JPH074884A - Heat transfer pipe with inner surface groove and its manufacturing method - Google Patents

Abstract

PURPOSE:To improve both an evaporation efficiency and a condensing efficiency by a method wherein some large projections are formed at an inner surface of a metallic pipe with a specified spacing therebetween and a pair of small projections are formed between the large projections and inclined toward the large projections. CONSTITUTION:Tubular grooves 16 with their opening width W2 being less than a bottom width W1 are formed between adjoining large projections 12 and small projections 14. In the case where they are used as evaporating tubes, air bubbles are easily formed inside the tubular grooves 16, these air bubbles act as evaporation cores so as to promote evaporation of thermal medium liquid. Accordingly, it is possible to increase the gasification efficiency as compared with that of the heat transfer pipe in which uniform simple grooves are formed in the same pitch. In addition, the extremity ends of the large projections 12 are projected from the inner circumferential surface of a metallic pipe 10 rather than from the small projections 14 and the tubular grooves 16, so that in the case where they are used as a condensing pipe, separation of thermal medium liquid from the extremity ends of the large projections 12 is well performed and a liquid film is hardly formed on this part. Accordingly, there the ratio of exposure of a metallic surface at the extremity ends of the large projections 12 is high, no prohibition of heat exchanging operation between the metal and the thermal medium gas through the liquid film, resulting in that a high condensing efficiency can be attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer tube with an inner groove and a method for manufacturing the same, and more particularly to improvements for improving heat transfer performance.

[0002]

2. Description of the Related Art This kind of heat transfer tube with an inner groove is mainly used as an evaporation tube or a condensation tube in a heat exchanger such as an air conditioner or a refrigerator. Recently, a spiral groove is rolled on the inner surface. The manufactured heat transfer tubes are widely commercially available.

In the heat transfer tube having the inner groove thus formed,
It has the following advantages over the heat transfer tube without grooves.

When the heat transfer tube is used as a condensing tube, the heat medium gas flowing in the condensing tube is made into a turbulent flow by the ridges between the grooves, and the ridges serve as condensation nuclei to condense the heat medium gas. Enhances and promotes liquefaction. Further, the condensed heat medium liquid is caused to efficiently flow in the longitudinal direction of the heat transfer tube by the surface tension in the groove, and the reflux effect is increased.

When used as an evaporation tube, the edge of the inner surface groove serves as an evaporation nucleus for generating bubbles, promotes boiling and improves the vaporization efficiency of the heat medium liquid. Further, due to the surface tension in the groove, the heat transfer liquid flows in the longitudinal direction of the heat transfer tube and is uniformly dispersed on the inner surface of the heat transfer tube.

By the way, as a means for further enhancing the heat transfer performance of this kind of inner surface grooved heat transfer tube, the opening width of the groove is made narrower than the bottom width to promote the generation of bubbles inside the groove to improve the evaporation efficiency. A way to raise it is proposed.

As one example, FIG. 14 shows US Pat.
The heat transfer tube described in No. 04,441 is shown. This is because after rolling a large number of spiral parallel grooves 2 on the inner surface of the metal tube 1, and further crushing the tips of the protrusions 3 between the grooves 2 with a rolling tool, the opening width of each groove 2 is increased. Is narrower than its bottom width.

[0008]

By the way, in order to obtain a high evaporation promoting effect in the heat transfer tube of FIG. 14, it is essential to narrow the pitch of the grooves 2 and the ridges 3. Then, the second rolling is performed. At the time of processing, each ridge 3 fell in the circumferential direction without being sufficiently crushed, the opening width of the groove 2 did not become narrower than the bottom width, and there was a problem that a groove having an ideal shape as shown could not be formed. . Therefore, it is not possible to make the groove pitch as small as that of the simple grooved heat transfer tube, and there is little performance advantage over the simple grooved heat transfer tube, and it is considered to be practical considering the manufacturing cost. I wanted

Further, even if this heat transfer tube is used as a condensation tube, there is not much advantage in terms of the condensation performance as compared with a normal simple grooved heat transfer tube.

[0010]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems. First, a heat transfer tube with an inner surface groove of the present invention is arranged in parallel on the inner surface of a metal tube at regular intervals. The large ridges are formed, and a pair of small ridges are formed between the large ridges in parallel with the large ridges, and these small ridges are inclined toward the adjacent large ridges. Therefore, a tubular groove having an opening width equal to or smaller than the bottom width is formed between the adjacent large ridges and small ridges.

On the other hand, according to the method of manufacturing the heat transfer tube with the inner groove of the present invention, the first plug in which the large ridge forming groove and the divided ridge forming groove which are parallel to each other are alternately formed is passed through the metal tube, and A large number of large ridges and divided ridges extending in parallel to each other are alternately formed on the inner surface of the metal pipe, and then the metal pipe is further provided with positioning grooves fitted to the large ridges and the divided ridges. The split ridges that divide the ridge into two in the width direction are passed through the second plug in which the split ridges that are parallel to each other and are formed alternately and through the positioning ridges along the large ridges Is divided into two in the width direction to form small ridges inclined toward the adjacent large ridges, and between the adjacent large ridges and small ridges, a tubular groove whose opening width is equal to or smaller than the bottom width is formed. It is characterized by forming.

[0012]

According to the inner grooved heat transfer tube of the present invention, a tubular groove having an opening width equal to or smaller than the bottom width is formed between the adjacent large ridges and small ridges. When used, bubbles are likely to be generated inside the tubular groove, and these bubbles act as evaporation nuclei to promote evaporation of the heat medium liquid. Therefore, as compared with the heat transfer tube in which the simple grooves are formed at the same pitch, the vaporization efficiency is improved.

Further, since the tip of the large ridge protrudes from the inner surface of the metal tube rather than the small protrusion and the tubular groove, when the heat transfer tube is used as a condenser tube, the tip of the large ridge is formed. The heat medium liquid runs out easily in this case, and a liquid film does not easily form in this part. Therefore, as compared with the case where the simple grooves are formed at the same pitch, the metal surface is more exposed at the tip of the large ridge, and the liquid film does not hinder the heat exchange between the metal and the heating medium gas. The condensation efficiency of the medium gas is also increased.

On the other hand, according to the manufacturing method of the present invention, the excellent heat transfer tube can be manufactured relatively easily as described above, and the positioning groove of the second plug is slid along the large ridge so that While accurately positioning the second plug, the divided ridges are divided into two and inclined by each divided ridge to form the small ridge and the tubular groove, so that the ridge has the same extent as a simple grooved heat transfer tube. It is possible to narrow the pitch and width of, and obtain high heat transfer performance.

[0015]

1 is a sectional view showing an embodiment of a heat transfer tube with an inner groove according to the present invention. This heat transfer tube is a metal tube 10.
A large number of large ridges 12 are formed in parallel with each other on the inner surface of the large ridges 12, and between each large ridge 12, a pair of small ridges 14 parallel to the large ridges 12 are formed. It was formed. In this example, the cross section of the large ridge 12 is substantially semicircular, and the cross section of the small ridge 14 is obtuse triangular.

As shown in FIG. 2, each small ridge 14 is inclined toward the adjacent large ridge 12, and the opening width is provided between the adjacent large ridges 12 and small ridges 14. A tubular groove 16 having a width W2 of not more than the bottom width W1 is formed. Further, a V groove 18 having a V-shaped cross section is formed between the small protrusions 14.

As the material of the metal tube 10, any material used in conventional heat transfer tubes may be used, and generally Cu, Al or alloys thereof are used. Also,
The outer diameter, wall thickness, and total length of the metal tube 10 are not limited.

The large ridges 12 and the small ridges 14 are metal tubes 1
It may have a spiral shape inclined with respect to the axis of 0, or may have a straight shape extending parallel to the axis. In the case of a spiral shape, the angle with respect to the tube axis is preferably 30 ° or less. If it exceeds 30 °, the flow resistance increases, which is not preferable.

The height T2 of the small ridge 14 is preferably 20 to 50% of the height T1 of the large ridge 12. If it is less than 20%, the depth of the tubular groove 16 cannot be sufficiently secured, and if it is more than 50%, the tubular groove 16 may be closed, and in any case, the effect of promoting evaporation is reduced. As more specific numerical values, for example, in the case of a general heat transfer tube having an outer diameter of 9.52 mm and a bottom wall thickness of about 0.3 mm, T1 is about 0.15 to 0.3 mm and T2 is 0.03 to 0. About 15 mm is suitable.

The formation pitch P of the large ridges 12 may be arbitrarily changed according to the required performance, but in the case of the above general heat transfer tube, it is preferably about 0.4 to 0.6 mm.

The opening width W2 of the tubular groove 16 is the bottom width W1 thereof.
It is desirable to be 50 to 100%. If it is less than 50%, the release of bubbles will be poor, while if it is more than 100%, the generation rate of bubbles will decrease, and in both cases, the evaporation efficiency will decrease. Specifically, in the case of the above general heat transfer tube, W1 is 0.04 to
About 0.1 mm, and W2 is preferably about 0.02 to 0.1 mm.

According to the heat transfer tube with internal groove having the above structure, the tubular groove 16 having the opening width W2 of not more than the bottom width W1 is formed between the adjacent large ridges 12 and small ridges 14. When this is used as an evaporation tube, bubbles tend to be generated inside the tubular groove 16 as shown in FIG. 3, and these bubbles act as evaporation nuclei to promote evaporation of the heat medium liquid. Therefore, the vaporization efficiency can be improved as compared with the heat transfer tube in which uniform simple grooves are formed at the same pitch.

Since the tip of the large ridge 12 projects from the inner surface of the metal tube 10 beyond the small projection 14 and the tubular groove 16, this heat transfer tube was used as a condenser tube as shown in FIG. In this case, the heat medium liquid is easily drained at the tip of the large ridge 12, and a liquid film is unlikely to occur at this portion. Therefore, as compared with the case where the simple grooves are formed at the same pitch, the metal surface is more exposed at the tip of the large protrusion 12, and the liquid film does not hinder the heat exchange between the metal and the heat medium gas. The condensation efficiency of the heat transfer gas can also be increased.

That is, the inner grooved heat transfer tube of the present invention can improve both the evaporation efficiency and the condensation efficiency as compared with the simple grooved heat transfer tube having the same pitch, and the overall heat transfer efficiency is enhanced.

Next, with reference to FIGS. 5 and 6, an embodiment of a method of manufacturing the heat transfer tube will be described.

In this method, first, as shown in FIG. 5, the first plug P1 is passed through the inside of the metal tube 10 to form the metal tube 10.
A large number of large ridges 12 and divided ridges 14A extending in parallel with each other are alternately rolled on the inner peripheral surface of. First plug P
On the outer peripheral surface of 1, there are formed large ridge-forming grooves 20 and divided ridge-forming grooves 22 parallel to each other and each having a semicircular cross section, which are spirally formed or alternately arranged parallel to the plug axis. The large ridge 12 and the divided ridge 14A are each formed in a semicircular cross section and in a spiral or linear shape.

Next, as shown in FIG. 6, the positioning groove 24 fitted into each large ridge 12 and the dividing ridge 26 dividing each divided ridge 14A into two in the width direction are parallel to each other and alternate. The second plug P2 formed in (1) is passed through the metal tube 10 with the positioning groove 24 fitted to the large ridge 12. Then, while the positioning groove 24 slides along the large protrusion 12,
The divided ridges 26 divide the divided ridges 14A into two in the width direction, and the divided portions are inclined toward the adjacent large ridges 12 to form the small ridges 14. As a result, a tubular groove 16 having an opening width equal to or smaller than the bottom width is formed between the adjacent large ridges 12 and small ridges 14.

The first plug P1 and the second plug P2
Of the grooves 20, 22, 24 and the split ridges 26 with respect to the plug axis are completely equal in angle and pitch.

The first plug P1 and the second plug P2 may be separately passed through the metal tube 10, but they may be connected to the same floating plug and rolled at the same time. In that case, the production efficiency is high, which is more preferable.

According to the above manufacturing method, the excellent heat transfer tube can be manufactured relatively easily as described above, and the positioning groove 24 of the second plug P2 is slid along the large ridge 12, While accurately positioning the second plug P2, the split projecting ridges 26 divide the split projecting ridges 14A into two parts to incline and form the small projecting ridges 14 and the tubular grooves 16. Therefore, the simple grooved heat transfer tube It is possible to narrow the pitch and width of the ridges to the same extent as, and obtain high heat transfer performance.

The heat transfer tube of the present invention is not manufactured by the above manufacturing method alone, but may be manufactured by, for example, an electric resistance welded pipe method. Moreover, the cross-sectional shape of the protrusions 12 and 14 may be changed as necessary.

[0032]

[Experimental Example] Next, the effect of the present invention will be demonstrated with reference to an experimental example. (Experimental Example 1) Large ridge forming groove having a semi-elliptical cross section with an opening width of 0.4 mm and a depth of 0.15 mm, and an opening width of 0.11
mm and depth of 0.04 mm, semi-elliptical cross-section, small ridge forming grooves are 0.49 mm in parallel and alternately.
Using a first rolling roll formed in the direction of the lead angle of 18 °, a copper plate having a thickness of 10 mm is rolled and the surface thereof is
As shown in FIG. 7, a large ridge and a small ridge having a cross-sectional shape complementary to each groove were formed.

Then, a second rolling roll having a cross-sectional shape and dimensions shown in FIG. 8 was used on the ridge forming surface, and the large ridges were rolled in the grooves shown in the drawing. Figure 9
[Fig. 3] is an enlarged cross-sectional view of an enlarged cross-sectional photograph of the obtained copper plate, and it can be seen that a tubular groove having a good shape is formed. The dimensions of each part are W1 = 0.08 mm and W2 = 0.08 mm according to the dimension display in the above embodiment.
Met.

(Experimental Example 2) Using the same first and second rolling rolls as in Experimental Example 1, a copper plate material having a thickness of 10 mm was rolled in the same manner as above. The cross-sectional shape after rolling is the same as in Experimental Example 1.

The obtained plate material was set in a measuring device as shown in FIGS. 10 and 11, and an evaporation test and a condensation test were conducted. This device liquid-tightly covers both sides of a plate material as a sample with box-shaped containers 30 and 32, and inside the container 30 warm water (or cold water) is flowed along a non-grooved surface of the sample at a constant flow rate in the longitudinal direction. In addition to flowing, the refrigerant (Freon R-11) flows in the longitudinal direction inside the container 32 along the groove forming surface of the sample. Sample size is thickness 1
0 mm x plate width 22 mm x length 50 mm, containers 30, 32
The dimensions were 5 mm in thickness x 22 mm in width x 50 mm in length.

Then, the flow rate of the hot / cold water, the outlet / inlet temperature of the hot / cold water, the flow rate of the refrigerant, the outlet / inlet temperature of the refrigerant, and the outlet / inlet pressure of the refrigerant were measured. The experimental conditions are as follows.

Evaporation test Refrigerant side evaporation temperature: 35 ° C. (0.
405 kg / cm ² G) Hot water inlet temperature: 50 ° C Condensation test Refrigerant condensation temperature: 70 ° C (3.098 kg /
cm ² G) Cold water inlet temperature: 50 ° C

On the other hand, as a comparative example, an opening width of 0.4 mm,
Grooves having a semi-elliptical cross section with a depth of 0.15 mm have a pitch of 0.
A comparative roll was prepared by rolling the same copper plate as described above using a rolling roll having a lead angle of 18 ° at 49 mm. This comparative example was set in the test device, and the evaporation and condensation efficiencies were examined under the same conditions as above.

The results of the heat exchange efficiency in the experimental example thus obtained expressed as a ratio to the heat exchange efficiency in the comparative example are shown in the graphs of FIGS. 12 and 13. As is clear from these graphs, good heat exchange efficiency was obtained with the plate material of the experimental example. Further, since these performances do not change even after being formed into a tubular shape, it can be inferred that the heat transfer tube of the present invention can obtain high heat exchange efficiency.

[0040]

As described above, according to the heat transfer tube with inner groove of the present invention, the tubular groove whose opening width is equal to or less than the bottom width is formed between the adjacent large ridges and small ridges. Therefore, when this is used as an evaporation tube, bubbles are likely to be generated inside the tubular groove, and these bubbles act as evaporation nuclei to promote evaporation of the heat transfer medium liquid. Therefore, as compared with the heat transfer tube in which the simple grooves are formed at the same pitch, the vaporization efficiency is improved.

Further, since the tip of the large ridge protrudes from the inner surface of the metal tube rather than the small protrusion and the tubular groove, when this heat transfer tube is used as a condenser tube, the tip of the large ridge is formed. The heat medium liquid runs out easily in this case, and a liquid film does not easily form in this part. Therefore, as compared with the case where the simple grooves are formed at the same pitch, the metal surface is more exposed at the tip of the large ridge, and the liquid film does not hinder the heat exchange between the metal and the heating medium gas. The condensation efficiency of the medium gas is also increased.

On the other hand, according to the manufacturing method of the present invention, the excellent heat transfer tube can be manufactured relatively easily as described above, and the positioning groove of the second plug is slid along the large ridge so that While accurately positioning the second plug, the divided ridges are divided into two and inclined by each divided ridge to form the small ridge and the tubular groove, so that the ridge has the same extent as a simple grooved heat transfer tube. The pitch and width of the heat transfer tube can be narrowed, and the heat transfer performance of the heat transfer tube can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a heat transfer tube with an inner groove according to the present invention.

FIG. 2 is an enlarged cross-sectional view of the heat transfer tube.

FIG. 3 is an explanatory view showing the action of a tubular groove when used as an evaporation pipe.

FIG. 4 is an explanatory view showing the action of a large ridge when used as a condenser tube.

FIG. 5 is an enlarged cross-sectional view showing a rolling process using the first plug in the embodiment of the manufacturing method of the present invention.

FIG. 6 is an enlarged cross-sectional view showing a rolling process using a second plug in the example.

FIG. 7 is an enlarged cross-sectional view of the plate material after the first rolling in Experimental Examples 1 and 2 of the present invention.

FIG. 8 is an enlarged cross-sectional view of a second rolling roll used in Experimental Examples 1 and 2 of the present invention.

FIG. 9 is an enlarged cross-sectional view of a plate material obtained in Experimental Example 1 of the present invention.

FIG. 10 is a cross-sectional view showing the main parts of a heat exchange efficiency measurement device of Experimental Example 2 of the present invention.

FIG. 11 is a plan view showing a main part of the heat exchange efficiency measurement device.

FIG. 12 is a graph showing the results of an evaporation test of the plate material obtained in Experimental Example 2.

FIG. 13 is a graph showing the results of a condensation test of the plate material obtained in Experimental Example 2.

FIG. 14 is a cross-sectional view showing an example of a conventional heat transfer tube with an inner groove.

[Explanation of symbols]

 10 metal tube 12 large ridge 14 small ridge 14A split ridge 16 tubular groove 18 V groove P1 first plug P2 second plug 20 large ridge forming groove 22 split ridge forming groove 24 positioning groove 26 split Ridge W1 Bottom width of tubular groove W2 Opening width of tubular groove P Large ridge pitch

Claims (2)

[Claims] 1. A large number of large ridges are formed on an inner surface of a metal pipe in parallel at regular intervals, and a pair of small ridges are formed between the large ridges in parallel with the large ridges. Is formed and these small ridges are respectively inclined toward the adjacent large ridges, a tubular groove whose opening width is equal to or smaller than the bottom width is formed between the adjacent large ridges and small ridges. Heat transfer tube with internal groove, characterized in that 2. A first plug, in which large ridge forming grooves and divided ridge forming grooves which are parallel to each other are alternately formed, is inserted into a metal pipe, and a large number of large ridges extending parallel to each other are formed on an inner surface of the metal pipe. After alternately forming the protruding ridges and the divided ridges, a positioning groove that fits into each of the large ridges and a dividing ridge that divides each of the divided ridges into two in the width direction are further formed on the metal pipe. While passing the second plugs formed in parallel and alternately with each other and sliding the positioning groove along the large ridge, the divided ridge divides the divided ridge into two in the width direction and the adjacent large ridges are formed. Of the inner surface grooved heat transfer tube characterized in that a tubular groove having an opening width equal to or less than the bottom width is formed between the adjacent large ridges and small ridges while forming a small ridge inclined toward Production method.