Air source heat pump system and control method thereof

Abstract

The invention belongs to the technical field of air source heat pumps, and discloses an air source heat pump system and a control method thereof. The air source heat pump system comprises a compressor, a flow path switching valve, a condenser and an evaporator which are connected through a pipeline to form a refrigerant main cycle; the evaporator comprises a heat exchanger, a plurality of liquid distributing pipes are arranged in the heat exchanger in a penetrating mode, a distributor is arranged at one end of each liquid distributing pipe, a gas collecting pipe is arranged at the other end of each liquid distributing pipe, the rear end of the heat exchanger is connected with a supercooling section, the distributor is communicated with a flow dividing front pipeline, and the flow dividing front pipeline is communicated with the supercooling section through a supercooling pipe. And the second valve body is arranged between the nth liquid distribution pipe and the (n + 1) th liquid distribution pipe. The air source heat pump system has high energy efficiency in both the refrigerating mode and the heating mode.

Description

Technical Field

[0001] The present invention relates to the technical field of air source heat pumps, and in particular to an air source heat pump system and a control method thereof. Background Art

[0002] Air source heat pump is the most widely used type of heat pump. Air source heat pump is an energy-saving device that uses high-level energy to make heat flow from low-level heat source air to high-level heat source, thereby achieving the purpose of saving some high-level energy. The air source heat pump system combines cold and hot sources, and does not require a special refrigeration room or boiler room. The unit can be placed on the roof or bottom surface at will, does not occupy the effective use area of ​​the building, and is very convenient for construction and installation. Air source heat pump has the advantages of low operating cost, environmental protection and pollution-free, small footprint and easy use, so it has been widely used, but due to different environments in different regions, the design and application methods of air source heat pumps in different regions are different.

[0003] However, in the prior art, air source heat pump systems usually share a heat exchanger flow path in cooling mode and heating mode. In heating mode, the refrigerant enters the condenser from the porous distributor, absorbs heat from the air through phase change, and returns to the compressor through the pipeline for a new round of compression after vaporization. In cooling mode, high-temperature gas enters the condenser through the gas collecting pipe, releases heat into the air through phase change, and then enters the system through the distributor for the next round of heat release after liquefaction. For heating mode and cooling mode, the number of flow paths required for the optimal state is not the same. Since the existing air source heat pump system absorbs and releases heat independently in cooling mode and heating mode, it is impossible to take into account the optimal energy efficiency of both modes.

[0004] Therefore, there is an urgent need to propose an air source heat pump system and a control method thereof to solve the above problems. Summary of the invention

[0005] An object of the present invention is to provide an air source heat pump system, which has high energy efficiency in both cooling mode and heating mode.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] An air source heat pump system, the air source heat pump system having a cooling mode and a heating mode, comprising:

[0008] A compressor, a flow path switching valve, a condenser and an evaporator that are connected through pipelines to form a main refrigerant circulation;

[0009] The evaporator includes a heat exchanger, and a plurality of liquid distribution pipes are arranged inside the heat exchanger. A distributor is arranged at one end of the liquid distribution pipe, and a gas collecting pipe is arranged at the other end. A subcooling section is connected to the rear end of the heat exchanger. The distributor is connected to a front-dividing pipeline, and the front-dividing pipeline is connected to the subcooling section through a subcooling pipe. A first valve body is arranged on the front-dividing pipeline, and a second valve body is arranged on the gas collecting pipe. The second valve body is arranged between the nth liquid distribution pipe and the n+1th liquid distribution pipe.

[0010] Optionally, the condenser is connected to the pre-diversion pipeline through a main path, and a plate heat exchanger is arranged on the main path.

[0011] Optionally, a main valve is provided on the main line, and the main valve is located between the first valve body and the plate heat exchanger.

[0012] Optionally, the air source heat pump system further includes an auxiliary circuit, which passes through the plate heat exchanger and connects the main circuit with the compressor.

[0013] Optionally, an auxiliary valve is provided on the auxiliary circuit.

[0014] Optionally, the flow path switching valve is a four-way valve.

[0015] Optionally, the compressor is connected to the flow path switching valve through the first circuit and the second circuit to form a circulation circuit.

[0016] Optionally, an evaporator temperature sensor is provided between the heat exchanger and the distributor.

[0017] Another object of the present invention is to provide an air source heat pump system, which has high energy efficiency in both cooling mode and heating mode.

[0018] To achieve this object, the present invention adopts the following technical solutions:

[0019] An air source heat pump system control method is applied to the above air source heat pump system, and the air source heat pump system control method includes:

[0020] In the heating mode, the first valve body and the second valve body are both open;

[0021] In the cooling mode, both the first valve body and the second valve body are closed.

[0022] Optionally, in the heating mode, when the ambient temperature is lower than a preset temperature, the auxiliary valve of the air source heat pump system opens.

[0023] Beneficial effects:

[0024] The air source heat pump system provided by the present invention is provided with a first valve body between the distributor and the condenser, and a second valve body between the nth liquid distributor and the n+1th liquid distributor. In the heating mode, the first valve body and the second valve body are both set to a conducting state, and the refrigerant enters the distributor in two ways for liquid distribution, one way is the pre-distribution pipeline and the first valve body, and the other way is the supercooling pipe and the supercooling section. The refrigerant flows out of the gas collecting pipe after completing the heat exchange in each liquid distributor; in the cooling mode, the first valve body and the second valve body are both set to a closed state, so the refrigerant can only flow through the 1st to nth liquid distributors, and after the heat exchange, it is reversed in the distributor, and then flows through other liquid distributors, and is cooled again through the supercooling section, and finally is collected through the supercooling pipe. In this way, different flow paths for cooling and heating are achieved, so that the system cooling and heating can achieve the optimal energy efficiency.

[0025] The air source heat pump system control method provided by the present invention is applied to the above-mentioned air source heat pump system. In the heating mode, the first valve body and the second valve body are controlled to be opened; in the cooling mode, the first valve body and the second valve body are controlled to be closed. The flow path of the refrigerant in different modes is controlled by opening and closing the first valve and the second valve, so as to achieve the effect of different flow paths in the cooling mode and the heating mode, so that the cooling and heating of the system can achieve the highest energy efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of the evaporator provided by the present invention;

[0027] Figure 2 It is a schematic diagram of the air source heat pump system provided by the present invention.

[0028] In the figure:

[0029] 100, compressor; 200, flow path switching valve; 300, condenser; 400, heat exchanger; 410, subcooling section; 500, distributor; 600, plate heat exchanger;

[0030] 10. Main line; 11. Main valve; 20. Pipeline before diversion; 21. First valve body; 30. Subcooling pipe; 40. Liquid distribution pipe; 50. Gas collecting pipe; 51. Second valve body; 60. Auxiliary line; 61. Auxiliary valve; 70. First circuit; 71. High-pressure switch; 72. Pressure sensor; 80. Second circuit; 81. Low-pressure switch; 90. Evaporator temperature sensor. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions, and the first feature "above", "above" and "above" the second feature include the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. The first feature "below", "below" and "below" the second feature include the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0033] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0035] In the heating mode of the air source heat pump system, the refrigerant liquid enters the condenser for evaporation and absorbs heat before gasification. For the heating mode, the pressure drop of the system will lead to a decrease in the heating capacity and a decrease in the system energy efficiency. According to the heat transfer rate formula Q = KAΔT (Q is the heat, K is the heat transfer coefficient, A is the heat transfer area, and ΔT is the temperature difference), when the heat exchange area A of the heat exchanger is constant, the factors affecting the heating capacity are the heat transfer coefficient K and the temperature difference ΔT. The heat transfer coefficient K is related to the flow rate of the refrigerant. The greater the flow rate, the higher the heat exchange system. For the air source heat pump system, the refrigerant flow rate can be increased by reducing the number of distributors. The reduction in the number of distributors will lead to an increase in the flow of a single distributor, an increase in the system pressure drop, and a decrease in the temperature difference ΔT. Therefore, for the heating mode, in order to increase the heat exchange, more distributors are needed to reduce the pressure drop; for the cooling mode, the refrigerant changes from gas to liquid, and the system is not sensitive to the influence of the pressure drop. Therefore, the heat exchange of heating can be increased by reducing the distributors and increasing the flow, thereby improving the cooling energy efficiency. Therefore, this embodiment adjusts the operation of the liquid distribution pipe of the heat pump unit condenser to achieve the optimal number of flow paths in both the cooling mode and the heating mode, thereby improving the system capacity and energy efficiency.

[0036] See also Figure 1 and Figure 2 The air source heat pump system provided in this embodiment includes a compressor 100, a flow path switching valve 200, a condenser 300 and an evaporator connected by pipelines to form a main refrigerant circulation; the evaporator includes a heat exchanger 400, and a plurality of liquid distribution pipes 40 are arranged in the heat exchanger 400. A distributor 500 is provided at one end of the liquid distribution pipe 40, and a gas collecting pipe 50 is provided at the other end. The rear end of the heat exchanger 400 is connected to a subcooling section 410, and the distributor 500 is connected to a front-dividing pipeline 20. The front-dividing pipeline 20 is connected to the subcooling section 410 through a subcooling pipe 30. A first valve body 21 is provided on the front-dividing pipeline 20, and a second valve body 51 is provided on the gas collecting pipe 50. The second valve body 51 is arranged between the nth liquid distribution pipe 40 and the n+1th liquid distribution pipe 40.

[0037] The air source heat pump system is provided with a first valve body 21 between the distributor 500 and the condenser 300, and a second valve body 51 is provided between the nth liquid distributor 40 and the n+1th liquid distributor 40. In the heating mode, the first valve body 21 and the second valve body 51 are both set to a conducting state, and the refrigerant enters the distributor 500 in two ways for liquid distribution, one way is the pre-distribution pipeline 20 and the first valve body 21, and the other way is the subcooling pipe 30 and the subcooling section 410. The refrigerant flows out of the gas collecting pipe 50 after completing the heat exchange in each liquid distributor 40; in the cooling mode, the first valve body 21 and the second valve body 51 are both set to a closed state, so the refrigerant can only flow through the 1st to nth liquid distributors 40, and after the heat exchange, it is reversed in the distributor 500, and then flows through other liquid distributors 40, and is cooled again through the subcooling section 410, and finally is collected through the subcooling pipe 30. This achieves different numbers of flow paths for cooling and heating, allowing the system to achieve optimal energy efficiency for cooling and heating.

[0038] It can be understood that the specific value of n should meet the requirement that the air source heat pump system can obtain the optimal energy efficiency in both heating mode and cooling mode. The specific value can be obtained based on experiments or calculations and will not be explained here. Optionally, the first valve body 21 and the second valve body 51 are both one-way valves, which are only opened in the heating mode. When the first valve body 21 and the second valve body 51 are opened, by setting the first valve body 21 and the second valve body 51 as one-way valves, the fluid can only flow in one direction to avoid refrigerant backflow, that is, the refrigerant flows from the front pipeline 20 of the diversion to the distributor 500, flows through the liquid distribution pipe 40 through the heat exchanger 400 and then merges into the gas collecting pipe 50. Optionally, the first valve body 21 and the second valve body 51 are both solenoid valves with good control accuracy and sensitivity.

[0039] Further, the plurality of liquid distributing tubes 40 are connected to the flow path switching valve 200 through the gas collecting pipe 50, and the second valve body 51 is disposed on the gas collecting pipe 50. It can be understood that the position of the second valve body 51 on the gas collecting pipe 50 is determined according to the calculated value of n.

[0040] Furthermore, the flow path switching valve 200 is a four-way valve, which is used to switch between the cooling mode and the heating mode. In the cooling state, the four-way valve is not energized, and the four-way valve is in the state of AB connection and CD connection. The refrigerant is compressed by the compressor 100 and converted into a high-temperature and high-pressure gas, passes through the A port of the four-way valve, is discharged from the B port, enters the evaporator, and becomes a medium-temperature and high-pressure liquid after absorbing cold and releasing heat in the evaporator. After passing through the main valve 11, it becomes a low-temperature and low-pressure liquid. After passing through the condenser 300, it absorbs heat and releases cold, and becomes a low-temperature and low-pressure gas. It passes through the D port of the four-way valve and returns to the compressor 100 from the C port, and then continues to circulate. In the heating state, the four-way valve is energized to connect AD and BC. The refrigerant is compressed by the compressor 100 and converted into a high-temperature and high-pressure gas. It passes through the A port of the four-way valve and is discharged from the D port to enter the condenser 300. After absorbing cold and releasing heat in the condenser 300, it becomes a medium-temperature and high-pressure liquid. After passing through the main valve 11, it becomes a low-temperature and low-pressure liquid. After the evaporator absorbs heat and releases cold, it becomes a low-temperature and low-pressure gas. It passes through the B port of the four-way valve and returns to the compressor 100 from the C port, and then continues the cycle.

[0041] Furthermore, the compressor 100 is connected to the flow path switching valve 200 through the first circuit 70 and the second circuit 80 to form a circulation loop. Optionally, a high-pressure switch 71 and a pressure sensor 72 are provided on the first circuit 70, and a low-pressure switch 81 is provided on the second circuit 80. The function of the low-pressure switch is to disconnect the contact and cut off the electromagnetic clutch coil circuit so that the compressor 100 cannot operate when there is a serious lack of refrigerant, resulting in the pressure on the high-pressure side being lower than a certain value, so as to prevent the compressor 100 from being damaged by operating without lubrication guarantee. That is, the low-pressure switch can complete the connection and disconnection of the circuit, and protect the circuit or electrical equipment from short circuit, serious overload and pressure loss. The function of the high-pressure switch is to prevent the system pressure from being too high, resulting in accidents such as system explosion, forcing the compressor 100 to stop working. When the system high-pressure pressure is abnormally high, the high-pressure switch is opened, the control circuit of the compressor 100 is cut off, and the system stops working.

[0042] Optionally, an evaporator temperature sensor 90 is provided between the heat exchanger 400 and the distributor 500 for detecting the temperature. The evaporator temperature sensor 90 senses the temperature of the evaporator and adjusts the system working time. The evaporator temperature sensor 90 protects the system and prevents frost on the evaporator surface, which reduces the heat exchange efficiency.

[0043] Furthermore, the condenser 300 is connected to the pre-dividing pipeline 20 through the main line 10, and a plate heat exchanger 600 is provided on the main line 10. The plate heat exchanger 600 is a device for increasing the air supply heat exchange capacity in the system, and has the characteristics of high heat exchange efficiency, small heat loss, compact and light structure, small footprint, wide application, and long service life.

[0044] Optionally, a main valve 11 is provided on the main circuit 10, and the main valve 11 is located between the first valve body 21 and the plate heat exchanger 600. Further, the main valve 11 is an electronic expansion valve, which can adjust the system pressure. In the cooling mode and the heating mode, the main valve 11 is controlled according to the suction superheat, which refers to the difference between the suction temperature and the evaporation temperature. In this embodiment, it is required to ensure that the suction superheat is greater than 3°C. In other embodiments, it is set according to the use needs. Further, the auxiliary valve 61 is an electronic expansion valve, which can adjust the system pressure. The auxiliary valve 61 is opened, the system is an air-injection enthalpy-increasing system, and the air-injection takes effect. By increasing the supercooling of the main circuit 10, the refrigerant circulation volume of the unit is increased, and the heating capacity at low ambient temperature is increased. The control of the auxiliary valve 61 is controlled according to the superheat of the auxiliary circuit 60. The superheat of the auxiliary circuit 60 is the temperature difference before and after the auxiliary circuit 60 passes through the plate heat exchanger 600. In this embodiment, the superheat of the auxiliary circuit 60 is ensured to be 3-5°C. In other embodiments, the superheat degree of the auxiliary circuit 60 is set according to usage requirements.

[0045] Optionally, the air source heat pump system further includes an auxiliary circuit 60, which passes through the plate heat exchanger 600 and connects the main circuit 10 and the compressor 100. Further, an auxiliary valve 61 is provided on the auxiliary circuit 60. Optionally, the auxiliary valve 61 is an electronic expansion valve with good control accuracy and sensitivity.

[0046] Further, the present embodiment provides an air source heat pump system control method, which is applied to the above air source heat pump system, and the air source heat pump system control method includes: in the heating mode, the first valve body 21 and the second valve body 51 are both opened; in the cooling mode, the first valve body 21 and the second valve body 51 are both closed. In the heating mode, by opening the first valve body and the second valve body, the refrigerant can enter the distributor 500 in two ways for liquid separation, one of which flows through the pre-splitting pipeline 20 and the first valve body 21, and the other flows through the cold pipe 30 and the supercooling section 410, and the refrigerant flows out of the gas collecting pipe 50 after completing the heat exchange in each liquid separation pipe 40; in the cooling mode, by closing the first valve body 21 and the second valve body 51, the refrigerant can only flow through the 1st to nth liquid separation pipes 40, and after heat exchange, it is reversed in the distributor 500, and then flows through other liquid separation pipes 40, and is cooled again through the supercooling section 410, and finally is collected through the supercooling pipe 30. The opening and closing of the first valve and the second valve are used to control the flow path of the refrigerant in different modes, so as to achieve the effect of different flow paths in the cooling mode and the heating mode, so that the cooling and heating of the system can achieve the highest energy efficiency.

[0047] Further, in the heating mode, when the ambient temperature is lower than the preset temperature, the auxiliary valve 61 of the air source heat pump system is opened. In other embodiments, the preset temperature is 10°C, in other embodiments, the preset temperature may be 8°C, 9°C or 11°C, etc. The specific value of the preset temperature may be set according to the use requirements and is not specifically limited here.

[0048] The operation process of the air source heat pump system provided in this embodiment is as follows:

[0049] In the cooling mode, the low-temperature and low-pressure refrigerant is compressed by the compressor 100 into a high-temperature and high-pressure gas, passes through the four-way valve, flows through the 1st to nth liquid distributors 40, is reversed in the distributor 500 after heat exchange, and then flows through other liquid distributors 40, condensed into a high-temperature and high-pressure liquid, and finally collected through the supercooling pipe 30, and then enters the main path 10, passes through the main valve 11 and the plate heat exchanger 600, evaporates into a low-temperature and low-pressure gas, and is then discharged to the condenser 300, and works in a cycle.

[0050] In the heating mode, the low-temperature and low-pressure refrigerant is compressed by the compressor 100 into a high-temperature and high-pressure gas, and is switched by the four-way valve to enter the condenser 300, and then enters the main path 10 to be discharged to the plate heat exchanger 600, where it is cooled and condensed into a high-temperature and high-pressure liquid. After passing through the main valve 11, the refrigerant enters the distributor 500 in two ways for liquid separation, one of which is the pre-diversion pipeline 20 and the first valve body 21, and the other is the subcooling pipe 30 and the subcooling section 410. After completing the heat exchange in each liquid distribution pipe 40, the refrigerant flows out of the collecting pipe 50 and returns to the compressor 100 to circulate.

[0051] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An air source heat pump system, wherein the air source heat pump system has a cooling mode and a heating mode, and is characterized in that: include: A compressor (100), a flow path switching valve (200), a condenser (300), and an evaporator are connected through pipelines to form a main refrigerant circulation; The evaporator comprises a heat exchanger (400), wherein a plurality of liquid distribution pipes (40) are arranged in the heat exchanger (400), a distributor (500) is arranged at one end of the liquid distribution pipe (40), and a gas collecting pipe (50) is arranged at the other end, the rear end of the heat exchanger (400) is connected to a subcooling section (410), the distributor (500) is connected to a pre-dividing pipeline (20), the pre-dividing pipeline (20) is connected to the subcooling section (410) through a subcooling pipe (30), a first valve body (21) is arranged on the pre-dividing pipeline (20), a second valve body (51) is arranged on the gas collecting pipe (50), and the second valve body (51) is arranged between the nth liquid distribution pipe (40) and the n+1th liquid distribution pipe (40).

2. The air source heat pump system according to claim 1, characterized in that: The condenser (300) is connected to the pre-dividing pipeline (20) through a main path (10), and a plate heat exchanger (600) is arranged on the main path (10).

3. The air source heat pump system according to claim 2, characterized in that: The main path (10) is provided with a main valve (11), and the main valve (11) is located between the first valve body (21) and the plate heat exchanger (600).

4. The air source heat pump system according to claim 3, characterized in that: The air source heat pump system further comprises an auxiliary path (60), wherein the auxiliary path (60) passes through the plate heat exchanger (600) and connects the main path (10) and the compressor (100).

5. The air source heat pump system according to claim 4, characterized in that: An auxiliary valve (61) is provided on the auxiliary path (60).

6. The air source heat pump system according to claim 1, characterized in that: The flow path switching valve (200) is a four-way valve.

7. The air source heat pump system according to claim 1, characterized in that: The compressor (100) is connected to the flow path switching valve (200) through a first circuit (70) and a second circuit (80) to form a circulation circuit.

8. The air source heat pump system according to claim 1, characterized in that: An evaporator temperature sensor (90) is provided between the heat exchanger (400) and the distributor (500).

9. An air source heat pump system control method, characterized in that: Applied to the air source heat pump system according to any one of claims 1 to 8, the air source heat pump system control method comprises: In the heating mode, the first valve body (21) and the second valve body (51) are both open; In the cooling mode, the first valve body (21) and the second valve body (51) are both closed.

10. The air source heat pump system control method according to claim 9, characterized in that: In the heating mode, when the ambient temperature is lower than a preset temperature, the auxiliary valve (61) of the air source heat pump system opens.

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