Variable fin density coil

Abstract

A heat exchanging coil that has at least one straight length of tube and at least one bend in the tube where fins are attached to the tube with unequal fin densities based upon tube orientation, and the fin density is different for straight lengths of tube than at bends in the tube.

Description

RELATED APPLICATION

This application claims the benefit, and priority benefit, of U.S. provisional patent application Ser. No. 60/873,096, filed Dec. 6, 2006, entitled Variable Fin Density Coil.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to heat exchanging coils in air conditioning equipment, and more particularly to use of, manufacture of, or systems with variable fin densities in lieu of constant fin densities on the heat-exchanging coils to reduce air flow restrictions at bends in the heat-exchanging coil to achieve greater efficiencies and cost savings.

2. Description of the Related Art

The use of heat-exchanging coils in air conditioning equipment is known in the art as a means of transferring heat from inside of an air-conditioned space to an external heat sink, typically the outdoor environment. The heat-exchanging coil is made of one or more tubes that are connected to allow a heat-exchanging medium to flow through the tubes.

The tubes have a series of protrusions, or fins, that are attached or secured to the exterior of the tubes by various methods and generally are disposed in planes substantially perpendicular to the longitudinal axis of the tubes at the point of connection. The fins increase the convective and conductive heat exchange as a fluid medium, typically air, is forced over the heat-exchanging coil by increasing the surface area for heat exchange between the heat-exchange medium inside of the tubes and the fluid medium passing over the tubes. The reason that the fins are typically disposed substantially perpendicular to the longitudinal axis of the tubes at the point of contact is an attempt to minimize any restrictions in the fluid medium flow as it is forced over the heat-exchanging coil.

The spacing, or fin density, of the fins along the tube is commonly referred to, or measured, as “fins per inch,” or generally the number of fins along a one-inch length of tube. In prior art coils, the fin density is consistent, or constant, no matter the location on the tube where it is measured, i.e., on a straight section of tube or on a bend in the tube. The result is that the fins located on bends in the heat-exchanging coil tube tend to restrict the fluid medium flow over the fins and the tube because the ends of the fins on the interior radial surface of the tube come close to touching or actually touch, thus restricting, or impeding, the air flow between the fins. This restriction in airflow caused by the fins at bends in the tube decreases the efficiency of the heat-exchanging coil, because the area of heat exchange is decreased due to the air restriction at the bend in the tube.

SUMMARY OF THE EMBODIMENTS OF THE INVENTION

An embodiment of the present invention relates to an improved heat-exchanging coil design for air-conditioning equipment and the manufacturing of heat-exchanging coils for air-conditioning equipment wherein variable fin densities are used depending upon the nature of a particular section, or length, of the tube of the heat exchanging coil, e.g. a straight section, or length, of tube; a section having a bend or sharp curve; or a curved section defined by a relatively large radius of curvature.

The tube may be provided with a series of fins disposed substantially perpendicular to the longitudinal axis of the tube at the point of connection between the fin and the outer wall surface of the tube. Straight sections of tube may have a first fin density, while bends in the tube may have a second fin density, and the first fin density may be greater than, or unequal to, the second fin density. Similarly, if the coil is formed with bends and curved sections having relatively large radii of curvature, the curved section may have a first fin density, while bends in the tube may have a second fin density, and the first fin density may be greater than, or unequal to, the second fin density. The second fin density for the bends in the tube may be a constant density or variable along the longitudinal axis of the tube. By using different fin densities based upon the tube orientation, or location on the tube, i.e., straight section, curved section, or at a bend, improved heat exchange is achieved by reducing fluid medium flow restrictions. In a constant fin density heat-exchanging coil, the fins at a bend tend to touch or come close to touching each other on one end, because the fins are perpendicular to the longitudinal axis of the tube at the point of contact.

An embodiment of the present invention relates to manufacturing of heat-exchanging coils with variable fin densities employing various methods for securing fins to the tube. For example, fins may be attached to a heat-exchanging coil tube by helically wrapping fins around the tube with either a first or second fin density. The wrapped fins may then be secured by either a mechanical or welded fastening method.

An alternative method of attaching fins to the tube may include disposing a series of fins along both straight sections of tube and bends in a tube at different densities. For example, a first fin density may be used on the straight lengths of tube, and a second fin density may be used at bends in the tube. Each of the fins may be provided with a fin collar that has a diameter that is greater than the initial outer diameter of the tube at the outer wall surface of the tube. The fin collar with its enlarged diameter allows the fins to be disposed at either a first or second fin density along the outer wall surface of tube. After the fins are disposed along the outer wall surface of tube, the tube may then be expanded from a first tube exterior diameter to a second, enlarged or expanded, tube exterior diameter that is greater than the diameter of the fin collars. Because the diameter of the fin collars is smaller than the second tube exterior diameter, the fins disposed along the tube at a first or second fin density are secured along the outer wall surface of tube by a mechanical bond.

Another embodiment of the present invention relates to air conditioning systems that utilize heat-exchanging coils with variable fin densities. Although any heat-exchanging coil in an air-conditioning system could be replaced with a variable fin density heat-exchanging coil, in a preferred embodiment the condenser coil utilizes the variable fin density of the present invention.

Although common materials for constructing heat exchanging coils include aluminum and copper, any material that conducts heat could be used for making a heat exchanging coil tube or fin. Since fewer fins are used at the bends of the tube, cost savings are achieved, since less fin material is used.

These embodiments of manufacture, methods, and products of the present invention beneficially provide enhanced efficiencies and costs savings benefits over prior art coils by reducing air-flow restrictions at bends in a coil, and by decreasing the amount of material used at a bend in a coil, or tube.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, advantages and features of the embodiments of the invention will become more apparent by reference to the drawings appended thereto, wherein like reference numerals indicate like parts, primed reference numerals indicate parts of similar design, and wherein illustrated embodiments of the invention are shown, of which:

FIG. 1 is a schematic elevation view of a standard air conditioning system with a condensing unit located externally of the space being air conditioned;

FIG. 2 is a plan view of a portion of a coil tube with a straight length of tube and a bend in the tube and having a constant fin spacing density for both the straight length of tube and the bend in the tube, in accordance with the prior art;

FIG. 3 is a plan view of a coil tube with a straight length of tube and a bend in the tube having a variable fin spacing density depending on the tube orientation, in accordance with an embodiment of the present invention;

FIG. 4 is a plan view of a fin with a fin collar;

FIG. 5 is a perspective view of another coil, in accordance with another embodiment of the present invention; and

FIG. 6 is a plan view of the coil of FIG. 5.

While embodiments of the invention will be described in connection with the preferred embodiments shown herein, it will be understood that it is not intended to limit the invention to those embodiments. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION

Referring to FIG. 1, a typical air conditioning system 10 is illustrated wherein the system 10 is broken into an interior unit 11 and an exterior condensing unit 15. The interior unit 11 includes at least one cooling coil 12 and a fan 16. The interior unit 11 is connected to an air supply ductwork 20 having diffuser grilles 25 for distributing conditioned air into the interior space 30. The interior unit 11 is also connected to a return air inlet 35. The interior unit 11 may be provided with suitable controls to activate the interior unit 11 and to operate interior unit 11 with exterior condensing unit 15. It should be understood by one of ordinary skill in the air conditioning field, that air conditioning system 10 may be of any type or design in that the embodiments herein described may be used with any system 10 that has a coil 40, 40′, 40″ as hereinafter described.

The exterior condensing unit 15 is located in a heat sink 55 which is typically the outdoor environment, and typically includes at least one condensing unit coil 40, a fan 45, a condensing unit compressor 50, and suitable controls to operate exterior condensing unit 15 with the interior unit 11, as are well known in the field of air conditioning.

Refrigeration tubing 60, 65 containing a refrigerant connects the interior unit 11 and exterior condensing unit 15 to form a closed-loop system. The system functions by moving compressed refrigerant from the exterior condensing unit 15 to the interior unit 11 and allowing the compressed refrigerant to expand, and then recompressing the refrigerant with condensing unit compressor 50 at exterior condensing unit 15.

Heat from the interior space 30 is transferred to the refrigerant by forcing air from the interior space 30 over the cooling coil 12 by using fan 16 to draw in air from interior space 30 through the return air inlet 35. The refrigerant then returns to the exterior condensing unit 15 with the heat transferred to it from the interior space 30. The heat from the interior space 30 is then transferred to heat sink 55 by forcing a fluid medium, typically outside air, from heat sink 55 across the condensing unit coil 40 with the aid of fan 45 and suitable controls.

Fan 45 can either draw air inwardly and downwardly from heat sink 55 into the interior 41 of condenser 15, and outwardly over coil 40; or fan 45 can draw air inwardly from heat sink 55 and across coil 40 and draw the air outwardly and upwardly from interior 41 of condenser 15 to heat sink 55, as shown in FIG. 1. In either orientation of air flow, fan 45 generally draws air flow over coil 40 at any given location on coil 40, as will be hereinafter described. The air flow is generally in a direction generally perpendicular to the longitudinal axis of the tubing of coil 40.

With reference to FIG. 2, a portion of a heat-exchanging coil 40 (FIG. 1) according to the prior art is shown. Coil 40 may include one or more tubes, or lengths of tubing, for the refrigerant to flow through. FIG. 2 shows, more specifically, a section, or portion, of a typical heat-exchanging coil tube 70 having an outer wall surface 71 and having both straight sections, or lengths, 72a, 72b and a bend, or bend section, 72c. Bend 72c has an exterior radial wall surface 74 defined by an outer radius of curvature R_o and an inner radial wall surface 75 defined by an inner radius of curvature R_i wherein R_o is generally greater in length than R_i.

As shown in FIG. 2, bend section 72c is generally shown as approximating a 90° bend, or elbow section, with the straight sections 72a, 72b disposed approximately 90° to each other. The length of tubing 70 has a longitudinal axis 76, with the longitudinal axes of sections 72a, 72b, and bend 72c, appearing as 76a, 76b, and 76c, respectively. The construction and shape or configuration of the coil 40, will of course affect the actual angle present between the straight sections 72a, 72b and the bend section 72c, or the angle formed by bend section 72c. In the prior art, fins 77, as shown in FIG. 2, are disposed at a constant fin density that is the same for both the straight sections 72a, 72b and the bend section 72c.

Fins 77 are disposed substantially perpendicular to the longitudinal axes 76a, 76b, 76c of tube 70 at the point of connection between any fin 77 and tube 70, and are generally aligned with the airflow, as shown by arrows AF, over the sections 72a, 72b, 72c of the tube 70. For illustrative purposes and drawing clarity only, a limited number of fins 77 are shown, it being readily apparent to one of ordinary skill in this field of technology that the fins are generally disposed over the entire length of coil tube 70. In FIGS. 2 and 3 the direction of airflow A_F is illustrated, wherein fan 45 is drawing air inwardly and across coil 40, and thereafter the air is forced outwardly and upwardly from interior 41 of condenser 15, as shown in FIG. 1.

As shown in FIG. 2 the ends, or outer circumferential surface, 770 (FIG. 4) of the fins 77 disposed along straight sections 72a and 72b of tube 70 are generally equally spaced from each other so as to not impede air flow A_F passing over fins 77 and tube sections 72a, 72b. In general fins 77 lie in planes which are substantially parallel with each other and are typically spaced substantially an equal distance apart, whereby the fins 77 are disposed on tube sections 72a, 72b with the same fin density.

Similarly the fins 77 disposed upon bend section 77c in FIG. 2 have the same fin density, but due to the presence of the bend, the ends 77, of the fins 77 disposed along the inner radial wall surface 75 of tube section 72c are much closer to each other and indeed may contact each other at some locations, thereby obstructing airflow A_F over tube section 72c.

With reference to FIG. 3, a portion of a heat-exchanging coil tube 40′ according to an embodiment of the present invention is shown, and may include one or more tubes, or lengths or sections of tubing, for the refrigerant to flow through. FIG. 3 shows a section, or portion, of a heat-exchanging coil tube 70 having an outer wall surface 71 and having both straight sections or lengths 72a, 72b and a bend, or bend section 72c, in tube 70. Tube 70 may preferably be constructed of a heat exchanging material, such as copper or aluminum, although any material having the requisite heat transfer and strength characteristics could be used. Fins 77 may be constructed of a heat exchanging material, such as copper or aluminum. Fins 77 may be made of the same heat exchanging material as tube 70, or may be a different heat exchanging material from tube 70. Bend 72c has an exterior radial wall surface 74 defined by an outer radius of curvature R_o and an inner radial wall surface 75 defined by an inner radius of curvature R_i wherein R_o is generally greater in length than R_i.

As shown in FIG. 3, bend section 72c is generally shown as approximating a 90° bend, or elbow section, with the straight sections 72a, 72b disposed approximately 90° to each other. The length of tubing 70 has a longitudinal axis 76, with the longitudinal axes of sections 72a, 72b, and bend 72c, appearing as 76a, 76b, and 76c, respectively. The construction and shape or configuration of the coil 40, will of course affect the angle present between the straight sections 72a, 72b and the bend section 72c or the angle formed by bend section 72c.

Fins 77 are disposed substantially perpendicular to the longitudinal axis 76a, 76b, 76c of tube 70 at the point of connection between any fin 77 and tube 70, and the fins generally aligned with the airflow, as shown by arrows A_F, over the sections 72a, 72b, 72c of the tube 70. For illustrative purposes and drawing clarity only, a limited number of fins 77 are shown, it being readily apparent to one of ordinary skill in this field of technology that the fins are generally disposed over the entire length of coil tube 70.

As shown in FIG. 3 the ends, or outer circumferential surface, 77_o (FIG. 4) of the fins 77 disposed along straight sections 72a and 72b of tube 70 are generally equally spaced from each other so as to not impede air flow A_F passing over fins 77 and tube sections 72a, 72b. In general fins 77 lie in planes which are substantially parallel with each other and are spaced substantially an equal distance apart, whereby the fins 77 are disposed on tube sections 72a, 72b with the same fin density, which may be considered, and defined, as a first fin density.

In FIG. 3, the fins 77 disposed upon bend section 72c have a second fin density, the second fin density being different from the first fin density of the fins 77 secured to the sections 72a, 72b. The second fin density is unequal to the first fin density, and preferably is less than the first fin density. Thus, there is a different density of fins 77 disposed upon, or secured to, the outer wall surface 71 of the bend section 72c. Preferably, there are fewer fins on wall surface 71 of the bend section 72c. As seen in FIG. 3, the ends 77_o of the fins 77 disposed along the inner radial wall surface 75 of tube section 72_c are spaced apart from each other and do not contact each other, whereby airflow A_F over and around the tube section 72c is not obstructed, and airflow A_F may more freely flow over tube section 72c. Additionally, if desired the second fin density of fins 77 disposed upon bend section, or sharp curve, 72c may be a constant density, or it may vary along the longitudinal axis of tube 70 within bend section 72c.

The straight sections 72a, 72b of the tube 70 may have a first fin density that may be approximately between 14 and 24 fins per inch, and the preferred first fin density is between 16 and 20 fins per inch. The bend section 72c in tube 70 has a second fin density that may be approximately between 6 and 13 fins per inch, and the preferred second fin density is between 8 to 13 fins per inch. By having two different fin densities and varying the fin density based upon the location of the fins 77 on tube 70, the airflow across tube 70 at bend section 72c is not restricted to the same degree as the constant fin density spacing arrangement on tube 70, shown in FIG. 2.

To manufacture a tube 70 with two fin densities generally requires a tube 70 that has at least one straight section 72a or 72b and one bend section 72c in the tube 70. Fins 77 are then disposed along the outer wall surface 71 of tube 70 at either a first or second fin density dependent upon the location of the fins 77. Fins 77 are then attached to tube 70. Fins 77 may be attached to the tube 70 by a variety of methods. One method of attaching, or securing, fins 77 to the tube 70, for example, is by helically wrapping fins 77 around tube 70 at either a first or second fin density based upon which section of the tube the fins will be attached, i.e. straight lengths 72a or 72b or bend section 72c. The fins 77 are then secured by either a mechanical or welding fastening method to tube 70. Of course other fastening techniques and materials could be used such as epoxy bonding.

Another preferred method of attaching, or securing, fins 77 to tube 70 is by disposing fins 77 along tube 70 at a first fin density where both straight sections 72a, 72b will occur, or be present, and disposing fins 77 upon tube 70 at a second fin density where the bend section 72c will occur, or be present, wherein fins 77 include a fin collar 95, shown in FIG. 4. Fin collar 95 has a diameter D_F that is greater than the initial outer diameter of tube 70 to allow fins 77 to be disposed at either a first or second fin density along the outer wall surface 71 of tube 70. After the fins 77 are disposed along the outer wall surface 71 of tube 70 at a first or second fin density based upon the orientation of the tube 70—straight or having a bend—tube 70 is then expanded from its first original tube exterior diameter to a second enlarged or expanded exterior diameter. The second diameter is greater, generally slightly greater, than the diameter D_F of fin collars 95. Because the diameter D_F of fin collars 95 is smaller than the second enlarged exterior diameter, fins 77 are mechanically secured along the outer wall surface 71 of tube 70. The tube is then bent, or otherwise suitably formed, into its desired configuration, whereby the tube 70 has straight sections 72a, 72b and bend section 72c.

A method of manufacturing a coil 40′ with a tube 70 for use in air-conditioning equipment comprises several steps. First, a tube 70, with an outer wall surface 71 with at least one straight length 72a or 72b of tube 70 and at least one bend section 72c in the tube 70, is provided or utilized. Fins 77 are then disposed along the outer wall surface 71 substantially perpendicular to the longitudinal axes (76a, 76b, and 76c) at the point of connection between fin 77 and the outer wall surface 71. The fins 77 are disposed at either a first or second find density based upon the orientation of tube 70, i.e. where the straight sections 72a, 72b or bend section 72c are to occur, or be present. The fin density for the straight sections 72a and 72b of tube 70 is unequal to the fin density for fins 77 on bend section 72c of tube 70. Preferably, the fin density for the straight sections 72a and 72b of tube 70 is greater than the fin density for fins 77 on end section 72c of tube 70. The fins 77 may then be attached or secured to tube 70 by one of the methods previously described or by other suitable fastening methods. The tube 70 may then be bent, or otherwise suitably formed, into the desired configuration, whereby the tube 70 has straight sections 72a, 72b and bend section 72c.

With reference to FIGS. 5 and 6, a portion of a heat-exchanging coil tube 40″ according to an embodiment of the present invention is shown, and may include one or more tubes, or lengths of sections of tubing for the refrigerant to flow through, 70′. The construction of coil 40″ includes a plurality of heat-exchanging coil tubes 70′, and coil 40″ is substantially of the same construction and design as that previously described in connection with FIGS. 1, 3 and 4. The tubes 70′ of coil 40″ include bends, or bend sections, 72c having an outer radius of curvature R_o and an inner radius of curvature R_i, wherein R_o is generally greater in length than R_i. The embodiment of coil 40″ of FIGS. 5 and 6 differs from coil 40′ of FIG. 3 in that instead of having straight sections, or lengths, 72a, 72b, as shown in FIG. 3, coil 40″ includes curved sections, or lengths, 72′a and 72′b which are defined by relatively large radii of curvature R′_o and R′_i which define the exterior radial wall surface and interior radial wall surfaces of curve section 72′a and 72′b. Again, the outer radius of curvature R′_o is generally greater in length than the inner radius of curvature R′_i. Fins 77 may be attached, or otherwise suitably secured to tubes 70′ in the manner previously described in connection with FIGS. 3 and 4, including utilizing unequal fin densities for bend sections 72c and sections 72′a and 72′b.

As seen in FIGS. 5 and 6, curve section 72′a and 72′b approximate straight sections 72a and 72b of FIG. 3. Thus, as used in the claims appended hereto, the use of the term “straight section” is defined to include both straight sections 72a, 72b, and curved sections 72′a and 72′b. The method of manufacturing coil 40″ may differ from that previously described in connection with coil 40′ in that as the tube 70′ is bent, or otherwise suitably formed, into the desired configuration whereby the tube 70′ has bend section 72c, it is also bent, or otherwise suitably formed, into the desired configuration, whereby the tube 70′ has curved sections 72′a, and 72′b.

Having described certain embodiments of the invention, various modifications and changes of the techniques, procedures, components and equipment will be apparent to those skilled in the art. It is intended that all such variations within the scope and spirit of the appended claims be embraced thereby.

Claims

1. A coil for air-conditioning equipment, comprising:

at least one tube having an outer wall surface, the at least one tube including at least one substantially straight section and at least one bend section;

the at least one tube having a plurality of fins attached to the outer wall surface of the at least one tube;

the fins being disposed in a spaced relationship from adjacent fins along the outer wall surface of the at least one tube;

the fins disposed along the at least one straight section having a first fin density;

the fins disposed along the bend section having a second fin density; and

the first fin density is unequal to the second fin density.

2. The coil of claim 1, wherein the first fin density is greater than the second fin density.

3. The coil of claim 1, wherein the first fin density is less than the second fin density.

4. The coil of claim 1, wherein the first fin density is approximately between 14 to 24 fins per inch, and the second fin density is approximately between 6 to 13 fins per inch.

5. The coil of claim 4, wherein the first fin density is approximately between 16 to 20 fins per inch, and the second fin density is approximately between 8 to 13 fins per inch.

6. The coil of claim 1, wherein the bend section in the at least one tube forms an angle approximately between 60 and 179 degrees.

7. The coil of claim 6, wherein the bend section in the at least one tube forms an angle between 90 and 120 degrees.

8. The coil of claim 1, wherein the fins are constructed from a heat conducting material, and the same heat conducting material is used for the at least one tube.

9. The coil of claim 1, wherein the fins are constructed from a different heat conducting material and the at least one tube is made of a different heat conducting material.

10. The coil of claim 1, wherein the at least one tube is made of copper or aluminum.

11. The coil of claim 10, wherein the fins are made of copper or aluminum.

12. The coil of claim 1, wherein the fins are wrapped around the outer wall surface of the at least one tube.

13. The coil of claim 1, wherein the fins include a fin collar having an interior diameter.

14. A method of manufacturing a coil for use in air-conditioning equipment, comprising the steps of:

providing at least one tube having an outer wall surface, the at least one tube to have at least one straight section and at least one bend section;

attaching a first plurality of fins at a first fin density upon the outer wall surface of the at least one tube where the at least one straight section will be present;

attaching a second plurality of fins at a second fin density upon the outer wall surface of the at least one tube where the at least one bend section will be present; and

utilizing a first fin density that is unequal to the second fin density.

15. The method of claim 14, wherein the first fin density is greater than the second fin density.

16. The method of claim 14, wherein the first fin density is less than the second fin density.

17. The method of claim 16, wherein the first fin density is approximately between 14 to 24 fins per inch, and the second fin density is approximately between 6 to 13 fins per inch.

18. The method of claim 17, wherein the first fin density is approximately between 16 to 20 fins per inch, and the second fin density is approximately between 8 to 13 fins per inch.

19. The method of claim 16, wherein the fins are attached by wrapping the fins around the outer wall surface of the at least one tube.

20. The method of claim 16, wherein at least some of the fins have a fin collar having a fin collar interior diameter and the at least one tube has a first exterior diameter, which diameter is smaller than the fin collar interior diameter; including the steps of:

expanding the at least one tube until the at least one tube has a second expanded diameter, and the second expanded diameter is greater than fin collar interior diameter.

21. An air-conditioning condenser unit, comprising:

a housing;

a compressor adapted to compress a refrigerant;

a condenser coil including at least one tube having an outer wall surface, the at least one tube having at least one straight section and at least one bend section;

a plurality of fins attached to the outer wall surface of the at least one tube, the fins being disposed in a spaced relationship from adjacent fins along the outer wall surface of the at least one tube;

the fins disposed along the at least one straight section having a first fin density;

the fins disposed along the at least one bend section having a second fin density;

the first fin density being unequal to the second fin density; and

a fan for drawing air across the condenser coil.

22. The air-conditioning condenser unit of claim 21, wherein the first fin density is greater than the second fin density.

23. The air-conditioning condenser unit of claim 21, wherein the first fin density is less than the second fin density.

24. The air-conditioning condenser unit of claim 21, wherein the first fin density is approximately between 14 to 24 fins per inch, and the second fin density is approximately between 8 to 13 fins per inch.

25. The air-conditioning condenser unit of claim 24, wherein the first fin density is approximately between 16 to 20 fins per inch, and the second fin density is approximately between 9 to 13 fins per inch.