EP2792437A1 - Method for producing an evaporator tube - Google Patents

Abstract

The present invention relates to a method for producing an evaporator tube (1), in particular for a motor vehicle heat exchanger, wherein the evaporator tube (1) comprises an inner tube (2) with a first channel (5) for passage of a first medium and an inner tube (2) second channel for vaporizing a second medium, wherein the method according to the invention is characterized by the following method steps:
Providing the inner tube (2),
- Applying a placeholder material on an outer circumferential surface (8) of the inner tube (2),
Positioning an outer mold over the inner tube (2), wherein an annular gap is created between outer lateral surface (8) of the inner tube (2) and inner lateral surface of the outer mold (13),
Filling of the annular gap with a sintered material,
- Sintering of the arrangement and simultaneous expelling of the placeholder material.

Description

The present invention relates to a method for producing an evaporator tube according to the features in the preamble of claim 1.

Motor vehicles are still driven today as a major source of fossil fuel energy via an internal combustion engine. However, as these are finite, it is an effort to maximize the energy harvesting efficiency for each fuel. Here, the pure combustion process is limited to the maximum efficiency of 40% of the ideal carnot process of natural law. This means that of the 100% energy contained in the fuel, a maximum of 40% in kinetic energy can be implemented and the remaining energy is dissipated via heat. For this purpose, however, it is known from the prior art, the heat generated during the combustion process by means of To use combined heat and power. Thus, working media are heated via heat exchangers, wherein the energy contained in the heat is also used to provide additional energy for the operation of the motor vehicle or peripheral components.

From the WO 2009/157611 A1 For this purpose, a production method for a heat exchanger is known, in which grooves are introduced into a surface, these are filled with a temporary placeholder, and subsequently the heat exchanger is provided with a sintered material, which retains a porous structure after the supply of heat. However, such a manufacturing method is costly, since a processing of the body is necessary and an increased wall thickness is needed. In addition, such a production is not transferable to a radial design.

The object of the present invention, starting from the state of the art, is to demonstrate a production method for an evaporator tube that is considerably simpler and at the same time less expensive to carry out than the production method known from the prior art, wherein the evaporator tube produced thereby has improved heat transfer properties.

The aforementioned object is achieved by a method according to the features in claim 1.

Advantageous embodiments of the method are the subject of the dependent claims.

• Bereitstellen des Innenrohres,
• Aufbringen eines Platzhaltermaterials auf eine Außenmantelfläche des Innenrohres,
• Positionieren einer Außenform über das Innenrohr, wobei zwischen Außenmantelfläche des Innenrohres und Innenmantelfläche des Mantelrohres ein Ringspalt entsteht,
• Auffüllen des Ringspaltes mit einem Sinterwerkstoff,
• Sintern der Anordnung und gleichzeitiges Austreiben des Platzhaltermaterials.

The inventive method for producing an evaporator tube, wherein the evaporator tube is used in particular in a motor vehicle heat exchanger and the evaporator tube has an inner tube with a first channel for passage of a first medium and a second channel surrounding the inner tube for evaporating a second medium, characterized by the following method steps :

• Providing the inner tube,
• Applying a placeholder material on an outer circumferential surface of the inner tube,
• Positioning an outer mold over the inner tube, wherein between the outer circumferential surface of the inner tube and inner lateral surface of the jacket tube, an annular gap is formed,
• Filling the annular gap with a sintered material,
• Sintering the assembly and simultaneously expelling the placeholder material.

With the production method according to the invention, it is thus possible to produce a channel structure in the sintered layer produced by the sintered material, wherein the spacer material for the production of the channel structure is expelled during the sintering process itself. In particular, a placeholder material is used which melts at the occurring sintering temperatures and flows out of the channel system or evaporates. There, where the placeholder material was arranged, thus creating a channel system on the outer circumferential surface of the inner tube. The outer shape is preferably a jacket tube. The outer shape may also be formed as a wire mesh. The jacket tube may be circular or elliptical in cross-section. In the longitudinal direction, the jacket tube can also be conical.

In the sintering layer itself, a capillary structure is generated due to a porosity of the sintered material, so that the second medium flows through the resulting channels through the second channel and from the first channel via the inner tube, a heat flow is introduced from the first medium into the second medium. As a result, the second medium evaporates such that the resulting vapor is removed via steam channels. The steam is then converted to a condenser again in the liquid state and this additional energy is recovered, which is withdrawn at the first channel in particular in the form of an exhaust gas passage to the exhaust gas. Due to the capillary action, liquid medium flows into the sintering structure simultaneously with the evaporation.

The workgroup process can be carried out, for example, according to the principle of a Clausius-Rankine process. Particularly preferably, the evaporator tubes are designed as a heat pipe, and consequently as heat pipes, and particularly preferably as a loopheat pipe.

The inventive method eliminates entirely a mechanical machining of the tube assembly produced. The necessary steps are limited to a minimum, with elaborate machining preliminary or post-processing eliminated altogether. Especially when using such a sintered material, which is not additionally compacted, the sintering process itself produces a sufficiently high porosity in the sintered layer, so that an optimum pumping action and consequently a removal of the vapor is made possible.

For this purpose, a plastic material is used in particular for the placeholder material itself, this being in particular a polymer material. Alternatively, an amide wax can also be used. The such placeholder material is applied in particular to the outer circumferential surface or wound or sprayed. Optionally, an adhesive is applied to the outer circumferential surface, wherein the adhesive produces a better cohesive connection between outer lateral surface and spacer material and / or outer lateral surface and sintered material.

In this case, the placeholder material is particularly preferably provided, for example, in the solid state of matter, and very particularly preferably in strand form. The strands of the placeholder material of this type are then placed or pressed onto the outer circumferential surface and glued to the outer lateral surface at least temporarily. In the context of the invention, the strands are pressed or glued. In particular, the placeholder material is applied in strip form, wherein the strips, represented by the strands, are preferably spaced parallel to one another. The strips, in turn, continue to run in particular parallel to the central longitudinal axis of the inner tube or else the strips are applied helically on the outer circumferential surface. In the latter variant, the strips extend at an angle to the central longitudinal axis of the inner tube and wind helically around the outer circumferential surface.

In the context of the invention, however, it is also possible that the placeholder material is sprayed in a liquid, gel or pasty state of aggregation on the outer circumferential surface. The placeholder material has a self-adhesive function in this state of aggregation, so that an additional gluing process does not have to be carried out.

An annular gap formed between the outer mold and the inner pipe is now filled with sintered material.

During the following sintering process, in which a vacuum sintering process can possibly be used, but also another sintering process can not be carried out under a vacuum atmosphere, the placeholder material melts and flows out of the annular gap. The temperatures used are preferably 500 ° to 1200 ° C, in particular 900 ° to 1100 ° C. In this case, the placeholder material melts and runs out of the arrangement via the resulting channels. Alternatively, the placeholder material can be expelled at about 600 ° before solidification of the sintered material and then the actual sintering process can be performed. The placeholder material itself begins in a temperature range between 150 ° C and 450 ° C, in particular 200 ° C to 400 ° C to melt or vaporize. Until the blank material is completely melted or completely evaporated, the assembly has further reached a temperature at which the sintering process has already begun, whereby the sintered material then begins to bond. By preferred use of a sintered material explained below in the form of a spattered metal powder, however, it can also be ensured that even if the spacer material is almost completely flowed out or vaporized, first of all the channel structure produced is retained during the subsequent sintering process.

So that the sintered material does not reseal the cavities created by the outflowing or vaporizing placeholder material by means of its own rearward movement, in particular a spattered metal powder is used. Under spratzigem metal powder is an angular and / or edged powder form to understand so that the individual powder particles interlock with each other and / or tilt and remain dimensionally stable to each other until the completion of the sintering process. The powder particles are thus square or edged or polygonal designed such that they interlock with each other and / or tilt. Due to the resulting channel structures, the second medium, in particular a working medium, then flows in the gaseous state of matter during later use. The resulting due to the spattery metal powder rough surfaces within the channel structure itself while a turbulent flow is generated, which generates an improved heat transfer into the second medium, whereby a stronger overheating of the steam takes place. The pumping function is to be regarded as being so preferred that an active pump can be dispensed with and the pumping function is effected exclusively by the capillary function.

With particular preference, a stainless steel material is used for the sintered material. In particular, furthermore, the inner tube, the sintered material and the optional jacket tube are likewise made of a stainless steel material, since this has a particularly good resistance to the corrosive properties of the exhaust gas while at the same time having good thermal conductivity. If all component components are formed from the same material, then the material has correspondingly equal thermal expansion coefficients, so that the arrangement assumes no damage, in particular with regard to the durability under thermal expansion.

In particular, the inner tube, the sintered material and optionally the jacket tube are made of a stainless steel material of the 1.4XXX group, most preferably of a stainless steel alloy 1.4404.

The sintered structure listed in the annular gap is not compacted according to the invention. Optionally additionally or alternatively, the sintered layer produced from the sintered material has a porosity of more than 50%, in particular between 50% and 80%, preferably between 50% and 60%, wherein a contact surface of 40 between the sintered layer and the outer lateral surface of the inner tube % to 60%, especially 50% is made. The latter means in the context of the invention that 40% to 60%, in particular 50% of the outer circumferential surface of the inner tube is in contact with the sintered layer. This will be an optimum achieved between produced channel structure and direct heat transfer from the first into the second medium, which is used for evaporation of the second medium.

In order for the sintered layer and the capillary structure likewise to obtain sufficient heat from a heat input, heat is then transferred into the sintered layer via the contact surface between the outer circumferential surface of the inner tube and the sintered layer due to heat conduction. Due to the capillary structure, a pumping function and a discharge of the evaporated second medium take place in the sintering layer.

The inventive method further provides that the sintered material is coupled by the sintering process cohesively with the outer circumferential surface of the inner tube.

Furthermore, it is possible to materially couple attachments, such as plugs or connections especially for the second channel with the inner tube and / or with the jacket tube, in particular by a soldering process, wherein the soldering is performed simultaneously and in parallel with the sintering process. Both can be performed in a same heating device, such as an oven. In particular, this is carried out at temperatures of substantially 800 ° to 1200 ° and very particularly preferably 900 ° to 1100 ° and optionally under protective gas.

Further particularly preferably, the outer mold is provided on its inner circumferential surface with a high temperature resistant release agent. This makes it possible to remove the jacket tube after the sintering process and curing of the sintered material.

Figur 1

ein erfindungsgemäßes Verdampferrohr in Längsschnittsansicht;

Figur 2a

ein erfindungsgemäß hergestelltes Verdampferrohr in Querschnitts-

und b

ansicht und vergrößerter Ansicht des Querschnittes.

Further advantages, features, characteristics and aspects of the present invention are the subject of the following description. Preferred embodiments are shown in the schematic figures. These are for easy understanding of the invention. Show it:

FIG. 1

an inventive evaporator tube in a longitudinal sectional view;

FIG. 2a

an evaporator tube produced according to the invention in cross-section

and b

View and enlarged view of the cross section.

In the figures, the same reference numerals are used for the same or similar components, even if a repeated description is omitted for reasons of simplicity.

FIG. 1 shows an inventive evaporator tube 1, comprising an inner tube 2 and the inner tube 2 relative to its longitudinal direction 4 at least partially enclosing housing tube 3. Between the housing tube 3 and the inner tube 2, a capillary structure is arranged in FIGS. 2a and b will be explained in detail. In the inner tube 2 itself, a first channel 5 is formed, through which a first medium can be conducted, so that the first medium emits a heat flow to an inner circumferential surface 6 of the inner tube 2, which then flows through the lateral surface 7 of the inner tube 2 and into the capillary structure K is transferred by means of heat conduction. Between the outer circumferential surface 8 and the housing tube 3 itself, a second channel 9 in the form of an evaporation tube is formed, through which a second medium flows, wherein the evaporation channel has a capillary structure K. For this purpose, closures 10, 11 are each end attached, which complete the second channel 9. The closures 10, 11 themselves may have further connections or be designed as a connection itself, in order to introduce the second medium into the second channel 9.

FIG. 2a shows a cross-sectional view of the inventive evaporator tube 1 and FIG. 2b a corresponding magnification according to the section A from FIG. 2a , In FIG. 2 is good to see that from an interior I a not shown exhaust gas flow emits a heat flow Q̇ to the inner circumferential surface 6 of the inner tube 2. From this there is a heat conduction to the outer circumferential surface 8 of the inner tube 2, where then the heat flow Q̇ in the second channel, shown here in the form of an evaporation channel 9, passes. The evaporation channel 9 is, here represented by in cross section semicircular evaporation channels 9, formed. The evaporation channels 9 themselves are in direct contact with the outer circumferential surface 8 of the inner tube. 2

A distance a is formed in each case between the individual evaporation channels 9, the sinter layer 12 being in direct contact with the outer jacket surface 8 of the inner tube 2 in the region of this distance. This results in a heat input into the sintered layer 12 itself, so that a capillary structure, not shown within the porous sintered layer 12 is also heated. Optionally, an outer mold 13, which is only schematically indicated here, can then be arranged on the sintering layer 12 from the outside. The outer mold 13 initially serves as a mold during the sintering process, wherein in particular within the scope of the invention, also between the outer mold 13 and inner tube 2, the entire second channel can be formed. A corresponding supply of the second medium and a discharge of the evaporated second medium then takes place via the in FIG. 1 shown connections in the closures 11, 12th

Reference numerals:

1 -

evaporator tube

2 -

inner tube

3 -

housing tube

4 -

Longitudinal direction to 2

5 -

first channel

6 -

Inner lateral surface to 2

7 -

Lateral surface to 2

8th -

Outer lateral surface to 2

9 -

Evaporation passage

10 -

shutter

11 -

shutter

12 -

sintered layer

13 -

external form

I -

inner space

K -

Kappilarstruktur

a -

distance

Q̇ -

heat flow

Claims (12)

Method for producing an evaporator tube (1), in particular for a motor vehicle heat exchanger, wherein the evaporator tube (1) has an inner tube (2) with a first channel (5) for passage of a first medium and a second channel surrounding the inner tube (2) for vaporising a Having second medium, characterized by the following process steps: Providing the inner tube (2), - Applying a placeholder material on an outer circumferential surface (8) of the inner tube (2), Positioning an outer mold (13) over the inner tube (2), whereby an annular gap is created between outer lateral surface (8) of the inner tube (2) and inner lateral surface (6) of the outer mold (13), Filling of the annular gap with a sintered material, - Sintering of the arrangement and simultaneous expelling of the placeholder material. A method for producing an evaporator tube according to claim 1, characterized in that a plastic material is used as a placeholder material, in particular a polymer material. A method for producing an evaporator tube according to claim 1 or 2, characterized in that the placeholder material is applied to the outer circumferential surface (8) or wound or sprayed on. Method for producing an evaporator tube according to one of the preceding claims, characterized in that an adhesive is applied to the outer circumferential surface (8). A method for producing an evaporator tube according to one of the preceding claims, characterized in that a spratziges metal powder is used as the sintered material, in particular of a stainless steel. A method for producing an evaporator tube according to any one of the preceding claims, characterized in that the outer mold (13) is provided on its inner circumferential surface (6) with a high temperature resistant release agent. A method for producing an evaporator tube according to any one of the preceding claims, characterized in that the placeholder material is applied in strips, wherein the strips are preferably spaced parallel to each other. Method for producing an evaporator tube according to one of the preceding claims, characterized in that the strips are applied parallel to the central longitudinal axis of the inner tube (2) or that the strips extend helically around the outer lateral surface (8). Method for producing an evaporator tube according to one of the preceding claims, characterized in that the inner tube (2), the sintered material and optionally the outer mold (13) are formed from the same material, in particular from a stainless steel. Method for producing an evaporator tube according to one of the preceding claims, characterized in that the sintered material is not compacted and / or that the sintered layer (12) has a porosity of more than 50%, in particular between 50 and 80%, preferably between 50 and 60 % and that between the sintered layer (12) and outer circumferential surface (8) of the inner tube (2) has a contact surface of 40 to 60%, in particular 50% is made. Method for producing an evaporator tube according to one of the preceding claims, characterized in that the Sintered material by the sintering process is materially coupled to the outer lateral surface (8) of the inner tube (2) and / or the other add-on parts with the evaporator tube (1) are coupled by a soldering process, wherein the soldering process and the sintering process are performed simultaneously and in a same heating device , A method for producing an evaporator tube according to any one of the preceding claims, characterized in that the placeholder material melts by the temperature effect of sintering and flows out of the assembly or evaporated.

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