Tube bundle heat exchanger

Abstract

A tube bundle heat exchanger having a tube sheet, an outer shell and an interior. The heat exchanger includes a tube bundle having tubes located in the interior for fluid flow. The tubes have outside ribs and a channel is formed between adjacent ribs. The tube sheet has openings as passage points. Outer fins of the tubes project into the openings, and a joint gap is formed between an inner surface defining the opening and the outer fins of a tube located therein. The tubes are bonded to the tube sheet by joining material with the involvement of the outer fins. The bond is only formed in a first portion of the opening. The first portion is filled with joining material such that a second portion of the opening remains which is not filled with joining material, and the tube has outer fins adjacent the second portion.

Claims

1. A tube bundle heat exchanger, comprising: an enveloping outer shell; at least one tubesheet, the outer shell and the at least one tubesheet together defining an interior of the tube bundle heat exchanger; a tube bundle having a plurality of heat exchanger tubes arranged in the interior and through which a first fluid can flow, the heat exchanger tubes having helically circumferential integral fins formed on an outside of the heat exchanger tube and having a fin foot, fin flanks, a fin tip and a channel having a channel bottom formed between the fins; at least one inlet at the outer shell for introducing a second fluid into the interior, and at least one outlet at the outer shell for discharging the second fluid from the interior; wherein: the at least one tubesheet has openings as passage points, each opening having an inner surface, the heat exchanger tubes project at least with their outer fins into the openings of the at least one tubesheet, and a joint gap is formed in each case between the inner surface of an opening and the outer fins of a heat exchanger tube located inside the opening, the heat exchanger tubes, via joining material and the outer fins, have a material-bonded connection to the at least one tubesheet, the material-bonded connection being formed only in a first portion of the opening extending in an axial direction from an end face of a heat exchanger tube and, in the first portion, the joint gap is filled with joining material so that a second portion of the opening remains, the joint gap not being filled with joining material in the second portion, the heat exchanger tube continuing to have outer fins on the outside of the heat exchanger tube in a region of the second portion.

2. The tube bundle heat exchanger as claimed in claim 1, wherein the first portion filled with joining material accounts for less than 70% of a length of an entirety of the joint gap in the axial direction.

3. The tube bundle heat exchanger as claimed in claim 1, wherein a clear width between the fin tips of a heat exchanger tube and the inner surface of the opening is not more than 30% of a fin height, measured from the channel bottom to the fin tip.

4. The tube bundle heat exchanger as claimed in claim 1, wherein the material-bonded connection is configured to be gas-tight and pressure-resistant.

5. The tube bundle heat exchanger as claimed in claim 1, wherein the heat exchanger tubes have a tube inside diameter in the openings as passage points, the tube inside diameter being is greater than a tube inside diameter of the heat exchanger tubes outside of the passage points.

6. The tube bundle heat exchanger as claimed in claim 1, wherein the heat exchanger tubes are soldered, adhesively bonded or welded into the at least one tubesheet.

7. The tube bundle heat exchanger as claimed in claim 1, wherein the tube bundle heat exchanger includes at least one plenum box arranged at the at least one tubesheet for distributing, diverting or collecting the first fluid.

8. The tube bundle heat exchanger as claimed in claim 1, further comprising support plates disposed to support the heat exchanger tubes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention will be explained in greater detail with reference to the schematic drawings, in which:

(2) FIG. 1 shows, schematically, a side view of a tube bundle heat exchanger with a detail view of a heat exchanger tube having outer fins;

(3) FIG. 2 shows, schematically, a front view of a detail of a tubesheet with a passage point;

(4) FIG. 3 shows, schematically, a perpendicular section of the tubesheet in the plane of the passage point of the heat exchanger tubes; and

(5) FIG. 4 shows, schematically, a detail view of a section of a material-bonded connection of the tubesheet to a heat exchanger tube.

(6) Parts which correspond with one another are provided with the same reference signs in all the figures.

DETAILED DESCRIPTION

(7) FIG. 1 shows, schematically, a side view of a tube bundle heat exchanger 1 having an enveloping outer shell 2 and two tubesheets 3, which together define an interior 4 of the tube bundle heat exchanger 1. The tube bundle heat exchanger 1 comprises a tube bundle having a plurality of heat exchanger tubes 5 which are arranged in the interior 4 and through which a first fluid for heat transfer can flow and which are supported by additional support plates 6. Such support plates 6 are often also additionally used as guide plates for the fluid flow. The tube bundle heat exchanger 1 additionally comprises plenum boxes 7, which distribute, divert or collect the first fluid in the interior of the heat exchanger tubes as required. There are provided at least one inlet 8 at the outer shell 2, by way of which inlet a second fluid for heat transfer can be introduced into the interior, and at least one outlet 9 by way of which the second fluid can be discharged from the interior. In the detail view, a heat exchanger tube 5 having outer fins 51 is magnified. By means of a rolling process which is otherwise known, integral fins 51 formed on the outside of the tube and running helically around the tube axis A are formed.

(8) FIG. 2 shows, schematically, a front view of a detail of a tubesheet 3 with passage points 31 each having an inner surface 311. At a passage point 31, the opening in the tubesheet 3 is preferably of such a size that a heat exchanger tube 5 can be introduced with its outer fins 51 into the opening and connected there by a material-bonded connection. Welded, adhesively bonded and soldered connections, as the material-bonded connection 20, can be carried out at the passage point 31, starting from the end face, over a first portion of the wall thickness of a tubesheet 3 and enter into a fluid-tight connection. In a second portion extending into the depth, a remainder, not visible in FIG. 2, of the joint gap that is not filled is retained in the tubesheet wall 3.

(9) FIG. 3 shows, schematically, a perpendicular section of the tubesheet 3 in the plane of the passage point 31 of a heat exchanger tube 5. The heat exchanger tube 5 shown has outer fins 51 on the outside. In the exemplary embodiment shown, the heat exchanger tube 5 passes through the tubesheet 3 at the opening 31 as the passage point. At this passage point 31, the heat exchanger tube 5 has continuous outer fins 51. A material-bonded connection 20, which has not yet been made in FIG. 3, for example in the form of a continuous weld seam with the tubesheet 3 around the tube circumference, is located, after the joining operation, in a portion of the joint gap 10. Depending on the material combination of the tubesheet 3 and the heat exchanger tube 5, advantageous intermetallic new phase formations in the melt bath can occur at the weld point 20. A suitable method for producing a material-bonded connection with a locally limited melt flow is in particular laser welding.

(10) FIG. 4 shows, schematically, a detail view of a section of a material-bonded connection 20 of the tubesheet 3 to a heat exchanger tube 5. In the embodiment shown, the heat exchanger tube 5 has been inserted in the direction of the tube axis A into the opening 31 formed in the tubesheet 3 and is flush at the end face 53 with the outer surface of the tubesheet.

(11) The heat exchanger tubes 5 have helically circumferential integral fins 51 which are formed on the outside of the tube and have a fin foot 511, fin flanks 512 and a fin tip 513. A channel 52 having a channel bottom 521 is formed between adjacent fins 51. In FIG. 4 there is shown as the material-bonded connection 20 a weld seam, which forms, for example, during laser welding. Welding additives that are suitable in terms of the material are optionally used during the joining. In this way, the material flow and the quantity can also be matched precisely to the desired joint connection. In the case of the material-bonded connection shown, for reasons relating to the process both certain regions of the tubesheet 3 and some outer fins 51 on the heat exchanger tube 5 are also at least partially melted and integrated as joining material 20 as a result of the heat input of a laser. During the joining, the melt, starting from the end face 53, enters the joint gap 10, but is blocked after a certain penetration depth, so that only a first portion 101 of the joint gap 10 at the end face is filled with the involvement of the outer fins 51. Further passage of the melt is prevented by a fin 51 which, owing to the decreasing temperature at the melt front, is no longer melted or flowed around and thus functions as a barrier. In this way, there is a defined flow process of the joining material 20 during the joining operation, which can close the joining point completely at or in the vicinity of the tube end face 53.

(12) The heat exchanger tubes 5 thus have a material-bonded connection 20 to the tubesheet 3, which connection is formed only in a first portion 101 of the opening 31 extending in the axial direction from the end face 53 of a heat exchanger tube 5. A second portion 102 of the opening 31 is not filled with joining material. In the second portion 102, the heat exchanger tube 5 continues to have outer fins 51 on the outside of the tube.