MANIFOLD ASSEMBLY FOR A PARALLEL FLOW HEAT EXCHANGER

Abstract: A manifold assembly (110) for use with heat exchangers comprises an extruded unitary tank (120) having a substantially U-shaped cross section and a unitary stamped header plate (150) which can either be substantially planar or have a substantially U-shaped cross section. The longitudinal bottom edges (144) of the tank (120) are crimped around the longitudinal side edges (160) of the header plate (150), and the mating surfaces are brazed substantially along their entire lengths. The inner walls (132, 152) of the manifold assembly (110) can include opposed transverse slots (180) therein for receiving baffles (190) for adjusting the flow path within the assembled manifold (110). The tank (120), header plate (150), and baffles (190) are formed of aluminum and aluminum alloy materials suitable for furnace brazing.

Description: MANIFOLD ASSEMBLY FOR A PARALLEL FLOW HEAT EXCHANGER BACKGROUND OF THE INVENTION The present invention is directed to the field of manifold assemblies for use with heat exchangers, particularly heat exchangers for refrigeration applications. Heat exchangers for refrigeration applications, particularly condensers and evaporators, are subjected to relatively high internal refrigerant pressure. Further, such heat exchangers cannot allow any leakage of refrigerant into the atmosphere and therefore preferably are designed with as few manufacturing connections as possible. Where manufacturing connections are necessary, their joints must be able to be manufactured economically and with a high probability that they will not leak. Automotive condensers have typically been constructed with a single length of refrigerant tube, assembled in a serpentine configuration with an inlet at one end and an outlet at the other end. In some cases, two or more of such serpentine coils are assembled into an intertwine configuration so as to provide a multiple path flow o refrigerant across the air flow. The ends of the separat serpentine coils are connected to common manifolds. Thi concept of multiple path flow is extended to what is called "parallel flow heat exchanger," in which all refrigerant tube are straight and parallel to each other with the individua ends of these tubes connected to respective inlet and outle manifolds. This configuration is commonly utilized in th construction of engine cooling radiators, oil coolers, an more recently, air conditioning condensers. Condenser application to parallel flow has been more difficult to achieve in practice because of the need for multiple high pressure joints. Also, the atmospheric problems associated with release of standard refrigerants has necessitated the change to newer, more ' chlorinated refrigerants such as R-134A. The R-134A refrigerant is not as efficient as R-12 refrigerants, and also operates at higher pressure than R-12 refrigerants. The lower efficiency of the R-134A refrigerant requires a condenser design which not only is more efficient, such as a parallel flow design, but also is able to withstand higher internal operating pressures. Manifolding multiple tubes to withstand high interna pressure can best be accomplished with a tubular manifold, th cross-section of which is circular for highest strength. U.S patent No. 4,825,941 to Hoshino et al. is an example of suc a manifold with a circular cross-section. The chie disadvantage to the tubular manifold with a circular cross section is the difficulty of piercing the series of holes i each manifold to receive the multiple parallel refrigeran tubes. Also, the tubular manifold with circular cross-sectio presents difficulties in assembly during manufacture. On partial solution to these problems is to flatten one side o each manifold tube as shown in Fig. 2, so as to provide a D shaped cross-section which can more easily be pierced an subsequently assembled. However, insertion of the tubes int the manifold is still difficult. Also, in some heat exchange designs, it is necessary to insert baffles in each manifold t create a multiple pass refrigerant flow. Insertion of th baffles into a tubular manifold can also present difficultie in assembly during manufacture. Accordingly, it has been proposed to use a two-piec manifold comprising a tank and a header plate. In one suc construction, shown in Figure 2 of U.S. patent No. 4,938,28 to Howells, the tank is formed with inwardly facing groove and the tank is slid into engagement with the header plate, which is planar. As shown in Figure 5 of the Howells patent, the tank can alternatively be formed with inwardly curved side wall members and the header plate can be formed with upturned longitudinal edges for gripping engagement with the side wall members of the tank when the tank is slid into engagement with the header plate. In both constructions, the tank is coated before assembly with a brazing material and flux to enable it to be secured upon assembly to the header plate. Although the constructions shown in the Howells patent provide both a mechanical and metallalurgical bond between the tank and header plate, sufficient clearance must be provided between the tank and the header plate to permit sliding of the one onto the other. This clearance prevents the good fit required for effective brazing. Further, it is often desirable to provide baffles in the assembled tank and header plate to adjust the flow path. When the tank and header plate are assembled by sliding, it is difficult, if not impossible, to place baffles between them prior to assembly. In another construction, the tank is provided with a flange, tabs are placed on the header plate, a gasket is inserted between the header plate and the tank, and the tabs are crimped over the tank flange. Examples of such a construction are shown in U.S. patent No. 4,455,728 to Hesse, U.S. patent No. 4,531,578 to Stay et al., and U.S. patent No. 4,600,051 to Wehrman. A leak-type seal is provided by compressing the gasket. However, compression of the gasket is not sufficient to seal the header plate and tank under the high,pressures found in condensers. A solution to these problems was proposed in co-pending U.S. application serial No. 503,798 of Calleson, which is expressly incorporated herein by reference. In the Calleson application, a pair of opposed parallel shelves are formed in the inner wall of the tank inwardly of the bottom edges to define a pair of flanges extending from the shelves. The shelves in the tank form stops against which the header plate abuts. The tank flanges are crimped inwardly to engage at least a portion of the edge portions of the header plate along the entire length of the header plate. Also, the tank and header plate are brazed together along substantially the entire lengths, of their mating surfaces in order to provide both a mechanical and a metallurgical bond which provides the strengths to withstand high internal pressures. A pair of opposed, longitudinally-extending horizontal ribs can be formed in the inner wall of the tank and provided with opposed slots to receive baffles, in order to adjust the flow pattern. The horizontal ribs can also serve as tube stops. Although the crimped flange proposed in the Calleson application is superior to the prior art flange and tab configurations, the crimping of the flange -around the header plate prevents the filler material or alloy from flowing well enough to provide as uniform or consistent a brazed joint or fillet as is ideally desired for high pressure applications. It is the solution of the above and other problems to which the present invention is directed. SUMMARY OF THE INVENTION Therefore, it is a primary object of this invention to provide a manifold assembly for heat exchangers which can withstand high internal operating pressures. It is another object of this invention . to provide a manifold assembly for heat exchangers which employs an exceptionally strong and uniform metallurgical bond between the tank and header plate. It is another object of the invention to provide a manifold assembly for heat exchangers which is easier and less costly to assemble. These and other objects of the invention are achieved by the provision of a manifold assembly which comprises a unitary tank having a substantially U-shaped cross-section and unitary header plate which has a substantially U-shaped semi-circular cross-section. The tank comprises an at least partially curved upp portion which in cross-section forms the base of the U, a pa of opposed sides extending from the ends of the upper porti and which in cross-section form the arms of the U, a pair opposed inner side walls, an inner upper wall intermediate t inner side walls, a pair of outer side walls, an outer upp wall intermediate the outer side walls, a pair of longitudin bottom edges extending between the inner and outer walls a the free ends of the sides, and a pair of longitudina channels formed in the bottom edges of the sides. Th channels divide the bottom edges into inner and oute portions. The header plate comprises an inner wall, an outer wall and a pair of upper edges intermediate the inner and oute wall which are matingly received in the channels formed in th bottom edges of the tank. A plurality of transverse tub holes are formed through the header plate along its cente line for receiving the tubes of the condenser or evaporator Preferably, a flange or lip is formed around the tube holes t provide both a tube lead-in and a joint filleting pocket. Th inner portions of the bottom edges of the tank form stop against which the tubes abut. The tank and header plate ar brazed together along substantially the entire lengths o their mating surfaces in order to provide an exceptionall uniform and consistent brazed joint or fillet which provide the strength to withstand high internal pressures. The tank and header plate are formed of aluminum an aluminum alloy materials suitable for furnace brazing, a least one of the mating surfaces being fabricated with a lowe temperature clad brazing material, so that when the tank, header plate, and tubes are assembled, fixtured, and brazed i a high temperature brazing furnace, the clad material provide the brazed material to braze the tubes to the header plate an the header plate to the tank. In one aspect of the invention, the tank is formed by extrusion and the header plate is formed by stamping. In another aspect of the invention, the tank is extruded from an aluminum alloy such as AA3003 or the like, and the header plate is fabricated from sheet aluminum of a desired based aluminum alloy such as AA3003 or the like, clad on both surfaces with aluminum alloy such as 4004 or any other suitable brazing alloy. In still another aspect of the invention, a plurality o opposed transverse slots can be formed through the tank an header plate along their center lines to receive baffle therein, in order to adjust the flow pattern. The baffles ar configured to engage the inner walls and sides of the slots and are also formed of aluminum and aluminum alloy material suitable for furnace brazing, so that when the manifol assembly is brazed in a high temperature brazing furnace, th baffles are brazed to the tank and the header plate. In yet another aspect of the invention, a bracket can b formed unitarily with one of the outer side walls of the tank. A better understanding of the disclosed embodiments o the invention will be achieved when the accompanying detaile description is considered in conjunction with the appende drawings, in which like reference numerals are used for the same parts as illustrated in the different figures. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view, partially cut away, of a manifold and heat exchanger assembly in accordance with the present invention. Figure 2 is an end view of the manifold a heat exchanger assembly of Figure 1. Figure 3 is a cross-sectional view of the manifold an heat exchanger assembly of Figure 1, taken along line 3-3 o Figure 1. Figure 4 is a cross-sectional view of the manifold an heat exchanger assembly in accordance with the presen invention, with the tank, header plate, and baffle unassembled. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In describing the preferred embodiments of the subjec invention illustrated in the drawings, specific terminolog will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalence which operate in a similar manner to accomplish a similar purpose. Referring now to Figs. 1-4, there is shown a manifold and heat exchanger assembly 100 in accordance with the present invention. Manifold and heat exchanger assembly 100 comprises a manifold assembly 110 into which are inserted a plurality of parallel condenser or evaporator tubes 112. Manifold assembly 110 comprises a unitary tank 120 having a substantially U-shaped cross-section and a unitary header plate 150 having a substantially semi-circular cross-section. Thus, manifold assembly 110 has a substantially circular cross-section. The use of a curved cross-section for both tank 120 and header plate 150 enables manifold assembly 110 to withstand higher internal pressures than D-shaped manifold assemblies. Tank 120 comprises an at least partially curved upper portion 122 which in cross-section forms the base of the U, a pair of opposed sides 124 extending from the ends of upper portion 122 and which in cross-section form the arms of the U, a pair of opposed inner side walls 130, an inner upper wall 132 intermediate inner side walls 130, a pair of outer side walls 140, an outer upper wall 142 intermediate outer side walls 140, and a pair of longitudinal bottom edges 144 extending between inner and outer side walls 130 and 140 at the free ends of sides 124. As shown in Figures 1, 2, and 4, inner side walls 130 are substantially planar and parallel to each other, while one of outer side walls 140 is curved and the other is unitaril provided with a mounting bracket 140a. Inner upper wall 132 is also curved. Outer upper wall 142 is formed with substantially planar, central longitudinal rib 142a. A pair of longitudinal channels 146 are formed in bottom edges 144. Channels 146 divide bottom edges 144 into inner and outer portions 144a and 144b. Header plate 150 has a length substantially equal to the length of tank 120 and comprises an inner wall 152, an outer wall 154 substantially parallel to inner wall 152, and a pair of longitudinal upper edges 160 extending between inner and outer walls 152 and 154. Inner wall 152 includes a pair of opposed . inner side walls 162 and an inner lower wall 164 intermediate inner side walls 162. A plurality of transverse tube holes 170 are formed through header plate 150 along its longitudinal center line for receiving tubes 112 of manifold and heat exchanger assembly 100. Flanges or lips 172 are formed around tube holes 170. Flanges 172 are very uniform formed sections which follow the internal contour of header plate 150, i.e. the contour in inner wall 152, thereby providing both a tube lead-in and a joint filleting pocket. Tank 120 preferably is formed by extrusion. Header plate 150 preferably is formed by stamping. Tank 120 can be extruded from an aluminum alloy such as AA3003 or the like, while header plate 150 is fabricated from sheet aluminum of a desired base aluminum alloy such as AA3003 'or the like, clad on both surfaces with aluminum alloy such as 4004, or other suitable brazing alloys. A plurality of opposed transverse slots 180 can be formed through tank 120 and header plate 150 along their longitudinal center lines to receive baffles 190 therein, in order to adjust the flow pattern. Baffles 190 are configured to form a tight fit with inner side walls 130 of tank 120 and inner side walls 162 of header plate 150, and to extend outwardly of outer upper wall 142 of tank 120 and outer wall 154 of header plate 150. Inner portions 144a of bottom edges 144 of tank 120 extend inwardly a sufficient amount to act as stops for tubes 112. Inner side and upper walls 130 and 132 of tank 120 can be coated with clad alloy in order to braze baffles 190 to inner wall 130. Tank 120 is assembled to header plate 150 by inserting upper edges 160 of header plate 150 into channels 146. This form of assembly permits a close fit between the abutting surfaces of tank 120 and header plate 150, resulting in effective brazing. Further, it allows the filler material or alloy to flow freely to provide a uniform and consistent brazed joint or fillet. Tubes 112 are assembled to head plate 150 through header flanges 172 with their ends abutti inner portions 144a of bottom edges 144 of tank 120. Assembly of tank 120 with baffles 190 and header pla 150 can also be accomplished as a unit prior to assembly manifold assembly 110 to tubes 112. Where, in certain brazi operations it is desired to use flux, the flux can be appli to the mating surfaces of the parts before their assembl The prior art makes this operation very difficult. Only a single manifold assembly is shown assembled to t tubes 112 in Figure- 1. However, it should be understood th in practice, a manifold assembly is assembled to tubes 112 either end. In manifolds formed from unitary circular or semi circular tubes as shown in the prior art, internal baffle must be installed from either end or through an external slo as shown in the Hoshino et al. patent. The use of the two piece construction in accordance with the present inventio allows installation of baffles 190 either before assembly o tank 120 and header plate 150 or through slots 180 afte assembly of tank 120 and header plate 150. In general, tank 120, header plate 150, and baffles 18 are formed of aluminum and aluminum alloy materials suitabl for brazing, at least one of the mating surfaces bein fabricated with a lower temperature clad brazing material. For example, a lower cost extruded alloy can be used for tan 120, while a clad brazing sheet can be used for header plat 150. Thus, when tank 120, header plate 150, baffles 190, an tubes 112 are assembled, fixtured in place, and brazed in a high temperature brazing furnace, the clad material on heade plate 150 provides the brazed material to braze tubes 112 to header plate 150, header plate 150 to tank 120, and baffles 190 to tank 120 and header plate 150. The pocket provided by header flanges 172 allows the braze to form a uniform fillet on flanges 172, which in turn allows a uniform tube-to-header fillet during braze. From the above, it is apparent that many modifications and variations • of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

Claims: WHAT IS CLAIMED IS: 1. A manifold assembly for use with an internal pressu heat exchanger comprising a plurality of parallel tubes, sa manifold assembly comprising: a unitary tank having a substantially U-shap cross-section, said tank comprising an upper portion which cross-section forms the base of the U, a pair of opposed sid extending from the ends of said upper .portion and which cross-section form the arms of the U, an inner wall, an out wall, and a pair of longitudinal bottom edges extendi between said inner and outer walls at the free ends of sa sides, each of said bottom edges having a longitudinal chann formed therein; and, a unitary header plate having a length substantial equal to the length of said tank, said header plate having substantially circular cross-section, an inner wall, an out wall, and a pair of longitudinal upper edges extending betwee said inner and outer walls at the free ends thereof, sa header plate having a plurality of tube holes forme therethrough along its longitudinal center line for receivin the tubes of the heat exchanger; said upper edges of said header plate being inserte into and matingly engaging said channels in said bottom edge of said tank; said header plate and said tank being brazed together along substantially the entire lengths of their mating surfaces; and said tank and said header plate being formed of aluminum and aluminum alloy materials suitable for furnace brazing, at least one of the mating surfaces being fabricated with a lower temperature clad brazing material. 2. The manifold assembly of claim 1, further comprising a bracket formed unitarily with said tank. 3. The manifold assembly of claim 2, wherein said outer surface of said tank includes a pair of outer side walls, and wherein ■ said bracket comprises a planar section formed unitarily with one of said outer side walls. 4. The manifold assembly of claim 1, wherein said header plate further comprises flanges formed around said tube holes, said flanges following the internal contour of said inner wall of said header plate. 5. The manifold assembly of claim 1, wherein said inner surface of said tank includes a pair of opposed inner side walls and an inner upper wall intermediate said inner side walls, and said inner surface of said header plate includes a pair of opposed inner side walls and an inner lower wal intermediate said inner side walls, wherein said tank and sai header plate have formed therethrough a plurality of oppose transverse slots along their longitudinal center lines, an wherein said manifold assembly further comprises a pluralit of baffles received in said slots, said baffles bein configured to form a tight fit with said inner side walls o said tank and said header plate. 6. The manifold assembly of claim 5, wherein said inne side walls of said tank are substantially planar and parallel to each ether. 7. The manifold assembly of claim 6, wherein said baffles extend outwardly of said outer wall of said tank and said outer wall of said header plate. 8. A method of making a manifold assembly for use with an internal pressure heat exchanger comprising a plurality of parallel tubes, comprising the steps of: (a) forming a unitary header plate of semi-circular cross-section from a material suitable for furnace brazing, said header plate having an inner wall, an outer wall, and a pair of longitudinal upper edges extending between said inner and outer walls at the free ends thereof, the inner wall including a pair of opposed inner side walls, and the inne and outer walls being clad with a brazing alloy; (b) forming a unitary tank of substantially U-shape cross-section from a material suitable, for furnace brazing, the tank comprising an upper portion which in cross-section forms the base of the U, a pair of opposed sides extending from the ends of said upper portion and which in cross-section form the arms of the U, an inner wall,, an outer wall, and a pair of longitudinal bottom edges extending.between said inner and outer walls at the free ends of said sides, the inner wall including a pair of opposed inner side walls, each of said bottom edges having a longitudinal channel formed therein; (c) forming a plurality of transverse baffle- receiving slots and tube-receiving holes through the header plate and forming a plurality of transverse baffle-receiving slots through the tank in registration with the baffle- receiving slots through the header plate; (d) forming a plurality of baffles from a material suitable for furnace brazing and configured to form a tight fit with the inner side walls of the header plate and tank and to extend outwardly of the outer walls of the tank and the header plate through the slots therein; (e) forming a plurality of tubes configured to be received through the tube-receiving holes in the header plate; (f) inserting the baffles into the slots in one o the header plate and the tank; (g) following step (f) , assembling the tank to the header plate by inserting said upper edges of said header plate into said channels in said bottom edges of said tank; (h) assembling the tubes to the header plate; and (i) brazing the assembled tank, header plate, baffles, and tubes in a high temperature brazing furnace. 9. The method of claim 8, wherein in said step (a) , the header plate is formed by stamping from sheet aluminum clad with a brazing alloy and wherein in said step (b) , the tank is formed by extrusion from an aluminum alloy. 10. The method of claim 8, wherein flux is applied to the mating surfaces of the header plate, the tank, and the baffles prior to their assembly. 11. The method of claim 8, wherein in said step (a) , the header plate is formed with an integral bracket. AMENDED CLAIMS [received by the International Bureau on 5 January 1993 (05.01.93); original claims 1 and 8 amended; other claims unchanged (5 pages)] 1. A manifold assembly for use with an internal pressure heat exchanger comprising a plurality of parallel tubes, said manifold assembly comprising: a unitary tank having a substantially U-shaped cross-section, said tank comprising an upper portion which in cross-section forms the base of the U, a pair of opposed sides extending from the ends of said upper portion and which in cross-section form the arms of the U, an inner wall, an outer wall, and a pair of longitudinal bottom edges extending between said inner and outer walls at the free ends of said sides, each of said bottom edges having a longitudinal channel formed therein; and a unitary header plate having a length substantially equal to the length of said tank, said header plate having a substantially semi-circular cross-section, an inner wall, an outer wall, and a pair of longitudinal upper edges extending between said inner and outer walls of said header plate at the free ends thereof, said header plate having a plurality of tube holes formed therethrough along its longitudinal center line for receiving the tubes of the heat exchanger; said upper edges of said header plate being inserted into and atingly engaging said channels in said bottom edges of said tank without a crimp being formed in said channels, said header plate and said tank when assembled having a substantially circular cross-section; said header plate and said tank being brazed together along substantially the entire lengths of their mating surfaces; and said tank and said header plate being formed of aluminum and aluminum alloy materials suitable for furnace brazing, at least one of the mating surfaces being fabricated with a lower temperature clad brazing material. 2. The manifold assembly of claim 1, further comprising a bracket formed unitarily with said tank. 3. The manifold assembly of claim 2, wherein said outer surface of said tank includes a pair of outer side walls, and wherein said bracket comprises a planar section formed unitarily with one of said outer side walls. 4. The manifold assembly of claim 1, wherein said header plate further comprises flanges formed around said tube holes, said flanges following the internal contour of said inner wall of said header plate. 5. The manifold assembly of claim 1, wherein said inner surface of said tank includes a pair of opposed inner side walls and an inner upper wall intermediate said inner side walls, and said inner surface of said header plate includes a pair of opposed inner side walls and an inner lower wall intermediate said inner side walls, wherein said tank and said header plate have formed therethrough a plurality of opposed transverse slots along their longitudinal center lines, and wherein said manifold assembly further comprises a plurality of baffles received in said slots, said baffles being configured to form a tight fit with said inner side walls of said tank and said header plate. 6. The manifold assembly of claim 5, wherein said inner side walls of said tank are substantially planar and parallel to each other. 7. The manifold assembly of claim 6, wherein said baffles extend outwardly of said outer wall of said tank and said outer wall of said header plate. 8. A method of making a manifold assembly for use with an internal pressure heat exchanger comprising a plurality of parallel tubes, comprising the steps of: (a) forming a unitary header plate of semi-circular cross-section from a material suitable for furnace brazing, said header plate having an inner wall, an outer wall, and a pair of longitudinal upper edges extending between said inner and outer walls at the free ends thereof, the inner wall including a pair of opposed inner side walls, and the inner and outer walls being clad with a brazing alloy; (b) forming a unitary tank of substantially U-shaped cross-section from a material suitable for furnace brazing, the tank comprising an upper portion which in cross-section forms the base of the U, a pair of opposed sides extending from the ends of said upper portion and which in cross-section form the arms of the U, an inner wall, an outer wall, and a pair of longitudinal bottom edges extending between said inner and outer walls at the free ends of said sides, the inner wall including a pair of opposed inner side walls, each of said bottom edges having a longitudinal channel formed therein configured to matingly receive the upper edges of the header plate; (c) forming a plurality of transverse baffle- receiving slots and tube-receiving holes through the header plate and forming a plurality of transverse baffle-receiving slots through the tank in registration with the baffle- receiving slots through the header plate; (d) forming a plurality of baffles from a material suitable for furnace brazing and configured to form a tight fit with the inner side walls of the header plate and tank and to extend outwardly of the outer walls of the tank and the header plate through the slots therein; (e) forming a plurality of tubes configured to be received through the tube-receiving holes in the header plate; (f) inserting the baffles into the slots in one of the header plate and the tank; (g) following step (f) , assembling the tank to the header plate by inserting said upper edges of said header plate into said channels in said bottom edges of said tank without a crimp being formed in said channels, said header plate and said tank when assembled having a substantially circular cross-section; (h) assembling the tubes to the header plate; and (i) brazing the assembled tank, header plate, baffles, and tubes in a high temperature brazing furnace. 9. The method of claim 8, wherein in said step (a), the header plate is formed by stamping from sheet aluminum clad with a brazing alloy and wherein in said step (b) , the tank is formed by extrusion from an aluminum alloy. 10. The method of claim 8, wherein flux is applied to the mating surfaces of the header plate, the tank, and the baffles prior to their assembly. 11. The method of claim 8, wherein in said step (a), the header plate is formed with an integral bracket.

Inventors: CREAMER HARVEY, LEJEUNE LIONEL J III, MATHEWS DONALD W, CREAMER, HARVEY, LEJEUNE, LIONEL, J., III, MATHEWS, DONALD, W.
Applicants: THERMAL COMPONENTS INC, THERMAL COMPONENTS, INC.
Application year: 1992
Main classification: F28F9
IPC codes: F28F9