JPS608057A - Method of forming droplet-shaped condensing surface - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming droplet condensation surfaces. More specifically, the present invention relates to a method for forming a droplet-like condensation surface on a metal condensation surface such as a heat exchanger.

Condensing heat exchangers are used in power plants, steam canisters on large ships,
It is widely used in heat pumps and evaporators in the chemical industry, where the latent heat of condensation of steam is effectively used as a heating source. The condenser when the condensed liquid is water is
It is usually called a condenser, but if you take a power plant as an example and divide it into components such as a boiler superheater and a turbine, the condenser is the largest structure among them. Currently, most of the manufacturing cost of a condenser is the material cost for the condensing surface, so if the condenser can be made smaller by reducing its area, a very large economic effect can be expected. Become.

By the way, the forms of condensation on the condensation surface are roughly divided into the following two types.

(1) Swelling and soft condensation: The condensate wets the condensing surface and flows down, covering the condensing surface like a film. (2) Droplet-like condensation: The condensing surface is wet with the condensate, so the condensate becomes drop-like. In the latter case of droplet condensation, which flows down on the condensation surface, the liquid film in the former case acts as a thermal resistance, whereas the released latent heat is directly transferred to the condensation surface, so the heat of droplet condensation under the same conditions is It is known that the transmission is ten to several tens of times greater than that of membranous condensation.

By the way, all condensing heat exchangers such as condensers are currently designed based on the film condensation theory, but if the droplet condensation theory could be used, the aforementioned miniaturization would be achieved, which would be extremely useful. The effect will be great. In order to achieve this droplet-like condensation, it is necessary to reduce the surface tension of the condensate surface so that it does not become wet with the condensate, and advantageous methods have been studied to date. There is. For example, (1) Precious metal plating: Gold plating and other metal plated surfaces take advantage of the property of not getting wet with water, but they are expensive.

(2) Sulfide coating: Silver sulfide 7''r takes advantage of the property that sulfides absorb water, but most fb oxides are saturated.

(3) Promoter addition: This is a method in which a fatty acid or the like is applied onto the condensing surface and added to the td water supply, but this method has drawbacks such as easy leakage and the need for replenishment and recovery.

(4) Polymer coating: Tetrafluoroethylene > ml F
'M' is a method of coating with silicone rubber, etc., but these generally have poor adhesion to metals, and the film thickness must be thinned to the extent that thermal resistance can be ignored while providing mechanical and thermal strength. There are some drawbacks, such as poor performance.

Among these various methods, the method of polymer coating is considered to have the highest possibility of practical application in terms of film life and material cost. Conventionally, polymer demolition has been carried out using a coating method, and it is possible to form a polymer film that adheres to the metal surface by baking the coating film, etc. : Thickness of 1μ
Since the inside of the film is made smaller than 0.0 m, and the formation of the film involves evaporation of the solvent, there are some caveats such as the unavoidable formation of pinholes in thin films.

The present inventor has conducted various studies on a method of forming a droplet-like condensation surface film using a fluororesin having a low surface tension as a coating material without exhibiting the drawbacks of the above-mentioned coating method. It has been found that forming a thin coating film of resin is extremely effective.

Therefore, according to the method for forming a droplet-shaped condensation surface of the present invention 1d, the formation of the droplet-shaped condensation surface is performed by forming a coating thin film of a fluororesin on the metal condensation surface by high-frequency sputtering.

The drawing schematically shows one embodiment of an apparatus used in the magnetron-type high-frequency sputtering method, which is preferably applied in the present invention because the temperature rise of the processed object during high-frequency sputtering is small.

That is, a substrate electrode 2 carrying objects to be processed 1 and 1' and a magnetron-type high-frequency electrode 4 holding a fluororesin target 3 are installed in a reaction tank 6 having an exhaust pipe 5 at positions facing each other. .

In the sputtering process, first, a vacuum pump (not shown) such as an oil diffusion pump is used to exhaust the air in the reaction chamber from the exhaust pipe to reduce the pressure to 10'' Torr or less, and then the barrier pull-leaf valve 7 is closed. While adjusting the stop valve 8, open the stop valve 8 and open the cylinder 9 of inert gas such as argon.
Argon gas or the like is introduced into the reaction tank, and the pressure there is adjusted to the order of IQ-' Torr. Now adjust the main valve (not shown) on the exhaust stack to reduce the pressure to 1
0-3~10゜Torr %Koseshikeke 6 X 10-
3 to i x 10-' Torr. If the pressure of argon gas, etc. is lower than this, discharge will not occur continuously,
If the pressure is higher than this, not only will the sputtering rate drop significantly, but the discharge will also become unstable, making it impossible to form a uniform coating film.

The sputtering operation is performed using a high frequency power source (13,56MHz
) 10 and a matching box (power meter) n to form a coating thin film of fluororesin on the condensed surface of the object to be treated.
When a predetermined film thickness (only L/, a thickness of 100 or more is required to make the film thickness uniform and eliminate pinholes) is obtained, the discharge is stopped and the argon gas is This is done by stopping the introduction of the substances, closing the main valve, and taking out the treated material from the reaction tank. Note that 12 is a leak valve, and 13 is a ground.

In this way, a condensing heat exchanger (having d1-order characteristics) is formed with a droplet-like condensation surface having a small surface energy similar to that of the fluororesin used as the coating material.

(1) Since the released latent heat is directly transferred to the condensing surface, the heat transfer under the same conditions is several ten times that of film condensation.

(2) Since the coating film can be formed with a thickness of 1 μm or less, the thermal resistance is low, and from this point of view as well, the heat transfer efficiency is improved.

(3) As a result of having a droplet-like condensation surface, the condensation area can be reduced.

(4) The adhesion of the coating thin film on the condensation surface is large;
Since there are fewer pinholes, the skin has a long lifespan.

(5) Since the film is formed by a sputtering method using a space, it can be applied regardless of the shape of the object to be treated, and a film of uniform thickness can be formed.

(6) The coating material is a fluororesin and is cheaper than other coatings such as plating coatings.

The method of the present invention is applicable to condensing heat exchangers such as waste heat district heating and cooling systems, factory waste heat recovery hot water supply and cooling systems, building cooling systems, solar absorption heat pumps, and condensers connected to steam turbines at power stations. Effectively applied to metal condensation surfaces. More specifically, the present invention is applied to the surface portion of a cooling pipe, for example in the case of a surface condenser of a steam turbine. Furthermore,
In addition to heat exchange analyzers, the present invention can also be applied to condensing surfaces such as distillers.

Next, the present invention will be explained with reference to examples.

EXAMPLE Using the illustrated apparatus, a high-frequency sputtering process of tetrafluoroethylene resin was performed on a trichlorethylene vapor-degreased 5US (304) substrate using a disc-shaped molded product of tetrafluoroethylene resin as a target. The treatment was performed at a discharge starting argon pressure of 0.1. Torr, carried out for 1 min at an effective power of 200 W, with a thickness of 0.5
A thin resin coating layer of μm was formed.

The critical surface tension of this thin coating layer is r. were measured to investigate its suitability as a droplet condensation surface. This r.

For example, it represents the surface tension of a liquid that warms the surface of a substance, and is widely used industrially as a parameter that indicates the surface properties of polymeric substances, and it almost coincides with the surface tension of the substance.

Tetrafluoroethylene resin is well known as a material with low surface tension, and its value is said to be 18 dyne/cm, and the material used this time is r. is 18-19
dyne/cm, which is almost the same as the above value. r of the tetrafluoroethylene resin film formed on the substrate. It was confirmed that the r value was 21 to 23 dynes/(7n), which is quite close to that of the resin material used. .

The value of 22 dynes/cnr is almost equivalent to that of 22 dynes/cnr, and therefore, it was confirmed that it has sufficient characteristics as a droplet condensation surface.

[Brief explanation of the drawing]

The drawing (FIG. 1) is a schematic diagram of one embodiment of an apparatus used in the high frequency sputtering method applied in the present invention. (Explanation of symbols) ]...Processed object 2...Substrate electrode 3...Fluorine resin target 4...
......High frequency electrode 6...Reaction tank 9...Cylinder 10...High frequency power source 11... ... Matching Box Patent Attorney Yoshi 1) Toshio

Claims (1)

[Scope of Claims] 1. A method for forming a droplet-like condensation surface, which comprises forming a coating thin film of a fluororesin on a metal condensation surface by high-frequency sputtering. 2. A method for forming a droplet-like condensation surface according to claim 1, which is applied to a metal condensation surface of a heat exchanger. The method for forming a droplet-like condensation surface according to claim 1, wherein the 3.7 iJl sputtering is performed as magnetron-type high-frequency sputtering. 4. The method for forming a droplet-like condensation surface according to claim 1, wherein a tetrafluoroethylene resin is used as the fluororesin.