A frost-preventing fin with a leaf edge curling shape of a boxwood leaf and a preparation method thereof

Abstract

The present application relates to air source heat pump technical field, especially to a kind of imitation cypress leaf leaf edge curling shape frost fin and preparation method thereof, including bionic V-shaped array fin;Bionic V-shaped array fin is formed by a plurality of bionic V-shaped fin equidistant arrangement along array direction, each bionic V-shaped fin includes first fin plate and second fin plate, first fin plate and second fin plate form the angle of intersection;Convex curvature structure is arranged at the angle, and convex curvature structure is integrally formed between first fin plate and second fin plate, the outer surface of convex curvature structure is outwardly convex arc surface, the radius of arc surface is R, the included angle between first fin plate and second fin plate is α, the single fin plate length of bionic V-shaped fin is L, the array pitch of bionic V-shaped fin is P;And satisfy: P≥3mm, 20°≤α≤90°, 0<R≤L / 5, solve the problem that a kind of active guiding frost area, keep the problem of large-area frost-free of fin surface in prior art is lacked.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of air source heat pump, and particularly relates to a frost-preventing fin with a curled shape of leaf edge imitating a cypress leaf and a preparation method thereof. BACKGROUND

[0002] The air source heat pump is a kind of energy utilization equipment with high efficiency and environmental protection, and has been widely applied to the fields of building heating, refrigeration and agricultural product drying. The outdoor heat exchanger generally adopts the finned tube structure to improve the heat exchange efficiency, but in the low-temperature and high-humidity environment in winter (when the temperature is lower than 5 DEG C and the relative humidity is high), the frost on the fin surface can increase the heat exchange thermal resistance, thereby causing the significant decrease of the heat pump heating performance coefficient, and even affecting the normal operation of the unit. The existing researches show that the defrosting energy consumption of the air source heat pump accounts for more than 10.2% of the total energy consumption of the unit system. The existing fin defrosting and frost-preventing technologies mainly include two types of active defrosting and passive frost-preventing: The active defrosting technology includes reverse cycle defrosting, hot gas bypass defrosting, phase change energy storage defrosting and resistance wire heating defrosting. Among them, the reverse cycle defrosting needs a four-way reversing valve to reverse, the heating is interrupted for a long time (generally more than ten minutes), the indoor temperature fluctuates greatly, and the frequent reversing affects the service life of the system; the hot gas bypass defrosting can maintain the indoor heating, but the defrosting efficiency is limited, the defrosting after the defrosting is low, the compressor is prone to liquid knock phenomenon, and the defrosting efficiency is limited; the phase change energy storage defrosting technology is not mature, the system is complex, the initial investment is high, and has not been widely promoted; the electric heating defrosting has high energy consumption, and does not meet the energy saving requirement.

[0003] The passive frost-preventing technology focuses on the modification of the super-hydrophobic coating to delay the freezing of the fin, inhibit the growth of frost and promote the drainage of the defrosting water. However, researches show that the frost-preventing effect of the hydrophobic surface is mainly concentrated in the initial stage of frosting, and has little effect on the later stage of frost growth, and the large-scale preparation technology and durability still need to be improved. Although the hydrophilic coating can reduce the frost amount and accelerate the defrosting, the liquid film is easily formed in the initial stage, and the crystallization into ice seriously affects the heat exchange.

[0004] In addition, the improvement of the fin geometry can improve the heat exchange and drainage capacity to a certain extent, for example, some patents disclose the improved fin structure to enhance the heat exchange efficiency, but the existing geometric improvement has limited effect on the improvement of the frost-preventing and heat transfer performance, and the cleaning after frosting is still very inefficient. SUMMARY

[0005] The present application aims to provide a frost-preventing fin with a curled shape of leaf edge imitating a cypress leaf and its preparation method, and solves the problem that there is no frost-preventing fin structure which can actively guide the frosting area, keep the large-area frost-free surface of the fin, has a simple preparation process and controllable cost in the low-temperature and high-humidity environment in the prior art.

[0006] To achieve the above object, the present invention provides a frost-resistant fin imitating the curled morphology of boxwood leaf margin and a preparation method thereof, comprising bionic V-shaped array fins; the bionic V-shaped array fins are formed by a plurality of bionic V-shaped fins arranged at equal intervals along the array direction, each bionic V-shaped fin comprises a first fin plate and a second fin plate, and the first fin plate and the second fin plate form a fold angle at the intersection; a convex curvature structure is arranged at the fold angle, and the convex curvature structure is integrally formed with the first fin plate and the second fin plate, the outer surface of the convex curvature structure is an outwardly protruding arc surface, the radius of the arc surface is R, and the arc surface extends along the ridge line direction at the fold angle; the included angle between the first fin plate and the second fin plate is α, the length of a single fin plate of the bionic V-shaped fin is L, the vertical distance from the top to the bottom of the bionic V-shaped fin is h, and the array pitch of the bionic V-shaped fins is P; and the following conditions are satisfied: P≥3mm, 20°≤α≤90°, 0<R≤L / 5, the V-shaped fin is a symmetrical structure, and the geometric relationship among its single fin plate length L, fin height h, array pitch P and included angle α satisfies the following: L=h / cos(α / 2), h=P / 2tan(α / 2).

[0007] Preferably, the value range of the array pitch P is 5mm≤P≤15mm.

[0008] Preferably, the value range of the included angle α between the first fin plate and the second fin plate is 45°≤α≤60°.

[0009] Preferably, the ratio of the radius R of the convex curvature structure to the fin plate length L satisfies: 1 / 30≤R / L≤1 / 15.

[0010] Preferably, the water contact angle θ on the surfaces of the bionic V-shaped fin and the convex curvature structure is θ≥50°.

[0011] Preferably, a metal base is further included, the bionic V-shaped array fins are arranged on the surface of the metal base, and the included angle β between the convex curvature axis of the bionic V-shaped array fin and the upper surface of the metal base satisfies: 0°≤β≤90°.

[0012] Preferably, the included angle β is 0°, and the bionic V-shaped fins are arranged in parallel and at equal intervals on the upper surface of the metal base.

[0013] Preferably, the included angle β is 90°, and the bionic V-shaped fins are arranged in parallel and at equal intervals on the upper surface of the metal base.

[0014] Preferably, a plurality of through holes are provided on the side surface of the metal base.

[0015] Preferably, a method for preparing frost-resistant fins imitating the curled morphology of the leaf margin of boxwood leaves comprises the following steps: S1: designing and machining a metal stamping die according to the geometric parameters of the bionic V-shaped fins and the convex curvature structure, wherein the geometric parameters at least include an included angle α, a radius R and an array pitch P; S2: subjecting a thin metal plate to stamping forming using the metal stamping die, to form a semi-finished bionic fin having a V-shaped array fin plate and a convex curvature structure; S3: cleaning the surface of the semi-finished bionic fin and performing surface energy modification treatment, so that the static contact angle θ of the surface to water is ≥ 150°.

[0016] The advantages and positive effects of the frost-resistant fin imitating the curled morphology of the leaf margin of boxwood leaves and the preparation method thereof according to the present invention are as follows: 1. By arranging the fins into a bionic V-shaped structure and arranging them at equal intervals in an array manner, combined with the geometric constraints of array pitch P ≥ 3 mm, included angle 20° ≤ α ≤ 90°, fin plate length L = h / cos(α / 2), and height h = P / 2tan(α / 2), continuous V-shaped flow guide channels can be formed between the fin groups, so as to increase the heat exchange area with air. In a low-temperature and high-humidity environment, the top of the fins has a larger exposed area, which is more likely to promote the condensation or frosting of water vapor, reduces the flux of water vapor entering the bottom of the V-shaped structure, so that frost in this area is difficult to grow and a stable frost-free zone is formed.

[0017] 2. A convex curvature structure imitating the boxwood leaf margin is introduced at the folded corner of the V-shaped fin, and the radius is defined as 0 < R ≤ L / 5. The arc surface increases the curvature gradient at the folded corner, making this area more sensitive to the condensation threshold of water vapor, and preferentially becoming the frosting initiation site. The convex curvature structure is combined with the high heat exchange area at the top of the V-shaped fin, which further enhances the ability of the top of the fin to capture water vapor, restricts the frosting behavior to specific "sacrificial regions" such as the tip of the top of the fin, significantly increases the area of the frost-free zone on the inclined surface in the middle of the fin and at the bottom of the V-shaped groove, and further improves the effective heat exchange area of the fin under continuous low-temperature and high-humidity working conditions. This structure inhibits the initial formation and growth of frost crystals from the physical level.

[0018] Based on the bionic design of the boxwood leaf structure, the present invention realizes active spatial regulation of the frosting region by inducing differential condensation distribution of water vapor at different heights of the fins. By optimizing the geometric parameters and surface wettability of the fins, the frost accumulation process on the fins can be significantly inhibited in a low-temperature and high-humidity environment, a large-area frost-free zone is realized, the heat exchange efficiency and continuous operation capacity are improved, and meanwhile, the number of defrosting shutdowns and later maintenance costs can be reduced.

[0019] Even without superhydrophobic modification, such as θ≈50°~70°, the V-groove and convex curvature structure in this invention can achieve stable frost suppression through structural features, maintain a large frost-free area, achieve a certain anti-frost effect, and drain water quickly through the groove structure during the defrosting stage. The superhydrophobic coating only plays a reinforcing role and is not a necessary technical feature.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a frost-proof fin structure that mimics the curled leaf margin of a boxwood leaf according to the present invention.

[0022] Figure 2 The curves show the change in the proportion of the frost-free zone over time during the frosting process of fins with apex angles α of 90°, 60° and 45° in this invention.

[0023] Figure 3 For the present invention Figure 2 The distribution of frost on fins at different angles one hour after frost formation.

[0024] Figure 4 This is a comparison of the size of the frost-free area after 1.5 hours of frost formation on fins of the present invention, where all α is 60° but have different convex curvature radii R.

[0025] Figure 5 This is a three-dimensional structural diagram of a fin assembly according to the present invention.

[0026] Figure 6 This is a three-dimensional structural diagram of another fin assembly according to the present invention.

[0027] Figure 7 The contact angles are those of the three wettable surfaces in this invention.

[0028] Figure 8 This invention describes the frosting and defrosting processes of three types of wettable surfaces.

[0029] Figure Labels 1. Bionic V-shaped array fins; 11. First fin plate; 12. Second fin plate; 13. Convex curvature structure; 2. Metal substrate; 3. Through hole. Detailed Implementation

[0030] In the description of this invention, it should be noted that the terms "upper," "lower," "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 is in use. They are used only for the convenience of describing the invention and 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. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" 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; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0031] In this application, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. In case of any inconsistency, the meaning set forth in this specification or derived from the content described herein shall prevail. Furthermore, the terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit the scope of this application.

[0032] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0033] like Figures 1-8 As shown, this invention provides a frost-resistant fin that mimics the curled edge of a boxwood leaf, comprising a metal substrate 2 and biomimetic V-shaped array fins 1 disposed on the surface of the metal substrate 2. The metal substrate 2 provides structural support. The biomimetic V-shaped array fins 1 are composed of several biomimetic V-shaped fins arranged equidistantly along the array direction. Each biomimetic V-shaped fin includes a first fin plate 11 and a second fin plate 12, which form a bend at their intersection. A convex curvature structure 13 is provided at the bend, which is integrally formed with the first fin plate 11 and the second fin plate 12, and the outer surface of the convex curvature structure 13 is an outwardly convex arc surface.

[0034] according to Figure 1 The structural parameters shown are R=0, h=5mm, α=90°, and 5 V-shaped fin arrays, forming a long fin with 9 bends. A metal block of the corresponding shape is machined by wire cutting and used as a stamping die, or a mold of this shape is made using 3D printing. The mold is then used to stamp or bend a thin metal sheet to obtain a fin with the above design parameters. By changing the apex angle, biomimetic V-shaped array fins 1 with α=60° and 45° are machined respectively.

[0035] A frosting experiment was conducted on the above-mentioned fins in a low-temperature, high-humidity environment. The frosting condition on the fin surface was recorded, and the proportion of frost-free areas was statistically analyzed. Figure 2 As shown, the experimental results indicate that after 10 minutes of frosting, the biomimetic V-shaped array fin 1 with α=60° consistently has a larger frost-free area, meaning that the frost coverage on the surface of this biomimetic V-shaped array fin 1 increases the slowest, and it still has approximately 40% frost-free area after 60 minutes of frosting. In contrast, the biomimetic V-shaped array fins 1 with α=90° and 45° have only about 20% frost-free area. Photos of the three biomimetic V-shaped array fins 1 after 60 minutes of frosting are shown below. Figure 3 As shown.

[0036] Example 2 in accordance with Figure 1 The structural parameters shown are selected as h=5mm and α=60°. Therefore, the length of a single fin is L=h / cos(α / 2). Following the ratio of the leaf margin curvature radius to the leaf width of a boxwood leaf (approximately 1 / 30), R / L=1 / 30 is selected. Based on these parameters, a biomimetic fin is designed, and the final biomimetic V-shaped array fin 1 is obtained using the die-stamping method described in Example 1. By changing the value of R, two types of biomimetic V-shaped array fins 1 with R / L=1 / 15 and 1 / 5 are manufactured respectively.

[0037] A frosting experiment was conducted on the above-mentioned fins in a low-temperature and high-humidity environment. After 1.5 hours of continuous frosting, the frosting condition on the surface of each fin was as follows: Figure 4 As shown. The results show that the biomimetic V-shaped array fin 1 without a biomimetic curvature structure (i.e., R=0, from Example 1) has only about 30% of the frost-free area remaining. The biomimetic V-shaped array fin 1 with R / L=1 / 30 has the largest proportion of the frost-free area, reaching as high as 48%; as the convex curvature radius R increases, the proportion of the frost-free area gradually decreases. Figure 4 The inset photos show the frosting conditions of the corresponding structures.

[0038] Example 3 An array of fins is obtained by arranging the arbitrary biomimetic V-shaped array fins 1 in Example 2 on a substrate at a spacing D0, such as... Figure 5 As shown, the axis of the fin's convex curvature is parallel to the base. In a specific implementation, the fin's convex curvature can be... Figure 5 The projected view from the left front is obtained through wire cutting, or by first obtaining a single biomimetic V-shaped array fin 1 through die stamping, and then fixing several biomimetic V-shaped array fins 1 to the substrate through welding, mechanical anchoring, or other methods to form the final fin assembly. This fin assembly can be used for heat exchange devices adapted to flat substrates.

[0039] Example 4 An array of individual biomimetic fins from Example 2 is obtained by arranging them at a spacing D1 on a substrate, such as... Figure 6As shown, the axis of the fin's convex curvature is perpendicular to the substrate. In specific implementation, a single biomimetic V-shaped array fin 1 is first obtained by die stamping, and then several of these biomimetic V-shaped array fins 1 are fixed to the substrate by welding, mechanical anchoring, or other methods to form the final fin assembly. In some embodiments, the substrate can be a solid thin plate or a thick plate with several through holes 3, which can be used for heat pipe assembly.

[0040] Therefore, the anti-frost fin with a leaf edge curling shape similar to that of boxwood described in this invention and its preparation method solve the problem in the prior art of lacking an anti-frost fin structure that can actively guide the frost area in a low temperature and high humidity environment, keep a large area of ​​the fin surface frost-free, and has a simple preparation process and controllable cost.

[0041] Example 5 Select any biomimetic V-shaped array fin 1 from Example 2, spray a commercial superhydrophobic coating onto several consecutive biomimetic V-shaped structures (e.g., 5), then coat the next consecutive biomimetic V-shaped structures with a hydrophobic silicone coating, leaving the remaining portion as the original hydrophilic surface. The water contact angles of the three surfaces are as follows: Figure 7 As shown, the water contact angles of the superhydrophobic surface, hydrophobic surface, and hydrophilic surface are 152°, 102°, and 70°, respectively.

[0042] A frosting experiment was conducted on the above-mentioned fins in a low-temperature and high-humidity environment. After 80 minutes of continuous frosting, the cooling circulation pump was turned off, and the fins were allowed to spontaneously defrost at room temperature (23℃). The frosting and defrosting processes on the three surfaces were observed and recorded. Figure 8 As shown, in the initial freezing stage (first 8 minutes), frost growth and coverage are fastest on the hydrophilic surface, followed by the hydrophobic surface, with the superhydrophobic surface growing the slowest. During subsequent frost growth, due to extreme water vapor supersaturation, frost coverage is similar on all three surfaces. In the melting stage, frost on the superhydrophobic surface melts first, followed by the hydrophobic surface, with the hydrophilic surface melting the slowest. In the first 7 minutes, the main frost layer at the top of the structure melts first. Between 9 and 11 minutes, the water film adhering closely to the fin surface begins to evaporate, exposing the dry substrate. The water film on the superhydrophobic surface fades the fastest, as shown by the dotted line in the figure. These results demonstrate the improving effect of surface wettability on delayed frost formation and defrosting of biomimetic fins in extremely supersaturated environments.

[0043] Example 7: Preparation method of anti-frost fins: This embodiment provides a method for preparing frost-resistant fins that mimic the curled leaf margins of boxwood, comprising the following steps: S1: Mold design and processing. A metal stamping mold is designed and processed based on the geometric parameters of the biomimetic V-shaped fins and the convex curvature structure 13. The geometric parameters include at least the included angle α, radius R, and array spacing P. The mold adopts a roll forming structure, enabling continuous stamping production.

[0044] S2: Stamping Forming. A metal sheet is stamped using a metal stamping die to form a finned semi-finished product with a first fin plate 11, a second fin plate 12, and a convex curvature structure 13. The metal sheet is made of aluminum foil or aluminum alloy foil. During the stamping process, the first fin plate 11 and the second fin plate 12 of the biomimetic V-shaped fin are formed in one step at the corner through a rounded transition convex curvature structure 13, ensuring the integrity and structural continuity between the convex curvature structure 13 and the fin plate. S3: Surface Cleaning and Superhydrophobic Modification. The surface of the finned semi-finished product is cleaned and modified to achieve a static water contact angle θ ≥ 150°. Specifically, this includes cleaning, surface roughening, and superhydrophobic coating preparation. The fin is immersed in the mixture, pulled into a film, and cured at 150°C for 30 minutes, forming a superhydrophobic coating on the fin surface with a static water contact angle exceeding 152°.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A frost-resistant fin that mimics the curled leaf margin shape of boxwood, characterized in that: Including biomimetic V-shaped array fins; The biomimetic V-shaped array fin is composed of several biomimetic V-shaped fins arranged at equal intervals along the array direction. Each biomimetic V-shaped fin includes a first fin plate and a second fin plate, and the first fin plate and the second fin plate form a bend at the intersection. The corner is provided with a convex curvature structure, and the convex curvature structure is integrally formed with the first wing plate and the second wing plate. The outer surface of the convex curvature structure is an outwardly protruding arc surface with a radius of R, and the arc surface extends along the ridge line direction at the corner. The included angle between the first fin and the second fin is α, the length of a single fin of the biomimetic V-shaped fin is L, the vertical distance from the top to the bottom of the biomimetic V-shaped fin is h, and the array spacing of the biomimetic V-shaped fin is P. And it satisfies: P≥3mm, 20°≤α≤90°, 0<R≤L / 5, The V-shaped fins have a symmetrical structure, and the following geometric relationships are satisfied between the length L of a single fin plate, the fin height h, the array spacing P, and the included angle α: L=h / cos(α / 2), h=P / 2tan(α / 2).

2. The frost-resistant fin with a leaf margin curling shape similar to that of a boxwood leaf according to claim 1, characterized in that: The range of the array spacing P is 5mm ≤ P ≤ 15mm.

3. The frost-resistant fin with a leaf margin curling shape similar to that of a boxwood leaf according to claim 2, characterized in that: The included angle α between the first fin and the second fin ranges from 45° to 60°.

4. The frost-resistant fin with a leaf margin curling shape similar to that of a boxwood leaf according to claim 3, characterized in that: The ratio of the radius R of the convex curvature structure to the length L of the fin satisfies: 1 / 30 ≤ R / L ≤ 1 / 15.

5. The frost-resistant fin with a leaf margin curling shape similar to that of a boxwood leaf according to claim 1, characterized in that: The contact angle θ of the biomimetic V-shaped fins and the convex curvature structure surface with water is ≥50°.

6. The frost-resistant fin with a leaf margin curling shape similar to that of a boxwood leaf according to claim 1, characterized in that: It also includes a metal substrate, and the biomimetic V-shaped array fins are disposed on the surface of the metal substrate. The angle β between the convex curvature axis of the biomimetic V-shaped array fins and the upper surface of the metal substrate satisfies: 0°≤β≤90°.

7. The frost-resistant fin with a leaf margin curling shape similar to that of a boxwood leaf according to claim 6, characterized in that: The included angle β is 0°, and the biomimetic V-shaped array fins are arranged in parallel and at equal intervals on the upper surface of the metal substrate.

8. The frost-resistant fin with a leaf margin curling shape similar to that of a boxwood leaf according to claim 6, characterized in that: The included angle β is 90°, and the biomimetic V-shaped array fins are arranged in parallel and at equal intervals on the upper surface of the metal substrate.

9. The frost-resistant fin with a leaf margin curling shape similar to that of a boxwood leaf according to claim 6, characterized in that: The metal substrate has several through holes on its side.

10. A method for preparing a frost-resistant fin with a leaf margin curling shape similar to that of a boxwood leaf, as described in any one of claims 1-9, characterized in that, Includes the following steps: S1: Design and process metal stamping dies based on the geometric parameters of biomimetic V-shaped fins and convex curvature structures. The geometric parameters include at least the included angle α, radius R, and array spacing P. S2: Using metal stamping dies to stamp and form metal sheets into biomimetic fin semi-finished products with V-shaped array fin plates and convex curvature structures; S3: Clean and modify the surface of the biomimetic fin semi-finished product to make its static contact angle with water θ≥150°.

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