DE3636177A1 - Process, in particular for producing a heat exchanger, and a heat exchanger - Google Patents

Abstract

Process for the permanent fastening of the end or ends of at least one rod, consisting at least partially of thermoplastic material and having in each case at least one continuous cavity, in at least one opening of a supporting plate encompassing at least one rod. In this process, for its fastening, each rod is positioned in openings of the supporting plate provided for it, each rod cavity having a hydraulic diameter which corresponds to at least 10% of the smallest outer cross-sectional dimension of the rod, and the rod walls may have pores which make up at most 20% of the wall volume. The said process is intended in particular for producing heat exchangers and is characterised in that the rods with the supporting plate are positioned in such a way that the ends of the rods are arranged substantially vertically upwards and the supporting plate is arranged substantially horizontally, in that then heat is supplied from above to the rod ends to such an extent that the rod ends soften at least partially and the outer walls of the rod end expand in such a way that they come to bear against the walls of the supporting plate openings and are adhesively bonded or fused with the latter. <IMAGE>

Description

The invention relates to a method for permanent Attach the end (s) from at least one existing thermoplastic, each having at least one continuous cavity Rod in at least one comprising at least one rod Opening of a support plate, with each rod becoming its own Attachment in the opening provided for him Support plate is positioned with each rod cavity has a hydraulic diameter of at least 10% of the thinnest wall thickness of the bar corresponds to that Rod walls can have pores that are a maximum of 20% fill the wall volume, and at least the support plate in the area of the openings made of thermoplastic exists, especially for the manufacture of heat exchangers.  

The invention also relates to a heat exchanger, consisting of from a number of thermoplastic, each at least a continuous cavity having rods, the Ends permanently connected to at least one support plate are, with the cavities towards the end of the thermoplastic Extend bars.

A generic method and a generic one Heat exchanger is known from DE-OS 33 38 157. In the known method, the tubes are in one tube plate designed as a perforated plate. After that the tube ends with the tube sheet via an ultrasound head welded. Making one as an ultrasound head suitable sonotrode is very expensive. Either in the known method, each pipe end must be individually to be welded to the tube sheet, which is very complex is, or is required for any desired pipe arrangement and / or number a specially manufactured sonotrode. If the tube ends are individually welded to the tube sheet, can also have individual, already welded pipe ends due to the effect of heat when welding adjacent Partially loosen the pipe ends again. The outer contour the sonotrode can be chosen to be conical. If such a sonotrode for welding the Tube ends used with the tube sheet, each has Pipe end at the end of the finished heat exchanger towards a conical extension. This extension favors the supply and discharge of the in the heat exchanger flowing medium. One reaches through these extensions a lower pressure drop when the fluid flows in into the pipes, which is not always desirable  for example, if the one produced by these processes Heat exchanger to be used as an evaporator. The heat exchanger manufactured by the known method has an annular bulge at each tube outlet end Elevation on the front of the tube sheet. Furthermore is a clear line between pipe material and Pipe base material when looking at the front of the Tube bottom visible.

The object of the present invention is a particular simple method of the type mentioned in particular to make available for the manufacture of a heat exchanger, which also does not require expensive tools, which is also independent of the desired arrangement the bars can be carried out. It is still Object of the present invention, a particularly inexpensive To provide heat exchangers. Prefers support plate material and rod material are to be seamless merge, that is, there should be no visible Border between support plate material and bar material be more visible. There should also be a heat exchanger available be put to use as an evaporator is suitable.

The object of the invention is at a Generic method solved in that the rods be positioned with the support plate such that the Ends of the bars substantially vertically upward and the Support plate are arranged substantially horizontally or is that there is so much warmth from above the rod ends is supplied that the rod ends at least partially soften, and the outer walls of the rod expand so that these stick to the walls of the support plate openings  put on and glue with them. The support plate must at least in the area of Openings consist of a material with which the rods used when using the invention Process can stick together.

It has been found that when the rods are arranged almost vertically, the upper ends the rods expand outward when the thermoplastic Rod material has reached the doughy state. This Circumstances are exploited in the method according to the invention. As a result of the heat radiation, the rod ends widen and then lie down on the inside of the openings of the Support plate and glue to this with another Heat supply. The heat supply can, as already mentioned, by heat radiation, for example by a hot plate respectively. But it can also be caused by sound waves, light, electromagnetic waves, hot gases, etc. occur. In special cases, the thermal treatment under Vacuum or protective gas atmosphere can be carried out.

The amount of heat required to carry out the method according to the invention can be determined by simple experiments. As a rule, the thermal treatment is carried out under the following conditions: where Q is the amount of heat supplied, per surface (end face) and time in J / m ² s
e is the linear expansion coefficient of the rod material in 1 / K,
t the duration of the heat in seconds,
ρ the density of the rod material in kg / m ³ ,
c _{p is} the specific heat of the rod material in J / kg K, and
λ is the thermal conductivity of the rod material in J / msK.

The degree of expansion of the rod ends is influenced most favorably by using rods made of a thermoplastic which has an average coefficient of linear expansion between 100 × 10 ^-6 and 400 × 10 ^-6 1 / K in the range between room temperature and melting temperature.

It is particularly favorable if the support plate at least in the area of the openings made of thermoplastic exists, and so much heat is supplied to the rod ends that the Melt the rod ends with the support plate. The insertion of the bars into the openings provided in the support plate is facilitated by using support plates the openings of which are at least in a cross-sectional dimension by an amount that is at least 20% of the wall thickness of the rod is larger than the corresponding outer cross-sectional dimension of the staff. It has also been shown that in this way the strength of the joint influenced particularly favorably between rod and support plate can be.  

The method according to the invention is particularly successful when rods are used which can have a porosity of up to 10% of the wall volume, the hydraulic diameter of each cavity between 0.3 and 15 mm, preferably between 0.5 and 7.5 mm, and the wall thickness at the thinnest point is between 5 and 25% of the hydraulic diameter, preferably between 7.5 and 17.5% of the hydraulic diameter. As is known, the hydraulic diameter ( d _h ) is defined as the quotient of the fourfold internal cross-sectional area of a channel of the rod divided by the wetted inner circumference (see also Dubbel, Taschenbuch für Maschinenbau, 13th edition, 1970, page 314, paragraph 4):

Support plates are preferably used, whose opening cross-sectional areas at least expanded towards the front are compared to the outer cross section of the rods used or staff groups. Here the rods should be like this be positioned so that the rod ends at least in the Extend extensions of the support plate openings. The type of cross-sectional enlargement or expansion towards the front of the support plate influences the inner contour of the rod achieved through the heat treatment becomes. The cross-sectional expansion of the openings takes place of the support plate towards the front, point the Cross sections of the rod towards the inside of the rod Narrowing on whose area is about 10 to 60% of the area of the inner cross section, and then the inside passes over the cross section of the rod. Is the cross section of the  Support plate openings suddenly expanded towards the front, the inside of the rod end has no or one barely noticeable narrowing of the inner cross section.

It turned out to be particularly favorable if the Rods before thermal treatment in such a way Openings of the support plate are positioned so that the Rod ends face the support plate 1 to 2 mm transfer.

The durability of the joint between the rod and Support plate can be influenced favorably in that after positioning, but before thermal Treatment of the bars an existing space between the outer jacket of the rods and the openings of the Support plate at least partially filled with polymer powder becomes. Polymer powder is advantageously used which has a melting temperature that is about 5 to 50 ° C, preferably 20 to 50 ° C below the melting temperature of the rod material. A polymer powder with an average particle size of 20 to 100 µm, preferably from 40 to 100 µm is preferred used. With a particle size of more than 100 µm in many cases there is an undesirable inhomogeneous surface.  

The method according to the invention works particularly well if Support plate, rods and possibly the polymer powder made of thermoplastic Polymers consist of their basic structure belong to the same type of polymer and / or the same or have almost the same melting point or melting range.

The one produced by the process according to the invention Heat exchanger has a number of features due to which is the one produced by the process according to the invention Heat exchanger from the previously manufactured heat exchangers differs. For example, a heat exchanger by the method known from DE-OS 33 38 157 manufactured, the end face of the support plate or of the tube sheet are smooth, are support plate material and Bar material not only because of the annular bulge Elevation on the front of the support plate is clearly visible demarcated from each other, and have the inside of the Rod traces from the contact sonotrodes used on. The end face of one according to the invention Process manufactured heat exchanger shows the typical Appearance of a thermoplastic solidified from the melt Material made with the surface of a crepe sole (Shoe sole) can be compared: the surface of the The front gives the impression that it is slightly blistered.  

There is also between support plate material and rod material when cutting through the plate and tube at after Heat exchangers produced by the method a transition can no longer be determined. Also points out Surface of the support plate material to the expert well-known for solidified from the melt thermoplastics typical shine.

The object of the invention is therefore also solved by a heat exchanger consisting of a number of thermoplastic, at least one continuous There are hollow bars, the Ends permanently connected to at least one support plate are, with the cavities towards the end of the thermoplastic Extend rods and which according to the invention Process can be produced.

As a rule, the heat exchanger according to the invention is distinguished also characterized in that each rod end with the Support plate at least to a depth that is the thinnest Wall thickness of the rod corresponds from the front of the Support plate seen here is fused.

As already mentioned above, the invention is distinguished Heat exchanger usually characterized in that the Rod material fused to the support plate material in this way is that there is a steady transition between the both materials.

The rods of the heat exchanger can be designed as tubes be one that has one or more continuous cavities, whose hydraulic diameter (of the individual  Cavity) between 0.5 and 15 mm and their wall thickness at the thinnest point between 5 and 25% of the hydraulic Diameter lies. The heat exchanger according to the invention can also contain bars made up of groups Pipes exist. These tube groups can be external have the shape of a plate, namely when the Pipes lie parallel to each other and the axes open are arranged in a straight line, but they can also the shape of a profiled or a spiral plate accept. In the case of a spiral plate, the tubes lie a group next to each other, their axes on one (imaginary) spiral line are arranged. A such a tube group can consist of 2 to 100,000, preferably 2 up to 20,000 tubes exist.

Are the heat exchanger according to the invention as an evaporator used, the heat exchanger according to the invention exhibits every expansion of the inside cross section of the rod ends in A narrowing to a cross-section in the direction of the rod interior whose area is about 10 to 60% of the area of the Inner cross section, this narrowing inwards then passes to the inside cross-section of the rod. Such a Heat exchanger is characterized in that every extension of the inner cross section of the rod ends in the direction of The inside of the rod is narrowed to a cross-section, the area of which is about 10 to 60% of the area of the inner cross section, before it goes over to the inside of the bar. The area of the narrowed cross section preferably has about 20 to 50% from the surface of the inner cross section.  

The heat exchangers according to the invention can at least partially consist of thermoplastic polymer, which is the fluoropolymer belongs. But you can also at least partially made of polyethylene or polypropylene.

The advantage of the method according to the invention is lost also in the fact that the production of the connection point between rod and support plate without mechanical force takes place and therefore no traces of one at the rod ends for example, the stamp used to exert force, because such tools for performing the invention Procedures are not required. The for Implementation of the method required The bars are pressed against the support plate opening walls solely by the result of the thermal treatment Extension of the bar ends. In addition, the cross-sectional area the heat source only depends on the outside diameter the support plate so that the same heat source can be used regardless of what type, arrangement and number of bars used as long as the cross-sectional area the heat source is adequately dimensioned. The method according to the invention is carried out without contact, so that the heat exchanger is glued to the heat source is omitted. The face of the support plate faces when in use of the method according to the invention also not that when used typical hairy surface of contact bodies.

The term "heat exchanger" in the sense of Invention also material exchanger for gases and silencers for gas or liquid jets.

The invention is illustrated by the following examples explained.  

The properties of the in the examples below The plastics used are compiled in the table.

table

example 1

In a plate made of PVDF type I (see table), whose External dimensions are 101 mm × 50 mm × 15 mm, are 28 continuous to the surface (101 mm × 50 mm) vertically arranged slots are provided, of which each is 40 mm long and 2 mm wide. The slots are there parallel to each other and run parallel to the broadside with the dimension 50 mm. The bridge between the Slitting is 3.5 mm. From about 1 mm below the Surface, the later face, at, up to At the front, the slots widen on all sides, whereby the contour of the extensions on opposite sides encloses an angle of 60 °. This results in that on the face of each slot an opening of about 41.2 mm x 3.2 mm.

A PVDF Type I rod is inserted into each slot which is 1 m long, 40 mm wide and 2 mm thick. Each rod has 20 continuous cavities with one hydraulic diameter of 1.6 mm, the Center distance between two adjacent continuous Cavities is 2 mm. The thinnest wall thickness between The cavity and outside of the rod is 0.2 mm. The bars are positioned so that the ends of the rods are the Extend the front of the plate 1.5 mm, the rods themselves are arranged vertically and the expansion of the slots and thus the face is directed upwards.

Now a flat, a surface of 50 cm × 50 cm having heating plate with an emission coefficient of 0.9 and a temperature of 430 ° C for two minutes a centimeter from the front directed against the PVDF plate and then further away.  

When you look at the front, you notice that now each rod is bent outwards at the end and has taken on the expansion of the slots. When cutting such a rod end parallel to Axis becomes recognizable in the area of enlargement of the rod over a length of 1.5 mm partly with the wall of the slits in the plate is fused.

Example 2

The same plate and the same rods are used as in Example 1, but now the rods are one Have a width of 39.5 mm. The bars will turn so inserted into the slots of the plate and positioned that the front of the plate about Transfer 1.5 mm. The one from the outside wall of the bars and the wall of the extensions of the slots formed wedge-shaped gap is now partially covered with PVDF powder, Type I, the average particle size of which is 0.06 mm filled. After the heat treatment described in Example 1 the powder has melted. On average parallel to the longitudinal axis of the rod can be seen that the Rod evenly over a depth of 1.5 mm with the surface of the slot is fused.

Example 3

A cylindrical plate with a diameter of 150 mm and a thickness of 30 mm consists of PVDF type II. The plate has 1440 through holes, the Diameter is 2 mm. On one surface with 150 mm diameter of the plate, the front, are all Holes expanded by leaps and bounds. This leaps and bounds Extensions have a diameter of 3 mm and one Depth of 0.8 mm. There is a tube in each hole  an outer diameter of 2 mm and a wall thickness of 0.15 mm inserted and positioned so that the ends of the tubes transfer the end face by 1.5 mm. The The tube material is PVDF type I.

The tubes are aligned vertically so that the Face of the plate is facing up. On the plate and the slots formed by the tubes and extensions is type I polymer powder with an average Particle size of 0.06 mm scattered, after which the in Example 1 described heating plate at a distance of 1 cm the front is directed. The hot plate temperature is 430 ° C. After 2 minutes the heating plate will come back on away. Then the plate with the one in this plate firmly connected tubes cooled to room temperature.

Example 4

Example 3 is repeated. However, it now becomes one Plate used, the extensions of which are conical are. The largest diameter of the conical Extensions, which is on the face of the plate, is 3 mm, while the tip angle of the cone conical extensions is 85 °. Each tube shows a ring-shaped narrowing after the thermal treatment at the point where the transition between cylindrical bore and conical extension.

Example 5

The production of a heat exchanger described in Example 1 can be carried out under the same process conditions be when as a material for the plate and the Polypropylene (PP) rods according to the table are used.  

The invention is also explained with reference to figures.

Show it:

Fig. 1 a prepared for the thermal treatment heat exchanger in which a heating plate is already positioned,

Fig. 2 shows the cross section through a connection point of a tube to the tube sheet

Fig. 3 is a perspective view of an arrangement of flat bar ends having a plurality of through holes in a support plate before the thermal treatment,

Fig. 4 is another perspective view of a possible arrangement of flat rods in a support plate before the thermal treatment,

Fig. 5 is a perspective view of a possible embodiment of the support plate,

Fig. 6 is a schematic representation of an embodiment of a support plate aperture,

FIGS. 7 to 12, the contours of different possible extensions of the openings of the support plate.

Fig. 1 shows schematically the cross section through a heat exchanger, in which according to the inventive method in a tube sheet (support plate) 2 , which are inserted on the upper side of the tube (rods) 1 , in such a way that the tube ends on the front side with protrude about 1.5 mm from the conical extensions (upper side). The cavities formed by the ends of the tubes 1 and the conical extensions are already filled with polymer powder 5 . The heat exchanger prepared in this way was already placed with the help of the housing 3 under a heating plate 6 which provides the heat radiation for carrying out the method according to the invention in such a way that the ends of the tubes are arranged vertically upwards and the support plate is essentially horizontal. After a long enough exposure to heat radiation, the tube ends are firmly connected to the tube sheet. The connection point between the tube and the tube sheet is shown in cross section in FIG. 2. The end of the tube 1 is arranged in the tube sheet 2 , the tube end in the tube sheet having a conical extension 7 towards the end and an annular bead-shaped constriction 8 towards the smallest cross section of this conical extension 7 . The end of the tube 1 is firmly glued to the tube sheet 2 in the region of the conical extension 7 and the annular bulge constriction 8 .

The conical extensions of the end face can be produced in a simple manner by countersinking the holes in the tube sheet. The connection between the tube and the tube sheet then has a particularly good strength, even if the tube sheet is made of thermoplastic material and in particular of the same thermoplastic material as the tubes. The dividing line shown in Fig. 2 between the tube end and tube sheet is no longer visible when the opening area of the tube sheet 2 is made of thermoplastic material and the tube end is supplied with so much heat that the tube end 7 is fused to the tube sheet 2 .

Fig. 3 is a perspective view of an array of flat bar 9 ends in a support plate 10. Each rod 9 has six through openings 11 here. The rod ends 9 are positioned in the support plate 10 in such a way that they transmit the support plate 10 on the end face. The openings of the support plate 10 (not visible) have extensions 12 towards the end face which are designed such that they have the shape of an elongated truncated pyramid.

In FIG. 4 is a further perspective view of a possible arrangement of flat rods 13, the ends of which have the contour of a circular ring segment, shown in a correspondingly shaped supporting plate 14. These rods 13 also have a plurality of through openings 16 . For the thermal treatment of an arrangement shown in Fig. 4, particularly a heating element 16, which in Fig. 4 is brought to the position shown in the thermal treatment is suitable.

The openings of the support plate 17 can also, as shown in FIG. 5, be designed such that they are extended towards the front side beyond the actual support plate body 17 by webs 18 . When using such support plates, a particularly strong connection between the rod ends and support plates is achieved. This also applies to the embodiment of an opening of a support plate 19 shown in FIG. 6. Here, the support plate 19 has an extension 20 towards the front side, which can be described as conical in the case of round bars and as a truncated pyramid in the case of flat bars . In addition, 20 webs 21 are arranged in the extension, which ensure a particularly intimate, solid fusion with the rod ends. The webs 21 expand together with the tube ends during the thermal treatment, so that the webs 21 abut the extensions 20 . After the thermal treatment, the webs 21 with the support plate 19 and the tube ends are fused with the webs 21st

In Figs. 7 to 13 examples of possible embodiments of extensions of the support plate openings are shown towards the end face.

In Fig. 7 in the support plate 23, a rod end 24 is inserted such that the end of the rod 24 projects beyond the end side of the support plate 23. The support plate opening (not designated) has a continuous widening 22 . In the case of round rods 24 , the configuration of FIG. 2 results after the thermal treatment.

In Figs. 8, 10, 11 and 12 erratic extensions 25, 31, 34 and 37 of the openings 27, 33 are shown, 36 and 39 in the support plates 26, 32, 35 and 38, respectively, while in FIGS. 9 and 13 continuous extensions 28 and 41 of the openings 30 and 44 in the support plates 29 and 42 are shown. In Fig. 13, the end of the rod 43 reaches into the extension 41 of the support plate 42 into but not project beyond the end face of the support plate 42.

Claims (29)

1. A method for permanently fastening the or the ends of at least one at least partially made of thermoplastic plastic, each having at least one continuous cavity in at least one at least one rod opening of a support plate, in which each rod for its fastening in openings provided for it the support plate is positioned, each rod cavity having a hydraulic diameter which corresponds to at least 10% of the smallest outer cross-sectional dimension of the rod, and the rod walls can have pores which fill a maximum of 20% of the wall volume, in particular for the production of heat exchangers, characterized in that the rods are positioned with the support plate in such a way that the ends of the rods are arranged substantially vertically upwards and the support plate is essentially horizontal, so that heat is then supplied to the rod ends from above so that the rod ends are at least partially soften and the outer walls of the rod end expand in such a way that they lie against the walls of the support plate openings and stick to them. 2. The method according to claim 1, characterized in that rods made of a thermoplastic are used, which has a mean linear expansion coefficient between 100 × 10 ^-6 and 400 × 10 ^-6 1 / K in the range between room temperature and melting temperature. 3. The method according to claim 1 or 2, characterized in that the support plate at least in the area of the openings consists of thermoplastic, and the So much heat is supplied to the rod ends that the rod ends fuse with the support plate. 4. The method according to one or more of claims 1 to 3, characterized in that the thermal treatment is carried out in compliance with the following condition: where Q is the amount of heat supplied, per surface (end face) and time in J / m ² s
e is the linear expansion coefficient of the rod material in 1 / K,
t the duration of the heat in seconds,
ρ the density of the rod material in kg / m ³ ,
C _{p is} the specific heat of the rod material in J / kg K, and
λ is the thermal conductivity of the rod material in J / msK. 5. The method according to one or more of claims 1 to 4, characterized in that rods are used which have a porosity of up to 10% of the wall volume can whose hydraulic diameter each Cavity between 0.3 and 15 mm and their wall thickness at the thinnest point between 5 and 25% of the hydraulic Diameter lies. 6. The method according to claim 5, characterized in that the hydraulic diameter of the cavities between 0.5 and 7.5 mm. 7. The method according to claim 5 or 6, characterized in that that the wall thickness at the thinnest point between 7.5 and 17.5% of the hydraulic diameter. 8. The method according to one or more of claims 1 to 7, characterized in that support plates are used be, the opening cross-sectional areas at least are extended towards the front compared to the outer cross section the members or groups of members used, and the rods are positioned so that the Rod ends at least in the extensions of the support plate openings reach in. 9. The method according to one or more of claims 1 to 8, characterized in that the rods in front of the thermal treatment such in the openings of the Support plate positioned that the rod ends protrude the face of the support plate 1 to 2 mm.   10. The method according to claim 8 or 9, characterized in that after positioning, however, before thermal Treatment of the bars, if any Space between the outer sheath of the bars and the Openings of the support plate at least partially with polymer powder is filled out. 11. The method according to one or more of claims 1 to 10, characterized in that the support plate, Rods and optionally the polymer powder from polymers consist of the same or almost the same melting point or melting range. 12. The method according to claim 10 or 11, characterized in that polymer powder is used which has a melting temperature has about 5 to 50 ° C below Melting temperature of the rod material is. 13. The method according to claim 12, characterized in that Polymer powder is used, which has a melting temperature has about 20 to 50 ° C below the Melting temperature of the rod material is. 14. The method according to one or more of claims 10 to 13, characterized in that polymer powder with a average particle size of 20 to 100 microns is used. 15. The method according to claim 14, characterized in that Polymer powder with an average particle size from 40 to 100 µm is used.   16. The method according to one or more of claims 1 to 15, characterized in that support plate, rods and optionally the thermoplastic polymer powder Polymers consist of their basic structure belong to the same type of polymer. 17. Heat exchanger consisting of a number of thermoplastic, at least one continuous one Hollow bars, the ends of which remain are connected to at least one support plate, wherein the cavities towards the end of the thermoplastic Extend rods towards them, producible according to the process according to one or more of claims 1 to 16. 18. Heat exchanger according to claim 17, characterized in that that each rod end with the support plate at least until to a depth equal to the thinnest wall thickness of the bar corresponds from the front of the support plate is fused. 19. Heat exchanger according to claim 17 or 18, characterized in that the rod material so with the Support plate material is fused that a steady Transition between the two materials takes place. 20. Heat exchanger according to one or more of the claims 17 to 19, characterized in that the rods as Tubes are formed. 21. Heat exchanger according to one or more of the claims 17 to 19, characterized in that to groups composite pipes are included as rods.   22. Heat exchanger according to claim 21, characterized in that the tube group consists of adjacent tubes is formed, the axes of which are on an (imaginary) spiral line are arranged. 23. Heat exchanger according to claim 21 or 22, characterized characterized in that each tube group from 2 to 100,000 Tubes. 24. Heat exchanger according to claim 23, characterized in that each tube group consists of 2 to 20,000 tubes. 25. Heat exchanger according to one or more of the claims 17 to 24, characterized in that each extension of the inner cross section of the rod ends in the direction of the interior of the rod narrowed to a cross section, the Area about 10 to 60% of the area of the inner cross section is before it hits the inside cross section of the rod transforms. 26. Heat exchanger according to claim 25, characterized in that the area of the narrowed cross section is about 20 to Is 50% of the area of the inner cross section. 27. Heat exchanger according to one or more of the claims 17 to 26, characterized in that it at least partially consists of thermoplastic polymer, which belongs to the fluoropolymers. 28. Heat exchanger according to one or more of the claims 17 to 26, characterized in that it at least partially consists of polyethylene.   29. Heat exchanger according to one or more of the claims 17 to 26, characterized in that it at least partly consists of polypropylene.