Structured heat exchanger tube and method for the production thereof

Abstract

The invention relates to a heat exchanger tube with at least one structured region on the inside of the tube, which has the following features: a) integral internal ribs of height H run on the inside of the tube in axially parallel or helical-line-shaped manner continuously over the circumference at an angle of inclination β1, measured with respect to the tube axis, with primary grooves being formed,b) the internal ribs are crossed over the entire circumference of the tube by spaced-apart secondary grooves which, parallel to one another at an angle of inclination β2, measured with respect to the tube axis, have a notch depth T2 and a groove opening angle α2, c) the internal ribs and the secondary grooves are crossed over the entire circumference of the tube by spaced-apart tertiary grooves which run continuously over the circumference parallel to one another at an angle of inclination β3, measured with respect to the tube axis, and have a notch depth T3 and a groove opening angle α3.

Description

Further advantages and refinements of the invention are explained in more detail with reference to schematic drawings, in which:

FIG. 1 shows, schematically, the production of a heat exchanger tube according to the invention by means of three mandrels with differing twist and differing separation,

FIG. 2 shows a schematic partial view of the internal structure produced,

FIG. 3 shows a photo of an internal structure,

FIG. 4 shows, schematically, part of the section through the internal structure from FIG. 3 along the line X-X, and

FIG. 5 shows a diagram which shows the improvement via the Reynolds' number of the internal heat transfer over the singly notched internal ribs. Furthermore, the ratio of the losses of pressure from the novel internal structure in comparison to the internal structure without tertiary grooves is illustrated.

Claims

1. Heat exchanger tube (1) with at least one structured region on the inside of the tube, which has the following features: a) integral internal ribs (2) of height H run on the inside of the tube in axially parallel or helical-line-shaped manner continuously over the circumference at an angle of inclination β1, measured with respect to the tube axis, with primary grooves (3) being formed,b) the internal ribs (2) are crossed over the entire circumference of the tube by spaced-apart secondary grooves (4) which, parallel to one another at an angle of inclination β2, measured with respect to the tube axis, have a notch depth T2 and a groove opening angle α2,c) the internal ribs (2) and the secondary grooves (4) are crossed over the entire circumference of the tube by spaced-apart tertiary grooves (5) which run continuously over the circumference parallel to one another at an angle of inclination β3, measured with respect to the tube axis, and have a notch depth T3 and a groove opening angle α3.

2. Heat exchanger tube according to claim 1, characterized in that the structured region on the inside of the tube differs in the pitch P2 of the secondary grooves and pitch P3 of the tertiary grooves.

3. Heat exchanger tube according to claim 2, characterized in that the pitch P2 of the secondary grooves (4) is smaller than the pitch P3 of the tertiary grooves (5).

4. Heat exchanger tube according to claim 1, characterized in that the structured region on the inside of the tube differs in the groove opening angle α2 of the secondary grooves (4) and α3 of the tertiary grooves (5).

5. Heat exchanger tube according to claim 1, characterized in that the structured region on the inside of the tube differs in the notch depth T2 of the secondary grooves (4) and T3 of the tertiary grooves (5).

6. Heat exchanger tube according to claim 5, characterized in that, in the structured region on the inside of the tube, the notch depth T2 of the secondary grooves (4) is smaller that the notch depth T3 of the tertiary grooves (5).

7. Heat exchanger tube according to claim 1, characterized in that integral external ribs (6) run around the outside of its tube in an axially parallel or helical-line-shaped manner.

8. Method for producing a structured heat exchanger tube according to claim 7, with integral external ribs (6), i.e. machined from the tube wall, running around the outside of the tube in a helical-line-shaped manner and running on the inside of the tube in an axially parallel or helical-line-shaped manner, and internal ribs (2) which are crossed and notched by secondary grooves (4) and by tertiary grooves (5), in which the following method steps are carried out: a) in a first forming region, external ribs (6a) running in a helical-line-shaped manner are formed on the outside of a smooth tube (7) by the rib material being obtained by displacement of material from the tube wall by means of a first rolling step and the ribbed tube produced being caused to rotate by the rolling forces and being pushed forwards in accordance with the helical-line-shaped ribs produced, the external ribs (6a) being formed with a rising height from the otherwise undeformed smooth tube,b) in the first forming region, the tube wall is supported by a first roll mandrel (10) which is situated in the tube, is mounted rotatably and is profiled, as a result of which the internal ribs (2) are constructed,c) in a second rolling step, the external ribs (6b) are constructed in a second forming region spaced apart from the first forming region with a further rising height, and the internal ribs (2) are provided with secondary grooves (4), the tube wall being supported in the second forming region by a second roll mandrel (20) which is situated in the tube, is likewise of rotatable and profiled design, but the profiling of which differs from the profiling of the first roll mandrel (10) with regard to the magnitude or the orientation of the angle of twist,d) in a third rolling step, the external ribs (6) are constructed in a third forming region spaced apart from the second forming region, with a further rising height, and the internal ribs (2) are provided with tertiary grooves (5), the tube wall being supported in the third forming region by a third roll mandrel (30) which is situated in the tube, is likewise of rotatable and profiled design, but the profiling of which differs from the profiling of the first roll mandrel (10) and of the second roll mandrel (20) with regard to the magnitude and/or orientation of the angle of twist.

9. Method according to claim 8, characterized in that essentially an integral multiple of the separation of the external ribs is set as the distance between the forming regions.

10. Method according to claim 8, characterized in that the external diameter of the second roll mandrel (20) is selected to be smaller than the external diameter of the first roll mandrel (10).

11. Method according to claim 8, characterized in that the external diameter of the third roll mandrel (30) is selected to be smaller than the external diameter of the second roll mandrel (20).

12. Method according to claim 8, characterized in that the depths T2 and T3 of the secondary grooves (4) and tertiary grooves (5) are set by selection of the diameters of the roll mandrels (20, 30) and by selection of the diameters of the respectively largest roll disks of the three roll tools (50, 60, 70).