EP0733871B1 - Heat transfer tube for a heat exchanger - Google Patents

Abstract

The pipe (1) has a smooth outer surface (2) and a structured inner surface (3) having parallel ribs (7) running at an angle ( alpha ) of 90 degrees to the longitudinal axis (6) of the exchange pipe. The ribs have sloping flanges (8) and form channels (13) and cross running troughs (14). The middle longitudinal plane of the troughs runs at 90 degrees to the longitudinal axis of the exchange pipe. The troughs have a sine curve formed shape in their longitudinal cross-section and are formed with a micro roughness (16) upper surface (8,10,11) and have rounded ribbed (7) heads. The oppositely lying, neighbouring ribs of the flanges are connected to the channel soles (12) by rounded transitions (11).

Description

The invention relates to an exchanger tube for a heat exchanger according to the features in the preamble of the claim 1.

Such an exchanger tube counts through the US-PS 53 32 034 on the prior art. Both the Ribs as well as the channels laterally delimited by the ribs each have a trapezoidal cross-section. The cross-sectional volume the rib is about half the size of that Dimensioned cross-sectional volume of the channels.

The troughs formed in the ribs are rolled manufactured. Here, the deformed from the ribs bulges Material into the channels at the front of the troughs. The floors the troughs are at a distance from the canal bases.

The known exchanger tube is manufactured by that first in a two-stage rolling process Structure of the later inner surface on one side Metal band created, then the metal band into one Slotted tube with internal surface structure formed is and then the slot edges are welded.

The two-stage rolling of the inner surface structure leads at a high manufacturing cost. There are several roll stamping tools required, which affect the economy. The troughs of the ribs are created by rolling over an initially existing volume fraction of that in the first rolling step pronounced ribs. This former volume share the ribs are distributed only in the immediate vicinity. A notable reduction in meter weight can but cannot be achieved.

Furthermore, it may be due to the flatness of the head sides and the flanks of the ribs in practical use for education of condensate films that are difficult to tear open and delay the condensation come, so that barrier layers with heat insulating Form properties. Stand for evaporation only a few edges available as vapor bubble germs.

The object of the invention is based on the prior art is based on an exchanger tube with an internal surface structure to create, in which on the one hand the Advantages of an equally good evaporation or condensation performance connect with reduced rib weight and on the other hand, a one-stage for the production of the exchanger tube Embossing process can be applied.

According to the invention, this object is achieved in the Features listed in the characterizing part of claim 1.

The core of the invention is such an internal rough surface structure, which has only rounded transitions and avoids sharp edges. Consequently, it can be particularly advantageous Way the rough surface structure by roll embossing generated in a single stage. The apparatus technology This significantly reduces effort.

Furthermore, it is now in terms of intensifying heat transfer between that flowing in the exchanger tube Fluid and the coarse surface structure of advantage that the Surfaces of the ribs up to the channel soles additionally be provided with a targeted micro roughness. This is particularly useful in condensation and evaporation of refrigerants noticeable when the exchanger tube is in one appropriate heat exchanger is incorporated. The cross-sectional volume the ribs is in favor of increasing the Number of ribs has been reduced. This makes it possible to heat-exchanging surface structure and thus enlarge to improve the heat transfer. Also in this Connection of very slim ribs and thus narrow channels be generated. The ribs rounded at the head have in particular the advantage that when pulling in an exchanger tube in fins of a heat exchanger, in particular by Widening by means of a moving through the exchanger tube Tool, the head areas of the ribs flattened only slightly be, so that with this also the formation of heavy tearable condensate films are effectively counteracted. Nevertheless, due to the large roughness due to the micro Rib surfaces which are advantageous for effective evaporation large number of projections, edges, tips and depressions can be provided as vapor bubble germs without that larger quantities of material are required for this.

The surfaces of the slats can also be coated with a Coarse structure corresponding to the internal structure of the exchanger tubes and / or be provided with a micro roughness.

The invention is applied to exchanger tubes Metal, but especially copper or copper alloys. Such exchanger tubes can e.g. a round or oval Have cross-section. Round exchanger tubes are preferred an outer diameter of about 6 mm to 20 mm.

Basically, it is conceivable according to the invention that the The median longitudinal planes of the troughs are parallel to one another, however run offset to one another in the longitudinal direction of the ribs.

In contrast, the embodiment according to claim 2 provides that the median longitudinal planes of the troughs of adjacent ribs run in alignment.

The micro-roughness of the fin surfaces can vary Way to be realized. For example a diffuse roughening by blasted corundum is conceivable. It is also conceivable to notch the rib surfaces in Form of linear micro-grooves (claim 3). These micro grooves then preferably extend parallel to each other. However, their longitudinal direction deviates from the longitudinal direction of the Ribs off.

The micro-roughness can also claim accordingly 4 by intersecting, from the longitudinal direction deviating micro grooves are formed in the ribs.

Instead of continuous micro grooves, you can also selectively Recesses are provided. These can also be linear or arranged in a cross in a row at a distance his.

The generation of the micro roughness can also be different Way. A preferred variant is here seen in the features of claim 5. Here is the micro roughness of the fin surfaces by radiation with hard particles, e.g. Corundum, or by texturing produced by means of laser beams. It is possible either that already provided with the surface structure To process the starting material (sheet metal strip) accordingly an embossing roller itself with the desired negative micro roughness to provide.

Profiling of the embossing roller by spark erosion is possible.

Internal investigations have shown that it is to achieve equally good condensation and evaporation performance according to claim 6 is advantageous if the depth the microroughness is dimensioned 0.075 mm or less.

According to claim 7, the flank angle of the ribs 5 ° to 60 °, however, preferably 10 ° to 40 °. In this way a very slim rib contour can be produced.

The course of the fins relative to the longitudinal axis of the exchanger tube takes place according to the features of claim 8 an angle of 1 ° to 89 °, preferably 20 ° to 55 °.

It also makes sense if according to claim 9 the between the longitudinal direction of the ribs and the Intermediate longitudinal planes of the troughs included angles of 90 ° and is smaller.

According to claim 10, it is advantageous if the distance between two adjacent ribs 0.10 mm to 2.0 mm, preferably 0.26 mm up to 0.6 mm.

The height of the fins will vary depending on the pipe diameter Claim 11 suitably between 0.03 mm to 1.0 mm, preferably 0.05 mm to 0.35 mm, dimensioned.

Furthermore, it is an advantage if after Claim 12 the distance between two adjacent troughs one Rib is 0.2 mm to 4.0 mm, preferably 0.3 mm to 1.0 mm.

The floors of the troughs and the channel soles must meet the requirements 13 do not lie on one level. The minimum distance the trough bottoms from the canal bases should then at least 0.01 mm.

According to the features of claim 14, it is also conceivable that the trough floors and the channel soles in the same Level.

Figur 1

in der Perspektive einen Längenabschnitt eines Austauscherrohrs;

Figur 2

in der Draufsicht einen Längenabschnitt eines strukturierten Blechbands;

Figur 3

in der Perspektive den Ausschnitt III der Figur 2;

Figur 4

in vergrößerter Darstellung einen vertikalen Querschnitt entlang der Linie IV-IV der Figur 2;

Figur 5

einen vertikalen Längsschnitt entlang der Linie V-V der Figur 4 und die

Figuren 6 und 7

anhand von Diagrammen einen Leistungsvergleich an Wärmeaustauschern in Koaxialbauweise mit verschiedenen Rohrausführungen.

The invention is explained in more detail below on the basis of exemplary embodiments illustrated in the drawings. Show it:

Figure 1

in perspective a length section of an exchanger tube;

Figure 2

in plan view a length section of a structured sheet metal strip;

Figure 3

in perspective the section III of Figure 2;

Figure 4

in an enlarged view a vertical cross section along the line IV-IV of Figure 2;

Figure 5

a vertical longitudinal section along the line VV of Figure 4 and

Figures 6 and 7

Based on diagrams, a performance comparison of heat exchangers in coaxial design with different pipe designs.

1 in FIG. 1 is a longitudinal section of a longitudinally welded seam Exchanger tube otherwise not closer to you heat exchanger shown for condensation and evaporation referred to by refrigerants.

The exchanger tube, which is circular in the outside and inside cross section 1 has a smooth outer surface 2 and a structured inner surface 3. To fix the exchanger tube 1 in one of several, possibly parallel to one another Exchanger tubes 1 pass through fins of a heat exchanger is the exchanger tube 1 in one at its Outside diameter adapted opening introduced in the lamella and set by widening in the opening. To this Purpose is a correspondingly trained one, not shown Expanding tool moved through the exchanger tube 1.

In the exemplary embodiment, the exchanger tube 1 has one Outside diameter D of 9.52 mm.

The exchanger tube 1 is produced from a Flat sheet metal strip, not shown, on both sides Copper. The sheet metal strip is a one-step roll stamping process subjected, whereby according to the representation of Figures 2 and 3 one side of the metal strip 4 remains smooth (the later one outer surface 2 of the exchanger tube 1) and the other Side with a textured surface (the later inside 3 of the exchanger tube 1) is provided. Only that the edge regions 5 of the sheet metal strip 4 used for welding (Figure 2) remain unstructured. After the roll embossing the metal strip 4 is formed into a slotted tube and then longitudinally welded and divided to length.

The structure of the inner surface 3 of the exchanger tube 1 will be explained in more detail with reference to Figures 2 to 5.

It comprises at an angle α of 45 ° to the longitudinal axis 6 of the Exchanger tube 1 parallel ribs 7 (Figures 2 and 3) with inclined flanks 8 (Figures 3 and 4). The Flank angle β of the ribs 7 is in the embodiment 20 ° and the distance A between two adjacent ribs 7 0.35 mm (Figures 2 and 4). Its height H is 0.30 mm (Figure 4). The base section connecting the ribs 7 in the foot area 9 has a thickness D1 of 0.30 mm (Figure 5).

It can also be seen from FIGS. 3 and 4 that both the head regions 10 of the ribs 7 and the transitions 11 are rounded from the flanks 8 to the channel soles 12. The Cross-sectional volume of the ribs 7 is smaller than the cross-sectional volume the channels 13 dimensioned between the ribs 7.

As particularly illustrated in FIGS. 3 and 5, is each rib 7 seen in longitudinal section with a sinusoidal Comb line. Because of this sinusoidal wave crest the ribs 7 in their longitudinal directions LR are in the Ribs 7 transverse troughs 14 are formed. Like this one 2 shows, troughs 14 are adjacent Ribs 7 at an angle γ of 45 ° to the longitudinal axis δ of the exchanger tube 1 aligned one behind the other. The between the longitudinal direction LR of the ribs 7 and the central longitudinal planes MLE of the troughs 14 included angle δ 90 °. The distance A1 between two in the longitudinal direction of a rib 7 adjacent troughs 14 0.50 mm (Figures 2 and 5) and the Distance A2 of the trough floors 15 from the channel soles 12 is 0.01 mm. The troughs 14 have a depth T1 of 0.25 mm (Figures 4 and 5).

Like FIG. 5 in a deliberately exaggerated representation of the wave crest of the ribs 7, the surfaces 8, 10, 11 of the ribs 7, i.e. the head areas 10, the Flanks 8 and the transitions 11 from the flanks 8 to the channel soles 12, but possibly also the channel soles 12, with a Microroughness 16 provided, the depth T is 0.005 mm.

The microroughness 16 is produced in the exemplary embodiment immediately during roll stamping. This is the embossing roller by means of radiation from corundum with a negative diffuse surface structure has been provided then the creation of the surface structure at the later inner surface 3 of the exchanger tube 1 guaranteed.

Due to the structured inner surface 3, the in Figure 1 does not illustrate exchanger tube 1 in comparison only to an exchanger tube with a smooth inner surface, but also to an internally grooved exchanger tube a much better heat transfer coefficient k '(W / mK).

This fact is from the due to comparative studies created diagrams according to Figures 6 and 7 recognizable without additional explanations (Figure 6 -Condensation, Fig. 7 - evaporation).

List of reference symbols

1

Exchanger tube

2nd

outer surface v. 1

3rd

inner surface v. 1

4th

Metal strip

5

Marginal areas v. 4th

6

Longitudinal axis v. 1

7

Ribs

8th

Flanks v. 7

9

Base section v. 4th

10th

Head areas v. 7

11

Transitions v. 8 on 12

12th

Channel soles

13

channels

14

Hopper

15

Trough floors

16

Micro roughness

A

Distance between two adjacent ribs 7

A1

Distance between two adjacent MLE on a rib 7

A2

Distance from 12 to 15

D

Outer diameter of 1

D1

Thickness v. 9

H

Height of 7

LR

Longitudinal direction v. 7

MLE

Middle longitudinal planes of directly adjacent troughs 14 on different ribs 7

T

Depth of 16

T1

Depth of 14

α

Angle between 6 u. 7

β

Flank angle v. 7

γ

Angle between 6 u. MLE

δ

Angle between LR and MLE

Claims (14)

1. Exchanger tube for a heat exchanger, which tube exhibits a smooth outer surface (2) and a structured inner surface (3) which is formed of parallel ribs (7) having inclined flanks (8) and running at an angle (α) other than 90° to the longitudinal axis (6) of the exchanger tube (1), of channels (13) bounded laterally by the ribs (7) and of hollows (14) formed in the ribs (7) and running transversely, the median longitudinal planes (MLE) of the hollows (14) running at an angle (y) other than 90° to the longitudinal axis (6) of the exchanger tube (1), characterised in that the hollows (14) are formed by sinusoidal shaping in the longitudinal section of the ribs (7) provided with a microroughness (16) as regards their surfaces (8, 10, 11) and rounded at the top, the facing flanks (8) of neighbouring ribs (7) being connected to the channel beds (12) by rounded junctions (11) .
2. Exchanger tube according to claim 1, characterised in that the median longitudinal planes (MLE) of the hollows (14) of neighbouring ribs (7) run in alignment.
3. Exchanger tube according to claim 1 or 2, characterised in that the microroughness (16) of the rib surfaces (8, 10, 11) is formed by microgrooves running parallel to one another in other than the longitudinal direction (LR) of the ribs (7).
4. Exchanger tube according to claim 1 or 2, characterised in that the microroughness (16) of the rib surfaces (8, 10, 11) is formed by microgrooves intersecting in a cruciform pattern in other than the longitudinal direction (LR) of the ribs (7).
5. Exchanger tube according to one of claims 1 to 4, characterised in that the microroughness (16) is produced by blasting with particles or by means of laser beams.
6. Exchanger tube according to one of claims 1 to 5, characterised in that the depth (T) of the microroughness (16) is 0.075 mm or less.
7. Exchanger tube according to one of claims 1 to 6, characterised in that the flank angle (β) of the ribs (7) is 5° to 60°, preferably 10° to 40°.
8. Exchanger tube according to one of claims 1 to 7, characterised in that the longitudinal direction (LR) of the ribs (7) runs at an angle (α) of 1° to 89°, preferably 20° to 55°, to the longitudinal axis (6) of the exchanger tube (1).
9. Exchanger tube according to one of claims 1 to 8, characterised in that the angle (δ) enclosed between the longitudinal direction (LR) of the ribs (7) and the median longitudinal planes (MLE) of the hollows (14) is 90° or less.
10. Exchanger tube according to one of claims 1 to 9, characterised in that the distance (A) between two neighbouring ribs (7) is 0.10 mm to 2.0 mm, preferably 0.26 mm to 0.6 mm.
11. Exchanger tube according to one of claims 1 to 10, characterised in that the height (H) of the ribs (7) is 0.03 mm to 1.0 mm, preferably 0.05 mm to 0.35 mm.
12. Exchanger tube according to one of claims 1 to 11, characterised in that the distance (A1) between two neighbouring hollows (14) of a rib (7) is 0.2 mm to 4.0 mm preferably 0.3 mm to 1.0 mm.
13. Exchanger tube according to one of claims 1 to 12, characterised in that the hollow bottoms (15) are arranged at a distance (A2) from the channel beds (12).
14. Exchanger tube according to one of claims 1 to 12, characterised in that the hollow bottoms (15) are arranged in the same plane as the channel beds (12).

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