HELICALLY WOUND FINNED TUBES FOR HEAT EXCHANGERS AND IMPROVED METHOD FOR SECURING FINS AT THE ENDS OF THE TUBES

Abstract

A finned tube for heat transfer from one medium to a second medium, and the method of manufacture, is disclosed. A helical fin of the finned tube has an area of compressed fins positioned proximate an insertion section which has a metal tube exposed with the helical fin removed therefrom. The compressed fins are a portion of the helical fin which has been compressed so that the helical fin in the area of the compressed fins is more closely spaced than the remaining portion of the helical fin. A base portion of the helical fin in the area of the compressed fins is layered and compressed on itself and is compressed against the metal tube. The layers of the base portion are compressed together and to the metal tube of the finned tube, which causes the layers of the base portion to bind together and bind to the metal tube to prevent movement of the helical fin in the area of the compressed fins in a direction parallel to the longitudinal axis of the finned tube.

Description

FIELD OF THE INVENTION

The present invention is directed to a finned tube which provides effective heat transfer and which is easily manufacturable. The invention is also directed to the method of manufacture of the finned tube.

BACKGROUND OF THE INVENTION

Finned tubes are well known to effect heat transfer from one medium to another. Fins on a tube improve heat transfer by increasing the outside surface area exposed to a heat transfer medium. One method of manufacturing a finned tube is to wrap a soft metal strip, such as aluminum, around the tube in a helical pattern so that an ‘L’ shaped foot or base is formed which is held in close contact with the tube by tension which is created during the wrapping process. Because fins manufactured by this method rely on the tension in the fins to maintain contact between the fin and the tube, it is necessary to secure the fins at the ends of the tube so that the fins do not spontaneously become unwrapped from the tube, reducing the desired close contact between the tube and the fin. The ends of each of the finned tubes are connected to plenums through holes or openings in the plenums. This allows a first fluid, such as water, to flow through the metal tube from a first plenum to a second plenum, while a second fluid, such as air, contacts the helical fin to transfer heat away from the fin.

While the use of finned tubes is an effective method of transferring heat from the first fluid, through the metal tube and helical fin, to the second fluid, the insertion of the finned tubes into the openings of the plenums requires that a certain length at the ends of the tubes be free of fins to allow the metal tubes to be inserted into the openings. Since the most efficient method of manufacturing the finned tubes is to create them in long lengths and then to cut the tubes to the required length, it is necessary to provide a method to form a fin-free length at the ends of the tubes for insertion into the plenum. Currently, this process requires a technician or installer to: measure the length of helical fins to be removed or stripped back; manually crimp three fins together at the measured length; fold the crimped fins away from the end of the metal tube; break the fin adjacent the crimped fins which is nearer the end of the metal tube by repeated folding motion; twist and remove a portion of the helical fin proximate the end of the metal tube which has been broken away from the crimped fins, thereby exposing an end of the metal tube which can be inserted into the opening of the plenum; and staple the crimped fins to each other to maintain the crimped fins in position. This is a relatively labor intensive and time-consuming process. It is also a process which is difficult to repeat with accuracy and predictability.

It would, therefore, be beneficial to provide a finned tube in which the areas proximate the exposed ends of the metal tube were accurately and predictably controlled to provide ease of insertion into an opening of a plenum or the like, thereby providing maximum heat transfer characteristics. It would also be advantageous to provide a method for removing the helical fins from the metal tubes which would be more easily repeatable and would require less time and resources.

SUMMARY OF THE INVENTION

The invention is directed to a finned heat tube which can be easily inserted into a plenum or the like. The invention is also directed to the method of manufacture of the same.

In one embodiment, a method of providing a fin-free area at an end of a finned tube to expose a metal tube of the finned tube is disclosed. This method comprises compression of a number of the helical fins upon themselves to provide the fin-free section of the tube in lieu of removal of a section of the helical fins. The method begins with positioning the finned tube in a fixture. A compression mechanism is advanced a predetermined distance into engagement with an end of the finned tube. The compression mechanism has a first end with an opening extending from the first end toward a second end. The opening is dimensioned to receive the metal tube of the finned tube therein. As the compression mechanism is advanced, the first end of the compression mechanism engages fin portions of the helical fin, causing the fin portions to compress upon themselves as the advancement of the compression mechanism continues. In addition, as the compression mechanism is advanced, base portions of the helical fin are moved and become layered. The layers of the base portion are compressed together and are compressed onto the metal tube, causing the layers of the base portion to bind together and bind to the metal. The compression mechanism is retracted to expose the metal tube of the finned tube from which the helical fin has been removed. The finned tube is then removed from the fixture.

In another embodiment, a method of removing a portion of a helical fin from an end of a finned tube to expose a tube portion of the finned tube is disclosed. The method begins with positioning the finned tube in a fixture. The finned tube is then clamped in position relative to the fixture. A force is applied to the end of the finned tube to compress the portion of the helical fin, causing fin portions of the helical fin to compress upon themselves as the force is applied. As the force is applied, a base portion of the helical fin is moved and becomes layered. The layers of the base portion are compressed together and are compressed to the tube portion, causing the layers of the base portion to bind together and to bind to the tube portion. Upon the removal of the force, the compressed portion of the helical fin is maintained in position by the binding of the layers together and to the metal tube, thereby preventing the helical fin from moving back over the exposed tube portion.

In another embodiment, a finned tube for heat transfer from one medium to a second medium is disclosed. The finned tube includes a metal tube and a helical fin. The helical fin extends around the metal tube. The helical fin has a base portion which conforms to an outside diameter of the metal tube. The helical fin also has a fin portion which extends from the base portion. An end of the finned tube has insertion sections in which the metal tube is exposed, with no helical fin projecting therearound. The helical fin has an area of compressed fins positioned proximate to the insertion section. The compressed fins are a portion of the helical fin which has been compressed so that the helical fin in the area of the compressed fins is more closely spaced than the remaining portion of the helical fin. The base portion in the area of the compressed fins is layered and compressed on itself and is compressed against the metal tube. The layers of the base portion are compressed together and to the metal tube, which causes the layers of the base portion to bind together and bind to the metal tube to prevent movement of the helical fin in the area of the compressed fins in a direction parallel to the longitudinal axis of the finned tube.

In another embodiment, the attachment of the compressed fins to the tubes is further strengthened by securing the compressed fins to each other by insertion of staples, rivets, or other devices through the compressed fins to prevent the compressed fins from rotating relative to each other and thus loosening the attachment of the compressed fins to the tube.

Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a finned tube according to the present invention.

FIG. 2 is an enlarged perspective view of an area of compressed fins of the finned tube.

FIG. 3 is a perspective view of the finned tube being positioned in a fixture prior to the compression of the fins.

FIG. 4 is a perspective view of the finned tube with an end portion of the finned tube extending beyond the fixture.

FIG. 5 is a perspective view of the finned tube clamped in the fixture with a compression mechanism advancing toward the free end of the finned tube.

FIG. 6 is an enlarged perspective view of the compression mechanism as it has advanced beyond the free end of the finned tube, causing fins of the finned tube to be compressed.

FIG. 7 is a perspective view of the finned tube clamped in the fixture with a compression mechanism retracting away from the free end of the finned tube, exposing the compressed fins.

FIG. 8 is a perspective view of the finned tube after the fins have been compressed at the free end thereof showing the a staple being inserted into the compressed fins.

FIG. 9 is enlarged view of the fins of the finned tube with foam from the clamp formed around the fins.

FIG. 10 is an enlarged perspective view of an end of the compression mechanism.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIGS. 1 and 2, a finned tube 10 has a metal tube 12 with a helical fin 14 wrapped around the metal tube 12. The helical fin 14 has a base portion 16 which essentially conforms to the shape of the outside diameter of the metal tube 12 and which is attached thereto using conventional means of attachment. Alternatively, the helical fin 14 may be tightly wound around the metal tube 12 in such a manner as to allow the helical fin 14 to be maintained in position by frictional engagement, eliminating the need for other means of attachment. A fin portion 18 of the helical fin extends from the base portion 16 away from the metal tube 12 in a direction which is essentially perpendicular to the base portion 16. Other configurations of the helical fin 14 may be used without departing from the scope of the invention. The helical fin 14 is generally comprised of one continuous piece of metal or other material having the proper heat transfer characteristics. Alternatively, the helical fin 14 may be made from various pieces of material which have been joined to form one continuous member.

The ends 20, 22 of the finned tube 10 have insertion sections 24 in which the metal tube 12 is exposed and no helical fin 14 is projecting therearound. These insertion sections 24, without helical fins 14, are dimensioned to be received in openings in plenums (not shown) or the like. An area of compressed fins 26 is positioned proximate to each insertion section 24. The compressed fins 26 are portions of the helical fin 14 which has been compressed so that a respective area of the fin portion 18 of the helical fin 14 is more closely spaced than the remaining portions of the helical fin 14. The base portion 16 in the area of the compressed fins 26 is compressed against the metal tube 12. The base portion 16 is also layered or folded over itself in this area. The combination of the base portion interacting with itself and the metal tube 12 provides a type of compression force which causes the layers of the base portion to bind together and bind to the metal tube to secure the base portion 16 to the metal tube 12. This compression force creates a frictional force between the layers of the base portion and between the base portion 16 and the metal tube 12. This prevents the movement of the base portion in the area of the compressed fins 26 in a direction parallel to the longitudinal axis of the finned tube 10.

With the compressed fins 26 secured in position by the compression of the base portion 16, the insertion sections 24 of the ends 20, 22 are free of the helical fin 14 and are in condition to be inserted into the openings of the plenum. Staples 28 may be inserted into the helical fin 14 of the compressed fins 26 to secure the compressed fins 26 to each other and to further secure the compressed fins 26 in position relative to the finned tube 10.

The insertion sections 24 of the finned tube 10 are moved into the plenums through holes or openings in the plenums (not shown) and are secured and sealed thereto. This allows a first medium or fluid, such as oil, natural gas, helium, oxygen, etc. to flow through the metal tube from a first plenum to a second plenum, while a second medium or fluid, such as air, water, etc., contacts the helical fin to transfer heat away from the fin and from the first fluid. The metal tube 12 and helical fin 14 may be made from any materials having the appropriate strength and heat transfer characteristics. Materials such as aluminum alloys allow for high heat transfer efficiency while operating at a lower temperature and reduced weight.

While the use of finned tubes is an effective method of transferring heat from the first fluid, through the metal tube and helical fin, to the second fluid, the insertion of the finned tubes into the openings of the plenums requires that the end of the metal tube be free of fins to allow the metal tubes to be inserted, secured and sealed in the openings.

Referring to FIGS. 3 through 8, the method of manufacturing the finned tubes is shown. Finned tubes 10 are made by applying the helical fin 14 to a metal tube 12 and attaching the helical fin 14 to the metal tube 12 in any conventional manner which provides the required strength and heat transfer characteristics required. The metal tube 12 may be one tube or a plurality of tubes. With the helical fin 14 properly mounted on the metal tube 12, the finned tubes 10 are cut to length. Upon cutting, the helical fin 14 extends to the end of the metal tube 12, so that the helical fin 14 and the metal tube 12 extend the entire length of the respective finned tube 10, as is shown in FIGS. 3 and 4.

The properly sized finned tube 10 is positioned in a base fixture 100, as shown in FIG. 3. In this embodiment, the base fixture 100 has a V-shaped configuration, with the finned tube 10 positioned in the channel of the base fixture 100. However, other configurations of the base fixture 100 can be used without departing from the scope of the invention. As shown in FIG. 4, an end of the finned tube 10 extends beyond the end of the base fixture 100 when the finned tube 10 is positioned in the fixture 100. However, depending upon the fixture and other devices used, the finned tube 10 may not be required to extend beyond the end of the fixture 100.

With the finned tube 10 in position, a clamp 102 is brought into engagement with the finned tube 10, as shown in FIGS. 5 and 6. The clamp 102 has a similar, but inverted, V-shaped profile to that of the base fixture 100. Foam 104 or other compliant material is provided in the channel of the V-shaped channel of the clamp 102. As the clamp is brought into engagement with the finned tube 10, the foam 104 forms around the helical fin 14 (as shown in FIG. 9), such that the foam 104 flows into the spaces between the helical fin 14. The clamp 102 is moved toward the base fixture 100 until sufficient force is applied to the finned tube 10 to prevent the finned tube 10 from moving in a direction parallel to the longitudinal axis of the base fixture 100. The clamp 102 is then maintained in position relative to the finned tube 10. The clamp 102 may be moved and locked in position by mechanical, pneumatic, electrical or any other known means. The use of the foam 104, and its ability to mold around the helical fin 14, allows the clamp 102 to maintain the finned tube in position relative to the base fixture 100 and the clamp 102 without damaging the helical fin 14.

As shown in FIG. 5, with the finned tube 10 maintained in position in the base fixture 100, a compression mechanism 110 is moved into engagement with the end of the finned tube 10 which extends from the base fixture 100. In the embodiment shown, the compression mechanism 110 has a generally cylindrical outer shape, although the outer shape of the compression mechanism may vary without departing from the scope of the invention. The compression mechanism 110 has an opening 112 (FIG. 10) which extends from a first end 114 of the compression mechanism 110 toward a second end 116. The opening 112 is dimensioned to have a diameter which is larger than the diameter of the metal tube 12, but smaller than the diameter of the helical fin 14. However, the opening 112 is dimensioned to be only slightly larger than the diameter of the metal tube 12 to allow for the compression mechanism to properly cooperate with the base portion 16 and the fin portion 18 of the helical fin 14. During operation, the compression mechanism 110 is moved toward the base fixture 100, as indicated by the arrow A, thereby applying a force to the helical fin 14 at the fin portion 18. The compression mechanism 110 may be moved by the use of mechanical, pneumatic or electrical devices or any other known devices used to move such mechanisms.

As best shown in FIGS. 5 and 6, the movement of the compression mechanism 110 causes the first end 114 to engage an end of the fin portion 18, causing the fin portion 18 of the helical fin 14 to collapse or compress upon itself. As the movement of the compression mechanism and the force continue, the continued collapse or compression of the fin portion forms the area of compressed fins 26. During this movement of the compression mechanism 110 and the compression of the fin portion 18, the base portion 16 of the helical fin 14 is caused to layer or ride over itself. The opening 112 of the compression mechanism 110 is dimensioned to be large enough to allow for the stacking of the base portion 16 to occur in the opening 112 while being small enough to allow the first end 114 to have sufficient surface area to properly cooperate with and support the fin portion 18 during the movement of the compression mechanism 110. While the opening 112 is dimensioned to receive the base portion 16 therein, the opening 112 may be dimensioned to exert a force on the base portion 16 to cause the base portion 16 to exert a force on the metal tube 12. In order for this to be effective, the opening 112 is dimensioned to allow for the insertion of the base portion 16, but is small enough to cause the base portion 16 to be compressed when the base portion begins to layer or ride over itself. This causes the layers of the base portion 16 to be compressed and bind together and causes the base portion 16 to compress against and bind with the metal tube 12.

The movement of the compression mechanism 110 in the direction of arrow A is controlled such that the portion of the helical fin 14 that is collapsed exposes the proper amount of metal tube 12 required for the insertion into the opening of the plenum. As the compression mechanism can be programmed through the use of hardware or software, the movement of the compression mechanism can be precisely and accurately controlled.

As the compression mechanism 110 is moved in the direction of the arrow A of FIG. 5, the finned tube 10 is prevented from moving in the direction of the arrow A due to the cooperation of the clamp 102 with a non-compressed section of the helical fin 14 of the finned tube 10. As the movement of the finned tube 10 is prevented by the clamp 102, the clamp 102 exerts forces on the portions of the helical fin 14 which are maintained in the clamp 102. Since the helical fin 14 is made of relatively thin material which is easily deformed, it is important that the clamp 102 and the helical fin 14 transfer the forces in such a manner so as to not damage the helical fin 14. Therefore, the foam 104 is configured to engage a large area of the helical fin 14 to allow the forces applied by the foam 104 on the helical fin 14 to be dissipated over a large area, thereby allowing the forces applied to the helical fin 14 at any particular location to be relatively small. Consequently, the use of the foam 104 allows the clamp 102 to maintain the finned tube 10 in position without damaging the helical fin 14.

Once the compression mechanism 110 has been advanced the designated or programmed distance, the compression mechanism 110 is retracted in the direction of the arrow B of FIG. 7. With the compression mechanism 110 fully retracted, the clamp 102 is released and the finned tube 10 is removed from the base fixture 100. The finned tube 10 has the appropriate insertion sections 24 with the compressed fins 26 positioned proximate thereto, as described above. The compressed fins 26 are maintained in position by the cooperation of the base portion 16 with the metal tube 12. This prevents the helical fin 14 from moving back over the insertion sections 24. Staples 28 or other fasteners may be applied to the ends of the compressed fins 26 to further secure the compressed fins 26 together and in position relative to the insertion sections 24, as shown in FIG. 8. While the positioning of the staples may vary, in one embodiment, the staples are spaced 180 degrees apart on the compressed fins 26.

The finned tubes and method of making the same of the present invention eliminate the relatively labor intensive and time-consuming process of terminating the finned tubes found in the prior art. The present invention also provides finned tubes and a process for manufacturing the same which is repeatable and predictable. The finned tubes of the present invention require less time and resources to terminate. The heat transfer characteristics of the finned tubes are maximized, as the precise dimensions associated with the insertion sections can be controlled, thereby allowing the helical fin to span a maximum surface area of the finned tube.

While the invention has been described with reference to a preferred 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 method of compressing a number of helical fins near the end of a finned tube to expose a metal tube of the finned tube, the method comprising:

positioning the finned tube in a fixture;

advancing a compression mechanism a predetermined distance into engagement with an end of the finned tube, the compression mechanism having a first end with an opening extending from the first end toward a second end, the opening dimensioned to receive the metal tube of the finned tube therein;

the advancement of the compression mechanism causing the first end of the compression mechanism to engage fin portions of the helical fin, causing the fin portions to compress upon themselves as the advancement of the stripping mechanism continues;

the advancement of the compression mechanism causing a base portion of the helical fin to move and become layered, the layers of the base portion being compressed together and to the metal tube, causing the layers of the base portion to bind together and bind to the metal tube as the advancement of the stripping mechanism continues;

retracting the compression mechanism to expose the metal tube of the finned tube from which the helical fin has been removed; and

removing the finned tube from the fixture.

2. The method of claim 1 wherein the compressed fin portions are maintained in position by the overlapping of the base portions of the fins, thereby preventing the helical fin from moving back over the exposed metal tube.

3. The method of claim 2 comprising applying fasteners to ends of the compressed fin portions to further secure the compressed fin portions in position.

4. The method of claim 4 wherein the fasteners are staples which are spaced apart on the compressed fin portions.

5. The method of claim 1 comprising clamping the finned tube in the fixture prior to advancing a compression mechanism the predetermined distance into engagement with the end of the finned tube.

6. The method of claim 5 wherein a clamp for clamping the finned tube in the fixture has a compliant material which forms around the helical fin when the clamp is brought into engagement with the finned tube, the compliant material molding around the helical fin to allow the clamp to maintain the finned tube in position relative to the fixture without damaging the helical fin.

7. The method of claim 6 wherein the compliant material engages a large area of the helical fin, whereby the forces applied by the compliant material on the helical fin are dissipated over a large area, allowing the forces applied to the helical fin at any particular location to be relatively small, allowing the clamp to maintain the finned tube in position without damaging the helical fin.

8. The method of claim 1 wherein the opening of the compression mechanism is dimensioned to allow for the layering of the base portion as the compression mechanism is advanced.

9. A method of compressing a section of fins at an end of a finned tube to expose a tube portion of the finned tube, the method comprising:

positioning the finned tube in a fixture;

clamping the finned tube in position relative to the fixture;

applying a force to the end of the finned tube to compress the portion of the helical fin, causing fin portions of the helical fin to compress upon themselves as the force is applied;

the applied force causing a base portion of the helical fin to move and become layered, the layers of the base portion being compressed together and to the tube portion, causing the layers of the base portion to bind together and bind to the tube portion as the force is applied;

whereby upon the removal of the force, the compressed portion of the helical fin is maintained in position by the binding of the layers together and to the metal tube, thereby preventing the helical fin from moving back over the exposed tube portion.

10. The method of claim 9 comprising applying fasteners to ends of the fin portions of the compressed helical fin to further secure the compressed helical fin in position.

11. The method of claim 10 wherein the fasteners are staples which are spaced apart on the fin portions.

12. The method of claim 9 wherein a clamp for clamping the finned tube in position relative to the fixture has a compliant material which forms around a non-compressed section of the helical fin when the clamp is brought into engagement with the finned tube, the compliant material molding around the non-compressed section of the helical fin to allow the clamp to maintain the finned tube in position relative to the fixture without damaging the helical fin.

13. The method of claim 12 wherein the compliant material engages a large area of the non-compressed section of the helical fin, whereby the forces applied by the foam on the non-compressed section of the helical fin are dissipated over a large area, allowing the forces applied to the non-compressed section of the helical fin at any particular location to be relatively small, allowing the clamp to maintain the finned tube in position without damaging the helical fin.

14. A finned tube for heat transfer from one medium to a second medium, the finned tube comprising:

a metal tube with a helical fin around the metal tube;

the helical fin having a base portion which conforms to an outside diameter of the metal tube;

the helical fin having a fin portion extending from the base portion;

an end of the finned tube having insertion sections in which the metal tube is exposed, with no helical fin projecting therearound;

the helical fin having an area of compressed fins positioned proximate to the insertion section, the compressed fins being a portion of the helical fin which has been compressed so that the helical fin in the area of the compressed fins is more closely spaced than the remaining portion of the helical fin;

the base portion in the area of the compressed fins being layered and compressed on itself and being compressed against the metal tube;

whereby the layers of the base portion being compressed together and to the metal tube causes the layers of the base portion to bind together and bind to the metal tube to prevent movement of the helical fin in the area of the compressed fins in a direction parallel to the longitudinal axis of the finned tube.

15. The finned tube as recited in claim 14 wherein the compressed fins of the helical fin are maintained in position on the metal tube by frictional engagement between the base portion of the helical fin and the metal tube.

16. The finned tube as recited in claim 14 wherein the compressed fins of the helical fin are maintained in position on the metal tube by frictional engagement between the layers of the base portion of the helical fin.

17. The finned tube as recited in claim 14 wherein the fin portion extends from the base portion in a direction which is essentially perpendicular to the base portion.

18. The finned tube as recited in claim 14 wherein fasteners may be inserted into the helical fin of the compressed fins to secure the compressed fins to each other and to further secure the compressed fins in position relative the metal tube.

19. The finned tube as recited in claim 18 wherein the fasteners are staples.