JPS63183392A - Heat transfer pipe - Google Patents

Abstract

PURPOSE:To prevent electrodeposited metal from stripping off or collapsing by preventing porous layers from coming into contact with a plug, by forming a plurality of projections which are continued to the axial direction on the inside surface of a metallic pipe nearly at predetermined intervals in the circumferential direction, and by forming porous layers which are thinner than the height of projections on the area except projections. CONSTITUTION:A plurality of projections 11... extending spirally to the axial direction are formed on the inside of a pipe 10 consisting of a metal such as copper at predetermined intervals in the circumferential direction. Porous plated layers 12 which are thinner than the height of projections 11 are electrodeposited on the inside of a pipe 10 excluding the area of projections 11.... The porous plated layers 12 are collective bodies of a number of electrodeposited metal pieces 13 with tree branches. When a pipe expansion plug is forcibly inserted into the pipe in order to fix fins on the outer surface of a pipe, the diameter of a heat transfer pipe is expanded with the projections 11... formed on the inner surface of a pipe 10 only by the outer face of a plug. During this time the porous plated layers 12 do not contact to the plug, so that the electrodeposited metal 13 does not collapse or strip off and they are kept in the complete state even after a pipe expanding work is completed.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention is applicable to, for example, evaporation tubes and condensation tubes of heat exchangers for air conditioning;
It also relates to heat transfer tubes such as heat pipes used in road snow melting devices and the like.

"Prior Art" The above-mentioned evaporation tube, condensation tube, or heat pipe all cause the phase transformation of the medium sealed inside the tube (gas ←→ liquid) due to the temperature difference between the inside and outside of the tube. The heat is transferred in the longitudinal direction of the tube.

For example, a heat pipe is a metal tube with a reduced pressure and a liquid such as water or alcohol sealed inside it. When one end of the vibrator is heated, the liquid boils and steam flows to the other end due to the vapor pressure difference, where it radiates heat. The pipe is designed so that it becomes a liquid and this liquid flows back to the heating section.To perform this function, a structure called a wick is formed on the inner surface of the pipe. Therefore, in order to improve the heat transfer performance in a heat pipe, (a) heat transfer performance inside and outside the tube, (
It is required to form a wick that has improved (b) ability to promote boiling or condensation on the inner surface of the tube, and (c) ability to transport a medium (particularly liquid) in the longitudinal direction of the tube.

As an improvement to this type of heat exchanger tube, the present applicant previously proposed the one shown in FIG. 4 in Japanese Patent Application No. 47763/1983.

This heat exchanger tube is characterized by forming a porous plating layer 3, which is an aggregate of dendritic or granular electrodeposited metal 2, on the inner surface of the metal tube l. The plating layer 3 increases the heat transfer area on the inner surface of the tube body l to improve the performance of (a) above, and also promotes nucleation for bubble generation and promotes nucleate boiling, thereby achieving the performance of (b) above. This improves the performance and further improves the performance (c) by utilizing capillary force to improve the heat transport ability.

"Problems to be Solved by the Invention" By the way, this type of heat transfer tube is often used with metal fins attached to its outer surface in order to improve the efficiency of heat exchange with the outside.

Such fins are usually plate-shaped with holes that are slightly larger than the outside diameter of the heat exchanger tube, and when the heat exchanger tube is inserted through these holes, the fins have an outer diameter that is larger than the inside diameter of the heat exchanger tube. By pushing a jig called a tube expansion plug having a diameter into the tube from one end, the heat transfer tube is expanded from the inside, and its outer surface is crimped to the fins to fix it.

However, in a heat transfer tube with a porous plating layer 3 formed on the inner surface as described above, when a tube expansion plug is passed inside the tube, the deposited metal 2 is crushed and falls off, which can cause clogging of the tube. There was a problem that the effect of promoting nucleate boiling was reduced.

"Means for Solving the Problems" The present invention is intended to solve the above problems, and includes a plurality of protrusions continuous in the axial direction of the pipe body at regular intervals in the circumferential direction on the inner surface of the metal pipe body. It is characterized in that a porous layer made of dendritic or granular electrodeposited metal and having a thickness smaller than the amount of protrusion of the protrusions is formed in the portion excluding these protrusions.

"Function" In the present invention, when fixing the fins to the outer surface of the heat exchanger tube,
When the tube expansion plug is pushed into the tube, only the protrusions formed on the inner surface of the tube are pushed out by the tube expansion plug, thereby expanding the diameter of the heat exchanger tube. Therefore, since the porous layer is protected by the protrusions and does not come into contact with the plug, the electrodeposited metal constituting the porous layer does not fall off.

"Embodiments" Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 and 2 both show a heat exchanger tube of one embodiment, with FIG. 1 being an enlarged view showing the cross-sectional surface properties, and FIG. 2 being an enlarged view showing the inner surface properties.

In these figures, the symbol IO is a tube made of metal such as copper, and on the inner surface of this tube IO, a plurality of protrusions 11 extending spirally in the axial direction are formed at regular intervals in the circumferential direction. has been done. The number of these protrusions 11 is determined by the number of tube expansion plugs (
It is desirable to reduce the width of each protrusion 11 as much as possible without interfering with the pipe expansion work (not shown), and it is also desirable to reduce the width of each protrusion 11 to the extent that it can sufficiently withstand the pipe expansion work.

Further, a porous plating layer 12 thinner than the amount of protrusion of the protrusions 11 is electrodeposited on the inner surface of the tube body 10 excluding the protrusions 11 . This porous plating layer 12 is an aggregate of a large number of dendritic deposited metals 13 .

Next, a method for manufacturing such a heat exchanger tube will be explained.

First, an insulating masking agent is applied to the entire inner surface of the tube body 10. Next, this tubular body IO is set in a rolling device, and wide grooves are formed on the inner surface on which the insulating film is formed, and the portions other than these grooves are closed off and left as is.

Then, the masking film on the bottom surface of the groove is destroyed by rolling and the metal surface is exposed, while the masking film remains on the protrusions 11 . . . .

Next, a hydrophobic substance such as silicone oil diluted with a volatile solvent such as ethanol is applied to the inner surface of the tube body 10,
The solvent is evaporated to form a hydrophobic film. The thickness of this hydrophobic thin film is preferably 0.1 to 5 μm,
If it exceeds 5 μm, the insulation becomes too high and a uniform porous plating layer 12 cannot be obtained.

Next, this tubular body IO is set in a plating apparatus as shown in FIG. 3, and a porous plating layer 12 is formed on its inner surface. In this device, a soluble anode wire 14 made of copper, nickel, zinc, etc. is stretched under tension along the axis of a tube 10, and insulating spacers I5 are provided around the wire 14 at appropriate intervals. , a storage tank 16 for storing a copper sulfate plating solution, and a chemical pump 17 for flowing the plating solution into the pipe body 10.

Then, between the anode wire 14 and the tubular body 1O, a pulse current such as an intermittent current 1, a normal pulse current, or a PR lightning current is used as appropriate. Then, the anode wire 14
is gradually dissolved to produce a conductive powdery slime, which is carried by the flow of the plating solution and a portion of it adheres to the inner surface of the tube IO. Then, metals are sequentially deposited using this conductive slime as a core.
A dendritic deposited metal 13 is formed. Note that the anode current density must be 20 A/dti" or more; if it is less than that, slime will not be sufficiently generated. In addition, the flow rate of the plating solution is preferably 0.5 to 5 i/sec, and 0.5 III If it is less than /see, only a brittle deposited film will be obtained, while if it is more than !l/sec, the energy cost will only increase and there will be no effect.

Eventually, when the porous plating layer 12 reaches a predetermined thickness,
The tube body 10 is removed from the apparatus and washed, and the masking agent is removed to obtain a heat transfer tube.

In a heat exchanger tube having such a structure, when the tube expansion plug is pushed into the tube when fixing the fins to the outer surface of the tube, only the protrusions 11 formed on the inner surface of the tube body 10 are pushed against the outer surface of the plug. The diameter of the heat transfer tube is expanded by expanding it. During this time, the porous plating layer 12 does not come into contact with the plug, so the electrodeposited metal 13 will not be crushed or fall off, and will remain in perfect condition even after the pipe expansion work. It is possible to fully demonstrate the characteristics and obtain high heat transfer performance.

In addition, in this heat exchanger tube, the protrusions II are formed in a spiral shape, so that the fluid such as steam flowing inside the tube is transferred to the protrusions II...
There is also an advantage that contact between the fluid and the plating layer 12 is promoted.

Note that, if necessary, instead of forming the protrusion 11 in a spiral shape, the protrusion 11 may be formed in a linear shape along the axial direction of the tube body 10.

Furthermore, in the above embodiment, the case where the porous plating layer I2 was formed by the dendritic electrodeposited metal 13 was shown, but by changing the plating conditions, the porous plating layer I2 could be formed by the granular electrodeposited metal. may be configured.

"Effects of the Invention" In the heat exchanger tube of the present invention, when the expansion plug is pushed into the heat exchanger tube when fixing fins to the outer surface of the tube, only the protrusions formed on the inner surface of the tube come into contact with the plug, and this The protrusions are pushed out and the diameter of the tube is expanded. Therefore, the porous layer does not come into contact with the plug, and the deposited metal does not peel off or collapse, making it possible to fully exhibit the characteristics of the porous layer and obtain high heat transfer performance.

[Brief explanation of the drawing]

Fig. 1 is an enlarged view showing the cross-sectional properties of a heat transfer tube according to an embodiment of the present invention, Fig. 2 is an enlarged view showing the properties of the inner surface of the heat transfer tube, and Fig. 3 is a plating for manufacturing the heat transfer tube. It is a block diagram of a device. Moreover, FIG. 4 is an enlarged view showing the cross-sectional properties of a heat exchanger tube previously filed by the present applicant. IO...Pipe body, 11...Protrusion, 12.
... Porous plating layer, 13... Electrodeposited metal.

Claims (1)

[Claims] A plurality of protrusions are formed on the inner surface of the metal tube at approximately regular intervals in the circumferential direction, and the parts other than these protrusions are made of dendritic or granular electrodeposited metal. A heat exchanger tube characterized in that a porous layer having a wall thickness smaller than the amount of protrusion of the protrusions is formed.