US 3643735 A
A metal fin and tube heat exchanger comprising laterally adjacent tubes and a helical fin around each tube in which each fin tip is closely adjacent the tip of the next fin so that shifting of the tube and its fin under thermal expansion and contraction tends to cause internesting and interlocking of these adjacent tips, and a helical metal strip around and engaging each fin adjacent its tip. Each strip has a pitch differing from that of its fin to provide barriers that block internesting and interlocking of the adjacent fins on relative movement between the adjacent fins.
Description (OCR text may contain errors)
United States Patent Huggins Feb. 22, 1972  FIN AND TUBE HEAT EXCHANGER  Appl. No.: 122,757
 U.S.Cl ..165/172, 165/69, 165/182, 165/ 184  Int. Cl ..FZS! H36  Field ofSearch ..165/69, 162, 172, 182, 184, [65/67  References Cited UNITED STATES PATENTS 3,249,154 5/1966 Legrand ..165/164 3,326,282 6/1967 .lenssen ..165/172 FOREIGN PATENTS OR APPLICATIONS 130,895 1/1949 Austria ..165/172 335,36] 3/1921 Germany ..165/172 Primary Examiner-Albert W. Davis, Jr. AnomeyHofgren, Wegner, Allen, Stellman & McCord  ABSTRACT A metal fin and tube heat exchanger comprising laterally adjacent tubes and a helical fin around each tube in which each fin tip is closely adjacent the tip of the next fin so that shifting of the tube and its fin under thermal expansion and contraction tends to cause internesting and interlocking of these adjacent tips, and a helical metal strip around and engaging each fin adjacent its tip. Each strip has a pitch differing from that of its fin to provide barriers that block internesting and interlocking of the adjacent fins on relative movement between the adjacent fins.
8 Claims, 6 Drawing Figures PAIENTuFa22 m2 SHEET 1 [IF 2 INVENTOR.
PAIENTEDFEBZZ m2 3.643 735 SHEET 2 OF 2 FIG4 FIG5
FIN AND TUBE HEAT EXCHANGER SUMMARY OF THE INVENTION One of the features of this invention is to provide a metal fin and tube heat exchanger in which the tubes are laterally adjacent each other for flow over and around the tubes of the first fluid for heat exchange with the second fluid within the tubes, each tube being provided with a helical fin to aid the heat transfer and with at least some of the fins each having a helical metal strip engaging the fin adjacent its tip and of a pitch differing from that of its fin tip to provide barriers that prevent internesting and interlocking of the tips on relative movement between adjacent tube and fin assemblies.
Other features and advantages of the invention will be apparent from the following description of certain embodiments thereof.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of one embodiment of the invention.
FIG. 2 is a view similar to FIG. I but illustrating a second embodiment.
FIG. 3 is a fragmentary side elevational view of one of the embodiments illustrating the invention.
FIG. 4 is a view similar to FIG. 3 but illustrating a further embodiment. I
FIG. 5 is an enlarged sectional view taken substantially along line 5-5 of FIG. 4.
FIG. 6 is a semidiagrammatic fragmentary end elevational view of a further embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment of FIG. 1 the tube and fin assemblies 10 each comprising a metal tube 11 and a helical fin l2 therearound and attached thereto are positioned so that the assemblies are in parallel rows that are parallel to the direction of airflow as indicated by the arrows 13. Thus the air comprises one fluid that is in heat transfer contact by way of the tubes 11 and fins 12 with a second fluid such as water flowing within the tubes 11.
In FIG. 2 the tube and fin assemblies 10 are the same as those of FIG. 1 but here they are arranged in tandem in relation to the airflow 14.
As is illustrated in the embodiment of FIG. 3 the tips or edges 15 of the fins are closely adjacent to each other. Any shifting of the assemblies relative to their neighbors and particularly shifting due to thermal expansion and contraction would ordinarily tend to cause the fin tips to internest and interlock and thereby interfere with each other as well as tend to cause damage to the fins. This problem occurs in very large tube and fin structures where the tubes are either horizontal or inclined as they tend to sag thereby bringing the fin edges or tips into contact with each other. The damaging interengagement of fin tips is also particularly acute when one tube of an adjacent assembly is subjected to temperatures that are considerably different from the temperatures of adjacent tubes. In an attempt to solve this problem tube supports have been tried and even cylindrical sleeves around the fin tips have been proposed. All of these, however, have been found to be unsatisfactory, as either not preventing the problem or interferring with the proper heat transfer and with the necessary fluid flow over and between the fins and tubes.
FIG. 3 illustrates one embodiment of a solution to this problem. As is illustrated there, the helical fins 12 around each tube 11 are each provided with a helical metal strip 16 attached to the fins 12 adjacent their tips 15. Each helical strip 16 is of a pitch differing from that of the fin tip 15 with the result that the strip provides an effective barrier as illustrated in FIG. 3 to prevent the tips 17 of one fin 12 from being shifted into the space between the tips 15 of the next set with possible damage and malfunctioning of the heat exchanger.
In the preferred construction as illustrated in FIG. 3 the helix of the metal barrier strip extends counter to the direction of the helix of the fin 12. Thus when viewed from the left of FIG. 3 the helix of the fin 12 is counterclockwise to the tube 11. The helix of the barrier strip 16, on the other hand, is clockwise to the tube 11 as viewed from the left side of FIG. 3.
The metal barrier strip 16 may be either a flat narrow ribbon as in FIG. 3 or a wire 18 as in the embodiment of FIG-5. Regardless of the form of the strip it is preferably metallurgically bonded to the metal of the fin 12 as by welding, soldering, brazing or the like in order to secure it fixedly in position and also to provide an additional heat transfer member having efficient heat transfer connections between the barrier strip and the fin tips.
In the embodiment of FIGS. 4 and 5 the fin adjacent its tip 20 is provided with a succession of metal tabs 21 struck from the fin 19 thereby leaving an opening 22 that extends generally radially from the tube 23. These tabs 21 engage the next adjacent turn of the fin 20 and are preferably themselves arranged in a helix as shown in FIG. 4. The ends of these tabs are metallurgically bonded to the next turn of the fin so as to provide a strong additional barrier and also to provide more efficient heat transfer between successive turns adjacent the fin tips 20. As illustrated in FIGS. 4 and 5 there may also be provided an additional barrier strip 18 of the type described in connection with the barrier strip 16 that also aids in preventing internesting and interlocking engagement of the successive fins which as described and as disclosed in FIG. 3 are closely adjacent each other.
In the preferred construction the succession of tabs 21 is arranged in a helix that is substantially diametrically opposite the helical barrier strip 18. As stated earlier, this barrier strip I 18 may be in the form of a wire as illustrated in FIG. 5 or a flat ribbon.
With both the-strip l8 and the helically arranged tabs 21 acting as barriers there can obviously be considerable shifting of the tube and'fin assemblies relative to each other without substantial intemesting or interlocking.
The barrier strips of this invention not only provide efficient interlocking and intemesting barriers but such structures can be manufactured automatically with the proper equipment and also require less labor to install than the conventional tube and fin heat exchanger assemblies. In addition, because the fluid such as the air can pass easily between the turns of the helicalbarriers there is 'no substantial interference to fluid flow. As mentioned earlier, when the barrier strips are metallurgically bonded to adjacent fin turns they provide added heat transfer paths and surfaces as well as promoting additional turbulence, all of which increases the total heat transfer coefficient.
A very important advantage of the invention is that now assemblies of multiple row tube and fin structures 24 can be bent to a desired curvature as is illustrated inFIG. 6. It is obvious that in bending such multiple rows the assemblies must be free to move relative to each other because all of the assemblies are bent to different radii. The provision of the helical barrier strips 25 of the type already described permits this bending of the tube and fin structures 24 in unison while preventing the intemesting and interlocking of adjacent fins 26. Thus with this invention it is now possible to bend many tube and'fin cores simultaneously while before it was necessa ry to bend each core individually to the required radius. This is obviously a considerable saving in time and labor.
Having described my invention as related to the embodiment shown in the accompanying drawings, it is my intention that the invention be not limited by any of the details of description, unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the ap pended claims.
I. A metal fin and tube heat exchanger, comprising: a plurality of laterally adjacent tube sections; a helical fin on each tube section attached thereto and extending therearound to provide an assembly, the outer tip of each fin being closely adjacent the tip of the next fin; and a helical metal strip engaging each said fin adjacent its tip of a pitch differing from that of its said fin tip to prevent internesting and interlocking of said tips on relative movement between said adjacent assemblies.
2. The heat exchanger of claim 1 wherein the helix of said metal strip extends in a direction counter to the direction of the helix of the fin engaged by the metal strip and has a pitch greater than that of its fin tip.
3. The heat exchanger of claim 1 wherein said metal strip comprises a flat metal ribbon.
4. The heat exchanger of claim 1 wherein said metal strip comprises a wire.
5. The heat exchanger of claim 1 wherein each fin tip is provided with a tab struck from the fin and engaging the next successive turn of the fin adjacent the tip to provide a succession of tabs as further barriers to said internesting and interlocking, said succession of tabs being arranged in a helix.
6. The heat exchanger of claim 1 wherein said helical metal strip is metallurgically bonded to its said fin.
7. The heat exchanger of claim 6 wherein the helix of said metal strip extends in a direction counter to the direction of the helix of the fin engaged by the metal strip and has a pitch greater than that of its fin tip.
8. The heat exchanger of claim 7 wherein each fin tip is provided with a tab struck from the fin and engaging the next successive turn of the fin adjacent the tip to provide a succession of tabs as further barriers to said internesting and interlocking, saidsuccession of tabs being arranged in a helix.