EP1232373A1 - Segment d'ailette a courbure aerodynamique - Google Patents

Segment d'ailette a courbure aerodynamique

Info

Publication number
EP1232373A1
EP1232373A1 EP99960560A EP99960560A EP1232373A1 EP 1232373 A1 EP1232373 A1 EP 1232373A1 EP 99960560 A EP99960560 A EP 99960560A EP 99960560 A EP99960560 A EP 99960560A EP 1232373 A1 EP1232373 A1 EP 1232373A1
Authority
EP
European Patent Office
Prior art keywords
fin
segment
heat exchange
segments
tube
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP99960560A
Other languages
German (de)
English (en)
Inventor
Don R. Reid
Hartman Mitchell
Robert C. Weierman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fintube Technologies Inc
Original Assignee
Fintube Technologies Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fintube Technologies Inc filed Critical Fintube Technologies Inc
Publication of EP1232373A1 publication Critical patent/EP1232373A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F1/00—Tubular elements; Assemblies of tubular elements
    • F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
    • F28F1/12—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element
    • F28F1/34—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element and extending obliquely
    • F28F1/36—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element and extending obliquely the means being helically wound fins or wire spirals

Definitions

  • 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.
  • 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.
  • the offset of the fin segments relative to the direction of helical attachment of the fin to the tube is critical and the direction of concave curvature of the segments relative to the direction of helical attachment of the fin to the tube is critical.
  • 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 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.
  • 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.
  • it is critical that the direction of offset of the fin segments is opposite the direction of helical attachment of the fin to the tube, and it is also critical that the concave curvature of the segments be in a direction opposite the direction of the helical attachment of the fin to the tube.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • the fin's apparent thickness is increased and also the strength of the segment is increased.
  • the fin In order to provide optimum flow around the finned tube, the fin must be attached to the tube properly. Specifically, it is critical that the direction of offset of the fin segments is opposite the direction of helical attachment of the fin to the tube, and it is also critical that the concave curvature of the segments be in a direction opposite the direction of the helical attachment of the fin to the tube.
  • FIGURE 1 is a schematic diagram illustrating the specialized serrating wheels and the process for creating from a flat fin strip a new type of aerodynamically curved segmented fin that is the subject of the present invention.
  • FIGURE 2 is an enlarged view of a flat fin strip as it enters and is being serrated by the serrating first set of wheels in Figure 1.
  • FIGURE 3 is an enlarged view of the fin strip of Figure 1 that has been serrated and is being coined by the first set of wheels in Figure 1.
  • FIGURE 4 is an enlarged view of the serrated and coined fin strip as it exits the first set of wheels in Figure 1.
  • FIGURE 5 is an enlarged view of the new type of aerodynamically curved segmented fin as it exits the final set of wheels in Figure 1.
  • FIGURE 6 is a side view of a heat exchange tube to which the fin of Figure 5 is being attached.
  • FIGURE 7 is an end view of the tube and fin of Figure 6.
  • FIGURE 8 is an enlarged view of a couple of segments from Figure 6.
  • FIGURE 9 is an enlarged view of one of the segments from Figure 8.
  • FIGURE 10 is an end view of a finned tube constructed with the fin and tube of Figures 6 and 7.
  • FIGURE 11 is a cut away perspective view of a portion of the finned tube of Figure 10 with the finned tube cut in half along its longitudinal axis for ease in viewing.
  • FIGURE 12 is a side view of the finned tube of Figure 11.
  • FIGURE 13 is a side view of the new type of aerodynamically curved, segmented fin as it exits the final set of wheels in Figure 1.
  • FIGURE 14 is a graph showing test results from a comparison of a first finned tube constructed in accordance with the present invention and a prior art finned tube.
  • FIGURE 15 is a graph showing test results from a comparison of a second finned tube constructed in accordance with the present invention and a prior art finned tube.
  • FIGURE 16 is a side view of the fin of Figure 6 illustrating the desired direction of offset and the desired direction of curvature of the fin segments.
  • FIGURES 17, 18, and 19 are each side views of a fin similar to Figure 16 illustrating undesirable directions of offset and curvature of the fin segments.
  • FIG. 1 there is illustrated a method or process 10 in accordance with a preferred embodiment of the present invention for creating a new type of segmented fin 12.
  • FIGs 2-4 there is illustrated specially designed serrating wheels 14 and 16 constructed in accordance with a preferred embodiment of the present invention for creating the new type of segmented fin 12.
  • FIGs 4 - 7 there is illustrate the new type of segmented fin 12 that is produced by employing the specially designed serrating wheels 14 and 16 and the process 10 illustrated in Figure 1.
  • Figures 10-12 there is illustrated a unique type of finned tube 18 constructed in accordance with a preferred embodiment of the present invention from a heat exchange tube 20 and the new type of segmented fin 12.
  • the method 10 involves first passing a flat metal fin strip 22 between the rotating two specially designed serrating wheels 14 and 16.
  • Each of the specially designed serrating wheels 14 and 16 is provided with a plurality of cutting edges, 14A and 16A respectively, provided around a perimeter, 14P and 16P respectively, provided on the wheels 14 and 16.
  • One of the wheels 14 is provided with a plurality of concave surfaces 14B, with one such concave surface 14B being located between each adjacent pair of cutting edges 14A provided on the perimeter 14P of that first wheel 14.
  • the other wheel 16 is provided with a plurality of convex surfaces 16B, with one such convex surface 16B being located between each adjacent pair of cutting edges 16A provided on the perimeter 16P of that second wheel 16.
  • the cutting edges 14A and 16A of the two wheels 14 and 16 are aligned with each other in cooperating fashion.
  • a first longitudinal edge of the flat metal fin strip 22 that will eventually become an outwardly extending side or serrated portion 24 of the segmented fin 12, is serrated by the cooperating cutting edges 14A and 16A of the wheels 14 and 16, forming a plurality of segments 26 in the serrated portion 24.
  • This serration process is shown in Figure 2.
  • the flat metal fin strip 22 is provided with an opposite second longitudinal edge that will remain unserrated and will form an inwardly extending side or base 28 of the segmented fin 12.
  • each of the segments 26 is approximately perpendicular to the longitudinal axis 32 of the base 28 of the segmented fin 12.
  • each segment 26 is curved in a plane so that a cross section of each of the segments 26 along the longitudinal axis 30 of that segment 26 would cut through the segment 26 in a straight line, forming two mirror image halves of the segment 26.
  • the curvature or arc of each segment 26 is defined by the curvature of the mating concave and convex surfaces 16B AND 14B provided on the specially designed serrating wheels 14 and 16. This curvature is at a radius range of 0.20 inches to 0.30 inches.
  • the base 28 of the fin 12 is then engaged by a second set of rotating wheels 34 and 36.
  • the wheels 34 and 36 have a slightly higher surface speed than the first set of wheels 14 and 16 so the second set of wheels 34 and 36 serve to apply a pulling force on the fin 12 in order to pull it clear of the first set of wheels 14 and 16.
  • This pulling force is set large enough to elongate the base 28 of the fin 12 approximately 1-6%, thereby facilitating the subsequent segment realignment. It is important that the second set of wheels 34 and 36 engage only the base 28 of the fin 12 so that the curvatures of the segments 26 are not disturbed.
  • the serrated portion 24 of the fin 12 passes through a third set of rotating wheels 38 and 40.
  • the wheels 38 and 40 are precisely positioned relative to each other so that as the segments 26 pass between the wheels 38 and 40, the wheels 38 and 40 push against the segments 26, causing the segments 26 to twist slightly and be pushed back into approximate alignment with the longitudinal axis of the base 28 of the fin 12.
  • the product of this cold working process is the serrated fin 12 that is provided with curved segments 26.
  • edges 42 and 44, that are provided on each of the segments 26 at the serrations are slightly pointed. This is illustrated in Figure 8 which shows the left and right edges 42 and 44 of each segment 26 being pointed by an angle of, "X" and "Y” respectively, from the normal perpendicular cut 46 that would exist except for the effect of coining on the segment 26.
  • the angles "X" and "Y” will preferably be between 10 and 20 degrees, depending on the force exerting on the segments 26 by the first set of wheels 14 and 16 during the coining process.
  • surface area of each of the segments are slightly pointed.
  • segments 26 are inherently stronger than flat or non-curved segments. Increased strength will result in less damage to fin surfaces during manufacturing assembly operations.
  • the normally weak fin segment has undergone a substantial improvement in resistance to deflection because of two features of the aero curved fin 12.
  • the coining process increases the minimum yield stress by approximately one-third (1/3).
  • the minimum yield stress changes from approximately 30,000 p.s.i to approximately 40,000 p.s.i.
  • the second improvement comes from the curved shape itself. With dimensions described herein, this improvement can be approximately a 30% increase in resistance to deflection.
  • a curved fin segment 26 of a height "H” and a base “B” is illustrated.
  • the actual metal thickness of the fin segment 26, not accounting for the curvature of the fin segment 26, is represented in Figure 9 by the numeral 48.
  • the actual segment metal thickness 48 is less that the height "H” by the amount of the sweep or depth "D" of the curvature of the segment 26.
  • the fin 12 In order to provide optimum flow around the finned tube 18, the fin 12 must be attached to the tube 20 properly. Specifically, as illustrated in Figure 16, it is critical that the direction of offset, as denoted by arrow "C”, of the fin segments 26 is opposite the direction of helical attachment, as denoted by arrow “E", of the fin 12 to the tube 20. It is also critical that the direction of the concave curvature, as denoted by arrow "F”, of the segments 26 be opposite the direction of helical attachment, as denoted by arrow "E", of the fin 12 to the tube 20.
  • Figures 17-19 illustrate improper arrangement of the direction of offset, as denoted by arrow "C", of the segments 26 and improper direction of concave curvature, as denoted by arrow “F", of the segments 26.
  • figure 17 illustrates improper arrangement of the direction of offset, as denoted by arrow “C”, of the segments 26 and improper direction of concave curvature, as denoted by arrow “F”', of the segments 26.
  • Figure 18 illustrates improper arrangement of the direction of offset, as denoted by arrow “C”, of the segments 26 and proper direction of concave curvature, as denoted by arrow “F”, of the segments 26.
  • Figure 19 illustrates proper arrangement of the direction of offset, as denoted by arrow "C”, of the segments 26 and improper direction of concave curvature, as denoted by arrow "F”', of the segments 26.
  • the chart shows a graphical comparison of the heat transfer performance (shown on the vertical axis of the chart in units of
  • Each tube represented in Figure 14 is one and a half (1 14) inch in diameter, each tube is provided with 0.75 inch high serrated fins, and each tube has six (6) fins per inch. Also, both tubes were employed in a staggered tube layout for testing.
  • the finned tube 18 constructed according to the present invention consistently outperformed a comparable conventional prior art finned heat exchange tube.
  • this chart also shows a graphical comparison of the heat transfer performance (also shown on the vertical axis of the chart in units of BTU/Hour/Square Foot/Degree Fahrenheit) for various gas mass velocities (also shown on the horizontal axis of the chart in units of Pounds/Square Foot/Hour) between another finned tube 18 constructed in accordance with the present invention, as indicated by numeral 56, and a standard prior art finned heat exchange tube, as indicated by numeral 58.
  • each tube represented in Figure 15 is two (2) inches in diameter, each tube is provided with 1.0 inch high serrated fins, and each tube has six (6) fins per inch. Also, both tubes were employed in a staggered tube layout for testing. As this chart also clearly shows, the finned tube 18 constructed according to the present invention consistently outperformed a comparable conventional prior art finned heat exchange tube.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Geometry (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

Abstract

L'invention concerne un nouveau type d'ailette segmentée (12) à utiliser sur un tube à ailettes (18), le type unique de tube à ailettes (18) fabriqué avec le nouveau type d'ailette segmentée (12), des roues à denteler spécialisées (14, 16) permettant de fabriquer le nouveau type d'ailette segmentée (12), et le procédé d'utilisation des roues à denteler spécialisées (14, 16) permettant de fabriquer le nouveau type d'ailette segmentée. Chaque segment (26) du nouveau type d'ailette segmentée (12) est dotée d'une courbure permanente, et les segments (26) sont stratifiés afin d'augmenter leur surface et de façonner davantage les bords cisaillés (42, 44) des segments (26) en une configuration plus pointue dans le but de rendre lesdits segments plus aérodynamiques.
EP99960560A 1999-11-22 1999-11-22 Segment d'ailette a courbure aerodynamique Withdrawn EP1232373A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1999/027713 WO2001038813A1 (fr) 1999-11-22 1999-11-22 Segment d'ailette a courbure aerodynamique

Publications (1)

Publication Number Publication Date
EP1232373A1 true EP1232373A1 (fr) 2002-08-21

Family

ID=22274120

Family Applications (1)

Application Number Title Priority Date Filing Date
EP99960560A Withdrawn EP1232373A1 (fr) 1999-11-22 1999-11-22 Segment d'ailette a courbure aerodynamique

Country Status (4)

Country Link
EP (1) EP1232373A1 (fr)
JP (1) JP2003515096A (fr)
KR (1) KR100570111B1 (fr)
WO (1) WO2001038813A1 (fr)

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1328302A (en) * 1970-06-25 1973-08-30 Escoa Fintube Corp Segmented finned tube and its method of manufacture
US4227572A (en) * 1978-03-27 1980-10-14 Seton-Scherr, Inc. Finned tubing
HU186052B (en) * 1982-04-06 1985-05-28 Energiagazdalkodasi Intezet Spiral-grilled tube particularly for heat exchangers
JPS5986896A (ja) * 1982-11-09 1984-05-19 Seiichi Konaka 小ビレ付フイン管熱交換装置
US5240070A (en) * 1992-08-10 1993-08-31 Fintube Limited Partnership Enhanced serrated fin for finned tube

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO0138813A1 *

Also Published As

Publication number Publication date
WO2001038813A1 (fr) 2001-05-31
KR20020053860A (ko) 2002-07-05
KR100570111B1 (ko) 2006-04-12
JP2003515096A (ja) 2003-04-22

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