JPS6262194A - Heat transfer tube and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a heat transfer tube having both of high evaporating characteristics and high condensating characteristics by forming a multitude of protuberances, having a substantially triangular sectional shape, on the inernal surface of the heat transfer tube. CONSTITUTION:A plurality of first internal grooves 2, pinched between parallel protuberances having substantially triangular secitonal shapes, a plurality of second internal grooves 3, intersecting with the first internal grooves 2 and shallower than said first internal grooves 2, and projected sections 5, formed by projecting the troughs of the second internal grooves 3 toward the trough sections of the first internal grooves 2, are formed on the inner surface of a heat transfer tube. According to this method, evaporating characteristics may be improved by the discontinuity of the width of the first internal grooves 2 while the condensating characteristics of the same tube may be improved by sharp protuberances.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a structure of a heat exchanger tube used for refrigeration, air conditioning, etc., and a method of manufacturing the same.

``Prior art'' For example, heat transfer tubes used in air heat exchangers have traditionally been smooth tubes with a perfectly circular inner surface, but recently, tubes with grooves on the inner surface are often used from the viewpoint of increasing efficiency and saving energy. It is becoming more and more popular. This is a pipe in which triangular or trapezoidal grooves are formed in a straight or spiral shape on the inner surface of the tube.In particular, the spiral grooves improve the agitation effect of the internal fluid and increase the inner surface area. In addition to increasing the heat transfer coefficient, the corners of the inner grooves form boiling nuclei, resulting in excellent boiling heat transfer characteristics. However, with the simple shape of the internally grooved tubes mentioned above, there are limits to their heat transfer characteristics even if improvements are made to the number of threads, lead angle, groove shape, etc., and efforts are being made to improve the heating capacity of heat pump air conditioners in winter. I can't.

The outdoor unit of a heat pump air conditioner acts as a condenser in the summer and as an evaporator in the winter, so the heat exchanger tubes used in the heat exchanger are required to have excellent characteristics in both condensation and oxidation. .

In response to this, heat exchanger tubes with fine spiral grooves provided on the inner surface of the tube are used, and in order to improve their performance, cross-grooved tubes are being developed.

``Problem to be solved by the invention'' However, in heat pump air conditioners, when the outside temperature drops during winter, the evaporator is installed outdoors, so the refrigerant is not emitted sufficiently, and the heating temperature decreases. This often leads to a decline.

This is due to a decrease in the heat of evaporation characteristics of the heat exchanger tube used in the evaporator, and is particularly noticeable when the outside air temperature is low.

Furthermore, since the outdoor unit of the heat pump air conditioner functions as a condenser in the summer, a decrease in condensing characteristics leads to a lack of cooling capacity in the summer.

``Object of the Invention'' The present invention was made in order to eliminate such conventional drawbacks, and provides a heat transfer tube having both high evaporation characteristics and condensation characteristics, for example for use in a heat pump air conditioner, and a manufacturing method using the same. The purpose is to

"Means for Solving the Problems" The main means adopted by the present invention to achieve the above object is to provide a plurality of first inner grooves sandwiched between parallel peaks having a substantially triangular cross-sectional shape. and a plurality of second inner grooves in which groove portions shallower than the first inner groove and peak portions having a trapezoidal cross-sectional shape are alternately formed in parallel to intersect with the first inner groove; An overhanging portion is formed on the inner surface of the tube so that the bottom surface of the trough of the second inner groove that intersects with the trough of the inner groove extends toward the trough of the first inner groove. The heat transfer tube is a heat exchanger tube, and the manufacturing method thereof is such that a first grooved plug having a plurality of grooves with a substantially triangular cross-sectional shape on the outer periphery is used to create parallel peaks with a substantially triangular cross-sectional shape on the inner surface of the tube. After forming a plurality of first inner grooves sandwiched between the parts, a plurality of grooves shallower than the grooves provided on the outer periphery of the first grooved plug are formed on the outer periphery, and the second grooved plug A method for manufacturing a heat exchanger tube is provided in which a second inner groove is formed so as to intersect with the first inner groove and press the peaks thereof at regular intervals so as to extend toward the troughs of the first inner groove. provided.

"Operation of the Invention" With the above structure, according to the present invention, the width of the first inner groove becomes narrower at the part where it intersects with the second inner groove, so that the width of the first inner groove becomes narrower at the part where the width is wider. Narrow portions are formed alternately and continuously. Therefore, the flow of the refrigerant liquid in the first inner groove is stirred and the evaporation characteristics are improved.

Furthermore, high condensation ability is maintained by the protrusions that are located between the first inner grooves and are not cut out by the second inner grooves.

"Embodiments" Examples of the present invention will be described below with reference to FIGS. 1 to 10 to provide an understanding of the present invention.

The following examples are merely specific examples of the present invention, and are not intended to limit the technical scope of the present invention.

Here, Figure 1 is a perspective view showing the inner surface of the heat exchanger tube according to an embodiment of the present invention developed into a plane, and Figure 2 is the first inner groove formed during the manufacturing process of the heat exchanger tube shown in Figure 3 is a sectional view when the second inner groove is carved, FIG. 4 is a side sectional view showing an example of the heat exchanger tube manufacturing apparatus according to the present invention, and FIG. 5 is a sectional view when the second inner groove is carved. The figure is a schematic side view of the first plug with a groove, FIG. 6 is a sectional view taken along the line Vl-Vl in FIG.
FIG. 9 is a diagram showing evaporation characteristics for explaining the effects of the heat exchanger tube of the present invention, and FIG. 10 is a diagram showing its condensation characteristics.

In FIG. 1, this heat exchanger tube 1 is formed by giving a special shape to a smooth tube with a perfectly circular inner surface and no irregularities on the inner surface. As shown in FIG. 2, this heat exchanger tube l has a plurality of parallel first inner grooves 2 each having a peak having a substantially triangular cross section.

The direction of the first inner groove 2 is indicated by an arrow P. A second internal groove 3, which is shallower than the first internal groove 2, is formed in a direction intersecting the first internal groove 2 as indicated by the arrow P. This second
The direction of the inner groove 3 is indicated by an arrow Q.

Furthermore, as shown in FIG.
Since the peaks between the inner grooves 2 are compressed and pushed out toward the grooves of the first inner groove 2, the width b) of the first inner groove 2 becomes b2.
become.

However, since the unstressed portions of the peaks between the first inner grooves 2 remain in their original shape, the width of the first inner grooves 2 is
remains wide. Therefore, in the first inner groove 2, wide portions of width S and portions of narrow width b2 appear in succession alternately. Therefore, the flow of the refrigerant liquid in the first inner groove 2 is agitated (
Being imprisoned will improve your artistic abilities.

In order to make the overhanging portion 5 that appears by pressing the peaks between the first inner grooves 2 to a sufficient size, the depth h2 of the second inner groove 3 needs to be large.
It is desirable that the depth be 1/3 or more of the depth of the first inner groove 2.

Moreover, if the width b (FIG. 1) of the second inner surface groove 3 is narrow, the volume to displace the peaks will be small, so that the overhang portion 5 of sufficient size cannot be formed. Therefore, b is desirably 0.05 tm or more, preferably 0.1 n or more.

On the other hand, if the width a (FIG. 2) of the groove bottom of the first inner groove 2 is small, the condensed refrigerant liquid will accumulate in the groove and the peaks will be submerged in the liquid, resulting in a decrease in condensation characteristics. For this reason, the width a of the groove bottom is preferably as large as possible.

Furthermore, when the peaks A of the first inner grooves 2 are sharp, the liquid film of the refrigerant liquid becomes thinner, so that the condensation characteristics are improved.

Next, the apparatus and method for manufacturing the heat exchanger tube 1 as shown in FIG. 1 will be explained.

In FIG. 4, the original tube A is pulled in the direction of arrow ．． The prototube A passes through continuously in cooperation with C2.

The material is compressed from the inside and outside to reduce its diameter and thickness. In this case, in order to reduce the frictional force in the circular die device B, the circular die device B may be of a rotating type, or it may be of a fixed type depending on the material of the original tube A.

In addition, a thin lubricating oil film is provided between the floating plug C and the inner surface of the tube to effectively prevent seizure during diameter and thinning processing. This lubricating oil film is formed by previously stretching the lubricant P thinly within the original tube A1.

The 1st f.
A plug E with an i is rotatably connected to the floating plug C independently.

As the pipe A2 passes through after diameter reduction, a tensile force in the tube axial direction acts on the first grooved plug E. A thrust bearing is provided at the rear of the first grooved plug E to support this axial tensile force. G is provided, which allows the first grooved plug E to rotate in position.

As shown in FIGS. 5 and 6, the first grooved plug E has a plurality of grooves E arranged regularly or irregularly (randomly) on its outer surface approximately in the tube axis direction. It is carved in a diagonal shape. The meat of tube A2 passing through is
It is buried in the recess of this groove E by pressure from outside the pipe,
The peaks of the first inner groove 2 of the inner grooved tube are formed, while the convex portions similarly form the troughs of the first inner groove 2.

Note that when the groove EI provided on the outer surface of the first grooved plug E is straight in the tube axis direction (that is, parallel to the tube axis), a straight groove is formed on the inner surface as the tube is pulled out. Plug E with No. 1a does not rotate as the pipe moves.

The first rolling device F, which is located outside the tube and continuously presses the tube flesh strongly against the first grooved plug, is pressed against the tube shaft by a contact/separation mechanism (not shown) during processing, and is During processing, the tube is kept away from the outside surface so as not to touch it. Such a first rolling device F
, are provided on the outer circumferential surface of the tube, and at the same time press the tube flesh with a contact/separation mechanism.

For internal grooves as described above, place pipe A3 in the direction of arrow
When the first rolling device F1 and the circular die device B are rotated as shown by the arrow Y while being pulled in the direction of
is held between the approach portion C7 of the floating plug C and the approach portion B of the circular die device B, and its diameter is reduced, and between the bearing portion B2 of the circular die device B and the bearing portion C2 of the floating plug C. As it passes through, the outside diameter of the tube is regulated and it is pulled out as tube A2 after diameter reduction. The pipe A2 is further pressed against the groove E of the first grooved plug E by the first rolling device F1, and a first inner groove 2 is formed in the inner surface thereof in a spiral shape corresponding to the inclination angle of the groove B. . The shape of the first inner groove 2 is shown in FIGS. 5 and 6.

Therefore, on the inner surface of the pipe processed by the first grooved plug E, as shown in FIG. 2, peaks having a triangular cross section with an apex and grooves having a bottom width of a are alternately formed.

A pipe A with the first inner groove 2 formed on the inner surface in this way,
further passes through the second rolling device F2. A second grooved plug E is provided in the pipe A3 corresponding to the second rolling device F.
3 is accommodated, and this second grooved plug E3 has an outer diameter d of the first grooved plug E, as shown in FIGS. 7 and 8.
It has a short cylindrical shape having an outer diameter d2 smaller than 1, and a groove 4 having a substantially trapezoidal cross-sectional shape.

Therefore, the inner surface of the pipe in the portion processed by the second grooved plug E3 is formed as shown in FIG. That is, since the peak portion of the first inner groove 2 shown by the two-dot chain line is pressed by the outer circumferential surface of the second grooved plug E3, the first
The depth from the top A of the inner groove 2 is as follows.

Also, due to this compression, the peak part of the first inner groove 2 is overhanged toward the groove part of the first inner groove 2 to form an overhang part 5, so the width b1 of the first inner groove 2 is the compressed part. So b
It becomes 2.

The peak between this second inner surface fI3 is the second grooved plug E.
Since it follows the trapezoidal part of No. 3, the mountain part remains as it was without being compressed. Therefore, the width of the groove is still .

The second grooved plug E is rotatably supported by a connecting rod D1 provided on an extension of the connecting rod, and is held at a fixed position in the axial direction by a thrust bearing G1.

In the above explanation, the first inner groove 2 is formed to have a right-hand thread, and the second inner groove 3 is formed to have a left-hand thread. However, the directions of the grooves E1 and E4 formed in each grooved plug may be adjusted appropriately. By doing so, it is also possible to make either the first inner groove or the second inner groove a straight groove parallel to the tube axis, and the other to be a spiral groove in the right-handed or left-handed direction that intersects with this. be.

In addition, in the above device, the floating plug C1, the first grooved plug E, and the second grooved plug E3 are connected to the connecting rod and D.
Although the apparatus and method for continuously forming the first and second internal grooves 2 and 3 by combining them into a unit by means of the above-described method has been described, it is also possible to separate them separately to form, for example, a floating plug C and a plug E with No. 1a. They are integrally assembled using a connecting rod, and first, a first inner groove 2 is formed,
After continuous winding, a new second grooved plug E3 combined with another floating plug is used to carve the second inner groove 3 onto the first inner surface a2 in a batch-like manner. It is also possible to form grooves on both inner surfaces.

The specific numerical values in this example are as shown in Table 1, and in order to confirm the effect of the heat exchanger tube according to the present invention, a comparison with a conventional internally grooved tube having the specifications listed in this table is made. The test was conducted.

The test results are as shown in FIGS. 9 and 10, and the heat exchanger tube of this example (marked with black circles) has about 100% of the stem generation characteristics compared to the conventional internally grooved tube (marked with white circles). The condensation properties were improved by 1.2 times and about 1.3 times.

Presentation l "Effects of the Invention" As explained above, the present invention provides a plurality of first inner grooves sandwiched between parallel peaks having a substantially triangular cross-sectional shape;
a plurality of second inner grooves intersecting with the first inner groove and having groove portions shallower than the first inner groove and peak portions having a trapezoidal cross-sectional shape alternately formed in parallel; and the first inner groove. An overhang is formed on the inner surface of the tube, the bottom surface of the valley of the second inner groove intersecting with the valley of the first inner groove extending toward the valley of the first inner groove. Since the tube is a heat transfer tube, the discontinuity in the groove width of the first inner groove improves the stem generation characteristics, and the sharp convex portions improve the condensation characteristics.

Furthermore, the present invention provides a first grooved plug having a plurality of grooves having a substantially triangular cross-sectional shape on the outer periphery, and a plurality of grooves sandwiched between parallel peaks having a substantially triangular cross-sectional shape on the inner surface of the tube. After forming the first inner groove, the outer periphery has a number of grooves shallower than the grooves provided on the outer periphery of the first grooved plug, and the second grooved plug intersects with the first inner groove. Since the method for manufacturing a heat transfer tube is characterized in that the second internal groove is formed by compressing the peaks at regular intervals so as to protrude toward the troughs of the first internal groove, as described above, This has the remarkable effect that a heat exchanger tube with excellent heat transfer characteristics can be easily manufactured using a simple device using a first grooved plug and a second grooved plug.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing the inner surface of a heat exchanger tube according to an embodiment of the present invention developed into a plane, and Fig. 2 shows a first inner groove carved in the manufacturing process of the heat exchanger tube shown in Fig. 1. 3 is a sectional view when the second inner groove is carved, FIG. 4 is a side sectional view showing an example of the heat exchanger tube manufacturing apparatus according to the present invention, and FIG. 5 is a sectional view when the second inner groove is carved. 1 Schematic side view of a grooved plug,
FIG. 6 is a sectional view taken along the line Ml-Ml in FIG. 5, FIG. 7 is a schematic side view of the second grooved plug, and FIG. 8 is a -
9 is a sectional view taken along the line (2), FIG. 9 is a chart showing the stem generation characteristics for explaining the effects of the heat exchanger tube of the present invention, and FIG. 10 is a chart showing the condensation characteristics thereof. (Explanation of symbols) 1... Heat exchanger tube 2... First inner groove 3...
・Second inner groove 5...Protrusion part E...First
Grooved plug E3...Second grooved plug

Claims (2)

[Claims] (1) A plurality of first inner grooves sandwiched between parallel ridges having a substantially triangular cross-sectional shape, a trapezoidal groove intersecting the first inner groove and shallower than the first inner groove; A plurality of second inner grooves in which peaks having a cross-sectional shape are alternately formed in parallel, and a bottom surface of the valley of the second inner groove that intersects with the valley of the first inner groove are connected to the first inner groove. A heat exchanger tube characterized in that an overhanging portion is formed on the inner surface of the tube so as to overhang toward the trough. (2) A first grooved plug having a plurality of grooves with a substantially triangular cross-sectional shape on the outer periphery has a plurality of grooves sandwiched between parallel peaks with a substantially triangular cross-sectional shape on the inner surface of the tube. After forming the first inner groove, the outer periphery has a number of grooves shallower than the grooves provided on the outer periphery of the first grooved plug, and the second grooved plug intersects the first inner groove and forms the peaks thereof. A method of manufacturing a heat exchanger tube, comprising: forming a second inner groove so as to extend toward a trough of the first inner groove by compressing the inner groove at regular intervals.