JPH09196582A - Pipe with protrusion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable preventing of wear-out breakage because of contact with a support metal while improving heat transfer performance by forming a plurality of protrusions made slender and linear or spiral with a circular or semi-circular section along the length of the external surface of a pipe. SOLUTION: Four linear protrusions 2 are formed at an interval of 90 deg. in the circumferential direction on the external surface along the length of a heat exchanger tube 1 and heat transfer surfaces 3 sandwiched between the protrusions 2 are formed. The linear protrusions 2 are made semicircular and the height of the protrusion 2 is determined by a relationship with the total intensity of the heat exchanger tube 1 considering its role of reinforcing the strength of the heat exchanger tube 1. The existence of the protrusion 2 on the surface of the heat exchanger tube 1 keeps a heat transfer surface 3 from directly contacting a support metal and causing wearing thereof thereby allowing reduction in the thickness of the heat transfer surface 3. This achieves higher heat transfer performance and can prevent wear-out breakage under contact with the support metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer tube for improving heat transfer characteristics and suppressing wear of a heat transfer surface, and more particularly to a heat transfer tube for general industrial and nuclear heat exchangers.

[0002]

2. Description of the Related Art Generally, a heat transfer tube of a heat exchanger has a smooth outer surface as shown in FIG. 4 and a uniform thickness in cross section. In many cases, the heat transfer tube is inserted and supported in the hole of the support fitting to prevent the deformation due to the temperature change and the vibration due to the fluid flow. However, when the heat transfer tube comes into strong contact with the support fitting, the surface of the heat transfer tube may be worn. The thinner the wall thickness, the better the heat transfer characteristics and the better the performance as a heat exchanger, but the wall thickness of the heat transfer tube is usually determined in consideration of the wear thickness.

[0003]

When the heat transfer tube is thin, the heat transfer characteristics are improved, but the margin of the wear allowance is reduced, while when the heat transfer tube is made thicker in consideration of the wear allowance, the heat transfer characteristics are deteriorated. There is.

It is an object of the present invention to provide a heat transfer tube which can improve heat transfer performance and at the same time prevent wear and damage due to contact with a support fitting.

[0005]

Means for achieving the above object can be achieved by providing the heat transfer tube with a thin wall portion for heat exchange and a thick wall portion on the surface of the heat transfer tube for contact with a metal support.

By the above means, even if the heat transfer tube is deformed or vibrates and comes into contact with the support fitting, wear of the heat transfer tube occurs at the protrusions, and the heat transfer tube surface of the thin portion for heat exchange is not damaged. Absent.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Specific examples of the present invention will be described below. FIG. 1 shows a circumferential direction 9 on the longitudinal outer surface of the heat transfer tube 1.
It is an example of a heat transfer tube in which four linear protrusions 2 and a heat transfer surface 3 sandwiched by the protrusions are formed at 0 ° intervals. The cross section of the protrusion 2 is semicircular. Normally, the height of the protrusion 2 may be the thickness corresponding to the wear allowance. However, since the protrusions 2 serve to reinforce the strength of the heat transfer tube 1, the height of the protrusions 2 is determined from the relationship with the strength of the entire heat transfer tube. Since the heat transfer surface 3 does not come into direct contact with the support fitting and wear due to the protrusions 2 on the surface of the heat transfer tube, the thickness of the heat transfer surface 3 can be reduced. FIG. 2 shows an embodiment of a heat transfer tube in which two spiral projections 2 are formed on the surface of the heat transfer tube 1 in the longitudinal direction at intervals of 180 ° in the circumferential direction. The cross-sectional shape of the protrusion 2 is semicircular. The design concept regarding the wall thickness of the heat transfer surface and the projection structure is the same as in the case of FIG. FIG. 3 shows a situation in which the heat transfer tube of the present invention described in FIG. 2 is supported by the support fitting 4. The inner diameter surface of the hole 5 formed in the support fitting 4 contacts only the outer peripheral surface of the protrusion 2 and does not contact the heat transfer surface 3. As a result, even if the heat transfer tube 1 vibrates and makes strong contact with the support fitting, the heat transfer surface 3 is not worn. Although the heat transfer tube with protrusions of the present invention is not shown here as an example, it can also be used as a fuel cladding tube for a nuclear reactor. In this case, the support fittings shown in FIG. 3 are not used, but the projections of the cladding tube are arranged so as to come into contact with each other.

[0008]

According to the present invention, the heat transfer surface can be made thinner and the heat transfer characteristics can be improved. At the same time, the heat transfer surface can be prevented from being worn by the support metal fittings and the heat transfer tube can be prevented from being damaged.

[Brief description of drawings]

FIG. 1 is an explanatory view of a heat transfer tube of the present invention having four linear protrusions on the outer surface of the heat transfer tube.

FIG. 2 is an explanatory view of the heat transfer tube of the present invention having two spiral protrusions on the outer surface of the heat transfer tube.

FIG. 3 is an explanatory view showing how the heat transfer tube of the present invention having two spiral projections on the outer surface of the heat transfer tube is supported by a support fitting.

FIG. 4 is an explanatory view showing a conventional general heat transfer tube.

[Explanation of symbols]

1 ... Heat transfer tube, 2 ... Protrusion, 3 ... Heat transfer surface, 4 ... Support metal fitting, 5
... holes.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazumasa Ozawa 7-2-1, Omika-cho, Hitachi-shi, Ibaraki Hitachi Co., Ltd.

Claims (1)

[Claims] 1. One or more elongated projections having a circular or semi-circular cross section formed in a linear or spiral shape along the longitudinal direction of the outer surface of the tube. Tube with protrusion.