Heat Exchanger Assembly

Abstract

A heat exchanger assembly including first and second manifolds for transferring heat between a coolant and a flow of air. Tubes extend between the manifolds for conveying the coolant therebetween. Air fins are disposed between adjacent tubes, and each air fin has a cross-section presenting a legs extending between the adjacent tubes at equal and opposing angles to one another and bases interconnecting alternate ends of the adjacent legs to present a serpentine pattern. Each base extends through an arc between the ends of the adjacent legs and defines a lead-in radius interconnecting each base with one of the legs and an exit radius interconnecting each base with the end of the adjacent leg. The equal and opposing angles are in the range of 1 to 4 degrees. The lead-in and exit radii are in the range of 0.05 to 0.15 mm. The middle radius is in the range of 0.5 to 1.5 mm.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

A heat exchanger assembly for transferring heat between a coolant and a flow of air, and specifically to an improved air fin design.

2. Description of the Prior Art

Japanese Patent Application No. 10365226, issued to Hiroshi et al., shows a heat exchanger assembly for transferring heat between a coolant and a flow of air. The '388 application includes a first manifold and a second manifold, and a plurality of tubes extending in spaced and parallel relationship with one another between the first and second manifolds for conveying the coolant between the first and second manifolds. Adjacent tubes are spaced from one another by a fin space, and a plurality of air fins are disposed in the fin spaces. Each of the air fins has a cross-section presenting a plurality of legs and a plurality of bases interconnecting alternate ends of adjacent legs and engaging the adjacent tubes to present a serpentine pattern. Each of the bases extends through an arc between the ends of the adjacent legs and defines a lead-in radius interconnecting each base with one of the legs and an exit radius interconnecting each base with the other of the adjacent legs. A middle radius extends between the lead-in and exit radii.

U.S. Pat. No. 6,439,300, issued to Falta et al. on Aug. 27, 2002, shows a heat exchanger assembly including a plurality of air fins having a cross-section presenting a plurality of legs extending at equal and opposing angles to one another.

SUMMARY OF THE INVENTION

The invention is for such a heat exchanger assembly wherein the equal and opposing angles of the legs of the air fins are in the range of 1 to 4 degrees, the lead-in radius is in the range of 0.05 to 0.15 mm, the exit radius is in the range of 0.05 to 0.15 mm, and the middle radius is in the range of 0.5 to 1.5 mm.

The legs of the air fins are angled to maintain the structural integrity of the heat exchanger, i.e. to prevent the legs from collapsing during the manufacturing or use of the heat exchanger. However, the maximum angle is set at 4 degrees to maximize the length of the louvers on the legs of the air fin, and thereby avoid a pressure drop penalty, which results from having shorter louvers. Such a pressure drop negatively impacts the performance of the heat exchanger. Additionally, the angled legs improve the ability of the heat exchanger to shed water.

The lead-in and exit radii are minimized in order to maximize the length of the louvers, and thereby limit the pressure drop penalty explained above. However, the lead-in and exit radii must be large enough to allow the forming tool to release from the air fin at production speeds.

Finally, during the brazing process of joining the manifolds, tubes, and air fins together, because the areas of contact between the air fins and the flat sides of the tubes is not flat, but instead has a middle radius, capillary action by the brazing material occurs during the brazing process. In other words, a portion of the liquefied brazing material is pulled along the middle radius of the air fin. Upon cooling, the brazing material solidifies to form a strong fillet bonding the tubes to the air fins. This fillet is not only structurally strong, but it is also thermally conductive, thereby improving heat conduction from the coolant in the tubes to the air fins.

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 and partially exploded view of the heat exchanger assembly of the subject invention;

FIG. 2 is a perspective and fragmentary view of the air fins and tubes of the subject invention; and

FIG. 3 is a front view of one of the air fins extending between adjacent tubes.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a heat exchanger assembly 20 for transferring heat between a coolant and a flow of air is generally shown in FIG. 1. The heat exchanger assembly 20 has a number of uses, including but not limited to use as a: radiator, condenser, heater, evaporator, chiller or cooler.

The assembly includes a first manifold 22 and a second manifold 24 in spaced and parallel relationship with one another. A plurality of tubes 26, generally indicated in FIGS. 2 and 3, extend in spaced and parallel relationship with one another between the first and second manifolds 22, 24 for conveying the coolant between the first and second manifolds 22, 24. Each of the tubes 26 has a cross-section presenting flat sides 28 extending in a transverse direction interconnected by round ends 30. The flat sides 28 of adjacent tubes 26 are spaced from one another by a fin space 32.

A plurality of air fins 34, generally indicated in FIGS. 2 and 3, are disposed in the fin spaces 32 between the flat sides 28 of adjacent tubes 26. Each of the air fins 34 has a cross-section presenting a plurality of legs 36 extending between the flat sides 28 of the adjacent tubes 26. Each of the legs 36 of the air fins 34 presents a plurality of louvers 38 for conveying the flow of air through the legs 36 between adjacent fin spaces 32. Heat exchangers having parallel legs have a tendency to collapse during the manufacturing or use. Therefore, in the subject invention, the legs 36 of the air fins 34 are disposed at equal and opposing angles Φ to one another to maintain the structural integrity of the heat exchanger assembly 20. However, the angle Φ the fins are disposed at is preferably minimized to enhance the length of the louvers 38, and thereby, improve the air flow between the adjacent fin spaces 32. The larger the angle Φ, the greater the pressure drop created by the louvers 38. Therefore, in the subject invention, the angle Φ of the opposing legs 36 is preferably in the range of 1 to 4 degrees and is most preferably 1.53 degrees. Another advantage to having the legs 36 of the air fins 34 disposed at an angle Φ is the improved ability to shed water when the heat exchanger assembly 20 is used as an evaporator. In other words, when water condenses on the legs 36 of the air fins 34, gravity carries it down the slope of the angled legs 36, and the liquid water eventually spills off the air fin 34. In contradistinction, water tends to rest on the legs of parallel air fins.

A plurality of bases 40 interconnect alternate ends of adjacent legs 36 and engage the flat sides 28 of the adjacent tubes 26. The bases 40 and legs 36 of the air fins 34 present a serpentine pattern extending between the first and second manifolds 22, 24. Each of the legs 36 of the air fins 34 has a length L, preferably in the range of 5 to 6 mm.

Each of the bases 40 of the air fins 34 has a base width W_b, and adjacent bases 40 are spaced from one another along the flat sides 28 of the tubes 26 by a span S. The ratio of the base width W_b to the span S is preferably in the range of 0.80 to 0.90 to maximize the length of the louvers 38, and thereby, minimize the pressure drop penalty explained above.

Each of the bases 40 extends through an arc between the ends of the adjacent legs 36. Each base 40 defines a lead-in radius R₁ integrally connected with one of the legs 36 and an exit radius R₂ integrally connected with the other of the adjacent legs 36. The lead-in and exit radii R₁, R₂ are minimized in order to maximize the length of the louvers 38, and thereby limit the pressure drop penalty explained above. However, the lead-in and exit radii R₁, R₂ must be large enough to allow the forming tool to release from the air fin 34 at production speeds. Additionally, the forming tool can overheat when making air fins 34 with small lead-in and exit radii R₁, R₂. The lead-in and exit radii R₁, R₂ are preferably the same, and in the range of 0.05 to 0.15 mm. A middle radius R₃ extends between the lead-in and exit radii R₁, R₂. The middle radius R₃ is greater than the lead-in and exit radii R₁, R₂, and is preferably in the range of 0.5 to 1.5 mm.

The manifolds 22, 24, tubes 26, and air fins 34 are joined together using a brazing process. Because the area of each air fin 34 in contact with the flat sides 28 of the tubes 26 is not flat, but instead has a middle radius R₃, capillary action by the brazing material occurs during the brazing process. In other words, a portion of the liquefied brazing material is pulled along the middle radius R₃ of the air fin 34. Upon cooling, the brazing material solidifies to form a strong fillet bonding the tubes 26 to the air fins 34. This fillet is not only structurally strong, but is also thermally conductive, thereby improving heat conduction from the coolant in the tubes 26 to the air fins 34.

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 from 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

1. A heat exchanger assembly for transferring heat between a coolant and a flow of air comprising: a first manifold;a plurality of tubes extending in spaced and parallel relationship with one another for conveying the coolant;adjacent ones of said tubes being spaced from one another by a fin space;a plurality of air fins disposed in said fin space having a cross-section presenting a plurality of legs extending between said adjacent tubes at equal and opposing angles to one another and said bases interconnecting alternate ends of adjacent legs and engaging said adjacent tubes to present a serpentine pattern;each of said bases extending through an arc between said ends of said adjacent legs and defining a lead-in radius interconnecting said bases with one of said legs and an exit radius interconnecting each of said bases with the other of said adjacent legs and a middle radius extending between said lead-in and exit radii;said equal and opposing angles being in the range of 1 to 4 degrees;said lead-in and exit radii being in the range of 0.05 to 0.15 mm; andsaid middle radius is in the range of 0.5 to 1.5 mm.

2. The assembly as set forth in claim 1 wherein said lead-in radius is equal to said exit radius.

3. The assembly as set forth in claim 1 wherein said lead-in and exit radii are each less than said middle radius.

4. The assembly as set forth in claim 1 wherein each of said bases has a base width and adjacent ones of said bases are spaced from one another by a span and the ratio of said base width to said span is in the range of 0.80 to 0.90.

5. The assembly as set forth in claim 4 wherein said base width is in the range of 1.00 to 2.25 mm.

6. The assembly as set forth in claim 1 wherein said equal and opposing angles are further defined as 1.53 degrees.

7. The assembly as set forth in claim 1 wherein each of said legs of said air fins presents a plurality of louvers for conveying the flow of air through said legs between adjacent fin spaces.

8. The assembly as set forth in claim 1 wherein each of said air fins has a length in the range of 5 to 6 mm.

9. The assembly as set forth in claim 1 further including a second manifold in spaced and parallel relationship with said first manifold and wherein said tubes extend between said first and second manifolds for conveying the coolant between said first and second manifolds.

10. The assembly as set forth in claim 1 wherein each of said tubes has a cross-section presenting flat sides extending in a transverse direction interconnected by round ends.

11. A heat exchanger assembly for transferring heat between a coolant and a flow of air comprising: a first manifold and a second manifold in spaced and parallel relationship with one another;a plurality of tubes extending in spaced and parallel relationship with one another between said first and second manifolds for conveying the coolant between said first and second manifolds;each of said tubes having a cross-section presenting flat sides extending in a transverse direction interconnected by round ends with said flat sides of adjacent tubes spaced from one another by a fin space;a plurality of air fins disposed in said fin space between said flat sides of said adjacent tubes;each of said air fins having a cross-section presenting a plurality of legs extending between said flat sides of said adjacent tubes at equal and opposing angles to one another and bases interconnecting alternate ends of adjacent legs and engaging said flat sides of said adjacent tubes to present a serpentine pattern extending between said first and second manifolds;said equal and opposing angles being in the range of 1 to 4 degrees;said equal and opposing angles being further defined as 1.53 degrees;each of said bases extending through an arc between said ends of said adjacent legs and defining a lead-in radius interconnecting each of said bases with one of said legs and an exit radius interconnecting each of said bases with the other of said adjacent legs and a middle radius extending between said lead-in and exit radii;each of said legs of said air fins presenting a plurality of louvers for conveying the flow of air through said legs between adjacent fin spaces;each of said legs of said air fins having a length;said length being in the range of 5 to 6 mm;each of said bases of said air fins having a base width;adjacent ones of said bases being spaced from one another along the associated one of said flat sides of said tubes by a span;the ratio of said base width to said span being in the range of 0.80 to 0.90;said lead-in radius being equal to said exit radius;said lead-in and exit radii being less than said middle radius;said lead-in and exit radii being in the range of 0.05 to 0.15 mm; andsaid middle radius being in the range of 0.5 to 1.5 mm.