JP3439644B2 - Manufacturing method of composite heat transfer tube - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a composite heat transfer tube used as a heat transfer tube for LNG, gas vaporizers and the like.

[0002]

2. Description of the Related Art Aluminum alloy heat transfer tubes used in LNG, gas vaporizers, etc. have fins on the outside of the outer tube to improve heat transfer, and the inner tube is twisted at a constant pitch to form an outer tube. It has a structure (for example, refer to FIG. 9 of Japanese Patent Laid-Open No. 7-35297) in which a core forming a spiral flow path is inserted. In this composite heat transfer tube, the outermost circumference of the core and the inner surface of the outer tube are required to be in close contact with each other. Therefore, conventionally, after inserting a twisted core into the outer pipe, a drawing die having a shape that follows the shape of the fins of the outer pipe is used, and the diameter of the outer pipe is reduced by drawing to reduce the diameter of the outer pipe to the inner surface. The outermost circumference of the child was in close contact.

A structure in which an inner tube is inserted inside an outer tube having fins on the outer side and the inner side, and a core twisted at a constant pitch is inserted therein (for example, Japanese Patent Laid-Open No. 8-2
A composite heat transfer tube (see FIG. 16 of Japanese Patent No. 9075) is also known. In the case of this composite heat transfer tube, the core can be manufactured by inserting the core into the inside of the inner tube and bringing them into close contact by a drawing process, and then inserting this into the inside of the outer tube and making a close contact by the drawing process.

[0004]

However, in the drawing method, the shape of the drawing die is complicated and not only expensive, but also the tips of the fins of the outer tube and the groove bottom are apt to seize, and the outer tube is Since the fins of the can interfere with the entire peripheral surface during the drawing process (the processing force applied to the fins does not directly affect the tightening of the pipe part of the outer pipe), the outermost periphery of the core and the inner surface of the outer pipe or There is a problem that the outer circumference of the inner tube and the inner surface of the outer tube cannot be brought into close contact with each other with good accuracy over the entire circumference. Therefore, the present invention does not require an expensive drawing die in the production of the composite heat transfer tube, and further aims to bring the outermost circumference of the core or the outer circumference of the inner tube and the inner surface of the outer tube into close contact with each other with good accuracy over the entire circumference. .

[0005]

The method of producing a composite heat transfer tube according to the present invention SUMMARY OF], insert the member defining a flow path for the fluid in the outer tube into the outer tube, the outer gripping the ends of the outer tube The pipe is stretched to reduce the diameter, and the inner surface of the outer pipe and the outer periphery of the member are
It is characterized in that the members are closely contacted over the entire length . In this case, it is preferable that the length of the member is shorter than that of the outer tube, and a gripping margin portion without the member is provided at both ends of the outer pipe, and the gripping margin is gripped by a chuck and pulled.
The member is, for example, a twisted core, or a twisted core assembled inside the inner tube.

The above-mentioned contacting method by tensioning can also be applied when assembling the twisted core inside the inner tube. In other words, insert the core inside the inner tube,
The grasped the inner tube tensile processed shrink the diameter, it is brought into close contact with the inner surface and outer circumference of the core of the inner tube over the entire length of the tang. In this case, it is preferable that the core is shorter than the inner tube, and the gripping portions having no core are provided at both ends of the inner tube, and the gripping portion is gripped by a chuck and pulled.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described more specifically with reference to the drawings. First, in the composite heat transfer tube shown in FIGS. 1 and 2, inside the outer tube 1 having fins formed outside,
The core 2 twisted at a constant pitch is assembled, and the outermost periphery of the core 2 is in close contact with the inner surface of the outer tube 1, and a spiral flow path is formed between the inner surface of the outer tube 1 and the core 2. 3 are configured.

In manufacturing this composite heat transfer tube, as shown in FIG.
As shown in FIG. 2, a twisted core 2 having an outermost periphery that can be inserted with a slight clearance between the outer tube 1 and the inner surface thereof is used. The core 2 has a length shorter than that of the outer tube 1. The outer tube 1 and the core 2 are manufactured by extruding an aluminum alloy, for example, and the core 2 is further twisted. As shown in FIG. 4, the core 2 is inserted into the outer tube 1 (a), the portions without the core 2 at both ends of the outer tube 1 are used as a grip margin A (b), and this is gripped by a chuck and pulled. When processed (c), the outer tube 1 extends in the length direction and at the same time the diameter is reduced, and the inner surface of the outer tube 1 becomes a core 2.
Evenly adheres to the outermost circumference and the entire circumference.

In the tensile processing of the present invention, the outer tube 1
If an aluminum alloy is used as the material for
Annealed material of soft material or medium-hard material showing elongation of 5% or more is preferable, and the tensile length is suitably 4 to 8% of the length excluding the grip margin A of the outer tube 1 (before tensile processing). Is. When the tensile length is less than 4%, it is difficult to bring them into close contact with each other (theoretically, it is possible to reduce the clearance between the outer tube 1 and the core 2, but it is not realistic because the insertion into the outer tube 1 becomes difficult. ), If it is more than 8%, the outer tube 1 is locally stretched, and it becomes difficult to make uniform adhesion over the entire circumference.

The composite heat transfer tube (before tensile processing) shown in FIG.
Fins for increasing heat transfer efficiency are formed on the inner surface of the outer tube 11. Similar to the composite heat transfer tube shown in FIG. 3 (before tension processing), the core 12 has an outermost circumference that can be inserted with a slight clearance between the core 12 and the inner surface of the outer tube 11, and is twisted. The manufacturing method is the same as that of the composite heat transfer tube shown in FIGS.

In the composite heat transfer tube shown in FIG. 6 (c), an inner tube 25 is assembled inside an outer tube 21 having fins formed on the inner surface, and a core 22 is twisted at a constant pitch inside the outer tube 21. The outer periphery of the inner tube 25 is in close contact with the inner surface of the outer tube 21, a flow path 24 is formed between the inner surface of the outer tube 21 and the inner tube 25, and the outermost periphery of the core 22 is the inner tube. 25
A spiral flow path 23 is formed between the inner surface of the inner tube 1 and the core 2 in close contact with the inner surface of the inner tube 1.

In manufacturing this composite heat transfer tube, the inner tube 25 and the core 22 are first assembled. As the assembling method, the same tensile processing as shown in FIG. 4 can be applied.
That is, a core 22 that has an outermost periphery that can be inserted with a slight clearance between the inner pipe 25 and its inner surface and that has been twisted is used, as shown in FIG.
2 is inserted into the inner tube 25 (the length of the core 22 is shorter than that of the inner tube 25), and a portion without the core 22 at both ends of the inner tube 25 is used as a gripping margin and is gripped by a chuck. Tensile processing. As a result, the inner tube 25 extends in the lengthwise direction and at the same time the diameter thereof is reduced, and the inner surface of the inner tube 25 is in close contact with the outermost circumference of the core 22 and the entire circumference thereof. If the inner pipe 25 is made of an aluminum alloy, the tensile margin may be 4 to 8%, as described above.

Subsequently, both ends of the assembly consisting of the inner tube 25 and the core 22 are cut off and inserted into the outer tube 21 as shown in FIG. 6 (b), and the same as shown in FIG. Is applied to bring the outer circumference of the inner tube 25 into close contact with the inner surface of the outer tube 21 (c).

[0014]

EFFECTS OF THE INVENTION According to the present invention, a complex heat transfer tube can be manufactured easily and inexpensively without the need for an expensive drawing die and without the steps of applying and removing drawing oil. The outer circumference or the outer circumference of the inner tube and the inner surface of the outer tube can be brought into close contact with each other with good accuracy over the entire circumference.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a composite heat transfer tube according to the present invention.

FIG. 2 is a partially cutaway perspective view thereof.

FIG. 3 is a cross-sectional view of the composite heat transfer tube before tensile processing.

FIG. 4 is a schematic diagram illustrating a manufacturing method of the present invention.

FIG. 5 is a cross-sectional view of another composite heat transfer tube before tensile processing.

FIG. 6 is a diagram illustrating another method of manufacturing a composite heat transfer tube.

[Explanation of symbols]

1, 11, 21 outer tube 2, 12, 22 Core 25 inner tube

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-8-215737 (JP, A) JP-A-6-285569 (JP, A) JP-A-1-317636 (JP, A) JP-A-2- 157597 (JP, A) JP-A-8-326624 (JP, A) JP-A-9-324993 (JP, A) Actual development 2-100075 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B21D 53/06 B21D 39/00 F28F 1/40

Claims (6)

(57) [Claims] [Claim 1] Insert the member defining a fluid flow path in the short outer tube than in the interior of the outer tube, the ends of the outer tube
There is a grip allowance part without the above-mentioned member inside, and the grip
A method for manufacturing a composite heat transfer tube, characterized in that the margin is held by a chuck, the outer tube is subjected to a tensile process to reduce the diameter, and the inner surface of the outer tube and the outer periphery of the member are brought into close contact with each other over the entire length of the member. 2. The method for manufacturing a composite heat transfer tube according to claim 1 , wherein the member is a core that is twisted. 3. The contract , wherein the member is an inner pipe and a twisted core assembled inside the inner pipe.
A method for manufacturing a composite heat transfer tube as set forth in claim 1 . 4. The method for producing a composite heat transfer tube according to claim 1 , wherein the outer tube is subjected to tensile processing in the lengthwise direction by 4 to 8%. 5. When a twisted core is assembled inside the inner tube to manufacture a member that defines a fluid flow path inside the outer tube of the composite heat transfer tube, a shorter length than that is formed inside the inner tube. br /> Insert the twisted core into the inner tube at both ends
Provide a gripping allowance that does not have children, and check the gripping allowance.
A method for manufacturing the above-mentioned member, characterized in that the inner tube is gripped with a plug and the inner tube is subjected to a tensile process to reduce the diameter, and the inner surface of the inner tube and the outer periphery of the core are brought into close contact with each other over the entire length of the core. 6. The method for producing the member according to claim 5 , wherein the inner tube is subjected to a tensile working for a length of 4 to 8%.