WO2021114727A1

WO2021114727A1 - Heating system and control method therefor

Info

Publication number: WO2021114727A1
Application number: PCT/CN2020/111283
Authority: WO
Inventors: 张霞
Original assignee: 珠海格力电器股份有限公司
Priority date: 2019-12-09
Filing date: 2020-08-26
Publication date: 2021-06-17
Also published as: CN110793186B; CN110793186A

Abstract

The present disclosure relates to a heating system and a control method therefor. The heating system comprises: a combustion device; a main heat exchange device arranged on one side of the combustion device, wherein the main heat exchange device can exchange heat with the combustion device; a liquid return pipe connected to a liquid intake end of the main heat exchange device; a liquid output pipe connected to a liquid output end of the main heat exchange device; and a heat exchange structure, wherein the liquid return pipe and the liquid output pipe selectively exchange heat by means of the heat exchange structure. According to the heating system, a liquid in a main heat exchange pipe exchanges heat with a liquid in the liquid output pipe by means of the heat exchange structure, such that a liquid output temperature of the liquid output pipe can be reduced while the liquid in the main heat exchange device is kept at a higher temperature, so as to meet a preset temperature requirement. Flue gas is also kept at a higher temperature so as to prevent the flue gas from condensing on the main heat exchange device.

Description

Heating system and its control method

Related application

This disclosure requires the priority of the Chinese patent application filed on December 9, 2019, with the application number 201911250413.4, titled "Heating System and Its Control Method", the full text of which is hereby incorporated by reference.

Technical field

The present disclosure relates to the field of heating equipment, in particular to a heating system and a control method thereof.

Background technique

The inventor knows that gas-fired water heaters, as a heating device that relies on natural gas to provide hot water and heating heat, are increasingly accepted by users and have become an important part of heating in cold regions. When the gas-fired water heater is in heating operation, when the user needs to increase the room temperature quickly, the outlet temperature of the gas-fired water heater and the circulation flow of the system need to be increased. At this time, the gas-fired water heater is in a heavy load state. When the room temperature reaches the required value, the outlet temperature and circulation flow of the gas-fired water heater need to be lowered. At this time, the gas-fired water heater is in a small load state.

However, the inventor found in the research that the current non-condensing gas heating water heaters on the market have a difference of more than 8% in thermal efficiency between the minimum load and the maximum load. The thermal efficiency of the heating water heater at the maximum load is about 93. %, the thermal efficiency at light load is about 85%, which leads to a waste of energy, and the fundamental reason for the lower thermal efficiency of the heating water heater under light load is when the gas heating water heater is at light load At this time, the exhausted flue gas takes away a lot of heat. In the heating operation process, the gas-fired water heater is in a light load state most of the time, so improving the thermal efficiency of the light load state can effectively reduce energy waste.

At present, the following two schemes are usually used to increase the thermal efficiency of gas-fired water heaters. One scheme is to increase the heat exchange capacity of the main heat exchanger and reduce the temperature of the flue gas produced by combustion, thereby reducing heat loss. The other scheme is to reduce heat loss. Excess air coefficient reduces the amount of smoke.

However, with the first scheme, the temperature of the flue gas is reduced. When the heating water heater is in a state of low load and low water temperature, the combustion power of the burner is small, and the amount and temperature of the flue gas are small, because the temperature of the flue gas is easy to reach Dew point temperature (the dew point temperature of the flue gas is the temperature at which the water vapor in the high temperature flue gas begins to condense). With the second scheme, the excess air is reduced and the dew point temperature of the flue gas is increased. When the heating water heater is under a small load, the flue gas temperature can easily reach the dew point temperature. The inventor realizes that after burning, part of the flue gas is condensed on the main heat exchanger, which corrodes the main heat exchanger, and ultimately reduces the service life of the heating water heater.

Summary of the invention

Based on this, it is necessary to solve the problem of low heat exchange efficiency of heating water heaters under light load conditions, and provide a heating system and control method thereof with higher heat exchange efficiency under light load conditions.

A heating system, the heating system comprising:

Burning device

The main heat exchange device is arranged on one side of the combustion device, and the main heat exchange device can exchange heat with the combustion device;

The liquid return pipe is connected to the liquid inlet end of the main heat exchange device;

The liquid outlet pipe is connected to the liquid outlet end of the main heat exchange device; and

Heat exchange structure, the liquid return pipe and the liquid outlet pipe can selectively exchange heat through the heat exchange structure.

In the above heating system, the liquid in the main heat exchange tube and the liquid in the outlet tube exchange heat through a heat exchange structure, which can reduce the outlet temperature of the outlet tube while maintaining the liquid in the main heat exchange device at a higher temperature. Thus, while meeting the preset temperature requirements, the flue gas is kept at a higher temperature to avoid the flue gas from condensing on the main heat exchange device.

In some embodiments, the liquid return pipe includes a first liquid return branch pipe and a second liquid return branch pipe connected in parallel, and the second liquid return branch pipe can exchange heat with the liquid outlet pipe through the heat exchange structure.

In some embodiments, the liquid return pipe further includes a first liquid return main pipe and a second liquid return main pipe, and the first liquid return branch pipe and the second liquid return branch pipe are connected in parallel to the first liquid return main pipe and the second liquid return branch pipe. Between the second liquid return main pipes, the first liquid return main pipe can optionally be connected to the second liquid return main pipe through the first liquid return branch pipe and/or the second liquid return branch pipe.

In some embodiments, the heating structure further includes a flow control unit, and the first liquid return main pipe, the first liquid return branch pipe, and the second liquid return branch pipe are connected by the flow control unit. The control unit is used to control the first liquid return main pipe to communicate with the first liquid return branch pipe and/or the second liquid return branch pipe.

In some embodiments, the flow control unit is an electric three-way valve. The electric three-way valve includes a first valve port, a second valve port, and a third valve port. The first valve port is connected to the outlet end of the first return liquid main pipe. The second valve port is connected to the inlet end of the first liquid return branch pipe. The third valve port is connected to the inlet end of the second liquid return branch pipe.

In some embodiments, the heating system further includes a control device, and the control device is in communication connection with the flow control unit.

In some embodiments, the control device controls the working state of the flow control unit according to the load state of the heating system.

In some embodiments, when the heating system is in a low temperature and low load state, the control device controls the first valve and the third valve of the flow control unit to be in an open state, and the second valve is in an open state. Disabled.

In some embodiments, when the heating system is in a low temperature and low load state, the first liquid return main pipe is connected to the second liquid return main pipe only through the second liquid return branch pipe.

In some embodiments, when the heating system is in a non-low temperature and low load state, the liquid in the liquid return pipe does not pass through the heat exchange structure.

In some embodiments, when the heating system is in a low temperature and low load state, the load of the heating system is less than 30% of the full load.

A control method of the above heating system includes the following steps:

Obtain the load status of the heating system;

According to the load state of the heating system, it is controlled whether the liquid in the liquid return pipe exchanges heat with the liquid in the liquid outlet pipe through the heat exchange structure.

In some embodiments, when the heating system is in a low temperature and low load state, the liquid in the liquid return pipe is controlled to exchange heat with the liquid in the liquid outlet pipe through the heat exchange structure.

In some embodiments, when the heating system is in a low temperature and low load state, the temperature of the liquid from the liquid outlet pipe is 20°C to 45°C.

In some embodiments, the liquid return pipe includes a first liquid return branch pipe and a second liquid return branch pipe connected in parallel, and the second liquid return branch pipe can exchange heat with the liquid outlet pipe through the heat exchange structure; When the heating system is in a low temperature and low load state, the step of controlling the liquid in the liquid return pipe to exchange heat with the liquid in the liquid outlet pipe through the heat exchange structure specifically includes the following steps:

When the heating system is in the low temperature and low load state, the control liquid flows through the second liquid return branch pipe.

In some embodiments, the liquid return pipe further includes a first liquid return main pipe and a second liquid return main pipe, and the first liquid return branch pipe and the second liquid return branch pipe are connected in parallel to the first liquid return main pipe and the second liquid return branch pipe. Between the second liquid return main pipes; when the heating system is in the low temperature and low load state, the step of controlling liquid to flow through the second liquid return branch pipe specifically includes the following steps:

When the heating system is in the low temperature and low load state, the first liquid return main pipe is controlled to communicate with the second liquid return main pipe through the second liquid return branch pipe.

In some embodiments, when the heating system is in a non-low temperature and low load state, the liquid in the liquid return pipe is controlled not to pass through the heat exchange structure.

In some embodiments, the liquid return pipe includes a first liquid return branch pipe and a second liquid return branch pipe connected in parallel, and the second liquid return branch pipe can exchange heat with the liquid outlet pipe through the heat exchange structure; When the heating system is in a non-low temperature and low load state, the step of controlling the liquid in the liquid return pipe not to pass through the heat exchange structure specifically includes the following steps:

When the heating system is in the non-low temperature and low load state, the liquid is controlled to flow through the first liquid return branch pipe.

In some embodiments, the liquid return pipe further includes a first liquid return main pipe and a second liquid return main pipe, and the first liquid return branch pipe and the second liquid return branch pipe are connected in parallel to the first liquid return main pipe and the second liquid return branch pipe. Between the second liquid return main pipes; when the heating system is in the non-low temperature and low load state, the step of controlling the liquid to flow through the first liquid return branch pipe includes the following steps:

When the heating system is in the low temperature and low load state, the first liquid return main pipe is controlled to communicate with the second liquid return main pipe through the first liquid return branch pipe.

Description of the drawings

In order to more clearly describe the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are the embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on the disclosed drawings without creative work.

Fig. 1 is a schematic diagram of a heating system according to an embodiment of the disclosure;

Figure 2 is a hydraulic circuit diagram of the heating system shown in Figure 1 in a low temperature and low load state;

Figure 3 is a hydraulic circuit diagram of the heating system shown in Figure 1 in a non-low temperature and small load state;

FIG. 4 is a flowchart of a control method of the heating system according to an embodiment of the disclosure.

Description of reference signs:

100. Heating system; 600. Control device; 10. Combustion device; 20. Main heat exchange device; 40. Outlet pipe; 30. Return pipe; 32. First return liquid main pipe; 34. Second return liquid main pipe; 36. The first liquid return branch pipe; 38. The second liquid return branch pipe; 50. Heat exchange structure; 60. Flow control unit.

Detailed ways

In order to make the above objectives, features and advantages of the present disclosure more obvious and understandable, the specific implementation manners of the present disclosure will be described in detail below with reference to the accompanying drawings. In the following description, many specific details are explained in order to fully understand the present disclosure. However, the present disclosure can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present disclosure. Therefore, the present disclosure is not limited by the specific implementations disclosed below.

In order to facilitate the understanding of the present disclosure, the present disclosure will be described in a more comprehensive manner with reference to related drawings. The preferred embodiments of the disclosure are shown in the accompanying drawings. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present disclosure more thorough and comprehensive.

It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or a central element may also be present. When an element is considered to be "connected" to another element, it can be directly connected to the other element or an intermediate element may be present at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of the disclosure. The terms used in the description of the disclosure herein are only for the purpose of describing specific embodiments, and are not intended to limit the disclosure. The term "and/or" as used herein includes any and all combinations of one or more related listed items.

As shown in FIG. 1, a heating system 100 according to an embodiment of the present disclosure is used for heating various rooms in the room. Hereinafter, taking the heating system 100 as a gas heating stove system as an example, the structure of the heating system 100 in the present application will be described. This embodiment is only used as an example for description, and does not limit the technical scope of the present application. It can be understood that in other embodiments, the heating system 100 may also be specifically a gas water heater system, etc., which is not limited herein.

Specifically, the heating system 100 includes a control device 600 (not shown), a combustion device 10, a main heat exchange device 20, a liquid outlet pipe 40, a heating pipe, and a liquid return pipe 30. Among them, the main heat exchange device 20, the liquid outlet pipe 40, the heating pipe, and the liquid return pipe 30 are connected to each other to form a heating pipeline. The main heat exchange device 20 is provided on the side of the combustion device 10, and the main heat exchange device 20 can be connected to the combustion device 10. Heat exchange occurs to obtain the heat of the high-temperature flue gas generated by the combustion of the combustion device 10.

In this way, under the control of the control device 600, natural gas is burned in the combustion device 10, and the high-temperature flue gas produced by the combustion can exchange heat with the liquid in the main heat exchange device 20, and the liquid after the heat exchange is completed flows out through the liquid outlet pipe 40 The main heat exchange device 20 heats each room through the heating pipe flowing into each room and the air in the room to exchange heat, and the liquid after the heat exchange is finally returned to the main heat exchange device 20 through the liquid return pipe 30.

Please continue to refer to FIG. 1, the liquid return pipe 30 includes a first liquid return main pipe 32, a second liquid return main pipe 34, a first liquid return branch pipe 36, and a second liquid return branch pipe 38. Wherein, the first liquid return branch pipe 36 and the second liquid return branch pipe 38 are connected in parallel between the first liquid return main pipe 32 and the second liquid return main pipe 34, and the inlet end of the first liquid return main pipe 32 is connected to the outlet end of the heating pipe. The outlet end of the first liquid return main pipe 32 is simultaneously connected to the inlet end of the first liquid return branch pipe 36 and the inlet end of the second liquid return branch pipe 38, the outlet end of the first liquid return branch pipe 36 and the outlet of the second liquid return branch pipe 38 Both ends are connected to the inlet end of the second liquid return main pipe 34, and the outlet end of the second liquid return main pipe 34 is connected to the liquid inlet end of the main heat exchange device 20. The inlet end of the liquid outlet pipe 40 is connected to the liquid outlet end of the main heat exchange device 20, and the outlet end of the liquid outlet pipe 40 is connected to the inlet end of the heating pipe.

In this way, the liquid that absorbs the heat of the flue gas in the main heat exchange device 20 enters the heating pipe through the liquid outlet pipe 40. After the liquid in the heating pipe completes heat exchange in the room, it passes through the first liquid return main pipe 32 and the first liquid return branch pipe in turn. 36. The second return liquid main pipe 34 returns to the main heat exchange device 20 again.

In some embodiments, the liquid in the main heat exchange device 20 that absorbs the heat of the flue gas enters the heating pipe through the liquid outlet pipe 40. After the liquid in the heating pipe completes heat exchange in the room, it passes through the first liquid return main pipe 32 and the second liquid return pipe in turn. The second liquid return branch pipe 38 and the second liquid return main pipe 34 return to the main heat exchange device 20 again.

In some embodiments, the liquid in the main heat exchange device 20 that absorbs the heat of the flue gas enters the heating pipe through the liquid outlet pipe 40. After the liquid in the heating pipe completes heat exchange in the room, it passes through the first liquid return main pipe 32 and the second liquid return pipe in turn. A liquid return branch pipe 36, a second liquid return branch pipe 38, and a second liquid return main pipe 34 are returned to the main heat exchange device 20 again.

Further, the heating system 100 further includes a flow control unit 60 communicatively connected with the control device 600. The first liquid return main pipe 32, the first liquid return branch pipe 36, and the second liquid return branch pipe 38 are connected by a flow control unit 60. The flow control unit 60 is used to control the first liquid return main pipe 32 and the first liquid return branch pipe 36 and/or The second liquid return branch pipe 38 is in communication, so that the liquid in the first liquid return main pipe 32 can selectively flow into the second liquid return main pipe 34 through the first liquid return branch pipe and/or the second liquid return branch pipe 38.

Specifically, the flow control unit 60 is an electric three-way valve, which includes a first valve port, a second valve port, and a third valve port that can be opened or closed under the control of the control device 600. The first valve port is connected to the outlet end of the first liquid return main pipe 32, the second valve port is connected to the inlet end of the first liquid return branch pipe 36, and the third valve port is connected to the inlet end of the second liquid return branch pipe 38. In this way, the control device 600 can control the opening of the valve port of the flow control unit 60 and change the flow path of the liquid.

Furthermore, the heating system 100 further includes a heat exchange structure 50, and the second liquid return branch pipe 38 can exchange heat with the liquid outlet pipe 40 through the heat exchange structure 50.

Specifically, since the liquid in the main heat exchange device 20 enters the main heat exchange device 20, the heat of the flue gas is absorbed in the main heat exchange device 20 to increase the temperature, so the liquid from the main heat exchange device 20 flows into the liquid outlet pipe 40. The temperature is higher than the temperature of the liquid in the liquid return pipe 30. Referring to Fig. 2, when the heating system 100 is in a low-temperature and low-load state, the outlet temperature of the outlet end of the outlet pipe 40 is required to be low. Therefore, the heat exchange structure 50 can be used to separate the liquid in the return pipe from the outlet pipe 40. The liquid performs heat exchange, and the heat of the liquid in the liquid outlet pipe 40 is transferred to the liquid return pipe 30 and the temperature is lowered to reach the preset liquid outlet temperature, so there is no need to directly reduce the liquid temperature in the main heat exchange device 20. Since the temperature of the flue gas is positively correlated with the temperature of the liquid in the main heat exchange device 20, the liquid in the main heat exchange device 20 can be maintained at a higher temperature to keep the flue gas at a higher temperature, which can be reduced by reducing the temperature of the flue gas. The method of emission increases the heat exchange rate of the heating system under low temperature and low load conditions, and at the same time prevents the flue gas from condensing on the main heat exchange device 20 and reduces the life of the main heat exchange device 20. On the contrary, if the temperature of the liquid in the main heat exchange device 20 is reduced to achieve the purpose of reducing the liquid temperature of the main liquid outlet pipe 40, the temperature of the flue gas that exchanges heat with the liquid in the main heat exchange device 20 will be lower. At this time, if the emission of flue gas is reduced in an attempt to increase the heat exchange rate of the heating system 100, the temperature of the flue gas will easily be lower than the dew point temperature and condense, which will corrode the main heat exchange device 20 and affect the main heat exchange device 20. Life.

Referring to Figs. 3 and 4, the present disclosure provides a control method of the above heating system 100, which includes the following steps:

S110: Obtain the load state of the heating system 100.

Specifically, the heating system 100 has two load states, a low-temperature low-load state and a non-low-temperature low-load state, and the non-low-temperature low-load state includes any other load states such as a high-load state other than the low-temperature low-load state. Specifically, in some embodiments, when the heating system 100 is in a low temperature and low load state, the temperature of the outlet pipe 40 is 20°C-45°C, and the load of the heating system 100 is less than 30% of the full load.

S120: Control whether the liquid in the liquid return pipe 30 exchanges heat with the liquid in the liquid outlet pipe 40 through the heat exchange structure 50 according to the load state of the heating system 100.

Specifically, the control device 600 controls the working state of the flow control unit 60 according to the load state of the heating system 100, and further controls the flow path of the liquid in the liquid return pipe 30, and finally controls the liquid outlet temperature of the liquid outlet pipe 40.

When the heating system 100 is in a low temperature and low load state, the control device 600 controls the first valve and the third valve of the flow control unit 60 to be in an open state, and the second valve is in a closed state, so the first return main pipe 32 only passes through the second return The liquid branch pipe 38 is connected to the second liquid return main pipe 34, and the liquid in the second liquid return branch pipe 38 exchanges heat with the liquid in the liquid outlet pipe 40 through the heat exchange structure 50. Since the temperature of the liquid in the second liquid return branch pipe 38 is lower than the temperature of the liquid in the liquid outlet pipe 40, the heat of the liquid in the liquid return pipe 40 is transferred to the second liquid return branch pipe 38, so the outlet of the liquid outlet pipe 40 The temperature of the liquid flowing out of the end is lower than the temperature in the main heat exchange device 20 and meets the preset liquid temperature requirement. In this way, the temperature of the liquid in the main heat exchange device 20 is higher, resulting in a higher temperature of the flue gas that exchanges heat with it. Therefore, while reducing the amount of flue gas discharged to increase the thermal efficiency of the heating system 100, the flue gas temperature is not easy to fall below Dew point temperature, so there is no condensation on the main heat exchange device 20.

When the heating system 100 is in a state of non-low temperature and low load, the control device 600 controls the first valve and the second valve for flow adjustment to be in an open state, the third valve is in a closed state, and the first liquid return main pipe 32 only passes through the second liquid return. The branch pipe 38 communicates with the second liquid return main pipe 34. In this way, the liquid in the return pipe 30 does not pass through the heat exchange structure 50, and the liquid in the outlet pipe 40 does not exchange heat in the heat exchange structure 50. Therefore, the outlet temperature of the outlet pipe 40 is the same as that of the main heat exchange device 20. The liquid temperature is the same. On the contrary, if when the heating system 100 is in a non-low temperature and low load state, the liquid in the liquid outlet pipe 40 still exchanges heat with the liquid in the second liquid return branch pipe 38, then the liquid outlet temperature of the liquid outlet pipe 40 reaches the preset In the case of a higher liquid outlet temperature, the temperature of the liquid in the main heat exchange device 20 will be higher and easy to vaporize. In some embodiments, the third valve may also be in a partially open state.

In the above heating system 100 and its control method, since the liquid outlet pipe 40 and the liquid return pipe 30 can exchange heat through the heat exchange structure 50, the liquid in the liquid return pipe 30 can be used to adjust the temperature of the liquid outlet pipe 40 according to different load conditions. The difference between the outlet liquid temperature and the liquid temperature in the main heat exchange device 20 enables the heating system 100 to reduce the amount of flue gas discharged to increase the heat exchange efficiency under small load conditions by 12%-14%, and heat exchange under heavy load conditions While the efficiency is increased by 3% to 5%, the flue gas is guaranteed to have a higher temperature, so as to avoid the flue gas from condensing due to the reduction of flue gas discharge, so as to achieve the purpose of energy saving and emission reduction, and at the same time extend the service life of the heating system 100 . In addition, since the condensation problem of the heating system 100 at a low load and low water temperature is overcome, the adjustment range of the combustion power of the combustion device 10 can be expanded, the number of starts of the heating system 100 is reduced, and the applicability of the heating system 100 is expanded. , To meet the different needs of users for heating, and greatly improve the user experience.

The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the various technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, All should be considered as the scope of this specification.

The above-mentioned embodiments only express several implementation manners of the present disclosure, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present disclosure, several modifications and improvements can be made, and these all fall within the protection scope of the present disclosure. Therefore, the protection scope of the disclosed patent should be subject to the appended claims.

Claims

A heating system, characterized in that, the heating system includes:

Combustion device (10);

The main heat exchange device (20) is arranged on one side of the combustion device (10), and the main heat exchange device (20) can exchange heat with the combustion device (10);

The liquid return pipe (30) is connected to the liquid inlet end of the main heat exchange device (20);

The liquid outlet pipe (40) is connected to the liquid outlet end of the main heat exchange device (20); and

The heat exchange structure (50), the liquid return pipe (30) and the liquid outlet pipe (40) can selectively exchange heat through the heat exchange structure (50).
The heating system according to claim 1, wherein the liquid return pipe (30) comprises a first liquid return branch pipe (36) and a second liquid return branch pipe (38) connected in parallel, and the second liquid return branch pipe (38) The heat exchange structure (50) can exchange heat with the liquid outlet pipe (40).
The heating system according to claim 2, wherein the liquid return pipe (30) further comprises a first liquid return main pipe (32) and a second liquid return main pipe (34), and the first liquid return branch pipe ( 36) is connected in parallel with the second liquid return branch pipe (38) between the first liquid return main pipe (32) and the second liquid return main pipe (34), and the first liquid return main pipe (32) can The second liquid return main pipe (34) is selectively connected with the first liquid return branch pipe (36) and/or the second liquid return branch pipe (38).
The heating system according to claim 3, wherein the heating structure further comprises a flow control unit (60), the first liquid return main pipe (32), the first liquid return branch pipe (36), and the The second liquid return branch pipe (38) is connected through the flow control unit (60), and the flow control unit (60) is used to control the first liquid return main pipe (32) and the first liquid return branch pipe ( 36) and/or the second liquid return branch pipe (38) is connected.
The heating system according to claim 4, wherein the flow control unit (60) is an electric three-way valve, and the electric three-way valve includes a first valve port, a second valve port, and a third valve port, The first valve port is connected to the outlet end of the first liquid return main pipe (32), the second valve port is connected to the inlet end of the first liquid return branch pipe (36), and the third valve port Connected to the inlet end of the second liquid return branch pipe (38).
The heating system according to claim 5, further comprising:

A control device (600), the control device (600) is in communication connection with the flow control unit (60).
The heating system according to claim 6, characterized in that the control device (600) controls the working state of the flow control unit (60) according to the load state of the heating system.
The heating system according to claim 6, characterized in that, when the heating system is in a low-temperature and low-load state, the control device (600) controls the first valve and the valve of the flow control unit (60) The third valve is in an open state, and the second valve is in a closed state.
The heating system according to claim 4, characterized in that, when the heating system is in a low-temperature and low-load state, the first liquid return main pipe (32) is only connected with the second liquid return branch pipe (38). The second liquid return main pipe (34).
The heating system according to claim 1, wherein when the heating system is in a non-low temperature and low load state, the liquid in the liquid return pipe (30) does not pass through the heat exchange structure (50).
The heating system according to claim 10, wherein when the heating system is in a low temperature and low load state, the load of the heating system is less than 30% of the full load.
A heating system control method according to any one of claims 1 to 11, characterized in that it comprises the following steps:

Obtain the load status of the heating system;

According to the load state of the heating system, it is controlled whether the liquid in the liquid return pipe (30) exchanges heat with the liquid in the liquid outlet pipe (40) through the heat exchange structure (50).
The heating system control method according to claim 12, characterized in that, when the heating system is in a low temperature and low load state, the liquid in the liquid return pipe (30) is controlled to pass through the heat exchange structure (50) Exchange heat with the liquid in the liquid outlet pipe (40).
The heating system control method according to claim 12, wherein when the heating system is in a low temperature and low load state, the load of the heating system is less than 30% of the full load.
The heating system control method according to claim 12, characterized in that, when the heating system is in a low-temperature and low-load state, the liquid outlet temperature of the liquid outlet pipe (40) is 20°C-45°C.
The heating system control method according to claim 13, wherein the liquid return pipe (30) comprises a first liquid return branch pipe (36) and a second liquid return branch pipe (38) connected in parallel, and the second liquid return branch pipe (36) and the second liquid return branch pipe (38) are connected in parallel. The liquid return branch pipe (38) can exchange heat with the liquid outlet pipe (40) through the heat exchange structure (50); when the heating system is in a low temperature and low load state, the liquid return pipe (30) is controlled The step of exchanging heat between the liquid in the liquid through the heat exchange structure (50) and the liquid in the liquid outlet pipe (40) specifically includes the following steps:

When the heating system is in the low temperature and low load state, the control liquid flows through the second liquid return branch pipe (38).
The heating system control method according to claim 16, characterized in that the liquid return pipe (30) further comprises a first liquid return main pipe (32) and a second liquid return main pipe (34), and the first liquid return pipe (30) The liquid branch pipe (36) and the second liquid return branch pipe (38) are connected in parallel between the first liquid return main pipe (32) and the second liquid return main pipe (34); when the heating system is in the In the low temperature and low load state, the step of controlling the liquid to flow through the second liquid return branch pipe (38) specifically includes the following steps:

When the heating system is in the low temperature and low load state, the first liquid return main pipe (32) is controlled to communicate with the second liquid return main pipe (34) through the second liquid return branch pipe (38).
The heating system control method according to claim 12, characterized in that, when the heating system is in a non-low temperature and low load state, the liquid in the liquid return pipe (30) is controlled not to pass through the heat exchange structure ( 50).
The heating system control method according to claim 18, wherein the liquid return pipe (30) comprises a first liquid return branch pipe (36) and a second liquid return branch pipe (38) connected in parallel, and the second liquid return branch pipe (36) and the second liquid return branch pipe (38) are connected in parallel. The liquid return branch pipe (38) can exchange heat with the liquid outlet pipe (40) through the heat exchange structure (50); when the heating system is in a non-low temperature and small load state, the liquid return pipe (30) is controlled The step of not passing the heat exchanging structure (50) in the liquid in the liquid crystal includes the following steps:

When the heating system is in the non-low temperature and low load state, the liquid is controlled to flow through the first liquid return branch pipe (36).
The heating system control method according to claim 19, wherein the liquid return pipe (30) further comprises a first liquid return main pipe (32) and a second liquid return main pipe (34), and the first liquid return pipe (30) further comprises a first liquid return main pipe (32) and a second liquid return main pipe (34). The liquid branch pipe (36) and the second liquid return branch pipe (38) are connected in parallel between the first liquid return main pipe (32) and the second liquid return main pipe (34); when the heating system is in the In the non-low temperature and low load state, the step of controlling the liquid to flow through the first liquid return branch pipe (36) includes the following steps:

When the heating system is in the low temperature and small load state, the first liquid return main pipe (32) is controlled to communicate with the second liquid return main pipe (34) through the first liquid return branch pipe (36).