EP2368086A1 - Condenser tube having increased hydrophobicity, production method and use thereof - Google Patents

Condenser tube having increased hydrophobicity, production method and use thereof

Info

Publication number
EP2368086A1
EP2368086A1 EP09751861A EP09751861A EP2368086A1 EP 2368086 A1 EP2368086 A1 EP 2368086A1 EP 09751861 A EP09751861 A EP 09751861A EP 09751861 A EP09751861 A EP 09751861A EP 2368086 A1 EP2368086 A1 EP 2368086A1
Authority
EP
European Patent Office
Prior art keywords
coating
condenser tube
condenser
structuring
water
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP09751861A
Other languages
German (de)
French (fr)
Inventor
Anett Berndt
Florian Eder
Heinrich Zeininger
Sebastian Kamps
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Original Assignee
Siemens AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens AG filed Critical Siemens AG
Publication of EP2368086A1 publication Critical patent/EP2368086A1/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
    • F28F13/04—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by preventing the formation of continuous films of condensate on heat-exchange surfaces, e.g. by promoting droplet formation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
    • F28F13/18—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by applying coatings, e.g. radiation-absorbing, radiation-reflecting; by surface treatment, e.g. polishing
    • F28F13/182—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by applying coatings, e.g. radiation-absorbing, radiation-reflecting; by surface treatment, e.g. polishing especially adapted for evaporator or condenser surfaces
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
    • F28F13/18—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by applying coatings, e.g. radiation-absorbing, radiation-reflecting; by surface treatment, e.g. polishing
    • F28F13/185—Heat-exchange surfaces provided with microstructures or with porous coatings
    • F28F13/187—Heat-exchange surfaces provided with microstructures or with porous coatings especially adapted for evaporator surfaces or condenser surfaces, e.g. with nucleation sites
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F2245/00—Coatings; Surface treatments
    • F28F2245/04—Coatings; Surface treatments hydrophobic
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F2255/00—Heat exchanger elements made of materials having special features or resulting from particular manufacturing processes
    • F28F2255/20—Heat exchanger elements made of materials having special features or resulting from particular manufacturing processes with nanostructures

Definitions

  • the invention relates to a superhydrophobic surface condenser tube, a process for producing a superhydrophobic surface of steam condenser tubes to achieve improved drainage of condensation droplets, and the use of condenser tubes.
  • cooling water condensers which are constructed either of titanium or austenitic steel tubes. Due to their surface properties, these pipes have a poor condensation effect. Due to the high surface energy of the metal, the condensed water vapor completely wets the cooling tube, so that a thin film of water always impedes the exchange of heat energy during operation (insulation effect) and thus degrades the condenser efficiency.
  • a coating agent for producing a hydrophobic surface for condenser tubes is known, with which it is possible to make at least condensation droplets from the water film.
  • a disadvantage of the known hydrophobic coating is that it is not possible to drain the condensation droplets on the tubes.
  • coatings are known in which neither their stability of the coating nor the hydrophobicity, which causes the drainage of the droplets, is sufficient. In addition, the coatings are often extremely expensive to manufacture.
  • a solution to the object and subject of the present invention is a condenser tube having a surface in which a microstructure cooperates with a coating such that droplets formed by condensation drain on the condenser tube in the structure as in channels.
  • the subject matter of the invention is a method for surface treatment for condenser tubes comprising at least two process steps, on the one hand being coated at least with a water-repellent, ie hydrophobic, coating composition and, on the other hand, producing at least one structure on the surface of the condenser tube and / or in the coating becomes.
  • the coating of the surface of the condenser tube preferably comprises water-repellent components, for example alkyl groups or fluorinated alkyl groups.
  • a liquid solvent may also be contained in the hydrophobic coating agent.
  • the coating material is, for example, selected from the group comprising sol-gel materials based on silica sol, fluoropolymers, silicones and / or polyurethane-forming components, where, in each case based on the total weight of the coating composition: - The solids content of the sol-gel material based on silica sol in the range of> 0.5 wt .-% to ⁇ 20 wt .-% is; and or
  • the hydrophobic coating composition is selected from the group comprising sol-gel paints based on silica, fluoropolymers, silicones and / or polyurethane-based paints.
  • the coating has a layer thickness in the range of> 100 nm to ⁇ 5 ⁇ m.
  • the solvent is preferably a liquid solvent.
  • liquid in the context of the present invention means that the solvent in a temperature range of 10 0 C to 100 ° C, preferably at room temperature, ie in a temperature range of 18 ° C to 25 0 C, liquid.
  • the application of the coating agent ie the coating of the surface can be carried out by any known coating methods, for example, by dipping, spraying, spin coating, deposition, printing and many others.
  • any known coating methods for example, by dipping, spraying, spin coating, deposition, printing and many others.
  • microstructuring takes place, for example, via sputtering processes, by means of etching processes, wet-chemical and / or dry-chemical or with other structuring methods.
  • Particularly advantageous are cost-effective structuring such as roll embossing, grinding, sandblasting and / or etching. Also An electrochemical treatment such as anodising or oxalizing can be used.
  • particles are dispersed in the coating agent or in a separate dispersion, which then, after being sprayed onto the surface of the coating, produce a roughness in that the particles are randomly distributed in the coating.
  • different roughnesses can be generated both by varying the particle size and / or combination of different particle size and by varying the particle concentration.
  • particle concentration a saturation effect occurs which does not permit a further increase in concentration.
  • sandblasting and / or grinding methods can be used to create a structure on the surface of the substrate, ie the condenser tube.
  • the grinding can take place, for example, by means of sandpaper of different surface roughness. In this case, contact angles of up to 130 ° were realized. Furthermore, a structuring by sand blasting can be done, it has become clear that an essential parameter is the type of sand with which sandblasted, in particular in terms of the aspect ratio. Both methods, sandblasting and grinding, produce roughness on the ductile and metallic substrate. The coating agent, which brings the chemical functionalities into the surface, only forms a thin film on the already structured substrate surface.
  • the application of the coating takes place only after the structuring of the tube surface, so that the structuring is imaged in the coating.
  • structuring is produced in the coating. This can be done by all common printing and embossing processes.
  • the surface structure is introduced by a rolling embossing process with, for example, a silicone stamp in the finished coating.
  • silicone stamps can be produced by molding sandpaper of different surface roughness with liquid silicone according to a further advantageous embodiment.
  • liquid silicone is poured onto sandpaper, after curing of the silicone, this is peeled off, where it shows the surface of the imprint of the sandpaper.
  • a roll-to-roll method can be used.
  • the structuring of the coating can also be effected by etching or by means of structuring particles.
  • structures in the coating can also be produced by the incorporation of templates, which are also removed, for example, after the structure of the structure. In the case of the particles, these can be mixed directly with the coating solution and painted on.
  • Hybrid-crosslinked sol-gel systems are preferably used as the layer material since, in addition to outstanding structurability, they show good adhesion to the substrate and a long-term stable water-repellent effect.
  • the structure can be produced in the coating by means of spray coating on a hot substrate.
  • the solvent evaporates immediately after impinging on the substrate and leaves, depending on the solvent used solid concentration and substrate temperature a structure with defined statistical roughness.
  • contact angle of> 150 0 C were already achieved in this way.
  • a coarse and a fine structure in which a (coarse) structure is first produced on a pipe surface, then a coating is applied, in which in turn a nano (fine) structure is produced.
  • the technical advantages of the hydrophobic, ie drop-forming, coating agents can be combined with those of the drainage structures.
  • great advantages in the condensation and dripping behavior of a condenser tube can be realized.
  • the adhesion of a formed drop is reduced due to the reduced surface energy of the substrate, so that it can more easily detach from the tube and drip off. Furthermore, especially small drops whose weight was previously too low to drip, can be easily detached from the tube.
  • the coating causes a strong reduction of the slip angle to less than 5 °, so that drops, no matter at which position of the pipe they form, run solely through the action of gravity and through the existing structures as in channels.
  • the invention enables extremely superhydrophobic coatings with which not only the above-mentioned water film on the pipe outer wall is prevented, but even allows drainage angle, which are not conceivable with anti-adhesive coatings alone. For example, drainage angles of less than 30 ° are possible, bearing in mind that in the case of layered pipes even in a vertical position no running off small drops of water takes place.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Paints Or Removers (AREA)

Abstract

The invention relates to a condenser tube having a superhydrophobic surface, to a method for producing a superhydrophobic surface of steam condenser tubes to achieve an improved runoff of condensation drops, and to the use of condenser tubes. The surface of the condenser tube is coated and structured so that the drops of condensation formed can run off well.

Description

Beschreibungdescription
Kondensatorrohr mit erhöhter Hydrophobie, Herstellungsverfahren und Verwendung dazuCondenser tube with increased hydrophobicity, manufacturing process and use thereof
Die Erfindung betrifft ein Kondensatorrohr mit superhydrophober Oberfläche, ein Verfahren zur Herstellung einer superhydrophoben Oberfläche von Dampfkondensatorrohren zur Erzielung eines verbesserten Ablaufens von Kondensationstropfen, sowie die Verwendung von Kondensatorrohren.The invention relates to a superhydrophobic surface condenser tube, a process for producing a superhydrophobic surface of steam condenser tubes to achieve improved drainage of condensation droplets, and the use of condenser tubes.
Im Kraftwerksbereich werden viele Turbinen zur Energieerzeugung mit Wasserdampf angetrieben. Das hierfür verwendete Wasser muss einen hohen Reinheitsgrad aufweisen, um Verkalkungen und Ablagerungen zu vermeiden. Da der Wasserdampfdurchsatz einer Kraftwerksturbine enorm ist, muss das aus der Turbine austretende Wasser durch Kondensation verflüssigt und schließlich wieder der Verdampfung zugeführt werden, so dass sich der Kreislauf schließt.In the power plant area, many turbines are powered by steam to generate energy. The water used for this purpose must have a high degree of purity in order to avoid calcification and deposits. Since the steam flow rate of a power plant turbine is enormous, the water leaving the turbine must be liquefied by condensation and finally fed back to the evaporation, so that the circuit closes.
Die Kondensation des noch etwa 500C heißen Dampfes erfolgt in mit Kühlwasser durchströmten Kondensatoren, welche entweder aus Titan- oder austenitischen Stahlrohren aufgebaut sind. Diese Rohre haben aufgrund ihrer Oberflächeneigenschaften ei- ne schlechte Kondensationswirkung. Durch die hohe Oberflächenenergie des Metalls benetzt der kondensierte Wasserdampf das Kühlrohr vollständig, so dass im Betrieb stets ein dünner Wasserfilm den Austausch von Wärmeenergie behindert (Isolationswirkung) und damit die Kondensatoreffizienz verschlech- tert.The condensation of the still about 50 0 C hot steam takes place in flowed through with cooling water condensers, which are constructed either of titanium or austenitic steel tubes. Due to their surface properties, these pipes have a poor condensation effect. Due to the high surface energy of the metal, the condensed water vapor completely wets the cooling tube, so that a thin film of water always impedes the exchange of heat energy during operation (insulation effect) and thus degrades the condenser efficiency.
Aus der DE 10 2007 015450 ist ein Beschichtungsmittel zur Herstellung einer hydrophoben Oberfläche für Kondensatorrohre bekannt, mit dem es gelingt, aus dem Wasserfilm wenigstens Kondensationstropfen zu machen. Nachteilig an der bekannten hydrophoben Beschichtung ist jedoch, dass auf den Rohren ein Ablaufen der Kondensationstropfen nicht möglich ist. Aus anderen Quellen sind Beschichtungen bekannt, bei denen weder deren Stabilität der Beschichtung noch die Hydrophobie, die ein ablaufen der Tropfen bewirkt, ausreichend ist. Zudem sind die Beschichtungen oft extrem kostspielig in der Her- Stellung.From DE 10 2007 015450 a coating agent for producing a hydrophobic surface for condenser tubes is known, with which it is possible to make at least condensation droplets from the water film. A disadvantage of the known hydrophobic coating, however, is that it is not possible to drain the condensation droplets on the tubes. From other sources coatings are known in which neither their stability of the coating nor the hydrophobicity, which causes the drainage of the droplets, is sufficient. In addition, the coatings are often extremely expensive to manufacture.
Aufgabe der vorliegenden Erfindung ist es deshalb, wenigstens einen Nachteil des Standes der Technik zu überwinden und insbesondere ein Ablaufen der Kondensationstropfen zu ermögli- chen.It is therefore an object of the present invention to overcome at least one disadvantage of the prior art and, in particular, to allow drainage of the condensation drops.
Die Lösung der Aufgabe ist in der Beschreibung und den Ansprüchen offenbart.The solution of the problem is disclosed in the description and the claims.
Dementsprechend ist Lösung der Aufgabe und Gegenstand der vorliegenden Erfindung ein Kondensatorrohr mit einer Oberfläche, bei der eine Mikrostruktur mit einer Beschichtung so zusammenwirkt, dass durch Kondensation gebildete Tropfen am Kondensatorrohr in der Struktur wie in Kanälen ablaufen. Au- ßerdem ist Gegenstand der Erfindung ein Verfahren zur Oberflächenbehandlung für Kondensatorrohre, zumindest zwei Prozessschritte umfassend, wobei zum einen zumindest mit einem wasserabweisenden, also hydrophoben Beschichtungsmittel beschichtet wird und zum anderen zumindest eine Struktur auf der Oberfläche des Kondensatorrohrs und/oder in der Beschichtung erzeugt wird. Schließlich ist die Verwendung von Kondensatorrohren mit derartiger Oberfläche im Kraftwerksbereich Gegenstand der Erfindung.Accordingly, a solution to the object and subject of the present invention is a condenser tube having a surface in which a microstructure cooperates with a coating such that droplets formed by condensation drain on the condenser tube in the structure as in channels. In addition, the subject matter of the invention is a method for surface treatment for condenser tubes comprising at least two process steps, on the one hand being coated at least with a water-repellent, ie hydrophobic, coating composition and, on the other hand, producing at least one structure on the surface of the condenser tube and / or in the coating becomes. Finally, the use of condenser tubes with such surface in the power plant area is the subject of the invention.
Die Beschichtung der Oberfläche des Kondensatorrohres umfasst bevorzugt wasserabweisende Komponenten, beispielsweise Al- kylgruppen oder fluorierte Alkylgruppen . Beispielsweise kann auch ein flüssiges Lösemittel im hydrophoben Beschichtungsmittel enthalten sein. Der Beschichtungsstoff ist beispiels- weise ausgewählt aus der Gruppe umfassend Sol-Gel-Materialien auf der Basis von Siliziumoxid-Sol, Fluorpolymere, Silikone und/oder Polyurethan-ausbildende Komponenten, wobei, jeweils bezogen auf das Gesamtgewicht des Beschichtungsmittels : - der Feststoffgehalt des Sol-Gel-Materials auf der Basis von Siliziumoxid-Sol im Bereich von > 0,5 Gew.-% bis ≤ 20 Gew.-% liegt; und/oderThe coating of the surface of the condenser tube preferably comprises water-repellent components, for example alkyl groups or fluorinated alkyl groups. For example, a liquid solvent may also be contained in the hydrophobic coating agent. The coating material is, for example, selected from the group comprising sol-gel materials based on silica sol, fluoropolymers, silicones and / or polyurethane-forming components, where, in each case based on the total weight of the coating composition: - The solids content of the sol-gel material based on silica sol in the range of> 0.5 wt .-% to ≤ 20 wt .-% is; and or
- der Gehalt an Fluorpolymer im Bereich von > 0,1 Gew.-% bis ≤ 5 Gew.-% liegt; und/oder- The content of fluoropolymer in the range of> 0.1 wt .-% to ≤ 5 wt .-% is; and or
- der Feststoffgehalt an Silikon, im Bereich von > 5 Gew.-- The solids content of silicone, in the range of> 5 wt.
% bis ≤ 30 Gew.-% liegt; und/oder% to ≤ 30 wt .-% is; and or
- der Gehalt an Polyurethan-ausbildenden Komponenten imthe content of polyurethane-forming components in the
Bereich von > 3 Gew.-% bis ≤ 30 Gew.-%, liegt.Range of> 3 wt .-% to ≤ 30 wt .-%, is.
Nach einer weiteren Ausführungsform der Erfindung ist das hydrophobe Beschichtungsmittel ausgewählt aus der Gruppe umfassend Sol-Gel-Lacke auf der Basis von Siliziumoxid, Fluorpolymere, Silikone und/oder Lacke auf Polyurethan-Basis.According to a further embodiment of the invention, the hydrophobic coating composition is selected from the group comprising sol-gel paints based on silica, fluoropolymers, silicones and / or polyurethane-based paints.
Beispielsweise weist die Beschichtung eine Schichtdicke im Bereich von > 100 nm bis ≤ 5 μm auf.By way of example, the coating has a layer thickness in the range of> 100 nm to ≦ 5 μm.
Das Lösemittel ist bevorzugt ein flüssiges Lösemittel. Der Begriff "flüssig" bedeutet im Sinne der vorliegenden Erfindung, dass das Lösemittel in einem Temperaturbereich von 100C bis 100°C, vorzugsweise bei Raumtemperatur, d.h. in einem Temperaturbereich von 18°C bis 25 0C, flüssig ist.The solvent is preferably a liquid solvent. The term "liquid" in the context of the present invention means that the solvent in a temperature range of 10 0 C to 100 ° C, preferably at room temperature, ie in a temperature range of 18 ° C to 25 0 C, liquid.
Die Aufbringung des Beschichtungsmittels, also die Beschichtung der Oberfläche kann durch alle bekannten Beschichtungs- methoden erfolgen, beispielsweise über Eintauchen, Besprühen, Aufschleudern, Abscheiden, Bedrucken und viele andere. Beim Bedrucken der Rohroberfläche mit Beschichtungsmittel ist es besonders vorteilhaft, wenn gleichzeitig eine Strukturierung der Beschichtung erfolgt.The application of the coating agent, ie the coating of the surface can be carried out by any known coating methods, for example, by dipping, spraying, spin coating, deposition, printing and many others. When printing the tube surface with coating agent, it is particularly advantageous if at the same time structuring of the coating takes place.
Die Mikrostrukturierung erfolgt beispielsweise über Sputter- Prozesse, mittels Ätzprozesse, nasschemischer und/oder tro- ckenchemischer oder mit sonstigen Strukturierungsmethoden .The microstructuring takes place, for example, via sputtering processes, by means of etching processes, wet-chemical and / or dry-chemical or with other structuring methods.
Besonders vorteilhaft sind kostengünstige Strukturierungen wie Walz-Prägen, Schleifen, Sandstrahlen und/oder Ätzen. Auch eine elektrochemische Behandlung wie Eloxieren oder Oxalieren kann eingesetzt werden.Particularly advantageous are cost-effective structuring such as roll embossing, grinding, sandblasting and / or etching. Also An electrochemical treatment such as anodising or oxalizing can be used.
Eine weitere Möglichkeit, die insbesondere bei geometrisch komplizierten drei-dimensionalen Oberflächen zum Einsatz kommt, ist die Sprüh-Beschichtung. Dazu werden in das Be- schichtungsmittel oder in einer separaten Dispersion Partikel dispergiert, die dann nach erfolgtem Aufsprühen auf die Oberfläche der Beschichtung eine Rauhigkeit dadurch erzeugen, dass die Partikel zufällig in der Beschichtung verteilt vorliegen. Dabei können unterschiedliche Rauhigkeiten sowohl durch Variation der Partikelgröße und/oder Kombination verschiedener Partikelgröße als auch durch Variation der Partikelkonzentration erzeugt werden. Bei der Partikelkonzentra- tion tritt ein Sättigungseffekt ein, der eine weitere Konzentrationssteigerung nicht zulässt.Another possibility, which is used in particular for geometrically complicated three-dimensional surfaces, is the spray coating. For this purpose, particles are dispersed in the coating agent or in a separate dispersion, which then, after being sprayed onto the surface of the coating, produce a roughness in that the particles are randomly distributed in the coating. In this case, different roughnesses can be generated both by varying the particle size and / or combination of different particle size and by varying the particle concentration. In the case of particle concentration, a saturation effect occurs which does not permit a further increase in concentration.
Außerdem können alternativ oder ergänzend Methoden zur Strukturierung des Substrates eingesetzt werden. Beispielsweise können Sandstrahl und/oder Schleifmethoden hergenommen werden, um eine Struktur auf der Oberfläche des Substrats, also des Kondensatorrohres, zu erzeugen.In addition, alternative or supplementary methods for structuring the substrate can be used. For example, sandblasting and / or grinding methods can be used to create a structure on the surface of the substrate, ie the condenser tube.
Das Schleifen kann beispielsweise mittels Sandpapier ver- schiedener Oberflächenrauhigkeit erfolgen. Dabei wurden Kontaktwinkel von bis zu 130° realisiert. Des Weiteren kann eine Strukturierung durch Sandstrahlen erfolgen, wobei klar wurde, dass ein wesentlicher Parameter der Sandtyp, mit dem sandgestrahlt wird, insbesondere in Bezug auf das Aspektverhältnis, ist. Beide Methoden, Sandstrahlen und Schleifen, erzeugen eine Rauhigkeit auf dem duktilen und metallischen Substrat. Das Beschichtungsmittel, das die chemischen Funktionalitäten in die Oberfläche einbringt, bildet auf der bereits strukturierten Substratoberfläche nur noch einen dünnen Film.The grinding can take place, for example, by means of sandpaper of different surface roughness. In this case, contact angles of up to 130 ° were realized. Furthermore, a structuring by sand blasting can be done, it has become clear that an essential parameter is the type of sand with which sandblasted, in particular in terms of the aspect ratio. Both methods, sandblasting and grinding, produce roughness on the ductile and metallic substrate. The coating agent, which brings the chemical functionalities into the surface, only forms a thin film on the already structured substrate surface.
Vorteilhafterweise erfolgt die Aufbringung des Beschichtungs- mittels erst nach der Strukturierung der Rohroberfläche, so dass die Strukturierung in der Beschichtung abgebildet ist. Nach einer anderen vorteilhaften Ausführungsform des Verfahrens wird eine Strukturierung in der Beschichtung erzeugt. Dies kann über alle gängigen Druck und Prägeverfahren erfol- gen .Advantageously, the application of the coating takes place only after the structuring of the tube surface, so that the structuring is imaged in the coating. According to another advantageous embodiment of the method, structuring is produced in the coating. This can be done by all common printing and embossing processes.
Nach einer bevorzugten Ausführungsform wird die Oberflächenstruktur durch ein Walzprägeverfahren mit beispielsweise einem Silikonstempel in die fertige Beschichtung eingebracht. Dazu können nach einer weiteren vorteilhaften Ausführungsform Silikonstempel durch Abformen von Sandpapier verschiedener Oberflächenrauhigkeit mit flüssigem Silikon hergestellt werden. Dazu wird flüssiges Silikon auf Sandpapier gegossen, nach erfolgter Härtung des Silikons wird dieses abgezogen, wobei es als Oberflächenstruktur den Abdruck des Sandpapiers zeigt. Durch Aufdrücken, u.U. mittels einer Walze, wird diese Struktur dann in die Beschichtung eingeprägt. Bei dieser Methode zur Erzeugung einer Oberflächenstruktur kann beispielsweise ein Rolle-zu-Rolle Verfahren eingesetzt werden.According to a preferred embodiment, the surface structure is introduced by a rolling embossing process with, for example, a silicone stamp in the finished coating. For this purpose, silicone stamps can be produced by molding sandpaper of different surface roughness with liquid silicone according to a further advantageous embodiment. For this purpose, liquid silicone is poured onto sandpaper, after curing of the silicone, this is peeled off, where it shows the surface of the imprint of the sandpaper. By pressing, u.U. by means of a roller, this structure is then embossed into the coating. In this method for producing a surface structure, for example, a roll-to-roll method can be used.
Andererseits kann die Strukturierung der Beschichtung auch durch Ätzen oder mittels strukturgebender Partikel erfolgen. Schließlich können Strukturen in der Beschichtung auch über den Einbau von Templates, die beispielsweise auch nach dem Aufbau der Struktur entfernt werden, erzeugt werden. Im Falle der Partikel können diese direkt mit der Beschichtungslösung vermengt und auflackiert werden.On the other hand, the structuring of the coating can also be effected by etching or by means of structuring particles. Finally, structures in the coating can also be produced by the incorporation of templates, which are also removed, for example, after the structure of the structure. In the case of the particles, these can be mixed directly with the coating solution and painted on.
Bevorzugt werden hybrid-vernetzte Sol-Gel-Systeme als Schichtmaterial eingesetzt, da diese neben einer hervorragenden Strukturierbarkeit eine gute Anhaftung zum Substrat und einen langzeitstabilen wasserabweisenden Effekt zeigen.Hybrid-crosslinked sol-gel systems are preferably used as the layer material since, in addition to outstanding structurability, they show good adhesion to the substrate and a long-term stable water-repellent effect.
Zudem kann die Struktur in die Beschichtung mittels Sprühbe- schichten auf einem heißen Substrat erzeugt werden. Dabei verdampft das Lösungsmittel sofort nach Auftreffen auf dem Substrat und hinterlässt, je nach verwendetem Lösungsmittel eingesetzter Feststoffkonzentration und Substrattemperatur eine Struktur mit definierter statistischer Rauhigkeit. Bei Verwendung von Fluor-Alkyl-haltigen Schichtmaterialien wurden auf diese Weise schon Kontaktwinkel von > 1500C erreicht.In addition, the structure can be produced in the coating by means of spray coating on a hot substrate. The solvent evaporates immediately after impinging on the substrate and leaves, depending on the solvent used solid concentration and substrate temperature a structure with defined statistical roughness. When using fluorine-alkyl-containing layer materials contact angle of> 150 0 C were already achieved in this way.
Nach einer Ausführungsform kann auch eine Kombination einer Grob und einer Feinstruktur vorliegen, in dem eine (Grob-) Struktur zunächst auf einer Rohroberfläche erzeugt wird, dann eine Beschichtung aufgebracht wird, in der dann wiederum eine Nano (Fein-) Struktur erzeugt wird. Somit können alle oben be- schriebenen Prozessschritte kombiniert werden.According to one embodiment, there may also be a combination of a coarse and a fine structure, in which a (coarse) structure is first produced on a pipe surface, then a coating is applied, in which in turn a nano (fine) structure is produced. Thus, all of the above-described process steps can be combined.
Gemäß der Erfindung können die technischen Vorteile der hydrophoben, also Tropfen-bildenden Beschichtungsmittel mit denen der AblaufStrukturen verbunden werden. So können mittels der vorgeschlagenen Beschichtung mit Struktur große Vorteile im Kondensations- und Abtropfverhalten eines Kondensatorrohrs realisiert werden.According to the invention, the technical advantages of the hydrophobic, ie drop-forming, coating agents can be combined with those of the drainage structures. Thus, by means of the proposed coating with structure great advantages in the condensation and dripping behavior of a condenser tube can be realized.
Einerseits wird die Haftung eines gebildeten Tropfens auf- grund der verringerten Oberflächenenergie des Substrats gemindert, so dass sich dieser leichter vom Rohr lösen und abtropfen kann. Des Weiteren können insbesondere kleine Tropfen, deren Gewicht zum Abtropfen bisher zu gering war, sich mühelos vom Rohr lösen.On the one hand, the adhesion of a formed drop is reduced due to the reduced surface energy of the substrate, so that it can more easily detach from the tube and drip off. Furthermore, especially small drops whose weight was previously too low to drip, can be easily detached from the tube.
Andererseits bewirkt die Beschichtung eine starke Verringerung des Gleitwinkels auf unter 5°, so dass Tropfen, egal an welcher Position des Rohres sich diese bilden, allein durch das Einwirken der Schwerkraft und durch die vorhandenen Strukturen wie in Kanälen ablaufen.On the other hand, the coating causes a strong reduction of the slip angle to less than 5 °, so that drops, no matter at which position of the pipe they form, run solely through the action of gravity and through the existing structures as in channels.
Die Erfindung ermöglicht extrem superhydrophobe Beschichtun- gen mit denen nicht nur der eingangs erwähnte Wasserfilm an der Rohraußenwand verhindert wird, sondern sogar Ablaufwinkel ermöglicht, die mit Anti-Haft-Beschichtungen allein nicht denkbar sind. Es werden beispielsweise Ablaufwinkel von kleiner 30° ermöglicht, wobei zu bedenken ist, dass bei unbe- schichteten Rohren selbst in senkrechter Position kein Ablaufen kleiner Wassertropfen erfolgt. The invention enables extremely superhydrophobic coatings with which not only the above-mentioned water film on the pipe outer wall is prevented, but even allows drainage angle, which are not conceivable with anti-adhesive coatings alone. For example, drainage angles of less than 30 ° are possible, bearing in mind that in the case of layered pipes even in a vertical position no running off small drops of water takes place.

Claims

Patentansprüche claims
1. Kondensatorrohr mit einer Oberfläche, bei der eine Mikrostruktur mit einer Beschichtung so zusammenwirkt, dass durch Kondensation gebildete Tropfen am Kondensatorrohr ablaufen.A condenser tube having a surface in which a microstructure cooperates with a coating such that drops formed by condensation drain on the condenser tube.
2. Kondensatorrohr nach Anspruch 1, wobei die Beschichtung wasserabweisend ist.2. Condenser tube according to claim 1, wherein the coating is water-repellent.
3. Kondensatorrohr nach einem der Ansprüche 1 oder 2, wobei als wasserabweisende Komponenten in der Beschichtung Al- kylgruppen und/oder fluorierte Alkylgruppen vorhanden sind.3. Condenser tube according to one of claims 1 or 2, wherein as water-repellent components in the coating alkyl groups and / or fluorinated alkyl groups are present.
4. Kondensatorrohr nach einem der vorstehenden Ansprüche, wo- bei das Beschichtungsmittel ausgewählt ist aus der Gruppe der4. Condenser tube according to one of the preceding claims, wherein the coating agent is selected from the group of
Sol-Gel-Lacke auf der Basis von Siliziumoxid, Fluorpolymeren, Silikone und/oder Lacke auf Polyurethan-Basis.Sol-gel lacquers based on silicon oxide, fluoropolymers, silicones and / or polyurethane-based lacquers.
5. Verfahren zur Oberflächenbehandlung von Kondensatorrohren, zumindest zwei Prozessschritte umfassend, einen Prozessschritt bei dem das Kondensatorrohr zumindest mit einem wasserabweisenden, also hydrophoben Beschichtungsmittel beschichtet wird und einen weiteren Prozessschritt bei dem zumindest eine Struktur auf der Oberfläche des Kondensatorrohrs erzeugt wird, wobei die Reihenfolge der Prozessschritte beliebig ist.5. A method for surface treatment of condenser tubes comprising at least two process steps, a process step in which the condenser tube is coated at least with a water-repellent, ie hydrophobic coating agent and a further process step in which at least one structure is produced on the surface of the condenser tube, wherein the order of Process steps is arbitrary.
6. Verfahren nach Anspruch 5, wobei die Aufbringung des Be- schichtungsmittels durch eine bekannte Beschichtungsmethode- erfolgt.6. A method according to claim 5, wherein the application of the coating agent is carried out by a known coating method.
7. Verfahren nach einem der Ansprüche 5 oder 6, wobei die Mikrostrukturierung der Substrat- oder Rohroberfläche über Schleifen, Sputter-Prozesse, mittels Ätzprozesse, durch WaIz- Prägen, Eloxieren, Oxalieren und/oder Sandstrahlen erfolgt. 7. The method according to any one of claims 5 or 6, wherein the microstructuring of the substrate or pipe surface via grinding, sputtering processes by means of etching processes, by WaIz embossing, anodizing, oxalizing and / or sandblasting takes place.
8. Verfahren nach einem der Ansprüche 5 bis 7, wobei eine Strukturierung der Beschichtung unabhängig von der Strukturierung der Rohroberfläche erfolgt.8. The method according to any one of claims 5 to 7, wherein a structuring of the coating takes place independently of the structuring of the tube surface.
9. Verfahren nach einem der Ansprüche 5 bis 8, wobei eine9. The method according to any one of claims 5 to 8, wherein a
Strukturierung der Beschichtung durch Prägemethoden und/oder durch Partikeleinbau erfolgt.Structuring of the coating is carried out by embossing methods and / or by particle installation.
10. Verwendung derartig behandelter Kondensatorrohre im Kraftwerksbereich Gegenstand der Erfindung. 10. Use of such treated condenser tubes in the power plant area subject of the invention.
EP09751861A 2008-12-19 2009-10-30 Condenser tube having increased hydrophobicity, production method and use thereof Withdrawn EP2368086A1 (en)

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