JPH10115476A - Heat transfer tube for condensation in tube - Google Patents

Abstract

(57) [Abstract] [Problem] To improve the heat transfer coefficient of condensation. SOLUTION: Low fins 12A and high fins 12B formed on the inner surface of a heat transfer tube main body 11 promote a turbulent flow effect near the tube wall of the heat transfer tube main body 11, thereby improving the condensation heat transfer rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-pipe condensing heat transfer tube applied to a heat exchanger and performing heat exchange by condensing a refrigerant in a pipe.

[0002]

2. Description of the Related Art In a heat exchanger in a refrigerator, an air conditioner, a heat pump, or the like, a refrigerant is passed through a heat transfer tube, and the refrigerant is condensed in the heat transfer tube to perform necessary heat exchange to perform a necessary heat exchange. Heat tubes are used.

[0003] The inner surface of the heat transfer tube as described above was initially smooth, but as the thermodynamics research progressed, the inner surface of the tube became more condensed if it had predetermined irregularities than the smooth surface. It has been found that the heat transfer coefficient is improved, and in recent years, those having continuous spiral grooves and spiral fins formed on the inner surface of the heat transfer tube have become the mainstream ("Thermal Design Handbook", written by Koichi Oshima, P572). An example is shown in FIG.

FIGS. 5 (a) and 5 (b) are views showing a main part of a conventional heat transfer tube for condensing heat in a pipe, wherein FIG. 5 (a) is a longitudinal sectional view, FIG. 5 (b) is a transverse sectional view, and FIG. It is the A section enlarged view of (b). In the drawing, β indicates an angle (twist angle) with respect to the tube axis direction. The in-pipe condensing heat transfer tube 1 has a continuous spiral groove 3 and spiral fins 4 formed on the inner surface of a heat transfer tube main body 2. By forming such spiral grooves 3 and spiral fins 4, the surface area inside the tube increases, and the heat transfer area increases. In addition, when heat is exchanged by condensing the refrigerant in the pipe, the refrigerant vapor condenses in the spiral groove 3 immediately after the condensation starts, and the condensed refrigerant liquid flows through the spiral groove 3 in the entire pipe. It flows while being lifted up by the spiral groove 3. Until the inside of the pipe is filled with the refrigerant liquid, the tip of the spiral fin 4 is in contact with the refrigerant vapor, so that the condensation of the refrigerant vapor also proceeds here. As a result, a high condensation heat transfer coefficient is obtained.

[0005]

However, according to the conventional in-pipe condensing heat transfer tube 1, the spiral groove 3 is formed on the inner surface of the heat transfer tube main body 2.
And since it is a structure only forming the spiral fin 4, when the inside of the spiral groove 3 is filled with the refrigerant liquid, the condensation is performed on the surface of the refrigerant liquid, and the condensation heat transfer rate is lower than immediately after the condensation. There are drawbacks. Further, as the condensation progresses, the liquid film of the refrigerant liquid becomes thicker, and the refrigerant liquid itself becomes a heat resistor, so that the heat transfer coefficient of condensation is further reduced.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an in-pipe condensing heat transfer tube with an improved heat transfer coefficient of condensation.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a heat transfer tube for condensing a refrigerant in a tube for heat exchange by forming a predetermined angle on the inner surface of the tube with respect to the axial direction of the tube. A heat transfer tube for condensing in a pipe, wherein fins having a predetermined height are formed continuously and fins having a height higher than the predetermined height are formed between the fins having the predetermined height. . The performance of the heat transfer tube is determined not only by the high heat transfer coefficient after the start of condensation but also by the overall performance until all of the refrigerant vapor condenses into the refrigerant liquid. If the condensation heat transfer coefficient is improved, the heat transfer performance of the heat transfer tube is greatly improved. That is,
If only spiral fins with a uniform height are provided on the inner surface of the heat transfer tube, the condensed refrigerant liquid flows in the spiral groove between the fins, and this flow becomes dominant and becomes a swirling flow along the tube wall. When the liquid film of the refrigerant liquid becomes thicker than the depth of the spiral groove, the turbulence effect near the pipe wall is small. However, when high fins are added between low fins as in the above configuration of the present invention, the liquid film of the refrigerant liquid is agitated due to the presence of the high fins, thereby improving the condensation heat transfer coefficient. Can be. Further, even in the refrigerant vapor before being condensed, the refrigerant fin is stirred near the tube wall by the high fins, the turbulence effect near the tube wall is promoted, and the heat transfer coefficient of condensation can be improved.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view showing a main part of a heat transfer tube for condensation in a tube according to an embodiment of the present invention, and FIG. 2 is a perspective view showing details of an inner surface of the tube. As shown in FIG. 1, the in-pipe condensing heat transfer tube 10 is provided on an inner surface of a heat transfer tube main body 11.
For example, an angle (torsion angle) β of 1 to 30 ° with respect to the tube axis direction
A continuous spiral fin 12A having a predetermined height is formed, and a continuous spiral fin 12B having a height higher than the predetermined height is formed between the spiral fins 12A having a predetermined height, as shown in FIG. A notch 13 is provided in the spiral fin 12B.

FIG. 3 is a view showing an example of a method of manufacturing the heat transfer tube 10. As shown in FIG. While moving the processing pipe 14 in the pipe axis direction, the processing pipe 14 is reduced in diameter by a spherical or roll-shaped rotary processing member 15 rotating in the pipe circumferential direction,
An inner groove having a predetermined twist angle is formed by an inner groove grooved plug 17 which rotates about the shaft 16. By such a rolling process, the heat transfer tube 10 having the continuous low spiral fins 12A and the continuous high spiral fins 12B as shown in FIG. 4 is formed. Next, the spiral fin 12
The heat transfer tube 10 having the A and 12B formed therein is again subjected to rolling processing only on the high spiral fin 12B by an inner grooved plug (not shown) having a different twist angle, and a notch 13 is provided. Thus, the heat transfer tube 10 shown in FIGS. 1 and 2 is manufactured.
In addition, two rolling processes using the inner surface grooved plug are performed on the shaft 16.
May be performed once by attaching two types of plugs with internal grooves. Thereby, the processing time can be reduced.

According to the heat transfer tube 10 configured as described above, the following effects can be obtained. When only the spiral fins 12 having a uniform height are provided on the inner surface of the heat transfer tube main body 11, the condensed refrigerant liquid flows in the spiral grooves between the spiral fins 12, and this flow becomes dominant, and is formed on the tube wall. When the liquid film of the refrigerant liquid becomes thicker than the depth of the spiral groove, the effect of turbulence near the pipe wall is small. However, when the high spiral fin 12B is added between the low spiral fins 12A as in the heat transfer tube 10 according to the present invention, the liquid film of the refrigerant liquid is agitated due to the presence of the high spiral fin 12B. In addition, the condensing heat transfer coefficient can be improved. Further, even in the refrigerant vapor before being condensed, the high spiral fins 12B allow
The refrigerant vapor is stirred near the tube wall of the heat transfer tube main body 11, the turbulence effect near the tube wall is promoted, and the condensation heat transfer coefficient can be improved. As a result, excellent performance can be exhibited as a condenser heat transfer tube.

Note that the present invention is not limited to the above-described embodiment, and various embodiments are possible. For example, in the above embodiment, the case where the condensing performance is greatly improved and used for condensing has been described. However, since the evaporating performance is equivalent to a conventional inner grooved tube having only a spiral groove and a spiral fin, , For evaporation. Alternatively, a plurality of continuous low fins with a twist angle of 0 ° may be formed on the inner surface of the heat transfer tube main body 11, and a plurality of high fins may be formed between these low fins. Thereby, the same effect as in the above embodiment can be obtained.

[0012]

As described above, according to the present invention, the turbulence effect in the vicinity of the tube wall of the heat transfer tube is promoted by providing a height difference between the fins formed on the inner surface of the tube. Can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a main part of a heat transfer tube for condensation in a tube according to the present invention.

FIG. 2 is a perspective view showing details of the inner surface of the heat transfer tube for condensation in a tube according to the present invention.

FIG. 3 is a cross-sectional view showing an example of a method for manufacturing a heat transfer tube for condensation in a tube according to the present invention.

FIG. 4 is a perspective view showing an example of a method for manufacturing a heat transfer tube for condensation in a tube according to the present invention.

FIG. 5 is a view showing a main part of a conventional heat transfer tube for condensing in a pipe, wherein FIG. 5 (a) is a longitudinal sectional view, FIG. 5 (b) is a transverse sectional view, and FIG.
(c) is an enlarged view of part A of Fig. (b)

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Condensation heat transfer tube in tube 11 Heat transfer tube main body 12A Low fin 12B High fin 13 Notch 14 Worked tube 15 Rotating member 16 Shaft 17 Plug with inner groove β Angle (twist angle) to tube axis direction

Claims (2)

[Claims] An in-pipe condensing heat transfer tube for exchanging heat by condensing a refrigerant in a pipe, wherein a fin having a predetermined height continuous at a predetermined angle with respect to a pipe axis direction is formed on an inner surface of the pipe. And a fin having a height higher than the predetermined height which is continuous between the fins having the predetermined height. 2. The heat transfer tube according to claim 1, wherein the high fin has a notch.