JPH01193597A - Heat exchanger - Google Patents

Abstract

PURPOSE:To obtain a heat exchanger, strong against corrosion, prominent in heat radiating property and capable of using for a long period of time, by forming a gas phase polymerized polymer film, having a specified thickness, at least on a fin and a jointing part between the fin and a tube. CONSTITUTION:In a heat exchanger, consisting of tubes, through which refrigerant flows, and heat conductive thin fins, provided integrally with the tubes, a gas phase polymerized polymer film, having the thickness of 0.01-2mum, is formed on at least the fin and the joining part of the fin and the tube. A high heat conductive metal of Cu, Al or the alloy of these metals is employed as the material of the fin and the alloy of Cu and Al, such as brass, cupro-nickel, Al-Zn-Mg alloy, Al-Cu-Zn alloy, or Fe-alloy, Ni-alloy and the like are employed as the material of the tube. The fin is jointed to the tube through soldering principally in the case of the heat exchanger constituted of the combination of Cu and Cu-alloy especially. The method of heat polymerization, light polymerization or especially plasma polymerization is suitable for forming the gas phase polymerized film in the heat exchanger and the vapor of hydrocarbon series organic compound is employed preferably.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an economical heat exchanger that has high heat exchange performance, is significantly lighter in weight, has a longer service life, and is particularly applicable to automobiles,
It is suitable for use in transport aircraft such as aircraft, electronic equipment, and the like.

[Conventional technology]

BACKGROUND ART Currently, various types of heat exchangers are widely used, each of which is composed of a tube through which various fluids (water, organic solvent, air, etc.) flow as a refrigerant, and fins provided integrally with the tube. The tube material used here is required to have strength and corrosion resistance, while the first requirement for the fin material is high heat conductivity, that is, high heat exchange performance, so in many cases, the tube material and fin material have different configurations. Different metals are used. In addition to mechanical methods such as caulking, welding, and adhesive methods, soldering methods are widely used as methods for joining tubes and fins, especially in Cu-based heat exchangers. This soldering method forms part of the fillet, so the area of the bonding interface is wide, and since the solder is a highly heat conductive metal, it has the characteristics of excellent strength and heat exchangeability.

By the way, in order to obtain a high-performance heat exchanger that is small, lightweight, and has high heat exchange performance, the combination of tube material and fin material must be made of the optimal one from among various metals.

These materials will be explained below using an example of a heat exchanger for an automobile, particularly a radiator for an engine system.

Automotive heat exchangers, especially radiators, are generally installed at the front of the car, circulate a heat exchange medium (hereinafter referred to as "medium") between it and the engine, and radiate heat from the medium heated up in the engine by the radiator. As shown in Fig. 2, a plurality of vertical tubes (13) through which the medium flows are arranged in parallel.
Fins (14) are installed between each tube (13) to form a core (15), and the tubes (
13) Tank (17a) with seat plates (16a) and (16b) on both ends.

(17b) is attached. In Fig. 2, (18) and (19) are the inlet/outlet for medium circulation, and (20).

(21) indicates an inlet/outlet for injecting and discharging the medium.

The tubes (13) are usually arranged in two rows and joined to one fin (14) as illustrated in the partial perspective view of Figure 3, but in some cases a core of one row of tubes is also realized.

Normally, brass is used for the tube, and the fins are made of Cu or Cu-3, since it directly affects the heat dissipation characteristics of the radiator.
Using a highly heat conductive Cu or Cu alloy thin strip (hereinafter abbreviated as Cu-based strip) such as n, Cu-A9 or Cu-Cd, corrugate or looper processing is performed to increase the heat dissipation area. They are combined, soldered, etc. to form a copper core.

[Problem to be solved by the invention] Cu or CU gold alloy is known as an alloy with inherently good corrosion resistance, but in recent years it has been used as a snow melting agent in areas close to the ocean where sea salt particles are scattered, as well as in passageways in snowy areas. Salt is being sprayed extensively, and this has become a problem because it adheres to the fins of the radiator and corrodes them abnormally quickly, reducing the strength of the fins and reducing the functionality of the radiator. . Usually fins have a thickness of 0.025~
0. OS-based Cu-based strips are used, but recently there has been a strong demand for lighter automobiles from the standpoint of energy conservation, and thinning of the fins of radiators is also being considered to reduce weight.

However, countermeasures against salt damage mentioned above have become a major problem.
Applying anti-corrosion coating was also considered, but in order to prevent salt damage, a coating film with a thickness of at least 10 μm was required.
This resulted in increased weight and cost, and lacked practicality. It was also considered to form the fins from a corrosion-resistant Cu alloy, but the corrosion-resistant Cu alloy had poor heat conductivity and could not be used for the fins. For example, the heat conductivity of a Cu-10%Ni alloy, which is known as a corrosion-resistant Cu alloy, is a fraction of the culm of Cu-based strips for fins, making it extremely difficult to achieve both weight reduction and salt damage prevention for radiators. Ta.

As described above, there are many conflicting problems in building a high-performance radiator, but these points to be solved can be summarized as follows.

(1) Improve the corrosion resistance of the heat exchanger itself, especially the fins.

(2) Improvement in corrosion resistance is not accompanied by a decrease in heat exchangeability or an increase in weight.

(3) Corrosion resistance must be sufficiently ensured even at the joint between the fin and tube.

(4) In a practical heat exchanger having a complicated shape, it is possible to effectively treat the parts that substantially require corrosion resistance.

(5) Electrical corrosion between dissimilar metals can be effectively prevented even in harsh environments such as salt damage.

(6) There is a compact and lightweight CU-based mature heat exchanger suitable for use in automobiles.

(Means for Solving the Problems) In view of this, and as a result of various studies, the present invention has developed a heat exchanger that solves the above problems.

That is, in a heat exchanger consisting of a tube through which a refrigerant flows and heat-conductive thin-walled fins integrally provided on the tube, at least a portion of the fin and the joint between the fin and the tube is coated with a thickness of 0.01 to 2 μm. It is characterized by forming a gas phase polymerized polymer film, and it is effective that the fin material and the tube material are made of different metals.

In terms of materials, the structure of such a heat exchanger is such that the fin material is made of Cu, Al, or a highly thermally conductive metal such as an alloy thereof, and the tube material is made of Cu, an alloy of Al, such as brass, cupronickel, or Al. -Zn-M! 7 alloy, A1-
Cu-Zn alloy, Fe alloy, Ni alloy, etc. are used. And the connection between these fins and tubes is especially C
Heat exchangers made of a combination of U and Cu alloys are mainly joined by soldering.

To form a gas-phase polymerized film on the heat exchanger constructed in this way, heat or photopolymerization, particularly plasma polymerization, is suitable, and it is preferable to use vapor of a hydrocarbon-based organic compound. Therefore, the procedure of plasma polymerization will be described below. For example, as shown in FIG. 1, the plasma generator that performs plasma polymerization is a Pelger (2), which can evacuate the inside of the vertically opposing electrodes (2^) (2B) using a vacuum evacuation device (5).
3) in which a solid or liquid organic compound (8) is placed on a resistance heating boat (9) in the Pelger (3);
A nozzle (11) for introducing carrier gas or organic compound gas into the Pelger (3) is provided. To carry out plasma polymerization with such an apparatus, heat the heat exchanger (1) to about 50 to 300°C in advance.
Set it on one of the electrodes (2^) (213) inside the Pel Jar (3), and after evacuating the inside of the Pel Jar (3), turn on the external heating power source (10) when using a solid or liquid organic compound (8). ) by applying a voltage to the resistance heating boat (9) to vaporize the organic compound (8), and by generating plasma between the electrodes (2A) and (2B) using the plasma generation power source (7). When using gas, the monomer gas supply source (12) is connected to the nozzle (
A polymer film is formed on the surface of the heat exchanger (1) by introducing an organic compound gas into the Pelger (3) through the heat exchanger (11) and then generating plasma. In the figure, (6) shows a vacuum gauge, and (4) shows a table of this device.

Generally speaking, the plasma generating device may be any reaction system equipped with an induction coil type, waveguide type, or condenser type high frequency generating device, but preferably a condenser type high frequency generating device is suitable. In addition, heating the heat exchanger (1) before setting it in the Pelger (3) is performed using the Pelger (3).
3) may be replaced by plasma heating before plasma polymerization occurs after setting in the heat exchanger (2A) (2[3) that roughly generates plasma
1) may be formed.

When plasma polymerization is performed using high frequency waves in this way, the energy density is 0.5% due to the high frequency output and the size of the electrode area.
2 to 4 W/clN, preferably 0.5 to 3'? I/cr
The range of A is good, and the oscillation frequency of the high frequency power source is usually 13.56) IH2, but it is not limited to this and may be any frequency from direct current to microwave.

Moreover, the pressure inside the venter is 0.005 to 3 torr.

The reaction time is preferably in the range of 0.01 to 1.5 torr', and the reaction time is usually 5 seconds to 60 minutes, although it is affected by the type of tank, vaporization rate, flow rate, carrier gas flow rate, and electrode arrangement. , preferably between 10 seconds and 3 minutes. The thickness of the film obtained under these conditions is 100 to 20,000, but preferably 500 to 6,000.

(Function) In order to increase the heat exchange area as much as possible, the heat exchanger with the protective anti-corrosion film formed has thin fins and is formed in a corrugated shape with high density as described above. The spacing between them is 1 to 2# or less, and there is an advantage that the heat exchange ability of the fluid can be further increased by providing grooves by louver processing or the like.

It is also possible to form a dense and continuous coating on complex surfaces, such as those in some types of heat exchangers, where the surface area is expanded by providing grooves and protrusions, or by forming a porous metal layer. Has characteristics.

Roughly speaking, plasma polymerization is particularly effective in that a coating with high density and effective corrosion resistance can be obtained using plasma energy.

Also, as mentioned above, the heat exchanger has fins and tubes made of different metals.
In many cases, electrolytic corrosion occurs, and this tendency is particularly strong in salt-damaged environments. Therefore, in the example of an automobile radiator, not only the thin Cu-based fins are corroded and worn out, but also the fins and tubes peel off as a result of the strong corrosion of base solder against Cu. This tendency is particularly noticeable due to the large surface area. However, if the heat exchanger of the present invention is used as a heat exchanger, both noble and base metals can be coated with insulation, which is advantageous in that electrolytic corrosion can be prevented.

In the present invention, the thickness of the gas phase polymerized polymer film is 0.01~
The reason why the value is 2μ is that if it is less than o, the corrosion resistance will be insufficient, and if it exceeds 2μ, no greater effect on corrosion resistance will be observed, and on the other hand, it will cause disadvantages such as an increase in weight and a decrease in heat exchange ability, so it is not practical. It is from. As mentioned above, for the purpose of weight reduction in automobiles, the thickness is 0.025~
This is because a thin fin of 0.05N11 is used, so a coating with a thickness exceeding 2 μm is not practical.

Furthermore, when comparing the present invention with conventional coating methods, it was found that when a protective film is formed using the coating method, the film is usually thicker than 10 μm, and if the film is made thinner than this, pinholes will occur, reducing the anticorrosion effect. Become. Furthermore, thicker membranes not only increase material costs but also increase the size of the heat exchanger, which does not meet the demands for weight reduction.

The organic compound used in the present invention may be solid, liquid, or gaseous at room temperature, but it is preferable to have an unsaturated bond.
A temperature of 00°C or lower is desirable. Specifically, ethylene and propylene.

Unsaturated hydrocarbon compounds such as butene, butadiene, acetylene or derivatives thereof, cyclobutene.

Cyclic unsaturated hydrocarbon compounds such as cyclopentene and cyclohexane or their derivatives, benzene.

Toluene, xylene, naphthalene, styrene.

Aromatic compounds such as anthracene or derivatives thereof, diphenyl, diphenylmethane.

Examples include aliphatic-aromatic hydrocarbons such as dibenzyl and derivatives thereof. In particular, for solids, those with high sublimability such as dibenzyl are preferred.

And these organic compounds alone or in combination with methane,
Plasma polymerization is carried out in the presence of a hydrocarbon-based organic gas such as ethane, propane, ethylene, or propylene, an inert gas such as helium, neon, argon, or krypton, or an inert gas such as hydrogen or nitrogen.

(Example〕 Next, examples of the present invention will be described.

In the automobile radiator shown in Fig. 2, Cu-0,1
A corrugated fin (14) made of 5% 3N alloy with a plate thickness of 0.046 m is attached to a tube (14) made of Cu-35% Zn brass.
3) is soldered with 3n-70% Pb alloy. The above radiator was set on the electrode (2I3) in the Pel jar (3) in Figure 1, dibenzyl was placed as a solid organic compound (8) on the resistance heating boat (9), and the Pel jar (3) was evacuated. and heated the boat (9) to 120°C.
heated to.

After that, Ar gas was introduced into the Pelger (3) at a vacuum level of 10-1°C orr, and at an output of 500 W, about 90 people/m!
Plasma polymerization was performed at a production rate of n to form a film having the thickness shown in Table 1 on the radiator surface.

Next, apply 1% NaCf at 40°C to each radiator! , ' was subjected to a cycle of 60 times of leaving it in humidified air of 0.5 hr@60' CX 75% RH after fogging for 23.5 hr, and then the following tests were conducted.

(1) Heat dissipation test: Based on JIS D 1614 method, the heat dissipation of the radiator before the above treatment is 100%,
The heat dissipation properties of each radiator after treatment were determined in percentage.

(2) Fin Corrosion Depth Test Two fin sections were cut out, washed with dilute sulfuric acid to remove corroded substances, and the weight of the remaining portion was measured to determine the average corrosion depth per area.

(3) Tensile strength test of fins or tubes: Cut out three periods of two adjacent tubes and the corrugated fin formed between them, pull these tubes in opposite directions, and test the strength before the above treatment. 100%
The strength of the fin or tube was calculated as a percentage.

(4) Corrosion amount of solder fillet: The solder joint between the tube and the fin was cut out, embedded in resin, and its cross section was examined under a microscope to semi-quantify the amount of solder corrosion and determine it as a percentage.

The above test results are also listed in Table 1. Similar tests were also conducted on conventional products that did not form a plasma polymerized film and those that formed a 15μ coating film using the conventional coating method.
The above (1) to (4)) were carried out, and the results are also listed in Table 1.

As is clear from Table 1, the products Nα1 to NQ4 of the present invention maintain heat dissipation properties and also exhibit corrosion resistance. Comparing this with the conventional product, the one without coating (Nα7
) is particularly severely corroded, the fins have lost strength, and 1
The 5μ coated material (Nα8) has corrosion resistance but is inferior in heat dissipation. In addition, the comparative amount Nα5 with a coating thickness of less than 0.01μ is insufficient in both corrosion resistance and heat dissipation, and the comparison amount NQ6 with a coating thickness of more than 2μ tends to be slightly inferior in heat dissipation.

(Effects of the Invention) As described above, the present invention is industrially remarkable because it is resistant to corrosion and has excellent heat dissipation properties even under severe usage conditions such as automobile radiators, and can be used stably for a long period of time. This has the following effects.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a plasma generator used in the present invention, FIG. 2 is an external view of a radiator, and FIG. 3 is a partial perspective view of the radiator. 1... Heat exchanger 2A, 2B... Electrode 3... Pelger 4... Table 5... Vacuum exhaust device 6... Vacuum gauge 7... Power source for plasma generation 8... Organic Compound 9... Resistance heating boat 1G... Heating power source 11... Nozzle 12... Monomer gas supply source 13... Tube 14... Fin 15... Core lea, 16b -... Seat Plates 17a, 17b...Tanks 18, 19...Medium circulation inlet/outlet 20.21...Inlet/outlet Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) In a heat exchanger consisting of a tube through which a refrigerant flows and heat-conductive thin-walled fins integrally provided on the tube, at least a portion of the fin and the joint between the fin and the tube has a thickness of 0.01 to 2 μm. A heat exchanger characterized by forming a vapor phase polymerized polymer film. (2) The heat exchanger according to claim 1, wherein the fin material and the tube material are made of different metals.