JPS62112996A - Heat-transmitting body - Google Patents

Abstract

PURPOSE:To enhance heat-transmitting capability through accelerating the nucleation for generation of bubbles for nucleate boiling, by providing the surface of a metallic substrate with a plurality of cavities each of which is in the form of a cylinder closed at one end and having an opening part relatively reduced in cross-sectional area. CONSTITUTION:A hydrophobic thin film 2 provided on the surface of a copper pipe 1 is provided by diluting a silicone oil with ethanol to increase the volume to 3 times the original volume, applying the diluted liquid to the inner surface of the copper pipe 1 and evaporating off ethanol. An anode wire 3 is fitted under tension on the axis of the copper pipe 1, with insulating spacers 4 disposed in the periphery of the wire 3 at appropriate intervals to prevent short-circuiting due to contact between the copper pipe 1 and the wire 3. A tank 5 for storing a plating liquid containing copper sulfate and a chemical pump 6 for feeding the plating liquid into the copper pipe 1 are provided, and the plating liquid is circulatedly used by refilling a set quantity of basic copper carbonate corresponding to the consumption of copper ions in plating at the tank 5. When the plating is carried out by regulating the temperature and flow rate of the plating liquid and the cathode current density, an electrodeposited metallic layer provided with pores with narrow openings is obtained. When the substrate provided with the cavities (the pores with narrow openings) is used as a heat-transmitting body, a nucleate boiling phenomenon is liable to occur in a fluid flowing along the surface of the substrate, and the heating surface area can be increased.

Description

Detailed Description of the Invention [Field of Application in Industry-1-] The present invention is applicable to, for example, evaporation tubes and condensation tubes of heat exchangers for air conditioning;
The present invention also relates to a heat transfer body used in a heat pipe having a wick, and particularly to a heat transfer body that is inexpensive to manufacture and has excellent heat transfer characteristics.

[Prior Art] In order to increase the heat transfer efficiency of a heat transfer tube for exchanging heat between an internal medium and an external medium, (1) the heat transfer area must be increased;

(2) Facilitates capillary action.

(3) Make it easier to cause turbulence.

(4) Make it easier to cause nucleate boiling.

It is said that this is effective.

As a heat exchanger tube that satisfies some of these conditions,
Some examples include those in which spiral grooves are formed on the inner surface of the tube by a rolling method, and those in which granular or linear metal is attached to the inner surface of the tube by brazing or the like.

[Problems to be solved by the invention] However, in the conventional technology as described in
Each had the following problems.

In other words, when forming a spiral groove, the nucleate boiling phenomenon, which is the most effective of the methods for increasing heat transfer efficiency -L, is not used, and the manufacturing technology of rolling tools and rolling Due to technological limitations, such as limitations on the inner diameter of the tube, the number of spiral grooves, and the angle of twist, the thermal characteristics are 1.2 to 1.5 times higher than ordinary grooveless tubes. The performance was insufficient. In addition, during manufacturing, the frictional force between the rolling tool and the inner surface of the tube is large, so a large pressing force is required, which in turn requires large-scale equipment, shortens the life of the tool, and increases production costs. There was a problem.

On the other hand, when attaching granular or linear metal to the inner surface of a tube, it is necessary to perform high-temperature work, and there are other problems such as difficulty in applying it to small-diameter tubes. l
21. [Means for Solving the Problems] In order to solve the above problems, the present invention provides a plurality of bottomed cylinders with relatively narrow openings on the surface of a metal base. A shaped recess (hereinafter referred to as a narrow hole) is formed, or four smaller diameter parts are formed at the bottom of this recess.

1 Function: In such a heat transfer body, the narrow pores increase the heat transfer area, generate turbulence, and promote nucleation of bubbles for nucleate boiling, which improves heat transfer ability. let

1 Example" Hereinafter, an example of a heat exchanger tube of the present invention will be described with reference to the drawings. 3. (Example 1) FIG. 1 and FIG. and surface properties, homogeneous narrow pores with a pore diameter of 250 μm and a porosity of 18% are formed on the inner surface of a steel pipe with a length of 1000 mm, an outer diameter of 9.35 mm, and a wall thickness of 0.35 mm. The heat exchanger tube in this example was manufactured by forming a hydrophobic thin film on the surface of a steel tube, and then electroplating using the steel tube as a cathode and an insoluble anode. This will be explained with reference to Figure 3.

The hydrophobic thin film 2 on the surface of the copper tube 1 is formed by diluting silicone oil three times with ethanol, applying it to the inner surface of the copper tube 1, and then evaporating the ethanol. The anode wire (made of Ti-Pt) 3 is stretched on the axis of the copper tube 1 under tension, and insulating spacers 4 are provided around the wire 3 at appropriate intervals to connect the copper tube 1 and the wire. 3. This prevents short circuits due to contact. Then, copper sulfate plating solution (copper sulfate 2
00g/f2, sulfuric acid 50g/(ri) storage tank 5,
A chemical pump 6 is provided to flow this plating solution into the copper pipe 1,
This storage tank 5 is replenished with basic copper carbonate in an amount corresponding to the copper ions reduced by plating, and is used for circulation.

As the plating current, use pulse current such as intermittent current, normal pulse current, or PR current as appropriate. Such a pulsed current facilitates the transport of metal ions into the pores compared to direct current, so it can increase the 11i deposition rate and eliminate the localized whisker-like precipitation that occurs in the case of direct current. This can prevent short circuits caused by deposited metal. In addition, 1) In the Tl current, since positive and reverse currents are passed alternately and periodically, the growth of the deposited film can be made uniform.

Using the apparatus described above, plating was performed for 10 minutes under the conditions of a plating solution temperature of 30°C, a cathode current density of 33 A/am', and a plating solution flow rate of 2 ml/g. An electrodeposited metal layer in which holes were formed was obtained.

After washing the inner surface of the copper tube 1 with water and drying it, a test was carried out by crushing the copper tube 1 with a vise.
After annealing for 0 minutes, tube expansion using a mandrel was attempted, but no peeling or falling off of the electrodeposited metal layer was observed in either case, demonstrating excellent adhesion and strength.

Figure 4 shows the steel pipe produced as described above.
．． The drying thermal properties were measured using a single thermal property testing device under the following conditions.

In this device, T is a temperature sensor, P is a pressure gauge, PD is a differential pressure gauge, 10 is a pump, 11 is a valve, 12 is a flow meter, 1
3 is an expansion valve, 14 is a compressor, 15 is a subcondenser, 16 is a subevaporator, 17 is a constant temperature water tank,
18 is a steel pipe as a test pipe. In this thermal property testing apparatus, refrigerant supplied from the compressor 14 is flowed inside the test tube 18, and hot water from the constant temperature water tank 17 is used as the refrigerant outside. It is designed to flow in the opposite direction. The temperature of the constant temperature water was controlled in accordance with each refrigerant flow rate so that the refrigerant system was stabilized.

In this figure, arrows A and A' indicate the flow directions of refrigerant and water, respectively, in the case of the evaporation test, and arrow 13. B“
indicate the flow direction of refrigerant and water, respectively, in the case of condensation test.

As a result of this test, the copper tube l of Example 1 of the present invention showed a film heat transfer coefficient on the inside as shown as C in FIG. It has been found to have thermal properties that are 7 to 8 times better than those of other types.

(Example 2) A spiral groove was formed on the inner surface of a copper tube having the same shape as the material of Example 1 by rolling, and then, by the method of Example 1, the inclined wall of the spiral groove was plated with narrow holes. formed a layer. The heat transfer properties were measured using the same method, and the results showed that the heat transfer properties were approximately 10 times higher than those of ordinary steel pipes.

(Example 3) A heat exchanger tube was manufactured in which a concave portion with a smaller diameter was formed in the bottom portion of the tube having one narrow hole (see FIG. 6). The heat transfer characteristics of this heat transfer tube were improved by about 20% compared to those without a concave portion at the bottom.

(Example 4) Pipe length 500mm, outer diameter 9.35mm, wall thickness 0.35mm
Electroplating was applied to a copper tube with a cathode current density of 20 A/dm' and a high plating solution flow rate (4 m/s), so that the axis was tilted approximately 20 degrees with respect to the normal to the heat transfer surface. A plated metal layer having narrow pores was obtained (see FIG. 7).

In such a heat transfer tube, when the flow direction of the internal fluid is set to be the same as the inclination of the narrow holes, the heat transfer characteristics are approximately 30% better than those without inclination.

In the manufacturing method described above, it is possible to control the cathode current density, the flow rate of the plating solution, the diameter and number of narrow holes, and also control the flow rate of the plating solution as in the case of two series. By changing , the inclination angle of the narrow hole can be controlled.

Note that the present invention is of course not limited to heat exchanger tubes.

[Effects of the Invention] As detailed above, the present invention provides the following effects:
Multiple bottomed cylindrical recesses with relatively narrow openings (
If the substrate is used as a heat transfer body, nucleate boiling will occur in the fluid flowing along the surface of the substrate. It is possible to provide a heat transfer body with good heat transfer properties by increasing the heat transfer area and reducing the production cost because it does not require large-scale equipment or high-temperature work. It has excellent effects such as being inexpensive and easy to manufacture small-diameter heat exchanger tubes.

[Brief explanation of drawings]

Fig. 1 is a photomicrograph showing the cross-sectional shape of the first embodiment of the present invention, Fig. 2 is a photomicrograph showing the surface profile, Fig. 3 is a schematic diagram showing the manufacturing method of the first embodiment, and Fig. 4 is a photomicrograph showing the cross-sectional shape of the first embodiment of the present invention. A schematic diagram of an apparatus for measuring heat transfer characteristics, FIG. 5 is a graph showing the heat transfer characteristics of the first embodiment, FIG. 6 is a micrograph of the third embodiment of the present invention, and FIG. 7 is a graph showing the heat transfer characteristics of the first embodiment. It is a micrograph of the fourth example. Engraving of the drawings (no changes to the contents) Figure 1 Figure 2 Ar = Figure 8 Filter y (ttJt (Kg/hr) N1+1-ko [k ■ Engraving of the drawings (no changes to the contents) Procedural amendment ( Method) % formula % 1. Indication of the case 1985 Patent Application No. 252358 2. Name of the invention Heat conductor 3. Person making the amendment Hour hand Applicant (6 6) Mitsubishi Kin 14 Co., Ltd. 4, Agent July 1985 - Date (@Sendichi) (1) "Page 10, line 14 of the specification, and lines 14 to 15 of the same"
Correct "microphotograph" to "one drawing." (2) "Microphotograph" on page 10, line 18 and line 19 of the specification is amended to read "a drawing showing a cross-sectional shape." (3) Correct the figures in Figures 1, 2, 6, and 7 as shown in the attached sheet. that's all

Claims (6)

[Claims] (1) A heat transfer body characterized in that a plurality of bottomed cylindrical recesses with relatively narrow openings are formed on the surface of a metal base. (2) The heat transfer body according to claim 1, wherein the base body is a tube body. (3) The recess is formed to be inclined in a plane including the axis of the tube with respect to the normal to the surface of the tube. The heat transfer body described. (4) A plurality of bottomed cylindrical recesses with relatively narrow openings are formed on the surface of the metal base, and a recess with a smaller diameter is formed at the bottom of each recess. A heat transfer body characterized by: (5) The heat transfer body according to claim 4, wherein the base body is a tube body. (6) The recess is formed to be inclined in a plane including the axis of the tube with respect to the normal to the surface of the tube. The heat transfer body described.