JP2628712B2 - Method of forming heat transfer surface - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming a heat transfer surface, and particularly to a method for improving the performance of a heat transfer tube used in a heat exchanger for an air conditioner or a refrigerator. It is.

[Prior art] Generally, a heat transfer tube used in a heat exchanger of an air conditioner or a refrigerator is a device in which a refrigerant liquid such as freon flows through the tube to perform heat exchange. In view of the above, the use of inner grooved tubes is increasing.

This heat transfer tube is on the inner surface of the tube. A triangular or trapezoidal groove with a fine cross section is formed continuously in a straight or helical shape with respect to the tube axis direction. The heat transfer performance is greatly improved due to effects such as action. Moreover, when such a heat transfer tube is expanded and assembled in a heat exchanger, the raised portion on the inner surface of the tube is not significantly collapsed, so that the heat transfer performance is not deteriorated.

By the way, as a method of forming such a groove in the heat transfer tube, a grooved plug held at a predetermined position in the tube and a rolling process of contracting the tube while revolving outside the tube at a position opposite to the plug. 2. Description of the Related Art There is known a method of continuously forming by forming with a roller or a ball.

[Problems to be solved by the invention]

In recent years, there has been a strong demand for higher performance, smaller size and lighter weight of heat exchangers. In particular, the spread of heat pump type air conditioners for air conditioners has been accompanied by the demand for even higher performance as heat transfer tubes. However, in the case of conventional inner grooved tubes, the number of grooves,
Only the improvement of the lead angle and the groove shape was added, and the improvement of the performance was naturally limited.

On the other hand, in order to meet these demands, a so-called inner cross-grooved tube in which spiral grooves cross each other has been developed in place of the conventional inner-grooved tube, and the performance as a heat transfer tube has been improved. For example, as shown in FIGS. 11 (a) and (b), the inner cross-grooved tube has various shapes of raised portions (3) formed by grooves (1) and (5) crossing each other on the inner surface of the heat transfer tube (4).
2) is formed.

The method of manufacturing such an inner cross grooved pipe is such that a first groove (5) is formed in the pipe with a tool such as a grooved plug, and then the first groove (5) is formed.
The second groove (1) and the raised portion (32) are formed by pressing a tool so as to cross the groove (5).

However, since the shape of the raised portion of the heat transfer tube is mainly a quadrangular pyramid or a saw blade, the raised portion is crushed when the heat transfer tube is incorporated into the heat exchanger with a pipe expansion plug or the like, and the performance is reduced by the conventional inner surface groove. There was a problem that the difference from the tube was almost eliminated.

[Means for solving the problem]

In view of this, as a result of various investigations, the present invention has a heat transfer surface with excellent heat transfer performance that can reduce the collapse of the bulge as much as a conventional inner grooved tube when incorporated into a heat exchanger by expanding the tube. This is a development method.

That is, the present invention provides a method for forming parallel first grooves on a heat transfer surface and then forming parallel second grooves intersecting the first grooves at a predetermined angle. After forming the first groove, the first protrusion provided between the first grooves is crushed and deformed when forming the second groove, and the second protrusion between the second grooves or the second protrusion between the second grooves is formed. It is characterized in that a number of cuts intersecting with these are formed in a slit shape in the portion and the second groove.

(Operation)

The method of the present invention will be described with reference to the drawings. As shown in FIG. 3 (a perspective view showing a state in which the inner surface of the heat transfer tube is flattened), a number of parallel first grooves (5) are formed in the inner surface of the heat transfer tube (4). To form a number of parallel first ridges (6) between these grooves. Next, a second groove which intersects the first groove (5) at a predetermined angle is formed so as to overlap the formation surface of the first groove (5) and the first raised portion (6). Therefore, when forming the second groove, the first groove (5) or the first groove (5) and the first raised portion (6) are squashed so as to crush the second groove (1) as shown in FIG. A notch (3) intersecting the second raised portion (2) between
Or a notch (3) intersecting the second groove (1) and the second ridge (2) as shown in FIG.

This notch, when used as a heat exchanger, greatly enhances nucleate boiling during evaporation as compared with a conventional heat transfer tube with an inner groove, and the slope formed in the second raised portion and the second groove due to the notch is An acute angle contributes to the improvement of the condensation performance.

And there is no square pyramid or saw-toothed sharp ridge on the inner surface of the pipe, so when the heat exchanger is assembled, the ridge will be greatly collapsed and performance will be reduced even if expanded processing is performed. There is no.

〔Example〕

 Next, examples of the present invention will be described.

Embodiment (1) As shown in FIG. 4, a copper tube (7) is used as a raw tube, and the copper tube (7) is reduced in diameter by a diameter reducing die (8) and a floating plug (9). At this time, the floating plug (9)
The connecting rod (10) provided with two plugs (11) and (12) having grooves formed at predetermined positions in the pipe opposite to each other at predetermined positions from the floating plug (9). At the position facing the plugs (11) and (12), three rolling rollers (13) and (14) for revolving from the outer surface of the pipe and reducing the diameter of the copper pipe (7) are provided. ) Was reduced in diameter to form a number of spiral grooves on the inner surface of the tube and raised portions between the grooves, and cuts were formed in the raised portions to intersect with the raised portions.

That is, the first grooved plug (11) and the first rolling roller (13)
As a result, as shown in FIG. 5, a fine first groove (5) with 90 grooves, a lead angle (left-handed twist) of 18 ° and a groove depth of 0.10 mm is formed on the heat transfer surface.
Are provided in parallel, and a first raised portion (6) is formed therebetween. Next, as shown in FIG. 6, a second groove having a number of grooves of 60, a lead angle of 18 ° and a groove depth of 0.20 mm is formed by a second grooved plug (12) and a second rolling roller (14). (1) and the second
The notch (3) crossing the second ridge (2) was formed by forming the second ridge (2) between the groove and the groove (1). At this time, if the second protrusion (2) is formed mainly between the second groove (1) and the second groove (1) by crushing the first protrusion (6), the second groove ( A cut (3) can be formed in the second raised portion (2) formed by 1) in such a manner that the first raised portion (6) is crushed.

Example (2) As shown in FIG. 7, one side of a copper strip (15) is formed on a heat transfer surface, and then formed into a tubular shape by forming roll groups (16) to (23). ) To produce a heat transfer tube (4) by high frequency induction welding. At this time, before the copper strip is formed into a tubular shape, the copper strip (15) is squeezed by a first grooved roller (25) having a spiral groove and a flat roller (27) as shown in FIG. A first groove (5) and a first raised portion (6) are formed obliquely in the longitudinal direction with a sectional waveform as shown in FIG. Next, the first groove (5) and the first raised portion (6) are formed by the second grooved roller (26) having a spiral groove in the opposite direction to the first grooved roller (25) and the flat roller (27). As a result of forming the second groove and the second raised portion mainly by crushing, the second groove (1) and the second raised portion (2) having the cut (3) as shown in FIG. 2 were formed. A heat transfer surface was prepared. (28) and (29) indicate squeeze rolls.

When the second groove is formed after the formation of the first groove, only the second raised portion or the second raised portion is formed as shown in FIGS. 1 and 2 depending on the size of the first groove and the first raised portion being crushed. Since cuts can be formed in the raised portions and the second grooves, the degree of crushing of the first grooves and the first raised portions may be appropriately selected as necessary.

Embodiment (3) As shown in FIG. 9, as a first groove (5), a groove pitch of 0.45 mm, an angle of the groove with respect to the tube axis of 25 °, a groove length of 3 mm, and a discontinuous portion are formed on the inner surface of the pipe (30). After providing a number of grooves having a width of 4 mm, a second groove (1) and a second raised portion as shown in FIG. 10 when a second groove having 60 grooves, a lead angle of 18 ° and a groove depth of 0.15 mm are provided. Heat transfer having a discontinuous cut (3) in the second groove (1) and the second ridge (2) by crushing the discontinuous first groove (5 ') so as to mainly form (2). A surface could be formed. (31) indicates a smooth inner surface where no groove is formed.

In any of the above embodiments, the first groove and the second groove are not particularly limited in the depth of the groove, and may be grooves having the same depth.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, the groove | channel or ridge which has a notch which is a high-performance heat transfer surface can be easily formed in the surface of a metal strip | irrespective of the inner surface or outer surface of a pipe, and such a transfer is possible. Even when the heat pipe is attached to the heat exchanger, the raised portions are not crushed, so that there is an industrially remarkable effect such as no performance deterioration.

[Brief description of the drawings]

1 and 2 are perspective views showing an example of a heat transfer surface formed by the method of the present invention, and FIGS. 3 and 8 show examples of a heat transfer surface after the formation of the first groove by the method of the present invention. FIG. 4 is a side sectional view showing an embodiment of the present invention. FIG. 5 is a sectional view showing a heat transfer tube after forming a first groove in the embodiment of the present invention.
FIG. 7 is a cross-sectional view showing a heat transfer tube after forming a second groove in one embodiment of the present invention, FIG. 7 is a configuration diagram showing another embodiment of the present invention, and FIG. 9 is still another embodiment of the present invention. FIG. 10 is a perspective view showing an example, FIG. 10 is a perspective view of a heat transfer surface having discontinuous cuts according to the method of the present invention, and FIGS. 11 (a) and (b) are perspective views showing a conventional example. DESCRIPTION OF SYMBOLS 1 ... 2nd groove 2 ... 2nd raised part 3 ... cut 4 ... Heat transfer tube 5, 5 '... 1st groove 6 ... 1st raised part 7 ... Copper pipe 8 ... Reduced diameter die 9 … Floating plug 10… Connecting rod 11… Plug with first groove 12… Plug with second groove 13… First rolling roller 14… Second rolling roller 15… Copper strip 16-23 ... Forming roll 24 ... Induction coil 25 ... First grooved roller 26 ... Second grooved roller 27 ... Flat roller 28,29 ... Squeeze roll 30 ... Tube 31 ... Smooth inner surface 32 ... Protrusion

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-237295 (JP, A) JP-A-61-175485 (JP, A) JP-A-62-182595 (JP, A) 27754 (JP, A)

Claims (1)

(57) [Claims] In a method of forming first grooves parallel to each other on a heat transfer surface and then forming second grooves parallel to each other at a predetermined angle, the first grooves may be continuous or non-continuous. After the continuous formation, the first protrusion provided between the first grooves is crushed and deformed when forming the second groove, and the second protrusion between the second grooves or the second protrusion between the second grooves is deformed. A method for forming a heat transfer surface, wherein a number of cuts intersecting with the raised portion and the second groove are formed in a slit shape.