JPH0587339B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to, for example, a heat pipe container for a heat pipe type waste heat recovery device in a boiler, etc., and a water heating type waste heat recovery device that uses waste heat to heat water. The present invention relates to a method for manufacturing finned metal pipes used in high-temperature environments, such as water pipes in heat recovery equipment.

Prior Art and its Problems In the following description, the term "aluminum" includes not only pure aluminum but also aluminum alloys.

For example, in the heat pipe type waste heat recovery device described above, a high-temperature gas flow path and a low-temperature gas flow path are formed in the casing by a partition wall, and the gas flow path passes through the partition wall and straddles both flow paths. A plurality of heat pipes each having spiral fins formed on the outer peripheral surface are arranged so that high temperature exhaust gas is introduced into a high temperature gas flow path.
In consideration of strength, corrosion resistance, heat resistance, heat transportability, etc., such heat pipes have been used in which water is sealed in a steel container. Furthermore, in order to further improve the exhaust heat recovery performance, aluminum spiral fins were provided on the outer peripheral surface of the heat pipe. Conventionally, such containers for heat pipes have been manufactured, for example, by the following two methods. The first method is to fit an aluminum outer tube onto the steel inner tube and form spiral fins on the outer circumferential surface of the outer tube by rolling.The second method is to apply aluminized treatment to the outer circumferential surface of the steel tube. This method involves wrapping the fin material in a spiral shape and brazing the two together. However, in the product manufactured by the first method above,
Due to long-term use in a high-temperature atmosphere, the difference in coefficient of thermal expansion between the inner and outer tubes causes a gap between the inner and outer tubes.
There were problems in that the heat transfer performance between the two tubes was reduced due to the gap between the two tubes, and the weight was large. Further, in the second method, there was a problem in that winding the fin material around the outer circumferential surface of the tube was troublesome.

An object of the present invention is to provide a method for manufacturing a finned metal tube that solves the above problems.

Means for Solving the Problems A method for manufacturing a metal tube with fins according to the present invention is to fit a metal tube for forming fins onto a metal tube to form a double tube, and to form a metal tube for forming fins by rolling. This method is characterized by forming spiral fins on the outer peripheral surface and then removing the bottom portion of the metal tube where the fins are formed.

Embodiments Examples of the present invention will be described below with reference to the drawings.

First, a double tube is prepared by fitting and covering a steel tube 1 with an aluminum tube 2 for forming fins. Then,
Spiral fins 3 are formed on the outer peripheral surface of the aluminum tube 2 by rolling using a rolling die (see FIG. 1). Thereafter, the bottom portion 2a of the aluminum tube 2 on which the fins 3 are formed is cut off using a disk-shaped cutting tool 4 (see FIG. 2).
The thickness of the tip of the cutting tool 4 is equal to the distance between the proximal ends of the fins. In this way, an aluminum finned steel tube is manufactured. The cutting tool 4 is preferably attached to the end of the rolling die to which the finishing fin-forming disk is attached, to which a large number of disc-shaped fin-forming disks are attached. In this way, the fins can be formed by rolling and the valley bottom portion 2a can be removed at the same time.

FIG. 3 shows a modification of the method of removing the valley bottom portion in the method of the present invention. In FIG. 3, the width of the tip of the disc-shaped cutting tool 14 is narrower than the width of the disc-shaped cutting tool 4 shown in FIG. I will remove it.

In the above embodiment, on the outer peripheral surface of the steel pipe,
An aluminum coating layer may be formed in advance. Furthermore, in the above embodiments, a steel tube is used as the first inner metal tube, and an aluminum tube is used as the fin-forming metal tube, but the present invention is not limited thereto.

Effects of the Invention In the method for manufacturing a metal tube with fins according to the present invention, a metal tube for forming fins is fitted over a metal tube to form a double tube, and a spiral shape is formed on the outer peripheral surface of the metal tube for forming fins by rolling processing. Since the method is characterized by forming fins and then removing the bottom portion of the metal tube on which the fins have been formed, the metal tube with fins manufactured by this method cannot be manufactured by the first conventional method mentioned above. It is lighter than manufactured metal tubes with fins. Furthermore, since the bottom portion is removed, the difference in thermal expansion due to the difference in coefficient of thermal expansion between the metal tube and the fin is absorbed by the removed portion, making it possible to withstand long-term use in a high-temperature atmosphere. Further, this invention is easier to work with than the second conventional method.

[Brief explanation of the drawing]

Fig. 1 is a partial vertical cross-sectional view of a state in which spiral fins are formed on an aluminum tube for forming fins, Fig. 2 is a partial longitudinal cross-sectional view showing a method for removing the valley bottom portion, and Fig. 3 is a modification of the method for removing the valley bottom portion. FIG. 3 is a partial longitudinal sectional view showing an example. DESCRIPTION OF SYMBOLS 1... Steel pipe, 2... Aluminum tube for forming fins, 2a... Valley bottom portion, 3... Spiral fins.

Claims (1)

[Claims] 1 A metal tube for forming fins is fitted over a metal tube to form a double tube, a spiral fin is formed on the outer peripheral surface of the metal tube for forming fins by rolling processing, and then the metal tube with the fins formed is A method for manufacturing a metal tube with fins, characterized by removing the valley bottom portion.