JPH0579783A - Heat transfer tube with internal groove - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a heat transfer tube with an inner groove, which has excellent heat transfer performance and reduces the unit weight. [Structure] The outer diameter of the pipe is 9.5 to 10 mm, and the inner surface has a spiral groove,
The twist angle (α) of the groove with respect to the tube axis is 16 to 22 degrees, and the groove depth
(Hf) to pipe inner diameter (Di) ratio (Hf / Di) is 0.023 to 0.025, and wall thickness (Tf) from groove bottom to outer diameter is 0.025 to 0.35 mm. Groove bottom width in cross section perpendicular to the axis
(W) to groove depth (Hf) ratio (W / Hf) is 1.22 to 1.27, and the apex angle (γ) of the crests formed between the grooves is set to 50 to 55 degrees in the groove cross section. Is characterized by.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an air conditioner, a refrigerator,
The present invention relates to a heat transfer tube used for a heat exchanger such as a boiler, and more particularly, to a heat transfer tube with an inner groove suitable for an application in which a fluid flowing in the tube undergoes a phase change.

[0002]

2. Description of the Related Art As shown in FIGS. 1 and 2, an inner grooved heat transfer tube 1 has a large number of spiral grooves 2 formed on the inner surface of a metal tube such as a copper tube to form peaks (fins) 3. The fluid flowing in the tube is used for the purpose of changing the phase between the liquid phase and the gas phase. For example, liquid evaporation will be described. The liquid flowing at a certain speed or higher in the tube rises up the spiral groove due to the capillary action of the fine groove and the force due to the flow velocity to form an annular flow, and evaporation is promoted in the entire tube.

In such a phase change state, the factors that determine the performance of the inner surface grooved heat transfer tube are the agitation effect of the fluid due to the unevenness of the inner surface, the heat transfer promotion effect due to the increase of the inner surface area, and the fluctuation of the liquid line at the uneven portion. The effect etc. can be considered. Table 1
An example of a typical shape of the internally grooved heat transfer tube currently used is shown in Japanese Patent Laid-Open No. 60-142195. It should be noted that each of these dimensions refers to the location shown in FIGS.

[0004]

[Table 1]

[0005]

The heat transfer tubes shown in Table 1 have a certain level of performance and are currently in practical use.
Further, there is a strong demand for miniaturization, weight reduction and cost reduction of the heat exchanger, and further improvement in performance is desired.

The present invention was developed as a result of a multifaceted examination of the correlation between the heat transfer performance of the heat transfer tube with the spiral groove on the inner surface and the shape of the groove and the shape of the ridge (fin) formed between the grooves. The purpose is to provide a heat transfer tube with an inner groove having excellent heat transfer performance and reduced unit weight.

[0007]

A heat transfer tube with an inner surface groove according to the present invention for achieving the above object has a tube outer diameter of 9.5 to 10 mm.
Has a spiral groove on the inner surface, the twist angle of the groove with respect to the pipe axis is 16 to 22 degrees, and the ratio of groove depth (Hf) to pipe inner diameter (Di) (Hf / Di) is
0.023 to 0.025, wall thickness (Tf) from groove bottom to outer diameter is 0.25
~ 0.35 mm, the ratio of the groove bottom width (W) to the groove depth (Hf) (W / Hf) in the cross section perpendicular to the axis in a heat transfer tube where the fluid in the tube undergoes a phase change
Is 1.21 to 1.27, and the apex angle of the crests formed between the grooves is 50 to 55 degrees in a cross section perpendicular to the groove.

The reason for limiting the numerical values in the present invention will be described.
The prerequisite shape is a pipe outer diameter (D) of 9.5 to 10 mm and a spiral groove on the inner surface. The twist angle (lead angle α) of the groove with respect to the pipe axis is 16 to 22 degrees and the groove depth (Hf). And pipe inner diameter (Di) ratio (Hf / Di)
Is 0.023 to 0.025, the wall thickness from the groove bottom to the outer diameter (bottom wall thickness
Tf) is 0.25 to 0.35 mm. Of these, (Hf / Di)
The range of the ratio is selected mainly from the viewpoint of the performance of the heat transfer tube, and the lead angle of the groove is determined in consideration of the ease of manufacturing the heat transfer tube. In the heat transfer tube of the present invention, maximum heat transfer performance can be obtained by combining these prerequisites with the geometrical requirements of the groove and the ridge described later.

The first geometrical requirement in the present invention is the groove bottom width (W) and groove depth in a cross section perpendicular to the axis, in other words, fin height.
The ratio (W / Hf) of (Hf) is limited to the range of 1.22 to 1.27. When the (W / Hf) ratio is less than 1.22, the fin portion is likely to be buried when the condensate is accumulated in the groove portion when the fluid in the tube is condensed, and the condensing ability is reduced. If the (W / Hf) ratio exceeds 1.27, the surface area inside the tube becomes small and the heat transfer performance becomes poor. For example, if the number of peaks (number of fins) is reduced, (W / Hf) becomes large, which is outside the specific range of the present invention.

The second geometrical requirement in the present invention is to set the apex angle (γ) of the crests (fins) to 50 to 55 degrees in a cross section perpendicular to the groove. Generally, the smaller the apex angle (γ) of the fins in evaporation and condensation, the more the heat transfer performance is improved, but the fin workability at the time of manufacturing the heat transfer tube is also taken into consideration and the heat transfer performance is limited to the range of 50 to 55 degrees.

[0011]

In the present invention, the groove shape is specified by limiting the ratio (W / Hf) of the groove bottom width (W) to the fin height (Hf) in the cross section perpendicular to the groove to the above range. By combining the groove shape with the fin shape with a limited apex angle, heat transfer is promoted, the streamlines of the irregularities are maintained moderately to improve performance, and the unit weight is light and processing during pipe manufacturing It is possible to obtain a heat transfer tube with an inner groove that does not hinder the performance.

[0012]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples.

Example 1 Freon-R22 was used as the refrigerant, and the refrigerant flow rate was changed into the inner spiral grooved tube having the shape shown in Table 3 under the conditions of Table 2, and the evaporation test and the condensation test were conducted.

[0014]

[Table 2]

[0015]

[Table 3]

The relationship between the refrigerant flow rate and the evaporation heat transfer coefficient of the heat transfer tube obtained by the above test is shown in FIG. 4, and the relationship between the refrigerant flow rate and the condensation transfer coefficient is shown in FIG.

Example 2 In a heat transfer tube with an internal spiral groove having a shape shown in Table 3, the fin width (groove width) was changed and the ratio of the groove width (W) to Hf (W
A condensation test was performed on the heat transfer tubes with different / Hf) under the same conditions as in Example 1. However, the refrigerant flow rate was 50 kg / h. The results are shown in Fig. 6.

Comparative Example 1 A heat transfer tube with an internal spiral groove having the shape shown in Table 3 and a smooth copper tube without an internal spiral groove having an outer diameter of 9.52 mm and an inner diameter of 8.52 mm were manufactured and subjected to an evaporation test under the same conditions as in Example 1. A condensation test was performed. The results are also shown in FIGS. 4 and 5.

From the results shown in FIGS. 4 and 5, it can be seen that the example of the present invention has an improved thermal conductivity, particularly at the time of aggregation, as compared with the comparative example. Also, from the results of Figure 6, (W / Hf) ratio
It can be seen that there is a peak near 1.25.

[0020]

As described above, according to the present invention, it is possible to provide an inner grooved heat transfer tube having excellent heat transfer performance and having a reduced unit weight as compared with the conventional product, and the cost of the heat exchanger can be reduced. Can contribute to the decline.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing the shape of a heat transfer tube with an inner groove.

FIG. 2 is a cross-sectional view showing the shape of a heat transfer tube with an inner groove.

FIG. 3 is a partially enlarged explanatory view of a cross section showing the shape of a heat transfer tube with an inner groove.

FIG. 4 is a graph showing a relationship between a refrigerant flow rate and an evaporation heat transfer coefficient.

FIG. 5 is a graph showing a relationship between a refrigerant flow rate and a condensation heat transfer coefficient.

FIG. 6 is a graph showing the relationship between the ratio of groove width to groove depth and the condensation heat transfer coefficient.

[Explanation of symbols]

 1 Heat transfer tube with inner groove 2 Spiral groove 3 Mountain part (fin)

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masahiko Kobayashi Sumitomo Light Metal Industry Co., Ltd. 100, Oki Shindo 100, Ikinomiya-cho, Aichi prefecture

Claims (1)

[Claims] 1. A pipe having an outer diameter of 9.5 to 10 mm and a spiral groove on the inner surface, the twist angle of the groove with respect to the pipe axis is 16 to 22 degrees, and the groove depth.
(Hf) to pipe inner diameter (Di) ratio (Hf / Di) is 0.023 to 0.025, wall thickness (Tf) from the groove bottom to the outer diameter is 0.25 to 0.35 mm, and the heat transfer tube undergoes a phase change in the fluid inside the tube. , The ratio (W / Hf) of the groove bottom width (W) to the groove depth (Hf) in the cross section perpendicular to the axis is 1.22 to 1.27, and the peak angle of the crests formed between the grooves is 50 Heat transfer tube with internal groove, characterized in that it is set to ~ 55 degrees.