JP3129565B2 - Heat exchanger tubes for heat exchangers - Google Patents

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 suitable for a heat exchanger of a find coil type or a shell and tube type used for a room air conditioner or the like.

[0002]

2. Description of the Related Art At present, as a heat transfer tube used in a heat exchanger such as a room air conditioner, a refrigerant such as chlorofluorocarbon is evaporated or condensed in the tube, and heat exchange with a fluid outside the tube is performed with high efficiency. As shown in FIG. 1, a triangular or trapezoidal fine groove 2 is spirally formed on the inner surface of the heat transfer tube 1 to increase the surface area, and the groove causes the refrigerant to be disturbed. Is increasing.

Further, as in a heat transfer tube 3 shown in FIG.
By providing the cavity 5 at the groove bottom of such a groove and providing the opening 6, particularly, the improvement of the evaporative heat transfer performance is achieved.
(See JP-A-62-62195).

Further, as in a heat transfer tube 7 shown in FIG. 3, semicircular recesses 10 are provided at a constant pitch at the bottom of the groove as shown in FIG. The heat transfer performance is enhanced by causing disturbance (Japanese Unexamined Patent Publication No.
70797).

[0005]

In the heat transfer tube shown in FIGS. 1 and 3, however, the flow is disturbed by providing grooves and depressions. In the case of the heat transfer tube 11 which is the protrusion 12, the reattachment point (the two refrigerant flows 14
Among them, high heat transfer performance can be achieved at the point where the upper flow reaches the groove portion 13), but heat transfer performance may be reduced immediately after the protrusion (vortex refrigerant flow 14),
Further, there is a problem that the pressure loss increases depending on the protrusion. Even if the heat transfer performance increases, if the pressure loss increases in proportion thereto, the power for flowing the refrigerant in the pipe increases, and there is a disadvantage that the heat transfer performance improvement becomes meaningless.

The heat transfer tube shown in FIG. 2 has been developed in order to improve the evaporative heat transfer performance in the tube. However, when manufacturing the heat transfer tube, the ridges 4 are formed after the cavities 5 are formed. Yes, the effect due to the cavity may be lost.

[0007] The present invention solves the above-mentioned problems of the prior art, and provides a heat exchanger tube for a heat exchanger that has improved evaporative heat transfer performance, lowers pressure loss, and is easier to form grooves than conventional heat exchanger tubes. It is intended to be.

[0008]

As a means for solving the above-mentioned problems, the present invention provides a first groove having a substantially rectangular or substantially inverted trapezoidal cross section parallel to the tube axis direction on the inner surface of the tube. A heat transfer tube in which a second groove having a depth smaller than that of the first groove and having a substantially rectangular or substantially trapezoidal cross section is provided on one groove in a spiral shape with respect to the tube axis direction. Ratio of groove width S to P
(S / P) is 1/10 <S / P < 1/2, and the ratio (L / L) of the depth L from the groove bottom of the second groove to the groove width S of the first groove.
S) is L / S> 1/2, and a projection is provided at the bottom of the first groove, and a ratio (t / h) of the height h of the projection to the pitch t of the projection.
Satisfies 1/2 ≦ t / h ≦ 2.

Hereinafter, the present invention will be described in more detail.

[0010]

[Action]

In the heat transfer tube of the present invention, first, as shown in FIG. 5, a first groove 16 having a substantially rectangular or inverted trapezoidal cross section having a projection 19 on the inner surface of the heat transfer tube 15 is formed. Is provided. Further, by providing the second groove 17 which is shallower than the first groove and has a substantially rectangular or substantially inverted trapezoidal cross section so as to intersect with the first groove, the heat transfer in the pipe can be more improved than the conventional single grooved pipe. The area can be increased. The first groove 19 has a substantially rectangular or substantially inverted trapezoidal shape with the groove bottom and the protrusions 19 on both sides thereof,
It can be understood from the drawing that the second groove 17 has a substantially rectangular or substantially inverted trapezoidal shape at the groove bottom and the ridges 18 on both sides thereof.

The lead angle of the first groove 16 is 0 °, that is, parallel to the tube axis. Conventional grooved tubes have a constant lead angle with respect to the tube axis to promote disturbance in the tube. However, although the disturbance effect increases as the lead angle increases, the increase in pressure loss exceeds the improvement in performance, so it is not preferable to set the lead angle too large. On the other hand, in the present invention, the first groove (deep groove) 16, which greatly affects the pressure loss, is made parallel to the pipe axis, so that the pressure loss can be made lower than that of a conventional grooved pipe.

FIG. 6 (exploded view of the inner surface groove) and FIG.
As schematically shown in FIG. 6 (enlarged sectional view of the portion A), the refrigerant flows smoothly in the first groove, flows smoothly over the ridges in the second groove, and simultaneously flows in the second groove. From first
It also branches into the groove and flows. In addition, as shown in FIG. 7, no vortex refrigerant flow occurs immediately after the protrusion 19 of the first groove or the crest 18 of the second groove.

Secondly, in the present invention, the ratio (S / P) of the groove width S to the circumferential groove pitch P of the first groove 16 is 1/10.
<S / P <1/2 is satisfied. If the S / P ratio is too small, the pressure loss increases. Conversely, if the S / P ratio is too large, the fin thickness becomes thin, causing a problem in formability. For this reason, in the present invention, S /
The P ratio is in the range of 1/10 <S / P <1/2.

Third, in the present invention, the groove width S of the first groove 16 is
And the ratio (L / S) of the groove depth L from the bottom of the second groove 17 to the groove bottom is L
/ S> 1/2. If the L / S ratio is too small, the second groove 17 having a lead angle
The effect of the swirling flow of the refrigerant due to this is hard to appear, and the performance cannot be improved. Therefore, the L / S ratio is preferably L / S> 1/2. Thereby, a swirling flow is generated as shown in FIGS.

Fourth, in the present invention, the projection 19 is provided at the bottom of the first groove 16 as described above.
The protrusions have a ratio (t / h) between the height h and the pitch t that satisfies the relationship of 1/2 ≦ t / h ≦ 2. In the first groove, the refrigerant flows along the groove. However, the provision of the protrusion in the first groove causes the refrigerant to separate and reattach (see FIG. 7). Since the heat transfer efficiency is increased at the point where reattachment occurs, the heat transfer performance is improved as compared with the case where there is no protrusion. However, if the t / h ratio becomes too small due to the height of the projections or the pitch being small, the pressure loss increases. On the other hand, if the protrusions become low or the pitch becomes large and the t / h ratio becomes too large, the disturbance effect becomes small, and improvement in heat transfer cannot be expected. Therefore, the t / h ratio is preferably 1/2 ≦ t / h ≦ 2.

The heat transfer tube of the present invention is manufactured by a rolling method as described later. At this time, since there is no cavity like the conventional heat transfer tube shown in FIG. 2, the first groove and the second groove are provided. It is not necessary to take care that the cavity is not collapsed when molding, and the molding is easy.

Next, an embodiment of the present invention will be described.

[0019]

【Example】

FIGS. 10 to 14 show a rolling apparatus. This rolling device arranges a roll pair consisting of a grooved roll shown in FIG. 10 and a guided flat roll shown in FIG. 13, and a roll pair consisting of a grooved roll shown in FIG. 12 and a guided flat roll shown in FIG. And the metal strip is rolled by these roll pairs. The grooved roll shown in FIG. 10 has projections with a depth L ₁ , pitch P ₁ and width S ₁ formed on the surface at a lead angle of 0 °, and the grooved roll shown in FIG. 12 has a predetermined lead on the surface. A spiral groove is formed at the corner. Further, the roll shown in FIG. 11 is a cross-sectional view of the roll shown in FIG. 10, and a groove having a pitch t and a depth h is formed in the crest of the roll groove in parallel with the roll axis.

Using this rolling device, copper strip (C1220)
After rolling and forming by roll forming, welding
A copper tube having an outer diameter of 9.52 mm was prepared according to the specifications shown in Table 1. This tube was incorporated into a double tube heat exchanger, and the evaporative heat transfer performance was measured under the following conditions.

Measurement conditions: (1) Refrigerant: R-22, (2) Refrigerant flow rate: 20 to 70 kg / h, (3) Refrigerant pressure: 5.4 kg / cm ² .

In this measurement, as shown in Table 1, a comparison was made between Comparative Products 1 to 6 and a conventional product (trapezoidal groove).

FIG. 15 shows the relationship between the refrigerant flow rate and the in-pipe evaporation heat transfer coefficient when comparing the depth L, pitch P, and width S of the first groove.
FIG. 16 shows the relationship between the refrigerant flow rate and the pipe pressure loss.

The performance of the product of the present invention is about 2.
A six-fold improvement in performance was observed. However, comparative product 3 (S /
(P <1/2, L / S <1/2) are about 1.
Compared to the product of the present invention, which is 6 times higher, and the performance is not improved.
(1/2) only improved about 1.4 times as compared with the conventional product.

The pressure loss in the pipe of the present invention was about 0.56 times lower than that of the conventional product. However, as in Comparative products 2 and 4, S / P <1/10 or S / P> 1
/ 2, the pressure loss in the pipe shows a slightly lower value as compared with the conventional product, but is higher than the product of the present invention, and when L / S <1/2 like the comparative products 1 and 3, Although the pressure loss in the pipe is lower than that of the product of the present invention, the improvement in heat transfer performance is low. Therefore, 1/10 <S / P <1/2 and L
If / S> 1/2, it is understood that the heat transfer tube has higher performance and lower pressure loss than the conventional product.

Next, when the protrusion is provided in the first groove portion, t /
The effect of h was compared. FIG. 17 shows the relationship between the refrigerant flow rate and the pipe evaporation heat transfer coefficient at that time, and FIG. 18 shows the relationship between the refrigerant flow rate and the pipe pressure loss.

The heat transfer performance of the product of the present invention was confirmed to be about 1.7 to 3.1 times that of the conventional product. However, when t / h> 2 as in the comparative product 5, the effect of the projection was not obtained, and the performance was equivalent to that of the comparative product 7 in which the projection was not provided in the first groove portion.

As for the pressure loss in the pipe, the comparative product 6
When t / h <1/2, the pressure loss tended to increase.

[0030]

[Table 1]

[0031]

As described in detail above, according to the present invention,
It is possible to provide a heat exchanger tube for a heat exchanger that has improved evaporative heat transfer performance and lower pressure loss than conventional heat exchanger tubes. Groove formation is also easy.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state where an inner surface of a conventional heat transfer tube is developed into a plane.

FIG. 2 is a perspective view showing a state in which the inner surface of another conventional heat transfer tube is developed in a plane.

FIG. 3 is a perspective view showing a state in which the inner surface of still another conventional heat transfer tube is developed in a plane.

FIG. 4 is a diagram illustrating a groove shape and a refrigerant flow in a conventional heat transfer tube.

FIG. 5 is a perspective view showing a state where the inner surface of the heat transfer tube of the present invention is developed into a plane.

FIG. 6 is a plan view showing a state where the inner surface of the heat transfer tube of the present invention is developed into a plane.

FIG. 7 is a cross-sectional view showing a state where the inner surface of the heat transfer tube of the present invention is developed in a plane.

FIG. 8 is a perspective view showing a state in which the inner surface of the heat transfer tube of the present invention is developed in a plane.

FIG. 9 is a sectional view taken along line AA ′ of FIG. 9;

FIG. 10 is a longitudinal sectional view showing a grooved roll of a first roll pair in a rolling device.

FIG. 11 is a cross-sectional view of FIG.

FIG. 12 is a side view showing a grooved roll of a second roll pair in the rolling device.

FIG. 13 is a side view showing a flat roll in a rolling device.

FIG. 14 is a perspective view showing a roll arrangement of a rolling device.

FIG. 15 is a diagram showing the relationship between the refrigerant flow rate and the in-pipe evaporation heat transfer coefficient when comparing the depth L, pitch P, and width S of the first groove.

FIG. 16 is a diagram showing the relationship between the refrigerant flow rate and the pressure loss in the pipe when the depth L, pitch P, and width S of the first groove are compared.

FIG. 17 is a diagram showing the relationship between the refrigerant flow rate and the in-pipe evaporation heat transfer coefficient when comparing the effects of t / h when a projection is provided in the first groove.

FIG. 18 is a diagram illustrating a relationship between a refrigerant flow rate and a pressure loss in a pipe when comparing the influence of t / h when a protrusion is provided in a first groove portion.

[Explanation of symbols]

 Reference Signs List 15 heat transfer tube 16 first groove 17 second groove 18 peak 19 protrusion 30 grooved roll 31 grooved roll 32 plane roll 33 plane roll guide 34 metal strip

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tetsuo Uchida 65, Hirasawa, Hadano City, Kanagawa Prefecture Inside the Hadano Plant, Kobe Steel Co., Ltd. (72) Inventor Mamoru Ishikawa 65, Hirasawa, Hadano City, Kanagawa Prefecture Hadano Plant, Kobe Steel Co., Ltd. (56) References JP-A-62-62195 (JP, A) JP-A-3-170797 (JP, A) JP-A-62-64421 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F28F 1/40

Claims (1)

(57) [Claims] 1. A first groove having a substantially rectangular or substantially inverted trapezoidal cross section parallel to the pipe axis direction on the inner surface of the pipe is provided, and the depth of the first groove is smaller than that of the first groove, and the cross section is substantially the same. Rectangular or nearly trapezoidal second
A heat transfer tube in which grooves are spirally provided in the tube axis direction. The ratio (S / P) of the groove width S to the circumferential pitch P of the first groove is 1 / S.
10 <S / P <１ ／, which is relative to the groove width S of the first groove.
The ratio (L / S) of the depth L from the groove bottom of the second groove is L / S> 1.
/ 2, and further, a projection is provided on the groove bottom of the first groove, and the ratio (t / h) of the height h of the projection to the pitch t of the projection is 1/2 ≦ t / h.
An electric heating tube for a heat exchanger, wherein ≦ 2.