JPH03234303A - Manufacture of electro-resistance-welded tube for heat transfer - Google Patents

Abstract

PURPOSE:To improve the heat-transfer performance of tube by rolling forming a lot of parallel primary grooves and the secondary grooves which are crossed in the primary grooves on the surface of bar stock of metallic plate and making into a tubular body by electric resistance welding after turning the surface where the grooves are formed inward after the width of opening of the primary grooves is intermittently narrowed between the secondary grooves in the manufacture of electro-resistance-welded tube for heat transfer. CONSTITUTION:A lot of parallel primary grooves 2 and a lot of parallel secondary grooves 3 which are crossed in the primary grooves at a certain angle are rolling formed on the surface of bar stock 1 of metallic plate. And, after the width of opening of the primary groove 2 is intermittently narrowed at the parts between these secondary grooves 3, a tubular body is made by electric resistance welding the bar stock 1 of metallic plate after turning the surface where grooves are formed inward. In this way, the evaporation efficiency of heating medium liquid can be raised and the heat transfer performance can be improved when the tubular body is used for the evaporation part of heat exchanger.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a method of manufacturing an electric resistance welded heat transfer tube used as an evaporation tube, a condensation tube, a heat vibrator, etc. of a heat exchanger, etc.
In particular, it relates to improvements to improve heat transfer performance.

``Prior art'' As a means to improve the heat transfer performance of heat transfer tubes, it has been well known that many spiral or linear grooves are formed on the inner surface of a tube body made of copper or the like by rolling or drawing. By forming such a groove, the following effects can be obtained.

■ When this heat transfer tube is used as a condensing tube, the heat medium vapor flowing inside the condensing tube is made into a turbulent flow by the ridges between the grooves, and the ridges serve as condensation nuclei to increase condensation efficiency and reduce liquefaction. Facilitate. Furthermore, the condensed heat transfer liquid is efficiently flowed in the longitudinal direction of the heat transfer tube by utilizing the surface tension within the grooves, thereby increasing the reflux effect.

On the other hand, when used as an evaporation tube, the edges within the grooves become evaporation nuclei that generate bubbles, promoting nucleate boiling and increasing the vaporization efficiency of the heat medium liquid supplied into the heat transfer tube. Furthermore, the surface tension within the grooves is used to efficiently flow the heat medium liquid in the longitudinal direction of the heat transfer tube, increasing the supply effect.

``Problems to be Solved by the Invention'' By the way, in order to improve the performance of this type of grooved heat exchanger tube, it is effective to narrow the opening width of the groove to make it smaller than the bottom width of the groove so that it approaches a tubular shape. It is expected to be. With such a tubular shape, air bubbles are likely to occur inside the tubular groove.
These bubbles serve as nuclei and promote evaporation, thereby greatly increasing the evaporation efficiency. It is also believed that the transport efficiency of the heat medium i and body due to the surface tension within the groove increases, and the overall heat transfer performance increases significantly.

However, in the method of forming simple grooves by machining described above, the opening width of the groove must be larger than the width of the bottom due to processing constraints, making it impossible to form the groove into a tubular shape. There were limits to the improvement of thermal performance.

"Means for Solving the Problems" The present invention has been made to solve the above problems, and after forming a large number of parallel main grooves on the surface of a metal plate strip material by rolling, By rolling and forming a large number of parallel minor grooves that intersect at an angle, the opening width of the main groove is intermittently narrowed in the areas between these minor grooves, and the strip material is rolled with the groove forming surface facing inward. It is characterized by being made into a tube body by electric resistance welding.

Note that it is preferable that the main groove is formed to have a U-shaped cross section, and the sub-grooves are formed to have a V-shaped cross section.

"Function" According to this method of manufacturing an electric resistance welded tube for heat transfer, the opening width of each main groove is narrowed relative to the bottom width of the groove at intervals in the longitudinal direction to form a tubular part. Is possible. When this heat transfer electric resistance welded tube is used particularly in the evaporation part of a heat exchanger, etc., air bubbles are likely to form inside the tubular part of the main groove, and these air bubbles act as nuclei and promote evaporation, causing heat The vaporization efficiency of the liquid medium is greatly increased.

In addition, when used in either the evaporation section or the condensation section, the tubular section increases the efficiency of liquid transport due to surface tension within the main groove, making it more efficient overall than a simple grooved heat exchanger tube. Heat transfer performance can be significantly improved.

"Example" Hereinafter, an example of the method for manufacturing an electric resistance welded tube for heat transfer according to the present invention will be described.

In this method, first, as shown in Fig. 1, a metal plate strip 1
is sequentially rolled with a main groove forming roll R1 and a sub-groove forming roll R2, and a large number of parallel main grooves 2 and sub-grooves 3 intersecting the main grooves at a constant angle are respectively formed on the surface thereof.

The plate material l is made of a conventionally used material such as copper, copper alloy, aluminum, etc., and its width is set to a value that allows a tubular body of a desired diameter to be obtained by electric resistance welding.

As shown in FIG. 2, on the outer circumferential surface of the main groove forming a-rule R1, a large number of protrusions T1 having a U-shaped cross section are formed parallel to each other and inclined at a certain angle with respect to the circumferential direction of the roll R1. As a result, a main groove 2 having a U-shaped cross section and inclined with respect to the longitudinal direction is formed on the surface of the strip material 1, as shown in FIG. The closer the cross-sectional shape of the main groove 2 is to a U-shape, the easier it is to narrow the opening width and form the tubular portion 4.

The width w1 of the main groove 2 is 40 to 140% of the depth DI, preferably 80 to 120%. If it is less than 40%, it will get stuck in the formation of the single groove 3 and the main groove 2 will be easily swamped, and if it is more than 140%, the opening width of the tubular portion 4 cannot be sufficiently narrowed. Main groove 2
The interval P1 is 1.5 to 3 times, preferably 1.8 to 22 times, the main groove width W1. If it is less than 1.5 times, forming the minor grooves 3 will cause the protrusions between the main grooves 2 to collapse, making it difficult to form the tubular portion 4. Moreover, if it is larger than 3 times, the formation density of the main grooves 2 becomes small, and the effect of improving heat transfer performance is reduced.

Specifically, in the case of a normal heat exchanger tube, the depth D of the main groove 2! =
0.2~Q, 3xx, width Wl=0.2~0°5z
z, P 1 = 0.4 to 1.5xx, bottom section angle is 7
5° or more is appropriate.

On the other hand, as shown in FIG. 3, a large number of parallel protrusions T2 having a V-shaped cross section are formed on the outer circumferential surface of the sub-groove forming roll R2. These protrusions T2 are inclined in the direction opposite to the main groove forming roll R1 with respect to the circumferential direction of the roll R2, so that the strip material 1 has the main groove 2 as shown in FIG. A large number of parallel sub-grooves 3 having a V-shaped cross section are formed, intersecting each other at a constant angle α.

The pitch P2 of the sub-grooves 3 may be equal to that of the main groove 2, or does not necessarily need to be equal to that of the main groove 2. The width W2 of the sub groove 3 is 25 to 90%, preferably 50 to 70%, of the main groove width Wl'. If it is less than 25%, the opening width of the main groove 2 cannot be sufficiently narrowed, and if it is more than 90%, the opening of the main groove 2 may be closed. Further, the depth D2 of the sub-groove 3 is set to 40 to 100%, preferably 80 to 100%, of the main groove depth Dl. If it is less than 40%, the opening width of the main groove 2 cannot be sufficiently narrowed, and if it is more than 100%, there is a risk that the main groove 2 will be closed in dogs.

Specifically, in the case of a normal heat exchanger tube, the depth D2- of the sub-groove 3 is
0.15~Q, 3xz, pitch P2=0.4~1
．． 5RR, the cross-sectional angle of the V-shape is preferably about 45 to 90'.

In addition, it is desirable that the intersection angle α between the main groove 2 and the sub-groove 3 is 20 to 60 degrees, particularly 30 to 400 degrees.

Outside this range, it becomes difficult to form the tubular portion 4. Further, it is desirable that the main groove 2 is within 30' in the longitudinal direction of the manufacturing method of the electric resistance welded tube for heat transfer.

If it is larger than this, the flow of the heat medium liquid in the longitudinal direction of the tube will be poor.

As shown in FIGS. 5 to 8 and 9 to 14, both side walls of the main groove 2 are inclined inward in the portion between the sub grooves 3, and the main groove 2 is The opening width is narrowed and a tubular portion 4 is formed.

The minimum opening width of these tubular portions 4 is 75 of the width W1 of the main groove 2.
% or less. When this rate is 75%, the effect of generating air bubbles in dogs decreases, and the effect of improving heat transfer performance compared to conventional grooved heat transfer tubes decreases.

Note that the space between the protrusions 11 of the sub-groove forming roll R2 may be curved as shown by the two-dot chain line A in FIG. In this way, when forming the sub-groove, the side wall portion of the main groove 2 is smoothly deformed along this curved surface 12, increasing the effect of narrowing the opening width of the main groove 2. Furthermore, a narrow flat portion may be formed at the tip of each protruding portion 11 as shown at the end of the numeral.

Next, after rolling the main/I42 and sub-grooves 3, set the plate material l in the electric resistance welding device with the groove forming surface facing the inner side, and pass it between the drive roll and idler in multiple stages. The plate material l is rolled up in the width direction, and finally both side edges of the plate material are welded to form it into a circular tube shape. The electric resistance stitching device may be one that is commonly used, and the electric resistance stitching conditions may be the same as those for normal processing. Thereafter, the welded portion on the outer circumferential surface of the tube is shaped as necessary, and then the tube is wound into a roll or cut to a predetermined length to obtain a long heat exchanger tube.

According to the above method for manufacturing an electric resistance welded tube for heat transfer, as shown in FIG. Since a large number of narrow tubular portions 4 can be formed in the heat transfer tube, especially when this heat transfer electric resistance welded tube is used in the evaporation section of a heat exchanger, etc., it is possible to form a heat transfer tube with a smooth inner surface as shown in Fig. 15. , compared to the case of a heat exchanger tube with simple grooves shown in FIG. 16, bubbles are more likely to be generated inside each tubular portion 4 as shown in FIG. It accelerates the evaporation of liquids (such as fluorocarbons) and greatly increases the evaporation efficiency.

In addition, since the tubular portions 4 are provided intermittently, each main groove 2
The heat medium liquid flowing into the main groove 2 is quickly transported along the main groove 2 by capillary action due to surface tension from the side wall. Therefore, the transport efficiency of the heat medium liquid is improved compared to the case of a simple grooved heat exchanger tube.

Furthermore, by forming the two types of grooves 2 and 3 in an intersecting state, the inner area is increased compared to a simple grooved heat exchanger tube, and the edges of the valley grooves 2 and 3 are sharpened, increasing surface activity. Therefore, when used in a condensing section, these edge sections can be easily drained of liquid, promoting condensation of heat medium vapor and increasing liquefaction efficiency.

Furthermore, in this method for manufacturing electric resistance welded heat transfer tubes, the two processes of rolling and electric resistance welding can be continuous as one line, so long and small diameter heat transfer tubes can be efficiently obtained. , mass production can reduce manufacturing costs.

In the above embodiment, the heat transfer electric resistance welded tube has a circular cross section, but the present invention is not limited to a circular cross section, but can also be implemented with an elliptical cross section, a flat tubular shape, etc.

In addition, in the above embodiment, the plate material 1 with the width of one heat exchanger tube was used, or instead, the plate material 1 with the valley grooves 2 was used in a sufficiently wide plate material.
, 3 are formed, then cut into narrow strips using a slitting machine, and these strips may be subjected to electric resistance welding to form heat exchanger tubes. In that case, productivity can be further improved.

"Experiment example" Using a deoxidized copper strip with a thickness of 0.50cm and a width of 38cm,
Rolling was performed continuously using a main groove forming roll and a sub groove forming roll, and the strip material was cut to confirm the cross-sectional shape.

The depth of the main groove is the same as 0.251, and the depth of the minor groove is 0.05xx, 0IQxx, 0. 15zx, 0.
It was changed to 4 stages of 20xz and the shape change of the tubular part was observed.

Both the main groove forming roll and the minor groove forming roll have an outer diameter of 120+yx and a thickness of 38ix, the main groove forming roll has a U-shaped cross section as shown in FIG.
The cross section was V-shaped as shown in the figure.

The cross-sectional shape of the tubular portion of the obtained strip material is shown in FIGS. 18 to 21. As shown in the figure, good tubular portions were formed in all cases in which the depth of the sub-groove was 0.10 square meters or more.

"Effects of the Invention" As explained above, according to the method of manufacturing an electric resistance welded tube for heat transfer of the present invention, the main groove is spaced apart in the longitudinal direction, and the opening width is relatively small compared to the inner width of the groove. Since a large number of narrow tubular sections can be formed, especially when this heat transfer electric resistance welded tube is used in the evaporation section of a heat exchanger, air bubbles are likely to occur inside each tubular section. The bubbles act as an evaporator, promoting the evaporation of the heat transfer liquid and greatly increasing the evaporation efficiency.

In addition, since the tubular portions are provided intermittently, the heat transfer liquid that has flowed into each main groove receives surface tension from the side wall portions and is quickly transported along the main groove by capillary action.
The transport efficiency of heat transfer liquid is improved.

In addition, by forming the main grooves and sub-grooves in an intersecting state, the internal area increases compared to a simple grooved heat exchanger tube, and the edges of the valley grooves become sharper, increasing surface activity. When an electric resistance welded tube is used in the #ring, these dinones act as condensation nuclei to promote condensation of heat medium vapor and improve oxidation efficiency.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the method for manufacturing an electric resistance welded heat transfer tube according to the present invention, FIG. 2 is an enlarged cross-sectional view of the outer circumferential surface of the main groove forming roll, and FIG. 3 is a cross-sectional view of the outer circumferential surface of the sub-groove forming roll. Enlarged views, Figures 4 to 8 are explanatory views of how the tubular portion is formed, Figure 9 is an enlarged view of the inner surface of the electric resistance welded tube for heat transfer obtained by this method, and Figures 10 to 14. The figure is a cross-sectional view taken along the line Ei to Hoh in Fig. 9, Figs. 15 to 17 are explanatory diagrams showing the effects of the present invention, and Figs. 18 to 21 are electric resistance welded tubes for heat transfer obtained in experimental examples. 22 and 23 are cross-sectional views of the main groove forming roll and the sub groove forming roll used in the experimental example. 1... Metal plate strip, 2... Main groove, 3... Minor groove, 4
...Tubular portion, R1--Main groove forming roll, R2...Sub-groove forming roll.

Claims (2)

[Claims] (1) After forming a large number of parallel main grooves on the surface of a metal plate strip by rolling, a large number of parallel sub-grooves that intersect with these main grooves at a certain angle are formed by rolling. An electric resistance welded tube for heat transfer, characterized in that the opening width of the main groove is intermittently narrowed at the part, and the plate material is subjected to electric resistance welding with the groove forming surface facing inward to form a tube body. manufacturing method. (2) The main groove is formed to have a U-shaped cross section, and the minor groove is formed to have a V-shaped cross section.
The method for manufacturing the electric resistance welded tube for heat transfer described above.