JPH0237292A - Condensing heat transmission pipe - Google Patents

Abstract

PURPOSE:To enhance the external heat transfer and improve the ease of handling by extending the ridge of an external fin like a hook to one of the sides of a groove, and extending the hook to the valley of an adjacent external fin. CONSTITUTION:An external fin 12 has a ridges 16 and valleys 18 alternately in the direction of its length, and the external fin 12 is divided by the valleys 18. The valleys 18 are arranged parallelly to each other but at an angle of 10-60 deg. relative to the normal line to the fin length. The respective ridges 16 are extended more toward their peak like a hook to at least one groove 14b of the grooves 14a, 14b present on either side. The hook configuration 20 extends toward the groove 14b and becomes sharper as it approaches the slope 16a of one of the valley 18 between the slopes 16a, 16b on either side of the fin length. Therefore, more contact area becomes available for the condensible gas, improving the condensing efficiency. Moreover, when the heat transmission pipes are superposed, the mutual intrusion between the ridges can be prevented.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a condensing heat transfer tube suitably used in a condenser as a heat exchanger for air conditioners, refrigerators, boilers, etc. This invention relates to a condensing heat exchanger tube that can effectively increase the

(Background Art) In general, such heat transfer tubes perform heat exchange between, for example, a heat transfer fluid (cooling liquid) that flows through the inner surface of the tube and a heat transfer fluid (condensable gas) that is brought into contact with the outer surface of the tube. It is used to condense and liquefy condensable gases. In condensing heat transfer tubes, an important issue is how to increase the heat transfer coefficient on the tube's outer surface, and thus the condensing efficiency.For this purpose, a low-in tube with spiral fins formed on the tube's outer circumferential surface is known. ing.

Therefore, in such a loaf-in tube, the formation of a large number of external fins ensures a wider contact area than a smooth tube with no fins at all, and it is expected that the heat transfer performance on the tube's outer surface will be improved to some extent. It can be done, but
However, this cannot be said to be sufficient.In order to satisfy the ever-increasing demand for improved heat transfer coefficient in this field, it is strongly necessary to develop an even more advanced condensing heat exchanger tube. What is required is the reality.

(Object of the Invention) The present invention has been made based on the above-mentioned circumstances, and its object is to integrally form outer fins in the circumferential direction on the outer surface of the tube at a predetermined pitch. It is an object of the present invention to provide a condensing heat transfer tube that can effectively increase the heat transfer coefficient of the outer surface of the heat transfer tube in which the outer surface fins are formed into grooves extending in the circumferential direction of the tube.

(Solution Means) In order to achieve the above object, in the present invention, peaks and troughs are formed alternately along the longitudinal direction of the outer fin, and the outer fin is formed by the troughs. At the same time, the troughs are inclined parallel to each other within a range of 10 to 60 degrees with respect to the direction perpendicular to the longitudinal direction of the fin, and the ridges are arranged so that the fins are divided as they approach the top, and The closer you get to one of the valleys in the direction, the more
One side of the grooves located on both sides of the crest is formed to extend in a hook shape, so that the hook-shaped portion extends toward the trough of the adjacent outer fin. .

(Function/Effect) In this way, by forming the troughs at an angle, the effective contact area on the outer surface of the tube can be increased. This contributed to an increase in area, and together these factors succeeded in effectively improving the heat transfer coefficient, especially the condensing performance, on the outer surface of the tube. In addition, in view of the good results actually obtained, it is not only possible to increase the contact area of the outer surface of the tube with the heat transfer fluid (for example, condensable gas), but also that the hook-shaped portions of the peaks are mainly responsible for condensation. It is speculated that a special role in improving performance is that the tips of the multiple hook-shaped portions form multiple points that promote condensation.

Furthermore, when simply forming peaks and valleys, the peaks take the form of sharp protrusions that protrude radially outward from the outer surface of the tube, but according to the present invention, the peaks have a hook-like shape. Since the heat exchanger tubes are formed so as to extend toward one side of the groove, the peaks are less likely to bite into each other when the heat exchanger tubes are loaded, and the heat exchanger tubes also have the advantage of being easier to handle. .

(Specific Configuration/Examples) In order to clarify the present invention more specifically, some embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a partially cutaway view showing an example of a condensing heat exchanger tube according to the present invention, in which numeral 10 indicates a condensing tube made of a metal with good heat transfer coefficient such as copper, copper alloy, aluminum or aluminum alloy. It is a heat exchanger tube. This heat exchanger tube 10
On the outer circumferential surface of the tube, spiral outer fins 12 are integrally formed at a predetermined pitch in the circumferential direction of the tube. As a result, a groove 14 is formed between these outer fins 12 and extends spirally in the tube circumferential direction. A part of the outer surface of the heat exchanger tube 10 is shown in enlarged form in FIGS. 2(a) and 2(b).

FIG. 2(a) is an enlarged plan view of the tube outer surface viewed from directly above, and FIG. 2(b) is an enlarged view of the tube outer surface viewed from diagonally above. As is clear from these figures, the outer fin 12 has peaks 16 and valleys alternately formed along its longitudinal direction, and the outer fin 12 is divided by the valleys 18. ing. Furthermore, the troughs 18 are provided so as to be inclined parallel to each other by an angle θ with respect to the tube axis direction, or more precisely, with respect to a straight line O perpendicular to the longitudinal direction of the outer fin 12. This angle θ is within the range of 10 to 60°.

Furthermore, each peak 16 does not simply protrude toward the top, but as it approaches the top, both sides of the peak 16 protrude. It is formed so as to extend in a hook shape on the side of one of the groove portions 14a and 14b located in the groove portion 14b, and the portion extending in this manner is the hook-shaped portion 20.

Moreover, as shown in FIG. 2(a), this hook-shaped portion 20 has slopes 16a on both sides in the longitudinal direction of the fin,
The closer to the slope 16a of one of the valleys 18 of the grooves 16b, the more the grooves 14b extend toward the groove 14b, and the tip of the hook-shaped portion 20 has a sharp point.

In other words, each peak 16 is twisted by an angle θ rather than perpendicular to the fin length direction, and a hook-shaped portion 20 is formed on one side of the peak 16.
They all extend to the same side.

Further, in the adjacent outer fins 12.12, the respective peaks 16 and troughs 18 are formed substantially alternately in the direction forming an angle θ with respect to the straight line 0, and are formed on the side of the groove 14b. The extending hook-shaped portion 20 extends toward the trough portion 18 of the adjacent outer fin 12 with the groove portion 14b in between, and the groove portion 14b has a zigzag shape while maintaining a substantially constant width and extending around the pipe circumference. extending in the direction. The above also applies to the outer fins 12 located between the grooves 14b and 14c, as well as to each groove 14a,
The same can be said for 14c as well.

Note that while Figures 2(a) and (b) are for the case of θ-30°, Figures 3(a) and (b) are for the case of θ=20°, and Figure 4(a) is for the case of θ=20°. ) and (b) respectively show embodiments when the angle is θ-45°. As is clear from those figures, the larger θ becomes, the more
The hook-shaped portion 20 is sharper and longer, and extends into the groove on one side.

Incidentally, in the conventional method, as shown in FIGS. 5(a) and 5(b), the valley portion 18 is parallel to the straight line 0 perpendicular to the fin longitudinal direction, that is, θ-0.

Therefore, the peak portion 16 is approximately in the shape of a square truncated pyramid,
Further, the bottom portion of the valley portion 18 is simply pushed out evenly toward the groove portions 14 on both sides.

In contrast, FIGS. 2(a), (b) to 4(a)
, (In the heat exchanger tube according to the present invention shown in BL, as described above, the valley portions 18 are inclined by the angle θ, and the peak portions 16 are twisted by that amount to provide the hook-shaped portions 20. The contact area for the condensable gas that is brought into contact with the outer surface of the tube is large, and therefore the condensation efficiency is effectively increased.In addition to simply increasing the contact area, the presence of the hook-shaped portion 20 also creates a large number of sharp points. By obtaining the portion, the existence of the hook-shaped portion 20 is reduced to the peak portion 16.
It is presumed that this prevents the formation of a thick liquid film on the slopes of the walls, promotes droplet condensation, and contributes to improved condensation performance. In fact, it has been confirmed that the condensing heat transfer performance is improved by about 30% or more compared to the conventional heat transfer tubes shown in FIGS. 5(a) and 5(b).

Further, the peak portion 16 of the conventional heat exchanger tube existed as a sharp protrusion in the shape of a square frustum, but in the case of the heat exchanger tube according to the present invention, the peak portion 16 sharply protrudes radially outward from the outer surface of the tube. Rather, the hook-shaped portion 20 is curved in a direction parallel to the tube axis, so it is difficult to handle the heat exchanger tube, for example, when an operator handles it with gloved hands. In this case, the fibers of the gloves are much less likely to adhere to the ridges 16 than in the past, and when the heat exchanger tubes are stacked, the ridges are prevented from digging into each other. In this state, there is an advantage that it becomes easy to align the heat exchanger tubes in the tube axis direction.

Note that the trough 18 with respect to the straight line O perpendicular to the fin longitudinal direction
The inclination angle θ is selected within the range of 10 to 60°, as described above. This is because when θ is made smaller than 10°, the result is as shown in FIG. 5(a).

Compared to the conventional heat transfer tube shown in (b), the superiority, that is, the improvement in heat transfer efficiency and ease of handling, is not recognized as much. On the other hand, when θ exceeds 60°, it is difficult to process the valley portion 18. This is not to say that it is impossible, but even if θ is increased in this way, it is difficult to obtain a commensurate effect (this is because processing costs will increase).

Therefore, it is necessary to select the angle θ within the range of lO to 60', and a range of 15 to 45 degrees is particularly suitable.

By the way, the condensing heat exchanger tube according to the present invention as described above can be easily manufactured, for example, as follows. A specific example of the manufacturing method will be explained based on FIGS. 6 and 7.

In FIG. 6, reference numeral 22 denotes a plurality of fin-forming disks whose diameters gradually increase are concentrically and integrally connected by a shaft 24 at intervals giving the pitch of the outer fins 12; Furthermore, a groove-forming disk 26 is attached to the shaft 24 adjacent to and concentrically with the largest diameter fin-forming disk 22 . This cutting groove forming disk 26 is disk-shaped, and is provided with a plurality of cutting teeth 28 at a predetermined pinch on its outer periphery.
The radius of the circumference drawn by the tips of the cutting teeth 28 is made smaller by a certain amount than the largest diameter of the fin-forming disk 22.

Moreover, as is clear from FIG. 7(a), these cutting teeth 28 are arranged with respect to the axis of the cutting groove forming disk 26.
Both are inclined by an angle θ, and this inclination angle θ
is selected within the range of lO~60', and Fig. 2(a)
This corresponds to the inclination angle θ of the valley portion 18 shown in FIG.

Then, the shaft 24 to which the outer fin forming disk 22 and the cut groove forming disk 26 are attached is set at a lead angle of the outer fin 12 to be formed with respect to the center line of the raw tube 30 that provides the intended heat transfer tube. The plug 31 is positioned at a corresponding angle, and a plug 31 is inserted inside the blank pipe 30.

In this state, the fin-forming disk 22 is inserted through the shaft 24.
By rotating and pressing against the outer peripheral surface of the raw tube 30, the outer surface fins 12 are gradually formed by rolling while rotating the raw tube 30 around the tube axis, while the white arrows on the fin forming disk 22 By pressing the cut teeth 28 of the cut groove forming disk 26 against the outer surface fin 12 formed as described above by the cut groove forming disk 26 disposed on the downstream side in the outer surface fin forming direction shown by , the pressed portion by the cutting teeth 28 is the trough portion 1
8, and the valley portions 18 and peak portions 16 as described above are formed alternately.

Therefore, since the cutting teeth 2 of the cutting groove forming disk 26 are inclined at an angle θ with respect to the axis thereof, as shown in FIG.
As shown in b), when the cut groove forming disk 26 is rotated and pressed against the raw pipe 30, due to the rotational pressing action, the portion pressed by the cut teeth 28 of the outer fin 12 is , as shown in FIG. 8, the cutting teeth 2 are
A pressing force P along the inclination direction of 8 is applied. This pressing force P
This acts on one side of the groove portion 14 located on both sides of the outer fin 12, and as a result, the metal material that was present in the portion that should become the trough portion 18 is moved to one side along the cutting tooth 28. is moved to the side of the groove 14, and the above-mentioned crest 12 and, in turn, the hook-shaped portion 20 are formed.

Incidentally, when manufacturing conventional heat exchanger tubes as shown in FIGS. 5(a) and 5(b), FIG. 9(a).

As shown in (b), the spur tooth groove forming disc 3
2. In other words, a disk 32 with cutting teeth 34 parallel to its axis is used; in this case, as shown in FIG. 10, by being crushed by the cutting teeth 34, The cross-sectional area of the tips of the outer fins 12 is significantly reduced, and the reduced area is pushed out to the grooves 14 on both sides, so that the portion G becomes a part of the condensate in the grooves 14 between the outer fins. It becomes easy to block the flow.

On the other hand, if the cutting groove forming disk 26 having the cutting teeth 28 inclined by the angle θ is used as described above, if the angle θ is about 20°, as shown in FIG. As shown in , the pressed portion of the outer fin 12 is hardly crushed, the outer fin 12 is divided with almost no reduction in cross-sectional area at the tip, and one groove 14 is separated. This results in a hook-shaped extension on the side.

Note that if the inclination angle θ of the cutting teeth 28 is selected in the range of 30 to 45 degrees, as shown in FIG. When the angle θ exceeds 60°, durability problems such as the cutting teeth 28 becoming easily chipped and an increase in processing cost for forming the cutting teeth 28 will be caused. Cutting tooth 2
This is the main reason why the inclination angle θ of No. 8 is set to 60° or less.

In any case, if the pressing force P is applied by the inclined cutting teeth 28 as described above, as shown in FIG. 2(a),
It is possible to easily manufacture a heat exchanger tube having peaks 16 and troughs 18 as shown in (b) etc., although the processing cost of the cutting teeth 28 is slightly higher than that of conventional ones without slopes. , since no special processing equipment is required, the increase in cost is practically negligible.

Next, data from tests conducted by the present inventors to determine how much the heat exchanger tube thus obtained can specifically improve condensing performance will be shown below.

This test was conducted under the following test conditions for a condensable gas (Freon R-22) that was brought into contact with the outside surface of the tube, and the results are shown in Table 1. However, for comparison, data regarding a conventional heat exchanger tube in which the inclination angle θ of the valley portion is Oo is also shown.

〔Test conditions〕

Outer diameter: 19.05mm (outer diameter of raw pipe)
Number of teeth: 19 threads/inch Cutting tooth: 1 pitch x O, 7mm depth Inner diameter: 14.
80+nm condensation Temperature: 40'C Cooling water inlet temperature: 30°C Cooling water flow rate: 1.5~3. Orn/sec\,\\\Table 1 As is clear from the results shown in Table 1, when the inclination angle θ of the valley (cutting tooth) is 20°, 30°, and 45°
In the heat exchanger tube according to the present invention, the tube outer surface condensation heat transfer coefficient: ho is approximately 30% to nearly 50% higher than that of the conventional heat exchanger tube whose inclination angle is Oo. This simply means that the condensation performance on the outer surface of the tube is improved accordingly.

Although the present invention has been described above based on specific examples and test data, it goes without saying that the present invention is not to be construed as limited by such specific descriptions.

For example, a recess (
It is also possible to form dimples and arrange inner protrusions in a spiral on the inner surface of the tube corresponding to the recesses. By forming a recess in the groove on the outer surface of the tube and an inner protrusion on the inner surface of the tube, the contact area on the outer surface of the tube can be further increased, and the condensation efficiency can be further increased. By applying turbulent flow to the flow of the heat transfer fluid (cooling water), it is possible to suppress the formation of a film that impairs the heat transfer coefficient.

In order to manufacture such a heat transfer tube, for example, a serrated disk is placed downstream of the external fin forming disk and upstream of the notched tooth forming disk, and the formed external surface is By pressing the serrations of the serrated disk against the bottom of the groove between the fins, the pressed portion of the serration is made to protrude into the inner surface of the tube as a recess. The crests and troughs may be formed using the cutting tooth forming disc as described above.

It goes without saying that the present invention can be implemented in various other forms with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway view of an embodiment of a condensing heat exchanger tube according to the present invention. However, to avoid complexity,
Peaks and valleys are omitted. Figures 2 (a) and (b) are drawings (sketches) of enlarged photographs taken from different angles of the outer surface of the heat exchanger tube, where the inclination angle θ is 30°. shows. Figure 3 (a) and (b) and Figure 4 (a) and (
b) is a diagram corresponding to FIGS. 2(a) and 2(b), showing cases where the inclination angle θ is 20° and 45°, respectively. FIGS. 5(a) and (b) show the inclination angle θ
Fig. 2(a) shows a part of a conventional heat exchanger tube where the angle is 0°.
and (b), respectively. FIG. 6 is a process diagram schematically showing a specific example of a method for manufacturing a heat exchanger tube according to the present invention, and FIGS. 7(a) and (b)
) are explanatory diagrams schematically showing the state in which peaks and valleys are formed by this method from different angles. FIG. 8 is an explanatory diagram for explaining the state in which pressing force is applied by the inclined cutting teeth. FIGS. 9(a) and (b) are
FIGS. 7A and 7B are diagrams schematically showing the conventional method for manufacturing the heat exchanger tubes shown in FIGS. 5A and 5B from different angles, and correspond to FIGS. 7A and 7B. be. 10th
The figures are diagrams briefly explaining the shapes of peaks and valleys formed according to the method shown in FIGS. 9(a) and (b), and FIGS. When using the method of manufacturing a heat exchanger tube according to the present invention shown in
10 is a diagram schematically showing the shapes of peaks and valleys formed depending on the magnitude of the inclination angle θ of the cutting teeth. 10: Condensing heat transfer tube 12: External fin 14: Groove 16
: Mountain part 18; Valley part 20: Hook-shaped part 22: External fin forming disk 26: Cut groove forming disk 28: Cut tooth 30; Material pipe applicant Sumitomo Light Metal Industries, Ltd. (and 2 others) ≦; 2 Figure 2 Figure 4 Figure 3 4C 14e) 4cL Figure 5

Claims (1)

[Scope of Claims] A heat exchanger tube in which outer fins in the tube circumferential direction are integrally formed on the outer surface of the tube at a predetermined pitch, and grooves extending in the tube circumferential direction are formed between the outer fins, Peaks and valleys are formed alternately along the direction, the outer fin is divided by the valleys, and the valleys are separated from each other within a range of 10 to 60 degrees with respect to the direction perpendicular to the longitudinal direction of the fin. The ridges are provided in a parallel inclined state, and the closer the ridges are to the top, or the closer they are to one of the troughs in the longitudinal direction of the fin, the more the grooves are located on both sides of the ridges. 1. A condensing heat exchanger tube, characterized in that it is formed to extend in a hook shape on one side, and the hook-shaped portion extends toward the valley of an adjacent outer surface fin.