JP2721755B2 - Heat transfer tube and method of manufacturing the same - Google Patents

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 suitable for use in an evaporator of a refrigerator or an air conditioner, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, heat transfer tubes developed or provided for the purpose of improving the heat exchange performance of this type of evaporator include:
The following items need to be improved from the viewpoint of improving the heat transfer performance when the refrigerant flowing in the pipe evaporates or boils. To increase the inner surface area. To increase the turbulence of the flow and lower the heat transfer resistance. Ensure that the boiling inside is active. To further improve the performance by a suitable combination of the above items.

As a heat transfer tube satisfying the above requirements, there is a tube in which a high fin is formed or a fin material is charged in the tube. For the item, there is a corrugated tube, and for the item, there is a heat transfer tube in which particles are sintered on the inner surface.

[0004]

By the way, in the above-mentioned heat transfer tube which can satisfy the requirements, the pressure loss of the refrigerant flowing in the tube becomes about 10 times as large as that of the smooth tube, and there is a problem in use.
The corrugated pipe also has a problem because the pressure loss is as large as about 5 times that of the smooth pipe.

On the other hand, a heat transfer tube obtained by sintering particles has a heat transfer performance about 5 to 10 times that of a smooth tube, but it is difficult to reduce the diameter and length, and the productivity is low and the cost is high. The disadvantage is that

In recent years, an internal grooved tube made of a combination of terms has been used in many room air conditioners and evaporators of refrigerators. It is relatively small, about twice as large, the inner area is increased by the groove to about 1.5 times that of the smooth pipe, and the groove is twisted at 5 ° to 30 ° with respect to the pipe axis, and the flow turns. This is because there is an advantage that the heat transfer performance is improved to about 2 to 3 times that of the smooth tube. Furthermore, it has been widely used because it has been manufactured by machining (centering with a drawing machine and the like) and can be made longer and smaller in diameter.

However, in order to further improve the performance of the heat pump machine in the future, it is necessary to further improve the heat transfer performance. However, the current groove shape has reached its limit, and it is necessary to increase the length and diameter of the heat pump machine. At the same time, it is said that anything that can be satisfied is never obtained.

In order to improve the heat transfer performance as described above, it is important to form a structure on the inner surface of the heat transfer tube so that boiling can occur more actively. Further, it is a main object of the present invention to provide a heat transfer tube having a novel structure capable of simultaneously increasing the length, the diameter, and the cost.

[0009]

SUMMARY OF THE INVENTION The present invention is characterized in that it has the following configuration to achieve the above object. First, the heat transfer tube according to the present invention is a heat transfer tube with an inner surface groove having a spiral groove on the inner surface, the lead angle β of the groove is in the range of 5 ° to 30 °, and the groove cross-sectional shape is substantially It has a trapezoidal shape, and a groove bottom width w, a groove depth h, and a mountain bottom width t have h ≧ 2w,
The relationship of t <w is established, and the mountain is substantially triangular in cross section with a peak angle α of 30 ° to 90 ° as a whole, and a triangular tunnel-like passage communicating with the longitudinal direction is provided inside the mountain. In addition, a slit-shaped opening intermittently provided at a predetermined interval is provided at the mountaintop in communication with the tunnel-like passage,
The opening has a width v of 0.05 to 0.15 mm and a length l of 0.05 to 0.1
In this case, the non-opening length c is 1 to 10 times the opening length l.

Next, the method for manufacturing a heat transfer tube according to the present invention is characterized in that a grooved roll or the like is pressed against a plate or a strip having excellent heat conductivity to thereby obtain a groove bottom width w, a groove depth h, and a mountain bottom width. h ≧ t during t
2w, a first step of forming a large number of grooves having a lead angle β of 5 ° to 30 ° on the surface, where a relationship of t <w is satisfied, and
By pressing a grooved roll or the like on a plate or a strip having a large number of grooves formed on the surface, the adjacent peaks are alternately approached and separated, and the peak angle α is 30 ° to 90 °, and the peak angle α is 30 ° to 90 °. The width v is 0.
A second step of forming between the grooves a mountain having a triangular cross section in which an opening of 05 to 0.15 mm is present and in which a tunnel-like passage communicating with the opening having a triangular cross section is provided. After being formed into a tube by the forming method,
And a third step of joining the butted edges by welding.

[0011]

According to the present invention, the tunnel structure as shown in FIG. 4, which is formed in a mountain having a triangular cross section and has an opening at the top of the mountain, is characterized in that all the bubbles generated when the refrigerant boils are transferred to the heat transfer surface. Without being separated from the opening, a part is held in the opening, and the state shown in FIG. 7 is exhibited, and a large degree of superheat is not required, as is clear from the relationship of “superheat degree = tube wall temperature−liquid temperature”. In addition, it exhibits high heat transfer performance.

Further, by adopting a method in which a plate is roll-formed and a pipe is formed by welding,
The length can be increased, and the diameter can be reduced by using a narrower strip.

Next, the reason for limiting the numerical value of the groove shape will be described. If the groove lead angle β is less than 5 °, when the flow rate of the refrigerant becomes large, the swirling flow cannot be obtained, so that the evaporation performance is reduced. On the other hand, when the flow angle exceeds 30 °, the pressure loss increases. When the heat transfer performance is reduced, and the walls forming both sides of the tunnel-like passage at the center of the mountain are individually roll-rolled, the tooth shape of the roll and the mountain forming the wall interfere with each other. In view of these problems, the lead angle β is set in the range of 5 ° to 30 °.

If the peak angle α is less than 30 °, when the walls forming both sides of the tunnel-shaped passage at the center of the peak are individually roll-rolled, interference occurs as described above, and forming is difficult. On the other hand, when the angle is 90 ° or more, the liquid film thickness on the mountain slope becomes thick, and the condensation performance decreases. Therefore,
The peak angle α is in the range of 30 ° to 90 °.

With respect to the size of the opening at the top of the mountain, if the width v and the length 1 are less than 0.05 mm, the internal pressure of the bubbles in the tunnel-like passage is not sufficiently increased, so that the bubbles are difficult to be discharged. On the other hand, if it exceeds 0.15 mm, the bubbles are released at a stretch, and the bubbles are separated from the inside of the tunnel-like passage so that a continuous boiling phenomenon does not occur. Therefore, the size of the top opening is v = 0.05 to 0.15 mm, l = 0.
05 to 0.15 mm.

Further, the relationship between the length 1 of the crest opening and the length c of the non-opening portion is determined by forming the opening portion and the non-opening portion by making a notch with a roll having a sawtooth-shaped groove. In the case where the cut portion is a non-opening portion and the non-cut portion is an opening, for example, what is referred to as an A type, if c / l is less than 1/1, the strength of the peak is insufficient and the pipe expansion at the time of assembling the heat exchanger. The peak is crushed during processing and the opening is closed. Also, as c / l increases, the effective numerical aperture for boiling decreases inevitably. Therefore, especially when c / l exceeds 10/1, the evaporation performance becomes about 2.5 times that of a smooth tube, and the conventional groove is used. Only the performance equivalent to that of an attached pipe can be obtained.

Further, for a type called a B type in which the cut portion is an opening and the non-cut portion is a non-opening, c /
If l is less than 1/1, the peak strength is insufficient and the peak is crushed flat by pipe expansion processing at the time of assembling the heat exchanger, and condensing performance is reduced. If c / l exceeds 10/1, the above-mentioned value is obtained. The same problem as the A type occurs. Therefore, c / l is 1/1 to 10
/ 1.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic view of a manufacturing process of a heat transfer tube with an inner surface groove according to the present invention. The heat transfer tube is made of a plate having excellent heat conductivity (1) a roll formed by winding a copper plate, for example. A feeding part (a) rotatably supported, a groove forming step (b) including a pair of grooved rolls (3) and (3) arranged vertically, a pair of ridged rolls arranged vertically ( Four),
The mountain forming step (c) consisting of (4), the opening forming step (d) consisting of a pair of notch rolls (5) and (5) also arranged up and down, A plurality of pairs of forming rolls arranged (6), (6) ……
.. And a welding step (f) for continuously welding the butted edges formed into a tubular shape by the welding machine (7).

From the feeding portion (a), for example, a width of 30 mm and a thickness
When the 0.5 mm copper plate (1) is unreeled, a pair of grooved rolls
(3), a groove with a depth h of 0.3 mm and a lead angle of 18 ° (8) and a mountain with a triangular cross-section having a peak angle α of 30 °
The groove processing of 70 grooves in which (9) is alternately arranged is performed in the groove forming step (b). FIG. 2 is a partially enlarged view of the groove-formed plate. As shown in the figure, the cross-sectional shape of the groove (8) is trapezoidal, and the groove bottom width w, the groove depth h, and the mountain bottom width t are between. h ≧ 2w,
The relationship of t <w holds.

Next, it is sent to a mountain forming step (c), and is passed between a pair of mountain-matching rolls (4), (4) to form an adjacent mountain
As shown in FIG. 3, a gap (11) having an opening width v of 0.05 to 0.15 mm is formed at the top of the mountain by bringing the (9) and (9) closer to each other, and at the same time, the gap (11) communicates with the gap (11). A tunnel-like passage (10) sandwiched between the mountains (9), (9) extends in the longitudinal direction and is formed.

Subsequently, it is sent to the opening forming step (d),
A pair of notching rolls (5), (5) having serrated grooves are cut in the crest at the gap (11) in the lead direction opposite to the groove (8), as shown in FIG. The material of the notched portion is deformed to form a waveform of the A type structure in which the groove top is closed.

In this step (d), a tunnel-like passage (10) having alternately closed portions and openings at the peak can be formed in the peak.

Next, the plate (1) processed as described above is guided to the forming rolls (6), (6),... In the tube forming step (e), and the surface having the peaks and grooves is formed on the inner surface. In order to form a pipe with a predetermined diameter, the pipe is bent into a pipe of a predetermined diameter in the order from the both edges, and the butted edges are subjected to high-frequency resistance welding by a welding machine (7) in the next welding step (f), and heat-transfer tubes with internal grooves are formed. To finish.

According to the above-mentioned manufacturing process and procedure, a heat-transfer copper pipe having a diameter of 9.52 mm as shown in Table 1 was manufactured, and together with a conventional trapezoidal grooved copper pipe and a smooth copper pipe, the evaporation performance (Eva. )
And a comparison of the condensation performance (Cond.).
Table 1 also shows the results. As is clear from Table 1, the heat transfer copper tube according to the present invention has an evaporating performance (Eva.).
And the condensing performance (Cond.) Was excellent.

In the above performance test, a pipe having a length of 5000 mm and Freon R-22 as a refrigerant were used, and a refrigerant was flowed into the pipe.
The tube inner film heat transfer performance was investigated under the conditions of a flow rate of 50 kg / hr, an evaporation temperature of 7 ° C, and an outlet superheat of 5 ° C.

In the tube specifications in Table 1, β is the lead angle of the groove, α is the peak angle, v is the width of the opening, l is the length of the opening, c is the length of the non-opening, h indicates the groove depth. Also N
o.25 is an inner smooth tube. The determination is made in Eva. 3.0 or more and Cond. If the value is 2.2 or more, ○, Eva. And Cond. The case where either one or both of them is equal to or less than the above value is defined as Δ.

[0027]

[Table 1]

Separately from the example described above, the peaks (9), (9) adjacent to each other are brought closer together by the forming roll (12) shown in FIG. It is also possible to produce a grooved tube (see FIG. 6) in which an opening is formed in the head by forming a portion, and the width v and the length l of the opening are both 0.05 to 0.15 mm, It is important that the non-opening portion length c is 1 to 10 times the length l.

[0029]

As described above, the heat transfer tube of the present invention having a large number of tunnel structures having slit-shaped intermittently arranged openings on the inner wall of the tube does not require a large degree of superheat at the time of refrigerant boiling. And high heat transfer characteristics.

Further, since the plate is processed and formed into a tube by welding, the diameter can be reduced and the length can be increased. Further, the tube can be formed continuously and in mass production, and a low-cost heat transfer tube can be easily obtained. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic view of a manufacturing process of a heat transfer tube according to an embodiment of the present invention.

FIG. 2 is a partially enlarged perspective view of an intermediate product in a groove forming step of FIG. 1;

FIG. 3 is a partially enlarged perspective view of an intermediate product in a mountain forming step of FIG. 1;

FIG. 4 is a partially enlarged perspective view of the inner wall of the heat transfer tube of the embodiment according to the present invention.

FIG. 5 is a partially enlarged cross-sectional view of an intermediate product in an opening forming step according to another embodiment of the present invention.

FIG. 6 is a partially enlarged perspective view of an inner wall of a heat transfer tube obtained by another embodiment according to the present invention.

FIG. 7 is an enlarged cross-sectional view for explaining a boiling state on a tube wall of the heat transfer tube of the present invention.

[Description of Signs] 1: Plate 2: Roll 3: Grooved Roll 4: Crest Roll 5: Notch Roll 6: Forming Roll 7: Welding Machine 8: Groove 9: Crest 10: Tunnel-like Passage 11: Gap Feeding part B: Groove forming process C: Mountain forming process D: Opening forming process E: Tube forming process F: Welding process α: Peak width w: Groove bottom width h: Groove depth t: Mountain bottom width v: Opening portion Width l: Length of opening c: Length of non-opening β: Lead angle of groove

Claims (2)

(57) [Claims] An internally grooved heat transfer tube having a spiral groove on an inner surface, wherein a lead angle β of the groove is in a range of 5 ° to 30 °, and a groove cross-sectional shape is substantially trapezoidal. The relationship h ≧ 2w, t <w is established among the bottom width w, the groove depth h, and the mountain bottom width t, and the mountain has a peak angle α of substantially 30 ° to 90 ° as a whole.
A triangular tunnel-like passage having a triangular cross-section and communicating with the longitudinal direction inside the mountain is provided, and a slit-shaped opening intermittently interrupted at a predetermined interval communicates with the tunnel-like passage at the top of the mountain. And the opening has a width v.
A heat transfer tube, wherein the heat transfer tube has a length of 0.05 to 0.15 mm and a length 1 in a range of 0.05 to 0.15 mm, and a non-opening length c is 1 to 10 times the opening length l. 2. A grooved roll w, a groove depth h, and a crest width t are pressed by pressing a grooved roll or the like against a plate or strip having excellent thermal conductivity.
A first step of forming on the surface a number of grooves having a relationship of h ≧ 2w and t <w, and a lead angle β of the grooves of 5 ° to 30 °; By pressing a grooved roll or the like on the formed plate or strip, adjacent peaks are alternately approached and separated, the peak angle α is 30 ° to 90 °, and the width v at the peak is 0.05 to 0.15 mm. A second step of forming between the grooves a triangular section having a triangular cross-section in which a tunnel-like passage communicating with the opening is provided, and then forming a tubular shape by a roll forming method. And a third step of welding the butted edges together by welding after the deformation.