JP3415013B2 - Heat transfer tube for condenser - 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 used in a refrigerator or the like, and more particularly to a heat transfer tube for a condenser capable of improving heat transfer performance.

[0002]

2. Description of the Related Art Conventionally, heat transfer tubes having fins on their outer surfaces have been used in refrigerators and the like, and in particular, heat transfer tubes having improved heat transfer performance by defining the shape of the fins. Has been devised (Shokai 59-42477)
Issue). FIG. 4 is a perspective view showing the shape of a conventional heat transfer tube. As shown in FIG. 4, a plurality of fins 21 are formed on the outer surface of the tube body 23. In this fin 21,
Two grooves 25 are provided to divide the peak along the direction parallel to the fins. Therefore, the fin 21 has a branch portion 24 on its head, which branches in three directions. Further, the fin 21 is provided with a plurality of notches 22 that divide the fin 21 in the longitudinal direction.

In the heat transfer tube 26 thus constructed, the refrigerant condensed on the surface of the heat transfer tube 26 flows into the grooves 25 between the branch portions 24, and then the refrigerant passes from the grooves 25 through the notches 22. It falls between the fins 21. Like this, fin 2
Since the refrigerant does not stay in the upper part of 1, it is possible to obtain good heat transfer performance.

As a heat transfer tube with improved heat transfer performance, there has been proposed a heat transfer tube in which a notch (notch) forming direction, depth, density and the like are defined (Japanese Patent Laid-Open No. 8-2196).
No. 75).

By the way, due to the recent regulation of CFCs, from a refrigerant containing chlorine-containing chlorodifluoromethane or the like as a refrigerant condensed on the surface side of a heat transfer tube, a refrigerant containing no chlorine, for example, 1, The transfer to those using 1,1,2-tetrafluoroethane etc. is in progress.

[0006]

However, in a conventional heat transfer tube, when a refrigerant that complies with CFC regulations is used as the refrigerant condensed on the surface, for example, as compared with the case where chlorodifluoromethane is used as the refrigerant, There is a problem that heat transfer performance is deteriorated. Further, in the conventional heat transfer tube shown in FIG. 4, the cutouts are retained in the grooves between the fins although the cutouts are provided in the fin heads to improve the liquid drainage property at the fin heads. It does not contribute to the discharge of condensed refrigerant. In particular, with a refrigerant having a low density (for example, 1,1,1,2-tetrafluoroethane, etc.), this tendency becomes remarkable.

The present invention has been made in view of the above problems, and provides a heat transfer tube for a condenser capable of obtaining good heat transfer performance even when a refrigerant compatible with CFC regulations is used. The purpose is to do.

[0008]

A heat transfer tube for a condenser according to the present invention has a tube main body and a heat transfer tube for a condenser having a fin provided on an outer surface of the tube main body and extending in a direction orthogonal to or inclined with respect to the tube axis direction. in the fin, a plurality of second grooves for dividing the first groove that will be formed by dividing along a direction parallel to its summit in the <br/> fins, the fins in the longitudinal direction And the second groove has a length of the fin.
The shape of the cross section including the hand direction is a triangle with a vertex at the bottom.
And the angle formed by the side surfaces is 55 ° or less.

The angle formed by the side surface of the second groove is preferably 40 ° or less.

In the present invention, the angle formed by the side surface of the second groove means the angle formed by both side surfaces of the projection formed by the second groove in the projection formed by providing the second groove. Say.

The inventors of the present application can obtain good heat transfer performance even when using a refrigerant (for example, 1,1,1,2-tetrafluoroethane) complying with CFC regulations. Various experiments were conducted to develop a heat tube. As a result, they found that the performance deterioration due to the change of the refrigerant was due to the difference in the density of the refrigerant. Then, the inventors of the present application give the heat transfer performance the angle formed by the first groove dividing the crest of the fin along the direction parallel to the fin and the angle formed by the side surface of the second groove dividing the fin in the longitudinal direction. As a result of examining the influence, it was found that the angle formed by the side surface of the second groove has a great influence on the heat transfer performance of the tube.

3 (a) and 3 (b) are front views showing the shape of the fins formed on the heat transfer tube. Fin 11
Grooves 1 that divide the fin in the longitudinal direction are provided in a and 11b.
By providing 7a and 17b, the protrusion 14a,
14b is formed. The protrusion 14
The angle θ ₁ formed by the side surface 12a of a is larger than the angle θ ₂ formed by the side surface 12b of the protrusion 14b, and the height h of the protrusions 14a and 14b is constant in order not to increase the size of the heat transfer tube. And

As shown in FIGS. 3 (a) and 3 (b), when the angle θ ₁ is larger than the angle θ ₂ , the area of the protrusion 14a becomes larger than the area of the protrusion 14b. The liquefied refrigerant easily wets and spreads on the surface of the portion 14a,
The liquid holding amount for discharging the liquid on the end face of the protrusion 14a is reduced. Therefore, it takes time for the refrigerant to collect on the end surface of the protrusion 14a, and the refrigerant is less likely to be discharged. In particular, when a refrigerant having a low density is used, a large amount of liquid is needed to be discharged, so that the protrusion 14
The liquid film at a becomes thick, and this becomes thermal resistance, and the performance deteriorates. Further, since the discharging property at the protrusion 14a is reduced, a condensed liquid film is formed in the groove between the fins, and as a result, the entire heat transfer tube is covered with the condensed liquid.

On the other hand, since the protrusion 14b has a smaller area than the protrusion 14a and the wetting and spreading on the surface is small,
The liquefied refrigerant easily accumulates on the end surface of the protrusion 14b, and the refrigerant is easily discharged in a short time. Further, since the refrigerant is discharged well, the liquid condensed in the grooves between the fins and the first groove provided at the top of the fins is guided to the protrusions 14b, and the entire heat transfer tube is covered with the condensed liquid. Since it becomes difficult, the heat transfer performance can be significantly improved.

As described above, when the angle formed by the side surface of the protrusion, that is, the side surface of the second groove is smaller than that of the conventional one, a heat transfer tube having good heat transfer performance can be obtained. In particular,
By setting the angle θ formed by the side surface of the second groove to be 55 ° or less, extremely excellent heat transfer performance can be obtained as compared with the case where the angle θ exceeds 55 °. When the formed angle θ is 40 ° or less, the heat transfer performance can be further improved.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A heat transfer tube for a condenser according to an embodiment of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1A is a perspective view showing a heat transfer tube for a condenser according to an embodiment of the present invention, and FIG. 1B is a sectional view thereof. As shown in FIG. 1, on the outer surface of the pipe body 3, the pipe body 3
A plurality of fins 1 extending along the circumferential direction, that is, in the direction orthogonal to the tube axis direction are provided. Also fin 1
Is formed with a first groove 5 that divides the mountain peak along a direction parallel to the fin 1, and further has a second groove 2 that divides the fin in the longitudinal direction. Therefore, the head of the fin 1 has a shape branched in two directions in a cross section orthogonal to the fin, and the second groove 2 is provided, so that the fin 1 is divided into a plurality of protrusions 4 in a cross section parallel to the fin. Has been done. As shown in FIG. 1B, the second groove 2
The angle θ formed by the side surface 2a of the above is 55 ° or less.

In the heat transfer tube 6 thus constructed, the angle θ formed by the side surface 2a of the second groove 2 is appropriately defined, so that the area of the protrusion 4 is smaller than that of the conventional heat transfer tube. Therefore, the liquefied refrigerant on the surface of the protrusion 4 is less likely to spread. Therefore, the refrigerant is likely to be dripped from the end surface of the protrusion 4, and the heat transfer performance can be improved.

In the present embodiment shown in FIG. 1, 1
Although one first groove is formed for each fin, the number of first grooves is not limited in the present invention, and a plurality of two or more grooves may be formed at the top of the fin 1. Further, the fin 1 may be annularly provided on the outer surface of the tube body in a direction orthogonal to the tube axis, or may be spirally provided on the outer surface of the tube body in a direction inclined to the tube axis. Further, in the present invention, the material of the heat transfer tube is not particularly limited, and various materials such as copper, copper alloy, aluminum, titanium, steel and stainless can be used.

[0019]

EXAMPLES Examples of a heat transfer tube for a condenser according to the present invention will be specifically described below in comparison with comparative examples. Figure 1
In the fin 1 having the shape shown in Fig. 2, heat transfer tubes were produced in which the angle θ formed by the side surface 2a of the second groove 2 was variously changed, and a condensation heat transfer performance test was performed. In this condensation heat transfer performance test, 1,1,1,2-tetrafluoroethane, which is an alternative CFC, is used as the refrigerant, the condensation temperature is 48 ° C., and the inlet temperature of the cooling water flowing in the heat transfer tube is 35 ° C. C., and the flow rate of the cooling water in the pipe was changed for evaluation. The shapes and sizes of the produced heat transfer tubes are shown in Tables 1 and 2 below. In Tables 1 and 2 below, the fin outer diameter refers to the outer diameter including the fins of the heat transfer tube where the fins are formed, and the number of fins is 1 inch (25.4 mm) in the tube axis direction. The number of fins formed on the Further, the bottom wall thickness T refers to the wall thickness of the tube body 3 in the portion where the fins are formed in the heat transfer tube.

[0020]

[Table 1]

[0021]

[Table 2]

FIG. 2 is a graph showing the evaluation results of the heat transfer performance of the heat transfer tubes in Examples and Comparative Examples, in which the vertical axis represents the overall heat transfer coefficient and the horizontal axis represents the water flow velocity in the tube. However, in FIG. No. 1 is Δ, and Example No. 2 is □, Example No. No. 3 is ■, Example No. 4 is indicated by ▽,
Comparative Example No. 5 is indicated by x. As shown in FIG. 2, the side surface 2
Example No. 3 in which the angle θ formed by a is 55 ° or less. Comparative Examples Nos. 1 to 4 have an angle θ of 60 °. As compared with No. 5, extremely excellent heat transfer performance could be obtained. That is,
If the angle θ is set to 55 ° or less and a heat transfer tube is manufactured, excellent heat transfer performance can be obtained. Further, when the angle θ is set to 40 ° C. or less, further excellent heat transfer performance can be obtained.

[0023]

As described in detail above, according to the present invention,
Since the angle formed by the side surface of the second groove that divides the fin in the longitudinal direction is appropriately defined, it is possible to obtain a heat transfer tube for a condenser with improved condensate drainage and excellent heat transfer performance. .

[Brief description of drawings]

FIG. 1A is a perspective view showing a heat transfer tube for a condenser according to an embodiment of the present invention, and FIG. 1B is a sectional view thereof.

FIG. 2 is a graph showing the evaluation results of the heat transfer performance of heat transfer tubes in Examples and Comparative Examples, in which the vertical axis represents the overall heat transfer coefficient and the horizontal axis represents the water velocity in the tube.

FIG. 3 is a front view showing the shape of fins formed on the heat transfer tube.

FIG. 4 is a perspective view showing the shape of a conventional heat transfer tube.

[Explanation of symbols]

1, 11a, 11b, 21; fins 22; notch 2a, 12a, 12b; side surface 3,23; tube body 4, 14a, 14b; protrusion 2, 5, 17a, 17b, 25; groove 6,26; Heat transfer tube 24; branch

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-5-231790 (JP, A) JP-A-51-24965 (JP, A) JP-A-8-219675 (JP, A) JP-A-59- 100396 (JP, A) JP 5-215442 (JP, A) JP 7-71889 (JP, A) Actual development Sho 59-42477 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) F28F 1/26 F25B 39/04 F28F 1/12 F28F 1/16 F28F 1/42 F25B 37/00

Claims (2)

(57) [Claims] And 1. A tube body, the condenser heat exchanger tube and a fin extending in a direction perpendicular or inclined to the provided tube axis direction on the outer surface of the tube body, the fins are parallel to the summit to the fin has a first groove that will be formed by dividing along the direction, and a plurality of second grooves for dividing the fin in a longitudinal direction, said second groove, said Fi
The shape of the cross section including the longitudinal direction of the triangle has a vertex at the bottom.
A heat transfer tube for a condenser , which has a shape and an angle formed by a side surface is 55 ° or less. 2. The heat transfer tube for a condenser according to claim 1, wherein an angle formed by a side surface of the second groove is 40 ° or less.