Method for bonding an aluminum rib to a steel pipe and heat exchanger having a unit produced in this way

Abstract: The invention relates to a method for bonding an aluminum rib to a steel pipe, a surface coating material of the steel pipe being used as the bonding material, so that supplying a separate soldering material, for example, may be dispensed with. The invention additionally relates to a heat exchanger which comprises a unit made of steel pipe and aluminum rib produced according to the method. (end of abstract)

Method for bonding an aluminum rib to a steel pipe and heat exchanger having a unit produced in this way description/claims

Brief Patent Description

Full Patent Description

Patent Application Claims

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority document 07020245.2 filed in Europe on Oct. 16, 2007, the entire contents of which are incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for bonding an aluminum rib to a steel pipe. Furthermore, the invention relates to a heat exchanger, preferably a condenser and in particular an air-cooled condenser, for industrial facilities and in particular for power plants, which comprises a unit or module produced according to the method.

2. Description of Related Art

Heat exchangers of the relevant type typically have, as described, for example, in EP 1 553 379 A1, a distributor pipe (preferred embodiment as a single-pipe system; SPS), whose external surface is at least partially provided with cooling ribs. The heat exchange (energy exchange process) occurs in that a first medium (or fluid) flowing through the distributor pipe and cooling down dissipates its heat into the cooling ribs surrounding the distributor pipe, which have a second medium or fluid, such as coolant air or coolant gas in particular, flowing around them, the heat being discharged to this second medium. A heat exchange is also possible in the reverse direction, of course.

If the first medium to be cooled is in a gaseous state upon entry into the heat exchanger, depending on the cooling gradient, condensation thereof may be achieved. Therefore, heat exchangers of this type are also used as condensers. In power plants, such condensers are used to condense the exhaust steam of steam turbines. Increasing water shortages and/or rising costs for the purchase and provision of coolant water have had the result that air-cooled condensers (ACC) are used ever more frequently in power plants in particular. However, using such heat exchangers in cooling devices in industrial facilities of the chemical and food industries is also known.

The distributor pipe (only pipe hereafter) is typically a steel pipe. This steel pipe is typically implemented as coated with a metal having good heat conduction, such as aluminum in particular. The cooling ribs themselves also essentially comprise aluminum. In addition to the good heat conductivity already mentioned, this offers the further advantage of saving weight, because the air-cooled heat exchangers or condensers, which are typically quite large, would otherwise be too heavy, which would result in disadvantages for transport and mounting.

The bond between pipe and aluminum cooling ribs is produced in a soldering process. For this purpose, the pipe is aluminum plated (typically already at the producer) and bonded to the aluminum ribs at a soldering temperature of approximately 600° C. For this purpose, the pipe must be heated up and cooled down again after the soldering procedure, however. Such a method therefore has a high power demand and/or power consumption. Furthermore, the different coefficients of thermal expansion are also problematic, which may result in warping tensions, whose prevention requires a complex process control.

DE 100 57 180 A1 makes suggestions to solve some of these problems. The provided suggestions result in heat exchangers having poor efficiencies, however.

BRIEF SUMMARY OF THE INVENTION

The object of the invention is to specify a method for bonding an aluminum rib to a steel pipe, which has a lower power demand. It is also the object of the invention to specify a heat exchanger (of the type cited at the beginning) having high efficiency, for whose production a lower power demand is required than in the prior art. Both the method and also the heat exchanger are additionally to allow cost-effective maintenance of the manufacturing.

This object is achieved by a method according to Claim 1, by a heat exchanger according to the first concurrent claim, and by the specified use according to the second concurrent claim. Advantageous refinements and embodiments are the subject matter of the particular dependent claims.

The method according to the invention for bonding an aluminum rib to a steel pipe comprises at least the following steps:

- providing at least one first component in the form of a surface-coated steel pipe,
- providing at least one second component in the form of an aluminum rib,
- bringing these components into contact, and