Low-power-consumption self-defrosting electric heating super-hydrophobic fin for air conditioner heat exchanger and preparation method of low-power-consumption self-defrosting electric heating super-hydrophobic fin

Abstract

The invention discloses a low-power-consumption self-defrosting electric heating super-hydrophobic fin for an air conditioner heat exchanger and a preparation method of the low-power-consumption self-defrosting electric heating super-hydrophobic fin. The low-power-consumption self-defrosting electric heating super-hydrophobic fin for the air conditioner heat exchanger comprises a metal fin substrate and an electric heating super-hydrophobic functional layer covering the surface of the metal fin substrate. The electric heating super-hydrophobic functional layer is prepared from a conductive nano material, a binder and a low-surface-energy substance. The preparation method comprises the steps that firstly, the surface of a metal fin substrate is pretreated, then the surface of a metal fin is coated with a super-hydrophobic conductive nano coating, then the super-hydrophobic conductive nano coating is further subjected to annealing reinforcement treatment, and finally the low-power-consumption self-defrosting electric heating super-hydrophobic fin for the air conditioner heat exchanger is obtained. The preparation method is simple and easy to operate, is suitable for industrial production and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of air conditioning heat exchanger technology, specifically relating to a low-power self-defrosting electrothermal superhydrophobic fin for air conditioning heat exchangers and its preparation method. Background Technology

[0002] When air conditioners and other refrigeration equipment are used for heating in low-temperature and high-humidity environments, the surface temperature of their outdoor heat exchangers is lower than the dew point and freezing point of the air, causing water vapor in the air to condense and form frost. Frost covering the fins severely hinders airflow, significantly reduces heat exchange efficiency, and leads to a deterioration in heating performance and a sharp increase in energy consumption.

[0003] Currently, the mainstream defrosting methods include active defrosting methods such as reverse cycle defrosting and refrigerant bypass defrosting. Reverse cycle defrosting involves reversing valves to direct the high-temperature refrigerant discharged from the compressor to the outdoor heat exchanger for defrosting. This process requires the air conditioner to switch from heating mode to cooling mode. Refrigerant bypass defrosting adds a defrosting branch to the refrigerant circuit, directly leading some of the high-temperature refrigerant to the outdoor heat exchanger. This method does not require interruption of heating, but the system control is complex.

[0004] Superhydrophobic coating technology has been attempted to delay frost formation, but its microstructure is easily damaged or fails due to capillary condensation under the harsh operating conditions of long-term air conditioning operation. Once ice bridges are formed, the anti-frost effect is lost.

[0005] Therefore, there is an urgent need in this field for a new defrosting technology solution that does not rely on complex system modifications, does not require interruption of heating, and can operate stably for a long time. Summary of the Invention

[0006] To overcome the shortcomings of existing defrosting technologies for air conditioner heat exchangers, the primary objective of this invention is to provide a method for preparing low-power self-defrosting electrothermal superhydrophobic fins for air conditioner heat exchangers. This method first pre-treats the surface of a metal fin substrate, then applies a superhydrophobic conductive nano-coating to the metal fin surface, followed by annealing to strengthen the superhydrophobic conductive nano-coating, ultimately obtaining a low-power self-defrosting electrothermal superhydrophobic fin for air conditioner heat exchangers. This preparation method is simple and easy to operate, suitable for industrial production, and has broad application prospects.

[0007] The second objective of this invention is to provide a low-power self-defrosting electrothermal superhydrophobic fin for air conditioner heat exchangers. Through material and structural innovation, this fin integrates passive anti-frost and active defrosting functions, achieving low-power self-defrosting and fundamentally avoiding heating interruptions and system energy waste.

[0008] A third objective of this invention is to provide an air conditioning defrosting system.

[0009] The primary objective of this invention can be achieved through the following technical solution. A method for preparing low-power self-defrosting electrothermal superhydrophobic fins for air conditioner heat exchangers includes the following steps: (1) Use organic solvent to ultrasonically clean the metal fin substrate to remove oil stains, then immerse it in an alkaline solution to remove the surface oxide layer, then rinse it thoroughly with deionized water and dry it, and finally form a rough structure on the metal fin substrate by chemical etching or anodizing to prepare the pretreated metal fin substrate. (2) Conductive nanomaterials, binders, and low surface energy substances are uniformly dispersed in a solvent in sequence to form a superhydrophobic conductive nanocoating; (3) Apply superhydrophobic conductive nano-coating to the surface of the pretreated metal fin substrate to form an electrothermal superhydrophobic functional layer; (4) The prepared electrothermal superhydrophobic functional layer is annealed and reinforced to prepare a low-power self-defrosting electrothermal superhydrophobic fin for air conditioning heat exchanger.

[0010] Preferably, the metal fin substrate in step (1) is made of one of aluminum and aluminum alloys, copper and copper alloys, or stainless steel.

[0011] Preferably, the conductive nanomaterial, binder, low surface energy substance and solvent in step (2) are prepared in a mass ratio of 15-30:1-10:1:59-83; the conductive nanomaterial is at least one of silver nanowires, carbon nanotubes, graphene, two-dimensional inorganic compound (MXene), and poly(3,4-ethylenedioxythiophene-polystyrene sulfonate) (PEDOT:PSS); the binder is epoxy adhesive, acrylic adhesive, phenolic resin adhesive, urea-formaldehyde resin adhesive, and polyurethane adhesive; the low surface energy substance is fluorosilane or polysiloxane compound.

[0012] Preferably, the coating method in step (3) is spraying, dipping, lifting or spin coating.

[0013] Preferably, the annealing temperature in step (4) is 23°C to 300°C, and the annealing atmosphere is air, inert or reducing gas.

[0014] The second objective of this invention can be achieved through the following technical solution: A low-power self-defrosting electrothermal superhydrophobic fin for air conditioner heat exchangers is prepared by the above-mentioned preparation method.

[0015] Preferably, the low-power self-defrosting electrothermal superhydrophobic fin for an air conditioner heat exchanger includes a metal fin substrate and an electrothermal superhydrophobic functional layer covering the surface of the metal fin substrate; the electrothermal superhydrophobic functional layer is made of conductive nanomaterials, binders and low surface energy materials.

[0016] Preferably, the contact angle between the electrothermal superhydrophobic functional layer and water is greater than 150° and the roll-off angle is less than 10°; the sheet resistance of the electrothermal superhydrophobic functional layer is from 10 Ω / □ to 1000 Ω / □.

[0017] The third objective of this invention can be achieved through the following technical solution: An air conditioning defrosting system includes: a low-power self-defrosting electrothermal superhydrophobic fin for an air conditioning heat exchanger, a low-voltage DC power supply, a controller, a temperature and humidity sensing unit, and a status monitoring module; the output terminal of the low-voltage DC power supply is electrically connected to the electrothermal superhydrophobic functional layer; the controller is controlled and connected to the low-voltage DC power supply; the temperature and humidity sensing unit is signal-connected to the controller and is used to monitor the ambient temperature and humidity during frosting; the status monitoring module is used to monitor changes in the electrical parameters of the electrothermal superhydrophobic functional layer.

[0018] Preferably, the working process of the air conditioning defrosting system is as follows: The ambient temperature and humidity of the low-power self-defrosting electrothermal superhydrophobic fins used in the air conditioning heat exchanger are obtained through a temperature and humidity sensing unit; the controller determines whether the temperature is lower than a preset frost risk temperature threshold and whether the humidity is higher than a preset frost risk humidity threshold; when the temperature is lower than the temperature threshold and the humidity is higher than the preset frost risk humidity threshold, the controller controls a low-voltage DC power supply to supply power to the electrothermal superhydrophobic functional layer to perform the defrosting operation; during the defrosting operation, the electrical parameter changes of the electrothermal superhydrophobic functional layer are monitored in real time by a status monitoring module; the controller determines the frost melting state based on the changes in the electrical parameters and adjusts the power supply strategy or terminates the power supply accordingly.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) Technological path innovation: This invention abandons the traditional system-level defrosting approach and pioneers a new intelligent defrosting mode on the fins of heat exchangers, which is a fundamental technological path innovation.

[0020] (2) Dual Synergistic Mechanism: Passive Delay (Superhydrophobic): The superhydrophobic functional layer greatly reduces the contact area and time between water and the fins, causing condensate to roll off quickly, which physically delays the formation and growth of ice nuclei and prolongs the frosting cycle. Active Removal (Electrothermal): When defrosting is still required in harsh environments, the conductive film generates uniform Joule heat after being energized, which directly and efficiently heats the surface of the fins, and can quickly melt the thin frost with extremely low power density.

[0021] (3) Advantages of application in air conditioning: Uninterrupted heating: The defrosting process only occurs locally on the fin surface, without interfering with the refrigerant circulation and operating mode of the air conditioning unit, resulting in an excellent user experience. Significant energy saving: Compared with traditional reverse circulation or electric heating tube defrosting, the fins of this invention have a conductive film, which can achieve efficient defrosting. Compact structure and compatibility: The ultra-thin functional layer hardly increases the fin thickness and wind resistance, and can be directly applied to existing air conditioning products. Long-term stability: Through chemical bonding low surface energy modification and heat treatment, the mechanical and chemical stability of the functional layer under long-term air conditioning operation conditions is ensured. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the low-power self-defrosting electrothermal superhydrophobic fin for an air conditioner heat exchanger according to the present invention, wherein 1-metal fin substrate, 2-electrothermal superhydrophobic functional layer; Figure 2 This is a process flow diagram of the preparation method of the low-power self-defrosting electrothermal superhydrophobic fins for air conditioner heat exchangers of the present invention; Figure 3 This is a flowchart illustrating the workflow of the air conditioning defrosting system described in Application Embodiment 1 of the present invention. Figure 4 This is a performance comparison diagram of the low-power self-defrosting electric heating superhydrophobic fins (left) and ordinary hydrophilic aluminum fins (right) used in air conditioning heat exchangers in Example 1 under frosting conditions. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. All materials used in the examples of the present invention are commercially available.

[0024] Example 1 The method for preparing the low-power self-defrosting electrothermal superhydrophobic fins for air conditioner heat exchangers described in this embodiment includes the following steps: (1) Take a standard air conditioner aluminum fin and clean it with acetone, ethanol and deionized water in sequence for 15 minutes. Then immerse it in a 60℃, 1M sodium hydroxide solution for 5 minutes to remove the oxide layer and rinse it with deionized water. Then immerse it in a 1wt% dilute nitric acid solution for 2 minutes to etch and build a rough structure. Dry it to prepare the pretreated metal fin substrate. (2) Silver nanowires, epoxy resin and heptadecanofluorodecyltrimethoxysilane were dispersed in ethanol. The mass ratio of silver nanowires: epoxy resin: heptadecanofluorodecyltrimethoxysilane: ethanol was 15:5:1:79. The mixture was ultrasonically dispersed to obtain a superhydrophobic conductive nano-coating. (3) Use a spray gun to uniformly spray the superhydrophobic conductive nano-coating onto the pretreated aluminum fin surface; (4) The coated fins were annealed at 80°C for 4 hours under argon protection and cooled to obtain silver nanowire-based electrothermal superhydrophobic fins, namely the low-power self-defrosting electrothermal superhydrophobic fins used in air conditioning heat exchangers.

[0025] The low-power self-defrosting electrothermal superhydrophobic fins (silver nanowire-based electrothermal superhydrophobic fins) prepared in this embodiment for use in air conditioning heat exchangers were tested to have a contact angle of 156° and a roll-off angle of 5° with water; their sheet resistance was tested to be 50 Ω / □.

[0026] Example 2 The method for preparing the low-power self-defrosting electrothermal superhydrophobic fins for air conditioner heat exchangers described in this embodiment includes the following steps: (1) Same as Example 1; (2) Multi-walled carbon nanotubes, acrylic resin, and heptadecafluorooctyltriethoxysilane are dispersed in N,N-dimethylformamide in a mass ratio of 30:10:1:59. The mixture is ultrasonically dispersed and stirred to form a stable and uniform coating. (3) The above coating is applied to the surface of the pretreated aluminum fins by a dip-coating method; (4) The film-formed fins are annealed at 100°C for 2 hours under nitrogen protection and cooled to obtain carbon nanotube-based electrothermal superhydrophobic fins, namely the low-power self-defrosting electrothermal superhydrophobic fins used in air conditioning heat exchangers.

[0027] The low-power self-defrosting electrothermal superhydrophobic fins (carbon nanotube-based electrothermal superhydrophobic fins) prepared in this embodiment for use in air conditioning heat exchangers were tested to have a contact angle of 158° and a roll-off angle of 4° with water; their sheet resistance was tested to be 100 Ω / □.

[0028] Application Example 1 The air conditioning defrosting system described in this application embodiment includes: a low-power self-defrosting electrothermal superhydrophobic fin for an air conditioning heat exchanger as described in Embodiment 1, a low-voltage DC power supply, a controller, a temperature and humidity sensing unit, and a status monitoring module; the output terminal of the low-voltage DC power supply is electrically connected to the electrothermal superhydrophobic functional layer; the controller is controlled and connected to the low-voltage DC power supply; the temperature and humidity sensing unit is signal-connected to the controller and is used to monitor the temperature and humidity of the frosting environment; the status monitoring module is used to monitor changes in the electrical parameters of the electrothermal superhydrophobic functional layer.

[0029] Preferably, the working process of the air conditioning defrosting system is as follows: the ambient temperature and humidity of the low-power self-defrosting electrothermal superhydrophobic fins used in the air conditioning heat exchanger are obtained through a temperature and humidity sensing unit; the controller determines whether the temperature is lower than a preset frost risk temperature threshold and whether the humidity is higher than a preset frost risk humidity threshold; when the temperature is lower than the temperature threshold and the humidity is higher than the preset frost risk humidity threshold, the controller controls a low-voltage DC power supply to supply power to the electrothermal superhydrophobic functional layer to perform the defrosting operation; during the defrosting operation, the electrical parameter changes of the electrothermal superhydrophobic functional layer are monitored in real time by a status monitoring module; the controller determines the frost melting state based on the changes in the electrical parameters and adjusts the power supply strategy or terminates the power supply accordingly.

[0030] Performance Testing and Application Examples 2 The fins prepared in Example 1 were assembled into an experimental evaporator and connected to a control system. A temperature and humidity sensor and a 36V / 2A DC power supply were also included. Heating-defrosting cycle tests were conducted in an artificial climate chamber with an ambient temperature of 0°C and a relative humidity of 85%. Figure 3 The diagram shown is a block diagram illustrating the principle of an air conditioning defrosting system according to an application embodiment of the present invention.

[0031] Comparative example: Using ordinary hydrophilic aluminum fins of the same specifications, after running for 60 minutes, if... Figure 4 As shown on the right, the frost layer between the fins is severely blocked, requiring the activation of traditional reverse circulation defrosting.

[0032] Application Example 2 of the Invention: After running for 240 minutes, as follows Figure 4 As shown on the left, the controller detected that the surface temperature of the fins had dropped to 0°C and automatically activated the electric defrosting function. After being powered on for 150 seconds at approximately 40W, the thin frost on the fin surface completely melted, and the functional layer returned to its superhydrophobic state. Throughout the entire process, the air conditioner maintained stable heating, and the indoor air supply temperature remained unchanged.

[0033] Test results show that the low-power self-defrosting electrothermal superhydrophobic fins for air conditioner heat exchangers provided by this invention, when assembled into an experimental evaporator, successfully extended the frosting cycle by four times and achieved uninterrupted defrosting with extremely low energy consumption. The overall energy efficiency and comfort far exceed those of existing technologies.

[0034] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a low-power self-defrosting electrothermal super-hydrophobic fin for an air conditioner heat exchanger, characterized in that, The method comprises the following steps: (1) preparing a pretreated metal fin substrate by using an organic solvent to ultrasonically clean the metal fin substrate to remove oil stains, then immersing the metal fin substrate in an alkaline solution to remove the surface oxide layer, then fully rinsing the metal fin substrate with deionized water and drying, and finally forming a rough structure on the metal fin substrate by chemical etching or anodic oxidation; (2) uniformly dispersing conductive nanomaterials, a binder and a low-surface-energy substance in a solvent in sequence to form a super-hydrophobic conductive nano-coating; (3) applying the super-hydrophobic conductive nano-coating to the surface of the pretreated metal fin substrate to form an electro-thermal super-hydrophobic functional layer; (4) annealing and reinforcing the prepared electro-thermal super-hydrophobic functional layer to prepare a low-power self-defrosting electro-thermal super-hydrophobic fin for an air conditioner heat exchanger.

2. The method of claim 1, wherein the method is characterized by: The metal fin substrate in step (1) is made of one of aluminum and aluminum alloy, copper and copper alloy, and stainless steel.

3. The method of claim 1, wherein the method further comprises the steps of: applying a layer of a hydrophobic material on the surface of the electrically conductive layer; and applying a layer of a hydrophilic material on the layer of the hydrophobic material. In step (2), the conductive nanomaterials, the binder, the low-surface-energy substance and the solvent are prepared in a mass ratio of 15-30:1-10:1:59-83; the conductive nanomaterials are at least one of silver nanowires, carbon nanotubes, graphene, two-dimensional inorganic compounds and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate); the binder is epoxy glue, acrylic glue, phenolic resin glue, urea-formaldehyde resin glue or polyurethane glue; and the low-surface-energy substance is fluorosilane or a polysiloxane compound.

4. The method of claim 1, wherein the method further comprises the steps of: applying a layer of a hydrophobic material on the surface of the electrically conductive layer; and applying a layer of a hydrophilic material on the layer of the hydrophobic material. In step (3), the coating method is spraying, dipping, pulling or spinning.

5. The method of claim 1, wherein the method further comprises the steps of: applying a layer of a hydrophobic material on the surface of the electrically conductive layer; and applying a layer of a hydrophilic material on the layer of the hydrophobic material. In step (4), the annealing temperature is 23-300°C, and the annealing atmosphere is air, inert gas or reducing gas.

6. A low power self-defrosting electro-thermal superhydrophobic fin for an air conditioner heat exchanger, characterized in that, The method is prepared according to any one of claims 1-5.

7. The low power self-defrosting electro-thermal superhydrophobic fin for air conditioner heat exchanger according to claim 6, characterized in that, The low-power self-defrosting electro-thermal super-hydrophobic fin for an air conditioner heat exchanger comprises a metal fin substrate and an electro-thermal super-hydrophobic functional layer covering the surface of the metal fin substrate; the electro-thermal super-hydrophobic functional layer is prepared from conductive nanomaterials, a binder and a low-surface-energy substance.

8. The low power self-defrosting electro-thermal superhydrophobic fin for an air conditioner heat exchanger according to claim 6, characterized in that, The contact angle of the electro-thermal super-hydrophobic functional layer with water is greater than 150°, and the rolling angle is less than 10°; the square resistance of the electro-thermal super-hydrophobic functional layer is 10-1000 Ω / □.

9. An air conditioning defrosting system, characterized by, The method comprises: The low-power self-defrosting electro-thermal super-hydrophobic fin for an air conditioner heat exchanger, a low-voltage direct-current power supply, a controller, a temperature and humidity sensing unit and a state monitoring module according to any one of claims 6-8; the output end of the low-voltage direct-current power supply is electrically connected to the electro-thermal super-hydrophobic functional layer; the controller is in control connection with the low-voltage direct-current power supply; the temperature and humidity sensing unit is in signal connection with the controller and is used for monitoring the temperature and humidity of the frosting environment; and the state monitoring module is used for monitoring the electrical parameter change of the electro-thermal super-hydrophobic functional layer.

10. The air conditioner defrosting system of claim 9, wherein, The working process of the air conditioner defrosting system is as follows: the temperature and humidity of the environment where the low-power self-defrosting electrothermal super-hydrophobic fin for air conditioner heat exchanger is located are obtained through a temperature and humidity sensing unit; whether the temperature is lower than a preset frost risk temperature threshold and whether the humidity is higher than a preset frost risk humidity threshold are determined by a controller; when the temperature is lower than the temperature threshold and the humidity is higher than the preset frost risk humidity threshold, the electrothermal super-hydrophobic functional layer is powered by a low-voltage direct-current power supply controlled by the controller to perform defrosting operation; During the power supply for defrosting operation, the change of the electrical parameter of the electrothermal super-hydrophobic functional layer is monitored in real time by a state monitoring module; the change of the electrical parameter is used by the controller to determine the frost melting state, and the power supply strategy is adjusted or the power supply is terminated accordingly.

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