MXPA00006044A - Fluid conveying tube and vehicle cooler provided therewith - Google Patents

Abstract

A fluid conveying tube (10) included in a vehicle cooler comprises on its inside first and second opposite longitudinal primary heat exchange surfaces (11', 12'), and flow-directing surface structures (16) which are arranged on the primary surfaces (11', 12'). Each surface structure (16) comprises a plurality of elongate directing elements (15) projecting from the primary surfaces (11', 12'). The surface structures (16) are alternatingly arranged on the first and second primary surfaces (11', 12') in such manner that directing elements (15), succeeding in the longitudinal direction (L) of the primary surfaces (11', 12'), are alternatingly arranged on the first and second primary surfaces (11', 12') and are mutually inclined at a given angle ( gamma ). Each surface structure (16) comprises a laterally extending row (17) of mutually parallel directing elements (15). Thus an input fluid flow is divided into a number of parallel partial flows which follow a respective spiral-shaped flow p ath through the tube, whereby a high heat exchanging capacity is achieved.

Description

FLUID CONVEYOR PIPE AND VEHICLE COOLER PROVIDED WITH THE SAME.

TECHNICAL FIELD The present invention relates in general to vehicle coolers and in particular to the design of fluid transport tubes included in said coolers.

TECHNICAL BACKGROUND One type of vehicle cooler which is, for example, described in EP-A1-0 590 945, comprises a heat exchanger assembly which is made of, on the one hand, fatty fluid transporting tubes, which are juxtaposed to be traversed by a first fluid, for example, liquid flowing through a motor block and, on the other, surface elongation means disposed between the tubes and adapted to be traversed by a second fluid, for example cooling air. Each tube has opposite large faces, to which the surface elongation means are applied and which form the first heat exchange surface of the tube. In this type of coolers, it is known to provide the primary surfaces on the inside of the tubes with projections in order to increase the heat exchange between the fluids. These projections decompose the insulating, laminar limiting layer which otherwise tends to form within the tube along its primary surfaces, at least at low fluid flow rates. The projections may be elongated, as is known from for example US-A-4, 470,452, or cylindrical, as is known from for example US-A-5, 730, 233. However, these constructions are not capable of combining a sufficiently high heat exchange capacity with a sufficiently low pressure drop in the longitudinal direction of the tubes. An alternate modality of fluid transport tubes is described in the doctor's thesis published in 1977 by Chalmers Institute of Technology entitled "Thermal and hydraulic performance of rectangular anhanced tubes for compact heat exchangers". Said tube is shown schematically in a plan view in Figure I. The opposing primary surfaces of the tube have transverse ribs 1 in zigzag, ie surface structures which each consist of a number of elongated rib elements 2 which are connected to each other in intermediate pointed areas 3. The transverse ribs 1 are arranged alternately in the longitudinal direction L of the tube on the opposite primary surfaces of the tube, the ribs 1 (complete lines in figure 1) arranged on the upper primary surface being raised transverse in relation to the ribs 1 (dotted lines in Figure I) disposed on the lower primary surface. Seen in the longitudinal direction L of the tube, the successive rib elements 2 are arranged alternately on the opposite primary surfaces and have a given mutual angle. In this way, the rib elements 2 will direct the flow of the first fluid through the tube to generate a swirling movement around! longitudinal axis of the tube, as shown schematically in the end view in Figure 2. More specifically, the flow input is divided into a number of parallel partial flows 4 to which a spiral movement is imparted as they pass through. of tube, each partial flow 4 having an opposite rotation in relation to the attached partial flows 4. By means of said partial flows, the limiting layer adjacent to the primary surfaces is interrupted and a better circulation is provided between the central portions and the portions wall of the tube. All this results in a potentially high heat exchange capacity of the tube. It has, however, been discovered that it is difficult to provide ribs connected in a zigzag fashion by means of the current manufacturing technique, and therefore a vacuum is practiced in the areas indicated 3 between the rib elements 3. The coolers of Vehicle with this type of "spiral flow tubes" has been discovered to have a high heat exchange capacity also at relatively small flows through the tubes, which is often desirable, for example, in vehicle coolers for loaded truck engines or air impellers, because those vehicles can generate large amounts of heat also at low engine speeds. The previous construction is, however, in its first stage and needs to be further developed to optimize its capacity.

BRIEF DESCRIPTION OF THE INVENTION It is an object of the present invention to provide an improved fluid transport tube, ie a tube which for a given size has a higher heat exchange capacity and / or a lower pressure drop than normal constructions, in particular when relatively small fluid flows pass through it. It is also an object to provide a fluid conveyor tube with a small risk of obstruction. Still another object is to provide a fluid conveyor tube which is easy to manufacture. Those and other objects which will appear from the following description, have now been completely or partially achieved by means of a fluid conveyor tube and a vehicle cooler according to the appended claims 1 and 13, respectively. Preferred embodiments are defined in the dependent claims. The construction of the invention divides a fluid flow inlet into a number of partial flows and a vortex movement about a respective axis extending in the longitudinal direction of the tube is imparted to each partial flow. Thanks to the fact that the elongated steering elements in the surface structures are placed in rows that extend laterally on the pipe and that the steering elements included in the respective rows are mutually parallel, the steering elements can be packed closer one to the other. to another than in the previous constructions. As a result, more partial flows can be obtained in the tube for a given width of the primary surfaces of the tube. It has been found that this results in a higher heat exchange capacity than in previous constructions, in particular at small fluid flows through the tube. The tube of the invention can be easily provided with suitable steering elements, for example by embossing a preform to form elongated recesses or depressions in the large faces of the tube.

BRIEF DESCRIPTION OF THE DRAWINGS Next, the invention and its advantages will be described in more detail with reference to the accompanying schematic drawings, which by way of example, show presently preferred embodiments of the invention.

Figures 1-2 are a plan view and an end view, respectively, of a fluid transport tube according to the prior art. Figures 3-8 are different views of a fluid transport tube according to the invention, figure 3 being an end view thereof, figure 4 being a plan view of a part thereof, the figure being a sectional view along the line V-V in figure 4, the figure 6 being a view in longitudinal section along the line VI-VI in Figure 4, and Figures 7-8 being seen in cross section along the lines VII-VII and Vlll-Vlll respectively, in the figure 4. Figures 9-10 are an end view and a plan view, respectively, of a fluid conveyor tube of the invention of the channel double type.

DESCRIPTION OF THE PREFERRED MODALITIES Figures 3-8 show a preferred embodiment of a fluid transport tube 10 according to the invention. The tube 10 is suitably made of a metal material, usually an aluminum material. As seen from Figure 3, the tube 10 is flat and has two opposite large faces 11, 12, which are substantially flat. The large faces 11, 12 are connected through two opposite curved short sides 13, 14. When the tubes 10 are mounted in a vehicle cooler, the means for elongating the surface (not shown), for example bent sheet, are brought into support against the large faces 11, 12. The main heat exchange between the medium flowing through the tubes 10 and the medium flowing through the surface elongation means around the outside of the tubes 10 has place therefore through those big faces 11, 12. The large faces 11, 12 form two opposite primary heat exchange surfaces 11 ', 12' on the inside of the tube 10. As seen from FIGS. 4-8, the primary surfaces 11 ', 12' are provided with a number of flow direction elements 15, which are projected, which are called depressions, in the form of small depressions on one side of the large faces 11, 12 of the tube 10, said depressions form corresponding projections on the sides opposite of it. These depressions can, for example, be formed by enhancing a preform, which is subsequently formed in a flat tube 10. The height F (see figure 6) of a depression 15 is typically around 0.1-0.3 mm, which corresponds substantially to the material thickness of the tube. The depressions 15 are elongated and inclined in relation to the longitudinal direction L of the tube 10. Furthermore, the depressions 15 are arranged in a number of surface structures or groups 16 on the respective primary surfaces 11 ', 12'. Figure 4 shows the depressions 15 on the upper primary surface 11 'in full lines and the depressions 15 on the lower primary surface 12' in dotted lines.

Next, the groups 16 of depressions 15 on the left side of the center line C-C of the tube 10 will be discussed first. It is evident from the plan view of Figure 4 that the groups 16 of cavities 15 on the upper and lower primary surfaces 11 ', 12' are relatively enhanced in the longitudinal direction L, so that the tube 10 in cross section it has no opposing depressions 15 (see figures 6-8). This makes it possible to avoid clogging of the tube 10. The groups 16 of depressions 15 are therefore arranged alternately on the upper and lower primary surfaces 11 ', 12' seen in the longitudinal direction L. Each group 16 consists of a first and second transverse row 17, 18 of inclined depressions 15. Within the respective rows 17, 18 all the depressions 15 are mutually parallel. The depressions 15 in the first row 17 are inclined in relation to a short side 13 of the tube 10 at an angle a in relation to the longitudinal direction L, while the depressions 15 in the second row 18 are inclined in relation to the second short side opposite 14 of the tube 10 at an angle β in relation to the longitudinal direction L. The depressions 15 in the first row 17 and the depressions 15 in the second row 18 therefore have a mutual inclination angle of? = 180 ° - -ß. Additionally, the depressions 15 in the second row 18 are relatively laterally enhanced to the depressions 15 in the first row 17, suitably so that the ends 19 of the depressions 15 in the first row 17, seen in the direction L longitudinal, are located in alignment with the ends 19 of the depressions 15 in the second row 18. Views in the longitudinal direction L, ie in the direction of main flow of a fluid through the tube 10, the successive depressions 15 are arranged alternatively on the upper and lower primary surfaces 11 ', 12', at least along a line through the center of the depressions 15 (see line VI-VI in Figure 4). Moreover, said successive depressions 15 are mutually inclined at an angle?. In a fluid transport tube according to Figures 3-8, a flow inlet of a fluid will be divided into a number of partial flows, to which, while being directed by the inclined depressions 15, a swirling movement is imparted. about a respective axis extending in the longitudinal direction L of the tube 10. Each group of depressions 15 parallel with the longitudinal direction L of the tube 10 therefore forms a virtual channel, in which the fluid performs a spiral movement. Thanks to the fact that the depressions 15 in the respective rows 17, 18 are mutually parallel, they can be placed in a compact pattern on the primary surfaces 11 ', 12' but still form well-defined virtual channels for the fluid inlet. In the embodiment according to Figures 3-8, the tube 10 has groups 16 of depressions 15 on both sides of its central line CC, but for manufacturing reasons there are no depressions 15 in the area around the current center line CC . The reason for this is that current manufacturing techniques require the application of a support member centrally on the preform during the embossing thereof.

Additionally, in the example shown, the depressions 15 in groups 16 on each side of the center line C-C are mutually mirror inverted. It should, however, be noted that the groups 16 can have the same appearance on both sides of the center line C-C. If it is admitted by the manufacturing technique, it is currently preferred that the depressions 15 extend continuously transversely of the primary surfaces 11 ', 12' between the short sides 13, 14. It should, however, be noted that the rows 17, 18 of the depressions 15 should not extend perpendicularly to the longitudinal direction L of the tube 10, but they can also extend obliquely on the surfaces 11 ', 12'. It has been discovered that the sizing and positioning of the depressions 15 on the primary surfaces 11 ', 12' of the tube 10 influences the capacity of the tube 10 in relation to the capacity of heat exchange and pressure drop. The parameters that have been investigated are the angles of inclination a and ß of the depressions 10 (see figure 4), the distance B between successive depressions 10 in the longitudinal direction L (see figure 4), the distance C between successive depressions 15 on the respective primary surfaces 11 ', 12' in the longitudinal direction L (see figure 4), the height F of the depressions 15 from the primary surfaces 11 ', 12' (see figure 5) and the length A of the depressions 15 (see figure 5). It has been discovered that the angles a and ß are preferably equal. In addition, the angles a and ß should be on the scale of approximately 40-80 °, and preferably on the scale of 45-75 °.

Currently, the most preferred value of y ß is approximately 45 °, which means that the successive depressions are substantially mutually perpendicular. Additionally, it has been discovered that appropriately the distance C is twice the distance B, that is to say that all the successive depressions 15 in the longitudinal direction L of the tube 10 have a constant mutual distance from center to center. When the tube 10 is to be passed through a fluid in the form of a liquid, for example water, the following preferred dimensions have been discovered. For a liquid flowing through the tube at an average velocity of approximately 0.8-2.2 m / s, the relationship between the distance B and the height F of the depressions 15 should be in the range of approximately 10-40, and preferably approximately 15-30. At the minimum limit value, the pressure drop across the pipe will be undesirably high, and at the maximum limit value the heat exchange capacity across the primary surfaces will be unsatisfactorily low. In a tube 10 having a distance G between the primary surfaces 11 12 * of 0.8-2.8 mm, the ratio between the length A of the depressions 15 and the height F of the depressions 15 should be on the scale of approximately 4- 14 At the minimum limit value, the pressure drop along the tube 10 will be undesirably high, and at the upper limit value the heat exchange capacity across the primary surfaces 11 ', 12' will be unsatisfactorily low. Additionally, the relationship between the mutual distance G of the primary surfaces 11 *, 12 'and the height F of the depressions 15 must be at least about 2.5. This is preferred in tubes having a mutual distance between the primary surfaces 11 ', 12 * of 0.8-2.8 mm in order to avoid clogging when a liquid flows through the tube at an average speed of approximately 0.8-2.2 m / s. . When the tube is to be traversed by a fluid in the form of a gas, for example air, it has been found that the relationship between the distance B and the height F of the depressions 15 should be on the scale of approximately 25-65, and preferably 35-55. At the minimum limit value, the pressure drop across the pipe will be undesirably high, and at the maximum limit value the heat exchange capacity across the primary surfaces will be unsatisfactorily low. Figures 9-10 show an alternate embodiment of a fluid transport tube. The parts having corresponding parts in Figures 3-4 have the same reference numbers and are not described in more detail. The tube 100 contains two separate fluid ducts or channels 101, 102 which are separated by a partition wall 103. The tube is suitably formed by bending a preform provided with depressions. The pattern of the depressions 15 on the large faces 11, 12 of the tube 100 is substantially identical with the pattern of the tube 10 in Figure 4, and therefore the corresponding advantages are achieved. It should be noted that the tube of the invention is applicable to all types of vehicle coolers having tubes arranged in parallel for coolant fluids, ie liquids or gases, such as liquid coolers, air charge coolers, condensers and oil coolers.

Claims (13)

NOVELTY OF THE INVENTION CLAIMS

1. - A fluid conveyor tube for vehicle coolers, which in its interior comprises first and second longitudinal opposite primary heat exchange surfaces (11 *, 12 *), and flow direction surface structures (16) which they are disposed on the primary surfaces (11 *, 12 *) and which each comprise a plurality of elongated steering elements (15) projecting from the primary surfaces (11 *, 12 *), the surface structures (16). ) being arranged alternately on the first and second primary surfaces (11 *, 12 *) in such a way that the steering elements (15), successive in the longitudinal direction (L) of the primary surfaces (11 *, 12 * ), are arranged alternately on the first and second primary surfaces (11 *, 12 *) and are mutually inclined at a given angle (?), characterized in that each surface structure (16) comprises a first row that is laterally extending (17) mutually parallel steering elements (15).

2. A fluid transport tube according to claim 1, further characterized in that at least one end (19) of each steering element (15) in said surface structure (16) is arranged, seen in the direction (L) ) longitudinally of the primary surfaces (11 *, 12 *), essentially in alignment with one end (19) of another steering element (15) in said surface structure (16).

3. A fluid conveyor tube according to claim 1 or 2, further characterized in that each surface structure (16) comprises a second row (18) extending laterally of mutually parallel steering elements (15), the elements of steering (15) of the second row (18) being arranged at said angle (?) in relation to the steering elements (15) of the first row (17).

4. A fluid conveyor pipe according to claim 3, further characterized in that at least one end (19) of each steering element (15) of the first row (17) is arranged, seen in the direction (L) longitudinal of the primary surfaces (11 *, 12 *), essentially in alignment with one end (19) of an associated address element (15) of the second row (18).

5. A fluid conveyor pipe according to claim 3 or 4, further characterized in that the steering elements (15) are raised relatively laterally in the first and second rows (17, 18).

6. A fluid transport tube according to any of the preceding claims, further characterized in that said angle (?) Is about 20-100 °, preferably 30-90 °, and more advantageously about 90 °.

7. - A fluid transport tube according to any of the preceding claims, further characterized in that said row or rows (17, 18) extend perpendicular to the longitudinal direction (L) of the primary surfaces (11 *, 12 ').

8. A fluid transport tube according to any of the preceding claims, further characterized in that it is designed to be traversed by a liquid, in which the distance from center to center (B) between the successive steering elements (15) in said longitudinal direction (L) is about 10-40, and preferably 15-35 times as long as the height (F) of the steering elements (15) perpendicular to the primary surfaces (11 ', 12').

9. A fluid conveyor tube according to any of claims 1-7, further characterized in that it is designed to be traversed by a gas, in which the distance from center to center (B) between the steering elements (15). ) successive in said longitudinal direction (L) is approximately 25-65, preferably 30-55 times as long as the height (F) of the steering elements (15) perpendicular to the primary surfaces (11 ', 12').

10. A fluid transport tube according to any of the preceding claims, further characterized in that each elongated steering element (15) has a length (A) which is about 4-14 times as long as its height (F). ) perpendicular to said primary surface (11 ', 12').

11. - A fluid transport tube according to any of the preceding claims, further characterized in that the distance (G) between said primary surfaces (11 ', 12') is at least about 2.5 times as long as the height (F) of the steering elements (15) perpendicular to said primary surfaces (11 ', 12').

12. A fluid transport tube according to any of the preceding claims, further characterized in that said surface structures (16) are arranged and designed to form a number of parallel flow paths that extend through the tube and at each one of which is imparted a swirling movement about a respective axis extending in said longitudinal direction (L) to a fluid flowing through the tube.

13. A vehicle cooler comprising a heat exchanger assembly and at least one tank connected to the heat exchanger assembly, further characterized in that the heat exchanger assembly comprises fluid transporting tubes according to any of claims 1-12 and means for lengthening the surface arranged between the tubes.