EP4589220A1

EP4589220A1 - Air conditioner

Info

Publication number: EP4589220A1
Application number: EP23872080.9A
Authority: EP
Inventors: Tomomitsu Yamaguchi; Keisuke Mitoma; Masamune OKINO; Yusuke Doi; Michiaki Nakanishi; Takaya KUSUMOTO; Masayoshi Hirasawa; Yasuaki Kaneko
Original assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Current assignee: Mitsubishi Heavy Industries Thermal Systems Ltd
Priority date: 2022-09-27
Filing date: 2023-09-20
Publication date: 2025-07-23
Also published as: WO2024070853A1; EP4589220A4; AU2023353506A1; JP2024047894A

Abstract

This air conditioner comprises: a compressor that compresses a refrigerant containing a refrigerator oil; an outdoor heat exchanger that exchanges heat between the refrigerant discharged from the compressor and outside air; a first expansion valve and a second expansion valve that sequentially depressurize the refrigerant which has passed through the outdoor heat exchanger; and an indoor heat exchanger that exchanges heat between the refrigerant, which has passed through the expansion valves, and outside air, and that supplies the refrigerant to the compressor. The air conditioner further comprises a gas-liquid separation mechanism provided between the first expansion valve and the second expansion valve. The gas-liquid separation mechanism includes: a storage unit into which the refrigerant that has passed the first expansion valve is introduced; and a first recirculation unit that is capable of recovering a liquid phase from the bottom part of the storage unit and introducing the liquid phase into the compressor.

Description

Technical Field

The present disclosure relates to an air conditioner.
This application claims priority to Japanese Patent Application No. 2022-153657, filed in Japan on September 27, 2022 , the content of which is incorporated herein by reference.

Background Art

As a type of air conditioner, various types of air conditioners using gas injection have been put into practical use. In the gas injection type air conditioner, a configuration is adopted in which a part of gas refrigerant vaporized after passing through an evaporator is taken out from the middle of a refrigerant circuit and is returned to a compressor. PTL 1 discloses a configuration in which a gas refrigerant among a liquid refrigerant and a gas refrigerant generated inside a gas-liquid separation mechanism is returned to a compressor.
Here, refrigeration oil that lubricates each part of the compressor is dissolved in a refrigerant and circulates in the refrigerant circuit. In the configuration using the above-described gas-liquid separation mechanism, most of the refrigeration oil is separated together with the liquid refrigerant and is stored in the gas-liquid separator.
In addition, a configuration in which the refrigeration oil is separated from the refrigerant by an oil separator provided on the downstream side of the compressor and returned to the compressor is also conceivable.

Citation List

Patent Literature

[PTL 1] Japanese Unexamined Patent Application Publication No. 2002-81779

Summary of Invention

Technical Problem

However, in a case where most of the refrigeration oil is dissolved in the liquid refrigerant and stored in the gas-liquid separation mechanism as in the device according to PTL 1, there is a possibility that the refrigeration oil does not reach the compressor that originally requires the refrigeration oil. In addition, in a case where the oil separator is used, a part of the refrigerant also returns together with the refrigeration oil returning to the compressor, and thus there is a possibility that the cooling efficiency of the air conditioner decreases. For this reason, there has been an increasing demand for an air conditioner that can be more stably operated under high cooling efficiency.
The present disclosure has been made to solve the above-described problems, and an object of the present disclosure is to provide an air conditioner that can be operated more stably under a high cooling efficiency.

Solution to Problem

In order to solve the above problems, an air conditioner according to the present disclosure includes: a compressor configured to compress a refrigerant containing a refrigeration oil; an outdoor heat exchanger configured to exchange heat between the refrigerant discharged from the compressor and outside air; a first expansion valve and a second expansion valve configured to sequentially reduce a pressure of the refrigerant passing through the outdoor heat exchanger; and an indoor heat exchanger configured to exchange heat between the refrigerant passing through any one of the first expansion valve and the second expansion valve and the outside air, and supply the refrigerant to the compressor, the air conditioner further includes a gas-liquid separation mechanism provided between the first expansion valve and the second expansion valve, and the gas-liquid separation mechanism includes a storage portion into which the refrigerant passing through the first expansion valve is introduced, and a first return section configured to collect a liquid phase component from a bottom portion of the storage portion and introduce the liquid phase component into the compressor.

Advantageous Effects of Invention

According to the present disclosure, it is possible to provide an air conditioner that can be more stably operated under high cooling efficiency.

Brief Description of Drawings

Fig. 1 is a schematic diagram showing a refrigerant circuit of an air conditioner according to a first embodiment of the present disclosure.
Fig. 2 is a schematic diagram showing a refrigerant circuit of an air conditioner according to a second embodiment of the present disclosure.

Description of Embodiments

(Configuration of Air Conditioner)

Hereinafter, an air conditioner 1 according to a first embodiment of the present disclosure will be described with reference to Fig. 1. The air conditioner 1 according to the present embodiment is, for example, a device that is installed in a building such as a house or a transport machine such as an automobile and that adjusts an indoor temperature to a designated value.
As shown in Fig. 1, the air conditioner 1 includes a refrigeration cycle 10, a four-way valve 20, and a gas-liquid separation mechanism 30. The refrigeration cycle 10 is a circuit for exchanging heat between indoor air and a refrigerant and between outdoor air and a refrigerant by compressing or expanding a refrigerant that sequentially flows through each device (to be described later) of the refrigeration cycle 10.

(Configuration of Refrigeration Cycle)

The refrigeration cycle 10 includes an indoor heat exchanger 11, an indoor fan 12, an outdoor heat exchanger 13, an outdoor fan 14, a compressor 15, a first expansion valve 17, a second expansion valve 18, a first flow path 41, a second flow path 42, and a compressor flow path 43.
The indoor heat exchanger 11 is disposed on the first flow path 41. The first flow path 41 is a flow path that connects the four-way valve 20 and the gas-liquid separation mechanism 30, which will be described later. The inside of the first flow path 41 is filled with a refrigerant. The indoor heat exchanger 11 exchanges heat between the refrigerant flowing through the first flow path 41 and the indoor air. The indoor heat exchanger 11 is, for example, a fin-and-tube type heat exchanger. An indoor fan 12 is provided in the vicinity of the indoor heat exchanger 11. By operating the indoor fan 12, the indoor air is forcibly supplied to the indoor heat exchanger 11.
The second expansion valve 18 is disposed at a position closer to the gas-liquid separation mechanism 30 than the indoor heat exchanger 11 on the first flow path 41. The second expansion valve 18 is, for example, an electromagnetic expansion valve, and the opening degree is regulated by an electric signal transmitted from the outside. The second expansion valve 18 is used to expand the refrigerant flowing in the first flow path 41 during the cooling operation to lower the pressure thereof.
The outdoor heat exchanger 13 is disposed on the second flow path 42. The second flow path 42 is a flow path that connects the four-way valve 20 and the gas-liquid separation mechanism 30 to each other, and is a flow path provided separately from the first flow path 41. The second flow path 42 is filled with the refrigerant. The outdoor heat exchanger 13 exchanges heat between the refrigerant flowing in the second flow path 42 and the outdoor air. The outdoor heat exchanger 13 is, for example, a fin-and-tube type heat exchanger. An outdoor fan 14 is provided in the vicinity of the outdoor heat exchanger 13. By operating the outdoor fan 14, outdoor air is forcibly supplied to the outdoor heat exchanger 13.
The first expansion valve 17 is disposed at a position closer to the gas-liquid separation mechanism 30 than the outdoor heat exchanger 13 on the second flow path 42. The first expansion valve 17 is, for example, an electromagnetic expansion valve, and the opening degree is regulated by an electric signal transmitted from the outside. The first expansion valve 17 is used to expand the refrigerant flowing in the second flow path 42 during heating operation to lower the pressure thereof.
The compressor 15 is provided on the compressor flow path 43. The compressor flow path 43 is a flow path that connects one opening and the other opening of the four-way valve 20, and is another flow path different from the first flow path 41 and the second flow path 42 described above. The compressor 15 compresses the gas refrigerant in the compressor flow path 43 to generate a high-temperature and high-pressure gas refrigerant. Specifically, a scroll compressor or a rotary compressor is preferably used as the compressor 15.

(Configuration of Four-Way Valve)

The four-way valve 20 switches the connection state of the first flow path 41, the second flow path 42, and the compressor flow path 43 to switch the circulation direction of the refrigerant. By switching the open state of the four-way valve 20, it is possible to switch between the heating operation and the cooling operation. In Fig. 1, an open state of the four-way valve 20 during the cooling operation is shown. Specifically, the open state of the four-way valve 20 is set such that the high-pressure refrigerant discharged from the compressor 15 directly flows to the outdoor heat exchanger 13 through the second flow path 42.

(Configuration of Gas-Liquid Separation Mechanism)

A gas-liquid separation mechanism 30 is provided between the first expansion valve 17 and the second expansion valve 18 (that is, between the first flow path 41 and the second flow path 42). The gas-liquid separation mechanism 30 has a storage portion 31, a first return section 32, a first regulating valve 33, and a second return section 34.
The storage portion 31 is an airtight container in which the refrigerant is stored, and the refrigerant that has passed through the first expansion valve 17 is introduced into the storage portion 31. In the storage portion 31, the liquid phase component of the refrigerant is stored in the bottom portion, and the gas phase component is retained in the upper portion. That is, the gas-liquid separation of the refrigerant is performed inside the storage portion 31. The refrigerant contains a refrigeration oil used for lubrication of each part of the compressor 15. In the gas-liquid separation mechanism 30, most of the refrigeration oil is stored in the bottom portion of the storage portion 31 as a liquid phase component.
The first return section 32 connects between the bottom portion of the storage portion 31 and the inlet side of the compressor 15. The first return section 32 collects the liquid phase component of the refrigerant containing the refrigeration oil from the bottom portion of the storage portion 31 and introduces the collected liquid phase component into the compressor 15. The first regulating valve 33 is provided at a middle position of the first return section 32. The first regulating valve 33 is, for example, a flow rate regulating valve. The flow rate of the liquid phase component of the refrigerant flowing through the first return section 32 is changed by regulating the opening degree of the first regulating valve 33.
The second return section 34 connects the bottom portion of the storage portion 31 and the second expansion valve 18 to each other and forms a part of the first path described above. The second return section 34 collects the liquid phase component of the refrigerant from the bottom portion of the storage portion 31 and introduces the liquid phase component into the first flow path 41. The liquid phase component of the refrigerant introduced into the first flow path 41 is supplied to the indoor heat exchanger 11 through the second expansion valve 18.

(Actions and Effects)

Next, the operation of the air conditioner 1 will be described. Here, the operation during the cooling operation will be described as a representative example. During the cooling operation of the air conditioner 1, the refrigerant flows through each part in accordance with arrows in Fig. 1. First, the refrigerant (gas phase) compressed by the compressor 15 becomes a high-temperature and high-pressure gas-phase refrigerant. Thereafter, the refrigerant passes through the four-way valve 20 and is introduced into the outdoor heat exchanger 13. In the outdoor heat exchanger 13, heat exchange is performed between the outdoor air and the refrigerant. As a result, the refrigerant is in a high-pressure gas-liquid mixed phase state. Thereafter, the refrigerant passes through the first expansion valve 17 on the second flow path 42. In addition, during the cooling operation, the first expansion valve 17 is in a fully open state, and even when the refrigerant passes through the first expansion valve 17, the pressure of the refrigerant does not change.
The refrigerant that has passed through the first expansion valve 17 is separated into a gas phase component and a liquid phase component by the gas-liquid separation mechanism 30. The liquid phase component is stored in the bottom portion of the storage portion 31, and the gas phase component is retained in the upper portion of the storage portion 31. The refrigeration oil, which is a part of the liquid phase component, is introduced into the compressor 15 through the first return section 32 described above. The refrigeration oil is used for lubrication of each part of the compressor 15. The other portion of the liquid phase component stored in the storage portion 31 is introduced into the first flow path 41 through the second return section 34. The refrigerant passes through the second expansion valve 18 on the first flow path 41, so that the pressure of the refrigerant is lowered to become a low-temperature and low-pressure liquid refrigerant. Thereafter, heat is exchanged between the indoor air and the refrigerant by the indoor heat exchanger 11. In this manner, the temperature of the refrigerant increases, and the temperature of the indoor air decreases. In addition, the refrigerant is in a low-pressure gas phase state. Thereafter, the refrigerant that has flowed into the compressor flow path 43 through the four-way valve 20 is compressed again by the compressor 15. The cooling operation of the air conditioner 1 is performed by the above cycle occurring continuously.
Meanwhile, as a type of air conditioner 1, various types of air conditioners using gas injection have been put into practical use. In the gas injection type air conditioner 1, a configuration is adopted in which a part of gas refrigerant vaporized after passing through an evaporator is taken out from the middle of a refrigerant circuit and is returned to a compressor 15. Specifically, a configuration in which only the gas refrigerant among a liquid refrigerant and a gas refrigerant generated inside the gas-liquid separation mechanism 30 is returned to a compressor 15 is exemplified. Here, refrigeration oil that lubricates each part of the compressor 15 is dissolved in a refrigerant and circulates in the refrigerant circuit. In the configuration using the above-described gas-liquid separation mechanism 30, most of the refrigeration oil is separated together with the liquid refrigerant and is stored in the gas-liquid separator.
However, in a case where most of the refrigeration oil is dissolved in the liquid refrigerant and stored in the gas-liquid separation mechanism 30 as described above, there is a possibility that the refrigeration oil does not reach the compressor 15 that originally requires the refrigeration oil. Therefore, each of the above-described configurations is adopted in the present embodiment.
According to the above-described configuration, the liquid phase component separated by the gas-liquid separation mechanism 30 is introduced into the compressor 15 through the first return section 32. In this manner, the refrigeration oil contained in the liquid phase component can be used as a lubricant in each part of the compressor 15 without waste. As a result, the smoothness of the operation of the compressor 15 is maintained for a long period of time, and thus the compressor 15 can be operated more stably. By improving the operability of the compressor 15, the performance of the air conditioner 1 can also be improved.
Further, according to the above configuration, the first regulating valve 33 is provided on the first return section 32. By regulating the opening degree of the first regulating valve 33, the flow rate of the liquid phase component flowing through the first return section 32 can be maintained constant under a predetermined value. In addition, the supply of the liquid phase component can be set to zero as necessary. In this manner, the supply amount of the refrigeration oil contained in the liquid phase component can be optimized according to the usage status of the compressor 15. Therefore, it is possible to operate the air conditioner 1 under a wide range of operating conditions according to the environment and specifications.
In addition, in the above configuration, the liquid phase component of the refrigerant is introduced into the indoor heat exchanger 11 by the second return section 34. Here, it is known that, in a case where the gas phase component of the refrigerant, instead of the liquid phase component, flows through the indoor heat exchanger 11, the pressure loss becomes larger than that in the case of the liquid phase component. This tendency is particularly remarkable in a fin-and-tube type heat exchanger. According to the above-described configuration, the liquid phase component of the refrigerant of which gas and liquid phases are separated is introduced into the indoor heat exchanger 11 by the second return section 34. In this manner, the pressure loss in the indoor heat exchanger 11 is suppressed. As a result, the refrigerant continues to smoothly pass through the indoor heat exchanger 11, and thus the entire air conditioner 1 can be operated more efficiently.
The first embodiment of the present disclosure has been described above. Various changes or improvements can be made to the above configuration without departing from the concept of the present disclosure. In addition, in the first embodiment, only the cooling operation of the air conditioner 1 has been described. However, during the heating operation, the circulation directions of the refrigerant in the first flow path 41 and the second flow path 42 excluding the compressor flow path 43 are opposite to each other. In addition, during the heating operation, in the gas-liquid separation mechanism 30, the refrigerant flows into the storage portion 31 from the second return section 34 through the second expansion valve 18, and the liquid phase component of the refrigerant is sent to the compressor 15 through the first return section 32.

Next, a second embodiment of the present disclosure will be described with reference to Fig. 2. The same configurations as those of the first embodiment will be assigned with the same reference numerals, and detailed description thereof will be omitted. As shown in Fig. 2, in the present embodiment, the configuration of the gas-liquid separation mechanism 130 is different from that of the first embodiment. Specifically, the gas-liquid separation mechanism 130 further includes a third return section 131 and a second regulating valve 132, in addition to each configuration of the gas-liquid separation mechanism 30 of the first embodiment.
The third return section 131 connects between the storage portion 31 and the inlet side of the compressor 15. The third return section 131 collects the gas phase component of the refrigerant from the upper portion of the storage portion 31 and introduces the gas phase component into the compressor 15. The second regulating valve 132 is provided at a middle position of the third return section 131. The second regulating valve 132 is, for example, a flow rate regulating valve. The flow rate of the gas phase component of the refrigerant flowing through the third return section 131 is changed by regulating the opening degree of the second regulating valve 132.

(Actions and Effects)

According to the above-described configuration, the gas phase component separated by the gas-liquid separation mechanism 30 is introduced into the compressor 15 through the third return section 131. As a result, the amount of the refrigerant supplied into the compressor 15 increases, and it is possible to improve the coefficient of performance (capacity/power consumption) as the air conditioner 1.
Further, according to the above-described configuration, by regulating the opening degree of the second regulating valve 132, the flow rate of the gas phase component flowing through the third return section 131 can be maintained constant under a predetermined value. In addition, the supply of the gas phase component can be set to zero as necessary. In this manner, the amount of the gas phase component of the refrigerant supplied to the compressor 15 can be optimized according to the operation state. As a result, it is possible to operate the air conditioner 1 under a wide range of operating conditions according to the environment and specifications.
The second embodiment of the present disclosure has been described above. Various changes or improvements can be made to the above configuration without departing from the concept of the present disclosure. In addition, in the second embodiment, only the cooling operation of the air conditioner 1 has been described. However, during the heating operation, the circulation directions of the refrigerant in the first flow path 41 and the second flow path 42 excluding the compressor flow path 43 are opposite to each other. In addition, during the heating operation, in the gas-liquid separation mechanism 130, the refrigerant flows into the storage portion 31 from the second return section 34 through the second expansion valve 18, and the liquid phase component of the refrigerant is sent to the compressor 15 through the first return section 32.

For example, the air conditioner 1 according to each embodiment is understood as follows.

(1) An air conditioner 1 according to a first aspect includes: a compressor 15 configured to compress a refrigerant containing a refrigeration oil; an outdoor heat exchanger 13 configured to exchange heat between the refrigerant discharged from the compressor 15 and outside air; a first expansion valve 17 and a second expansion valve 18 configured to sequentially reduce a pressure of the refrigerant passing through the outdoor heat exchanger 13; and an indoor heat exchanger 11 configured to exchange heat between the refrigerant passing through the expansion valves and the outside air, and supply the refrigerant to the compressor 15, the air conditioner 1 further includes a gas-liquid separation mechanism 30 provided between the first expansion valve 17 and the second expansion valve 18, and the gas-liquid separation mechanism 30 includes a storage portion 31 into which the refrigerant passing through any one of the first expansion valve 17 and the second expansion valve 18 is introduced, and a first return section 32 configured to collect a liquid phase component from a bottom portion of the storage portion 31 and introduce the liquid phase component into the compressor 15.

According to the above-described configuration, the liquid phase component separated by the gas-liquid separation mechanism 30 is introduced into the compressor 15 through the first return section 32. Accordingly, the refrigeration oil contained in the liquid phase component functions as a lubricant in each part of the compressor 15. As a result, the compressor 15 can be operated more stably.
(2) The air conditioner 1 according to a second aspect is the air conditioner 1 of (1), in which the gas-liquid separation mechanism 30 further includes a first regulating valve 33 that is provided in the first return section 32 and is configured to regulate a flow rate of the liquid phase component.
According to the above-described configuration, by regulating the opening degree of the first regulating valve 33, the flow rate of the liquid phase component flowing through the first return section 32 can be maintained constant under a predetermined value. In addition, the supply of the liquid phase component can be set to zero as necessary. In this manner, it is possible to operate the air conditioner 1 under a wide range of operating conditions according to the environment and specifications.
(3) The air conditioner 1 according to a third aspect is the air conditioner 1 of (1) or (2), in which the gas-liquid separation mechanism 30 further includes a second return section 34 configured to collect the liquid phase component from the bottom portion of the storage portion 31 and introduce the liquid phase component into the indoor heat exchanger 11 through the second expansion valve 18.
Here, it is known that, in a case where the gas phase component of the refrigerant flows through the indoor heat exchanger 11, the pressure loss becomes larger than that in the case of the liquid phase component. According to the above-described configuration, the liquid phase component of the refrigerant of which gas and liquid phases are separated is introduced into the indoor heat exchanger 11 by the second return section 34. In this manner, the pressure loss in the indoor heat exchanger 11 is suppressed, and the air conditioner 1 can be operated more efficiently.
(4) The air conditioner 1 according to a fourth aspect is the air conditioner 1 according to any one aspect of (1) to (3), in which the gas-liquid separation mechanism 30 further includes a third return section 131 configured to collect a gas phase component from an upper portion of the storage portion 31 and introduce the gas phase component into the compressor 15.
According to the above-described configuration, the gas phase component separated by the gas-liquid separation mechanism 30 is introduced into the compressor 15 through the third return section 131. As a result, the amount of the refrigerant supplied into the compressor 15 increases, and it is possible to improve the coefficient of performance (capacity/power consumption) as the air conditioner 1.
(5) The air conditioner 1 according to a fifth aspect is the air conditioner 1 of (4), in which the gas-liquid separation mechanism 130 further includes a second regulating valve 132 that is provided in the third return section 131 and is configured to regulate a flow rate of the gas phase component.
According to the above-described configuration, by regulating the opening degree of the second regulating valve 132, the flow rate of the gas phase component flowing through the second return section 34 can be maintained constant under a predetermined value. In addition, the supply of the gas phase component can be set to zero as necessary. In this manner, it is possible to operate the air conditioner 1 under a wide range of operating conditions according to the environment and specifications.

Industrial Applicability

Reference Signs List

1: Air conditioner
10: Refrigeration cycle
11: Indoor heat exchanger
12: Indoor fan
13: Outdoor heat exchanger
14: Outdoor fan
15: Compressor
17: First expansion valve
18: Second expansion valve
20: Four-way valve
30: Gas-liquid separation mechanism
31: Storage portion
32: First return section
33: First regulating valve
34: Second return section
41: First flow path
42: Second flow path
43: Compressor flow path
130: Gas-liquid separation mechanism
131: Third return section
132: Second regulating valve

Claims

An air conditioner comprising:
a compressor configured to compress a refrigerant containing a refrigeration oil;

an outdoor heat exchanger configured to exchange heat between the refrigerant discharged from the compressor and outside air;

a first expansion valve and a second expansion valve configured to sequentially reduce a pressure of the refrigerant passing through the outdoor heat exchanger; and

an indoor heat exchanger configured to exchange heat between the refrigerant passing through any one of the first expansion valve and the second expansion valve and the outside air, and supply the refrigerant to the compressor,

wherein the air conditioner further includes a gas-liquid separation mechanism provided between the first expansion valve and the second expansion valve, and

the gas-liquid separation mechanism includes
a storage portion into which the refrigerant passing through the first expansion valve is introduced, and

a first return section configured to collect a liquid phase component from a bottom portion of the storage portion and introduce the liquid phase component into the compressor.
The air conditioner according to Claim 1,
wherein the gas-liquid separation mechanism further includes a first regulating valve that is provided in the first return section and is configured to regulate a flow rate of the liquid phase component.
The air conditioner according to Claim 1 or 2,
wherein the gas-liquid separation mechanism further includes a second return section configured to collect the liquid phase component from the bottom portion of the storage portion and introduce the liquid phase component into the indoor heat exchanger through the second expansion valve.
The air conditioner according to Claim 1,
wherein the gas-liquid separation mechanism further includes a third return section configured to collect a gas phase component from an upper portion of the storage portion and introduce the gas phase component into the compressor.
The air conditioner according to Claim 4,
wherein the gas-liquid separation mechanism further includes a second regulating valve that is provided in the third return section and is configured to regulate a flow rate of the gas phase component.