WO2019149060A1

WO2019149060A1 - Heat exchanger, refrigerator having the heat exchanger, and heat exchange fins and design method thereof for heat exchanger

Info

Publication number: WO2019149060A1
Application number: PCT/CN2019/071742
Authority: WO
Inventors: 张建; 陆彭飞; 张磊; 彭博; 崔港
Original assignee: 合肥华凌股份有限公司; 合肥美的电冰箱有限公司; 美的集团股份有限公司
Priority date: 2018-01-31
Filing date: 2019-01-15
Publication date: 2019-08-08
Also published as: CN108019986A

Abstract

A heat exchanger, a refrigerator having the heat exchanger, and heat exchange fins and a design method thereof for the heat exchanger. The heat exchanger comprises: a heat exchange pipe (100), comprising multiple parallel sections and connecting sections (130) for sequentially connecting two adjacent parallel sections; and multiple heat exchange fins (200) arranged on the heat exchange pipe (100), at least part of an outer edge of each of the heat exchange fins (200) having a curved section for agitating an airflow.

Description

Heat exchanger, fin of refrigerator and heat exchanger therewith and design method thereof

Cross-reference to related applications

The present application is based on a Chinese patent application filed on Jan. 31, 2011, the entire disclosure of which is hereby incorporated by reference.

Technical field

The present application relates to the field of electrical appliance manufacturing technology, and in particular to a heat exchanger, a refrigerator having the heat exchanger, fins of the heat exchanger, and a method of designing fins of the heat exchanger.

Background technique

In the refrigerator of the related art, a heat exchange chamber is formed between the air duct and the tank, and a finned heat exchanger is installed in the heat exchange chamber for heat exchange, and the airflow is easy to form a relatively stable thermal boundary layer when passing through the surface of the fin. The heat transfer efficiency of the fins is not high.

Summary of the invention

The present application is intended to address at least one of the technical problems existing in the prior art. To this end, the present application proposes a heat exchanger that has the advantages of good heat exchange effect, low cost, and the like.

The application also proposes a refrigerator having the heat exchanger.

The application also proposes a fin of a heat exchanger.

The present application also proposes a method of designing fins of a heat exchanger.

To achieve the above object, a heat exchanger according to an embodiment of the first aspect of the present application is provided, the heat exchanger comprising: a heat exchange tube comprising a plurality of parallel segments and sequentially connecting adjacent two a connecting section of the parallel segments, each of the fins being respectively connected to the plurality of parallel segments; a plurality of fins, a plurality of the fins being arranged on the heat exchange tube, each of the fins At least a portion of the rim has a wave segment for disturbing the airflow.

The heat exchanger according to the embodiment of the present application has the advantages of good heat exchange effect, low cost, and the like.

In addition, the heat exchanger according to the above embodiment of the present application may further have the following additional technical features:

According to one embodiment of the present application, the wave segment has a peak that projects outwardly of the fin and a valley that is recessed into the fin.

According to an embodiment of the present application, the length direction of the connecting section is at a predetermined angle with the longitudinal direction of the fin, and the parallel section includes an upper parallel section and a lower parallel section, located on the same side of the heat exchanger Each of the connecting segments respectively connects the corresponding upper parallel segment and the lower parallel segment.

According to an embodiment of the present application, the wave segment includes an upper wave segment and a lower wave segment, and the upper wave segment and the lower wave segment are respectively located at opposite edges of the fin width direction, the upper wave A peak of the segment is disposed adjacent to the upper parallel segment in a length direction of the fin, and a peak of the lower wave segment is disposed adjacent to the lower parallel segment in a length direction of the fin.

According to an embodiment of the present application, the projections of the troughs of the upper wave segment and the troughs of the lower wave segment in the horizontal plane do not coincide.

According to an embodiment of the present application, the wave segment includes an upper wave segment and a lower wave segment, and the upper wave segment and the lower wave segment are respectively located at opposite edges of the fin width direction.

According to the embodiment of the second aspect of the present application, a refrigerator is provided, the refrigerator includes a tank; an air duct, the air duct is disposed in the tank and defines a heat exchange chamber together with the tank; A heat exchanger, the heat exchanger according to the embodiment of the first aspect of the present application, the heat exchanger being disposed in the heat exchange chamber.

According to the refrigerator of the embodiment of the present application, by using the heat exchanger according to the embodiment of the first aspect of the present application, there is an advantage that the refrigeration effect is good.

According to an embodiment of the present application, the inner wall surface of the tank is provided with an upper wave surface adapted to the shape of the fin.

According to an embodiment of the present application, the air passage faces a side surface of the heat exchanger with a lower wave surface adapted to the shape of the fin.

A fin according to a third aspect of the present application is directed to a fin of a heat exchanger having at least a portion of an outer rim of the fin having a wave segment for disturbing the airflow.

According to the fin of the heat exchanger according to the embodiment of the present application, the heat exchange effect of the heat exchanger can be improved, and the cost is low.

According to an embodiment of the fourth aspect of the present application, there is provided a method for designing a fin of a heat exchanger according to the first aspect of the present application, comprising the steps of:

A) establishing a Cartesian coordinate system with the center of one end of the fin as an origin, with the length direction of the fin being the X axis and the width direction being the Y axis;

B) using the coordinates of the peak point of the wave segment and the coordinate value of the valley point as a variable, using a super-Latin square design method to design a numerical experiment to generate a sample;

C) analyzing the sensitivity of each parameter, the maximum heat exchange amount of the fin surface is the optimization target, and the genetic algorithm is used for optimal solution;

D) After finding the optimal solution of the trough coordinate point, the optimal solution position of the fixed trough point is taken as the variable in the X direction coordinate of the peak point, and the same numerical algorithm is used to find the optimal value;

E) After completing step D, repeat steps B and C to find the optimal solution of the valley point;

F) In the statistical iterative optimization process, the iterative value difference of each point, when the difference is less than the predetermined value, the iteration is stopped, and the output calculates the peak and valley point coordinate values to obtain the wave segment line type.

According to the method for designing the fin of the heat exchanger according to the embodiment of the present application, the heat exchange effect of the heat exchanger can be improved.

According to an embodiment of the present application, after the step A is completed, within the same quadrant, the distance d between the adjacent two parallel segments of the heat exchanger in the X-axis direction, the initial height h of the fin, and the distance coordinate are set. The coordinates of the second parallel segment of the origin are (X0, Y0), and in step B, the peak points P(X1, Y1), P(X2, Y1), P(X3, Y1), P of the wave segment are used. X4, Y1), P(X5, Y1) coordinates, and coordinate values in the valley points P(x1, y1), P(x2, y2), P(x3, y3), P(x4, y4) are taken as Variable, a total of 8 variables, the boundary conditions are: x1 ∈ (X0, X0 + d), x2 ∈ (X0 + d, X0 + 2d), x3 ∈ (X0 + 2d, X0 + 3d), x4 ∈ (X0 +3d, X0+4d), y1∈(y0, Y1), y2∈(y0, Y1), y3∈(y0, Y1), y4∈(y0, Y1).

According to an embodiment of the present application, after finding the optimal solution of the trough coordinate point in step D, the fixed trough points P(x1, y1), P(x2, y2), P(x3, y3), P(x4, Y4) The optimal solution position, with the X-direction coordinates in the peak points P(X1, Y1), P(X2, Y1), P(X3, Y1), P(X4, Y1), P(X5, Y1): X1, X2, X3, and X4 are variables, totaling 4 variables, using the same numerical algorithm to find the best.

According to an embodiment of the present application, the predetermined value is 5%.

Additional aspects and advantages of the present invention will be set forth in part in the description which follows.

DRAWINGS

The above and/or additional aspects and advantages of the present application will become apparent and readily understood from

1 is a schematic view of a fin structure of a heat exchanger according to an embodiment of the present application.

2 is a schematic structural view of a heat exchanger according to an embodiment of the present application.

3 is a schematic structural view of a heat exchanger according to an embodiment of the present application.

4 is a partial structural schematic view of a refrigerator according to an embodiment of the present application.

FIG. 5 is a partial structural schematic view of a refrigerator according to an embodiment of the present application.

FIG. 6 is a partial structural schematic view of a refrigerator according to an embodiment of the present application.

FIG. 7 is a partial structural schematic view of a refrigerator according to an embodiment of the present application.

Reference numerals: refrigerator 1, evaporator 10, heat exchange tube 100, upper parallel section 110, lower parallel section 120, connecting section 130, fins 200, upper wave section 210, peak 211, trough 212, lower wave section 220, The tank 20, the upper wave surface 21, the air passage 30, and the lower wave surface 31.

Detailed ways

The embodiments of the present application are described in detail below, and the examples of the embodiments are illustrated in the drawings, wherein the same or similar reference numerals are used to refer to the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are intended to be illustrative only, and are not to be construed as limiting.

In the description of the present application, it is to be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", " After, "Left", "Right", "Vertical", "Horizontal", "Top", "Bottom", "Inside", "Outside", "Clockwise", "Counterclockwise", "Axial", The orientation or positional relationship of the indications of "radial", "circumferential", etc., is based on the orientation or positional relationship shown in the drawings, and is merely for convenience of description of the present application and simplified description, and does not indicate or imply the indicated device or component. It must be constructed and operated in a particular orientation, and is therefore not to be construed as limiting. Furthermore, features defining "first" and "second" may include one or more of the features, either explicitly or implicitly. In the description of the present application, "a plurality" means two or more unless otherwise stated.

In the description of the present application, it should be noted that the terms "installation", "connected", and "connected" are to be understood broadly, and may be fixed or detachable, for example, unless otherwise specifically defined and defined. Connected, or integrally connected; can be mechanical or electrical; can be directly connected, or indirectly connected through an intermediate medium, can be the internal communication of the two components. The specific meanings of the above terms in the present application can be understood in the specific circumstances for those skilled in the art.

A heat exchanger according to an embodiment of the present application will be described below with reference to the drawings.

In particular, the heat exchanger can be the evaporator 10.

As shown in FIGS. 1 to 6, a heat exchanger according to an embodiment of the present application includes a heat exchange tube 100 and fins 200.

The heat exchange tube 100 includes a plurality of parallel segments and a connecting segment 130 that sequentially connects adjacent two parallel segments. A plurality of fins 200 are arranged on the heat exchange tubes 100, each fin 200 being connected to a plurality of said parallel segments, and at least a portion of the outer edge of each fin 200 has a wave segment for disturbing the air flow.

According to the heat exchanger of the embodiment of the present application, by arranging the wave segments on the outer edge of the fin 200, the wave passage can be used to disturb the passing airflow, so that the airflow is generated in the normal direction of the edge of the wave segment. The disturbance drives the airflow to generate turbulent flow in the direction, avoiding the regular movement of the airflow to generate a thermal boundary layer that hinders heat exchange, thereby improving the heat exchange effect of the heat exchanger.

Moreover, since the wave segments are formed at the outer edges of the fins 200, not only can the airflow flowing through the outer edges of the fins 200 be disturbed to avoid formation on both sides of the heat exchanger. a relatively regular thermal boundary layer, thereby improving the heat exchange effect of the heat exchanger, and being able to avoid the interference of the overall wave-shaped fins when the airflow passes through the inside of the fins, compared to the manner in which the fins 100 are entirely wavy. The flow rate of the airflow ensures the airflow of the airflow and further improves the heat exchange effect of the heat exchanger.

In addition, since the wave segments are disposed only at the outer edges of the fins 200, it is not necessary to greatly improve the production process and apparatus of the existing fins, as compared with the fins which are generally wavy, thereby facilitating the fins. The production and manufacture of 200 reduces the difficulty in manufacturing the fins 200 and reduces the cost of the fins 200.

Therefore, the heat exchanger according to the embodiment of the present application has the advantages of good heat exchange effect, low cost, and the like.

The heat exchanger according to an embodiment of the present application will be described below with reference to the accompanying drawings.

In some embodiments of the present application, as shown in FIGS. 1-6, the heat exchanger according to an embodiment of the present application includes a heat exchange tube 100 and fins 200.

In particular, the heat exchanger can be an evaporator.

The wave section includes a peak 211 that projects outwardly of the fin 200 and a valley 212 that is recessed into the fin 200. In this way, a wave-shaped perturbation structure can be formed on the outer surface of the heat exchanger to cause disturbance when the airflow passes through the outer surface of the heat exchanger, thereby avoiding forming a relatively regular thermal boundary layer on the outer surface of the heat exchanger. Thereby, the heat exchange effect of the heat exchanger is improved, and the embodiment in which the wave structure is disposed in the thickness direction of the fin 200 can prevent the airflow from being disturbed by the wave structure when passing between the adjacent two fins. Thereby ensuring the air volume of the heat exchanger, further improving the heat exchange effect of the heat exchanger.

Further, compared with the embodiment in which the wave structure is provided in the thickness direction of the fin 200, the manufacturing process of the fin 200 can be further simplified, the manufacturing difficulty of the fin 200 can be reduced, and the production efficiency of the fin 200 can be improved.

Specifically, the plurality of parallel segments and the plurality of connecting segments 130 may be formed by bending the same pipe, and each of the parallel segments fits within the plurality of fins 200 and is closely attached to the mating fins 200. Hehe. In this way, the heat transfer tube 100 can be sufficiently thermally conducted by the fins 200 to facilitate control of the size of the heat exchanger.

Optionally, as shown in FIG. 2 and FIG. 3, the length direction of the connecting section 130 is at a predetermined angle with the longitudinal direction of the fin 200, and the parallel section includes an upper parallel section 110 and a lower parallel section 120 (up and down direction as shown in the figure) The arrows indicate that the up and down direction is only for convenience of description, and is not limited to the direction in which the heat exchanger is actually disposed.) Each connecting section 130 located on the same side of the heat exchanger is connected to the corresponding upper parallel section 110 and lower, respectively. Parallel section 120. Specifically, the predetermined angle is an acute angle, preferably 35-45 degrees. A plurality of the parallel segments are divided into a plurality of upper parallel segments and a plurality of lower parallel segments. For example, a plurality of the parallel segments are arranged in a plurality of rows spaced apart in the up and down direction, the first row and the third row are upper parallel segments, and the second row and the fourth row are lower parallel segments. This can further improve the utilization of space, and further facilitates controlling the size of the heat exchanger while ensuring the heat exchange effect of the heat exchanger.

Advantageously, as shown in FIGS. 1-3, the wave segment includes an upper wave segment 210 and a lower wave segment 220, and the upper wave segment 210 and the lower wave segment 220 are respectively located at opposite edges of the fin 200 in the width direction. In this way, the upper wave segment 210 and the lower wave segment 220 can be used to respectively perturb the airflow flowing above and below the heat exchanger to avoid forming a thermal boundary layer above and below the heat exchanger, thereby improving the heat exchanger. Heat transfer effect.

More advantageously, as shown in FIGS. 1-3, the wave segment includes an upper wave segment 210 and a lower wave segment 220, and the upper wave segment 210 and the lower wave segment 220 are respectively located at opposite edges of the fin 200 in the width direction. The peak 211 of the upper wave section 210 is disposed adjacent to the upper parallel section 110 in the longitudinal direction of the fin 200, and the peak 211 of the lower wave section 220 is disposed adjacent to the lower parallel section 120 in the longitudinal direction of the fin 200. Since the peak 211 of the upper wave section 210 is disposed adjacent to the upper parallel section 110 in the longitudinal direction of the fin 200, the peak 211 of the lower wave section 220 is disposed adjacent to the lower parallel section 120 in the longitudinal direction of the fin 200, so that the The structure arrangement of the heat exchanger is more reasonable, so that the heat exchange tube 100 can fully utilize the fins 200 for heat exchange, further improve the heat exchange effect of the heat exchanger, and can improve the heat exchange tubes to the edges of the adjacent fins 200. The disturbance effect of the airflow at 10, thereby further improving the heat exchange effect of the heat exchanger.

Alternatively, as shown in FIG. 7, the projections of the troughs of the upper wave section 210 and the troughs of the lower wave section 220 in the horizontal plane do not coincide. In this way, not only the upper wave segment 210 and the lower wave segment 220 can be staggered in the horizontal direction, the two can be arranged in parallel, thereby further improving the disturbance effect on the airflow, and can also play a certain limit on the installation of the heat exchanger. To prevent the heat exchanger from being reversed.

A refrigerator 1 according to an embodiment of the present application will be described below. The refrigerator 1 according to an embodiment of the present application includes a tank 20, a duct 30, and a heat exchanger.

The air duct 30 is disposed in the tank 20 and defines a heat exchange chamber together with the tank 20. The heat exchanger is the heat exchanger according to the above embodiment, and the heat exchanger is disposed in the heat exchange chamber.

The refrigerator 1 according to the embodiment of the present application has advantages such as a good cooling effect by utilizing the heat exchanger according to the above embodiment of the present application.

Specifically, the inner wall surface of the tank 20 is provided with an upper wave surface 21 that is adapted to the shape of the fins 200. Specifically, the upper wave section 210 and the upper wave surface 21 cooperate with each other.

More specifically, the side surface of the air duct 30 facing the heat exchanger is provided with a lower wave surface 31 adapted to the shape of the fin 200. Specifically, the lower wave section 220 and the lower wave surface 31 cooperate with each other.

In this way, the heat exchanger can be positioned not only by the upper wave surface 21 and the lower wave surface 31, so that the heat exchanger can be installed in the heat exchange chamber, and the upper wave surface 21 and the lower wave surface can be utilized. The gas stream is further disturbed to further avoid the generation of a thermal boundary layer, thereby further improving the heat exchange effect of the heat exchanger.

The fins of the heat exchanger according to embodiments of the present application are described below. At least a portion of the outer edge of the fin of the heat exchanger according to an embodiment of the present application has a wave segment for disturbing the air flow.

Specifically, the line shape of the wave segment is a Bezier curve.

A method of designing a fin 200 of a heat exchanger according to an embodiment of the present application is described below with reference to FIG. 7, which includes the following steps:

A) establishing a Cartesian coordinate system with the center of one end of the fin 200 as the origin, with the length direction of the fin 200 being the X axis and the width direction being the Y axis;

C) Analyze the sensitivity of each parameter, and maximize the heat transfer on the surface of the fin 200 as the optimization target, and use the genetic algorithm to optimize the solution;

According to the method for designing the fin of the heat exchanger according to the embodiment of the present application, the most ideal wavy line shape can be obtained by using the simulation iteration, thereby further improving the heat exchange effect of the heat exchanger.

Further, after step A is completed, within the same quadrant, the distance d between the adjacent two parallel segments of the heat exchanger in the X-axis direction, the initial height h of the fin 200, and the second parallel segment from the origin of the coordinate are set. The coordinates are (X0, Y0), and in step B, the peak points P(X1, Y1), P(X2, Y1), P(X3, Y1), P(X4, Y1), P of the wave segment are used. (X5, Y1) coordinates, and the coordinate values in the valley points P (x1, y1), P (x2, y2), P (x3, y3), P (x4, y4) as variables, a total of 8 variables The boundary conditions are: x1∈(X0,X0+d), x2∈(X0+d,X0+2d), x3∈(X0+2d,X0+3d), x4∈(X0+3d,X0+4d ), y1∈(y0, Y1), y2∈(y0, Y1), y3∈(y0, Y1), y4∈(y0, Y1).

Specifically, after finding the optimal solution of the trough coordinate point in step D, the optimal solutions of the fixed trough points P(x1, y1), P(x2, y2), P(x3, y3), P(x4, y4) are obtained. Position, X-direction coordinates in the peak points P (X1, Y1), P (X2, Y1), P (X3, Y1), P (X4, Y1), P (X5, Y1): X1, X2, X3 , X4 is a variable, a total of 4 variables, using the same numerical algorithm to find the best.

More specifically, the predetermined value is 5%.

In other words, the method for designing the fin 200 of the heat exchanger according to the specific embodiment of the present application includes the following steps:

B) Within the same quadrant, determine the distance d of the adjacent two parallel segments of the heat exchanger in the X-axis direction, the initial height h of the fin 200, and the coordinate of the second parallel segment from the origin of the coordinate is (X0, Y0);

C) with the peak points P (X1, Y1), P (X2, Y1), P (X3, Y1), P (X4, Y1), P (X5, Y1) coordinates of the wave segment, and the valley point P The coordinate values in (x1, y1), P(x2, y2), P(x3, y3), P(x4, y4) are used as variables, and there are a total of 8 variables whose boundary conditions are: x1 ∈ (X0, X0+) d), x2∈(X0+d, X0+2d), x3∈(X0+2d, X0+3d), x4∈(X0+3d, X0+4d), y1∈(y0,Y1), y2∈( Y0, Y1), y3∈(y0, Y1), y4∈(y0, Y1); in a specific embodiment of the present application, h=Y1, in other words, the coordinates of each peak point are P(X1, h), P (X2,h), P(X3,h), P(X4,h), P(X5,h), d=38mm, h=30mm, X0=27mm, Y0=18mm;

D) Eight variables were designed using the super-Latin square design method, and 81 samples were actually generated. The sensitivity of each parameter was analyzed. The maximum heat transfer on the surface of the fin 200 was the optimal target, and the genetic algorithm was used to optimize the solution. ;

E) After finding the optimal solution of the valley coordinate points, the optimal solution positions of the fixed valley points P(x1, y1), P(x2, y2), P(x3, y3), P(x4, y4), and the peak points X-direction coordinates in P(X1, Y1), P(X2, Y1), P(X3, Y1), P(X4, Y1), P(X5, Y1): X1, X2, X3, X4 are variables, A total of 4 variables, using the same numerical algorithm to find the best;

F) After completing step E, repeat steps C and D to find the optimal solution of the valley point;

G) In the statistical iterative optimization process, the iterative value difference of each point, when the difference is less than 5%, the iteration is stopped, and the output calculates the peak and valley point coordinate values to obtain the wave segment line type.

Finally, the line shape of the wave segment in the other quadrant is obtained in the same way. For example, the line shape of the upper wave segment 210 can be obtained by the above method, and the line shape of the lower wave segment 220 is obtained in the same manner.

Other configurations and operations of the refrigerator 1 according to embodiments of the present application are known to those of ordinary skill in the art and will not be described in detail herein.

In the description of the present specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiment", "example", "specific example", or "some examples", etc. Particular features, structures, materials or features described in the examples or examples are included in at least one embodiment or example of the application. In the present specification, the schematic representation of the above terms does not necessarily mean the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples.

While the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art The scope of the present application is defined by the claims and their equivalents.

Claims

A heat exchanger, comprising:

a heat exchange tube comprising a plurality of parallel segments and a connecting segment connecting the adjacent two parallel segments in sequence;

a plurality of fins, a plurality of the fins being arranged on the heat exchange tube, each of the fins being respectively connected to a plurality of the parallel segments, at least a portion of an outer edge of each of the fins being used A wave segment that disturbs the airflow.
The heat exchanger of claim 1 wherein said wave segments have peaks that project outwardly of the fins and valleys that are recessed into the fins.
The heat exchanger according to claim 1, wherein a length direction of said connecting section is at a predetermined angle with a longitudinal direction of said fin, said parallel section comprising an upper parallel section and a lower parallel section, said Each of the connecting segments on the same side of the heat exchanger is connected to the corresponding upper parallel segment and the lower parallel segment, respectively.
The heat exchanger according to claim 3, wherein said wave segment comprises an upper wave segment and a lower wave segment, said upper wave segment and said lower wave segment being respectively opposite in said fin width direction a wave edge of the upper wave segment is disposed adjacent to the upper parallel segment in a length direction of the fin, and a peak of the lower wave segment is adjacent to the lower parallel segment in a length direction of the fin .
The heat exchanger according to claim 4, wherein the projection of the trough of the upper wave section and the trough of the lower wave section in a horizontal plane does not coincide.
The heat exchanger according to claim 1, wherein said wave segment comprises an upper wave segment and a lower wave segment, said upper wave segment and said lower wave segment being respectively opposite in said fin width direction Both sides.
A refrigerator, comprising:

Box gall

a duct, the air duct is disposed in the tank and defines a heat exchange chamber together with the tank;

A heat exchanger, the heat exchanger according to any one of claims 1 to 6, wherein the heat exchanger is disposed in the heat exchange chamber.
The heat exchanger according to claim 7, wherein the inner wall surface of the tank is provided with an upper wave surface adapted to the shape of the fin.
The heat exchanger according to claim 7, wherein said air passage faces a side surface of said heat exchanger with a lower wave surface adapted to the shape of said fin.
A fin of a heat exchanger characterized in that at least a portion of the outer edge of the fin has a wave segment for disturbing the air flow.