The invention relates to a heat exchanger, in particular to the heat exchanger for a motor vehicle.

BACKGROUND OF THE INVENTION Automobile radiators are constructed of a pair of metal or plastic header tanks, linked by a core with many narrow passageways, giving a high surface area relative to volume. This core is usually made of stacked layers of metal sheet, pressed to form channels and soldered or brazed together. For many years radiators were made from brass or copper cores soldered to brass headers. Modern radiators have aluminum cores, and often save money and weight by using plastic tanks with rubber gaskets.

This construction is more prone to failure and less easily repaired than traditional materials, yet it benefits from better heat transfer properties and lightweight construction.

However, the ongoing interest in continuous weight and size reduction of vehicle’s sub- components may lead to undesired decrease in efficiency of the whole heat exchange system. This may be caused by, for example, uneven thermal expansion between heat exchanger’s sub-components and also within the particular component, such as the core. The thermal expansion of the heat exchanger depends, for example, on the coolant fluid velocity in different sections of the heat exchanger. Another factor that may handicap the flow of the coolant fluid is the deployment of the inlet and the outlet on the header tanks. In industry, the deployment of the inlet and the outlet is usually predefined by the vehicle’s manufacturer requests which are not necessarily feasible in terms of even flow of the coolant fluid. Infeasible deployment of the inlet and outlet in the heat exchanger may lead to undesired flow disruption that can impact its performance and longevity.

It would be desired to provide the means of promoting the flow of the coolant fluid in the neglected parts of the heat exchanger core.

SUMMARY OF THE INVENTION

The object of the invention is, among others, a heat exchanger, in particular for a motor vehicle, comprising a first manifold and a second manifold connected by a plurality of primary tubes with a first cross-section (A-A) and at least one secondary tube with a second cross-section, characterised in that the second cross-section (B-B) is different than the first cross-section (A-A), wherein the outer diameter of the secondary tube is constantly the same as the outer diameter of the primary tubes.

Preferably, at least one secondary tube is deployed on one of the peripheral ends of the manifolds.

Preferably, at least one primary tube is deployed between at least two secondary tubes.

Preferably, the first cross section (A-A) has bigger hydraulic diameter than the second cross section (B-B).

Preferably, the second cross section comprises corrugations on the inner side of the secondary tube.

Preferably, the second cross section comprises surplus material on the inner side of the secondary tube compared to the first cross section.

Preferably, the primary tubes and the secondary tubes are made from the folded sheet of metal.

Preferably, the primary tubes and the secondary tubes are extruded. BRIEF DESCRIPTION OF DRAWINGS

Examples of the invention will be apparent from and described in detail with reference to the accompanying drawings, in which:

Fig. 1 shows a schematic view of a heat exchanger comprising two different types of tubes.

Fig. 2 shows a cross section of the primary tube.

Fig. 3 shows a cross section of the secondary tube. Fig. 4 shows an exemplary deployment of the primary and secondary tubes in one of the examples.

DETAILED DESCRIPTION OF EMBODIMENTS

The invention relates to heat exchangers, in particular radiators used in automobiles. The heat exchanger is configured to convey a cooling medium, such as a coolant through its sub-components so that the temperature of the cooling medium flowing out of the heat exchanger would be lower than the temperature of the cooling medium flowing into the heat exchanger thanks to heat exchange with a second medium, e.g. air. The cooling medium is usually delivered into the heat exchanger by an inlet and collected by an outlet. Depending on the architecture, i.e. the number of passes, desired heat exchanger deployment in the engine bay, etc., the inlet and the outlet are usually deployed either on the opposite sides of the heat exchanger, or on the same side thereof. The inlet and the outlet have usually circular cross-section protruding from inlet and/or outlet of the tanks respectively.

Fig.1 presents a heat exchanger 1 , in particular for a motor vehicle, comprising a first manifold 2 and a second manifold 3 connected by a plurality of primary tubes 10 and at least one secondary tube 20. The manifolds 2, 3 are usually associated with an assembly of the header and the tank, wherein the header may be configured to receive the primary tubes 10 or secondary tubes 20 and the tank may provide a coolant fluid distribution and fluidal communication with the rest of the system. The first manifold 2 may comprise the inlet to the heat exchanger, whereas the outlet may be located on the second manifold. Alternatively, the configuration of the inlet and the outlet may be different from the aforementioned one, i.e. the inlet could be located on the second manifold 3, whereas the outlet could be located on the first manifold 2. Alternatively, both inlet and the outlet may be located on the same manifold 2, 3. Multiple inlets and outlets are also envisaged.

The primary tubes 10 and the secondary tubes 20 are usually made of a single sheet of metal which is folded inwardly, so that the terminal ends of metal sheet create an inner wall that can be attached (e.g. by brazing) to the flat, portion of the tube. The inner wall may be deployed between the two opposite walls of the tube. Alternatively, the tubes 10, 20 can be made in the process of extrusion. It is also possible for the tubes 10, 20 to not comprise any inner walls 5.

The primary tubes 10 and the secondary tubes 20 comprise two open ends, and they are usually deployed in parallel to each other between the first manifold 2 and the second manifold 3, wherein the open ends of the tubes 10, 20 are received in a slots of the headers. To provide a tight connection, the manifolds 2, 3 and the tubes 10, 20 may be brazed together.

Fig. 2 presents a cross-section (A-A) of the single primary tube 10. The primary tube 10 comprises three dimensions characterising its outer periphery, i.e. a tube height a-i, a tube width bi and a tube length (not shown), wherein the length is perpendicular to the cross-section (A-A) presented in the Fig.2. The primary tube 10 comprises also three dimensions characterising its inner dimensions, i.e. a channel height ci, a channel width d-i, and a channel length (not shown) which is essentially the same as the tube length. The inner dimensions of the primary tube 10 presented in Fig. 2 are indicated for a single channel as in one of the embodiments the aforementioned inner wall 5 may be omitted.

Fig. 3 presents a cross-section (B-B) of the single secondary tube 20. The secondary tube 20 comprises three dimensions characterising its outer dimensions, i.e. a tube height aå, a tube width b2 and a tube length (not shown), wherein the length is perpendicular to the cross-section (B-B) presented in the Fig.3. The primary tube 10 comprises also three dimensions characterising its inner dimensions, i.e. a channel height C2, a channel width d2, and a channel length (not shown) which is essentially the same as the tube length. The inner dimensions of the secondary tube 20 presented in Fig. 3 are indicated for a single channel as in one of the embodiments the aforementioned inner wall 5 may be omitted.

The outer dimensions may be used to determine, for example, the approximate outer diameter of the primary tubes 10 and the secondary tubes 20, as well as the inner dimensions may be used to determine, for example, the approximate inner diameter of the primary tubes 10 and the secondary tubes 20.

According to Figs. 2 and 3 the second cross-section (B-B) is different than the first cross-section (A-A), wherein the outer diameter of the secondary tube 20 is constantly the same as the outer diameter of the primary tubes 10. Consequently, the first cross section (A-A) has different hydraulic diameter than the second cross section (B-B). The second cross-section (B-B) may be for example bigger that the first cross-section (A-A), so that the primary tubes comprise a bigger hydraulic diameter than the secondary tubes 20.

Using the different cross-section (B-B) of the secondary tubes 20 may significantly improve the heat exchanger’s performance by increasing the coolant fluid velocity at the certain sections of the heat exchanger 1 , depending on the deployment of the secondary tubes 20 in the stack.

The secondary tubes 20 may comprise a smaller hydraulic diameter in comparison with the primary tubes 10. The smaller internal dimensions of the secondary tubes 20 forces grater velocity of the coolant fluid thanks to increased local hydraulic pressure.

For example, Fig. 3 presents an example, wherein at least one secondary tube 20 is deployed on one of the peripheral ends of the manifolds 2,3. In this particular example, the heat exchanger 1 comprises two secondary tubes 20 deployed on the bottom of the stack to increase the coolant fluid in that area.

Analogically, the heat exchanger 1 could comprise at least one secondary tube 20 deployed on the top of the stack to increase the coolant fluid in that area. Alternatively, the heat exchanger 1 could comprise at least one primary tube 10 deployed between at least two secondary tubes 20. Such configuration is covered, for example by Fig.1 , however other deployments are also envisaged. For example, the section of secondary tubes 20 stacked, for example on the top of the stack, could be separated by at least one primary tube 10 to ensure a precise coolant fluid flow in that area.

The secondary tubes 20 may be in fact manufactured using several different methods. One of the methods may comprise using a metal sheets of different thickness for the primary tubes 10 and the secondary tubes 20. For example, the sheet of metal used for manufacturing the primary tubes 10 could be thinner than the sheet of metal used for manufacturing the secondary tubes 20. Another method for increasing the cross section (B-B) of the secondary tubes 20 could comprise corrugations on the inner surface of the channel, so as to decrease its inner dimensions. The corrugations could increase the fluid velocity in the secondary tubes 20, analogically to aforementioned method, however the costs of manufacturing a secondary tube 20 of the corrugated sheet of metal would be significantly higher compared to the thicker sheet of metal. Another method for increasing the cross section (B-B) of the secondary tubes 20 could comprise surplus material on the inner side of the secondary tube 20. The surplus material could have different physical properties than the secondary tube 20, yet it would be desired so that is remains unreactive to coolant fluid i.e. the surplus material should keep its form, so it is not, for example, washed out from the inner side of the secondary channel.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of drawings, the disclosure, and the appended claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to the advantage.