JP2000161886A - Heat exchanger tube with grooves formed therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively utilize resources and materials and to comprehensively reduce costs of air conditioners and refrigerating machines by supplying a heat exchanger tube having high performance and being light in weight per unit length. SOLUTION: There is provided a heat exchanger tube 1 with grooves formed therein. The heat exchanger has a first area in which a plurality of fins 2 are formed along a line forming a first predetermined angle 51 with respect to a tube axis, and a second area in which a plurality of fins 3 are formed along a line forming a second predetermined angle β2 with respect to the tube axis, and these fins are abutted against each other on a boundary portion of the first and second areas, to thereby form a pair of V-shaped fins. In the first area, a ratio (Pf1/Hf) of a fin pitch Pf1 crossing at right angles with the fin to a fin height Hf from the bottom of the groove is set to 2.7 to 3.6, and in the second area, a ratio (Pf2/Hf) of a fin pitch Pf2 crossing at right angles with the fin to the fin height Hf is set to 2.7 to 3.6. Each abutting portion of the fins may have a groove in the direction of the tube axis.

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 more particularly to a heat transfer tube having an inner groove which is excellent in refrigerant evaporation and condensation characteristics and has a reduced weight per meter.

[0002]

2. Description of the Related Art Heat exchangers such as air conditioners and refrigerators use a heat transfer tube which causes a phase-change refrigerant to flow in a tube and exchanges heat with an extra-tube fluid to cause the refrigerant to evaporate or condense. Have been.

As this heat transfer tube, for example, a heat exchanger such as a room air conditioner has an inner groove provided with a spiral continuous groove on the inner surface to promote heat conduction by evaporation and condensation of a refrigerant in the tube. Heat transfer tubes are frequently used.

However, in recent years, global environmental problems such as global warming, destruction of the ozone layer, acid rain, and marine pollution have become major issues. Above all, in order to prevent the destruction of the ozone layer, CFC regulations have been implemented. CFC R22 (HCFC-22), which has been used as a refrigerant for air conditioners, has been reduced by 99.5% in 2020 and has been substantially abolished. You. As an alternative refrigerant to R22, R407C was selected for a package air conditioner and R410A was selected for a room air conditioner. Each of these refrigerants is a mixture of two or three refrigerants. R407C is R32, R1
25, R134a is mixed with the current R
The refrigerants have substantially the same physical properties as those of No. 22, and each refrigerant is a non-azeotropic refrigerant mixture which evaporates and condenses at different temperatures. On the other hand, R410A is a refrigerant in which R32 and R125 are mixed at 50% each, and there is almost no azeotropic reduction in heat transfer performance, but the pressure is about 1.6 times as high as R22. Therefore, a heat transfer tube used for both condensation and evaporation of such a refrigerant needs a configuration different from a conventional heat transfer tube.

[0005] Against this background, a heat transfer tube having a new groove structure has been developed. Fins are formed on one of these heat transfer tubes having a new structure so as to face each other in the tube axis direction.
There are twin grooved tubes.

[0006] Such a grooved heat transfer tube is disclosed in JP-A-9-42.
No. 880, Japanese Unexamined Patent Publication No. Hei 8-31812, and the like. In these, the refrigerant flowing along the grooves facing each other is turbulent in the flow of the refrigerant in the pipe due to the collision of the refrigerant at the abutting portion of the grooves, thereby aiming at improving the heat transfer performance.

[0007] As another structure, fins are formed so as to face each other in the tube axis direction, and adjacent fin abutting portions have grooves in the tube axis direction. There are three pairs of grooved tubes.

[0008] Such a grooved heat transfer tube is disclosed in JP-A-9-79.
778, JP-A-9-26279 and the like. In each of these, the refrigerant flowing along the grooves facing each other is disturbed in the flow of the refrigerant in the pipe due to the collision of the refrigerant at the butting portion of the grooves, thereby aiming at improving the heat transfer performance, and further aiming at the pipe axial direction. The liquefied refrigerant flows through the groove attached to the groove. These tubes are
Generally, it is manufactured through rolling, forming, and welding processes.

[0009]

SUMMARY OF THE INVENTION Japanese Patent Application Laid-Open No. 9-79778
JP, JP-A-9-26279, JP-A-9-42
The heat transfer tubes disclosed in Japanese Patent Application Laid-Open No. 880 and Japanese Patent Application Laid-Open No. H8-31812 are disclosed in the 34th Japan Heat Transfer Symposium Lecture Papers (1997-5), "Three-Component Non-azeotropic Tubes with Target Shape Internal Grooves As described in “Promotion of heat transfer of mixed refrigerant”, the liquid is biased in the circumferential direction of the heat transfer tube. Therefore, a thin portion of the liquid film is formed in the circumferential direction, and condensation or evaporation is promoted in that portion. As described above, the V-shaped groove has a large influence on the improvement of the heat transfer performance due to the uneven distribution of the liquid. However, in the prior art, the fin height and the fin pitch are similar to those of the spiral grooved tube, and the heat transfer performance is improved, but the weight per unit length is equal to that of the spiral grooved tube. From the viewpoint of effective utilization of resources or materials, it is a problem that the weight per unit length is not reduced.

Accordingly, an object of the present invention is to provide a heat transfer tube having high performance and a small weight per unit length to effectively use resources and materials, and to further comprehensively use an air conditioner and a refrigerator. An object of the present invention is to provide an inner grooved heat transfer tube capable of reducing costs.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a plurality of metal pipes formed along a line at a first predetermined angle with the pipe axis in the inner circumferential surface direction of the metal pipe. A first region of the fins, and a second region of the plurality of fins formed along a line at a second predetermined angle to the tube axis, each of which is a boundary between the first and second regions. The fin pitch Pf1 at a right angle to the fin in the first region and the fin height Hf from the groove bottom in the inner surface grooved heat transfer tubes formed into a pair of V-shaped fins by abutting the respective fins. (Pf1 / Hf) is 2.7 to 3.6, and the ratio (Pf2 / Hf) between the fin pitch Pf2 and the fin height Hf at a right angle to the fin in the second region is 2.7 to 3. 6 is provided. Here, a groove in the tube axis direction may be provided at the abutting portion of each fin.

According to the present invention, when the fin pitch Pf1 of the first region and the fin pitch Pf2 of the second region are collectively referred to as the fin pitch Pf, the ratio of the fin pitch Pf to the fin height Hf (Pf / Hf) ) Is increased to 2.7 to 3.6 to reduce the weight per unit length. When the fin height is low, the weight of the fin portion is reduced, so that the number of fins can be increased. The large number of fins means that the fin pitch Pf is small. on the other hand,
When the fin height is high, the weight of the fin portion increases. Therefore, the number of fins is reduced. That is, the fin pitch increases. As described above, the fin pitch Pf and the fin height Hf are related to the reduction of the unit weight.

To reduce the weight per unit length, there is a method of reducing the thickness of the groove bottom, that is, the thickness of the groove bottom. However, it is difficult to make this thinner than the current state from the viewpoint of durability against the refrigerant pressure and the like. On the other hand, there is a method of reducing the fin apex angle, reducing the volume of the fin portion, and reducing the weight per unit length. However, even in the prior art, the fin apex angle is 10 to 25 °, and if the fin apex angle is smaller than this, the heat exchanger is manufactured, and in order to increase the adhesiveness with the slit fin attached to the outside of the tube, when expanding the heat transfer tube, The amount of fins formed on the inner surface of the pipe is increased, and the effect of increasing the height of the fins formed in the pipe to increase the depth of the groove in the pipe is diminished.

When the fin abutment has a groove in the axial direction of the tube, it is possible to improve the performance, especially the condensation performance. The refrigerant gas flowing into the heat transfer tube contacts the inner surfaces of the first region and the second region, respectively, and liquefies. The liquefied refrigerant flows along the fins in the respective regions and collects at the fin abutments. Here, since the liquefied refrigerant moves in the tube axis direction along the groove in the tube axis direction, a thin portion of the liquid film is formed on the inner surfaces of the first and second regions, and condensation is promoted.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention is shown in FIGS.
Shown in FIG. 1 is a development view of a heat transfer tube 1 with an inner groove according to the present invention. The fins 2 and 3 are formed at a predetermined pitch with opposite angles to the tube axis in the first region and the second region. The fins 2 and 3 are abutted at the boundary between the first region and the second region to form a V-shape. A
FIG. 2 shows a cross section taken along line −A ′. Fins 2 are provided on the inner surface of the heat transfer tube 1. Basically, the cross-sectional shape of the fin 2 in the first region is equal to the cross-sectional shape of the fin 3 in the second region. The angle between the fin 2 in the first region and the tube axis is β1, and the fin 2
In contrast, the fin pitch in the perpendicular direction is Pf1, the angle formed by the fins 3 in the second region with the tube axis is β2, and the fin pitch in the perpendicular direction to the fins is Pf2. Also,
The bottom wall thickness of the grooves 4 and 5 of the heat transfer tube 1 is Tw, the fins 2 and
3, the height of the fins 2 and 3 is α.

The heat transfer tube 1 is a seam pipe made of, for example, copper or a copper alloy and has a fin apex angle α of 25 to 1 on the inner surface of the tube.
0 °, fin 2 having a fin height Hf of 0.1 to 0.3 mm,
3 are formed. Fin pitch Pf1 of first area
And the fin height Hf (Pf1 / Hf) is 2.7 to
3.6, fins having a ratio (Pf2 / Hf) of the fin pitch Pf2 of the second region to the fin height Hf (Pf2 / Hf) of 2.7 to 3.6 are formed on the inner surface of the heat transfer tube 1.

FIG. 1 shows a case where the sum of the first area and the second area is an even number 4. Fin 2 whose angle with the tube axis is β1
There is a first area and a second area where there are fins 3 whose angle with the tube axis is β2, and the areas are alternately arranged in the circumferential direction. At the boundary between the first area and the second area, the fins 2 and 3 abut each other, forming a V-shape when viewed from the tube axis direction.

There are the following methods for manufacturing such a heat transfer tube. In a roll configuration similar to that of a normal rolling mill, a grooved roll on which fins 2, 3 and grooves 4, 5 are transferred is used as a roll on one side, and a metal plate strip having a predetermined width is used.
For example, copper and a copper alloy are rolled. When rolled, fins 2 and 3 and grooves 4 and 5 are formed on one surface of the metal strip. The strip material after rolling is formed into a pipe so that the formed surfaces of the fins 2 and 3 and the grooves 4 and 5 are on the inside, and the butt portion is welded to produce a seam pipe with an inner surface groove. You.

Table 1 shows an example of the product of the present invention and the shape and dimensions of a comparative product. The sum of the first area and the second area is four.

[0020]

[Table 1]

Number 1 is a comparative material, and numbers 2 to 6 are examples of the heat transfer tube of the present invention. Number 1 is an example of a conventional product.

The heat transfer performance was measured using a heat transfer measuring device shown in FIG. Valves 12, 13, 14, 15, 16, 1
Reference numerals 7 and 18 denote valves for switching circuits when measuring the condensation performance and the evaporation performance, respectively. In the case of the measurement of the condensation performance, the valves 13, 15, 17, and 19 are opened and the valve 1 is opened.
Close 2,14,18. The refrigerant flowing out of the compressor 11 is
Along the broken arrows, gas enters the heat transfer tube 21 installed in the performance measurement area 20 via the valves 13 and 15. Heat transfer tube 2
The refrigerant condenses in the pipe 1, passes through the valve 17, the liquid receiver 24, the dryer 25, the subcooler 26, the flow meter 27, the expansion valve 28, the valve 19, turns into gas again in the evaporator 29, and returns to the compressor 11. . In the case of measuring the evaporation performance, the valves 12, 14, 16, 18 are opened, and the valves 13, 15, 1,
7 and 19 are closed. The refrigerant flowing out of the compressor 11 becomes liquid through the condenser 30 along the solid line arrow, and becomes a liquid.
4, liquid receiver 24, dryer 25, subcooler 26,
The heat transfer tube 2 passes through a flow meter 27, an expansion valve 28, and a valve 18.
1 and returns to the compressor 11 through the valve 16 and the evaporator 29.

The performance measurement area 20 has a double structure, in which a refrigerant flows inside the heat transfer tube 21, and cold / hot water supplied from a water cooler / heater 23 flows out of the heat transfer tube 21.
Flow through 2. Table 2 shows the measurement conditions. Under the conditions shown in Table 2, the heat transfer characteristics of the heat transfer tube were evaluated from the cold / hot water inlet / outlet temperature, flow rate, refrigerant flow rate, refrigerant inlet / outlet temperature and pressure. R22 was used as a refrigerant.

[0024]

[Table 2]

Using such a heat transfer measuring device 10, Table 1
Were evaluated for the heat transfer performance of each sample. Table 3 shows an example of evaluation results at a refrigerant flow rate of 30 kg / hr. The heat transfer performance shown in Table 3 is shown in comparison with a heat transfer tube with a spiral groove, which is a comparative product of No. 1.

[0026]

[Table 3]

From the results shown in Table 3, the products of the present invention were numbered 2 to 6.
Is a performance comparable to that of the comparative product No. 1. On the other hand, weight per unit length (weight per meter: unit weight)
Is 11 to 15% lighter than the conventional product as shown in Table 3. As described above, according to the present invention, the heat transfer performance is equivalent to that of the conventional product, and the weight per unit length can be reduced.

If the ratio (Pf / Hf) between the fin pitch Pf and the fin height Hf is 2.7 or less, the weight per unit length cannot be reduced as in the conventional case. On the other hand, the ratio between the fin pitch Pf and the fin height Hf (Pf / Hf)
When it is 3.6 or more, there is a possibility that the performance may be reduced due to the decrease in the surface area.

On the other hand, in the present invention, the fin pitch P
The ratio (Pf / Hf) between f and the fin height Hf is 2.7 to
In the range of 3.6, the sum of the first area and the second area is preferably 3 to 8. Preferably, 4 to 6 is good. When the sum of the first area and the second area is 2 or less, the number of divisions is small, and the stirring effect due to collision of the refrigerant flowing along the groove is weakened, and the performance is reduced. If the sum of the first region and the second region is 9 or more, the pressure loss increases. Furthermore, one groove roll for embossing rolling performed when manufacturing these heat transfer tubes is used by laminating rolls having grooves corresponding to the first region and the second region in the axial direction of the rolls. I have. When the sum of the first region and the second region is 9 or more, the thickness of the rolls corresponding to the first region and the second region to be laminated becomes thinner, and the durability is reduced, and the productivity is reduced. ,
This leads to an increase in cost due to the consumption of the embossing rolls.

The angle β between the pipe axis and the groove is desirably in the range of 20 to 40 ° in absolute value. Preferably, β24
It is in the range of ３５35 °. When β is equal to or less than 20 °, the evaporation pressure loss is small, but the stirring effect due to the collision of the refrigerant at the groove butting portion is weakened, and the heat transfer performance is reduced. On the other hand, when β is 40 ° or more, the heat transfer performance is improved by the stirring effect due to the collision of the refrigerant at the groove butting portion, but the evaporation pressure loss increases. When the evaporation pressure loss increases, the temperature difference between the refrigerant inlet and the outlet of the heat transfer tube increases, and the efficiency of the heat exchanger decreases, which is not practical.

FIG. 3 shows a second embodiment of the present invention. FIG. 3 is a development view of the inner surface of the pipe developed from the welded portion, schematically showing the pattern of the fins, where the first region and the second region are odd number three. There is a first area where fins 2 whose angle with the tube axis is β1 are present, and a second area where fins 3 whose angle with the tube axis is β2 are present, and these areas are alternately arranged in the circumferential direction. . At the boundary between the first area and the second area, the fins 2 and 3 abut each other, forming a V-shape when viewed from the tube axis direction.

As shown in FIG. 3, when the sum of the first area and the second area is an odd number, when the refrigerant flows from the direction shown by the arrow A in FIG. , The refrigerant flowing along the fins 2 and 3 is in the same state. As a result, even if the refrigerant flows to the heat transfer tube from either direction of arrows A and B in FIG. 3, the performance is the same, and the heat transfer tube has no directionality. There is no need to control the direction of the heat transfer tubes during the manufacture of the heat transfer tubes and in the design and manufacture of the heat exchanger. In addition, a predetermined performance can be obtained regardless of the flow direction.

A third embodiment of the present invention is shown in FIGS.
FIG. 4 is a developed view of the heat transfer tube 1 with an inner groove according to the present invention. The fins 2 and 3 are formed at a predetermined pitch with opposite angles to the tube axis in the first region and the second region. The fins 2 and 3 have a width d at the V-shaped portion which is abutted at the boundary between the first region and the second region.
Is formed in the groove 6 in the pipe axis direction.

FIG. 5 is a sectional view taken along the line AA ′ of FIG. Fins 2 are provided on the inner surface of the heat transfer tube 1. Basically, the cross-sectional shape of the fin 2 in the first region is equal to the cross-sectional shape of the fin 3 in the second region. The angle between the fins 2 in the first region and the tube axis is β1, the fin pitch in the direction perpendicular to the fins 2 is Pf1, the angle between the fins 3 in the second region and the tube axis is β2, , The fin pitch in the perpendicular direction is Pf2. In addition, the bottom wall thickness of the grooves 4 and 5 of the heat transfer tube 1 is Tw, the height of the fins 2 and 3 is Hf, and the apex angle of the fins 2 and 3 is α.

The heat transfer tube 1 is a seam pipe made of, for example, copper or a copper alloy, and has a fin apex angle α of 25 to 1 on the inner surface of the tube.
0 °, fin 2 having a fin height Hf of 0.1 to 0.3 mm,
3 are formed. Fin pitch Pf1 of first area
And the fin height Hf (Pf1 / Hf) is 2.7 to
3.6, fins having a ratio (Pf2 / Hf) of the fin pitch Pf2 of the second region to the fin height Hf (Pf2 / Hf) of 2.7 to 3.6 are formed on the inner surface of the heat transfer tube 1. Further, a groove 6 in the tube axis direction is formed at the abutting portion of the fins 2 and 3 and the width d is set to 0.1.
1 to 0.5 mm, and the depth Hd of the groove 6 is formed to be 50% or more of the height Hf of the fins 2 and 3.

FIG. 4 shows a case where the sum of the first area and the second area is an even number 4. Fin 2 whose angle with the tube axis is β1
There is a first area and a second area where there are fins 3 whose angle with the tube axis is β2, and the areas are alternately arranged in the circumferential direction. At the boundary between the first area and the second area, the fins 2 and the fins 3 abut each other to form a V-shape when viewed from the tube axis direction. Are formed.

For the manufacture of such a heat transfer tube, the same method as in the first embodiment can be employed.

Here, when the groove depth Hd in the tube axis direction formed at the fin abutting portion becomes 50% or more of the fin height Hf, the fin acts as a low fin, and the condensed refrigerant acts as a fin. When the flow is hindered by the groove 6, the condensation is hindered and the performance is reduced. On the other hand, if the width d of the groove 6 is 0.1 mm or less, there is a problem in assembling the groove roll used for embossing and durability of the groove roll. Width d
If it is 0.5 mm or more, the liquefied refrigerant entering the heat transfer tube at the time of evaporation flows along the groove 6, which hinders the spread of the liquid in the circumferential direction of the tube, leading to a reduction in performance.

On the other hand, the ratio of fin pitch to fin height (P
f / Hf) and the angle β between the tube axis and the groove are selected within the same ranges as in the first embodiment.

Table 4 shows an example of the product of the present invention and the shape and dimensions of a comparative product. The sum of the first area and the second area is four.

[0041]

[Table 4]

Reference numeral 7 is a comparative material, and reference numerals 8 to 12 are examples of the heat transfer tube of the present invention. Number 7 is an example of a conventional product.

Using the heat transfer measuring device shown in FIG. 7, the heat transfer performance of each sample shown in Table 4 was evaluated under the same performance measuring conditions as in the first embodiment. Table 5 shows an example of evaluation results at a refrigerant flow rate of 30 kg / hr. The heat transfer performance shown in Table 5 is shown in comparison with a heat transfer tube with a spiral groove, which is a comparative product of No. 7.

[0044]

[Table 5]

From the results shown in Table 5, the products of the present invention Nos. 8 to 12
Is a performance comparable to that of the comparative product No. 7. On the other hand, weight per unit length (weight per meter: unit weight)
Is 11 to 14% lighter than the conventional product as shown in Table 5. Thus, according to the invention, the heat transfer performance is the same as that of the conventional product, and the weight per unit length can be reduced.

FIG. 6 shows a fourth embodiment of the present invention. FIG. 6 is a development view of the inner surface of the pipe developed from the welded portion, schematically showing the pattern of the fins, in which the first region and the second region have an odd number of three. There is a first area where fins 2 whose angle with the tube axis is β1 are present, and a second area where fins 3 whose angle with the tube axis is β2 are present, and these areas are alternately arranged in the circumferential direction. . At the boundary between the first area and the second area, the fins 2 and 3 abut each other, forming a V-shape when viewed from the tube axis direction.

As shown in FIG. 6, when the sum of the first area and the second area is an odd number, the refrigerant flows from the direction shown by the arrow A in FIG. , The refrigerant flowing along the fins 2 and 3 is in the same state. As a result, even if the refrigerant flows into the heat transfer tube from either direction of arrows A and B in FIG. 6, the performance is the same, and the heat transfer tube has no directionality. There is no need to control the direction of the heat transfer tubes during the manufacture of the heat transfer tubes and in the design and manufacture of the heat exchanger. In addition, a predetermined performance can be obtained regardless of the flow direction.

[0048]

As shown in the embodiments of the present invention, in the present invention, the performance is improved as compared with the prior art, thereby improving the performance of the heat exchanger and saving energy. In addition, the length of heat transfer tubes incorporated in heat exchangers such as air conditioners is based on the length. However, since the unit weight is light, the weight of heat transfer tubes per heat exchanger is reduced, and resources or materials are effectively used. Leads to. In addition, it is possible to achieve effects such as a reduction in the weight of a heat exchanger such as an air conditioner.

[Brief description of the drawings]

FIG. 1 is a developed view showing an example of a heat transfer tube with an inner surface groove according to the present invention.

FIG. 2 is a sectional view taken along line A-A 'of FIG.

FIG. 3 is a development view showing another example of the heat transfer tube with an inner surface groove according to the present invention.

FIG. 4 is a developed view showing still another example of the heat transfer tube with inner grooves according to the present invention.

FIG. 5 is a sectional view taken along line A-A 'of FIG.

FIG. 6 is a development view showing still another example of the heat transfer tube with an inner groove according to the present invention.

FIG. 7 is a system diagram of performance measurement of a heat transfer tube with an inner groove.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat transfer tube with internal groove 2, 3 Fin 4, 5, 6 groove 10 Heat transfer measuring device Hf Fin height W3 Groove bottom width Tw Bottom wall thickness α Fin apex angle β1, β2 Angle between tube axis and fin

Claims (5)

[Claims] 1. A first region of a plurality of fins formed along a line forming a first predetermined angle with a tube axis in a direction of an inner peripheral surface of a metal tube; There is a second region of a plurality of fins formed along a line that forms an angle, and at the boundary between the first and second regions, a pair of V-shapes are formed by abutment of the respective fins. The ratio (Pf1 / Hf) of the fin pitch Pf1 at a right angle to the fin in the first region and the fin height Hf from the groove bottom is 2.7 to 3.6. Wherein the ratio (Pf2 / Hf) of the fin pitch Pf2 and the fin height Hf at a right angle to the fin in the second region is 2.7 to 3.6, wherein the heat transfer tube has an inner surface groove. 2. A butt portion of each of the fins,
The heat transfer tube with an inner surface groove according to claim 1, wherein the heat transfer tube has a groove in a tube axis direction. 3. The depth of the groove in the tube axis direction of the fin abutting portion is at least 50% of the fin height of the first region or the second region, and the groove width is 0.1 to 0.5 mm. The heat transfer tube with an inner surface groove according to claim 2, wherein: 4. The inner surface according to claim 1, wherein a total sum of the first region and the second region in the circumferential direction of the tube is 3 or more and 8 or less. Groove heat transfer tube. 5. An angle β1 formed by the fins of the first region with the tube axis is 20 to 40 °, and an angle β2 formed by the fins of the second region with the tube axis is -20 to -40 °. The heat transfer tube with an inner surface groove according to any one of claims 1 to 4, wherein