the indoor pressure reducing valve (6a) and the user side heat exchanger (7
a), and each device (1), (3), (
4) are sequentially connected through the main pipe (9) of the refrigerant piping,
Each indoor unit (A) above, each device (6a) and (
7a),... are connected by branch pipes (9a),... of the refrigerant piping, respectively, and the branch pipes (9a),... are connected to the main pipe (9).
In an air conditioner including a refrigerant circuit (10) connected in parallel to each other, each of the branch pipes (9a),
Each branch pipe (
9a), a pressure reducing mechanism (20a) for reducing the pressure of the refrigerant to...
), ... are interposed, and the degree of pressure reduction of each of the pressure reduction mechanisms (20a), ... is set lower as the length of the branch pipe (9a), ... is longer. [Claim 2] In the air conditioner according to claim 1, the degree of pressure reduction of each pressure reduction mechanism (20a), ... is such that the capacity of the user-side heat exchanger (7a), ... of the indoor unit (A), ... is large. An air conditioner characterized by being set at a low temperature. 3. The air conditioner according to claim 1 or 2, wherein the degree of pressure reduction of each pressure reducing mechanism (20a),... is set higher as the diameter of the branch pipe (9a),... is larger. air conditioning equipment.