Heat exchange – Tubular structure – With discrete heat transfer means
Reexamination Certificate
1998-07-02
2001-05-22
Leo, Leonard (Department: 3743)
Heat exchange
Tubular structure
With discrete heat transfer means
C165S184000
Reexamination Certificate
active
06234245
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a new type of segmented fin for use on a finned tube, specialized serrating wheels for creating the new type of segmented fin, and the process for employing the specialized serrating wheels to create the new type of segmented fin.
The new type of segmented fin is unique because it is provided with individual segments that are curved in order to increase the heat transfer rate of the finned tube that is created when the fin is welded onto a heat exchanger tube. In addition, the segments are coined by the specialized serrating wheels, thus increasing the surface area of the segments and further shaping the sheared edges of each of the segments to result in segments with less air drag.
2. Description of the Related Art
Adding fins to the external surface of a heat exchange tube is an old and well-known way to increase the heat transfer rate between the exterior of the tube and the interior of the tube. Increased heat transfer rate is desirable because the purpose of the heat exchange tubes is to transfer heat between a liquid or gas located within the tube and a liquid or gas located outside the tube. Fins are normally attached to the external surface of the finned tube by employing a long, continuous fin that is wound in helical fashion around the tube so that the fin extends approximately perpendicular to the tube's longitudinal axis.
The practice of serrating the outward extending side of the fin to create segments in the fin prior to winding the flat, non-serrated inwardly extending side or base of the fin to the tube is also a commonly employed way of further increasing the heat transfer rate of the finned tube.
In addition, a variety of surface enhancements to the serrated portion of the fin have been proposed as means for further increasing the surface area of the segments and thus increase the heat transfer rate of the finned tube. One of the disadvantages of creating most of these types of surface enhancements in the segments is that the enhancements increase drag on the outside of the finned tube, either by the gas or liquid flowing past the fins external to the tube.
The present invention further increases the heat transfer rate of serrated finned tubes by creating a serrated fin that has curved segments. Each of these curved segments is concave on one side of the segment and is convex on the opposite side of the segment. This curvature of the segments results in better attachment of the external gas or liquid to the surfaces of the segments, resulting in a higher heat transfer rate. The curvature of the segments also makes them stronger. In addition, the segments are coined or pressed between the serrating wheels to further increase the surface area of the segments and to shape the edges of the segments. Increasing the surface area of the segments allows them to be more efficient at transferring heat and shaping the edges of the segments allows them to be more aerodynamic so that there is decreased drag on the fin when the finned tube is in service.
Finally, after serrating and coining the segments, the segments are passed between a final set of wheels in order to precisely align the segments relative to their base, making the fin ready for winding onto the tube to create a finned tube.
SUMMARY OF THE INVENTION
The present invention consists of a process for creating a new type of segmented fin, specially designed serrating wheels for creating the new type of segmented fin, the new type of segmented fin thus produced, and the unique type of finned tube that is created with the new type of segmented fin.
The method involves first passing a flat metal fin strip between two specially designed serrating wheels. Each of the specially designed serrating wheels is provided with a series of cutting edges around the wheel's perimeter. One of the wheels is provided around its perimeter with a series of concave surfaces, with one such concave surface being located between each adjacent pair of cutting edges provided on that first wheel. The other wheel is provided at its perimeter with a series of convex surfaces, with one such convex surface being located between each adjacent pair of cutting edges provided on that second wheel. The cutting edges of the two wheels are aligned with each other in cooperating fashion so that when the flat fin strip is passed between the wheels, the outward extending side of the fin is serrated by the cooperating cutting edges of the wheels, but the base of the fin strip remains unserrated.
The convex and concave surfaces of the two wheels are engaged and mated so that as the serrated portion of the fin completes its travel between the wheels, the segments are pressed or coined between the opposing convex and concave surfaces. This coining causes each of the segments to be stressed beyond the yield point of the metal and thereby causes each of the segments to be permanently bent into a curved configuration corresponding to the curvature of the mating concave and convex surfaces of the first set of wheels.
Once the serrated and coined fin completes its travel through the wheels, the base of the fin is then engaged by a second set of wheels that serve to apply a pulling force on the fin in order to pull it clear of the first set of wheels with sufficient tension so as to elongate the base of the fin. It is important that the second set of wheels engage only the base of the fin so that the curvatures of the serrations are not disturbed by the gripping action of the second set of wheels.
Finally, after the serrated and coined fin passes between the second set of wheels, it passes between a third set of wheels. The wheels comprising the third set of wheels are precisely spaced apart from each other so that as the segments pass between the third set of wheels, the segments are realigned with the longitudinal axis of the base without disturbing the curvature of the segments.
The final result of this process is a serrated fin having curved segments. Each segment is curved in a plane approximately parallel to the longitudinal axis of the fin's base so that each segment is provided with a concave side and an opposite convex side, with the two sides meeting at the serrated edges.
Also because of the coining process that the segments undergo as they pass between the serrating first set of wheels, the surface area of the segment is slightly increased and the edges of the segments are slightly pointed.
One of the added benefits of producing a fin with curved segments is that the segments, by virtue of their curved configuration, are inherently stronger. A segment will resist deflection by an amount that is proportional to the moment of inertia, and the moment of inertia is proportional to the cube of the thickness of the fin, including its curvature. Thus, by creating a curvature in the segments, the fin's apparent thickness is increased and also the strength of the segment is increased.
REFERENCES:
patent: 808490 (1905-12-01), Swan
patent: 2965555 (1960-10-01), Hall
patent: 3073385 (1963-01-01), Peters
patent: 3183970 (1965-05-01), Worley
patent: 3723693 (1973-03-01), Boose et al.
patent: 3752228 (1973-08-01), Bosse
patent: 4227572 (1980-10-01), Harlan
patent: 4258782 (1981-03-01), Kao
patent: 5240070 (1993-08-01), Ryan
patent: 235639 (1945-04-01), None
patent: 1939199 (1971-02-01), None
patent: 0091127 (1983-06-01), None
patent: 340765 (1931-01-01), None
patent: 579610 (1946-08-01), None
patent: 906282 (1962-09-01), None
patent: 5-130598 (1981-10-01), None
patent: 86896 (1984-05-01), None
patent: 507767 (1976-04-01), None
patent: 1059412 (1983-12-01), None
patent: 1560977 (1990-04-01), None
Mitchell Hartman
Reid Don R.
Weierman Robert C.
Fintube Technologies, Inc.
Leo Leonard
McKay Molly D.
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