JP2749673B2 - Heat transfer tube and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer tube having excellent heat transfer performance used for a heat exchanger for a refrigerator, an air conditioner, and the like, and a method for manufacturing the same.

[Conventional technology and its problems]

In general, heat transfer tubes used in air conditioners and refrigerators exchange heat between fluid flowing outside the tubes by evaporating or condensing refrigerant such as freon inside the tubes. From the viewpoint of energy saving, the use of internally grooved tubes is increasing. This inner grooved tube is a tube in which a triangular or trapezoidal groove with a fine cross section is formed linearly or spirally along the tube axis in the tube. Heat transfer performance can be improved by the action.

In recent years, there has been a strong demand for heat exchangers for air conditioners to have higher performance and smaller size and lighter weight, and with the spread of heat pump type air conditioners, higher performance has been demanded for heat transfer tubes. However, although the number of grooves, the lead angle, the shape of the grooves, and the like have been improved in the conventional inner grooved pipe, there is a limit to the performance improvement.

Therefore, instead of these conventional inner grooved tubes, a heat transfer tube in which a first groove is formed on the heat transfer surface and second grooves that are parallel to each other and intersect at a predetermined angle (see Japanese Patent Application Laid-Open No. -15015)
And inner cross grooved pipe (Japanese Patent Application Laid-Open No. 58-83189,
-150799). These heat transfer tubes improve the heat transfer performance by promoting the nucleate boiling during evaporation by making the inner wall surface finer.

However, heat exchangers using these heat transfer tubes exhibit high heat transfer characteristics at the start of use, but as the use time increases, the performance gradually deteriorates due to the attachment of dirt such as refrigerating machine oil on the miniaturized inner wall surface. There was a problem to do.

[Problems to be solved by the invention]

As a result of studying the above problems, the present invention has developed a heat transfer tube and a method of manufacturing the heat transfer tube, which have less adhesion of refrigerating machine oil and other dirt in the groove of the inner wall even during long-term use, and prevent a decrease in heat transfer performance. It was done.

[Means and actions for solving the problem]

The present invention is a heat transfer tube having a plurality of fine and linear or spiral fine lines along the longitudinal direction on the inner surface of the tube, and a ridge and a groove having a triangular or trapezoidal cross section with respect to the tube axis, wherein the ridge is It consists of independent ridges having a predetermined length in the longitudinal direction, and each ridge is formed so as to be parallel to or adjacent to the width direction of the adjacent ridge and have a deviation from each other at a predetermined angle. The heat transfer tube according to claim 1, wherein the heat transfer tube according to claim 1 is characterized in that a large number of cross grooves intersecting the misaligned portion of the peak portion are formed. The heat transfer tube according to claim 1 or 2, wherein the ratio of the shift amount S to the length P is S / P ≧ 0.02, wherein the tube is reduced in diameter by a floating plug and a die, Subsequently, a first groove is formed in the pipe by a first grooved plug and a rolling roller. After forming the ridge at the depth and then crushing the ridges separated by the first groove by the second grooved plug and the rolling roller with the second groove, the diameter is reduced at a predetermined diameter reduction rate. 4. A method for manufacturing a heat transfer tube according to claim 1, wherein a cross groove intersecting a deviation portion of the peak is formed. The method according to claim 1, wherein the metal strip is supplied to a rolling mill having a smooth roll to form grooves or ridges on the surface of the metal strip, and the metal strip is formed into a tubular shape by a forming roll, and then the seam is welded. A method of manufacturing a heat transfer tube according to claim 2, 2 or 3.

That is, according to the present invention, as shown in an enlarged perspective view in which a part of the heat transfer tube is developed in FIG. 1, a fine groove portion (2) and a mountain portion (3) are formed on the inner surface of the heat transfer tube (1). The ridges are independent ridges having a predetermined length (P) in the length direction and being separated by a cross-section (4). Parts (3), (3 '),
(3 ″) is formed so as to have a deviation portion (S) mutually parallel or at a predetermined angle to the width direction of the peak portion.

It is preferable that the ratio of the shift amount S of the shift portion (S) to the length (P) of the peak portion is S / P ≧ 0.02,
If it is smaller than this, the effect of giving a turbulent flow to the refrigerant liquid is small.

FIG. 2 shows a case where the S / P is large, and the peak (3 ') closes the groove (2). This heat transfer tube also has a turbulent flow effect.

Further, as another example of the present invention, as shown in FIG. 3, a cross groove (5) intersecting with the peak is formed in a shift (S) between the peaks (3), (3 ') and (3 "). ) Is a heat transfer tube in which a large number of) are formed.

In these heat transfer tubes, for example, a turbulent flow in which the flow of the refrigerant liquid in the groove (2) collides with one side of the ridge (3) to disturb the flow by forming the ridge with a deviation as shown in FIG. A part (6) is formed, and on the other side, a holding part (7) is formed to stagnate the liquid with respect to the flow to form a liquid film distribution in the groove part to promote the condensation and evaporation of the liquid. This is to improve the heat transfer performance.

Further, the cross groove which intersects with the misaligned portion of the peak shown in FIG. 3 is attached to the above-mentioned misaligned portion by the turbulent flow action together with the condensation and evaporation due to the increase of the surface area due to the cross groove. This has the effect of removing refrigerating machine oil and dirt, thereby preventing performance degradation.

 Next, the manufacturing method of the present invention will be described.

FIG. 5 is a cross-sectional view of an apparatus for manufacturing a heat transfer tube having a ridge having a deviation portion on the inner surface of the tube and a cross groove intersecting the ridge. First, the copper tube (11) is reduced in diameter using a diameter reducing die (12) and a floating plug (13), and then held in a fixed position in the tube by a floating plug via a connecting rod (14). A first grooved plug (15) having a groove having a lead angle and a plurality of first rolling rollers (17) pressing the tube while revolving from outside the tube at a position facing the first grooved plug. And a first groove having a straight or predetermined lead angle and a predetermined groove depth is formed in the pipe. Next, a second grooved plug (16) having a lead angle opposite to that of the first grooved plug and a second rolling roller (18) are used.
A cross groove having a predetermined number of grooves, a lead angle, and a groove depth is formed so as to crush the first groove.

Next, the above-mentioned tube is successively reduced in diameter at a predetermined diameter reduction ratio by a diameter reduction die (19) in order to give a deviation amount, whereby the peak portion is divided by a cross groove, and as shown in FIG. A heat transfer tube in which a number of cross grooves (5) intersecting the misaligned portions are obtained.

In this case, the deviation amount S is equal to the depth Hmm of the first groove. Related to The relationship is as shown in FIG. That is, the greater the depth of the first groove, the greater the amount of displacement. By applying this relationship, it is possible to manufacture a heat transfer tube having crossed cross grooves having a predetermined shift amount. Further, as another manufacturing method of the present invention, there is a method shown in FIGS.

In this method, first, as shown in FIG.
1) is formed by a flat roll (70) at a position facing a grooved roll (71) having a predetermined lead angle and a groove depth on the surface. At this time, as shown in FIG. 8, the grooved roll is formed by joining a plurality of grooved rolls (93) having a groove (2) and a ridge (3) with a deviation in the groove and joining them. Good. After forming peaks and grooves having a certain deviation on the surface of the strip in this way, the strip is inserted into a group of forming rolls (80 to 87) as shown in FIG. The heat transfer tube (1) is welded.

By this method, heat transfer tubes having various inner surface shapes as shown in FIGS. 1, 2 and 3 can be manufactured. (90) and (91) are squeeze rolls, and (92) is an induction coil.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described.

Example 1 A tube was formed from a grooved strip shown in FIGS. 7 to 9 by a forming roll using a forming roll, and the outer diameter was 9.53 mm by a method of welding the joint.
Heat transfer tubes having various deviation amounts S with 60 grooves and a lead angle of 18 ° were produced. This tube and outer diameter 9.53mm, number of grooves 60, lead angle 18
° A conventional heat transfer tube with a peak height of 0.20 mm without displacement was assembled in a double tube heat exchanger, and the heat transfer characteristics were measured. The result is the tenth
Shown in the figure. As is clear from the figure, the conventional heat transfer tube has an up ratio of 0, but the tube having the deviation portion of the present invention evaporates when the ratio S / P of the deviation amount S to the peak length P is 0.02 or more,
It can be seen that all of the condensation properties are significantly improved.
If the evaporation characteristic exceeds 0.3, the up ratio tends to decrease.

Example 2 Using a grooved plug and a rolling roll shown in FIG. 5, first, a copper pipe (11) was reduced in diameter to 12.7 mmφ by a reduced diameter die (12) and a floating plug (13), and then reduced. The number of grooves is 60 with the first grooved plug (15) and the first roll (17).
A groove having a lead angle (left-handed twist) of 18 ° and a groove depth of 0.3 mm is formed, and then the first groove is crushed by a second grooved plug (16) and a second rolling roller, so that the number of grooves is 60, A tube having a cross groove with an outer diameter of 11 mmφ with a groove having a lead angle (right twist) of 18 ° and a groove depth of 0.20 mm was obtained. Subsequently, the diameter was reduced to 9.53 mm (diameter reduction rate: 0.13) by a diameter reducing die (19),
As shown in the figure, a heat transfer tube having a displacement amount S of 0.05 mm and a large number of cross grooves (5) formed in the displacement portion of the peak was obtained. This heat transfer tube and a conventional cross-grooved tube having no deviation were assembled in a double-tube heat exchanger, and a refrigerant was flowed in the tube, and the heat transfer coefficient was measured every unit time. The result is shown in FIG. From this result, the heat transfer coefficient of the conventional cross-grooved tube having a displacement amount of 0 decreases with time, whereas the heat transfer tube having the displacement portion of the present invention has a significantly small decrease in the heat transfer coefficient. It is clear that a decrease in heat transfer performance due to contamination of the refrigerator oil or the like can be prevented.

〔effect〕

As described above, according to the present invention, the evaporation and condensation performance can be significantly improved as compared with the conventional inner grooved pipe, and the heat transfer performance due to refrigerating machine oil and dirt can be improved over a long period of use. A heat transfer tube capable of preventing the drop is obtained, which has an industrially remarkable effect.

[Brief description of the drawings]

1 to 3 are partially enlarged exploded perspective views showing an example of a heat transfer tube according to the present invention, FIG. 4 is a partially enlarged developed view of a heat transfer tube for illustrating the operation of the present invention, and FIG. FIG. 6 is a cross-sectional view showing an example of an apparatus used in the method for manufacturing a heat transfer tube according to the present invention. FIG. 6 is a diagram showing the relationship between the amount of displacement and the diameter reduction ratio of the heat transfer tube according to the present invention. FIG. 8 is a perspective view for explaining another method of manufacturing the heat transfer tube according to the present invention, FIG. 8 is a side view of the grooved roll of FIG. 7, and FIG. 10 shows the heat transfer performance of the heat transfer tube according to the present invention. FIG. 11 is a diagram showing the relationship between the heat transfer coefficient and the use time of the heat transfer tube according to the present invention. 1 ... heat transfer tube, 2 ... groove, 3, 3 ', 3 "... mountain, 4 ...
… Partition section, 5… cross groove.

Claims (5)

(57) [Claims] 1. A heat transfer tube having a plurality of fine and linear helical shapes along the longitudinal direction on the inner surface of the tube, and a peak and a groove having a triangular or trapezoidal cross section with respect to the tube axis. The portions are composed of independent ridges having a predetermined length in the longitudinal direction, and each ridge is formed so as to be parallel to or adjacent to the width direction of the adjacent ridges at a predetermined angle and to be displaced from each other. A heat transfer tube, characterized in that: 2. The heat transfer tube according to claim 1, wherein a large number of cross grooves intersecting the misaligned portions of the peaks are formed. 3. The ratio of the shift amount S to the peak length P is S / P.
The heat transfer tube according to claim 1, wherein ≧ 0.02. 4. A pipe is reduced in diameter by a floating plug and a die, and a first groove is formed in the pipe to a predetermined groove depth by a first grooved plug and a rolling roller, and then a second groove is formed. After the ridge separated by the first groove is crushed by the second groove by the attached plug and the rolling roller, the diameter is reduced at a predetermined reduction ratio to form a cross groove intersecting the misaligned portion of the ridge. The method for manufacturing a heat transfer tube according to claim 1, 2, or 3. 5. A metal strip is supplied to a rolling mill having a grooved roll having grooves or ridges around it and a smoothing roll to form grooves or ridges on the surface of the metal strip, and the metal strip is formed into a tube by a forming roll. The method for manufacturing a heat transfer tube according to claim 1, wherein the seam is welded after being formed into a strip.