JPH0641838B2 - Heat pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to, for example, an evaporation pipe or a condensation pipe of a heat exchanger for air conditioning,
Or, regarding the heat pipe used as a heat transfer material in the snow melting device of the road, in particular, the manufacturing cost is low,
A heat pipe having excellent heat transfer characteristics

[Prior Art] A heat pipe puts a liquid such as water or alcohol inside a depressurized pipe, and when one of them is heated, the liquid boils and flows to the other, where it radiates heat and becomes a liquid, which causes capillary action. The liquid is configured to return to the heating portion, and a structure called a wick is formed on the inner surface of the pipe in order to cause the capillary phenomenon. As this wick, one having a groove is known, and such a grooved heat pipe is usually manufactured by a rolling method or the like.

[Problems to be Solved by the Invention] Generally, in a heat transfer tube for causing heat exchange between an internal medium and an external medium as described above, in order to increase the heat transfer efficiency, (1) Increase the heat area.

(2) Make capillarity more likely to occur.

(3) Make nucleate boiling easier.

Although it is said that in the grooved heat pipe as described above, among the methods for increasing the heat transfer efficiency,
The most effective nucleate boiling phenomenon is not used, and there are restrictions on the inner diameter of the pipe, the number of spiral grooves, and the angle of twist due to the manufacturing technology of rolling tools and rolling technology. Due to the above reasons, the thermal characteristic value was only 1.2 to 1.5 times that of the normal grooveless heat pipe, and the performance was insufficient. Further, in manufacturing, since the rolling tool and the inner surface of the pipe have a large frictional force, a large pressing force is required, so that a large-scale device is required, the life of the tool is shortened, and the manufacturing cost is increased. There was a problem.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a plurality of cylindrical cylinders with a bottom whose openings are relatively narrowed on the inner surface of a metal tubular body. The heat pipe is formed by forming the porous layer wick having the recesses.

[Operation] In such a heat pipe, the recess of the porous layer (i) increases the heat transfer area, and (ii) promotes the nucleation of bubble generation for nucleate boiling to promote boiling, (iii) Promote capillary action.

Thereby, the heat transport capacity of the heat pipe is improved.

If the surface area ratio of the recess is 10% or less, the effect is small, and if the surface area ratio is 50% or more, it is difficult to manufacture, and the heat transfer ability does not improve to the extent that the manufacturing cost rises. do not have to.

[Examples] Examples of the heat pipe of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows a copper heat pipe H according to a first embodiment of the present invention.
It is sectional drawing which shows the property of the cross section. This heat pipe H
Is manufactured by electroplating the inner surface of a copper tube having a tube length of 300 mm, an outer diameter of 9.52 mm and a wall thickness of 0.30 mm, using a plating apparatus A as shown in FIG. The apparatus and method will be described below with reference to FIG.

First, apply silicon oil to the inner surface of copper tube 1 with ethanol
A double diluted product was applied, and then ethanol was evaporated to form a hydrophobic thin film 2.

The plating device A is an insoluble anode wire (made of Ti-Pt) 3
A storage tank for storing copper sulfate plating solution (copper sulfate 200 g /, sulfuric acid 50 g /) by providing an insulating spacer 4 around the wire 3 at appropriate intervals around the wire of the copper tube 1 under tension. 5 and a chemical pump 6 for supplying a plating solution to the copper pipe 1. In this storage tank 5, basic copper carbonate in an amount commensurate with the copper ions reduced by plating is replenished for cyclic use. There is.

As the plating current, a continuous current, a normal pulse current or a pulse current such as a PR current is properly used, and the plating solution temperature is 30 ° C., the cathode current density is 40 A / dm ² , and the plating solution flow rate is 2 m / s. Tube plating was performed for 10 minutes to obtain a porous layer S made of a plated metal having a thickness of 70 μm. In this porous layer S, a bottomed cylindrical recess C having an opening relatively narrowed,
The area ratio is 25%. A heat pipe H was obtained by enclosing water as a working fluid in the copper tube 1 thus manufactured.

(Example 2) A spiral groove was formed by rolling on the inner surface of a copper tube having the same diameter and the same length as in the first example, and the same pretreatment as in the first example was performed on the inner surface of the copper tube. Plating was performed under the conditions to obtain a similar porous layer (not shown). A heat pipe H was manufactured from this copper pipe.

(Measurement Results) With respect to these heat pipes H, the heat transport amount was measured by the test apparatus B as shown in FIG.

In this test apparatus B, a heater 7 for heating is provided at one end of the heat pipe H, and a water jacket 8 for cooling is provided at the other end thereof, and a thermocouple 9 for measuring temperature is appropriately provided on the surface of the heat pipe H between them. With the attached one, the surface temperature is almost 1
The test was conducted while adjusting the amount of electric power to the heater 7 and the amount of water flowing to the water jacket 8 so as to keep it at 00 ° C., and the heat transport amount was calculated from the temperature difference between the water inlet 8a and the water outlet 8b of the water jacket 8.

Table 1 shows the measurement results of the heat pipes of the first and second examples and a heat pipe manufactured as a comparative example from a raw copper pipe having the same diameter and the same length as each example.

According to this result, the heat transfer amount of the heat pipe of the present invention is
Compared with the comparative example, the first embodiment increased the number 2.4 times, and the second example increased about three times. This is because the porous layer S formed on the inner surface of the heat pipe H increases the heat transfer area, and the opening of the recess C is relatively narrowed, so that the nucleate boiling of the working fluid inside is prevented. It is considered that this is because it is easy to cause this and promotes the phase transition between liquid and gas on the heat transfer side of the heat pipe H.

[Effects of the Invention] As described in detail above, the present invention forms a porous layer having a plurality of bottomed cylindrical recesses with relatively narrow openings on the inner surface of a metal tubular body. Since the heat pipe is configured as described above, the recess increases the heat transfer area and promotes nucleate boiling on the heat transfer side of the heat pipe, thereby dramatically improving the heat transport characteristics. . It is also easy to manufacture and low in cost, and because it can be applied to small diameter heat pipes, by adopting it as a heat transfer element for air conditioning equipment,
This is an excellent effect that the device can be downsized and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a cross-sectional shape of a heat pipe according to a first embodiment of the present invention, FIG. 2 is a schematic view showing a manufacturing apparatus of the first embodiment, and FIG. 3 is for measuring heat transfer characteristics. 1 is a schematic representation of the device. 1 ... Copper tube (tube), C ... Recess, S ... Porous layer, H ... Heat pipe.

Claims (3)

[Claims] 1. A heat pipe characterized in that a porous layer having a plurality of bottomed cylindrical recesses each having a relatively narrow opening is formed on the inner surface of a metal pipe body. 2. The heat pipe according to claim 1, wherein the porous layer is a metal layer deposited by electroplating. 3. The surface area ratio of the recess is 10% to 5
It is 0%, The heat pipe of Claim 1 characterized by the above-mentioned.