DE102008014272A1 - Coating for a heat transfer element of a heat transfer device at a side that is turned to a media space with vapor-liquid-phase change, comprises a matrix made of a metallic material, and hydrophobic polymer islands arranged at the matrix - Google Patents

Abstract

The coating comprises a matrix made of metallic material, and hydrophobic polymer islands arranged at the matrix. Surfaces of the islands are turned to a media space (18) with vapor-liquid-phase change. A matrix material is arranged between the islands. A surface of the coating, which is turned to the media space, is formed outside of the islands by the matrix material. A coherent matrix material layer forms rear side of the coating. The coating is disposed on a carrier with the matrix material layer. A layer thickness of the coating is 0.5-25 mu m. The islands are formed by polymer particle. The coating comprises a matrix made of a metallic material, and hydrophobic polymer islands arranged at the matrix. Surfaces of the islands are turned to a media space (18) with vapor-liquid-phase change. A matrix material is arranged between the islands. A surface of the coating, which is turned to the media space, is formed outside of the islands by the matrix material. A coherent matrix material layer forms a rear side of the coating. The coating is disposed on a carrier with the matrix material layer. A layer thickness of the coating is 0.5-25 mu m. The islands are formed by polymer particle, have an average diameter of smaller than 0.5 mu m and a surface of a size, which lies in the magnitude of drops developed during the phase change, and have an average diameter in the nanometer range. The polymer material in the coating has a portion of 30-40 volume.%. The coating is amorphously formed and annealed. Independent claims are included for: (1) a heat transfer element; and (2) a method for producing a coating for a heat transfer element at a side, which is turned to a media space with vapor-liquid-phase change.

Description

The The invention relates to a coating for a heat transfer element on a Side facing a media room with vapor-liquid phase change is.

The The invention further relates to a heat transfer element with a first side, which is a media room with vapor-liquid phase change is facing.

The The invention further relates to a heat transfer device.

The Invention further relates to a method for producing a Coating.

At Heat transfer elements with a vapor-liquid phase change can basically a film condensation take place or a drop condensation. The film condensation forms a coherent one Film on a surface the heat transfer element out. Dropwise condensation forms droplets.

It has been shown to be higher Heat transfer coefficient and thus heat transfer coefficients for one Heat transfer device achieved when drop condensation occurs.

Of the Invention is based on the object, a coating of the above to provide said type, which advantageous properties in terms of Drop condensation has.

These The object is achieved according to the invention in the above-mentioned coating that this one matrix of a metallic material with islands out a hydrophobic polymer disposed on the matrix are, with surfaces the islands facing the media room.

The hydrophobic islands form condensation nuclei and ensure dropwise condensation. The Metallic matrix material ensures that the thermal resistance is minimized; the metallic material has a low thermal conductivity on. This will ensure that the positive effect of the drop condensation not by a "bad" thermal resistance is nullified.

The surface the heat transfer element with the coating leaves form smoothly to allow a quick drop drain.

It has been shown to be an appropriate coating with produce high long-term stability leaves. Further leaves It can easily achieve that the coating does not with condensing heat transfer medium (Especially water) or its impurities reacts.

The Matrix material ensures in addition to good thermal conductivity and mechanical Fixation of the islands also for a good adhesion to a carrier, which in particular of a metallic material such as stainless steel is made.

All it is particularly advantageous if between matrix material matrix material is arranged. By doing so leaves a low thermal resistance to reach.

Out for the same reason it is favorable if a surface the coating, which faces the media room, outside the islands is formed by matrix material. As a result, heat conduction paths provided, which for a low thermal resistance to care.

It is also advantageous if a coherent matrix material layer is provided is what a back the coating forms, with which this arranged on a support is. By doing so leaves heat in the carrier over the entire surface of the carrier einkoppeln and deliver it to a working medium.

ever the lower the layer thickness, the lower the thermal resistance. Leave with the solution according to the invention In particular, layer thicknesses between 0.5 .mu.m and 25 .mu.m realize. Especially the layer thickness is between 1 μm and 20 μm. In a concrete embodiment was a layer thickness of 5 microns realized.

Cheap is it when islands of polymer material formed by polymer particles are. By doing so leaves to simplify the production. Furthermore, can be in the production achieve a homogeneous island distribution.

It is particularly advantageous when an island of exactly one Polymer particles is formed. This allows the coating with create defined properties.

Cheap is if the islands have a size at least at the surface, which in the Magnitude is due to the phase change resulting drops. Thereby forming the islands optimized condensation nuclei for droplet formation in the vapor-liquid phase change.

It has proved to be favorable if the islands (on the surface) have an average diameter of less than 0.5 μm and in particular less than 0.2 μm exhibit. In particular, the islands have a mean diameter (at the surface of the coating) which is in the nanometer range. Typically, droplet sizes of droplets which are formed during droplet condensation are in the nanometer range.

It has been considered favorable proven when the polymer content of the coating between 20 % By volume and 50% by volume, preferably between 25% by volume and 45% by volume, and more preferably between 30% by volume and 40% Volume% is. This results in an optimum on the one hand between advancement the drop condensation and on the other hand between minimizing the Thermal resistance, which is a long-term stable and mechanically stable coating can be realized.

It has been considered favorable proven when the coating is formed amorphous. Thereby let yourself For example, achieve a homogeneous island distribution on the matrix.

Further it has to be cheap proven when the matrix material is Ni-based. Nickel has one high thermal conductivity. Further leaves Good adhesion of the coating on a metallic support such as stainless steel carrier to reach.

Especially receives you have a high adhesion, when the matrix material contains phosphorus and is in particular Ni-P.

It has been considered favorable proven when the phosphorus content between 2% and 15% and in particular between 5% and 10%.

When favorable Polymer material has proven to be perfluoroalcohol copolymer (PFA). This material is hydrophobic and promotes droplet condensation.

Especially It is advantageous if the coating is tempered. It has It was shown that this high long-term stability of the coating reached.

Of the Invention is also the object of a heat transfer element of the type mentioned above, by means of which achieve a high heat transfer coefficient leaves.

These Task is the invention in the heat transfer element mentioned above solved, that arranged on the first side of a coating according to the invention is. The heat transfer element is part of a heat transfer device. It is, for example, plate-shaped educated. On the first side flows heat transfer medium in the form of phase change medium past.

Especially is a carrier made of a metallic material to which the coating is arranged. The carrier takes care of the mechanical stability. He stops For example, seals to a media room for phase change medium and a Media room for Separate working medium. Further, corresponding to the carrier surface structures be arranged to the heat transfer through geometric training and to increase the turbulence promote, to also in this way the heat transfer to improve.

Especially is the carrier grooved on a coating side or he has a corrugated sheet-like training on. Corresponding grooves (channels) can also at an angle to a main flow direction in a media room be arranged, with different angles are possible.

at an embodiment has a heat transfer element a second side opposite the first side, which faces a media room, which of a working medium flows through is. A heat transfer element thus has a "phase change page" on and a "working medium side". The heat transfer element let yourself to train accordingly thin, so that there is an optimized heat transfer from the heat transfer medium (Phase change medium) can be achieved to the working medium.

Especially is the second side on a carrier for the Coating formed around the heat transfer element train sparingly to be able to.

One Heat transfer element according to the invention let yourself advantageously in a heat transfer device deploy.

A such heat transfer device has in particular a feed device and discharge device each for Heat transfer medium (Phase change medium) and working medium. The heat transfer device has a flow device with one or more media rooms for heat transfer medium on and a flow device with one or more media rooms for working medium.

advantageously, Water is used as a phase change medium (heat transfer medium).

When Working medium is used in particular thermal oil.

Of the The invention is further based on the object, a process for the preparation to provide a coating of the type mentioned.

These Task is inventively characterized solved, that for producing the coating according to the invention a coating material from aqueous solution is deposited.

It It has been found that by this method, a coating according to the invention can be produced in a simple manner with high long-term stability.

Especially becomes the watery solution heated. By doing so leaves Homogeneous distribution of polymer material islands in the matrix to reach.

It has been considered favorable proven when the temperature of the aqueous solution is not more than 90 ° C.

All it is particularly advantageous if the applied layer is tempered becomes. For example, it is at a temperature of about 320 ° C for four hours annealed. This preserves one has a high long-term stability.

The The following description of preferred embodiments is used in conjunction with the drawings of the closer explanation the invention. Show it:

1 a schematic representation of a test arrangement with a heat transfer device;

2 an exploded view of an embodiment of a heat transfer device with heat transfer elements;

3 a schematic sectional view of a heat transfer device;

4 a schematic representation of the structure of a coating according to the invention;

5 a photograph of droplet formation on a coating according to the invention; and

6 the heat flow as a function of the volume flow of a working medium under different conditions and experimental procedures.

An embodiment of a heat transfer device according to the invention, which in 1 With 10 is designated and in an overall system 12 is arranged, wherein the entire system is a pilot plant, comprises a flow device 14 for a heat transfer medium. The heat transfer device according to the invention works with a heat transfer medium, which performs a vapor-liquid phase change. An example of such a heat transfer medium is water.

The heat transfer device 10 also has a flow device 16 for working medium. The working medium takes on the heat transfer device 10 Heat from the heat transfer medium on.

The Working medium is for example a thermal oil.

The flow device 14 for heat transfer medium has, as will be explained in more detail below, at least one media room 18 in which the phase change from vapor to liquid can take place. It has been shown that it is possible to obtain high heat transfer coefficients and thus also high heat transfer coefficients from the heat transfer medium to the working medium when dropwise condensation takes place.

The experimental setup 12 according to 1 includes an evaporator 20 , which provides vaporous heat transfer medium. In the experimental arrangement 12 becomes the evaporator 20 charged with hot thermal oil. For a specific application, the evaporator 20 Part of the application.

From the evaporator 20 leads a line 22 to a steam dryer 24 , At the steam dryer 24 are still separated liquid components abge separated and via a line 26 a condensate collector 28 fed. The condensate collector 28 is preheatable via thermal oil.

The administration 26 that of the steam dryer 24 to the condensate collector 28 leads, is a liquid line. The steam dryer 24 has a further output for vaporous heat transfer medium, from which a line 30 to an input of the heat transfer device 10 leads, which with a flow device 14 connected in a fluid-effective manner.

On the line 30 is a volume flow measuring device 32 arranged.

Another line 34 leads from an outlet of the heat transfer device 10 , which in fluid-effective connection with the flow device 14 is connected to the condensate collector 28 , Via this line is condensed liquid from the heat transfer device 10 dissipated.

From an outlet of the condensate collection tank 28 leads a line 34 to the evaporator 20 ,

On the line 34 is a pump 36 arranged for the transport of the heat transfer medium.

Further, on the line 34 a preheater 38 arranged. Further, on the line 34 a measuring device 40 arranged to measure the flow rate.

The heat transfer device 10 is designed for example as a plate heat exchanger. In 2 is an embodiment of a heat transfer device 10 shown in exploded view. This has heat transfer elements 42 on, on which a heat transfer of heat transfer medium can take place on working medium.

A heat transfer element 42 has a first page 44 on which the media room 18 is facing. The first page 44 is thus part of the flow-through space 14 facing.

A heat transfer element 42 also has a second page 46 on which a media room 48 is facing, which is flowed through by working medium. The media room 48 is thus part of the flow-through device 16 ,

Surfaces of the heat transfer elements 42 are on the first page 44 and on the second page 46 with a surface-enlarging (and turbulence-promoting) structure 50 Mistake. This structure 50 is formed, for example corrugated sheet-like. One known surface texture is the chevron pattern. The structure 50 is preferably designed so that in addition to increasing the heat transfer and turbulence promotion is achieved. Through the structure 50 Channels are formed, which also at an angle to the main flow direction in a media room 18 respectively. 48 can lie.

Between adjacent heat transfer elements 42a . 42b is a seal 52 arranged.

At the heat transfer elements 42 are openings 54a . 54b formed, which on the first page 44 outside a seal 52 and thus outside of a media room 18 lie. Through these openings working medium the respective media spaces 48 to be provided.

There are also openings 56a . 56b formed by which heat transfer medium in a media room 18 can be coupled and heat transfer medium from the media room 18 can be decoupled. The openings 56a . 56b lie on the first page 44 inside the seal 52 to a media room 18 To provide heat transfer medium can.

At the second page 46 a heat transfer element 42 which the media room 48 facing, lie the openings 54a . 54b inside the seal 52 to make a fluid-efficient connection with the media room 48 to produce and be able to provide this working medium or to be able to dissipate this. The openings 56a . 56b lie on the second page 46 outside the seal 52 in order to achieve a fluid-effective separation.

The heat transfer device 10 has end plates 58 . 60 on, between which the heat transfer elements 42 are arranged. At the end plate 60 is a first connection 62 arranged for coupling of working medium. There is also a second connection 64 arranged for decoupling of working medium. Furthermore, on the end plate 60 a third connection 66 arranged for coupling of heat transfer medium and a fourth connection 68 for decoupling of heat transfer medium.

To a drop condensation in the vapor-liquid phase change in the media room 18 to obtain, has a heat transfer element 42 on the first page 44 a coating 70 on ( 4 ). The coating 70 has hydrophobic character.

The coating 70 has a smooth surface 72 on to a quick drop drain in the flow device 14 to enable. The coating 70 follows the structure 50 ,

The coating 70 is designed so that it does not react with the heat transfer medium or impurities in the heat transfer medium and is stable over a longer period of time.

The thermal resistance of the coating 70 must be as small as possible. For this purpose, the layer thickness should be as low as possible. In the solution according to the invention, layer thicknesses S between 0.5 μm and 25 μm and in particular between 1 μm and 20 μm were produced, with which good results can be achieved.

Furthermore, the thermal conductivity of the material of the coating should be 70 be very high, to keep the thermal resistance low.

In the solution according to the invention, the coating 70 , which on the first page 44 a heat transfer element 42 is arranged from a metallic matrix material 74 made into which islands 76 are embedded from a hydrophobic polymer material. The coating 70 has a matrix 75 on which the islands 76 are arranged. Part of the surface 72 the coating 70 , which is the media room 18 assigns is at the islands 76 formed, ie the islands 76 have surface areas 78 on which in the media room 18 the corresponding heat transfer element 42 point.

Through the islands 76 made of hydrophobic polymer material is provided for a drop condensation. The metallic matrix material 74 ensures a minimization of thermal resistance.

Between neighboring islands 76 lies matrix material 74 , Furthermore, on a back 80 the coating 70 the matrix material 74 continuous, ie there is a continuous matrix material layer 82 with which the coating 70 on a carrier 84 is arranged.

The carrier 84 forms the base plate of a heat transfer element 42 and is particularly made of a metallic material. The coating 70 is on the carrier 84 over the back 80 arranged. Through the continuous matrix material layer 82 is for a low heat resistance for the heat flow from the media room 18 in the media room 48 taken care of.

The carrier 84 the heat transfer elements 42 is formed for example by a stainless steel heat transfer plate. For example, stainless steel heat transfer plates TS6 from Alfa Laval are used.

Part of the surface 72 the coating 70 is by matrix material 74 formed, namely by that part of the matrix material 74 which is between islands 76 lies.

The islands 76 are made by polymer particles. In particular, it is an island 76 formed from exactly one polymer particle.

The islands 76 act as condensation nuclei for the droplet condensation. It is therefore most advantageous when the expansion of the island 76 at their surface area 78 is of the order of magnitude of drops of the heat transfer medium produced during the phase change. In particular, this is a mean diameter of such a surface area 78 below about 0.5 microns and especially below about 0.2 microns. In particular, the mean diameter is in the middle nanometer range.

It has proved to be favorable when the polymer content in the coating 70 is between 20% by volume and 50% by volume and in particular between 25% by volume and 45% by volume and in particular between 30% by volume and 40% by volume.

at a concrete embodiment lay the polymer content of the coating is between 32% by volume and 35% Volume-%.

In a specific embodiment, the coating 70 with a matrix material 74 made of nickel, wherein the matrix material is in particular Ni-P. The phosphorus content was between 2% and 15% and in particular between 5% and 10%. In a specific embodiment, the phosphorus content was between 6% and 9%.

The coating 70 is an amorphous layer.

As an advantageous polymer material for the islands 76 Perfluorooxycopolymer (PFA) was used. The coating 70 was tempered for long-term stabilization.

In one embodiment, the coating becomes 70 on the carrier 84 made as follows:
The carrier is a stainless steel heat transfer plate. The coating 70 is made with a thickness S of 5 microns. A layer (with matrix material and island material) is prepared by deposition from a heated aqueous solution. The temperature of the aqueous solution is at most 90 ° C. The coating material (Ni-P as matrix material and PFA as island material) is dissolved in the aqueous solution.

To Deposition of the layer, this is annealed. The annealing finds for example at 320 ° C in a four-hour period.

In 5 is the drop formation at one with the coating according to the invention 70 provided heat transfer element 42 shown. You recognize the drops. These have different sizes.

In 6 a diagram of the heat flow as a function of the volume flow of working medium is shown. The curve 86 corresponds to measured values, wherein the coating according to the invention 70 was used with a Ni-P matrix with PFA islands. The pressure on the phase change side was 2 bar. The curve 88 in comparison, it was determined under the same flow conditions, but with the corresponding support 84 no coating 70 was present.

It can be seen that the heat flow at the same time method is significantly higher.

The curve 90 corresponds to the curve 86 but the pressure on the phase change side was 1 bar. The comparison curve 92 corresponds to the experimental procedure without coating 70 , Again, it can be seen that due to the coating of the invention 70 a higher heat flow is achieved with the same procedure.

According to the invention, a heat transfer device 10 or a heat transfer element 42 or a coating 70 provided, one being the media room 18 facing surface can be smooth. The coating 70 has a high long-term stability in the inventive solution. The coating 70 does not react with condensing heat transfer medium or impurities contained therein.

This results in a low thermal resistance for the heat flow from the media room 18 to the media room 48 , The coating 70 can be produced thinly (with a layer thickness S of 25 μm or less). The thermal conductivity is due to the matrix material 74 high. The islands 76 promote the droplet condensation.

Furthermore, a good adhesion to the carrier can be achieved via a Ni-P matrix material 84 to reach.

The solution according to the invention can be used in connection with, for example, steam condensers. For example, can be appropriate heat transfer devices 10 use in seawater desalination or in the food industry.

Claims (34)

Coating for a heat transfer element ( 42 ) on one side ( 44 ), which corresponds to a media room ( 18 ) with vapor-liquid phase change, comprising a matrix ( 75 ) of a metallic material ( 74 ) and islands ( 76 ) of a hydrophobic polymer attached to the matrix ( 75 ) are arranged, wherein surfaces ( 78 ) of the islands ( 76 ) the media room ( 18 ) are facing. Coating according to claim 1, characterized in that between islands ( 76 ) Matrix material ( 74 ) is arranged. Coating according to claim 1 or 2, characterized in that a surface ( 72 ) of the coating ( 70 ), which the media room ( 80 ), outside the islands ( 76 ) by matrix material ( 74 ) is formed. Coating according to one of the preceding claims, characterized by a coherent matrix material layer ( 82 ), which has a back ( 80 ) of the coating ( 70 ), with which these on a support ( 84 ) is arranged. Coating according to one of the preceding claims by a layer thickness between 0.5 microns and 25 microns. Coating according to one of the preceding claims, characterized in that the islands ( 76 ) are formed of polymer material by polymer particles. Coating according to claim 6, characterized in that an island ( 76 ) is formed from exactly one polymer particle. Coating according to one of the preceding claims, characterized in that the islands ( 76 ) have at least one surface of a size which is of the order of magnitude of drops formed during the phase change. Coating according to one of the preceding claims, characterized in that the islands ( 76 ) have a mean diameter less than 0.5 microns. Coating according to one of the preceding claims, characterized in that the islands ( 76 ) have a mean diameter smaller than 0.2 microns. Coating according to one of the preceding claims, characterized in that the islands ( 76 ) have a mean diameter in the nanometer range. Coating according to one of the preceding claims, characterized in that the polymer material in the coating ( 70 ) has a proportion between 20% by volume and 70% by volume. Coating according to one of the preceding claims, characterized in that the polymer material in the coating ( 70 ) has a share between 25% by volume and 45% by volume. Coating according to one of the preceding claims, characterized in that the polymer material in the coating ( 70 ) has a proportion between 30% by volume and 40% by volume. Coating according to one of the preceding claims through an amorphous training. Coating according to one of the preceding claims, characterized in that the Matrix material ( 74 ) is Ni-based. Coating according to one of the preceding claims, characterized characterized in that the matrix material contains phosphorus. Coating according to one of the preceding claims, characterized in that matrix material ( 74 ) Ni-P is. Coating according to claim 18, characterized in that that the phosphorus content is between 2% and 15%. Coating according to claim 17, characterized in that that the phosphorus content is between 5% and 10%. Coating according to one of the preceding claims, characterized in that the polymer material is perfluoro-alkoxy copolymer is. Coating according to one of the preceding claims through a heat treatment. Heat transfer element with a first side ( 74 ), which corresponds to a media room ( 18 ) faces with vapor-liquid phase change, wherein on the first side ( 44 ) a coating ( 70 ) is arranged according to one of the preceding claims. Heat transfer element according to claim 23, characterized by a support ( 84 ) of a metallic material to which the coating ( 70 ) is arranged. Heat transfer element according to claim 24, characterized in that the support ( 84 ) is groove-shaped on a coating side. Heat transfer element according to one of claims 23 to 25, characterized by a second side ( 46 ) which faces the first side (44) facing a media room ( 48 ), which is flowed through by a working medium. Heat transfer element according to claim 26, characterized in that the second side ( 46 ) on a support ( 84 ) for the coating ( 70 ) is formed. Heat transfer device comprising at least one heat transfer element according to one the claims 23 to 27. Heat transfer device according to claim 28, characterized by water as a phase change medium. Heat transfer device according to claim 28 or 29, characterized by thermal oil as the working medium. Process for the preparation of a coating for a heat transfer element on one side, which is a media room with vapor-liquid phase change facing, wherein the coating is a matrix of a metallic Comprising material and islands of a hydrophobic polymer which are arranged on the matrix material and wherein surfaces of the Islands facing the media room, in the coating material from aqueous solution is deposited. Method according to claim 31, characterized in that that the watery solution is heated. Method according to claim 32, characterized in that that the temperature of the aqueous solution is at most 90 ° C is. Method according to one of claims 31 to 33, characterized that the applied layer is tempered.