JP2001033185A - Heat conductive pipe provided with inside groove, and its design method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat conductive pipe provided with inside grooves excellent in inner heat conduction performance and processability and easy in design. SOLUTION: This heat conductive pipe 10 has many grooves 12 slant to its axis made at its inner face. In this case, the tilt angle (θ) to pipe axis of the groove 12 is set to 5-45 deg., and also it is so arranged that the shape parameter: [2(d/D)2.A/a] being expressed by the diameter (D) of the pipe, the sectional area (a) per groove 12, the depth (d) of the groove, and the area (A) of the circle contacting with the tip of the fin 16 made between the grooves 12 and 12, centering upon the axis of the pipe enters the range of more than 0.8 and less than 2.0.

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 and a method of designing the same, and more particularly, to a heat transfer tube having an inner groove having excellent heat transfer performance and workability in the tube and easy to design, and such an inner grooved heat transfer tube. The present invention relates to a method for advantageously designing a heat transfer tube.

[0002]

2. Description of the Related Art Conventionally, in a heat exchanger such as an evaporator or a condenser in an air conditioner represented by an air conditioner or a refrigerator, generally, a plurality of heat transfer tubes are respectively connected to a fin stock or the like. It is configured by being expanded and attached in a state of extending in a predetermined direction and integrally assembled, and comes into contact with a refrigerant as a heat transfer fluid circulated in the plurality of heat transfer tubes and an outer surface of each heat transfer tube. Heat is exchanged with the heat transfer fluid such as air or water to be conveyed, and the refrigerant introduced into the heat transfer tube can be evaporated or condensed.

[0003] By the way, various types of heat transfer tubes mounted on such a heat exchanger have been proposed so far. For example, a large number of grooves are inclined on the inner surface of the tube with respect to the tube axis. A so-called heat transfer tube with an internal spiral groove formed in a spiral shape, and a plurality of (even number of) inner surfaces of the tube in the circumferential direction
In each of these areas, a number of grooves that are inclined at a predetermined angle with respect to the pipe axis are formed in each of the areas, and the inclination directions of the grooves are opposite to each other in adjacent areas. , Internally grooved heat transfer tubes (inner pine needle grooved heat transfer tubes) having a groove structure exhibiting a shape like pine needles,
Widely used. That is, in such a heat transfer tube with an internal spiral groove and a heat transfer tube with an internal crutch, an inclined groove such as a spiral groove or a pine needle groove is formed on the inner surface of the tube.
The heat transfer area in the pipe is advantageously increased by increasing the contact area of the refrigerant circulated in the pipe, in other words, increasing the heat transfer area of the heat transfer pipe. There is an inherent problem that the condensing performance cannot be sufficiently improved, and the expected heat transfer performance in the pipe cannot be effectively exhibited.

In order to address such a problem, in recent years, in the heat transfer tube with the internal spiral groove or the heat transfer tube with the internal Matsuba groove, the depth of the inclined groove is increased so that the distance between the adjacent grooves is increased. High fins to increase the height of the ridges (fins) formed in the fins, narrow fins to narrow the pitch of the inclined grooves to reduce the width of the fins, and decrease the width of the pitch and the bottom of the groove To increase the number of grooves and increase the number of grooves,
Further, the inclination angle of the groove with respect to the tube axis is defined, or, as disclosed in Japanese Patent Application Laid-Open No. 10-2600000, the apex angle of the fin, that is, the intersection of the slopes on both sides constituting the fin. Various measures, such as setting the angle to a size within a predetermined range, have been taken alone or in combination.

However, in the case of increasing the fins, making the fins thinner, increasing the number of grooves, and defining the inclination angle of the grooves or the fin apex angle, any of them can improve the evaporation performance and the condensation performance to some extent. However, even if they are implemented in combination, they have not reached the point at which the heat transfer promoting effect can be greatly increased. In particular, in the case of higher fins and finer fins, it can be achieved even more highly by the recent remarkable progress of processing technology. It has been found that a heat transfer tube having a fin formed on its inner surface can provide only a very small difference in performance as compared with a conventional product.

Further, in the case of the heat transfer tube with an inner groove having the inclined groove as described above, the specification is restricted depending on the heat exchanger to which the tube is applied, and furthermore, the air conditioner and the refrigerator. For example, the outer diameter of the tube and the thickness of the groove bottom are defined based on the pressure resistance required for the inner grooved heat transfer tube, and the heat transfer tube is attached to a fin stock or the like in the production of a heat exchanger. Depending on the shape of the expansion plug used in such a case, the groove depth may be determined in advance. However, due to such restrictions, some of the above-described measures cannot be implemented (such specific examples). In the example, it is not possible to increase the fins), which causes a problem that the required heat transfer performance cannot be sufficiently ensured. In addition, when such a constraint exists as described above, the constraint is imposed. Under no conditions Since it is not possible to design the heat transfer tube by using the previously determined factors related to the shape of the heat transfer tube such as the groove depth, both good evaporation performance and good condensation performance are advantageously realized. In order to design the heat transfer tube to be obtained, it is necessary to carry out an experiment every time the constraint conditions change, and to find the optimum value of each factor by trial and error, which makes the design work extremely troublesome. The problem is inherent.

[0007]

Under such circumstances, the inventors of the present invention have developed a heat transfer tube with an inner spiral groove or a heat transfer tube with an inner pine needle groove, the outer diameter of the tube, the groove depth, the inclination angle of the groove with respect to the tube axis, the fin apex angle, and the like. Rather than individually defining the heat transfer tube shape such as the width of the groove bottom, the width of the fin, the number of grooves, and the thickness of the groove bottom as in the past, these factors are considered together. As a result of intensive research based on the prediction that the one obtained by setting the values of each factor while grasping the tube shape from various angles, the factors related to the tube shape were correlated with each other. Specific shape parameters that are grouped based on the relationship, and the inclination angle of the groove,
Each of the inner grooved heat transfer tubes within a predetermined range has excellent groove forming workability and high performance in both evaporation and condensation, thereby exhibiting good heat transfer performance in the tube. I found something to gain. in addition,
In the heat transfer tube with an inner groove having such a configuration, the design can be easily performed by setting the value of a predetermined factor so that the shape parameter and the inclination angle of the groove fall within a predetermined range. And that even if such a design imposes some restrictions on the specifications of the heat transfer tubes, the heat transfer performance in the tubes can be maximized within the specifications. I also got

Accordingly, the present invention has been completed on the basis of this finding, and the object of the present invention is to achieve both high evaporation performance and high condensation performance while achieving excellent heat transfer in a pipe. Another object of the present invention is to provide a heat transfer tube with an inner groove having good workability and capable of effectively exhibiting performance. Another object of the present invention is to provide a heat transfer tube with an inner groove that can be advantageously designed with good heat transfer performance.

Further, according to the present invention, it is possible to easily design a heat transfer tube with an inner groove having excellent heat transfer performance in the tube, and to maximize the heat transfer performance even when the specification is limited. A method for designing a heat transfer tube with an inner surface groove that can be made is also an object to be solved.

[0010]

According to the present invention, in order to solve such a problem, a large number of grooves having an inclination angle of 5 ° to 45 ° with respect to a pipe axis are formed on a pipe inner surface. ,
The outer diameter of the pipe (D), the cross-sectional area per groove (a) in a cross section perpendicular to the pipe axis, the depth of the groove (d), and the tip of the fin formed between the grooves with the pipe axis as the center. Shape parameter expressed by the area (A) of the tangent circle: [2 (d / D)
² · A / a] is within the range of 0.8 or more and 2.0 or less.

That is, in the heat transfer tube with an inner groove according to the present invention, a large number of grooves are formed on the inner surface at the specific inclination angle with respect to the tube axis, and the outer diameter of the tube (D ), The cross-sectional area per groove in a cross section perpendicular to the pipe axis (a), the groove depth (d), and the area of a circle centering on the pipe axis and in contact with the tip of a fin formed between the grooves (A ) Have a great feature in that the shape parameter represented by the mathematical formula as described above is within a specific range.

In short, in the present invention as described above, the cross-sectional area (a) per groove in a cross section perpendicular to the tube axis generally indicates the groove depth (d) and both sides of the fin formed between the grooves. Are defined by factors related to the shape of the heat transfer tube, such as the intersection angle of the slope (fin apex angle), the width of the groove bottom, the number of grooves, the tip width or radius of curvature of the fin, and the inclination angle of the groove.
Further, the area (A) of the circle contacting the tip of the fin formed between the grooves around the pipe axis depends on factors such as the pipe outer diameter (D), the groove depth (d), and the thickness of the groove bottom. From what is specified, the shape parameters are various factors related to the tube shape, which are linked based on the correlation between each other, so that they are united, in other words, The fact that the value of such a shape parameter is determined means that the value of each factor is determined by comprehensively taking into account the interrelationship between them.

Accordingly, the heat transfer tube with an inner surface groove according to the present invention is configured so that the shape parameter having such a characteristic property together with the inclination angle of the groove becomes a value within a predetermined range. Without impairing its grooved workability.
Both the evaporation performance and the condensation performance can be effectively enhanced, whereby the superior heat transfer performance in the tube can be advantageously exhibited as compared with the conventional heat transfer tube, and thus the heat transfer can be enhanced. The effect could be greatly and effectively increased.

Further, in the heat transfer tube with an inner groove according to the present invention, the value of a predetermined factor is simply set so that the shape parameter and the inclination angle of the groove are within a predetermined range. It can be easily designed with excellent functions. In addition, even when there are restrictions on the specifications of the heat transfer tube, the design using such a design method has an advantage that the heat transfer performance can be improved to the utmost within such specifications. -ing

According to a preferred embodiment of the heat transfer tube with internal grooves according to the present invention, the intersection angle between the slopes on both sides of the fin formed between the grooves is in the range of 10 ° to 45 °. -ing In the heat transfer tube with the inner surface groove having such a configuration, higher heat transfer performance can be more advantageously realized, and the groove workability is further improved.

In the heat transfer tube with an inner groove according to the present invention as described above, the heat transfer tube through which a predetermined refrigerant can flow at a refrigerant mass speed of 100 kg / (m ² · s) or more is particularly used. , So that the benefits of good heat transfer performance can be maximized.

In the present invention, the inside of the pipe is 100 k
When designing a heat transfer tube through which a predetermined refrigerant can flow at a refrigerant mass velocity of g / (m ² · s) or more, a number of grooves having an inclination angle of 5 ° to 45 ° with respect to the tube axis are formed on the inner surface of the tube. And a pipe outer diameter (D), a cross-sectional area per one groove at a cross section perpendicular to the pipe axis (a), a groove depth (d),
And the area (A) of a circle contacting the tip of the fin formed between the grooves around the pipe axis is expressed by the following equation: 0.8 ≦ [2 (d /
D) The design method of the heat transfer tube with inner grooves, characterized in that the respective values are set so as to satisfy ² · A / a] ≦ 2.0, is also the gist of the invention.

In the method for designing a heat transfer tube with an inner surface groove according to the present invention, a large number of grooves are formed so that the inclination angle with respect to the tube axis is 5 ° to 45 °, and as described above. Specific shape parameter: [2 (d / D) ² · A
/ A], the outer diameter (D) of the pipe, the cross-sectional area per groove (a) in a cross section perpendicular to the pipe axis, and the depth of the groove ( d) and the value of the area (A) of the circle which is in contact with the tip of the fin formed between the grooves around the tube axis are set. In short, the pipe outer diameter (D), the groove depth (d), the intersection angle of the slopes on both sides of the fin formed between the grooves, and the width of the groove bottom so that the value of the shape parameter falls within a predetermined range. , The number of grooves, the width of the fin tip or the radius of curvature of the tip, the inclination angle of the groove, the thickness of the bottom of the groove, and other factors related to the shape of the heat transfer tube. However, there is a remarkable feature in determining at the same time in a well-balanced manner.

Therefore, in the method for designing a heat transfer tube with an inner groove according to the present invention, the above-described relatively simple method is used so that the inclination angle of the groove and the specific shape parameter fall within a predetermined range. By simply performing the setting work, the values of various factors can be optimized without any extra experiment,
Therefore, the inner grooved heat transfer tube capable of advantageously realizing a high evaporation performance and condensation performance, and furthermore, an effective heat transfer performance in the tube, among which 100 kg in the tube having such a characteristic performance.
A heat transfer tube through which a predetermined refrigerant flows at a refrigerant mass velocity of / (m ² · s) or more can be designed very easily. Therefore, according to the method of the present invention, the design work can be significantly simplified and made more efficient.

In addition, according to the method for designing a heat transfer tube with an inner groove according to the present invention, even when the specification of the heat transfer tube is limited, the values of various factors are optimized under the limitation. As a result, the heat transfer performance in the pipe can be improved to the utmost, and as a result, it is possible to easily and quickly cope with various specifications.

In a preferred embodiment of the method for designing a heat transfer tube with an inner groove according to the present invention, the intersection angle of the slopes on both sides of the fin formed between the grooves is 10 ° to 10 °. The design is to be within the range of 45 °. According to such a design method, it is possible to extremely advantageously design a heat transfer tube with an inner groove having higher heat transfer performance and good groove workability.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, in order to make the present invention clearer, a specific configuration of the present invention will be described in detail with reference to the drawings.

First, FIG. 1 is a plan view showing a specific example of a heat transfer tube with an inner groove having a structure according to the present invention, which is cut open along a cutting surface in the tube axis direction and developed into a flat plate shape. (However, in FIG. 1, the vertical direction is the tube axis direction of the heat transfer tube.) FIGS. 2 and 3 show the tube axis direction of the heat transfer tube with the inner surface groove shown in FIG. Cross-sectional views in a direction perpendicular to the tube axis are respectively shown. In such FIGS. 1 to 3, the heat transfer tube 10 with an inner groove is
As a whole, it has a straight pipe shape with a circular cross section, and its outer peripheral surface is a smooth surface, while its inner peripheral surface is provided with a large number of grooves 12. It is used as a heat transfer tube which constitutes a heat exchanger such as an evaporator or a condenser in a refrigerator or a refrigerator, and various known refrigerants as a heat transfer fluid can be circulated therein.

More specifically, each of the large number of grooves 12 formed on the inner peripheral surface of the heat transfer tube 10 having an inner surface groove has a tube shaft 1.
In a cross section perpendicular to 4, the pipes have the same trapezoidal shape, the width of which becomes narrower toward the bottom, and which are inclined with respect to the pipe axis 14, extend continuously in the circumferential direction in a spiral shape, and They are provided so as to be separated from each other by a predetermined distance in the axial direction. And the heat transfer tube 10 with an inner surface groove
The groove 12 is provided on the inner peripheral surface as described above, so that the groove 12 is provided between the adjacent grooves 12.
A fin 16 having a cross-section perpendicular to the tube axis and having a flat surface at the end is formed, and the fin 16 is attached to the tube shaft 14. It extends in a spiral shape in the circumferential direction while being inclined with respect to it, and is formed in a large number at intervals with each other. That is,
The heat transfer tube with internal grooves 10 shown in FIGS. 1 to 3 is a heat transfer tube with internal spiral grooves, in which a spiral groove is engraved on the inner surface.

Then, the heat transfer tube 10 with an inner groove according to the present invention is provided.
In this case, the inclination angle of the groove 12 (fin 16) with respect to the tube axis 14 (the angle indicated by θ in FIG. 2) is 5 °.
The angle (angle) is up to 45 °, and the value of a specific shape parameter (R) (dimensionless number) represented by the following equation (1) is set to be in a range of 0.8 to 2.0. This is where the major features of the present invention reside. R = [2 (d / D) ² · A / a] (1) The shape parameter represented by the above equation (1): R
, D is the pipe outer diameter [dimension indicated by D in FIGS. 2 and 3 (i)], and a is the cross-sectional area of the groove 12 in a cross section perpendicular to the pipe axis [in FIG. 3 (ii), Area defined by a bottom surface and both slopes forming the groove 12, and a line 17 that linearly connects the centers of the tip surfaces of the adjacent fins 16, 16 forming the slope], and d is the groove. Depth [Figure 2
In the above, the dimension shown by d]
In the section perpendicular to the tube axis, the area of a circle centered on the tube axis 14 and in contact with the tip of the fin 16 [the area of the tangent circle 18 shown by a two-dot chain line in FIG.

That is, the specific shape parameter R introduced in the present invention as described above is an outer tube diameter D:
Cross-sectional area of the groove 12 in a cross section perpendicular to the tube axis: a, groove depth:
d, the area of the tangent circle 18: A is configured in combination, and in such a specific shape parameter: R, the cross-sectional area of the groove 12 as a component thereof: a is generally the groove depth. : D, the intersection angle of the slopes on both sides constituting the fin 16 [dimension indicated by ψ in FIG. 3 (ii)],
The width of the bottom of the groove 12 in a section perpendicular to the tube axis [FIG. 3 (ii)
Medium, dimension indicated by W _db ], number of grooves 12: n, width of tip of fin 16 in cross section perpendicular to tube axis [dimension indicated by W _ft in FIG. Tilt angle: θ
The area A of the tangent circle 18 is usually the outer diameter of the tube: D, the depth of the groove: d, and the bottom of the groove 12. It is apparent from the fact that the shape parameters are determined based on factors related to the tube shape such as the wall thickness (dimensions indicated by t in FIGS. 2 and 3 (ii)): R is configured by associating various factors related to such a tube shape based on a mutual correlation and grouping them.

In short, the heat transfer tube with inner groove 1 according to the present invention
In the case of 0, in addition to the inclination angle θ of the groove 12 and the characteristic shape parameter R related to the tube shape as described above being within the above-mentioned range, the groove 12 can be processed with good quality. Not only can it be easily formed on the inner surface of the tube, but also the evaporation performance and the condensation performance can be effectively enhanced, and therefore,
It is possible to advantageously exhibit extremely excellent heat transfer performance in the pipe, and consequently a remarkable increase in the heat transfer promoting effect can be achieved.

In the heat transfer tube 10 having the inner groove, as described above, the inclination angle θ of the groove 12 is 5 ° to 4 °.
It is required that it be 5 °, and advantageously it is more preferably between 15 ° and 30 °. However, if the inclination angle θ is less than 5 °, the cycle of the refrigerant flowing through the inside of the pipe from the bottom to the top of the pipe becomes too long due to the groove 12 having such an inclination angle. In particular, when the inner grooved heat transfer tube 10 is used for an evaporator, a dryout in which the inner surface of the tube is dried is caused. Problems such as deterioration of performance occur. On the other hand, at present, it is difficult to form the groove 12 in which the inclination angle θ exceeds 45 °, and even if the groove 12 can be formed, the manufacturing speed is greatly increased. In addition, the fins 16 formed between the grooves 12, 12 block the flow of the refrigerant and increase the pressure loss. Since the temperature becomes high, especially when the heat transfer tube 10 with the inner surface groove is applied to an evaporator, it is not possible to sufficiently secure a temperature difference with a predetermined heat transfer fluid outside the tube, and as a result, the evaporation There are inherent problems such as a decline in ability.

On the other hand, in the present invention, the value of the shape parameter: R, which defines the shape of the heat transfer tube 10 with an inner surface groove, is 0.8 to 2.0, preferably 1.0 to 1.
It is required to be 8 or less. A typical case in which the value of the shape parameter: R is smaller than 0.8 is a case where the number of grooves: n is extremely small. In this case, the contact area of the refrigerant with the inner surface of the pipe is considered. That is, a significant reduction in the heat transfer area is caused, so that no particular enhancement of the evaporation performance can be made. vice versa,
As a typical example in which the value of the shape parameter: R exceeds 2.0, it is conceivable that the number of grooves: n is extremely large.
In the heat transfer tube 10 having the inner groove, the groove 12 is inevitably formed.
Since the opening width (the dimension indicated by W _do in FIG. 3 (ii)) becomes too small, the heat transfer tube 1
When 0 is used for the condenser, the entire groove 12 is covered with the refrigerant at the time of condensation, so that the groove 12 is easily immersed.
The condensation performance is extremely deteriorated.

Further, in the heat transfer tube 10 having the inner surface groove as described above, the intersection angle ψ of the slopes on both sides of the fin 16 is preferably 10 ° to 45 °, more preferably 10 ° to 20 °.
Is desirable. If the intersection angle 角度 in such a fin 16 becomes too small, a large number of grooves 12 are formed so as to sandwich such a fin 16 therebetween.
Not only is it extremely difficult to groove the inner surface of the tube, but even if it can be processed, the fins 16 may not work when the heat transfer tube 10 is expanded at the time of assembling the target heat exchanger. This is because they are crushed and the groove depth: d cannot be sufficiently secured, or the opening of the groove 12 is closed. If the intersection angle 場合 is too large, the number of the grooves 12 formed per unit area decreases, and accordingly, the value of the shape parameter R becomes too small, and the heat transfer area decreases. At the same time, the heat transfer performance may not be improved due to a reduced holding volume of the condensed liquid at the time of condensation.

By the way, when designing the heat transfer tube 10 with an inner surface groove which can exhibit such an effective effect, according to the present invention, the groove 12 (fin 16) is formed so that the above-described configuration can be advantageously realized. Angle of inclination with respect to tube axis 14:
θ is set to 5 ° to 45 °, preferably 15 ° to 30 °, and the value of the shape parameter: R represented by the above formula (1) is 0.8 ≦ R ≦ 2.0, preferably Is 1.0
In order to satisfy ≦ R ≦ 1.8, its shape parameter:
The outer diameter of the pipe as a component of R: D, the cross-sectional area of the groove 12 in a cross section perpendicular to the pipe axis: a, the depth of the groove: d, and the area of the circle 18 in contact with the tip of the fin 16 around the pipe axis 14: A Are set, respectively.

In the design of such an inner grooved heat transfer tube 10, values are set so as to satisfy the above-mentioned specific requirements. The cross-sectional area of the groove 12 in the cross section perpendicular to the tube axis: a and the area of the tangent circle 18: In the case of A, as described above, the predetermined factors (d, ψ, W _db , n, W _ft , θ,
D, t, etc.), setting the values of D, a, d, A as described above means that the value of the shape parameter: R falls within the above range. In addition, various factors related to the tube shape: d, ψ, W _db , n,
For W _ft , θ, D, t, etc., taking into account the interrelationship among them, in other words, the shape of the whole pipe is grasped from multiple angles, and the values of each factor are balanced and integrated. It is no less than to make a decision.

Therefore, according to the design method according to the present invention, a relatively simple predetermined setting operation can be performed.
By advantageously optimizing the value of each factor relating to the tube shape,
This makes it possible to easily design the heat transfer tube 10 having an inner groove, which can realize high evaporation performance and condensation performance, and excellent heat transfer performance in the tube. In short, in the method of the present invention, in order to secure the expected performance in the heat transfer tube 10 with the inner surface groove, it is necessary to perform any special trial experiment aimed at obtaining the optimum values of the factors relating to the tube shape. This is advantageous because it can effectively reduce the burden on the worker and the work time required for the design work from the point of lack of performance.

Further, in order to realize the pressure resistance required for the heat transfer tube 10 with an inner surface groove, the outer diameter of the tube:
According to the method of the present invention, even if there are constraints in the specification of the heat transfer tube 10 such as when the thickness of the bottom of the tube: t is predetermined, the values of the factors not subject to the constraints are optimized and given. Within the range of the specification, it is possible to design the heat transfer tube 10 exhibiting a sufficiently high heat transfer performance in the tube.
As a result, it is possible to flexibly cope with various specification conditions.

In the design method of the heat transfer tube 10 having the internal groove according to the present invention, particularly when designing the heat transfer tube 10 having the internal groove used in the evaporator of an air conditioner or the like, the groove depth: d and the groove width are used. When the number: n is large and there is a concern about an increase in pressure loss that greatly affects the evaporation performance, in order to effectively suppress the increase in pressure loss,
It is preferable that the inclination angle of the groove 12 be as small as possible among the angles of 5 ° to 45 ° as θ. Also, in recent years, in order to improve the heating performance of the air conditioner, during the condensation operation, operating conditions that increase the degree of supercooling at the outlet are adopted, or an auxiliary heat exchanger dedicated to the supercooling area is provided on the outlet side of the refrigerant in the main condenser. There are many attempts to connect and add, and there is a strong demand for improvement of the heat transfer coefficient in the supercooled region. However, a condenser for achieving such purpose is constructed. When designing the heat transfer tube 10, it is desirable to set the inclination angle θ of the groove 12 as large as possible within the range of 5 ° to 45 ° to increase the heat transfer area. It is.

Further, in the method of the present invention, in order to design a heat transfer tube 10 with an inner groove, which is more excellent in grooving workability and more effectively exhibits effective heat transfer performance,
The intersection angle of the slopes on both sides of the fin 16: 、, preferably 1
The angle is set at 0 ° to 45 °, more preferably at 10 ° to 20 °.

Thus, the heat transfer tube 10 with an inner groove according to the present invention
In, based on such a design, as before,
It is produced by a method of bending and welding a copper strip or the like that has been subjected to rolling or grooving of a steel pipe, etc., and a plurality of the pieces are arranged in parallel with a pre-pressed fin stock or the like. In a state where the pipes are arranged horizontally in a form, they are expanded and mounted, and are integrally assembled, so that a heat exchanger such as an evaporator or a condenser is formed. In short, the internal grooved heat transfer tube 10 can be advantageously used as a heat transfer tube constituting a heat exchanger such as an evaporator or a condenser, and can exhibit the excellent heat transfer performance in the tube as described above. In the invention, in particular, 100 k
g / (m ² · s) or more, preferably 150 kg / (m ²
(S) By using the heat transfer tube through which a predetermined refrigerant is circulated at the above-described mass flow rate of the refrigerant, excellent effects can be more effectively exerted.

In the above description, a specific example is shown in which the present invention is applied to a heat transfer tube with an inner spiral groove having an inner spiral groove formed therein. It should be understood that the present invention can be applied to any of the internally grooved heat transfer tubes having a large number of inclined grooves.

For example, FIGS. 4 and 5 show that the inner surface of the pipe is divided into a plurality (even number) of areas by a virtual boundary line 20 extending in the pipe axis direction. A number of inclined grooves 12 are formed, and the grooves 1
An example in which the present invention is applied to a heat transfer tube with an inner groove having a flute groove structure (a heat transfer tube with an inner creasing groove) in which the inclination directions of the two are reversed in the adjacent regions 22 is an axial direction. It is shown in a plan view that is cut open at the cut surface and developed into a flat plate shape.

More specifically, in the heat transfer tubes 24 and 26 having the inner surface grooves as shown in FIGS. 4 and 5, a plurality of regions 22 defined by the virtual boundary line 20 on the inner surfaces of the tubes. In each case, a groove 12 having a required shape in a cross section perpendicular to the tube axis is continuous in the circumferential direction as a whole, and is adjacent to the groove 12 at a predetermined interval in the tube axis direction.
A large number of fins 16 are formed between the fins 12, and the grooves 12 having such a configuration are provided at a predetermined inclination angle with respect to the tube shaft 14. . In addition, in the heat transfer tubes 24 and 26 with the inner surface grooves, although not clear from the drawing, the cross-sectional shape of the groove 12 at right angles to the tube axis has a trapezoidal shape that becomes narrower toward the bottom.

And, the heat transfer tube 2 with an inner groove according to the present invention
4 and 26, each of the inclination angles of the groove 12 in each region 22 is set to an angle in the range of 5 ° to 45 °, and the shape parameter represented by the above-described formula (1):
The value of R is in the range of 0.8 or more and 2.0 or less, whereby it is possible to easily and advantageously design the heat transfer tube 10 in the same manner as the heat transfer tube 10 with the inner surface groove. Heat transfer tubes made based on such a design and constituting a heat exchanger such as an evaporator or a condenser, in particular, 100 kg inside the tubes
/ (M ² · s) It is advantageously used as a heat transfer tube through which a predetermined refrigerant is circulated at a refrigerant mass speed of not less than / (m ² · s), and effectively has the same function and effect as the heat transfer tube 10 with the inner surface groove as described above. It is able to demonstrate.

It should be noted that such heat transfer tubes 24, 2 having an inner groove are provided.
Also in 6, it is desirable that the intersection angle between the slopes on both sides constituting the fin 16 is preferably 10 ° to 45 °. In addition to the inclination angle of the groove 12, the cross-sectional area of the groove 12 in the cross section perpendicular to the tube axis, the groove depth, and the intersection angle between the slopes on both sides of the fin 16, the values of the respective regions 22 In, even if it is the same as each other,
Or, even if they are different from each other, there is no problem. Further, when the values of the cross-sectional area and the groove depth of the groove 12 are different for each region 22, the values of a, d and A constituting the shape parameter: R cannot be uniquely determined. The average value is adopted as the values of a, d, and A. The average value adopted as the value of the area A of the circle in contact with the tip of the fin 16 is calculated by calculating the average value of the groove depth in each region 22.
It can be easily obtained by deriving the radius of the circle contacting the tip of.

Further, the heat transfer tube 24 with the inner surface groove as described above
In the heat transfer tube 26 and the inner grooved heat transfer tube 10 described above, the cross-sectional shape of the groove 12 is trapezoidal, and the end face of the tip of the fin 16 is a flat surface. The shape of the tip of the fin 16 is by no means limited to this. For example, the cross-sectional shape of the groove 12 is employed in a conventional spiral groove structure or a pine needle groove structure such as a V-shaped shape. Any of various shapes can be advantageously employed, and there is no problem even if the cross section in the direction perpendicular to the tube axis is a curved convex surface having a saddle shape on the distal end surface of the fin 16. When such a curved convex surface is adopted as the end surface shape of the tip of the fin 16, when the shape parameter: R, the area of a circle in contact with the tip of the fin 16, which is a component of R, is one of the factors that define A. First, it goes without saying that the radius of curvature of the tip end surface (curved convex surface) of the fin 16 in the section perpendicular to the tube axis is included.

[0044]

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 shown in FIGS. 1 to 3, on the inner surface of the pipe, a number of spiral grooves (12) inclined with respect to the pipe axis (14) are provided, and adjacent spiral grooves (12, 12).
According to the present invention, according to the present invention, the heat transfer tube (10) having an inner surface having a fin (16) formed between the shape parameter: R and the inclination angle (θ) of the groove with respect to the tube axis are shown in the following table. The test tubes of Examples 1 to 11 of the present invention were designed and designed to have the value shown in FIG. Table 1 below also shows the dimensions of the test tubes thus designed and manufactured. However, in Table 1 below, the fin apex angle indicates the intersection angle between the slopes on both sides of the fin.

For comparison, a heat transfer tube made of copper and having a spiral groove on its inner surface, which is currently generally mass-produced, was prepared as a test tube (comparative example). The specifications of the sample tube of this comparative example, such as the value of the shape parameter R and the inclination angle of the groove with respect to the tube axis, were as shown in Table 1 below.

[0047]

[Table 1]

Next, using the test tubes according to the present invention and the comparative example prepared above, each of them was transferred to a test section 50 of a heat transfer performance measuring experiment apparatus as shown in FIG. Assembled for each test, 200 and 300 kg according to standard test conditions as shown in Table 2 below.
At two refrigerant mass velocities of / (m ² · s), an evaporation performance test and a condensation performance test were performed. In the experimental apparatus for measuring heat transfer performance shown in FIG.
Is a compressor, 56 is a condenser, and 58 is a refrigerant mass flow meter. The test section 50 is configured such that a test tube to be tested is assembled thereto to form a double-tube heat exchanger in which test tubes are provided as the inner tube 60. At that time, hot water or cooling water was passed through an annular portion 64 between the outer tube 62 and the inner tube 60 (test tube) constituting the heat exchanger. Further, in this example, R-22 was used as a refrigerant to be circulated in the test tube.
As shown by the black arrows in FIG. 6, the hot water or the cooling water was circulated in a direction forming a counterflow. Furthermore, the test section length in the evaporation performance test and the condensation performance test was 4 m in both cases.

[0049]

[Table 2]

Then, by the heat transfer performance test as described above,
The heat transfer coefficient in the pipe of each test tube was measured, the heat transfer coefficient ratio in the test tube was determined based on the measurement result, and the obtained value of the heat transfer coefficient in the pipe was used as the mass velocity of the adopted refrigerant. Each of the following Tables 3 and 4 and graphs showing the relationship between the in-pipe heat transfer coefficient ratio and the value of the shape parameter: R are shown in FIGS. 7 and 8 for each refrigerant mass velocity. In addition,
Here, the ratio of the heat transfer coefficient in the pipe is a percentage of the heat transfer coefficient in the pipe of each test pipe when the heat transfer coefficient in the pipe of the test pipe of the comparative example is set as a reference (100). is there.

[0051]

[Table 3]

[0052]

[Table 4]

Tables 3 and 4 and FIGS. 7 and 8
As is clear from the results of the above, the shape parameter: R
Is in the range of 0.8 to 2.0, and in most of the test tubes of the present invention examples in which the inclination angle of the groove is 5 ° to 45 °, in any refrigerant mass velocity range. Also, it was recognized that both the evaporation performance and the condensation performance could be improved as compared with the test tube of the comparative example, which is a conventional product, and it was understood that this exhibited excellent heat transfer performance. Is done.

[0054]

As is clear from the above description, in the heat transfer tube with an inner surface groove according to the present invention, the inclination angle of the groove with respect to the tube axis and the specific shape parameter are each within a predetermined range. From the fact that it is, grooved workability is good, and high evaporation performance and condensing performance are realized at the same time, and excellent heat transfer performance in the pipe can be effectively exhibited, and as a result, A significant improvement in the heat transfer promoting effect can be advantageously achieved.

Further, in the case of the heat transfer tube with an inner groove which exhibits the above-mentioned excellent effects, if the design is carried out in accordance with the present invention, the inclination angle of the groove with respect to the tube axis and the shape parameter will be within predetermined ranges. It can be easily designed simply by setting a relatively simple predetermined factor. Further, even if the specification of the heat transfer tube is restricted, it is advantageous with the best heat transfer performance under the restricted condition. It can be designed for.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a specific example of a heat transfer tube with an inner surface groove having a structure according to the present invention, and is a plan view in which the inner surface of the tube is cut open along a cutting surface in the tube axis direction and developed into a flat plate shape. It is shown.

FIG. 2 is an enlarged cross-sectional view in the axial direction of a tube of the heat transfer tube with an inner surface groove shown in FIG.

FIG. 3 (i) is a cross-sectional view in a direction perpendicular to the tube axis, showing an enlarged main part of the heat transfer tube with an inner surface groove shown in FIG. 1, and (ii).
FIG. 4 is an explanatory view showing a further enlarged main part thereof.

FIG. 4 is an explanatory view showing another specific example of a heat transfer tube with an inner surface groove having a structure according to the present invention, and is a plan view in which the inner surface of the tube is cut open along the axial direction of the tube and developed into a flat plate shape. It is shown.

FIG. 5 is an explanatory view showing still another specific example of the heat transfer tube with an inner surface groove having the structure according to the present invention, and is a plan view in which the inner surface of the tube is cut open along a cutting surface in the tube axis direction and developed into a flat plate shape. It is shown by.

FIG. 6 is a schematic configuration diagram for explaining a heat transfer performance measurement experiment apparatus used in the examples, where (i) is an apparatus used for an evaporation performance test, and (ii) is an apparatus used for a condensation performance test. Are shown, respectively.

FIG. 7 shows that the refrigerant mass velocity obtained in the example is 2
00Kg / when the (m ² · s), a graph showing the relationship between the value of the tube heat transfer coefficient ratio and shape parameter of each test試管.

FIG. 8 shows that the refrigerant mass velocity obtained in the example is 3
00Kg / when the (m ² · s), a graph showing the relationship between the value of the tube heat transfer coefficient ratio and shape parameter of each test試管.

[Explanation of symbols]

 10, 24, 26 Heat transfer tube with internal groove 12 Groove 14 Tube shaft 16 Fin

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[Procedure amendment]

[Submission date] July 22, 1999 (July 7, 1999
2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0047

[Correction method] Change

[Correction contents]

[0047]

[Table 1]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0051

[Correction method] Change

[Correction contents]

[0051]

[Table 3]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0052

[Correction method] Change

[Correction contents]

[0052]

[Table 4]

Claims (5)

[Claims] 1. A plurality of grooves having an inclination angle of 5 ° to 45 ° with respect to a tube axis are formed on the inner surface of the tube, and the grooves 1 have a tube outer diameter (D) and a cross section perpendicular to the tube axis. With the cross-sectional area per unit (a), groove depth (d), and tube axis as the center,
Area of the circle that contacts the tip of the fin formed between the grooves (A)
Shape parameter represented by: [2 (d / D) ² · A
/ A] is in the range of 0.8 or more and 2.0 or less. 2. The heat transfer tube with internal grooves according to claim 1, wherein the intersection angle between the slopes on both sides of the fin formed between the grooves is in the range of 10 ° to 45 °. 3. The heat transfer tube with an inner groove according to claim 1, wherein the heat transfer tube allows a predetermined refrigerant to flow through the inside of the tube at a refrigerant mass velocity of 100 kg / (m ² · s) or more. 4. When designing a heat transfer tube through which a predetermined refrigerant can flow at a refrigerant mass velocity of 100 kg / (m ² · s) or more in a tube, an inclination angle of 5 ° to 45 ° with respect to the tube axis is set. A large number of grooves are formed on the inner surface of the pipe, and the outer diameter (D) of the pipe, the cross-sectional area per groove (a) perpendicular to the pipe axis, the depth (d) of the groove, and the center of the pipe axis. The area (A) of the circle formed between the grooves and in contact with the tip of the fin is represented by the following equation: 0.8 ≦
A method of designing a heat transfer tube with an inner surface groove, wherein each value is set so as to satisfy [2 (d / D) ² · A / a] ≦ 2.0. 5. The method according to claim 4, wherein the intersection angle between the slopes on both sides of the fin formed between the grooves is in the range of 10 ° to 45 °.