Tube with grooves on inner surface and its manufacturing method, and fluted plug

Abstract

The invention provides a tube with grooves formed in an inner surface thereof, a method of producing the tube and a grooved plug. The tube having grooves formed in its inner surface. The grooves are formed in a reverse trapezoidal cross section, and the corners at the root of each groove have a circular arc shape and the ratio (R / delta) of the radius R (mm) of each corner to the width delta (mm) of the groove is not less than 0.10 and not more than 0.25. A grooved plug having ridges and grooves formed on the outer peripheral surface of the plug is inserted into a blank tube, and the outer peripheral surface of the blank tube is pressed. This causes a blank tube material to flow into the grooves of the plug to form grooves in the inner surface of the blank tube. In this process, the blank tube material can easily flow into the grooves of the plug, so that cracks of the grooves and fins can be prevented.

Description

technical field [0001] The present invention relates to an inner surface grooved pipe, a method for producing the same, and a grooved plug used for the production thereof, and more particularly to an inner surface grooved pipe which prevents cracking or breakage of the inner surface grooved pipe during manufacture, a method for producing the same, and a plug for use therein. for the manufacture of grooved plugs. Background technique [0002] In recent years, as heat transfer tubes of heat exchangers (so-called finned tube heat exchangers) such as refrigerators, inner grooved tubes in which a plurality of grooves are formed on the inner surface of the tubes to improve heat transfer performance are often used. For example, in the inner surface grooved tube of Patent Document 1, a plurality of fins extending helically in the tube axis direction are formed on the inner surface, and grooves are formed between these fins. In this internally grooved tube, the fins have a tapered m...

AI Technical Summary

Problems solved by technology

[0004] However, in the existing inner surface grooved tubes, the shapes of the fins and grooves are determined only based on the design conditions of heat transfer performance, and there is a problem that gaps are generated in the fins or cracks are generated in the bottom of the grooves during manufacture ( refer to Figure 8 )

In addition, in the assembly of the heat exchanger, when the pipe with grooved inner surface passing through a plurality of finned plates is expanded so as to make it closely adhere to the through hole, if the above-mentioned fins etc. If there is a nick or a crack, then there is the problem that the crack develops and in the worst case the fins come off or the tube itself breaks

As the fluidity of the blank tube material deteriorates, chips or cracks occur on the fins, etc.

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