JP2003166794A - Internally threaded tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internally threaded tube preventing decrease of heat conductivity of fins even when forming the high and sharp inner fins and having high heat conductivity as the entire tube by fully transferring heat transferred from outer surface of the tube to the tip of the fins. <P>SOLUTION: Many fins 10 with a fin level H of 0.2-0.4 mm having a predetermined lead angle β for the tube axis are formed in parallel on inner surface of the tube. A ratio SH/H of a sectional area SH and the fin level H of the respective fins 10 on a section orthogonal to the lead angle β is 0.06-0.09. A width between both side inclined faces at a predetermined level in a root direction of the fins 10 preferably gradually increases as approaching the root than a width between extending faces in the root direction of both side inclined faces at a predetermined level in a top direction of the fins 10. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner grooved tube (heat transfer tube) used for heat exchangers such as refrigerators and air conditioners.

[0002]

2. Description of the Related Art As a heat transfer tube for a heat exchanger as described above, an inner grooved tube having a large number of spiral fins formed in parallel on the inner surface of the tube is often used. In this type of heat transfer tube,
With the trend toward miniaturization and higher performance of heat exchangers, there is a demand for smaller size and higher performance. Therefore, the fin height of the inner surface fins is made higher and the fin cross-section shape becomes sharper (thinner). Moreover, attempts have been made to form them densely.

[0003]

However, if the fins are made too thin and sharp, the heat from the outside of the tube becomes harder to transfer to the tip of the fins, and the heat transfer efficiency of the fins as a whole (fin heat transfer efficiency) decreases. As a result, heat exchange between the outside of the pipe and the inside of the pipe is hindered, which in turn hinders the transfer of heat as the entire inner surface of the pipe. Further, the higher the fin is, the more the heat transfer efficiency in the tube is improved, but if the fin height is set higher than a certain height, the fin processing efficiency is extremely lowered. The purpose of the present invention is to
Even if the fin height is made as high as possible and sharp inner fins are formed within the range that does not hinder workability, the heat transfer efficiency of the fins is not reduced, and the heat transferred from the outer surface of the pipe is sufficiently transferred to the fin tips. An object of the present invention is to provide an inner grooved tube having high thermal efficiency as a whole tube.

[0004]

The inner grooved tube according to the present invention is constructed as follows in order to solve the above-mentioned problems. That is, the inner grooved tube according to claim 1,
A large number of fins 10 having a predetermined lead angle β with respect to the pipe axis and having a fin height H = 0.2 to 0.4 mm are formed in parallel on the inner surface of the pipe, and each fin 10 in a cross section orthogonal to the lead angle β. Ratio SH / H = of cross-sectional area SH of fin and height H of fin
It is characterized by being 0.06 to 0.09.

The inner grooved pipe according to claim 2 is the pipe according to claim 1.
In the inner grooved tube, the width between the inclined surfaces on both sides at a predetermined height portion in the root direction of the fin 10 is equal to that of the fin 1
It is characterized in that it gradually widens as it approaches the root than the width between the extension surfaces of the inclined surfaces on both sides in the root direction at the predetermined height portion of 0.

[0006] The inner grooved pipe according to claim 3 is the pipe according to claim 1.
Or in the inner grooved tube of 2, the lead angle β is 25 to
It is characterized by being 45 °.

The inner grooved pipe according to claim 4 is the pipe according to claim 1.
To the inner grooved pipe of any one of 3 to 3, the fin pitch P
Is 0.35 to 1.0 mm.

The inner grooved pipe according to claim 5 is the pipe according to claim 1.
In the inner grooved tube of any one of to 4, the outer diameter of the tube is 10
It is characterized by being less than mm.

The inner grooved tube according to the sixth aspect is the first aspect.
In the inner grooved tube of any one of to 5, the material of the tube is copper or copper alloy.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment of an inner grooved tube according to the present invention will be described below with reference to the drawings. 1A is a partially developed plan view of an inner grooved tube according to an embodiment of the present invention, and FIG. 1B is a partially enlarged sectional view taken along the arrow AA of FIG.

As shown in FIG. 1, a large number of fins 10 having a lead angle β of 25 to 45 ° with respect to the tube axis are formed in parallel on the inner surface of the tube 1. The tube 1 is made of copper or a copper alloy and has an outer diameter of 4 to 10 mm and a groove bottom wall thickness (thickness of the deepest part of the groove bottom) T = 0.3 mm. Each fin 10 has a fin height H = 0.2 to 0.4 mm and a fin pitch P =.
The ratio SH / H of the cross-sectional area SH of each fin 10 and the fin height H (a value excluding the unit) in the cross section orthogonal to the lead angle β is 0.06 to 0.
It is within the range of 09.

The cross-sectional shape of the fin 10 has a width W between the inclined surfaces on both sides at a predetermined height portion (root portion) in the root direction thereof as shown in FIG. The width w between the extension surfaces of the inclined surfaces on both sides of the salient portion in the direction of the root gradually widens toward the root. In the diagram (b), the root portion 11 is formed in a trapezoidal shape having an opening angle α1 larger than the fin apex angle α, but, for example, as shown by the chain double-dashed line in FIG. Can also be implemented by forming a concave arc shape in cross section.

In the inner grooved tube of this embodiment, firstly, the fin height H is 0.2 to 0.4, and the cross-sectional area SH of each fin 10 in the cross section perpendicular to the lead angle β and the fin Since the fins 10 are formed on the inner surface so that the ratio SH / H with the height H is 0.06 to 0.09, the fins having the highest and sharpest cross-sectional shape can be formed within the range that does not hinder the workability. However, the heat transfer efficiency from the outside of the tube through the tube wall is sufficiently transmitted to the tips of the fins 10 without lowering the fin heat transfer efficiency, and the entire tube exhibits high thermal efficiency. If the fin height H is less than 0.2 mm, the heat transfer coefficient in the pipe cannot be expected to improve. On the other hand, if the fin height H exceeds 0.4 mm, the heat transfer coefficient improves, but it becomes difficult to machine the fin at high speed. Productivity is significantly reduced. When the SH / H is less than 0.06, the cross-sectional shape of the fin 10 becomes too sharp and heat from the outside of the tube is less likely to be transferred to the tips of the fin 10, and the heat transfer efficiency of the fin decreases and the heat inside and outside the tube decreases. The heat exchange is hindered, and thus the heat transfer through the entire inner surface of the tube is hindered. On the other hand, if SH / H exceeds 0.09, the fin 10
Since the sectional shape of is not sharp, the heat transfer efficiency is reduced.

Secondly, in each fin 10, the width between the inclined surfaces on both sides at a predetermined height portion (root portion) in the root direction is such that the width between both inclined surfaces at the predetermined height portion in the top direction of the fin 10 is in the root direction. The width between the extension surfaces of the fins gradually widens toward the root, so that the heat conductivity to the fin tips and the thermal efficiency can be improved.

Thirdly, the lead angle β of the fin 10 is 25 to
Since it is 45 °, even if the fin height H is relatively low, the flow of the refrigerant in the tube is well agitated, and the thermal efficiency at the thin fin tips is further improved. If the fin lead angle β is less than 25 °, agitation of the refrigerant in the pipe becomes slow when the fin height H is relatively low, and high heat transfer efficiency cannot be expected. On the other hand, if the lead angle β exceeds 45 °. For example, it becomes difficult to process the fin with a rolling tool.

Fourth, the fin pitch P = 0.35 to 1.
Since it is 0 mm, more fins are formed in the tube 1, the heat transfer area in the tube is increased, and the heat transfer efficiency is further increased. If the fin pitch P is less than 0.35 mm, the groove width is too narrow, and the grooves are filled with the condensate, resulting in poor performance. On the other hand, if the fin pitch P exceeds 1.0 mm, it becomes impossible to effectively utilize the advantage of forming a large number of fins in the tube and increasing the heat transfer area. Fifthly, since the outer diameter of the tube 1 is 10 mm or less, the above-mentioned effects are more effectively exhibited. Pipe outer diameter is 1
If it exceeds 0 mm, the influence of gravity acting on the refrigerant liquid flowing in the pipe becomes large, and the refrigerant easily accumulates in the lower side of the pipe when the pipe is installed in the heat exchanger, and the fin efficiency in the circumferential direction is optimized. Becomes difficult. Sixth, fin efficiency can be further improved by using copper or a copper alloy having excellent thermal conductivity as the material of the inner grooved tube.

Test Example As shown in Table 1, any one of the number of fins, the fin lead angle β, the fin height H, the fin pitch P, and the fin cross-sectional area SH in the cross section orthogonal to the lead angle β is different, and Sample No. of inner grooved pipe made of phosphorus deoxidized copper with diameter = 10 mm, groove bottom wall thickness T = 0.3 mm. 1 to 14 were prototyped, and the single tube heat transfer performance was measured for them in the following manner. The measurement results are also shown in Table 1.

Single-tube heat transfer measuring method A sample is inserted as an inner tube of a double-tube heat exchanger installed horizontally, and a refrigerant (freon) is flown into the sample, and a double tube between the outer tube and the inner tube is inserted. Cooling water was made to flow in the pipe portion in opposition to the refrigerant, and heat was exchanged between the cooling water and the refrigerant to condense the refrigerant. The in-tube condensation heat transfer coefficient was calculated from the amount of heat exchanged at that time. The heat transfer coefficient in the tube was obtained based on the outer surface of the tube, and was calculated in the form that includes the thermal conductivity of the tube itself. The refrigerant mass flow rate during measurement is 300 kg.
/ M ² s.

[0019]

As is clear from the measurement results of Table 1, SH / H is 0.0 in the region where the fin height H is 0.2 to 0.4 mm.
Samples within the range of 6 to 0.09 (inside the thick frame in Table 1) are
It exhibits higher average heat transfer performance than the other samples. Even if SH / H is 0.06 to 0.09, the heat transfer performance is deteriorated in the case where the fin height is less than 0.2 mm (No. 1). High heat transfer performance is shown in the case where the fin height H exceeds 0.4 mm (No. 8 and 14), but in these cases, for example, when rolling a pipe using a rolling tool, the processing speed is There was a problem in terms of productivity because it could be processed if it was not suppressed. The fin lead angle β is in the range of 25 to 45 °, and the performance is further improved. No. 2 to 7 are cases within the scope of the present invention,
Among these, for example, No. Nos. 2 to 4 show relatively high heat transfer performance because the fin lead angle β is 25 ° or more, although the fin height H is relatively low.
In Nos. 6 and 7, the fin height H is relatively high, but the fin lead angle β is as small as 15 °, so the degree of improvement in heat transfer performance is small. From the results of Table 1, the fin pitch P is preferably 0.35 mm or more and 1.0 mm or less. For example, No. 6 has a relatively high fin height H, but the fin pitch is less than 0.35 mm, so N
o. In No. 5, since the fin pitch P is too large to secure the required heat transfer area, the heat transfer coefficient in each tube is relatively low.

[0021]

INDUSTRIAL APPLICABILITY The inner grooved tube according to the present invention has a fin height H = 0.2 to 0.4, and the cross-sectional area SH and fin height of each fin 10 in a cross section orthogonal to the lead angle β. Since the fin 10 is formed on the inner surface so that the ratio SH / H with H is 0.06 to 0.09, even if a fin having a high and sharp cross-sectional shape is formed, the fin heat transfer efficiency decreases. Instead, the heat from the outside of the pipe through the pipe wall is sufficiently transmitted to the tips of the fins 10, and the heat transfer efficiency of the entire pipe is improved. Also, by making the fin shape sharper, more fins can be formed on the inner surface to maximize the heat transfer area,
The heat transfer performance can be improved.

[Brief description of drawings]

FIG. 1 (a) is a partially developed plan view of an inner grooved tube according to an embodiment of the present invention, and FIG. 1 (b) is an enlarged sectional view taken along the arrow AA of FIG. 1 (a).

[Explanation of symbols]

1 Tube 10 Fin 11 Root part α Fin apex angle α 1 Root opening angle β Fin lead angle H Fin height T Groove bottom wall thickness SH Fin cross-sectional area P Fin pitch W Both slopes on both sides of root direction Width w The width between the extension surfaces in the root direction of the inclined surfaces on both sides of the top part of the fin

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshiaki Hashizume             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd.

Claims (6)

[Claims] 1. A predetermined lead angle β with respect to the tube axis on the inner surface of the tube
A large number of fins 10 having a fin height H = 0.2 to 0.4 mm are formed in parallel, and the ratio SH of the cross-sectional area SH of each fin 10 and the fin height H in the cross section orthogonal to the lead angle β. /H=0.06 to 0.09, an inner grooved tube. 2. The width between the inclined surfaces on both sides at a predetermined height portion in the root direction of the fin 10 is defined by the distance between the extension surfaces in the root direction of both inclined surfaces at the predetermined height portion in the top direction of the fin 10. The inner grooved pipe according to claim 1, wherein the inner surface grooved pipe is wider than the width gradually toward the base. 3. The inner grooved tube according to claim 1 or 2, wherein the lead angle β is 25 to 45 °. 4. The fin pitch P is 0.35 to 1.0 mm.
The inner grooved tube according to any one of claims 1 to 3, characterized in that 5. The inner grooved pipe according to claim 1, wherein the outer diameter of the pipe is 10 mm or less. 6. The inner grooved tube according to claim 1, wherein the material is copper or a copper alloy.