JPH10300379A - Heat exchanger tube having groove in internal surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce a pressure loss in the tube while improving the heat transfer capability. SOLUTION: In the tube internal surface, two or more virtual border lines 22 extending in the tube axial direction, are provided, and from the virtual border line 22 to both adjacent virtual lines 22 across it, a large number of diagonal grooves 12 are formed, and in the meantime, the diagonal grooves 12 which are formed across the virtual border line 22 on both sides, are constituted in such a manner that they may tilt in the opposite directions from each other, and also a ratio : 2d/D for a twice of the groove depth : (d) of the diagonal grooves 12 and a tube internal maximum diameter : D is constituted in a manner to become 0.05-0.1. At the same time, on the virtual border line 22, a straight groove 14 extending in the tube axial direction at a groove depth : ds which is shallower than the groove depth : (d) of the diagonal grooves 12 is provided under a state wherein the straight groove 14 communicates with the diagonal grooves 12, and in addition, the value of the relational expression: ds×Ws×n/(π×D) for the groove depth : ds (mm) of the straight groove 14, the groove width : Ws (mm), and the number of lines : (n), and the tube internal maximum diameter : D (mm), is constituted in a manner to stay within a range of 0.001-0.05.

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 groove used for a refrigerator or an air conditioner, and more particularly, to improving the heat transfer performance of the heat transfer tube having an inner groove and greatly reducing a pressure loss in the tube. This is related to a groove configuration that can be used.

[0002]

2. Description of the Related Art Conventionally, in a heat exchanger such as an evaporator or a condenser in a refrigerator or an air conditioner, a plurality of heat transfer tubes are piped in predetermined directions and attached. Heat exchange is performed between the heat transfer fluid circulated in the plurality of heat transfer tubes and the heat transfer fluid brought into contact with the outer surface of each heat transfer tube, and the heat transfer fluid guided into the heat transfer tubes evaporates. Or it can be condensed.

[0003] Generally, as a heat transfer tube attached to such a heat exchanger, a so-called tube with an internal spiral groove having a spiral groove formed on the inner surface of the tube is employed. In the inner spiral grooved tube, the spiral groove is formed, so that the contact area of the heat transfer fluid circulated in the tube, that is, the heat transfer area of the heat transfer tube is increased, and so on.
Although the heat transfer coefficient in the tube has been improved, it is not possible to sufficiently improve the evaporation performance and the condensation performance by itself, and therefore, the heat transfer promoting effect as expected cannot be obtained. Was something.

However, in such an inner spiral grooved tube,
By increasing the depth of the spiral groove to increase the height of the ridges (fins) formed between adjacent spiral grooves (high fins) or to narrow the pitch of the spiral grooves, It is known that evaporating performance and condensing performance can be improved to some extent by reducing the width (thickness) (slim fin). However, such high fins and slim fins naturally have processing limits, and even if processing in a range exceeding such processing limits is possible, as high fins and slim fins progress, Since the degree of improvement in the evaporation performance and the condensation performance is remarkably slowed, it is almost impossible to greatly increase the heat transfer promoting effect by using such high fins or slim fins.

On the other hand, in Japanese Utility Model Laid-Open No. 57-183487, a plurality of grooves extending from the bottom to the top at a predetermined inclination angle with respect to the pipe axis are formed in one virtual direction in the pipe diameter direction including the pipe axis. An internally grooved heat transfer tube (hereinafter, referred to as a pine needle groove) having a groove structure (hereinafter, referred to as pine needle groove) formed continuously in the circumferential direction on the inner surface of the tube so as to be symmetrical with respect to the surface, (Referred to as a heat transfer tube with inner pine needle grooves). Further, in this publication, when such a heat transfer tube with inner pine needle grooves is used for a condenser, droplets of a refrigerant as a heat transfer fluid condensed on the inner surface of the tube are transferred to the plurality of grooves (pine needles). By being arranged so as to flow downward toward the bottom side in the groove), such refrigerant liquid is quickly guided to the bottom side of the heat transfer tube through each groove, and the inner surface of the tube is easily dried, While the condensing performance is improved by this, when used in the evaporator, the refrigerant liquid is arranged so as to flow upward in the plurality of grooves toward the top, so that the refrigerant liquid flows through each groove. The refrigerant liquid is guided to the top side of the heat transfer tube, whereby the thinning of the refrigerant liquid is more advantageously achieved, and drying of the inner surface of the tube is suppressed, so that a sufficient effective heat transfer area is secured, and thus the evaporation performance is improved. Revealed that it can be enhanced There.

However, according to the study by the present inventors, such heat transfer tubes with inner pine flutes have a higher heat transfer promoting effect than the conventional tube with inner helical grooves. However, it was confirmed that the heat transfer promoting effect was not much different from that of the internally spiral grooved tube made into a high fin or slim fin, and in some cases, it was inferior to that. It has been clarified that even the heat transfer tube with inner pine needle grooves disclosed in the above publication does not provide a sufficiently satisfactory heat transfer promotion effect in practical use.

[0007] In addition, in the heat transfer tube with inner pine needle grooves, as described above, when used in an evaporator, the refrigerant liquid flows upward in the pine needle grooves toward the top.
In addition, when used in a condenser, the refrigerant liquid can be disposed in a state where the refrigerant liquid flows downward in the pine needle groove toward the bottom side, so that both the evaporation performance and the condensation performance can be enhanced for the first time. Thus, in order to improve the heat transfer performance, there is a disadvantage that the flow direction of the refrigerant (heat transfer fluid) in the pine needle groove is restricted. Therefore, when assembling heat exchangers such as evaporators and condensers, the work of assembling each heat transfer tube must be performed while checking the inclination direction of the pine needle grooves in the tube one by one. This significantly deteriorated the manufacturability of the exchanger.

The inventors of the present invention have previously disclosed a heat transfer tube with an inner surface groove in which the restriction of the heat transfer performance due to the flow direction of a heat transfer fluid such as a refrigerant has been solved.
No. 04 and Japanese Patent Application No. 8-136194, in a heat transfer tube in which a plurality of pine needle grooves having the structure as described above are formed on the inner surface of the pipe, the groove depth of each pine needle groove is determined with respect to the maximum diameter in the pipe. An inner grooved heat transfer tube configured to be deeper than before in a specific range has been clarified. And
In such heat transfer tubes with internal grooves, the configuration is adopted in which the depth of the pine flutes is deeper than before, so that the transferability of the groove for the heat transfer tubes is not impaired. The heat performance can be greatly improved, and the heat transfer performance can be improved regardless of the flow direction of the heat transfer fluid.

However, the present inventors have further studied and found that such a heat transfer tube with inner pine flutes exhibits excellent heat transfer performance during evaporation and condensation. In addition, because of the crutch structure provided on the inner surface of the tube, the resistance to the heat transfer fluid that is circulated is increased, thereby increasing the pressure loss in the tube, particularly the pressure loss in the tube during evaporation, which is remarkable. It became clear that this would be a challenge to realization.

[0010]

The present invention has been made in view of the above circumstances, and an object of the present invention is to effectively reduce pressure loss in a pipe while improving heat transfer performance. In particular, the present invention is to provide a heat transfer tube with an inner groove capable of effectively reducing the pressure loss in the tube at the time of evaporation and having a sufficient heat transfer promoting effect as compared with the conventional inner grooved tube having a spiral groove. An object of the present invention is to provide a heat transfer tube having an inner surface groove having a groove.

[0011]

The present inventors have made various studies to solve such a problem, and as a result, as described above,
In the heat transfer tube with internal groove, where the groove depth of the pine needle groove is specified, the straight groove of a predetermined width is provided on a virtual boundary line extending in the tube axis direction, thereby effectively suppressing an increase in pressure loss in the tube. It has been found that the heat transfer can be carried out sufficiently.

That is, the present invention has been completed based on such findings, and the features thereof are as follows:
The pipe inner surface has at least two or more virtual boundary lines extending in the pipe axis direction, and a number of inclined grooves are formed from each of the virtual boundary lines toward two adjacent virtual boundary lines sandwiching the virtual boundary lines. Are formed in such a manner that the inclined grooves are formed at a predetermined angle with respect to the virtual boundary line, while the inclined grooves formed on both sides of the virtual boundary line are inclined in opposite directions to each other. The groove depth of the groove: a ratio of 2 times d to the maximum diameter in the tube: D: 2d / D is set to be 0.05 to 0.1, and each of the virtual boundary lines is At a groove depth: ds which is shallower than d: ds, a straight groove extending in the pipe axis direction is provided so as to communicate with the inclined groove, and a groove depth of the straight groove: d
Relational expression of s (mm), groove width: Ws (mm) and number of strips: n, and maximum diameter in pipe: D (mm): ds × Ws × n /
An inner grooved heat transfer tube configured so that the value of (π × D) is in the range of 0.001 to 0.05.

In short, the heat transfer tube with an inner groove according to the present invention has a groove configuration in which a straight groove is combined with the above-mentioned inclined groove, that is, the heat transfer tube with an inner groove previously proposed by the present inventors. In the above, a predetermined continuous straight groove is provided thereon along a virtual boundary line extending in the pipe axis direction that defines the inclined groove, and therefore, a heat transfer fluid such as a liquid refrigerant is easily concentrated. At the imaginary boundary line, the colliding fluid easily flows downstream along the straight groove,
In addition, in the virtual boundary line portion where the dispersion is easy, the fluid to be dispersed can be smoothly supplied along the straight groove, so that the pressure loss in the pipe is remarkably reduced. That is, the straight groove in the pipe axis direction along the virtual boundary line serves as a flow liquid groove,
In particular, in places where a heat transfer fluid such as a refrigerant collides, it is considered that the effect of reducing the pressure loss in the pipe becomes remarkable. In addition, the flow along the flow groove and the V-shaped structure disposed end of the inclined groove are considered. Disturbance effects due to collisions with the guided flow are also exerted.

Moreover, since such a straight groove is formed such that its groove depth: ds is smaller than the groove depth: d of the inclined groove, the boundary between the straight groove and the inclined groove is formed. Since the heat transfer fluid collides with the step, the same effect of collision and scattering of the heat transfer fluid can be obtained as in the case where such a straight groove is not formed. It is possible to effectively secure the improvement effect of the above. If the groove depth of the straight groove: ds and the groove depth: d of the inclined groove are set to the same depth, the effect of the heat transfer promoting mechanism of collision and scattering of the heat transfer fluid, which is a heat transfer promotion mechanism, is reduced. It becomes weakened by the flow along the groove.

In the heat transfer tube with internal grooves according to the present invention, a combination of two types of inclined grooves having inclined shapes opposite to each other is configured as an inner grooved tube having a pine needle groove shape. Therefore, on the inner surface of the pipe, a virtual boundary line portion where the heat transfer fluid is easily concentrated and a virtual boundary line where the heat transfer fluid is easily dispersed are formed, so that the evaporative heat transfer performance and the condensation heat transfer performance are both effective. Needless to say, it can be improved in terms of quality.

That is, at the time of evaporation, in a region where the heat transfer fluid tends to concentrate, collision of the heat transfer fluid, for example, liquid refrigerant, which is not seen in the conventional heat transfer tube with the spiral groove inside, occurs.
Due to the collision, the disturbance of the liquid refrigerant is promoted, and accordingly, the heat transfer performance is promoted. And
When the liquid refrigerant after the collision is scattered by the collision energy and becomes an upward flow toward the top along the inclined groove, it falls to the lower surface of the heat transfer tube, and also, from the top to the bottom along the inclined groove. In the case of a downward flow toward, the liquid refrigerant is wound up in the gas phase, but at this time, the scattered liquid refrigerant also disturbs the refrigerant vapor, thereby further increasing the heat transfer promoting effect. You get it. Further, in a portion where the liquid refrigerant as the heat transfer fluid is easily dispersed, the supplied liquid refrigerant is easily formed into a thin film in a ring shape, so that the occurrence of the heat transfer inhibition phenomenon due to the thickness of the liquid refrigerant film is advantageously reduced. Will be done. Furthermore, since these phenomena are repeated in a sufficiently short cycle along the flow direction of the refrigerant liquid,
As compared with the conventional heat transfer tube with the internal spiral groove, a large disturbance effect of the liquid refrigerant is advantageously obtained, and excellent heat transfer performance can be exhibited.

On the other hand, at the time of condensation, the condensed heat transfer fluid, for example, liquid refrigerant, is effectively removed from the portion where the heat transfer fluid is easily dispersed by the inclined groove having a downward slope along the flow direction of the heat transfer fluid. As a result, exposure of the new surface to the inner surface of the tube is promoted, and a remarkable heat transfer promoting action can be exhibited. In addition, the excluded liquid refrigerant collides with the flow of the liquid refrigerant along the adjacent groove having an upward gradient, and thus the liquid refrigerant that has been sprayed due to the collision between the liquid refrigerants has a gas phase. Therefore, condensation is further promoted, and excellent heat transfer performance can be exhibited.

In addition, in the heat transfer tube with an inner groove according to the present invention, the groove depth of the inclined groove with respect to the maximum diameter in the tube: D is d.
Is formed so that the ratio of 2d / D is in the range of 0.05 to 0.1, and the groove depth of each inclined groove with respect to the maximum diameter in the pipe is within a specific range and is greater than that in the related art. Since it is configured to be deep, both the evaporation performance and the condensation performance can be effectively enhanced without impairing the workability of the groove processing.

According to the preferred embodiment of the heat transfer tube with an inner groove according to the present invention as described above, the ratio of the depth of the inclined groove twice as large as d and the maximum diameter in the tube as D is 2d /.
D will be in the range of 0.058 to 0.087. In particular, in the inner grooved heat transfer tube having the ratio in such a range, the evaporation performance and the condensation performance,
It can be improved even further.

According to another preferred embodiment of the present invention, the depth of the straight groove in the tube axis direction is ds.
, Groove width: Ws and number of strips (number): n, and maximum diameter in tube: D, and their relational expressions: ds × Ws × n /
It is configured such that the value of (π × D) is in the range of 0.005 to 0.04, whereby the object of the present invention can be achieved even more advantageously.

Further, according to another preferred embodiment of the heat transfer tube with internal grooves according to the present invention, the number of the virtual boundary lines is one.
It is an even number equal to or less than zero, and by adopting such a configuration, more stable heat transfer performance can be exhibited while maintaining excellent heat transfer performance.

Further, in the heat transfer tube with an inner groove according to the present invention, the pitch of the inclined groove in the circumferential direction of the tube is preferably in the range of 0.35 to 0.50 mm, and The inclination angle of the groove with respect to the pipe axis is 5 to 45 °
And the portion between adjacent inclined grooves is 10 to
It is formed as a ridge having an apex angle in the range of 35 °. As a result, the heat transfer performance of the heat transfer tube can be further enhanced, and a greater heat transfer promoting effect can be obtained.

[0023]

1 to 3 show a specific example of a heat transfer tube 10 having an inner surface groove having a structure according to the present invention. The heat transfer tube with inner grooves 10 has a straight pipe shape with a circular cross section as a whole, and its outer peripheral surface is a smooth surface, while the inner peripheral surface has a large number of inclined grooves 12.
And two straight grooves 14 are provided.

More specifically, those figures, especially FIG.
As can be seen from (b), the large number of inclined grooves 12 provided on the inner peripheral surface have a trapezoidal shape in which the cross section (the cross section perpendicular to the tube axis) becomes narrower toward the bottom. I have. Further, as shown in FIG. 2, in such a large number of inclined grooves 12, two half surfaces of the inner surface of the pipe divided into two imaginary surfaces 16 in the pipe diameter direction including the pipe axis of the heat transfer pipe 10, that is, , The left half surface 18a and the right half surface 18b are respectively continuous in the circumferential direction as a whole, and are adjacent to each other at a predetermined interval in the tube axis direction.
In between, while forming the ridge 20, while being provided,
In the left half 18a and the right half 18b, two types of inclined grooves 1 forming a predetermined inclination angle: θ with respect to the pipe axis.
2, 12 are provided to be inclined in opposite directions.
Furthermore, two virtual boundary lines 22, 22 extending in the pipe axis direction
Exist in the plane of the imaginary plane 16 and are located at the upper and lower tube inner surface portions in the cross section shown in FIG.

As is clear from FIGS. 1 and 2, each inclined groove 12 is provided from one virtual boundary line 22 to the other virtual boundary line 22.
A straight groove 14 extending in the pipe axis direction with a predetermined groove width: Ws is formed on the virtual imaginary boundary lines 22, 22.
2 is formed at a groove depth: ds shallower than d. Furthermore, as is clear from FIG. 3, each inclined groove 12 is formed so as to form a V-shaped or inverted V-shaped bending point as a whole at each virtual boundary line portion. In short, the large number of inclined grooves 12 are inclined in opposite directions on both sides of the straight groove 14 so as to exhibit independent closed channel forms. The inclined grooves 12 are inclined in opposite directions to each other.
Are combined to form a pine needle-shaped groove structure as a whole.

Further, in particular, in the heat transfer tube 10 with the inner surface groove having such a pine needle groove structure and formed with two kinds of inclined grooves 12 whose inclination directions are opposite to each other, the maximum diameter in the tube: D The value of the groove depth of the inclined groove 12: twice the ratio of d: 2d / D is in the range of 0.05 to 0.1,
In this respect, the configuration is significantly different from that of the conventional inner creasing tube, and by having such a configuration, an excellent feature not found in the conventional heat transfer tube is advantageous. It is possible to be demonstrated in. That is, by defining such a 2d / D value to be 0.05 or more, the inclined groove 12 is formed with a groove depth deeper than the pine needle groove formed in the conventional heat transfer tube. Both the evaporation performance and the condensation performance can be effectively enhanced, and 2d
Since the / D value is limited to 0.1 or less, such an inclined groove 12 can easily form the left half surface 18a and the right half surface 18b on the inner surface of the heat transfer tube 10 with good workability. It can be formed in the.

In addition, it is desirable that the heat transfer tube 10 with the inner surface groove is configured so that the 2d / D value is in the range of 0.058 to 0.087. This is because the heat transfer performance can be further improved by setting the 2d / D value in such a specific range, and thereby, the refrigerant liquid in the inclined groove 12 can be improved. This is because heat transfer performance superior to that of the conventional heat transfer tube can be advantageously exhibited regardless of the flow direction of the refrigerant vapor. By the way, in the attached drawings, the inclined groove 12
In order to emphasize the shape of the heat transfer tube 1,
0 is shown with an enlargement factor greater than the overall enlargement factor, so that the ratio of the groove depth of the inclined groove 12 to the maximum diameter in the pipe: 2 d / D is defined in the drawings in the present invention. It should be understood that it is larger than the above, and the same applies to the case of the relational expression described later.

Further, the heat transfer tube 10 having an inner surface groove as described above.
, The straight groove 14 provided on each imaginary boundary line 22 and extending in the pipe axis direction is a groove depth of the inclined groove 12: d
At a shallower groove depth: ds, preferably ds =
It is formed so as to be 0.5d to 0.9d, so that the effect of reducing the pressure loss by the straight groove 14 can be advantageously exerted while securing the heat transfer promoting action by collision and scattering of the heat transfer fluid. Has become.

That is, as is apparent from the schematic diagrams of the flow of the heat transfer fluid (refrigerant) shown in FIGS.
In the heat transfer tube 10 provided with the straight groove 14 having a shallower groove depth, as is clear from FIGS. 4A and 5A, the inclined flow is related to the refrigerant flow indicated by the arrow. What is guided at 12 collides with a step existing between the straight groove 14 and changes in an upward direction (toward the tube axis), and is scattered, thereby exerting a disturbing action. As a result, the effect of improving the heat transfer performance based on the collision and scattering similar to the case where the straight groove 14 is not formed can be obtained. On the other hand, as shown in FIGS. 4B and 5B, when the groove depth of the straight groove 14 'is made equal to the groove depth of the inclined groove 12', the inclined groove The refrigerant flow guided along 12 'smoothly merges with the refrigerant flow along the straight groove 14', and the collision and scattering action of the refrigerant, which is a heat transfer promoting mechanism, is weakened. The heat transfer promoting effect expected from the combined pine groove structure cannot be sufficiently exhibited.

In addition, in the heat transfer tube 10 having the inner groove, the groove depth of the straight groove 14 is ds (mm), its groove width is Ws (mm), and its number (number) is n, and The maximum diameter in the tube: D (mm) is the relational expression: ds ×
In the value of Ws × n / (π × D), 0.001-0.
05. However, when the value of such a relational expression is smaller than 0.001, the effect of reducing the pressure loss due to the provision of the straight groove 14 is reduced, and when it is larger than 0.05, such a value is obtained. This is because the effect of reducing the pressure loss becomes excessive, and a sufficient heat transfer promoting effect cannot be obtained due to the reduction of the heat transfer area. In particular, the value of such a relational expression: ds × Ws × n / (π × D) is 0.005 to
By configuring to be within the range of 0.04,
The object of the invention can be achieved even more advantageously.

In this specific example, in the characteristic groove structure as described above, the cross-sectional shape of the inclined groove 12 is trapezoidal. It is needless to say that various shapes such as a V-shape and the like, which are adopted in a conventional spiral groove structure or a pine needle groove structure, are all adopted.

The pitch of the inclined groove 12 in the circumferential direction of the pipe [dimension indicated by P in FIG. 1B].
Is not particularly limited, but 0.35 to
Desirably, it is about 0.50 mm. If the pitch P is smaller than 0.35 mm, the groove width (opening width) of the inclined groove 12 becomes too small.
When used in a condenser, the inclined groove 12 is more likely to be submerged by the condensed liquid of the refrigerant as the heat transfer fluid, thereby making it impossible to expect an improvement in the condensing performance. Also has a large pitch,
Inclined groove 1 per unit area on inner surface of heat transfer tube 10
2, the contact area of the heat transfer fluid with the inner surface of the pipe, that is, the effect of increasing the heat transfer area of the heat transfer pipe 10, which is obtained by forming a large number of inclined grooves 12, is reduced. Is no longer possible.

Further, the inclination angle of the inclined groove 12 with respect to the pipe axis (the angle indicated by θ in FIG. 2) is determined by the flow velocity of the heat transfer fluid such as the refrigerant liquid or the refrigerant vapor, ie, the retention of the heat transfer fluid in the pipe. Although it is appropriately determined in consideration of time and the like, here, such an inclination angle θ is advantageously set to about 5 to 45 °. If the angle of inclination: θ is smaller than 5 °, the period of collision, scattering or falling off of the refrigerant becomes longer, so that the effect of disturbing the liquid and gas phases cannot be sufficiently obtained. This is because, when the pressure increases, it becomes difficult for the refrigerant to be guided to the top of the pipe, and the pressure loss increases significantly.

Further, the apex angle (the angle indicated by γ in FIG. 1) of the ridge 20 formed between the adjacent inclined grooves 12, 12, ie, the four angles in the two adjacent inclined grooves 12, 12. It is preferable that the angle between two adjacent side walls of the one side wall is in the range of 10 to 35 °. To form a ridge 20 having an apex angle: γ smaller than 10 °, in other words, a number of inclined grooves 12 are formed on the inner surface of the pipe so as to sandwich such a ridge 20 therebetween. Not only is it extremely difficult to perform the attachment processing, but even if it can be processed, when a plurality of heat transfer tubes 10 are integrally assembled to expand the heat transfer tubes 10 when assembling a heat exchanger, This is because the projection 20 may be crushed and the depth of the inclined groove 12 may be reduced, or the opening of the inclined groove 12 may be closed. When the size of the apex angle is larger than 35 °, the number of the inclined grooves 12 formed per unit area on the inner surface of the tube is reduced, and the heat transfer area of the heat transfer tube 10 is reduced, and at the time of condensation. This is because the holding volume of the condensed liquid of the heat transfer fluid becomes small, so that it becomes difficult to improve the heat transfer performance.

Incidentally, in the heat transfer tube with an inner surface groove according to the above-described specific example, the inner surface portion (two half surfaces) of the tube defined by two virtual boundary lines 22 and 22 symmetrical with respect to the tube axis is provided. Two types of inclined grooves 12, 1 inclined in opposite directions to each other
2 is symmetrically formed, and the number of virtual boundary lines 22 extending in the pipe axis direction that defines the inner surface of the pipe is an even number in the range of 2 to 10 and Is preferably performed. If the number of virtual boundary lines exceeds 10, the collision and scattering effects of the refrigerant at the intersection of the adjacent inclined grooves 12 and 12 become small, and it becomes difficult to obtain a predetermined heat transfer promoting effect. is there. Further, the virtual boundary lines 22 (straight grooves 14) are not only provided at equal intervals, but may be provided at different intervals in the circumferential direction of the pipe.

The pipe inner surface portion defined by such a number of virtual boundary lines, in other words, the inclined groove 12 formed in the inclined groove forming portion has the above-described groove depth (d) and groove lead angle. (Θ), protruding apex angle (γ), number of grooves per unit length in the tube axis direction (groove interval), groove width, etc., can be configured in various forms in each section screen. Some examples of such various configurations of the groove structure are shown in FIGS. 6 and 7. In these figures, various types of heat transfer tubes 10 with internal grooves according to the present invention having various groove structures are respectively developed to schematically show the form of the grooves 12 on the inner surface of the tubes.

In these figures, in the example shown in FIG. 6, a large number (in this case, six) drawn in parallel with the center axis of the tube located on the straight groove 14 on the inner surface of the tube.
A large number of inclined grooves 12 are respectively asymmetrical (d,
θ, γ, the number of inclined grooves, and the width of the inclined groove forming portion are asymmetric.) In the example of (a), the inclined groove forming portions having different d, θ, γ, the number of grooves, etc. An example is shown in which the widths of the formation portions of the inclined grooves 12 are changed alternately in the circumferential direction.
An example in which the inclined grooves 12 having different θ, γ, the number of grooves, and the like are alternately combined is shown. Further, FIG. In the example shown in FIG. Although the basic operation and effect of the heat transfer tube 10 with the inner surface grooves having different formation patterns of the inclined grooves 12 are not different from those of the specific example described above, further, by forming the inclined grooves 12 asymmetrically, The following effects can be enjoyed. That is, the groove depth (d), the lead angle (θ), the protrusion apex angle (γ), the number of grooves of the inclined groove 12 in the two left and right regions defined by the virtual boundary line forming the inflection point of the inclined groove 12 Since the width of the groove forming portion and the like are different from each other, the inclined grooves 12
Differences also occur in the flow velocity of the liquid film flowing between them, the liquid film thickness, and the like, so that the mechanical energy balance is greatly disturbed as compared with the case where the inclined grooves 12 are formed symmetrically. The effect of disturbing the liquid refrigerant (liquid phase) and the refrigerant vapor (gas phase) is further promoted, and the heat transfer performance is accordingly improved.

FIGS. 7 (a) to 7 (d) correspond to FIGS.
Of the virtual boundary line (straight groove 1)
4), inclined grooves 12 in opposite directions are provided on both sides thereof.
The straight groove 14 is also provided between the adjacent virtual boundary lines (straight grooves 14).
FIG. 4 shows an inner grooved heat transfer tube 10 provided with an axial groove 24 extending in the tube axis direction, similar to FIG.
In the example of (a), all virtual boundaries (straight grooves 1)
4) an axial groove 24 is provided between them, and (b)
In the example of (1), the inclined groove forming area where the axial groove 24 is provided and the inclined groove forming area where the axial groove 24 is not provided are alternately formed. ) And (d), the two inclined groove forming regions sandwiched by three virtual boundary lines (straight grooves 14) and having mutually opposite inclination directions are formed in the axial direction, respectively. A groove 24 is provided. In this way, by providing an axial groove 24 similar to the straight groove 14 at an arbitrary position between the adjacent virtual boundary lines (straight grooves 14) in addition to the straight groove 14 along the virtual boundary line, It is possible to obtain a greater pressure loss reduction effect.

In the inner grooved heat transfer tube 10 having the above-described structure, a plurality of tubes are formed on a pre-pressed fin stock in the same manner as the conventional inner grooved tube. In a state where the pipes are arranged horizontally in a parallel form, they are expanded and mounted, and are integrally assembled, whereby a heat exchanger such as a condenser or an evaporator is configured.

The heat transfer tube 10 with an inner groove according to the present invention.
Is such that excellent heat transfer performance can be exhibited irrespective of the flow direction of the heat transfer fluid such as the refrigerant liquid or the refrigerant vapor in the inclined groove 12, and thus the inner surface according to the present invention as described above When assembling a plurality of the grooved heat transfer tubes 10 to form a heat exchanger, each heat transfer tube 10 is formed such that a refrigerant liquid or a refrigerant vapor as a heat transfer fluid flows in the inclined groove 12 of each heat transfer tube 10 in an arbitrary direction. Even if the heat transfer tubes 10 are arranged to flow, in other words, even if the heat transfer tubes 10 are arranged at random without considering the groove direction, the heat exchanger configured is superior to the conventional device. The heat transfer performance can be advantageously exhibited. Therefore, by using the heat transfer tube 10 with the inner groove according to the present invention, a heat exchanger having not only excellent heat transfer performance but also good manufacturability can be advantageously obtained, and the heat transfer performance of the obtained heat exchanger can be improved. Is stable.

Incidentally, the characteristic inclined groove 12 as described above is used.
Heat transfer tube 10 having an inner surface groove provided with a straight groove 14
Is advantageously produced as follows using a rolling and tube forming apparatus 30 as shown in FIG.

That is, as is clear from FIG.
Strip 32 made of copper or copper alloy as heat transfer tube material
Is sandwiched between a pair of guide rolls 34 disposed on the inlet side of the rolling and tube forming apparatus 30, and is driven in one direction in a longitudinal direction (in FIG. 8, by an arrow) by a drive roll (not shown). To move continuously. Then, in the device 30, the strip 32 is sandwiched between a rolling roll 36 and a support roll 38 arranged on the front side in the moving direction of the strip 32,
Pressing is performed at a predetermined pressure to perform rolling. On the outer peripheral surface of the rolling roll 36, a number of ridges corresponding to the inclined grooves 12 formed on the inner surface of the target heat transfer tube 10 are formed.
A ridge corresponding to No. 4 is formed. Thereby, at the time of rolling by the rolling roll 36, the strip 3
A large number of inclined grooves 12, a predetermined number of straight grooves 14, and an axial groove 24 are formed on one surface of the second 2 in a form in which the inner surface of the target heat transfer tube 10 is developed.

Next, nine pairs of forming rolls 40, 4 arranged on the front side in the moving direction of the strip 32 with respect to the rolling rolls 36.
2, 44, 46, 48, 50, 52, 54, 56, the band plate 32 was formed into a tubular shape with the surface on which the inclined groove 12 and the straight groove 14 and the like were formed as described above facing inward. Thereafter, the pair of seam guide rolls 57, 57 further guides forward, and then, the high-frequency induction coil 58 is used for high-frequency induction welding of the widthwise opposite edges of the strip 32, which is positioned to face each other by such molding. Then, one continuous tube body 60 is formed.

Thereafter, the pipe 60 is shaped by a pair of squeeze rolls 62 so that the cross section thereof is substantially circular, and then cut to a predetermined length as necessary. . Thus, the heat transfer tube 10 having an inner surface groove formed by forming a large number of the inclined grooves 12 and the straight grooves 14 having the above-described characteristic structure on the inner surface of the tube can be manufactured.

[0045]

EXAMPLES Hereinafter, some examples of the present invention will be described to clarify the present invention more specifically. However, the present invention imposes some restrictions by the description of such examples. It goes without saying that you don't receive anything. In addition, the present invention, in addition to the following examples, in addition to the above specific description, various modifications based on the knowledge of those skilled in the art, unless departing from the spirit of the present invention,
It should be understood that modifications, improvements and the like can be made.

First, as an example of the present invention, as shown in FIG. 1 to FIG. 3, two virtual boundary lines 22 are provided, and inclined grooves 12 in opposite directions are provided on both sides of each virtual boundary line. The inner grooved heat transfer tube 10 having the straight groove 14 provided on each imaginary boundary line is subjected to grooving and rolling of a copper strip with a device as shown in FIG. It was machined into a cylindrical shape by roll forming and prepared by welding its butt. Further, for comparison, a straight groove is not provided in the virtual boundary line portion, and in the virtual boundary line portion, the inclined grooves on both sides inclined in opposite directions to each other are connected in a V-shape. An inner grooved heat transfer tube was prepared as a comparative example. Table 1 below
, The number of grooves indicates the number of inclined grooves 12 per revolution, that is, the number of inclined grooves 12 formed on the end face in a cross section perpendicular to the pipe axis, and the number of virtual boundary lines is virtually The number of boundary lines of the divided pipe inner surface is shown.

[0047]

[Table 1]

Next, using the prepared heat transfer tubes with inner grooves according to the present invention example and the comparative example, the heat transfer tubes were transferred to a test section of a heat transfer performance test apparatus as shown in FIG. And a single tube, and an evaporation performance test and a condensation performance test were performed under the test conditions shown in Table 2 below. In addition, the direction of arrangement of each heat transfer tube to the test section of the heat transfer performance test device is as shown in FIG.
With respect to the flow direction of the heat transfer fluid (refrigerant) indicated by the arrow,
The inclined groove was set so as to rise forward, the inflow direction at the time of condensation was reversed to the direction at the time of evaporation, and the test section length in the condensation performance test and the evaporation performance test was 4 m. As the heat transfer fluid, refrigerant Freon (R22) was used, and the mass flow rate of the refrigerant was 250 kg / (m ² · s), which was almost the same as the actual machine operation conditions.

[0049]

[Table 2] *: Gauge pressure (1 MPa = 10.1978 kgf / cm ² )

Then, based on the results obtained in the heat transfer performance measurement experiment, the heat transfer coefficient and the pressure loss in the pipes of the current mass-produced heat transfer pipes with internal spiral grooves are set to 1 respectively. Relative comparison was performed, and for the heat transfer tubes according to the present invention example and the comparative example, the results of the heat transfer ratio in the tube-pressure loss ratio in the tube are shown in FIG. 10, and as is clear from FIG. In the case of evaporation of the heat transfer tube according to the above, while maintaining the same heat transfer performance as the heat transfer tube of the comparative example, 1
The pressure loss reduction effect of about 0% is obtained.
On the other hand, in the case of condensation, the heat transfer tube according to the present invention not only promotes heat transfer by nearly 20%, but also obtains a pressure loss reduction effect of nearly 20%, as compared with the heat transfer tube of the comparative example. It is.

[0051]

As is apparent from the above description, in the heat transfer tube with an inner surface groove according to the present invention, the inclined grooves formed on both sides of the imaginary boundary portion are formed so as to be inclined in directions opposite to each other. By doing so, excellent heat transfer performance can be exhibited regardless of the flow direction of the heat transfer fluid, and
By providing such a straight groove extending in the axial direction along the virtual boundary line, it was possible to effectively suppress an increase in pressure loss in the pipe while sufficiently retaining such an excellent heat transfer promoting effect. This has made a significant contribution to the practical application of this type of heat transfer tube with internal grooves,
There is great technical significance of the present invention.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a heat transfer tube with an inner surface groove having a structure according to the present invention, wherein (a) is an explanatory view showing the inner surface of the tube by developing such a heat transfer tube; (b) is an enlarged end view of a main part in a cross section perpendicular to the pipe axis.

FIGS. 2A and 2B are main-part enlarged cross-sectional explanatory views showing a vertical longitudinal cross-section of the heat transfer tube with inner grooves shown in FIG. 1, wherein FIG. 2A is a left-half cutaway view, and FIG. The right half cut is shown respectively.

FIGS. 3A and 3B are main-part enlarged cross-sectional explanatory views showing a horizontal vertical cross-section of the heat transfer tube with inner grooves shown in FIG. 1, wherein FIG. 3A is an upper half cutaway view, and FIG. The lower half views are shown respectively.

FIGS. 4A and 4B are schematic diagrams showing a refrigerant flow on the inner surface of the heat transfer tube, where FIGS. 4A and 4B show ds <d and d, respectively.
It is explanatory drawing which expands and shows the cross section of a pipe | tube inner surface development view and a virtual boundary part in the case of s = d.

FIG. 5 is an enlarged schematic view showing a refrigerant flow similar to FIG. 4, wherein (a) and (b) show ds <d and ds, respectively.
It is a perspective explanatory view showing the refrigerant flow near the straight groove when = d.

FIG. 6 is a development view showing various inner surfaces of the heat transfer tube with an inner groove according to the present invention, wherein (a) to (d) schematically show different patterns of inclined grooves formed on the inner surface of the tube. FIG.

FIG. 7 is a developed view showing various inner surfaces of the heat transfer tube with inner grooves according to the present invention, wherein (a) to (d) schematically show different patterns of inclined grooves formed on the inner surface of the tube. FIG.

FIG. 8 is an explanatory view schematically showing a rolling and tube-making apparatus for manufacturing the heat transfer tube with inner grooves according to the present invention.

9A and 9B are diagrams illustrating a heat transfer performance test in an example, in which FIG. 9A is an explanatory diagram schematically illustrating a test device for measuring the heat transfer performance of a heat transfer tube, and FIG. It is explanatory drawing which shows the arrangement structure of the heat transfer tube in a simple test apparatus.

FIG. 10 is a diagram showing a heat transfer ratio in a tube and a pressure loss ratio in a tube of the heat transfer tubes according to the present invention and the comparative example obtained in the example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Heat transfer tube with an inner groove 12 Slant groove 14 Straight groove 16 Virtual surface 18a Left half surface 18b Right half surface 22 Virtual boundary line 24 Axial groove 30 Rolling and tube forming device 32 Strip plate 34 Guide roll 36 Rolling roll 38 Support roll 40, 42, 44, 46, 48, 50, 52, 54, 5
6 Forming Roll 57 Seam Guide Roll 58 High Frequency Induction Coil 60 Tube 62 Squeeze Roll

Claims (5)

[Claims] 1. A pipe inner surface having at least two or more virtual boundary lines extending in the pipe axis direction, and a plurality of inclined lines extending from each of the virtual boundary lines to two adjacent virtual boundary lines sandwiching the virtual boundary lines. The grooves are formed in a form in which the grooves are inclined at a predetermined angle with respect to the pipe axis, while the inclined grooves on both sides formed respectively with the virtual boundary line are inclined in opposite directions. And the groove depth of these inclined grooves: d 2
Ratio and the maximum diameter in the tube: D: 2d / D is 0.05 to
0.1, and a straight groove extending in the pipe axis direction at a groove depth: ds smaller than d of the inclined groove: d on each of the virtual boundary lines. The straight groove is provided in a state of communicating with the groove, and furthermore, the relational expression of the groove depth: ds (mm), the groove width: Ws (mm) and the number of strips: n, and the maximum diameter in the pipe: D (mm): d
The value of s × Ws × n / (π × D) is 0.001 to 0.0
5. An inner grooved heat transfer tube, wherein the heat transfer tube is configured to be within the range of 5. 2. The ratio of the groove depth of the inclined groove: twice as large as d to the maximum diameter in the pipe: D: 2d / D is 0.058 or more.
2. The heat transfer tube with an inner surface groove according to claim 1, wherein the heat transfer tube is set within a range of 0.087. 3. The relational expression: ds × Ws × n / (π ×
3. The heat transfer tube with an inner groove according to claim 1, wherein the value of D) is configured to be in a range of 0.005 to 0.04. 4. 4. The heat transfer tube with internal grooves according to claim 1, wherein the number of said virtual boundary lines is an even number of 10 or less. 5. A pitch of the inclined groove in a circumferential direction of the pipe is in a range of 0.35 to 0.50 mm, and an inclination angle of the inclined groove with respect to the pipe axis is in a range of 5 ° to 45 °. And the portion between adjacent inclined grooves is 10 ° to 3 °.
The heat transfer tube with an inner surface groove according to any one of claims 1 to 4, wherein the heat transfer tube is formed as a ridge having an apex angle within a range of 5 °.