JPH112498A - Heat transfer pipe with inner face groove and manufacture of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote refrigerant boiling and refrigerant stirring by changing fin pattern regularly along a circumferential direction and a lengthwise direction of a pipe and providing either one of a network cross-fin part, a strip fin part and a strip flat part in the lengthwise direction of the pipe. SOLUTION: A fin pattern comprises an inclined fin part 10 and a network cross-fin part 20 and the inclined fin part 10 is formed in such a manner that fins 11 are arranged with lead angles of β1 and β2 regularly and alternately changed one after another at a predetermined pitch P1 in a circumferential direction of a pipe and the network cross-fin part 20 is formed in an alignment with the circumferential direction. A pitch P2 is formed by the inclined fin part 10 and the network cross-fin part 20. Refrigerant flowing from the inclined fin part 10 causes turbulent flow to promote boiling so that heat transfer characteristic is enhanced. This network cross-fin part promotes boiling of the refrigerant and the strip fin part and the strip flat part enhance refrigerant stirring further.

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 having an inner surface groove, which is used in a heat exchanger for air conditioning and has greatly improved both the condensation performance and the evaporation performance.

[0002]

2. Description of the Related Art In a heat exchanger of an air conditioner or the like, a heat transfer tube having a spiral groove formed on an inner surface thereof is used as a heat transfer tube for evaporating or condensing a refrigerant. Conventionally, this inner grooved heat transfer tube is a drawing method in which a grooved plug is held in a tube having a smooth inner surface, the tube outer surface is pulled out while being pressed with a rolling tool, and the groove of the grooved plug is transferred to the tube inner surface. Had been manufactured. The fin pattern on the inner surface of the tube formed by this drawing method was a monotonous one in which the fin 11 was formed in one direction, as shown in a developed view in FIG. On the other hand, in recent years, fins have been formed on the surface of a metal strip by rolling, and the metal strip is rolled into a tubular body with the fin forming surface inside, and the butted end face of the tubular body is a high-frequency welding machine. For example, a rolling welding method of welding by using a method such as that described above has been adopted.
In this rolling welding method, the fins are formed by rolling, so that the pattern of the fins 11 can be formed in a complicated manner as shown in FIG. 17, and the resulting heat transfer tube has higher heat transfer characteristics than that obtained by the drawing method, The processing speed is faster and the productivity is higher than the method. In this rolling welding method, various fin patterns have been proposed for the purpose of improving heat transfer characteristics. For example, an offset fin is provided in a pipe, and a new concentration boundary layer is developed from the tip thereof to reduce diffusion resistance and realize a high heat transfer coefficient to a non-azeotropic mixed refrigerant (Japanese Patent Laid-Open No. Hei 8-210730). . A fin having an apex angle of 30 ° or less, which is difficult to manufacture by the drawing method (JP-A-8-52)
78). Japanese Patent Application Laid-Open No. 4-158193 discloses a technique in which the fin flow angle is changed in a direction perpendicular to the tube axis so that the refrigerant flows in two directions to enhance the turbulent flow effect.

[0003]

However, each of the above methods has the following problems. That is, the method is effective for a non-azeotropic mixed refrigerant such as R407C, but the pseudo-azeotropic refrigerant such as R410A which is promising for room air conditioners does not have a concentration boundary layer, so that the evaporation performance is improved. However, the condensation performance is not improved. In the method described above, it is not possible to expect a dramatic improvement in both the performance of evaporation and condensation. In the method (1), since there is no region for promoting the boiling of the refrigerant, the evaporation performance is not improved. An object of the present invention is to provide a heat transfer tube with an inner surface groove in which both the condensation performance and the evaporation performance are significantly improved, and a method for manufacturing the same.

[0004]

According to the first aspect of the present invention,
An inner grooved heat transfer tube in which a number of fins are formed in a predetermined pattern on an inner surface, wherein the fin pattern includes at least one of a fin lead angle, a fin apex angle, and a fin pitch in a circumferential direction of the tube and in a direction of the tube. At least one of a mesh-like cross fin portion, a band-like fin portion, and a band-like flat portion is provided at a predetermined position in the length direction of the tube of the fin pattern, which is formed so as to change regularly in the length direction. It is a heat transfer tube with an inner surface groove characterized by being made.

[0005] According to a second aspect of the invention, characterized in that the pitch P ₂ of the pitch P ₁ to the length direction of the circumferential direction of the regular change of fin patterns following each (1), thereby satisfying the expression (2) The heat transfer tube with an inner surface groove according to claim 1. (L / 16) ≦ P ₁ ≦ (L / 4) (1) (2 × L) ≦ P ₂ ≦ (18 × L) (2) where L is a heat transfer tube with an inner surface groove. Circumference length.

According to a third aspect of the present invention, there is provided a grooved combination roll and a flat roll formed by combining a plurality of divided rolls each having a predetermined groove pattern formed on an outer peripheral surface of a metal strip fed in a predetermined direction. Forming a predetermined fin pattern on one surface of the metal strip by pressing the metal strip in between, and forming the metal strip into a tubular body by rolling the metal strip in the width direction with the fin pattern forming surface inside. In the method for manufacturing an inner surface grooved heat transfer tube including a step of welding a butt end face of the tubular body, a groove pattern is different between adjacent split rolls of the split rolls constituting the grooved combination roll, 3. The heat transfer tube with an inner groove according to claim 1 or 2, wherein any one of a mesh-like groove, a band-like groove, and a band-like flat portion is provided at a predetermined location with consistency between adjacent split rolls. It is a method.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a mesh-like cross fin portion provided at a predetermined position on the inner surface of a tube promotes boiling of a refrigerant, and a band-like fin portion and a band-like flat portion further improve refrigerant stirring. By combining two or more of the mesh-like cross fin portions, the band-like fin portions, and the band-like flat portions, the evaporation performance is dramatically improved. In the present invention, the lead angle, apex angle, pitch, etc. of the fins can be set arbitrarily.

Hereinafter, the shape of the fin pattern formed on the heat transfer tube of the present invention will be described with reference to the drawings. 1A and 1B are a developed perspective view and a developed plan view, respectively, showing a first example of a fin pattern of the heat transfer tube of the present invention. The fin pattern is formed from the inclined fin portion 10 and the mesh-like cross fin portion 20, the inclined fin portion 10 that lead angle is ₂ beta ₁ and beta in the circumferential direction of the fins 11 is the tube at predetermined pitches P ₁ It is formed so as to change regularly, and the mesh-like cross fin portions 20 are provided so as to be aligned in the circumferential direction. Pitch P ₂ in the longitudinal direction is composed of the inclined fin portion 10 and the mesh-like cross fin portion 20. The refrigerant flowing from the inclined fin section 10 is
Turbulence is generated in the mesh-like cross fin portion 20 to promote boiling and improve heat transfer characteristics.

FIG. 2 is a developed plan view showing a second example of the fin pattern of the heat transfer tube of the present invention. This fin pattern is the same as that shown in FIG. 1 except that a band-like fin portion 21 is provided instead of the mesh-like cross fin portion, and the refrigerant flowing from the inclined fin portion 10 is Boiling is promoted by stirring, and heat transfer characteristics are improved.

FIG. 3 is a developed plan view showing a third example of the fin pattern of the heat transfer tube of the present invention. This fin pattern is the same as that shown in FIG. 1 except that a band-shaped flat portion 22 is provided instead of the mesh-shaped cross fin portion, and the refrigerant flowing from the inclined fin portion 10 is the band-shaped flat portion 22. Boiling is promoted by stirring, and heat transfer characteristics are improved.

[0011] In the present invention, each pitch P ₂ of the pitch P ₁ to the length direction of the circumferential direction of the regular change of fin patterns following (1), it is desirable to satisfy the expression (2). (L / 16) ≦ P ₁ ≦ (L / 4) (1) (2 × L) ≦ P ₂ ≦ (18 × L) (2) where L is a heat transfer tube with an inner surface groove. Circumference length. The reason is that the P ₁ is processed easily chipping of grooved rolls in the rolling occurs is difficult is less than L / 16. The stirring of the refrigerant in the inclined fin portion pitch P ₁ is greater than L / 4 is not sufficient. The pitch P ₂ is less than 2 × L, evaporation performance too wide an area, such as contributing reticulated cross fin portion is because the condensation performance with it relatively lowered, the pitch P ₂ is a 18 × L If it exceeds, the mesh-like cross fin portion contributing to the evaporation performance is reduced, and the evaporation performance is reduced.

Next, the grooved combination roll used for manufacturing the heat transfer tube of the present invention by the rolling welding method will be described. FIG. 4 shows the first combination roll with grooves used in the present invention.
It is a front view which shows the example of. This grooved combination roll 30
Is formed by alternately arranging two divided rolls 32 each having an inclined groove 31 having a lead angle of β ₁ or β _{2 with} a narrow flat roll 33 interposed therebetween. A mesh-like groove portion 34 is provided at a location in parallel with the roll axis, with consistency between adjacent split rolls 32. The fin pattern shown in FIG. 1 is formed by the grooved combination roll 30.

FIG. 5 is a front view showing a second example of the grooved combination roll used in the present invention. In the grooved combination roll 40, a band-shaped groove portion 44 is provided in a predetermined position of each divided roll 42 in a straight line parallel to the roll axis. The fin pattern shown in FIG. 2 is formed by the grooved combination roll.

FIG. 6 is a front view showing a third example of the grooved combination roll used in the present invention. In the grooved combination roll 50, a band-shaped flat portion 54 is provided in a predetermined position of each divided roll 52 in a straight line parallel to the roll axis. The grooved combination roll 50 forms the fin pattern shown in FIG.

[0015]

The present invention will be described in more detail with reference to the following examples.
You. (Example 1) Deoxidized copper strip (thickness 0.5 mm, width 20 mm)
From a grooved combination roll (see Fig. 4) and a flat roll.
Rolled by a two-high rolling mill, and the surface shown in FIG.
Pattern (height 0.2 mm, vertex angle 30 °)
Was. The lead angle of the groove of the grooved combination roll is β₁= 2
0 ゜, β_Two= −20 °. For the width direction of the strip
P at which pattern (lead angle) changes₁Is 5mm
(L (20mm) / 4), and the fin lead angle is the length direction of the strip.
Pitch P changing to _TwoIs 180mm (9 × L (20mm))
did.

(Comparative Example 1) A heat transfer tube (seamless tube) having an inner surface groove having a fin pattern shown in FIG. 16 was manufactured by a drawing method. Further, a heat transfer tube having an inner surface groove having a fin pattern shown in FIG. 17 was produced by a rolling welding method. Here, the fin lead angle of the heat transfer tube of FIG. 16 is 20 °, the fin height is 0.2 mm,
The apex angle was 30 °. The fin lead angles of the heat transfer tube of FIG. 17 are β ₁ = 20 ° and β ₂ = −20 °, and the pitch at which the fin lead angle changes in the strip width direction is L / 4 (= 5 mm).

The condensation performance and evaporation performance of the three types of heat transfer tubes were measured and evaluated by changing the flow rate of the refrigerant in various ways. The condensing performance (condensation heat transfer coefficient in the tube) was measured using a measuring device in which the test section was a double tube consisting of an inner tube and an outer tube, and an inner grooved heat transfer tube was set as the inner tube. A coolant was flowed in a pressurized state, a predetermined amount of cooling water was allowed to flow through the outer tube, and the temperature of the cooling water was measured and evaluated. Evaporation performance (in-pipe evaporation heat transfer coefficient) was measured using a similar measuring device, by flowing a refrigerant under reduced pressure into the inner grooved heat transfer pipe as the inner pipe, flowing cooling water through the outer pipe, and flowing the cooling water. The falling temperature was measured and evaluated.

FIG. 7 shows the results of the condensation performance. As is clear from FIG. 7, the condensation performance (curve a ₁ ) of the sample of the present invention is the highest at all refrigerant flow velocities, and the condensation performance (curve b ₁ ) of the fin pattern heat transfer tube shown in FIG. The order of the condensation performance (curve b ₂ ) of the heat transfer tubes having the fin pattern shown in FIG. When the refrigerant flow rate is 300 (kg / m ² s), the condensation performance ratio of the curves a ₁ , b ₁ , and b ₂ is approximately 24:16:
It is 10.

FIG. 8 shows the results of the evaporation performance. As is clear from FIG. 8, the evaporation performance (curve a ₁ ) of the sample of the present invention is the highest at all the refrigerant flow velocities, and the evaporation performance (curve b ₁ ) of the heat transfer tube having the fin pattern shown in FIG. The order of the evaporation performance (curve b ₂ ) of the heat transfer tube having the fin pattern shown in FIG.
Curves a ₁ and b at a refrigerant flow rate of 300 (kg / m ² s)
_1, b ₂ of the condensation performance ratio is approximately 18:13:10.

[0020] The heat transfer tube of fins pattern used in Example 2 following Example 1, effects on condensation performance and evaporation performance of the pitch P ₁ in the circumferential direction of the tube fins lead angle changes regularly investigated. The condensation performance and the evaporation performance were measured in the same manner as in Example 1. Pitch P ₁ is L / 2
The range was changed from 0 to L / 2. Pitch in length direction P ₂
Is 180 mm (9 × L) and the refrigerant flow rate is 200 (kg /
m ² s). The results are shown in FIGS.

The condensation performance As is clear from Figure 9 the pitch P ₁ is up to L / 4 showed high values, greatly reduced when more than L / 4. The evaporation performance, pitch P ₁ As is clear from FIG. 10 decreases and increases beyond the L / 4. When the pitch P ₁ is chipping is likely to occur machining grooved roll during rolling and smaller than L / 16 to consider that the difficulty, the pitch P ₁ is L / 16 ≦ P ₁ ≦ L
A range of / 4 is desirable.

[0022] The heat transfer tube of fins pattern used in Example 3 following examples 1, effect on the condensation performance and evaporation performance of the pitch P ₂ in the length direction of the tube fins lead angle changes regularly investigated. The condensation performance and the evaporation performance were measured in the same manner as in Example 1. The pitch P ₂ was varied in the range of L~20 × L. Incidentally, in the circumferential direction of the pitch P ₁ is 5mm (L / 4), the refrigerant flow rate 200 (k
g / m ² s). The results are shown in FIGS.

As is apparent from FIGS. 11 and 12, the condensing performance was remarkably improved when the pitch P ₂ was larger than 2 × L.
This is because if the pitch P ₂ is smaller than 2 × L, the area of the mesh-like cross fins contributing to the evaporation performance is widened and the condensation performance is relatively reduced. Condensing performance is 1 pitch P ₂
High values were maintained even where the value was greater than 3 × L. On the other hand, the evaporating performance maintained a substantially constant high value up to 7 × L, and then decreased little by little, and suddenly decreased when it exceeded 18 × L. This is because the area of the mesh cross fins that contributes to the evaporation performance has become too narrow. For this reason, the pitch P ₂ is desirably in the range of (2 × L) ≦ P ₂ ≦ (18 × L) mm.

Example 4 Condensing performance and evaporating performance of the heat transfer tube having the fin pattern shown in FIG. 2 or 3 were measured in the same manner as in Example 1. The results are shown in FIGS. 13 and 14 also show the results of Example 1 and Comparative Example 1. As is clear from FIGS. 13 and 14, the products a ₁ , a
_2, a ₃ are all comparative examples are significantly higher performance than the (conventional). Among the products a ₁ , a ₂ , and a ₃ of the present invention, the performance of the heat transfer tube a ₃ provided with the band-shaped fin portion was the highest, and the other two products had almost the same performance.

(Example 5) The evaporating pressure loss in the tubes was measured for the heat transfer tubes of Examples a ₁ , a ₂ and a ₃ of the present invention used in Examples 1 and 4. The results are shown in FIG. As is clear from FIG. 15, the heat transfer tube of the present invention product a ₂ is particularly low pressure loss, in which can best reduce the burden of the compressor when incorporated in an actual machine.

[0026]

As described above, in the heat transfer tube with an inner groove according to the present invention, the fin pattern changes regularly in the circumferential direction and the length direction of the tube, and at a predetermined position in the length direction of the tube. Is provided with any one of a mesh-like cross fin portion, a band-like fin portion, and a band-like flat portion, so that the boiling of the refrigerant or the stirring of the refrigerant is promoted, and both the condensation performance and the evaporation performance are greatly improved. The internally grooved heat transfer tube of the present invention can be easily manufactured by a rolling welding method. Therefore, an industrially remarkable effect is achieved.

[Brief description of the drawings]

FIG. 1 is a developed perspective view (a) and a developed plan view (b) showing a first example of a fin pattern of the heat transfer tube of the present invention.
It is.

FIG. 2 is a developed plan view showing a second example of the fin pattern of the heat transfer tube of the present invention.

FIG. 3 is a developed plan view showing a third example of the fin pattern of the heat transfer tube of the present invention.

FIG. 4 is a front view showing a first example of a grooved combination roll used in the present invention.

FIG. 5 is a front view showing a second example of the grooved combination roll used in the present invention.

FIG. 6 is a front view showing a third example of a grooved combination roll used in the present invention.

FIG. 7 is a comparison diagram of the condensation performance of the heat transfer tube of the present invention and a conventional heat transfer tube.

FIG. 8 is a comparison diagram of the evaporation performance of the heat transfer tube of the present invention and a conventional heat transfer tube.

FIG. 9 is a relationship diagram of the pitch P ₁ and the condensing performance.

FIG. 10 is a relationship diagram of the pitch P ₁ and the evaporation performance.

FIG. 11 is a relationship diagram of the pitch P ₂ and the condensing performance.

FIG. 12 is a relationship diagram of the pitch P ₂ and the evaporation performance.

FIG. 13 is a comparison diagram of the condensation performance of the heat transfer tube of the present invention.

FIG. 14 is a view showing the evaporation performance of the heat transfer tube of the present invention.

FIG. 15 is a comparison diagram of evaporating pressure loss in the heat transfer tube of the present invention.

FIG. 16 is a development view of a fin pattern on the inner surface of the tube formed by a drawing method.

FIG. 17 is a developed view of a fin pattern on the inner surface of the pipe formed by the rolling welding method.

[Explanation of symbols]

10: inclined fins 11: fins 20: mesh-like cross fins 21: band-like fins 22: band-like flat parts 32: split roll β ₁ … lead angle of fin (groove) β ₂ … fin ( Groove) lead angle

Claims (3)

[Claims] 1. A heat transfer tube having an inner surface having a plurality of fins formed in a predetermined pattern on an inner surface, wherein the fin pattern includes at least one of a fin lead angle, a fin vertex angle, and a fin pitch. It is formed by changing regularly in the circumferential direction and the length direction of the tube, and at a predetermined position in the length direction of the tube of the fin pattern, a mesh-like cross fin portion, a band-like fin portion, and a band-like flat portion. Characterized in that at least one of the heat transfer tubes is provided. 2. A circumferential regular change of fin pattern pitch P ₁ and a length-direction pitch P ₂ respectively below (1), according to claim 1, characterized by satisfying the expression (2)
The heat transfer tube with an inner surface groove as described. (L / 16) ≦ P ₁ ≦ (L / 4) (1) (2 × L) ≦ P ₂ ≦ (18 × L) (2) where L is a heat transfer tube with an inner surface groove. Circumference length. 3. A metal strip which is fed in a fixed direction is sandwiched between a grooved combination roll formed by combining a plurality of divided rolls each having a predetermined groove pattern formed on an outer peripheral surface thereof and a plane roll. Forming a predetermined fin pattern on one side of the metal strip by pressing, forming the metal strip into a tubular body by rolling the metal strip in the width direction with the fin pattern forming surface inside, and projecting the tubular body. In the method for manufacturing an inner surface grooved heat transfer tube including a step of welding a mating end face, a groove pattern is different between adjacent split rolls of a split roll constituting a grooved combination roll, and a mesh-shaped groove portion is provided at a predetermined position of the split roll. 3. The method according to claim 1, wherein any one of the band-shaped groove portion and the band-shaped flat portion is provided between adjacent divided rolls with consistency.