JPH04260793A - Heat transfer tube with inner surface groove - Google Patents

Abstract

PURPOSE:To enhance heat transfer performance in a tube, to improve a manufacturing amount per unit time, to prevent collapse of a groove due to extension of the tube when fins are mounted on an outside of the tube and to limit a decrease in the heat transfer performance to a minimum limit by specifying a crest state of a heat transfer tube with an inner surface groove for a heat exchanger. CONSTITUTION:In a heat transfer tube 1 in which a spiral or many axially continuous grooves 2 and crests 3 are formed on an inner surface, an angle alphaof a vertex is formed -20 deg.<alpha< 20 deg., a depth of the groove 2 is formed 0.10-0.25mm, a radio W/H of a width W of the vertex to a depth H of the groove 2 is W/H = 0.3-1.5, and a width W1 of the bottom of the groove is W1 0.1-0.3mm.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internally grooved heat exchanger tube used in a heat exchanger for refrigerators, air conditioners, etc.

0002

[Prior Art and its Problems] In recent years, there has been a strong demand for energy saving and space saving for heat pump air conditioners, and it has become important to make the heat exchanger, which is the main part of the air conditioner, more efficient and more compact. Heat pump air conditioners use aluminum fins with louvers or other cutouts on the surface for heat exchange with the air on the outside of the tube.A tube expansion plug is inserted into the heat transfer tube, the tube is expanded, and the tube is brought into close contact with the aluminum fin. Cross-fin type heat exchangers are mainly used, which are installed vertically in aluminum fins and allow a refrigerant such as Freon to flow through the tubes. In the past, smooth tubes were used as heat transfer tubes. However, an internally grooved tube in which many fine spiral grooves are formed on the inner surface of the tube has been developed, and this has improved the heat transfer performance within the tube. Currently, to improve heat exchangers, trapezoidal grooves with outer diameters of 9.53 mm and 7.00 mm and triangular mountain-shaped inner grooved tubes are mainly used, but heat exchangers can also be made more compact and highly efficient. There is a demand for Therefore, from a cost perspective, various groove shapes are being improved in order to allow for the same amount of production per unit time as at present and to improve heat transfer performance. One of the effective methods is to reduce the groove apex angle. However, in this case, there was a problem in that the peaks were easily crushed during tube expansion during the assembly of the heat exchanger (in particular, the smaller the diameter of the tube, the more likely it was to collapse), resulting in a decrease in heat transfer performance.

0003

[Problems to be Solved by the Invention] In view of this, as a result of various studies, the present invention has been developed to achieve the same production volume per unit time, improved heat transfer performance, and improved tube expansion compared to conventional internally grooved tubes. We have developed an internally grooved heat exchanger tube that dramatically improves efficiency as a heat exchanger by reducing the collapse of the grooves.

0004

[Means for Solving the Problems and Effects] The present invention provides a heat transfer tube in which a large number of grooves and ridges are formed on the inner surface of the tube in a spiral shape or continuous in the axial direction of the tube, and the crest angle is set to -20°<α<20.
°, the groove depth is 0.10 to 0.25 mm, and the ratio of the peak width to the groove depth W/H = 0.3 to 1.5, and the groove bottom width W1
This is a heat exchanger tube with inner grooves having a diameter of 0.1 to 0.3 mm. That is, the present invention, as shown in FIG.
By limiting the ratio of the groove depth (H) and the groove bottom width (W1) as described above, the heat transfer performance is excellent, the production amount per unit time does not decrease, and the groove width during pipe expansion is improved. This provides an internally grooved tube that improves its performance as a heat exchanger by reducing its collapse.

[0005] And the above mountain top angle is -20°<α<20
The reason for this is that outside this range, there is no difference from the conventional triangular peak shape, and the groove collapses during tube expansion, and the production amount per unit time decreases. Groove depth 0.10~0
．． 25mm is less than 0.10mm and 0.25mm.
This is because if it exceeds mm, the ratio of the peak width to the groove depth will not reach a predetermined value, and the heat transfer performance will deteriorate. The ratio W/H of the peak width to the groove depth is set to 0.3 to 1.5 because if it is less than 0.3, the peak width will be small relative to the groove depth, that is, the bottom width will become extremely narrow. The specified groove depth cannot be formed. On the other hand, if it exceeds 1.5, the bottom width becomes too wide and a predetermined groove depth cannot be achieved, and in either case, the production amount per unit time decreases. Furthermore, the groove bottom width W1 is set to 0.1 to 0.3.
The reason why it is set as mm is that if it is less than 0.1 mm or more than 0.3 mm, the evaporation performance will deteriorate.

[0006]

[Embodiment] An embodiment of the present invention will be described below. Various grooved tubes made of phosphorus-deoxidized copper and having an outer diameter of 6.00 mmφ were manufactured by rolling using a grooved plug. The shape at this time is that the peak angle is constant α = 15°, and the groove depth is H = 0.
．． The thickness was 1 to 0.2 mm, the bottom thickness was about 0.27 mm, and the width of the top was varied. Figure 1 shows its typical shape. Further, FIG. 2 shows the production amount per unit time with respect to the peak width/groove depth. In the figure, when W/H is less than 0.3, the production amount decreases rapidly because the crest width is small relative to the groove depth, that is, the crest width becomes extremely narrow, and when the predetermined groove depth is This is because groove processing cannot be performed, and the reason why it decreases at 1.5 or more is because the groove becomes extremely wide and the specified groove depth cannot be achieved, and the ratio W of the peak width/groove depth /
It can be seen that when H is in the range of 0.3 to 1.5, the production amount per unit time is greater than that of the conventional triangular mountain shape.

[0007] Next, this sample was 4
After dry drawing to mmφ and annealing, 0.6 m from the maximum inner diameter
m, a large-diameter tube expansion plug was used to insert it into the tube and expand the tube. Figure 3 shows the amount of groove collapse versus the ratio of the peak width to the groove depth. According to this, the larger the W/H,
It can be seen that the pipe has become more resistant to expansion, and the collapse of the groove has become smaller. In particular, when W/H<0.3, the ridge shape becomes too thin and the groove collapses so much that the ridge shape becomes the same as a conventional triangular product. From these facts, the groove shape is W/H=
It can be seen that by forming the groove to have a diameter of 0.3 to 1.5, it is possible to achieve workability equivalent to or better than that of the conventional triangular mountain shape, and to reduce the collapse of the groove during tube expansion. Next, in a heat exchanger tube with an outer diameter of 7 mmφ, α=10°, H=
In the mountain shape of 0.15 to 0.20 mm, W = 0.1 mm, the lead angle is 18°, the number of grooves is changed, and the groove bottom width W
We made several prototype samples with variations in 1. This was installed in the inner tube of a double tube heat exchanger, Freon R-22 was flowed inside the heat exchanger tube, water to be cooled was flowed outside the tube, and the heat transfer coefficient inside the tube and its value were measured under the measurement conditions shown in Table 1. Pressure drop was measured.

[0008]

[Table 1] Figure 4 shows the groove bottom width and the rate of increase in the evaporative heat transfer coefficient compared to the conventional product. In this case, the value when the refrigerant flow rate is 50 kg/h is used.

The conventional product has a triangular peak shape as shown in FIG. 7, and has 60 grooves, a lead angle of 18°, and a groove depth of 0.15 mm.
The peak angle is 55° and the groove bottom width is 0.15 mm. As is clear from FIG. 4, the pressure loss was equal to or higher than that of the conventional product in all cases. In the case of the conventional triangular ridge shape, the optimal shape for evaporation was 60 grooves with a groove bottom width of around 0.15 mm, but in the case of the ridge shape with a small apex angle of the present invention, the groove bottom width W1 = 0.2
It can be seen that the optimum value is around mm, and in order to improve the performance over conventional products, it is desirable to form 0.1≦W1≦0.3. Next, in the present invention, the apex angle is 0° to 2
The method for manufacturing a heat exchanger tube with a 0° mountain shape as shown in FIG. 5 is to groove the groove shape around 0° in the same manner as described above, and then reduce the diameter by 20 to 40%. By doing so, the apex angle can be reduced. The same tendency as described above was also found for shapes with apex angles of α=0 to −20°, which were created in the same manner. Furthermore, the same tendency could be found without any problem even when the heat exchanger tube of the present invention has a rounded tip as shown in FIG. 6.

0010

[Effect of the invention] As described above, the internally grooved heat exchanger tube of the present invention has
The heat transfer performance within the tube can be improved, and when the expanded tube is brought into close contact with the fins on the outside of the tube, the collapse of the groove can be suppressed and the close contact can be strengthened, thereby improving the performance of the heat exchanger. Furthermore, it has workability that is equal to or better than conventional products.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of an example of an internally grooved tube of the present invention.

FIG. 2 is a diagram showing the relationship between the production volume of heat transfer tubes and the peak width/groove depth.

FIG. 3 is a diagram showing the relationship between the amount of groove collapse and the peak width/groove depth.

FIG. 4 is a diagram showing the relationship between the rate of increase in evaporation performance and the groove bottom width relative to the conventional product.

FIG. 5 is a sectional view of a main part of an example of an internally grooved tube of the present invention.

FIG. 6 is a sectional view of a main part of an example of an internally grooved tube of the present invention.

FIG. 7 is a sectional view of a main part of a conventional internally grooved heat exchanger tube.

[Explanation of symbols]

1 Heat exchanger tube 2 groove 3 Mountain

Claims (1)

[Claims] Claim 1: In a heat exchanger tube in which a large number of grooves and ridges are formed spirally or continuously in the tube axis direction on the inner surface of the tube, the crest angle is -20°<α<20°, and the groove depth is 0.10~. 0.25m
m, and the ratio of the peak width to the groove depth W/H = 0.3 ~
1.5. An internally grooved heat exchanger tube characterized in that the groove bottom width W1 is 0.1 to 0.3 mm.