Antifreeze method for plate heat exchangers based on heat pumps and heat pump systems

Abstract

This invention relates to the field of heat pump technology, and more particularly to an antifreeze method and system for a heat pump-based plate heat exchanger. The antifreeze method for the heat pump-based plate heat exchanger mainly includes the following steps: S1. After the unit meets the defrosting conditions, it enters defrosting mode. S2. The compressor frequency is controlled to decrease to the defrosting switching frequency. S3. The expansion valve is controlled to open to the defrosting opening degree, the four-way valve is switched, and the solenoid valve is closed, so that the refrigerant flows only through the lower finned flow path of the finned heat exchanger. S4. The compressor frequency is controlled to increase to the defrosting operating frequency, so that the frost layer in the lower finned flow path melts. S5. According to the high pressure of the heat pump system and the evaporation temperature of the plate heat exchanger, the opening and closing of the solenoid valve is controlled to adjust the high pressure and evaporation temperature. S6. When the defrosting exit conditions are met, the defrosting mode is exited. This antifreeze method for the heat pump-based plate heat exchanger can reduce the risk of freezing and cracking of the plate heat exchanger, and improve the safety and reliability of the heat pump system.

Description

Technical Field

[0001] This invention relates to the field of heat pump technology, and in particular to an antifreeze method for a plate heat exchanger based on a heat pump and a heat pump system. Background Technology

[0002] As a highly efficient and energy-saving heating device, air source heat pumps are prone to frost formation on the surface of outdoor finned heat exchangers when operating in low-temperature winter environments. This leads to a decrease in heat exchange efficiency and a decline in system performance, thus requiring periodic defrosting operations.

[0003] Currently, reverse refrigerant cycle defrosting is the most common defrosting method. It uses a four-way valve to switch the refrigerant flow, switching the heat pump from heating mode to cooling mode, and utilizing the high-temperature refrigerant discharged from the compressor to melt the frost layer on the fins. In heat pump systems using plate heat exchangers as the water-side heat exchanger, due to their compact structure and high heat exchange efficiency, they are used as condensers in heating mode and as evaporators in defrosting mode. However, the narrow internal flow channels and small water-side volume of plate heat exchangers pose a risk of icing on the water side when the refrigerant evaporation temperature is below 0°C. Especially during defrosting, plate heat exchangers are more prone to freezing, cracking, and leakage, affecting the safety and reliability of the heat pump system.

[0004] Therefore, there is an urgent need to design an antifreeze method and a heat pump system based on a heat pump plate heat exchanger to solve the above technical problems. Summary of the Invention

[0005] The purpose of this invention is to propose an antifreeze method and a heat pump system for plate heat exchangers based on heat pumps, which can reduce the risk of plate heat exchangers freezing and cracking, and improve the safety and reliability of heat pump systems.

[0006] To achieve this objective, the present invention adopts the following technical solution: On one hand, the present invention provides an antifreeze method for a plate heat exchanger based on a heat pump, wherein the heat pump includes a compressor, a four-way valve, a plate heat exchanger, a finned heat exchanger, a solenoid valve, and an expansion valve; wherein the compressor, the four-way valve, the plate heat exchanger, the expansion valve, and the finned heat exchanger are sequentially connected to form a refrigerant circulation loop, the finned heat exchanger includes an upper finned flow path and a lower finned flow path, and the solenoid valve is disposed on the finned heat exchanger and used to control the on / off state of the upper finned flow path; The antifreeze method for the heat pump-based plate heat exchanger includes the following steps: S1. The unit enters defrosting mode after meeting the defrosting conditions; S2. Control the compressor to first reduce its frequency to the defrost switching frequency and maintain it for the first preset time; S3. Control the expansion valve to open to the defrost opening, switch the four-way valve to reverse and close the solenoid valve so that the refrigerant only flows through the lower fin flow path of the finned heat exchanger. S4. Control the compressor to increase its frequency to the defrosting operating frequency so that the frost layer in the lower fin flow path melts, thereby enabling the heat pump system to quickly build up high pressure. S5. Based on the high pressure of the heat pump system and the evaporation temperature of the plate heat exchanger, control the opening and closing of the solenoid valve to adjust the high pressure and evaporation temperature. S6. Once the defrost exit conditions are met, restore the four-way valve, solenoid valve, and compressor to normal heating mode.

[0007] As an optional technical solution for antifreeze methods of plate heat exchangers based on heat pumps, the defrosting switching frequency is lower than the defrosting operating frequency, and the defrosting operating frequency is lower than the operating frequency of the compressor of the heat pump system in heating mode.

[0008] As an optional technical solution for antifreeze methods of plate heat exchangers based on heat pumps, step S5 includes: When the high pressure of the heat pump system reaches the first preset pressure value and the evaporation temperature of the plate heat exchanger is less than or equal to the preset safe temperature, the solenoid valve remains closed.

[0009] As an optional technical solution for antifreeze methods of plate heat exchangers based on heat pumps, step S5 includes: When the high pressure of the heat pump system reaches the first preset pressure value and the evaporation temperature of the plate heat exchanger is greater than the preset safe temperature, the solenoid valve is opened, allowing the refrigerant to flow through both the upper and lower finned flow paths simultaneously for complete defrosting.

[0010] As an optional technical solution for antifreeze methods of plate heat exchangers based on heat pumps, step S5 includes: When the high pressure of the heat pump system reaches the second preset pressure value, the solenoid valve is forcibly opened; wherein the second preset pressure value is greater than the first preset pressure value.

[0011] As an optional technical solution for antifreeze methods of plate heat exchangers based on heat pumps, in step S6, the defrosting exit conditions include: The coil temperature of the finned heat exchanger reaches the preset defrosting completion temperature; Alternatively, the high pressure of the heat pump system may reach the high pressure protection threshold. Alternatively, the defrosting mode of the heat pump system may continue for the maximum permissible duration.

[0012] As an optional technical solution for antifreeze method of plate heat exchanger based on heat pump, the solenoid valve is a normally open solenoid valve, and the solenoid valve is set at the inlet of the upper fin flow path; In heating mode, the solenoid valve remains open, and the refrigerant flows through the upper fin flow path and the lower fin flow path; In defrost mode, the solenoid valve selectively opens or closes to regulate the distribution of refrigerant in the upper fin flow path and the lower fin flow path.

[0013] As an optional technical solution for antifreeze methods of plate heat exchangers based on heat pumps, the expansion valve is an electronic expansion valve, and the defrost opening degree is the maximum opening degree of the expansion valve or a preset fixed opening degree.

[0014] On the other hand, the present invention provides a heat pump system, including a compressor, a four-way valve, a plate heat exchanger, a finned heat exchanger, a solenoid valve, an expansion valve, and a controller; The compressor, the four-way valve, the plate heat exchanger, the expansion valve, and the finned heat exchanger are sequentially connected to form a refrigerant circulation loop. The finned heat exchanger includes an upper finned flow path and a lower finned flow path. The solenoid valve is connected in series at the inlet of the upper finned flow path and is used to control the opening and closing of the upper finned flow path. The controller is configured to perform the antifreeze method for plate heat exchangers based on heat pumps as described in any of the above optional technical solutions.

[0015] As an optional technical solution for a heat pump system, the heat pump system further includes an exhaust pressure sensor, a return gas pressure sensor, a fin temperature sensor, and a water-side temperature sensor, wherein the exhaust pressure sensor, the return gas pressure sensor, the fin temperature sensor, and the water-side temperature sensor are all signal-connected to the controller.

[0016] The beneficial effects of the present invention include at least the following: This invention provides a method for preventing freezing of a plate heat exchanger based on a heat pump, mainly comprising the following steps: S1. After the unit meets the defrosting conditions, it enters the defrosting mode. S2. The compressor is controlled to reduce its frequency to the defrosting switching frequency and maintain this for a first preset time. S3. The expansion valve is controlled to open to the defrosting opening, the four-way valve is switched, and the solenoid valve is closed, so that the refrigerant flows only through the lower fin flow path of the finned heat exchanger. S4. The compressor is controlled to increase its frequency to the defrosting operating frequency, so that the frost layer in the lower fin flow path melts, allowing the heat pump system to quickly establish high pressure. S5. According to the high pressure of the heat pump system and the evaporation temperature of the plate heat exchanger, the opening and closing of the solenoid valve is controlled to adjust the high pressure and evaporation temperature. S6. When the defrosting exit conditions are met, the four-way valve, solenoid valve, and compressor are restored to normal heating mode.

[0017] The above-described anti-freeze method for a heat pump-based plate heat exchanger significantly reduces the condensation heat exchange area by first closing the solenoid valve and using only the lower finned flow path for defrosting. This prevents a large amount of refrigerant from migrating into the finned heat exchanger when the four-way valve switches, thus reducing refrigerant loss within the plate heat exchanger. Simultaneously, it allows for the rapid establishment of high pressure in the heat pump system, thereby increasing the evaporation pressure and temperature within the plate heat exchanger, which acts as the evaporator. This reduces the risk of the plate heat exchanger freezing and cracking, improving the safety and reliability of the heat pump system.

[0018] The present invention also provides a heat pump system with high reliability and safety, which can reduce the risk of plate heat exchangers freezing and cracking. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings without creative effort.

[0020] Figure 1 This is a schematic flowchart of the antifreeze method for a plate heat exchanger based on a heat pump provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the heat pump system in heating mode provided in an embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram of the heat pump system in defrost mode provided in an embodiment of the present invention.

[0022] Figure Labels 10. Compressor; 20. Four-way valve; 30. Plate heat exchanger; 40. Finned heat exchanger; 41. Upper finned flow path; 42. Lower finned flow path; 50. Solenoid valve; 60. Expansion valve; 70. Exhaust pressure sensor; 80. Return gas pressure sensor; 90. Gas-liquid separator. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0025] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0026] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0027] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0029] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0030] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] This embodiment provides a method for preventing the plate heat exchanger from freezing, which can reduce the risk of the plate heat exchanger freezing and cracking, and improve the safety and reliability of the heat pump system.

[0032] like Figures 1-3 As shown, the heat pump includes a compressor 10, a four-way valve 20, a plate heat exchanger 30, a finned heat exchanger 40, a solenoid valve 50, and an expansion valve 60. The compressor 10, the four-way valve 20, the plate heat exchanger 30, the expansion valve 60, and the finned heat exchanger 40 are connected in sequence to form a refrigerant circulation loop. The finned heat exchanger 40 includes an upper finned flow path 41 and a lower finned flow path 42. The solenoid valve 50 is installed on the finned heat exchanger 40 and is used to control the upper finned flow path 41.

[0033] The antifreeze method for this heat pump-based plate heat exchanger mainly includes the following steps: S1. The unit enters defrosting mode after meeting the defrosting conditions.

[0034] Specifically, defrosting conditions can be determined based on ambient temperature, fin temperature, heating operation time, or a combination thereof. When frost is detected on the surface of the finned heat exchanger 40 to a preset level, or the heating operation time reaches a preset value, or the difference between the fin temperature and the ambient temperature reaches the frost determination threshold, the defrosting conditions are deemed met, and the defrosting mode is activated.

[0035] S2. Control the compressor 10 to reduce its frequency to the defrost switching frequency and maintain it for the first preset time.

[0036] Specifically, before defrosting is initiated, compressor 10 typically operates at a higher heating frequency. By actively reducing the frequency to a lower defrosting switching frequency, the system pressure can be stabilized, reducing the kinetic energy of the high-pressure liquid refrigerant within plate heat exchanger 30. After maintaining this position for a first preset time, the high-pressure state within plate heat exchanger 30 stabilizes, preparing for the subsequent switching of four-way valve 20.

[0037] S3. Control the expansion valve 60 to open to the defrost opening, switch the four-way valve 20 to reverse and close the solenoid valve 50, so that the refrigerant only flows through the lower fin flow path 42 of the finned heat exchanger 40.

[0038] Specifically, opening the expansion valve 60 to the defrost opening position increases the refrigerant flow cross-sectional area and reduces throttling resistance. After the four-way valve 20 reverses, the finned heat exchanger 40, originally an evaporator, becomes a condenser (heat release defrosting), and the plate heat exchanger 30, originally a condenser, becomes an evaporator (heat absorption). At this time, closing the solenoid valve 50 cuts off the upper finned flow path 41, allowing all the refrigerant to flow through the lower finned flow path 42, thus achieving zoned defrosting.

[0039] S4. Control the compressor 10 to increase its frequency to the defrosting operating frequency, so that the frost layer in the lower fin flow path 42 melts, so that the heat pump system can quickly build up high pressure.

[0040] Specifically, by closing the solenoid valve 50 and using only the lower finned flow path 42, the condensation heat exchange area is significantly reduced, preventing a large amount of refrigerant from accumulating in the finned heat exchanger 40. As the frost layer on the lower finned flow path 42 gradually melts, the heat exchange resistance decreases, and the high pressure of the heat pump system can be quickly established. The evaporation pressure in the plate heat exchanger 30, which acts as the evaporator, increases accordingly, and the evaporation temperature rises accordingly, thereby preventing ice formation on the water side.

[0041] S5. Based on the high pressure of the heat pump system and the evaporation temperature of the plate heat exchanger 30, control the opening and closing of the solenoid valve 50 to regulate the high pressure and evaporation temperature. By monitoring the system's high pressure and the evaporation temperature inside the plate heat exchanger 30 in real time, determine the current defrosting status and the safety status of the plate heat exchanger 30, and dynamically control the opening or closing of the solenoid valve 50 to achieve coordinated control of the high pressure and evaporation temperature.

[0042] S6. Once the defrosting exit conditions are met, restore the four-way valve 20, solenoid valve 50, and compressor 10 to normal heating mode. That is, after defrosting is completed, the four-way valve 20 switches back to the heating direction, the solenoid valve 50 returns to the open state, the compressor 10's frequency returns to the heating operating frequency, and the system resumes normal heating cycle.

[0043] Based on the above design, the anti-freezing method for the heat pump-based plate heat exchanger in this embodiment significantly reduces the condensation heat exchange area by first closing the solenoid valve 50 and using only the lower finned flow path 42 for defrosting. This prevents a large amount of refrigerant from migrating into the finned heat exchanger 40 when the four-way valve 20 switches, thus reducing refrigerant loss within the plate heat exchanger 30. Simultaneously, it allows the high pressure of the heat pump system to be established quickly, thereby increasing the evaporation pressure and temperature within the plate heat exchanger 30, which acts as the evaporator. This reduces the risk of the plate heat exchanger 30 freezing and cracking, improving the safety and reliability of the heat pump system.

[0044] In this embodiment, the defrost switching frequency is lower than the defrost operating frequency, which is lower than the operating frequency of the compressor 10 in the heating mode of the heat pump system. Specifically, before entering defrost mode, the unit first reduces to a lower defrost switching frequency, which reduces refrigerant migration. After the switching is completed, the frequency is increased to a medium defrost operating frequency, which enhances the defrost capability of the finned heat exchanger 40.

[0045] Step S5 of the antifreeze method for a heat pump-based plate heat exchanger in this embodiment includes: When the high pressure of the heat pump system reaches the first preset pressure value, and the evaporation temperature in the plate heat exchanger 30 is less than or equal to the preset safe temperature, the solenoid valve 50 remains closed.

[0046] Specifically, when the high pressure of the heat pump system reaches the first preset pressure value, and the evaporation temperature inside the plate heat exchanger 30 is less than or equal to the preset safe temperature, it indicates that although the high pressure of the heat pump system has been initially established, the evaporation temperature inside the plate heat exchanger 30 is still in the freezing risk zone. At this time, the solenoid valve 50 is kept closed to maintain the small flow path defrosting and high pressure establishment state, without expanding the heat exchange area, thereby maintaining a higher condensing pressure and corresponding evaporation pressure, ensuring that the evaporation temperature of the plate heat exchanger 30 continues to rise to a safe range. In other words, the evaporation temperature of the plate heat exchanger 30 is used as a necessary prerequisite for opening the solenoid valve 50, prioritizing the antifreeze safety of the plate heat exchanger 30, rather than simply pursuing defrosting efficiency.

[0047] Step S5 further includes: when the high pressure of the heat pump system reaches the first preset pressure value and the evaporation temperature of the plate heat exchanger 30 is greater than the preset safe temperature, opening the solenoid valve 50 allows the refrigerant to flow simultaneously through the upper finned flow path 41 and the lower finned flow path 42 for comprehensive defrosting. At this point, it indicates that the high pressure of the heat pump system has been stably established and the evaporation temperature of the plate heat exchanger 30 has returned to a safe range, eliminating the risk of icing. Opening the solenoid valve 50 at this time allows the refrigerant to flow simultaneously through the upper finned flow path 41 and the lower finned flow path 42, increasing the heat exchange area for comprehensive defrosting, improving defrosting efficiency, and preventing localized residual frost from affecting subsequent heating.

[0048] Step S5 further includes: when the high pressure of the heat pump system reaches the second preset pressure value, forcibly opening the solenoid valve 50; wherein the second preset pressure value is greater than the first preset pressure value.

[0049] In other words, when the high pressure of the heat pump system reaches the second preset pressure value, regardless of whether the evaporation temperature of the plate heat exchanger 30 has reached the preset safe temperature, the solenoid valve 50 will be forcibly opened to increase the heat exchange area to release pressure, prevent the heat pump system from being damaged due to excessive pressure, achieve automatic balance between high pressure protection and defrosting rhythm, and improve the reliability of the heat pump system operation.

[0050] In step S6, the defrosting exit conditions include the following three parallel judgment conditions: The first exit condition is that the coil temperature of the finned heat exchanger 40 reaches the preset defrost completion temperature. Specifically, when the coil temperature rises back to the preset defrost completion temperature, it indicates that the frost layer on the fin surface has completely melted, and the finned heat exchanger 40 has restored its normal heat exchange capacity. The preset defrost completion temperature must be set higher than the ambient temperature to ensure that the frost layer has completely melted rather than just softened.

[0051] The second exit condition is that the high pressure of the heat pump system reaches the high pressure protection threshold. Specifically, when the high pressure of the heat pump system continues to rise to the high pressure protection threshold due to the defrosting process, it indicates that the defrosting has reached a high level or the system load is abnormal, and the defrosting mode needs to be exited to ensure the safety of the compressor 10.

[0052] The third exit condition is that the defrosting mode of the heat pump system continues for the maximum allowable duration. Specifically, when the defrosting duration reaches the maximum allowable duration, the defrosting mode will be forcibly exited regardless of whether the frost layer has completely melted or whether the high pressure is up to standard. This condition is set to prevent indefinite defrosting due to sensor failure or abnormal operating conditions, ensuring the reliability of the heat pump system.

[0053] Defrosting can be terminated if any one of the three exit conditions is met. The multiple exit logic ensures timely termination of defrosting, avoids ineffective or excessive defrosting, balances defrosting effectiveness with heat pump system energy consumption, and protects components in the heat pump system.

[0054] In this embodiment, the solenoid valve 50 is a normally open solenoid valve, located at the inlet of the upper finned flow path 41. In heating mode, the solenoid valve 50 remains open, and the refrigerant flows through the upper finned flow path 41 and the lower finned flow path 42. In defrosting mode, the solenoid valve 50 selectively opens or closes to regulate the distribution of refrigerant in the upper finned flow path 41 and the lower finned flow path 42.

[0055] It should be noted that the normally open solenoid valve is characterized by remaining open in the absence of power or in the default state, and closing when powered on.

[0056] In defrost mode, solenoid valve 50 selectively opens or closes to regulate the distribution of refrigerant in the upper finned flow path 41 and the lower finned flow path 42. Initially, solenoid valve 50 closes, cutting off the upper finned flow path 41, reducing the heat exchange area, and preventing a large amount of refrigerant from migrating into the finned heat exchanger 40 when the four-way valve 20 reverses, thus reducing refrigerant loss from the plate heat exchanger 30. When the high-pressure of the heat pump system reaches the first preset pressure value, and the evaporation temperature of the plate heat exchanger 30 exceeds the preset safe temperature, solenoid valve 50 opens, diverting refrigerant to the upper finned flow path 41, achieving full defrosting.

[0057] Optionally, the expansion valve 60 in this embodiment is an electronic expansion valve, and the defrosting opening is the maximum opening of the expansion valve 60 or a preset fixed opening.

[0058] like Figures 2-3 As shown, this embodiment also provides a heat pump system, which mainly includes a compressor 10, a four-way valve 20, a plate heat exchanger 30, a finned heat exchanger 40, a solenoid valve 50, an expansion valve 60, and a controller. The compressor 10, four-way valve 20, plate heat exchanger 30, expansion valve 60, and finned heat exchanger 40 are sequentially connected to form a refrigerant circulation loop. The finned heat exchanger 40 includes an upper finned flow path 41 and a lower finned flow path 42. The solenoid valve 50 is connected in series at the inlet of the upper finned flow path 41 and is used to control the on / off state of the upper finned flow path 41. The controller is configured to execute the above-described antifreeze method for a heat pump-based plate heat exchanger.

[0059] For example, the controller is a common PLC controller on the market, which receives signals from various sensors, outputs control signals according to preset control logic, and drives the actions of various actuators.

[0060] By implementing the above-mentioned antifreeze method for heat pump-based plate heat exchangers, the heat pump system achieves high reliability and safety, and reduces the risk of plate heat exchanger 30 freezing and cracking.

[0061] The heat pump system also includes an exhaust pressure sensor 70, a return gas pressure sensor 80, a fin temperature sensor, and a water-side temperature sensor. The exhaust pressure sensor 70, the return gas pressure sensor 80, the fin temperature sensor, and the water-side temperature sensor are all connected to the controller signal.

[0062] Specifically, the exhaust pressure sensor 70 is located at the exhaust port of the compressor 10 to monitor the high-pressure of the heat pump system. The return gas pressure sensor 80 is located at the return gas port of the compressor 10 to monitor the low-pressure of the heat pump system. The fin temperature sensor is located on the coil of the finned heat exchanger 40 to monitor the temperature of the finned heat exchanger 40. The water-side temperature sensor is located on the water side of the plate heat exchanger 30 to monitor the evaporation temperature of the plate heat exchanger 30.

[0063] like Figures 2-3 As shown, the heat pump system in this embodiment also includes a gas-liquid separator 90, which is connected in series between the suction end of the compressor 10 and the four-way valve 20.

[0064] Obviously, the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection 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, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

[0065] Note that in the description of this specification, the references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

Claims

1. A method for preventing freezing of a plate heat exchanger based on a heat pump, characterized in that, The heat pump includes a compressor, a four-way valve, a plate heat exchanger, a finned heat exchanger, a solenoid valve, and an expansion valve; wherein the compressor, the four-way valve, the plate heat exchanger, the expansion valve, and the finned heat exchanger are sequentially connected to form a refrigerant circulation loop, the finned heat exchanger includes an upper finned flow path and a lower finned flow path, and the solenoid valve is disposed on the finned heat exchanger and used to control the on / off state of the upper finned flow path; The antifreeze method for the heat pump-based plate heat exchanger includes the following steps: S1. The unit enters defrosting mode after meeting the defrosting conditions; S2. Control the compressor to first reduce its frequency to the defrost switching frequency and maintain it for the first preset time; S3. Control the expansion valve to open to the defrost opening, switch the four-way valve to reverse and close the solenoid valve so that the refrigerant only flows through the lower fin flow path of the finned heat exchanger. S4. Control the compressor to increase its frequency to the defrosting operating frequency so that the frost layer in the lower fin flow path melts, thereby enabling the heat pump system to quickly build up high pressure. S5. Based on the high pressure of the heat pump system and the evaporation temperature of the plate heat exchanger, control the opening and closing of the solenoid valve to adjust the high pressure and evaporation temperature. S6. Once the defrost exit conditions are met, restore the four-way valve, solenoid valve, and compressor to normal heating mode.

2. The antifreeze method for a plate heat exchanger based on a heat pump according to claim 1, characterized in that, The defrost switching frequency is lower than the defrost operating frequency, and the defrost operating frequency is lower than the operating frequency of the compressor in the heating mode of the heat pump system.

3. The antifreeze method for a plate heat exchanger based on a heat pump according to claim 1, characterized in that, Step S5 includes: When the high pressure of the heat pump system reaches the first preset pressure value and the evaporation temperature of the plate heat exchanger is less than or equal to the preset safe temperature, the solenoid valve remains closed.

4. The antifreeze method for a plate heat exchanger based on a heat pump according to claim 3, characterized in that, Step S5 includes: When the high pressure of the heat pump system reaches the first preset pressure value and the evaporation temperature of the plate heat exchanger is greater than the preset safe temperature, the solenoid valve is opened, allowing the refrigerant to flow through both the upper and lower finned flow paths simultaneously for complete defrosting.

5. The antifreeze method for a plate heat exchanger based on a heat pump according to claim 4, characterized in that, Step S5 includes: When the high pressure of the heat pump system reaches the second preset pressure value, the solenoid valve is forcibly opened; wherein the second preset pressure value is greater than the first preset pressure value.

6. The antifreeze method for a plate heat exchanger based on a heat pump according to claim 1, characterized in that, In step S6, the defrosting exit conditions include: The coil temperature of the finned heat exchanger reaches the preset defrosting completion temperature; Alternatively, the high pressure of the heat pump system may reach the high pressure protection threshold. Alternatively, the defrosting mode of the heat pump system may continue for the maximum permissible duration.

7. The antifreeze method for a plate heat exchanger based on a heat pump according to claim 1, characterized in that, The solenoid valve is a normally open solenoid valve, and the solenoid valve is located at the inlet of the upper fin flow path; In heating mode, the solenoid valve remains open, and the refrigerant flows through the upper fin flow path and the lower fin flow path; In defrost mode, the solenoid valve selectively opens or closes to regulate the distribution of refrigerant between the upper fin flow path and the lower fin flow path.

8. The antifreeze method for a plate heat exchanger based on a heat pump according to claim 1, characterized in that, The expansion valve is an electronic expansion valve, and the defrost opening is the maximum opening of the expansion valve or a preset fixed opening.

9. A heat pump system, characterized in that, Includes compressors, four-way valves, plate heat exchangers, finned heat exchangers, solenoid valves, expansion valves, and controllers; The compressor, the four-way valve, the plate heat exchanger, the expansion valve, and the finned heat exchanger are sequentially connected to form a refrigerant circulation loop. The finned heat exchanger includes an upper finned flow path and a lower finned flow path. The solenoid valve is connected in series at the inlet of the upper finned flow path and is used to control the opening and closing of the upper finned flow path. The controller is configured to perform the antifreeze method for a heat pump-based plate heat exchanger as described in any one of claims 1-8.

10. The heat pump system according to claim 9, characterized in that, The heat pump system also includes an exhaust pressure sensor, a return gas pressure sensor, a fin temperature sensor, and a water-side temperature sensor. The exhaust pressure sensor, the return gas pressure sensor, the fin temperature sensor, and the water-side temperature sensor are all connected to the controller.

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