JPH02198728A - Fitting method for internal face groove heat transfer tube to plate fin - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method for attaching an internally grooved heat exchanger tube to a plate fin, and particularly relates to a method for attaching a finned heat exchanger tube with excellent heat transfer performance. It is something.

(Background technology) Spiral grooves are formed at a predetermined pitch on the inner surface of the tube as a heat transfer tube installed in a heat exchanger such as a condenser or evaporator to promote solidification and evaporation of the refrigerant flowing through the tube. A heat exchanger tube with an internally grooved structure has been known for some time. In recent years, due to its excellent heat transfer performance, spiral protrusions with a roughly triangular cross section are formed on the inner surface at a predetermined pitch, resulting in a spiral with a smooth bottom surface of a predetermined width. Heat exchanger tubes with internal grooves having a structure in which grooves are formed on the internal surface at a predetermined pitch are often used.

By the way, when an internally grooved heat exchanger tube having such a structure is used in an air-to-air heat exchanger, a plurality of plate fins are usually attached to the outer surface of the internally grooved heat exchanger tube. To attach plate fins to grooved heat exchanger tubes,
In many cases, this is carried out by inserting a tube expansion plug into the internally grooved heat exchanger tube and expanding the diameter of the internally grooved heat exchanger tube with the tube expansion plug.

However, in the past, as a tube expansion plug for expanding the diameter of such an internally grooved heat exchanger tube, a tube expansion plug whose plug head had a smooth outer circumferential surface was used. As shown in FIG. 8, the tip portion (top portion) of the protrusion 2 formed on the inner surface of the heat exchanger tube
There was a problem in that the heat transfer tubes were crushed almost evenly, and the heat transfer performance of the heat transfer tubes after expansion was significantly lower than before expansion.

As shown in FIG. 8, when the tips of the protrusions 2 on the inner surface of the heat exchanger tube are crushed approximately evenly, the protrusions 2 are crushed as shown by the two-dot chain line in the same figure. It is inevitable that the heat transfer performance will be significantly lower than when the tip is not crushed.

On the other hand, in a grooved heat exchanger tube, the opening of the spiral groove located between adjacent protrusions is made as narrow as possible, and the space inside the spiral groove is formed into a so-called re-end land cavity shape. In particular, it is known that the heat transfer performance of the heat transfer tube can be substantially improved by the reentrant cavity effect obtained based on the spatial shape within the spiral groove.

However, the reality is that a mass-production method for forming a reentrant cavity shape inside a heat transfer tube has not yet been established.

(Problem to be solved) The present invention has been made against the background of the above-mentioned circumstances, and the problem to be solved is that the spiral protrusions having a substantially triangular cross section are arranged at a predetermined pitch as described above. By expanding the diameter of an internally grooved heat exchanger tube, which has a structure in which spiral grooves with a smooth bottom surface of a predetermined width and a predetermined pitch are formed on the inner surface by forming grooves on the inner surface with excellent heat transfer performance. , when attaching plate fins to the outer surface of the tube,
Through the diameter expansion operation, a reentrant groove shape is formed on the inner surface of the heat transfer tube that can substantially improve heat transfer performance, and the heat transfer performance of the internally grooved heat transfer tube after expansion is improved compared to the conventional method.
The object of the present invention is to establish a method for improving the heat transfer performance of a finned heat exchanger tube having a structure in which plate fins are attached to the outer surface of the inner grooved heat exchanger tube.

(Solution Means) In order to solve this problem, in the present invention, spiral protrusions having a substantially triangular cross section as described above are formed on the inner surface at a predetermined pitch, so that the bottom surface is A tube expansion plug is inserted into an internally grooved heat transfer tube having a structure in which spiral grooves with a smooth surface of a predetermined width are formed on the internal surface at a predetermined pitch, and the tube expansion plug is used to expand the diameter of the internally grooved heat transfer tube. By doing so, when attaching a plurality of plate fins to the outer surface of the internally grooved heat exchanger tube, the expansion plug is constructed such that the plug head is rotatably supported at the tip of the insertion rod, and As a plug head of the tube expansion plug, the top width is narrower than the bottom width of the spiral groove of the internally grooved heat exchanger tube, and both side surfaces are sloped surfaces gentler than those of the spiral groove of the internally grooved heat exchanger tube. The protrusions of the above-mentioned structure have a helical shape corresponding to the helical groove of the internally grooved heat exchanger tube on the outer circumferential surface, and two of the helical grooves
The diameter of the virtual circle touching the top of the protrusion is the same as that of the inner grooved heat exchanger tube at the smallest diameter part on the tip side. A state in which the diameter of the imaginary circle in contact with the bottom surface of the helical groove of the internally grooved heat exchanger tube is smaller than the diameter of the imaginary circle in contact with the bottom surface of the helical groove of the heat exchanger tube, while the diameter of the imaginary circle in contact with the bottom surface of the helical groove of the internally grooved heat exchanger tube is larger by a predetermined dimension at the maximum diameter portion of the base end example. The depth of the spiral groove formed between the protrusions of the plug head is set to be shallower than the height of the protrusions of the internally grooved heat exchanger tube. When the inner grooved heat exchanger tube is expanded by the tube expansion plug, the plug head of the tube expansion plug is screwed into the spiral groove on the inner surface of the inner grooved heat exchanger tube by the protrusion provided on the outer peripheral surface of the tube expansion plug. While being rotated and moved forward, by expanding the diameter of the internally grooved heat transfer tube by the tube expanding plug, the internal groove is positioned within the helical groove between the same protrusions of the plug head of the tube expanding plug. Based on the two protrusions of each heat exchanger tube coming into contact with the inner surface of the spiral groove,
The parts near their tops were pushed down toward each other.

In addition, when expanding the diameter of the internally grooved heat exchanger tube using the above-mentioned tube expansion plug, it is necessary to avoid the seizure phenomenon between the plug head of the tube expansion plug and the internally grooved heat exchanger tube, and to increase the diameter of the tube expansion plug. In order to guide the protrusion of the plug head well along the spiral groove of the internally grooved heat exchanger tube, a predetermined groove is applied to the inner surface of the internally grooved heat exchanger tube before inserting the tube expansion plug into the internally grooved heat exchanger tube. An inner groove whose diameter is enlarged by the plug head of the tube expansion plug through a lubricant supply path provided in the tube expansion plug, either by applying lubricating oil in advance or as the expanding operation of the internally grooved heat transfer tube with the tube expansion plug progresses. Preferably, a predetermined lubricating oil is supplied and applied to the inner surface of the heat exchanger tube.

(Example) Hereinafter, in order to clarify the present invention more specifically,
One embodiment thereof will be described in detail based on the drawings.

Here, first, the structure of the internally grooved heat exchanger tube 10 to be expanded will be explained based on FIG. 3 and FIG. 4, and then, based on FIG. 1 and FIG. The structure of the tube expansion plug 12 that expands the diameter of the internally grooved heat exchanger tube 10 will be explained.

Then, the inner grooved heat exchanger tube 10 and the tube expansion plug 1
After explaining the structure of No. 2, the operation of attaching the plate fins 14 to the outer surface of the internally grooved heat exchanger tube 10 using the tube expansion plug 12 will be explained based on FIGS. 5 and 6.

That is, FIG. 3 shows a longitudinal cross-sectional view of the internally grooved heat exchanger tube 1O that is to be expanded in the method of this embodiment, and FIG. An enlarged view of the main part of the surface is shown.

As is clear from these figures, the internally grooved heat exchanger tube 10 to be expanded in the method of this embodiment has a cylindrical smooth outer surface, and usually has an outer diameter of about 4 to 10 mm. have. On its inner surface, a protrusion 16 of a predetermined height exhibiting a substantially triangular chevron-shaped cross section with an apex angle set at a predetermined angle is usually formed with a twist angle of 16 to 30 degrees with respect to the tube axis. A large number of spiral strips (generally about 40 to 70 strips) are formed at a constant pitch, so that the opposing side surfaces 18, 18 of the adjacent protrusions 16, 16 serve as both side walls, respectively. The bottom surface 20 is a smooth surface with a predetermined width, and a large number of spiral grooves 22 are formed at a constant pitch on the inner surface of the tube.

Note that the apex angle of the protrusion 16 of the internally grooved heat exchanger tube 10 is as follows:
The size is usually set to about 30 to 50 degrees so that the portion near the top can be pushed down well during diameter expansion, which will be described later. , usually 0.15 to 0.25 so that the height of the protrusion 16 can be maintained at an appropriate height.
The height will be set to about mm.

On the other hand, in the tube expansion plug 12 for expanding the internally grooved heat exchanger tube 10, as shown in FIG. It has a structure in which it is rotatably supported by a mounting bolt 28.

A thrust bearing 30 is interposed between the plug head 24 and the insertion rod 26, and a heat exchanger tube 1 (to be described later)
0, the plug head 24 and insertion rod 2
Even if a large axial force is applied between the plug head 24 and the insertion rod 26, the plug head 24 can be smoothly rotated with respect to the insertion rod 26.

As shown in FIG. 1, the plug head 24 of the tube expansion plug 12 that is pressed against the inner surface of the internally grooved heat exchanger tube 10 is configured such that its outer diameter increases from the distal end toward the proximal end. It has a bell-shaped block shape, and its outer peripheral surface has a diameter of an imaginary circle touching the top that is equal to the diameter of the inner surface of the inner grooved heat exchanger tube 10 at the smallest diameter part on the tip side of the plug head 24. The plug head 24 is smaller than the diameter of the virtual circle that is in contact with the bottom surface 20 of the spiral groove 22 .
At the maximum diameter portion of the base end example, the inner grooved heat exchanger tube 10
The inner grooved heat exchanger tube 1 is in a state where the inner grooved heat exchanger tube 1
Half of the protrusions 32 of the helical grooves 22 of 0 have a helical shape corresponding to the helical groove 22 of the internally grooved heat exchanger tube IO, that is, have the same twist angle as the helical groove 22, and the protrusions 32
A certain height dimension is slightly lower than the depth dimension of the spiral groove 22 so that the depth of the spiral groove 33 located between .degree. The grooves are formed at a pitch that is 1/2 that of the spiral groove 22.

Here, as shown in detail in FIG. 2, a protrusion 3 formed on the outer peripheral surface of the plug head 24 is
2 is a smooth surface 34 that is slightly narrower than the smooth surface width of the bottom surface 20 of the spiral groove 22 of the internally grooved heat exchanger tube 10, while both side surfaces 36 and 36 of the internally grooved heat exchanger tube 10, more specifically, the slope angle at the hem part is the both sides 18.1 of the spiral groove 22 of the internally grooved heat exchanger tube IO.
It is said that the curved surface is significantly smaller than that of 8.
As a result, as will be described later, when the internally grooved heat exchanger tube IO is expanded, the plug head 24 spirally closes the internally grooved heat exchanger tube 10 using the flat surface 34 at the top of the protrusion 32 formed on the outer peripheral surface of the plug head 24. It is adapted to be brought into pressure contact with the bottom surface 20 of the groove 22, and at the same time, the bottom portion of the projection 32 is brought into pressure contact with a portion near the top of the projection 16 on the inner surface of the internally grooved heat exchanger tube 10. .

By the way, when expanding the diameter of the internally grooved heat exchanger tube 10 using the tube expansion plug 12 having such a structure and attaching the plate fins 14 to the outer surface thereof, it is necessary to insert the tube expansion plug 12 into the internally grooved heat exchanger tube 10. Prior to this, the internally grooved heat exchanger tube lO
Apply the specified lubricating oil to the inner surface of the Then, as shown in FIG. 5, the internally grooved heat exchanger tube 10 coated with such lubricating oil is inserted into the through holes of the plural plate fins 14 arranged in parallel, and in this state, the plug head 24 By matching the phase of the protrusions 32 on the outer circumferential surface of the tube expansion plug I2 with that of the spiral grooves 22 of the internally grooved heat exchanger tube 10,
Insert it inside and move it forward.

In this way, the side surface 36 of the protrusion 32 of the plug head 24 comes into contact with the side surface 18 of the protrusion 16 of the heat exchanger tube 10 under the lubricating action of the lubricating oil applied to the inner surface of the internally grooved heat exchanger tube 10. Due to the contact, the protrusion 32 of the plug head 24 is well guided along the helical groove 22 of the screwed internally grooved heat exchanger tube IO without causing a seizure phenomenon, and therefore The plug head 24 is rotated and moved forward within the internally grooved heat exchanger tube 10 with the protrusion 32 on its outer circumferential surface screwed into the spiral groove 22 of the internally grooved heat exchanger tube 10. .

Here, as mentioned above, the diameter of the imaginary circle touching the top of the protrusion 32 of the plug head 24 of the tube expansion plug 12 is
It is larger toward the proximal end of the plug head 24, and is smaller at the minimum diameter portion on the distal end side than the virtual circle in contact with the bottom surface 20 of the spiral groove 22 of the internally grooved heat exchanger tube 10, and at the maximum diameter portion on the proximal end side. Since the diameter of the helical groove 22 of the internally grooved heat exchanger tube 10 is larger than the imaginary circle in contact with the bottom surface 20, as the plug head 24 moves forward, the plug head 24 moves toward the protrusion 32. The top part is gradually pressed against the bottom surface 20 of the spiral groove 22 of the internally grooved heat exchanger tube 10, and as a result, the internally grooved heat exchanger tube 10 is expanded in diameter and the plate fin 14 is attached to the outer surface of the tube. It happens.

And here, as mentioned above, such a tube expansion plug 1
2, when the internally grooved heat exchanger tube 10 is expanded, the plug head 2 is placed near the top of the protrusion 16 of the internally grooved heat exchanger tube 10.
Since the protrusion 32 of No. 4 is pressed against the gently sloped hem portion, the pressure contact action causes
As shown in FIG. 6, the two protrusions 16 and 16 located in the same spiral groove 33 of the plug head 24 are pushed down toward each other in the vicinity of their respective tops. , As a result, the internally grooved heat exchanger tube 10
The opening of the space in every other spiral groove 22 is as large as possible.
Preferably, the width is narrowed to about 0.1 mm or less,
The space within the spiral groove 22 has a reentrant cavity shape that can substantially improve heat transfer performance.

Therefore, compared to the case where the diameter of the internally grooved heat exchanger tube 10 is expanded using a conventional expansion plug with a smooth outer peripheral surface of the plug head, the heat transfer performance of the internally grooved heat exchanger tube 10 after expansion is significantly improved. As a result, the heat transfer performance of the finned heat exchanger tube having the structure in which the plate fins 14 are attached to the outer surface of the tube is significantly improved compared to the case where a conventional tube expansion plug is used.

In addition, in the method of this embodiment, as described above, the top of the protrusion 32 of the plug head 24 is made into a smooth surface 34, and the bottom surface 20 of the spiral groove 22 of the internally grooved heat exchanger tube IO is Since the protrusions 32 of the plug head 24 are pressed against the smooth surface 34 and the internally grooved heat exchanger tube IO is expanded, the tops of the protrusions 32 do not form curved surfaces or sharp points. Compared to the case where a heat exchanger tube with internal grooves is used,
There is also the advantage that by increasing the contact area between O and the plate fins 14, the heat transfer performance between the internally grooved heat exchanger tube 10 and the plate fins 14, and by extension the heat transfer performance of the finned heat exchanger tube, can be improved. .

Although one embodiment of the present invention has been described in detail above, this is a literal illustration, and the present invention is not limited to such a specific example, and within the scope of the spirit thereof,
It goes without saying that the present invention can be implemented with various changes, modifications, improvements, etc.

For example, in the embodiment described above, the height of the protrusion 32 formed on the outer circumferential surface of the plug head 24 of the tube expansion plug 12 was set to be constant over its entire length. The height does not necessarily have to be constant over its entire length; for example, the height may be lower on the proximal end side of the plug head 24.

Further, in the embodiment described above, lubricating oil was applied to the inner surface of the internally grooved heat exchanger tube 10 prior to inserting the tube expansion plug 12 into the internally grooved heat exchanger tube 10. A lubricating oil supply path is formed by passing through the insertion rod 26, mounting bolt 28, and plug head 24, and as the expansion operation of the internally grooved heat transfer tube 1O progresses, the expansion plug is inserted through the lubricating oil supply path. It is also possible to supply and apply lubricating oil to the inner surface of the internally grooved heat exchanger tubes 10 that are expanded by the 12 plug heads 24, and also in a state in which the internally grooved heat exchanger tubes 10 are arranged one above the other. In the case of expanding the diameter of the internally grooved heat exchanger tube 1O, it is also possible to perform the diameter expansion operation of the internally grooved heat exchanger tube 1O while dropping lubricating oil into the internally grooved heat exchanger tube 1O.

Furthermore, as shown in FIG. 7, the internally grooved heat exchanger tube 10 is usually set on the plate fin 14 in a U-shaped curved state, and in this state, tube expansion plugs are inserted from the openings at both ends. 12.12 will be inserted at the same time and the diameter will be enlarged, but in this way, the internally grooved heat exchanger tube 10
When used in a curved form, the processing oil used during the bending process of the internally grooved heat exchanger tube 1O generally remains inside, so the residual oil from the processing oil must be removed. It can also be used as a lubricant.

In addition, without applying lubricating oil to the inner surface of the internally grooved heat exchanger tube 10 in advance, or without appropriately supplying lubricating oil to the inner surface portion of the internally grooved heat exchanger tube 10 that is expanded by the plug head 24 of the tube expansion plug 12, The inner grooved heat exchanger tube 1 is simply coated with lubricating oil only on the plug rad 14 of the tube expansion plug 12.
In the case where the expansion operation of 0 is performed, lubricating oil runs out as the expansion operation progresses, and a seizure phenomenon occurs between the internally grooved heat exchanger tubes IO and the plug head 24. There is a risk that the protrusions 32 of the plug head 24 will ride over the protrusions 16 of the internally grooved heat exchanger tube 10 and damage the internally grooved heat exchanger tube 10, but as described above, the internally grooved heat exchanger tube If lubricating oil is applied in advance to the inner surface of the lO, or if lubricating oil is appropriately supplied to the inner surface of the internally grooved heat exchanger tube 10 whose diameter is expanded by the plug head 24 of the tube expansion plug 12, lubricating oil can be prevented from running out. Therefore, it is possible to avoid such problems from occurring due to such problems.

(Effect of the invention) As is clear from the above explanation, according to the method of the present invention,
The portion near the top of two adjacent protrusions formed on the inner surface of the internally grooved heat transfer tube by inserting a tube expansion plug into the internally grooved heat transfer tube and expanding the diameter of the internally grooved heat transfer tube. By pushing down the grooves toward each other, the spaces of the spiral grooves on the inner surface of the inner grooved heat exchanger tube can be made into reentrant cavity-like spaces at every other groove. Therefore, the outer peripheral surface of the plug head can be made smooth. Compared to the case where plate fins are attached to the outer surface of an internally grooved heat exchanger tube using a conventional tube expansion plug, the deterioration of the heat transfer performance of the internally grooved heat exchanger tube is effectively avoided and the heat transfer performance is improved. Thus, a heat exchanger tube with fins can be obtained.

In the method of the present invention, prior to expanding the diameter of the internally grooved heat transfer tube, lubricating oil is applied to the inner surface of the tube in advance, or a lubricating oil supply path is provided in the tube expansion plug, and the tube is expanded by the plug head. By supplying and applying lubricating oil to the inner surface of the internally grooved heat exchanger tube through the lubricant supply passage, the occurrence of seizure between the plug head and the internally grooved heat exchanger tube can be effectively avoided. This makes it possible to constantly expand the diameter of the internally grooved heat exchanger tube without causing any serious trouble.

[Brief explanation of the drawing]

FIG. 1 is a half-cut sectional view for explaining an example of a tube expansion plug used in the method of the present invention, and FIG. 2 shows the shape of a protrusion formed on the outer peripheral surface of the plug head of the tube expansion plug shown in FIG. It is an explanatory sectional view for explaining. FIG. 3 is a longitudinal cross-sectional view for explaining the internally grooved heat exchanger tube whose diameter is expanded using the tube expansion plug shown in FIG. 1, and FIG.
It is an enlarged cross-sectional view of the main part. FIG. 5 is an explanatory sectional view for explaining the operation of attaching plate fins to the outer surface of the internally grooved heat exchanger tube shown in FIG. 3 using the tube expansion plug shown in FIG. 1, and FIG. It is a sectional view for explaining the shape of the protrusion on the inner surface of the tube after the expansion operation of the heat exchanger tube. FIG. 7 is an explanatory diagram showing another application example of the method of the present invention. FIG. 8 is a cross-sectional view for explaining the shape of the protrusions on the inner surface of the inner grooved heat exchanger tube expanded by the conventional method. lO: Internally grooved heat transfer tube 12: Tube expansion plug 14 Nibrate fin 16: Projection 18: Side surface 20: Bottom surface 22: Spiral groove 24 Nib lug head 26: Insertion rod 28: Mounting bolt 30 Nybrate bearing
32: Projection 33: Spiral groove 36: Side surface Applicant: Sumitomo Light Metal Industries, Ltd. Figure 1 Figure 4

Claims (2)

[Claims] (1) A structure in which spiral protrusions with approximately triangular cross sections are formed on the inner surface at a predetermined pitch, and spiral grooves with a smooth bottom surface of a predetermined width are formed on the inner surface at a predetermined pitch. When attaching a plurality of plate fins to the outer surface of the internally grooved heat transfer tube by inserting a tube expansion plug into the internally grooved heat transfer tube and expanding the diameter of the internally grooved heat transfer tube with the tube expansion plug, The tube expansion plug used has a structure in which a plug head is rotatably supported at the tip of an insertion rod, and the top width of the plug head of the tube expansion plug is equal to the bottom width of the helical groove of the internally grooved heat exchanger tube. A protrusion having a structure in which the helical groove of the internally grooved heat exchanger tube is narrower than that of the helical groove of the internally grooved heat exchanger tube on the outer circumferential surface has a structure in which both side surfaces are sloped surfaces gentler than that of the helical groove of the internally grooved heat exchanger tube. A plug with a corresponding spiral shape and a pitch twice that of the spiral groove is used, and the diameter of the imaginary circle touching the top of the protrusion of the plug head of the tube expansion plug is the most on the distal end side. In the small diameter part, the diameter of the virtual circle that is in contact with the bottom surface of the spiral groove of the internally grooved heat exchanger tube is smaller than the diameter of the virtual circle that is in contact with the bottom surface of the spiral groove of the internally grooved heat exchanger tube, while in the maximum diameter part on the proximal end side, the diameter of the virtual circle that is in contact with the bottom surface of the spiral groove of the internally grooved heat exchanger tube. The groove depth of the helical groove formed between the protrusions of the plug head is set to be a predetermined dimension larger than the diameter of the heat exchanger tube. The height is set to be shallower than the height of the inner grooved heat exchanger tube, so that when the tube expansion plug expands the inner grooved heat exchanger tube, the plug head of the tube expansion plug is set to be shallower than the inner grooved heat exchanger tube by the protrusion provided on its outer peripheral surface. While being rotated and advanced while being screwed into the helical groove of the tube, by expanding the diameter of the internally grooved heat exchanger tube with the tube expansion plug, the spiral between the same protrusions on the plug head of the tube expansion plug is Each of the two protrusions of the internally grooved heat exchanger tube positioned in the groove is pushed down in a direction near the top of each of the protrusions to approach each other based on the contact with the inner surface of the spiral groove. A method for attaching an internally grooved heat exchanger tube to a plate fin. (2) Prior to inserting the tube expansion plug into the internally grooved heat exchanger tube, predetermined lubricating oil is applied to the inner surface of the internally grooved heat exchanger tube, or the tube expansion plug is applied to the internally grooved heat exchanger tube. As the expansion operation progresses, a predetermined lubricating oil is supplied through the lubricating oil supply path provided in the tube expanding plug to the inner surface portion of the internally grooved heat exchanger tube whose diameter is expanded by the plug head of the tube expanding plug. - The mounting method according to claim (1), characterized in that the method is applied by coating.