DE9103291U1 - Radiator for room temperature control and device for producing sections of the radiator - Google Patents

Description

U 215 Ma (Dr.S/lz) 9 September 1991

Radiator for room temperature control and device for producing sections of the radiator

Radiators for room temperature control are used for heating buildings. The material of such radiators is selected based on aspects such as formability and reasonable raw material and processing costs. Modern radiators are increasingly made of aluminum or an aluminum alloy, e.g. AlMgSi 0.5. Radiators made of iron or an iron alloy are also still used. Unless you want to pay the costs for corrosion-resistant steel, there is often a risk that the heat-emitting heat transfer fluid in the radiators will gradually destroy the radiator from the inside through corrosion.

The risk of corrosion of iron or iron alloys due to oxygen content in the heat exchange fluid does not require any further explanation. However, in the case of aluminum and aluminum alloys, there is also a considerable risk of corrosion due to the formation of AlOH or, in special cases, other aluminum compounds. In the particularly common case where water or steam is used as the heat-emitting heat transfer fluid, it can be assumed that a residual content of 0.5 to 1 mg/l of oxygen in the water or steam is still relatively harmless, even in continuous operation. However, there are a number of cases in which this oxygen content is permanently exceeded, causing considerable corrosion. This applies, for example, when the radiator is connected to a domestic water circuit. To a somewhat lesser extent, comparable effects occur when an installer in a closed heating water system

or heating steam circuit, the heating fluid is constantly renewed by filling it with service water. In other cases, a closed heat transfer fluid circuit can have a leak through which oxygen from the surrounding atmosphere constantly seeps into the heat transfer fluid circuit. Finally, it also happens that sections are built into a closed heat transfer fluid circuit in which oxygen can slowly diffuse directly through the material used, especially when certain plastics are used.

An installer usually counteracts the oxidation risk described above by adding oxygen-binding agents to a closed heat transfer fluid circuit, usually in excess as a precaution. The excess of such oxygen-binding agents can very easily cause the pH value of the heat transfer fluid in the closed circuit to continuous operating limits of 9 and more in the alkaline range, so that corrosive reaction products are now formed between the material of the radiator and the chemicals added in excess. The reaction products can vary depending on the type of chemical additive. The effect of such risks of damage cannot be predicted by the specialist who installed the heating system, as he does not know the practice of the respective installer. Similar unforeseeable risks of damage exist when connecting the radiator to a district heating system, as experience has shown that foreign chemicals can migrate intermittently, which are then harmful even in continuous operation. In addition to chemicals deliberately added to the district heating system, decomposition products in the pipe system are also a possibility.

Corrosion problems can also occur with heat transfer fluids other than water or steam.

As can be seen from the above cases, the materials that are normally used for radiators cannot be optimally selected as corrosion-resistant materials, if one ignores the particularly costly case of using stainless steel or corrosion-resistant

chromium/nickel steels, which also require additional effort during processing.

People have already thought about anodizing the inner surface of known radiators, e.g. made of aluminum or an aluminum alloy. However, this has resulted in technical problems that are difficult to overcome.

The invention is based on the object of creating a radiator for room temperature control by means of a heat-emitting heat transfer fluid, in particular water or water vapor, using the materials usually used for radiator construction, but which is also reliably protected on the inside against corrosive influences of the type of heat transfer fluid mentioned on the usual materials.

This object is achieved in a radiator according to the preamble of claim 1 by its characterizing features.

The generic term of claim 1 refers to the usual design of a radiator with inlets and outlets for the heat transfer fluid and at least one radiator section which effects the heat exchange between the heat exchange fluid and the ambient air.

In the radiator according to the invention, only an outer wall area of the respective heat-exchanging radiator section is made of conventional material, while an inner wall is also inserted, which consists of material resistant to the corrosion effects of the heat transfer fluid or is pretreated accordingly. Metallic materials are expediently used for the inner wall and the outer wall. The surface connection between the outer and inner walls of the respective radiator section has little effect on its thermal conductivity, especially if metals that are good heat conductors are chosen for the inner wall. The inner wall does not need to be very thick, and the overall design can be such that the inner and outer walls together, i.e. not just the outer wall, provide the required static strength. By connecting the respective inner wall to the inflow and outflow, the heat transfer fluid can be reduced to a minimum.

is closed, you can see the entire area of the radiator
The flow-carrying areas of the heat transfer fluid are corrosion-resistant. A flow-carrying connection of the inlets and outlets to the usual material of radiators is avoided. A mechanical connection between the inlets and outlets and the outer wall area can also be completely dispensed with.
of the respective radiator.

The inner and outer walls of the radiator section refer to the areas that conduct the heat transfer fluid in a tubular manner. Heat exchange ribbing on the outer wall can also be present, either integrally with the outer wall or connected to it in a heat-conducting manner as a separate structural part.

In principle, it is possible for the inner wall of the radiator and the inlets and outlets to be made of different materials that are corrosion-resistant to the heat exchange fluid, as long as the parts can be tightly connected to one another. Preferably, however, the inlets and outlets as well as the inner wall of the respective radiator section are made of the same material.

The invention also includes radiators
which have only one heat transfer effective radiator section. In particular, however, the invention is concerned with
such radiators in which several radiator sections are arranged in a register arrangement. In particular, the design according to claim 4 with collecting pipes is considered, but without the design with connecting elbows, which is also known per se.
to want to exclude.

The invention relates to the preferred
Manufacturing method of double-walled radiator sections primarily with radiator sections that run in a straight line.
However, the invention also provides a manufacturing method in which an expansion operation in such radiator sections is carried out by utilizing the centrifugal force of an expansion tool.
which are curved to a certain extent in relation to a straight axis. Straight-line radii

Gate sections are therefore only a preferred special case.

Two preferred designs of radiators according to the invention, whose external geometry is known per se, are shown in claims 6 and 7.

The invention also includes non-circular cross-sections, e.g. oval cross-sections, of the inner wall and outer wall of the radiator and also specifies a possible manufacturing process for this. However, axial symmetry of at least the inner wall and outer wall in the sense of claim 8 is preferred, which is also the basis for the other manufacturing process according to the invention, which relates to expansion by means of a rotating tool under the influence of centrifugal force.

The last mentioned manufacturing process also enables the geometry of a radiator according to claim 9. In contrast to an axial profiling, which is also conceivable, a profiling that runs predominantly in the circumferential direction, as here, has a turbulence-generating effect on the flow of the heat transfer fluid and thus improves the heat transfer properties. In radiators that are essentially manufactured using the extrusion process, it has not yet been possible to produce such a turbulence-enhancing profiling.

Furthermore, the additional wall thickness of the inner wall provided according to the invention can in many cases be compensated for in whole or in part by reducing the wall thickness of the outer wall of the respective radiator section by focusing on the static strength of the double wall design. The turbulence generation is then all the more effective.

In other cases, it is more important that the pressure fluid flows through the radiator as undisturbed as possible, for example when adapting the flow resistance to specified circulation pumps. In this case, a smooth interior design is preferred.

The features according to claim 11 promote the possibility of connecting the radiator section to the respective inlet and outlet.

The intimate heat-conducting connection between the inner wall and the outer wall of the respective radiator section, which is the aim of the invention, can also be seen in the external appearance and the corresponding material deformation lines in the cross section according to claim 12.

Claims 13 and 14 specify preferred material choices and wall thicknesses.

It is conceivable to produce a radiator according to the invention by shrinking the future outer wall onto the future inner wall. However, this is very expensive in terms of energy consumption. In addition, experience has shown that radiator parts, as previously used as radiator sections, are subject to manufacturing-related tolerances with regard to out-of-roundness. Such out-of-roundness can lead to significant errors in the connection between the outer wall and the inner wall during the shrinking process, which can disrupt heat conduction.

According to claim 15 of the invention, it is therefore preferred to expand the initially loosely inserted part that forms the later inner wall onto the part that may also deform and serves as an outer radial abutment, which forms the later outer wall of the radiator section. It is conceivable to use pressure pads to expand a fluid. However, mechanical expansion by mechanical pressing is preferred.

In this context, claims 16 and 17 can be implemented by two alternative procedures, of which the first (claim 16) is based on the expansion technique known in another context using an expansion mandrel, and the second (claim 17), in contrast, expediently requires a dynamic procedure using the centrifugal force of a loosely inserted rotating working tool. The first-mentioned procedure is particularly suitable for producing non-circular configurations of the radiator section or its walls and wall surfaces. The second-mentioned procedure, on the other hand, also makes it possible to take into account manufacturing-related irregularities.

roundness of otherwise essentially cylindrical pipe cross-sections by using the radial movement of a working tool under centrifugal force so that even with such tolerances an optimal flat and good heat-conducting connection between the inner and outer wall of the radiator section exists. At the same time, the latter method opens up the possibility of creating the turbulence-generating profiles mentioned in claim 9 on the flow-guiding inner surface of the inner wall of the radiator section. In one operation, one can achieve a helical profile or several parallel helical profiles. With multiple operations, one can even create profiles that intersect, either with different pitches of the helical profiles with the same direction of rotation of the working tool during production, or with opposite, in the limiting case absolutely the same pitch angle with different directions of rotation of the working tool during production. The profiles are essentially impressions in the inner surface of the inner wall of the radiator section, with web-like structures remaining between these impressions or even being bulged inwards by material displacement. If an inner abutment is advanced in a spiral shape with an axial feed in the range of 1 to 20 mm per revolution and at a speed of 20 to 500 revolutions per minute, more or less practically usable pitch angles of the spiral profile(s) can be combined with the application of the necessary centrifugal force of the working tool; because the centrifugal force effect must be so great that it always reliably ensures the required contact pressure of the inner wall on the outer wall of the manufactured radiator section. In particular, if no such profiling is to be formed on the inner surface of the inner wall of the radiator section, other operating conditions are also possible.

A radiator according to claim 19 specifically develops a radiator according to claim 10. A radiator according to claim 20 specifically develops a radiator according to claim 11.

The device according to claims 21 to 24 relates to the execution of the second-mentioned method. According to claim 22, a rolling element is used as the active expansion part on the working head. Depending on the type of rolling element according to claim 23 or 24, or comparable rolling elements, one can use either internally unprofiled radiators
according to claim 10 in the sense of claim 19 or internally profiled radiators according to claim 9 in the sense of claim 18.

In addition to the entire radiator with inlets and outlets, the invention also includes the individual, in the area of the guidance of the
Heat transfer fluid double-walled radiator section, as can be produced in particular with the device according to the invention.

The invention is explained in more detail below using schematic drawings of several exemplary embodiments. They show:

Fig. 1 is a partially sectioned side view of a first embodiment of a radiator according to the invention;

Fig. 2 is a partially sectioned side view of a second embodiment of a radiator according to the invention;

Fig. 3 is a front view of one of the radiators
according to Fig. 1 and 2 possible spatial shape of a radiator section;

Fig. 4 is a detailed partial view of the double-walled area of a radiator section, which carries the heat-emitting heat transfer fluid of the radiator, for example that of Fig. 3, in front view with a section through the inner wall at the
Front side of the outer wall;

Fig. 5 is a functional diagram of a first embodiment of a device according to the invention;

Fig. 5a shows a radial section through the double-walled tubular region of a radiator section, as can be produced by means of a device of the type shown in Fig. 5;

Fig. 6 is a functional diagram of a second embodiment of a device according to the invention;

Fig. 7 a functional sketch of a third embodiment

embodiment of a device according to the invention and

Fig. 7a is a front view of the double-walled tube area of a radiator section, as can be produced with the device according to Fig. 7.

Fig. 1 and 2 show two prototypes of radiators in a register arrangement. Two, three or more radiator sections 2 run parallel to each other, usually in the assembled state with the axes A of their respective pipe 4 aligned vertically, through which a heat-emitting heat transfer fluid, in particular water or steam, can flow.

Without loss of generality, the radiator section 2 may have the profile whose geometry is shown in Fig. This profile is based on Fig. 4 of the German
Patent P 32 29 757.2-09. Here, the pipe 4 is provided with a heat-conducting ribbing in the form of webs
or ribs which are manufactured integrally with the pipe 4. The entire radiator section is an extruded part. The webs form a flat front plate 6 extending along one side of the pipe 4. This is rectangular in plan view and is connected along its vertical imaginary bisector B via a web attachment 8 to the outer surface of the pipe 4. The heat-conducting
In addition to the front plate 6 and the web attachment 8, the ribbing also has a web arrangement 10 which is open on the side of the pipe 4 facing away from the front plate 6. In this case, the web arrangement extends along an imaginary plane C which is arranged at right angles to the plane of the front plate 6 and which
middle symmetry line B of plate 6 and at the same time represents the imaginary middle plane of the web attachment 8, a
straight central web 12, which extends on the side of the pipe 4 opposite the web attachment 8 from its outer
surface and thus emerges directly from the pipe 4. Two straight side webs 14 and 16 extend
on both sides of the central web 12 parallel to it and at equal distances from each other, whereby the distance

distances between the facing side surfaces. The free ends 18 of the central web 12 and the
Side webs 14 and 16 lie in a common plane which describes the back of the open web arrangement.

The opposite ends of the side webs 14 and 16 extend essentially at right angles into an intermediate web 20
which extends in a straight line parallel to the front panel 6 at a distance from it and extends from both sides of the conduit 4. The respective lateral extension
the intermediate webs 20 are slightly smaller than those of the front panel 6, so that the latter optically covers the ribbing. The pipe 4 is closer to the front panel 6 than to the imaginary
plane through the free ends 18 of the web arrangement which is open to the rear. As shown in Fig. 3, the thicknesses of the ribs are different,
partly also graded, whereby in addition to static aspects, aspects of optimal thermal conductivity from the pipe 4 into all the ambient air
effective areas of the ribbing taken into account
are.

As is illustrated in the detail of Fig. 4 of the radiator section 2 according to Fig. 3, the pipe of the respective radiator section 2 is double-walled, namely with an inner wall 22 and an outer wall 24. The outer wall 24 is integrally prefabricated with the entire ribbing of the webs 6, 8, 20 as well as 12, 14 and 16, as
also Fig. 4 of the aforementioned German patent 32 29 757
shows.

The inner wall 22 is a pipe subsequently inserted into the outer wall 24, which in turn serves to directly conduct the heat-emitting heat transfer fluid. The
The inner wall 22 lies completely against the inner surface of the outer wall 24, so that optimal radial heat transfer from the inside to the outside over all surface areas of the pipe 4
the relevant radiator section 2 is ensured.

The configuration according to Fig. 3 and 4 represents

the possible configurations of a radiator section 2 represents a preferred geometric shape.

In the case of the radiators in Fig. 1 and 2 in a register arrangement, the front panels 6 of the individual radiator sections 2 cover both their pipe 4 and their entire web arrangement. The upper and lower edges (not shown in Fig. 1) of the individual front panels 6 are aligned with one another in a horizontal direction. The radiator sections 2 are mechanically combined to form the radiator by means not shown. A small vertical longitudinal gap 28 remains between the individual front panels 6.

At the top and bottom, the extension of the respective line pipe 4 is cut back compared to the vertical extension of the associated front panel 6 in such a way that inlets and outlets for the heat-emitting heat transfer fluid can be arranged in the cut-back area. The web arrangement is cut back completely or partially accordingly or tunneled through in the transverse direction. In the specific embodiments of Fig. 1 and 2 - if necessary simplifying a specifically more complicated cutting back situation - the outer walls 24 of the line pipes 4 and the webs 8, 20 and 12, 14 and 16 are the same on the front side when cut back in the axial direction, since they have a common plane or lower front side. This can be seen in Figs. 1 and 2 with regard to the inner wall 22 and the intermediate webs 20 of the web arrangement 10 and can be thought of as being supplemented accordingly with regard to the remaining webs 12, 14 and 16 as well as 8 of the web arrangement 10. The cut-back end faces 30 are horizontally aligned in adjacent radiator sections 2.

In the embodiment according to Fig. 1, only the upper area of the radiator is shown; the lower area is designed in the same way.

It can be seen that both in the embodiment of a radiator according to Fig. 1 and in the embodiment according to Fig. 2, the respective inner walls 22 of the pipes 4 extend axially over the outer walls 24 and the adjoining end face 30

the ribbing. The respective projection 32 serves to connect the pipes 4 of the radiator sectors 2 with the respective inlet and outlet for the heat-emitting heat transfer fluid.

In the radiator according to Fig. 1, the pipes 4 are connected parallel to each other at both ends to a collecting pipe 34, which forms the inflow and outflow for the heat transfer fluid and, in the specific embodiment of Fig. 1, is provided with a connecting screw thread 36 at one end. The respective collecting pipe 34 extends parallel to the upper edges and lower edges 26 of the front panels 6 slightly below and, accordingly, slightly above their level. The respective collecting pipe 34 has circumferential bores 38 in its casing, each of which faces the pipe 4 of each radiator section 2. The free end 40 of the projection 32 of the inner wall 22 of the respective pipe 4 of the associated radiator section 2 is inserted in a sealed manner into the circumferential bores 38. Seals of the usual kind can be provided, such as with special sealing agents or by soldering, welding, etc. Other connection methods could also be provided, such as with connecting flanges, socket connections, etc.

Specifically, a socket connection is provided for the alternative radiator according to Fig. 2. In this radiator, the header pipes 34 of Fig. 1 are replaced by pipe bends 42, which are also arranged in a cut-back area behind the front panels 6 of the radiator sections 2 and overlap with external sockets 44 of adjacent projections 32 of the respective inner walls 22 of the pipes 4 of adjacent radiator sections. In this arrangement with bends, in contrast to the parallel connection of the flow according to Fig. 1, the individual radiator sections are now connected in series. It goes without saying that other conventional sealing connection means can also be provided between the connections of the projections 32 to the bends. The other geometry of the radiator according to Fig. 2 is the same as in the radiator.

tor according to Fig. 1.

Fig. 5 to 7 illustrate only the basic principle of devices according to the invention, with which an inner wall 22, initially loosely inserted into the outer wall 24 with a sliding fit, can be pressed against the outer wall 24 of the double-walled pipe 4 of a radiator section 2.

Fig. 7a first shows that the cross-section of a manufactured pipe 4 can also deviate from the usual circular configuration, e.g. it can be oval as shown. The double wall obtained is not shown specifically in Fig. 7a.

For this purpose, the part forming the inner wall 22 can be inserted into the part serving as a radial abutment, namely the outer wall 24, initially with a slightly radial undersize and then expanded radially against the outer wall 24 by an expanding mandrel 46, which has a conical head part 48. In this case, the expanding mandrel 46 has a slightly radial undersize in relation to the radial inner dimension of the inner wall, which is initially loosely inserted into the outer wall 24, with dimensions such that after expansion, the outer surface of the inner wall 22 is pressed against the inner surface of the outer wall 24 over its entire surface. The expanding mandrel is pulled out of the inner wall 22 again after expansion.

In the described method of operation, the expanding mandrel also has the cross-section of the line pipe to be produced 4, and in the case of the configuration according to Fig. 7a, therefore also an oval cross-section.

This method of operation can also be used to produce circular configurations of the pipe 4. However, it has been shown that prefabricated outer walls 24 of pipes 4 of radiator sections are significantly out of round, and the tolerance fluctuations do not allow the use of expanding mandrels 46 to be adapted to the out of roundness with the desired adaptability. The method of operation according to Figs. 5 and 6, on the other hand, is geared precisely to compensating for such out of roundness.

In this mode of operation, a rotatable expanding mandrel 50, which is conveniently only supported on one side, has a working head 52 which is inserted along the axis D into the assembled unit consisting of the inner wall 22 and the outer wall 24 with a helical movement, i.e., simultaneous advance and rotation, and is pressed against the inner wall 22 and the outer wall 24, which serves as an abutment for it, under the centrifugal force of the working head during rotation.

If, as shown in Fig. 6, a rolling element in the form of an axially parallel roller 54 is provided on the working head 52, a uniform, unprofiled surface is obtained on the inner surface of the inner wall 22 of the pipe 4 facing the heat exchange fluid.

If a rolling element in the form of a ball 56 is chosen instead of the roller 54, a helical profile 58 is embossed into the inner surface of the inner wall 22 facing the heat transfer fluid. In Fig. 5, two further balls 56a and 56b also make it clear that several profiles with the same direction of rotation can also be produced simultaneously. Analogously, several rollers could also be provided in Fig. 6 to further smooth the inner surface of the inner tube 22.

Finally, Fig. 5a makes it clear that when the inner wall 22 and outer wall 24 of the respective pipe 4 of a radiator section 2 are pressed together, a deformation of the outer wall 24 also occurs, which is represented here as the outer profile 60 of the outer wall 24 opposite the profile 58.

The graphical representation of the functioning of the device according to the invention and the associated methods is roughly schematic. For example, holding means for pressing together the inner wall 22 and outer wall 24 of the respective pipe 4 are not shown, nor are drive means for the expanding mandrels 46 and 50. While, for example, the expanding mandrel 46 is provided with a pure feed drive

In order to be able to cope with this, the expanding mandrel 50 requires a combined feed and rotary drive.

Claims (24)

Protection claims 1. Radiator for room temperature control by means of a heat-emitting heat transfer fluid, in particular water or water vapor, which is guided via inlets and outlets through at least one radiator section (2), the outer surface of which exchanges heat with the ambient air, characterized , that the radiator section(s) (2) or their respective pipe (4) is (are) double-walled, that the inner wall (22) of the respective radiator section covers the inner surface of the outer wall (24) of the radiator section associated with the inner wall, that the inlets and outlets (34; 42) are connected to the inner wall (22) of the respective radiator section, and that the material of the inner wall (22) of the respective radiator section (2) is inert to corrosion by the heat transfer fluid and is different from the material of the outer wall (24) of the respective radiator section. 2. Radiator according to claim 1, characterized in that the inlets and outlets (34; 42) consist of the same material as the inner wall (22) of the respective radiator section (2). 3. Radiator according to claim 1 or 2, characterized in that several radiator sections (2) are arranged in a register arrangement. 4. Radiator according to claim 3, characterized in that the inlets and outlets (34; 42) are collecting pipes connected to the two ends of the respective radiator sections (2). 5. Radiator according to one of claims 1 to 4, characterized in that the radiator section(s) (2) runs (or runs) in a straight line. 6. Radiator according to one of claims 1 to 5, characterized in that the outer wall (24) of the respective radiator section (2) has a cylindrical surface. 7. Radiator according to one of claims 1 to 5, characterized in that the outer wall (24) of the respective radiator section (2) is provided with heat exchange ribbing (6, 8, 20, 12, 14, 16), preferably in the form of the outer wall together with the heat exchange ribbing as an extruded part (Fig. 3). 8. Radiator according to one of claims 1 to 7, characterized in that the inner surface of the outer wall (24) and the inner wall (22) of the respective radiator section (2) are cylindrical. 9. Radiator according to one of claims 1 to 8, characterized in that the inner surface of the inner wall (22) of the respective radiator section (2) is provided with at least one helical profile (58), wherein preferably in the case of several helical profiles at least two of them intersect. 10. Radiator according to one of claims 1 to 8, characterized in that the inner surface of the inner wall (22) of the respective radiator section (2) is unprofiled. 11. Radiator according to one of claims 1 to 10, characterized in that the inner wall (22) of the respective radiator section (2) forms, at least at one end thereof, preferably at both ends, a projection (32) projecting beyond the end face (30) of the outer wall (24) of the same radiator section (2). 12. Radiator according to one of claims 1 to 11, characterized in that the inner wall (22) of the respective radiator section (2) is pressed against the co-deformed outer wall (24) of the same radiator section at least in a frictionally engaged manner such that the intimate heat-conducting surface adhesion of the inner tube to the outer tube of the respective radiator section is maintained at all operating temperatures. 13. Radiator according to one of claims 1 to 12, characterized in that the material of the outer wall (24) of the respective radiator section is aluminum or an aluminum alloy, preferably AlMgSi 0.5, or iron or an iron alloy, and that the material of the inner wall (22) of the respective radiator section is copper or a pliable copper alloy, preferably brass or a wrought copper alloy. 14. Radiator according to one of claims 1 to 13, characterized characterized in that the wall thickness of the inner wall (22) of the respective radiator section is in the range from 0.3 to 1.0 mm, preferably from 0.4 to 0.6 mm, most preferably 0.5 mm. -A- 15. Radiator according to one of claims 1 to 14, characterized in that a tube forming the inner wall (22) of the radiator section (2) is axially inserted into an outer radial abutment forming the outer wall (24) of the manufactured radiator section and is pressed against the inner surface of the abutment with radial expansion. 16. Radiator according to claim 15, characterized in that the part forming the inner wall (22) of the radiator section is expanded progressively axially, preferably with some simultaneous radial deformation of the outer abutment. 17. Radiator according to claim 15, characterized in that the part forming the inner wall (22) of the radiator section (2) is pressed in a progressive spiral shape, preferably with some simultaneous radial deformation of the outer abutment. 18. Radiator according to claim 17, characterized in that helical profiles (58) are formed in the inner surface of the inserted part. 19. Radiator according to claim 17, characterized in that the inner surface of the inserted part is left unprofiled. 20. Radiator according to one of claims 15 to 19, characterized in that the inserted part (22) has a greater axial length than the part serving as an outer abutment (24) and is preferably arranged so that the inserted part protrudes at both axial ends of the outer abutment. 21. Device for producing a radiator according to one of claims 1 to 20, characterized by an expanding mandrel (50) with a working head (52) which has a radial undersize in relation to the part forming the inner wall (22) of the manufactured radiator section before its expansion to the outer wall (24) of the manufactured radiator section, by a drive for a helical feed of the expanding mandrel (50) and by such a bearing and such a feed of the expanding mandrel that its working head during its helical feed flies radially in the inserted part under the centrifugal force of the helical feed with such force that the inserted part (22) is pressed against the outer abutment forming the outer wall (24) of the manufactured radiator section under the centrifugal force. 22. Device according to claim 21, characterized in that the working head (52) of the expanding mandrel (50) is provided with at least one radially projecting rolling body (54; 56) which comes into expanding engagement with the inserted part (22). 23. Device according to claim 22, characterized in that the rolling body is an axially extending roller (54). 24. Device according to claim 23, characterized in that the rolling body is a ball (60).