US 2402262 A
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Description (OCR text may contain errors)
June 18, 1946. c. A. sEwELL 2,402,262
HEAT EXCHANGE FIN Filed ug. 30, 1945 2 Sheets-Sheet l @4. JMW
CLEVELAND A. SEI/VEL L June 18, 1946. c. A. sEwELL HEAT EXCHANGE FIN Filed Aug. 30, 1943 2 Sheets-Sheet 2 31u/ummm ci. EvEmA/DASEWHLL Patented June 18, 1945 HEAT EXCHANGE FIN Cleveland A. Sewell, Newark, N. J., assgnor to American Coils Co., Newark, N. J., a firm consisting of Bessie Binder, Thomas Binder, and
Harold Binder Application August ao, '1943. seriaiNo. 500,567
This invention is directed to a methodof fabri eating and the construction of heat-exchange fins, with the particular purpose of increasing the heat-exchange function, avoiding the possibility of iin insulation by retarded air flowI and provide for a perfect mechanical bond between the iin and the carrying tube.
In heat exchange constructions involving the provision of 'a carrying tube and a plurality of heat-exchange fins secured thereon, it has been found that the conventional arrangement is more or less ineiilcient for desired heat exchange, in that it usually provides a flat surface with parallel air iiow, causing a small film of air in immediate contact with the n to act as an insulating layer for the iin and materially retard the effective heat exchange, and necessitating the increase of fin surface or the quantity of air passing over the fins for proper results.
` An essential object of the present invention is therefore to so form the iin area. as to, in effeet, materially increase the iin area with which the air contacts to thereby expose a relatively greater fin surface to the flow of air per lineal feet of iin surface, to thereby avoid insulating air film and permit effective heat exchange with s air under lower volume andpressure.
" Again many fins have been designed to create turbulence in the air stream to break up interfering and insulatingair films, but such constructions have, for effective heat exchange, been formed to retard the air flow and require higher air-flow pressure or greater volume of air.
It is a further object of the present invention to form the iin with a view to creating the necessary turbulence without material retarding of air flow to thereby permit.active clearance of air past the iin in a mannery to insure, maximum heat exchange.
The conventional heat-exchange units involve the use of a tube and heat-exchange fins secured to the tube normal to its axis, with the fins having integral spacer strips which overlie and bear on the tube and limit the positions of the adjacent fins. The conventionally formed spacer strips have their roots in the margin of the tube receiving opening in the fin, and in this particular provide a. decided objection to the use of a mechanical bond between the fin and tube, espe.l
cially where such mechanical bond involves the expanding of the tube to embed the edge of the iin opening.
A'further, and particularly important feature of the present invention is the provision of the desired spacer strips for the n with such strips 4 Claims. (Cl. 257-262) integral with and extending from the fin, but
with the strips so connected to the iin that the edge margin of the tube opening in the fin is completely free of any strip connection, to permit such edge margin of the tube opening to retain throughout its circumferential length its normal relatively sharp edge for-conveniently embedding the tube under expansion of the latter, for certainty and rigidity of fin mounting form Fig. 6 is a front elevation of a slightly modifiedY type of fin construction.
Fig. 7 is a perspective view of the modified type of fin shown in Fig. 6.
Figure 8 is a view partly in elevation and partly in section of the modification shown in Figures 6 and 7.
Fig. 9 is an elevational view of a fin constructed in accordance with another embodiment of the invention, and
Fig. 10 is a sectional View taken substantially on the line' lll- IIJ of Fig. 9, a second position of the spacer strips being indicated by broken lines? The method of construction resides in slitting the outer edge of the iin body on radial lines extending a predetermined distance toward but not meeting the usual tube receiving opening formed centrally of the iin, and then deiiecting the independent vanes so formed from the normal piane of the fin body to provide increased heatexchange surface; the method also involvingthe provision of 1in-spacer strips integral with the fin, but with their roots projecting from the iin body 'at points outwardly of the margin of the tube tube opening, the n-vanes being then relatively distorted or deected with respect to the normal n plane; the iin body being then cut out at desired spaced intervals to provide spacer strips,v
the spacer strips being so cut from the body as to have their root portions extending from the body at points adjacent but wholly beyond the margin of the tube opening in the iin, for the purpose of leaving such margin completely uninterrupted for mechanical bonding of the fin and tube.
With a view to a better understanding of the method the mechanical construction of the iin will be explained in the light of the drawings.
In the form shown yin Figs. l to inclusive, the fin body I is shown as rectangular in form, centrally formed with an opening 2 to receive the conventional tube 3. 'I'he tube is of a character to permit a mechanical bond between the tube and n by appropriately expanding the tube after application of the ns to cause the edge of the opening 2 to embed itself in the material of the tube, and obviously to provide a proper thermal contact and effective securing of the n in place, the full, uninterrupted margin of the tube opening 2 must be so embedded.
The outer edge of the fin body is slitted on radial lines 4, opening through the outer edge and extending toward the tube opening 2, but terminating materially short thereof to leave a flat area 5 in the normal plane of the fin between the tube opening 2 and the ends of the radial slits 4. The slits provide n-vanes 6, each connected with the fin body but each independent of the other beyond the area 5 of the body.
The fin-vanes are in the form-being described twisted on their longitudinal axes, as'at 7, to present one half of each vane on opposites of the normal plane of the body. The vanes 6 are so twisted as to present parallel air contact areas deilnitely spaced one from the other and each at a slight angle to the normal plane of the n relative to the tube. 'I'he material -of the flat area 5 of the iin is utilized to form the spacer-strips indicated at 8, which strips are cut from the fiat area 5 so as to leave the connected portion o'r root of the strip at a point 9, which as clearly shown in Fig. 4 is outwardly of and wholly free of the margin of the tube opening 2. The strips 8 are then bent from their roots into a position to extend at substantially right angles to the iin to overlie and bear on the tube 3 when the iin is applied. This particular construction of the spacer strips, of which there may be any desired number, avoids any interference with the sharp edge of the margin of opening 2 and at the same time leaves a small margin of n body, as at IB'to provide an abutting area for the ends of the strips of adjacent iins for spacing purposes. It is of course understood that the spacer strips are of such lengths as to provide the usual spacing function relative to adjacent iins in the application of the ns.
In the form of the invention shown more particularly in Figs. 6, 7, and 8, the construction of the fin is identical with that previously described, and the same reference numerals are used in these gures to identify the same parts previously described. This modled form, however, diilers from the preferred form in that the n-vanes, shown in the modilled form at II, are not twisted in angular relation to the normal plane of the fin, but are bodily deected at the roots in successively opposite directions from the normal plane of the fin and then extended in planes radial oi "but slightly offset from the normal plane of the body. In this form, viewing the lin ln edge relation, the vanes I I are successively oppositely positioned and define an uninterrupted space between them for air ow, with the marginal edges fully open to air contact.
In this modified form the spacer strips 8 are formed as previously described, and in effect the modied form differs from the preferred form only in the relation of the iin-vanesto the normal plane of the 1in body.
From the constructions described it will be seen that the amount each nn vane is deflected olf the center of the plane of the 1in is equal tov one-half the iin spacing of the iinal surface, and in setting the fins on the tube care must be taken that the alternate iins be the full iin spacing, so that vanes of adjacent fins when on the tube shall project on the similar sides of the iin planes to maintain this spacing.
The iin vanes act as individual n sections, but as they act alternately and oppositely on the air stream, the air is permitted to flow through Without undue obstruction, and yet no part of the air stream is permitted to form an air lm adjacent the fln surface. By this formation approximately fifty per cent more of the iin surface is subject to the air stream than is possible by a flat iin. Thel improved n is more elective as a heat-exchange unit because more fln area is exposed to the air stream per lineal feet of surface; the exposed edges of the vanes provide additional exchange surface, being effective in their obstructive function; and as there is no air nlm on the surface effective heat exchange may be accomplished with a lower pressure drop in the ow of the air.
In the particular construction of the spacer strips, it will be apparent that if the strip had its root directly at the margin of the tube opening Ci, such root would present an obstruction to the free embedding of the margin in the tube in the mechanical bonding. Thus effective bonding would be diiilcult preventing not only proper contact of the tube and-fin, but proper xing of the iin in place. By the .improved spacer-strip formation the margin of the tube opening 2 is completely unobstructed presenting a uniform edge which, under expansion of the tube under anyusualr or preferred method, may be evenly and correctly embedded into the material of the tube to insure a proper holding of the iin and also a proper metallic contact between the tube and n.
In the embodiment of the invention as illustrated in Figures 9 and 10, the iin body I2 is initially produced with the spacer strips I4 extending inwardly and radially of the central opening I5. However, as the body I2 is placed upon the tube I6, the spacer strips I4 ex outwardly, as indicated by broken lines in Figure 10. It is believed to be obvious that these strips I4 are of such length to provide the required spacing between adjacent bodies. It is believed to be obvious that the body as illustrated in Figures 9 and 10 can be initially stamped and in a manner wherebythere is but a minimum of waste material.
While the present invention is more particularly designed for use in cooling air, it is to be understood that the improved iin is equally effective in other heat-exchange requirements, and that any and all such additional uses are contemplated as within the spirit of the present invention.
Having thus described the invention, what is `claimed as new, is:
1. A heat-exchange iin comprising, a central annular fin body having an opening therethrough u assembly formed by an even number of radial' vanes each attached at one end to-said body and projecting radially from said body, said vanes being offset axially with respect to said central body with the vanes being in two groups offset in opposite directions and with the vanes in the two groups alternately positioned whereby each vane is oiiset in the opposite direction from the two next adjacent vanes, said body being substantially in a single plane and with the vanes of the two groups being substantially in single planes respectively n Opposite sides of the plane of said body.
2. A heat-exchange iin as described in claim 1, wherein the o'uter contour of the lin is substantially rectangular and wherein the vanes are separated by radial slits which extend inwardly from the n periphery.
3. A rectangular heat-exchange fin comprising, a central fin body having an opening therethrough defined by a substantially uninterrupted inner margin which is adapted to receive snugly an expansible metal tube, and a heat-exchange vane assembly formed by an even number of peripherally positioned vanes each attached at one end to ,said central n body and projecting from said central n body, said vanes being separated by slits which extend inwardly from the periphery of the fin to said central body and with the vanes ybeing offset with respect to said central body and being in two groups which are offset in opposite directions with the vanes in the two groups alternately positioned whereby each two adjacent tins are offset in the opposite directions, said central n body being substantially in a single plane and said tins of the two groups being respectively in -two parallel planes which are olfset with respect to each other and also on opposite sides of and offset with respect to the plane of said central body.
' 4. A heat-exchange fin as described in claim 3 which includes a plurality of integral spacing members which are attached to said central iln body at points spaced fromsaid central body and which project from said central body and act as spacer members and heat-exchange 1in portions.
CLEVELAND A. SEWELL.