WO2003085344A1

WO2003085344A1 - Heat exchanger assembly

Info

Publication number: WO2003085344A1
Application number: PCT/EP2002/003971
Authority: WO
Inventors: Anders Tage Jensen; Leif Petersen
Original assignee: Norsk Hydro Asa
Priority date: 2002-04-08
Filing date: 2002-04-08
Publication date: 2003-10-16
Also published as: AU2002304735A1

Abstract

Heat exchanger assembly comprising an inner tube (3) forming a first channel (24) for a first fluid and an outer tube (1) completely surrounding the inner tube (3) and extending in a parallel manner with respect to the inner tube, thereby defining a second channel (25) for a second fluid. Fins (2) are extending between the outside wall of the inner tube (3) and the inside wall of the outer tube (1) and further extending in the longitudinal direction of these tubes. The fins (2) are integrated with the inner tube (3) only. Heat exchanger assembly further comprising a connector (8) having a block provided with a bore allowing the introduction of the tube ends of both tubes and further a first bore (9) in fluid communication with the first channel (24) and a second bore (10) in fluid communication with the second channel (25).

Description

Heat exchanger assembly

The invention relates to a heat exchanger assembly comprising an inner tube forming a first channel for a first fluid, an outer tube completely surrounding the inner tube and extending in a parallel manner with respect to the inner tube, thereby defining a second channel for a second fluid, fins extending between the outside wall of the inner tube and the inside wall of the outer tube and further extending in the longitudinal direction of these tubes.

Such a heat exchanger is known from US-A-6 098 704.

Coaxial heat exchangers are normally made of an inner tube and an outer tube mutually connected by connection walls. A first fluid having a first temperature flows through the channel formed by the inner tube and a second fluid having another temperature is flowing through the channel formed between the inner and the outer tube. The inner tube wall and to some extent the intermediate ribs will transfer heat from the first fluid to the second fluid or vice versa. In order to get the best heat transfer between the fluids it is important to ensure a good contact between the tubes and the ribs formed by the connection walls..

According to US-A 6 098 704 the outer and inner tube and the connection walls are extruded as a one piece profile whereby the connecting walls are integrated with the inner and the outer tube. In order to connect the manifold or a connection member to the heat exchanger according to this publication, the end portion of the outer tube has to be removed before the heat exchanger can be connected to a manifold or connecting member. This is an additional step in the production process and a waste of material. This is especially impor- tant as the profile is difficult to extrude and the extrusion speed relatively slow for such a coaxial heat exchanger.

It is therefor an object of the invention to provide a heat exchanger as described in the preamble of claim 1 in which the above mentioned problems can be avoided.

This object is achieved in that the fins are integrated with the inner tube only. In this way it becomes possible have two separate extrusions one inner tube and one outer tube, the inner tube being able to be inserted into the outer tube while having a somewhat greater length. The connection to a header or connecting member is now possible without the need to remove part of the outer tube. Moreover it becomes possible to use two differ- ent alloys for the two tubes, such as a high corrosion resistant alloy for the simple outer tube, which normally has a somewhat lower extrudability and a lean and therefor cheap alloy for the inner tube enabling a higher extrusion speed.

It must be noted that US-A 6 098 704 also describes a coaxial heat exchanger consisting of two tubes, in which the inner tube is a standard round tube and the outer tube is an extruded tube with internal ribs. The heat exchanger is made by pushing or threading the inner tube into the outer tube. In this way the same type of heat exchanger can be made except for the fact that the fins are integrated with the outer tube. As a result of the mounting method, the contact between the inner tube and the ribs is not always complete. As most of the fluid in the second channel is in contact with the fins, and the contact with the fins and the inner tube might be defective the ability to transfer heat from the fluid in the inner tube through the inner tube and ribs to the outer fluid or vice versa is lowered.

Other advantages and characteristics of the invention will become clear from the following description of different embodiments of the invention reference being made to drawings in which: fig. 1 shows a cross-section of a first embodiment of a heat exchanger according to the invention, fig. 2 shows a cross-section of a second embodiment of a heat exchanger according to the invention, fig. 3 shows in a perspective view of a connector leading in or out a first and a second fluid into or out of the channels of the heat exchanger according to the invention, fig. 4 shows a top view of the connector of fig. 3, fig. 5 shows a cross sectional view of the connector of fig. 3, fig. 6 shows the same cross sectional view of the connector of fig. 3 with the the heat exchanger according to the invention connected thereto, fig. 7 shows a perspective view of a second embodiment of a connector. Fig. 1 shows the cross section of a heat exchanger according to the present invention. The heat exchanger comprises an inner tube 3, an outer tube 1 and fins 2 extending between the inner tube 3 and the outer tube 1. The intermediate fins 2 are extruded in one part with the inner tube 3. Through an inner channel 24 formed by the inner tube 3 a first fluid can flow. The inner tube 3, the outer tube 1 and the ribs form a number of channels 25 through which a second fluid can flow, whereby, if the temperature of the two fluids is different, heat exchange can take place between the first fluid and the second fluid. The flow direction of the two fluids may be a counter flow or they may flow in the same direction, dependent upon the application of the heat exchanger.

Both tubes 1 and 3 can be made by means of extrusion as is common in the art. After extrusion the heat exchanger can be assembled by inserting the inner tube 3 into the outer tube 1. In view thereof the external diameter of the fins 2 is substantially equal to the inner diameter of the outer tube 1. Preferably the dimensions are selected in such a way that a small defor- mation of the end of the fins 2 is needed to insert the inner tube into the outer tube, so that the inner tube 3 is somewhat fixed with respect to the outer tube 1 and the heat transfer between the fins 2 and the outer tube 1 is improved.

As the outer tube 1 is made separately it is possible to select a different alloy for the outer tube 1 and the inner tube 3. In this way the inner tube 1 and intermediate fins 2 can be made of a lean or softer alloy than normally used in heat exchangers, leading to a considerable gain in extrusion speed. This is especially important as this tube has a complicate cross- section shape and therefor needs a complicated die. The outer tube 1 can be made of a stronger and more corrosion resistant material. In this way a corrosion resistant outer surface is ensured while a cheap and flexible inner part is obtained.

As can be seen in Figure 1, the first fluid in channel 24 is completely surrounded by the inner tube 3, whereas the second fluid in the channels 25 is for the greater part in contact with portions belonging to the inner tube, and for a smaller part with portions of the outer tube 1. As there might be some heat transfer deficiency in the contact zones between the top of the fins 2 and the inner wall of the outer tube 1, these deficiencies will influence in a negative way the total heat transfer between the first and the second fluid, but as most of the surrounding surface of the second fluid is constituted by the inner tube, this has less influence than according to the prior art.

Fig. 2 shows a second embodiment of a heat exchanger according to the invention. This heat exchanger is almost identical to the heat exchanger shown in Figure 1, with the exception of the shape of the inner channel 24. To increase the contact surface between the first fluid in the channel 24 and the inner tube 3, protrusions 6 are provided to the inner wall of the inner tube 3. Preferably these protrusions are extruded integrally with the inner tube and intermediate fins. The protrusions 6 have the shape of continuous ribs extending parallel to the axis of the tube 3, but can also be shaped in different forms, such as screw-line shaped ribs, interrupted protrusions as seen along the axis of the tube etc.

In the figures 3, 4, 5 and 6 there is shown a connector 8 to be used together with the heat exchanger according to the invention. As shown, the connector consists of a block member, which may be an aluminium block obtained by extrusion and cut to an appropriate length. In the embodiment shown, the extruded profile has a semicircular cross-section with one flat surface 101, and the block has two end faces 102 and 103. In the end face 103 a bore 104 has been made with a diameter which is almost equal to the external diameter of the heat exchanger 7 and extending in the axial direction of the extruded profile and parallel to the surface 101. This bore extends to somewhat halfway the length of the block 8 in a wall 105.

In this wall 105 a second bore 106 has been made extending in the same direction as the bore 104. This bore has a diameter which is substantially equal to the inner diameter of diameter of the inner tube 3. In the flat surface and perpendicular to the bores 104 and 106 two parallel bores are made, a first bore 9 and a second bore 10 ending respectively in the bore 106 and 104 respectively. These bores 9 and 10 may be provided with standard implements for connecting a bore to another tube or hose for fluid transport. The bores as described are cylindrical but the bores may also have any other cross section, such as rectangular, within the scope of the invention.

The heat exchanger 7 is assembled in such a way that the inner tube is extending from the outer tube over a distance which is about equal to the diameter of the bore 10. After insertion of one end of the heat exchanger 7 in the bore 104 a situation as shown in figure 6 will be obtained, in which the inner tube 3 extend up till the wall 105, and the channels 25 are in fluid communication with the bore 10. The inner channel 24 is in fluid communication with the bore 9. After brazing the heat exchanger 7 to the connector 8 whereby fluid tight connections can be made the heat exchanger 7 is provided with a connector 8 allowing the supply and the removal of the fluids through standard connectors, as commonly used in the art.

The connecting lines leading the fluids into and out from the connector 8 and heat exchanger 7 can be placed parallel to each other, due to the bores being arranged in the same direction. This leads to a space saving way of organising the connecting lines leading into and out from the heat exchanger.

As clearly visible in Figure 6 an annular chamber 11 in the connector 8 is surrounding the end part of the inner tube 3. The annular chamber 11 enables the second fluid to flow around the inner tube 3 and to be led into the openings to the channels 25 between the inner and the outer tubes in a equally distributed fluid flow. In this way, a processing step is eliminated, thereby saving production time and costs.

The chamber 11 is leading the second fluid into or out of the outer channels 25 between the inner tube 3 and the outer tube 1 of the heat exchanger. The arrangement of the chamber 11 allows the intermediate fins 2 (shown on fig. 4) to be integrated with the inner tube, saving production costs.

Fig. 7 shows a second embodiment of a connector 110 for the coaxial heat exchanger according to the invention. The difference with the first embodiment as described with respect to the figures 3-6, resides in the fact that the bore 9 is made as a prolongation of the bore 106.

The two embodiments of the connector enables a flexible system suitable for the narrow spaces in a vehicle body.

It should be understood that both ends of the heat exchanger can be provided with connectors in accordance with the present invention.

Claims

1. Heat exchanger assembly comprising an inner tube (3) forming a first channel (24) for a first fluid, an outer tube (1) completely surrounding the inner tube (3) and extending in a parallel manner with respect to the inner tube, thereby defining a second channel (25) for a second fluid, fins (2) extending between the outside wall of the inner tube and the inside wall of the outer tube and further extending in the longitudinal direction of these tubes, characterised in that, the fins (2) are integrated with the inner tube (3) only.

2. Heat exchanger (7) according to claim 1 characterised in that at least one of the tubes is made by extrusion.

3. Heat exchanger according to any of the preceding claims characterised in that at least one of the tubes is made of aluminium or an aluminium alloy.

4. Heat exchanger according to any of the preceding claims characterised in that the inner tube (3) and the outer tube (1) consist of different materials, especially of different aluminium alloys.

5. Heat exchanger assembly according to any of the preceding claims 1-4 characterised in that the heat exchanger (7) is connected to a heating or cooling system by means of a connector (8).

6. Heat exchanger assembly according to claim 5 characterised in that the connector (8) comprises a block provided with a bore allowing the introduction of the tube ends of both tubes and further has a first bore (9) in fluid communication with the first channel (24) and a second bore (10) in fluid communication with the second channel (25).

7. Heat exchanger assembly according to claim 6 characterised in that one of the first or second bores is placed perpendicular to the length axis of the heat exchanger (7).

8. Heat exchanger assembly according to claim 7 characterised in that both the first bore (9) and the second bore (10) are placed perpendicular to the length axis of the heat exchanger (7) .

9. Heat exchanger assembly according to claim 6 characterised in that both the first bore (9) and the second bore (10) extend in a parallel manner to each other.

10. Heat exchanger assembly according to claim 1 characterised in that the inner tube (3) has fins (2) the outside surface and protrusions (6) on the inside surface.