TITLE OF THE INVENTION

WINGLET PLATE FOR HEAT EXCHANGER BUILT ON METAL PLATES BONDED IN SOLID PHASE BY COLAMINATION OR OTHER COMPRESSION PROCESSES.

FIELD OF THE INVENTION

[001] This patent request concerns a construction of a winglet plate for heat exchangers using metal sheets bonded in solid phase by colamination or other compression processes. The basic members of aforesaid heat exchangers are tubes and winglets used in manufacturing absorber plates for solar collectors, nuclear reactors, refrigerator evaporators, automobile and airplane radiators, refrigeration condensers and several other applications. Said heat exchangers are used for transferring heat from a higher temperature fluid to another with a lower temperature, by heating, cooling or vaporizing fluids, such as water, air, ammonia, dichlorodifluoromethane (freon-12). Tube is understood here as a cross section tube: square, oval, round, etc. A significant increase in heat exchange and thermal yield is observed when using, said tubes with winglets as an increase in transfer area is ensured.

BACKGROUND OF THE INVENTION

[002] Such heat exchangers are comprised of two parts: tubes and winglets. Said winglets are comprised of rectangular metal strips or circular disks and fixed onto tube walls in both cases. However, a firm thermal/mechanic contact between tubes and winglets is required for heat transfer, which is currently obtained by soldering or pressing. Nevertheless, such processes create boding mechanisms that reduce heat transfer and hence thermal yield as thermal resistance is brought about between tubes and winglets. Moreover, soldering is mostly discontinued, which further increases thermal resistance. Pressing is even less efficient as it produces no direct contact between tubes and winglets. Tubes and winglets produced by means of soldering or pressing are usually

made in an artisanal manner thus at low productivity rates, such as: absorber plates for solar collectors, which are made of a soldered copper tube grate and fixed onto a copper or aluminum sheet (winglet); an improvement in collector plates has been proposed by the Brazilian patent request Pl 9806493-2A, which concerns sheath-shaped tubes made by pressing that require soldering tubes and winglets though.

[003] A similar proposal has been made by the American patent request US 4.249.519 through which two sheets are overlaid and pressed by a low heat soldering, the latter, however, requiring preparation of said sheets. Another American patent - US 4.074.406 - has proposed pressed copper tubes placed onto a sheet, which however causes thermal resistance between tubes and sheet; another American patent numbered US 4.023.557 has proposed an absorber plate with an internal copper tubulation and an outer aluminum tubulation, which however cause an even higher thermal resistance. Winglet tubes have also been proposed by the Brazilian patent request Pl 9803049-3A that were constructed with tubes having a larger diameter, which through pressing operations had their walls partly folded resulting in smaller diameter tubes with lateral winglets. Nevertheless, the making of such a kind of winglet tubes is impaired as far as their length is concerned, due to the need of adequate equipment for their mechanical shaping. Another shape for an absorbier plate was proposed by the American patent request US 4.911.353, through which a selective surface would be obtained by pulverizing cast metal onto tubulation, but this process requires temperature control of cast metal, which also causes thermal resistance between cast metal and tubulation.

INVENTION DESCRIPTION

[004] With a view to solve such inconveniences, this patent request proposes a winglet plate for a heat exchanger using metal sheets bonded in solid phase by colamination or other compression processes.

[005] Colamination is a mechanic shaping process in which lamination occurs simultaneously with soldering, i.e., metal bonding in solid phase by means of

laminating cylinders. Reduced thickness occurs in sheet lamination that provokes an increase in length. And solid phase bonding results from the surface conditions of both sheets, level of plastic deformation of metals and compressive stress.

[005] For this, metals must be submitted to a mechanical shaping that causes compressive stresses, as for example, plane state compression, lamination, etc. Such compressive stresses happen in the area between the two lamination cylinders, an area also called contact arch. In this way, when two previously prepared sheets overlay and enter the contact arch area, compressive stresses arise that provoke plastic deformation of both sheets and - according to some researchers - bonding occurs between said sheets, which is also called solid- phase bonding. The latter is a permanent metal soldering of similar or different metals achieved in temperatures that prevent melting of said metals.

[006] Nowadays, an explanation mostly accepted for this is that metallic connection is needed between surfaces to be bonded. For this, critical deformation is essential, which is a minimum plastic deformation necessary for a permanent bonding of a metallic pair. To the extent that a metallic pair (sheets) enters the contact arch area, applied pressures rise and plastic deformation produces a surface expansion then provoking virgin metal areas to appear that promote metal bonding between the surfaces of the aforesaid metallic pair. Therefore, colamination results in a sole piece and, precisely for this reason, a significant increase in heat transfer and its thermal yield will occur that conventional soldering or contact by pressing are rendered unnecessary, in this way with reduced costs.

[007] This process is a high productivity fabrication mainly if obtained through colamination. Additionally, there are no significant restrictions as to plate (sheet) length, since the ultimate length of material is only dependent on the initial length of said material and not on equipment as colamination is a continuous- typed process. Due to such an advantage, a winglet plate can be fabricated in both dimensions - length and breadth - and any tube diameter for a sole tube or multiple tubes. A winglet plate with several tubes is obtained in this way,

which may be used for solar collectors or heat exchangers or dissipaters or other equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

[008] A metal winglet plate can be better understood in the attached figures, as follows:

[009] FIGURE 1, from 1.a to 1.e, represents the winglet plate making. [010] FIGURE 2 shows different kinds of tubes. [011] FIGURE 3 shows different kinds of masks. [012] FIGURE 4 shows different kinds of exchangers. EXAMPLES

[013] As for such figures, the making of a winglet plate in figure 1 - from 1.a to I .e. Initially, two metal sheets (figure 1 , 1.a, "a" and "b") are given a baking thermal treatment viewing removal of internal stress that eases deformation imposed by lamination cylinders (figure 1 , 1.d, "e"). Afterwards, the oxidation layer is removed from one surface side with a rotary brush (figure 1 , 1.a, "d"); such a procedure can also be accomplished through other processes, such as: chemical decapping.

[014] A "mask" is then placed after oxidation removal (figure 1 , 1.b, "c") (e.g., a dehumidified piece of paper) onto a sheet (figure 1 , 1.b, "a"); following this, another sheet is overlaid (figure 1 , Ic, "a" and "b"). The set obtained in figure 1 , 1.c is then submitted to a mechanical shaping called colamination shown in figure 1 , Id, i.e., a sheet lamination simultaneously carried out with a solid phase bonding through cylinders (figure 1 , Ld ₁ "e"), except for the area covered or protected by the "mask" (figure 1 , Lb, "c"), which will create tube walls. In the specific case of lamination, the set obtained in figure 1 , Ld, "a", "b" and "c" can be submitted to several passes (of lamination) until a desired length is obtained.

[015] As colamination finishes, the set obtained in figure 1 , Ld, "a", "b" and "c" becomes now a sole piece of metal. A spigot (figure 1 , 1.and, "f") is then fixed in the area protected by the "mask" (figure 1 , Le, "c") through which a hydraulic

pressure injection of oil, water or air will create tube walls. Figure 2 shows different kinds of tube forms: round (figure 2, "g"); oval (figure 2, "h"); square (figure 2, "i"); lozenge (figure 2, "j") or even of other forms if needed. As for other forms, placement of matrices is necessary (figure 2, "k"), (figure 2, "I"), depending on the desired form for the tube profile. The tube diameter is directly proportional to the "mask" breadth (figure 1 , 1.b, "ci"). The tube diameter (figure 2, "g") is given by the length shown in figure 1 , 1.b, "ci" through hydraulic or pneumatic pressure injection until the whole wall is expanded. As for oval tube (figure 2, "h"), however, its smaller diameter can be controlled by means of pressure injection until a desired dimension is obtained.

[016] The masks on sheet shown in figure 3 can be made in various forms (figure 3, "m", "n" and "o") or other models. The aforesaid heat exchangers can be constructed with winglet tubes or winglet plates in different ways, as shown in figure 4: parallel to this (figure 4, "p"), these heat exchangers can be used for radiators or, at the same level, they are ideal for solar collectors that can comprise several winglet tubes (figure 4, "q") or a winglet plate (figure 4, "r"). Copper and aluminum are mostly used materials as they are economically feasible. However, other materials can also be used for the making of winglet plates even with different ones, according to technical necessities.