US3313343A

US3313343A - Heat exchange apparatus

Info

Publication number: US3313343A
Application number: US355036A
Authority: US
Inventors: Chester D Ware; Albert O Tadewald
Original assignee: Trane Co
Current assignee: Trane US Inc
Priority date: 1964-03-26
Filing date: 1964-03-26
Publication date: 1967-04-11
Anticipated expiration: 1984-04-11

Description

April 11, 1967 c. D. WARE ETAL HEAT EXCHANGE APPARATUS 5 Sheets-Sheet l Filed March 26, 1964 INVENTORS' CHESTER D. WARE BYALBERT o. TADE WA LD M April 11, 1967 c. D. WARE ETAL 3,333,343

HEAT EXCHANGE APPARATUS Filed March 26, 1964 3 Sheets-Sheet 2 F l G. 6 16' -111, {KHZ/M /1mu \1\\\ J L 3 ,I i

- Fl 6. 0000 46 7 j gfiooooo H 0 4 0 0 oo 00 0 \.J o A o 00 00000000 0 00 0 00000 0 0 W000 00 o 0 0 000 00 o \oooo 0 000000000 0 0 00 INVENTORS CHESTER D. WARE ALBERT O, TADEWALD April H, 3%? c. D. WARE ETAL HEAT EXCHANGE APPARATUS 5 Sheets-Sheet 5 Filed March 26, 1964 IN VENTORS CHESTER 0. WARE ALBERT o. TADEWALD BY United States Patent M 3,313,343 HEAT EXCHANGE APPARATUS Chester D. Ware and Albert 0. Tadewaid, La Crosse, Wis, assignors to The Trane Company, La Crosse, Wis., a corporation of Wisconsin Filed Mar. 26, 1964, Ser. No. 355,036 8 Claims. (Cl. 165-166) This invention relates to heat exchange apparatus and more particularly to extended heat transfer surface of the pin fin type.

Conventional pin fin extended heat transfer surfaces have desirable heat transfer qualities but characteristically are low in surface area due to limitations imposed on the pin spacing by the applicable fabricating techniques.

It is thus an object of this invention to provide a novel pin fin structure wherein the fin spacing is not unduly limited by the fabricating techniques.

Another object of the invention is to provide an improved pin fin structure wherein the pin fins are supported during and after fabrication by wire positioning members which extend at an oblique angle with the fins.

A further object is to provide a pin fin structure which may be fabricated from a wire mesh screen.

Another object of the invention is to provide a pin fin structure which may be fabricated from a wire mesh screen having lower wire count per unit distance than the final pin fin count per unit distance.

Another object of this invention is to provide a pin fin construction wherein the pin fins are supported by elongated fin positioning members the ends of which may be connnected to both walls of the heat exchange passage to give added support to the relatively delicate pin fins.

A further object of this invention is to provide a heat exchange pin fin packing having wire fins and wire fin positioning members which may be fabricated by corrugating a wire mesh screen wherein said fins may be positioned to conduct heat to the passage walls in a most direct manner while the positioning wires extend obliquely to the corrugations in a manner so as not to severely deform such corrugations.

Another object of our invention is to provide a corrugated pin fin structure wherein fin positioning members may be spaced at random, i.e. without fixed relation to the corrugations of the structure.

Still a further object of the instant invention is to provide pin fin extended heat exchange surface wherein said pin fins are arranged in undulated rows.

Other objects and advantages will become apparent as this description proceeds to describe the invention with reference to the accompanying drawings in which:

FIGURE 1 is a perspective view of a plate type brazed heat exchanger with a portion broken away to show the instant invention;

FIGURE 2 is an enlarged perspective of the broken away portion of FIGURE 1;

FIGURE 3 is an elevational side view of the heat exchange pin fin packing taken at 33 of FIGURE 1;

FIGURE 4 is a semi-diagrammatic plan view of the pin fin packing taken at line 4-4 of FIGURE 3, only the foreground structure being shown for purposes of clarity;

FIGURE 5 is an end view of the pin fin packing taken at line 5-5 of FIGURE 4;

FIGURE 6 is a View similar to FIGURE 4 of a modi- Patented Apr. 11, 1967 fied form of pin fin packing wherein the corrugations and rows of pin fins are undulated;

FIGURE 7 is a diagrammatic view showing the relative positioning of the pin fins in the modified form of fin packing; and

FIGURE 8 is a perspective view of a plate type brazed heat exchanger similar to that shown in FIGURE 1 but utilizing the modified form of fin packing as shown in FIGURES 6 and 7.

Now looking to FIGURE 1 of the drawing, it will be noted that heat exchanger 10 is comprised of a stack of elongated rectangular plate like members 12 disposed in superposed spaced parallel relationship. The spaces formed between plate members 12 constitute elongated passages through which heat exchange media may be circulated. Side closing bar members 14 and end closing bar members 15 are placed at the periphery of the passages to provide a fluid seal for the passages. At least some of the passages are provided with extended heat exchange surface or pin fin packing generally designated by numberal 16. The plate members 12,

closing bars

14 and 15 and fin packing may be bonded into an integral unit heat exchanger core by either salt bath or furnace brazing.

Ingress and egress of the heat exchange media is made via several sets of headers. In the heat exchanger shown in FIGURE 1 it will be seen that several of the passages 17 have no closing bars at the ends thereof. Headers 18 and 20 may be welded to the heat exchanger core at the ends thereof to provide ingress and egress respectively for the flow of a first heat exchange medium to and from these passages. A second set of

headers

22 and 24 may be provided at the side of the core near the ends thereof for ingress and egress respectively of a second heat exchange medium in other passages. The particulars as to the manner in which

headers

22 and 24 communicate with these other passages is not material to the instant inven tion and it will suffice to say that such communication may be effected by providing apertures in the-side of closing bar members 14 thereof under

headers

22 and 24.

The fin packing 16 serves two basic functions; to provide strength to the heat exchanger core and to conduct heat between the exchange media and the plates 12. The heat transfer between the two heat exchange media is through plates 12. As aforementioned, fin packing 16 may be brazed or otherwise bonded in position at the crowns of the corrugations thereof to provide an enhanced thermal and structural bond with plates 12.

A first form of extended heat exchange surface or pin fin packing 16 is shown in FIGURES 1-5. The structure of the pin fin packing 16 may be described in conjunction with one method of fabricating the same.

The pin fin packing may be fabricated from a fiat wire mesh screen (not shown) comprised of a plurality of interwoven warp and woof wires, the warp wires preferably having a diameter between about .008 inch and about .250 inch. It will be understood that these warp wires ultimately become wires 26 of the pin fin packing 16 and are comprised of material having a relatively high coeifiicent of thermal conductivity such as aluminum, copper, nickel, steel or alloys thereof. The warp wire count of the screen in wires per inch may be between about .400 and about .700 divided by the warp wire diameter in inches. In the example from which the accompanying.

angers drawing was made, the warp wire count was wires per inch and the wire diameter was .015 inch.

The wire screen woof wires which extended generally normally to the warp wires may have a wire count of between about .050 and about .165 divided by the warp wire diameter in inches. These woof wires as will be seen ultimately become wires 28 of the pin fin packing. In the example, the woof wire count was selected at 8 wires per inch. It should be understood that the woof Wires serve to support the warp Wires before, during and after the formation of the pin fin packing to be described.

The flat wire screen thus defined is then stretched on the bias whereby both the warp and woof wires are brought closer together and the wire count is increased. The biased wire screen is then calendered by passage through rollers to reduce its thickness and enhance the engagement of woof and warp wires. The biasing of the example screen increased the warp wire count from 40 to 53 wires per inch. The woof wire count was increased proportionately.

The biased and calendered wire screen is then corrugated by passage through dies of a fin press to form the pin fin packing as shown in FIGURES 15. The press may be of the construction shown in US. Patent 2,489,- 125. The oblique angular relationship of woof and warp wires of the biased screen and the aforementioned calendering greatly improve the fitnes of the wire screen for passage through the corrugating dies with minimum deformation to the corrugation crowns 30 and minimum shifting of the woof wires as seen in FIGURE 4.

The warp wires 26 extend generally in a plane which is normal to the longitudinal axes of the crowns 30 of the corrugations 32 in the pin fin packing thus formed and each fold of each warp wire becomes an elongated pin fin 26a. It will be understood that this angular relationship between crown and warp wire is desirable as the pin fins 26a are thus oriented to provide the shortest path through which heat may be conducted from the midpoint of the pin fins to the crown and hence to the heat transfer plates 12 which are disposed in abutting relationship therewith and brazed or bonded thereto.

The pin fins thus formed are preferably equally spaced from one another in the direction of fluid flow on centers spaced between about 1 /2 to about 2 warp wire diameters. It is preferred that the spacing of the corrugations transverse to the direction of flow be selected between about 2 to about 4 warp wire diameters.

It was found from experience that when the woof wires were arranged parallel to the crowns of the corrugations that spacing the woof wires had to be properly indexed with the spacing of the corrugations to avoid variations in fin height resulting from severe deformation of complete crowns that happen to coincide with these woof wires. The inventive pin fin packing thus permits the woof wires to be placed at random with respect to the corrugations. The reduction in necessary screen stock for fins having different corrugation spacings and the accompanying saving will be apparent.

Further, it will be noted that the woof wires 28 of the corrugated screen 16 extend across the fluid passage from one wall or plate 12 to the other adjacent the corrugation crowns as shown in FIGURES 2 and 3. Since the crowns 30 of the corrugations 32 are normally brazed to the plates 12, the pin fin supporting woof wire segments or members 28a are firmly anchored at their ends to plates 12 and make an acute angle therewith.

It will thus be seen that a pin fin packing is formed wherein one side of a corrugation fold forms a straight row of a plurality of generally parallel elongated pin fins 26a in juxtaposed relationship, each extending normally to the axis of the said row or crown, obliquely crossing at least one fin supporting member 28:: as viewed in FIGURE 3, and preferably extending normally to the heat transfer plates 12 (FIGURES 2 and 5). Further the fin count is substantially higher than the wire count of the screen from which the fin packing was formed.

At this point it is Well to point out that the pin fin wires have been described as having been formed from warp wires and the pin fin positioning members as having been formed from the woof wires. Warp and woof are terms well known in the art of weaving and connote a definite relation to the loom upon which the screen is made. However it should be understood that these terms have been used for purposes of illustration only and it is quite possible that the pin fins be formed from woof wires and the fin positioning members formed from the warp wires. In any event, the rows of pin fins and the axes of the crowns of the corrugations would preferably be positioned to extend in a direction gen erally parallel with the main flow of heat exchange medium through the fluid passage in which they are placed.

A second form of extended heat exchange surface of the pin fin type is illustrated in FIGURES 6, 7 and 8.

FIGURE 6 shows a plan view similar to that of FIG= URE 4 of the modified form of pin fin packing. The modified form of packing 16 may be constructed with warp wires 26 and woof wires 28 in the same manner as that of the first form, however the crowns 30' of corrugations 32 and consequently the rows of elongated pin fins 26a are undulated in a direction generally transverse to the rows of fins as well as transverse to the longi tudinal axes of the elongated fins thereof. These undulations may be formed either simultaneously with the aforementioned corrugating step or subsequently thereto as a separate operation. The resulting undulated rows of pin fins shown in FIGURE 7 are considered a substantial improvement in enhancing heat transfer to the fins from the heat exchange medium flowing therethrough as illustrated by the arrows. Again it may be said with respect to this modified form of fin packing that the rows of pin fins and corrugation crowns thereof would nor mally be positioned to extend in a direction with the main fiow of heat exchange medium passing therethrough as illustrated in FIGURE 8.

Although we have described in detail the preferred embodiments of our invention, we contemplate that many changes may be made without departing from the scope or spirit of our invention and we desire to be limited only by the claims.

We claim:

1. A heat exchanger comprising two fluid confining planar plates disposed in generally parallel spaced relationship defining a fluid passage therebetween; and a corrugated screen defining an elongated row of elongated fins disposed in said fluid passage, said elongated fins being arranged in juxtaposed generally parallel relationship, each of said fins extending between said plates and having its ends disposed in heat conductive relationship with said plates, said row of fins being undulated in a direction parallel to said plates normal to the general axis of said row; and a plurality of elongated fin positioning members disposed in spaced generally parallel relationship, each of said elongated positioning members extending between said plates supportingly engaging said fins and the general axis thereof defining an acute angle with said plates, said elongated positioning members crossing said elongated fins between the ends thereof at a substantial oblique angle as measured in a plane passing through the crossing substantially parallel to the general axes of the crossing fin and the fin positioning member, and substantially spaced one from the other a greater distance relative to the individual spacing of said first mentioned elongated fins.

2. A heat exchanger comprising two fluid confining planar plates disposed in generally parallel spaced relationship defining a fluid passage therebetween; and a corrugated screen defining an elongated row of elongated fins disposed in said fluid passage, said elongated fins being arranged in juxtaposed generally parallel relationship, each of said fins extending substantially normally to and between said plates and having its ends disposed in heat conductive relationship with said plates, said row of fins being undulated in a direction parallel to said plates normal to the general axis of said row; and a plurality of elongated fin positioning members disposed in spaced generally parallel relationship, each of said elongated positioning members extending between said plates supportingly engaging said fins and the general axis thereof defining an acute angle with said plates, said elongated positioning members crossing said elongated fins between the ends thereof at a substantial oblique angle as measured in a plane passing through the crossing substantially parallel to the general axes of the crossing fin and fin positioning member, and substantially spaced one from the other a greater distance relative to the individual spacing of said first mentioned elongated fins.

3. A heat exchanger comprising two fluid confining planar plates disposed in generally parallel spaced relationship defining a fluid passage therebetween; and a corrugated screen defining an elongated row of elongated fins disposed in said fluid passage, said elongated fins being arranged in juxtaposed generally parallel relationship, each of said fins extending substantially normally to and between said plates and having its ends disposed in heat conductive relationship with said plates; and a plurality of elongated fin positioning members disposed in spaced generally parallel relationship, each of said elongated positioning members extending between said plates supportingly engaging said fins and the general axis thereof defining an acute angle with said plates, said elongated positioning members crossing said elongated fins between the ends thereof at a substantial oblique angle as measured in a plane passing through the crossing substantially parallel to the general axes of the crossing fin and fin positioning member, the center to center spacing between adjacent elongated fins being equal to the diameter of said fins divided by a number of between .400 and .700, and the center to center spacing between adjacent elongated positioning members being greater than said spacing of said fins and equal to the diameter of said positioning members divided :by a number between .050 and .165.

4. A heat exchanger comprising two fluid confining planar plates disposed in generally parallel spaced relationship defining a fluid passage therebetween; and a corrugated screen defining an elongated row of elongated fins disposed in said fluid passage, said elongated fins being arranged in juxtaposed generally parallel relationship, each of said fins extending between said plates and having its ends disposed in heat conductive relationship with said plates; and a plurality of elongated fin positioning members disposed in spaced generally parallel relationship, each of said elongated positioning members extending between said plates supportingly engaging said fins and the general axis thereof defining an acute angle with said plates, said elongated positioning members crossing said elongated fins between the ends thereof at a substantial oblique angle as measured in a plane passing through the crossing substantially parallel to the general axes of the crossing fin and fin positioning member, the center to center spacing between adjacent elongated fins being equal to the diameter of said fins divided by a number of between .400 and .700, and the center to center spacing between adjacent elongated positioning members being greater than said spacing of said fins and equal to the diameter of said positioning members divided by a number between .050 and .165.

5. A heat exchanger comprising two fluid confining plates disposed in generally parallel spaced relationship defining a fluid passage therebetween; and a corrugated screen defining an elongated row of elongated fins disposed in said fluid passage, said elongated fins being arranged in juxtaposed generally parallel relationship,

each of said fins extending between said plates and having its ends disposed in heat conductive relationship with said plates; and a plurality of elongated fin positioning members disposed in spaced generally parallel relationship, each of said elongated positioning members extending between said plates supportingly engaging said fins and the general axis thereof defining an acute angle with said plates, said elongated positioning members crossing said elongated fins between the ends thereof at a substantial oblique angle as measured in a plane passing through the crossing substantially parallel to the general axes of the crossing fin and fin positioning member, the center to center spacing between adjacent elongated fins being equal to the diameter of said fins divided by a number of between .400 and .700, and the center to center spacing between adjacent elongated positioning members being greater than said spacing of said fins and equal to the diameter of said positioning members divided by a number between .050 and .165.

6. A heat exchanger comprising two fluid confining plates disposed in generally parallel spaced relationship defining a fluid passage therebetween; and a corrugated screen defining an elongated row of elongated fins disposed in said fluid passage, said elongated fins being arranged in juxtaposed generally parallel relationship, each of said fins extending between said plates and having its ends disposed in heat conductive relationship with said plates, said row of fins being undulated in a direction parallel to said plates normal to the general axis of said row; and a plurality of elongated fins positioning mem bers idsposed in spaced generally parallel relationship, each of said elongated positioning members extending between said plates supportingly engaging said fins and the general axis thereof defining an acute angle with said plates, said elongated positioning members crossing said elongated fins between the ends thereof at a substantial oblique angle as measured in a plane passing through the crossing substantially parallel to the general axes of the crossing fin and fin positioning member, and substantially spaced one from the other a greater distance relative to the individual spacing of said first mentioned elongated fins.

7. In a heat exchanger having two fluid confining plates disposed in generally parallel spaced relationship defining a fluid passage therebetween, a corrugated wire screen disposed in said passage and oriented with the crowns of its corrugations extending in the direction of fluid flow through said passage; said screen including a plurality of wires each following the undulated contour of said corrugated screen and being generally parallel to a plane which is normal to the direction of flow through said passage; said wires being arranged side-by-side in the directoin of fluid flow through said passage; and the crowns of at least several corrugations of said screen being undulated in a direction parallel to said plates transverse to said direction of flow; a plurality of elongated fin supporting members positioned to cross said wires at a substantial oblique angle and spaced one from the other a greater distance than the spacing between said wires.

8. A heat exchanger comprising two fluid confining plates disposed in generally parallel spaced relationship defining a fluid passage therebetween; and a corrugated screen defining an elongated straight row of elongated fins disposed in said fluid passage, said elongated fins being arranged in juxtaposed generally parallel relationship, each of said fins extending between said plates and having its ends disposed in heat conductive relationship with said plates; and a plurality of elongated fin positioning members disposed in spaced generally parallel relationship, each of said elongated positioning members extending between said plates supportingly engaging said fins and the general axis thereof defining an acute angle with said plates, said elongated positioning members crossing said elongated fins between the ends thereof at a substantial oblique angle as measured in a plane passing throughv the crossing substantially parallel to the general axes of the crossing fin and fin positioning member, the center to center spacing between adjacent elongated fins being equal to the diameter of said fins divided by a number of between .400 and .700, and the center to center spacing between adjacent elongated positioning members being greater than said spacing of said fins and equal to the diameter of said positioning members divided by a number between .050 and .165.

References Cited by the Examiner UNITED STATES PATENTS 8 Poole 165185 Trumpler 29-157 Preston 165182 Rogers et a1 165167 X Boestad 165-10 Hodson et al. 165-166 X FOREIGN PATENTS ROBERT A. OLEARY, Primary Examiner.

CHARLES SUKALO, LIEYER PERLIN, Examiners. 15 'r. W. STREULE, Assistant Examiner.