Manifold and heat exchanger assembly

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 of the tank (120) are crimped around the longitudinal side edges of the header plate (150), and the mating surfaces are brazed substantially along their entire lengths. The inner wall of the tank (120) can include opposed longitudinal ribs having opposed slots therein for receiving baffles (184) for adjusting the flow path within the assembled manifold. The tank (120), header plate (150), and baffles (184) are 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, so that when the tank (120), header plate (150), baffles (184) and heat exchanger tubes (112) are assembled, fixtured, and brazed in a high temperature brazing furnace, the clad material provides the brazed material to braze the tubes (112) to the header plate (150), the header plate (150) to the tank (120), and the baffles (184) to the tank (120) and the header plate (150).

Description: The present invention is directed to the field of manifold and heat exchanger assemblies, 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 intertwined configuration so as to provide a multiple path flow of refrigerant across the air flow. The ends of the separate serpentine coils are connected to common manifolds. This concept of nultiple path flow is extended to what is called a "parallel flow heat exchanger," in which all refrigerant tubes are straight and parallel to each other with the individual ends of these tubes connected to respective inlet and outlet manifolds. This configuration is commonly utilized in the construction of engine cooling radiators, oil coolers, and 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 internal pressure can best be accomplished with a tubular manifold, the cross-section of which is circular for highest strength, as shown in Figure 1. US-A- 4,825,941 is an example of such a manifold with a circular cross-section. The chief disadvantage to the tubular manifold with a circular cross-section is the difficulty of piercing the series of holes in each manifold to receive the multiple parallel refrigerant tubes. Also, the tubular manifold with circular cross-section presents difficulties in assembly during manufacture One partial solution to these problems is to flatten one side of each manifold tube as shown in Fig. 2, so as to provide a D-shaped cross-section which can more easily be pierced and subsequently assembled. However, insertion of the tubes into the manifold is still difficult. Also, in some heat exchanger designs, it is necessary to insert baffles in each manifold to create a multiple pass refrigerant flow. Insertion of the baffles into a tubular manifold can also present difficulties in assembly during manufacture. DE-A-4004949 discloses a manifold and heat exchanger assembly said heat exchanger comprising a plurality of parallel tubes. The illustrated manifold assembly comprises a unitary tank and a unitary header plate. The unitary tank has a substantially U-shaped cross-section, the tank comprising an upper portion which in cross-section forms the base of the U and a pair of a substantially straight opposed parallel sides. The sides of the tank define a pair of opposed parallel shelves. The header plate is a unitary header plate having a length substantially equal to the length of the tank. The plate has a plurality of tube holes extending therethrough for receiving the tubes of the heat exchanger. The header plate has upturned end edges and is engaged with the tank being retained by flanges formed with the sides of the tank which are crimped inwardly to contact the header plate. The upturned edges of the header plate substantially abut the shelves defined in the tank. Therefore, it is a primary object of this invention to provide a manifold and heat exchanger assembly which can withstand high internal operating pressures. This assembly should be easier and less costly to assemble. According to this invention there is provided a manifold and heat exchanger assembly, said 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 and a pair of substantially straight opposed parallel sides and a unitary header plate having a length substantially equal to the length of the tank, the header plate having a plurality of tube holes extending therethrough for receiving the tubes of the heat exchanger, the header plate having upturned end edges and being engaged with the tank and being retained by flanges formed with the tank which are crimped inwardly to engage the header plate, the said flanges comprising longitudinally-extending flanges formed integrally with the opposed parallel sides of the unitary tank, the sides of the tank further defining a pair of opposed parallel shelves the header plate abutting said shelves of the tank, the header place and the tank being brazed together along substantially the entire lengths of their mating surfaces, wherein the end edges of the header plate are upturned, and the shelves are provided with channels formed therein for receiving the upturned edges of the header plate, the tank and the header plate being formed of aluminium or aluminium alloy materials suitable for furnace brazing, at least one of the mating surfaces being fabricated with a lower temperature clad brazing material. The tank may be formed by extrusion and the header plate may be formed by stamping. The tank may be extruded from an aluminium alloy such as AA3003 or the like, and the header plate is fabricated from sheet aluminium of a desired based aluminium alloy such as AA3003 or the like, clad on both surfaces with aluminium alloy such as 4004 or any other suitable brazing alloy. In one preferred embodiment a pair of opposed, longitudinally-extending horizontal ribs can be formed in the inner wall of the tank and provided with opposed slots to receiving baffles, in order to adjust the flow pattern. The horizontal ribs can also serve as tube stops. The baffles are also formed of aluminium and aluminium alloy materials suitable for furnace brazing, so that when the manifold assembly is brazed in a high temperature brazing furnace, the baffles are brazed to the tank and the header plate. In one embodiment of the invention, a longitudinally-extending vertical rib can be provided in the inner wall to serve as a tube stop or to act as a continuous centre separator which brazes to the centre line of the header plate to provide a two pass heat exchanger. The invention also provides a method of making a manifold and heat exchanger assembly, said heat exchanger comprising a plurality of parallel tubes, said method comprising the steps of a) forming a unitary tank having a substantially U-shaped cross-section, the tank comprising an upper portion which in cross-section forms the base of the U and also defines a pair of substantially straight opposed parallel sides having integrally formed longitudinally extending flanges, the sides of the tank further defining a pair of shelves the tank being formed of aluminium or aluminium alloy materials suitable for furnace brazing, b) forming a unitary header plate having a length substantially equal to the length of the tank, the header plate having upturned edges and a plurality of holes formed therethrough for receiving the tubes of the heat exchanger, the header plate being formed of aluminium or aluminium alloy material suitable for furnace brazing, c) inserting the header plate in the tank, d) crimping flanges formed integrally with the said side walls to engage the header plate along substantially the entire lengths thereof, and e) brazing together the header plate and the tank along substantially the entire lengths of their mating surfaces, wherein the method comprises the steps of providing the shelves with channels, upturning the edges of the header plate and inserting the upturned edges in the channels and cladding the tank and/or the header plate with a low temperature brazing material. A better understanding of the disclosed embodiments of the invention will be achieved when the accompanying detailed description is considered in conjunction with the appended drawings, in which like reference numerals are used for the same parts as illustrated in the different figures. FIGURE 1 is a cross-sectional view of a first prior art manifold and heat exchanger assembly, FIGURE 2 is a cross-sectional view of a second prior art manifold and heat exchanger assembly, FIGURE 3 is a cross-sectional view of an embodiment of a manifold and heat exchanger assembly in accordance with the present invention, with the tank and header plate unassembled. FIGURE 3A is a cross-sectional view of the manifold and heat exchanger assembly of Figure 3, with the tank and header plate assembled. FIGURE 4 is a perspective view, partially cut away, of another embodiment of a manifold and heat exchanger assembly in accordance with the present invention, FIGURE 5 is a cross-sectional view of the manifold and heat exchanger assembly of Figure 4, with the tank, header plate, and baffles unassembled. FIGURE 5A is a cross-sectional view of the manifold and heat exchanger assembly of Figure 4 with the components assembled, FIGURE 6 is a cross-sectional view of yet another embodiment of a manifold and heat exchanger assembly in accordance with the present invention, FIGURE 7 is a cross-sectional view of a fourth embodiment of a manifold and heat exchanger assembly in accordance with the present invention, FIGURE 8 is a perspective view of yet a further embodiment of a manifold and heat exchanger assembly in accordance with the present invention, and FIGURE 9 is a cross-sectional view of the manifold and heat exchanger assembly of Figure 8, taken along line 9-9 of Figure 8. In describing the preferred embodiments of the subject invention illustrated in the drawings, specific terminology 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 equivalents which operate in a similar manner to accomplish a similar purpose. Referring now to Figures 3 and 3A there is shown a first embodiment of 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 planar cross-section. Thus, manifold assembly 110 has a substantially D-shaped cross-section. Tank 120 comprises an at least partially curved upper portion 122 which in cross-section forms the base of the U, a pair of substantially straight opposed, parallel sides 124 extending from the ends of upper portion 122 and which in cross-section form the arms of the U, an inner wall 130, an outer wall 132, and a pair of longitudinal end edges 134 extending between inner and outer walls 130 and 132 at the free ends of sides 124. A pair of opposed parallel longitudinal shelves 140 are formed in inner wall 130 inwardly of t end edges 134 to define a pair of longitudinal flanges 142 extending from shelves 140. The shelves 140 are each provided with a respective channel 144. Header plate 150 has length substantially equal to the length of tank 120 and comprises a pair of opposed, parallel upturned longitudinal edge portions 152, a centre portion 154 extending between edge portions 152, an upper wall 160, a lower wall 162, and a pair of longitudinal end edges 164 extending between upper and lower walls 160 and 162. Centre portion 154 has a plurality of tube holes 170 formed therethrough for receiving tubes 112. Header plate 150 is assembled to the ends of tubes 112. The ends of tubes 112 can be expanded into tube holes 170 prior to assembly of tank 120 to header plate 150. Tank 120 is then assembled to header plate 150 with upper wall 160 abutting or in close proximity to shelves 140, and the upturned edge portions 152 being received in the channels 144 so that header plate 150 is inserted in tank 120 inwardly of end edges 134. Flanges 142 are crimped to header plate 150 by folding flanges 142 over and around edge portions 152 of header plate 150. Assembly of tank 120 with baffles (not shown) and header plate 150 can also be accomplished as a unit prior to assembly of manifold assembly 110 to tubes 112. Where, in certain brazing operations it is desired to use flux, the flux can be applied to the mating surfaces of the parts before their assembly. The prior art makes this operation very difficult. Only a single manifold assembly is shown assembled to the tubes 120 in the Figures. However, it should be understood that in practice, a manifold assembly is assembled to tubes 120 at either end. Tank 120 preferably is formed by extrusion. Header plate 150 preferably is formed by stamping, but also can be formed by extrusion. Tank 120 can be extruded from an aluminium alloy such as AA3003 or the like, while header plate 150 is fabricated from sheet aluminium of a desired base aluminium alloy such as AA30003 or the like, clad on both surfaces with aluminium alloy such as 4004, or other suitable brazing alloys. The inner wall of the tank can be provided with a pair of opposed longitudinally extending ribs having pairs of opposed slots therein for receiving baffles. In manifolds formed from circular or semi-circular tubes as shown in Figures 1 and 2, internal baffles must be installed from either end or through an external slot as shown in US-A-4825921. The use of the two-piece construction as described allows installation of baffles before assembly of tank 120 and header plate 150. In general, tank 120, header plate 150, and baffles are formed of aluminium and aluminium alloy materials suitable for brazing, at least one of the mating surfaces being fabricated with a lower temperature clad brazing material. For example, a lower cost extruded alloy can be used for tank 120, while a clad brazing sheet can be used for header plate 150. Thus, when tank 120, header plate 150, baffles and tubes 112 are assembled, fixtured in place and brazed in a high temperature brazing furnace, the clad material on header plate 150 provides the brazed material to braze tubes 112 to header plate 150, header plate 150 to tank 120 and baffles to tank 120 and header plate 150. It is to be observed that edge portions 152 of header plate 150 are upturned, and shelves 140 are formed with channels 144 for receiving upturned edge portions 152. Referring now to Figures 4, 5 and 5A, there is shown another embodiment of a manifold and heat exchanger assembly 100 in accordance with the present invention. In this embodiment, tank 120 has a central longitudinal ridge 190 formed on outer wall 132 and a mounting bracket 192 extending upwardly at one of sides 124. Also, header plate 150 has a substantially U-shaped cross-section with lips 200 formed around tube holes 170. Lips 200 are very uniform formed sections which follow the internal contour of header plate 150, allowing a precise tube-to-header fit. This precise tube-to-header fit in turn allows the braze to form a uniform fillet on lips 200. Inner wall 130 of tank 120 and upper wall 160 of header plate 150 can be provided with a plurality of opposed transverse indentations 201 positioned between tube holes 170, for receiving the upper and lower edges of baffles 184. Similar indentations 201 can be provided in inner wall 130 of tank 120 and upper wall 160 of header plate 150 of manifold and heat exchanger assembly shown in Figure 3. Preferably, indentations 201 are 0.5 mm (.020 inch) deep. As will be recognised by those of skill in the art, baffles 184 will be sized to extend into indentations 201. Indentations 201 not only aid in positioning baffles 184, but also improve braze joint strength and reduce the potential for leakage after braze. Longitudinal shelves 202 can be formed in header plate 150 for engaging the lower surface of shelves 140 of tank 120, and thus provide one means for sealing from baffle leakage around baffles 184. The use of a curved cross-section fro both tank 120 and header plate 150 enables manifold assembly 110d to withstand higher internal pressures. Inner wall 130 can be spray clad for surface protection or brazing. Referring now to Figure 6 there is shown yet another embodiment of a manifold and heat exchanger assembly 100. This embodiment is similar to the embodiment shown in Figures 4, 5 and 5A, in that tank 120 is provided with a mounting bracket 192, and header plate 150 has a substantially U-shaped cross-section and is provided with lips 200 formed around tube holes 170. However, in this embodiment, horizontal ribs 180 and baffles 184 are omitted. Instead, a longitudinally extending vertical rib 204 is formed along the centre line of inner wall 130, and an inlet/outlet 210 is formed through curved upper portion 122 centred over vertical rib 204. Vertical rib 204 serves as a stop for tubes 112, and tubes 112 can have notches 212 formed int he ends thereof to engage vertical rib 204. This embodiment, with inlet/outlet 210 centre over vertical rib 204 represents a single pass configuration of the present invention. A further embodiment of a manifold and heat exchanger assembly 100 in accordance with the present invention is shown in Figure 7, and illustrates how the single pass configuration shown in Figure 6 can be altered to provide a two pass configuration. As shown in Figure 7, a separate inlet 210a and outlet 210b can be provided on either side of vertical rib 204, and header plate 150 can be formed with an inwardly extending longitudinal ridge 220. Vertical rib 204 can then be brazed to upper wall 160 of header plate 150 at ridge 220 to provide a continuous centre separator. Referring now to Figures 8 and 9, there is shown yet a further embodiment of a manifold and heat exchanger assembly 100 in accordance with the invention. This embodiment is similar to the embodiment shown in Figures 4, 5 and 5A, except that a plurality of opposed transverse slots 300 are provided in tank 120 and header plate 150, and baffles 184 extend outwardly of tank 120 and header plate 150 through slots 300. Preferably baffles 184 protrude approximately 0.5mm (.020 inch) to 2.4 mm (.095 inch) form outer wall 132 of tank 120 and lower wall 162 of header plate 150. This configuration allows baffles 184 to be inserted after tank 120 and header plate 150 are assembled. It also allows better outgoing after vacuum brazing, as well as creating both internal and external brazed joints between baffles 184 and tank 120 and header plate 150. A higher burst pressure for the heat exchanger is thus achieved.

Claims: A manifold and heat exchanger assembly (100), said heat exchanger comprising a plurality of parallel tubes (112), said manifold assembly comprising a unitary tank(120) having a substantially U-shaped cross-section, said tank comprising an upper portion(122) which in cross-section forms the base of the U and a pair of substantially straight opposed parallel sides(124) and a unitary header plate(150) having a length substantially equal to the length of the tank(120), the header plate having a plurality of tube holes(170) extending therethrough for receiving the tubes(112) of the heat exchanger, the header plate having end edges(152) and being engaged with the tank and being retained by flanges(142) formed with the tank which are crimped inwardly to engage the header plate, the said flanges comprising longitudinally-extending flanges(142) formed integrally with the opposed parallel sides of the unitary tank, the sides of the tank further defining a pair of opposed parallel shelves(140) the header plate(152) substantially abutting said shelves of the tank, the header plate and the tank being brazed together along substantially the entire lengths of their mating surfaces, characterised in that the end edges(152) of the header plate(150) are upturned, and the shelves(140) are provided with channels(144) formed therein for receiving the upturned edges(152) of the header plate(150), the tank and the header plate being formed of aluminium or aluminium alloy materials suitable for furnace brazing, at least one of the mating surfaces being fabricated with a low temperature clad brazing material. A manifold and heat exchanger assembly according to Claim 1 further comprising at least one baffle(184), the tank being provided with at least one pair of opposed longitudinally-extending horizontal ribs(180) having at least one pair of opposed slots for receiving said baffle. A manifold and heat exchanger assembly according to any one of the preceding Claims wherein the header plate(150) has a substantially U-shaped cross-section, and the tank(120) and the header plate, when assembled together, have a substantially elliptical cross-section. A manifold and heat exchanger assembly according to any one of the preceding Claims wherein the tank further comprises a longitudinally-extending vertical rib(204) formed along the centre line of the inner wall, the rib engaging the header plate(150). A method of making a manifold and heat exchanger assembly (100), said heat exchanger comprising a plurality of parallel tubes, said method comprising the steps of a) forming a unitary tank(120) having a substantially U-shaped cross-section, the tank comprising an upper portion(122) which in cross-section forms the base of the U and also defines a pair of substantially straight opposed parallel sides(124) having integrally formed longitudinally extending flanges, the sides of the tank further defining a pair of shelves(140) the tank being formed of aluminium or aluminium alloy materials suitable for furnace brazing. b) forming a unitary header plate(120) having a length substantially equal to the length of the tank, the header plate having edges(152) and a plurality of holes(170) formed therethrough for receiving the tubes of the heat exchanger, the header plate being formed of aluminium or aluminium alloy material suitable for furnace brazing, c) inserting the header plate in the tank, d) crimping flanges formed integrally with the said side walls to engage the header plate along substantially the entire lengths thereof, and e) brazing together the header plate and the tank along substantially the entire lengths of their mating surfaces, characterised in that the method comprises the steps of providing the shelves with channels(144), upturning the edges(152) of the header plate(150) and inserting the upturned edges(152) in the channels(144) and cladding the tank and/or the header plate with a low temperature brazing material.

Inventors: CALLESON GERALD C, CALLESON, GERALD C
Applicants: INSILCO CORP, INSILCO CORPORATION
Application year: 1991
Main classification: F28F9
IPC codes: F28F21, F28F9