JPH09264695A - Method and device for transferring heat of condensation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the heat transfer coefficient by forming the surface of condensation transfer surface in contact with the condensate element in the super-dropwise condensed condition in which no drops generated from the condensate element are adhered to easily separate the condensate from the condensation surface. SOLUTION: A paint layer 24 consisting of the powder particles (0.015-20μm) 22 of low surface tension and the binder 23 to fix the particles is formed on the surface of a base material 21 of a condensation surface of a condensation pipe. Fine rugged parts 25 are formed on the whole paint layer by projecting powder particles 22. The material of the particles 22 is silica, etc., and silicone oil, etc., is coated on the surface as the treatment agent for low surface tension. The formed condensation surface forms the super-dropwise condensed condition with a thin air film between the condensate element and the fine rugged parts, and the generated condensate is spheroidized so as to be rapidly detached from the condensation surface. Thus, the continuous heat flow of the vapor latent heat is formed to the condensation surface to remarkably improve the heat transfer coefficient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a condensation heat transfer method and apparatus for releasing latent heat of vapor of a heat medium to a condensation surface to transfer heat, and particularly to facilitating separation of a condensate from the condensation surface. The present invention relates to a condensation heat transfer device having improved heat transfer performance by super-droplet condensation.

[0002]

2. Description of the Related Art Condensation heat transfer devices that release the latent heat of vapor of a heat medium to a condensation surface to transfer heat are used in power plants, condensers of large ships, various distillers in the chemical industry, heat pipes, heat pumps, etc. Widely used. Condensation heat transfer in these various devices, it is necessary to release the vapor latent heat of the heat medium to the condensation surface to condense and liquefy, and to continuously generate this condensation, but depending on the condensation form of the condensation surface, It makes a big difference in the heat transfer rate.

The transfer behavior of the heat of condensation is roughly divided into the following two forms. The first is film-like condensation in which the condensate covers the condensing surface in a film shape, and the second is the condensate is condensed. Dropwise condensation that covers the surface in drops. In the first film condensation, the condensation surface is covered with the condensed liquid in a film shape, and the heat transfer on the condensation surface is performed through the liquid film, so that the liquid film has a large heat transfer resistance. On the other hand, in the second droplet condensation, since the condensate is generated in droplets on the condensation surface, the area of the portion where the vapor directly contacts the condensation surface increases, and as a result, under the same conditions as in the case of the film condensation. In comparison, the heat transfer coefficient can be increased ten times or more.

Therefore, various studies on the droplet condensation have been studied. For example, the following methods are available as a method for causing the droplet condensation of water vapor. A method in which a chain fatty acid (oleic acid, stearic acid, etc.), amines, silicone resin, mercaptan, montan wax, or other accelerator is directly attached to the condensation surface.

A method in which the above-mentioned accelerator is added to steam or feed water and adsorbed on the condensation surface during condensation. A method of coating the condensation surface with copper sulfide, silver sulfide, etc. A method of coating (plating) the surface of the condensation surface with a thin film of a noble metal such as gold, silver, rhodium, or palladium. A method of coating the surface of the condensation surface with a fluororesin.

[0006]

However, the above-mentioned prior art has the following problems. That is, the method (3) has a problem in durability because the accelerator easily flows out. In the method (1), it is necessary to replenish and recover the accelerator, and there are problems that the water supply and the condensate are contaminated and the condensing surface is corroded. However, there is a problem that sulfide is toxic in general.
The method (1) has a problem that the cost of the precious metal is high and it is not practical. The method (1) has a problem that the film characteristics deteriorate with time and the initial characteristics cannot be maintained in the long term.

Furthermore, in all the prior arts, the contact angle of the condensate with respect to the condensing surface is not yet sufficiently large, so that the condensate has a property of coming into considerable contact with the condensing surface and spreading on the surface, A part of the liquid adheres to the condensing surface to form a notched sphere that crushes the sphere. For example, in the case where water is used as the condensate when the condensing surface is coated with a fluororesin, the contact angle is at most 110 °.
However, the condensate is likely to adhere to the condensing surface, and thus droplet condensation with high heat transfer coefficient has not been realized yet.

The present invention solves the above-mentioned problems of the prior art. The object of the present invention is to form a "thin air film" with the condensate component, that is, a so-called "super-droplet condensed state". Therefore, it is an object of the present invention to provide a condensing heat transfer method and a device therefor, which are not present in the prior art, in which the heat transfer coefficient is improved by easily releasing the condensate from the condensing surface. In addition to solving the above problems, it also contributes to the creation of new devices.

[0009]

The method and apparatus for condensing heat transfer of the present invention is constructed as follows. A) The condensing surface constituting the condensing heat transfer device has a surface formed of a material having a low surface tension and has fine irregularities, and when contacted with the condensate component, the condensate component and the fine component are contacted. It is characterized in that a condensate is prevented from adhering to the condensing surface (heat transfer surface) by forming a film having an air film forming capability between the concavo-convex portion and the rough surface.

B) The low surface tension material forming the condensing surface is a hydrophobic powder particle having a low surface tension at least on its surface, or polytetrafluoroethylene (hereinafter referred to as PT).
It is composed of one or more selected from powder particles (referred to as FE). C) Further, in the condensation heat transfer device, the fine concavo-convex portion is formed of the material itself having a low surface tension.

D) Further, fine concavo-convex portions are formed on the condensing surface at least by machining, rolling, photolithography,
It is formed by one kind or two or more kinds selected from high-density energy processing, and the surface of the fine uneven portion is covered with a material having a low surface tension. E) Further, a paint layer is formed on the condensing surface, and powder particles are fixed on the surface of the paint layer so as to be exposed, and the powder particles protruding from the paint layer have a low surface tension at least on the surface. It is composed of one kind or two or more kinds selected from the hydrophobic powder particles subjected to the above, or the PTFE powder particles.

F) Further, a coating layer is formed on the condensing surface, powder particles are fixed to the surface of the coating layer so as to project, and the surface is coated with a material having a low surface tension. . G) Further, a plating layer is formed on the condensing surface, and eutectoid plating is performed on the surface of the plating layer so as to project powder particles, and the powder particles protruding from the plating layer have a low surface tension at least on the surface. Hydrophobic powder particles or PTF
It is composed of one kind or two or more kinds selected from the powder particles of E.

As described above, the condensing surface forming the condensing heat transfer device according to the present invention has a surface formed of a material having a low surface tension, has fine irregularities, and has a super-droplet condensed state. The feature is that it is processed on the surface to be formed. As a result, the contact area between the condensate condensed on the condensing surface and the sphere becomes extremely small, and when it comes into contact with the condensate component, the air that was previously attached in the air to these fine irregularities is contained.
The state is held. That is, when this surface is immersed in the condensate component liquid, air is retained on the surface. Then, this air becomes a thin film on the surface and exists in the state of a so-called air film, and light is totally reflected at the part of the air film, so that the condensation surface looks silver.

On the contrary, when the condensate component liquid is placed on this condensing surface, the liquid becomes spherical due to the surface tension action and is lifted up to the fine convex portion formed on the condensing surface, as if rolling. You can see that it rolls like mercury.
Therefore, by forming a film having the ability to form an air film with the condensate component on the condensing surface, the condensate produced by heat exchange is spheroidized like mercury on the condensing surface,
The separation from the condensation surface can be facilitated. So to speak
The ultra-drop-like condensed state appears, the generated condensate does not become large water droplets, and quickly falls off the condensing surface and the area where the direct steam contacts the condensing surface significantly increases, condensing the vapor latent heat. By forming a continuous heat flow on the surface, the heat transfer coefficient can be dramatically improved.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic diagram of a condensing heat transfer device showing an embodiment of the present invention, and in this embodiment, it relates to steam condensation. Steam generator 1
The steam generated in 1 is supplied into the condensing chamber 3 via the separator 2. The condensing pipe 4 is provided across the condensing chamber 3, and the surface of the condensing pipe 4 forms a condensing surface 5.

The condensing tube 4 is made of copper and has an outer diameter of 19 mm, an inner diameter of 17 mm, and a heat transfer portion length of 1000 mm, and the condensing surface 5 has a film having the air film forming ability of the present invention formed on the surface thereof. Since a condensate is generated in the condensing pipe 4, a condensate collector 6 is arranged below the condensate to collect the condensate. The cooling water is pumped by the pump 11, supplied to the inside of the condensing pipe 4 through the cooling constant temperature bath 7, the flow meter 8, and the mixing chamber 9, and after passing through the condensing pipe 4, passes through the mixing chamber 10 to the pump 11. I'm supposed to come back.

The amount of heat transfer on the condensing surface 5 of the condensing pipe 4 was obtained from the temperature rise and the amount of cooling water when the cooling water passed through the condensing pipe 4. In addition, the morphological observation of condensation of the condensate was carried out through a viewing window in which the conductive glass was energized to prevent fogging. Next, a film having an air film forming ability formed on the surface of the condensation surface 5 in this embodiment and a method for forming the film will be described.

FIG. 2 is a schematic cross-sectional view showing an embodiment in which a coating film having an air film forming ability is formed by a coating method. Reference numeral 21 denotes a condensing surface base material, which in this case indicates the surface portion of the condensing surface base material 4. On the surface of the condensing surface base material 21, the powder particles 22 and the powder particles 22 which are low surface tension materials are fixed. A paint layer 24 made of a binder 23 is formed. Then, on the coating layer 24, the powder particles 22 that are a material having a low surface tension are formed so as to project, and have fine irregularities 25 as a whole.

Although the uneven portion 25 has no fixed shape, the small unevenness formed by the powder particles 22 and the powder particles 22.
Form a double-structured concavo-convex structure having a large concavo-convex structure formed by being embedded in the binder 23. More specifically, the condensing surface base material 21 has its shape, structure, material, etc. appropriately determined according to the purpose and application of various condensing heat transfer devices. For example, there is a heat exchanger having a tubular or plate-like shape and a structure divided by a plurality of tubes or partition walls, and the material of the condensation surface base material 21 is aluminum, stainless steel, copper, copper alloy, nickel. , Titanium and the like.

As the powder particles 22, hydrophobic powder particles whose surface is made to have a low surface tension or PTFE powder particles are used, and the former includes, for example, hydrophobic silica using a silane compound. Further, the material of the hydrophobic powder particles may basically be any one capable of lowering the surface tension of the powder particle surface. In addition to silica particles, for example, inorganic particles such as alumina and titania, and polymethacryl Organic particles such as methyl acid and polyester, and metal particles such as aluminum are used.

As the surface tension reducing agent for the surface of the powder particles 22, there are silane compounds such as silane, silazane and silicone oil, titanate coupling agents, amine amides, alcohols and glycols. In other words, it is preferable to use the powder particles treated with the fluorine-containing treatment agent because the air film forming ability and the durability are generally high. However, in order to have an excellent air film forming ability, it is necessary to cover the hydrophilic portion of the surface of the powder particles 2 with the surface treatment agent as much as possible, and it is necessary to match the powder particles 22 with the treatment agent.

The method for treating the surface of the powder particles 22 and the conditions relating to this treatment are not particularly limited, and may be appropriately selected depending on the type of the powder particles 22 and the surface treatment agent to be used, material characteristics and the like. Further, for the purpose of completely hydrophobizing the surface of the powder particles, the surface of the powder particles is subjected to a multi-step treatment with a surface treatment agent, or various kinds of surface treatment agents are used, or the surface of the particles is subjected to a low surface tension treatment. After that, it may be further fluorinated by using F ₂ gas or the like.

The powder particles 22 are fine particles having an average particle diameter of 0.015 μm to 20 μm, preferably 0.1 μm.
The range of 10 μm is preferable. If it is larger than the above range, the condensate can easily fall off, but the coating layer 24 including the powder particles 22 becomes thicker, and the heat transfer resistance of the coating film can be increased due to the effect of facilitating the fall off of the condensate. The impact is greater, which is not preferable. Further, when the particle size is smaller than the above range, when the concavo-convex structure is formed on the condensing surface base material 21, the concavo-convex portion is small and the surface structure becomes too smooth, so that the contact area with the condensate becomes large and the air film forming ability is increased. Is inferior, the desorption of the condensate is not performed smoothly, and the durability is poor.

The binder 23 is used for fixing the powder particles 22, and in consideration of adhesion with the material of the condensation surface base material 21, condensation liquid resistance, paintability, heat resistance of the material, etc. It may be appropriately selected, and examples thereof include silicone resin, fluororesin, epoxy resin, and acrylic resin. As a forming method, first, a silicone resin is used as a binder 23, and the hydrophobic silica powder particles 22 having an average particle diameter of 1 μm are obtained by subjecting this silicone resin to a coating agent to reduce the surface tension with perfluoroalkylsilane. 30% by weight was added to the solid content in the coating agent, and the mixture was sufficiently stirred and dispersed. Next, this is condensed surface substrate 2
It was applied to one surface, dried and cured to form a film having a thickness of 5 μm and having an air film forming ability having a fine concavo-convex structure on the surface.

As described above, if the coating becomes too thick, the effect of increasing the heat transfer resistance of the coating itself is greater than the effect of facilitating the falling off of the condensate. It is necessary to take into consideration the adhesion, the air film forming ability, the heat transfer resistance of the film, and the like to obtain matching. The method for forming a coating film having the ability to form an air film on the condensation surface in the condensation heat transfer device of the present invention is basically such that the surface of the condensation surface substrate 21 is formed of at least a material having a low surface tension, and fine irregularities are formed. Any method capable of forming a structure having

Specifically, a method of forming a paint layer on the surface of the condensing surface substrate of this embodiment and forming powder particles having a low surface tension on the surface of the paint layer so as to project is there. Furthermore, there are the following three forming methods, for example. First, a paint layer is formed on the surface of the condensing surface, the powder particles are fixed to the surface of the paint layer so as to project, and fine irregularities are formed on the surface in advance. Coating with a material having In this case, the powder particles may be hydrophilic materials as long as they can be subjected to the surface tension lowering treatment later. First, the condensation surface substrate surface is machined, rolled, photolithographically processed, high-density energy processed, etc. to form fine irregularities on the surface in advance, and then this surface is coated with a material having low surface tension. Process and form.

In this case, fine concavo-convex shape imparting processing may be performed directly on the surface of the condensing surface substrate, but it may be used as a surface material for imparting fine concavo-convex shape, for example, through a synthetic resin. Further, the surface of the condensing surface substrate may be coated with a material having a low surface tension material in advance, and the surface may be processed to have fine irregularities. A plating layer is formed on the condensation surface base material, and eutectoid plating is performed so that powder particles are projected on the surface of the plating layer, and the powder particles protruding from the plating layer have a low surface tension at least on the surface. Hydrophobic powder particles or PTFE
A coating film having fine irregularities made of powder particles is formed.
In the case of eutectoid plating using hydrophilic powder particles, a low surface tension treatment is performed later.

Test Example The air film forming characteristics when various liquids were brought into contact with the surface having the air film forming ability thus formed were evaluated. The evaluation methods include a) the surface of the present embodiment, b) a plate-shaped PTFE resin surface, and c) a surface formed by applying a silicone resin coating agent ...
A test piece having three types of surfaces was prepared. Then, dip these test pieces in various liquids such as water and organic solvent,
It was observed whether an air film was formed on the surface.

The results are shown in Table 1. As shown in Table 1, it was confirmed that on the surface of the present embodiment, an air film was formed in all liquids other than ethanol among the liquids under test, and the surface exhibited silver color. This air film was not easily peeled off, and the air film was retained on the surface. Also, when a droplet is dropped on this surface,
It was observed that all liquids, except ethanol, rolled around the surface, rolling like mercury.

[0030]

Then, 30 μl of the test liquid was brought into contact with the leveled surface, and then the surface was gradually tilted, and the inclination angle of the surface when the spherical liquid rolled down was determined by the falling angle of the liquid. Then, all liquids other than ethanol had a falling angle of 1 ° to 3 °, and even if it was slightly tilted, it fell down. On the other hand, whether or not an air film was formed on the plate-shaped PTFE resin surface and the surface formed by applying the silicone resin coating agent was confirmed by the above method. An air film was formed in the test liquid on both surfaces. Was not done.

Further, even if the liquid droplet is dropped, the surface does not roll around, and even if the falling angle is tilted at 90 °, it does not drop. To drop it from the surface, a considerably large amount of test liquid of more than 30 μl is contacted. It was necessary, and it was in a state where it drooped like a streak and flowed downward. In addition,
In addition to the liquids tested in this test example, any liquid capable of forming an air film is capable of super-droplet condensation and can be used as a condensed liquid, and is not particularly limited.

According to the above-mentioned various points of view, a film having the ability to form an air film of the present embodiment was formed on the actual surface of the condensation surface 5 and used for steam condensation, and the heat transfer performance was investigated. As a condensation experiment, first, the cooling water inlet temperature was set to 30 ° C. and the flow velocity was 1.2 m / s. Then, steam having a temperature of 100 ° C. was introduced into the condensing chamber 3, and after the steady state was reached, the cooling water outlet temperature was measured.

The condensed form shows a super-drop-like condensed form, in which the water condensed on the outer circumference of the condenser tube becomes a spherical drop like a micro glass bead and covers the condensed surface, and a drop that grows a little larger in it. When he started moving along the outer circumference, he fell on the surface in a blink of an eye while coalescing the surrounding water droplets. Such a phenomenon was repeated everywhere on the outer circumference of the condensing tube and did not stay on the condensing surface for a long time. Further, the coating film has excellent durability and can maintain the ultra-drop-like condensed form for 8,000 hours or more.

At this time, the cooling water outlet temperature was 48.8 ° C., which was 18.8 ° C. higher than the cooling water inlet temperature. Than this,
The amount of heat transfer was 18,398 kcal / h. [Comparative Example 1] For comparison, the same condensation experiment was performed using an untreated copper tube without a film formation, instead of the surface having an air film forming ability. Regarding the condensation form, condensed water covered the outer circumference of the copper pipe in a film-like form in a wet state, and showed a so-called film-like condensation form.

At this time, the cooling water outlet temperature was 44.8 ° C.
It was 14.8 ° C. higher than the cooling water inlet temperature. From this, the amount of heat transfer was 14,484 kcal / h. [Comparative Example 2] For comparison, the surface of a copper tube was coated with PTF having a thickness of 2 μm
A similar condensation experiment was conducted using a condenser tube formed of the E resin coating. The condensed form shows a so-called drop condensation form, in which condensed water covers the outer circumference of the condensation tube in a drop shape, and when the grown water drops start moving downward, they coalesce with the surrounding water drops and at a relatively slow speed. It fell down like a streak along the outer circumference and accumulated at the bottom of the tube, and when the amount exceeded a certain amount, it dropped as water droplets from the bottom of the tube. At this time, the cooling water outlet temperature was 47.5 ° C., which was 17.5 ° C. higher than the cooling water inlet temperature. From this, the amount of heat transfer was 17,126 kcal / h.

The duration of droplet condensation of the PTFE resin coating was about 2000 hours, and thereafter the film condensation form was obtained. From the above comparison test, the heat transfer amount of the condensation tube having the film having the air film forming ability on the condensation surface of the condensation heat transfer device is 27% as compared with the copper tube of film condensation, and the PTF of droplet condensation is
The heat transfer performance was 7.4% higher than that of the condensing tube formed with the E resin coating, and showed excellent heat transfer performance.

Further, the coating film having the ability to form an air film of the present invention was far more excellent in durability than the PTFE resin coating film. The condensation heat transfer device of the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the scope of the present invention.

[0039]

EFFECTS OF THE INVENTION The method of condensation heat transfer according to the present invention is a super drop condensation in which the condensation heat transfer surface in contact with the condensate component does not substantially adhere to the liquid droplets generated by the condensation of the condensate component. The condensate component is formed on the surface forming the state, and the condensate component is fed to the condensate heat transfer surface to exchange heat with the condensate component.

In the condensation heat transfer device according to the present invention, the condensing surface of the condensation heat transfer device is made of a material having a low surface tension and has fine irregularities, which come into contact with the condensate component. At this time, a film having a characteristic of forming a thin air film is formed between the condensate component and the fine irregularities. Therefore, the contact area between the condensing surface and the condensate becomes remarkably small, and as a result, the generated condensate is spheroidized like mercury on the condensing surface and can be easily separated from the condensing surface.

Due to such an ultra-drop-like condensed state, the generated condensate does not turn into large water droplets and quickly falls off the condensing surface, so that the area of the portion where the direct vapor comes into contact with the condensing surface remarkably increases. By forming a continuous heat flow to the condensation surface of the latent heat of vapor, the heat transfer coefficient can be dramatically improved. Further, the condensation heat transfer device of the present invention has excellent durability and can maintain and maintain a stable ultra-drop-like condensed state for a long period of time.

As a result, the applicable range of power plants, condensers of large ships, heat pipes, heat pumps, evaporators in the chemical industry and the like is extremely wide. Further, since the heat flux on the condensing surface can be increased, the size and weight of the device including the condensing surface can be reduced, and along with that, the effects such as material cost reduction and running cost reduction are extremely large.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a condensation heat transfer device showing an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing an embodiment in which a coating film having an air film forming ability of the present invention is formed by a coating method.

[Explanation of symbols]

 1 Steam Generator 2 Separator 3 Condensing Chamber 4 Condensing Tube 5 Condensing Surface 6 Condensate Collector 7 Cooling Constant Temperature Tank 8 Flow Meter 9 Mixing Chamber 10 Mixing Chamber 11 Pump 21 Condensing Surface Base Material 22 Powder Particles 23 Binder 24 Paint Layer 25 Unevenness

Claims (8)

[Claims] 1. A condensing heat transfer surface in contact with a condensate component,
Droplets generated by condensation of this condensate component are formed on the surface forming a super-drop-like condensed state where substantially no adherence occurs. A method of condensing heat transfer, characterized by exchanging. 2. The condensing surface of the condensing heat transfer device is made of a material having a low surface tension and has fine irregularities. A condensation heat transfer device, characterized in that a film having a characteristic of forming a thin air film is formed between the concavo-convex portion and the uneven portion. 3. The low surface tension material comprises at least one kind selected from hydrophobic powder particles whose surface has been subjected to low surface tension, or polytetrafluoroethylene powder particles. The condensing heat transfer device according to claim 2, wherein 4. The condensation heat transfer device according to claim 3, wherein the fine irregularities are formed of the material having the low surface tension. 5. The fine concavo-convex portion is at least machined,
It is formed by one kind or two or more kinds selected from a rolling process, a photolithography process, and a high-density energy processing, and the surface of the fine uneven portion is coated with a material having a low surface tension. 2. The condensation heat transfer device as described in 2. 6. A coating layer is formed on a condensation surface, and powder particles are fixed on the surface of the coating layer so as to project, and the powder particles projecting from the coating layer have a low surface tension on at least the surface. The condensing heat transfer device according to claim 2, wherein the condensing heat transfer device is made of one kind or two or more kinds selected from the hydrophobic powder particles subjected to the above, or the polytetrafluoroethylene powder particles. 7. A coating layer is formed on the condensation surface, powder particles are fixed to the surface of the coating layer so as to project, and the surface is coated with a material having a low surface tension. 2. The condensation heat transfer device as described in 2. 8. A plating layer is formed on the condensing surface, and eutectoid plating is performed on the surface of the plating layer so as to project powder particles, and the powder particles protruding from the plating layer have a low surface on at least the surface. 1 selected from tensioned hydrophobic powder particles or polytetrafluoroethylene powder particles
The heat transfer device for condensing heat according to claim 2, characterized in that the heat transfer device comprises two or more kinds.