US3250325A

US3250325A - Heat exchange device

Info

Publication number: US3250325A
Application number: US445073A
Authority: US
Inventors: Eugene E Rhodes; Alvin M Kurz
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1963-02-19
Filing date: 1965-04-02
Publication date: 1966-05-10
Anticipated expiration: 1983-05-10

Description

y 1966 E. E. RHODES ETAL 3,250,325

HEAT EXCHANGE DEVICE Original Filed Feb. 19, 1963 INVENTORS BY 6m ATTORN EYS United States Patent 0 3,250,325 HEAT EXCHANGE DEVIQE Eugene E. Rhodes, Belleville, and Alvin M. Kurz, Oak

Park, Mich, assignors to Ford Motor Company, Dearhorn, Mich a corporation of Delaware Original application Feb. 19, 1963, Ser. No. 259,547, now Patent No. 3,214,954, dated Nov. 2, 1965. Divided and this application Apr. 2, 1965, Ser. No. 445,073

4 Claims. (Cl. 165-153) This is a division of application Serial No. 259,547, filed February 19, 1963, now US. Patent 3,214,954. This invention relates to heat exchange devices and to methods for the manufacture of the same. In particular, this invention relates to a novel heat exchange fin structure or spacer strip for use in a device wherein heat exchange is effected between a liquid and a gas, as, for example, in automobile radiators and heaters. Although the use of the fin structure here involved is not restricted to any particular field, it is especially adapted for use as a part of the main cooling system of an engine and will be so referred to for the purpose of disclosing the novel features embodied therein.

' Although details of construction may vary, an engine cooling radiator ordinarily includes an inlet tank and an outlet tank for suitable connection with the water jacket of the engine, and a core or heat dissipating unit interposed between the two tanks for the travel of water in thin streams from one tank to the other through a number of spaced passageways or water tubes of suitable heat exchange material. Between each pair of these water conduits fiows an air stream to take up or absorb heat carried by the water. A heat exchange fin structure and spacer element comprising a thin strip of a suitable metal or alloy, e.g. copper, brass, etc., is generally folded back and forth and interposed between the water tubes for cooperation therewith to divide the intervening space into a number of small air cells.

In this type of spacer strip the portion extending between folds or major corrugations will herein be referred to as the heat exchange fin, the fin proper or merely the fin.

It was early recognized that more eificient use could be made of the air flow between the water tubes if a greater proportion of the air stream is brought into direct contact with the metal of the spacer strip and/or the walls of the water tubes. This led to the incorporation of transverse serpentine corrugations to provide an undulating flow in the air passage through the individual cells. In other designs, openings have been provided in the fin proper to allow air to flow from one cell into another in its passage through the core. In modifications of this design louvers have been employed adjacent to such openings to divert air through such openings.

The louvered fins heretofore employed exhibit certain undesirable characteristics. Some of these are inadequacies of the basic design while others result from the methods and tools employed to form the intended design.

Design weaknesses include improper positioning, alignment and shaping of the louvers employed. This can reduce the efficiency of the entire cooling system by misdirecting or failing to direct the air flow. Maximizing the cooling efficiency of the core results from maximizing the wiping contact of the air on metal without undue impedance or resistance to flow. Too often in the past the value of laminar flow either has been overlooked or rejected in a misguided search for designs adapted to maximize turbulence. Furthermore, methods heretofore employed to form the design on the fin strip have resulted in uneven fin surfaces which impair the efficiency of the soldering process whereby the fin'is made fast to the ad- 3,259,325 Patented May to, isles jacent water tubes. This results in both inadequate connections and the plugging of the air passages.

It is one object of this invention to provide an improved fin structure for use in a heat exchange device as hereinbefore described which will increase the heat absorption of an air stream passing through such device while reducing obstructions to such flow which do not contribute to heat exchange eificiency.

It is another object of this invention to provide an improved fin structure that will reduce losses in heat exchange efiiciency that result from prolonged contact between air and the metal of such devices after a practical level of heat absorption has been reached.

Many other objects and advantages of this invention will be obvious to those skilled in the art from the disclosure herein given:

In the drawings, wherein like reference characters indicate like or corresponding parts:

FIGURE 1 is a partially completed front view of an automobile radiator illustrating one use of the spacer strips or fin structures of this invention;

FIGURE 2 is a perspective view of a fin strip of this invention with portions thereof shown in the folded and unfolded state to illustrate the relationship of adjacent fins in the spacer strips of this invention; and

FIGURE 3 is a schematic view of two fins positioned on either side of an air cell and illustrating both the novel alignment and positioning of the fin louvers and representative paths of air particles passing therethrough.

Referring to FIGURES 1 to 3, the radiator assembly, as will be readily understood, includes a heat dissipating unit or core 11, having at opposite ends a top tank or inlet header 12, and a bottom tank or outlet header 13, adapted for connection, respectively, with the discharge and intake conduits of a cylinder block cooling jacket. For the flow of cooling medium from one tank to the other the core'is made up of a number of fiuid passageways or water tubes 14, spaced apartby fin strips 15. The fin strip shown in the drawing is of folded or corrugated outline providing a series of fins 16 between folds or connecting members 17. The strips 15 therefore extend between adjacent walls to the adjoining tubes to divide the space into a number of relatively small air cells or conduits l3. Ordinarily, the opposite edges or front and rear faces of the core assembly are dipped first in a fiux and then in molten solder to seal the margins of the walls of the water tubes where necessary and to join the fin strips to the walls. It the passageways and tin strips are evenly formed so as to make possible continuous contact from edge to edge, there will be an inward capillary flow of solder toward the center of the core, and a positive bond will result throughout substantially the entire depth of the core to insure the free flow of heat into the fins.

Attention is now directed to the novel design of the fin proper and specifically to FIGURES 2 and 3 of the drawings. Pin 16 is planar, i.e. a single plane and be passed. simultaneously through the entire length of both the longitudinal and transverse axes. For purposes of convenience such plane is hereinafter referred to as the central plane or base plane.

Provided in the planar fin 16 are groups of parallel

transverse slots

19, 24 and 26 through which air can pass from cell to cell. The slots 19 and the adjacent louvers are formed by slitting the planar fin and turning the interpositioned strips out of the central plane. Thus, in the embodiment shown the fin may be viewed as providing a pair of spaced apart louvered windows each of which provide a plurality of transverse openings between louvers which are aligned in parallel relationship with respect to the other louvers of the same window but inclined from the central plane of the fin at an equal and opposite angle from those of the next adjacent window. Although the fin of this embodiment provides only two of such windows it is to be understood that one or more additional windows may be provided in other embodiments with the same order of louver reversal with respect to adjacent Windows.

The portion of the end supports adjacent the terminal slots 24 form outer diversion louvers 25 which are pivoted from their base so as to project outward from one side of the central or fin plane. The edges of central support 21 adjacent the central terminal slots 26 form inner or central diversion louvers 27. The term terminal herein is used with respect to a given window, i.e. grouping of louvers and hence may or may not mean terminal with respect to the entire fin. Louvers 27 are also pivoted from their base so as to project from the central plane on the side opposite louvers 25. It will be noted that each of the outer diversion louvers 25 is aligned in parallel relationship with the nearest inner or central diversion louver 27 and that

louvers

25 and 27 extend from opposite sides of the central or fin plane. While the projecting edge of each of the outer diversion louvers 25 is inclined toward the nearest central support and in a two window fin toward the center thereof, the projecting edge of each of the inner or central diversion louvers 27 is inclined toward the nearest outer diversion louver or away from the center of the fin. The remainder of the fin provides a central support 21, positioned between such windows, side supports 22 and end supports 23.

The strips between slots 19 and

terminal slots

24 and 26 form intermediate louvers 28 each of which is turned out of the central plane by pivoting about its longitudinal axis so that louvers 28 extend out of the central plane in two opposing directions. However, it will be noted that louvers 28 extend from the central plane for a lesser distance on each side of the central plane than do the diversion louvers extending from the corresponding side. In addition to being aligned in parallel relationship with each other within each set, louvers 28 are also in parallel relationship with the

diversion louvers

25 and 27 with which they are grouped.

Louvers 25, 27 and 28, except for the edges thereof where they are pivoted or twisted in relation to the supporting fin, are planar providing a smooth, flat surface along essentially their entire length and breadth. In this embodiment central support member 21 between inner diversion louvers 27 supported thereby is substantially equal in width to each of the louvers 27. The major transverse measurement of such louvers is preferably as small as the method of manufacture and requirements of structural strength will permit. Such louvers en masse therefore present to an air stream the largest practical wiping surface coupled with the minimum of impedance to air flow commensurate with maximum heat exchange efficiency.

The

diversion louvers

25 and 27 as aforementioned extend farther from the central plane than intermediate louvers 28. Terminal slots 24 are also somewhat larger than intermediate slots 19. Slots 24, louvers 25, and louvers 27 being located in terminal and central positions are thus properly shaped, sized and positioned to provide a primary diversion effect upon an air stream entering one of the cells 18, escaping into an adjoining cell and eventually passing out of the radiator on the side pposite from whence it entered. In cooperation with slots 19 and louvers 28 the wiping air is passed along the louver faces from cell to cell until the path of a representative particle of air is directed into contact with central support 21 from whence it is diverted by the inner diversion louver 27 that obstructs its original directional movement from cell to cell. This louver is aligned to divert the movement of the air particle toward a window of the adjoining fin opposite the window through which it passed t before being diverted by louver 27 as illustrated in FIG- URE 3.

The number, size, alignment and positioning of the louvers as herein disclosed provides an unexpected advance in the art making possible an important reduction in the metal requirements of a given unit as hereinafter demonstrated. In the embodiment shown each fin is about 1.27 inches in its longest measure and has a distance of about 1.17 inches between the bend lines of the outer louvers 25. This embodiment therefore provides a center support, two inner or central diversion louvers, fourteen intermediate louvers and two outer diversion louvers Within a distance of 1.17 inches. In this type of fin there should be at least 12, and preferably 14 or more, louvers per inch of fin, measured along the longitudinal axis of the fin proper. It will be understood that such measurement is along a line transverse to the longitudinal measurement of the fin strip of which the individual fins form a Bart.

This fin is thus designed to increase laminar flow and permits the contact of a greater amount of unheated and lightly heated air to a greater area of unclogged heat exchange surface per unit of time or per air unit pass. The term clogging here relates to the phenomenon whereby a heat exchange surface is blanketed by a clinging film of air.

A device suitable for use in manufacturing the heat exchange fin structures or spacer strips of this invention and the method of its operation are disclosed in detail in the aforementioned patent application of which this application is a division. These disclosures are incorporated herein by reference.

In the cutting and forming of the heat exchange fin structures or spacer strips hereinbefore and hereinafter described transverse line contact upon the sheet material is continuously maintained from initiation of such contact with opposing parts of a cutting and forming device until termination of the same. The resulting ironing effect not only produces smooth regular surfaces on the finished product in general but also makes possible the formation of straight or planar louvers, i.e., louvers which except for their twisted ends are fiat sheets.

The advantages of the heat exchange fin structures of this invention will be more fully understood from the following operative examples which should be considered as illustrative and not as limitations upon the true scope of the invention as set forth in the claims.

Example I Fin strips of the configuration illustrated in FIGURE 2 and having the louvers thereof turned out of the planar base of the fin so as to'form an angle of 35 with such base were tested for cooling efficiency in an automobile radiator under operating conditions hereinafter described' The performance of the structure was compared with a commercially used slit fin structure of equal external dimensions and total surface area. The comparison fin provided two terminal louvers, six intermediate louvers, and a central support bearing two central louvers. The: fins of the comparison fin strip prepared on conventional roll dies bearing essentially straight faced essentially triangular teeth were somewhat curved in general outline and of generally uneven surface. All louvers of the comparison fin extended from the main body of the fin for essentially the same distance in contrast to the configuration of the planar fins of this invention.

Tests were conducted usingthe fin strips of this invention and the comparison fin strips in automobile radiators otherwise constructed alike. The tests were conducted on a S-mile circular track with an automobile having an S-cylinder, 221 cubic inch displacement, gasoline engine. Tests were made at road speeds of 60, and miles per hour. Both fin strips were tested using a 14 fin per inch ratio and the cooling etficiency of each recorded. The cooling efficiency of the planar fin of this invention proved to be higher than that of the control at each speed tested as measured by air-to-boil temperature. Airto-boil temperature, a conventional measure of cooling systems, measures the ambient air temperature at which the liquid medium, in this example Water, will boil.

These results were confirmed by other tests in which the vehicle was connected to a suitable dynamometer to simulate defined road grades by pulling a measured load. Tests were made at 30 miles per hour with a 7 grade, at 45 miles per hour with a 5% grade and at 60 miles per hour with a 4% grade. The fin of this invention again demonstrated significantly higher cooling eificiency than the comparison fin.

In both series of tests the degree of superiority demonstrated by the fin of this invention was most pronounced at the higher speeds, i.e. at the more severe conditions.

Example 11 The testing procedure of Example I was repeated but with the following difierences:

(1) The vehicle employed for the tests was equipped with an 8-cylinder, 260 cubic inch displacement, gasoline engine.

(2) The fin of this invention was tested using a 14 fin per inch ratio while 15 fin per inch ratio was used for the comparison fin.

The fin of this invention demonstrated a higher cooling efiiciency than the comparison fin in the simulated grade tests.

Example III In standard Wind tunnel tests simulating the conditions of Example I and using an S-cylinder, 260 cubic inch displacement gasoline engine, the cooling efiiciency of the fin of the invention was found to be essentially equal to that of the comparison fin when a 15 fin per inch ratio was employed for the comparison fin and only a 13 fin per inch ratio for the fin of this invention.

Example IV The testing procedure of Example I was repeated but with the following differences:

(1) The vehicle employed was equipped with an 8- cylinder, 352 cubic inch displacement, gasoline engine.

(2) The fin strip of this invention here used was a 1.27 inch copper strip of the design shown in FIGURE 2 and was employed at the rate of 13 fins per running inch.

(3) The comparison fin was a copper strip 1.95 inches wide and of the design used in Example II except that each fin included three louvered windows separated by two internal supports similar to the central support in the two window fins. The results of these tests are set forth in the following table:

TABLE I Thus, even with a surface area smaller than that of the comparison fin by a ratio of about 16.5 to 23.4 the planar fin displayed a cooling etficiency substantially equal to the larger fin strip.

Having thus described the invention with particularity, it is obvious that modifications can be made in the same without departing from the spirit and scope of the invention as set forth in the appended claims.

We claim:

1. In a heat exchange device having inlet means, outlet means, a core including at least two conduits admitting of fluid flow therethrough and spaced apart to form an air passageway therebetween and a spacer element positioned between and in heat exchange relationship with said conduits which strip includes a plurality of fin elernents and connecting members which together divide said passageway into a plurality of communicating air cells, the improvement in said spacer element which comprises a fin element between each pair of said connecting members comprising a planar base member; a plurality of spaced apart louvers integral with said base member, arranged in spaced apart groups, and turned out of the plane of said planar base member leaving at least one opening in said base member adjacent each of said louvers; and between each pair of said spaced groups a transverse member integral with said base member, each of said spaced groups including a first diversion louver supported by the next adjacent transverse member and extending out of said plane'on a first side of said base member, a second diversion louver extending out of said plane on a second side of said base member opposite said first side, and a plurality of intermediate louvers between said first diversion louver and said second diversion louver, said intermediate louvers extending through said plane and from said base member on said first side for a distance less than said first diversion louver and on said second side for a distance less than said second diversion louver.

2. In a heat exchange device having inlet means, outlet means, a core comprising a plurality of conduits communicating with said inlet means and said outlet means, admitting of fluid fiow therethrough and spaced apart so that each adjacent pair thereof forms an air passageway therebetween and a spacer element positioned within each such passageway and in heat exchange relationship with the conduits forming the same, said element including a plurality of fin elements integral with and positioned between connecting members and dividing the passageway within which the spacer element is positioned into a plurality of communicating air cells, the improvement in said spacer element which comprises a fin element between each pair of said connecting members comprising a slitted planar base member; a plurality of spaced apart louvers integral with said base member, arranged in spaced apart groups and pivoted out of the plane of said planar base member leaving at least one opening in said base member adjacent each of said louvers; and between each pair of said spaced groups a transverse planar member integral with said base member, each of said spaced groups including a first diversion louver supported by the next adjacent transverse planar member and extending out of said plane on a first side of said base member, a second diversion louver extending out of said plane on a second side of said base member opposite said first side, and a plurality of intermediate louvers between said first diversion louver and said second diversion louver, pivoted at two ends thereof from said base member so as to extend from said base member on said first side for a distance less than said first diversion louver and on said second side for a distance less than said second diversion louver, the major and central portions of said intermediate louvers being planar and parallel to the said first diversion louver and said second diversion louver.

3. In a heat exchange device having inlet means, outlet means, a core including at least two conduits admitting of fiuid flow therethrough and spaced apart to form an air passageway therebetween and a spacer element positioned between and in heat exchange relationship with said conduits which strip includes a plurality of fin elements and connecting members which together divide said passageway into a plurality of communicating air cells, the improvement in said spacer element which comprises a fin element between each pair of said connecting members comprising a fiat base member the longitudinal and major transverse axes of which extend through a base plane; a plurality of spaced louvers integral with said base member, pivoted from said base member to extend out of said base plane and leave at least one opening in said base member adjacent each of said louvers, said louvers being arranged in a first group of louvers and a second group of louvers spaced apart therefrom; and positioned between the louver groups a transverse planar member integral with said base member, each group of said louvers including a first diversion louver pivoted along one side thereof from said transverse planar member and extending out of said plane on a first side of said base member, a second diversion louver pivoted along one side thereof from said base member and extending out of said plane on a second side of said base member opposite said first side, and a plurality of intermediate louvers between said first diversion louver and said second diversion louver and pivoted at two ends thereof from said base member so as to extend from said base member on said first side for a distance less than said first diversion louver and on said second side for a distance less than said second diversion louver, said first group of louvers bein'g aligned for the major part of their respective lengths in parallel relationship with each other and forming a constant acute angle with said base member on the side of their respective extensions, said second group of louvers being aligned for the major part of their respective lengths in parallel relationship with each other and forming a constant acute angle with said base member on the side of their respective extensions which is equal and opposite to the angle formed by louvers of said first group.

4. In a heat exchange device having inlet means, outlet means, a core including at least two conduits admitting of fluid flow therethrough and spaced apart to form an air passageway therebetween and a spacer element positioned between and in heat exchange relationship with said conduits which strip includes a plurality of fin elements and connecting members which together divide said passageway into a plurality of communicating air cells, the improvement in said spacer element which comprises a fin element between each pair of said connecting members comprising a planar base member; a plurality of spaced apart louvers integral with said base member, arranged in spaced apart groups, and turned out of the plane of said planar base member leaving at least one opening in said base member adjacent each of said louvers; and between each pair of said spaced groups a transverse planar member integral with said base member, each of said spaced groups including a first diversion louver supported by the next adjacent transverse member and extending out of said plane on a first side of said base member, a second diversion louver extending out of said plane on a second side of said base member opposite said first side, and a plurality of intermediate louvers between said first diversion louver and said second diversion louver, said intermediate louvers extending through said plane and from said base member on said first side for a distance less than said first diversion louver and on said second side for a distance less than said second diversion louver, said fin element having a minimum of 12 louvers per running inch as measured along the longitudinal axis thereof, said louvers each forming with said base member an angle of about 25 to about References Cited by the Examiner UNITED STATES PATENTS 2,063,757 12/1936 Saunders -153 2,133,502 10/1938 Emmons 165-153 2,252,211 8/1941 Seemiller 165-152 2,647,731 8/1953 Ludlow 165-152 X 2,703,226 1/1955 Simpelaar 165153 2,838,830 6/1958 Huggins 29-1573 6,003,749 10/1961 Morse 165-152 3,136,038 6/1964 Huggins et al. 29-1573 ROBERT A. OLEARY, Primary Examiner. FREDERICK L. MATTE SON, JR., Examiner. M. A. ANTONAKAS, Assistant Examiner.

Claims

1. IN A HEAT EXCHANGER DEVICE HAVING INLET MEANS, OUTLET MEANS, A CORE INCLUDING AT LEAST TWO CONDUITS ADMITTING OF FLUID FLOW THERETHROUGH AND SPACED APART TO FORM AN AIR PASSAGEWAY THEREBETWEEN AND A SPACER ELEMENT POSITIONED BETWEEN AND IN HEAT EXCHANGE RELATIONSHIP WITH SAID CONDUITS WHICH STRIP INCLUDES A PLURALITY OF FIN ELEMENTS AND CONNECTING MEMBERS WHICH TOGETHER DIVIDE SAID PASSAGEWAY INTO A PLURALITY OF COMMUNICATING AIR CELLS, THE IMPROVEMENT IN SAID SPACER ELEMENT WHICH COMPRISES A FIN ELEMENT BETWEEN EACH PAIR OF OF SAID CONNECTING MEMBERS COMPRISING A PLANAR BASE MEMBER; A PLURALITY OF SPACED APART LOUVERS INTEGRAL WITH SAID BASE MEMBER, ARRANGED IN SPACED APART GROUPS, AND TURNED OUT OF THE PLANE OF SAID PLANAR BASAE MEMBER LEAVING AT LEAST ONE OPENING IN SAID BASE MEMBER ADJACENT EACH OF SAID LOUVERS; AND BETWEEN EACH PAIR OF SAID SPACED GROUPS A TRANSVERSE MEMBER INTEGRAL WITH SAID BASE MEMBER, EACH OF SAID SPACED GROUPS INCLUDING A FIRST DIVERSION LOUVER SUPPORTED BY THE NEXT ADJACENT TRANSVERSE MEMBER AND EXTENDING OUT OF SAID PLANE ON A FIRST SIDE OF SAID BASE MEMBER, A SECOND DIVERSION LOUVER EXTENDING OUT OF SAID PLANE ON A SECOND SIDE OF SAID BAASE MEMBER OPPOSITE SAID FIRST SIDE, AND A PLURALITY OF INTERMEDIATE LOUVERS BETWEEN SAID FIRST DIVERSION LOUVER AND SAID SECOND DIVERSION LOUVER, SAID INTERMEDIATE LOUVERS EXTENDING THROUGH SAID PLANE AND FROM SAID BASE MEMBER ON SAID FIRST SIDE FOR A DISTANCE LESS THAN SAID FIRST DIVERSION LOUVER AND ON SAID SECOND SIDE FOR A DISTANCE LESS THAN SAID SECOND DIVERSION LOUVER.