US3016921A - Heat exchange fin element - Google Patents

Description

A. o. TADEWALD 3,016,921

HEAT EXCHANGE FIN ELEMENT Jan. 16, 1962 Filed April 14, 1958 2 Sheets-Sheet 1 INVENTOR. ALBERT 0. TADEWALD ATTORNEYS Jan. 16, 1962 A. o. TADEWALD 3,016,921

HEAT EXCHANGE FIN ELEMENT Filed April 14, 1958 2 Sheets-Sheet 2 /60 /80 /2 lUJJlUIDUDUIDUlDE /I II J Fig. 7.

200 /4 200 Fig. 6.

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- INVENTOR.

10. ALBERT 0. TADEWALD /QWVW ATTORNEYS United States Patent Office filfififi Patented Jan. 16, 1962 3,016,921 HEAT EXCl-EANGE FEN ELEMENT Alhert if Tadewald, La Crosse, Wis, assigner to The Trade Company, La Crosse, Wis, a corporation of Wisconsin .Fiied Apr. 14, 1958, Ser. No. 728,226 15 Claims. (Cl. 3138-38) This invention relates to heat exchangers for the transfer of heat between two confined fluids and more particularly to a novel serrated fin type heat exchange element capable of operating at high pressures and tem' peratures with efficient heat transfer characteristics.

Previous to this invention, perforated fin type heat exchange elements were used in brazed aluminum cores since no economical and practical serrated fin type heat exchange element has been developed which would have high heat transfer characteristics and still be capable of withstanding high operating pressures and temperatures without injury to the heat exchanger.

It is an object of this invention to provide a heat exchanger which is eflicient at high pressures and temperatures, and which is practical, and economical to manufacture.

Another object of the invention is to provide a serrated fin type heat exchange element which is simple and economical to produce, has a high heat transfer coefficient, and is also capable of withstanding high operating pressures and temperatures without injury.

A third object of the invention is to provide a serrated fin type heat exchange element for a brazed aluminum core which is simple, economical, and practical to manufacture and which has excellent operating characteristics at pressures at high as 3500' psi.

Another object of the invention is to provide a serrated fin type heat exchange of aluminum, stainless steel, or other suitable material which is efficient at high operating pressures and temperatures.

A fifth object of the invention is to provide a serrated fin type heat exchange element which allows the flux to be easily washed therefrom after brazing of the heat exchange element to the parting sheets.

Other objects and advantages of the invention will be clearly apparent as the specification proceeds to describe the invention with reference to the accompanying drawings in which:

FIG. 1 is a left elevation view of the heat exchange element shown in FIG. 2.

PEG. 2 is a plan view of one embodiment of the heat exchange element with the parting sheet rolled away and with part of the exposed fin heat exchange element in section.

FIGS. 3 and 4 are sectional elevation views taken on lines 3-3 and -l respectively of FIG. 2.

FIG. 5 is a bottom view of the embodiment shown in FIG. 2 with the parting sheet rolled away and with part of the exposed fin heat exchange element in section.

FIG. 6 is a left elevation view of the modified heat exchange element shown in FIG. 7.

FIG. 7 is a plan view of a modified form of the heat exchange element with the parting sheet rolled away and with part of the exposed fin heat exchange element in section.

FIGS. 8 and 9 are sectional elevation views taken on lines 88 and 9-3 of FIG. 7.

FIG. 10 is a bottom view of the embodiment shown in FIG. 7 with the parting sheet rolled away and with part of exposed fin heat exchange element in section.

In the drawings, a serrated fin type heat exchange element ill is shown located between parting sheets 12 and 14. As is Well known in the art, the heat exchange ele- 2 ment 10 and parting sheets 12 and l4 will be multiplied in any manner known to the art to provide a counterfiow of the heat exchange fluids. The number and any other arrangement of the heat exchange elements fl) is optional and may be used in any manner known to the art since such does not constitute part of the invention.

The heat exchange element 10, shown in FIG. 2, is formed with a series of staggered projections 16 and 18 and a series of staggered depressions 2d and 22 from a blank sheet of metal by bending, stamping, rolling, or any other suitable method. Projection 18 will herein be referred to as offset projection 18.

As is readily seen, the projection 16, offset projection 13, and depressions 20 and 22 are created by forming the metal so as to depress the metal around projection 16 and offset projection 13 and at the same time insetting wall 24 of offset projection 18 from wall 26 to a point substantially at the centerline of projection 16 and projecting wall 28 of offset projection 18 from wall 36 to a point substantial'y on the centerline of depression 20 to form the staggered relationship of the projections and depressions.

It should be noted that wall 28 is greater in length than wall 24 so that there is a predetermined amount of bridging material 32 between wall 24 and wall 39, The difference in lengths between wall 24 and wall 23 allows a greater offset of olfset projection 18 than was previously known in the art. Such greater offset results in a lower pressure drop through the heat exchange element. Further, the flow paths created by said offset are substantially equal which in turn enhances the transfer of heat because of better distribution of the fluid. Also, if walls 24 and 23 were of equal length a large offset could not be accomplished without destroying the element by cutting the heat exchange element in strips in a direction normal to the preferred heat exchange fluid path. The length of wall 26 is optional but preferably wall 26 is equal in length to wall 28 in order to produce a practical heat exchange element. Bridging material 32 which is the result of the difference in lengths of walls 24 and 28 adds considerable strength to the heat exchange element 19 so that rupture of the elements M will not occur at the points of inset 34 and 36 and the points of olfset 38 and 46 when the heat exchange element It? is used under high pressure operating conditions. The heat exchange element performs well at low pressures but is preferably used at pressures in the range of 5003500 p.s.i.

Heat exchange fluid is introduced into the heat exchange element in multiple paths 42. and 44. Looking at FIG. 2, path 42 is initially in the depression 20 and path 44 is initially in projection 16. As the fluid progresses through the heat exchange element, the film created by said fluid moving over the heat exchange surface is broken up by the interrupted heat exchange surface of my invention thereby preventing any substantial build-up of the film surface. By preventing the build-up of the film surface the heat transfer characteristics of the heat exchange element are improved. It should be noted that at the points of inset 34 and 36 and at points'of' offset 38 and d9 that the heat exchanger element 1t) is severed from walls 2-6 and walls 30 so that the heat exchange fluid may pass from projection 16 and depression 2t) through inset point34 andoifset point 38 to depression 22 and offset projection 18 and then through inset point 36 and offset point 40 tothe next proceeding projection 16 and depression 20.

Looking at FIG. 5 which is a bottom view of the heat exchange element 10, it is seen that the heat exchange element pattern is reversed. The projections 16 and 18 are shown as depressions 46 and 48 and the depressions 2t) and Marc shown as projections 50 and 52. Naturally, the heat exchange fluid path 44 will initially flow in de pression 46 and fluid path 42 will flow in projection Stl looking at the heat exchange element from the bottom.

The advantages of this design are that it breaks up the film created on the heat exchange surface by the heat exchange fluid thereby increasing the heat transfer characteristics of the element, provides a stronger heat exchange element which will not rupture at high operating pressures and temperatures, and provides passages for washing out of the flux deposited on the heat exchange element during the brazing process. It should be noted that the heat exchange element need not be perforated in order to wash out the flux since the above design provides passages which are large enough to allow the flux to be washed out without clogging the before mentioned passages. Previous to my invention, the corrugated or serrated fin type heat exchange element had to be perforated in order to avoid the plugging of the fin elements by the flux. Another advantage of this design is that it may be used in applications where it is desired to maintain the heat exchange fluid in the heat exchanger for longer periods of time to effect greater transfer of heat since it is possible to introduce the heat transfer fluids at an angle to the preferred paths shown in FIGS. 1-5.

Referring to FIGS. 6-10, there is shown a second embodiment of the invention. The fin type heat exchange element of this modification is shown located between parting sheets 12 and 14 in the same manner as that of the first modification.

The heat exchange element 100, shown in FIG. 7, is formed with a series of staggered projections 160 and 18% and a series of staggered depressions 200 and 220 from a blank sheet of metal by bending, stamping, rolling, or any other suitable method. Projection 180 will herein be referred to as offset projection 180.

As is readily seen, the projection 160, offset projection 189, and depressions 200 and 220 are created by forming the metal so as to depress the metal around the projections and at the same time insetting wall 240 of projection 156 from wall 260 to a point where it is substantially in line with wall 300 and offsetting wall 280 of offset projection 180 from wall 309 to a point immediately adjacent the next adjacent wall 260 thereby closing off any flow of heat exchange fluid normal to the fin structure. The double wall portion 2% thus formed adds rigidity and strength to the heat exchange element. Further, the overlapping construction of double wall 290 creates turbulence in the heat exchange fluid thereby increasing the heat transferability of said fluid. It should be noted that wall 280 is greater in length than wall 240 so that there is a predetermined amount of bridging material 329 between wall 24-0 and wall 300. The length of wall 26% is optional but preferably wall 260 is equal in length to wall 28d in order to produce a practical heat exchange element. Bridging material 32% gives considerable strength to the heat exchange element 1% so that rupture of the element 1% will not occur at the points of inset 340 and 360 and at the points of offset 380 and 400 when the heat exchange element 100 is used under high operating pressures up to 3500 psi Heat exchange fluid is introduced into the heat enchange element in multiple paths 420 and 440. Looking at FIG. 7, path 420 is initially in the depression 200 and path 440 is initially in projection 160. As the fluid progresses through the heat exchange element, the film created by said fluid moving over the heat exchange surface is broken up by the interrupted heat exchange surface of my invention alleviating any substantial build-up of the film surface, such interruption of the film surface increases the heat transfer characteristics of the heat exchange element. It should be noted that at the points of inset 340 and 360 and at the points of offset 380 and 490, that the heat exchange element 100 is actually severed from walls 260 so that the heat exchange fluid may pass from projection 169 and depression 200 through inset point 340 and offset point 380 to depression 229 and oflset projection 13th and then through inset point 360 and oifset point 4% to the next proceeding projection and depression 2%.

Looking at FIG. 10 which is a bottom view of the heat exchange element 106), it is seen that the heat exchange element pattern is reversed. The projections 164i and 134) are shown as depressions 461i and 430 and the depressions 29% and 224) are shown as projections 5% and 529. Naturally the heat exchange fluid path 446? will initially flow in depression 469 and fluid path 420 will flow in projection 480 when looking at the heat exchange element itifl from the bottom.

This modification also effects a breaking up of the film on the heat exchange element created by the heat exchange fluid and provides a path for the heat exchange fluid with minimum pressure drop, thereby increasing the heat transfer properties of the heat exchange element. This design also produces a heat exchange element which will withstand high operating pressures and temperatures without rupture. This modification further increases the ease of washing the flux from the heat exchange element since the above design provides wider passages in which the flux flushing fluid may flow to flush the excess flux deposited on the heat exchange element during the brazing process.

Although I have described in detail the preferred embodiments of my invention, 1 contemplate that many changes may be made without departing from the scope or spirit of my invention, and I desire to be limited only by the claims.

I claim:

1. A heat transfer element for use in a plate type heat exchanger, comprising an elongated metal strip provided with a series of transversely extending rows of longitudinally interconnected projections, said series of projections consisting of first projections and offset projections, depressions between the projections in each of said rows, said offset projections being in alternate rows and being offset from said first projections in the same direction as the preceding row of said offset projections, said first projections of each series of said interconnected projections being on a common centerline in the longitudinal direction, said first projections and said offset projections having two side walls, one of said side walls of said offset projection being longer than the other side wall of said offset projections, said longer side wall of said offset projection overlapping the opposite side walls of the next adjacent first projections in each series whereby the longitudinally inter-connected projections will have bridging material therebetween substantially equal in width in the longitudinal direction to the amount of overlap of said longer side wall to prevent rupture of the heat transfer element.

2. The structure of claim 1 wherein the longer side walls of the offset projections in each row have a common centerline with the longer side walls of the other offset projections in the same series.

3. The structure of claim 2 wherein the longer side wall of the offset projection is equal in length to the opposite side wall of the adjacent first projections in the series.

4. The structure of claim 2 wherein the longer side walls of the offset projections are equal in length.

5. The structure of claim 4 wherein the shorter side walls of the offset projections are equal in length.

6. A heat transfer element for use in a plate type heat exchanger, comprising an elongated metal strip provided with a series of transversely extending rows of longitudinally interconnected projections, said series of projections consisting of first projections and offset projections, depressions between the projections in each of said rows, said offset projections being in alternate rows and being offset from said first projections in the same direction as the preceding row of said offset projections, said first projections of each series of interconnected projections being on a common centerline in the longitudinal direction,

said first projections and said offset projections having two side walls, one of said side walls of said offset projections being longer than the other side wall of said offset projections, said longer side wall being substantially on the centerline of the adjacent depression, said longer side wall of said offset projection overlapping the opposite side walls of the next adjacent first projections in each series whereby the longitudinally interconnected projections will have bridging material therebetween substantially equal in width in the longitudinal direction to the amount of overlap of said longer side wall to prevent rupture of the heat transfer element.

7. The structure of claim 6 wherein the shorter side wall of the offset projections substantially coincides with said centerline of said first projections.

8. The structure of claim 7 wherein the longer side wall of the offset projection is equal in length to the opposite side of the adjacent first projections in the series.

9. The structure of claim 7 wherein the longer side walls of the offset projections are equal in length.

10. The structure of claim 9 wherein the shorter side walls of the offset projections are equal in length.

11. A heat transfer element for use in a plate type heat exchanger, comprising an elongated metal strip provided with a series of transversely extending rows of longitudinally interconnected projections, said series of projections consisting of first projections and offset projections, depressions between the projections in each of said rows, said offset projections being in alternate rows and being offset from said first projections in the same direction as the preceding row of said offset projections, said first projections of each series of said interconnected projections being on a common centerline in the longitudinal direction, said first projections and said offset projections having two side walls, one of said side walls of said offset projection being longer than the other side wall of said offset projections, said longer wall bearing against the side walls of said projections in the neXtadjacent series of projections, said longer side Wall of said offset projection overlapping the opposite side walls of the next adjacent first projections in each series whereby the longitudinally interconnected projections will have bridging material therebetween substantially equal in width in the longitudinal direct-ion to the amount of overlap of said longer side Wall to prevent rupture of the heat transfer element.

12. The structure of claim 11 wherein the shorter side walls of said offset projections substantially coincide with the centerline of the side wall of the next adjacent first projections in said series which are nearest the side walls which the longer side walls of said offset projections bear against.

13. The structure of claim 12 wherein the longer side walls of the offset projections are equal in length to the opposite side wall of the adjacent first projections in the series.

, 14. The structure of claim 12 wherein said longer side walls of the offset projections are equal in length.

15. The structure of claim 14 wherein the shorter side walls of the offset projections are equal in length.

References Cited in the file of this patent UNITED STATES PATENTS

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