CN115507568A

CN115507568A - Refrigerant circulating system of central air conditioner and refrigerating and heating method thereof

Info

Publication number: CN115507568A
Application number: CN202211294806.7A
Authority: CN
Inventors: 杨凡; 邹鑫; 郁伟荣; 张义武
Original assignee: Guangdong Yibai Fluid Technology Co ltd
Current assignee: Guangdong Yibai Fluid Technology Co ltd
Priority date: 2022-10-21
Filing date: 2022-10-21
Publication date: 2022-12-23
Also published as: CN116772321A

Abstract

The invention discloses a coolant circulating system of a central air conditioner and a refrigerating and heating method thereof, wherein the circulating system comprises: the system comprises a storage tank, a supercharger, a first air energy host, a second air energy host and a secondary refrigerant heat exchanger; a first backflow pipeline is arranged between the second port of the first air energy host and the first port of the second air energy host; a second backflow pipeline is arranged between the second port of the second air energy host and the first port of the first air energy host; the first air energy main machine and the second air energy main machine are respectively connected with the low-pressure inlet end of the supercharger through pipelines; the outlet end of the booster is respectively connected with the storage tank, the secondary refrigerant heat exchanger and the second port of the first air energy host machine through pipelines; and the outlet of the secondary refrigerant heat exchanger is respectively connected with the first air energy host and the second air energy host. The invention does not adopt a reverse defrosting mode for defrosting, but can effectively defrost, and the condition that no warm air is blown out can not occur in the defrosting process, thereby having good use experience.

Description

Refrigerant circulating system of central air conditioner and refrigerating and heating method thereof

Technical Field

The invention relates to the technical field of air conditioning systems, in particular to a refrigerant circulating system of a central air conditioner and a refrigerating and heating method thereof.

Background

The artificial refrigeration mode mainly comprises phase change refrigeration, gas expansion refrigeration, vortex tube refrigeration and thermoelectric refrigeration, and each refrigeration method has the characteristics. Meanwhile, the manual heating mode mainly comprises phase change heating, vortex tube heating and thermoelectric heating, and each heating mode also has the characteristics.

In the refrigerating and heating process, a process that the refrigerant can be recycled is required, the refrigerant absorbs heat to be a refrigerating process, and the refrigerant releases heat to the secondary refrigerant to be a heating process.

There are also many prior art air conditioning systems that have both cooling and heating cycles, however, many of these prior art cycles still have room for improvement, such as: in the heating mode, because the air energy host machine of the circulating system as the outdoor machine is used for absorbing heat from the outdoor environment, the temperature of the air energy host machine is low, water vapor in the outdoor environment can be gradually condensed on the surface of the air energy host machine and frost is formed, the frost can be gradually thickened if not removed, the heating capacity can be reduced when the frost is thickened to a certain degree, the use experience is influenced, in the using process, the indoor temperature of the place where the indoor machine is located can reach the desired temperature by heating the system for a longer time, and the power consumption is increased. In addition, the conventional system generally adopts a reverse defrosting mode to defrost, that is, the system is directly switched to a refrigeration mode, so that the air as the outdoor unit can be in a heat release state by a main machine, and frost is melted after absorbing heat.

Accordingly, there is a need for improvements in the art.

Disclosure of Invention

The invention aims to provide a refrigerant circulating system of a central air conditioner and a refrigerating and heating method thereof, which can ensure effective defrosting without adopting a reverse defrosting mode, avoid the condition of no warm air blowing during defrosting and have good use experience.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a refrigerant circulating system of a central air conditioner includes: the system comprises a storage tank, a supercharger, a first air energy host, a second air energy host and a secondary refrigerant heat exchanger;

an outlet of the storage tank is respectively connected with a first port of the first air energy host machine, a first port of the second air energy host machine and a low-pressure inlet end of the supercharger through pipelines so as to correspondingly output refrigerants;

a first return pipeline is communicated between a second port of the first air energy host machine and a first port of the second air energy host machine and used for conveying the refrigerant output by the first air energy host machine to the second air energy host machine; a second return pipeline is communicated between a second port of the second air energy host machine and a first port of the first air energy host machine and used for conveying the refrigerant output by the first air energy host machine to the first air energy host machine;

the second port of the first air energy main machine and the second port of the second air energy main machine are respectively connected with the low-pressure inlet end of the supercharger through pipelines and can be used for inputting gaseous refrigerants to the supercharger for supercharging;

the high-pressure outlet end of the supercharger is respectively connected with the inlet of the storage tank, the inlet of the secondary refrigerant heat exchanger and the second port of the first air energy main machine through pipelines, and the inlet of the secondary refrigerant heat exchanger is provided with a first expansion valve; the gaseous refrigerant is converted into gaseous or supercritical high-pressure and high-temperature refrigerant after being pressurized by the booster; in a refrigeration mode, gaseous or supercritical high-pressure and high-temperature refrigerants can be correspondingly input into the first air energy host machine for cooling; in the heating mode, gaseous or supercritical high-pressure and high-temperature refrigerants can be input into the secondary refrigerant heat exchanger through the first expansion valve for heat exchange;

a first port of the first air energy host is connected with an inlet of the secondary refrigerant heat exchanger through a pipeline; in a refrigeration mode, the refrigerant is cooled to be a high-pressure normal-temperature refrigerant through the first air energy host, then is converted into a gaseous low-temperature refrigerant through the first expansion valve due to the JT effect, and enters the secondary refrigerant heat exchanger for heat exchange;

the outlet of the secondary refrigerant heat exchanger is respectively connected with the first port of the first air energy main machine, the first port of the second air energy main machine and the low-pressure inlet end of the supercharger through pipelines; in a refrigeration mode, gaseous refrigerants output by the secondary refrigerant heat exchanger after heat exchange are input into the supercharger for supercharging, and circulation is achieved; in the heating mode, after heat exchange, the liquid high-pressure normal-temperature refrigerant output by the secondary refrigerant heat exchanger is input into the first air energy host or the second air energy host, so that circulation is realized.

For the additional structure of the above technical scheme, the following scheme is also included:

as a specific embodiment, a second expansion valve is arranged on the first return pipeline for throttling and pressure regulating the refrigerant; a third expansion valve is arranged on the second return pipeline and used for throttling and regulating pressure of the refrigerant;

when the central circulation system starts to be started, the second expansion valve or the third expansion valve is used for throttling and regulating pressure of a refrigerant, so that the pressure value of the corresponding second port of the first air energy main machine or the second port of the second air energy main machine is kept at a set value;

in the heating mode, the refrigerant may enter the second air energy host after passing through the first air energy host and the second expansion valve, or may enter the first air energy host after passing through the second air energy host and the third expansion valve.

In a specific embodiment, a fourth expansion valve is respectively arranged at the inlet and the outlet of the storage tank, and can be used for expansion and pressure reduction.

As a specific embodiment, a first control valve is further arranged on a pipeline between the outlet of the storage tank and the first port of the first air energy main machine; a second control valve is further arranged on a pipeline between the outlet of the storage tank and the first port of the second air energy host; a third control valve is arranged on a pipeline between the high-pressure outlet end of the supercharger and the second port of the first air energy main machine; and a fourth control valve is also arranged on a pipeline between the first port of the first air energy main machine and the inlet of the secondary refrigerant heat exchanger.

As a specific embodiment, a first electromagnetic valve is arranged on a pipeline between the second port of the first air energy main machine and the low-pressure inlet end of the supercharger; a second electromagnetic valve is arranged on a pipeline between a second port of the second air energy main machine and the low-pressure inlet end of the supercharger; and a third electromagnetic valve is arranged on a pipeline between the outlet of the secondary refrigerant heat exchanger and the low-pressure inlet end of the supercharger.

As a specific embodiment, the number of the secondary refrigerant heat exchangers is one or more than two arranged in parallel.

Furthermore, the number of the secondary refrigerant heat exchangers is more than two; in a refrigerating mode, when the using number of the secondary refrigerant heat exchangers is increased, the refrigerant circulating system of the central air conditioner needs to increase the quality of the refrigerant due to the increase of the required refrigerating capacity, and the storage tank outputs the refrigerant to the supercharger to supplement the refrigerant with the quality required by the circulating system; in the heating mode, when the number of the secondary refrigerant heat exchangers is increased, the refrigerant circulating system of the central air conditioner needs to increase the quality of the refrigerant due to the increase of the required heating capacity, the storage tank outputs the refrigerant to the corresponding first air energy host or the second air energy host, the refrigerant is input into the other air energy host through the corresponding first return pipeline or the corresponding second return pipeline for vaporization, and the vaporized refrigerant is input into the supercharger to supplement the refrigerant with the quality required by the circulating system; in the cooling or heating mode, when the using number of the secondary refrigerant heat exchangers is reduced, the refrigerant needed by the refrigerant circulating system of the central air conditioner is reduced, and redundant refrigerant flows back to the storage tank.

The invention also provides a refrigerant refrigerating and heating method of the central air conditioner, which adopts the refrigerant circulating system of the central air conditioner and comprises the following steps:

a cooling mode:

s1, starting a circulating system, outputting a refrigerant to the first air energy host machine or the second air energy host machine through the storage tank and vaporizing the refrigerant when the pressure at the high-pressure outlet end of the supercharger does not reach a set value, and inputting the refrigerant to the low-pressure inlet end of the supercharger so as to enable the pressure value at the high-pressure outlet end of the supercharger to reach and be kept at the set value; when the pressure at the high-pressure outlet end is higher than a set value, the refrigerant is recovered by the storage tank, so that the pressure at the high-pressure outlet end of the supercharger is not higher than the set value;

s2, after the supplement of the refrigerant is finished, closing a storage tank, closing a fan in the second air energy host and opening a fan in the first air energy host, converting the gaseous refrigerant into a gaseous or supercritical high-pressure and high-temperature refrigerant after the pressurization of the supercharger, and inputting the gaseous or supercritical high-pressure and high-temperature refrigerant into a second port of the first air energy host through a pipeline;

s3, the gaseous or supercritical high-pressure and high-temperature refrigerant entering the first air energy host from the second port of the first air energy host is converted into a high-pressure normal-temperature refrigerant by releasing heat to air in the environment, and the high-pressure normal-temperature refrigerant is output from the first port of the first air energy host and then enters the first expansion valve through a pipeline;

s4, after entering the first expansion valve, the high-pressure normal-temperature refrigerant is converted into a gaseous low-temperature refrigerant due to the JT effect and enters the secondary refrigerant heat exchanger from the inlet of the secondary refrigerant heat exchanger;

s5, after entering the secondary refrigerant heat exchanger, gaseous low-temperature refrigerants exchange heat with the secondary refrigerants on the outer surface of the secondary refrigerant heat exchanger, the secondary refrigerants release heat to the refrigerants to achieve cooling and refrigeration of the secondary refrigerants, and the gaseous low-temperature refrigerants absorb the heat of the secondary refrigerants and then are reheated to raise the temperature;

s6, inputting the gaseous refrigerant discharged by the secondary refrigerant heat exchanger to a low-pressure inlet end of the supercharger, pressurizing the gaseous refrigerant by the supercharger to form a gaseous or supercritical high-pressure and high-temperature refrigerant, and inputting the gaseous or supercritical high-pressure and high-temperature refrigerant to a second port of the first air energy host machine through a pipeline;

s7, repeating the steps S3-S6;

heating mode:

s11, starting a circulating system, outputting a refrigerant to the first air energy host machine or the second air energy host machine through the storage tank and vaporizing the refrigerant into a gaseous low-temperature refrigerant when the pressure at the high-pressure outlet end of the supercharger does not reach a set value, and inputting the gaseous low-temperature refrigerant into the supercharger so as to enable the pressure value at the high-pressure outlet end of the supercharger to reach and be kept at the set value; when the pressure at the high-pressure outlet end is higher than a set value, the refrigerant is recovered by the storage tank, so that the pressure at the high-pressure outlet end of the supercharger is not higher than the set value;

s12, after the refrigerant supplement is completed, opening a first electromagnetic valve, closing a second electromagnetic valve, opening a third expansion valve, closing a second expansion valve, closing a first control valve, opening a second control valve, closing a fan in the second air energy host and opening the fan in the first air energy host;

s13, the gas low Wen Lengmei vaporized by the air energy main machine is input into the supercharger for supercharging, then is converted into a gas or supercritical high-pressure high-temperature refrigerant, and enters the inlet of the secondary refrigerant heat exchanger after passing through the first expansion valve;

s14, exchanging heat between the gaseous or supercritical high-pressure and high-temperature refrigerant entering the secondary refrigerant heat exchanger and the secondary refrigerant on the outer surface of the secondary refrigerant heat exchanger, enabling the secondary refrigerant to absorb heat of the high-pressure and high-temperature refrigerant to realize heating of the secondary refrigerant, and enabling the high-pressure and high-temperature refrigerant to release heat to become a liquid high-pressure normal-temperature refrigerant and be discharged from an outlet of the secondary refrigerant heat exchanger;

s15, the liquid high-pressure normal-temperature refrigerant discharged by the secondary refrigerant heat exchanger firstly passes through the second air energy host of the stopped fan and defrosts the second air energy host by using the waste heat of the liquid high-pressure normal-temperature refrigerant, and then the refrigerant is input into the first air energy host through a second return pipeline and is vaporized through the first air energy host;

s16, repeating the steps S13-S15;

s17, when the air energy host is switched, closing a first electromagnetic valve, opening a second electromagnetic valve, closing a third expansion valve, opening a second expansion valve, opening a first control valve, closing a second control valve, opening a fan of the second air energy host and closing the fan of the first air energy host;

s18, the liquid high-pressure normal-temperature refrigerant discharged by the secondary refrigerant heat exchanger firstly passes through the first air energy host of the stopped running fan and defrosts the first air energy host by using the waste heat of the liquid high-pressure normal-temperature refrigerant, and then the refrigerant is input into the second air energy host through the first return pipeline and is vaporized through the second air energy host;

s19, converting the vaporized refrigerant into a gaseous low-temperature refrigerant, converting the refrigerant into a gaseous or supercritical high-pressure high-temperature refrigerant after being pressurized by the supercharger, inputting the gaseous or supercritical high-pressure high-temperature refrigerant into the secondary refrigerant heat exchanger through the first expansion valve for heat exchange, and discharging the liquid high-pressure normal-temperature refrigerant after heat exchange at an outlet of the secondary refrigerant heat exchanger;

and S20, repeating the steps S18-S19.

As a specific example, in steps S1 and S11, when starting the air conditioning cooling and heating cycle system of the new energy vehicle, a pressure value of the second port of the first air energy main unit is smaller than a set value, so that the refrigerant in the secondary refrigerant heat exchanger and in a corresponding pipeline is delivered to the first air energy main unit, after the refrigerant is vaporized, the pressure value of the second port of the first air energy main unit reaches the set value, the second expansion valve is opened, the refrigerant is input to the second air energy main unit through throttling and pressure regulating of the second expansion valve to maintain the pressure value of the second port of the first air energy main unit, and finally the refrigerant is input to the supercharger to supplement the pressure, when the pressure at the high pressure outlet end of the supercharger does not reach the set value, the storage tank is opened to supplement the pressure to the supercharger, until the pressure value at the high pressure outlet end of the supercharger reaches and is maintained at the set value, and the storage tank is closed.

As a specific example, the cooling mode:

the method further comprises the step S8 of opening the storage tank when the number of the secondary refrigerant heat exchangers is increased and the pressure of the high-pressure outlet end of the supercharger does not reach a set value, inputting gaseous refrigerant to the supercharger for supercharging, then enabling the refrigerant to enter the secondary refrigerant heat exchangers after sequentially passing through the first air energy host and the first expansion valve, stopping refrigerant output until the pressure of the high-pressure outlet end of the supercharger reaches the set value, and enabling redundant refrigerant to flow back into the storage tank through an inlet of the storage tank;

s9, when the number of the secondary refrigerant heat exchangers is reduced, enabling the pressure at the high-pressure outlet end of the supercharger to exceed a set value, and enabling redundant refrigerants to flow back to the storage tank so as to enable the pressure at the high-pressure outlet end of the supercharger to be kept at the set value;

heating mode:

step S21, when the number of the secondary refrigerant heat exchangers is increased, enabling the pressure at the high-pressure outlet end of the supercharger to be lower than a set value, opening the corresponding second expansion valve or third expansion valve, enabling the refrigerant in the storage tank to firstly pass through the air energy host machine without starting the fan, then conveying the refrigerant to the air energy host machine with the fan started through the corresponding first return flow channel or second return flow channel, vaporizing the refrigerant into the refrigerant, conveying the vaporized refrigerant to the supercharger for supplementing the refrigerant, and finally conveying the refrigerant to the secondary refrigerant heat exchanger through the first expansion valve until the pressure at the high-pressure outlet end of the supercharger reaches the set value, stopping the output of the refrigerant, and enabling the redundant refrigerant to flow back into the storage tank through the inlet of the storage tank;

and S22, when the number of the secondary refrigerant heat exchangers is reduced, the pressure of the high-pressure outlet end of the supercharger is enabled to exceed a set value, and redundant refrigerants flow back to the storage tank.

The invention has the beneficial effects that:

the refrigerant in the invention circularly flows between the two air energy hosts, the supercharger and the secondary refrigerant heat exchanger, and is subjected to vaporization, pressurization, heat exchange and other processes, so that the recycling of the refrigerant can be realized, and the operation cost of a refrigerant circulating system of the central air conditioner is effectively reduced.

In the refrigerating mode, the circulating system can utilize the supercharger to pressurize the refrigerant, then utilizes the first air energy host machine to cool, and then reduces the pressure and adiabatically expands the cooled refrigerant through the first expansion valve, so that the enthalpy change value of the refrigerant during refrigeration is improved to obtain higher energy efficiency ratio, and the refrigerant enters the secondary refrigerant heat exchanger, thereby finally realizing the refrigeration purpose of the secondary refrigerant through the secondary refrigerant heat exchanger.

In the heating mode, the circulating system utilizes the air energy main machine to vaporize the refrigerant output by the storage tank when in use, then the supercharger is utilized to pressurize the refrigerant, then the refrigerant is input into the secondary refrigerant heat exchanger to exchange heat, the refrigerant discharged by the secondary refrigerant heat exchanger firstly enters the air energy main machine without starting the fan by utilizing the first return pipeline or the second return pipeline, so that the ice and frost melting speed on the air energy main machine can be accelerated by utilizing the waste heat of the normal-temperature refrigerant in the liquid circulating and returning process, the defrosting efficiency is improved, then the refrigerant enters the other normally working air energy main machine to be vaporized, the vaporized refrigerant enters the supercharger to be pressurized and enters the secondary refrigerant heat exchanger to exchange heat, and the circulation is completed. Therefore, according to the above description, the indoor unit does not need to be defrosted by using the reverse defrosting operation during use, so that cold air cannot be blown out from the indoor unit during defrosting, specifically, two air energy hosts which are used alternately are utilized, one air energy host heats and heats the other air energy host, and defrosts the other air energy host, so that the indoor temperature can be maintained in a temperature range comfortable for a user, the use experience of the user is improved, and one air energy host in the two air energy hosts can be alternately used after working for several minutes, so that too much frost cannot be condensed by the air energy host in working, the defrosting is facilitated, and the heating effect of the system is also ensured.

Meanwhile, the defrosting system has a good defrosting effect, so that the heating effect of the system can be ensured, and the condition that the indoor temperature can reach the temperature desired by people only by heating for a long time is avoided, so that compared with the prior art, the defrosting system saves a power supply to a certain extent, and ensures the energy efficiency ratio.

In the invention, when the pressure at the high-pressure outlet end of the supercharger is lower than a set value (for example, when the using number of the refrigerating medium heat exchangers is increased) through the matching of the supercharger and the storage tank in the refrigerating or heating process, the storage tank continuously outputs the refrigerant to compensate the pressure, the refrigerant is stopped to be discharged until the pressure at the high-pressure outlet end of the supercharger reaches the set value, and when the pressure at the high-pressure outlet end of the supercharger is higher than the set value (for example, when the using number of the refrigerating medium heat exchangers is reduced), redundant mass of the refrigerant flows into the storage tank by utilizing pressure difference to reduce the pressure at the high-pressure outlet end of the supercharger so as to stop inputting the refrigerant until the pressure at the high-pressure outlet end of the supercharger reaches the set value; if the pressure at the high pressure outlet of the booster is always at the set value, the storage tank does not need to output the refrigerant nor input the refrigerant. Therefore, the invention can adjust the flow of the refrigerant in real time according to the real-time use condition, for example, the flow is used when the use number of the secondary refrigerant heat exchanger is increased or decreased, the change of the mass flow (namely, the increase or decrease of the number of the refrigerant in the flowing process) of the refrigerant can be realized according to different working conditions in the closed operation, the self-adaptive adjustment is realized, and meanwhile, the supercharger can basically keep the high energy efficiency ratio of the control system under the state that the set value of the high-pressure side pressure of the supercharger is not changed, and the purpose of saving electricity is realized.

Drawings

FIG. 1 is a schematic diagram of a refrigerant circulation system of a central air conditioner according to the present invention;

FIG. 2 is a schematic flow chart of a refrigerant refrigerating method of a central air conditioner according to the present invention;

fig. 3 is a schematic flow chart of a method for heating a refrigerant of a central air conditioner according to the present invention.

Reference numerals:

1. a storage tank; 2. a supercharger; 3. a first air energy host; 31. a first port of a first air-energy host; 32. a second port of the first air-energy host; 4. a second air energy host; 41. a first port of a second air-energy host; 42. a second port of the second air energy host; 43. a second return conduit; 5. a secondary refrigerant heat exchanger; 6. a first return conduit; 7. a second return conduit; 8. a first expansion valve; 9. a second expansion valve; 10. a third expansion valve; 11. a fourth expansion valve; 12. a first control valve; 13. a second control valve; 14. a third control valve; 15. a fourth control valve; 16. a first solenoid valve; 17. a second solenoid valve; 18. A third electromagnetic valve; 19. a proportional valve.

Detailed Description

The invention will be further elucidated with reference to the drawings and the embodiments, which are exemplary only and do not limit the scope of the invention.

The first embodiment is as follows:

referring to fig. 1, a refrigerant circulation system of a central air conditioner includes: the system comprises a storage tank 1, a supercharger 2, a first air energy main machine 3, a second air energy main machine 4 and a refrigerating medium heat exchanger 5.

The storage tank 1 is used for supplying a refrigerant to a control system, for example, for supplying a carbon dioxide refrigerant to the system, and the refrigerant described below is exemplified by using a carbon dioxide refrigerant. The supercharger 2 may be used to supercharge and warm the refrigerant. In the circulation system, the first air energy main unit 3 and the second air energy main unit 4 are used as outdoor unit parts, and the coolant heat exchanger 5 is used as an indoor unit part. The first air energy host 3 and the second air energy host 4 respectively comprise at least one fan with adjustable air quantity, an air energy evaporator, two ambient air temperature measuring probes respectively arranged at two ports of the air energy evaporator, a refrigerant pressure sensor arranged in the air energy evaporator pipe and temperature sensors respectively arranged at two ports of a refrigerant. The secondary refrigerant heat exchanger 5 is a sealed structure, a heat exchanger, a pressure sensor and a temperature sensor are arranged in the secondary refrigerant heat exchanger, and the secondary refrigerant transfers cold and heat with the refrigerant through the pipe wall of the heat exchanger. The inlet end and the outlet end of the supercharger 2 are also respectively provided with a pressure sensor.

Carbon dioxide is a new natural working medium, and is the refrigeration and heating working medium which is most friendly to the environment except water and air from the viewpoint of influence on the environment.

The outlet of the storage tank 1 is connected to the first port 31 of the first air energy main unit, the first port 41 of the second air energy main unit, and the low-pressure inlet end of the supercharger 2 through pipes, respectively, for outputting the refrigerant, wherein the storage tank 1 can transport the refrigerant to different places in different modes. For example, in the cooling mode, the storage tank 1 may output the refrigerant to the low-pressure inlet end of the supercharger 2; in the heating mode, the storage tank 1 can output the gaseous refrigerant to the first air energy main machine 3 or the second air energy main machine 4. In the heating mode, the first air energy host 3 and the second air energy host 4 can be used for vaporizing the refrigerant output by the storage tank 1 into a gaseous low-temperature refrigerant with a certain superheat degree, and the specific method is that the refrigerant is input into the first air energy host 3 or the second air energy host 4, and is vaporized after absorbing the heat of the outdoor environment to finally become the gaseous low-temperature refrigerant;

a first return pipeline 6 is communicated between the second port 32 of the first air energy main machine and the first port 41 of the second air energy main machine and is used for conveying the refrigerant output by the first air energy main machine 3 to the second air energy main machine 4; a second return pipeline 7 is communicated between the second port 42 of the second air energy host machine and the first port 31 of the first air energy host machine and is used for conveying the refrigerant output by the second air energy host machine 4 to the first air energy host machine 3; therefore, the arrangement of the first return pipeline 6 and the second return pipeline 7 is mainly used for the mutual flowing of the refrigerant between the two air energy main machines, so that the air energy main machines can be defrosted by utilizing the residual heat of the refrigerant;

the second port 32 of the first air energy main machine and the second port 42 of the second air energy main machine are respectively connected with the low-pressure inlet end of the supercharger 2 through pipelines and can be used for inputting gaseous refrigerants to the supercharger 2 for supercharging;

the high-pressure outlet end of the supercharger 2 is respectively connected with the inlet of the storage tank 1, the inlet of the secondary refrigerant heat exchanger 5 and the second port 32 of the first air energy main machine through pipelines, and the inlet of the secondary refrigerant heat exchanger 5 is provided with a first expansion valve 8; the inlet of the storage tank 1 can be used for inputting a refrigerant; the gaseous refrigerant is converted into gaseous or supercritical high-pressure and high-temperature refrigerant after being pressurized by the supercharger 2; in the refrigeration mode, gaseous or supercritical high-pressure and high-temperature refrigerant can be correspondingly input into the first air energy heat exchanger 3 for cooling; in the heating mode, gaseous or supercritical high-pressure and high-temperature refrigerant can be input into the secondary refrigerant heat exchanger 5 through the first expansion valve 8 for heat exchange; therefore, the refrigerant output routes of the supercharger 2 in different modes are different;

a first port 31 of the first air energy main machine is connected with an inlet of the secondary refrigerant heat exchanger 5 through a pipeline; in a refrigeration mode, the refrigerant is cooled to be a high-pressure normal-temperature refrigerant through the first air energy host 3, then is converted into a gaseous low-temperature refrigerant through the first expansion valve 8 due to the JT effect, and enters the secondary refrigerant heat exchanger 5 for heat exchange; therefore, in the normal operation process of the refrigeration mode, the refrigerant needs to be cooled by the first air energy heat exchanger 3, then enters the secondary refrigerant heat exchanger 5 after passing through the first expansion valve 8;

the outlet of the secondary refrigerant heat exchanger is respectively connected with the first port 31 of the first air energy main machine, the first port 41 of the second air energy main machine and the low-pressure inlet end of the supercharger 2 through pipelines; in a refrigeration mode, gaseous refrigerants output by the secondary refrigerant heat exchanger 5 after heat exchange are input into the supercharger 2 for supercharging, and circulation is realized; in the heating mode, the liquid high-pressure normal-temperature refrigerant output by the secondary refrigerant heat exchanger 5 after heat exchange is input into the first air energy host 3 or the second air energy host 4 to realize circulation, and of course, the subsequent steps are the same as the above, and are not repeated herein.

Wherein, the first return pipeline 6 is provided with a second expansion valve 9 for throttling and pressure regulating the refrigerant; a third expansion valve 10 is arranged on the second return pipeline 7 and used for throttling and regulating pressure of the refrigerant; specifically, when the central circulation system starts to start, the second expansion valve 9 or the third expansion valve 10 is used for throttling, regulating and switching on/off the refrigerant, so that the pressure value of the second port 32 of the corresponding first air energy main machine or the second port 42 of the corresponding second air energy main machine is kept at a set value; in the heating mode, the refrigerant may enter the second air energy main unit 4 after passing through the first air energy main unit 3 and the second expansion valve 9, or the refrigerant may enter the first air energy main unit 3 after passing through the second air energy main unit 4 and the third expansion valve 10.

A fourth expansion valve 11 is provided at the inlet and outlet of the storage tank 1, respectively, for expansion, pressure reduction, and opening and closing.

A first control valve 12 is also arranged on a pipeline between the outlet of the storage tank 1 and the first port 31 of the first air energy main machine; a second control valve 13 is also arranged on a pipeline between the outlet of the storage tank 1 and the first port 41 of the second air energy main machine; a third control valve 14 is arranged on a pipeline between the high-pressure outlet end of the supercharger 2 and the second port 42 of the first air energy main machine; a fourth control valve 15 is also arranged on a pipeline between the first port 31 of the first air energy main machine and the inlet of the secondary refrigerant heat exchanger 5; the first control valve 12, the second control valve 13, the third control valve 14, and the fourth control valve 15 are used to control the flow of the refrigerant.

A first solenoid valve 16 is arranged on a pipeline between the second port 32 of the first air energy main machine and the low-pressure inlet end of the supercharger 2; a second solenoid valve 17 is arranged on the pipeline between the second port 42 of the second air energy heat exchanger and the low-pressure inlet end of the supercharger 2; a third solenoid valve 18 is provided in the conduit between the outlet of the coolant heat exchanger 5 and the low-pressure inlet end of the booster 2. The first solenoid valve 16, the second solenoid valve 17, and the third solenoid valve 18 are also used to control the flow of the refrigerant.

Meanwhile, a proportional valve 19 is provided at an outlet of the coolant heat exchanger 5 to adjust the flow rate of the coolant to control the amount of cooling or heating, so that the coolant temperature in the tubes of the coolant heat exchanger 5 is maintained at a set value, and the coolant temperature is not easily fluctuated due to changes in the coolant mass flow or volume flow.

Preferably, the number of the coolant heat exchangers 5 may be one or more than two coolant heat exchangers arranged in parallel, that is, the number of the coolant heat exchangers 5 may be one, two, three or four, and the like, and the coolant heat exchangers 5 are arranged in parallel, so that people can increase or decrease the number of the coolant heat exchangers 5 at any time to increase or decrease the cooling capacity or the heating capacity. A first expansion valve 8 and a proportional valve 19 are provided at the inlet and outlet of each coolant heat exchanger 5, respectively.

Preferably, in the present embodiment, the number of the coolant heat exchangers 5 is two or more, specifically three. In the using process, for example, in a cooling mode, when the using number of the secondary refrigerant heat exchangers 5 is increased, the refrigerant circulating system of the central air conditioner needs to increase the quality of the refrigerant due to the increase of the required cooling capacity, the pressure value of the high-pressure outlet end of the supercharger 2 is lower than a set value, and the storage tank 1 outputs the refrigerant to the supercharger 2 so as to supplement the refrigerant with the quality required by the circulating system; in the heating mode, when the number of the secondary refrigerant heat exchangers 5 is increased, the pressure value of the high-pressure outlet end of the supercharger 2 is lower than a set value, so that the refrigerant circulation system of the central air conditioner needs to increase the quality of the refrigerant due to the increase of the required heating capacity, the storage tank 1 outputs the refrigerant to the corresponding first air energy host 3 or second air energy host 4 and inputs the refrigerant into the other air energy host through the corresponding first return pipeline 6 or second return pipeline 7 for vaporization, for example, after the storage tank 1 outputs the refrigerant to the first air energy host 3, the refrigerant is input into the second air energy host 4 through the first return pipeline 6 for vaporization or after the storage tank 1 outputs the refrigerant to the second air energy host 4, the refrigerant is input into the first air energy host 3 through the second return pipeline 7 for vaporization, and the vaporized refrigerant is input into the supercharger 2 for supplementing the refrigerant with the quality required by the circulation system, and then the refrigerant is processed according to a normal flow; meanwhile, in the cooling or heating mode, when the number of the secondary refrigerant heat exchangers 5 is reduced, the refrigerant requirement of the refrigerant circulation system of the central air conditioner is reduced, and the redundant refrigerant flows back to the storage tank 1.

In order to prevent the refrigerant from flowing backwards to affect the operation, a plurality of check valves are further disposed in the refrigerant circulation system of the central air conditioner, and specific reference may be made to the positions shown in fig. 1, which are not described herein again in detail.

In use, the heating mode is performed when the first port 51 of the coolant heat exchanger is used for inputting coolant and the second port 52 of the coolant heat exchanger is used for outputting coolant; the cooling mode is selected when the second port 52 of the coolant heat exchanger is used for inputting the coolant and the first port 51 of the coolant heat exchanger is used for outputting the coolant.

For use with a coolant, the coolant on the coolant heat exchanger 5 can be a gaseous coolant or a liquid coolant, such as: the gaseous coolant is air, nitrogen or argon, and the liquid coolant is water, saline, ethylene glycol or propylene glycol solution.

Each of the electromagnetic valves used in this embodiment is a normally closed type electromagnetic valve.

Example two:

referring to fig. 1 to 3, the present invention further provides a refrigerant cooling and heating method of a central air conditioner, which adopts the refrigerant circulation system of the central air conditioner, including the following steps:

a cooling mode:

s1, starting a circulating system, outputting a refrigerant to a first air energy host machine 3 or a second air energy main body 4 through a storage tank 1 and vaporizing the refrigerant when the pressure at the high-pressure outlet end of a supercharger 2 does not reach a set value, and then inputting the refrigerant to the low-pressure inlet end of the supercharger 2 so as to enable the pressure value at the high-pressure outlet end of the supercharger 2 to reach and be kept at the set value; when the pressure at the high-pressure outlet end is higher than a set value, the refrigerant is recovered by the storage tank 1, so that the pressure at the high-pressure outlet end of the supercharger 2 is not higher than the set value; specifically, the output and the recovery of the refrigerant are both regulated by throttling of a fourth expansion valve 11; more specifically, if the storage tank 1 outputs the refrigerant to the first air energy host 3, the refrigerant is input into the second air energy host 4 through the first return pipe 6 to be vaporized, and similarly, if the storage tank 1 outputs the refrigerant to the second air energy host 4, the refrigerant is input into the first air energy host 4 through the second return pipe 7 to be vaporized, and the vaporized refrigerant is input into the supercharger 2;

s2, after the supplement of the refrigerant is finished, the storage tank 1 is closed, a fan (not shown) in the second air energy host machine 4 is closed, a fan (not shown) in the first air energy host machine 3 is opened, the gaseous refrigerant is converted into a gaseous or supercritical high-pressure and high-temperature refrigerant after being pressurized by the supercharger 2, the gaseous or supercritical high-pressure and high-temperature refrigerant is input into the second port 32 of the first air energy host machine through a pipeline provided with a third control valve 14, and the third control valve 14 is opened at the moment;

s3, converting the gaseous or supercritical high-pressure and high-temperature refrigerant entering the first air energy host 3 from the second port 32 of the first air energy host into a high-pressure normal-temperature refrigerant by releasing heat to air in the environment, and enabling the high-pressure normal-temperature refrigerant to enter the first expansion valve 8 at the first port 31 of the first air energy host through a pipeline provided with the fourth control valve 15, namely opening the fourth control valve 15;

s4, the high-pressure normal-temperature refrigerant enters the first expansion valve 8, is converted into a gaseous low-temperature refrigerant due to the JT effect, and enters the secondary refrigerant heat exchanger 5 from the inlet of the secondary refrigerant heat exchanger;

s5, after entering the secondary refrigerant heat exchanger 5, the gaseous low-temperature refrigerant exchanges heat with the secondary refrigerant on the outer surface of the secondary refrigerant heat exchanger 5, the secondary refrigerant releases heat to the refrigerant to realize cooling and refrigeration of the secondary refrigerant, and the gaseous low-temperature refrigerant absorbs the heat of the secondary refrigerant and then heats up in a reheating mode;

s6, inputting the gaseous refrigerant discharged by the secondary refrigerant heat exchanger 5 to a low-pressure inlet end of a supercharger 2, and supercharging the gaseous refrigerant into a gaseous or supercritical high-pressure and high-temperature refrigerant by the supercharger 2, wherein the gaseous or supercritical high-pressure and high-temperature refrigerant is input to a second port 32 of the first air energy host through a pipeline;

s7, repeating the steps S3-S6, thereby realizing the recycling of the refrigerant;

heating mode:

s11, starting a circulating system, outputting a refrigerant to the first air energy host machine 3 or the second air energy host machine 4 through the storage tank 1 and vaporizing the refrigerant into a gaseous low-temperature refrigerant when the pressure at the high-pressure outlet end of the supercharger 2 does not reach a set value, and inputting the gaseous low-temperature refrigerant into the supercharger 2 so as to enable the pressure value at the high-pressure outlet end of the supercharger to reach and be kept at the set value; when the pressure at the high-pressure outlet end is higher than a set value, the refrigerant is recovered by the storage tank 1, so that the pressure at the high-pressure outlet end of the supercharger is not higher than the set value; specifically, if the storage tank 1 outputs the refrigerant to the first air energy host 3, the refrigerant is input into the second air energy host 4 through the first return pipe 6 to be vaporized, and similarly, if the storage tank 1 outputs the refrigerant to the second air energy host 4, the refrigerant is input into the first air energy host 4 through the second return pipe 7 to be vaporized, and the vaporized refrigerant is input into the supercharger 2;

s12, after the refrigerant supplement is completed, opening a first electromagnetic valve 16, closing a second electromagnetic valve 17, opening a third expansion valve 10, closing a second expansion valve 9, closing a first control valve 12, opening a second control valve 13, closing a fan (not shown) in a second air energy host 4 and opening a fan in a first air energy host 3;

s13, the gaseous low Wen Lengmei vaporized by the air energy main machine is input into a supercharger 2 to be supercharged, then is converted into a gaseous or supercritical high-pressure high-temperature refrigerant, and enters the inlet of the secondary refrigerant heat exchanger after passing through a first expansion valve 8;

s14, the gaseous or supercritical high-pressure and high-temperature refrigerant entering the secondary refrigerant heat exchanger 5 exchanges heat with the secondary refrigerant on the outer surface of the secondary refrigerant heat exchanger 5, the secondary refrigerant absorbs the heat of the high-pressure and high-temperature refrigerant to realize the heating of the secondary refrigerant, and the high-pressure and high-temperature refrigerant releases the heat to become a liquid high-pressure normal-temperature refrigerant and is discharged from an outlet of the secondary refrigerant heat exchanger; the third electromagnetic valve 18, the third control valve 14 and the fourth control valve 15 are all in a closed state at this time;

s15, the liquid high-pressure normal-temperature refrigerant discharged by the secondary refrigerant heat exchanger 5 firstly passes through the second air energy host 4 (namely, an air energy evaporator entering the host) of which the running fan is stopped, and the secondary air energy host 4 is defrosted by using the waste heat of the liquid high-pressure normal-temperature refrigerant, and then the refrigerant is input into the first air energy host 3 through the second return pipeline 7 and is vaporized through the first air energy host 3; specifically, before entering the first air energy host 4, the liquid high-pressure normal-temperature refrigerant firstly passes through the third expansion valve 10, and then enters the first air energy host 4;

s16, repeating the steps S13-S15, thereby realizing the recycling of the refrigerant;

s17, when the air energy main machine is switched, the common air energy main machine needs to be switched when being used for about 30-60 minutes, so that the heating effect is prevented from being influenced by too much frost condensed by the air energy main machine, therefore, when the air energy main machine is switched, the first electromagnetic valve 16 is closed, the second electromagnetic valve 17 is opened, the third expansion valve 10 is opened, the second expansion valve 9 is opened, the first control valve 12 is opened, the second control valve 13 is closed, a fan (not shown) of the second air energy main machine 4 is opened, and a fan (not shown) of the first air energy main machine 3 is closed;

s18, the liquid high-pressure normal-temperature refrigerant discharged by the secondary refrigerant heat exchanger firstly passes through the first air energy host 3 (namely, an air energy evaporator entering the host) of the stopped running fan and defrosts the first air energy host 3 by utilizing the waste heat of the liquid high-pressure normal-temperature refrigerant, and then the refrigerant is input into the second air energy host 4 through the first return pipeline 6 and is vaporized through the second air energy host 3; similarly, before entering the second air energy host 4, the liquid high-pressure normal-temperature refrigerant firstly passes through the second expansion valve 9 and then enters the second air energy host 4;

s19, converting the vaporized refrigerant into a gaseous low-temperature refrigerant, boosting the refrigerant by a booster 2, converting the refrigerant into a gaseous or supercritical high-pressure high-temperature refrigerant, inputting the gaseous or supercritical high-pressure high-temperature refrigerant into a secondary refrigerant heat exchanger 5 through a first expansion valve 8 for heat exchange, and discharging the liquid high-pressure normal-temperature refrigerant subjected to heat exchange at an outlet of the secondary refrigerant heat exchanger;

and S20, repeating the steps from S18 to S19, thereby realizing the recycling of the refrigerant.

Of course, if the air energy host needs to be switched again, the steps S17 to S19 may be referred to again, and the principle is consistent, and will not be described in detail here.

The technical scheme can also comprise that:

in a cooling or heating mode:

in steps S1 and S11, when the air-conditioning cooling and heating cycle system of the new energy vehicle starts to be started, the pressure value of the second port 31 of the first air energy main unit is smaller than a set value, so that the refrigerant in the secondary refrigerant heat exchanger 5 and in the corresponding pipeline is conveyed to the first air energy main unit 3, after the refrigerant is vaporized, and the pressure value of the second port of the first air energy main unit reaches the set value, the second expansion valve 9 is opened, the refrigerant is throttled and pressure-regulated by the second expansion valve 9 and is input to the second air energy main unit 4 to maintain the pressure value of the second port 32 of the first air energy main unit, and is finally input to the supercharger 2 to supplement the pressure, and when the pressure at the high-pressure outlet end of the supercharger 2 does not reach the set value, the storage tank 1 is opened to supplement the pressure to the supercharger 2 until the pressure value at the high-pressure outlet end of the supercharger 2 reaches and is maintained at the set value, and the storage tank 1 is closed. Similarly, when the air-conditioning cold and heat circulation system of the new energy vehicle starts, the refrigerant in the secondary refrigerant heat exchanger 5 and in the corresponding pipeline may be first conveyed to the second air energy host 3, after the refrigerant is vaporized, and when the pressure value of the second port of the first air energy reaches a set value, the refrigerant is then input to the first air energy host 3 through throttling and pressure regulating of the third expansion valve 10 to maintain the pressure value of the second port 32 of the second air energy host, and finally input to the supercharger 2 to supplement the pressure, when the pressure at the high-pressure outlet end of the supercharger 2 does not reach the set value, the storage tank 1 is opened to output the refrigerant to the second air energy host 4, and after the refrigerant is vaporized, the refrigerant is input to the supercharger 2, until the pressure value at the high-pressure outlet end of the supercharger 2 reaches and is maintained at the set value, and the storage tank 1 is closed. The above two modes can be selected as needed, and after the above steps, the subsequent steps are determined to perform step S2 or step S12 according to the cooling mode or the heating mode. Through the arrangement, a small amount of liquid-state refrigerant reserved in places such as the secondary refrigerant heat exchanger 5 can be removed by the air energy main machine when the system is just started, the phenomenon that the liquid and gas refrigerants are mixed in the supercharger 2 to damage the supercharger 2 is avoided, and the service life of the supercharger 2 is prolonged.

Preferably, in the cooling mode: step S8, when the number of the secondary refrigerant heat exchangers 5 is increased, and the pressure at the high-pressure outlet end of the supercharger 2 does not reach a set value, the storage tank 1 is opened, the gaseous refrigerant is input into the supercharger 2 for supercharging, then the refrigerant sequentially passes through the first air energy host 3 and the first expansion valve 8 and enters the secondary refrigerant heat exchanger 5, the refrigerant output is stopped until the pressure at the high-pressure outlet end of the supercharger 2 reaches the set value, and redundant refrigerant flows back into the storage tank 1 through the inlet of the storage tank 1;

s9, when the number of the used secondary refrigerant heat exchangers 5 is reduced, the pressure of the high-pressure outlet end of the supercharger 2 exceeds a set value, and redundant refrigerants flow back into the storage tank 1 to keep the pressure of the high-pressure outlet end of the supercharger 2 at the set value;

in the heating mode: step S21, when the number of the secondary refrigerant heat exchangers 5 is increased, the pressure at the high-pressure outlet end of the booster 2 does not reach a set value, the corresponding second expansion valve 9 or third expansion valve 10 is opened, the refrigerant in the storage tank 1 firstly passes through an air energy host machine (namely an air energy evaporator entering the host machine) without starting a fan, then is conveyed to the air energy host machine with the fan started through the corresponding first return channel 6 or second return channel 7 to be vaporized into gaseous low-temperature refrigerant, the vaporized refrigerant is conveyed to the booster 2 to be used for supplementing the refrigerant, finally the refrigerant enters the secondary refrigerant heat exchanger 5 through the first expansion valve 8 until the pressure at the high-pressure outlet end of the booster 2 reaches the set value, the refrigerant output is stopped, and the redundant refrigerant flows back into the storage tank 1 through the inlet of the storage tank 1;

and S22, when the number of the refrigerating medium heat exchangers 5 is reduced and the pressure at the high-pressure outlet end of the supercharger 2 is made to exceed a set value, the redundant refrigerating medium flows back to the storage tank 1.

For the above switch use of each control valve, expansion valve and electromagnetic valve, when the corresponding pipeline is needed, the control valve or expansion valve on the pipeline is opened, and the above method partially reflects the use condition of each valve, and no specific details are given here.

In this embodiment, the pressure set value at the high-pressure outlet end of the supercharger 2 may be set to be 3.5MPa to 18MPa, and the pressure at the high-pressure outlet end of the supercharger 2 is detected by a pressure sensor.

For use with a coolant, the coolant on the coolant heat exchanger 5 can be a gaseous coolant or a liquid coolant, such as: the gaseous coolant is air, nitrogen or argon, and the liquid coolant is water, brine, ethylene glycol or propylene glycol solution.

Other corresponding technical features implemented by the invention for assisting the implementation of the technical solution can be implemented correspondingly or improved on the basis of the existing conventional technical means by a skilled person, and further details of other related technical means are not described herein.

In the description of the present specification, if the terms "embodiment one," "embodiment," "implementation," and the like are used, they mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example; furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

In the description of the present specification, the terms "connect", "mount", "fix", "set", "have", and the like are used in a broad sense, for example, the "connect" may be a fixed connection or an indirect connection through intermediate components without affecting the relationship and technical effects of the components, or may be an integral connection or a partial connection, as in this case, for a person skilled in the art, the specific meaning of the above terms in the present invention can be understood according to specific situations.

The foregoing description of the embodiments is provided to enable any person skilled in the art to make and use the embodiments, and it is to be understood that various modifications may be readily apparent to those skilled in the art, and that the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present disclosure is not limited to the above embodiments, and modifications for the following situations should be within the scope of the present disclosure: (1) a new technical scheme implemented on the basis of the technical scheme of the invention and by combining the prior common general knowledge; (2) equivalent replacement of part of the features of the technical scheme of the invention by adopting the known technology produces the same technical effects as the invention, for example, equivalent replacement is carried out on conventional production equipment, devices and the like used in the process; (3) the technical scheme of the invention is used as a basis for expansion, and the substantial content of the expanded technical scheme does not exceed the technical scheme of the invention; (4) the technical means obtained by using the equivalent transformation made by the text description content or the drawings of the specification of the invention can be applied to other schemes in the related technical fields.

Claims

1. A refrigerant circulation system of a central air conditioner is characterized by comprising:

the system comprises a storage tank, a supercharger, a first air energy host, a second air energy host and a secondary refrigerant heat exchanger;

an outlet of the storage tank is respectively connected with a first port of the first air energy host, a first port of the second air energy host and a low-pressure inlet end of the supercharger through pipelines so as to correspondingly output a refrigerant;

the high-pressure outlet end of the supercharger is respectively connected with the inlet of the storage tank, the inlet of the secondary refrigerant heat exchanger and the second port of the first air energy main machine through pipelines, and the inlet of the secondary refrigerant heat exchanger is provided with a first expansion valve; the gaseous refrigerant is converted into gaseous or supercritical high-pressure and high-temperature refrigerant after being pressurized by the booster; in a refrigeration mode, gaseous or supercritical high-pressure and high-temperature refrigerants can be correspondingly input into the first air energy host to be cooled; in the heating mode, gaseous or supercritical high-pressure and high-temperature refrigerant can be input into the secondary refrigerant heat exchanger for heat exchange through the first expansion valve;

2. The refrigerant circulation system of a central air conditioner as claimed in claim 1, wherein:

a second expansion valve is arranged on the first return pipeline and used for throttling and regulating pressure of a refrigerant; a third expansion valve is arranged on the second return pipeline and used for throttling and regulating pressure of the refrigerant;

when the central circulation system starts to be started, the second expansion valve or the third expansion valve is used for throttling and regulating pressure of a refrigerant, so that the pressure value of the corresponding second port of the first air energy host machine or the second port of the second air energy host machine is kept at a set value;

3. The refrigerant circulation system of a central air conditioner as claimed in claim 1, wherein:

and the inlet and the outlet of the storage tank are respectively provided with a fourth expansion valve which can be used for expansion and pressure reduction.

4. The refrigerant circulation system of a central air conditioner as claimed in claim 1, wherein:

a first control valve is further arranged on a pipeline between the outlet of the storage tank and the first port of the first air energy host; a second control valve is further arranged on a pipeline between the outlet of the storage tank and the first port of the second air energy host; a third control valve is arranged on a pipeline between the high-pressure outlet end of the supercharger and the second port of the first air energy main machine; and a fourth control valve is also arranged on a pipeline between the first port of the first air energy main machine and the inlet of the secondary refrigerant heat exchanger.

5. The refrigerant circulation system of a central air conditioner as claimed in claim 1, wherein:

a first electromagnetic valve is arranged on a pipeline between the second port of the first air energy main machine and the low-pressure inlet end of the supercharger; a second electromagnetic valve is arranged on a pipeline between a second port of the second air energy main machine and the low-pressure inlet end of the supercharger; and a third electromagnetic valve is arranged on a pipeline between the outlet of the secondary refrigerant heat exchanger and the low-pressure inlet end of the supercharger.

6. The refrigerant circulation system of a central air conditioner as claimed in claim 1, wherein:

the number of the secondary refrigerant heat exchangers is one or more than two in parallel.

7. The refrigerant circulation system of a central air conditioner as claimed in claim 6, wherein:

the number of the secondary refrigerant heat exchangers is more than two; in a refrigeration mode, when the using number of the secondary refrigerant heat exchangers is increased, the refrigerant circulating system of the central air conditioner needs to increase the quality of the refrigerant due to the increase of the required refrigerating capacity, and the storage tank outputs the refrigerant to the supercharger to supplement the refrigerant with the quality required by the circulating system; in the heating mode, when the number of the secondary refrigerant heat exchangers is increased, the refrigerant circulating system of the central air conditioner needs to increase the quality of the refrigerant due to the increase of the required heating capacity, the storage tank outputs the refrigerant to the corresponding first air energy host or the second air energy host, the refrigerant is input into the other air energy host through the corresponding first return pipeline or the corresponding second return pipeline for vaporization, and the vaporized refrigerant is input into the supercharger to supplement the refrigerant with the quality required by the circulating system; in the cooling or heating mode, when the using number of the secondary refrigerant heat exchangers is reduced, the refrigerant needed by the refrigerant circulating system of the central air conditioner is reduced, and redundant refrigerant flows back to the storage tank.

8. A method for cooling and heating refrigerant of a central air conditioner, which is characterized in that the refrigerant circulating system of the central air conditioner as claimed in any one of claims 1 to 7 is adopted, comprising the following steps:

a cooling mode:

s5, after entering the secondary refrigerant heat exchanger, the gaseous low-temperature refrigerant exchanges heat with the secondary refrigerant on the outer surface of the secondary refrigerant heat exchanger, the secondary refrigerant releases heat to the refrigerant to realize cooling and refrigeration of the secondary refrigerant, and the gaseous low-temperature refrigerant absorbs the heat of the secondary refrigerant and then reheats and heats;

s6, inputting the gaseous refrigerant discharged by the secondary refrigerant heat exchanger to a low-pressure inlet end of the supercharger, and pressurizing the gaseous refrigerant into a gaseous or supercritical high-pressure and high-temperature refrigerant by the supercharger, wherein the gaseous or supercritical high-pressure and high-temperature refrigerant is input to a second port of the first air energy host through a pipeline;

s7, repeating the steps S3-S6;

heating mode:

s14, the gaseous or supercritical high-pressure and high-temperature refrigerant entering the secondary refrigerant heat exchanger exchanges heat with the secondary refrigerant on the outer surface of the secondary refrigerant heat exchanger, the secondary refrigerant absorbs heat of the high-pressure and high-temperature refrigerant to realize temperature rise and heating of the secondary refrigerant, and the high-pressure and high-temperature refrigerant releases heat to become a liquid high-pressure normal-temperature refrigerant and is discharged from an outlet of the secondary refrigerant heat exchanger;

s16, repeating the steps S13-S15;

and S20, repeating the steps from S18 to S19.

9. The refrigerant cooling and heating method of a central air conditioner according to claim 8, wherein:

in steps S1 and S11, when starting the air conditioning cooling and heating cycle system of the new energy vehicle, the pressure value of the second port of the first air energy main unit is smaller than a set value, so that the refrigerant in the secondary refrigerant heat exchanger and in the corresponding pipeline is conveyed to the first air energy main unit, after the refrigerant is vaporized, when the pressure value of the second port of the first air energy reaches the set value, the second expansion valve is opened, the refrigerant is input to the second air energy main unit through the throttling and pressure regulating of the second expansion valve to maintain the pressure value of the second port of the first air energy main unit, and finally is input to the supercharger to supplement the pressure, when the pressure at the high-pressure outlet end of the supercharger does not reach the set value, the storage tank is opened to supplement the supercharger to supplement the pressure until the pressure value at the high-pressure outlet end of the supercharger reaches and is maintained at the set value, and the storage tank is closed.

10. The refrigerant cooling and heating method of a central air conditioner according to claim 8, wherein:

a refrigeration mode:

heating mode: