CN114017941A

CN114017941A - Air conditioning system

Info

Publication number: CN114017941A
Application number: CN202111422171.XA
Authority: CN
Inventors: 武连发; 熊建国; 申传涛; 焦华超; 金孟孟
Original assignee: Gree Electric Appliances Inc of Zhuhai
Current assignee: Gree Electric Appliances Inc of Zhuhai
Priority date: 2021-11-26
Filing date: 2021-11-26
Publication date: 2022-02-08

Abstract

The invention discloses an air conditioning system, which comprises an indoor unit and an outdoor unit, wherein high-pressure exhaust gas of the outdoor unit is respectively communicated with the indoor unit through a first branch and a second branch, a first mode reversing valve, an outdoor heat exchanger and a heating throttling device are sequentially arranged on the second branch, the air conditioning system also comprises a third branch communicated with a low-pressure air suction pipe of the outdoor unit, a fourth branch is arranged between the third branch and an outlet pipe of the first mode reversing valve on the second branch, and a second mode reversing valve is arranged on the fourth branch. The invention adopts the design of the dual-mode reversing valve, the compressor does not need to reduce the frequency when the operation modes are switched, the valve switching time is short, the failure of valve switching is effectively avoided, and the influence of the valve switching on the operation capacity of the unit and the indoor temperature fluctuation is reduced.

Description

Air conditioning system

Technical Field

The invention relates to the technical field of air conditioners, in particular to a heat-recoverable air conditioning system.

Background

The multi-split air conditioner sold in the market at present adopts a four-way valve to control the flow direction of a refrigerant in a heat exchanger, wherein a system adopting a double four-way valve is not lacked, the system adopting the double four-way valve has a complex structure and high cost, in addition, the frequency of a compressor needs to be reduced in the mode switching process, and the pressure difference of an inlet and an outlet of a valve body is reduced, so that the valve switching success of the four-way valve is ensured, the output fluctuation of the compressor is large, the fluctuation of the indoor air outlet temperature is severe, and the comfort of an indoor air conditioner is influenced. In addition, the reversing control requirement of the four-way valve is high, and the pilot four-way valve is easy to cause reversing failure under the condition of overlarge or undersize pressure. In addition, if the compressor does not reduce the frequency when the four-way valve is reversed, the pressure difference between the inlet and the outlet is too large when the four-way valve is reversed, and abnormal noise can be caused by sudden reversing.

Disclosure of Invention

The invention provides a heat recovery type air conditioning system, which aims to solve the problems that the indoor air outlet temperature fluctuation is severe and the comfort of an indoor air conditioner is influenced because a compressor needs to reduce the frequency when a four-way valve is reversed during the switching of an operation mode in the prior art.

The air conditioning system provided by the invention comprises an indoor unit and an outdoor unit, wherein high-pressure exhaust gas of the outdoor unit is respectively communicated with the indoor unit through a first branch and a second branch, a first mode reversing valve, an outdoor heat exchanger and a heating throttling device are sequentially arranged on the second branch, the air conditioning system also comprises a third branch communicated with a low-pressure air suction pipe of the outdoor unit, a fourth branch is arranged between the third branch and an outlet pipe of the first mode reversing valve on the second branch, and a second mode reversing valve is arranged on the fourth branch.

The first branch is communicated with one interface of the indoor unit through a first branch, and a first throttling device is arranged on the first branch; the second branch is communicated with the other interface of the indoor unit through a second branch, and a second throttling device is arranged on the second branch; a third branch is led out between the first throttling device on the first branch and the indoor unit, the other end of the third branch is communicated with the third branch, and a third throttling device is arranged on the third branch.

Preferably, the first mode selector valve and the second mode selector valve are throttle valves.

And a subcooler is arranged between the heating throttling device and the second throttling device on the second branch, one end of the subcooler is led out to form a fifth branch communicated with the third branch, the fifth branch is provided with a subcooling throttling device, and part of refrigerant at the outlet of the subcooler is throttled by the subcooling throttling device and then exchanges heat with refrigerant in the subcooler.

In one embodiment, an electrical appliance box heat dissipation plate is further arranged between the heating throttling device and the subcooler.

Furthermore, a sixth branch is arranged between the exhaust pipeline and the air inlet pipeline of the compressor of the outdoor unit, and a pressure reducing device and an oil return electromagnetic valve are arranged on the sixth branch.

The air conditioning system provided by the invention comprises the following five operation modes: a full cooling mode, a full heating mode, a full heat recovery mode, a main body cooling mode, and a main body heating mode. When the air conditioning system is switched between modes, the compressor does not need to adjust the frequency according to the system pressure.

In the full cooling mode, the first mode switching valve, the heating throttling device and the third throttling device on the third branch are opened, and the second mode switching valve and the first throttling device on the first branch are closed.

In the complete heating mode, the second mode reversing valve, the heating throttling device and the first throttling device on the first branch are opened, and the first mode reversing valve and the third throttling device on the third branch are closed.

The full heat recovery mode includes a dual low pressure operating mode and a single low pressure operating mode.

In the full heat recovery mode of double low-pressure operation, the first mode reversing valve is closed, the second mode reversing valve and the heating throttling device are opened, for a refrigerating indoor unit, the first throttling device on the first branch is closed, the third throttling device on the third branch is opened, for a heating indoor unit, the first throttling device on the first branch is opened, and the third throttling device on the third branch is closed.

In the single low-pressure operation of the complete heat recovery mode, the first mode reversing valve, the second mode reversing valve and the heating throttling device are all closed, for the refrigerating internal machine, the first throttling device on the first branch is closed, the third throttling device on the third branch is opened, for the heating internal machine, the first throttling device on the first branch is opened, and the third throttling device on the third branch is closed.

In the main body refrigeration mode, the first mode reversing valve and the heating throttling device are both opened, the second mode reversing valve is closed, for the refrigeration indoor unit, the first throttling device on the first branch is closed, the third throttling device on the third branch is opened, for the heating indoor unit, the first throttling device on the first branch is opened, and the third throttling device on the third branch is closed.

In the main heating mode, the first mode reversing valve is closed, the second mode reversing valve and the heating throttling device are opened, for the refrigerating indoor unit, the first throttling device on the first branch is closed, and the third throttling device on the third branch is opened; for the heating internal machine, the first throttling device on the first branch is opened, and the third throttling device on the third branch is closed.

Compared with the prior art, the invention has the following beneficial effects:

1. in the brand-new valve switching combination scheme designed by the invention, the mode reversing valve is used for replacing the conventional four-way reversing valve, the frequency reduction of the compressor is not required during the switching of the operation mode, the valve switching time is short, the failure of valve switching is effectively avoided, and the influence of the valve switching on the operation capacity of a unit and the indoor temperature fluctuation is reduced.

2. The invention has multiple operation modes, can realize multiple functions of independent refrigeration, independent heating, mixed refrigeration and heating, hot water production, cold water production and the like, and meets multiple requirements under different conditions.

3. On the premise of meeting the requirements of refrigeration and heating, the invention can also synchronously radiate the electric appliance box, thereby realizing energy conservation and reasonable utilization of a cold source.

4. The invention has simple structure and low production, use and maintenance cost.

Drawings

The invention is described in detail below with reference to the following figures and specific examples, wherein:

FIG. 1 is a schematic view of an outdoor unit according to the present invention;

FIG. 2 is a flow chart of the full cooling mode of the present invention;

FIG. 3 is a flow chart of the full heating mode of the present invention;

FIG. 4 is a flow chart of dual low pressure operation in full heat recovery mode of the present invention;

FIG. 5 is a flow chart of single low pressure operation in full heat recovery mode of the present invention;

FIG. 6 is a flow chart of the cooling mode of the main body of the present invention;

FIG. 7 is a flow chart of a heating mode of the main body of the present invention;

fig. 8 is a schematic view of an outdoor unit as a modular combination.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings and examples. It should be understood that the following specific examples are only for illustrating the present invention and are not to be construed as limiting the present invention.

As shown in fig. 1 and 2, the air conditioning system provided by the present invention includes an indoor unit and an outdoor unit, wherein the outdoor unit includes: the air conditioner comprises a compressor 1, an oil component 2, a first branch 3 and a second branch 4, wherein the first branch is communicated with the high-pressure exhaust of the compressor, and is provided with a check valve 31 and communicated with an indoor unit through a high-pressure stop valve 32. The second branch 4 is provided with a first mode reversing valve 41, an outdoor heat exchanger 42, a heating throttling device 43, an electrical appliance box heat dissipation plate 44 and a subcooler 45 in sequence, and is communicated with the indoor unit through a liquid pipe stop valve 46. The refrigerant pipe and the electrical box radiate the heat of the electrical box through the heat radiating plate.

The third branch 6 is communicated with the compressor inlet pipe and is communicated with the indoor unit through a low-pressure stop valve 61. And a steam branch 5 is arranged at the front end of the air inlet of the compressor on the third branch. A fourth branch 7 is arranged between the outlet pipe of the first mode reversing valve 41 on the second branch 4 and the third branch, and a second mode reversing valve 71 is arranged on the fourth branch. A fifth branch 8 communicated with the third branch 6 is led out of the second branch 4 between the subcooler 45 and the liquid pipe stop valve 46, a subcooling throttling device 81 is arranged on the fifth branch, and part of the refrigerant at the outlet of the subcooler is throttled by the subcooling throttling device 81 and then exchanges heat with the refrigerant in the subcooler 45. A sixth branch 9 is also arranged between the compressor exhaust pipeline and the air inlet pipeline, and a pressure reducing device 91 and an oil return electromagnetic valve 92 are arranged on the sixth branch. In this embodiment, the pressure reducing device 91 uses a capillary tube.

As shown in fig. 2, the first branch 3 is communicated with one interface of an air conditioner internal unit 13 and a water making unit 14 through a first branch 10, and a first throttling device 101 is arranged on the first branch; the second branch 4 is communicated with the other interfaces of the air conditioner internal unit 13 and the water generator 14 through a second branch 11, and a second throttling device 111 is arranged on the second branch. A third branch 12 is led out between the first throttling device 101 and the air conditioner internal unit 13 on the first branch and between the first throttling device 101 and the water maker 14 on the first branch, the other end of the third branch is communicated with a third branch 6, and a third throttling device 121 is arranged on the third branch.

In the above embodiment, the first mode switching valve 41 and the second mode switching valve 71 are both throttle valves, and in this embodiment, the throttle valves are electronic expansion valves. The invention uses the throttle valve to replace a four-way valve, and the compressor does not need to reduce the frequency when the valve is cut. As an alternative embodiment, the first mode switching valve 41 and the second mode switching valve 71 may be an electric ball valve or a solenoid valve, and the second mode switching valve 71 may be an electric ball valve or a solenoid valve.

In the above embodiment, the indoor unit includes three air conditioner indoor units and one water generator connected in parallel. The water generator may be used to provide hot or cold water.

The heat recovery type air conditioning system provided by the invention comprises the following five operation modes: a full cooling mode, a full heating mode, a full heat recovery mode, a main body cooling mode, and a main body heating mode. When the air conditioning system is switched between modes, the compressor does not need to adjust the frequency according to the system pressure.

As shown in fig. 2, in the complete cooling mode, the high-pressure refrigerant gas discharged from the compressor 1 passes through the discharge pipe and the oil 2, enters the second branch 4, flows through the first mode switching valve 41, enters the outdoor heat exchanger 42, is condensed, passes through the heating throttle device 43 and the subcooler 45, and then flows into the indoor unit through the liquid pipe stop valve 46. The refrigerant is throttled by the second throttling device 111 on the second branch 11 and flows into the air conditioner internal unit 13 for refrigeration, and at the moment, the water making machine is used for making cold water. The refrigerant evaporated in the air conditioner indoor unit and the refrigerant at the outlet of the water generator are converged into the third branch 6 through the third throttling device 121 on the third branch 12, the third branch is a low-pressure air pipe, and the refrigerant returns to the compressor through the low-pressure air pipe stop valve 61 and the steam separator 5. The open and closed states of the valves are as follows:

electric valve name	Open and closed state
		First mode selector valve 41	Opening device
Second mode selector valve 71	Closing device
		Heating throttle device 43	Opening device
First throttle device 101	Closing device
		Third throttling means 121	Opening device
Subcooler throttling device 81	According to refrigeration demand and supercooling degree control

As shown in fig. 3, in the full heating mode, the high-pressure refrigerant gas discharged from the compressor 1 flows into the indoor unit through the oil 2 to the first branch passage 3, and then through the check valve 31 and the high-pressure gas pipe shutoff valve 32. High-temperature and high-pressure gas flows into an air conditioner indoor unit 13 through a first throttling device 101 on a first branch 10 to be heated, a refrigerant which is condensed and releases heat in the air conditioner indoor unit flows into a second branch 4 through a second throttling device on a second branch 11, then flows into an outdoor heat exchanger 42 through a liquid pipe stop valve 46, a subcooler 45 and a heating throttling device 43 in sequence to be evaporated, and the evaporated refrigerant flows into a steam branch 5 through a second mode reversing valve 71 and then returns to a compressor. In this mode, the water generator can provide hot water. The open and closed states of the valves are as follows:

electric valve name	Open and closed state
		First mode selector valve 41	Closing device
Second mode selector valve 71	Opening device
		Heating throttle device 43	Opening device
First throttle device 101	Opening device
		Third throttling means 121	Closing device
Subcooler throttling device 81	According to refrigeration demand and supercooling degree control

The complete heat recovery mode aims at the condition that an indoor unit has the requirements of refrigeration and heating at the same time, and comprises two conditions of double-low-voltage operation and single-low-voltage operation. The double low pressure operation refers to that when the heat recovery mode is adopted, two paths of refrigerants return air. Single low pressure operation refers to a heat recovery mode in which only one refrigerant is returned (in a colloquial manner, only one main pipe is returned).

Double low pressure run entry conditions: the environment temperature is more than Tsd (Tsd can be set, and the suggested value is 5 ℃), the startup load rate is more than C1 (C1 can be set, and the suggested value is 50%); ③ the IPM module temperature of the driving plate is more than Ti (Ti can be set, and the recommended value is 60 ℃). And if one of the three conditions is met, the dual low-pressure mode can be entered, and otherwise, the single low-pressure mode is recommended.

Fig. 4 shows a dual low pressure mode, in which high pressure refrigerant gas discharged from the compressor 1 flows into the indoor unit through the oil 2 to the first branch passage 3, and then flows into the check valve 31 and the high pressure gas pipe stop valve 32. High-temperature and high-pressure refrigerant flows into a heating air conditioner indoor unit 13 through a first throttling device 101 on a first branch 10 to be condensed and released heat (the air conditioner indoor unit on the right side in the embodiment), the condensed liquid refrigerant is divided into two paths, one part of the condensed liquid refrigerant enters a refrigerating air conditioner indoor unit (the two air conditioner indoor units on the left side) through a second branch 11 to be evaporated, and the evaporated gas flows to a steam branch 5 through a third branch 6 and then returns to a compressor; the other part passes through the subcooler 45, the heating throttling device 43, the outdoor heat exchanger 42 and the second mode reversing valve 71 on the second branch 4 to the steam separator 5 and then returns to the compressor. Under the double low pressure mode, can dispel the heat to electrical apparatus box (IPM heating panel), can also provide hot water through the water generator. The open and closed states of the valves are as follows:

electric valve name	Open and closed state
		First mode selector valve 41	Closing device
Second mode selector valve 71	Opening device
		Heating throttle device 43	Opening device
First throttle device 101	Refrigeration switch and heating switch
		Third throttling means 121	Refrigeration switch and heating switch
Subcooler throttling device 81	According to refrigeration demand and supercooling degree control

Fig. 5 shows a single low pressure mode, in which high pressure refrigerant gas discharged from the compressor 1 flows to the first branch line 3 through the oil component 2, and is communicated with the indoor unit through the check valve 31 and the high pressure gas pipe stop valve 32, and then flows into the heating air conditioner indoor unit (one air conditioner indoor unit on the right in the figure) through the first throttling device 101 on the first branch line 10 to be condensed and release heat, the condensed liquid refrigerant completely enters the refrigerating air conditioner indoor units (two air conditioner indoor units on the left in the figure) to be evaporated, and the evaporated gas returns to the steam component 5 through the third branch line 6 and then returns to the compressor. In this mode, the water generator can provide cold water. The open and closed states of the valves are as follows:

electric valve name	Open and closed state
		First mode selector valve 41	Closing device
Second mode selector valve 71	Closing device
		Heating throttle device 43	Closing device
First throttle device 101	Refrigeration switch and heating switch
		Third throttling means 121	Refrigeration switch and heating switch
Subcooler throttling device 81	According to refrigeration demand and supercooling degree control

As shown in fig. 6, in the main cooling mode, the high-pressure refrigerant gas discharged from the compressor 1 flows to the first branch line 3 through the oil component 2, and then is divided into two paths, and a small part of the refrigerant directly enters the air conditioner indoor units (one air conditioner indoor unit on the right side in the figure) for heating through the first branch line 10 to be condensed and release heat; most of the refrigerant enters the outdoor heat exchanger 42 through the first mode reversing valve 41 to be condensed, the condensed liquid enters the indoor refrigerating air conditioner indoor units (the left two air conditioner indoor units in the figure) through the second branch line 11 to be evaporated, the condensed liquid of the heating air conditioner indoor units also enters the refrigerating air conditioner indoor units to be evaporated, and the evaporated refrigerant returns to the compressor after passing through the third branch line 6 and the steam separator 5. In this mode, the water generator 14 can provide cold water. The open and closed states of the valves are as follows:

electric valve name	Open and closed state
		First mode selector valve 41	Opening device
Second mode selector valve 71	Closing device
		Heating throttle device 43	Closing device
First throttle device 101	Refrigeration switch and heating switch
		Third throttling means 121	Refrigeration and heatingClosing device
Subcooler throttling device 81	According to refrigeration demand and supercooling degree control

As shown in fig. 7, in the main heating mode, the high-pressure refrigerant gas discharged from the compressor 1 flows to the first branch line 3 through the oil component 2, and is communicated with the indoor units through the high-pressure gas pipe stop valve 32, and then flows into the air-conditioning indoor units for heating (two air-conditioning indoor units on the right side in the figure) through the first throttling device 101 to be condensed and release heat, the condensed liquid refrigerant, a part of the refrigerant enters the air-conditioning indoor units for cooling (one air-conditioning indoor unit on the left side in the figure) to be evaporated, and the evaporated gas flows to the third branch line 6 and returns to the compressor through the steam component 5; the other part of the refrigerant enters the outdoor heat exchanger 42 through the subcooler 45 and the heating throttling device 43 on the second branch 4 to be evaporated, and the evaporated gaseous refrigerant flows to the steam separator through the second mode reversing valve 71 and then returns to the compressor. In this mode, the water generator 14 can provide hot water. The open and closed states of the valves are as follows:

The outdoor unit can be made into a modularized combination and then used with the indoor unit, and is particularly suitable for large indoor units. As shown in fig. 8, a check valve 31 is provided in a pipe between the outdoor unit oil 2 and the high pressure pipe shut-off valve 32, and a check valve may be provided outside the high pressure pipe shut-off valve 32, for example, in the form of a separate construction kit, and installed at the time of field installation. After the check valve is additionally arranged, the modular combination function can be supported, namely a plurality of external units are combined into a high-power unit.

The check valve 31 can be omitted for a single outdoor unit, thereby saving cost.

The invention has the following advantages:

1. the invention adopts the mode switching of the double-throttling device control system, when the unit is switched between modes, the frequency of the compressor is not required to be reduced, the valve switching mode is switched without waiting for the pressure difference between the high pressure of the system and the low pressure of the system to be reduced to the application range of the four-way valve, and the valve body can be successfully switched under the condition that the frequency of the compressor is not reduced, namely the stability of the air outlet temperature is ensured;

2. the mode reversing valve can adopt valve bodies in various forms, has strong flexibility, and can control the noise in the mode switching process by controlling different opening degrees;

3. in a complete refrigeration or main refrigeration mode, the outdoor heat exchanger of the unit is used as a condenser; when the heating is completed or the main body is heated, the outdoor heat exchanger is used as an evaporator; in the complete heat recovery mode, the outdoor heat exchanger can be not used (when the load is small), so that the pressure loss and the power consumption of an outdoor fan are reduced, and the energy efficiency is improved; when the load is large or the temperature of the electric appliance box is high, the outdoor heat exchanger can also be used as an evaporator, and at the moment, the refrigerant can synchronously dissipate heat of the electric appliance box (IPM heat dissipation plate);

4. the complete heat recovery mode has double-low-pressure operation and single-low-pressure operation modes, the unit can be selected according to parameters such as load, ambient temperature and the like, and the flexibility is strong. Two different refrigerant flowing and distributing modes ensure that the unit runs more safely and reliably, and is energy-saving and efficient;

5. the invention supports and matches with a water generator, can be used for preparing domestic hot water and cold water or supplying water for floor heating, and can be satisfied by controlling the opening degree of the throttling device on the branch road according to the hot water requirement (time, temperature and the like).

The foregoing is considered as illustrative only of the embodiments of the invention. It should be understood that any modifications, equivalents and changes made within the spirit and framework of the inventive concept are intended to be included within the scope of the present invention.

Claims

1. The air conditioning system is characterized by further comprising a third branch communicated with a low-pressure air suction pipe of the outdoor unit, a fourth branch is arranged between the third branch and an outlet pipe of the first mode reversing valve on the second branch, and a second mode reversing valve is arranged on the fourth branch.

2. The air conditioning system according to claim 1, wherein the first branch is communicated with an interface of the indoor unit through a first branch path, and a first throttling device is provided on the first branch path; the second branch is communicated with the other interface of the indoor unit through a second branch, and a second throttling device is arranged on the second branch; a third branch is led out between the first throttling device on the first branch and the indoor unit, the other end of the third branch is communicated with the third branch, and a third throttling device is arranged on the third branch.

3. The air conditioning system as claimed in claim 1, wherein the first mode switching valve and the second mode switching valve each employ a throttle valve.

4. The air conditioning system as claimed in claim 2, wherein a subcooler is disposed on the second branch between the heating throttling device and the second throttling device, a fifth branch communicated with the third branch is led out from one end of the subcooler, a subcooling throttling device is disposed on the fifth branch, and part of refrigerant at an outlet of the subcooler is throttled by the subcooling throttling device and then exchanges heat with refrigerant in the subcooler.

5. The air conditioning system as claimed in claim 4, wherein an appliance box heat dissipation plate is further provided between the heating throttle device and the subcooler.

6. The air conditioning system as claimed in claim 1, wherein a sixth branch is provided between a discharge duct and an intake duct of the compressor of the outdoor unit, and a pressure reducing device and an oil return solenoid valve are provided on the sixth branch.

7. Air conditioning system according to any of claims 1 to 6, characterized in that it comprises the following five operating modes: a full cooling mode, a full heating mode, a full heat recovery mode, a main body cooling mode, and a main body heating mode.

8. The air conditioning system as claimed in claim 7, wherein the compressor does not need to adjust the frequency according to the system pressure when the air conditioning system is in mode switching.

9. The air conditioning system as claimed in claim 7, wherein in the full cooling mode, the first mode switching valve, the heating throttling means, and the third throttling means on the third branch are opened, and the second mode switching valve, the first throttling means on the first branch are closed.

10. The air conditioning system as claimed in claim 7, wherein in the full heating mode, the second mode switching valve, the heating throttling device and the first throttling device on the first branch are opened, and the first mode switching valve and the third throttling device on the third branch are closed.

11. The air conditioning system as claimed in claim 7, wherein in the dual low pressure operation of the full heat recovery mode, the first mode switching valve is closed, the second mode switching valve and the heating throttling device are opened, the first throttling device on the first branch is closed for the cooling indoor unit, the third throttling device on the third branch is opened, the first throttling device on the first branch is opened for the heating indoor unit, and the third throttling device on the third branch is closed.

12. The air conditioning system as claimed in claim 7, wherein in the single low pressure operation of the full heat recovery mode, the first mode switching valve, the second mode switching valve and the heating throttle device are all closed, the first throttle device on the first branch is closed for the cooling indoor unit, the third throttle device on the third branch is opened, the first throttle device on the first branch is opened for the heating indoor unit, and the third throttle device on the third branch is closed.

13. The air conditioning system as claimed in claim 7, wherein in the main cooling mode, the first mode switching valve and the heating throttle device are both open, the second mode switching valve is closed, the first throttle device on the first branch is closed for the cooling indoor unit, the third throttle device on the third branch is open, and the first throttle device on the first branch is open and the third throttle device on the third branch is closed for the heating indoor unit.

14. The air conditioning system as claimed in claim 7, wherein in the main heating mode, the first mode switching valve is closed, the second mode switching valve and the heating throttling device are opened, and for the cooling indoor unit, the first throttling device in the first branch is closed, and the third throttling device in the third branch is opened; for the heating internal machine, the first throttling device on the first branch is opened, and the third throttling device on the third branch is closed.