EP2402699A2

EP2402699A2 - Fin and heat exchanger comprising the same

Info

Publication number: EP2402699A2
Application number: EP11003220A
Authority: EP
Inventors: Jiang Jianlong; Linjie Huang
Original assignee: Danfoss Sanhua Hangzhou Micro Channel Heat Exchanger Co Ltd
Current assignee: Sanhua Hangzhou Micro Channel Heat Exchanger Co Ltd; Danfoss AS
Priority date: 2010-06-29
Filing date: 2011-04-16
Publication date: 2012-01-04
Also published as: CN101865625B; US20110315362A1; CN101865625A; EP2402699A3

Abstract

A corrugated fin (4) comprises connection segments (42) each formed with a plurality of louvers (43); and substantially-circular arc segments (41) connected with the connection segments (42) alternatively in a longitudinal direction such that a plurality of corrugations are formed and the substantially-circular arc segments (41) form crests and troughs of the corrugations respectively, wherein 0≤H ₂≤(H ₁-2R+2Rsinβ)/cosβ, in which H ₂ is a louver length of the louver (43), H ₁ is a height of the fin (4), R is a radius of the substantially-circular arc segment (41), and β is an inclination angle of the connection segment (42).

Description

TECHNICAL FIELD

The present disclosure generally relates to a fin and a heat exchanger comprising the same, more particularly, to a corrugated fin and a heat exchanger comprising the same.

BACKGROUND

When a heat exchanger is used as an evaporator, a lot of condensate may be accumulated on surfaces of the fins due to structure limitation of the conventional corrugated fin, thus not only influencing the heat transfer performance of the heat exchanger, but also increasing the air resistance of the surface of the heat exchanger and thereby the power consumption of the air blower. Particularly, when the conventional fin is used in an inverted V-shaped or flat plate-shaped heat exchanger, an inclination angle is formed between the surface of the heat exchanger and a horizontal plane. Because the condensate is accumulated on the surface of the heat exchanger during operation, the condensate may directly drop into an air pipe below the heat exchanger from the surface of the heat exchanger, so that water leakage may occur in the unit using the heat exchanger and the air pipe may be corroded and bacteria may breed in the corroded air pipe, thus shortening the service life of the unit such as air conditioner and causing damage to human health.

SUMMARY

The present disclosure is directed to solve at least one of the problems existing in the prior art. Accordingly, a corrugated fin used for heat exchanger is provided, the fin has a good water drainage performance such that no condensate drops directly from the surface of a heat exchanger during operation and stoppage. In addition, a good heat exchange performance is ensured and the air side pressure drop is not too large.
Further, a heat exchanger comprising the corrugated fin is provided.
According to a first aspect of the present disclosure, a corrugated fin, comprising: connection segments each formed with a plurality of louvers; and substantially-circular arc segments connected with the connection segments alternatively in a longitudinal direction such that a plurality of corrugations are formed and substantially-circular arc segments connected with the connection segments alternatively in a longitudinal direction such that a plurality of corrugations are formed and the substantially-circular arc segments form crests and troughs of the corrugations respectively, in which 0≤H ₂≤(H ₁-2R+2Rsinβ)/cosβ, where H ₂ is a louver length of the louver, H ₁ is a height of the fin, R is a radius of the substantially-circular arc segment, and β is an inclination angle of the connection segment.
With the corrugated fin according to embodiments of the present disclosure, a good heat exchange performance and a normal air side pressure drop are ensured. In addition, it may reduce or eliminate the phenomenon that condensate drops from or accumulates on the louvers and the surface of the fins, so that the condensate may flow onto the tubes along the fins and gather into a water collecting pan along the tubes rather than drop into the air pipe. Therefore, no water leakage may occur in the unit using the heat exchanger, and the air pipe may not be corroded and bacteria may not breed in the corroded air pipe, thus lengthening the service life of the unit without causing damage to human health.
In some embodiments, the radius R is greater than or equal about 0.1 mm and less than or equal to about 0.85 mm. By setting the radius R in the above range, the accumulated water at the substantially-circular arc segments may be reduced, so that no water may drop from the substantially-circular arc segments.
Particularly, the inclination angle β is larger than or equal to about 5°. More particularly, the inclination angle β is less than or equal to about 20°.
In one embodiment, a fin pitch P of the fin is larger than about 2.5 mm. More particularly, the fin pitch P is larger than or equal to about 2.8 mm and less than or equal to about 7 mm.
In one embodiment, W × sinα≥ 0.6 mm, in which W is an interval between adjacent louvers, and α is a louver angle of the louver. More particularly, 0.8 mm ≤ W x sinα≤ 3.0 mm.
According to a second aspect of the present disclosure, a heat exchanger is provided, comprising: a first header; a second header spaced apart from the first header; a plurality of tubes spaced apart from each other and each connected between the first and second headers in fluid communication therewith; and a plurality of corrugated fins each disposed between adjacent tubes, in which the fin is one according to the first aspect of the present disclosure.
Moreover, each tube comprises two straight segments and a bent segment connected between the two straight segments and twisted relative to the two straight segments by a predetermined angle, and no fins are disposed between adjacent the bent segments.
The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The Figures and the detailed description which follow more particularly exemplify illustrative embodiments.
Additional aspects and advantages of the embodiments of the present disclosure will be given in part in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and advantages of the disclosure will become apparent and more readily appreciated from the following descriptions taken in conjunction with the drawings in which:

Fig. 1 is schematic view of a portion of the corrugated fin according to an embodiment of the present disclosure;
Fig. 2 is a sectional view of the fin taken along a line B-B in Fig. 1;
Fig. 3 is a principle force diagram of the condensate on the connection segment of the fin shown in Fig. 1;
Fig. 4 shows a relationship between a louver length of the louver, a capacity of the fin and an air velocity on the surface of the fin;
Fig. 5 shows a relationship between a louver length of the louver, an air resistance of the fin and an air velocity on the surface of the fin;
Fig. 6 is a relational graph between the radius of the substantially-circular arc segment, the adsorption force of the condensate and the sum of the gravity of the condensate and the pushing force of the air;
Fig. 7 is a schematic view of the heat exchanger according to an embodiment of the present disclosure;
Fig. 8 is a perspective view of the heat exchanger according to another embodiment of the present disclosure;
Fig. 9 is a side view of the heat exchanger shown in Fig. 7 in use; and
Fig. 10 is a side view of the heat exchanger shown in Fig. 8 in use.

DETAILED DESCRIPTION

Reference will be made in detail to embodiments of the present disclosure. The embodiments described herein with reference to the accompany drawings are explanatory and illustrative, which are used to generally understand the present disclosure. The embodiments shall not be construed to limit the present disclosure. The same or similar elements and the elements having same or similar functions are denoted by like reference numerals throughout the descriptions.
In the description, relative terms such as "longitudinal", "lateral", "front", "rear", "right", "left", "lower", "upper", "horizontal", "vertical", "above", "below", "up", "top", "bottom" as well as derivative thereof (e.g., "horizontally", "downwardly", "upwardly", etc.) should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of description and do not require that the present disclosure be constructed or operated in a particular orientation.
Terms concerning attachments, coupling and the like, such as "connected" and "interconnected", refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.
The corrugated fin according to an embodiment of the present disclosure will be described in detail with reference to the drawings.
As shown in Figs. 1-2, the corrugated fin 4 according to an embodiment of the present disclosure comprises substantially-circular arc segments 41 and connection segments 42. The substantially-circular arc segments 41 are connected with the connection segments 42 alternatively in a longitudinal direction such that a plurality of corrugations are formed and the substantially-circular arc segments 41 form crests and troughs of the corrugated fin 4 respectively. In other words, the connection segment 42 can be referred as "fin wall" of a corrugation of the corrugated fin 4 and the substantially-circular arc segment 41 can be referred as "crest" and "trough" of a corrugation of the corrugated fin 4.
Each connection segment 42 is formed with a plurality of louvers 43. In some embodiments, for example, the corrugated fin 4 may be made of aluminum material, however, the present disclosure is not limited to this.
In the example shown in Figs. 1-2, the connection segment 42 is a straight segment. It will be appreciated that the present disclosure is not limited to this, for example, the connection segment 42 may also have an actuate shape.
A portion of the corrugated fin 4 is shown in Fig. 1. It will be appreciated that the corrugated fin 4 may have any suitable length in the longitudinal direction (i.e., an up and down direction in Fig. 1). In other words, the corrugated fin 4 may have any suitable number of corrugations.
As shown in Figs. 1-2, in order to improve the heat exchange performance, a plurality of louvers 43 are formed in each connection segment 42, the louver 43 may be formed by cutting and bending a certain portion of the connection segment 42 so as to form a vane 431 and an opening 432. For example, a portion of the connection segment 42 is cut and turned over from a surface of the connection segment 42, in which α is the louver angle (i.e., an inclination angle of the vane 431 with respect to the plane of the connection segment 42, as shown in Fig. 2), W is an interval between adjacent louvers 43 (i.e., a straight line length between adjacent louvers 43 in the a transversal direction to the length direction of the louver 43), H ₂ is a louver length of the louver 43 (i.e., a dimension of the louver 43 in a right and left direction in Fig. 1), and S is an vane distance (i.e., a straight line distance between the adjacent vanes 43, as shown in Fig. 2). A fin pitch P is a spacing between adjacent crest and trough (i.e., adjacent substantially-circular arc segments), in other words, the fin pitch P is a straight line distance between two points with the same phase relationship of the corrugated fin 4 in the longitudinal direction.
If the heat exchanger is used as an evaporator, when the heat exchanger is the flat plate-shaped heat exchanger and inclined with respect to a horizontal direction (as shown in Fig. 9) or the heat exchanger is a bent heat exchanger (as shown in Fig. 10), during the operation or stoppage, the condensate on the surface of the corrugated fin 4 may directly drop from the surface of the corrugated fin 4.
More particularly, the condensate may be accumulated on the surface of the corrugated fin under the following conditions: 1) the smaller the radius R of the substantially-circular arc segment, the greater the surface tension of the condensate is, so that the condensate tends to be accumulated on the substantially-circular arc segment; 2) the smaller the fin pitch P of the fin is, the more condensate tends to accumulate between adjacent connection segments; and 3) the smaller the interval W between adjacent louvers is, the more condensate tends to accumulate between adjacent louvers.
The heat exchange performance, the air resistance and the accumulated water on the surface of the heat exchanger using the corrugated fin have direct relationship to the louver length H₂. The larger the louver length H ₂ of the louver, the better the heat exchange performance is and the larger the air resistance is, consequently, more water is accumulated on the fin.
As shown in Figs. 4-5, the inventors of the present disclosure find that: when the louver length H ₂ is greater than a length L of the connection segment 42 that is, the louver 43 is extended into the substantially-circular arc segment 41, the increasing trend of the performance of the heat exchanger becomes weak and the increasing trend of the air resistance becomes strong.
It may be obtained from the geometry that: L = (H ₁-2R+2Rsinβ)/cosβ.
Certainly, the larger the louver length H ₂, the more water accumulated on the louver is, and the easier the water drops. For this, it is proved by the inventors of the present disclosure through comprehensive considerations and experiments that: it is advantageous to set 0 ≤ H ₂ ≤ (H ₁-2R+2Rsinβ)/cosβ for preventing water from dropping downwards from the fin, in which H ₂ is the louver length, H ₁ is the height of the fin, R is the radius of the substantially-circular arc segment, and β is the inclination angle of the connection segment.
In order to ensure that no water drops directly from the substantially-circular arc segments 41, the radius R shall be small enough. Considering actual use, there is a limit to decrease the radius R, that is, the radius R can not be decreased infinitely, so that the condensate is unavoidable to accumulate on the substantially-circular arc segments 41. Therefore, it is advantageous to increase the surface tension of water and reduce the weight of the water.
It is confirmed by the inventors that the water may not drop directly from the substantially-circular arc segment 41 if the radius R is less than or equal to 0.85 mm.
The adsorption force of the condensate to the substantially-circular arc segment 41 may be calculated by the following formula: $F = πRcσ / 180$

in which F is the adsorption force, σ is the surface tension coefficient, c is the central angle of the substantially-circular arc segment, and R is the radius of the substantially-circular arc segment.
The weight of the condensate on the substantially-circular arc segment may be calculated by the following formula: $G = (4 / 3) π R^{3} ρg$

in which ρ is the density of the condensate, g is the acceleration of gravity, and R is the radius of the substantially-circular arc segment.
At the same time, if the air blows downwards, the air will apply a downward pushing force M to the accumulated water on the corrugated fin 4, $M = π R^{2} μ^{2} / 2 ρ_{k}$

in which ρ _k is the density of the air, R is the radius of the substantially-circular arc segment, and µ is the flowing velocity of the air.
In order to ensure that no water drops from the substantially-circular arc segment 41, the following formula shall be satisfied: F ≥ G + M.
As shown in Fig. 4, it may be obtained that the adsorption force shall be greater than or equal to the sum of the gravity of water and the pushing force of the air in order to avoid dropping of the condensate from the substantially-circular arc segment 41, that is, the radius R of the substantially-circular arc segment 41 shall be less than or equal to about 0.85 mm. Meanwhile, considering the machinability, the radius R is advantageous to be greater than or equal to about 0.1 mm.
Certainly, under the above conditions, when the air blows upwards, it can be also ensured that no condensate drops from the substantially-circular arc segment 41.
Therefore, by setting the radius R in a range of about 0.1 mm-about 0.85 mm, the adsorption force of the condensate on the substantially-circular arc segment 41 may be greater than the sum of the gravity of the condensate and the pushing force of the air, thus avoiding dropping of the condensate from the substantially-circular arc segment 41. Therefore, the water is prevented from dropping downwards into the air pipe from the substantially-circular arc segment 41.
For the connection segments 42 of the corrugated fin 4, if the condensate thereon may not be removed in time, it may drop from the connection segments 42 into the air pipe, so that the water leakage may occur in the unit using the heat exchanger, the air pipe may be corroded and bacteria may breed in the corroded air pipe, thus shortening the service life of the unit and causing damage to human health.
In order to ensure that no water drops from the connection segments 42, as shown in Figs. 1 and 3, the inclination angle β of the connection segment 42 shall be big enough. Therefore, the condensate will flow downwards along the connection segment 42, and consequently flow into the water collecting pan (not shown) along the tube 3, so that no water is accumulated on and dropped from the connection segment 42. Meanwhile, the fin pitch P shall be large enough.
As analyzed by experiments, when the down sliding force of the water on an inclined surface of aluminum alloy fin 4 is greater than the friction force, that is, mg.sinβ > ƒN, in which ƒ is the friction coefficient, and β is the inclination angle of the connection segment, as shown in Fig. 1, water may slide downwards. As shown in Fig. 3, according to the force analysis, an equation N = mg.cosβ is obtained, and tanβ > ƒ is obtained by substituting the equation into the formula mg. sinβ > ƒN. It may be obtained by the inventors of the present disclosure that: when the inclination angle β is greater than or equal to about 5°, water starts to flow downwards on the surface of connection segment. Therefore, it is obtained that the inclination angle β shall be greater than or equal to about 5°. Meanwhile, considering machinability, β shall be in a range of about 5°-about 20°.
It is confirmed by the inventors of the present disclosure that: when the fin pitch P is substantially larger than about 2.5 mm, no condensate presents between adjacent connection segments 42. However, the larger the fin pitch P, the lower the performance of the heat exchanger is. Meanwhile, considering machinability, it is advantageous that the fin pitch P is substantially in a range of about 2.8 mm-7 mm.
The accumulated water between adjacent louvers 43 is mainly caused by the surface tension of water. If the vane distance S of the louver 43 is increased, the surface tension of water between the adjacent louvers 43 may be reduced or eliminated, thus decreasing or eliminating the accumulated water between the adjacent louvers 43. It is confirmed by the inventors of the present disclosure that: the surface tension of water between the adjacent louvers 43 may be effectively decreased if the vane distance S = W × sinα ≥ 0.57 mm. For this reason, it is advantageous that W × sinα ≥ 0.6 mm. More particularly, 0.8 mm ≤ W × sinα ≤3.0 mm.
With the corrugated fin 4 according to an embodiment of the present disclosure, the water drainage performance is improved, and it may be reduced or eliminated that the condensate drops into the air pipe from the surface of the heat exchanger using the corrugated fin 4, thus prolonging the life of the unit and reducing the harm of the bacteria.
The heat exchanger according to an embodiment of the present disclosure will be described below with reference to the drawings.
As shown in Fig. 7, the heat exchanger according to an embodiment of the present disclosure comprises a first header 1, a second header 2, a plurality of tubes 3 and a plurality of corrugated fins 4.
The second header 2 is spaced apart from and substantially parallel to the first header 1. The tubes 3 are arranged and spaced apart from each other in a direction parallel to the axial direction of the first and second headers 1 and 2. Two ends of each tube 3 are connected to the first header 1 and the second header 2 respectively to communicate the first header 1 and the second header 2. The fins 4 are disposed between adjacent tubes 3, in which the corrugated fin 4 may be one described with reference to the above embodiments.
In one embodiment, the tube 3 may be a flat tube, for example, the shape of the cross section of the tube 3 may be a rectangle, an oblong presenting flat sides interconnecting two round ends, or a flat ellipse.
In an example, the heat exchanger may have a flat plate shape. When used as an evaporator, the heat exchanger is inclined with respect to the horizontal plane, and as shown in Fig. 9, air blows from an air outlet to the surface of the heat exchanger in a direction A. As described above, because no condensate drops, the performance of the heat exchanger may not be influenced, the heat exchanger may not be damaged, and the harm of the bacteria may be avoided.
As shown in Fig. 8, in some embodiments, the heat exchanger has a bent structure. In a specific example, each tube 3 comprises two straight segments 31 and a bent segment 32 connected between the two straight segments 31 and twisted relative to the two straight segments 31 by a predetermined angle, and each fin 4 is only disposed between adjacent straight segments 31, in other words, no fins are disposed between adjacent bent segments 32.
Certainly, the heat exchanger having a bent structure is not limited to the above examples, for example, the bent heat exchanger may be formed by two flat plate-shaped heat exchangers connected in series via a connecting pipe and forming a certain intersection angle therebetween.
With the heat exchanger having a bent structure according to an embodiment of the present disclosure, in use, the heat exchanger portions on two sides are inclined at a certain angle with respect to the horizontal plane, and as shown in Fig. 10, air blows from an air outlet to the heat exchanger in a direction A. As described above, because no condensate drops, no water leakage may occur, the air pipe may not be corroded and bacteria may not breed in the corroded air pipe, thus lengthening the life of the unit such as an air conditioner without causing damage to human health.
Reference throughout this specification to "an embodiment", "some embodiments", "one embodiment", "an example", "a specific example", or "some examples" means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the disclosure. Thus, the appearances of the phrases such as "in some embodiments", "in one embodiment", "in an embodiment", "an example", "a specific example", or "some examples" in various places throughout this specification are not necessarily referring to the same embodiment or example of the disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.
Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that changes, alternatives, and modifications all falling into the scope of the claims and their equivalents may be made in the embodiments without departing from spirit and principles of the disclosure.

Claims

A corrugated fin, comprising:
connection segments each formed with a plurality of louvers; and

substantially-circular arc segments connected with the connection segments alternatively in a longitudinal direction such that a plurality of corrugations are formed and the substantially-circular arc segments form crests and troughs of the corrugations respectively,

wherein 0≤H ₂≤(H ₁-2R+2Rsinβ)/cosβ
in which H ₂ is a louver length of the louver, H ₁ is a height of the fin, R is a radius of the substantially-circular arc segment, and β is an inclination angle of the connection segment.
The corrugated fin according to claim 1, wherein the radius R is greater than or equal about 0.1 mm and less than or equal to about 0.85 mm.
The corrugated fin according to claim 1 or 2, wherein the inclination angle β is larger than or equal to 5°.
The corrugated fin according to claim 3, wherein the inclination angle β is less than or equal to 20°.
The corrugated fin according to any one of claims 1-4, wherein W × sinα ≥ 0.6 mm, in which W is an interval between adjacent louvers, and α is a louver angle of the louver.
The corrugated fin according to claim 1, wherein a fin pitch P of the fin is larger than 2.5 mm.
The corrugated fin according to claim 6, wherein the fin pitch P is larger than or equal to 2.8 mm and less than or equal to 7 mm.
The corrugated fin according to claim 6 or 7, wherein W × sinα≥ 0.6 mm, in which W is an interval between adjacent louvers, and α is a louver angle of the louver.
The corrugated fin according to claim 8, wherein 0.8 mm ≤ W × sinα≤ 3.0 mm.
A heat exchanger, comprising:
a first header;

a second header spaced apart from the first header;

a plurality of tubes spaced apart from each other and each connected between the first and second headers in fluid communication therewith; and

a plurality of corrugated fins each disposed between adjacent tubes, in which each fin is one according to any of claims 1-9.
The heat exchanger according to claim 10, wherein each tube comprises two straight segments and a bent segment connected between the two straight segments and twisted relative to the two straight segments by a predetermined angle, and no fins are disposed between adjacent the bent segments.