JPH01131895A - Heat transfer tube with inner surface groove - Google Patents

Abstract

PURPOSE:To improve a tube evaporation heat transfer rate and a tube condensation heat transfer rate in a low flow rate region of a heat exchange medium by setting the sectional area of the groove part of a rectangular cross section of a heat transfer tube several times the section of adjacent crest part. CONSTITUTION:In the rectangular cross section of a heat transfer tube 1, the sectional area S1 of a groove 2 is set 2-5 times the sectional area S2 of the crest 3, and the outside diameter D of the heat transfer tube 1 is selected to be as small as 8mm or less to increase the tube flow rate of the heat exchange medium in a low flow rate region, to promote a turbulent low to prevent laminar flow. Further, a groove bottom width W1 sufficient for lowering the retention height (f) of the condensate 4 of a heat exchange medium is imparted. By doing so, no remarkable performance lowering is found in the tube condensation transfer rate of the heat transfer tube even in a low speed flow region of the heat exchange medium. With the tube evaporation heat transfer rate, the performance is improved as the flow rate becomes low in the low speed flow region of the heat exchange medium.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an internally grooved heat exchanger tube in a heat exchanger such as an air conditioner or a refrigerator.

[Conventional technology]

In heat transfer tubes in heat exchangers such as air conditioners and refrigerators, the fifth
As shown in Fig. 6 and Fig. 6, by providing a large number of continuous spiral grooves (2) and peaks (3) adjacent to each other on the inner surface of the heat exchanger tube (1), the heat exchange area is increased. Improves efficiency (in-pipe heat transfer coefficient).

[Problem that the invention seeks to solve]

Currently, heat exchanger tubes in heat exchangers such as air conditioners and refrigerators have a large number of continuous spiral grooves (2) and ridges on the inner surface of the heat exchanger tube (1) with a diameter of 9.538 mm, as shown in Figure 7. A grooved heat exchanger tube (3) is used, in which refrigerant R-22 is flowed as a heat exchange medium inside the tube, and water or air is flowed outside the tube to perform heat exchange. However, when heat exchange is performed by flowing a heat exchange medium inside the tube and flowing water outside the tube, the flow rate of the heat exchange medium inside the tube decreases (the flow velocity inside the tube decreases), and the evaporative heat transfer coefficient inside the tube increases. Transmission rate decreases. In other words, in evaporation inside a tube, when the flow rate of the heat exchange medium flowing inside the tube decreases (the flow velocity inside the tube becomes slower), the heat exchange medium becomes a laminar flow, and a film of the heat exchange medium is formed along the inner wall of the tube, causing a turbulent flow effect. heat exchange efficiency. Therefore, the smaller the flow rate of the heat exchange medium, the less the difference in performance from the smooth tube. In addition, when condensing in the pipe, as shown in Figure 8, the bottom width (Wl) of the groove (2) is narrower than the bottom width (Wl) of the peak (3), so the condensate (4) tends to accumulate and the drop occurs. Reduces heat exchange efficiency in the flow rate range.

However, in recent years, heat exchanger tubes in air conditioners and refrigerators have been increasingly used in low flow ranges by increasing the number of passes, and there is a strong desire to improve heat exchange efficiency in low flow ranges.

[Means for solving problems]

In view of this, as a result of various studies, the present invention has been developed to prevent the laminar flow of the heat exchange medium and the stagnation of condensate in the low flow rate region of the internally grooved tube, and to achieve extremely high heat exchange efficiency even in the low flow rate region. This is a developed heat exchanger tube that has a large number of continuous grooves and ridges adjacent to each other on the inner surface of the tube.The outer diameter of the tube is D, the depth of the groove is N1, the bottom width of the groove is W1, and the ridges are The bottom width of W1,
If the number of grooves is N and the peak angle is α, then D is 8m or less and H is 0.
．． 1-0.5M, Wl is H≦W1≦3H or W2≦W1
≦3W2, N is 40-60°, α is 20-60°,
It is characterized in that the cross-sectional area of the groove portion of the right-angled cross section is 2 to 5 times the cross-sectional area of the adjacent mountain portion.

[For production]

The heat exchanger tube of the present invention has the above-mentioned configuration. In particular, as shown in FIG. 1, the outer diameter of the heat exchanger tube (1) is D, the depth of the groove (2) is N1, the bottom width of the groove (2) is W1, and the peak 3) Bottom width of W1, groove (2)
When the apex angle of N1 mountain (3) is α, D is 8s or less, and H is 0.1 to 0.5s.

Wl is H≦W1≦3H or W2≦W1≦3W2, N is 4
0 to 60" and α is 20 to 60", and by combining these, the cross-sectional area (Sl) of the groove (2) is reduced to a mountain (3 ) cross-sectional area (S
2), and the outer diameter of the heat exchanger tube (1) is smaller than the conventional one to 8 m or less to increase the flow velocity of the heat exchange medium in the tube in the low flow area, promoting turbulent flow and creating laminar flow. The groove bottom width (Wl) is sufficient to prevent this and to reduce the retention height (f) of the condensate (4) as a heat exchange medium.

The tip of the mountain formed between the grooves is semicircular, trapezoidal, or trapezoidal.
It may be triangular or rectangular, or a combination of these shapes may be used as appropriate. Furthermore, the groove may be spiral or parallel to the tube axis.

〔Example〕

A heat transfer tube of the present invention was fabricated in which the following grooves and peaks were formed adjacent to each other on the inner surface of a heat transfer tube having an outer diameter of 7#, and the heat transfer coefficient within the tube was measured.

The results are shown in FIGS. 3 and 4 in comparison with a conventional heat exchanger tube with a grooved inner surface and a heat exchanger tube with a smooth inner surface having a diameter of 9.35 m.

The heat exchanger tube of the present invention has an outer diameter of 7, a groove bottom wall thickness of 0.25 m, a groove depth of 0.15 m, and 50 grooves with a groove bottom width of 0.25 m, which are tilted upward at an angle of 18 degrees to the right with respect to the tube axis. The apex angle of the peak formed between the grooves was 50°, and the protrusion tip shape was semicircular.

The heat transfer coefficient inside the tube was measured by flowing refrigerant R-22 into the tube and flowing water outside the tube to perform heat exchange, and then measuring the evaporative heat transfer coefficient within the tube and the condensation heat transfer coefficient within the tube. Figure 3 shows the measurement results for the evaporative heat transfer coefficient in the tube, and Figure 4 shows the measurement results for the condensation heat transfer coefficient in the tube.

(2°) shows the conventional internally grooved heat exchanger tube, and (3) and (3') show the heat exchanger tube of the present invention.

As can be seen from the figure, the in-tube evaporative heat transfer coefficient of the conventional internally grooved heat exchanger tube is such that the flow rate of the heat exchange medium flowing inside the tube decreases (
When the flow rate in the tube becomes slower), the heat exchange medium becomes a laminar flow, and a film of the heat exchange medium is formed along the inner wall of the tube, reducing the evaporative heat transfer coefficient in the tube, and the lower the flow rate of the heat exchange medium, the smoother the inner surface of the heat exchange tube. There is no difference in performance between the two. Furthermore, in the condensing heat transfer coefficient within the tube of a conventional internally grooved heat exchanger tube, the width of the groove bottom is narrower than the width of the mountain bottom, so the condensate tends to accumulate, which significantly reduces the heat exchange efficiency in the low-velocity region of the heat exchange medium.

In contrast, in the heat exchanger tube of the present invention, there is no significant performance deterioration in the condensing heat transfer coefficient within the tube even in the low-velocity region of the heat exchange medium, and the performance improves as the flow rate decreases in the low-velocity region of the heat exchange medium in terms of the evaporative heat transfer coefficient within the tube. I understand that.

〔Effect of the invention〕

The heat exchanger tube of the present invention has a smaller outer diameter than conventional heat exchanger tubes with internal grooves and increases the flow velocity of the heat exchange medium flowing through the tube, resulting in moderate turbulence even in the low flow rate range, which allows heat exchange. This prevents the medium from forming a laminar flow, eliminates the formation of a film of heat exchange medium along the inner wall of the pipe, and makes the groove bottom wider than before to prevent the condensate of the heat exchange medium from stagnation. By reducing the height and the synergistic effect of these effects, the in-pipe evaporative heat transfer coefficient and the in-pipe condensation heat transfer coefficient are dramatically improved in the low flow rate range of the heat exchange medium.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing an example of the heat exchanger tube of the present invention, Figure 2 is an explanatory diagram showing the cross-sectional area of the inner groove and the cross-sectional area of the peak of the heat exchanger tube of the present invention, and Figure 3 is the inside of each inner grooved tube. An explanatory diagram showing the relationship between the evaporative heat transfer coefficient and the refrigerant flow rate (heat exchange medium flow rate). Figure 4 shows the relationship between the in-pipe condensation heat transfer coefficient and the refrigerant flow rate (heat exchange medium flow rate) of each internally grooved tube. Explanatory drawings, FIG. 5 is a sectional view showing an example of a conventional internally grooved heat exchanger tube, FIG. 6 is a side sectional view of the heat exchanger tube shown in FIG. 5, and FIG. 7 is an example of a conventional internally grooved heat exchanger tube. FIG. 8 is an explanatory diagram showing an enlarged cross section of a conventional internally grooved heat exchanger tube. 1. Heat exchanger tube 2, groove 3, ridge 4, condensate sump, diameter H0 groove depth W1, groove bottom width W2, ridge bottom width α, ridge top angle Fig. 1 7/ TS Fig. 2 7 111111■ Figure 3 IO Lingyin 5 Tomo (Kg/hr) Figure 4 XIO 2050to. ; Rei 9 scents, love! tt (Kg/hr) Fig. 5 Fig. 6

Claims (1)

[Claims] In a heat exchanger tube that has a large number of continuous grooves and ridges adjacent to each other on the inner surface of the tube, the outer diameter of the heat exchanger tube is D, the depth of the groove is H, the bottom width of the groove is W_1, the bottom width of the ridge is W_2, and the groove If the number is N and the peak angle is α, then D is 8 mm or less and H is 0.1 to 0.5 mm.
, W_1 is H≦W_1≦3H or W_2≦W_1≦3W
_2, N is 40 to 60, α is 20 to 60 degrees, and the cross-sectional area of the groove part of the right-angled cross section is 2 to 5 times the cross-sectional area of the adjacent peak part. heat exchanger tube.