US20090173479A1 - Louvered air center for compact heat exchanger - Google Patents

Abstract

A louvered fin of a heat exchanger assembly includes a louvered portion having a plurality of first louvers each extending along a first louver centerline as well as a plurality of second louvers each extending along a second louver centerline. Each set of louver centerlines are parallel to one another and disposed side by side along a respective axis extending transversely to the centerlines. The first louvers are disposed at a first angle and the second louvers are disposed at a second angle relative to the respective axes. The two axes extend parallel to one another and are spaced from one another in a length direction transverse to the centerlines and the axes.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• A heat exchanger assembly for dissipating heat and more specifically, a heat exchanger assembly having fins.
• 2. Description of the Prior Art
• A heat exchanger assembly generally includes a plurality of tubes each extending parallel to and spaced from one another for transferring heat from a refrigerant flowing through the tubes. A plurality of undulating fins zigzag back and forth between adjacent ones of the tubes to define air channels.
• Each one of the fins typically define at least one louvered portion which has a plurality of louvers each extending parallel to one another and disposed along a single axis, referred to as the louvered air center. Generally, if included the louvers of a second louvered portion are also disposed along the same single axis. The louvers are angled relative to the fin surface such that the louvers divert some of the air flowing through each of the air channels through the fin and into adjacent air channels.
• Louvered air center performance is critical to the heat transfer rate of compact heat exchangers, such as radiator, heaters, condensers, and evaporators. A typical louvered air center includes a plurality of louvered portions on each fin, e.g., a leading margin, a turn-around margin, and a trailing margin. The actual airflow path in the air center can be theoretically divided into two different flow paths, louver flow and channel flow. Channel flow is defined as the flow along the air channels. Louver flow is defined as the flow between the louvers into adjacent air channels. The greater the percentage of air flowing between the louvers as louver flow, the greater the heat transfer and airflow efficiency.
• For a given distance between two groups of louvers, i.e., the width of each air channel formed by the zigzagging fin, smaller louver widths result in a thinner thermal boundary layer which increases heat transfer for the assembly. On the other hand, the smaller louver widths also result in a larger gap between two adjacent groups of louvers, i.e., a larger air channel width, which results in a higher percentage of channel flow and therefore lower heat transfer performance. Accordingly, in the current heat exchanger fin designs, there is an optimum louver width for a given air channel width wherein performance cannot be further improved.
• Although the prior heat exchanger assemblies are sufficient for their intended purposes, there is a continuing need for more efficient and improved assemblies.
SUMMARY OF THE INVENTION
• The invention includes a louvered portion having a plurality of first louvers each extending in a height direction along a first louver centerline as well as a plurality of second louvers each extending in the height direction along a second louver centerline. The first louver centerlines are parallel to one another and disposed side by side along a first axis extending in a width direction transverse to the height direction and the second louver centerlines are parallel to one another and disposed side by side along a second axis extending in the transverse width direction. The first louvers are disposed at a first angle and the second louvers are disposed at a second angle relative to the transverse width direction. The second axis extends parallel to said first axis and spaced from said first axis in a length direction transverse to the height direction and the width direction.
• The invention reduces the thermal boundary layer of each louver which improves performance while simultaneously reducing the amount of channel flow which also improves performance.
BRIEF DESCRIPTION OF THE DRAWINGS
• Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
• FIG. 1 is a perspective view of a heat exchanger assembly illustrating two fins each having a plurality of louvered portions;
• FIG. 2 is an enlarged view of a fin of FIG. 1 illustrating the first and second louvers of one louvered portion;
• FIG. 3 is a schematic view showing a cross-section of an alternative embodiment of the fins of FIG. 1 illustrating parallel first and second louvers;
• FIG. 3A is an enlarged view of area 3A in FIG. 3;
• FIG. 4 is a schematic view showing a cross-section of an alternative embodiment of the fins of FIG. 1;
• FIG. 5 is a schematic view showing a cross-section of an alternative embodiment of the fins of FIG. 1 illustrating parallel first, second, and third louvers;
• FIG. 5A is an enlarged view of area 5A in FIG. 5;
• FIG. 6 is a schematic view showing a cross-section of an alternative embodiment of the fins of FIG. 1 illustrating non-parallel first and second louvers;
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
• Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a heat exchanger assembly for dissipating heat is generally shown. As shown in FIG. 1, a plurality of tubes 20 each extend between ends in a length direction A_L and between sides in a width direction A_W transverse to the length direction A_L for transferring heat from a refrigerant flowing through the tubes 20. The tubes 20 are parallel to one another and spaced from one another in a height direction A_H transverse to the length direction A_L and the width direction A_W. The length direction A_L is perpendicular to the height direction A_H and the width direction A_W is perpendicular to the height direction A_H and the length direction A_L.
• A plurality of fins 22 each are zigzagged back and forth in the height direction A_H between adjacent ones of the tubes 20 for receiving heat from the tubes 20. The fins 22 are disposed along the length direction A_L between the ends of the tubes 20 to define an air channel 24. The air channels 24 extend between the sides of the tubes 20 in the width direction A_W.
• Each one of the fins 22 define at least one louvered portion 26 to divert some of the air flowing through each of the air channels 24, through the fin 22 and into an adjacent one of the air channels 24.
• As shown in FIG. 2, the louvered portion 26 has a plurality of first louvers 28 each extending in the height direction A_H along a first louver centerline CL₁. The first louver centerlines CL₁ are parallel to one another and are disposed side by side along a first axis A₁. The first axis A₁ extends in the transverse width direction A_W. The first louvers 28 are parallel to one another and are all disposed at a first angle θ₁ relative to the transverse width direction A_W.
• The louvered portion 26 also has a plurality of second louvers 30 each extending in the height direction A_H along a second louver centerline CL₂. Similarly, the second louver centerlines CL₂ are parallel to one another and disposed side by side along a second axis A₂ extending in the transverse width direction A_W. The second louvers 30 are also parallel to one another and are all disposed at a second angle θ₂ relative to the transverse width direction A_W.
• The second axis A₂ extends parallel to the first axis A₁ and is spaced from the first axis A₁ in the length direction A_L, as best shown in FIGS. 3-6.
• As best shown in FIGS. 3 and 4, each one of the second louver centerlines CL₂ is spaced from a corresponding one of the first louver centerlines CL₁ in the length direction A_L by a first distance a. Each one of the second louver centerlines CL₂ is also offset from the corresponding one of the first louver centerlines CL₁ in the width direction A_W by a second distance b.
• The first distance a, the second distance b, and the first angle θ₁ are interrelated according to a first relationship defined as tan⁻¹(a/b)≠₁. FIGS. 3 and 5 illustrate an embodiment wherein the tan⁻(a/b)>θ₁. FIGS. 4 and 6 illustrate an embodiment wherein the tan⁻¹(a/b)<θ₁.
• In one embodiment shown in FIG. 4, the first distance a, the second distance b, and the first angle θ₁ are interrelated according to a second relationship defined as tan⁻¹(a/b)<θ₁ and the first angle θ₁ and the second angle θ₂ are interrelated according to a third relationship defined as θ₁<θ₂.
• The first angle θ₁ may be equal to the second angle θ₂, as shown in FIGS. 2-5. Alternatively, the first angle θ₁ may be different than the second angle θ₂, as shown in FIG. 6. If the first angle θ₁ is different than the second angle θ₂, as shown in FIG. 6, the difference between the first angle θ₁ and the second angle θ₂ is preferably in the range of 0 to 50% of the first angle θ₁.
• The first louver centerlines CL₁ of the first louvers 28 are each spaced equidistant from one another. Similarly, the second louvers 30 are each spaced equidistant from one another.
• In one embodiment shown in FIG. 5, the louvered portion 26 has a plurality of third louvers 32 each extending in the height direction A_H along a third louver centerline CL₃. The third louver centerlines CL₃ extend parallel to one another and are spaced equidistant from one another. The third louvers 32 are parallel to one another and are all angled at a third angle θ₃ relative to the transverse width direction A_W. Each of the third louvers 32 are disposed side by side along and perpendicular to a third axis A₃. The third axis A₃ extends parallel to and spaced from the second axis A₂ in the length direction A_L.
• Each one of the third louver centerlines CL₃ is spaced from a corresponding one of the second louver centerlines CL₂ in the length direction A_L by the first distance a. Each one of the third louver centerlines CL₃ is also offset from the corresponding one of the second louver centerlines CL₂ in the width direction A_W by the second distance b.
• Each of the third louver centerlines CL₃ are offset from corresponding ones of the second louver centerlines CL₂ in the width direction A_W by the first distance a and are spaced from corresponding ones of the second louver centerlines CL₂ in the length direction A_L by the second distance b. The angles (θ₁, θ₂, θ₃) may all be equal to one another, as shown in FIG. 5 or alternatively may be different (not shown).
• In operation, air flowing through the air channels 24 is diverted through the louvered portions 26 of the zigzagging fin 22 and into adjacent air channels 24. Because the invention requires multiple rows of louvers 28, 30, 32 for each louvered portion 26, the width of each louver may be reduced, reducing the thermal boundary layer and increasing heat transfer, without reducing the gap in the length direction A_L between two parallel louvered portions 26, i.e., without reducing the width of the air channels 24. Accordingly, the invention surpasses the heat transfer of prior assemblies by decreasing louver width below that of the optimum width of the prior assemblies while maintaining the same air channel 24 width.
• While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing form the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (14)

1. A heat exchanger assembly for dissipating heat comprising:

a plurality of tubes each extending between ends in a length direction and between sides in a width direction transverse to said length direction and parallel to and spaced from one another in a height direction transverse to said length direction and said width direction for transferring heat from a refrigerant flowing through said tubes;

a plurality of fins each being zigzagged back and forth between adjacent ones of said tubes in said height direction and disposed along said length direction between said ends of said tubes to define an air channel extending between said sides in said width direction for receiving heat from said tubes;

each of said fins defining at least one louvered portion to divert some of the air flowing through each of said air channels through said fin and into an adjacent one of said air channels;

said louvered portion having a plurality of first louvers each extending in said height direction along a first louver centerline;

said first louver centerlines being parallel to one another and disposed side by side along a first axis extending in said transverse width direction;

said first louvers disposed at a first angle relative to said transverse width direction;

said louvered portion having a plurality of second louvers each extending in said height direction along a second louver centerline;

said second louver centerlines being parallel to one another and disposed side by side along a second axis extending in said transverse width direction;

said second louvers disposed at a second angle relative to said transverse width direction; and

said second axis extending parallel to said first axis and spaced from said first axis in said length direction.

2. The assembly as set forth in claim 1 wherein each of said second louver centerlines are spaced from corresponding ones of said first louver centerlines in said length direction by a first distance and are offset from corresponding ones of said first louver centerlines in said width direction by a second distance.

3. The assembly as set forth in claim 2 wherein said length direction is perpendicular to said height direction and said width direction is perpendicular to said height direction and said length direction.

4. The assembly as set forth in claim 3 wherein said first distance and said second distance and said first angle are interrelated according to a first relationship defined as

${\tan }^{-1}\left(\frac{a}{b}\right)\ne {\theta }_1.$

5. The assembly as set forth in claim 4 wherein said first distance and said second distance and said first angle are interrelated according to a second relationship defined as

${\tan }^{-1}\left(\frac{a}{b}\right)<{\theta }_1$

and said first angle and said second angle are interrelated according to a third relationship defined as θ₁<θ₂.

6. The assembly as set forth in claim 2 wherein said first angle is equal to said second angle.

7. The assembly as set forth in claim 2 wherein said first angle is different than said second angle.

8. The assembly as set forth in claim 2 wherein said first louver centerlines of said first louvers each are spaced equidistant from one another and second louvers are each spaced equidistant from one another.

9. The assembly as set forth in claim 7 wherein a difference between said first angle and said second angle is in a range of 0 to 50% of said first angle.

10. The assembly as set forth in claim 2 wherein said louvered portion has a plurality of third louvers each extending in said height direction along a third louver centerline.

11. The assembly as set forth in claim 10 wherein said third louver centerlines extend parallel to and spaced equidistant from one another and said third louvers are angled at a third angle relative to said transverse width direction;

each of said third louvers being disposed side by side along and perpendicular to a third axis extending parallel to and spaced from said second axis in said length direction.

12. The assembly as set forth in claim 11 wherein each of said third louver centerlines are spaced from corresponding ones of said second louver centerlines in said length direction by said first distance and are offset from corresponding ones of said second louver centerlines in said width direction by said second distance.

13. The assembly as set forth in claim 12 wherein said angles are equal to one another.

14. A heat exchanger assembly for dissipating heat comprising:

a plurality of tubes each extending between ends in a length direction and between sides in a width direction and parallel to and spaced from one another in a height direction for transferring heat from a refrigerant flowing through said tubes;

a plurality of fins each being zigzagged back and forth between adjacent ones of said tubes in a height direction transverse to said length direction and disposed along said length direction between said ends of said tubes to define air channels in said width direction transverse to said length direction and height direction for receiving heat from said tubes;

each of said fins defining at least one louvered portion to divert some of the air flowing through each of said channels through said fin and into an adjacent one of said air channels;

each louvered portion having a plurality of first louvers each extending in said height direction along a first louver centerline;

said first louver centerlines being parallel to and spaced equidistant from one another and disposed at a first angle relative to said transverse width direction;

said first louver centerlines being disposed side by side along and perpendicular to a first axis extending transversely to said tubes in said width direction;

said louvered portion having a plurality of second louvers each extending in said height direction along a second louver centerline;

said second louver centerlines being parallel to and spaced equidistant from one another and angled at a second angle relative to said transverse width direction;

said second louver centerlines being disposed side by side along and perpendicular to a second axis extending parallel to said first axis and spaced from said first axis in said length direction;

said louvered portion having a plurality of third louvers each extending in said height direction along a third louver centerline;

said third louver centerlines being parallel to and spaced equidistant from one another and angled at a third angle relative to said transverse width direction;

said third louvers each being disposed side by side along and perpendicular to a third axis extending parallel to and spaced from said second axis in said length direction;

each of said second louver centerlines being spaced from corresponding ones of said first louver centerlines in said length direction by a first distance and being offset from corresponding ones of said first louver centerlines in a width direction by a second distance;

each of said third louver centerlines being spaced from corresponding ones of said second louver centerlines in said length direction by said first distance and being offset from corresponding ones of said second louver centerlines in a width direction by said second distance;

said first distance and said second distance and said first angle being interrelated according to a first relationship defined as

${\tan }^{-1}\left(\frac{b}{a}\right)\ne {\theta }_1;$

and

said angles being equal to one another.

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