HEAT EXCHANGER TUBE

Abstract

The invention relates to heat exchanger tube having a longitudinal tube axis; axially parallel or helically circumferential continuous fins are formed from the tube wall on the outer tube face and/or inner tube face, and continuous primary grooves are formed between adjacent fins; the fins have at least one structured zone on the outer tube face and/or inner tube face, said structured zone being provided with a plurality of projections which project from the surface an have a height such that the projections are separated by notches. According to the invention, the projections are arranged in groups which are periodically repeated along the extension of the fin. Furthermore, at least two notches between the projections within the group have a varying notch depth in a fin.

Claims

1. A heat exchanger tube having a longitudinal tube axis, wherein axially parallel or helically circumferential continuous fins are formed from the tube wall on the outer tube face and/or inner tube face, continuously extending primary grooves are formed between respectively adjacent fins, the fins have at least one structured region on the outer tube face and/or inner tube face, the structured region has a multiplicity of projections which project from the surface with a projection height, wherein adjacent projections are separated by notch formations, characterized in that the projections are arranged in groups which repeat periodically along the fin profile, and in that at least two notch formations are formed between the projections within the group with a changing notch depth in one fin.

2. The heat exchanger tube as claimed in claim 1, characterized in that the notch formations which are adjacent at least by one projection vary by at least 10% in the notch depth.

3. The heat exchanger tube as claimed in claim 1, characterized in that the greatest notch depth extends at maximum as far as the tube wall.

4. The heat exchanger tube as claimed in claim 1, characterized in that the notch formations are formed between primary grooves by making cuts into the inner fins (3) at a cutting depth transversely with respect to the fin profile to form fin segments and by raising the fin segments in a main orientation along the fin profile.

5. The heat exchanger tube as claimed in claim 1, characterized in that at least one projection protrudes from the main orientation along the fin profile over the primary groove.

6. The heat exchanger tube as claimed in claim 1, characterized in that the sub-section of the fin is present unchanged between the groups.

7. The heat exchanger tube as claimed in claim 1, characterized in that a plurality of projections have a surface parallel to the longitudinal tube axis at the location furthest away from the tube wall.

8. The heat exchanger tube as claimed in claim 1, characterized in that the projections vary with respect to one another in terms of projection height, shape and orientation.

9. The heat exchanger tube as claimed in claim 1, characterized in that a projection has a tip, running to a point, at the face facing away from the tube wall.

10. The heat exchanger tube as claimed in claim 1, characterized in that a projection) has, on the face facing away from the tube wall, a curved tip whose local curvature radius is decreased starting from the tube wall as the distance increases.

11. The heat exchanger tube as claimed in claim 1, characterized in that the projections have a different shape and/or height from the start of the tube along the longitudinal tube axis as far as the end of the tube located opposite.

12. The heat exchanger tube as claimed in claim 1, characterized in that the tips of at least two projections are in contact with one another or cross over one another along the fin profile.

13. The heat exchanger tube as claimed in claim 1, characterized in that the tips of at least two projections are in contact with one another or cross over one another over the primary groove.

14. The heat exchanger tube as claimed in claim 1, characterized in that at least one of the projections is shaped in such a way that its tip is in contact with the inner tube face or the outer tube face.

Description

[0036] In the drawings:

[0037] FIG. 1 shows a schematic, oblique view of a detail of the tube with the inventive structure on the inner tube face;

[0038] FIG. 2 shows a schematic view of a fin section with a different notch depth;

[0039] FIG. 3 shows a schematic view of a fin section with a structure element which protrudes over the primary groove;

[0040] FIG. 4 shows a schematic view of a fin section with a projection on the tip which is curved in the fin direction;

[0041] FIG. 5 shows a schematic view of a fin section with a projection with a parallel surface at the location furthest away from the tube wall;

[0042] FIG. 6 shows a schematic view of a fin section with two projections which are in contact with one another along the fin profile;

[0043] FIG. 7 shows a schematic view of a fin section with two projections which cross over one another along the fin profile;

[0044] FIG. 8 shows a schematic view of a fin section with two projections which are in contact with one another over the primary groove;

[0045] FIG. 9 shows a schematic view of a fin section with two projections which cross over one another over the primary groove.

[0046] Mutually corresponding parts are provided in all figures with the same reference signs.

[0047] FIG. 1 is a schematic, oblique view of a tube detail of the heat exchanger tube 1 with the inventive structure on the inner tube face 22. The heat exchanger tube 1 has a tube wall 2, an outer tube face 21 and an inner tube face 22. Helically circumferential continuous fins 3 are formed from the tube wall 2 on the inner tube face 22. The longitudinal tube axis A runs at a certain angle with respect to the fins 3. Continuously extending primary grooves 4 are formed between respectively adjacent fins 3.

[0048] The projections 6 are formed in groups 10 which repeat periodically along the fin profile. The projections 6 are formed between primary grooves 4 by making cuts into the fins 3 at a cutting depth transversely with respect to the fin profile to form fin segments and by raising the fin segments in a main orientation along the fin profile. The notch formations 7 are formed between the projections 6 within the group 10 with a changing notch depth in one fin 3.

[0049] FIG. 2 shows a schematic view of a fin section 31 with a different cutting depth or notch depth t.sub.1, t.sub.2, t.sub.3. The terms cutting depth and notch depth express the same concept within the scope of the invention. The projections 6 have alternately changing notch depths t.sub.1, t.sub.2, t.sub.3 by means of a fin 3. The original, shaped helically circumferential fin 3 is indicated by dashed lines in FIG. 2. The projections 6 are formed from said fin 3 by making cuts into the fin 3 at a notch/cutting depth t.sub.1, t.sub.2, t.sub.3 transversely with respect to the fin profile to form fin segments and by raising the fin segments in a main orientation along the fin profile. The different notch/cutting depths t.sub.1, t.sub.2, t.sub.3 are consequently measured at the notch depth of the original fin in the radial direction.

[0050] The projection height h is expediently defined in FIG. 2 as the dimension of a projection in the radial direction. The projection height h is then the distance starting from the tube wall as far as the point on the projection which is furthest away from the tube wall in the radial direction.

[0051] The notch depth t.sub.1, t.sub.2, t.sub.3 is the distance measured in the radial direction starting from the original fin tip as far as the deepest point of the notch. In other words: The notch depth is the difference between the original fin height and the residual fin height remaining at the deepest point of a notch.

[0052] FIG. 3 shows a schematic view of a fin section 31 with a structure element 6 which protrudes over the primary groove 4. This is a projection 6 which extends along the fin profile from the main orientation with the tip 62 over the primary groove 4. The wider the protrusion is made, the more intensive the disruption of the boundary layer of the fluid which is formed in the fin intermediate space, which brings about improved heat transfer.

[0053] FIG. 4 shows a schematic view of a fin section 31 with a projection 6 which is curved at the tip 62 in the direction of the fin. The projection 6 has a changing curvature profile at the curved tip 62. In this context, the local curvature radius decreases starting from the tube wall as the distance increases. In other words: The curvature radius becomes smaller along the line leading to the tip indicated by the points P1, P2, P3. This has the advantage that the condensate which is produced at the tip 62 in the case of two-phase fluids is transported more quickly to the fin foot by the increasing convex curvature. This optimizes the heat transfer when liquefaction occurs.

[0054] FIG. 5 shows a schematic view of a fin section 31 with a projection 6 with a parallel surface 61 at the location which is furthest away from the tube wall, in the region of the tip 62.

[0055] The fin sections 31 which are illustrated in FIGS. 3 to 5 can be integrated individually or else in large numbers into the respective groups.

[0056] FIG. 6 shows a schematic view of a fin section 31 with two projections 6 which are in contact with one another along the fin profile. Furthermore, FIG. 7 shows a schematic view of a fin section 31 with two projections 6 which cross over one another along the fin profile. FIG. 8 also shows a schematic view of a fin section 31 with two projections which are in contact with one another over the primary groove 4. FIG. 9 shows a schematic view of a fin section 31 with two projections 6 which cross over one another over the primary groove 4.

[0057] With the structure elements illustrated in FIGS. 6 to 9, it is advantageous, specifically in the reversible operating mode with two-phase fluids, that they form a type of cavity for the evaporation. The cavities of this particular type form the starting points for bubble nuclei of an evaporating fluid.

LIST OF REFERENCE SIGNS

[0058] 1 Heat exchanger tube [0059] 2 Tube wall [0060] 21 Outer tube face [0061] 22 Inner tube face [0062] 3 Fin [0063] 31 Fin section [0064] 4 Primary groove [0065] 6 Projection [0066] 61 Parallel surface [0067] 62 Tip [0068] 7 Notch formations [0069] 10 Group of projections [0070] A Longitudinal tube axis [0071] t.sub.1 First cutting depth [0072] t.sub.2 Second cutting depth [0073] t.sub.3 Third cutting depth [0074] h Projection height