JPH0926279A - Heat transfer tube with internal surface groove - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat transfer tube with internal surface groove capable of improving heat exchange performance without increasing pressure drop. SOLUTION: An internal peripheral surface of a metal tube is divided into regions R1 to R4 of two or more in the periperal direction, and many fins 2 are formed in each region, arranged axially of the heat transfer tube 1. The fins 2 contained in the odd numbered regions R1, R3 are inclined by 10 to 25 degree with respect to the heat transfer tube axial line while the fins 2 contained in the even numbered regions R2, R4 are inclined by -10 to -25 degree with respect to the heat transfer tube axial line. Further, a gap 4A is formed between the fins 2 adjoining peripherally.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A heat transfer tube with an inner groove of this kind is mainly used as an evaporation tube or a condensation tube in a heat exchanger of an air conditioner or a cooling device, and recently, it has a spiral shape over the entire inner surface. A heat transfer tube having a fin shape is widely available on the market.

The heat transfer tube, which is currently the mainstream, is a metal tube obtained by passing a floating plug having a spiral groove formed on the outer peripheral surface inside a seamless (seamless) tube obtained by drawing or extruding. The fins are manufactured by a method of rolling the fins over the entire inner peripheral surface of the, and in a commonly used heat transfer tube having an outer diameter of about 10 mm, the fin height is 0.15 to 0.20 mm. Pitch (distance between vertices of adjacent fins) is 0.45
0.55 mm, the bottom width of the groove formed between the fins is 0.2
It is about 0 to 0.30 mm.

[0004] In such a heat transfer tube with an inner surface groove formed with a spiral fin, the heat transfer liquid accumulated in the lower portion inside the heat transfer tube is
It is blown by the steam flow flowing in the pipe, is wound up along the spiral fins, and spreads over the entire inner peripheral surface of the pipe. By this action, the entire inner peripheral surface of the pipe is almost uniformly wetted. Therefore, when the pipe is used as an evaporating pipe for evaporating the heating medium liquid, the area of the region where boiling occurs can be increased to increase the boiling efficiency. When used as a condensing tube for liquefying the heat transfer medium gas, the fin tips are exposed from the liquid surface, so that the contact efficiency between the metal surface and the heat transfer medium gas can be increased and the condensation efficiency can be increased.

[0005]

SUMMARY OF THE INVENTION By the way, the inventors of the present invention produced various kinds of inner grooved heat transfer tubes by variously changing the developed shape of the grooves of the heat transfer tube, and as a result of comparing these performances, It was found that when a large number of fins extending in a zigzag pattern in the circumferential direction are formed on the inner surface of the heat transfer tube, higher heat exchange performance can be obtained compared to other groove shapes.

However, at the same time, in this case, the pressure loss of the heat medium flowing in the inner surface grooved heat transfer tube increases, and a load is placed on the heat medium circulating device, so that it is actually used despite the high heat exchange performance. It turned out to be difficult. Therefore, as a result of further studies by the present inventors, it was found that the heat exchange performance can be improved without increasing the pressure loss by forming a gap in each bent portion of the zigzag-shaped fin. It was

[0007]

In the heat transfer tube with inner groove according to the present invention, the inner peripheral surface of the metal tube is divided into two or more regions in the circumferential direction, and the axial line of the heat transfer tube is provided in each of these regions. A large number of fins arranged in the same direction are formed, and the fins included in the odd-numbered region counting from any one region are inclined by 10 to 25 ° with respect to the axis of the heat transfer tube, and The fins included in the even-numbered region are inclined at −10 to −25 ° with respect to the axis of the heat transfer tube, and a gap is formed between the end portions of the fins adjacent in the circumferential direction. It is characterized by being.

[0008]

1 is a partially developed plan view showing a first embodiment of a heat transfer tube with an inner groove according to the present invention. The inner peripheral surface of the heat transfer tube 1 with inner groove has a circumferential direction 90
It is divided into four regions R1 to R4 for each degree.
A large number of fins 2 arranged in the axial direction of the heat transfer tube 1 are formed in parallel with each other in each of 1 to R4.
A groove portion 3 is formed between the adjacent portions.

The inner grooved heat transfer tube 1 of the present invention is characterized mainly by the arrangement of the fins 2. That is, in this heat transfer tube 1, the fins 2 included in odd-numbered areas R1 and R3 counting from any one area (R1 in this case) form an angle α of 10 to 25 ° with respect to the heat transfer tube axis. Fins 2 included in the even-numbered regions R2 and R4 while being formed as described above.
Are formed to form an angle β of −10 to −25 ° with respect to the heat transfer tube axis. If the absolute values of the inclination angles α and β of the fins 2 exceed 25 °, the fins 2 become nearly perpendicular to the flow, which interrupts the flow and increases the pressure loss, which is not preferable. If the absolute values of the inclination angles α and β of the fins 2 are less than 10 °, the fins 2 become nearly parallel to the flow, and the effect of turbulent flow generation by the fins 2 decreases.

The positive and negative inclination angles α and β may be reversed. In short, the fins 2 adjacent to each other in the circumferential direction are alternately arranged with respect to the heat transfer tube axis so that the fins 2 are arranged in a zigzag shape as a whole. It may be inclined in the opposite direction. In this embodiment, the ends of the adjacent fins 2 are aligned in the circumferential direction. Further, in FIG. 1, the fins 2 in the same region are parallel to each other, but they may not necessarily be parallel, and the inclination angle may be different for each fin within the above range.

Grooves 4 which are continuous in the longitudinal direction of the heat transfer tube 1 are formed at the boundaries of the respective regions R1 to R4, whereby a constant gap is provided between the fins 2 adjacent in the circumferential direction. 4A is formed. The bottom surface of the groove portion 4 may be flush with the bottom surface of the groove portion 3, or may be slightly higher than the groove portion 3. In the case of a general-purpose heat transfer tube having an outer diameter of about 1 cm, the width C1 of the gap 4A is preferably 0.05 to 0.5 mm, particularly 0.1 to 0.3 mm. When the width C1 is in the range of 0.05 to 0.5 mm, the balance between pressure loss and heat exchange efficiency is good. However, the present invention is not limited to the above range, and it goes without saying that other values can be adopted.

Although the cross-sectional shape of the fins 2 is not necessarily limited, in the present invention, as shown in FIG. 2, the pitch P of the fins 2 in the same region is 0.3 to 0.4 mm and the fins 2 are made of metal. Height H from the inner peripheral surface of the pipe is 0.15 to 0.30
It is preferably mm. In this way, when the fin shape that is taller than the conventional one is adopted, the turbulent flow generation effect is good, and in combination with the effect of the special fin arrangement,
The heat exchange efficiency of the heat transfer tube 1 can be further improved. In addition, since the fin 2 having such a thin shape has a good drainage property at the tip of the fin 2 even when the inner surface of the metal tube 1 is covered with the heat medium liquid, it is used as a condenser tube. In this case, the tip metal surface of the fin 2 is likely to come into direct contact with the heat transfer gas,
Good condensing performance can be obtained.

An angle γ (vertical angle) formed by both side surfaces of the fin 2
Is not necessarily limited, but is more preferably 10 to 25 °. When the apex angle of the fins 2 is small as described above, the side surfaces of the fins 2 stand upright almost vertically from the inner peripheral surface of the tube, so that the heat transfer medium flows onto the fins 2 due to the wind pressure of the heat transfer gas flowing in the heat transfer tube 1. Less often blown up. For this reason, not only the effect of restricting the flow of the heat medium liquid by the fins 2 to cause turbulent flow is increased, but also when the heat transfer pipe 1 is used as a condensing pipe, the tips of the individual fins 2 are exposed. The tendency becomes higher, the contact area between the heat medium gas and the metal surface is increased, and high condensation efficiency can be obtained. In the illustrated example, the apexes of the fins 2 are semicircular in cross section, but the present invention may have a trapezoidal cross section or a triangular cross section.

The dimensions such as the outer diameter, the wall thickness, and the length of the heat transfer tube 1 are not limited, and the present invention can be applied to any heat transfer tube of any size conventionally used. Copper or a copper alloy is generally used as a material of the heat transfer tube 1, but the present invention is not limited thereto, and various metals such as aluminum can be used. Although the heat transfer tube 1 has a circular cross section in this embodiment, the present invention is not limited to the circular cross section, and may have an elliptical cross section, a flat tubular shape, or the like as necessary. Further, it is also effective to use the heat pipe as a main body.

In order to manufacture such a heat transfer tube with an inner surface groove, the following method can be adopted. First, a strip-shaped metal sheet material is prepared, and the sheet material is rolled by passing it between a rolling roll and a receiving roll having a cross section complementary to the fin 2, the groove portion 3, and the groove portion 4, respectively. The fins 2, the groove portions 3, and the groove portions 4 are simultaneously formed on the surface of the strip material. As the rolling roll, it is also possible to use a laminated roll in which a rolling roll with a spiral groove for forming the fin 2 and the groove portion 3 and a disc-shaped roll for forming the groove portion 4 are alternately stacked. In this case, by exchanging the rolls to be laminated, the shape of each part can be set arbitrarily.

Next, the metal sheet material to which the fins 2 and the groove portions 3 and 4 have been transferred is set in an electric sewing machine with the groove forming surface facing the inner surface side, and is passed between the forming rolls in multiple stages. The sheet material is rounded in the width direction, and the two edge portions 5 that are finally butted are welded to each other to form a circular tube shape to obtain a heat transfer tube with an inner groove. The electric sewing machine may be one that is normally used, and the electric sewing conditions may be the same as in normal processing. Then, after shaping the welded portion on the outer peripheral surface of the heat transfer tube, the heat transfer tube is wound into a roll or cut into a predetermined length.

According to the heat transfer tube 1 with the inner surface groove having the above-described structure, the fins 2 formed on the inner surface are provided with two pairs of Vs which are opened toward the upstream of the flow of the heat medium flowing in any direction. Since they are arranged so as to form a character, the heat medium collected by the side surface of each fin 2 collides and merges at the V-shaped abutting portion, and further passes through the gap 4A between the fins 2. In this process, the heat medium is agitated and irregular turbulence is generated, so that a temperature gradient can be prevented from being generated in the flow of the heat medium, and heat exchange between the heat medium and the metal surface of the heat transfer tube is promoted. It is possible to increase the heat transfer efficiency. In particular, when a mixed heat medium (a mixture of a plurality of heat media) is used, separation of the heat medium components can be prevented, and the original performance of the mixed heat medium can be brought out.

A gap 4A is provided between the ends of the fins 2.
Since the heat transfer fluid is allowed to escape through these gaps 4A, the pressure loss flowing in the heat transfer tube 1 can be suppressed to be small despite the high rate of improvement in heat transfer efficiency. Thus, it is an important effect of the present invention that the two contradictory effects of improving the heat transfer efficiency and reducing the pressure loss can be achieved at the same time.

[Second Embodiment] FIG. 3 shows a second embodiment of the present invention. In the first embodiment, the ends of the fins 2 adjacent to each other in the circumferential direction are aligned, but this second
The embodiment is characterized in that the fins 2 in the adjacent regions are shifted by a half pitch. Other configurations may be the same as in the first embodiment.

By thus shifting the fins 2 by a half pitch in each of the regions R1 to R4, the gap 4A between the fins 2 adjacent in the circumferential direction can be substantially expanded without changing the width of the groove portion 4. Further, as shown by the arrow in the figure, the flow of the heat medium tends to meander.

[Third Embodiment] FIG. 4 shows a third embodiment of the present invention. In the first and second embodiments, the inner surface of the heat transfer tube 1 is divided into four regions R1 to R4 in the circumferential direction, but in this example, it is divided into only two regions R1 and R2 in the circumferential direction. I am trying. Therefore, if the outer diameters of the heat transfer tubes are the same, the length of the fins 2 is approximately twice as long as that in each of the above embodiments. Other configurations may be the same as in the above embodiments.

According to such a third embodiment, the fins 2 formed on the inner surface form a single V-shape that opens toward the upstream side of the flow of the heat medium flowing in either direction. The heat medium gathers in the groove portion 4 on the side corresponding to the V-shaped valley. In order to make full use of this characteristic, in the third embodiment, it is preferable to set the upper and lower sides of the heat transfer tube 1 according to the usage mode.

For example, when it is used as a condenser tube, it is preferable to directly contact the metal surface with the heating medium gas, so that the groove portion 4 on the side corresponding to the V-shaped valley with respect to the vapor flow is arranged downward. To do. Then, the heat medium liquid that collects and flows in the heat transfer tube 1 is less likely to spread to the upper side of the inner surface of the heat transfer tube 1 along the fins 2, and it is possible to enhance the condensation efficiency in combination with the above effect. Also in this embodiment, it is possible to shift the pitch of the fins in the adjacent regions.

[Fourth Embodiment] FIG. 5 shows a fourth embodiment of the present invention. This example is characterized in that the inner peripheral surface of the heat transfer tube 1 is divided into six regions R1 to R6 in the circumferential direction, and the heat transfer tube 1 is provided in each of these regions R1 to R6.
A large number of fins 2 arranged in the axial direction are formed in parallel with each other. The other configuration is the same as that of the first embodiment, and the same reference numerals are given and the description is omitted.

Heat transfer tube 1 with internal groove having the above structure
Also, the same excellent effect as that of the first embodiment can be obtained.

[Fifth Embodiment] FIG. 6 shows a fifth embodiment of the present invention. This example is similar to the first embodiment in that the inner peripheral surface of the heat transfer tube 1 is divided into four in the circumferential direction, but the groove portion 4 is not formed at the boundary of each region, and Instead, the fins 2 are shifted by a half pitch in each of the regions R1 to R4 to form a gap 6 therebetween. In the case of a general-purpose heat transfer tube having an outer diameter of about 1 cm, the width C2 of the gap 6 in the heat transfer tube axial direction is 0.05 to 0.5 mm,
In particular, it is preferably 0.1 to 0.3 mm. Width C2
Is in the range of 0.05 to 0.5 mm, the balance between pressure loss and heat exchange efficiency is particularly good. However, the present invention is not limited to the above range, and it goes without saying that other values can be adopted.

With this structure as well, the fins 2 formed on the inner surface of the heat transfer tube have two pairs of V-shapes (y) that open toward the upstream of the heat medium flowing in any direction.
The fins 2 are arranged so that each fin 2
The heat mediums collected by the side surfaces of the fins collide with each other at the V-shaped butting portions and merge with each other, and further pass through the gap 6 between the fins 2. In this process, the heat transfer fluid is agitated to generate an irregular turbulent flow, so that it is possible to prevent a temperature gradient from occurring in the flow of the heat transfer fluid, and to perform heat exchange between the heat transfer medium and the metal surface of the heat transfer tube. It is possible to promote and improve heat transfer efficiency. Further, since the gap 6 is formed between the ends of the fins 2, the heat transfer fluid can escape through these gaps 6,
It has an excellent effect that the pressure loss flowing in the heat transfer tube 1 can be suppressed to a small level, despite the high improvement rate of the heat transfer efficiency.

The inner surface grooved heat transfer tube according to the present invention is not limited to the above-mentioned embodiments, but various other structures are possible. For example, when the outer diameter of the heat transfer tube is large, the inner peripheral surface of the heat transfer tube can be divided into eight or more regions, and if necessary, each fin can be formed in an arc shape. It is. Further, a concave portion or a notch may be separately formed in the central portion or the like of each fin 2.

[0029]

EXAMPLES Next, the effects of the present invention will be demonstrated with reference to examples. The following eight different heat transfer tubes having different fin shapes were formed, and the heat transfer efficiency and the pressure loss of these heat transfer tubes were compared.

A1 type: heat transfer tube having spiral grooves formed on the inner surface (Comparative Example 1) b1 type: two rows of fins are formed on the inner surface so as to form a single V-shape, but in the circumferential direction Transfer tube in which no gap is formed between the fins adjacent to each other (Comparative Example 2) c1 type: four rows of fins are formed on the inner surface so as to form two pairs of V-shapes, but they are adjacent in the circumferential direction Heat Transfer Tube with No Gap Between Fins (Comparative Example 3) d1 type: Six rows of fins are formed on the inner surface so as to form three pairs of V-shapes, but between fins adjacent in the circumferential direction. Heat Transfer Tube with No Gap (Comparative Example 4) c2 type: Four rows of fins are formed on the inner surface so as to form two pairs of V-shapes, and gaps are formed between the fins adjacent in the circumferential direction. Heat transfer tube (Example 1): FIG. 1 d2 type: Six rows of fins are formed on the inner surface to form three pairs of V-shapes. A gap is formed between the fins adjacent to each other in the circumferential direction (Example 2): FIG. 5 c3 type: Four rows of fins are formed on the inner surface so as to form two pairs of V-shapes, and the fins are adjacent to each other in the circumferential direction. Heat transfer tubes in which the fins are displaced by a half pitch from each other to form a gap (Example 3):
FIG. 6 d3 type: Heat transfer tube in which six rows of fins are formed on the inner surface so as to form three pairs of V-shapes, and the fins adjacent to each other in the circumferential direction are displaced from each other by a half pitch to form a gap (Example 4). )

The following dimensions are common to all heat transfer tubes. Fin pitch P = 0.36 mm Fin height H = 0.24 mm Angle between both sides of the fin γ = 17 ° (fin cross-section angle in cross section perpendicular to tube axis = 20
°) Groove width between fins = 0.22 mm (groove width in tube axial direction = 0.85 mm) Furthermore, the fin inclination angle with respect to the axis of the heat transfer tube is a
15 degrees for Type 1 heat transfer tubes, 1 for all other heat transfer tubes
The angles were 5 ° and -15 °. The gap amount C1 in the c2 type and d2 type heat transfer tubes is 0.2 mm,
The shift amount C2 in the mold heat transfer tube was also set to 0.2 mm.

Next, the heat transfer performance (evaporation performance, condensation performance) of each of the obtained heat transfer tubes was measured using the apparatus shown in FIGS. 7 and 8. At the time of measurement, each heat transfer tube was set in the "measurement section" in the figure, and the evaporation performance and the condensation performance were measured by the following evaluation methods. At the same time, the pressure loss at that time was measured. The evaluation conditions are as follows.

[Evaluation method] Counterflow double tube system Water velocity: 1.5 m / s Total length of heat transfer tube: 3.5 m Saturation temperature at evaporation: 5 ° C Superheat degree 3 deg Saturation temperature at evaporation: 45 ° C Supercooling degree 5 deg Heat medium: Freon "R-22"

FIGS. 9 and 10 show the results of the evaporation performance, the condensation performance, and the pressure loss obtained by the above experiment expressed as a ratio to the a1 type heat transfer tube. As is clear from these graphs, the c2 type, c3 type, d2 according to the present invention
The type 3 and type d3 heat transfer tubes exhibited high heat transfer performance, although the pressure loss was about the same as that of the a1 type simple grooved tube.

[0035]

As described above, according to the inner surface grooved heat transfer tube of the present invention, the fins formed on the inner surface form one or more pairs of V-shapes that open upstream of the flow of the heat transfer fluid. The heat transfer fluid flowing along the side surface of each fin collides and joins at the V-shaped abutting portion,
Furthermore, it passes through the gap between the fins. In this process, the heat medium fluid is agitated to generate irregular turbulence, so that it is possible to prevent a temperature gradient from occurring in the flow of the heat medium and to promote heat exchange between the heat medium and the metal surface. It is possible to improve heat transfer efficiency.

Further, since a gap is formed between the end portions of the fins, the heat transfer fluid can escape through this gap, and the pressure loss can be suppressed to a small level in spite of the high improvement rate of the heat transfer efficiency. be able to.

[Brief description of drawings]

FIG. 1 is a partially expanded plan view showing a first embodiment of a heat transfer tube with an inner groove according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a partially expanded plan view showing a second embodiment of the present invention.

FIG. 4 is a partially expanded plan view showing a third embodiment of the present invention.

FIG. 5 is a partially expanded plan view showing a fourth embodiment of the present invention.

FIG. 6 is a partially expanded plan view showing a fifth embodiment of the present invention.

FIG. 7 is a schematic view showing an apparatus for measuring evaporation performance.

FIG. 8 is a schematic view showing an apparatus for measuring condensation performance.

FIG. 9 is a graph of evaporation performance and pressure loss during evaporation.

FIG. 10 is a graph of condensation performance and pressure loss during condensation.

[Explanation of symbols]

 1 Heat Transfer Tube with Inner Surface Groove 2 Fins 3, 4 Groove 5 Side Edges Abutted 4A, 6 Gap R1 to R6 Areas C1 and C2 Gap between Fins

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor ▲ Sukumo ▼ Shun Tad ▲ Green ▼ 128-7 Ogimachi, Aizu-Wakamatsu City, Fukushima Prefecture Wakamatsu Works, Mitsubishi Shindoh Co., Ltd.

Claims (6)

[Claims] 1. The inner peripheral surface of the metal tube is 2 in the circumferential direction.
The fins are divided into the above areas, and a large number of fins arranged in the axial direction of the heat transfer tube are formed in each of these areas. The fins included in the even-numbered areas counting from the area 1 are inclined by -10 to -25 degrees with respect to the axis of the heat transfer tube, and further, are inclined by 10 to 25 degrees. A heat transfer tube with an inner groove, wherein a gap is formed between the ends of the fins that are adjacent to each other in the direction. 2. The heat transfer tube with internal groove according to claim 1, wherein the fins included in the same region are parallel to each other. 3. The fins included in the regions adjacent to each other are formed line-symmetrically with respect to the boundary line between these regions,
The heat transfer tube with an inner surface groove according to claim 1 or 2, wherein the width of the gap is 0.05 to 0.5 mm. 4. The fins included in the regions adjacent to each other are formed so that their pitches are displaced from each other in the axial direction of the heat transfer tube, and the width of the gap is 0.05 to 0.5 mm. The heat transfer tube with an inner groove according to claim 1 or 2. 5. The pitch of fins included in the same region is 0.3 to 0.4 mm, the height of the fin from the inner peripheral surface of the metal tube is 0.15 to 0.30 mm, and the angle formed by both side surfaces of the fin. Is 10 to 25 degrees, The heat transfer tube with an inner groove according to any one of claims 1 to 4, wherein 6. The inner surface grooved heat transfer tube according to claim 1, wherein the number of the regions is 2, 4, or 6.