Abstract
A heat exchanger tube with a tube axis, a tube wall and with ribs extending around on the tube outer side. The ribs have a rib foot, rib flanks and a rib tip, wherein the rib foot projects substantially radially from the tube wall. The rib flanks are provided with additional structural elements which are arranged laterally on the rib flank. First material projections, which extend substantially in the axial and radial direction, adjoin second material projections which extend substantially in the axial and circumferential direction of the tube, wherein the first and second material projections have a common boundary line. The axial extent of the first material projections along this boundary line is less than the axial extent of the second material projections.
Claims
1. A metal heat exchanger tube comprising a tube wall and fins on the tube outer side which have a fin root, fin flanks and a fin tip, wherein the fin root projects essentially radially from the tube wall, and the fin flanks are provided with additional structural elements which are arranged laterally on the fin flanks, wherein first material projections, which extend both in an axial direction and a radial direction wider than in a circumferential direction, and second material projections, which extend both in the axial direction and the circumferential direction wider than in the radial direction of the tube, are formed, and wherein the first material projections are arranged at a distance from the second material projections.
2. The metal heat exchanger tube as claimed in claim 1, wherein the first material projections extend from the fin tip in the radial direction and a radial extent of the first material projections is smaller than a radial distance of the second material projections from the fin tip.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIG. 1 shows a perspective partial view of a fin section of a heat exchanger tube with material projections according to the invention.
(2) FIG. 2 shows a section through the fin of a heat exchanger tube with an embodiment of the material projections according to the invention.
(3) FIG. 3 shows a section through the fin of a heat exchanger tube with a preferred embodiment of the material projections according to the invention.
(4) FIG. 4 shows a section through the fin of a heat exchanger tube with an especially preferred embodiment of the material projections.
(5) FIG. 5 shows a section through the fin of a heat exchanger tube with a further preferred embodiment of the material projections.
(6) FIG. 6 shows a section through the fin of a heat exchanger tube with first and second material projections in contact only at one point.
(7) FIG. 7 shows a section through the fin of a heat exchanger tube with first and second material projections at a distance from each other.
DETAILED DESCRIPTION OF THE INVENTION
(8) Parts which correspond to each other are provided with the same designations in all the figures.
(9) FIG. 1 shows a perspective partial view of a fin section of a heat exchanger tube 1 with material projections 41 and 42 according to the invention. From the tube outer side 21, only a part of one of the encompassing, integrally formed fins 3 is depicted. The fins 3 have a fin root 31, which is attached to the tube wall 2, fin flanks 32 and a fin tip 33. The fins 3 project radially from the tube wall 2. The fin flanks 32 are provided with additional structural elements which are designed as material projections 41 and 42. The material projections which are formed can be divided into two groups. First material projections 41 mainly extend in the axial and radial directions of the tube 1. Second material projections 42 mainly extend in the axial and circumferential directions of the tube. In FIG. 1, five first material projections 41 and three second material projections 42 are represented. First material projections 41 adjoin second material projections 42, wherein an angle greater than 90° is included on the boundary line 43. As a result of the material projections 41 and 42, the surface of the tube 1 is enlarged. Furthermore, the edges of the material projections 41 and 42 which face away from the fin flank represent convex edges 52 on which the condensation process preferably takes place.
(10) As is represented in FIG. 1 to FIG. 5, the axial extent x.sub.1 of the first material projections 41 along the boundary line 43 is smaller according to the invention than the axial extent x.sub.2 of the second material projects 42. As a result, only slightly pronounced, pocket-like structures 51 are created on the fin flank 32. Consequently, in the case of a heat exchanger tube 1 according to the invention, hardly any condensate can accumulate in the pocket-like structures 51, but the condensate drains off quickly. Little of the surface of the tube 1 is covered with a condensate film, which represents a considerable heat resistance. This is beneficial to the condensation process and the efficiency of the tube is increased.
(11) FIG. 2 shows in cross-section an advantageous embodiment of the heat exchanger tube 1 according to the invention, in which the first material projections 41 begin close to the fin tip 33 and extend in the radial direction of the tube 1 right up to second material projections 42. On account of the production process, the first material projections 41 cannot extend any further in the radial direction than as far as the second material projections 42. Therefore, the radial extent of the first material projections 41 is maximum if these begin at the fin tip 33. The surface of the tube 1 and the length of the convex edges 52 are then greatly increased. As represented in FIG. 2, the second material projections 42 are attached preferably approximately half way up the height of the fins 3. The radial extent of the first material projections 41 is therefore approximately equal to half the fin height in the case represented in FIG. 2.
(12) FIG. 3 shows in cross-section a particularly advantageous embodiment of the heat exchanger tube 1 according to the invention. The maximum axial extent x.sub.m of the first material projections 41 is in the region of the fin tip 33. Furthermore, the axial extent x.sub.1 of the first material projections 41 from the fin tip 33 towards the second material projections 42 is made smaller. The first material projections 41 therefore taper in the direction of the tube axis. Therefore, on the one hand, the surface of the tube 1 is enlarged even further by means of the first material projections 41 than in the case represented in FIG. 2. On the other hand, only small pocket-like structures 51, which can retain only little condensate, are formed.
(13) In the case of the embodiment of the heat exchanger tube 1 according to the invention represented in FIG. 4, the first material projections 41 have the shape of an ear. In their principle of operation, they are comparable with the first material projections 41 of the embodiment represented in FIG. 3. The maximum axial extent x.sub.m of the first material projections 41 is slightly further away from the fin tip 33 than in the case of the embodiment represented in FIG. 3.
(14) FIG. 5 shows in cross-section a further advantageous embodiment of the heat exchanger tube 1 according to the invention. The axial extent x.sub.1 of the first material projections 41 has a further local maximum between the fin tip 33 and the second material projections 42. The contour characteristic of the first material projections 41 is, however, selected so that the first material projections 41 taper tendentially from the fin tip 33 towards the second material projections 42. In the case of this advantageous embodiment, a large surface and especially a long length of the convex edge 52 are achieved. The pocket-like structures 51 in the region of the second material projections 42 extend only over a small area.
(15) As represented in FIG. 1 to FIG. 5, the axial extent x.sub.1 of the first material projections 41 along the boundary line 43 is at most half as large as the axial extent x.sub.2 of the second material projections 42. As a result, the effect is achieved of the pocket-like structures 51 having only a small prominence on the fin flank 32.
(16) A further aspect of the invention includes a heat exchanger tube 1 in which the first material projections 41 taper in the direction of the tube axis in such a way that they adjoin the second material projections 42 only at one point 44, as is represented in FIG. 6. This aspect of the invention represents the limit case in a way that the boundary line 43 depicted in FIGS. 1-5 between first 41 and second material projections is reduced to one point 44. The axial extent x.sub.1 of the first material projections 41 is equal to zero at this limit point 44. As a result, the size of the pocket-like structures 51 is further reduced. These can then accumulate even less condensate. On the other hand, the achievable surface enlargement in this case is smaller than in the cases represented in FIGS. 1-5. Therefore, it is advantageous that the first material projections 41 begin at the fin tip 33 in the case represented in FIG. 6.
(17) A further aspect of the invention includes a heat exchanger tube 1 in which the first material projections 41 are arranged at a distance from the second material projections 42. An advantageous embodiment of such a heat exchanger tube 1 according to the invention is represented in cross section in FIG. 7. The radial extent of the first material projections 41 does not reach from the fin tip 33 as far as the second material projections 42. The first material projections 41 do not make contact with the second material projections 42 at any point. The first material projections 41 extend from the fin tip 33 in the radial direction and the radial extent y.sub.1 of the first material projections 41 is smaller than the radial distance y.sub.2 of the second material projections 42 from the fin tip 33. The capillary forces, which hold the condensate in the pocket-like structures 51, are minimal in this case. On the other hand, only a smaller surface enlargement can be achieved in this case than in the cases represented in FIGS. 1-6. Therefore, it is particularly advantageous that the first material projections 41 begin at the fin tip 33 in the case represented in FIG. 7.
(18) The immersion process of the toothed wheel-like tool which is used for forming the material projections 41 and 42 according to the invention brings about a circumferentially asymmetrical displacement of the material of the fin flank 32. Therefore, two circumferentially adjacent, first material projections 41 can have different shapes.
(19) Furthermore, the solution according to the invention also embraces the fact that the structuring of the fin flanks described above is advantageous not only for the condensation of vapors, but can also have a performance-enhancing effect in other heat transfer processes. In particular, during the evaporation of liquids the evaporation process can be intensified as a result of the structures according to the invention.
LIST OF DESIGNATIONS
(20) 1 Heat exchanger tube 2 Tube wall 21 Tube outer side 3 Fin on the tube outer side 31 Fin root 32 Fin flank 33 Fin tip 41 First material projection 42 Second material projection 43 Boundary line 44 Boundary point 51 Pocket-like structure 52 Convex edge x.sub.1 Axial extent of the first material projections x.sub.2 Axial extent of the second material projections x.sub.m Maximum axial extent of the first material projections
