Heat pump condenser anti-freezing control method and heat pump system

Abstract

The invention relates to the technical field of heat pump systems, in particular to a heat pump condenser anti-freezing control method and a heat pump system. The heat pump condenser anti-freezing control method comprises the steps that a defrosting mode instruction is received; closing the compressor and the fan, opening the opening degree of the main expansion valve to the defrosting preset opening degree, and waiting for first preset time; switching the four-way valve; closing the electromagnetic valve, and closing the main expansion valve; waiting for second preset time, and opening the opening degree of the main expansion valve to the defrosting preset opening degree; opening an electromagnetic valve; and a compressor is started, and a defrosting mode is operated. According to the anti-freezing control method for the heat pump condenser, the refrigerant migration path is regulated and controlled by stages, enough refrigerant can be stored in the condenser before a defrosting mode, the defrosting evaporation temperature is increased through sufficient heat exchange between the refrigerant and the condenser, and the phenomena of freezing and frost cracking of the condenser are reduced. According to the anti-freezing control method for the heat pump condenser, the risks of liquid blockage of the gas-liquid separator and liquid impact of the compressor due to the fact that a large number of refrigerants flow into the gas-liquid separator can be reduced or avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pump systems, and particularly to an anti-freezing control method for a heat pump condenser and a heat pump system. Background Art

[0002] At present, existing air-source heat pump systems have significant technical defects under the defrosting condition in winter. The core problem stems from the dynamic imbalance of the refrigerant circulation system during the switching process of the four-way valve.

[0003] When existing air-source heat pump systems are in the defrosting mode, the refrigerant flow direction is reversed through the switching of the four-way valve to achieve defrosting. During this process, the liquid refrigerant accumulated on the high-pressure side will migrate uncontrollably to the low-pressure side along with the sudden change in pressure. This migration leads to two systematic defects:

[0004] Firstly, due to the instantaneous lack of refrigerant on the evaporator side, the evaporation temperature drops sharply, resulting in the rapid formation of local ice layers on the surface of the plate heat exchanger. Material fatigue damage occurs during repeated freeze-thaw cycles, and finally the heat exchanger freezes and fails.

[0005] Secondly, a large amount of unevaporated liquid refrigerant directly enters the gas-liquid separator and the compressor suction end through the four-way valve. When the liquid refrigerant carrying capacity exceeds the design capacity of the gas-liquid separator, a liquid slugging phenomenon in the compressor will be triggered, generating mechanical stress shocks caused by liquid compression. At the same time, the liquid blockage effect formed by the liquid accumulation in the gas-liquid separator will block the normal return air path, thereby damaging the compressor.

[0006] Therefore, there is an urgent need to design an anti-freezing control method for a heat pump condenser and a heat pump system to solve the above technical problems. Summary of the Invention

[0007] The first object of the present invention is to propose an anti-freezing control method for a heat pump condenser, which is used to solve the phenomenon of ice formation on the plate heat exchanger caused by insufficient refrigerant on the evaporation side and low evaporation temperature due to refrigerant migration during the switching of the four-way valve during the defrosting process; and to solve the problems of liquid blockage in the gas-liquid separator and liquid slugging in the compressor caused by a large amount of refrigerant flooding into the gas-liquid separator.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] The present invention provides an anti-freezing control method for a heat pump condenser, including:

[0010] Receiving a defrosting mode instruction;

[0011] Closing the compressor and the fan, opening the main expansion valve to a defrosting preset opening and waiting for a first preset time;

[0012] Switching the four-way valve;

[0013] Closing the solenoid valve and closing the main expansion valve;

[0014] Wait for the second preset time and open the main expansion valve to the defrost preset opening degree;

[0015] Open the solenoid valve;

[0016] Start the compressor and run the defrost mode.

[0017] As an alternative technical solution of a heat pump condenser anti-freezing control method, the steps of shutting down the compressor and the fan, opening the main expansion valve to the defrost preset opening degree and waiting for the first preset time include:

[0018] Shut down the compressor and the fan, close the auxiliary expansion valve, open the main expansion valve to the defrost preset opening degree and wait for the first preset time.

[0019] As an alternative technical solution of a heat pump condenser anti-freezing control method, the first preset time is set to 5s - 15s.

[0020] As an alternative technical solution of a heat pump condenser anti-freezing control method, the second preset time is set to 20s - 40s.

[0021] As an alternative technical solution of a heat pump condenser anti-freezing control method, in the defrost mode, the opening degree of the main expansion valve is 480 steps.

[0022] As an alternative technical solution of a heat pump condenser anti-freezing control method, the steps of switching the four-way valve include:

[0023] Switch the four-way valve so that the solenoid valve is connected to the exhaust port of the compressor through the four-way valve.

[0024] As an alternative technical solution of a heat pump condenser anti-freezing control method, the heat pump condenser anti-freezing control method further includes:

[0025] After the defrosting is completed, exit the defrost mode;

[0026] The steps of exiting the defrost mode include:

[0027] Shut down the compressor, start the fan, switch the four-way valve to the state before the defrost mode, and open the main expansion valve to the defrost preset opening degree;

[0028] Wait for the third preset time and restart the heat pump unit.

[0029] As an alternative technical solution of a heat pump condenser anti-freezing control method, the third preset time is set to 1min - 2min.

[0030] The second object of the present invention is to provide a heat pump system, which can avoid or reduce the phenomenon of ice formation or freezing and cracking of the condenser during the defrosting mode, and at the same time can avoid the risks of liquid blockage in the gas-liquid separator and liquid slugging of the compressor, extend the service life and save costs.

[0031] To achieve this object, the present invention adopts the following technical solutions:

[0032] The present invention provides a heat pump system, which executes the heat pump condenser anti-freezing control method described in any one of the above optional technical solutions. The heat pump system includes a compressor, a four-way valve, a solenoid valve, a condenser, a gas-liquid separator and a fin heat exchanger;

[0033] When the heat pump system is in the defrosting mode, the exhaust port of the compressor is sequentially connected to the D port and the C port of the four-way valve, the C port is sequentially connected to the solenoid valve, the condenser and the fin heat exchanger, the fin heat exchanger is sequentially connected to the E port, the S port of the four-way valve and the gas-liquid separator, and the gas-liquid separator is connected to the suction port of the compressor.

[0034] As an optional technical solution of a heat pump system, the heat pump system further includes an economizer, a main expansion valve and an auxiliary expansion valve. The economizer includes a first inlet, a first outlet, a second inlet and a second outlet;

[0035] The first inlet is connected to the condenser, and the first outlet is connected to the main expansion valve;

[0036] One end of the auxiliary expansion valve is connected to the second inlet, and the other end is connected to the pipeline between the first outlet and the main expansion valve. The second outlet is connected to the gas injection and enthalpy increase port of the compressor.

[0037] The beneficial effects of the present invention at least include:

[0038] The present invention provides a heat pump condenser anti-freezing control method, which mainly includes receiving a defrosting mode instruction; closing the compressor and the fan, opening the main expansion valve to a defrosting preset opening and waiting for a first preset time; switching the four-way valve; closing the solenoid valve and closing the main expansion valve; waiting for a second preset time, opening the main expansion valve to the defrosting preset opening; opening the solenoid valve; opening the compressor and running the defrosting mode.

[0039] Before the four-way valve switches, by opening the main expansion valve to the defrost preset opening and maintaining it for the first preset time, the refrigerant on the high-pressure side (the water-side heat exchanger, i.e., the condenser) is forced to migrate directionally to the low-pressure side (the fin heat exchanger), so that the high-pressure side and the low-pressure side of the heat pump system achieve preliminary pressure balance through the main expansion valve, reducing the pressure difference impact during the four-way valve switching. Immediately after the four-way valve switches, the solenoid valve and the main expansion valve are closed to physically block the abnormal reflux path of the high-pressure liquid refrigerant flowing through the four-way valve to the gas-liquid separator. At the same time, through the delay waiting for the second preset time, the refrigerant is concentrated and stored in the water-side heat exchanger (condenser), realizing precise control of the refrigerant storage amount before the compressor starts, reducing the phenomenon of liquid refrigerant entering the gas-liquid separator, thereby reducing or avoiding the risks of liquid blockage of the gas-liquid separator and liquid slugging of the compressor in the traditional technology. This heat pump condenser anti-freezing control method controls the refrigerant migration path in stages, forcing the refrigerant to flow through the defrost main circuit (the circuit between the solenoid valve and the main valve) intensively, so that the water-side heat exchanger (condenser) can effectively store a certain amount of refrigerant. Through the full heat exchange between the refrigerant and the condenser, the defrost evaporation temperature is increased, avoiding or reducing the phenomenon of ice formation and freezing damage of the condenser.

[0040] The present invention provides a heat pump system, which can avoid or reduce the phenomenon of ice formation or freezing damage of the condenser in the defrost mode, and at the same time can avoid the risks of liquid blockage of the gas-liquid separator and liquid slugging of the compressor, prolong the service life and save costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the content of the embodiments of the present invention and these drawings.

[0042] Figure 1 is a schematic flow chart of the heat pump condenser anti-freezing control method provided by the embodiment of the present invention;

[0043] Figure 2 is a schematic flow chart of the heat pump system provided by the embodiment of the present invention.

[0044] REFERENCE NUMERALS

[0045] 100, compressor; 200, four-way valve; 300, solenoid valve; 400, condenser; 500, economizer; 600, fin heat exchanger; 700, gas-liquid separator; 800, main expansion valve; 900, auxiliary expansion valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. Components of the embodiments of the present invention usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0047] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0048] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0049] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is usually placed during use. It is 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 thus should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive distinction and should not be construed as indicating or implying relative importance. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0050] In the description of the present invention, it should also be noted that unless otherwise clearly specified and defined, the terms "installed" 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. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0051] In the present invention, unless otherwise clearly specified and defined, the first feature being "above" or "below" the second feature may include direct contact between the first and second features, or may include the first and second features not being in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature. The first feature being "below", "beneath" and "underneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the first feature has a lower horizontal height than the second feature.

[0052] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where like or similar reference numerals denote like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0053] This embodiment provides a method for preventing freezing of a heat pump condenser, which is used to solve the phenomenon of ice formation on the plate heat exchanger caused by insufficient refrigerant on the evaporation side and low evaporation temperature due to refrigerant migration during the switching of the four-way valve during the defrosting process; and to solve the problems of liquid blockage in the gas-liquid separator and liquid slugging of the compressor caused by a large amount of refrigerant surging into the gas-liquid separator.

[0054] As Figure 1 - Figure 2 shown, the method for preventing freezing of the heat pump condenser mainly includes the following steps:

[0055] Receive a defrost mode instruction.

[0056] Specifically, the controller of the heat pump system determines the defrosting condition based on the surface temperature of the fin heat exchanger, the signal of the frost sensor or the cumulative operation time, triggers the mode and switches the defrost mode instruction. Thereby, accurate judgment of the defrosting timing is achieved, and problems such as energy efficiency loss or frost deterioration caused by premature or late defrosting are avoided.

[0057] Turn off the compressor and the fan, open the main expansion valve to the opening position required for the defrost mode (i.e., the defrost preset opening) and wait for the first preset time.

[0058] Specifically, immediately stop the operation of the compressor, cut off the power supply of the fan to terminate the heat exchange on the air side. Quickly adjust the main expansion valve from the opening in the heating mode to the defrost preset opening (such as 480 steps), and maintain this state and wait for the first preset time (for example, the first preset time is set to 5s - 15s).

[0059] The operating steps for shutting down the compressor can prevent the high-pressure refrigerant from impacting the low-pressure side during the switching of the four-way valve, reducing the risk of liquid slugging in the compressor. The operating steps for shutting down the fan can avoid the phenomenon of insufficient refrigerant evaporation due to intensified forced convection in the evaporator (fin heat exchanger) at the initial stage of defrosting. After the compressor stops and before the four-way valve switches, the water-side heat exchanger (condenser) still belongs to the condensing side and has a higher pressure; the air-side heat exchanger (fin heat exchanger) still belongs to the evaporating side and has a lower pressure. At this time, opening the main expansion valve to the defrost preset opening degree allows the refrigerant to quickly migrate from the high-pressure side to the low-pressure side through the main expansion valve, thereby achieving a preliminary pressure balance between the high-pressure side and the low-pressure side of the heat pump system through the main expansion valve and reducing the pressure difference impact during the switching of the four-way valve.

[0060] Further, in this step, after shutting down the compressor and the fan, the auxiliary expansion valve is closed, and then the opening degree of the main expansion valve is adjusted to the opening degree position required for the defrost mode and waits for the first preset time. Closing the auxiliary expansion valve can prevent the refrigerant from flowing along the auxiliary expansion valve into the gas injection and enthalpy increase port of the compressor, avoiding insufficient refrigerant in the condenser.

[0061] Switch the four-way valve.

[0062] Specifically, power is supplied to the four-way valve coil to drive the valve core to change direction, so that the refrigerant flow path switches from the heating mode (the refrigerant flows from the compressor exhaust port to the fin heat exchanger) to the defrost mode (the refrigerant flows from the compressor exhaust port to the plate heat exchanger), thereby converting the plate heat exchanger into a condenser for defrosting, and converting the fin heat exchanger into an evaporator to absorb ambient heat. By switching the four-way valve, the solenoid valve is connected to the compressor exhaust port through the four-way valve. At this time, the path of the high-pressure side is "compressor exhaust - four-way valve port D - four-way valve port C - plate heat exchanger (which acts as a condenser for heat release and defrosting at this time)".

[0063] In this embodiment, the four-way valve is commutated when the compressor is in a stopped state, avoiding problems such as seal wear or commutation failure caused by the valve core bearing dynamic pressure difference.

[0064] It should be noted that when switching the four-way valve, it is necessary to ensure that the solenoid valve is in the open state because the switching of the four-way valve relies on the high pressure of the condenser to improve the switching efficiency of the four-way valve. If the solenoid valve is not open at this time, it may lead to the failure of the four-way valve to switch.

[0065] Close the solenoid valve and close the main expansion valve.

[0066] After the switching of the four-way valve is completed, immediately closing the solenoid valve can effectively block the refrigerant from flowing from the water-side heat exchanger (condenser), through the four-way valve, and into the gas-liquid separator, thus causing problems such as liquid blockage in the gas-liquid separator and liquid slugging in the compressor. In other words, the step of closing the solenoid valve at this time can block the refrigerant flow in the non-defrost path, forcing the refrigerant to flow concentratedly through the main defrost circuit (the circuit between the solenoid valve and the main valve). At the same time, closing the main expansion valve can cut off the connection between the high-pressure side and the low-pressure side before the compressor restarts, preventing the liquid refrigerant from migrating to the gas-liquid separator due to the pressure difference, thereby avoiding risks such as liquid blockage in the gas-liquid separator and liquid slugging in the compressor.

[0067] Wait for the second preset time, and open the main expansion valve to the opening position required for the defrost mode.

[0068] Specifically, wait for 20s - 40s, maintain the compressor in the shutdown state, and at the same time provide a certain buffer time for the subsequent startup of the compressor. In addition, waiting for the second preset time can also ensure that the four-way valve is fully commutated in place and the pressure in the valve body is stable, avoiding gas leakage in the flow path. At this time, the refrigerant can be effectively stored in the main defrost circuit (the circuit between the solenoid valve and the main valve). If the volume of the pipeline is ignored, the refrigerant can be regarded as being effectively stored in the water-side heat exchanger (condenser) at this time.

[0069] Then, before the compressor starts, reopen the main expansion valve from step 0 to the defrost preset opening (such as 480 steps) to ensure that the main expansion valve is unobstructed before the compressor starts, ensure that the refrigerant flow rate is controllable at the initial stage of defrosting, and suppress the phenomenon of overcooling and icing of the evaporator (fin heat exchanger).

[0070] Open the solenoid valve.

[0071] Specifically, supply power to the solenoid valve to open it, so that the condenser can be connected to the four-way valve and the exhaust port of the compressor in sequence through the solenoid valve. In other words, before the compressor starts, give priority to supplying power to the coil of the solenoid valve to fully open its spool. After the solenoid valve is opened, a bypass pipeline is formed between the exhaust port of the compressor and ports C and D of the four-way valve.

[0072] Conduct the exhaust port of the compressor and the high-pressure flow path of the four-way valve (ports C and D to the condenser) through the solenoid valve to eliminate the residual high pressure in the exhaust cavity before the compressor starts. At the same time, it can also force the refrigerant to flow along the designed defrost path (compressor → four-way valve → solenoid valve → plate heat exchanger) at the moment the compressor starts, avoiding refrigerant retention or reverse migration.

[0073] Start the compressor and run the defrost mode.

[0074] Specifically, after the solenoid valve is fully opened, the compressor is started with a delay of 100 ms - 300 ms and runs slowly at a low frequency (such as 30 Hz) initially. When the pressure stabilizes at 1.0 MPa - 1.2 MPa, it is gradually increased to the rated defrosting frequency (80 Hz).

[0075] In this embodiment, the step of first opening the solenoid valve and then starting the compressor can quickly balance the pressure in the compressor exhaust cavity and the high-pressure side of the heat pump system, reducing the starting impact. It avoids the high-frequency tremor of the four-way valve caused by the direct start of the compressor and prolongs the service life of the valve body.

[0076] In this step, the water-side heat exchanger (condenser) effectively stores a certain amount of refrigerant in the above steps. Through the full heat exchange between the refrigerant and the condenser, the defrosting evaporation temperature is increased, avoiding or reducing the phenomenon of icing and freezing damage of the condenser.

[0077] The anti-freezing control method for the heat pump condenser in this embodiment further includes:

[0078] After the defrosting is completed, exit the defrosting mode.

[0079] Specifically, exiting the defrosting mode includes shutting down the compressor, turning on the fan, switching the four-way valve to the state before the defrosting mode, opening the main expansion valve to the opening position before the defrosting mode; waiting for the third preset time and restarting the heat pump unit. Exemplarily, the third preset time is set to 1 min - 2 min.

[0080] Shutting down the compressor terminates the defrosting cycle, avoiding the additional mechanical stress borne by the compressor due to the sudden change in the pressure difference between the high-pressure side and the low-pressure side during the mode switch. Turning on the fan, and then restoring the forced convection heat transfer effect on the air side of the fin heat exchanger. Switching the four-way valve to the original state and resetting the opening of the main expansion valve to the original set position, waiting for the third preset time, maintaining the static state of the system, waiting for the natural migration of the refrigerant to a stable distribution, fully vaporizing the liquid refrigerant remaining in the gas-liquid separator or the heat exchanger, reducing the risk of liquid compression of the compressor, and prolonging the service life of the compressor.

[0081] The anti-freezing control method for the heat pump condenser in this embodiment systematically solves the problem of unbalanced refrigerant distribution caused by the switching of the four-way valve during the traditional defrosting process by phased control of the refrigerant migration path and the pressure balance mechanism.

[0082] Before the four-way valve is switched, by opening the main expansion valve to the defrosting preset opening and maintaining the first preset time, the refrigerant on the high-pressure side (water-side heat exchanger) is forced to migrate directionally to the low-pressure side (fin heat exchanger), so that the high-pressure side and the low-pressure side of the heat pump system achieve preliminary pressure balance through the main expansion valve, reducing the pressure difference impact during the switching of the four-way valve.

[0083] Immediately after the four-way valve switches, close the solenoid valve and the main expansion valve to physically block the abnormal return path of the high-pressure liquid refrigerant flowing through the four-way valve to the gas-liquid separator. At the same time, through the delay waiting for the second preset time, make the refrigerant concentrate and be stored in the water-side heat exchanger (condenser), realize the precise control of the refrigerant storage amount before the compressor starts, reduce the phenomenon of liquid refrigerant entering the gas-liquid separator, thereby reducing or avoiding the risks of liquid blockage of the gas-liquid separator and liquid slugging of the compressor caused by a large amount of refrigerant surging into the gas-liquid separator in the traditional technology.

[0084] Before the compressor starts, reopen the main expansion valve to the defrost preset opening and preferentially conduct the solenoid valve to establish a pre-channel for refrigerant circulation. Combining with the heat absorption effect of the water-side heat exchanger (condenser) storing a certain amount of refrigerant, it can quickly balance the pressure between the compressor exhaust cavity and the high-pressure side of the heat pump system, reducing the starting impact. While avoiding the differential pressure impact, ensure that the evaporation temperature remains higher than the freezing point to avoid or reduce the phenomenon of ice formation in the condenser.

[0085] As Figure 2 shown, this embodiment also provides a heat pump system, and this heat pump system executes the above-mentioned heat pump condenser anti-freezing control method. The heat pump system includes a compressor 100, a four-way valve 200, a solenoid valve 300, a condenser 400, a gas-liquid separator 700, and a fin heat exchanger 600.

[0086] When the heat pump system is in the defrost mode, the exhaust port of the compressor 100 is sequentially connected to the D port and the C port of the four-way valve 200. The C port is sequentially connected to the solenoid valve 300, the condenser 400, and the fin heat exchanger 600. The fin heat exchanger 600 is sequentially connected to the E port, the S port, and the gas-liquid separator 700 of the four-way valve 200. The gas-liquid separator 700 is connected to the suction port of the compressor 100.

[0087] The heat pump system further includes an economizer 500, a main expansion valve 800, and an auxiliary expansion valve 900. The economizer 500 includes a first inlet, a first outlet, a second inlet, and a second outlet. The first inlet is connected to the condenser 400, and the first outlet is connected to the main expansion valve 800. One end of the auxiliary expansion valve 900 is connected to the second inlet, and the other end is connected to the pipeline between the first outlet and the main expansion valve 800. The second outlet is connected to the gas injection and enthalpy increase port of the compressor 100.

[0088] Specifically, in the defrost mode of this heat pump system, the flow direction of the refrigerant is as follows ( Figure 2 the direction of the arrow in

[0089] The high-temperature and high-pressure gaseous refrigerant is discharged from the exhaust port of the compressor 100 and flows through the D port and C port of the four-way valve 200 to the solenoid valve 300. The refrigerant flows through the solenoid valve 300 and enters the condenser 400 (the water-side heat exchanger in the original heating mode), where it releases the latent heat of condensation for defrosting and gradually condenses into high-pressure liquid. The liquid refrigerant is throttled and depressurized by the main expansion valve 800 to form a low-temperature and low-pressure two-phase flow. The two-phase flow enters the finned heat exchanger 600 (the outdoor evaporator in the original heating mode), absorbs the ambient heat and evaporates into low-pressure gas. The low-pressure gaseous refrigerant enters the gas-liquid separator 700 through the E port and S port of the four-way valve 200. The pure gaseous refrigerant separated by the gas-liquid separator 700 returns to the suction port of the compressor 100 to complete the cycle.

[0090] The solenoid valve 300 in this embodiment conducts forced diversion, thereby ensuring that most of the refrigerant can flow through the main defrosting circuit concentratedly.

[0091] Further, the high-pressure liquid refrigerant flowing out of the condenser 400 is divided into two paths: one path (main path) of the refrigerant is throttled by the main expansion valve 800 and enters the finned heat exchanger 600; the other path (auxiliary path) of the refrigerant is throttled twice by the auxiliary expansion valve 900, exchanges heat with the refrigerant in the main path in the economizer 500, is vaporized by absorbing heat, and is injected into the intermediate cavity of the compressor 100 from the gas injection and enthalpy increase port.

[0092] The exhaust temperature of the compressor 100 is increased by the method of gas injection and enthalpy increase, the defrosting ability of the condenser 400 is strengthened, and at the same time, the power consumption of the compressor 100 is reduced. The main expansion valve 800 controls the main path flow rate, and the auxiliary expansion valve 900 adjusts the gas injection amount to achieve fine distribution of the refrigerant flow rate and phase state, and avoid the phenomenon of local subcooling and icing of the finned heat exchanger 600.

[0093] Since the heat pump system uses the above heat pump condenser anti-freezing control method, therefore, when the heat pump system is in the defrosting mode, it can avoid or reduce the phenomenon of icing or freezing of the condenser 400, and at the same time, it can also avoid the risks of liquid blockage of the gas-liquid separator 700 and liquid hammer of the compressor 100, extend the service life and save costs.

[0094] Obviously, the above is only the preferred embodiment of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments here. Various obvious changes, re-adjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments only. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

[0095] Note that in the description of this specification, the descriptions referring to the reference terms "some embodiments", "other embodiments", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

Claims

1. A heat pump condenser antifreeze control method, characterized in that: include: receiving a defrost mode command; Turn off the compressor and the fan, open the main expansion valve to the defrost preset opening and wait for a first preset time; Switch the four-way valve; Close the solenoid valve and the main expansion valve; Waiting for a second preset time, opening the main expansion valve to a defrosting preset opening; Open the solenoid valve; Turn on the compressor and run the defrost mode.

2. The heat pump condenser antifreeze control method according to claim 1, characterized in that: The steps of shutting down the compressor and the fan, opening the main expansion valve to a preset defrosting opening, and waiting for a first preset time include: Turn off the compressor and the fan, close the auxiliary expansion valve, open the main expansion valve to the defrost preset opening and wait for the first preset time.

3. The heat pump condenser antifreeze control method according to claim 1, characterized in that: The first preset time is set to 5s-15s.

4. The heat pump condenser antifreeze control method according to claim 1, characterized in that: The second preset time is set to 20s-40s.

5. The heat pump condenser antifreeze control method according to claim 1, characterized in that: In the defrost mode, the opening degree of the main expansion valve is 480 steps.

6. The heat pump condenser antifreeze control method according to claim 1, characterized in that: The step of switching the four-way valve comprises: Switch the four-way valve so that the solenoid valve is connected to the exhaust port of the compressor through the four-way valve.

7. The heat pump condenser antifreeze control method according to claim 1, characterized in that: The heat pump condenser antifreeze control method further comprises: After defrosting is completed, exit the defrost mode; The exiting defrost mode includes: Turn off the compressor, turn on the fan, switch the four-way valve to the state before the defrost mode, and open the main expansion valve to the defrost preset opening; Wait for the third preset time and restart the heat pump unit.

8. The heat pump condenser antifreeze control method according to claim 7, characterized in that: The third preset time is set to 1 min-2 min.

9. A heat pump system, characterized in that: The heat pump system implements the heat pump condenser antifreeze control method described in any one of claims 1 to 8, and the heat pump system includes a compressor, a four-way valve, a solenoid valve, a condenser, a gas-liquid separator and a fin heat exchanger; When the heat pump system is in defrost mode, the exhaust port of the compressor is connected to the D port and the C port of the four-way valve in sequence, the C port is connected to the solenoid valve, the condenser, and the fin heat exchanger in sequence, the fin heat exchanger is connected to the E port, the S port of the four-way valve, and the gas-liquid separator in sequence, and the gas-liquid separator is connected to the suction port of the compressor.

10. The heat pump system according to claim 9, characterized in that: The heat pump system further comprises an economizer, a main expansion valve and an auxiliary expansion valve, wherein the economizer comprises a first inlet, a first outlet, a second inlet and a second outlet; The first inlet is connected to the condenser, and the first outlet is connected to the main expansion valve; One end of the auxiliary expansion valve is communicated with the second inlet, and the other end is communicated with the pipeline between the first outlet and the main expansion valve. The second outlet is communicated with the air supplement and enthalpy increase port of the compressor.

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