JPH01314898A - Heat transfer tube - Google Patents

Abstract

PURPOSE:To provide a heat transfer tube wit heat transfer performance not inferior to a traditional heat transfer tube with cross grooves and contrive an extremely enhanced production by forming repeatedly projections, having a predetermined length and provided with slanted parts slanted into the same direction on the upper surface thereof, between respective grooves, along the lengthwise direction of the heat transfer tube. CONSTITUTION:When a material tube (a) is pushed against the tip end of a grooved plug 4 from the outer periphery thereof by rolling rolls 7 rotated through planetary rotation while penetrating the material tube (a) between the grooved plug 4 and a plurality of rolling rolls 7 and moving it with a given speed, a part, pushed many times against the grooved plug by the rolling rolls 7, and another part, pushed only few times against the end of the grooved plug 4, are generated on the material tube (a) while the part, pushed many times, is invaded deeply into the grooves 40 of the plug 4 and is protruded and the part, pushed few times, is invaded slightly into the groove 40 whereby the projections 3 having the slanted part 31 is formed repeatedly and continuously simultaneously with the forming of the grooves 2. The projection 3 is provided with the slanted parts 31, formed higher at the tip end side of the moving direction of the material tube (a) and lower as the position thereof approaches to the rear end side of the same, while the slanted parts 31 are formed so as to be arranged in spiral form with intermediary of the grooves 2.

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 a refrigerator or an air conditioner. The present invention relates to a boiling type or condensing type internally processed heat exchanger tube that exchanges heat with a fluid outside the tube.

"Conventional technology" In recent years, there has been a strong demand for smaller and lighter heat exchangers for air conditioning equipment, etc., and with the spread of heat pump air conditioners, there is also a demand for smaller diameter and higher performance heat transfer tubes used in these devices. has been done.

In response to these requests, we have recently crossed over into the inner world! ! By machining a large number of linear grooves, an inner cross-grooved heat exchanger tube is provided in which numerous pyramid-shaped or truncated pyramid-shaped projections are formed on the inner surface.

[Problems to be Solved by the Invention] The above-mentioned internal cross-grooved heat exchanger tube has a method in which, after machining a first normal spiral groove in one direction, a second @linear groove is formed so as to intersect with the first normal spiral groove. Since the grooves are machined, there are two processing steps, which increases the manufacturing cost.

Furthermore, as disclosed in, for example, Japanese Patent Application Laid-Open No. 61-140321, a technique has been proposed for processing the heat exchanger tube in one step. When the load is large.

Thin-walled tubes are at risk of breaking during processing, and the processing speed must be extremely slow to prevent breakage, resulting in low productivity and high costs.

The purpose of the present invention is to have heat transfer performance comparable to that of conventional cross-grooved heat transfer tubes, and to have an inner surface processed in the process.
It is an object of the present invention to provide a heat exchanger tube that can be manufactured with much higher productivity than conventional cross-grooved heat exchanger tubes.

"Means for Solving the Problem" In order to achieve the above-mentioned purpose, one of the heat exchanger tubes according to the present invention is a heat exchanger tube in which a large number of grooves are formed on the inner surface in a linear or spiral shape along the longitudinal direction. , between each of the grooves, protrusions of a predetermined length are repeatedly formed along the yam direction and have sloped portions on the upper surface that are inclined in the same direction.

Another heat exchanger tube according to the present invention is a heat exchanger tube in which a large number of linear or spiral grooves are formed along the longitudinal direction on the inner surface, and between each of the grooves, a groove is formed on the upper surface along the yam direction. A protrusion of a predetermined length having an inclined part inclined in the same direction is repeatedly formed, and the bottom of each groove has an inclined part inclined in a direction opposite to the inclined part of the protrusion at each adjacent portion to the protrusion. It is formed repeatedly in the longitudinal direction. The groove described above can be formed so that the width of the groove gradually becomes narrower in the upward slope direction from the bottom thereof.

In each of the above inventions, it is preferable that the length of the protrusion formed is 0.20 to 3 mm.

Each heat exchanger tube as described above can be manufactured using a known manufacturing apparatus.

For example, a grooved plug held so as to rotate freely is inserted into the raw pipe, and a plurality of rotatable rolling rolls rotate planetarily around the grooved plug while moving the raw pipe in a fixed direction. By pressing the tip of the grooved plug from the outer periphery of the raw pipe, it can be easily manufactured in one step. In this manufacturing process, the process of forming grooves and protrusions having the above-mentioned shapes will be described in detail in the Examples.

"Function" As described above, the heat exchanger tube according to the present invention repeatedly forms protrusions of a predetermined length on the upper surface along the longitudinal direction between the grooves and having sloped portions that are synonymous in the same direction.

Or in addition to such a configuration, at the bottom of the groove.

The sloped surface that slopes in the opposite direction to the sloped part of the projection is repeatedly formed in the longitudinal direction at each adjacent portion of the projection, and this creates countless unevenness on the inner surface of the tube, so it is different from the conventional inner surface. Demonstrates heat transfer performance comparable to cross-grooved heat transfer tubes.

In addition, since the heat exchanger tube according to the present invention can be manufactured in one step using known manufacturing equipment as described above, it has better productivity and can be manufactured at a lower cost than conventional cross-grooved heat exchanger tubes. However, there is no risk of breakage during processing.

"Example" FIG. 1 is an enlarged perspective view of a part of a heat exchanger tube showing one example, and there are 60 spiral grooves 2 formed on the inner surface of the tube.
A heat exchanger tube 1 made of a steel tube in which the groove 2 has a helix angle of 018 degrees with respect to the tube axis is shown.

Between the grooves 2, there is a length fL3111 having an inclined part 31 inclined in a certain direction on the upper surface along the yam direction of the groove 2.
The protrusions 3 are formed repeatedly without interruption, and a stepped portion 32 is formed between the protrusions 3 and the adjacent protrusions 3. The height h of the highest part of each protrusion 3 (depth of groove 2) is 0.15+s■,
The outer diameter of the heat exchanger tube 1 is 9.53 mm.

The heat exchanger tube 1 of this embodiment exhibits the same heat transfer properties as the conventional heat exchanger tube with internal cross grooves by forming the countless protrusions 3 that repeat without interruption as described above.

Sample Ex-1 of the heat exchanger tube 1 having the structure of the above embodiment, and sample Ex-2 of the conventional heat exchanger tube with a DS edge line groove formed in one direction on the inner surface (outer diameter 9.53 mm, yt number 60.
fJO') with a helix angle of 18 degrees and a groove depth of 0.20 mm), and incorporated them into a double-tube heat exchanger. When measurements were carried out, the results shown in FIGS. 6 and 7 were obtained. According to the results, sample Ex-1, which is the heat exchanger tube of the above example, is superior to sample Ex-2 in terms of evaporative heat transfer coefficient by about 60% and condensation heat transfer coefficient by about 30%.

The heat exchanger tube 1 of the above embodiment can be easily manufactured using a known manufacturing apparatus as shown in FIG. 4, for example.

In the figure, while the raw tube a is moved at a constant speed to the right by an appropriate drawing machine (not shown), it is shrunk by the cooperation of a floating plug 5 and a diameter-reducing die 6 before being manufactured into a heat exchanger tube l. diameter.

A rod 41 is fixed to the tip end of the floating plug 5, and a grooved plug 4 having parallel spiral grooves 40 with a predetermined helix angle on the circumferential surface is attached to the tip of the rod 41. Around the grooved plug 4, rolling rolls 7 are provided that are rotatable at equal angular intervals of 120 degrees. Each rolling roll 7 is formed with a suitable taper 71 on the insertion side of the raw tube a.

While rotating this rolling roll 7 planetarily, the grooved plug 4
The diameter-reduced raw tube a is pressed against the tip of the plug 4 from the outer periphery, and while the diameter of the raw tube a is m,
A heat exchanger tube l having a large number of grooves 2 and protrusions 3 inside as described above is manufactured.

In this way, while the raw pipe a is passed between the grooved plug 4 and the plurality of rolling rolls 7 and moved at a constant speed, the raw pipe a is rolled into the grooved plug 4 from the outer periphery by the planetary rolling rolls 7. When the tip is compressed, there are parts of the raw pipe a that are compressed many times by the grooved plug by the rolling roll 7 and parts that are compressed only a few times, and the parts that are compressed more often are inside the grooves 40 of the plug 4. The part that is deeply sunk into the groove 40 and raised high, and is compressed less often, is less likely to sink into the groove 40, so the inclined part col as described above is
The protrusions 3 having the same shape are formed repeatedly and without interruption.

The protrusion 3 is formed in a shape having an MM portion 31 which is high on the distal end side in the moving direction of the blank tube a and gradually becomes lower toward the rear end side.

The contact locus of the rolling roll 7 against the heat exchanger pipework becomes a spiral with respect to the tube l, and thereby the protrusions 3 are formed in a spiral arrangement with the grooves 2 interposed between them. When cut at right angles to the tube axis, the protrusions 3 lined up in the inner circumferential direction of the heat exchanger tube 1 exhibit a state in which the protrusions 3 are gradually lowered from one side to the other as shown in FIG.

For the same reason, the predetermined length of the protrusion 3 and the inclined surface 3
The inclination angle of 1 can be appropriately set depending on the correlation between the number of revolutions of the rolling rolls 7 and the moving speed of the blank pipe a. When the pressing force and number of revolutions of the rolling rolls 7 are kept constant, increasing the moving speed of the raw tube a increases the length of the protrusion 3, the inclination angle of the tilting surface 31 becomes smaller, and the moving speed of the raw tube a increases. If you lower it, the opposite will happen.

In the example shown in FIG. 4, a floating plug 5 and a diameter reducing die 6 are used for diameter reduction, but these are unnecessary if diameter reduction of the blank pipe a is not required.

As described above, the heat exchanger tube 1 of the embodiment can be easily manufactured using conventional manufacturing equipment almost as is, and an infinite number of protrusions 3 can be manufactured in one step, resulting in high productivity and low manufacturing cost. . Further, even when a thin-walled raw pipe is used, it can be manufactured without causing breakage, and there is no need to extremely slow down the moving speed of the raw pipe a in order to prevent breakage.

FIG. 2 shows another embodiment, in which the outer diameter of the heat transfer 'fl, the number of grooves 2, the helix angle of the grooves 2, etc. are the same as in the example of FIG. 1, and the end of the protrusion 3 The height h (depth of groove 2) is 0.2
0 mm, the length of each protrusion 3 or 0.15 mm.

The protrusion 3 of this embodiment is formed in the same manner as in the embodiment of FIG. Adjacent inclined surfaces 21 are separated by steps 22 having the same height, and the convergence W of the groove 2 rises in the inclined surface 21. It is formed so that it gradually becomes narrower as it goes in the direction.

In the heat exchanger tube 1 having the structure shown in FIG. 2, in the manufacturing apparatus illustrated in FIG.
It can be manufactured by moving it slightly to the left of the illustrated position (slightly moving it to the left of the tip of the YT plug 4). The process of forming the protrusion 3 is the same as that explained in FIG. Since they are similar, the explanation will be omitted.

The heat transfer tube 1 shown in FIG. 2 has a structure in which the bottom of the groove 2 has a repeating slope 21 divided by steps 22, so that the heat transfer performance is improved compared to the heat transfer tube shown in FIG. 1.

FIG. 3 shows yet another embodiment, in which the protrusions 3 and grooves 2 are formed in almost the same manner as the heat exchanger tube shown in FIG. 2, but the width of the grooves 2 is formed narrower than in the example shown in FIG. ing. The function of the heat exchanger tube l in this example and its manufacturing method are substantially the same as those in the example shown in FIG. 2, so a description thereof will be omitted.

In each of the above embodiments, the groove 2 is formed in a spiral shape with respect to the axis of the pipe 1, but it is also possible to form the groove 2 in a straight line. The groove 40 may be formed in a straight line.

In each example, the length of the protrusion 3 is 0.20 to 3 m.
It is desirable to set it within a range of m. That is, 0.20
If the thickness is less than the thickness layer, manufacturing tends to be difficult, and if the thickness is 3 am or more, the slope of the slope portion 31 becomes too gentle, and there is a possibility that the heat transfer performance will not improve much.

"Effects of the Invention" The heat exchanger tube according to the present invention repeatedly forms protrusions of a predetermined length having sloped parts in the same direction on the upper surface along the longitudinal direction between the grooves, or in addition to such a structure. At the bottom of the groove, a sloped surface that slopes in the opposite direction to the slope of the projection is formed in the longitudinal direction at each adjacent part to the projection, and countless unevenness is formed on the inner surface. As a result, it exhibits heat transfer performance comparable to conventional heat transfer tubes with internal cross grooves.

In addition, as mentioned above, the heat exchanger tube of the present invention can be manufactured in one step using known manufacturing equipment without significantly reducing the moving speed of the raw tube, so it is more productive than the conventional cross-grooved heat exchanger tube. In addition to being cheaper to manufacture, there is no risk of breakage during processing even with thin pipes.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged exploded perspective view showing an example of a heat exchanger tube according to the present invention, FIG. 2 is a partially enlarged exploded perspective view showing another embodiment, and FIG. 3 is a partially enlarged exploded perspective view showing still another embodiment. Perspective view,
FIG. 4 is a schematic cross-sectional view showing an example of an apparatus for explaining the method for manufacturing a heat exchanger tube according to the present invention, FIG. 5 is a partially enlarged developed cross-sectional view taken along arrow A-A in FIG. 4, and FIG. 7 is a diagram comparing the evaporative heat transfer coefficient between a conventional heat exchanger tube with internal grooves and the heat exchanger tube of the embodiment shown in FIG. 1, and FIG. Comparison of condensation heat transfer coefficient with heat tube!
This is a diagram i1. Explanation of the symbols in the main drawings: 1 is a heat exchanger tube, 2 is a groove, 21 is an inclined surface, 22 is a stepped portion, 3 is a protrusion, 31 is an inclined portion, 32 is a stepped portion, 4 is a grooved plug, 4
0 is the groove, 41 is the rod, 7 is the rolling roll, a is the raw pipe, sho is the length of the protrusion 3, and W is the width of the groove 2. No. House Map No. S

Claims (4)

[Claims] (1) In a heat exchanger tube having a plurality of linear or spiral grooves formed on the inner surface along the longitudinal direction, between each of the grooves, there is an inclined part inclined in the same direction on the upper surface along the longitudinal direction. A heat exchanger tube characterized by repeatedly forming protrusions of a predetermined length. (2) In a heat exchanger tube in which a large number of grooves are formed in a linear or spiral shape along the longitudinal direction on the inner surface, between each of the grooves, there is an inclined part inclined in the same direction on the upper surface along the longitudinal direction. Protrusions of a predetermined length are repeatedly formed, and at the bottom of each groove,
A heat exchanger tube characterized in that an inclined surface inclined in a direction opposite to the inclined portion of the protrusion is repeatedly formed in the longitudinal direction at each portion adjacent to the protrusion. (3) The heat exchanger tube according to claim 2, wherein the groove is formed so that the width of the groove gradually becomes narrower in an upward slope direction. (4) The heat exchanger tube according to any one of claims 1 to 3, wherein the length of the protrusion is 0.20 to 3 mm.