JPH0970612A - Manufacture of heat transfer tube with double groove - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method to manufacture a heat transfer tube with a double groove suitable for promoting boiling of non-azeotropic refrigerant at high speed by holding balls in a first row and a second row by flanges arranged on the outer side of the balls in the first row and the second row, and a ball holder to specify the space between balls to firmly hold each ball. SOLUTION: In a method in which two plugs 21, 22 provided with grooves on their outer periphery are arranged in a metallic tube 20, balls 31, 32 in the first row and the second row are pressed against the outer side of the metallic tube 20 at the position where the plugs 21, 22 are arranged wile planetarily rotating the balls to form a double groove on the inner surface of the metallic tube 20, the balls 31, 32 in the first row and the second row are held by flanges 54, 55 arranged on the outer side of the balls 31, 32 in the first row and the second row and ball holders 51, 52 to specify the space between the balls 31, 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for drawing a double grooved heat transfer tube used for a heat exchanger such as a refrigerator or an air conditioner at a high speed.

[0002]

2. Description of the Related Art Heat transfer tubes used in heat exchangers for air conditioners such as refrigerators and room air conditioners have a refrigerant such as Freon gas (Freon is a DuPont trade name for fluorochloro substitution products of hydrocarbons). Is flowed to evaporate or condense the refrigerant to exchange heat with the fluid flowing outside the pipe. As the heat transfer tube, as shown in FIG. 6, an inner grooved heat transfer tube having a large number of fine grooves 27 formed on the inner surface to improve heat transfer characteristics is often used. By the way, Freon R22 and R12 have been conventionally used as refrigerants, but since these destroy the ozone layer, a plan to completely abolish them is being promoted from the viewpoint of environmental protection. Alternatives to Freon R22 and R12 include Freon R32, R134a and R12 that do not affect the ozone layer.
5 etc. are listed. Especially when these refrigerants are mixed [R
32 / R134a / R125] and [R32 / R125] mixed refrigerant,
It has a cooling capacity close to that of the conventional Freon R22 and is nonflammable, so it is highly evaluated as a substitute.

The above-mentioned mixed refrigerant includes an azeotropic refrigerant and a non-azeotropic refrigerant, and the above-mentioned [R32 / R134a / R125] and [R32 /
R125] and other mixed refrigerants are non-azeotropic refrigerants. The azeotropic refrigerant is
Since the liquefaction start temperature (dew point) and the liquefaction end temperature (boiling point) are the same and behaves the same as a single refrigerant, there is no particular problem,
Since the non-azeotropic refrigerant has different liquefaction start temperature and liquefaction end temperature, when the refrigerant evaporates or condenses, the high boiling point component is concentrated on the liquid phase side and the low boiling point component is concentrated on the gas phase side. This difference in concentration causes diffusion resistance and heat resistance, and reduces the heat transfer coefficient in evaporation or condensation. Therefore, as shown in FIG. 7, the boiling heat transfer tube using the non-azeotropic refrigerant has double grooves.
A double grooved heat transfer tube has been developed in which 25 and 26 are formed (cavity structure) and the turbulent effect of the refrigerant is activated to promote boiling (JP-A-1-317637).

By the way, since the double-groove heat transfer tube has double grooves, the frictional resistance and plastic deformation resistance during drawing are doubled as compared with the case of a single groove (FIG. 6). Therefore, there is a problem that the drawing process cannot be performed at a high speed. As a countermeasure against this, there is a method of reducing the resistance applied to the tube by changing the pressure member from a roll to a ball by changing the angle of the spiral projections provided in the two grooved plugs in the same direction with respect to the axis and different angles. Kaisho 57-36016) was applied. In this method, as shown in FIG. 8, the metal tube 10 is reduced in diameter by a die 11 and a floating plug 12, and then, in the diameter-reduced metal tube 20, two plugs each having a spiral groove engraved on the outer periphery are engraved. 21,22
Is arranged, and the balls 31 and 32 are pressed from the outside while rotating the planets and pulled out, and finally the heat transfer tube with double groove 28 is processed through the finishing die 59. The method of gripping the balls 31 and 32 in the above method is as shown in FIG.
The conical surfaces of the members 71 to 73 having conical surfaces are pressed against the balls 31 and 32 whose intervals are defined by 70 from the outside.

[0005]

However, in the above-described method for manufacturing the double-groove heat transfer tube, the metal tube 20 is hardened by the first groove processing, and the mark of the ball 31 remains on the surface. Therefore, in the second grooving, the balls 32 roll irregularly on the surface of the metal tube 20 and ramp up, and this rampage cannot be suppressed only by the conical surfaces of the members 71 to 73, and thus the inner surface formed. The shape of the groove became non-uniform and the heat transfer characteristics deteriorated. Furthermore, when attempting to perform high-speed withdrawal by speeding up the planetary rotation (revolution) of the ball, the centrifugal force acting on the ball becomes large and the rampage of the ball becomes even more severe. There was a problem of doing. It is an object of the present invention to provide a method for manufacturing a double grooved heat transfer tube which can be drawn at a high speed.

[0006]

DISCLOSURE OF THE INVENTION According to the present invention, two grooved plugs having a large number of grooves on the outer peripheral surface are held in a metal pipe drawn in a predetermined direction so as to be rotatable in the drawing direction in order. Then, the balls in the first row and the balls in the second row are arranged on the outer peripheral surfaces of the two places of the metal tube holding the plug, respectively.
A method of pressing the balls of the first and second rows against the outer peripheral surface of the metal tube while rotating the planets to form double grooves on the inner surface of the metal tube, wherein the balls of the first and second rows are Is held by flanges arranged outside the balls in the first and second rows and a ball retainer that defines the distance between the balls, respectively. is there.

In the present invention, the balls in the first row and the balls in the second row are
The balls are gripped by the flanges arranged outside the balls in the first row and the balls in the second row, respectively, and the ball retainers that define the intervals between the balls.
Therefore, it is possible to form the double groove having a different direction with respect to the tube axis at a high speed. Further, in the present invention, since the force applied in the pulling direction of the balls in the first row and the balls in the second row is received by the single ball retainer, the machining head can be made smaller and lighter, and the drive motor for rotating the machining head can be obtained. Power consumption can be reduced.

In the present invention, the angle 62 of the holes 62 of the balls in the second row formed in the ball cage is set to 40 to 90 degrees.
By thickening the inner surface or the end of the surface of the wall portion, it is possible to reliably prevent the damage. Further, by setting the clearance C between the ball 32 and the hole 62 to be 0.50 mm or less, it is possible to more surely prevent the ball 32 from being rough (see FIG. 2).

In order to firmly press the ball against the ball retainer to prevent the ball from moving roughly, the pulling force applied to each ball during the groove processing is made sufficiently larger than the centrifugal force applied to each ball in the radial direction. There is a need. When a double grooved heat transfer tube with an outer diameter of 10 to 6 mm, which is normally used in air conditioners, is manufactured at high speed according to the present invention, the total number of balls in the first and second rows is 4 to 6, and the ball diameter is 6 to 15 mm, grooved plug outer diameter 5 to 12 mm, groove depth 0.1 to 0.3 mm
Is appropriate.

In the present invention, when the total number of balls in the first row and the second row is less than 4, the shaft of the metal tube swings during the drawing process, which makes groove processing difficult. On the other hand, the balls are gripped by the ball cage by the pulling force, and if the number of balls is too large, the pulling stress applied to each ball becomes small,
When the centrifugal force becomes higher than this, the ball begins to rampage. Therefore, the total number of balls in the first and second rows is preferably 4 to 6. It is effective to increase the number of balls distributed in the first and second rows to the larger groove machining force. Grooving force depends on the depth and number of grooves. If the total number of balls is four, there are two ways, one is for each two and one is for three, but the latter is more reliable with three balls having a metal tube axis. There is an advantage that it is held and it is difficult for shaft deviation to occur during the drawing process.

[0011]

The present invention will be described below in detail with reference to examples. (Embodiment 1) FIG. 1A is an explanatory view showing an embodiment of a method for manufacturing a double grooved heat transfer tube of the present invention. The copper tube 10 having an outer diameter of 13 mm is reduced in diameter by the die 11 and the floating plug 12, and then the first and second two outer peripheral grooved plugs (hereinafter referred to as plugs) are provided inside the reduced diameter copper tube 20. 21 and 22 are arranged, and the balls 31 in the first row and the balls 32 in the second row that rotate in a planetary state are pressed from the outside to form a double groove on the inner surface of the copper pipe and finally finish die. Finished to a specified outer diameter through (not shown). The first and second two plugs 21,22
Was supported integrally with the mandrel 13 at the tip of the floating plug 12. First and second row balls 31,32
Are loosely fitted in the holes of the ball holders 51 and 52, respectively. The ball holder 52 is rotatably attached to the processing head 53 via a bearing 54. The processing head 53
Two first and second cylindrical flanges 54 and 55 are attached to the ends of the cylindrical flanges 54 and 55, and the balls 31 and 32 of the first and second rows are in contact with the inner surfaces of the cylindrical flanges 54 and 55, respectively. , Its radial movement is suppressed. Balls 1 and 2
The movement of 1,32 in the pull-out direction is suppressed by the ball retainer 52.

Here, the inner peripheral surfaces of the cylindrical flanges 54, 55 are slightly reduced in diameter in the pulling-out direction.
Is moved in the axial direction to finely adjust the distance between the flanges 54, 55 and the copper tube 20 and adjust the pressing force of the balls 31, 32 on the copper tube 20. To move the flanges 54 and 55 in the axial direction, the thickness of the liners 56 and 57 is changed. FIG. 1B is a view on arrow AA. The two balls 32 in the second row are the second
The copper tube that fits into the hole 62 formed in the ball cage 52 of
They are arranged opposite to each other with 20 in between. Since the ball portion in the first row has the same structure as the ball portion in the second row, the description thereof will be omitted.

Here, when the processing head 53 is rotated, the balls 31 and 32 are rotated around the copper tube 20 as a planet. When the copper pipe 20 is pulled out in this state, the balls 31 in the first row form a first groove, and then the balls 32 in the second row form a second groove.

A double grooved heat transfer tube having an outer diameter of 9.53 mm was manufactured by the method shown in FIG. The first plug has an outer diameter of 9.8 m
m, the number of grooves was 70, the twist angle was 25 degrees (the twist direction was left), and the groove depth was 0.10 mm. The second plug has an outer diameter of 9.5
mm, the number of grooves was 50, the twist angle was 10 degrees (the twist direction was right), and the groove depth was 0.20 mm. The ball has an outer diameter of 14.0 mm
The clearance C between the ball in the second row and the hole of the second cage during groove processing was 0.1 mm, and the hole angle θ was 60 degrees (see FIG. 2). The number of balls in the first and second rows was changed variously.

The shape of the inner surface grooves of the manufactured heat transfer tube is such that the directions of the grooves 25 and 26 are different from the tube axis, as shown in FIG. Fin 24 and groove 25 with a height of 0.20 mm in the first groove processing
Then, the fins 24 were intermittently crushed by the second groove processing to form the grooves 26. The force required for grooving was larger in the first grooving than in the second grooving.

(Embodiment 2) FIG. 3 is an explanatory view of a ball holding method showing a second embodiment of the present invention. In this method, the balls 31 in the first row and the balls 32 in the second row are held by one ball holder 58, and the movement of the balls 31, 32 in the pulling direction is suppressed by the ball holder 58. . Others are the same as those in FIG.

A ball was gripped by the method shown in FIG. 3 to produce a double grooved heat transfer tube having an outer diameter of 6.5 mmφ. A copper tube having an outer diameter of 10 mm was used. The first plug has
The outer diameter is 7.6 mm, the number of grooves is 50, the twist angle is 20 degrees (the twist direction is right), the groove depth is 0.20 mm, and the second plug is
The outer diameter was 7.2 mm, the number of grooves was 20, the twist angle was 20 degrees (the twist direction was left), and the groove depth was 0.30 mm. The ball diameter was 7.0 mm in the first row and 6.5 mm in the second row.

(Comparative Example 1) A ball is gripped by the conventional method shown in FIG.
A double grooved heat transfer tube was manufactured.

The inner groove shape and appearance of the double grooved heat transfer tube manufactured by each of the above-mentioned methods were investigated. The results are shown in Table 1.

[0020]

[Table 1] *: Good, Fair, Poor

As is clear from Table 1, the products of the present invention (N
All of o.1 to 5) had good inner groove shape and appearance. Regarding the number of balls arranged in the first and second rows, 4-2 (No. 1) in which more balls are arranged in the first row, which has a large groove processing force, is
2-4 (No. 2) could be pulled out more stably. The same production was carried out with the total number of balls being 7 (4-3), but the drawing stress applied to each ball was lowered, and the appearance and the drawing stability were slightly lowered. On the other hand, in the conventional product, when the revolution speed is 20,000 rpm and the drawing speed is as low as 40 m / min. (No. 6)
However, when the inner groove shape and appearance became a little poor, and the ball revolution speed and drawing speed were increased to 30,000 rpm and 50 m / min. Respectively (No. 7), the rampage of the ball in the second row became severe. The internal groove shape and appearance were both poor. Furthermore, when the number of balls was reduced (No. 8), the metal tube broke. still,
In the present invention, since the force applied in the pull-out direction of the balls in the first row and the balls in the second row is received by the single ball retainer, the machining head becomes smaller and lighter, and the power consumption of the machining head rotating motor is reduced. It was saved.

Example 3 In Example 1, a double grooved heat transfer tube was manufactured by changing the shape of the hole of the ball cage variously. Table 2 shows the results.

[0023]

[Table 2]

As is clear from Table 2, the ball cage has a hole angle of 40 to 90 degrees and a clearance of 0.1 to 0.5 mm.
In Nos. 10 to 13 and 15, the end of the hole wall was not damaged, and the ball rotated well. However, in Nos. 9 and 14, the hole angle θ was too small or too large, and the hole wall inner surface side or surface side edge was thinned and partly damaged. Was slightly hindered, and No. 17 had too much clearance and the ball ran a little. However, there was no particular problem in practical use in the quality of the obtained heat transfer tube.

Non-azeotropic refrigerant [R32 / R134a / R125] was placed in the No. 1 double grooved heat transfer tube manufactured by the method of the present invention, and the evaporation heat transfer coefficient in the tube was measured. As a result, as shown in FIG. 5, the heat transfer characteristics were higher than those of the conventional single-grooved inner grooved tube with R-22.

[0026]

As described above, according to the present invention, a double grooved heat transfer tube suitable for promoting boiling of a non-azeotropic refrigerant can be manufactured at a high speed, and a remarkable effect is industrially achieved.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a first embodiment of a method for manufacturing a double grooved heat transfer tube of the present invention.

FIG. 2 is an explanatory diagram of a contact portion between a ball and a hole of a ball cage.

FIG. 3 is an explanatory view of a ball holding method showing a second embodiment of the method for manufacturing the double grooved heat transfer tube of the present invention.

FIG. 4 is a perspective view of an inner surface groove in which the direction of the groove of the double grooved heat transfer tube is different from the tube axis.

FIG. 5 is a relationship diagram between the in-tube evaporation heat transfer coefficient and the refrigerant flow velocity of the double grooved heat transfer tube manufactured by the method of the present invention.

FIG. 6 is a perspective view of inner surface grooves of the heat transfer tube with a single groove.

FIG. 7 is a perspective view of a double grooved heat transfer tube.

FIG. 8 is an explanatory view of a conventional method for manufacturing a double-grooved heat transfer tube.

FIG. 9 is an explanatory diagram of a ball portion of a conventional method for manufacturing a double-grooved heat transfer tube.

[Explanation of symbols]

 10 ………… Metal tube 11 ………… Die 12 ………… Floating plug 13 ………… Mandrel 20 ………… Reduced diameter metal tube 21,22 …… Peripheral grooved plug 24 ………… … Fin 25,26,27… Groove 28 ………… Double grooved heat transfer tube 31 ………… First row ball 32 ………… Second row ball 51,52,58… Ball cage 53 ………… Machining head 54,55 …… Flange 56,57 …… Liner 59 ………… Finishing dies 61,62 …… Hole drilled in the ball cage 70 ………… Spacer 71,72,73… A member having a conical surface

Claims (3)

[Claims] 1. A metal pipe that is pulled out in a predetermined direction,
Two grooved plugs provided with a large number of grooves on the outer peripheral surface thereof were rotatably held in order in the drawing direction, and two rows of outer peripheral surfaces were held on the outer peripheral surfaces of the metal pipes holding the plugs, respectively. Two
Arrange the balls in the first row and the balls in the first and second rows,
Press the outer peripheral surface of the metal tube while rotating the planet,
In the method of forming a double groove on the inner surface of the metal tube, a flange in which the balls in the first row and the second row are respectively arranged outside the balls in the first row and the second row, and an interval between the balls A method for manufacturing a double-grooved heat transfer tube, characterized in that it is gripped by a ball retainer that defines the above. 2. Two ball cages are used, the first ball cage defines the spacing between the balls in the first row, and the second ball cage defines the spacing between the balls in the second row. The method for manufacturing a double-grooved heat transfer tube according to claim 1, wherein the balls of the first row and the balls of the second row are gripped while being regulated. 3. The total number of balls in the first and second rows is 4 to 4.
The method for manufacturing a double-grooved heat transfer tube according to claim 1 or 2, wherein the number is six.