JP2002350080A - Internally grooved heat exchanger tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internally grooved heat exchanger tube that can be improved in transmissibility for both heat of condensation and heat of vaporization in a well-balanced state without increasing the pressure loss in the tube nor increasing the mass of the tube. SOLUTION: This internally grooved heat exchanger tube 10 is obtained by spirally forming high fins 12a having heights of 0.1-0.3 mm on the internal surface of the main body 11 of the tube 10 at a helix angle of 15-35 deg. from the axis of the main body 11 and one or a plurality of low fins 13a having heights of 1/15 to 1/5 of the heights of the fins 12a between the high fins 12a.

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 surface groove, which is applied to a heat exchanger and performs heat exchange by evaporating or condensing a refrigerant in a tube, and more particularly to pressure loss in the tube and mass of the heat transfer tube. The present invention relates to a heat transfer tube with an inner groove that can improve the condensation heat transfer coefficient and the evaporation heat transfer coefficient in a well-balanced manner without increasing them.

[0002]

2. Description of the Related Art A heat exchanger in a refrigerator, an air conditioner, a heat pump, or the like is provided with a heat transfer tube that exchanges heat by passing a refrigerant through a heat transfer tube and evaporating or condensing the refrigerant in the heat transfer tube. It is used.

[0003] The inner surface of the heat transfer tube as described above was initially smooth, but as the thermodynamics research progressed, the formation of predetermined irregularities on the inner surface of the tube improved the heat transfer coefficient. Recently, an inner groove having a substantially trapezoidal cross section and a generally triangular cross section fin separating the groove in a spiral shape is mainly formed on the inner surface of a heat transfer tube having an outer diameter of 7 to 9.52 mm. Tubes have become the mainstream ("Compact Heat Exchanger", Hiroshi Seshita, p. 138).

FIGS. 7A and 7B show a conventional heat transfer tube with an inner groove for evaporation and condensation in a tube. FIG. 7A is a longitudinal sectional view, FIG. 7B is a transverse sectional view, and FIG. FIG. 4 is an enlarged view of a portion A in FIG. In the figure, H indicates the fin height, β indicates the angle (twist angle) with respect to the tube axis direction, and W indicates the groove bottom width.
The heat transfer tube 1 with an inner groove has a spiral groove 3 and a spiral fin 4 formed on the inner surface of a heat transfer tube main body 2.

[0005] By forming such spiral grooves 3 and spiral fins 4, the surface area inside the tube is increased, and the heat transfer area is increased. In addition, due to the promotion of the turbulence effect and the decrease in the thickness of the refrigerant liquid, a high evaporation heat transfer coefficient,
Further, a condensed heat transfer coefficient can be obtained, and the performance of a refrigerator, an air conditioner, a heat pump, and the like can be improved.

[0006]

However, according to the conventional heat transfer tube 1 with an inner groove, when the number of the spiral fins 4 is increased to increase the surface area of the inner surface of the tube, the heat transfer area is increased and the evaporative heat transfer rate and the heat transfer area are increased. Although the condensed heat transfer coefficient is improved, the condensed heat transfer coefficient is reduced if the number of grooves is excessively increased to further improve the performance. This is because if the number of the spiral fins 4 is too large, the groove bottom width W becomes narrow, and the condensed liquid immediately fills the spiral groove 3. When the refrigerant liquid covers the spiral fins 4, the condensed refrigerant liquid itself becomes thermal resistance, and the heat transfer coefficient decreases. Further, when the torsion angle β of the spiral groove 3 is increased in order to improve the condensation heat transfer coefficient, a phenomenon that the evaporation performance is reduced occurs. Conversely, if the helix angle β of the spiral groove 3 is reduced, the heat transfer coefficient of evaporation increases,
A phenomenon occurs in which the condensation heat transfer coefficient decreases. Therefore,
Simply increasing the number of grooves or changing the helix angle cannot simultaneously and significantly improve the condensation heat transfer coefficient and the evaporative heat transfer coefficient.

On the other hand, when the height of the spiral fin 4 is increased,
Although both the condensation heat transfer coefficient and the evaporative heat transfer coefficient are improved, the pressure loss in the pipe increases, so that the load on the compressor that sends out the refrigerant increases, and the mass of the heat transfer pipe also increases.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a heat transfer tube having an inner surface groove capable of improving the condensation heat transfer coefficient and the evaporation heat transfer coefficient in a well-balanced manner. Another object of the present invention is to provide a heat transfer tube with an inner surface groove which does not increase the pressure loss in the tube or increase the mass of the heat transfer tube.

[0009]

According to the present invention, in order to achieve the above object, a high fin having a predetermined height is spirally formed on an inner surface of a tube body, and a high fin is provided between the high fins. An inner grooved heat transfer tube having one or more low fins having a low height, wherein the low fins have a height of 1/15 to 1/5 of a height of the high fins. Provide an inner grooved heat transfer tube. If the height of the low fins is larger than 1/5 of the height of the high fins, the condensation heat transfer coefficient is greatly reduced as compared with a conventional heat transfer tube with internal fins having no low fins. Is smaller than the height of the low fin, the height of the low fin is one of the height of the high fin.
/ 15 to 1/5 is desirable.

The height of the high fin is desirably 0.1 to 0.3 mm. If the height of the high fin is smaller than 0.1 mm,
If the heat transfer performance is deteriorated, and if it is larger than 0.3 mm, the cost increases due to an increase in the mass of the heat transfer tube, and the pressure loss of the refrigerant increases. Therefore, in consideration of both cost and performance, it is desirable that the distance be in the range of 0.1 to 0.3 mm.

The high fin preferably has a twist angle of 15 to 35 degrees with respect to the pipe axis of the pipe body. When the twist angle of the high fin with respect to the tube axis is smaller than 15 degrees, the condensed heat transfer coefficient decreases. When the twist angle is larger than 35 degrees, the evaporative heat transfer coefficient decreases. Therefore, the twist angle is in the range of 15 to 35 degrees. Desirably.

[0012]

FIG. 1A is a cross-sectional view showing a heat transfer tube with an inner groove according to an embodiment of the present invention, and FIG. 1B is an enlarged view of a portion A in FIG. 1A. . The inner grooved heat transfer tube 10
Has a high fin 12a formed spirally on the inner surface of the heat transfer tube main body 11 with a twist angle β of 15 to 35 degrees, and a high fin 12a is formed between the high fins 12a and 12b between the high fins 12a.
One or a plurality of low fins 13a having a lower height than the lower fin 13a are formed. For example, the fin height Hf of the high fin 12a is 0.1 to 0.3 mm, and the apex angle α is 10 to 5 mm.
0 °, the fin height hf of the low fin 13a is 0.02
0.08 mm, the deep groove bottom width Wf is 0.1 to 0.3 mm, and the ratio of the fin height of the low fin 13a to the high fin 12a is 1 /
15 to 1/5.

FIG. 2 shows a heat transfer tube performance measuring device. The heat transfer tube performance measuring device 100 includes a compressor 101 for compressing a refrigerant vapor, a condenser 102 for condensing the refrigerant vapor compressed by the compressor 101 to obtain a refrigerant liquid, and depressurizing the refrigerant liquid from the condenser 102. And an evaporator 104 for evaporating the refrigerant decompressed by the expansion valve 103 to obtain a refrigerant gas. The heat transfer tube 10 having an inner surface groove to be measured is incorporated into the evaporator 104 with an effective length of 5000 mm. The heat transfer coefficient of the heat pipe 10 can be measured. The evaporator 104 has a double-pipe structure, in which water flows outside the heat transfer tube 10 to evaporate the refrigerant in the heat transfer tube 10. When measuring the condensation heat transfer coefficient, the measurement is performed by incorporating the heat transfer tube 10 with the inner surface groove to be measured into the condenser 102. The refrigerant used is Freon R410A. During the evaporation test, the inlet dryness of the evaporator 104 is 0.2, the outlet saturation temperature is 8.5 ° C, and the outlet superheat is 5 °. During the condensation test, the inlet superheat of the condenser 102 is used. Was set to 22.5 degrees, the inlet saturation temperature was set to 40 degrees, and the degree of outlet supercooling was set to 5 degrees.

FIG. 3 shows the result of measuring the effect of the fin height ratio between the low fin 13a and the high fin 12a on the heat transfer coefficient of condensation and evaporation using the measuring apparatus 100 shown in FIG. The horizontal axis shows the fin height ratio, and the vertical axis shows the heat transfer coefficient ratio with the conventional inner grooved tube. Here, the conventional inner grooved pipe refers to an inner grooved pipe in which the fin height ratio between the low fin and the high fin is 0, that is, only the high fin. The heat transfer coefficient ratio is for the case where the refrigerant flow rate is 30 kg / h.

As is apparent from FIG. 1, when the fin height ratio exceeds 0.2, the rate of decrease in the condensation heat transfer rate becomes larger than the improvement in the evaporation heat transfer rate. This is because if the volume occupied by the low fins 13a is large, the condensed refrigerant liquid fills the inside of the groove at an early stage, and lowers the condensation heat transfer coefficient. Therefore, the low fin 13a and the high fin 12
The fin height ratio of a is desirably 0.2, that is, 1/5 or less.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described. The heat transfer tube with an inner surface groove according to the first embodiment has a fin height of 0.2 mm, a twist angle of 16 degrees, a fin number on the inner surface of a heat transfer tube main body 11 made of a steel tube having an outer diameter of 7 mm and a bottom wall thickness of 0.25 mm. 50 high fins 12a are formed, and four low fins 13a having a height of 0.03 mm (equivalent to 250 peaks) are formed between the high fins 12a and 12b between the high fins 12a. The “equivalent number of peaks” is the number of peaks when it is assumed that the low fins 13 a are arranged at the same pitch on the inner surface of the heat transfer tube main body 11.

According to the first embodiment, the high fins 12
a is 0.2 mm, and the fin height of the low fin 13a is 0.03 mm.
As shown in FIG. 3, the evaporative heat transfer coefficient is 1.1 times and the condensing heat transfer coefficient is 0.97 times as compared with the conventional inner grooved tube. Therefore, the inner grooved heat transfer tube improves the evaporation heat transfer coefficient while making the condensed heat transfer coefficient almost equal to the conventional inner grooved heat transfer tube, and the refrigeration using the inner grooved tube according to the present invention. The performance of equipment such as air conditioners, air conditioners, and heat pumps can be improved.

FIG. 4 shows a second embodiment of the present invention. The second embodiment has an outer diameter of 7 mm and a bottom thickness of 0.25 mm.
The inner surface of the heat transfer tube main body 11 has a fin height of 0.22 mm,
A high fin 12a having a twist angle of 30 degrees and 50 fins is formed, and a low fin 13a having a fin height of 0.03 mm and an equivalent number of peaks of 100 is formed between the high fins 12a.

FIG. 5 shows a third embodiment of the present invention. This third embodiment is different from the second embodiment in that the low fins 13 are used.
The number of peaks of a is 150.

FIG. 6 shows a fourth embodiment of the present invention. This fourth embodiment is different from the second embodiment in that the low fins 13 are used.
The number of peaks of a is 200, and the fin height of the low fin 13a is 0.02 mm. As shown in the figure,
The low fin 13a may be provided so that a groove is not formed between the high fin 12a and the low fin 13a.

The same effects as those of the first embodiment can be obtained in the second to fourth embodiments.

[0022]

As is apparent from the above, according to the heat transfer tube with the inner groove of the present invention, the high fin having a predetermined fin height is formed in a spiral shape on the inner surface of the tube body, and the high fin and the high fin are formed. Since the low fins having a predetermined height are formed between them, the condensation heat transfer coefficient and the evaporation heat transfer coefficient can be improved in a well-balanced manner. Further, by setting the height of the high fins to 0.1 to 0.3 mm, the performance can be improved without increasing the pressure loss in the tube or the mass of the heat transfer tube.

[Brief description of the drawings]

1A is a cross-sectional view of an inner grooved heat transfer tube according to an embodiment of the present invention, and FIG. 1B is an enlarged view of a portion A in FIG.

FIG. 2 is a view schematically showing a heat transfer tube performance measuring device.

FIG. 3 is a graph showing a relationship between a fin height ratio and a heat transfer coefficient ratio of a heat transfer tube with an inner surface groove.

FIG. 4 is a cross-sectional view of a main part of an inner grooved heat transfer tube according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of a main part of a heat transfer tube with an inner surface groove according to a third embodiment of the present invention.

FIG. 6 is a cross-sectional view of a main portion of an inner grooved heat transfer tube according to a fourth embodiment of the present invention.

7A and 7B show a conventional heat transfer tube with an inner groove, in which FIG. 7A is a longitudinal sectional view, FIG. 7B is a transverse sectional view, and FIG. 7C is an enlarged view of a portion A in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 heat transfer tube with internal groove 2 heat transfer tube main body 3 spiral groove 4 spiral fin 5 groove 10 heat transfer tube with internal groove 11 heat transfer tube main body 12a high fin 12b between high fin and high fin 13a low fin 100 heat transfer tube performance measuring device 101 compression Machine 102 Condenser 103 Expansion valve 104 Evaporator H, Hf, hf Fin height W Groove bottom width Wf Deep groove bottom width α Apex angle β Helix angle

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yukihisa Okumura 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Within Hitachi Shinzai Co., Ltd. (72) Ryuichi Kobayashi 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Hitachi Cable, Ltd. Tsuchiura factory

Claims (3)

[Claims] 1. An inner surface in which high fins having a predetermined height are spirally formed on an inner surface of a tube main body, and one or a plurality of low fins having a height lower than the high fins are formed between the high fins. In the grooved heat transfer tube, the height of the low fin is 1/15 of the height of the high fin.
An inner grooved heat transfer tube, characterized in that the heat transfer tube has an inner groove diameter of about 1/5. 2. The high fin has a height of 0.1 to 0.3 m.
The heat transfer tube with an inner surface groove according to claim 1, wherein m is m. 3. The heat transfer tube with an inner surface groove according to claim 1, wherein said high fin has a twist angle of 15 to 35 degrees with respect to a tube axis of said tube main body.