DE29705214U1 - Finned heat exchanger - Google Patents

Description

Vaillant ·<· &bull; &bull; 1521 &bull; *
·
··· U. John GmbH Co. GM

The invention relates to a plate heat exchanger according to the preamble of claim 1.

In conventional heat exchangers of this type, the pipes are soldered or welded to the shaft wall of a heating shaft, for example, or several pipes are connected to one another via elbows.

During operation of such a heat exchanger, the pipes fitted with fins, e.g. copper pipes, are subjected to strong expansion stresses between the heating shaft and the finned pipe or finned block due to the greatly differing temperatures. These expansion stresses may lead to the failure of the component.

Due to the different thermal expansion coefficients of the material of the fins and the material of the shaft wall, which is usually made of steel, thermal expansion occurs between the shaft wall and the fins when the pipes of the finned heat exchanger are soldered to the shaft wall. This causes the pipe connected to both components, usually a copper pipe, to deform so much that the soldering gap geometry required for the seal soldering is adversely affected. Due to the resulting leaks, some heat exchangers have to go through the soldering process a second time.

The aim of the invention is to avoid these disadvantages and to propose a finned heat exchanger of the type mentioned at the beginning in which these problems do not occur.

According to the invention, this is achieved in a plate heat exchanger of the type mentioned at the outset by the characterizing features of claim 1.

By using bushings, the thermal expansion behavior of the pipes can be influenced by choosing an appropriate material for the bushings, thus reducing the loads on the pipes. In particular, the problems mentioned above when soldering the pipes to a shaft wall can be avoided by using the bushings. In addition, this also results in a longer service life for the finned heat exchanger.

The features of claim 2 ensure good heat transfer from the pipe to the medium flowing through it via the bushing and thus also prevent the occurrence of boiling noises.

The features of claim 3 ensure that the soldering gaps are positively influenced during the soldering process, both when using a soldering foil and when welding the pipe to the shaft wall.

The features of claim 4 enable easier soldering of the pipes to the wall of the heating shaft, especially when the bushings are deformed, e.g. widened. This results in an improvement in the joining process and also an improvement in the flow guidance, which results in a reduction in the flow resistance.

It has proven particularly useful if the lamellae are made of a chromium-molybdenum-titanium steel, e.g. X2CrMoTi182 steel, and the tubes are made of a chromium-nickel-molybdenum-titanium steel, e.g. X6CrNiMoTi1722 steel.

The features of claim 5 result in the advantage of continuous protection of the pipe, which results in an increase in the service life of the heat exchanger.

The invention will now be explained in more detail with reference to the drawing. Fig. 1 and 2 schematically show various embodiments of the inventive plate heat exchanger.

The finned heat exchanger 1 according to the invention has a copper tube 2 onto which fins 3 are pushed and soldered or welded to the tube 2.

The slats 3 have openings surrounded by a collar 4 through which the tube 2 passes.

In the embodiment according to Fig. 1, a continuous bushing 5 is inserted into the pipe 2 and soldered to the pipe 2 over its entire surface. The continuous bushing is widened in the area of one end, just like the pipe 2, which is held in the area of this end in a hole 6 in a shaft wall 7. The widening 8 engages behind the shaft wall 7.

The second end of the pipe 2 is also held in a bore 6 of a second shaft wall 7' and engages behind it with an expansion 8.

In this end area, the continuous bushing 5 protrudes slightly from the pipe 2. The pipe 2 is soldered tightly into the shaft wall 7, T.

The embodiment according to Fig. 2 differs from that according to Fig. 1 only in that instead of a continuous bushing 5, bushings 5', 5" are inserted in the two end areas of the pipe 2, the bushing 2' being widened at one end in accordance with the widening 8 of the pipe 2.

The second bushing 5" has only continuously straight surface lines and ends essentially in the plane of the front side of the expanded pipe 2.

Both bushings 5', 5" are fully soldered to the inner wall of the pipe 2.

During operation of the heat exchanger, the pipe 2, which is usually made of copper, is subjected to strong expansion stresses between the shaft wall and the finned block due to very different temperatures. These expansion stresses ultimately lead to the failure of the component. By using the bushings 5, or 5' and 5" in the pipe 2, or by soldering the bushings over the entire surface into the pipe 2, these expansions can be reduced, whereby the full-surface soldering ensures a material-tight connection. This also ensures that the heat transfer is not impaired and boiling noises are avoided.

It is necessary to select a material whose coefficient of expansion is higher than the coefficient of expansion of the material of the slats in order to achieve good soldering gaps during the soldering process. The greater expansion of the socket 5, 5', 5" during the soldering process has a positive effect on both the soldered connection when using a foil and the expected welding of copper and stainless steel pipes.

Due to the different thermal expansion coefficients of the fin material and the shaft material, thermal expansion occurs between the shaft and fin 3 during the soldering process. This causes the pipe 2 connected to both components to deform so much that the solder gap geometry required for the seal soldering is adversely changed. Due to the resulting leaks, part of the heat exchanger has to go through the soldering process a second time. Here too, the soldering result is positively influenced by the use of the bushings 5, 5', 5".

The pipe 2 and the bushings 5, 5', 5" can be designed with smooth walls, whereby the bushings can protrude more or less far from the pipe 2. The bushings 5, 5', 5" can vary in their length. Deformations of the pipe or bushing ends are also conceivable, which make the joining process easier, allow for a better soldering result, make the assembly of pipe bends easier and bring advantages in terms of flow guidance or a reduction in pressure loss.

Claims (1)

Joh. Vaillant GmbH u. Co. GM 1521 EXPECTATIONS Fin heat exchanger with fins (3) made of a good heat-conducting material, e.g. copper, pushed onto a tube (2) made of a good heat-conducting material and soldered or welded to the tube (2), the tube (2) being soldered into a wall (7, 7 ¹ ) of a heating shaft, characterized in that a bushing (5, 5', 5") is pushed into the interior of the tube (2) and soldered or welded to it. Plate heat exchanger according to claim 1, characterized in that the bushing (5, 5', 5") is soldered or welded to the pipe (2) over its entire length. Fin heat exchanger according to claim 1 or 2, characterized in that the bushing (5, 5', 5") has a thermal expansion coefficient which is greater than that of the fins (3). Plate heat exchanger according to one of claims 1 to 3, characterized in that the bushings (5, 5', 5") protrude from the tube (2) and are optionally deformed. A finned heat exchanger according to claim 1, characterized in that a bushing (5) extending over the length of the tube (2) is inserted into the tube (2) and soldered to the tube (2), one end of the continuous bushing (5) being deformed if necessary.