JP2002181478A - Heat transfer tube having grooved inner surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat transfer tube having grooved inner surface improved in the rate of heat transfer with condensation. SOLUTION: A heat transfer tube 1 having grooved inner surface comprises a plurality of tilt grooves 4 having a predetermined tilt angle with respect to the axis 2 thereof and further a drainage groove 6, which crosses the tilt grooves 4 and communicates therewith and the bottom of which is positioned lower than those of the tilt grooves.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner grooved heat transfer tube used for a heat exchanger of an air conditioner or a cooling device.

[0002]

2. Description of the Related Art An inner grooved heat transfer tube of this type is mainly used as an evaporator tube or a condenser tube in a heat exchanger of an air conditioner or a cooling device. There are many groove shapes that have been devised in various ways.

For example, in Japanese Patent Application Laid-Open No. 11-63877, as shown in a partially developed view of a structure of an inner peripheral surface of a pipe main body, a predetermined inner peripheral surface of a pipe main body 101a is provided in a pipe axial direction. A plurality of rows of groove groups a and c in which a V-shaped groove (V-shaped groove) 103 having a sharp shape at a pitch is continuous are provided in parallel in the circumferential direction, and the plurality of rows of groove groups a and c are provided. There has been proposed a configuration in which flat surfaces b and d having no grooves are formed at positions where liquid films join at the time of condensation between refrigerant flows in the direction of the arrow. The flat surfaces b and d are formed at the same height as the bottom surface of the V-shaped groove 103 in parallel with the tube axis of the heat transfer tube with the inner surface groove, so that a larger liquid film flow rate of the refrigerant is obtained at the time of condensation. Can be concentrated on the flat surfaces b and d, and the thickness of the liquid film flowing through the V-shaped groove 103 is reduced.
Condensation heat transfer efficiency can be improved.

[0004]

However, in the above-mentioned conventional heat transfer tube with an inner groove, the flat surfaces b and d provided at the junction of the liquid films flowing through the V-shaped groove 103 are the same as the bottom surface of the V-shaped groove. Due to the height, a large amount of liquid film cannot flow on the flat surfaces b and d, and the V-shaped groove 1 near the flat surfaces b and d
The liquid film thickness in 03 increases. Therefore, there is a problem that the condensation heat transfer coefficient of the V-shaped groove 103 near the flat surfaces b and d is not improved.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a heat transfer tube with an inner surface groove having a further improved heat transfer coefficient of condensation. is there.

[0006]

According to the present invention, there is provided a heat transfer tube having an internal groove, which has a plurality of inclined grooves having a predetermined inclination angle with respect to a tube axis on the inner surface of the tube. And a drain groove whose bottom surface is deeper than the bottom surface of the inclined groove.

[0007] The inclination angle of the drain groove with respect to the tube axis is smaller than the inclination angle of the inclined groove with respect to the tube axis.

The thickness of the heat transfer tube at the portion where the drain groove is provided is made larger than the thickness of the heat transfer tube at the portion where the inclined groove is provided.

Further, the outer surface of the heat transfer tube at the portion provided with the drainage groove protrudes.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 1 to 3 are diagrams for explaining a heat transfer tube with an inner surface groove according to a first embodiment of the present invention. FIG. 1 is a cross-sectional view, and FIG. 3 is an exploded perspective view showing a part of the structure of the inner peripheral surface of the pipe. In the figure, 1 is a heat transfer tube, 2 is a tube axis of the heat transfer tube 1, and 3 is an inclined fin having a predetermined inclination angle with respect to the tube axis 2. 4 is an inclined groove between the inclined fins 3,
It has the same inclination angle as the inclination fin 3 with respect to the tube axis 2. Reference numeral 6 denotes a drainage groove intersecting with and communicating with the inclined groove 4, 7 denotes a liquid film of the refrigerant, and 70 denotes an arrow indicating the flow of the liquid film 7. Also, w
0 is the width of the inclined groove 4, w1 is the width of the drain groove 6, and z is the inclined groove 4.
And h is the height of the inclined fin 3 with respect to the bottom surface of the drain groove 6 with reference to the bottom surface of FIG. In FIG. 2, the inclined grooves 4 and the drain grooves 6 are hatched for easy understanding.

The depth z from the bottom of the inclined groove 4 to the bottom of the drain groove 6 is set so that z> 0, that is, the bottom of the drain groove 6 is positioned deeper than the bottom of the inclined groove 4. It is configured to be. Thus, a large flow rate of the liquid film can flow along the drain groove 6. Further, the width w of the drain groove 6
By configuring 1 to be larger than the width w0 of the inclined groove 4, a larger liquid film flow rate can flow along the drain groove 6.

Further, the inclination angle of the drain groove 6 with respect to the tube axis 2 is formed to be smaller than the inclination angle of the inclined groove 4 (inclined fin 3) with respect to the tube axis 2. This allows
The resistance that the liquid film 7 receives from the drain groove 6 can be smaller than the resistance that the liquid film 7 receives from the inclined fins 3, and the liquid film 7 can easily flow along the drain groove 6.

Further, the drain groove 6 is provided in a spiral shape, whereby the liquid film 7 can be continuously flowed along the drain groove 6, and since the drain film 6 is formed in a spiral shape, the heat transfer tube is formed. It is not necessary to be conscious of the upper and lower sides when mounting.

The above-mentioned heat transfer tube with an inner groove can be manufactured, for example, as follows. First, a strip-shaped metal plate made of, for example, copper or a copper alloy is passed between a roll having irregularities corresponding to the inclined fins 3, the inclined grooves 4, and the drain grooves 6, and a receiving roll pressed against the roll. Then, the unevenness of the rolling roll is transferred to one surface of the strip-shaped metal plate. Next, the band-shaped metal plate is set on the ERW device with the uneven transfer surface facing inward, and is passed through the ERW device between each pair of forming rolls installed in a multi-stage manner and rounded in the width direction. Then, the butted ends in the width direction are welded to each other to form a tubular shape. Further, the weld bead portion of the tubular molded product is deleted, and this is reduced to a predetermined diameter by emptying it with a predetermined drawing device, and is formed.

Next, the operation will be described. The liquid film 7 flowing along the inclined groove 4 merges with the liquid film 7 flowing along the drain groove 6, and thereafter, most of the liquid film 7 flows along the drain groove 6.

As a result, the thickness of the liquid film 7 in the inclined groove 4 on the downstream side of the drain groove 6 is significantly reduced, so that the condensation heat transfer coefficient can be greatly improved.

FIG. 4 shows that the outer diameter is 7.5 mm, the number of the inclined grooves 4 is 50, and the height of the inclined fins 3 (trapezoid) is 0.24 m.
m, the thickness of the bottom surface of the inclined groove 4 is 0.5 mm, and the inclined fin 3
The angle Z is 13 degrees with respect to the tube axis, that is, the vertical angle of the inclined fins 3 (the angle between the two non-parallel sides of the trapezoid) is 30 degrees.
m (the bottom is the same depth as the bottom of the inclined groove 4), 0.20m
FIG. 9 is a characteristic diagram showing a result of calculating an average condensation heat transfer coefficient using numerical analysis in a case where a drain groove 6 having a diameter of m and 0.24 mm is provided and a groove width w1 of the drain groove 6 is changed. The horizontal axis in the figure indicates the ratio of the groove width w1 of the drain groove to the circumference of the radius R (drain groove ratio), and the vertical axis indicates the average condensation heat transfer coefficient.

FIG. 4 shows that the average condensation heat transfer coefficient increases when the bottom surface of the drain groove 6 is deeper than the bottom surface of the inclined groove 4 as compared with the case where the bottom surface of the drain groove 6 is at the same position as the bottom surface of the inclined groove 4. You can see that there is. However, even when the bottom surface of the drain groove 6 is at a position deeper than the bottom surface of the inclined groove 4, the drain groove ratio is zero when the drain groove ratio is about 60% or more (the drain groove 6 was not provided. ) The average condensation heat transfer coefficient is lower than in the case. If the drainage groove ratio is too large, the ratio of the inclined groove 4 becomes small, and the contact area between the steam flowing in the center of the pipe and the inclined fin 3 decreases. To do that. In FIG. 4, when the drainage groove ratio is about 30%, the average condensed heat transfer coefficient reaches the maximum value. Clearly, by setting the width of the drainage groove 6 to an appropriate value, the average condensed heat transfer coefficient is improved. I understand.

Although FIG. 1 shows a case where one drain groove 6 is provided in the cross section of the heat transfer tube, a plurality of drain grooves 6 may be provided, and FIG. 5 shows a case where two drain grooves 6 are provided. In FIG. 5, the inclination angles of the left and right inclined grooves 4 separated by the upper and lower drainage grooves 6 with respect to the tube axis 2 can be different from each other.

In the above-described embodiment, the case where the inclined grooves 4 (inclined fins 3) and the drain grooves 6 have the same inclination direction (helical twisting direction) with respect to the tube axis 2 has been described. In this case, the resistance when the liquid film 7 flowing along the inclined groove 4 merges with the liquid film 7 flowing along the drain groove 6 is:
Since the inclination direction of the inclined groove 4 and the drain groove 6 with respect to the pipe shaft 2 is different from each other, the pressure loss at the time of merging is reduced. Further, since the liquid film 7 flows into the drain groove 6 smoothly, a larger flow rate of the liquid film flows along the drain groove 6 and the thickness of the liquid film 7 flowing along the inclined groove 4 is further reduced. Therefore, the condensation heat transfer coefficient can be further improved. However, it goes without saying that the inclined directions of the inclined groove 4 and the drain groove 6 with respect to the tube axis 2 may be different.

Embodiment 2 FIG. 6 and 7 are views for explaining a heat transfer tube with an inner surface groove according to the second embodiment of the present invention. FIG. 6 is a cross-sectional view, and FIG. . In the figure, t0 is the thickness of the heat transfer tube 1 at the portion where the inclined groove 4 is provided, and t1 is the thickness of the heat transfer tube 1 at the portion where the drain groove 6 is provided. Embodiment 1
Although the case where the drainage groove 6 is provided in a spiral shape having a predetermined inclination angle with respect to the tube axis 2 has been described, in this embodiment, the drainage groove 6 is provided linearly in parallel with the tube axis 2. As a result, the flow rate of the liquid film 7 flowing through the drain groove 6 increases because the flow velocity of the liquid film 7 increases due to the strong shearing force of the vapor of the refrigerant flowing through the heat transfer tube 1, and the condensation heat transfer rate further improves. I do. Further, the thickness of the heat transfer tube at the portion where the drain groove 6 is provided can be easily made larger than the thickness of the heat transfer tube at the portion where the inclined groove 4 is provided. Therefore, in the first embodiment, the thickness of the heat transfer tube 1 is made equal in the transverse cross section. However, in the present embodiment, the inner and outer circumferences of the heat transfer tube 1 are eccentric to each other, and the portion where the drain groove 6 is provided is provided. The thickness t1 of the heat transfer tube 1 is configured to be larger than the thickness t0 of the heat transfer tube 1 in a portion where the inclined groove 4 is provided. Thus, by increasing the thickness of the heat transfer tube 1 only where necessary without increasing the wall pressure, it is possible to withstand high pressure in the heat transfer tube while saving unnecessary heat transfer tube material and reducing the weight. it can.

Although FIG. 7 shows a case where the inclined groove 4 is spiral, it may be a V-shaped groove as in the conventional case. By providing the drainage groove 6 whose bottom surface is deeper than the bottom surface of the inclined groove 4, the condensation heat transfer coefficient in the pipe can be improved, and further, while saving unnecessary heat transfer tube material and reducing the weight, Pressure resistance is also obtained.

Embodiment 3 FIG. FIG. 8 is a cross-sectional view for explaining a heat transfer tube with an inner surface groove according to Embodiment 3 of the present invention. In the figure, 60 is a drainage groove member,
The inner peripheral side of the drainage groove member 60 is the drainage groove 6.
In the first embodiment, the strip-shaped metal plate on which the irregularities corresponding to the inclined fins 3, the inclined grooves 4, and the drain grooves 6 are transferred is rolled in the width direction, and the butted ends in the width direction are welded to each other to form a tube. However, in the present embodiment, the strip-shaped metal plate on which the irregularities corresponding to the inclined fins 3 and the inclined grooves 4 have been transferred is rounded halfway in the width direction, leaving a gap by the width of the drainage groove 6. The drain groove member 60 was disposed on the outer peripheral side of both butted ends having a gap, and the end of the strip-shaped metal plate and the drain groove member 60 were welded into a tubular shape.

In the above configuration,
Since the depth of the drain groove 6 is increased by the thickness of the heat transfer tube 1, the flow rate of the liquid film 7 flowing through the drain groove 6 is increased, and the heat transfer coefficient of condensation is improved. Further, since the thickness of the drain groove 6 can be ensured, the high pressure inside the heat transfer tube 1 can be cut off.
Further, by welding the drain groove member 60 to the heat transfer tube 1,
A convex portion is formed on the outer peripheral portion of the heat transfer tube, that is, the drainage groove 6
Since the outer surface of the heat transfer tube at the portion where the heat transfer tube is provided protrudes, the portion where the drainage groove 6 is provided can be recognized from the outside of the heat transfer tube 1. The groove 6 can be positioned in the circumferential direction.

Embodiment 4 FIG. 9 is a view for explaining a heat transfer tube with an inner surface groove according to Embodiment 4 of the present invention, and is a cross-sectional view. In the present embodiment, the tube wall of the heat transfer tube 1 at the position where the drainage groove 6 is provided is projected to the outer peripheral portion, and even with such a configuration, the same effect as that of the third embodiment can be obtained. Can be

Embodiment 5 10 and 11 are views for explaining a heat transfer tube with an inner surface groove according to a fifth embodiment of the present invention. FIG. 10 is a cross-sectional view, and FIG. . This embodiment is different from the second embodiment shown in FIGS. 6 and 7 in that a linear drain groove 6 is formed.
Is provided with a linear weir member that protrudes in a band shape in the inner circumferential direction of the heat transfer tube 1 in the center of the heat transfer tube 1. In the figure, 3a, 3
b is an inclined fin having a predetermined inclination angle with respect to the tube axis 2. Reference numerals 4a and 4b denote spiral inclined grooves between the inclined fins 3a and 3b, which are formed continuously with respect to the tube axis 2 at the same inclination angle as the inclined fins 3a and 3b. 6a, 6b
Is a drainage groove which crosses and communicates with the inclined grooves 4a and 4b and whose bottom surface is deeper than the bottom surfaces of the inclined grooves 4a and 4b. Is provided. Reference numeral 5 denotes a weir member provided in the drain grooves 6a and 6b. The weir member is provided in a straight line parallel to the pipe shaft 2 and has a spiral inclined groove 4a to stop the flow of the refrigerant flowing through the spiral inclined groove 4. 4b, and is formed to protrude in a belt shape in the inner circumferential direction of the heat transfer tube 1. 7a, 7b, 7d and 7e are liquid films of the refrigerant, and 9 is an arrow indicating the direction in which the refrigerant flows. In addition,
In FIG. 11, the inclined grooves 4a and 4b and the drain grooves 6a and 6b are hatched for easy understanding.

Next, the operation will be described. When the refrigerant flows in the direction shown by the arrow 9, the liquid film 7a flowing in the upstream inclined groove 4a joins with the liquid film 7b which is stopped by the weir member 5 and flows along the upstream drain groove 6a. Thereafter, most of the liquid film 7b flows along the drain groove 6a. A part of the liquid film 7b flowing along the drain groove 6a passes over the weir member 5 and the liquid film 7d flows along the drain groove 6b on the downstream side.
And flows along the drain groove 6b. Further, the liquid film 7e branches off from the liquid film 7d flowing along the drain groove 6b, and the liquid film 7e flows through the upstream inclined groove 4b.

As described above, by providing the weir member 5, most of the liquid film 7a flowing along the inclined groove 4a becomes the liquid film 7b.
As the thickness of the liquid film 7e flowing along the drain groove 6a and flowing along the inclined groove 4b becomes thinner as compared with the case where the dam member 5 is not provided, the heat transfer coefficient of condensation is greatly improved. be able to.

Although FIG. 11 shows a case where the inclined groove 4 is spiral, a V-shaped groove similar to the conventional one may be used as shown in FIG. Also in this case, the drain groove 6 and the weir member 5 whose bottom surface is deeper than the bottom surface of the inclined groove 4 are located at the position where the liquid films merge at the time of condensation.
Is provided, it is possible to greatly improve the condensation heat transfer coefficient in the tube.

Embodiment 6 FIG. FIG. 13 is a view for explaining an inner grooved heat transfer tube according to Embodiment 6 of the present invention.
FIG. This embodiment is different from the third embodiment shown in FIG. 8 in that the drainage groove member 60 has an L-shaped cross section, and one end of the L-shaped cross section has a linear shape protruding in the inner circumferential direction of the heat transfer tube 1. Of the weir member 5. In the present embodiment, the drain groove 6a whose bottom surface is deeper than the bottom surfaces of the inclined grooves 4a and 4b is provided on the upstream side of the weir member 5 so as to communicate with the upstream inclined groove 4a.

Also in this structure, the liquid film 7a flowing in the upstream inclined groove 4a joins with the liquid film 7b which is stopped by the weir member 5 and flows along the upstream drain groove 6a. After that, most of the liquid film 7b is
Since the gas flows along the line a, the heat transfer coefficient of condensation in the pipe can be significantly improved as in the fifth embodiment.

[0032]

As described above, according to the present invention, in a heat transfer tube having an inner surface groove having a plurality of inclined grooves having a predetermined inclination angle with respect to the tube axis on the inner surface of the tube, the heat transfer tube intersects with the inclined grooves. Since a drain groove is provided in communication with this and the bottom surface of which is located at a position deeper than the bottom surface of the inclined groove, it is possible to obtain a heat transfer tube with an inner surface groove having an improved condensation heat transfer coefficient in the tube.

Further, since the inclination angle of the drain groove with respect to the pipe axis is smaller than the inclination angle of the inclined groove with respect to the pipe axis, the liquid film is more likely to flow along the drain groove, and the condensation heat transfer coefficient in the pipe is reduced. A more improved heat transfer tube with an inner groove can be obtained.

Further, since the thickness of the heat transfer tube at the portion where the drain groove is provided is made larger than the thickness of the heat transfer tube at the portion where the inclined groove is provided, only the necessary portion is required without increasing the overall wall pressure. By increasing the thickness, it is possible to obtain pressure resistance while saving unnecessary heat transfer tube material and reducing the weight.

Further, since the outer surface of the heat transfer tube in the portion provided with the drain groove protrudes, the portion provided with the drain groove can be recognized from the outside of the heat transfer tube, and a heat exchanger or the like is assembled using the heat transfer tube. At this time, it becomes possible to position the drain groove in the circumferential direction.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a heat transfer tube with an inner surface groove according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a heat transfer tube with an inner surface groove according to the first embodiment of the present invention.

FIG. 3 is a view for explaining a heat transfer tube with an inner surface groove according to the first embodiment of the present invention.

FIG. 4 is a characteristic diagram for explaining an effect of the heat transfer tube with an inner surface groove according to the first embodiment of the present invention.

FIG. 5 is a diagram for explaining a heat transfer tube with an inner surface groove according to the first embodiment of the present invention.

FIG. 6 is a diagram for explaining a heat transfer tube with an inner surface groove according to a second embodiment of the present invention.

FIG. 7 is a view for explaining an inner grooved heat transfer tube according to a second embodiment of the present invention.

FIG. 8 is a diagram for explaining a heat transfer tube with an inner surface groove according to a third embodiment of the present invention.

FIG. 9 is a view for explaining a heat transfer tube with an inner surface groove according to a fourth embodiment of the present invention.

FIG. 10 is a view for explaining a heat transfer tube with an inner surface groove according to a fifth embodiment of the present invention.

FIG. 11 is a view for explaining a heat transfer tube with an inner surface groove according to a fifth embodiment of the present invention.

FIG. 12 is a view for explaining a heat transfer tube with an inner surface groove according to a fifth embodiment of the present invention.

FIG. 13 is a view for explaining a heat transfer tube with an inner surface groove according to a sixth embodiment of the present invention.

FIG. 14 is a view for explaining a conventional heat transfer tube with an inner surface groove.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Heat transfer tube, 2 Tube axis, 3, 3a, 3b Inclined fin, 4, 4a, 4b Inclined groove, 5 Weir member, 6, 6
a, 6b Drainage groove, 60 Drainage groove member, 7, 7a, 7
b, 7d, 7e Liquid film, 9 Arrow indicating the direction in which the refrigerant flows.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Ishibashi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Inventor Masahiro Nakayama 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Ryo Denki Co., Ltd.

Claims (4)

[Claims] 1. A heat transfer tube having an inner surface groove having a plurality of inclined grooves having a predetermined inclination angle with respect to a tube axis on an inner surface of the tube. An inner grooved heat transfer tube having a drain groove located at a position deeper than a bottom surface of the groove. 2. The heat transfer tube with an inner surface groove according to claim 1, wherein the inclination angle of the drain groove with respect to the tube axis is smaller than the inclination angle of the inclination groove with respect to the tube axis. 3. The thickness of the heat transfer tube where the drain groove is provided,
The heat transfer tube with an inner groove according to claim 1 or 2, wherein the heat transfer tube has a larger thickness than a portion of the heat transfer tube where the inclined groove is provided. 4. The heat transfer tube with an inner surface groove according to claim 1, wherein an outer surface of the heat transfer tube at a portion where the liquid drain groove is provided protrudes.