阅读说明：本技术 用于空气源热泵机组的控制方法 (Control method for air source heat pump unit ) 是由 张宝库 韩伟涛 张丽娟 毛守博 卢大海 于 2021-07-30 设计创作，主要内容包括：本发明涉及空气源热泵机组防冻技术领域,具体提供一种用于空气源热泵机组的控制方法,旨在解决现有空气源热泵机组的水侧换热器容易在使用过程中被冻裂的问题。为此目的,本发明通过将水循环回路中的水流量与预设水流量进行对比,以控制冷媒循环回路运行,还能够通过获取空气源热泵机组处于制热工况时的水循环回路中的出水温度控制冷媒循环回路的运行工况和辅助电加热装置的开闭状态,通过获取空气源热泵机组处于制冷工况时的冷媒循环回路的低压压力控制压缩机和电子膨胀阀的运行状态,进而有效保证在任何工况下第二换热器都不会受水流量过少、水温过低等因素的影响而导致其被冻裂的问题,以便有效保证其可靠性。(The invention relates to the technical field of air source heat pump unit anti-freezing, and particularly provides a control method for an air source heat pump unit, aiming at solving the problem that a water side heat exchanger of the existing air source heat pump unit is easy to be frozen and cracked in the using process. For the purpose, the water flow in the water circulation loop is compared with the preset water flow to control the operation of the refrigerant circulation loop, the operation condition of the refrigerant circulation loop and the opening and closing state of the auxiliary electric heating device can be controlled by acquiring the outlet water temperature in the water circulation loop when the air source heat pump unit is in the heating condition, the operation states of the compressor and the electronic expansion valve are controlled by acquiring the low-pressure of the refrigerant circulation loop when the air source heat pump unit is in the refrigerating condition, and therefore the problem that the second heat exchanger is frostbitten due to the influence of factors such as too little water flow, too low water temperature and the like can be effectively solved, and the reliability of the second heat exchanger can be effectively guaranteed.)

1. The control method for the air source heat pump unit is characterized in that the air source heat pump unit comprises a refrigerant circulation loop, a water circulation loop and an auxiliary electric heating device, a compressor, a four-way valve, a first heat exchanger, an electronic expansion valve and a second heat exchanger are arranged on the refrigerant circulation loop, a circulating water pump is arranged on the water circulation loop, the refrigerant circulation loop and the water circulation loop can realize heat exchange through the second heat exchanger, the auxiliary electric heating device can heat water in the water circulation loop, and the control method comprises the following steps:

when the air source heat pump unit starts to start, the circulating water pump is controlled to start firstly;

acquiring the water flow in the water circulation loop;

if the water flow is larger than or equal to the preset water flow, controlling the refrigerant circulation loop to operate;

when the air source heat pump unit is in a heating working condition, acquiring the outlet water temperature of the water circulation loop;

controlling the operation condition of the refrigerant circulation loop and the opening and closing state of the auxiliary electric heating device according to the outlet water temperature;

when the air source heat pump unit is in a refrigeration working condition, acquiring the low-pressure of the refrigerant circulation loop;

and controlling the running state of the compressor and the running state of the electronic expansion valve according to the numerical range of the low-pressure.

2. The control method according to claim 1, wherein the step of obtaining the leaving water temperature of the water circulation loop specifically comprises:

when the water circulation loop is started, acquiring the initial outlet water temperature of the water circulation loop;

after the preset operation time, acquiring the current outlet water temperature of the water circulation loop;

the step of controlling the operation condition of the refrigerant circulation loop and the opening and closing state of the auxiliary electric heating device according to the outlet water temperature specifically comprises the following steps:

and controlling the operation condition of the refrigerant circulation loop and the opening and closing state of the auxiliary electric heating device according to the initial outlet water temperature and the current outlet water temperature.

3. The control method according to claim 2, wherein the step of controlling the operation condition of the refrigerant circulation circuit and the on/off state of the auxiliary electric heating device according to the initial outlet water temperature and the current outlet water temperature specifically comprises:

and if the difference value between the current outlet water temperature and the initial outlet water temperature is less than or equal to a preset outlet water temperature difference and the current outlet water temperature is less than or equal to a first preset outlet water temperature, controlling the operation condition of the refrigerant circulation loop to be unchanged and starting the auxiliary electric heating device.

4. The control method according to claim 3, characterized by further comprising:

under the condition that the auxiliary electric heating device is started, the water outlet temperature of the water circulation loop is obtained again;

when the obtained outlet water temperature is higher than a second preset outlet water temperature, the auxiliary electric heating device is turned off;

and the second preset outlet water temperature is greater than the first preset outlet water temperature.

5. The control method according to claim 4, wherein a high-pressure and low-pressure balance valve is further provided on the refrigerant circulation circuit, and the control method further comprises:

and when the air source heat pump unit starts to operate in a defrosting condition, the four-way valve is controlled to change direction and the high-low pressure balance valve is controlled to be opened.

6. The control method according to claim 5, wherein the step of controlling the opening of the high-low pressure balancing valve specifically includes:

and controlling the opening of the high-low pressure balance valve for a preset protection duration.

7. The control method according to any one of claims 1 to 6, wherein the step of controlling the operating state of the compressor and the operating state of the electronic expansion valve according to the range of values in which the low pressure is located, comprises:

and if the low-pressure is less than a first preset low-pressure and greater than or equal to a second preset low-pressure for a first preset time, controlling the running frequency of the compressor and the opening of the electronic expansion valve to be unchanged.

8. The control method according to claim 7, wherein the step of controlling the operating state of the compressor and the operating state of the electronic expansion valve according to the numerical range in which the low pressure is located further comprises:

and if the low pressure is less than the second preset low pressure and greater than or equal to a third preset low pressure for a second preset time, controlling the running frequency of the compressor not to be increased and controlling the opening of the electronic expansion valve to be increased.

9. The control method according to claim 8, wherein the step of controlling the operating state of the compressor and the operating state of the electronic expansion valve according to the numerical range in which the low pressure is located further comprises:

and if the low-pressure is less than the third preset low-pressure and greater than or equal to the fourth preset low-pressure for a third preset time, controlling the running frequency of the compressor to be reduced and controlling the opening of the electronic expansion valve to be increased.

10. The control method according to claim 9, wherein the step of controlling the operating state of the compressor and the operating state of the electronic expansion valve according to the numerical range in which the low pressure is located further comprises:

and if the low-pressure is less than the fourth preset low-pressure for a fourth preset time, controlling the compressor and the electronic expansion valve to be closed.

Technical Field

The invention relates to the technical field of air source heat pump unit anti-freezing, and particularly provides a control method for an air source heat pump unit.

Background

Along with the ever-increasing demand of users, the development of the existing heat exchanger tends to be fine, the volume is small, the heat exchange efficiency is high, and the heat exchanger is widely applied to an air source heat pump unit. However, if the water flow passing through the inside of the existing water side heat exchanger is insufficient or the water temperature is too low, or the temperature is too low in the refrigeration process, the problem that the water side heat exchanger is frozen is caused. In addition, the condition that frosting can appear at the in-process of heating in current air source heat pump unit's outdoor heat exchanger, in order to guarantee air source heat pump unit's the effect of heating, after outdoor heat exchanger frosting reaches the certain degree, air source heat pump unit will get into the defrosting operating mode, current air source heat pump unit adopts the mode of reverse defrosting mostly, however, based on this kind of defrosting mode, when air source heat pump unit switches to the defrosting operating mode, the refrigerant in its return circuit can lead to the fact great thermal shock to water side heat exchanger, easily cause water side heat exchanger to damage from this. When the air source heat pump unit is in a refrigeration working condition, if the low-pressure side pressure in the loop is too low, when the temperature of a refrigerant entering the water side heat exchanger is lower than the freezing point temperature of the refrigerant, the water side heat exchanger can possibly generate a freezing and cracking phenomenon, and further the air source heat pump unit cannot be used.

Disclosure of Invention

The invention aims to solve the technical problem that a water side heat exchanger of the existing air source heat pump unit is easy to be frozen and cracked in the operation process.

The invention provides a control method for an air source heat pump unit, wherein the air source heat pump unit comprises a refrigerant circulation loop, a water circulation loop and an auxiliary electric heating device, a compressor, a four-way valve, a first heat exchanger, an electronic expansion valve and a second heat exchanger are arranged on the refrigerant circulation loop, a circulating water pump is arranged on the water circulation loop, the refrigerant circulation loop and the water circulation loop can realize heat exchange through the second heat exchanger, the auxiliary electric heating device can heat water in the water circulation loop, and the control method comprises the following steps: when the air source heat pump unit starts to start, the circulating water pump is controlled to start firstly; acquiring the water flow in the water circulation loop; if the water flow is larger than or equal to the preset water flow, controlling the refrigerant circulation loop to operate; when the air source heat pump unit is in a heating working condition, acquiring the outlet water temperature of the water circulation loop; controlling the operation condition of the refrigerant circulation loop and the opening and closing state of the auxiliary electric heating device according to the outlet water temperature; when the air source heat pump unit is in a refrigeration working condition, acquiring the low-pressure of the refrigerant circulation loop; and controlling the running state of the compressor and the running state of the electronic expansion valve according to the numerical range of the low-pressure.

In the preferred technical solution of the above control method, the step of "obtaining the outlet water temperature of the water circulation loop" specifically includes: when the water circulation loop is started, acquiring the initial outlet water temperature of the water circulation loop; after the preset operation time, acquiring the current outlet water temperature of the water circulation loop; the step of controlling the operation condition of the refrigerant circulation loop and the opening and closing state of the auxiliary electric heating device according to the outlet water temperature specifically comprises the following steps: and controlling the operation condition of the refrigerant circulation loop and the opening and closing state of the auxiliary electric heating device according to the initial outlet water temperature and the current outlet water temperature.

In a preferred technical solution of the above control method, the step of controlling the operation condition of the refrigerant circulation circuit and the open/close state of the auxiliary electric heating device according to the initial outlet water temperature and the current outlet water temperature specifically includes: and if the difference value between the current outlet water temperature and the initial outlet water temperature is less than or equal to a preset outlet water temperature difference and the current outlet water temperature is less than or equal to a first preset outlet water temperature, controlling the operation condition of the refrigerant circulation loop to be unchanged and starting the auxiliary electric heating device.

In a preferred embodiment of the above control method, the control method further includes: under the condition that the auxiliary electric heating device is started, the water outlet temperature of the water circulation loop is obtained again; when the obtained outlet water temperature is higher than a second preset outlet water temperature, the auxiliary electric heating device is turned off; and the second preset outlet water temperature is greater than the first preset outlet water temperature.

In a preferred technical solution of the above control method, the refrigerant circulation loop is further provided with a high-low pressure balance valve, and the control method further includes: and when the air source heat pump unit starts to operate in a defrosting condition, the four-way valve is controlled to change direction and the high-low pressure balance valve is controlled to be opened.

In a preferred embodiment of the above control method, the step of "controlling the opening of the high-low pressure balancing valve" specifically includes: and controlling the opening of the high-low pressure balance valve for a preset protection duration.

In a preferred embodiment of the above control method, the step of controlling the operating state of the compressor and the operating state of the electronic expansion valve according to a numerical range in which the low pressure is within includes: and if the low-pressure is less than a first preset low-pressure and greater than or equal to a second preset low-pressure for a first preset time, controlling the running frequency of the compressor and the opening of the electronic expansion valve to be unchanged.

In a preferred embodiment of the above control method, the step of controlling the operating state of the compressor and the operating state of the electronic expansion valve according to a numerical range in which the low pressure is located further includes: and if the low pressure is less than the second preset low pressure and greater than or equal to a third preset low pressure for a second preset time, controlling the running frequency of the compressor not to be increased and controlling the opening of the electronic expansion valve to be increased.

In a preferred embodiment of the above control method, the step of controlling the operating state of the compressor and the operating state of the electronic expansion valve according to a numerical range in which the low pressure is located further includes: and if the low-pressure is less than the third preset low-pressure and greater than or equal to the fourth preset low-pressure for a third preset time, controlling the running frequency of the compressor to be reduced and controlling the opening of the electronic expansion valve to be increased.

In a preferred embodiment of the above control method, the step of controlling the operating state of the compressor and the operating state of the electronic expansion valve according to a numerical range in which the low pressure is located further includes: and if the low-pressure is less than the fourth preset low-pressure for a fourth preset time, controlling the compressor and the electronic expansion valve to be closed.

Under the condition of adopting the technical scheme, the invention can control the operation of the refrigerant circulation loop by comparing the water flow in the water circulation loop with the preset water flow, and can also control the operation condition of the refrigerant circulation loop and the opening and closing state of the auxiliary electric heating device by acquiring the outlet water temperature in the water circulation loop when the air source heat pump unit is in the heating condition, and control the operation state of the compressor and the operation state of the electronic expansion valve by acquiring the low pressure of the refrigerant circulation loop when the air source heat pump unit is in the refrigerating condition, so that the control method can effectively ensure that the second heat exchanger is not frozen and cracked under any condition due to the influence of factors such as too low water flow, too low water temperature and the like, so as to effectively ensure the reliability thereof.

Drawings

Preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

FIG. 1 is a schematic view of the construction of an air source heat pump unit of the present invention;

FIG. 2 is a flow chart of the main steps of the control method of the present invention;

FIG. 3 is a flowchart illustrating the detailed steps of a first preferred embodiment of the control method of the present invention;

FIG. 4 is a flowchart illustrating the detailed steps of a second preferred embodiment of the control method of the present invention;

reference numerals:

1. a compressor; 2. a four-way valve; 3. a first heat exchanger; 4. an electronic expansion valve; 5. a second heat exchanger; 6. a gas-liquid separator; 7. a low pressure sensor; 8. a water circulating pump; 9. a flow meter; 10. an effluent temperature sensor; 11. high-low pressure balancing valve.

Detailed Description

Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only for explaining the technical principle of the present invention, and are not intended to limit the scope of the present invention. And can be adjusted as needed by those skilled in the art to suit particular applications. For example, the air source heat pump unit in the invention can be a split air source heat pump unit or an integral air source heat pump unit, which are not restrictive, and technicians can set the application object of the control method according to actual use requirements. Such changes in the application object do not depart from the basic principle of the present invention and belong to the protection scope of the present invention.

It should be noted that, unless otherwise explicitly stated or limited, the term "connected" in the description of the preferred embodiments is to be interpreted broadly, e.g. directly or indirectly through an intermediate medium, or internally or indirectly through two elements, and thus should not be interpreted as limiting the invention. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

Further, it should be noted that in the description of the present invention, although the steps of the control method of the present invention are described in a specific order in the present application, the order is not limited, and those skilled in the art may perform the steps in a different order without departing from the basic principle of the present invention.

Specifically, referring to fig. 1, fig. 1 is a schematic structural diagram of an air source heat pump unit according to the present invention. As shown in fig. 1, the air source heat pump unit of the present invention includes a refrigerant circulation loop, a water circulation loop and an auxiliary electric heating device (not shown in the figure), the refrigerant circulation loop is provided with a compressor 1, a four-way valve 2, a first heat exchanger 3, an electronic expansion valve 4, a second heat exchanger 5 and a gas-liquid separator 6, a low pressure sensor 7 is arranged at an air inlet of the compressor 1, and the specific arrangement position is not limited; a circulating water pump 8 and a flowmeter 9 are arranged on the water circulation loop, the circulating water pump 8 and the flowmeter 9 are arranged on the water inlet side of the second heat exchanger 5, and a water outlet temperature sensor 10 is arranged on the water outlet side of the second heat exchanger 5 so as to detect the temperature of water in the water circulation loop after flowing through the second heat exchanger 5; it should be noted that, although the water circulation circuit shown in the drawings is open, this is only illustrative, and a water inlet and a water intake may be provided on the water circulation circuit to exchange chilled water with the outside. The refrigerant circulation loop and the water circulation loop can realize heat exchange through the second heat exchanger 5, and the auxiliary electric heating device can heat water in the water circulation loop.

It should be noted that the present invention does not limit the specific types of the first heat exchanger 3, the second heat exchanger 5, the low-pressure sensor 7, and the outlet water temperature sensor 10, the first heat exchanger 3 and the second heat exchanger 5 may be plate heat exchangers or double-pipe heat exchangers, the low-pressure sensor 7 may be a capacitive pressure sensor, a piezoresistive pressure sensor, a piezoelectric pressure sensor, and the outlet water temperature sensor 10 may be a thermal sensor or a thermocouple sensor, and the technical staff may set the types according to the actual situation.

In addition, the air source heat pump unit is provided with a heating working condition, a refrigerating working condition and a defrosting working condition, and specifically, when the air source heat pump unit is in the heating working condition, the first heat exchanger 3 is used as an evaporator, and the second heat exchanger 5 is used as a condenser; when the air source heat pump unit is in a refrigeration working condition and a defrosting working condition, the first heat exchanger 3 is used as a condenser, and the second heat exchanger 5 is used as an evaporator. Of course, it should be noted that the present invention does not limit the specific types of the working conditions set by the air source heat pump unit, and obviously, other working conditions may be set, and technicians may set the working conditions according to actual situations.

Further, the air source heat pump unit of the present invention further comprises a controller, wherein the controller is capable of executing the control method of the present invention, such as: the controller can control the operation condition of the refrigerant circulation loop, control the opening and closing state of the auxiliary electric heating device, control the operation states of the compressor 1, the electronic expansion valve 4, the circulating water pump 8 and the like. It can be understood by those skilled in the art that the present invention does not limit the specific structure and type of the controller, and the controller may be the original controller of the air source heat pump unit, or may be a controller separately configured to execute the control method of the present invention, and the structure and type of the controller may be set by those skilled in the art according to the actual use requirement.

Referring next to fig. 2, fig. 2 is a flow chart of main steps of the control method of the present invention. As shown in fig. 2, based on the air source heat pump unit described in the above embodiment, the control method of the present invention includes the following steps:

s1: when the air source heat pump unit starts to start, the circulating water pump is controlled to start firstly;

s2: acquiring water flow in a water circulation loop;

s3: if the water flow is greater than or equal to the preset water flow, controlling the refrigerant circulation loop to operate;

s4: when the air source heat pump unit is in a heating working condition, acquiring the outlet water temperature of the water circulation loop;

s5: controlling the operation condition of the refrigerant circulation loop and the opening and closing state of the auxiliary electric heating device according to the outlet water temperature;

s6: when the air source heat pump unit is in a refrigeration working condition, acquiring the low-pressure of a refrigerant circulation loop;

s7: and controlling the running state of the compressor and the running state of the electronic expansion valve according to the numerical range of the low-pressure.

In steps S1 to S3, when the air source heat pump unit starts to start, the controller first controls the circulation water pump 8 to start, and then obtains the water flow rate in the water circulation loop, and if the water flow rate is greater than or equal to a preset water flow rate, the controller controls the refrigerant circulation loop to operate. It should be noted that, the specific value of the preset water flow is not limited, and a technician can set the value according to actual use requirements; preferably, the preset water flow is 70% of a standard water flow, and the standard water flow is a water flow when the unit operates stably.

In addition, it should be noted that the water flow rate may be obtained by monitoring the water flow rate or by monitoring the water intake time, the water flow rate obtaining method is not limited in the present invention, and a technician may set the water flow rate according to actual conditions.

In steps S4 and S5, when the air source heat pump unit is in a heating condition, the outlet water temperature of the water circulation loop is obtained, and the outlet water temperature sensor 10 can convert the outlet water temperature into an output signal and transmit the output signal to the controller; and then, the controller controls the operation condition of the refrigerant circulation loop and the opening and closing state of the auxiliary electric heating device according to the received outlet water temperature. It should be noted that, the present invention does not limit the specific control manner, and a technician can set the control manner according to actual requirements, and it is within the protection scope of the present invention as long as the operation condition of the refrigerant circulation loop and the on-off state of the auxiliary electric heating device are controlled according to the outlet water temperature; in addition, the invention does not limit the specific acquisition mode and the acquisition position of the outlet water temperature, and technicians can set the temperature according to actual conditions.

In steps S6 and S7, when the air source heat pump unit is in a refrigeration condition, the low pressure in the refrigerant circulation loop is obtained, and the low pressure sensor 7 can convert the low pressure into an output signal to be transmitted to the controller; then, the controller controls the operation state of the compressor 1 and the operation state of the electronic expansion valve 4 according to the numerical range in which the low pressure is located. It should be noted that, the present invention does not limit the specific value range of the numerical range, and the specific value range can be set through a plurality of tests, or can be set according to the actual operation condition of the air source heat pump unit, and a technician can set the value range according to the actual condition.

First preferred embodiment

Referring to fig. 3, fig. 3 is a flowchart illustrating specific steps of the first preferred embodiment of the control method according to the present invention. As shown in fig. 3, based on the air source heat pump unit described in the above embodiment, the control method of the first preferred embodiment of the present invention includes the following steps:

s101: when the air source heat pump unit starts to start, the circulating water pump is controlled to start firstly;

s102: acquiring water flow in a water circulation loop;

s103: if the water flow is greater than or equal to the preset water flow, controlling the refrigerant circulation loop to operate;

s104: under the condition that the air source heat pump unit is in a heating working condition, when the water circulation loop is started, acquiring the initial outlet water temperature of the water circulation loop;

s105: after the preset operation time, acquiring the current effluent temperature of the water circulation loop;

s106: if the difference value between the current outlet water temperature and the initial outlet water temperature is less than or equal to the preset outlet water temperature difference and the current outlet water temperature is less than or equal to the first preset outlet water temperature, controlling the operation condition of the refrigerant circulation loop to be unchanged and starting the auxiliary electric heating device;

s107: under the condition that the auxiliary electric heating device is started, the water outlet temperature of the water circulation loop is obtained again;

s108: when the obtained outlet water temperature is higher than the second preset outlet water temperature, the auxiliary electric heating device is turned off;

s109: when the air source heat pump unit starts to operate in a defrosting condition, the four-way valve is controlled to change direction, and the high-low pressure balance valve is controlled to be opened for a preset protection duration.

In steps S101 to S103, when the air source heat pump unit starts to start, the controller first controls the circulation water pump 8 to start, and preferably, after the circulation water pump 8 runs for a preset running time, the water flow in the water circulation loop is obtained, so as to effectively ensure that the second heat exchanger 5 is filled with enough water, and further effectively avoid the phenomenon of "emptying" of the second heat exchanger 5, specifically, if the water flow is greater than or equal to a preset water flow, the controller controls the refrigerant circulation loop to run, and if the water flow is less than the preset water flow, the controller controls the circulation water pump 8 to continue to run and controls the refrigerant circulation loop not to run until the water flow is greater than or equal to the preset water flow. In the preferred embodiment, the preset operation time is 2 to 3 minutes, and the preset water flow is 70% of the standard water flow. It should be noted that the water flow rate obtaining mode can be monitored by the water flow rate and also by the water inlet time, the water flow rate obtaining mode is not limited in any way, and a technician can set the water flow rate according to actual conditions. It should be noted that the setting of the standard water flow rate may be a default setting of the air source heat pump unit when the air source heat pump unit leaves a factory, or may be a self-setting by a user according to an actual operation condition.

In steps S104 and S105, when the air source heat pump unit is in a heating condition, when the water circulation loop is started, an initial outlet water temperature of the water circulation loop is obtained, and after a preset operation duration, a current outlet water temperature of the water circulation loop is obtained, the outlet water temperature sensor 10 can convert the initial outlet water temperature and the current outlet water temperature into output signals and transmit the output signals to the controller, and then the controller controls an operation condition of the refrigerant circulation loop and an open/close state of the auxiliary electric heating device according to the received signals of the initial outlet water temperature and the current outlet water temperature. In the preferred embodiment, the preset operation time period is set to 30 minutes according to the results of multiple tests, however, this is only a preferred setting value and is not limiting, and the technician can set the operation time period according to the actual operation condition of the air source heat pump unit. It should be noted that, the present invention does not limit the manner of obtaining the initial outlet water temperature and the current outlet water temperature, and the technician can set the temperature according to the actual situation.

In step S106, if the difference between the current leaving water temperature and the initial leaving water temperature is less than or equal to a preset leaving water temperature difference and the current leaving water temperature is less than or equal to a first preset leaving water temperature, the operation condition of the refrigerant circulation loop is controlled to be unchanged and the auxiliary electric heating device is turned on.

In steps S107 and S108, under the condition that the auxiliary electric heating device is turned on, the outlet water temperature of the water circulation loop is obtained again, and when the obtained outlet water temperature is greater than a second preset outlet water temperature, the auxiliary electric heating device is turned off.

In this embodiment, the preset outlet temperature difference is preferably 5 ℃, the second preset outlet temperature is greater than the first preset outlet temperature, wherein the first preset outlet temperature is preferably 20 ℃, and the second preset outlet temperature is preferably 22 ℃, and certainly, the present invention does not limit the specific values of the preset outlet temperature difference, the first preset outlet temperature, and the second preset outlet temperature at all, and the preset outlet temperature difference, the first preset outlet temperature, and the second preset outlet temperature can be obtained through multiple tests or can be obtained through user self-setting, which is not restrictive, and technicians can set the preset outlet temperature difference according to actual situations.

Preferably, the air source heat pump unit further comprises a high-low pressure balance branch, one end of the high-low pressure balance branch is connected between the exhaust port of the compressor 1 and the four-way valve 2, the other end of the high-low pressure balance branch is connected between the air inlet of the compressor 1 and the gas-liquid separator 6, and a high-low pressure balance valve 11 is arranged on the high-low pressure balance branch. In step S109, when the air source heat pump unit starts to operate the defrosting condition, the four-way valve 2 is controlled to reverse and the high-low pressure balance valve 11 is controlled to open for a preset protection period, so that the refrigerant and water passing through the second heat exchanger 5 cannot generate large cold-hot alternation due to the switching of the air source heat pump unit, and the setting of the high-low pressure balance valve 11 can effectively ensure that the second heat exchanger 5 cannot generate frost cracking, thereby ensuring the service life thereof. In the preferred embodiment, after a plurality of tests, the preset protection duration is 30 seconds, which is only a preferred setting value and is not restrictive, and a technician can set the specific duration of the preset protection duration according to different air source heat pump units.

In addition, it should be noted that the invention does not limit the specific time when the air source heat pump unit enters the defrosting condition, and technicians can set the time according to actual use requirements.

Second preferred embodiment

Referring to fig. 4, fig. 4 is a flowchart illustrating specific steps of a second preferred embodiment of the control method according to the present invention. As shown in fig. 4, based on the air source heat pump unit described in the above embodiments, the control method of the second preferred embodiment of the present invention includes the following steps:

s201: when the air source heat pump unit starts to start, the circulating water pump is controlled to start firstly;

s202: acquiring water flow in a water circulation loop;

s203: if the water flow is greater than or equal to the preset water flow, controlling the refrigerant circulation loop to operate;

s204: when the air source heat pump unit is in a refrigeration working condition, acquiring the low-pressure of a refrigerant circulation loop;

s205: controlling the running state of the compressor and the running state of the electronic expansion valve according to the numerical range of the low-pressure;

s206: if the low-pressure is less than the first preset low-pressure and greater than or equal to the second preset low-pressure for the first preset time, controlling the running frequency of the compressor and the opening of the electronic expansion valve to be unchanged;

s207: if the low-pressure is less than the second preset low-pressure and greater than or equal to the third preset low-pressure for a second preset time, controlling the running frequency of the compressor not to be increased and controlling the opening of the electronic expansion valve to be increased;

s208: if the low-pressure is less than the third preset low-pressure and greater than or equal to the fourth preset low-pressure for a third preset time, controlling the running frequency of the compressor to be reduced and controlling the opening of the electronic expansion valve to be increased;

s209: and if the low-pressure is less than the fourth preset low-pressure for a fourth preset time period, controlling the compressor and the electronic expansion valve to be closed.

In steps S201 to S203, when the air source heat pump unit starts to start, the controller first controls the circulation water pump 8 to start, and preferably, after the circulation water pump 8 runs for a preset running time, the water flow in the water circulation loop is obtained, so as to effectively ensure that the second heat exchanger 5 is filled with enough water, and further effectively avoid the phenomenon of "emptying" of the second heat exchanger 5, specifically, if the water flow is greater than or equal to a preset water flow, the controller controls the refrigerant circulation loop to run, and if the water flow is less than the preset water flow, the controller controls the circulation water pump 8 to continue to run and controls the refrigerant circulation loop not to run until the water flow is greater than or equal to the preset water flow. In the preferred embodiment, the preset operation time is 2 to 3 minutes, and the preset water flow is 70% of the standard water flow. It should be noted that the water flow rate obtaining mode can be monitored by the water flow rate and also by the water inlet time, the water flow rate obtaining mode is not limited in any way, and a technician can set the water flow rate according to actual conditions. It should be noted that the setting of the standard water flow rate may be a default setting of the air source heat pump unit when the air source heat pump unit leaves a factory, or may be a self-setting by a user according to an actual operation condition.

In steps S204 and S205, under the condition that the air source heat pump unit is in the refrigeration condition, the low pressure of the refrigerant circulation loop is obtained, and the low pressure sensor 7 can convert the low pressure into an output signal and transmit the output signal to the controller; then, the controller controls the operation state of the compressor 1 and the operation state of the electronic expansion valve 4 according to the numerical range in which the low pressure is located. It should be noted that, the present invention does not limit the specific value range of the numerical range, and the specific value range can be set through a plurality of tests, or can be set according to the actual operation condition of the air source heat pump unit, and a technician can set the value range according to the actual condition.

In steps S206 to S209, if the low pressure is less than a first preset low pressure and greater than or equal to a second preset low pressure for a first preset time period, the controller controls the operation frequency of the compressor 1 and the opening degree of the electronic expansion valve 4 to be constant; if the low-pressure is greater than or equal to the first preset low-pressure, the controller controls the air source heat pump unit to operate according to normal logic, that is, as long as the low-pressure is greater than or equal to the first preset low-pressure, the operating parameters of the air source heat pump unit can be automatically adjusted at any time according to actual requirements, and the specific control logic is not restrictive; if the low pressure is less than the second preset low pressure and greater than or equal to a third preset low pressure for a second preset time, the controller controls the operation frequency of the compressor 1 not to be increased and controls the opening of the electronic expansion valve 4 to be increased; if the low-pressure is less than the third preset low-pressure and greater than or equal to a fourth preset low-pressure for a third preset time, the controller controls the operation frequency of the compressor 1 to be reduced and controls the opening of the electronic expansion valve 4 to be increased; if low-pressure is less than the fourth preset low-pressure and lasts for a fourth preset duration, the controller controls the compressor 1 and the electronic expansion valve 4 to be closed, namely the air source heat pump unit stops running, so that the second heat exchanger 5 can be effectively prevented from being frozen under the refrigerating working condition, and the service life of the second heat exchanger can be effectively prevented from being shortened due to freezing.

It should be noted that, the specific durations of the first preset duration, the second preset duration, the third preset duration and the fourth preset duration are not limited in the present invention, and may be the same or different, and a technician may set the durations according to the actual operation condition of the air source heat pump unit. In the preferred embodiment, the specific durations of the first preset duration, the second preset duration, the third preset duration and the fourth preset duration are all 3 minutes through a plurality of tests, that is, when the specific duration exceeds 3 minutes, the second heat exchanger 5 is at risk of freezing, but this is not restrictive, and the specific durations may be set differently for different air source heat pump units.

It should be further noted that the values of the first preset low-pressure, the second preset low-pressure, the third preset low-pressure and the fourth preset low-pressure are not restrictive, and a technician can set the values by himself or herself according to the multiple test results of the air source heat pump unit, as long as it is ensured that the second heat exchanger 5 is not damaged due to freezing.

So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can fall into the protection scope of the invention.