Heat Exchanger

Abstract

A heat exchanger includes a core portion and at least one substantially straight header plate. The core portion includes a plurality of heat exchanger tubes and fins disposed alternatively. The at least one substantially straight header plate has a plurality of insertion slots extending therethrough for receiving a respective end of the heat exchanger tubes therein, the core portion and the at least one header plate being brazeable together

Description

FIELD OF THE INVENTION

[0001] The invention relates to heat exchangers and, more particularly, to a method for manufacturing heat exchangers such as radiators, oil coolers, air-to-air heat exchangers (charge air coolers "CAC"), compressors, fuel coolers, conditioned air units, and the like.

DESCRIPTION OF THE PRIOR ART

[0002] Radiators are heat exchangers that are used to reject heat from the coolant of an internal combustion engine to the ambient. The engine coolant is typically circulated through coolant passages in the engine block to the so-called liquid side of the radiator where it is cooled and then returned to the engine block. Cooling occurs by forcing ambient air through the radiator core.

[0003] The thermal efficiency of an engine typically increases as its operating temperature is increased. Consequently, it is desirable to raise the operating temperature of the engine as much as possible to maximize efficiency. The operating temperature can hardly be raised to the point where the coolant within cooling passages in the engine begins to vaporize.

[0004] Consequently, if engines are to be operated at higher temperatures, it is necessary that the boiling point of the coolant being employed be raised. This can be done by increasing system pressure. At the same time, it becomes necessary to increase the strength of the radiator I heat exchanger so that the same can operate at the increased pressure.

[0005] Oil coolers are heat exchangers wherein heat dissipation occurs through oil. Oil viscosity increases in cold temperature. Thus, when operating in relatively cold conditions or when the motor associated with the oil cooler is cold, the oil cooler must sustain high pressure.

[0006] Finally, radiators and charge air coolers have a longer operating life if they can support higher pressure when operating in high vibrating environment.

BRIEF SUMMARY OF THE INVENTION

[0007] It is therefore an aim of the present invention to address the above mentioned issues.

[0008] According to a general aspect, there is provided a heat exchanger comprising: a core portion including a plurality of heat exchanger tubes and fins disposed alternatively; and at least one substantially straight header plate having a plurality of insertion slots extending therethrough for receiving a respective end of the heat exchanger tubes therein, the core portion and the at least one header plate being brazeable together.

[0009] According to another general aspect, there is provided a heat exchanger comprising: a core portion including a plurality of heat exchanger tubes; at least one substantially straight header plate having a plurality of insertion slots defined therein for receiving a respective end of the heat exchanger tubes therein, the core portion and the at least one header plate being brazeable together; and at least one tank cover securable to the at least one header plate and defining a tank cavity with the at least one header plate when secured thereto, the heat exchanger tubes being in fluid communication with the tank cavity.

[0010] According to still another general aspect, there is provided a method for manufacturing a heat exchanger comprising: inserting a respective end of a plurality of heat exchanger tubes in a respective insertion slot extending through a substantially straight header plate to define a heat exchanger tube and header plate assembly; and brazing the heat exchanger tube and header plate assembly.

[0011] According to a further general aspect, there is provided a heat exchanger header comprising: a brazeable substantially straight header plate having an inner surface, an outer surface opposed to the inner surface, a plurality of tube insertion slots extending throughout the header plate and extending in a longitudinal succession; and a tank cover having peripheral edges secured to the outer surface of the header plate, proximate to external edges of the header plate, and defining a tank cavity with the header plate, the tube insertion slots being in fluid communication with the tank cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a perspective view of a heat exchanger in accordance with an embodiment;

[0013] FIG. 2 is a sectional view taken along cross-section lines 2-2 of FIG. 1 of the heat exchanger;

[0014] FIG. 3 is a perspective view of a core portion and two header plates of the heat exchanger shown in FIG. 1;

[0015] FIG. 4 includes FIG. 4a and FIG. 4b, FIG. 4a is a top plan view of the core portion and one of the header plates shown in FIG. 3 and FIG. 4b is an enlarged view, fragmented, of heat exchanger tubes inserted in cavities defined in one of the header plates;

[0016] FIG. 5 is a perspective view, partly sectioned and fragmented, of the heat exchanger shown in FIG. 1; and

[0017] FIG. 6 is a flow chart illustrating a method for manufacturing the heat exchanger shown in FIG. 1.

[0018] It will be noted that throughout the appended drawings, like features are identified by like reference numerals.

DETAILED DESCRIPTION

[0019] FIGS. 1 and 2 show a heat exchanger 10 having a housing 12 covering a core portion 14 and extending between a pair of hollow headers 16 disposed in parallel with each other. Fluid inlet and outlet connectors 18 are mounted to the headers 16 and are in fluid communication with a tank cavity 20 defined in the hollow headers 16, as will be described in more details below.

[0020] The housing 12 includes two opposed and spaced-apart side plates 24 having an edge secured to headers 16.

[0021] FIGS. 2 and 3 show an internal view of the heat exchanger 10. The core portion 14 includes a plurality of heat exchanger flat tubes 26 disposed in parallel with their opposite sides in fluid communication with the hollow headers 16. Corrugated fins 28 are disposed between adjacent heat exchanger tubes 26 and outside the outermost heat exchanger tubes 26. The side plates 24, defining a portion of the housing 12, are disposed outside the outermost corrugated fins 28.

[0022] The heat exchanger tubes 26 are hollow extruded articles defining an inner channel 30 with an obround cross-section. The inner channel 30 is in fluid communication with the tank cavities 20. The inner channel 30 can be divided into a plurality of passages with partition walls (not shown), also called micro-channel tubes, extending longitudinally therein to reinforce the tubes 26.

[0023] Each header 16 includes a substantially straight rectangular header plate 32 having an inner surface 34 and an opposed outer surface 36. The substantially straight header plates 32 do not include upwardly extending peripheral edges like in prior art heat exchangers. The inner surfaces 34 of both headers 16 face one another when the heat exchanger 10 is assembled. A plurality of tube insertion slots 38 extend throughout the header plates 32 in a longitudinal succession as shown in FIG. 4a. The insertion slots 38 are defined to receive therein an end of one heat exchanger tube 26. FIG. 4b shows that the outer surface of the heat exchanger tubes 26, proximate to an end thereof, is juxtaposed to the inner surface of the insertion slots 38. Thus, the external size of the heat exchanger tubes 26 is slightly smaller than the size of the insertion slots 38. In an embodiment, the insertion slots 38 in header plate 32 are created by machining.

[0024] FIGS. 2 and 5 show that each header 16 also includes a tank cover 40 having an upper wall 42, two opposed and spaced-apart lateral walls 44, and two opposed and spaced-apart side walls 46, extending between the lateral walls 44. The lateral walls 44 and the side walls 46 have peripheral edges 48 secured to the outer surface 36 of the header plate 32, proximate to external edges 50 of the header plate 32. For example and without being limitative, the peripheral edges 48 of the tank cover 40 can be welded to the header plate 32. In the embodiment shown, the side walls 46 are recessed internally from the external edges 50 of the header plate 32. The tank cover 40 and the header plate 32 define the tank cavity 20 when secured together.

[0025] In an alternative embodiment (not shown), the peripheral edges 48 of the tank cover 40 can be welded to the lateral walls of the heater plate 32, i.e. the walls extending between the inner surface 34 and the outer surface 36. In another alternative embodiment (not shown), the outer surface 36 of the heater plate 32 can include a peripheral recess section in which the peripheral edges 48 of the tank cover 40 are inserted and secured. The peripheral recess section can be machined in the header plate 32. In another alternative embodiment (not shown), both the edges of the header plate 32 and the peripheral edges 48 of the tank cover 40 can be beveled edges which are matingly engaged when securing the tank cover 40 to the header plate 32.

[0026] The tank cavity 20 is in fluid communication with the inner channels 30 of the heat exchanger tubes 26 inserted in the tube insertion slots 38 and with the fluid inlet and outlet connectors 18.

[0027] In the embodiment described above, the heat exchanger is a single tube pass heat exchanger wherein the fluid enters the heat exchanger at one end, flows once in the tubes, and exits at the opposed heat exchanger end. In alternative embodiments, the heat exchanger can be a multiple tube pass heat exchanger such as and without being limitative a double tube pass or a triple tube pass heat exchanger. For example and without being limitative, in a double tube pass heat exchanger, the fluid enters the heat exchanger at a first end, flows twice in the tubes, and exits at the first end. Similarly, in a triple tube pass heat exchanger, the fluid enters the heat exchanger at a first end, flows thrice in the tubes, and exits at the opposed heat exchanger end. In multiple tube pass heat exchangers, at least one of the tank covers includes a partition wall which separated the tank cavity into separated chambers. It is appreciated that the heat exchanger can include more than three passes.

[0028] Referring now to FIG. 6, for manufacturing a heat exchanger, the core portion is first assembled to the header plates 70. The heat exchanger tubes and the corrugated fins are stacked alternatively and the opposite ends of the heat exchanger tubes are inserted in the corresponding insertion slots defined in the header plates to form a provisional assembly, as shown in FIG. 3. The edges of the heat exchanger tubes extend substantially flush with the outer face of the header plate in which they are inserted. Furthermore, side plates are assembled to the core portion. Then, this provisional assembly is integrally brazed in a furnace 72.

[0029] The brazing step is carried out in a controlled environment in an atmosphere of inert gas such as nitrogen, for instance, during 10 to 20 minutes and, in an alternative embodiment, during 12 to 18 minutes. The temperature in the furnace ranges between approximately 1000 and 1200.degree. F. (approximately 530 and 650.degree. C.). It is appreciated that the brazing conditions (temperature, atmosphere, time, etc.) can vary in accordance with the heat exchanger size and materials.

[0030] More particularly, in an embodiment, prior to the brazing step, a brazing flux is deposited on the provisional assembly through electromagnetism. The use of these fluxing agents with aluminum heat exchangers promotes the dissociation and disruption of the native aluminum oxide (Al.sub.2O.sub.3). Then, the provisional assembly is introduced in a controlled environment where vacuum is created. Nitrogen is introduced and the temperature in the controlled environment is increased to approximately 400-450.degree. F. (approximately 200 and 230.degree. C.) for a pre-heating step. Following the pre-heating step, the provisional assembly is brazed as mentioned above. The brazed assembly is then cooled in the controlled environment, under nitrogen, wherein the temperature is lowered to approximately 400.degree. F. Finally, the brazed assembly is removed from the controlled environment and cooled to ambient temperature under forced air convection.

[0031] Then, the tank covers are mounted to a respective header plate and secured thereto 74. In an embodiment, the peripheral edges of the tank covers are secured to the outer face of the header plate, proximate to external edges of the header plate, to define the tank cavity. The peripheral edges can be welded to the header plate for securing the tank covers.

[0032] Finally, the side plates are sawed to create dilatation joints 54 (FIG. 1) therein 76. It is appreciated that, in an alternative embodiment, the dilatation joints can be sawed before securing the tank cover to the brazed assembly.

[0033] In an alternative embodiment, the provisional assembly can include tank covers. The tank covers are thus secured by brazing simultaneously with the other components. They can also be welded to the header plates prior to the brazing step.

[0034] The heat exchanger tubes, the corrugated fins, and the headers 16 are made of an aluminum alloy adapted for heat exchanger applications. For example and without being limitative, they can be made of AA 3003. The heat exchanger tubes, the corrugated fins, and the header plates include a surface clad. For example and without being limitative, the clad material can be 4000 series aluminum. It is appreciated that, in alternative embodiments, other aluminum alloys adapted for heat exchanger and brazing applications can be used.

[0035] The header plates can either have a clad on both sides or on only one side, either the inner surface or the outer surface. Similarly, the corrugated fins can have a clad on both sides or on only one side. The outer surface of the heat exchanger tubes includes the clad material. The clad material can represent between 2 and 15% of the heat exchanger component thickness. In an alternative embodiment, the clad material can represent between 5 and 10% of the heat exchanger component thickness.

[0036] In a non-limitative embodiment, the header plates are rectangular with a length ranging between 75 and 1020 millimeters (mm) (2.95 and 40.0 inches), a width ranging between 12.7 and 180 mm (0.5 and 7.0 inches), and a thickness ranging between 2.0 and 12.7 mm (0.08 and 0.5 inch). In an alternative embodiment, the header plates have a length ranging between 100 and 950 mm (4 and 37.5 inches), a width ranging between 19 and 170 mm (0.75 and 6.75 inches), and a thickness ranging between 2.5 and 10 mm (0.1 and 0.4 inch).

[0037] In an embodiment, the heat exchanger tubes have a cross section length (major diameter) ranging between 19 and 120 mm (0.75 and 4.8 inches) and a cross-section width (minor diameter) ranging between 2 and 12 mm (0.08 and 0.5 inch). In an alternative embodiment, the heat exchanger tubes have a cross section length ranging between 25 and 80 mm (1.0 and 3.15 inches) and a cross-section width ranging between 3.7 and 7 mm (0.15 and 0.28 inch).

[0038] In an embodiment, the thickness of the heat exchanger tube wall ranges between 0.1 and 3.6 mm (0.004 and 0.14 inch) and in an alternative embodiment, the thickness of the heat exchanger wall ranges between 0.2 and 3.2 mm (0.008 and 0.125 inch). In an embodiment, the thickness of the heat exchanger tube wall can vary along the tube length.

[0039] In an embodiment, the distance between the external edges of the header plate and the outermost heat exchanger tubes ranges between 1.3 and 3.2 mm (0.05 and 0.125 inch). In an alternative embodiment, this distance ranges between 1.3 and 6.4 mm (0.05 and 0.25 inch).

[0040] As mentioned above, the thickness of the header plates ranges between 2.0 and 12.7 mm (0.08 and 0.50 inch). In comparison with the headers of prior art heat exchangers, the header plate is thicker, providing an increased stiffness to the resulting heat exchanger and a stronger physical bond between the heat exchanger tubes and the header plate since brazing occurs on a larger surface area. The resulting header plate and tube exchanger assembly can thus support higher pressure.

[0041] Moreover, the outermost heat exchanger tubes are mounted proximate to the external edge of the header plate since the header plate is substantially straight. Thus, the moment arm between the junction of the exchanger tubes and the header plate and the external edges of the header plate is reduced. The resulting heat exchangers have improved mechanical properties, such as higher pressure resistance, stiffness, vibration resistance, and impact strength, comparatively to prior art heat exchangers.

[0042] Comparatively, to prior art heat exchangers wherein the tank cover is mounted inwardly of the header plates having turn up edges, the heat exchanger has a higher burst pressure strength. For example, in an embodiment, the heat exchanger withstood 1825 psi comparatively to 580 psi for the prior art heat exchanger. Moreover, the heat exchanger did not show any cracking comparatively to the prior art heat exchanger which showed cracking at 300 psi.

[0043] It is appreciated that the heat exchangers described above can be used in radiators, compressors, fuel coolers, conditioned air units, air-to-air heat exchangers (charge air coolers), oil coolers, and the like.

[0044] It can be used in new products (OEM) or replacement products.

[0045] The embodiments of the invention described above are intended to be exemplary only. For example, the shape of the heat exchanger tubes can vary and the shape of the insertion slots can vary accordingly. Furthermore and without being limitative, the shape of the headers can vary. The position of fluid inlet and outlet connectors can be modified from the one described above in reference to FIG. 1, which is typically associated with oil coolers. For example and without being limitative, for radiators and charge air coolers, the fluid inlet and outlet connectors can be centrally mounted to a respective hollow header.

[0046] The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.

Claims

1. A heat exchanger comprising: a core portion including a plurality of heat exchanger tubes and fins disposed alternatively; and at least one substantially straight header plate having a plurality of insertion slots extending therethrough for receiving a respective end of the heat exchanger tubes therein, the core portion and the at least one header plate being brazeable together.

2. A heat exchanger as claimed in claim 1, wherein the distance between external edges of the at least one header plate and the outermost heat exchanger tubes ranges between 1.3 and 3.2 mm.

3. A heat exchanger as claimed in claim 1, wherein the at least one header plate has a thickness ranging between 2.0 and 12.7 mm.

4. A heat exchanger as claimed in claim 1, comprising at least one tank cover weldable to the at least one header plate and defining a tank cavity with the at least one header plate when secured thereto, the heat exchanger tubes being in fluid communication with the tank cavity.

5. A heat exchanger as claimed in claim 4, wherein the at least one tank cover is welded to an outer surface of the at least one header plate, proximate to external edges thereof.

6. A heat exchanger as claimed in claim 4, wherein the at least one tank cover is welded to the brazed core portion and the at least one header plate assembly.

7. A heat exchanger as claimed in claim 1, wherein at least one of the heat exchanger tubes, the fins, and the at least one header plate includes a clad for brazing the core portion and the at least one header plate together.

8. A heat exchanger as claimed in claim 1, wherein the at least one header plate comprises two header plates parallel to each other and wherein the header plates are upwardly extending external edge free.

9. A heat exchanger as claimed in claim 8, wherein the header plates are substantially rectangular and have a length ranging between 75 mm and 1020 mm and a width ranging between 12.7 mm and 180 mm.

10. A heat exchanger comprising: a core portion including a plurality of heat exchanger tubes; at least one substantially straight header plate having a plurality of insertion slots defined therein for receiving a respective end of the heat exchanger tubes therein, the core portion and the at least one header plate being brazeable together; and at least one tank cover securable to the at least one header plate and defining a tank cavity with the at least one header plate when secured thereto, the heat exchanger tubes being in fluid communication with the tank cavity.

11. A heat exchanger as claimed in claim 10, wherein the distance between external edges of the at least one header plate and the outermost heat exchanger tubes ranges between 1.3 and 3.2 mm.

12. A heat exchanger as claimed in claim 10, wherein the at least one header plate has a thickness ranging between 2.0 and 12.7 mm.

13. A heat exchanger as claimed in claim 10, wherein the at least one tank cover is weldable to an outer surface of the at least one header plate, proximate to external edges thereof.

14. A heat exchanger as claimed in claim 10, wherein the at least one tank cover is welded to the brazed core portion and the at least one header plate assembly.

15. A heat exchanger as claimed in claim 10, wherein at least one of the heat exchanger tubes and the at least one header plate includes a clad for brazing the core portion and the at least one header plate together.

16. A heat exchanger as claimed in claim 10, wherein the at least one header plate comprises two header plates parallel to each other and wherein the header plates are upwardly extending external edge free,

17. A heat exchanger as claimed in claim 10, wherein the core portion comprises fins in alternating succession with the heat exchanger tubes.

18. A method for manufacturing a heat exchanger comprising: inserting a respective end of a plurality of heat exchanger tubes in a respective insertion slot extending through a substantially straight header plate to define a heat exchanger tube and header plate assembly; and brazing the heat exchanger tube and header plate assembly.

19. A method as claimed in claim 18, further comprising securing a tank cover to the straight header plate for defining a tank cavity, the heat exchanger tubes being in fluid communication with the tank cavity.

20. A method as claimed in claim 19, further comprising welding the tank cover to an outer surface of the header plate, proximate to external edges thereof.

21. A method as claimed in claim 19, wherein the securing step is carried out after the brazing step.

22. A method as claimed in claim 18, further comprising disposing corrugated fins between consecutive heat exchanger tubes and wherein the brazing step is carried out on the heat exchanger tube and straight header plate assembly including the corrugated fins.

23. A method as claimed in claim 18, further comprising creating the insertion slots in the header plate wherein the distance between external edges of the header plate and the outermost insertion slots ranges between 1.3 and 3.2 mm.

24. A heat exchanger header comprising: a brazeable substantially straight header plate having an inner surface, an outer surface opposed to the inner surface, a plurality of tube insertion slots extending throughout the header plate and extending in a longitudinal succession; and a tank cover having peripheral edges secured to the outer surface of the header plate, proximate to external edges of the header plate, and defining a tank cavity with the header plate, the tube insertion slots being in fluid communication with the tank cavity.

25. A heat exchanger header as claimed in claim 24, wherein the distance between the external edges of the header plate and the outermost insertion slots ranges between 1.3 and 3.2 mm.

26. A heat exchanger header as claimed in claim 24, wherein the header plate has a thickness ranging between 2.0 and 12.7 mm.

27. A heat exchanger header as claimed in claim 24, wherein the tank cover is welded to the header plate after the header plate has been brazed.

28. A heat exchanger header as claimed in claim 24, wherein the header plate includes a clad to braze the header plate with a core portion.

29. A heat exchanger header as claimed in claim 24, wherein the header plate is substantially rectangular and has a length ranging between 75 mm and 1020 mm and a width ranging between 12.7 mm and 180 mm.