JPS6352314B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a heat exchanger tube with improved performance when immersed in a liquid and heated to boiling.

Conventionally, various surface structures have been proposed as means for improving this type of heating and boiling performance, but each has advantages and disadvantages due to problems in heat transfer performance, manufacturing difficulty, manufacturing cost, etc.

For example, pipes with a porous layer of metal powder on their surface are susceptible to performance deterioration due to clogging, while pipes with a surface structure that has many minute cavities and openings communicating with the outside. In many cases, the cavities are only provided in one direction, such as in the circumferential direction of the tube, and therefore, if the pitch between the cavities is made smaller to improve performance, manufacturing becomes difficult and costs increase. In terms of manufacturing, there are almost no products that can be manufactured in one step and that can be handled in the same way as smooth tubes or ordinary loaf inch tubes when incorporated into a heat exchanger.

As a result of various studies in view of these circumstances, the present invention provides a heat exchanger tube that improves boiling performance outside the tube by providing a surface mechanism that promotes boiling not only in the circumferential direction of the tube but also in the axial direction of the tube. It was possible to provide a manufacturing method for.

The present invention provides a circumferential cavity formed under the outer surface of a tube, which has a spiral shape with a desired pitch in the axial direction of the tube, and whose cross-sectional shape and size vary irregularly with respect to the longitudinal direction. The cavity has a limited narrow irregular shape that communicates with the outside along its longitudinal direction, and has a gap or opening that may be continuous or discontinuous with respect to its longitudinal direction. Furthermore, small cavities in the tube axis direction are provided under the outer surface of the tube at desired pitches in the tube circumferential direction so as to connect these adjacent gaps or openings, and this cavity is also connected to the above-mentioned cavity. Similarly, the present invention relates to a method of manufacturing a heat exchanger tube having a gap or an opening communicating with the outside, and small grooves having irregularities can be formed on both sides or the bottom of the latter cavity.

In carrying out the above-mentioned invention, the center position between adjacent spiral-shaped cavities in the circumferential direction of the former pipe, and between the cavities or grooves in the longitudinal direction of the latter pipe existing adjacently. It is also possible to provide chevron-shaped fins that protrude in the circumferential direction, or to knurl the entire surface of the tube except for the protruding portions of the chevron-shaped fins.

The present invention will be described in detail below with reference to the drawings.

FIGS. 1 and 2 are partially enlarged views of the heat transfer surface of the heat transfer tube manufactured according to the present invention. They are arranged with a desired pitch in the axial direction.
Small axial cavities or grooves 3 are also arranged between the cavities 1, 1 at desired circumferential pitches below the outer surface of the tube. The former circumferential cavity 1 has different shapes and sizes at the part where it intersects with the small cavity or groove 3 in the axial direction and the intermediate part thereof, and the shape and size of the cavity 1 in the tube circumferential direction are different between the part where it intersects with the small cavity or groove 3 in the tube axis direction, and the shape and size of the hollow part 1 in the tube circumferential direction are different. It is deformed in various ways and continues in its longitudinal direction.

The fact that the cavity 1 is varied in this way is more advantageous in promoting nucleate boiling than a cavity that is continuous in a constant shape and does not change in the longitudinal direction. 2 indicates an almost continuous gap communicating with the outside of the cavity 1 in the former, or in some cases an opening discontinuously provided at the pitch of the small cavity or groove 3 in the latter; Since the shape is irregular with many waves and irregularities, it is more advantageous in promoting nucleate boiling than a simple shape as described above.

In order to promote nucleate boiling, it is necessary to create a surface structure on the heat transfer surface that allows residual bubbles to form, but in this case, the average width of the narrow gap or opening 2 affects the heat transfer performance. It has a big impact. This is because if the average width of the gap or opening 2 is too large, the generated air bubbles cannot be secured within the cavity 1, and the number of remaining air bubbles decreases, preventing nucleate boiling from being promoted.

Furthermore, the smaller the surface tension of the heated and boiling liquid and the specific volume of the vapor, and the larger the latent heat of vaporization,
Since the size of the generated bubbles is small, the limit value for ensuring the average width of the residual bubbles in the gap or opening 2 will differ depending on the liquid being heated and boiled. Figure 8 shows Freon R-11 and R-22.
Average width of gap and boiling heat transfer coefficient outside the tube (heat transfer performance)
Indicates the relationship between

The size of the bubbles generated is R-11>R-22. In Fig. 8, the heat transfer performance of R-22 rapidly decreases when the average width of the gap or opening 2 becomes 0.13 to 0.15 mm, so the boiling liquid R-11,
In order to obtain high heat transfer performance for any R-22, the average width of the gaps or openings 2 must be 0.13 mm or less. On the other hand, the small cavity 3 in the tube axis direction also has a narrow gap or opening 4 that communicates with the outside, and from the results shown in FIG. 8, the maximum average width of this is also set to 0.13 m/m or less as described above.

Furthermore, since the total length of these small cavities 3 is approximately equal to the length of the spiral cavity 1, this means that the boiling nucleus density is much larger than that of a surface structure consisting of only the cavity 1. performance is improved. This is extremely effective in promoting boiling since the shape and surface condition of the cavity 3 and opening 4 can become the nucleus of many bubbles.

A small cavity or groove 3 and 3 in the center position of the adjacent spiral cavities 1 and 1 and in the circumferential direction
The chevron-shaped fins 5, which protrude in between with their longitudinal direction facing the circumferential direction, are effective in improving performance by making use of their characteristics as fins, especially in cases such as in liquids under turbulent flow containing a large amount of bubbles. I will be working.

Furthermore, the knurled surface 6 provided over the entire circumference of the tube excluding the fins 5 in FIG. 1 becomes a heat transfer surface with a larger number of bubble nuclei than the smooth surface shown in FIG. 2, improving its performance. It is effective for

Either or both of the above-mentioned fins and knurled surfaces may be omitted depending on the case.

On the other hand, the heat exchanger tube manufactured according to the present invention described above can be easily manufactured by forming fins on a smooth tube and then subjecting it to deformation processing. Regardless of the number of strips, fin forming and deformation may be performed continuously or in separate steps.

Hereinafter, details of the manufacturing method according to the present invention will be explained with reference to the drawings.

Figure 3 is an example of the processing method of the present invention, and shows an enlarged view of the heat exchanger tube and the processing tool cut in the axial direction, showing the continuous fin forming and deformation processing, and the chain line The area inside the circle X shows the cross section of the part where the processing has been completed. Three tool axes A are arranged at equal intervals around the tube, and a disk tool for fin forming and a tool for deformation are attached to the tool axis A so that they can rotate together. By rotating the tool axis A, the pipe is rotated in the opposite direction to the tool axis A, and is subjected to fin forming and deformation processing. Further, since the tool axis A is in a twisted position with respect to the axis of the tube, the tube is fed in the axial direction of the tube while being processed.

In FIG. 3, reference numeral 7 indicates a final-stage disc tool for forming fins, by which fins 7' are formed on the surface of the tube. Reference numeral 8 indicates a first-stage deforming disc tool provided with chevron-shaped teeth around the entire circumference, as shown in FIG. 3-1.

The outer diameter of this disk tool 8 is made slightly smaller than the outer diameter of the above-mentioned disk tool 7 for forming fins, and the shape and pitch of the tips of the teeth on the circumferential surface may be determined as appropriate. It is better that the tip has an appropriate width as shown in the enlarged view S in Figure 3-2.

FIG. 4 shows an example of the shape of the fin 7' when it is compressed and deformed by the first-stage deforming disc tool 8 from a top view.

That is, the first stage deforming disc tool 8 having tapered chevron-shaped teeth as shown in the chain line circle Y in FIG. 3-1 and as shown in FIG. 3-2 is placed on the top surface of each fin 7'. When the fins 7' are rolled in the direction of the arrow 11, each fin 7' is compressed and deformed into a gear shape corresponding to the chevron-shaped teeth on the circumferential surface of the disc tool 8, and at this time, the flesh of the valley part 7'' is perpendicular to the fin 7'. , that is, in the direction orthogonal to the arrow 11, in the direction of the inter-fin portion (indicating the gap between the fins 7' and 7') 7 on both the left and right sides, and its amount reaches its maximum at the bottom of the valley 7''. . After the final processing is completed, the valley 7″ formed by this deformation processing is
This results in a small cavity or groove 3 in the tube axis direction. By modifying the shape of the chevron-shaped teeth on the circumferential surface of the tool 8, it is easy to form the groove 3 having irregularities on the inner surface. In this deformation process, the compressive stress acting on the portion directly below the valley 7'' is alleviated by the shape of the tool 8 and the distribution of force, and therefore the amount of deformation due to buckling is small.

Note that if the fin 7 to be deformed is a single thread, it is only necessary to deform one fin using the deforming tool 8, but if the fin is a multi-thread,
Even if multiple fins are processed at the same time using the deforming tool 8, it is also possible to process multiple fins using the multiple tools 8.
The deformation process may be carried out in an arbitrary manner, and in any case, the mutual positional relationship between the peaks and valleys of adjacent fins 7' is arbitrary and is not limited in any way. Next, the top surface portion (mountain portion) of the fin 7', which has been deformed into a gear shape, is deformed by the second stage deformation tools 9 and 9-1 shown in FIG. The outside diameter of the tool 9 is normally slightly smaller than the outside diameter of the tool 8, and the thickness is slightly smaller than the pitch W of the fins 7'.
The outer diameter of tool -1 is slightly larger than that of tool 9. At this time, both sides of the outer circumferential surfaces of the tools 9 and 9-1 should be made sharp so as to serve as a shear, as shown in Figure 3-4, and the angle should not exceed 90 degrees. preferable.

FIG. 2 shows an example of the process completed using the second-stage deforming tools 9 and 9-1, and the surface structure of the heat exchanger tube manufactured according to the present invention is basically completed through such a process. . That is, deformation processing tools 9, 9-1
When the shoulders of the peaks of the gear-shaped fins 7', 7' on both sides adjacent to each other are compressed and deformed from the top surface with the inter-fin area 7 as the center, these peaks are It is compressed and deformed from side to side to form a cavity 1 centered on the interfin portion 7 and a small cavity or small groove 3 centered on the trough 7'', respectively.

In addition, in this compression deformation process, the compressive stress is stronger on the end 11 of the top surface of the fin 7' than on the intermediate portion 12, so that the top surface of the fin 7' as shown in FIG. −2 It is compressed and deformed as shown in Figure 2.
The deformed end 11' protrudes a little more toward the interfin portion 7 or the valley portion 7'' than the deformed intermediate portion 12'. Therefore, for example, the tools 9 and 9-
By changing the degree of compression change by changing the outer diameter of cavity 1, a continuous or discontinuous narrow gap or opening 2 or 4 that communicates with the outside is formed along the longitudinal direction of cavity 1 or 3. be able to.

That is, when the degree of compressive deformation is large, the openings are discontinuous, and when the degree of compressive deformation is small, the openings are continuous and narrow.

Although Fig. 3 shows an example of machining using two tools, tools 9 and 9-1, it is possible to use a plurality of tools with different outer diameters and widths, or tools such as those shown by 9' in Fig. 3-3. Only 1
Processing may be performed using individual tools.

In addition, if thin-walled angled fins 5 are not formed, the width of the tool 9, etc. may be made larger than the fin pitch W. In this case, the entire ridges of the fins 7', 7' are compressed and deformed to form a shape as shown in Fig. 6. A surface structure without chevron fins is obtained.

Next, as shown in Fig. 3, when machining is performed using a knurling roll 10 with a slightly larger outer diameter and the same or slightly smaller width than the tool 9-1, the shape shown in Fig. 1 is obtained. A stable surface structure with better performance than the shape shown in FIG. 2 can be obtained.

The shape and size of the knurling may be determined as appropriate, but if the width of the tool 9 is larger than the fin pitch W, it is preferable that the width of the knurling roll 10 is also larger than the fin pitch W. In this case, the fifth A surface structure without the fins 5 shown in the figure is obtained.

In the above description, the fin forming disk tool 7, the deforming tools 8, 9, 9-1, and the knurling roll 1
Although a method has been described in which the fins are mounted coaxially and processed continuously, fin forming and deformation may be performed in separate processes. Furthermore, as a method for forming the fins, instead of the rolling process as described above, cutting processes may be used to form the fins.

Next, examples of the present invention will be shown.

Example 1 Outer diameter 18.88 according to the processing method shown in Figure 3
Two fins 7' with a fin pitch of 35 m/m and a wall thickness of 1.35 m/m are formed on a copper tube.
Next, the first stage deformation process was carried out using a serrated tool 8 with an outer diameter of 51.6 m/m and 216 chevron-shaped teeth on the outer periphery. The second stage deformation process has an outer diameter of 51.2m/m.
Tool 9 with a width of 1.4 m/m and an outer diameter of 51.7 m/m and a width of 1.4
Two steps were carried out using m/m tool 9-1. The width of these second-stage deformation tools 9 and 9-1 is 1.4
m/m is Fin Pitch 1/35 inches (=0.726m/m)
It is larger, and naturally the fins 5 seen in FIGS. 1 and 2 are not formed, and a surface structure as shown in FIG. 6 is obtained.

The bottom of the valley 7'' shown in FIG. 4, which was formed by the first stage deformation process, caved in by about 0.2 m/m after the second stage deformation process was completed.

Finally, using tool 10, the outer diameter is 51.8m/m and the width is
Knurling was performed with a 0.85 m/m pitch and a 0.5 m/m pitch.

As a result of the above, the gap or opening 2 has an average width of 0.06 m/m and continues in a spiral pattern, the corresponding cavity 1, and the above spiral gap or opening has an average width of 0.08 m/m. A gap or opening 4 is provided at a pitch of approximately 0.75 m/m in the circumferential direction so as to connect the two in the axial direction of the pipe, and a corresponding small cavity 3 is formed on the entire surface of the pipe. A heat exchanger tube having an outer diameter of 18.38 m/m as shown in FIG. 5 and having a surface structure consisting of knurled surfaces 6 was obtained.

Example 2 Based on the processing method shown in Figure 3, the outer diameter was 18.88 m/
Two fins 7' with a fin pitch of 35 m/m are formed on a copper tube with a wall thickness of 1.35 m/m, and then the first stage of deformation is performed with an outer diameter of 51.6 m/m and a fin 7' on the outer periphery. teeth
A serrated tool 8 with 216 chevron teeth was used. The second stage deformation process has an outer diameter of 51.3m/m and a width of
0.62m/m tool 9 and outside diameter 51.75m/m, width 0.62
It was carried out in two stages using m/m tool 9-1. At this time, the bottom of the valley 7'' shown in FIG. 4, which was formed by the first stage deformation process, caved in by about 0.2 m/m after the second stage deformation process was completed.

Finally, we knurled a twill pattern with an outer diameter of 51.8 m/m and a width of 0.6 m/m.

As a result of the above, there is a spiral gap or opening 2 with an average width of 0.04 m/m and a corresponding cavity 1, and the spiral gap or opening with an average width of 0.07 m/m. Gaps or openings 4 are provided at a pitch of approximately 0.75 m/m in the circumferential direction so as to connect the parts 2 in the axial direction of the tube, and small cavities 3 corresponding to the gaps or openings 4 exist adjacent to each other. At the center position of the spiral or annular cavity parts 1 and 1 and between the small cavities or grooves 3 and 3 in the circumferential direction, the longitudinal direction protrudes in the circumferential direction and has a thickness of about 0.1 m/m. ,
It has a surface structure consisting of chevron-shaped fins 5 with a height of about 0.25 m/m and a knurled surface 6 applied to the entire surface of the tube except for the fins, and has an outer diameter of 18.88 m/m as shown in Fig. 1.
m heat exchanger tubes were obtained.

Freon R-11 using the heat exchanger tubes of Examples 1 and 2
A graph of the boiling heat transfer coefficient per unit length in the inside is shown in FIG. In the figure, A is the heat exchanger tube of Example 1, B
For comparison with the heat transfer tube of Example 2, the boiling heat transfer coefficient per unit length of the finch tube having substantially the same outer diameter (18.8 m/m) and 26 finch pitches is also shown as C. The above graphs are the performance measured using a single tube, and the boiling pressure is 1.5Kg/cm ² abs.
It was hot.

The features and effects of the present invention described above are summarized as follows.

(1) Various types of heat transfer tubes with surface features to improve boiling performance have been proposed, but conventional ones have cavities only in one direction, such as in the circumferential direction. There are many things,
Furthermore, in order to improve the performance, it is necessary to make the pitch between the cavities finer, which leads to manufacturing difficulties and high costs. According to the present invention, it is easy to manufacture a high-performance heat exchanger tube having a boiling promotion mechanism not only in the circumferential direction but also in the axial direction.

(2) In addition, in the surface structure of the present invention, the annular or spiral cavity can have a continuous cross-sectional shape that changes irregularly in the longitudinal direction, and the boiling effect of the resulting heat transfer tube can be improved. can be encouraged.

(3) Generally, the refrigerant vapor generated in the evaporator of a refrigerator needs to be in a superheated state. It is possible to provide thin-walled chevron-shaped fins on the entire surface of the tube.
It is particularly effective in improving performance by superheating bubbles by taking advantage of their fin characteristics.

(4) To install a tube in a shell-and-tube heat exchanger, insert the tube into the tube hole from the tube sheet on one side of the assembled shell, and fix the tube end to the tube sheet by expanding or welding. , the outside diameter of the tube must be smaller than the tube plate bore diameter over its entire length. In addition, tube supports are often used, and in this case, to ensure support of the tube,
At the location of the tube support, the outer diameter of the tube is required to be equal to the outer diameter of the tube at the tube end.

The outer diameter of the heat transfer tube to which the surface structure of the present invention is applied is not larger than that of the original tube, and like the loaf inch tube, a skip portion of the same size as the smooth portion of the unprocessed tube end is freely provided. It has the advantage of being possible to process in one step. Therefore,
When incorporated into a heat transfer exchanger manufactured according to the present invention,
It can be handled in the same way as smooth tubes and loaf inch tubes, and can be obtained at a relatively low cost.

[Brief explanation of drawings]

Fig. 1 is a partially enlarged view of a heat transfer surface having a surface structure manufactured according to the present invention, Fig. 2 is a partially enlarged view of the same heat transfer surface with the knurling surface removed from the surface structure of Fig. 1, and Fig. The figure is an exemplary diagram showing the processing method and tool arrangement for the surface feature manufactured according to the present invention.
-1 is a plan view of the first stage deformation processing tool 8 same as above, Fig. 3-2 is an enlarged view of the chevron-shaped tooth portion of the above-mentioned tool 8, and Fig. 3-3 is another processing according to the present invention. 3-4 is a side view of the tools 9 and 9-1, and FIG. 4 is a partially enlarged view of the shape after processing with the tool 8 in FIG. 3. 4-1
The figure shows the shape of the top surface of the fin 7', FIG. 4-2 is an explanatory diagram of the shape after it has been compressed and deformed, and FIG. FIG. 6 is an enlarged view of a portion of the heat transfer surface manufactured according to the present invention, with the fins removed from the surface structure of FIG. 2, and FIG. Figure 8 is a graph showing the outside boiling heat transfer characteristics of each heat exchanger tube manufactured by 2 and a comparison product.Figure 8 is a graph showing the outside boiling heat transfer characteristics when the average width of the opening 2 is changed. be. 1... Cavity in the circumferential direction of the tube, 2... Gap or opening as above, 3... Small cavity or groove in the axial direction of the tube, 4... Gap or opening as above, 5... Chevron fin, 6...Knurled surface, 7...Disc tool for fin forming, 7'...Thick wall fin, 7''...Trough part as above, 7...Between the fins, 8...For deforming the first stage Disc tool, 9, 9-1, 9'... Disc tool for second stage deformation, 10... Knurling roll.

Claims (1)

[Scope of Claims] 1. After forming spiral fins with a predetermined pitch in the axial direction of the tube by rolling or cutting on the outer surface of the tube, first The tops of the fins are compressed and deformed into a gear shape using a disc tool for rolling the stages, and then the peaks of the fins adjacent to each other in the tube axis direction and the tube circumferential direction formed in the gear shape are By compressing and deforming the section using a disk rolling tool in the second stage, a spiral hollow section whose cross section changes in the circumferential direction and the upper part of this hollow section are formed along the circumferential direction. At the same time, it forms a continuous or discontinuous narrow gap or opening that communicates with the outside, and at the same time forms a hollow section in the tube axis direction whose hollow section is the valley of the fin compressed and deformed into the shape of a gear. A method for manufacturing a boiling type heat exchanger tube, characterized by forming a narrow gap or opening in the upper part that communicates with the outside along the tube axis direction. 2. After forming spiral fins with a predetermined pitch in the axial direction of the pipe on the outer surface of the pipe by rolling or cutting, first-stage rolling is provided with chevron-shaped teeth around the entire circumference. The tops of the fins are compressed and deformed into a gear shape using a disc tool, and then the peaks of the gear-shaped fins that are adjacent to each other in the tube axis direction and the tube circumferential direction are processed into a second stage. By compressing and deforming using a rolling disk tool, a spiral hollow section whose cross section changes in the circumferential direction of the tube and a continuous section in the upper part of this hollow section that communicates with the outside along the circumferential direction are formed. Or, at the same time, a discontinuous narrow gap or opening is formed, and at the same time, a hollow part in the pipe axis direction whose hollow part is the valley part of the fin compressed and deformed into the shape of a gear, and a hollow part in the pipe axis direction in the upper part of this hollow part. A method for producing a boiling type heat exchanger tube, which comprises forming a narrow gap or opening communicating with the outside along the tube, and then forming a knurled surface on the tube surface using a knurling roll.