GB2320957A

GB2320957A - Heat exchanger and header

Info

Publication number: GB2320957A
Application number: GB9700060A
Authority: GB
Inventors: Cheng-Tsai Wan
Original assignee: Man Zai Industrial Co Ltd
Current assignee: Man Zai Industrial Co Ltd
Priority date: 1997-01-03
Filing date: 1997-01-03
Publication date: 1998-07-08
Anticipated expiration: 2017-01-03
Also published as: GB9700060D0; GB2320957B; AU678545B3

Abstract

A heat exchanger includes a parallel pair of header pipes (2) and a plurality of transverse tubes disposed between the header pipes. Each header pipe (2) includes first and second complementary longitudinal pipe sections (3, 4). Pipe section (3) has a U-shaped cross-section with two opposite first longitudinal edges (32) and is formed with a plurality of axially aligned slits (31) to permit extension of one of the opposite ends of the tubes therethrough. Pipe section (4) has a wall portion (40) with two opposite second longitudinal edges (41). Each of the second longitudinal edges (41) is formed with a forked extension (42) which confines a longitudinal engaging groove (421) that engages tightly a respective one of the first longitudinal edges (32) of the first pipe section (3). The tight engagement is provided for either the groove (421) tapering inwardly or by a longitudinal projection (44', figures 6 and 7).

Description

HEAT EXCHANGER AND HEADER PIPE USED THEREIN The present invention relates to a heat exchanger and a header pipe for use in the heat exchanger, more particularly to a heat exchanger that includes an improved header pipe which is easier to assemble as compared to the prior art.

A heat exchanger employed in air conditioning equipment generally includes transverse tubes and upright header pipes for introducing coolant into the tubes and for discharging the coolant after it has circulated throughout the tubes. A conventional heat exchanger (H) is shown in Figure 1 to include a parallel pair of header pipes 10. Each of the header pipes 10 is provided with two partition plates 17 to divide the header pipe 10 into three isolated chambers.

A plurality of parallel tubes 20 are disposed between the pair of header pipes 10 and are transverse to the header pipes 10. The tubes 20 have opposite ends welded to the header pipes 10 and are in fluid communication with the header pipes 10. The outer sides of the tubes 2 are provided with a plurality of radiator fins 21.

Coolant is introduced into the tubes 20 from an inlet pipe 11. Due to the partition plates 17 provided in the header pipes 10, the coolant meanders in the tubes 20 in a zigzag pattern and is discharged through an outlet tube 12.

The tubes 20 and the header pipes 10 of the heat exchanger should be perfectly sealed so as to avoid leakage of the coolant in the heat exchanger.

Therefore, the quality requirement for soldering during the manufacture of the heat exchanger is relatively stringent.

U.S. Patent No. 4,945, 635 discloses a process for manufacturing a heat exchanger which includes a header, fins and tubes whose ends are connected to the header.

The process includes the following steps: preparing a brazing sheet which includes a core sheet coated with a brazing substance at least on one surface; forming a bulged portion with a semi-circular cross-section in the brazing sheet; providing apertures in the bulged portion; rolling the brazing sheet into a cylinder to form a header, the opposite ends of the sheet being butt jointed to each other; providing a tube for each aperture; inserting the end of each tube into the corresponding aperture of the header; placing fins between adjacent tubes so as to fabricate a provisional assembly of the tubes, the fins and the header; and heating the provisional assembly in a brazing furnace to effect a permanent joint among the tubes, the fins and the header.

Since the brazing sheet is rolled into a cylinder to form a header after the apertures are provided in the bulged portion thereof, the sizes of the apertures are likely to deviate during rolling of the brazing sheet.

Moreover, the header is likely to twist when it is heated in the brazing furnace. This might result in leakage of coolant in the heat exchanger when the heat exchanger is in use.

U.S. Patent No. 5,107,926 discloses a two-piece manifold assembly for heat exchangers in which the rolling process is avoided. The manifold assembly comprises a unitary tank having a substantially Ushaped cross-section and a unitary header plate which can either be substantially planar or have a substantially U-shaped cross-section. The tank comprises a curved upper portion which in cross-section forms the base of the U, a pair of substantially straight opposed, parallel sides extending from the ends of the upper portion and which in cross-section form the arms of the U, an inner wall, an outer wall, a pair of tank end edges extending between the inner and outer walls at the free ends of the sides, and a pair of opposed parallel shelves formed in the inner wall inwardly of the tank end edges to define a pair of flanges extending from the shelves. The header plate comprises a pair of opposed, parallel edge portions and a center portion extending between the edge portions, an upper wall, a lower wall, and a pair of longitudinal end edges extending between the upper and lower walls.

The center portion has a plurality of tube holes formed therethrough for receiving the tubes of the condenser or evaporator. The tank flanges are crimped inwardly to engage the header plate along the entire lengths of their mating surfaces in order to provide the strengths to withstand internal pressures.

The aforementioned manifold assembly is still not satisfactory in that an additional crimping device is required to fold the flange over and around the edge portion of the header plate so as to secure the header plate to the tank before the manifold assembly is brought into a brazing furnace. Moreover, opposed slots must be formed in the inner wall of the tank for receiving baffles. Forming the slots in the inner wall of the tank is a relatively difficult task which will increase the manufacturing cost.

The main object of the present invention is to provide a heat exchanger and a header pipe used therefore, the rolling and crimping processes being unnecessary when assembling the header pipe before the latter is placed in a furnace.

According to a first aspect of the present invention, there is provided a heat exchanger having a parallel pair of header pipes and a plurality of transverse tubes disposed between the header pipes.

Each of the tubes has opposite ends connected respectively to and communicated fluidly with the header pipes. Each of the header pipes includes first and second complementary longitudinal pipe sections.

The first pipe section has a U-shaped cross-section with two parallel first longitudinal edges and is formed with a plurality of axially aligned slits to permit extension of one of the opposite ends of the tubes therethrough. The second pipe section has a wall portion with two parallel second longitudinal edges.

In one embodiment, each of the second longitudinal edges is formed with a forked extension which confines a longitudinal engaging groove that tapers inwardly so as to engage tightly a respective one of the first longitudinal edges of the first pipe section.

In another embodiment, each of the second longitudinal edges is formed with a forked extension which includes inner and outer branches that confine a longitudinal engaging groove. At least one of the inner and outer branches is formed with a longitudinal retaining projection so as to engage tightly a respective one of the first longitudinal edges of the first pipe section.

According to another aspect of the present invention, there is provided a header pipe for use in a heat exchanger that includes a plurality of tubes transverse to the header pipe. The header pipe includes first and second complementary longitudinal pipe sections. The first pipe section has a U-shaped crosssection with two opposite first longitudinal edges. The first pipe section is formed with a plurality of axially aligned slits adapted to permit extension of one of two opposite ends of the tubes therethrough. The second pipe section has a wall portion with two parallel second longitudinal edges.

In one embodiment, each of the second longitudinal edges is formed with a forked extension which confines a longitudinal engaging groove that tapers inwardly for engaging tightly a respective one of the first longitudinal edges of the first pipe section.

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments with reference to the accompanying drawings, of which: Figure 1 is a front view showing a conventional heat exchanger; Figure 2 is an exploded perspective view illustrating the header pipe according to a first preferred embodiment of the present invention; Figure 3 is an enlarged schematic view illustrating the relationship between an engaging groove formed in a second pipe section and a longitudinal edge of a first pipe section of the header pipe of the first preferred embodiment; Figure 4 is a perspective view illustrating how a partition plate is assembled to the second pipe section of the header pipe of the first preferred embodiment; Figure 5 is a top, cross-sectional view illustrating the header pipe of the first preferred embodiment; Figure 6 is an exploded view illustrating the header pipe according to a second preferred embodiment of the present invention; Figure 7 is a schematic top view illustrating a second pipe section of the header pipe according to a third preferred embodiment of the present invention; Figure 8 is an exploded perspective view illustrating the header pipe according to a fourth preferred embodiment of the present invention; Figure 9 is a perspective view illustrating the heat exchanger according to the present invention; and Figure 10 is an enlarged schematic view illustrating a pair of longitudinal passages formed between a forked extension of a second pipe section and a longitudinal edge of a first pipe section of the header pipe of the first preferred embodiment.

Before the present invention is described in greater detail with reference to the disclosed embodiments, it should be noted that like elements are denoted by the same reference numerals throughout the disclosure.

The first preferred embodiment of the present invention is embodied in a heat exchanger that includes a parallel pair of header pipes and a plurality of transverse tubes disposed between the header pipes.

Each of the tubes has opposite ends connected respectively to and communicated fluidly with the header pipes. As shown in Figure 2, each of the header pipes 2 of the first preferred embodiment includes first and second complementary longitudinal pipe sections 3, 4. The first pipe section 3 includes a core layer and a clad layer formed on the core layer. The clad layer is made of aluminum alloy and has a melting point lower than that of the core layer. The first pipe section 3 has a U-shaped cross-section and includes a curving portion 33 with two parallel first longitudinal edges 32. The curving portion 33 of the first pipe section 3 is formed with a plurality of axially aligned slits 31 by punching to permit extension of one of the opposite ends of the tubes 6 therethrough. The edge portion of each of the slits 31 may be chamfered so as to facilitate insertion of the tubes 6. The first longitudinal edges 32 have a predetermined thickness.

The second pipe section 4 is made of aluminum by extrusion. The second pipe section 4 has a wall portion 40 with two parallel second longitudinal edges 41. Each of the second longitudinal edges 41 is formed with a forked extension 42 that includes inner and outer branches 422, 423 and that confines a longitudinal engaging groove 421 which tapers inwardly so as to engage tightly a respective one of the first longitudinal edges 32 of the first pipe section 3. As shown in Figure 3, the engaging groove 421 has a closed end with a width (a) and an open end with a width (c).

The first longitudinal edges 32 of the first pipe section 3 have a thickness (b), wherein (a) < (b) < (c). Therefore, the first longitudinal edges 32 of the first pipe section 3 engage the forked extensions 42 of the second pipe section 4 tightly and can be frictionally retained therein due to the surface property of the first and second pipe sections 3, 4.

Referring again to Figure 2, the wall portion 40 of the second pipe section 4 has an upper end portion formed with a coolant inlet/outlet 43. The header pipe 2 is further provided with a plurality of partition plates 45 for dividing the header pipe 2 into at least two isolated chambers. In this embodiment, two partition plates 45 are provided to divide the header pipe 2 into three isolated chambers. As shown in Figure 4, the partition plate 45 has a first engaging portion 451, a second engaging portion 452, and a middle portion between the first and second engaging portions 451, 452. The middle portion is formed with two opposite notches 453. The inner branches 422 of the forked extensions 42 define a longitudinal slot 401 with the wall portion 40 of the second pipe section 4.

The first engaging portion 451 of the partition plate 45 extends into the longitudinal slot 401. The notches 453 formed in the middle portion of the partition plate 45 engage the inner branches 422 of the forked extension 42. The partition plate 45 can be assembled to the second pipe section 4 before the latter is assembled to the first pipe section 3. To assemble the partition plate 45 to the second pipe section 4, the partition plate 45 is kept in an upright orientation and is brought between the forked extensions 42 so that the first engaging portion 451 is in contact with the wall portion 40 of the second pipe section 4. The partition plate 45 is then turned so as to be in a horizontal orientation such that the first engaging portion 451 engages the longitudinal slot 401 of the second pipe section 4. The partition plate 45 can thus be frictionally retained on the second pipe section 4.

After the first pipe section 3 is assembled to the second pipe section 4, the second engaging portion 452 of the plate 45 extends into the first pipe section 3.

The first and second pipe sections 3, 4 are assembled to form a tubular body which is then provided with two caps 5 for covering two opposite ends thereof.

Transverse tubes 6 are subsequently inserted into the header pipes through the slits 31. As shown in Figure 5, the distance between the inner branches 422 of the forked extensions 42 is smaller than the width of the transverse tubes 6 so that the tubes 6 can be stopped by the forked extensions 42.

Each of the partition plate 45 and the caps 5 includes a core layer and a clad layer formed on the core layer. The clad layer has a melting point lower than that of the core layer.

A pair of the header pipes 2, including the first and second sections 3, 4, the partition plates 45, the caps 5, and the transverse tubes 6 can be preliminarily assembled into a relatively stable structure as shown in Figure 9, without the need for an additional clamping device. When the heat exchanger is subsequently placed in a furnace, the clad layers melt so that the first pipe sections 3 are fused to the transverse tubes 6 and the second pipe sections 4, and so that the partition plates 45 and the caps 5 are fused to the first and second pipe sections 3, 4. Since the open ends of the tubes 6 are stopped by the inner branches 422 of the forked extensions 42 of the second pipe section 4, the melted clad layers will not be drawn into the tubes 6. A reduced "freon flow resistance" in the tubes 6 can be achieved.

Since the engaging groove 421 of each of the forked extensions 42 tapers inwardly, a pair of longitudinal passages 425 with substantially V-shaped cross-sections are formed in each of the engaging grooves 421 between the inner branch 422 and a respective one of the first longitudinal edge 32 of the first pipe section 3 and between the outer branch 423 and a respective one of the first longitudinal edge 32 of the first pipe section 3, as shown in Figure 10. Melted clad layer can flow within the longitudinal passages 425 during the soldering process and fills the longitudinal passages 425 uniformly after the soldering process is completed.

An excellent sealing effect can thus be achieved.

Figure 6 illustrates a second preferred embodiment of the present invention. In this embodiment, the second pipe section also includes a wall portion 40' with two parallel second longitudinal edges 41', each of which is formed with a forked extension 42 that includes inner and outer branches 422', 423' and that confines a longitudinal engaging grooves 421'. The inner surface of each of the outer branches 423' is formed with a longitudinal retaining projection 44' so as to engage tightly a respective one of the first loiigitudinal edges 32 of the first pipe section 3. As shown in Figure 7, the retaining projection 44' preferably has a wedge-shaped horizontal cross-section that increases in size in an inward direction of the engaging groove so as to prevent removal of the first longitudinal edge of the first pipe section from the engaging groove of the second pipe section, thereby resulting in enhanced engagement between the first and second pipe sections.

Referring to Figure 8, in a fourth preferred embodiment, the caps used in the first preferred embodiment can be replaced by partition plates 45' which are assembled to the second pipe section 4 at two opposite end portions thereof before the first pipe section 3 is assembled to the second pipe section 4.

In light of the foregoing, the heat exchanger and the header pipe of the present invention offer the following advantages: 1. The first longitudinal edges 32 of the first pipe section 3 engage tightly the forked extensions 42 of the second pipe section 4. Therefore, the first pipe section 3 can be readily retained on the second pipe section 4 before soldering due to friction between the clad layer on the first pipe section 3 and the second pipe section 4 which is made of extruded aluminum without the need for an external clamping device or an additional crimping procedure. The manufacturing cost can thus be significantly reduced.

2. The transverse tubes 6 are stopped by the inner branches 422 of the forked extensions 42 of the second pipe section 4 which does not include a clad layer. The open ends of the tubes 6 will not be blocked during the soldering process.

3. The partition plates 45 can be directly positioned and retained on the second pipe section 4 before the first pipe section 3 is assembled to the second pipe section 4. A mounting hole is not required to be formed in either the first pipe section 3 or the second pipe section 4.

4. Melted material of the clad layers generated during the soldering process can be guided by the longitudinal space formed between the inwardly tapered engaging groove 421 and a respective first longitudinal edge 32 of the first pipe section 3. The melted material will not accumulate on the surface of the first pipe section 3. Therefore, the soldering efficiency can be significantly improved.

Claims

CLAIMS:

1. A heat exchanger having a parallel pair of header pipes and a plurality of transverse tubes disposed between said header pipes, each of said tubes having opposite ends connected respectively to and communicated fluidly with said header pipes, each of said header pipes including first and second complementary longitudinal pipe sections, said first pipe section having a U-shaped cross-section with two parallel first longitudinal edges and being formed with a plurality of axially aligned slits to permit extension of one of said opposite ends of said tubes therethrough, said second pipe section having a wall portion with two parallel second longitudinal edges, wherein each of said second longitudinal edges is formed with a forked extension which confines a longitudinal engaging groove that tapers inwardly so as to engage tightly a respective one of said first longitudinal edges of said first pipe section.

2. The heat exchanger according to Claim 1, wherein said forked extension of each of said second longitudinal edges of said second pipe section includes inner and outer branches, distance between said inner branches of said forked extensions being smaller than width of said transverse tubes so that said tubes can be stopped by said forked extensions.

3. The heat exchanger according to Claim 1, wherein said first pipe section of each of said header pipes includes a core layer and a clad layer made of an aluminum alloy and formed on said core layer, said clad layer having a melting point lower than that of said core layer, said second pipe section of each of said header pipes being made of aluminum, whereby said clad layer melts so as to fuse said first pipe section to said transverse tubes and said second pipe section when said heat exchanger is placed in a furnace.

4. The heat exchanger according to Claim 2, wherein each of said header pipes is further provided with at least one partition plate for dividing said header pipe into at least two isolated chambers, said partition plate having a first engaging portion, a second engaging portion and a middle portion between said first and second engaging portions, said inner branches of said forked extensions defining a slot with said wall portion of said second pipe section, said first engaging portion extending into said slot, said middle portion being formed with two opposite notches for engaging said inner branches of said forked extensions, said second engaging portion extending into said first pipe section, said partition plate being frictionally retained on said second pipe section of said header pipe.

5. The heat exchanger according to Claim 3, wherein each of said header pipes is further provided with at least one partition plate for dividing said header pipe into at least two isolated chambers, said partition plate having a first engaging portion, a second engaging portion and a middle portion between said first and second engaging portions, said inner branches of said forked extensions defining a slot with said wall portion of said second pipe section, said first engaging portion extending into said slot, said middle portion being formed with two opposite notches for engaging said inner branches of said forked extensions, said second engaging portion extending into said first pipe section, said partition plate being frictionally retained on said second pipe section of said header pipe, said partition plate including a core layer and a clad layer formed on said core layer, said clad layer having a melting point lower than that of said core layer, whereby said clad layer melts so as to fuse said partition plate to said header pipe when said heat exchanger is placed in the furnace.

6. The heat exchanger according to Claim 1, wherein each of said header pipes further comprises two caps for covering two opposite ends thereof, each of said caps having a core layer and a clad layer formed on said core layer, said clad layer having a melting point lower than that of said core layer, whereby said clad layer melts so as to fuse said caps to said header pipe when said heat exchanger is placed in a furnace.

7. A heat exchanger having a parallel pair of header pipes and a plurality of transverse tubes disposed between said header pipes, each of said tubes having opposite ends connected respectively to and communicated fluidly with said header pipes, each of said header pipes including first and second complementary longitudinal pipe sections, said first pipe section having a U-shaped cross-section with two parallel first longitudinal edges and being formed with a plurality of axially aligned slits to permit extension of one of said opposite ends of said tubes therethrough, said second pipe section having a wall portion with two parallel second longitudinal edges, wherein each of said second longitudinal edges is formed with a forked extension which includes inner and outer branches that confine a longitudinal engaging groove, at least one of said inner and outer branches is formed with a longitudinal retaining projection so as to engage tightly a respective one of said first longitudinal edges of said first pipe section.

8. The heat exchanger according to Claim 7, wherein said retaining projection has a wedge-shaped horizontal cross-section that increases in size in an inward direction of said engaging groove.

9. A header pipe for use in a heat exchanger that includes a plurality of tubes transverse to said header pipe, said header pipe including first and second complementary longitudinal pipe sections, said first pipe section having a U-shaped cross-section with two parallel first longitudinal edges and being formed with a plurality of axially aligned slits adapted to permit extension of one of two opposite ends of said tubes therethrough, said second pipe section having a wall portion with two parallel second longitudinal edges, wherein each of said second longitudinal edges is formed with a forked extension which confines a longitudinal engaging groove that tapers inwardly so as to engage tightly a respective one of said first longitudinal edges of said first pipe section.

10. The header pipe according to Claim 9, wherein said first pipe section of each of said header pipes includes a core layer and a clad layer made of an aluminum alloy and formed on said core layer, said clad layer having a melting point lower than that of said core layer, said second pipe section of each of said header pipes being made of aluminum, whereby said clad layer melts so as to fuse said first pipe section to said second pipe section when said header pipe is placed in a furnace.

11. The header pipe according to Claim 9, further comprising at least one partition plate for dividing said header pipe into at least two isolated chambers, said partition plate having a first engaging portion, a second engaging portion and a middle portion between said first and second engaging portions, said inner branches of said forked extension defining a slot with said wall portion of said second pipe section, said first engaging portion extending into said slot, said middle portion being formed with two opposite notches for engaging said inner branches of said forked extensions, said second engaging portion extending into said first pipe section, said partition plate being frictionally retained on said second pipe section.

12. The header pipe according to Claim 10, further comprising at least one partition plate for dividing said header pipe into at least two isolated chambers, said partition plate having a first engaging portion, a second engaging portion and a middle portion between said first and second engaging portions, said inner branches of said forked extension defining a slot with said wall portion of said second pipe section, said first engaging portion extending into said slot, said middle portion being formed with two opposite notches for engaging said inner branches of said forked extensions, said second engaging portion extending into said first pipe section, said partition plate being frictionally retained on said second pipe section, said partition plate including a core layer and a clad layer formed on said core layer, said clad layer having a melting point lower than that of said core layer, whereby said clad layers melts so as to fuse said partition plate to said first and second pipe sections when said header pipe is placed in the furnace.

13. The header pipe substantially as hereinbefore described with reference to and as illustrated in Figures 2 to 8 of the accompanying drawings.

13. The header pipe according to Claim 9, further comprising two caps for covering two opposite ends thereof, each of said caps having a core layer and a clad layer formed on said core layer, said clad layer having a melting point lower than that of said core layer, whereby said clad layer melts so as to fuse said caps to said first and second pipe sections when said header pipe is placed in a furnace.

14. A header pipe for use in a heat exchanger that includes a plurality of tubes transverse to said header pipe, said header pipe including first and second complementary longitudinal pipe sections, said first pipe section having a U-shaped cross-section with two parallel first longitudinal edges and being formed with a plurality of axially aligned slits adapted to permit extension of one of two opposite ends of said tubes therethrough, said second pipe section having a wall portion with two parallel second longitudinal edges, wherein each of said second longitudinal edges is formed with a forked extension which includes inner and outer branches that confine a longitudinal engaging groove, at least one of said inner and outer branches being formed with a longitudinal retaining projection so as to engage tightly a respective one of said first longitudinal edges of said first pipe section.

15. The header pipe according to Claim 14, wherein said retaining projection has a wedge-shaped horizontal cross-section that increases in size in an inward direction of said engaging groove.

16. The header pipe according to Claim 14, wherein said first pipe section includes a core layer and a clad layer made of an aluminum alloy and formed on said core layer, said clad layer having a melting point lower than that of said core layer, said second pipe section being made of aluminum, whereby said clad layer melts so as to fuse said first pipe section to said second pipe section when said header pipe is placed in a furnace.

17. The heat exchanger substantially as hereinbefore described with reference to and as illustrated in Figures 2 to 10 of the accompanying drawings.

18. The header pipe substantially as hereinbefore described with reference to and as illustrated in Figures 2 to 10 of the accompanying drawings.

Amendments to the claims have been filed as follows 1. A heat exchanger having a parallel pair of header pipes and a plurality of transverse tubes disposed between said header pipes, each of said tubes having opposite ends connected respectively to and communicated fluidly with said header pipes, each of said header pipes including first and second complementary longitudinal pipe sections, said first pipe section having a U-shaped cross-section with two parallel first longitudinal edges and being formed with a plurality of axially aligned slits to permit.

extension of one of said opposite ends of said tubes therethrough, said second pipe section having a wall portion with two parallel second longitudinal edges, wherein each of said second longitudinal edges is formed with a forked extension which confines a longitudinal engaging groove that tapers inwardly so as to engage tightly a respective one of said first longitudinal edges of said first pipe section.

7. A header pipe for use in a heat exchanger that includes a plurality of tubes transverse to said header pipe, said header pipe including first and second complementary longitudinal pipe sections, said first pipe section having a U-shaped cross-section with two parallel first longitudinal edges and being formed with a plurality of axially aligned slits adapted to permit extension of one of two opposite ends of said tubes therethrough, said second pipe section having a wall portion with two parallel second longitudinal edges, wherein each of said second longitudinal edges is formed with a forked extension which confines a longitudinal engaging groove that tapers inwardly so as to engage tightly a respective one of said first longitudinal edges of said first pipe section.

8. The header pipe according to claim 7, wherein said first pipe section of each of said header pipes includes a core layer and a clad layer made of an aluminum alloy and formed on said core layer, said clad layer having a melting point lower than that of said core layer, said second pipe section of each of said header pipes being made of aluminum, whereby said clad layer melts so as to fuse said first pipe section to said second pipe section when said header pipe is placed in a furnace.

9. The header pipe according to claim 7, further comprising at least one partition plate for dividing said header pipe into at least two isolated chambers, said partition plate having a first engaging portion, a second engaging portion and a middle portion between said first and second engaging portions, inner branches of said forked extension defining a slot with said wall portion of said second pipe section, said first engaging portion extending into said slot, said middle portion being formed with two opposite notches for engaging said inner branches of said forked extensions, said second engaging portion extending into said first pipe section, said partition plate being frictionally retained on said second pipe section.

10. The header pipe according to claim 8, further comprising at least one partition plate for dividing said header pipe into at least two isolated chambers, said partition plate having a first engaging portion, a second engaging portion and a middle portion between said first and second engaging portions, inner branches of said forked extension defining a slot with said wall portion of said second pipe section, said first engaging portion extending into said slot, said middle portion being formed with two opposite notches for engaging inner branches of said forked extensions, said second engaging portion extending into said first pipe section, said partition plate being frictionally retained on said second pipe section, said partition plate including a core layer and a clad layer formed on said core layer, said clad layer having a melting point lower than that of said core layer, whereby said clad layers melts so as to fuse said partition plate to said first and second pipe sections when said header pipe is placed in the furnace.

11. The header pipe according to claim 7, further comprising two caps for covering two opposite ends thereof, each of said caps having a core layer and a clad layer formed on said core layer, said clad layer having a melting point lower than that of said core layer, whereby said clad layer melts so as to fuse said caps to said first and second pipe sections when said header pipe is placed in a furnace.

12. The heat exchanger substantially as hereinbefore described with reference to and as illustrated in Figures 2 to 8 of the accompanying drawings.