Heat exchangers
United States Patent 1 1 1111 3,877,517  
 Pasternak Apr. 15, 1975 HEAT EXCHANGERS 3,692,105 9/1972 OConnor 165/18] 41 61 ll 1. 165 I46 [75] Inventor: Stephan F. Pasternak, Park Ridge, 3 739 8 l 973 Sma et a I I1]. Primary ExaminerAlbert W. Davis, Jr. [73] Assignee: Peerless of America, Incorporated, Attorney, Agent, or Firm-Root &amp; OKeeffe Chicago, ll]. 22 Filed: July 23, 1973 [571 f 1 ABSTRACT A heat trans er e ement, and the method of making [21] Appl 381565 the same, wherein fins are formed on an elongated tubular member by cutting them from sidewall portions 52 us. c1. 165/146; 165/172; 165/181; f h tubular member, with h fins being progres- 29/1573 3; 62/515 sively more closely spaced relative to each other longi- [51] Int. Cl .f. F28f 13/14 tudinally of the tubular member from area to area [58] Field of Search 165/146, 147, 181, 172; therealong, and ng the l r mem r into a 29/1573 B; 62/515 serpentine pattern effective to dispose the different v areas on different passes, so that the fins on adjacent [56] References Cited passes are progressively more closely spaced from one UNITED STATES PATENTS side to the opposite side of the heat transfer element. 1,524,520 1 1925 Junkers 165 146 6 Claims, 3 Drawing Figures Ill]  1 jllltklljllllllll a 3 e g q 1111111111111111111111111 1111 1 |)l/||l\|jlllllll if 7 3 5 4 HEAT EXCHANGERS BACKGROUND OF THE DISCLOSURE This invention relates to heat transfer elements and, more particularly, to heat transfer elements of the spined type, and to the method of making the same.  
  It is a primary object of the present invention to afford a novel heat transfer element.  
  Another object of the present invention is to afford a novel method of making a heat transfer element.  
  Another object of the present invention is to afford a novel heat transfer element of the spined type.  
  Heat exchangers embodying outwardly projecting fins, wherein the fins are progressively more closely spaced from one side to the opposite side thereof, have been heretofore known in the art. However, insofar as is known, heat exchangers heretofore known, which embodied such construction, have been of the plate-fin type, wherein laterally spaced, elongated passes in the form of tubular members are mounted on or in fin plates, such as, for example, heat exchangers of the type disclosed in US. Pat. No. 3,114,963 issued to R. W. Kritzer on Dec. 24, 1963. Such heat exchangers are often used as evaporators in refrigeration or airconditioning systems, and the like, wherein air flows across the heat exchanger between the fins. With this construction, with the air flow being from the wider spacing of the fins to the narrower spacing thereof, space is afforded between the more widely spaced fins for frost to accumulate thereon by reason of the condensation and subsequent freezing of moisture from the warmer air initially contacting the heat exchanger. As such air passes across such heat exchangers it progressively becomes drier so that little or no frosting of the fins will occur, and by disposing the fins in more closely adjacent relation to each other additional heat transfer surface is afforded for greater and faster cooling of the air.  
  An object of the present invention is to afford a novel heat transfer element embodying elongated passes disposed in side-by-side relation to each other, and fins projecting outwardly from the passes transversely to the length of the passes, with&#39;the fins being spaced progressively closer to each other from one side to the opposite side of the heat transfer element transversely to the length of the passes and to the direction of projection of the aforementioned fins.  
  An object ancillary to the foregoing is to afford a novel heat transfer element of the aforementioned type wherein the fins are formed integrally with the body portion of the passes.  
  Another object of the present invention is to afford a novel heat transfer element, embodying an elongated tubular member bent into a serpentine pattern, with fins spaced therealong in a novel and expeditious manner whereby the spacing of the fins on the return bends and passes of the heat transfer element is progressively closer from one end of the tubular member to the other.  
  Another object of the present invention is to afford a novel heat transfer element which is practical and efficient in operation, and which may be readily and economically produced commercially.  
  Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show the preferred embodiment of the present invention and the principles thereof and what I now consider to be the best mode in which I have contemplated applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims.  
 DESCRIPTION OF THE DRAWINGS In the drawings:  
  FIG. 1 is a fragmentary, perspective view of an end of a tubular member illustrating the preferred manner in which integral fins may be formed thereon in accordance with the principles of the present invention;  
  FIG. 2 is a fragmentary, side elevational view of a tubular member, illustrating the programmed spacing of fins therealong in accordance with the principles of the preferred embodiment of the present invention; and  
  FIG. 3 is a somewhat diagrammatic top plan view of a heat exchanger embodying the principles of the present invention.  
 DESCRIPTION OF THE EMBODIMENT SHOWN HEREIN A tubular heat exchanger or heat transfer element 1 is shown in the drawings to illustrate the presently preferred embodiment of the present invention.  
  The heat exchanger 1 embodies an elongated tubular member 2 bent into a serpentine pattern which affords a plurality of laterally spaced, substantially parallel passes 3, interconnected by return bends 4, with fins 5 projecting outwardly from the tubular member 2 transversely to the serpentine pattern of the passes 3 and the return bends 4, FIG. 3. The fins 5 are progressively spaced closer together from one end A to the other end B of the tubular member 2. As somewhat diagrammatically illustrated in FIG. 3, the progressively closer spacing of the fins 5 is by areas, with the fins in each respective area being uniformally or substantially uniformally spaced.  
  The heat exchanger l, shown in FIG. 3, embodies six parallel passes 3, with three such areas of fin spacing, the first area embodying the pair 7 of passes 3 disposed most closely adjacent to the end A of the tubular member 2; the next area embodying the central pair 8 of passes 3; and the other area embodying the pair 9 of passes 3 disposed most closely adjacent to the end B of the tubular member 2. The spacing of the fins 3 on the various areas may be any desired spacing, such as, for example, the fins 5 on the pair 7 of passes 3 being spaced two fins per inch; the fins 5 on the pair 8 of passes 3 being spaced four fins per inch; and the fins 5 on the pair 9 of passes 3 being spaced six fins per inch;  
  With such construction, it will be seen that, with the heat exchanger 1 comprising an evaporator in a refrigeration of air conditioning system, or the like, air may be passed across the heat exchanger 1 in the direction of the arrow 10 from one side 11 to the opposite side 12 thereof between the fins 5 on the passes 3. The spacing of the fins 5 on the heat exchanger 1 is such that the paths for the passage of air between adjacent fins 5 progressively narrows from one to the other of each adjacent pair 7-9 of the passes 3. Thus wider spacing between fins 5 is afforded at the portion of the heat exchanger 1 wherein air passing thereacross initially contacts the same. Nornially, such air is relatively warm and contains a substantial amount of moisture, and the cooling thereof commonly causes the moisture to condense and freeze on the fins 5. As the air continues to pass across the heat exchanger 1 in the direction of the arrow 10, it becomes progressively cooler and drier so that there is less tendency to condense and freeze moisture therefrom. The wider spacing of the fins at the earlier stages of the passage of air therebetween, affords space for frost to build up on the fins 5 for prolonged periods of time without causing complete blockage against the passage of air therebetween. The progressively narrower spacing between the fins 5, as the air passes across the heat exchanger 1, is also possible, without the buildup of frost causing complete blockage of the passage of air therebetween for the same prolonged periods of time, because the air, as it passes across the heat exchanger 1, progressively becomes cooler and drier so that frost buildup on the fins correspondingly decreases. The progressively closer spacing of the fins affords increased heat transfer surface for affording greater heat transfer between the heat exchanger and the air passing thereacross.  
  As will be appreciated by those skilled in the art, the showing of the heat exchanger 1 in FIG. 3 as embodying six parallel passes, and the aforementioned progressively closer spacing of two, four and six fins per inch is merely by way of illustration and not by way of limitation, and heat exchangers embodying a greater or lesser number of passes, and a different programming of fin spacing may be used without departing from the purview of the present invention.  
  In making the presently preferred form of heat exchanger 1, by the presently preferred method, an elongated, substantially straight tubular member 2a, FIG. 1, is first formed. The tubular member 2a is preferably rectangular in transverse cross section, and embodies two substantially parallel, wider opposite sidewalls l3 and 14 and two oppositely disposed, substantially parallel narrower sidewalls and 16, FIG. 1. The tubular member 20, thus formed, also embodies two elongated ribs 17 and 18 projecting outwardly from and extending in parallel relation to each other longitudinally of each of the sidewalls l5 and 16.  
  After the tubular member 2a has been so formed, the fins 5 may be formed thereon by successively, from one end portion C toward the other end portion D thereof, cutting or gouging the fins 5 from the respective pairs of ribs 17 and 18 and the underlying portions of the sidewalls 15 and 16 in the manner disclosed in U.S. Pat. No. 3,692,105 issued to Joseph M. OConnor on Sept. 19, 1972. In this operation, the fins -5 are formed on each of the sidewalls 15 and 16 by means of a suitable cutting tool which first cuts along lengthwise of each respective rib l7 and 18 on each sidewall 15 and 16 to form spines 19 and 20, respectively, FIG. 1. Thereafter the cutting tool continues to cut along lengthwise of the respective sidewalls l5 and 16 to thereby cut the portion thereof underlying the respective ribs 17 and 18 thereon to form a base 21 for each fin 5, the base 21 preferably extending across the entire width of the respective sidewall 15 or 16, and the spines l9 and 20 projecting outwardly from opposite ends of the outer longitudinal edge of each base 21 in parallel spaced relation to each other, FIG. 1. The fin 5 which has been cut or gouged from the sidewall 15 or 16, is then bent outwardly preferably to a position of approximately perpendicular relationship to the plane of the respective sidewall 15 or 16 on which it is formed.  
  Although, because of the spacing of the fins 5 along the ribs 17 and 18, the fins 5 are initially formed with enlarged portions, such as the portions 22 shown in FIGS. 1 and 2, the cutting operation causes the fins 5 to compress longitudinally so that, as a practical matter, the enlarged portions 22 substantially disappear on fins of usual thickness, to thereby afford a relatively smooth-sided appearance for the outer ends of the fins 5.  
  Thereafter, in the practice of the preferred method of the present invention, the tubular member 2a may be cut off to the desired length, such as, for example, the length of the tubular member 2 embodied in the heat exchanger 1 shown in FIG. 3.  
  In the forming of the fins 5, the spacing thereof is programmed so as to afford the adjacent areas of progressively more closely spaced fins, with the fins of each particular area preferably being equally spaced. This may be accomplished in any desirable manner, such as, for example, by varying the rate of feed of the tubular member 2a through the cutting machine relative to the speed of reciprocation of the cutting tools.  
  In the forming of the tubular member 2 of the heat exchanger 1 shown in FIG. 3, three variations in spacing were used in the programming of the formation of the fins 5, resulting in three separate areas, such as the areas 23, 24 and 25 shown in FIG. 2, the fins 5 in area 23 being most widly spaced, the fins 5 in area 24 being the next most widely spaced, and the fins 5 in the area 25 being the most closely spaced. In forming the heat exchanger 1, the bending of the tubular member 2 preferably is programmed so as to dispose the pair 7 of passes 3 in the area 23, the pair 8 of passes 3 in the area 24 and the pair 9 of passes 3 in the area 25. Preferably, the changeover from one area to another is made at the midpoint of one of the return bends 4. v  
  In the bending of the tubular member 2, it preferably is bent into a serpentine pattern, as shown in FIG. 3, wherein the passes 3 are disposed in parallel relation to each other, with the passes 3 and the return bends 4 being disposed in substantially uniplanar relation, and with the fins 5 projecting outwardly from both sides of the tubular member 2 transversely to the plane extending between the sides 11 and l2&#39;of the heat exchanger 1.  
  Of course, it will be understood, by those skilled in the art that fins 5 are shown projecting outwardly from two opposite sides of the tubular member 2 merely by way of illustration of the preferred form of the present invention, and not by way of limitation, and that, if desired, the fins 5 may be formed only on one of the sidewalls 15 or 16 of the tubular member 2a without departing from the purview of the broader aspects of the present invention.  
  From the foregoing it will be seen that the present invention affords a novel heat exchanger which is practical and efficient in operation, and which may be readily and economically produced commercially.  
  Also, it will be seen that the present invention affords a novel method of making a heat exchanger of the fin type, wherein the spacing of the fins is programmed to afford progressively closer spacing from one side to the opposite side of the heat exchanger.  
  Thus, while I have illustrated and described the preferred embodiment of my invention, it is to be understood that this is capable of variation and modification, and I therefore do not wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall into the purview of the following claims.  
 I claim: 1. A heat transfer element comprising a. a tubular member having an elongated wall, having two pairs of oppositely disposed longitudinally extending sides, b. said tubular member being bent back and forth in a serpentine pattern to afford 1. a plurality of elongated passes laterally spaced from each other from one side to the opposite side of said pattern, and  
 2. a plurality of return bends interconnecting respective pairs of said passes, c. said return bends and said passes being disposed in substantially uniplanar relation to each other, (1. said oppositely disposed sides in one of said pairs being disposed on the outside and inside of said return bends, e. a plurality of fins 1. having base portions formed integrally with at least one of said oppositely dispoed sides in only the other of said pairs,  
 2. spaced from each other longitudinally of passes,  
 and  
 3. projecting outwardly from said wall transversely to said plane, and  
 f. said fins on respective ones of said passes being spaced progressively closer to each other longitudinally of said tubular member from said one side to said opposite side of said pattern.  
 2. A heat transfer element as defined in claim 1, and  
 in which a. said tubular member is substantially rectangular in transverse cross-section and has 1. two substantially parallel, oppositely disposed sidewalls forming said sides in said one pair, and  
 2. two other substantially parallel, oppositely disposed sidewalls extending between said first mentioned two sidewalls and forming said sides in said other pair,  
 b. said two other sidewalls are narrower in width than said first mentioned two sidewalls.  
 3. A heat transfer element as defined in claim 2, and  
 in which a. said fins comprise spines spaced from each other across the width of said two other sidewalls.  
 4. A heat transfer element as defined in claim 2, and  
 in which a. said fins comprise l. elongated base portions a. extending across the width of said two other sidewalls, and b. having an outer longitudinal edge, and 2. a plurality of spines a. spaced along said longitudinal edges, and b. projecting outwardly therefrom.  
 5. A method of making a heat transfer element comprising a. forming an elongated tubular member having two pairs of oppositely disposed longitudinally extending sides,  
 b. cutting fins, which are spaced from each other longitudinally of said tubular member, from one of said sides in only one of said pairs, with the fins in predetermined areas, which are adjacent to each other longitudinally of said tubular member from one end portion to the other end portion thereof, being spaced closer together longitudinally of said tubular member than the fins in the preceding area,  
 c. turning said fins into outwardly projecting relation to said sides from which they are cut, and  
 d. bending said tubular member back and forth around said sides in the other of said pairs to afford a serpentine pattern 1. embodying a. a plurality of return bends, and b. a plurality of elongated passes laterally spaced from each other from one side to the opposite side of said pattern, and 2. in which said fins in respective ones of said areas project from respective ones of said passes.  
 6. The method of making a heat transfer element as defined in claim 5, and which includes a. so forming said tubular member that 1. it is substantially rectangular in transverse crosssection, and 2. said two pairs of sides comprise two pairs of substantially parallel oppositely disposed sidewalls,  
 b. cutting said fins from each of said sidewalls in said one pair, and  
 c. turning said fins into outwardly projecting relation to each of said last mentioned sidewalls.