JPS5870919A - Manufacture of heat transmitting pipe - Google Patents

Abstract

PURPOSE:To obtain a surely and strongly stuck heat transmitting pipe of stable quality by small number of processes in sticking sharply tapered tips of fins formed parallel to the inner face of a pipe by performing to stick them in use of drawing work accompanied by vibration. CONSTITUTION:Smooth inner face of a pipe 1 is cut by, for instance, a lathe as if breaking by a plow, and fine fins 5 having sharply pointed tips continueing spirally, slanting to the pipe axis are raised. A plug having projected stripes having V-shaped sectional form parallel to the axial line and connected to a ultrasonic horn is inserted into the pipe 1, and drawing work is performed in the direction in which slanted face 51 of the fin abuts on the plug. By this way, parts of the tips of fins 5 where they abut on the projected stripes and surrounding are deformed largely by pressing force and vibration, and stuck fast to adjoining fins and close the upper part of the grooves 6 to form the roofs of tunnels 2. In this case, edges of unstuck parts are also deformed toward adjoining fins and form independent through holes 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a heat exchanger tube having an inner surface structure excellent in boiling heat transfer.

In an attempt to improve boiling heat transfer, it has been proposed to arrange a large number of fine tunnels close to each other under the surface of a heat transfer wall, and to communicate each tunnel with the outside through a large number of small through holes.

With such a heat transfer surface, the siphon action that occurs between adjacent through holes, which is determined probabilistically, continues in a regular and stable state, so it is difficult to use a heat transfer surface with a porous layer or with continuous narrow openings. It shows higher heat transfer characteristics than those equipped with .

Conventionally, the method for forming such a heat transfer surface has been described in Japanese Patent Publication No. 52-
A method as disclosed in Japanese Patent No. 26622 is known. That is, after cutting the surface of the heat transfer wall provided with shallow grooves in a plow-like manner to stand up fins having notches at the tips,
In this method, the tips of the fins are extended in the lateral direction by brushing and brought into close contact with the middle of adjacent sulfins.

However, this method requires many processing steps and is difficult to control quality, so it is more difficult to apply it inside pipes.

In view of the above, the present invention has been made to provide a method for easily obtaining a pipe with an internally processed surface of stable quality. The method is characterized in that a plug having protrusions is inserted into the tube, and drawing is performed while applying relative vibration between the tube and the plug, thereby bonding the fins at intervals. The reason why the tips of the fins are tapered at an acute angle is that only the tips are deformed by contact with the plug during the subsequent drawing process, making it easier to maintain the distance between the bases.

In order to promote this, it is desirable that the fins be inclined in the same direction, and such fins can be extruded, pulled out,
It can be easily obtained by cutting or other means.

The following description will be made with reference to the drawings. The figure shows a case where the present invention is applied to the inner surface of a steel pipe, and 2 shows a V-shaped crushed portion where a fine tunnel 4 communicates with the outside through a fine through hole B. The tunnel 2 is spirally provided substantially parallel to the inner surface of the copper tube 1. This tunnel 2 may be ring-shaped or linear in the axial direction.

The through holes 6 that communicate the tunnel 2 with the outside are regularly arranged along the tunnel 2 and have a square triangular shape. Moreover, the crushing portions 4 are provided substantially parallel to each other and linearly along the axis.

This crushed portion 4 may be spiral-shaped.

A steel pipe having such a heat transfer surface structure can be obtained by preparing a pipe material with a smooth inner surface, cutting the inner surface, and then drawing the pipe material. In that case, the cutting process is a process in which the inner surface of the steel pipe is deformed in an exciting manner without being removed. Such cutting can be performed by selecting the shape of the cutting tool, cutting angle, cutting tool holder, etc.

Attach the steel pipe to the support that is on the table of the lathe and is engaged with the lead screw, grip the tool holder in the chuck of the lathe, align the steel pipe and the support, and place the tool so that its cutting edge is the copper pipe. After adjusting the inner surface to the specified depth,
The chuck is rotated to move the support along the lead screw at a predetermined speed.

As a result, as shown in FIG. 2, fine fins 5 are formed on the inner surface of the copper tube 1 in a spiral manner, inclined with respect to the tube axis, and each having an acutely pointed tip. Thus, one side 51 of the tip of the fin 5 has a portion of the surface of the original tube and is inclined in the same direction.

This exciting cutting is extremely effective when forming the fins 5 with high density. Furthermore, since the fins 5 can be formed with a height greater than the cutting depth, this method is also effective for thin-walled pipe materials.

Such fins 5 can also be formed by extrusion, drawing, rolling, or other means.

After the fins 5 are formed, the drawing process is carried out by inserting into the copper tube a plug having a V-shaped protrusion parallel to the axis and connected to an ultrasonic horn. You can also add it to the side. If the fins 5 extend parallel to the tube axis, a rotatable plug with spiral protrusions is used.

The direction in which the inclined surface 51 of the fin 5 comes into contact with the plug is selected as the pulling direction.

This is because if the opposite side of the surface 51 is selected, the tips of the fins 5, which are raised and stretched, will exceed the limit of expansion and break, making it impossible to obtain the desired heat transfer surface. .

As a result of this drawing process, the tip of the fin 5 is greatly deformed by the pressing force and vibration at the part where it contacts the protrusion of the plug and its vicinity, and is firmly bonded to the adjacent fin, and the upper part of the groove 6 separating the fins 5 is It closes off at intervals and forms the ceiling of the tunnel 2 as shown in FIG. In this case, most of the tips of the fins 5 are deformed in the opposite direction to the pulling direction, but the edges of the non-bonded parts are also restricted by the plug and deformed in the direction of the adjacent fins, causing displacement in the direction of the adjacent fins. An independent through-hole 6 is formed in the form of a.

If a wire brush is attached to the tip of the plug, or if a wire brush is passed through the tube after drawing, the inner surface will be appropriately roughened and the heat transfer performance of the tube will be further improved.

The size of the through hole 3 can be adjusted by selecting the height of the protrusion on the plug, the pinch, the amount of reduction of the outer diameter, etc. Although it is not necessarily necessary to reduce the outer diameter using a drawing die, dimensional accuracy can be improved by using this.

As is clear from the above, this invention is a method of deforming the inner fin tips by drawing with vibration and bonding them to adjacent fins at intervals.
The adhesion between the tips of the fins is reliable and strong, and there is an advantage that a pipe with a stable inner surface of quality can be easily obtained with a small number of steps.

[Brief explanation of the drawing]

FIG. 1 is an enlarged perspective view showing the inner surface of the heat exchanger tube according to the present invention, FIG. 2 is an explanatory view showing the middle part of the method according to the present invention, and FIG. 6 is an enlarged sectional view of the inner surface according to the present invention V. be. 1: Pipe material, 2 tunnel, 6: Through hole, 4: Squeezed part, 5
: Fin, 6: Groove, 51: Slope.

Claims (1)

[Claims] After forming parallel fins with sharp tapered tips on the inner surface of the tube, a plug with protrusions is inserted into the tube, and the drawing process is performed while applying relative vibration between the plug and the tube. A method for manufacturing a heat exchanger tube characterized by bonding fins at intervals.