JPS62182595A - Heat transfer tube and manufacture thereof and plug with groove for manufacturing it - Google Patents

Abstract

PURPOSE:To restrict pressure loss to the same level as a smooth tube and permit to promote boiling phenomenon by a method wherein a multitude of axial or spiral grooves are formed on the inner surface of a tube while cavities, having V-shape or sector-shape sections and communicated with the grooves, are formed at the tip ends of the grooves on the wall along the direction of the grooves. CONSTITUTION:Axial or spiral grooves 2 are formed on the inner surface of a tube 1 and cavities 5, having sector-shape or V-shape sections and communicated with the grooves 2, are formed continuously along the direction of the groove 2. One or a plurality of grooves 7, intersecting said grooves 2 and having a depth to arrive at said cavities, is formed on the inner surface of the tube 1. According to this method, the width of the opening of the groove can be narrowed and cavities, communicating with said grooves, can be formed in the wall of the tube 1, therefore, boiling phenomenon in the heat transfer tube may be promoted and the evaporating heat transfer rate of refrigerant, flowing in the tube, may be improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a heat exchanger tube used in a heat exchanger such as an air conditioner or a refrigerator, a manufacturing method thereof, and a plug for manufacturing the same. This improves the evaporation performance of refrigerant.

[Conventional technology]

In general, heat exchangers for small air conditioners and refrigerators are being made with grooves on the inner surface of the tube (1), as shown in Figure 7, as heat exchanger tubes with excellent heat transfer performance due to the miniaturization of equipment and promotion of energy conservation. (2) An internally grooved tube is used. However, due to the thinning of the heat exchanger tube itself, there is a limit to the improvement of the groove shape on the inner surface of the tube. Therefore, the internally grooved tube was further processed to form grooves (2) on the internal surface of the tube (1) as shown in Figure 8.
Squeeze the tip of the mountain side (3) toward the groove side to create the groove opening (4).
Specially grooved heat transfer tubes have been used which have narrowed openings (4) to form cavities (5) that communicate with the tubes (1). It is known that this heat transfer tube can improve the evaporation performance of the refrigerant flowing inside the tube and increase the boiling heat transfer coefficient.

(Problems to be Solved by the Invention) Specially grooved heat transfer tubes are generally manufactured by inserting a floating plug having a smooth surface into a conventional internally structured tube and expanding or contracting the tube by drawing. However, simply inserting a floating plug into a conventional internally structured pipe to expand the pipe only deforms the tip of the mountain side in one direction, narrowing the width of the groove opening and actively promoting the boiling phenomenon. It is not a structure that can promote this.

Therefore, if an attempt is made to increase the processing rate to narrow the width of the groove opening, the cavity itself to be formed in the inner wall of the tube will be blocked, making it impossible to improve the evaporative heat transfer coefficient. Furthermore, in the drawing process that involves diameter reduction, the swelling of the bottom wall thickness and the compression of the peak side tip overlap, which also causes problems such as making it difficult to form a cavity inside the tube wall.

[Means for solving problems]

In view of this, as a result of various studies, the present invention has developed a heat exchanger tube with a new shape that facilitates forming a cavity inside the tube wall that communicates with the inside of the tube, a method for manufacturing the same, and a grooved plug for manufacturing the same.

One of the heat exchanger tubes of the present invention has a large number of axial or spiral grooves formed on the inner surface of the tube that communicate with the inside of the tube, and a V-shaped or sector-shaped cavity in cross section that communicates with the grooves at the inner end of the groove. It is characterized in that the body is formed in the direction of the groove.

Another heat transfer tube of the present invention has a large number of axial or spiral grooves formed on the inner surface of the tube that communicate with the inside of the tube, and a V-shaped or fan-shaped cross section that communicates with the grooves at the inner end of the groove. A cavity is formed in the direction of the groove, and one or more grooves are formed on the inner surface of the tube to intersect with the groove and reach the cavity.

In addition, one of the methods for manufacturing the heat exchanger tube of the present invention is to form a double-headed peak in the tube axis direction or a spiral cross section, or a projection having a triangular cross section in conjunction with the peak, on the inner surface of the tube by rolling using a grooved plug. A large number of troughs are formed, and then a taper plug is used to expand or contract the double-headed crest to the left and right to form a groove opening that communicates with the inside of the tube, and a groove is formed at the tip of the wall of the groove. It is characterized by forming a cavity with a V-shaped or sector-shaped cross section in communication with the groove in the direction of the groove.

Another method of manufacturing the heat exchanger tube of the present invention is to form a double-headed peak in the tube axis direction or a spiral cross section, or a protrusion that is triangular in cross section with the peak, by rolling using a grooved plug. A groove that communicates with the inside of the pipe by forming a large number of valleys and then expanding or shrinking the double-headed peak using a taper plug provided with one or more protrusions that intersect with the peaks to the left and right. In addition to forming an opening, a cavity with a V-shaped or fan-shaped cross section communicating with the groove is formed in the groove direction at the inner end of the wall of the groove, and a cavity with a depth that intersects with the groove and reaches the cavity is formed on the inner surface of the tube. It is characterized by forming one or more grooves in the groove.

Furthermore, the grooved plug for manufacturing heat exchanger tubes of the present invention has a large number of axial or spiral grooves formed on the outer peripheral surface of the rolling plug, and protrusions having a triangular cross section are formed at the bottoms of the grooves. It is characterized by the formation of protrusions and the top of the mountain having a double-headed cross section.

That is, one of the heat exchanger tubes of the present invention, as shown in enlarged view in FIGS. and the wall (1) of the groove (2)
a) At the inner tip, a cavity (5) with a fan-shaped cross section communicating with the groove (2) is formed continuously in the direction of the groove (2) as shown in (B), or as shown in (B). A cavity (5) having a V-shaped cross section and communicating with the groove (2) is formed continuously in the direction of the groove (2). In addition, as shown in FIG. 2, another heat exchanger tube of the present invention has the inner surface of the tube (1) as shown in FIG.
B) A groove in the axial direction or a spiral shape communicating with the inside of the pipe (2)
), and a cavity having a fan-shaped or V-shaped cross section communicating with the groove (2) is formed continuously in the direction of the groove (2) at the inner end of the wall of the groove (2), and ) is formed with one or more grooves (7) having a depth that intersects with the groove (2) and reaches the cavity.

The heat exchanger tube of the present invention is manufactured using the same conventional equipment as shown in FIG. That is, the draw plug (8) inserted into the pipe (1)
), a grooved plug (9) and a taper plug (10) are coaxially rotatably connected to the rear of the grooved plug (9) by a connecting pin (11), and a draw plug (8) on the outside of the pipe (1) is connected. The drawing die (12) is placed in the position corresponding to the slotted one, and the plug (9
) and a diameter-reducing or expanding die (14) at a position corresponding to the tapered plug (10).
After arranging the tube (1) and first drawing the tube (1), grooves are formed on the inner surface of the tube (1) using a plug (9), and then expanded or contracted using a taper plug (10). According to
Squeeze the peaks of the groove. In the figure, (15) indicates a thrust bearing.

As shown in Figure 4 (a), the grooved plug (9) has a large number of axial or spiral grooves (17) on its outer periphery, and a protrusion (18) with a triangular cross section at the bottom of the valley side. Alternatively, as shown in FIG. 4(B), a protrusion (18) having a triangular cross section is formed at the bottom of the valley side, and the top portion (19) of the mountain side is made to have a double-headed cross section. In this way, the rolling process is performed as shown in Figure 5 (
As shown in a), a groove (2°) is formed on the inner surface of the tube (1), and the top of the mountain side (3°) has a double-headed cross section;
Alternatively, as shown in FIG. 5(b), the top of the mountain side (3°) is made double-headed in cross section, and the bottom of the valley side is formed with a protrusion (6") having a triangular cross section. Next, this is formed into a taper plug (10"). )
The double-headed shape of the mountain side top (3') is crushed from side to side by expanding or shrinking the pipe using a pipe, and grooves (2) are formed on the inner surface of the pipe (1) as shown in Figure 1 (a) and (b). A cavity (5) having a V-shaped or sector-shaped cross section is formed. At this time, one or more protrusions (16) are provided on the outer periphery of the taper plug (10) to intersect with the groove (2) formed on the inner surface of the tube (1).
) to reach a V-shaped or sector-shaped cavity in cross section (
7).

[Effect]

According to the present invention, the width of the groove opening can be narrowed and it can be finished to form a cavity in the wall communicating with the groove, so that the boiling phenomenon can be promoted as a heat transfer tube, and the refrigerant flowing inside the tube can be heated. The evaporative heat transfer coefficient can be significantly improved. Further, it is easy to form a second groove that is deep enough to intersect with the groove and reach the cavity, and it is possible to improve the diffusion of bubbles due to boiling.

When grooving the inner surface of the tube in the production of the heat exchanger tube of the present invention, it is preferable that the opening angle (θ) of the double-headed shape at the top end of the groove formed on the inner surface of the tube is 60 to 100°. In other words, if the opening angle (θ) is less than 60°, there is a risk that the peaks will be crushed in the same direction, and if it exceeds 100°, the height of the double-headed peak will be insufficient, and the groove opening after crushing will be narrowed. This also makes it difficult to form a cavity that communicates with the groove.

〔Example〕

In the manufacturing process shown in Figure 3, heat exchanger tubes having the dimensions shown in Table 1 were manufactured using steel pipes using the grooved nib lugs shown in Figures 4 (a) and (b). Evaporative heat transfer coefficient and pressure drop were measured under the conditions shown in the table. The results are shown in Figures 6(a) and 6(b). A double-tube heat exchanger was used for the measurement.

Figure 6 (a) shows the refrigerant flow! (Kff/hr) and the in-pipe evaporative heat transfer coefficient (Kcal/Tl1h'C),
Figure 6 (b) shows the relationship between the refrigerant flow it (Kg/hr) and the pressure loss inside the tube (K!j/ctA), and as is clear from the figure, the heat exchanger tubes NO. With almost the same pressure loss as smooth tubes NO, F, conventional heat exchanger tubes NO, F
It can be seen that the evaporative heat transfer coefficient is far superior to that of . Particularly when compared at a refrigerant flow rate of 5ONg/h, the heat exchanger tubes No., A-D of the present invention have a 3.0 to 4.0
The evaporative heat transfer coefficient within the tube is improved by 2.0 to 2.5 times compared to conventional heat exchanger tubes No. and E.

〔Effect of the invention〕

As described above, the heat transfer tube according to the present invention not only can suppress pressure loss to the same level as a smooth tube, but also promotes boiling phenomenon and exhibits excellent heat transfer characteristics. Grooving the inner wall of the pipe with a pass line allows processing and forming a cavity at the tip of the wall of the groove, which reduces manufacturing costs, and also allows the heat exchanger body to be smaller and lighter. It has remarkable industrial effects such as:

[Brief explanation of drawings]

Figures 1 (a) and (opening) are a cross-sectional view showing an example of the heat exchanger tube of the present invention, Figure 2 is a side cross-sectional view showing still another example of the heat exchanger tube of the present invention, and Figure 3 is a heat exchanger tube of the present invention. 4(a) and 4(b) are an explanatory diagram showing the manufacturing process of the heat exchanger tube of the present invention, and FIG.
(B) is a side cross-sectional view showing the inner surface shape of the grooved tube of the heat transfer tube of the present invention in the process, and Figures 6 (A) and (B) show the measured values of the evaporative heat transfer coefficient and pressure loss of the heat transfer tube. (a) shows the relationship between refrigerant flow rate and evaporative heat transfer coefficient, and (b) shows the relationship between refrigerant flow rate and pressure loss. 1. Pipe 2. Groove 3, mountain top 4. Groove opening 5, cavity 8. Drawn plug 9, grooved plug 10. Taper plug 12, drawing die 13. Rolling roll 14, pipe expansion (pipe contraction) die No. (a) No. (a) Fig. 6 Fig. 4 (b) Fig. 5 (b): +a flow i (Kg/h) Second age calculated flow t (K9 /Old procedure manual (method) May 7, 1985 1, Indication of the case 1988 Patent application No. 24781 2, Name of the invention Heat exchanger tube and its manufacturing method and grooved for manufacturing is a plug 3, Person making amendment 4, agent address: 16 Kanda Kita Jorimono-cho, Chiyoda-ku, Tokyo
101 5th floor, 3rd floor of Ei Building, content 1 of date correction of notice of reasons for refusal, page 14, lines 14 to 15, added the following sentence next to "Shows the relationship between cold ts'am and pressure loss." do. FIG. 7 is a partially cutaway perspective view of an example of a conventional heat exchanger tube, and FIG. 8 is a cross-sectional view of another example of a conventional heat exchanger tube. ”

Claims (5)

[Claims] (1) A large number of axial or spiral grooves are formed on the inner surface of the tube to communicate with the inside of the tube, and a cross-section V communicating with the grooves is formed at the inner end of the groove.
A heat exchanger tube characterized in that a letter-shaped or sector-shaped cavity is formed in the direction of the groove. (2) A large number of axial or spiral grooves are formed on the inner surface of the tube to communicate with the inside of the tube, and a cross section V communicating with the grooves is formed at the inner end of the groove.
A heat exchanger tube characterized in that a letter-shaped or sector-shaped cavity is formed in the direction of the groove, and one or more grooves are formed on the inner surface of the tube with a depth that intersects with the groove and reaches the cavity. (3) By rolling using a grooved plug, a large number of double-headed peaks with a cross-section in the tube axis direction or in a spiral shape, or valleys having protrusions with a triangular cross-section in conjunction with the peaks, are formed on the inner surface of the tube, and then a taper is formed. By expanding or contracting the pipe using a plug, the double-headed crest is crushed left and right to form a groove opening that communicates with the inside of the pipe, and the inner tip of the groove has a V-shaped or fan-shaped cross section that communicates with the groove. A method for manufacturing a heat transfer tube, characterized in that a cavity is formed in the direction of the groove. (4) By rolling using a grooved plug, a large number of double-headed peaks in the tube axis direction or a spiral cross section or valleys having triangular protrusions in conjunction with the peaks are formed on the inner surface of the tube, and then the above-mentioned peaks are By expanding or shrinking the double-headed portion using a taper plug provided with one or more protrusions that intersect with the portion, the double-headed portion is crushed from side to side to form a groove opening that communicates with the inside of the tube. A cavity with a V-shaped or sector-shaped cross section communicating with the groove is formed at the tip of the wall in the direction of the groove, and one or more grooves are formed on the inner surface of the tube with a depth that intersects with the groove and reaches the cavity. A method for manufacturing a heat exchanger tube, characterized by forming a heat exchanger tube. (5) Form a large number of axial or spiral grooves on the outer circumferential surface of the rolling plug, and form protrusions with a triangular cross section at the bottom of the grooves, or form the protrusions and have the top part cross-sectionally A grooved plug for manufacturing heat exchanger tubes characterized by its double-headed shape.